CA1067781A - Fluid flow control system - Google Patents

Abstract

ABSTRACT OF THE DISCLOSURE
This invention relates generally to improvements in fluid flow control systems for parenteral administration of medical liquids.
Positive pressure infusion pumps of the syringe type are known. However, since a portion of each operating cycle with such syringe type pumps is concerned with filling the syringe, rather than delivering fluid to the patient in a pumping mode, the accuracy of such devices tends to fall off, particularly at very high flow rates, where the fill stroke is of significantly large duration relative to the pump stroke period.
The present invention overcomes this deficiency by providing a system for fluid flow control utilizing a syringe pump operated by a stepping motor to repetitively fill and empty a syringe cartridge over a plurality of operational cycles of successive fill stroke and pump stroke periods.
The stepping motor is driven by electrical drive pulses from a digital pulse generation and control system. Means are provided for maintaining a proportional relationship between the preselected pumping rate and the actual fluid flow pumping rate over each complete cycle of successive fill and pump strokes, the motor drive pulse frequency during each pump stroke is automatically increased to compensate for the time lost during each fill stroke. A detection device is provided which responds to a high rate of motor drive pulses in the absence of a concurrent selected high flow rate.

Description

106778~
Thls lnvention relates generally to im~rovements in fluid flow control systems and, more particularly~ to a new and improved automatic~ highly accurate~ poRitive pressure infusion pump of the syringe pump type, for parenteral administration of medical liguids over a wide range of fluid flow rates.
The usual medical procedure for the gradual parenteral : adminlstration o~ liquids into the human body~ such as liquid n-~trients~
blood or plasma, m~ke~ use of apparatus which i8 commonly referred to in the medical arts as an intravenouR adminlstration set. me intra-venous set usually comprises a bottle of liquid~ normally supported in an inverted position~ an intravenous feeding tube~ typlcally of clear pl~stic, and a suitable valve mechani~m, such as a roll clamp, which a11oWB the liquid to drip out of the bottle at a ~electively ad~ustable rate lnto a transparent drip chamber below the bottle. The drip cham-ber serves the dual function of allowing a nurse or other attendant to ob~erve the rate at which the liquld drips out of the bottle, and also creates a reservoir for the liquid at the lower end of the drip chamber to insure that no air enters the main feedlng tube leadlng to the patlent.
While observation of the rate of drop flow via the drip chamber i8 a slmple way of controlling the amount of liquid fed to a patlent over a period of time~ lts ultimate effectiveness requires that a relatlvely constant vigil be maintained on the drop flow~ lest lt cease entirely due to exhaustlon of the liquid supply or become a ; contlnuous stream and perhaps increase the rate of liquid introduction .. . .
to the patient to dangerous levels.
; By way of example~ it has been the general practice in hospitals to have nurses periodically monitor drop flow rate at each intravenous feeding or parenteral infusion station. Such monitoring of drop flow is a tedlous and time consuming process~ prone to error and associated~ possibly serious consequences, and resulting in a substantial reduction of the available time of qualified medical -; pereonnel for other important duties. Typically~ the nurse monitoring '. -1_ -', , ~ ' ' - " ' : , 106:~
drop flow rate will use a watch to time the number of drops flowing in an interval of one or more minutes, and she will then mentally perform the mathematics necessary to convert the observed data to an appro-::; . .: ., .
priate fluid flow rate~ e.g.~ in cubic centimeters per hour or drops per minute. If the calculated flow rate is substantially dlfferent than thé prescribed rate~ the nurse must manually ad~ust the roll clamp ; for a new rate, count drops again, and recalculate to measure the new rate.
Obviously~ each of the aforedescribed measurements and calculations and flow rate adjustments usually takes several minutes' time which~ when multiplied by the number of stations being monitored snd the number of times each station should be monitored per day~ can . ~ . .
, result in a substantial percentage of total personnel time available.
~.; .. , i l In addition~ under trhe pressure of a heavy schedule, the observations j~ and calculations performed by a harried nurse in measuring and ad~ust-... .
lng flow rate may not always prove to be reliable; hence~ errors do occur~ resulting in undesired~ posslbly dangerous infusion ~low rates.
In add$tion to the aforedescribed difficulties~ the paren_ ` teral ~dminlstration of medical liquids by gravity_induced hydro6tatic pressure infusion of the liquid from a bottle or other container ;~
su6pended above a patient, is very susceptible to fluid flow rste - ~ariatlon due to change6 in the liquid level in the bottle~ chsnges in temperature~ chsnges in the venous or grterial pressure of the patient, p3tient movement~ and drift in the effective setting of the roll clamp '~ or other valve mechanism pinching the feeding tube. Moreover, there i~ are B number Or situations~ 6uch as in intensive care~ cardiac and pedlatrlc patients~ or when rather potent drugs are being administered~
- where the desired fluid flow rate must be capable of precise selectlon ~5 ~ and must not drift beyond certaln prescribed limits. In addition~ it' :~

;`~i is ex*remsly important in such situations for medical personnel to be informed of undesirable fluctuations in flow rate, failure of the , .
fluid delivery system for any reason, leakage of the system, or exhaustlon of liquid supply when the bottle is emptied.
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_2_ ,:, ' " ' ',' ' ' ' , ' . ' ' ': ' ~; t ` ! 106~7781 It will be ap~ent, trlere~ore~ that some o~ the most crltlcal problems confronting hospital personnel ~aced wlth an over_ ;~ whelming duty schedule and limited time availability are the problems qulckly~ ea6ily~ reliably and accurately maintalning proper rluld flow rates in the parenteral administratlon o~ med$cal llquids.
-~i In recent years, a number of electrlcal monltoring sy~tems, drop ~low controller6 and infusion pumps have been developed to accom-pllsh the various tasks Or nltorlng and regulating drop flow rate6.
S e of theee devices have aleo been capable Or actlvating slarm6 when 0 8 potentially dangerous condition exists~ thu6 freelng medical per-sonnel to eome extent~ for other dutles. However~ whlle such monitorlng and drop rate control devlces have generally served their purpose~ they have not always proven entirely satieractory irom the standpoi~t of cost~ complexity~ stablllty, reliability, accuracy~ or ~ preclslon of adJustment over a wlde range Or selected fluld flow rates.
; f~ In addition~ such sy6tems have sometimes been subJect to drift and substantlal i'low rate variatlons due to changes in temperature~ feeding ~ tube crimps~ varlatlons in venou6 or arterlal pre6sure of the patlent~
:~ or vsriatlons in the helght of the bottle or sQlutlon level wlthln the ¦~ 20 bottle. 8ubeta~tlal diriiculties have also been experienced p~rtlcu~lsrly in connectlon wlth establlshlng and maintaining accurate flow ij.~.i, .
at ~ery low ~lcw rates.
Pbeltive pressure pumps of the closed loop peristaltic type hsve been provided which overcome some of the aforementloned difflcul_ `~; f~ tles wlth regard to drlft, and accurate flow at low flow rates.
However~ even such cloæed loop positive pressure systems only serve to malntsin accuracy of flow in terms of stabilizing to a preselected volume Or fluld~ e.g.~ ln cublc centimeters per hour. me reason for ' ~ this 1B thst the sccuracy Or such systems ie llmited inherently to the *:~ 30 accuracy of the size of the drops produced by an intravenous adminls-tratlon set~ and the actual drops produced by the latter apparatus can vary from lts aeslgnated drop size, e.g.~ by vlrtue of drlp chamber structural varlation~ by as much-a6 30 percent.

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1067781;
Positlve pressure Tnfusion pumps of the syrlnge type have also been provided~ wherein a syringe having a precise displacement volume is repeatedly fTlled and emptled on alternate piston strokes during a combined flll stroke and pump stroke operational cycle, so that control of the rate at which the syringe Is filled and emptled provides an accurate means for precise fluid volume delivery wtthin a pre~scribed perlod of time. However, since a portlon of each operatlng cycle with such syrlnge type pumps Is concerned with fllling the syrlnge, rather than dellverlna fluid to the patlent In a pumping mode, the accuracy of such devices tends to fall off, partlcularly at very hlgh flow rates, where the flll stroke period is of stgnificantly large duration relatlve to the pump stroke perlod. Attempts have been made to provlde varlous types of non-llnear callbratlon for such syrlnge ~ ::
type systems, In an attempt to com,ensate for the lost tlme error due to syrlnge i'flll' tlme In each complete pumplng cycle. However, these efforts, at best, have only reduced the degree of inaccuracy In certaln llmlted flow rate ranges, e.g., at low flow rates, and have falled to provlde an unlformly hlgh degree of accuracy over a wlde range of flow ;; rates~ and partlcularly at very hlgh fluld flow rates.
~ 20 Hence, those concerned wlth the development and use of , i , .
parenteral fluld adminlstratlon systems, and partlcularly those con-cerned wlth the deslgn of automatlc fluid flow control systems, have ~;~ long recognlzed the need for Improved, relatively slmple, economlcal~
~m ~ rellable, stable and accurate devlces for fluld flow control whlch ' j, obvlate the aforedescrlbed dlfflcultles. The present Inventlon provldes a new and Improved ftuld flow control system In the form of , I
a syrlnge pump whlch clearly fulfllls this need.
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` ~067781 ':'' Brlefly, and In general terms, the present tnventTon provldes motor for drlvlng the-syrlnge of a syrlnge pump through a flll stroke In whlch the syringe Is fllled wlth fluld throuqh ah Input llne and through a pump stroke durtng which fluid Is dellvered frcm the syrlnge through an output llne. A pulse generator Ts also provlded for generatlng motor drlve pulses to energlze the motor and a detector Is responslve to a hlgh r~te of m~tor drlve pulses In the sbsence of concurrent high flow rate selocted to provlde an ~larm Indlcatlon.
In a preferred embodlment, the system may further comprlse an alarm responslvo to the detector for de-energlzlng the motor.
These and other obJects and advantages ot the Inventlon wlll ~ecomo apparent from the followlnq more deta1ied descrlptlon, when taken In conJunctlon wlth the accompanylng drawlngs of IllustratIve ombcdlmonts.
FIGURE I is a generallzed block dlagrsm of an overall system for a syrlnge pump of the type used In practlclng the present Invontlon;
~ FIGURE 2 Is a block dlagrum of an overall electrlcal system ; In whlch some of tho baslc concepts of the fluld control system of the i prosent Inventlon aro embodted;
- 20 FIGURE 3 Is a comblned block dtagram and electrlcol sshematlc of a slmpllfled system for c~mpensatlng motor drive pulses generated , ,''''' ` ~' ' , ., ' , i~ ;

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-10677~31 . , .
during the pump stroke for time lost during the fill stroke;
FIGURES 4 and 5 are graphical representations illustrating the basic motor drive pulse co~pensation concepts of the present lnvention;
FIGURES 6a, 6b and 6c are comblned block diagrams and ~ -electrical schematics of one embodiment of an overall fluid flow control system in accordance with the present invention, F5GURE 6a being primarily directed to the stepping motor drive pulse generation and compenæation subsystems~ FIGURE 6b being primarily directed to the motor direction and speed control subsystems, and ~IGURE 6c being primarily dlrected to the start_up and alarms subsystems;
FIGURES 7a_7g are waveforms for various portions of the pulse generatlon and control sub6ystems in the overall system of FIGURES 6a, ;;
6b and 6c; and FIGURES 8a_ad are graphlcal representations illustrating varlous electrical states relating primarily to operation of the alarms subsystem in the overall system of FIGURES 6a, 6b and 6c.
Referrlng now to FIGURE 1 of the drawings~ there is shown ;;
Bn overall system for fluid flow control, capable of embodying features . I .
of the present invention. In the ensuing description~ while reference 16 made to the term "I.V.", normally connoting intravenous administra-tion~ it is to be understo~d that this is by way of example only, and , ~ , the flow control system of the present invention is suitable for other ; ~forms of parenteral administration as well as intravenous administra-. ~
tion.
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` iThe system shown in FIG. 1 depicts a syrlnge pump embodying ~ts ~yringe lO which preferably is in the form of a disposable cartridge, ;lbut it will become apparent that many features of the present invention ..msy be practiced independently of whether or not the syringe 10 is .~ .
disposable. The syringe lO is typically fabricated of molded plastic and essentially includes a cylinder 1OB in which a piston lOb is :`;
~slidably received and adapted to be reciprocated back and forth along . ~.,~
the axis of the cylinder by an integrsl piston rod lOc whlch ls coupled !~ .

