CA1089914A - Vector magnetic ink jet printer with stabilized jet stream - Google Patents
Vector magnetic ink jet printer with stabilized jet streamInfo
- Publication number
- CA1089914A CA1089914A CA293,407A CA293407A CA1089914A CA 1089914 A CA1089914 A CA 1089914A CA 293407 A CA293407 A CA 293407A CA 1089914 A CA1089914 A CA 1089914A
- Authority
- CA
- Canada
- Prior art keywords
- droplets
- deflector
- unselected
- course
- catcher
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Expired
Links
- 239000013598 vector Substances 0.000 title claims abstract description 12
- 238000007639 printing Methods 0.000 claims description 23
- 239000011554 ferrofluid Substances 0.000 claims description 5
- 238000007641 inkjet printing Methods 0.000 claims description 4
- 230000003993 interaction Effects 0.000 abstract description 3
- 230000000087 stabilizing effect Effects 0.000 abstract description 2
- 238000000034 method Methods 0.000 description 8
- 238000010276 construction Methods 0.000 description 4
- 238000004804 winding Methods 0.000 description 4
- 230000009471 action Effects 0.000 description 3
- 230000008901 benefit Effects 0.000 description 3
- 230000000694 effects Effects 0.000 description 3
- 230000005389 magnetism Effects 0.000 description 3
- 230000002411 adverse Effects 0.000 description 2
- 238000006073 displacement reaction Methods 0.000 description 2
- 230000033001 locomotion Effects 0.000 description 2
- 230000008569 process Effects 0.000 description 2
- 239000002699 waste material Substances 0.000 description 2
- 230000004075 alteration Effects 0.000 description 1
- 230000002301 combined effect Effects 0.000 description 1
- 230000003247 decreasing effect Effects 0.000 description 1
- 230000001419 dependent effect Effects 0.000 description 1
- 230000005284 excitation Effects 0.000 description 1
- 230000005415 magnetization Effects 0.000 description 1
- 238000000926 separation method Methods 0.000 description 1
Classifications
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B41—PRINTING; LINING MACHINES; TYPEWRITERS; STAMPS
- B41J—TYPEWRITERS; SELECTIVE PRINTING MECHANISMS, i.e. MECHANISMS PRINTING OTHERWISE THAN FROM A FORME; CORRECTION OF TYPOGRAPHICAL ERRORS
- B41J2/00—Typewriters or selective printing mechanisms characterised by the printing or marking process for which they are designed
- B41J2/005—Typewriters or selective printing mechanisms characterised by the printing or marking process for which they are designed characterised by bringing liquid or particles selectively into contact with a printing material
- B41J2/01—Ink jet
- B41J2/015—Ink jet characterised by the jet generation process
- B41J2/02—Ink jet characterised by the jet generation process generating a continuous ink jet
- B41J2/035—Ink jet characterised by the jet generation process generating a continuous ink jet by electric or magnetic field
-
- G—PHYSICS
- G01—MEASURING; TESTING
- G01D—MEASURING NOT SPECIALLY ADAPTED FOR A SPECIFIC VARIABLE; ARRANGEMENTS FOR MEASURING TWO OR MORE VARIABLES NOT COVERED IN A SINGLE OTHER SUBCLASS; TARIFF METERING APPARATUS; MEASURING OR TESTING NOT OTHERWISE PROVIDED FOR
- G01D15/00—Component parts of recorders for measuring arrangements not specially adapted for a specific variable
- G01D15/16—Recording elements transferring recording material, e.g. ink, to the recording surface
- G01D15/18—Nozzles emitting recording material
Abstract
VECTOR MAGNETIC INK JET PRINTER WITH STABILIZED JET STREAM
Abstract of the Disclosure A vector magnetic ink jet printer is arranged so that the ink droplets in the initial jet stream are alternately selected (i.e., magnetized) and unselected (unmagnetized). The interposition of unselected droplets between selected droplets prevents undesired magnetic interactions between selected droplets and gives them optimum spacing before they are deposited upon the recording surface, while at the same time keeping all of the droplets in sufficiently close prox-imity to give the stream aerodynamic stability. The gutter or catcher for unselected droplets is located between the second axial deflector (X deflector) and the recording surface. The magnetic field of the second deflector is specially shaped so that it can effectively control the trajectories of all selected droplets that have passed through the field of the first axial deflector (Y deflector), but without affecting the trajectories of unselected droplets aimed at the gutter. The selected and unselected droplets form separate substreams which have sufficient angular divergence in the X direction for enabling the unselected droplets to be guttered without excessively spreading their individual trajectories along that direction, since they are not affected by the X reflecting field, but the divergence is not great enough to disrupt the aerodynamic stabilizing action of each sub-stream upon the other.
Abstract of the Disclosure A vector magnetic ink jet printer is arranged so that the ink droplets in the initial jet stream are alternately selected (i.e., magnetized) and unselected (unmagnetized). The interposition of unselected droplets between selected droplets prevents undesired magnetic interactions between selected droplets and gives them optimum spacing before they are deposited upon the recording surface, while at the same time keeping all of the droplets in sufficiently close prox-imity to give the stream aerodynamic stability. The gutter or catcher for unselected droplets is located between the second axial deflector (X deflector) and the recording surface. The magnetic field of the second deflector is specially shaped so that it can effectively control the trajectories of all selected droplets that have passed through the field of the first axial deflector (Y deflector), but without affecting the trajectories of unselected droplets aimed at the gutter. The selected and unselected droplets form separate substreams which have sufficient angular divergence in the X direction for enabling the unselected droplets to be guttered without excessively spreading their individual trajectories along that direction, since they are not affected by the X reflecting field, but the divergence is not great enough to disrupt the aerodynamic stabilizing action of each sub-stream upon the other.
Description
24 Back~round o the In~ention This invention relates generally to ink jet printers and 26 particularly to ve_~or ~agnetic ink jet printers, othe~ise known 27 as ''V~IJ'I printers.
.. ~
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1 In a V~IIJ prin~er a stream of ferrofluid ink drople~s
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1 In a V~IIJ prin~er a stream of ferrofluid ink drople~s
2 emitted under pressure from a vibratory nozzle is passed through
3 the respective magneeic fiPlds of successively arranged X and Y
4 electromagnetic deflectors which have the combined effect of causing ink droplees to be deposited upon a reçording surface along selected 6 vectors or line seg~ents to form printed characters or graphic plots 7 thereon. Printers of this type are able to form printed characters 8 in cursive fa~hion at higher speed with grea~er accuracy and with 9 lèss waste of ink than other types of ink ~et printers such as those which opera~e on the raster scan principle, whether they use electro-11 magnetic or electrostatic deflection.
12 In a conventional VMIJ printer the X deflector (which deflects 13 the magnetic ink droplets along a horizontal X axis) is positioned 14 ahead of the Y deflector (whlch deflects the droplets along a vertical Y axis). In carrying out the present invention, it has been found 16 preferable to reverse this sequence and have the Y deflector precede 17 the X deflector. This is not a necessary conditlon, however. For 18 convenience, in the present portion of this description, these two 19 deflectors will be referred to simply as l'firstl7 and "second" deflectors without specifying their respective deflection axes, it being understood 21 that such axes are in orthogonal relationship to each other and in 22 substantially parallel relationship wlth the recording surface.