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- ` 1067781 to and appropriately driven by a suitAble drive subsystem 12. The drive subsystem 12 typically lncludes a reversible d.c.~stepping - motor driving, through appropriate gearing, a lead screw which i8, in - turn~ coupled to the plston rod lOc of the syringe lO. me d.c. step_ ping motor of the drive subsystem 12 is energized by a pulse train of motor drive pulses generated by an electrical control subsystem 13 - and appropriately fed to the drive ~ubsystem.
e syrlnge lO lncludes an inlet port lOd and an outlet port lOe. me inlet port lOd communicates through a suitable I.V.
line 14 wlth any approprlate fluld source 15, typlcally an I.Y. bottle contalning appropriate drugs and/or nutrients in liquid form.
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- Typically~ the I.V. line 14 is part of an I.V. administration set which includes a transparent drip chamber (not shown) in the fluid ~l line between the syringe lO and the fluid source 15.

ri ~ A similar I.V. line 16 is connected~ at one end~ to the ~:~"'~
outlet port lCe of the syringe lO and conveys fluid from the syringe ,;i s ~ to B patient. The syringe lO and drive subsystem l~ m~y be of con_ ;i~ ventional deslgn.
A,pair of valves 17~ 18, typically of the tube plncher or clsmping typ2~ are selectively opened and closed at appropriate times ln the ow rall pumping cycle~ under the control Or a suitable valve control subsystem 19. The val~e 17 controls the inlet port lOd and 18 open during the fill stroke to enable fluid to be drawn from the fluid source 15, through the line 14, into the syrin8e lO, the valve 17 , ;". ~. : .
being closed during the pump stroke to prevent any fluid from exiting the syrlnge through the inlet port. The valve 18 controls the outlet port lOe and is open during the pump stroke to enable fluid delivery from the syringe lO to the patlent through the line 16~ the valve 18 belng closed during the fill stroke.
The valve control subsystem l9 is also driven, through ;
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~ appropriate gearing~ by the same drive subsystem 12 used to reclprocate ; the plston lOb of the syringe lO. The valve control subsy6tem l9 also provides information to the electrical control subsystem 13~indtc~ting : . .

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that the syringe 10 i6 either in the fill stroke or pump stroke, and this information, in turn, enables the electrical control subsystem to establish the proper direction of rotation of the stepping ~otor in the drive subsystem 12. me ~alves 17, 18 and valve control subsystem 19 may be of conventional design.
A sultable drop detector 20 monitors drop flow in the I.V.
line 14, at the drip chamber (not shcwn), to insure that drop flow occurs during the fill stroke of the syringe 10 and that drop flcw does not occur during the pump stroke of the syringe. In this regard~
drop flow should occur in the drip chamber below the fluid source 15 during the fill period of the syringe cycle, and the absence of such ~; flcw is an indlcation of an exhausted fluid source, e.g., an empty I.V. bottle, or a leak between the fluid source and the syringe 10.
In contrast~ the absence of such drop flow i8 a requirement during the pump stroke of the syringe cycle, the presence of drop6 indicating some kind of leakage, such a6 improper clamping off of. the I.V. line 14 by the valve 17.
- me drop detector 20 monitors drop flow in the drip chamber of the I.V. administration set and typically may include a sensor ~; 20 housing (not shown) containing a reference llght source located opposite a photocell to define an optical sensing gap therebetween, with a reference light beam normally impinging upon the photocell. me housing is appropriately clamped upon the drip chamber of the I.V.
set~ with the transparent drip chamber positioned within the sensing gap to intercept the reference beam. A falling drop of liquid within the drip chamber interrupts~the reference beam~ and a variation in ` electrical response of the photocell i6 directed to appropriate ` circuitry indicating the presence of a drop.
One example of a suitable drop detector 20 i6 set forth in ` 30 U.S. Patent NO. 3,596,515, inventor, Rlchard A. Cramer. ~hile a photo_ cell type drop detector 20 has been described, it will be appreciated that any drop sen6ing device capable of providing an electrical indica-tion of the detection of a drop may be used without departing from the ~ "`

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,' ' ~ ' ' :: . ~`, . ~ ......... " ' 677~1 ~pirit and scope of the invention.
The electrical output of the drop detector 20 is directed as an input to the electrical control subsystem 13 in connection with a variety of alarms subsystems (not shcwn in FIGURE 1).
me displacement volume of the syringe cartridge 10 iB
determined by the volume swept by the piston lOb on each stroke and iB ldentical for the fill stroke and for the pump stroke. Therefore~
an identical number of motor drive pulses from the electrical control sub6ystem 13 to the drive subsystem 12 is required for each fill stroke during which the syringe is filled wlth liquid from the fluid source 15, and for each pump stroke during which the syringe delivers its precise volume of liquid under positive pressure to a patient.
; The number of motor drive pulses energizing the stepping motor of the drive sub6ystem 12 for a complete stroke in either direction, either for the flll stroke or Por the pump stroke, is typically 3600 steps in a presently preferred embodiment of the invention.
The frequency of the motor drive pulses during the fill stroke iB a predetermined, fixed frequency, typically 404 Hz., selected to rapidly fill the syringe 10 as quickly 8S po~sible without creating a vacuum which might suck air into the syringe or which might create a continuous stream (as opposed to flow in discrete drops) in the drip chamber. Preferably, the time interval for performance of a fill stroke (hereinafter referred to as the fill stroke period) is as short a8 possible BO that its influence on the overall time for each complete operational cycle of the syringe 10 is minimal. However, as the desired fluid output pumping rate increases, the pump stroke period becomes shorter and~ hence~ the time lost during the fill stroke period becomes more and more significant in reducing the actual average fluid flow rate of delivery by the pump.
In accordance with the invention, the motor drive pulses to the stepping motor of the drive subsystem 12 are increased ln frequency during the pump stroke of each operational cycle of the pump to compensate for the time lost during each corresponding fill stroke of , - ` ~1)6778~ -each operational cycle. The entire fill stroke period correction is spread over the full pump stroke period by compensating each and every individual motor pulse during the pump stroke period for a uniform portlon of the time lost during the immediately preceding fill stroke.
To accomplish this, the electrical control subsystem 13 counts up the increments defining each pump stroke motor drive pulse twic~ as fast for the first portion of the counting cycle equal in time to the duration of a motor drive pulse period generated during the fill stroke of the operational cycle.
The compensated output motor drive pulses from the electrical control subsystem 13 to the drive subsystem 12 are, therefore, at a ; frequency which produces an average pumping rate over successive pumplng cycles equal to the desired fluid flow rate.
; Referring now to FIG. 2~ there i6 shown a new and improved : electrical control system embodying various features of the present inventlon.
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A d.c. stepping motor 22 drives a suitable syringe pump 23, such B8 that of the general type shown in FIG. 1. The stepping motor 22 ls energized by motor drive pulses received from a drive pulse generator 6ubsystem 24, and the direction of rotation of the stepping ~; motor to produce either a fill stroke or a pump stroke ls established by a direction control subsystem 25.
A suitable high frequency clock 27 drives a pump rate determining subsystem 28 and a fill rate determining subsystem 29.
me fill rate subsystem 29 feeds the drive pulse generator ~ubsystem r'`~' 24 directly during the fill stroke period of the syringe pump cycle . .
and~ therefore, produces motor drive pulses at the output of the pulse generator subsystem 24 at a fixed fill rate frequency. In contrast~
the pump rate subsystem 28 feeds ~n intermediate drive pulse control subsy6tem 31 which, in turn, energizes the drive pulse generator subsystem 24.
The drlve pulse control subsystem 31 also receives a con_ trolling input from the fill rate subsystem 2g. In this connection, ' ,~, _ ~

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1(~67781 when the syringe pump operational cycle is in the pump stroke period, , .. .
the drive pulse control subsystem 31 provides a pulse output to the drive pulse generator subsystem 24 which is compensated ~or the lost tlme during the fill stroke period to provide an output pulse train from the pulse generator which will maintain an average fluid flow rate equal to the desired fluid flcw rate. mis is accomplished by : havin~ the fill rate subsystem 29 dominate the drive pulse control subsystem 31 for the first portion of each motor drive pulse period of the pump stroke equal to a motor drive pulse period in the fill stroke.
During thls first time interv&l of each pump stroke motor drive pulse, the drive pulse control subsystem 31 is counted up at twice the frequency as that which is used to count up the control subsystem for the remaining portion of the motor drive pulse period. Therefore, the output of the drive pulse control subsystem 31 and, hence~ the motor drive pulse output from the pulse generator subsystem 24 i8 at a higher frequency over the entire pump stroke period of the operating cycle than would othervise be provided lf the pump rate subsystem 28 drove the subsystem 24 directly without its output being first compensated for the timè' lost during each fill stroke.
An alarms subsystem 32 recei~es input from a drop sensing subsystem 33 for appropriate leakage or empty bottle detection, a rotation sensing subsystem 34 for detecting a stalled stepping motor 22, a syringe cartridge detection subsystem 35 to determine whether an appropriate syringe cartridge hss been properly installed prior to initiation of pump operation, and a bubble detecting subsystem 36 to determine if there is air in the I.V. line. The alarms subsystem 32 also receives inputs from the pump rate determining subsystem 28, the drive pulse generator subsystem 24 and the direction control subsystem 25, so that other alsrm functions can be performed with knavledge of the particular portion of the operational cycle in effect, e.g., fill stroke, pump stroke, or the translent ~tate between either of these strokes. The alarms subsystem also responds~ with the inputs shown in FIGUR~ 2, ln the event of component failure somewhere in the pumping \~

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~0677~31 system which may produ;:e a lack of luid flaw or induce a runaway pumping state generating an uncalled-for high pumping rate.
- Referring ncw to FIG. 3, there is shown a simplified system for compensating the frequency of stepping motor drive pulses generated during the pump stroke period for the time lost during the fill stroke period.
- A stepping motor drive 40 for the syringe pump, typically embodying a ~.c. stepping motor (not shcwn)~ receives appropriate incremental drive pulses over line 42 which is the output of a drive pulse OR gate 43. The stepping motor drive 40 also receives an input over line 44 from a suitable direction sensor 45 (typically in the ~alve control subsystem for the syringe pump) which conditions the stepping motor direction of rotation so that the drive pulses received over line 42 will stép the motor either in the direction to perform a fill stroke or in the direction to perform a pump stroke.

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me direction sensor 45 also determines whether the output pulses appearing on line 42 are at the fiil frequency or at the pu~p frequency. In this regard, the system of FIG. 3 includes an Ah~ gate 4~ which is the control Bate for the output of pump frequency motor drive pulses and a second AND gate 48 which is the control gate for - the output of fill frequency motor drive pulses.
me pump frequency control gate 47 receives as one input over line 49 a pump frequency pulse train, and receives as a second enabling input over line 50 the inverted electrical output of the direction sensor 45. The latter is accomplished by directing the output of the direction sensor 45 through an inverter 51 to the gate 47.
me output of the directlon sensor 45 is also directed as an enabling input, over line 52, as one input to the fill frequency con-trol gate 48, the other input to the gate 48 being the fill frequency pulse train over line 53.
Hence, it will be appsrent that the direction sensor 45 selectively enables either the pump frequency control gate 47 or the fill frequency control gate 48, depending upon whether or not a pump :: ., ~, \~
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:~067781 stroke or a fill atrok~ is about to be performed by the syringe pump.
me output pulses fro~ the control gates 47 or 48 are directed over lines 54, 55, respectively, as inputs to the drive pulse gate 43 which~ in turn, passes motor drive pulses to the stepping motor.
A suitable high frequency clock 60 feed6 a pump rate pulse : generator 61 over line 62 and a fill rate pulse generator ~4 over line 63. The pump rate pulse generator 61 is typicall~ a rate multi_ pller and is under the control of a pump rate selector 65, typically in the form o, rate selector switches for the rate multiplier.
Ihe electrical output of the pump rate pulse generator 61, over line 67, is a pulse tr~in d1rectly proportional to the desired instantaneous fluid flow rate delivered by the syringe pump during the pump stroke period of the syringe pump operational cycle. ~owever, as previously indicated, the average fluid flow rate delivered by the syrlnge pump~ in the absence of compensation, will be less than the desired fluid flow rate and will be a non-linear function of thé
selected pulse rate produced by the pulse generator 61, because of the tlme lost during the fill stroke period of the operational cycle.
The fill rate pulse generator 64 may be a separate subsystem for divlding down the clock frequency to the desired fill frequency or .' , it may conveniently be derived from the appropriate high order decades of the pump rate pulse generator rate multiplier. For purposes of ; simplicity, however, the fill rate pulse generator 64 is shown as a separate divider 6ubsystem. me ~ill frequency pulse train generated by the pulse generator 64 i~ directed as electrical input over line 53 to the fill frequency control gate 48 which passes the pulse train to the drive pulse OR gate 43 whenever the direction sensor 45 c811s for performance of a fill stroke.
In order to smooth out the electrical output of the pump rate pulse generator 61, a divider network ls provided which includes ; a dlvide-by-two counter 70 and a divide-by-101 counter 71, thus - dividing the output of the pulse generator 61 by a total of "202".