23 In a V~IIJ printer lt is desirable that the ink droplets be 24 produced at a rate such that they will follow one another in sufficiently close succession to provide an aerodynamically stable jet stream. When 26 the ink droplets are emitted at this rate, however, not all of the 27 droplets which issue frox the nozzle can be utilized for printing charac-28 ters, and to separate those droplets which are to be used from those 29 which are not needed in printing, the stream of droplets is first passed through a special type of maghetic deflector called a "selec~or" before ~' :
1 it reaches the first of the two axial deflectors described a~ove. The 2 present arrange~ent is such that when the droplets issue from the 3 nozzle in which they are formed, they are aimed at an excess ink 4 collection device called a "gutter" or "catcher". If a droplet is to be used in printing, it is "selected" by being m~gneti~ed by the 6 selector. An "unselécted" droplet (one not to be used in printing) 7 is not magnetized as it passes through the selector. The selector 8 exerts some deflecting action upon those droplets which it magnetizes, 9 sufficient to divert such droplets from a course aimed at the catcher to one which will enable these droplets to reach the recording surface ll after passing successively through the magnetic deflecting fields of 12 the first and second deflectors that are positioned between the 13 selector and the recording surface. It should be understood, of course, 14 that the selection process can be reversed, so that droplets which are to be guttered are magnetized while the "selected" droplets are not 16 magnetized by the selector and are aimed away from the gutter.
17 In order that the catcher may function effectively to inter-18 cept the unselected droplets, it has ~een customary heretofore in 19 designing VMIJ printers ts place the c~tcher between the first and second deflectors where it catches the unselected droplets before they 21 are subjected to the second deflecting field. Experience gained in ~2 working with prior designs of such deflectors has dictated the necessity 23 of placlng the catcher in this position because if the unselected 24 droplets were permitted to pass through both deflecting fields before being caught ? their respective courses ~ay be so widely divergent by 26 the time they~pass through the second deflecting field that it would 27 be impossi41e to locate~the catcher properly for intercepting all or ~8 the unselected droplets.
2~ Placing the catcher between the first and second deflectors 30 has several disadvantages, however. First, it causes the spacing .
Y0~76-019 -3-9~4 1 between the two de~lecting rields to be greater than it should be for 2 optimum control, so that by the time the stream of selected droplets 3 reaches the second deflector, it is apt ~o have an undesirably 4 large "spread" along the axls of ~he first deflecting field, thereby decreasing the likelihood that the second deflecting ~ield can 6 effectively control all of the droplets that have passed through the 7 first deflector.
8 A second disadvantage of catching the unselected droplets 9 before they can enter the second deflector is that it prevents the employment of an "alternate selection" principle whereby the droplets ll to be used in princing are effectively separated from each other by 12 unselected droplets. For best results it has been found that the 13 droplets which are to be used for printing should not follow one 14 another too closely. If the selected droplets are traveling too closely together, the leading droplet often is overtaken by and merged 16 with the droplet behind it before it reaches the recording surface, 17 with adverse effect upon the printing quality~ ~t has been observed 18 also that undesirable magneeic interactio~s will taka place be~ween l9 selected droplets and~cause erratic movements of these droplets if they are not adequately spaced from each other at every point in 21 their travel. There is a better opportunity to produce printing of 22 high graphic quality if the selected and unselected droplets are 23 alternately arranged as they leave the selector and are caused to 24 travel concurrently m slightly diverging substreams. This produces the desired spacing between selected droplets along their course of 26 travel, and with the two substreams traveling in angular proximity 27 to each other, each contributes a certain amount of aerodynamic 28 stability to the other. This advantage i9 lost, however, if the 29 substream of unselected droplets is abruptly intercepted by the catcher as is. leaves the first deflector so that the substream l of selected droplets passes by itself into the second de1ector. ~here 2 appears to be some need for the two substreams to proceed together 3 on their divergent courses through both deflec~ing fields in order 4 to minimize aerodynamic disturbances and obtain a s~abilized stream S of selected droplets all the way to the recording surface. For some 6 reason not fully known, stream stability is adversely affected if the 7 catcher halts the progress of the unselected substream as it emerges 8 from the first deflecting field, thereby forcing the substream of 9 selected droplets to proceed alone to the second deflector.
Thus, designers of prior V~IJ printers have been confronted 11 with a dilemma. In order to retrieve the unselected droplets effectively, 12 they have considered it necessary to place the catcher between the 13 first and second deflectors; otherwise, the unselected droplets 14 would be so widely scattered by the second deflecting 'ield ln the direction of the second deflection axis that they could not be 16 "guttered" effectively. By doing this, however, designers of such 17 equipment have in several ways substantially reduced the probability 18 of obtaining high quality printing using the VMIJ technique. The l9 innate advantages of the vector magne~ic ink jet technique over other ink jet printing techniques are such that it would be highly desirable 21 to produce a V~IJ printing apparatus wherein the above dPscribed 22 factors which tend to detract from high graphic quality are rendered 23 negligible, thereby enabling users of such printers to realize their 24 full potential for achteving high quality printing with ninimum waste 25 of ink.
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26 Summary of the Invention 27 An object of the present invention is to improve the design 28 of vector magnetic ink jet prineers so that the catcher or gutter 29 can be located between the final deflecting field and the recording Y~976-019 _5_ . .
1 surface rather than between successive deflec~ing fields. Specifically, 2 it is an object to improve the conf~guration of the final deflecting 3 field so that it has little or no effect upon unselec~ed ink droplets L that are passing in its vicinity. An ancillary object is to utilize the alternate selec~ion principle whereby selected droplets initially 6 are interspersed with unselected droplets, and the two sets of 7 droplets are caused to travel in divergent substreams, each of which 8 contributes to the aerodynamic stability of the other substream, so 9 that the selected ink droplets will be guided toward their target points with maximum accuracy and without any undesired ~erging of these 11 droplets in flight.
12 In carrying out the aforesaid objectives, substantial 13 departures have been made from the prior VMIJ printer desig~. The 14 gutter or catcher now is located between the final deflector and lS the recording surface. This enables the two axial deflectors to be 16 located more closely together, thereby reducing the spread of selected 17 droplets along the axis of the first deflector while they are in the 18 field of the second deflector. The final deflector, which in the 19 present embodiment is the X deflector, has a unique construction enabling it to produce an ~ deflecting field that can accurately 21 control che tra~ectosies of selected ink droplets occupying a large 2~ span o~ positions along the Y axis without substantially afrecting the 23 tra~ectorles of unselected droplets passing by this deflector toward the 24 catcher... The X de~lecting field9 instead o being produced by pole pieces ~hose faces are arranged in a conventional wedge ~oniguration on 26 opposite sides of the droplet stream, is now produced by pole pieces 27 having parallel faces located on one side of the stream 90 that the gap 28 between pole pieces and the deflecting field lines produced thereby will 29 extend generally parallel wlth ~he stream of selected droplets rather chan transversely across it. Selected droplets pass through a strong ~'0976-019 -6- ~
1~?~
l inner region of this ~ deflecting field having an adequate spread in the 2 Y direction, whereas unselected droplets (which travel a course angularly 3 displaced in the X direction from the course along which selected 4 droplets travel as they enter the X deflection field) will pass through a weak outer fringe of this field tha~ has little or no effect upon 6 their trajectories. Hence, unselected droplets now may flow through 7 boeh deflecting fields and be caught by a Y-oriented gutter, located 8 adjacent to the recording surface, which does not have to be made unduly 9 large in the X direction since the trajectorles of unselected droplets have no significant angular separation in that direction. Between the X
11 and Y deflectors there is no intervening gutter structure to disturb the 12 trajectories of ink droplets as they pass from the Y field to the ~
13 field. Because of this, it now is possible to use the alternate selection 14 technique whereby the selector magneti~es alternate droplets so that each pair of selected (i.e., magnetized) droplets is separated from each 16 other by at least one intervening unselected (i.e., unmagnati~ed) 17 droplet, thereby greatly increasing the likelihood of producing printed 18 records or documents having high graphic quality for the reasons noted 19 above.