Overflow of the counter 71 at the count of "101" produces a pump _~, . .
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- frequency motor drive pulse over line 49 to the control gate 47 which passes the pump frequency pulse train over line 54 through the drive pulse OR gate 43 whenever thé direction sensor 45 calls for performance - of a pump stroke.
The manner in which the pump frequency is compensated for ti~e loæt during the fill stroke period, to ~ake the average flow rate equal to the desired flow rate selected by the pump rate selector 65, is next described. In this regard, the divide-by-two counter 70 is selectively bypassed~ under control of the fill frequency pulse trsin, to count up the counter 71 at twice the normal rate during the first portion of each motor drive pulse period for a pump stroke equal in time to a motor drive pulse period for a fill stro~e. To this end, the "101" counter 71 is counted up by countlng pulses received over line 73 from an OR gate 74 which receiveæ a pair of inputs over lines 75, 76. ~he pulse rate on line 75 i6 one-half Gf the pulse rate on line 76, the former pulse rate being the output of the divide-by-two counter 70, whereas the latter count rate is the full pulse rate output from the pulse generator 61 with the divide-by~two counter 70 bypassed.
In this rega,rd, the AND gate 77 bypasses the counter 70 and receives the output of the pump rate pulse generator 61 over line 78. The gate 77 also receives an enabling input o~er line 79 from a control flip_flop 80. The AND gate 77 is enabled each time the Q output of the control flip-flop 80 is "true", and the gate 77 is disabled when_ ever the Q output of the flip-flop 80 is "false".
Each time the counter 71 overflows, generating a pump frequency motor drive pulse, it also resets the fill rate pulse gener-ator 64 and sets the control flip-flop 80, over line 82, so that its Q output is "true". ~ence, the output of the pump rate pulse generator .:.
67 bypasses the divide-by-two counter 70,~through the AND gate 77 and OR gste 74, until such time as the AND gate 77 is disabled by the control flip-flop 80. In this connection, the ';reset" input of the - control flip-flop 80 is under the control of the fill rate pulse generator 64~ over llne 84. Thus~ the AND gate 77 will be disabled~

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by the Q output cf the control flip-flop 80 going "false , at the end of a single fill rate pulse period which resets the flip-flop 80.
In summary, the fill rate pulse generator 64 directly provides output motor drive pulses over line 53, through gates 48 and 43, durlng the fill stroke period of the syringe pump operational cycle.
However~ during the pump stroke period of the operational cycle~
the motor drive pulses are defined by the overflow of B divider network which simultaneously functions to smooth out the pulses from the pump rate pulse generator 61 and also co~pensates the motor drive pulse frequency for time lost during the fill stroke period. This is . .
accomplished by counting up the "101" counter 71 at twice the rate during the first portion of each pump stroke motor drive pulse period for a tlme interval equal to a fill stroke motor dr$ve pulse~ under the control of the fill rate pulse generator 64, control fllp-flop 80 and D gate 77, after which the gate 77 is disabled and the pulse rate from the pump rate pulse generator 61 is divided in half by the counter 70 prior to being fed through the OR gate 74 to the counter 71.
. The result is a uniform, motor pulse by motor pulse compensation for time lost during the fill stroke period, the compensation being spread ~ 20 over the entire pump stroke period.
.~ FIGS. 4 and 5 graphically illustrate the basic motor drive ; pulse frequency compensation technique accomplished by the system of FIG. 3. In FIG. 4, it will be apparent that the fill stroke period and the pump stroke period are defined by an equal number of motor drive pulse steps, e.g., 3600 steps in a presently preferred embodiment .;....................................................................... ... .
; Or the invention, slnce the pump stroke and fill strokes are identlcal except for direction. ~owever, the period of a single motor drive pulse during the pump stroke i6 at least equal to or greater than the period of a single motor drive pulse during the fill stroke, i.e., the ~ -,:
fill frequency is equal to or greater than the maximum contemplated pump frequency.

Referring now more partlcularly to FIG. 5, there is shown an enlarged vlew (on a time scale) of the period of a slngle motor drlve . ' . - . . , . ' ' ' ' . - , . . .
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~ .

~067781 pul~e durln6 a pump stroke. The latter period is defined by a total of 101 counts into the cou~ter 71 in the system of FIG. 3. Note that, for the first portion of the counting cycle, equal in time duration to ;
a motor drlve pulse period during a fill stroke, the counter 71 is -counted up at twice the counting rate as during the r~mainder of the counting cycle defining the pump stroke motor drive pulse. Hence~
durlng the first part of the pulse period, the counter 71 is counted up by the full pulse rate output of the pump rate pulse generstor 61 ln FIG. 3~ whereas for the balance of the counting cycle defining the ; 10 pump stroke motor drive pulse period, the output of the pulse generator 61 passes through the divide-by-two counter 70, thereby cutting the counting frequency in half.
FIGS. 6a, 6b and 6c are combined block diagrams a~d electrical ~chematics of one embodiment of an overall fluid flow control system ;~
for accomplishing the aforedescribed motor drive pulse frequency compensation technique and providing a number of additional features . .
~; regarding proper system conditioning for receipt of a syringe cartridge prior to initiation of an operational cycle, as well as the provision , of appropria,te alarm safeguard6. FIGS. 6a, 6b and 6c are arranged -~ 20 with their respective input and output connections aligned so that the three figures can be used as a single drawing for the entire ; fluid flow control system. In this regard~ the various subsystem . ., electrical connections overlap with each other to such a degree that the system is best described with regard to the combined figures, and the balance of the description will accordingly be made with reference to such a composite drawing.
Prior to a detailed description of the operation of the oYerall system depicted in FIGS. 6a, 6b and 6c, the main elements of each ma~or subsystem area, and their functions, are first summarized.

FIG. 6a i8 primarily directed to the frequency generating and compensating sections of the overall system for generating the ~tepplng frequency of the motor and includes, referring to FIG. 2 previously discussed, the clock 27, pump rate determining subsystem 2~, ~06778~
fill rate determining subsystem 29, drive pulse control Oubsystem 31 and portions of the drive pulse generator subsystem 24. The system shown in FIG. 6a has two primary output frequencies, one being the pump frequency for stepping the syringe pump drive motor in the forward direction during the pump stroke~ while the other output freque~cy iô
the fill frequency which is at a fixed rate and drives the stepping motor drive in the re~erse direction during a fill stroke. ~he fill frequency is also used to bring the piston actuator for the syringe cartrldge to its start_up condition for easy lnsertion of the syringe cartridge into the pumping apparatus when the overall pump system is about to be put into operation.
FIG. 6b relates primarily to the forward_reverse and speed control section of the overall system and, referring again to FIG. 2, primarily includes the stepping motor 22, the direction control sub_ system 25~ and portions of the drive pulse generator subsystem 24.
FIG. 6c is directed primarily to the details of the alarms subsystem 32 in FIG. 2, and the related input subsystems for the alarms~
including the drop senslng subsystem 33, rotation sensing subsystem 34, cartridge de,tection subsystem 35 and bubble detection subsystem 36, as well as inputs from other appropriate portions of the sy6tem necessary to determine the alarm and start-up conditions.
- Referring now to FIGS. 6a, 6b and 6c, as a composite system ; diagram~ a conventional high frequency clock generator 100 (FIG. 6a) directs digital pulses (the CLK signal) over line 101 to a conventional .digital rate multiplier 102 which embodies a plurality of digital rate selector switches 102a associated therewith for determining the output pulse frequency of the rate multiplier. The clock 100 ls the mast0r clock for the entire system and controls the frequencies and tlming.
me rate multlplier 102 multiplies the input frequency by a maximum factor of unlty. The output of the rate multlpller 102 over line 103 ls a digltal pulse rate (the RM signal) proportionsl to the setting of the rate selector switches 102a and, therefore, proportional ., : :

to the desired output fluid flcw rate to which the overall system is intended to stabilize. The electrical output (RM) of the rate multi_ plier 102 over line 103 is not, however, a continuous pulse train, but rather an irregular burst of pulses, due to the nature of the fractional multiplication which can occur in the rate multiplier. The typically non-uniform pulse train on line 103 is directed through AND gates 104, 106 to a conventional div~der network in the form of counters 105 and 107 which serve to smooth out the jitter iA the rate multiplier pulse train.
; 10 The electrical output of the counter 107 is decoded by an AND gate 108 to produce an output signal on line 109 each time the counter 107 counts to its "101" state. me output pulse train created on line 109 by each "101" counts of the counter 107 i~ at the compen_ s~ted pump frequency used to generste the motor drive pul6es for the pump stroke and corresponds to the output of the drive pulse control sub6y6tem 31 in FIG. 2.
The clock frequency generated by the clock 100 is, in a ., ., .. , ~ .
pre6ently preferred embodiment of the invention~ selected to be 40.4 kilohertz. ~IThe fill frequency is conveniently derived from the hieh order decade6 of the rate multiplier 102 by dividing the clock frequency .;.i .
by a factor of "100" to produce a fill frequency of 404 Hz. The fill ~i~ fre~uency i6 depicted schematically as electrical pulse output over line 111 from the rate multiplier 102. me latter fill Prequency is directed as one input to an AND ~ate 112 in the drive pulse control eubsystem~ and i8 also directed 6imultaneously over line 113 as an lnput to the drive pulse generator 6ubsystem (corresponding to the drive pulse generator subsystem 24 in FIG. 2) to control generation of tor drive pulses when the overall system is performing a fill stroke .
me clock frequency (CLX) of the clock 100 iB determined by taking into account a number of factors such as the number of motor steps to complete a stroke, the size of the syringe pump ¢hamber, l.e.~ syringe volume displacement, the nu~ber of counting pulses '~' ' , 10~7781 defining a single motor drive pulse period, and the maximum freguency at which the selected stepping motor is designed to operate. Using a fill frequency of 404 Hz.~ a 5 cubic centimeter displacement volume for the syringe, 3600 steps of the stepping motor to accomplish e~ch syri~ge stroke and a maximum pump rate of approximately 1000 cc. per hour, a clock frequency of 40.4 kilohertz has been determined to be suitable for the presently preferred embodiment illustrated in FIGURES 6a_6c.
The reason for selecting a count of "101" for the counter 107 as determinatlve of the pump frequency ls directly related to the relationship of the fill frequency to the clock frequency. Since~ as previously pointed out, it is essential to the bssic compensation technique utilized in the present invention that the pump ~troke period be equal to or greater than the fill stroke period (since the compensa-tion period in each pump stroke motor drive pulse must be equal to a fill stroke motor drive pulse period), the requirement for a count of - "101", l.e., 101 RM pulses, insures that the pump stroke motor pulse perlod will always be at least one percent greater than the fill stroke motor pulse period even at the maximum pumping rate. This follows logically since~ at the highest pumping rate of spproximately 1~000 cc.
! per hour, the output pulse irequency of the rate multiplier 102 will be equal to the full clock frequency (CLK) of the clock 100. Since the fill frequency of 404 Hz. is obtained by dividing the 40.4 kilo-hertz clock frequency by a factor of "100", the process of limiting the maximum pump frequency (via the counter 107) to the clock frequency divided by a factor of "101", obviously insures that the maximum pump freque~cy will be less than the fill frequency by approximately one percent and, hence, the pump stroke period will be longer than the ~ill stroke period by at least that same percentage at all times.
With a fill frequency of 404 ~z. and 3600 steps of the step-ping motor to accomplish each syringe stroke, the fill stroke takes a time period of approximately 9 seconds. The reason for the selection of 9 seconds for the "fill" period is to make the fill perlod as .
' ~hort as practical~ yet ~void pulling so fQst as to pull a vacuum on the I.V. tubing and theref'ore draw air bubbles from the drip chonber into the tubing. In addition, having too hi~h a fill rate can produce a contlnuous stream in the drip chamber which would cause failure of the drop detection subsystem and, as will subsequently bécome apparent~
would cause the overall syætem to go into alarm. A further factor involved in determininB the fill rate i8 the consideration of motor pcwer~ ln that ~ore battery power and a more powerful steppin~ motor ~ould be required for a higher fill rate. merefore, it 1B practical to limit the fill rate to a rate close to the maximum pumping rate requlred by the system.
Ihe rate multiplier 102 ls typically a binary coded decimal rate multiplier having three decadeæ~ a "hundreds'7 decade lQ2b, a "tens" decade 102c, and a 'lunits" decade 102d, thus enabling selectable ~luld flcw pumping rates of from 1 to 999 cc. per hour. me electrical output from the "tens" decade 102c over line 111 iB~ as previously indicated~ the fill frequency of 404 Hz.
An additlonal electrical output is provided from the "units"
decade 102d~ over line 115, and is at a frequency of 40.4 Hz. obtained by dividlng the clock frequency by a factor of "1~000". The latter 40.4 ~z. freguency is subsequently utilized by the forward-reverse speed control loglc as timing pulses to enable the stepping motor to come to a stop and reverse direction, in going from a fill stroke to a pwmp stroke or from a pump stroke to a fill stroke.
e AND gate 104 controls the feeding of clock pulses~ over llne 117~ to the flip-flop 105. Essentially, the gate 104 gates the RM pulse output from the rate multiplier 102 to the flip~flop 105~ in synchronism with the clock 100. The same RM pulse train ls also provlded~ over line 118~ as one input to the AND gate 106 which controls -. .
the counting input to the counter 107, over line 119. The other ; ~ inputs to the AND gate 106 are the CLK signal, over line 101, and the Q state of the flip-flop 105 over line 121.