The foregoing and other objects, features and advantages 21 or the invention will be apparent from the following more particular 22 description of a preferred embodiment of the invention, as illustrated 23 in the accompanying drawings.
24 Brief Descrlption of the Drawings FIG. 1 is a schematic perspective view showing the esseneial 26 elements of a vector magnetic ink jet printing apparatus whlch embodies ~7 the invention.
1 FIG. 2 is a top view of the apparatus schematically represented 2 in FIG. l, showing the ~anner in which selected and unselecced droplets 3 are formed into separate substreams.
4 FIG. 3 is a detail side view of the first or Y deflector, indicating its magnetic field distribution.
6 FIG. 4 is a detail plan view of the second or X deflector, 7 indicating its magnetic field distribution.
8 FIGS. 5 and 6 are graphs which respectively represent the 9 deflection-versus-current and deflection-versus-distance characteristics lO of the seoond or X deflector shown in FIG. 4. `~
ll Detailed Description of a Preferred Embodiment 12 The drawings depict the significant features of a vector 13 magnetic ink jet (~IJ) printer embodying the invention. Details of 14 mechanical construction and electrical circuitry that are familiar lS to persons skilled in the art of magnetic ink jet printing have been 16 omitted from these views. The omitted details have been disclosed in 17 prior references such as United States patent NoO 3,805,272, issued 18 on April 16, 1974 to ~eorge J. Fan et al, and United Stateq patent 19 No. 3,971,033, issued on July 20, 1976 to George J. Fan, both of these patents being assigned to the assignee of the present patent applica-~1 eion. The structure shown in the accompanying drawings is deemed 22 adequate or an understanding of the present invention.
23 Referring to FIG. 1, ferrofluid ink o a type described in . .
24 the aforesaid U.S. patent 3,805,272, for example, is fed under pressure thro~gh a feed valve~mechani5m 10 to a nozzle 12, fro~ which the ink 26 issues as a iet stream o~ discrete droplets due to the action of a 27 vibrator comprising a piezoelect~ic transducer 14 mounted upon the 28 valve lO. As shown best in FIG. 2, the nozzle 12 iniSially directs 29 the stream of droplets issuing therefrom toward a gutter or catcher 16 ~0976-019 -8-, ~ , ~3~
1 which is located in front of a recording surface 18 such as a sheet 2 of paper upon which prin~ing i9 to be accomplished. After leaving the 3 nozzle 12, the stream of initially unmagnetized droplets passes through 4 a gap between the pole pieces of an electromagnet 20 called a "selector".
The winding of the selector Z0 is intermittently e~cited by current 6 pulses which are appropriately timed so to produce a magnetic field in 7 the gap of the selector 20 whenever a droplet which is to be selected 8 ~or printing is passing through this gap. Thus, the selected droplet 9 becomes magnetized and is attracted away from its original path 22 aimed at the catcher 16 into a slightly divergent path 24 as indicated 11 in FIGS. 1 and 2. Hence, as each droplet enters the field of the first 12 axial deflector 26, which in this embodiment is the Y deflector, it 13 will be traveling along a path 22 aimed at the catcher 16 if it is a~
14 unselected droplet 26 (that is, one that was not magnetized by the selector 20) or along a path 24 aimed away from the catcher 16 if it 16 is a selected dro~let 28 (one that was magnetized by the selector 20).
17 In order to optimize the aerodynamic stability of the ink 18 jet stream, it has been found desirable to emit ink droplets from the 19 nozzle 12 at a requency that is likely to be too high for best graphic quality if all of these droplets were selected for printing. There are 21 several factors that would tend to detract from graphic quality if 22 every droplet emitted by the nozzle 12 at this high rate were magnetized 23 by the selector 20 and thus directed along a course 24 which would 24 cause them to impinge the recording surface 18. If the magnetized droplets are not adequately spaced from each other when leaving the 26 selector 20, magnetic interactions among them may produce undesired 27 deviatlons in their respective trajectories or variations in spacing 28 among them. There also is a possibility that some of the leading 29 droplets may become merged with droplets that are following too closely behind them as a result of these magnetic aberrations or simply because ' .
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1 of the fact that each droplet progressively loses speed as the distance 2 between it and the nozzle increases, such loss of speed being greater 3 for some droplets than for others.
4 In order to achieve a satisfactory resolution of the conflicting requirements that there be, on the one hand, emission of droplets from the nozzle at a sufficiently high rate to produce a jet stream which is 7 highly stabilized aerodynamically and, on the other hand, adequate 8 spacing of droplets that are destined to impinge the target surface so 9 as to optimize the vector printing operation, an "alternate selec~ion"
technique is herein proposed. Thus, in accordance with this concept, 11 every second droplet passing through the gap pf selector 20 during a 12 vector printing operati~n becomes magnetized by the field of this 13 selector and is attracted into a path 24 that is aimed away from the 14 ink catcher 16. Hence, the spacing between these selected droplets as they leave the selector 20 is-about double the initial spacing 16 between droplets as they enter the selector 20, with an unselected 17 droplet in~ervening between each pair of successively selected droplets.
18 It ls understood, of course, that this selection technique may be 19 modified, if desired, to interpose more than one unselected droplet between each pair of successively selected droplets.
21 The action of the selector effectively creates ewo substreams 22 of droplets, one substream consisting of unselected droplets traveling 23 along the original course 22 toward the catcher 16, and the other 24 substream consisting of selected droplets that have been diverted into a course 24 that has a slight but significant angular displacement from 26 the substream that was first described. These two substreams of 27 selected and unselected droplets continue on their slightly divergent 28 courses through (or in some caaes, past) the respective magnetic fields 29 of a Y deflector 30 and an X deflector 3~, arranged in the sequence .
1 named between the selector 20 and the recording surface 18. No signifi-2 cant loss of aerodynamic stability is caused by this s2para.ion since 3 the two jet strea~s are still in fairly close proximity to each other.
4 The substream of unselected droplets i5 terminated at the catcher 16 just a short distance from the recording surace 18, after these 6 droplets ha~e traversed both the first and second axial deflectors 30 7 and 32. By the time it reaches this point, the substream of selected 8 droplets has been so well stabili~ed ~hat these droplets can traverse 9 the remaining distance to the surface 18 with accuracy.
For veceor printing purposes, a succession of selected ll droplets is subjected to varying amounts of deflection along two 12 orthogonally related axes herein designated Y and X, the Y axis being 13 substantially vertical and ehe X axis substantially horizontal in an 14 assumed environment where the recording surface 18 is in a vertical plane parallel to both oE these axes. The X and Y deflecting fields 16 are "gradient" magnetic fields, ~hat is, fields in which the magnetic 17 intensity at any point is dependent upon not only the electrical 18 current in the winding of the deflector but also the distance of 19 the point from the pole faces of the deflector. The particular construction of each deflector will be described presently. In 21 accordance with the invention, both selected and unselected drople~s 2~ are sub~ected to any deflecting force in the Y (upward) dirertion 23 that may be exerted upon them by the magnetic field of the first 24 de1ector 30, but only the selected droplets will be sub~ected to ~5 any significant deflection in the X (right horizontal) direct$on by 26 the second deflector 32, because the =agnetic field of this second 27 deflector is specially shaped 50 that unselected droplets pass througn 28 only a weak outer Eringe of this field and are substantially unaffected 29 by it.