The flip_flop 105, as well as all of the other flip-flops ', ',,: .ri _~
": ~ '' ' '~ ~ '~" ' , shawn in the system of FIGS. 6a_6c are all conventional D_type flip-flops wh$ch essentially produce at the Q output of the flip-flop, after the clock pulse, the signal present at the D lnput of the flip-flop at the time the clock pulse occurred. Hence~ the D_type flip-flop introduces a delay of one clock period between the input and the output of the flip-flop. -The AND gate 108, as previously indicated~ is an AIID gate thet decodes out the "101" state of the counter 107 for purposes of 8enerating the compensated pump frequency. The output of the gate 108, on line 109, is slso directed as one input to 8 NAND gate 125 which forms part of the subsystem for generating reset pulses for the rate multlplier 102, counter 107, flip-flop 105 and a compensation control flip_flop 127. In sddition to receiving the "101" state as input over ; line 109~ the NAND gate 125 also receives the RM signal over line 128 and the CIK signal over line 129~ as additional inputs.
The electrical output of the NAND gate 125 is directed to a differentiator 131 consisting of a capacitor 131a~ a resistor 131b and a diode 131c~ forming a conventional differentiating circuit and ,~ ,, : .
`. providlng the differentiated pulse output on line 132.
.
The differentiated pulse on line 132 is directed over llne 133 as an asynchronous setting input to the compensation control flip_ -flop 127. The fllp_flop 127 controls the flip_flop 105 since the Q
output of the fllp-flop 127 is the controlling condition on the "settlng" lnput of the fllp-flop 105~ over line 134. This, in turn, -controls the actual counting rate~ over line 119~ to the counter 107.
In this regard, when the Q output of the control flip-flop 127 i5 - .~.
"true", the flip_flop 105 is asynchronously forced into its "true"
state which thereby enables the AND gate 106 to pass the full rate multlpller pulse rate (I~M) to.the counter 107. In contrast, when the -Q output of the flip-flop 127 is 'ifalse", the flip-flop 105 behaves as a divide-by-two binary counter~ and only every other RM pulse from the rate multiplier 102 i8 passed over line 121, through gate 106 to the counter 107.

~' ' ' ":' ' ' ' - . . ' ..

; - 10~7'781 Gate 112 controls the clocking lnput over line 136~ to the control ~lip_~lop 127, the gate 112 having as its three inputs, the CLK signal over line 137, the Q state of the control flip-flop 127 ~- over llne 138~ and the 404 Hz. fill frequency over line 111.
A direct$on sensor 140, forming part of the direction control subsystem for the forward-reverse and speed control logic, typically forms par1; of the mechanical valve control sub~ystem for the syrlnge cartridge and typically comprises a light and photocell coDIblnation which generates an electrical output indicative of whether 10 or not the valve control 6ubsystem is conditioned for a pump stroke ., or a fill stroke of the operational cycle.
me direction sensor 140 is schematicslly illustrated as a switch 140a which provides a "O" input when the syringe has reached the "pump" position (about to initiate a pump ~troke) and provides a "1" input when the syringe has reached the "fill" position ~about to lnitiate a fill stroke). In other words, when the syringe cartridge h~Ls completed a pump stroke, and i8 about to begin a fill stroke, the switch 140a closes to the "fill" position and enables the D input of a tlming flip_~lop 141. me flip-flop 141, together with a second 20 timlng ~lip-flop 142~ are used to synchronize the input from the direc-tion sensor 140 with the actual clocking of the overall system. me timing flip-flops 141, 142 are clocked by the 40.4 Hz. frequency output from the rate multiplier 102~ on line 115, which provides clocking inputs to these ~lip-flops over lines 143, 144, respectively.

.
When the pump mechanism reaches the end oP its ~troke in elther direction, the timing flip-flop 141 changes state on the first 40.4 Hertz pulse which occurs on line 143. On the very next 40.4 Hz.
pulse~ the timing flip_~lop 142, which has its D input connected to the Q output of the flip-flop 141, over line 146, folla~s the setting Or the flip-flop 141, thus providlng a pulse period delay of approxi-mately 24.75 millisecond6 during which the pair of flip-flops 141, 142 are not in the same ~tate. The latter time interval iB used to stop the stepplng motor so that it has time to reverse properly, rather than ' 1067'781 calling for reverse rotation of the motor without providing adequate tlme for coming to 8 stop between strokes.
AND gates 148, 149~ 151, 152 and OR gates 154, 155 comprise the gating for the speed control subsystem and receive the CLK signal - over line 101~ the pump frequency signal over 109 and the fill frequency 6$gnsl over llne 113, to selectively provide output motor drive pul6es of appropriate frequency, over line 157~ dependln~ upon whether a rlll stroke or a pump stroke i8 to be performed~ as input to the step-ping motor driver 158 for the syringe pump.
~avlng thus ldentified the ma~or subsystem compone~ts in the pump rate~ flll rate and motor drive pulse generating and control ~ubsystems~ the bssic operation of these subsystem areas, particularly - ~ dl6closed in FIGS. 6a and 6b are next described;
As previously pointed out, the clock 100 feeds hieh frequency clocking pulses over llne 101 to the rate multiplier 102 and the electrical output (RM) of the rate multlplier~ over line 103, is a pulse ~requency proportional to the clock frequency times the rate ~elector switch setting established by the switches 102a. For example, lf the rate selector switches have been set to "100"~ representing a i 20 desired output pumping flow rate of 100 cc. per hour, the RM output frequency would be 100/1000 or l/lOth Or the C~K frequency~ which le 4.04 kilohertz. If the rate selector switches are set to "10"~
representing 10 cc. per hour, the RM frequency would be 10/1000 or l/lOCth of the clock frequency~ which i8 404 Hz. The RM output fre_ quenoy from the rate multiplier 102, over line 103, is the normal frequency for driving the flip-i`lop 105~ assumin~ the Q output of the control flip-flop 127 is "false". In this connection, the flip-flop 105 hss its Q output tied to its D input in a conventional toggle arrangement. m is causes the flip_flop 105 to alternate its Q output - 30 state with esch clock pulse received over line 117~ thus converting ` the fllp_flop 105 into B binary counter with the output frequency on line 121 from the Q output terminal of the flip-flop being half of the lnput pulse frequency to the clocking input of the flip-flop.
8~ :
'~ :

106~78~
The sa~e RM frequency passed by the AND gate 104, over line 117~ to the clocking ~nput of the flip-flop 105 i5 also dlrected over line 118 as one input to the AND gate 106. The other inputs to the gate 106 are the CLK signal over line 101 and the Q state o~ the fllp-flop 105, over line 121. Hence, the gate 106 is enabled only - when the Q output of the flip-flop 105 is "true". Since the fllp-flop 105 is a dlvide-by_two binary counter~ its Q output wlll be "true" only on every other RM pulse. Hence~ the electrical output over llne 119 to the counter 107 ls half of the frequency of the RM lnput pulse traln to the 8ste 106.
m e counter 107 counts up to a state of "101" and the latter countlng state 18 decoded out by the AND gate 108 whlch recelves the "1"~ "4", "32", and "64" states of the counter fllp_flops, over llnes 110~ as gate lnputs. When the gate 108 goes "true" on the count of "101"~ the electrlcal output on llne 109~ together wlth the very next RM pulse over llne 128, enables the NAND gate 125 to pass the next CLK pulse whlch overlaps wlth the RM pulse. In thls regQrd~
the electrlcal output of the NAND gate 125 i8 normslly posltive ana goes negative when enabled~ for the period of a single clock pulse.
The electrlcal output pulse from the enabled gate 125 ls dlfferentlated by the dlfferentiator 131 and provides a reset pulse output over . ~ line 132.
, .
The re~et output from the differentiator 131 18 fed to the reset inputs of the hlgh order decades of the rate multipller 102, over llnes 162~ 163~ ls dlrected over line 133 to the "set" input of :~ the compen6atlon control fllp_flop 127 and 16 also fed over llne 164 to the "reset" input of the counter 107.
The resson for resetting the BCD rate multipller 102 at the ~` "101" state of the counter 107 is that the rate multlplier in the system of FIG. 6a is also being used to generate the fill frequency over llne 111. Since the "101" counter state of the counter 107 is not necessarily 6ynchronous with the count in the rate multlplier 102, the hi~h order decades 102b and 102c o~ the rate multiplier (u~ed to .- ;:

generate the fill freguency? must be reset to "zero" ~t the beginnlng ~;-of each pump stroke motor drive pulse period. This is necessary ~;
dnce the fill frequency output of the rQte multipller 102 ls belng used, through the AND gate 112~ to reset the compensatlon control i'lip_Slop 127~ and the tlme perlod between setting and resetting Or the ~atter fllp-flop must be exactly equal to a single fill stroke motor drlve pulse perlod~ l.e.~ 1/404 seconds. If the high order -. ~ . .
decsde8 102b and 102c of the rate multlplier 102 were ~ot reset at the "101" state of the counter 107~ the time perlod between setting ~0 ~d resettlng of the control flip-flop 127 would u6ually be shorter than the aesired illl irequency pulse perlod d would introduce error6 lnto the frequency compensatlon technls:le.
Tne "reset" pulse over line 164 forces the counter 107 to its "zero" state~ and ælmultaneously forces the control fllp-~lop 127~ through its "set" input o~rer line 133~ to the "true" state.
Wlth the ilip_rlOp 127 ncw set so that its Q output is "true"~ the ~l~ride_by_two flip-flop 105 ls also forced into the "true" state through its "set" input over line 134. The fllp_flop 105 i5 thus "~et" asynchronously and is therefore independent oi lts clocked lnput 20 over line 117.
llence, as long aæ the Q output of the control flip-rlop 127 remsin~ "true"~ the Q output of the flip_flop 105 also stays "true"
a~l enables the AND gate 106~ over llne 121~ continuously a~ long as these condltions subsist. mis results ln all of the RM pulses from the rate multlpller 10~! belng fed through the enabled gate 106~ over ; line 119, to the counter 107. Thuæ~ durlng the entire time perlod thst the flip-ilop 127 (and hence the fllp-rlop 105) remalns "true"~
the countlng lnput over line 119 to the counter 107 18 at tw~ce the ~; pulse frequency that would otherrise occur. The c~unter 10~ i3 thu~
30 counted up during this period st twice the normal rate~ l.e.~ st the ~11 RM pulse rate.
Counting at the rull RM pulæe rate contlnues~ untll the rate multiplier output over line 111 complete~ a single 404 ~Iz. pulse , 3~S
.
, . ' ' . . ,:

~ 1067781 period (2.475 milllseconds), thus provldlng a "true" output on line ~ 111 as one input to the AND gate 112~ the other lnputs to the gate ;~ 112 being the CLK slgnal on line 137 snd the "true" Q output of the ~.
lip rlop 127. Hence, since all Or lts lnpute are "true", the cloc~
pulse pa~ses through the AND gate 112 to the clocklne lnput o~ the control flip_rlop 127 and resets the nlp nOp 127 8c that lts Q
output goes "ralse". The reason this change o~ state occurs 18 that ~ ,.
- the ~ output Or the rllp-flop 127 18 tled to the ~ lnput Or the rlip~

rlop, as in the case of the flip_rlop 105, thue eetabllshlng the ~lip flop 127 as a toggle or blnary counter which alternate~ state~

each time lts clcckiDg input 18 pulsed.