1 At this point in the description it is thought advisable to 2 restate the definition of a "selected" droplet as one that has been 3 exposed to a magnetic field generated by the selector 20 so that suc'n 4 a droplet is diverted from its origi~al course Z2 to an angularly displaced course 24. All droplets which are not magnetized by the 6 selector 20 and which therefore continue on their original course 22 7 are "unselected". The selection process naturally causes the ferrofluid 8 in the selected droplet to beco~e magnetized. Whether thi~ ini~ial 9 magnetization persists, and for how long, will depend upon the degree of remanence that the ferrofluid possesses. The remanence need not be 11 high. As each selected droplet enters a subsequent deflection field, 12 whe~her such field is produced by the first deflector 30 or the second 13 deflector 32, it is remagnetized by that field at the same time that 14 it is being deflected thereby. It is not accurate to use the terms "selected" and "magnetized" inteschangeably, however, because a droplet 16 once selected remains "selected", irrespective of what may happen to 17 its remanent magnetism while it traverses the distances between 18 successive magnetic fields. Conceivably a selected droplet ~ay be 19 devoid of remanent magnetism when it is outside of any magnatic field.
It should be noted also that an unselected droplet may become at least 21 temporarily magnetized while passing through the Y de1ecting field, 22 and conceivably it may retain ~uch magnetism at least for a time while 23 traveling toward the catcher 16. Thus, selected droplets are not 24 neces9arily magnetized at all points of their travel between the selector 20 and the paper 18, nor are unselected droplets unmagnetized 26 at all points of their travel between the selector 20 and the catcher 16.
27 The distinction resides solely in the choice of divergent courses 22 28 and 24 into which each droplet may be directed by the selector 20.
29 In the present embodiment both the selector 20 and the Y
30 de~lector 30 have pole faces disposed in converging plane~ ~o define .
~'0976-019 -12-;P~
l a wedge-shaped air gap in each instance. As explained in the aforesaid 2 Fan paten~ 3,805,272, this type of pole construction causes a gradient 3 magnetic field to be produced in the air gap between pole ~aces, the 4 configuration of the magnetic field lines being indicated (in the case of the deflector 30) by the curves drawn in FIG. 3. Both the seiected 6 droplets 28 and the unselected droplets 26 enter this gap and are 7 deflected upwardly in directions normal to the field lines therein 8 when the electromagnet is energized. In the case of the deflector 30 9 the amount of deflection varies with the current in the winding. In the case o~ the selector 20, the amount of deflection is the same for 11 all deflected droplets and is zero for unselected droplets. The 12 slanted pole faces are separated by a substan~ial clearance opening 13 even at their closest points (FIG. 3) so that a droplet may be deflected 14 past these points without striking the pole structure.
Upon leaving the first deflector 30, each drople~ will be~
16 traveling at the desired angle upwardly from ~he path which it initially 17 had when it entered the fieId of this defiector. This chosen amount of 18 Y deflection will place each selected droplet at the desired vertical 19 coordinate on the paper 18 when it impinges that surface. It remains, however, to impart the proper amount of horizontal or rightward 21 deflection to each selected droplet so that it also will impinge the 22 surface 18 at the desired horizontal coordinate thereon. This is the 23 function of the X deflector 32. Unselected droplets are not given any 24 significant X deflection and are capt;ured by the gutter 16.
Referring now to FIGS. ~ and 4, selected droplets 28 which 26 have been directed along a course having the horizontal angular position 27 denoted by the line 24 will pas~ through a part of the magnetic deflecting 28 field generated by the X deflector 32 whlch is much stronger than the 29 weak outer frlnge portion of this magnetic field through which unselected droplets 26 traveling along the divergent course 22 will pass. The pole 1 structure of the .~ deflector 32 is so designed that even with maximum 2 exciting current in the coil or winding of deflector 32, there will be 3 no significant deflection of unselect2d droplets 26 in the X direction.
4 The pole faces 34 and 36 are parallel with the path 24 of the selected droplets, and they establish a magnetic field whose lines 6 of force likewise extend generally parallel with this path and are 7 concentrated near the plane in which the pole faces 34 and 36 lie.
8 The excitation current intensity is varied in accordance with the 9 amount of angular deflection which must be given to each selected drople~ 26 in order to accomplish the desired vector printing function.
11 As shown by the graph of deflection-versus-current in FIG. 5, the 12 deflection along the X axis varies linearly with the current. On 13 the other hand, as shown by FIG. 6, the deflection will vary inversely 14 and nonlinearly with the distance between a pole face and a droplet which is passing by it, so that even a strong current will not cause 16 significant deflection of a droplet that has been diverted a relatively 17 short distance away from the pole qtructure 349 36, as in the case 18 of the unselected droplets 26, FIGS. 2 and 4.
19 Inasmuch as the unselected droplets 26 are given no signiflcant deflection in the X direction by the second deflector 32, 21 the catcher 16, FIGS. 1 and 2, may have a relati~ely narrow dimension 22 in the X direction to correspond with the very slight spread of 23 unselected droplet trajectories in that direction. Moreover, since 24 the catcher 16 is located relatively close to the recording surface 18, it does not disrupt the stabilizing aerodynamic interaction between 26 the ~et streams of unselected a~d select~d droplets until each selected 27 droplet has almost reached the end of its travel, by which time i~ no 28 longer needs further stab$1ization t~ find its correct target point.
29 ~he magnetic field produced by the X deflector 32 has a sufficient spread along the Y axis to exert uniform X deflecting forces upon 1 selected drople~s 28 for any given current value regardless of the 2 displacements respec~ively imparted to such droplets along the Y axis 3 by the Y deflector 30.
4 The illustrated apparatus is designed to print one character at a time upon ~he recording surface 18~ and the appropriate relative 6 motions are produced between the surface 18 and the printing apparatus 7 to arrange the printed characters at selected positions in successive 8 lines. If it is desired to print a whole line of characters at a time, 9 the character printing apparatus can be modified to acco~plish this. The first deflector 30 would be oriented so that it deflects the droplets 11 in the X direction, and the second deflec~or 32 would be oriented to 12 deflect selected droplets in the Y direction without imparting any 13 significant Y deflections tO unselected droplets. This would ma~e 14 it feasible ~o use a gutter that extenda parallel with the printed line in a position above or below it, ànd the nozzle which emits the 16 droplets then is aimed at such a gutter. In a line printer the 17 character printers may be arranged in staggered relationship in two 18 rows, one row of printers using a g-~tter positioned abo~e the printed 19 line while the other row uses a gutter below this line.
While the invention has been particularly shown and described 21 with reference to a preferred e~bodi~en* thereof, it will be understood 22 by those 9killed in the art that che foregoing and other changes in 23 orm and details may be made thereln without departing from the spirit 24 an~ ~cope of the invention.
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What is claimed is:
, , .
12 In a conventional VMIJ printer the X deflector (which deflects 13 the magnetic ink droplets along a horizontal X axis) is positioned 14 ahead of the Y deflector (whlch deflects the droplets along a vertical Y axis). In carrying out the present invention, it has been found 16 preferable to reverse this sequence and have the Y deflector precede 17 the X deflector. This is not a necessary conditlon, however. For 18 convenience, in the present portion of this description, these two 19 deflectors will be referred to simply as l'firstl7 and "second" deflectors without specifying their respective deflection axes, it being understood 21 that such axes are in orthogonal relationship to each other and in 22 substantially parallel relationship wlth the recording surface.
23 In a V~IIJ printer lt is desirable that the ink droplets be 24 produced at a rate such that they will follow one another in sufficiently close succession to provide an aerodynamically stable jet stream. When 26 the ink droplets are emitted at this rate, however, not all of the 27 droplets which issue frox the nozzle can be utilized for printing charac-28 ters, and to separate those droplets which are to be used from those 29 which are not needed in printing, the stream of droplets is first passed through a special type of maghetic deflector called a "selec~or" before ~' :
1 it reaches the first of the two axial deflectors described a~ove. The 2 present arrange~ent is such that when the droplets issue from the 3 nozzle in which they are formed, they are aimed at an excess ink 4 collection device called a "gutter" or "catcher". If a droplet is to be used in printing, it is "selected" by being m~gneti~ed by the 6 selector. An "unselécted" droplet (one not to be used in printing) 7 is not magnetized as it passes through the selector. The selector 8 exerts some deflecting action upon those droplets which it magnetizes, 9 sufficient to divert such droplets from a course aimed at the catcher to one which will enable these droplets to reach the recording surface ll after passing successively through the magnetic deflecting fields of 12 the first and second deflectors that are positioned between the 13 selector and the recording surface. It should be understood, of course, 14 that the selection process can be reversed, so that droplets which are to be guttered are magnetized while the "selected" droplets are not 16 magnetized by the selector and are aimed away from the gutter.
17 In order that the catcher may function effectively to inter-18 cept the unselected droplets, it has ~een customary heretofore in 19 designing VMIJ printers ts place the c~tcher between the first and second deflectors where it catches the unselected droplets before they 21 are subjected to the second deflecting field. Experience gained in ~2 working with prior designs of such deflectors has dictated the necessity 23 of placlng the catcher in this position because if the unselected 24 droplets were permitted to pass through both deflecting fields before being caught ? their respective courses ~ay be so widely divergent by 26 the time they~pass through the second deflecting field that it would 27 be impossi41e to locate~the catcher properly for intercepting all or ~8 the unselected droplets.
2~ Placing the catcher between the first and second deflectors 30 has several disadvantages, however. First, it causes the spacing .
Y0~76-019 -3-9~4 1 between the two de~lecting rields to be greater than it should be for 2 optimum control, so that by the time the stream of selected droplets 3 reaches the second deflector, it is apt ~o have an undesirably 4 large "spread" along the axls of ~he first deflecting field, thereby decreasing the likelihood that the second deflecting ~ield can 6 effectively control all of the droplets that have passed through the 7 first deflector.
8 A second disadvantage of catching the unselected droplets 9 before they can enter the second deflector is that it prevents the employment of an "alternate selection" principle whereby the droplets ll to be used in princing are effectively separated from each other by 12 unselected droplets. For best results it has been found that the 13 droplets which are to be used for printing should not follow one 14 another too closely. If the selected droplets are traveling too closely together, the leading droplet often is overtaken by and merged 16 with the droplet behind it before it reaches the recording surface, 17 with adverse effect upon the printing quality~ ~t has been observed 18 also that undesirable magneeic interactio~s will taka place be~ween l9 selected droplets and~cause erratic movements of these droplets if they are not adequately spaced from each other at every point in 21 their travel. There is a better opportunity to produce printing of 22 high graphic quality if the selected and unselected droplets are 23 alternately arranged as they leave the selector and are caused to 24 travel concurrently m slightly diverging substreams. This produces the desired spacing between selected droplets along their course of 26 travel, and with the two substreams traveling in angular proximity 27 to each other, each contributes a certain amount of aerodynamic 28 stability to the other. This advantage i9 lost, however, if the 29 substream of unselected droplets is abruptly intercepted by the catcher as is. leaves the first deflector so that the substream l of selected droplets passes by itself into the second de1ector. ~here 2 appears to be some need for the two substreams to proceed together 3 on their divergent courses through both deflec~ing fields in order 4 to minimize aerodynamic disturbances and obtain a s~abilized stream S of selected droplets all the way to the recording surface. For some 6 reason not fully known, stream stability is adversely affected if the 7 catcher halts the progress of the unselected substream as it emerges 8 from the first deflecting field, thereby forcing the substream of 9 selected droplets to proceed alone to the second deflector.
Thus, designers of prior V~IJ printers have been confronted 11 with a dilemma. In order to retrieve the unselected droplets effectively, 12 they have considered it necessary to place the catcher between the 13 first and second deflectors; otherwise, the unselected droplets 14 would be so widely scattered by the second deflecting 'ield ln the direction of the second deflection axis that they could not be 16 "guttered" effectively. By doing this, however, designers of such 17 equipment have in several ways substantially reduced the probability 18 of obtaining high quality printing using the VMIJ technique. The l9 innate advantages of the vector magne~ic ink jet technique over other ink jet printing techniques are such that it would be highly desirable 21 to produce a V~IJ printing apparatus wherein the above dPscribed 22 factors which tend to detract from high graphic quality are rendered 23 negligible, thereby enabling users of such printers to realize their 24 full potential for achteving high quality printing with ninimum waste 25 of ink.
.:
26 Summary of the Invention 27 An object of the present invention is to improve the design 28 of vector magnetic ink jet prineers so that the catcher or gutter 29 can be located between the final deflecting field and the recording Y~976-019 _5_ . .
1 surface rather than between successive deflec~ing fields. Specifically, 2 it is an object to improve the conf~guration of the final deflecting 3 field so that it has little or no effect upon unselec~ed ink droplets L that are passing in its vicinity. An ancillary object is to utilize the alternate selec~ion principle whereby selected droplets initially 6 are interspersed with unselected droplets, and the two sets of 7 droplets are caused to travel in divergent substreams, each of which 8 contributes to the aerodynamic stability of the other substream, so 9 that the selected ink droplets will be guided toward their target points with maximum accuracy and without any undesired ~erging of these 11 droplets in flight.