;: It wlll be apparent that when the compensation control .. rllp ~lop 127 goes "ralse", the "set" input Or the rlip-~lop 105 18 : also "ralse", 80 that the nip-rl~p 105 resumes operati~n ~8 ~ b~D~ry . coucter~ whereby the RM pulse trsln output rr~m the rate multlpller 1oe IB agaln divided by two before belng passet tbrough the g~te 106 ;~ to the counter 107. In thls way~ the rlrst portlon Or the countlng . .
; cycle aeflning each pump stroke tor drlve pulse ~erloa 18 counted :. u~ ror a tl~e lnterval egual to one rlll str~ke mot~r drlv~ pulse ~;
~erloa, at twlce the normal counting rate which prevall~ over the balsnce Or the pump stroke motor drl~e pulse countlng cycle. Hence, `:~ co~ensatlon 18 accompllshed, as ln the slmpllrled system ~f FIG. 3, ao~ a8 l~ trated graphlcally in FIGS. 4 and 5 previously dl~cw ~ea.

. ~ FlCS. 7a through 7g are tlmlng waverorms ~hlch further om~llry the runctlons and operatlon Or the rrequency determln~tlon nnd . .
.~ compensatlon subsystems descrlbed ln connectlon with FIG. 6s. FIG. 7a illustrates the CLK output rrom the clock lO0 whlch 18 a regularly . ~ .
occurrlng clock pulse traln, the numbers above the clock pulses repre~
~entlng the countlne stste of the rate multlpller loe (hlgh order .
decades).
It has been as~umed, for purposes Or lllustratlon, that the rate selector swltches lOQa have been set to Q flow rate of 300 cc. ::
per hour, whlch mean~ th~t the nctual countlng frequency out o~ the -~3? ,.
'a~O ., rate multlplier 102 is 0.3 times the clock frequency (CLK). Hence~ it !~
wlll be apparent in FIG. 7b thst the RM pulse output from the rste multipller shows three RM pulses for esch ten CLK pulses. However~
since the number "10" 18 not exsctly divislble by the number "3"~
the RM output pulse traln is not evenly distributed in the grou~s o~
ten CIK pul~es. Rsther, the RM pulses come in non-uniform bunches~
snd for the particulsr way illustrsted for decodlng the rste multi_ .:
~llers~ FIG. 7b shows RM output pul6e6 on the "2"~ "4" and ~r~ countc, of the rate multlplier.
FIG. 7c shows the "Q" output of the blnsry counter fllp_flop 105 which constltutes the divide_by_two network. It wlll be apparent from the leSt balS of tbe wareSorm tbst tbe Slip Slop 105 i8 dividing the pulse train ~reguency RM of the rate multiplier loe in halS~ by produclng a single output pulse waveSorm ior every two RM pulses.
FIG. 7d illustrstes the countlng pulses dlrected as lnput :,, ~
i to the counter 107 snd Surtber illustrates the output countlng state , . . .
i; Or the counter 107. The left hslf oS the waveSorm shows the upper , countlng states "g8" through the overflow count oS "101" leadlng up ,, :
to tbe "reset" condltlon where the next RM pulse resets the counter ~;~ 20 107 to lt~ "zero" state. The rlght half oS the waveform shows how~
aiter the counter 107 has been "reset"~ the counter 18 then counted ; up at twlce the rate.
FIG. 7e 1~ a waveform of the electrical output ot the NAND
gste 125 and illustrates the nature of the NAND 8ate output when the gate 18 enabled by the coincidence of the "101" count from the counter !.,~ 107 (through D gste lOô) wlth the RM output from the rate multlplier loe and the CLK output Srom the clock 100. In thls regard~ the rmally positive output of the NANJ 8ate 125 goes negative. me RM
output pulse whlch counts the counter 107 to the "101" state does not generste an output pulse Srom the NAND gate 125. Instead~ the next ~M pulse, whlch does not pass as countlng lnput to the counter 107 slnce the Q output oS the flip_flop 105 is then "false", gates the next clock pulse through the NAND 8ate 125 (rate multiplier countlng .. ..

10~7781 8tate "4") to create a neg~tive pu~se out of the NAND gat~ with a perlod equal in duration to the posltive clock puIse.
FIG. 7f illustrates the electrical output of the differentla_ tor 131 and show3 a "reset" pulse in the form of a positi~e spike~
shorter than the normal CLK period, generated by the po6itive going output (trailing edge of the negati~e pulse) of the NAND gate 125 (FIG. 7e). As can be seen from the timing wa~eforms~ the "reset"
pul6e from the dlfferentiator 131 appears at the t~me that the clock goes ~rom it8 "true" state to its "false" state, or from a positive to a negative transitlon, assuming positive loglc.
FIG. 7g illustrates the Q output of the compensation control fllp-flop 127 whlch enables counting up of the counter 107 at double the count rate (i.e., at the full RM output rate) for the period of 100 clock pulse6~ the latter being the period of a single motor drive pulse at the fill frequency of 404 Hz.
Considering now the transition period for the "lOl't count 8tate of the counter 107, assume that the counter input ha~ Just placed the counter in the "101" state. As a result~ the gate 108 has been enabled and the binary flip-flop 105 has also been "reset". It will be observed that the counting input to the counter 107 is generated by coincidence of the "true" state of the flip-flop 105 and the occurrence of an RM rate multiplier pulse. merefore, the same pulse that advances the counter 107 to its "101" state also always resets .~ ., the flip_flop 105. The very next rate multiplier pulse will now enable the NAND gate 125, but, as previously indicated~ does not count up the counter 107 because of the "false" Q output from the flip-flop 105 which had been reset. At the end of the clock period, the "reset"
. output appears from the differentiator 131 to force the flip_flop 127 into its "true" state (FIG. 7g) while simultaneously resetting the rate multiplier to its "zero" state (FIG. 7a). From thls point on~
the flip-flop 127 will remain "true"~ which results in the flip_flop 105 belng forced into the "true" state through its asynchroDous "set"
lnput. Thls~ ln turn, results in enablement of all the RM pulses into - . . . . . .

.

106'7781 the counter 107. All of the changes in counting state o~ the counter - 107 occur at the same times tbat the RM pulses sppear, with a one_to_one pulse correlation 80 that the RM pulse frequency i~ no longer divided by two prior to counting up the counter 107.
After 100 clock pulses, or a period equal to 2.475 milli-seconds, st the "9" state of the rate multiplier, the fill ~requency slgnal enableæ gate 112 at the clock transition from "true" to "false" ~-and resets the fllp-flop 127. The flip-flop 105~ however~ stays "true"
- for one more RM pulse. This latter RM pulse will stlll be passed as a counting pulse to the counter 107, but the flip-flop 105 will be "re3et" at the same time and, from that point on, alternate RM pulses ~ill be suppre~sed by the divide-by-two flip-flop 105.
The reason should naw also be apparent for resetting the hlgh order decades of the rate multiplier 102. Since the decoding provide~ the divide_by_ten output at the count of "~"~ the rate multipliers could start out at any number other than zero~ Just by chance~ lf the rate multipliers were not "reset" at the beglnning of each counting cycle of the counter 107. Such a random state Or the ; rate multiplier would shorten the period of time durlng which counting is accompllshed at double counting rates for compensation purposes.
. . .
Thl8. time for doubling the counting frequency could vary randomly from zero to 2.475 milli6econds, whereas correct compensation calls ~ ~ .
for double counting rate of the counter 107 for exactly 2.475 milli-seconds during the generation of each pump stroke tor drive pulse.
Referring now more particularly to FIG. 6b~ forward-reverse epeed control~ i.e.~ the selection of fill frequency or pump frequency ~or the motor drlve pulses over line 157 to the stepping motor ~ . .
driver 158J is next described.
Directional control, as previously indicated, is accomplished :- 30 wlth the aid of the tlming flip-flops 1~1~ 142 under the control of the dlrection sensor 140. When the switch 140a is closed, indicatlng that the ~alve control system is at the end of the pump stroke and prepared to lnitiate a flll stroke~ a non_synchronOus enabling slgnal ls ~- .

. .

dlrected over line 170 to the D input of the flip-flop 141. q~he clocklng lnput of the flip-flop 141 receives the 40.4 Rz. slgnal from the rate multlplier 10~ over line 143~ and will set the flip-flop 141 "true" on the very next 40.4 Hz. clock pulse.
q~he "true" state of the illp-flop 141 is directed over llne 146 to the D input of the flip-flop 142 and~ a slngle 40.4 Hz.
pulse period later~ l.e.~ 24.75 milliæeconds later~ the flip-flop 142 will also be set "true" on the very next 40.4 Hz. pulse, dlrected over llne 144 to the clocklng lnput of the illp-flop 142. Hence~ the ilip_flop 142 always folla~s the fllp-flop 141 by a perlod of approxi-matel~r 25 milliseconds~ thus provlding sufficient time for the stepping tor driver 158 to come to a complete ~top aiter each stroke and reverse direction for the next stroke.
It wlll be apparent~ therefore~ that wlth the Q outputs Or both rllp-flops 141, 142 "true", the system 18 about to perform a .
flll stroke to iill the syringe cartrldge from a suitable llquld source~ whereas when the ~ outputs of both rllp_rlops are "true", the system 1B about to perform a pump stroke. When the rlip_ilops ;~
141~ 142 are not set to the same state~ the system is in the minlmum 20 25-mllllsecond translent period between strokes, alla.ilng the motor to come to a stop and reverse.
It wlll also be apparent that~ while the minimum period for swltchlng both of the flip_flops 141~ 142 irom one state to another is approximately 25 milliseconds~ the period can be as long as twice that period. ~he latter condltion would occur lf the asynchronous signal over line 170 rrom the direction sensor 140 occurs immediately arter a 40.4 Hz. clocking input on line 143 hae ~ust occurred~ thus regulring an addltlonal 40.4 Hz. clock perlod (25 milliseconds) beiore the rirst tlming nip flop 141 changes state. In contrast, 30 li the signal over line 170 occurs immedi~tely before such a clocXing pulse on line 143, the perlod for motor reversal will be at the minimum time Or 25 milli6econds~ since the tlmlng fllp flop 141 wlll change state almost lmmediately.

,' ~3~ ' ~ 3~
i , .
- , .. . . . . . . .

: ` :
106778~ ~
The AND gate 148 receive6 as inputs, over lines 172, 173, the Q outputs of both of the flip_flops 141, 142, respectlvely. The output of the AND gate 142, over line 175~ will be "true" only when ; both of its inputs from the tlming flip_flops 141~ 142 are "true".
However, since the Q states of both flip-flops 141, 142 belng "true"
defines the "fill" state for the system, a "true" output from the gate 148 over line 175 indicates performance of a Sill stroke. The latter output over line 175 passes through the 0~ gate 154 as enabling i~put over line 176 to the AND gate 151, the other input to the gate 151 being the 404 ~z. fill frequency over llne 113. The fill ~requency 18 thus passed by the enabled gate 151~ over line 178~ through the OR gate 155~ and over line 179 as input to the motor drive pulse ANDf gate 152~ the other input to the gate 152 being the CIK pulse over line 101 for synchronlzatlon purposes. Rence~ durlng the flll stroke ;~ Or the syrlnge pump~ motor drive pulses to the stepping motor drlver 158 are provided on line 157 at the output of the gate 152, at the designated fill frequency Or 404 Hz.
When the syringe is completely filled, the valve control ubsyf3tem controlling the direction sensor 140 causes the swltch 140a to open to the "pump" position and thereby provides a "false'l input to the D termlnal of the flip-flop 141. Tbe next 40.4 Hz. clock ~'~ pul~fe~ over line 143, resets the flip-flop 141 "false" whlch immediately dlsables AND gate 148 and, consequently, also disables the fill f frequency AND gate 151 (througb the OR gate l54), 80 that no further otor drive pulses are generated at the fill frequency. Indeed~ as wlll become apparent, in the tlme interval durlng whlch the tlming rllp_flops 141, 142 are in different 6tates from each other~ no motor ... .
drlve pulses at all are provlded to the stepplng motor driver 158, thus allowlng the motor to stop between strokes prior to rever~ing ` 30 direction.
; ,J Another 24.75 milliseconds later, the timing flip_flop 142 ~ -follows the setting of tbe flip-flop 141 and goes "false", thus establifsfhing the "pufmp" 6tate where Ohe ~ outputs of both flip-f'ops . -~.s .
, 141~ 142 are "true". The Q outputs of the timing fllp-flops 141, 142 are both directed as enabling inputs over lines 181, 182, re~pectively, to the pump frequency AND gate 149 which receives a8 a third input - over line 109 the pump frequency output from the counter decoding gate 108 (FIG. 6a). A fourth lnput to the pump frequency 8ate 149, over line 183~ is normally "true", except when the system is being ; inltlally started and no syringe cartridge has yet been installed.
Assuming, for the moment, that the syringe cartridge i8 already lnstalled, all inputs to the pump frequency gate 149 are "true", thus passing the pu~p frequency over llne 1*, through OR gate 155~ over line 179~ through AND gate 152 in synchronism with the CLK
i frequency~ to provide frequency compensated motor drive pulses on ... . .
line 157 at the selected pump flow rate in accordance with the setting the rate selector swltches 102a (FIG. 6a).
, Agsln~ when the pump stroke has oeen completed~ th~ tlmlng fllp_flop 141 will sgain change state~ the motor will come to a stop urlng the transltlon period when the flip_flops 141, 142 are in dlfferent states (wlth all motor drlve pulses belng gated off) snd~
.
when the rlip_flops 141~ 142 assume the same state after the transltlon ; 20 perlod~ motor drlve pulses of the approprlate frequency wlll agaln be lrected over llne 157 to the stepping motor drlver 158.
me particular dlrectlon ln which the stepping motor driver 158 rotates is determlned by conventional forwsrd-reverse control loBic well known in the art for such stepplng motors, and the control slgnal for such conventional circuitry is directed to the motor driver 158~ over line 187, from the ~ output of the timing fllp_flop 142.
Typlcally~ such stepping motors lnvolve a two-phase drive system with ; two separate wlndings. The current is alternately inverted ln one of .. .
these wlndlng~ at a tlme. merefore, to make one step of the motor, the current 18 lnverted ln one of the wlndlngs, whlle the next step 18 accompllshed by invertlng the current ln the other of the palr of wlndlngs. The forward or reverse rotatlon of the motor ls dependent ., :
merely on the relatlve phase of the two windin6s.

.

' ,~ , ~ " , . ,. , ! . . . .
"~ ' 1067~8~ :
me alarm snd ~t~rt_up subsystems for the syringe pump will now be more specifically descrlbed~ reference being made partlcu-larly to FIG. 6c for the ensuing description.
The slarms subsystem contslns 8 drop detector 190 whlch le easentlally a comblned llght beam and photocell detector, as previouely aescrlbea ln connectlon wlth the drop detector 20 in the baslc system o~ FIG. 1.
A drop rate dlscrlmlnator 191 generates an output slgnsl lf ~ the ~ropa eensed by the drop detector 190 are recelved at below a ,, . .: .
presorlbea minlmum rate. Since the syringe cartridge 18 filled durlng the flll stroke at 8 pre_e6tablished, fixed flow rate o~ 5 cubic ¢entimetere in spproximately 9 secona~, the minlmum rate at which drops ~hou1d appear ln the drlp chsmber of the I.V. set 1~ readlly ascertaln_ . ! . , `~ ~ble. I~ the arop rste ia below the prescrlbea minimum, the drop rate ~ crlminBtor 191 generates an output signal which 18 ueed to place I/~ 1: . .
the eyetem lnto al3rn. me drop rate diecrlminator 191 include~ e conventlonal dlode pump rate meter circult well kncwn ln the art~ the r~te meter feedlng an appropriate gate havlng a threshola representing the mlnimum drop flcw rate and thereby providing the aesirea discrimlna~
tlou functlon.
An AND g~te 193 is the alarm gate for leak detectlon during pwmp etroke, i.e.~ the detection of drop flow in the drip chamber ;1 when a pump stroke ie being performed, while a NoR gate 194 is the , ;, ..... .
lsrm Bate for leak detectlon or detection Or an exhaustea llqula eource during the flll stroke. A delay 195, typlcally a conventlo~al ! ~ resistance_cspscit~nce delay circuit, introduces a delay of approximate-ly two seconde in the response of the 1eak detection gates 193, 194 at the beginning of a pump stroke in the csse of the g~te 193 and at the beginning of a flll stroke in the case of the gate 194.
The reason ~or the introduction of the delay 195 is that~
when the ~yringe is Just beginning to be filled, there is ususlly no Actual drop flow ln the drip chamber slnce it tBke8 B short period of time for the pressure to build up when the fill stroke begins.
:, , , ,,~
` ~ ~ ` 3~
i `: ~

. .

Therefore, a sbort delay is needed during this lnitial "no drop"
period to avoid going into an lmmediate false alarm condition~ me ssme delay i8 alBo u6ed after the flll gtroke has been completed since when the motor stop6~ drops may still ~&11 through the drip chamber of the I.V. set ~or a very brlef interval. These drops~ lr detected at the beglnnlng o~ the pump stroke, would otherwise indicate a leak ln the system and~ ewise~ would produce an lmmediate ~alse slsrm condition.
An air detector 197~ typically comprising a light emltting ;i lO dloae and photocell detector comblnatlon, disposed on opposite sides Or the I.V. tube or syrlnge cartridge nlpple~ detects any air bubbles pssslr~ tbrough the line whlch lnterrupt a reference llght be~m snd geDerate sn output pulse for placing the system lnto slarm.
, . :
; A "power on and reset" subsystem 198~ whlch 18 essentially ; ~ delayed signal produced whenever the main power switch 1B turned on~
provides a "true" signal for a prescribed perlod of time until all the pcwer supplies hava reached thelr normal operatlng voltages and all Or the required delay~ have occurred for the oversll system clectronlcs to initialize to lts normal operatlng state.
Ihe subsystem 198 i8 used to force the system inltially lnto an alsrm condltion when the power 1B flrst turned "on" and 16 also , ~ .
used to sense the conditlon when the power 1B "on" but no syrlnge cartrldge has yet been installed ln the pumplng &ppar&tus. In thls reg~rd~ a syringe detector l99, whlch may also be a llght beam and photocell sensing arrangement to detect the physical presence of a ~yrl~ge cartridge~ is utillzed. me detector 199 provldes an output .
; slgnal whlch ls inverted by an inverter 201 and~ ln conJunction wlth ~ .. ~ .
other gatln~, forces the system to generate a control slgnal~ when the pcwer i8 first turned "on" and no syringe cartrldge has been detected. m is control signal (GTS) causes the syringe plston actuator (represented by the drlve subsystem 12 in FIG. l) to be driven all the uay to the end of the pump stroke in preparatlon for subsequent --initiation of a fill stroke after & syringe has been properly installed ., ~ .
. ~ ,. , ,- , . ................................................ .
, . .

and detected. 106'7781 ~
Thls is another feature of the inventlon, in that lt has been determined that a syringe should be completely empty and mounted into the pumplng apparatus wlth the syringe piston all the way ln (tawards the inlet and outlet ports in EIG. l) as the prescribed format for lnsertion of the syringe into the apparatus for lnitial start_up, i.e.~ lt has been determlned that system operation should beein with a flll stroke. ~Ience, the system ls designed to force the pumplng appsrstus into the condltion where the syrlnge cartrldge can be easlly 10 inserted prlor to sctual operatlonal start_up.
The detectlon of a stslled stepplng motor also forces an slsrm condition upon the 6ystem. The stalled motor alarm comprlses ~ rotation sensor 203 directing an appropriate motor rotatlon slgnal to a counter 204 through an OR gate 205. me counter 204 counts motor , . . .
drive pulses and 18 "reset" by the motor rotation slgnal. Such motor stalllng has a greater probablllty oî occurring when the pump is used ~rith a downstream filter which may clog and lnduce hlgh bac~ pressure on the pumplng system. ~ ~
The rotatlon sensor 203 ls typlcally a dlsc mounted on the ; `
20 stepplng motor output shaft for rotation therewlthJ the disc having . . .
alternate transparent snd opaque sectors. A photocell detects llght from a reference light source passln~s through the disc~ as it rotates~
. .
and generates the "reset" pulses to the counter 204. If the counter reaches a predetermined number of motor drive pulses without belng "reset"~ the system læ put into alarm.
An OR gste 207, which ls the master alsrm gate, collects all of the ~rarious alarm llnes from the alarm monitorlng subsystems pre_ ~riously described. The output of the alarm gate 207 i6 dlrected to a psir of cross-coupled NOR gstes 209, 210 definlng a latchlng circult 30 which latche~ either in the alarm state or 1D the normal system opera-tion state. A "true" output from the OR gate 207 to the input of the NOR gate 210 wlll normally force the system lnto the alarm state.
A "6tart" switch 212 selectively grounds the input of the . j ~
~5 106778~ ~
; NCR gate 210 and forces the system lnto the normal operational state ; lf all of the alarm conditions have been removed 80 thQt the output o~ the OR Bate 207 is "~alse"~ thus enabllng the system to start.
Another pair o~ cross-coupled NOR gate~ 214~ 215 define a "start_up" latch ror the system whlch~ in con~unction with the power_on reoet subsystem 198 and syringe detector 199~ operate to provide an ~
- output "go to start" (GTS) signal which causes the system to operate ~-the otepping motor driver at the high fill frequency rate and rapidly . ;. ~ ~ :
move the syringe piston actuator to the position for readily receiving a syringe cartridge and initiatinB a fill stroke. In this regsrd~ an -;~ A~D gste 216 is u~ed to sense the condition where the syringe actuator haJ ~irst arrived at the latter position~ which occur~ in the transient perlod between the end of a pump stroke and the beBinning of the next ~111 stroke.
A ~econd or back-up "no drop" alarm which normally does not operate~ but assumes control lr the normal "no drop" alarm rsiled to detect a lack Or flow during a fill stroke~ is uoed in the syotem to pre~ent the pumping Or air into a patient which miBht otherwise be caused by a sinele system component failure.
~ 20 The back_up "no drop" al~rm system includes an accumulator-',~A' dlscrlminator 21.8~ an A~D gate 219 and a latch 220. The accumulator-~ diocriminator 218 is again a conventional diode pump clrcuit which .; .
contains a charging capacitor. me latter capacitor gets charged up by output pulses from the drop detector 190. At the eDd Or the fill ;~,~ - , . -.
otroke~ the accumulator charge is sensed and~ i~ it is too low~ the ~ ~ latch 220 i6 acti~ated to shut orf the stepping motor driver 158.