12 In carrying out the aforesaid objectives, substantial 13 departures have been made from the prior VMIJ printer desig~. The 14 gutter or catcher now is located between the final deflector and lS the recording surface. This enables the two axial deflectors to be 16 located more closely together, thereby reducing the spread of selected 17 droplets along the axis of the first deflector while they are in the 18 field of the second deflector. The final deflector, which in the 19 present embodiment is the X deflector, has a unique construction enabling it to produce an ~ deflecting field that can accurately 21 control che tra~ectosies of selected ink droplets occupying a large 2~ span o~ positions along the Y axis without substantially afrecting the 23 tra~ectorles of unselected droplets passing by this deflector toward the 24 catcher... The X de~lecting field9 instead o being produced by pole pieces ~hose faces are arranged in a conventional wedge ~oniguration on 26 opposite sides of the droplet stream, is now produced by pole pieces 27 having parallel faces located on one side of the stream 90 that the gap 28 between pole pieces and the deflecting field lines produced thereby will 29 extend generally parallel wlth ~he stream of selected droplets rather chan transversely across it. Selected droplets pass through a strong ~'0976-019 -6- ~
1~?~
l inner region of this ~ deflecting field having an adequate spread in the 2 Y direction, whereas unselected droplets (which travel a course angularly 3 displaced in the X direction from the course along which selected 4 droplets travel as they enter the X deflection field) will pass through a weak outer fringe of this field tha~ has little or no effect upon 6 their trajectories. Hence, unselected droplets now may flow through 7 boeh deflecting fields and be caught by a Y-oriented gutter, located 8 adjacent to the recording surface, which does not have to be made unduly 9 large in the X direction since the trajectorles of unselected droplets have no significant angular separation in that direction. Between the X
11 and Y deflectors there is no intervening gutter structure to disturb the 12 trajectories of ink droplets as they pass from the Y field to the ~
13 field. Because of this, it now is possible to use the alternate selection 14 technique whereby the selector magneti~es alternate droplets so that each pair of selected (i.e., magnetized) droplets is separated from each 16 other by at least one intervening unselected (i.e., unmagnati~ed) 17 droplet, thereby greatly increasing the likelihood of producing printed 18 records or documents having high graphic quality for the reasons noted 19 above.
The foregoing and other objects, features and advantages 21 or the invention will be apparent from the following more particular 22 description of a preferred embodiment of the invention, as illustrated 23 in the accompanying drawings.
24 Brief Descrlption of the Drawings FIG. 1 is a schematic perspective view showing the esseneial 26 elements of a vector magnetic ink jet printing apparatus whlch embodies ~7 the invention.
1 FIG. 2 is a top view of the apparatus schematically represented 2 in FIG. l, showing the ~anner in which selected and unselecced droplets 3 are formed into separate substreams.
4 FIG. 3 is a detail side view of the first or Y deflector, indicating its magnetic field distribution.
6 FIG. 4 is a detail plan view of the second or X deflector, 7 indicating its magnetic field distribution.
8 FIGS. 5 and 6 are graphs which respectively represent the 9 deflection-versus-current and deflection-versus-distance characteristics lO of the seoond or X deflector shown in FIG. 4. `~
ll Detailed Description of a Preferred Embodiment 12 The drawings depict the significant features of a vector 13 magnetic ink jet (~IJ) printer embodying the invention. Details of 14 mechanical construction and electrical circuitry that are familiar lS to persons skilled in the art of magnetic ink jet printing have been 16 omitted from these views. The omitted details have been disclosed in 17 prior references such as United States patent NoO 3,805,272, issued 18 on April 16, 1974 to ~eorge J. Fan et al, and United Stateq patent 19 No. 3,971,033, issued on July 20, 1976 to George J. Fan, both of these patents being assigned to the assignee of the present patent applica-~1 eion. The structure shown in the accompanying drawings is deemed 22 adequate or an understanding of the present invention.
23 Referring to FIG. 1, ferrofluid ink o a type described in . .
24 the aforesaid U.S. patent 3,805,272, for example, is fed under pressure thro~gh a feed valve~mechani5m 10 to a nozzle 12, fro~ which the ink 26 issues as a iet stream o~ discrete droplets due to the action of a 27 vibrator comprising a piezoelect~ic transducer 14 mounted upon the 28 valve lO. As shown best in FIG. 2, the nozzle 12 iniSially directs 29 the stream of droplets issuing therefrom toward a gutter or catcher 16 ~0976-019 -8-, ~ , ~3~
1 which is located in front of a recording surface 18 such as a sheet 2 of paper upon which prin~ing i9 to be accomplished. After leaving the 3 nozzle 12, the stream of initially unmagnetized droplets passes through 4 a gap between the pole pieces of an electromagnet 20 called a "selector".
The winding of the selector Z0 is intermittently e~cited by current 6 pulses which are appropriately timed so to produce a magnetic field in 7 the gap of the selector 20 whenever a droplet which is to be selected 8 ~or printing is passing through this gap. Thus, the selected droplet 9 becomes magnetized and is attracted away from its original path 22 aimed at the catcher 16 into a slightly divergent path 24 as indicated 11 in FIGS. 1 and 2. Hence, as each droplet enters the field of the first 12 axial deflector 26, which in this embodiment is the Y deflector, it 13 will be traveling along a path 22 aimed at the catcher 16 if it is a~
14 unselected droplet 26 (that is, one that was not magnetized by the selector 20) or along a path 24 aimed away from the catcher 16 if it 16 is a selected dro~let 28 (one that was magnetized by the selector 20).
17 In order to optimize the aerodynamic stability of the ink 18 jet stream, it has been found desirable to emit ink droplets from the 19 nozzle 12 at a requency that is likely to be too high for best graphic quality if all of these droplets were selected for printing. There are 21 several factors that would tend to detract from graphic quality if 22 every droplet emitted by the nozzle 12 at this high rate were magnetized 23 by the selector 20 and thus directed along a course 24 which would 24 cause them to impinge the recording surface 18. If the magnetized droplets are not adequately spaced from each other when leaving the 26 selector 20, magnetic interactions among them may produce undesired 27 deviatlons in their respective trajectories or variations in spacing 28 among them. There also is a possibility that some of the leading 29 droplets may become merged with droplets that are following too closely behind them as a result of these magnetic aberrations or simply because ' .
~ 5~
1 of the fact that each droplet progressively loses speed as the distance 2 between it and the nozzle increases, such loss of speed being greater 3 for some droplets than for others.
4 In order to achieve a satisfactory resolution of the conflicting requirements that there be, on the one hand, emission of droplets from the nozzle at a sufficiently high rate to produce a jet stream which is 7 highly stabilized aerodynamically and, on the other hand, adequate 8 spacing of droplets that are destined to impinge the target surface so 9 as to optimize the vector printing operation, an "alternate selec~ion"
technique is herein proposed. Thus, in accordance with this concept, 11 every second droplet passing through the gap pf selector 20 during a 12 vector printing operati~n becomes magnetized by the field of this 13 selector and is attracted into a path 24 that is aimed away from the 14 ink catcher 16. Hence, the spacing between these selected droplets as they leave the selector 20 is-about double the initial spacing 16 between droplets as they enter the selector 20, with an unselected 17 droplet in~ervening between each pair of successively selected droplets.
18 It ls understood, of course, that this selection technique may be 19 modified, if desired, to interpose more than one unselected droplet between each pair of successively selected droplets.
21 The action of the selector effectively creates ewo substreams 22 of droplets, one substream consisting of unselected droplets traveling 23 along the original course 22 toward the catcher 16, and the other 24 substream consisting of selected droplets that have been diverted into a course 24 that has a slight but significant angular displacement from 26 the substream that was first described. These two substreams of 27 selected and unselected droplets continue on their slightly divergent 28 courses through (or in some caaes, past) the respective magnetic fields 29 of a Y deflector 30 and an X deflector 3~, arranged in the sequence .
1 named between the selector 20 and the recording surface 18. No signifi-2 cant loss of aerodynamic stability is caused by this s2para.ion since 3 the two jet strea~s are still in fairly close proximity to each other.
4 The substream of unselected droplets i5 terminated at the catcher 16 just a short distance from the recording surace 18, after these 6 droplets ha~e traversed both the first and second axial deflectors 30 7 and 32. By the time it reaches this point, the substream of selected 8 droplets has been so well stabili~ed ~hat these droplets can traverse 9 the remaining distance to the surface 18 with accuracy.
For veceor printing purposes, a succession of selected ll droplets is subjected to varying amounts of deflection along two 12 orthogonally related axes herein designated Y and X, the Y axis being 13 substantially vertical and ehe X axis substantially horizontal in an 14 assumed environment where the recording surface 18 is in a vertical plane parallel to both oE these axes. The X and Y deflecting fields 16 are "gradient" magnetic fields, ~hat is, fields in which the magnetic 17 intensity at any point is dependent upon not only the electrical 18 current in the winding of the deflector but also the distance of 19 the point from the pole faces of the deflector. The particular construction of each deflector will be described presently. In 21 accordance with the invention, both selected and unselected drople~s 2~ are sub~ected to any deflecting force in the Y (upward) dirertion 23 that may be exerted upon them by the magnetic field of the first 24 de1ector 30, but only the selected droplets will be sub~ected to ~5 any significant deflection in the X (right horizontal) direct$on by 26 the second deflector 32, because the =agnetic field of this second 27 deflector is specially shaped 50 that unselected droplets pass througn 28 only a weak outer Eringe of this field and are substantially unaffected 29 by it.
1 At this point in the description it is thought advisable to 2 restate the definition of a "selected" droplet as one that has been 3 exposed to a magnetic field generated by the selector 20 so that suc'n 4 a droplet is diverted from its origi~al course Z2 to an angularly displaced course 24. All droplets which are not magnetized by the 6 selector 20 and which therefore continue on their original course 22 7 are "unselected". The selection process naturally causes the ferrofluid 8 in the selected droplet to beco~e magnetized. Whether thi~ ini~ial 9 magnetization persists, and for how long, will depend upon the degree of remanence that the ferrofluid possesses. The remanence need not be 11 high. As each selected droplet enters a subsequent deflection field, 12 whe~her such field is produced by the first deflector 30 or the second 13 deflector 32, it is remagnetized by that field at the same time that 14 it is being deflected thereby. It is not accurate to use the terms "selected" and "magnetized" inteschangeably, however, because a droplet 16 once selected remains "selected", irrespective of what may happen to 17 its remanent magnetism while it traverses the distances between 18 successive magnetic fields. Conceivably a selected droplet ~ay be 19 devoid of remanent magnetism when it is outside of any magnatic field.
It should be noted also that an unselected droplet may become at least 21 temporarily magnetized while passing through the Y de1ecting field, 22 and conceivably it may retain ~uch magnetism at least for a time while 23 traveling toward the catcher 16. Thus, selected droplets are not 24 neces9arily magnetized at all points of their travel between the selector 20 and the paper 18, nor are unselected droplets unmagnetized 26 at all points of their travel between the selector 20 and the catcher 16.
27 The distinction resides solely in the choice of divergent courses 22 28 and 24 into which each droplet may be directed by the selector 20.
29 In the present embodiment both the selector 20 and the Y
30 de~lector 30 have pole faces disposed in converging plane~ ~o define .
~'0976-019 -12-;P~
l a wedge-shaped air gap in each instance. As explained in the aforesaid 2 Fan paten~ 3,805,272, this type of pole construction causes a gradient 3 magnetic field to be produced in the air gap between pole ~aces, the 4 configuration of the magnetic field lines being indicated (in the case of the deflector 30) by the curves drawn in FIG. 3. Both the seiected 6 droplets 28 and the unselected droplets 26 enter this gap and are 7 deflected upwardly in directions normal to the field lines therein 8 when the electromagnet is energized. In the case of the deflector 30 9 the amount of deflection varies with the current in the winding. In the case o~ the selector 20, the amount of deflection is the same for 11 all deflected droplets and is zero for unselected droplets. The 12 slanted pole faces are separated by a substan~ial clearance opening 13 even at their closest points (FIG. 3) so that a droplet may be deflected 14 past these points without striking the pole structure.
Upon leaving the first deflector 30, each drople~ will be~
16 traveling at the desired angle upwardly from ~he path which it initially 17 had when it entered the fieId of this defiector. This chosen amount of 18 Y deflection will place each selected droplet at the desired vertical 19 coordinate on the paper 18 when it impinges that surface. It remains, however, to impart the proper amount of horizontal or rightward 21 deflection to each selected droplet so that it also will impinge the 22 surface 18 at the desired horizontal coordinate thereon. This is the 23 function of the X deflector 32. Unselected droplets are not given any 24 significant X deflection and are capt;ured by the gutter 16.
Referring now to FIGS. ~ and 4, selected droplets 28 which 26 have been directed along a course having the horizontal angular position 27 denoted by the line 24 will pas~ through a part of the magnetic deflecting 28 field generated by the X deflector 32 whlch is much stronger than the 29 weak outer frlnge portion of this magnetic field through which unselected droplets 26 traveling along the divergent course 22 will pass. The pole 1 structure of the .~ deflector 32 is so designed that even with maximum 2 exciting current in the coil or winding of deflector 32, there will be 3 no significant deflection of unselect2d droplets 26 in the X direction.
4 The pole faces 34 and 36 are parallel with the path 24 of the selected droplets, and they establish a magnetic field whose lines 6 of force likewise extend generally parallel with this path and are 7 concentrated near the plane in which the pole faces 34 and 36 lie.
8 The excitation current intensity is varied in accordance with the 9 amount of angular deflection which must be given to each selected drople~ 26 in order to accomplish the desired vector printing function.
11 As shown by the graph of deflection-versus-current in FIG. 5, the 12 deflection along the X axis varies linearly with the current. On 13 the other hand, as shown by FIG. 6, the deflection will vary inversely 14 and nonlinearly with the distance between a pole face and a droplet which is passing by it, so that even a strong current will not cause 16 significant deflection of a droplet that has been diverted a relatively 17 short distance away from the pole qtructure 349 36, as in the case 18 of the unselected droplets 26, FIGS. 2 and 4.
19 Inasmuch as the unselected droplets 26 are given no signiflcant deflection in the X direction by the second deflector 32, 21 the catcher 16, FIGS. 1 and 2, may have a relati~ely narrow dimension 22 in the X direction to correspond with the very slight spread of 23 unselected droplet trajectories in that direction. Moreover, since 24 the catcher 16 is located relatively close to the recording surface 18, it does not disrupt the stabilizing aerodynamic interaction between 26 the ~et streams of unselected a~d select~d droplets until each selected 27 droplet has almost reached the end of its travel, by which time i~ no 28 longer needs further stab$1ization t~ find its correct target point.
29 ~he magnetic field produced by the X deflector 32 has a sufficient spread along the Y axis to exert uniform X deflecting forces upon 1 selected drople~s 28 for any given current value regardless of the 2 displacements respec~ively imparted to such droplets along the Y axis 3 by the Y deflector 30.
4 The illustrated apparatus is designed to print one character at a time upon ~he recording surface 18~ and the appropriate relative 6 motions are produced between the surface 18 and the printing apparatus 7 to arrange the printed characters at selected positions in successive 8 lines. If it is desired to print a whole line of characters at a time, 9 the character printing apparatus can be modified to acco~plish this. The first deflector 30 would be oriented so that it deflects the droplets 11 in the X direction, and the second deflec~or 32 would be oriented to 12 deflect selected droplets in the Y direction without imparting any 13 significant Y deflections tO unselected droplets. This would ma~e 14 it feasible ~o use a gutter that extenda parallel with the printed line in a position above or below it, ànd the nozzle which emits the 16 droplets then is aimed at such a gutter. In a line printer the 17 character printers may be arranged in staggered relationship in two 18 rows, one row of printers using a g-~tter positioned abo~e the printed 19 line while the other row uses a gutter below this line.