'~ The bQck_up "no drop" alarm system is deactivated in the .~, .
"go to start" mode which occurs when the power is turned "on" and no oyringe cartridge has yet been installed. ~owever, the back_up ~ . , alsrm system~ once activated~ cannot be reset by the st~rt swltch 212 `~
(as in the ca6e ~or other alsrm conditions) since its activstion indlcstes ~ basic system malrunction. The back_up alarm system can be cleared only by turning the instrument power "off".
.: ,.
31~ :
:. .

-An additional back_up alarm system is provided in the form of a high rste alarm which alarms and deactivates the stepplng motor drlver 158 in the event of component failure which induces a runaway ; condltion. This condition is manifested by the pump running ~t maximum .~
pumplng rates, even though a low pumping rate has been selected by the rate selector switches 102a. me hlgh rate alarm subsystem includes a rate comparator 222 which compares the motor drive pulses ln the pump stroke with the current from a high order decade rate selection ~ sensing subsystem 223 (FIG. 6a)~ to selectively energi~e the latch 220 whenever the motor drive pulses being generated exceed the drive pul~e - rate whlch should be generated in accordance wlth the 6elected fluid rlo~ rste.
Bssentially, the rate comparator 222 i8 a diode pump rate tor circult that generate~ a current which is counteracted by the current generated by the welghted resistors in the rate selectlon senslng subsystem 223. Hence~ the rate meter generates a current whlch ; 18 proportlonal to the frequency of the motor drive pulses in the pump stroke. This current 18 compared with the current generated by a serles of weighted re~istors 223a-223d connected to the high order ; 20 rate selector swltches 102a. m us~ when the curre~t sensed by the rate meter exceeds the current generated by the resistors~ the system 18 put . ., '.,''.J into alsrm by activation of the latch 220 which then prevents the step-:i, .
- ping motor driver 158 from runnlng. Agaln~ this alarm can be cleared :
only by turnlng off the electrical power, since activation of the al3rm , .
indicates a bsslc system malfhnction.
Wlth the aforedescribed outline of the basic alarm~ and ''"4 ~tart_up subsystems components and their functional interrelatlonship~
the various operational sequences for these subsystems are further ~- detalled in the following description.
`~ 30 As prevlously indicated~ the NOR Bates 209~ 210 are elec_ trically interconnected as a cross_coupled latch which essentially defines a non-synchronous set-reset alarm flip-flop providin~ an output over line æs deflned as the alarm signal (AIA). The AIA

,~
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: 1067~81 :
signal i6 also directed over line 226 to the stepping motor drlver 158 (FIG. 6b) and thereby provides, by conventional steppine motor cir-cultry~ a shut-of$ control signal for turning off the power to the stepping tor.
me NOR 8ates 214, 215 represent another cross-coupled latch whlch is the "start-up" latch for syrlnge cartridge loading, and the latter latch gets activated when the system power is first turned "on" and a syringe cartridge has not yet been installed. In this regard~ regardless of the positlon of the syringe plston actustor in the drlve system, when the power is first turned "on'i~ it will always be driven to its positlon at the completion of a pump stroke~ 80 that the syringe cartridge can be easily lnserted in preparatlon ~or a fill stroke.

. . .
; Assume~ for purpo6es of explanation~ that a syringe has not yet been lnstalled~ and the syringe piston actuator of the drlve system 18 in ~ome random positlon between lnltiatlon and completlon of any : . .
~troke. When the electrical power 18 initially turned "on"~ the power on reset subsystem 198 provides for a brie~ period~ typically 200 milliseconds~ a "true" output slgnal over line 228 which 18 also dlrected over line 229 as an lnput to the alarm gate 207, consequently providlng a "true" output from the latter gate, over line 230, a~ an iDpUt to the NOR 8ate 210. mis drive~ the output of NOR gate 210~
over llne 231~ "false". The power on reset signal on line 228 is also directed as an lnput to the NQR gate 214, thus driving the output of that gate likewise "false" on line 233.
Slnce a syringe has not yet been installed~ the syrlnge detector l99~provides a "false" output~ over llne 234~ as one input to the NOR gate 215. me gate 215 recelves a ~econd "false" lnput, over , . i line 235~ from the output of the NOR gate 214 prevlously discussed.

The gate 215 receives a thlrd input~ over llne 236~ from the gate 216 ~hlch is normally disabled and therefore provldes a normally "false"

output. Hence~ since all of its lnputs are "false"~ the NOR gate 215 1~ enabled and provides a "true" output on llne 237 which is deflned a8 :.

- 1067~81 the "go to start" (GTS) signal.
The "true" output (GTS) oi the gste 215 18 a1BO directed as an lnput~ over line 238, to the NOR gate 214. me latter input holds the gate 214 disabled to m~intaln a "false" output, over llne 235~ as lnput to the gate 215 (e~ren after the power on reset period has passed)~ and there~ore latches the NOR gate 215 in the "true"
(a!rs) ~tate.
!rne "true" output of the gate 215, or GTS slgnal~ is also directed over lines 240~ 241 as one input to the NOR gate 209~ thus ; 10 holdlng the output oP the gate 209 "fslse". Although the pa~er on reeet subsystem 198, through the alarm gate 207~ had activated one input oP the NOR gate 210 on line 230 and, therePore, resulted in a "ralse" lnput to the gate 209 over llne 231, the "true" GTS signal on llne 241 still holds the output o~ the gate 209 "ralse" and there..
fore prevents the system from golng into alarm and shuttlng ofP the ~tepplng motor driver 158. Moreover~ as soon as the power on reset period has passed~ both oP the inputs to the NOR gate 210 will be "~lse"~ since the "false" output o~ the gate 209 is connected over llne 243 a8 the second input to the gate 210, thus driving the output Or the gate 210 "true" on line 231, to again latch the gate 209 80 that ;~ lts ALA signal output is held "false". This dePines the stable "go to start" or GTS condltion.
The electrical output of the NCOE'~ gate 215, or GTS signal~
lc dlrected over line 240 as sn input to the OR gate 154 (Fla. 6b) ~rhlch enables the AND gate 151, over line 176, to pass the 404 Hz.
flll freguency through gates 151, 155 and 152 and thereby provide flll frequency tor drive pulses over line 157 to the stepping motor drlver 158. Hence~ the gate 151 1s enabled by the GTS ~ignal inde-pendently oP the gate 148 and~ therePore, independently oP the status Or the dlrectlon control timing fllp_Plops 141, 142.
The Pill Prequency drive pulses energlze the stepping motor drlver 158 untll the system senses that the syringe piston actuator has b~en driven to the posltlon whlch lndlcates completion of a pump - ~ .3~

.

8troke and transition to a fill stroke~ the latter condition signaling the end of the "go to start" or GTS state. The GTS signal over line 240 ls also directed through an inverter 242 (FIG. 6b) to disable - -the AND gate 149 and thereby prevent the pump frequency fro~ being spplied slmultaneously with the fill frequency while the system 18 in the GTS state with no syringe cartridge yet lnstalled.
It ls, of course, nece~sary to disable the stepping motor drlver 15~ when~ at the end of the GTS state~ the desired position of the syringe piston actuator hae been reached~ 80 that a syringe car-tridge can be installed. In thls regard, as the piston actuator is . . ~ .
ving towards the desired position calling for initlatlon of a fill stro~e~ the system will be performing a pump stroke, which means that ; the ~ output of the timing flip_flop 142 will be "true".
As soon as the pump stroke has been completed, the direction sensor 140 will be switched to the "fill" position and the timing flip-Plop 141 wlll be set "true" while the flip-flop 142 remains .~ . .
"false" for a period of 24.75 milllseconds. It wlll be apparent that~ when the flip-Plop 142 is "false", its ~ output over line 244 i provides a "true" input over line 245 to the AND.gate 216. In sddltlon~ while the fllp-flop 141 is "true"~ the other input to the AND gste 216~ over line 246, is likewise "true"~ thus enabling the gste 216 and providing a "true" output over llne 236, as one input to the NOR gate 215. This causes the output oP the gate 215 to go ; "fslse"~ thereby terminatlng the GTS signal and the "go to start"
state~ the latter state being latched out by the interaction of the NOR
6ates 215 and 214. In this regard, æince no syrlnge cartridge has yet been installed~ a "Palse" input over line 234 is fed to the NOR gate 215~ but is of no effect ~n view of the "true" input over llne 236 from the gate 216.
The "false" output from the gate 215~ over line 230~ is dlrected as one lnput to the ~OR gate 214, the other input to the gate 214~ over line 228, being al~o "false" slnce the power on re~et perlod has long ~lnce passed durlng the GT~ state. This re~ults in ^ 4~ :
.. ~- .~.
. .
.. .. . ... . ~ ,. ..
.

10~7'781 enablement of the NOR gate 214 and ~ "true" ou~put, over llne 235, a8 input to the NOR gate 215 to latch the gate 215 in its "false"
output state~ thus holding off the GTS signal.
The absence of a syringe cartridge produces a "false" output from the ~yringe detector 199, the output being in~erted by a "true"
slgnal by the inverter 201 and directed over line 250 a6 input to the slarm OR gate 207 which result8 in a "true" output from the gate 207 as input over line 230 to the NOR gate 210, thus driving the output o~ the gate 210 "false". Since the GqS signal is now "false" as ~ust described~ both of the inputs to the NOR gate 209 are now "false"~
; thereby enabling the gate 209 snd providing a "true" output over line 225 which places the system into the alarm state and shuts off the stepping motor driver 158, via the ALA signal over line 226.
The pair of NOR gates 209~ 210 are latched in this alarm condltion and cannot be brought out of this condition until a syringe cartridge hQs been inserted and detected by the syringe detector 199, to drive the input over line 250 to the alarm gate 207 "false". When thls ha8 occurred~ the "start" switch 212 is manually closed and forces the input to the ~OR gate 210~ over line 243, "false". In this regard, the output of the gate 209 is connected to ground by the "start"
switch 212. A current-limiting series resistor 251 is provided, ln view of the high level output from the gate 209. Since all the other alarm li~es providing input to the alarm gate 207 should also be "~alse"~ the other input to the NOR 8ate 210, over line 230~ should also be "false"~ which makes the output of gate 210 go "true"~ thereby - forcing the output of NOR gate 209 "false" and removing the alarm condition.
~ ence, the normal "start_up" sequence of events in operating the overall syringe pump system is summarized a8 foll~ws. Turning on the power with no ~yringe cartridge yet installed results in the "go to start" stQte generating a "true" GTS signQl which cQuses the syringe plston actuator to be driven rapidly at the fill frequency to the position where a fill stroke is about to be initiated, which i8 the :`~ 4l ~ ` .

1067781 ~
proper position for receipt of the syringe cartridge. During the transition period between t~e completion of the pump stroke and lnitlation of the Sill stroke~ the gate 216 disables the GTS signsl and the gate 209 generates the ALA signal which shuts off the stepping motor. A syrlnge cartridge is then inserted and detected. Closlng the - "stsrt" switch 212, after the syringe cartridge has thus been installed, ~ latches out the alarm condition and ensbles normal system operation to -; proceed~ wlth filling of the syringe preparatory to a pump stroke and subsequeDt repetitive operational cycle3 in the normal mode of ~equential fill and pump strokes.
me drop detector 190 provides s "true" output signal over ~; line 253 each time s drop is detected, to provide a pulse input to the AND gate 193. The gate 193 also receives input over line 254 from the ~ output of the timing flip_flop 142~ and thus receives a "true"
enabling lnput whenever the system is in the pump stroke. In additlon~
; the AND gate 193 receives a third input~ over line 255, which is the pump stroke signsl on line 254 delayed by the delay network 195, and , :
whlch typically introduces a delay of approximately two seconds.

Hence~ aSter the delay has passed, the input over line 255 to the Bate 193 wlll be "true" only while s pump stroke is being performed.