While the invention has been particularly shown and described 21 with reference to a preferred e~bodi~en* thereof, it will be understood 22 by those 9killed in the art that che foregoing and other changes in 23 orm and details may be made thereln without departing from the spirit 24 an~ ~cope of the invention.
.
What is claimed is:
, , .
Claims (6)
1. In a vector magnetic ink jet printing apparatus wherein droplets of ferrofluid ink are directed alternatively to a recording surface or to an intercepting catcher, the combination comprising:
means for producing a stream of ink droplets substantially all of which are initially directed along a first course toward said catcher, an electromagnetic selector operable to divert selected ones of the droplets in said stream from said first course to a second course which enables the selected droplets to avoid said catcher and impinge said surface while permitting the unselected droplets to continue traveling along said first course toward said catcher, a first electromagnetic deflector which is operable to deflect at least some of the droplets in said stream selectively along a first one of two axes orthogonal to said stream, thereby to place such deflected droplets into selected trajectories according to the respective deflections imparted to them along said first axis, and a second electromagnetic deflector positioned between said first deflector and said catcher which is operable to impart selected deflections along the second of said orthogonal axes to at least some of those selected droplets that previously were directed along said second course, whereby the final trajectory of each such droplet is determined by the respective deflections imparted to it along said two axes by said first and second deflectors, said second deflector having a pole structure so arranged that its magnetic field is unable to prevent unselected droplets that were not diverted out of said first course from reaching said catcher.
means for producing a stream of ink droplets substantially all of which are initially directed along a first course toward said catcher, an electromagnetic selector operable to divert selected ones of the droplets in said stream from said first course to a second course which enables the selected droplets to avoid said catcher and impinge said surface while permitting the unselected droplets to continue traveling along said first course toward said catcher, a first electromagnetic deflector which is operable to deflect at least some of the droplets in said stream selectively along a first one of two axes orthogonal to said stream, thereby to place such deflected droplets into selected trajectories according to the respective deflections imparted to them along said first axis, and a second electromagnetic deflector positioned between said first deflector and said catcher which is operable to impart selected deflections along the second of said orthogonal axes to at least some of those selected droplets that previously were directed along said second course, whereby the final trajectory of each such droplet is determined by the respective deflections imparted to it along said two axes by said first and second deflectors, said second deflector having a pole structure so arranged that its magnetic field is unable to prevent unselected droplets that were not diverted out of said first course from reaching said catcher.
2. A printing apparatus as specified in claim 1 wherein the pole structure of said second deflector is arranged to produce a magnetic field whose lines of force extend generally parallel with said second course and whose intensity in the portions thereof traversed by said unselected droplets is insignificant compared with its intensity in the portions thereof traversed by said selected droplets.
3. A printing apparatus as specified in claim 2 wherein said pole structure has faces spaced from each other along said second course and arranged substantially parallel therewith.
4. A printing apparatus as specified in claim 1 wherein said selector is adapted to be operated as to cause those droplets which are selected for diversion into said second course to be interspersed with unselected droplets that will continue to be directed along said first course.
5. A printing apparatus as specified in claim 4 wherein said selector causes selected and unselected droplets to be directed alternately along said second and first courses, respectively.
6. A printing apparatus according to any of claims 1 to 3, wherein said catcher has an edge lying between said first and second courses which edge is parallel to the said first orthogonal axis.
Applications Claiming Priority (2)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| US05/752,948 US4068240A (en) | 1976-12-20 | 1976-12-20 | Vector magnetic ink jet printer with stabilized jet stream |
| US752,948 | 1976-12-20 |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA1089914A true CA1089914A (en) | 1980-11-18 |
Family
ID=25028554
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA293,407A Expired CA1089914A (en) | 1976-12-20 | 1977-12-19 | Vector magnetic ink jet printer with stabilized jet stream |
Country Status (7)
| Country | Link |
|---|---|
| US (1) | US4068240A (en) |
| JP (1) | JPS5376840A (en) |
| CA (1) | CA1089914A (en) |
| DE (1) | DE2749695A1 (en) |
| FR (1) | FR2374167A1 (en) |
| GB (1) | GB1575090A (en) |
| IT (1) | IT1114934B (en) |
Families Citing this family (8)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US4274100A (en) * | 1978-04-10 | 1981-06-16 | Xerox Corporation | Electrostatic scanning ink jet system |
| WO1981003149A1 (en) * | 1980-05-01 | 1981-11-12 | Commw Scient Ind Res Org | Control of droplets in jet printing |
| KR100209515B1 (en) * | 1997-02-05 | 1999-07-15 | 윤종용 | Ejection apparatus and method of ink jet printer using magnetic ink |
| WO2000047419A1 (en) | 1999-02-09 | 2000-08-17 | Source Technologies, Inc. | Acicular particle ink formulation for an inkjet printer system |
| US6659598B2 (en) * | 2000-04-07 | 2003-12-09 | University Of Kentucky Research Foundation | Apparatus and method for dispersing nano-elements to assemble a device |
| US7380911B2 (en) * | 2004-05-10 | 2008-06-03 | Eastman Kodak Company | Jet printer with enhanced print drop delivery |
| KR100649445B1 (en) * | 2005-10-17 | 2006-11-27 | 삼성전기주식회사 | Wiring forming method and device |
| DE102005059328A1 (en) * | 2005-12-09 | 2007-06-21 | Kba-Metronic Ag | Method and apparatus for changing the trajectory of ink drops |
Family Cites Families (4)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JPS4721636U (en) * | 1971-03-03 | 1972-11-10 | ||
| US3805272A (en) * | 1972-08-30 | 1974-04-16 | Ibm | Recording system utilizing magnetic deflection |
| US3959797A (en) * | 1974-12-16 | 1976-05-25 | International Business Machines Corporation | Ink jet printer apparatus and method of printing |
| US3971033A (en) * | 1975-05-27 | 1976-07-20 | Ibm Corporation | Method and apparatus for applying magnetic liquid droplets to a recording surface |
-
1976
- 1976-12-20 US US05/752,948 patent/US4068240A/en not_active Expired - Lifetime
-
1977
- 1977-11-01 JP JP13037077A patent/JPS5376840A/en active Granted
- 1977-11-07 DE DE19772749695 patent/DE2749695A1/en not_active Withdrawn
- 1977-11-10 FR FR7734667A patent/FR2374167A1/en active Granted
- 1977-12-01 GB GB50161/77A patent/GB1575090A/en not_active Expired
- 1977-12-02 IT IT30297/77A patent/IT1114934B/en active
- 1977-12-19 CA CA293,407A patent/CA1089914A/en not_active Expired
Also Published As
| Publication number | Publication date |
|---|---|
| GB1575090A (en) | 1980-09-17 |
| JPS5725391B2 (en) | 1982-05-29 |
| US4068240A (en) | 1978-01-10 |
| IT1114934B (en) | 1986-02-03 |
| FR2374167B1 (en) | 1980-09-05 |
| FR2374167A1 (en) | 1978-07-13 |
| JPS5376840A (en) | 1978-07-07 |
| DE2749695A1 (en) | 1978-06-22 |
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