~ ThereSore~ if any drops are detected by the drop detector 190 after -~ thls delay period~ the output of the gate 193 will go "true"~ over : llne 257, as an input to the alarm gste 207, putting the NOR gstes 209, 210 lnto the alarm condition. In this regard~ no drops should be detected during the normsl pump stroke. The purpose of the delsy 195, as previously lndicated~ is to svoid going into a fslse alsr~ condi_ ; tion~ ~ince drops may continue Just momentsrily at the beglnning of the pump stroke.
; When the ~ystem is performing a fill stroke, the ~ output -oS the timing flip-flop 142 will be "false"~ disabling gate 193 ~o that the latter gate csnnot possibly place the system into an alsrm condition. However~ the "false" ~ output of the Plip-flop 142 provides an enabling input~ over line 254, to the NOR gate 194 which .~., ,., ;~

~ 4 , . . . ~ .

csn go "true" only when all of its i~pu~s are "~alse". Another input to the NOR gate 194, over line 255, is the delayed Q output sienal from the flip-flop 142, which will go "false" only after ap~roximately two seconds. The third input to the NOR gate 194~ over line 259~ 18 the output of the drop rate discrlminator 191.
.. ..
In the fill stroke, a prescribed minimum drop rate should appear in the drip chamber of the I.V. administration set and be detécted by the drop rate discriminator 191. If the detected drop rate is below the prescribed minimum rate~ the output of the discrim-inator 191 goes "false". me latter condition, ln turn~ provides a third "fslse" input to the NOR gate 194~ thus enabllng tbe gate 194 to provide a "true" output, over line 260~ a8 input to the alarm gste 207 which places the system into an alarm state through the cross-coupled NOR gates 209~ 210. If~ however, the detected drop rate ls above the prescribed minlmum rate~ then the output of the discriminator 191 wlll be "true"~ and the output of the NOR gate 194 wlll be "false"~
thus avoiding the slarm state.
The operatlon of the aforedescribed "no drop" leakage detection subsystems is further described in connection wlth the waveforms of FIGS. 8a_8d.
FIG. 8a indicates the Q output status of the direction control timing flip_flop 142 (FIG. 6b) and indicates that when Q is "true", the system ls ln a pump stroke~ whereas when ~ ls "fal~e"~
the system i8 in a fill ~troke.
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FIG. 8b illustrates the electrical output of the delay 195 over llne 255~ to the AND gate 193 and NOR gate 194. Note that the resistance-capacltance clrcultry of the delay 195 bul~ds up voltage ~hene~er the ~ output of the flip_flop 142 is "true"~ and decays ; through a slmllar delay perlod when the ~ output goe~ "fal~e".
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Referrlng now to FIGS. & and 8d~ the waveforms depict the `-; effects of the comblnatlon of enabling inputs on the AND gate 193 in FIG. &~ and on the NOR gate 194 in FIG. 8d. The combined gate inPut~
are from the ~ output of the timing fllp-flop 142, over line 254~ and ~.
~, . . . . . .
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the delayed Q output signal from the delay lg5J over line 255. In ; FIG. 8c, the combined inputs to the AND gate 193 are enabling when the slgnal is hlgh~ and the inputs are disablin~ when the input is low. In FIG. &~ the combined inputs to the NOR gate 194 are enabling when the slgnal is low and the inputs are disabli~g when the signal 1B
- hlgh.
; In FIG. &~ it will be apparent that the input to the gate - 193 is enabled wlth a del~y from the time that the system switches ~rom the "flll" state to the "pump" state. However, the eate is disabled lmmediately ln switching from the "pump" state to the "fill"
state. Hence~ the gate 193 will not place the system lnto alarm, : : :
;~ even though some drops may be detected durlng the initlal portion of ~ i , .-, , the pump stroke~ 80 long as no drops are detected after the delay perlod has been completed and the gate 193 is enabled to respond to such detected drops.
In contrast~ as observed ln FIG. 8d~ the input circuitry of the NOR gate 194 is enabled during the fill stroke and is dlsabled lmmedlately when the system switches from the fill stroke to the pump ~` stroke. However~ the NOR gate 194 input circuitry is not enabled agaln until after the delay period has passed in switching from the pump state to the fill state. Hence, the gate 194 will not generate a ralse alarm at the beginning of the fill stroke~ even though no drops have yet been detected~ 80 long as the drop rate has bullt up to the prescrlbed minimum level by the time that the delay has passed and the gate 194 is enabled.
The bubble detector alarm includes the air detector 197 whlch~ as previously indicated~ typically comprlses a photocell~and ~i reference light beam comblnation across some portion of the transp~rent I.V. llne or across one nlpple of the syringe cartrldge. If the alr detector senses bubbles~ which are detected by lnterruptlon of the light beam~ a "true" signal 18 produced by the air detector, over line 262~ to the alarm gate 207 whlch places the system into an alarm .. . .
condltion and shut~ off the stepplng motor drlver 158.
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:~ The back_up "no drop" alarm subsystem~ comprising the drop detector 190~ accumulator-discrimlnator 218, AND gate 219 and latch ~- 220 senses if a sufflcient number of drop6 were received durlng the fill ~troke. If a sufficient number of drops were not received, and the primary "no drop" alarm system has not been enabled for æome reason~ as might occur in the case of a faulty system component, the bsck_up system will turn off the system power to the stepp~ng motor driver 158. The back-up "no drop" alarm subsystem is effective only subseguent to the operation of the normal leakage detection subsystem.
In thls regard~ the normal "no drop" alarm system wiil be activated durlng the flll stroke, in the manner previously described, whereas the bsck_up system will be activated only after the fill stroke has been completed.
e accumulator-alscriminator 218 18 also a diode pump clrcult simllar to the clrcuitry used for the drop rate dlscriminator 191~ and the latch 220 18 typlcally an operatlonal ampllfier but could readlly be other circultry such as a set-reset flip-flop or a pair of cross-coupled NOR gates similar to the gates 209, 210. When the latch 220 is actlvated~ it provides an electrical output~ over line 264~ to shut off the stepping motor driver 158.
,I
The electrical output of the accumulator_discriminator 218 over line 265~ 18 normally "true", and i6 directed as one input to ~ the AND gate 219. The gate 219 also receives an input, over line ; 266~ whlch 18 the Q state of the timing flip-flop 142~ and receives ; ~n additional input over line 267 from the ~ output of the timing fllp-flop 141. ~oth of these inputs over lines 266~ 267 will be "true"
at the very end of a flll stroke when the flip_flop 141 has ~ust been eet "false" to lndlcate that Q pump stroke is next to be performed.
An addltional lnput to the gate 219 18 provided,over llne 268~ from the output of the NOR gate 214~ the latter input being ~'true" only when the sy3tem i6 not in the "go to start" state, during which tlme the alarms should be deactivated.

i . :
The Q ~tate of the timing flip_flop 142 is also directed~
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over line 266~ to the accumulator_discriminator 218 so that the discriminator is operative only during the fill stroke. The accumula-tor-dlscriminator 218 recelves an input~ over line 269, from the drop detector 190 and goes "false" when the correct number of drops have been detected. Hénce, when the system switches from the fill stroke to the pump stroke, the gate 219 will stay disabled if enough drops have been detected to provide a "false" output from the accumulator-aiscrlminator 218 over line 265. On the other hand~ if a sufficlent number of drops were not detected by the drop detector 190 during the ~111 stroke~ the output of the accumulator-discriminator 218 over line 265 wlll be "true"~ the AND gate 219 will be enabled during the ~-; transition from the fill stroke to the pump stroke, and an output willbe directed over line 270 to set the latch 220 and shut off the step_ ping tor driver 158.
Reference is now made to the stalled motor alarm~ which ~ lncludes the rotation sensor 203~ the OR gate 205 and the counter;~ 204. The counter 204 is continuously reset over line 272 each time ; a pulse is generated by the rotation sensor 203~ over llne 273, through the OR gate 205. me counter 204 is counted up~ over line 274~ by the stepping motor drive pulse6 from the output of gate 152 '~r' (FIG. 6b). An additional input, over line 275, is fed to the OR
., :
g~te 205 from the output of the NOR gate 209. The purpose of thls addltional input over line 275 is to reset the counter 204 whenever , . . .
there is an alarm state, so that the counter will start out in the . .
"zero" state each time the power is turned "on". Otherwise~ the counter might come on in any random state and the next motor drive pulse .. j could put the system into alarm. In this connection~ unless the ;~ system is in the "go to start" state, the system alarms whenever the power on reset subsystem 198 ls activated~ as previously indicated.
~owever~ when the "start" switch 212 is closed after installation Or ; a syringe~ and the power on reset period has passed, the ALA signal is lstched out.
The high rate alarm subsystem, comprising the rate comparator '. ~,~ ~
'- ' , , , , ~ :' , :-, . . ~

222~ the high rate select~on sensing subsystem 223 (FIG. 6a)~ anAND gate 277 and the l~tch 220~ s next descrlbed.
The rate comparator 222 ls typically a diode pump circuit-which compares the pulse rate received over line 278 w~th the current genersted on line 279 by the weighted resistors 223a~ 223b~ 223c~
223d proportlonal to the settlng of the high order rate selector swltches 102a. The pulse input, over line 278, 18 the output from the AND Bate 277~ which is only enabled by the "true" Q output of the timing flip_flop 142 (FIG. 6b) over line 244~ indicatlng that the 6ystem ls performing a pump stroke. The gate 277 receives as a second lnput~ over llne 274~ the stepplng motor drlve pulse output from the AND gate 152 tFIG. 6b). Hence~ the rate comparator 222 18 opera-tlve only during the pump stroke to compare the sctual motor drive pulses belng generated with the flow rate actually selected by the rate selector swltches 102a.
If the motor drlve pulse rate 18 higher than the rate that has been selected~ as indlcated by the high rate 6election senslng i;~ ., ; suOsystem 223, the comparator 222 will generate a signal~ over line 280~ to set the latch 220 and shut off the motor-drive vla the latch ~ 20 output on line 264. The latter alarm state wlll occur only lf a hlgh - rate of motor drive pulses is generated whlle the rate selector switch settlng calls for a low rate of motor drive pulses. In the event a high flow rate has been called for by the settlng Or the rate selector ~;~ swltches 102a~ the detection of high rate motor drive pulses wlll ` not cause the rate comparator 222 to activate the latch 220. Hence~
.. . . . .
the hlgh rate alarm subsystem prevents an extreme runaway pumplng condition ~hlch might occur~ for example, lf a faulty gate were to apply the flll frequency contlnuously to the stepping motor driver 158 ~'I' and overrlde the actual pump frequency belng generated.
The aforedescrlbed fluid flow control system has been set forth ln sufflclent detall to readlly enable practlce of the teachings of the present lnvention. For purposes of convenlence and f~rther clarlflcation, a more detalled electrical schematic of such a fluid ., . ~ .

. .

106~7781 .
flow control system is attached hereto as Appendix C.
me new and improved ~luid flcw control system of the present inventlon is extremely accurate~ rellable and easy to une. The system provldes enhanced precision in selecting and maintaining flu$d rlow ratec over a wlde range~ and the system is quick to inform medical persoDnel of any conditions which might pose a hazard to the patient.
~ence~ the system o~ the present invention ~inimizes the time-consuming snd error-prone aspects of human monitoring and flow rate adJustment and provides substantial improvement in economy, reliability~ stability snd accuracy over previous automatic control systems~ including peristaltlc pumps, syringe pumps and drop flow controllers.

It will be apparent from the foregolng that~ while particular rormB Or the invention have been illustrated and described, various moalrlcatlons can be made without departing from the splrlt and scope Or the lnventlon. Accordingly> it 18 not intended that the invention be llmited except as by the appended claims.

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Claims (2)

The embodiments of the invention in which an exclusive property or privilege is claimed are defined as follows:

1. Apparatus for use in a syringe pump for delivering fluid at selected flow rates said apparatus comprising: motor means for driving the syringe through a fill stroke in which the syringe is filled with fluid through an input line and through a pump stroke during which fluid is delivered from the syringe through an output line; means for generating motor drive pulses to energize said motor means; and detection means responsive to a high rate of said motor drive pulses in the absence of concurrent high flow rate selected to provide an alarm indication.

2. The apparatus as claimed in Claim 1 and further comprising:
alarm means responsive to said detecting means for de-energizing said driving means.