PERISTALTIC PUMP

3,128,716

Patented Apr. 14, 1964

1

3,128,716 PERISTALTIC PUMP Richard C. Stallman and William M. Gates, San Carlos, Calif., assignors to Bcckman Instruments, Ihc, a corporation of California

Filed July 17,1961, Ser. No. 124,532
39 Claims. (CI. 103—149)

This invention relates, in general, to peristaltic pumps and more particularly to peristaltic pumps wherein a plurality of tubes are employed.

Peristaltic, or tube pumps, are well known in the art. However, prior art pumps have had several major disadvantages. Ordinarily, circular tubes are employed and are repeatedly kneaded by multiple fingers such that there is always one or more fingers engaged with the tube. In other pumps of the prior art, the tubing is arranged in a circular arc with two or more rollers rotating within the arc against the tube.

In each of the aforementioned pumps, a roller continually and progressively contacts the tube, and the tube consequently is continually stretched with a tendency to drag it through the pump. The result of this continuous stretching and drag is tube scuffing which develops rapid tube wear.

Moreover, the circular cross section of the tube has relatively poor wearing characteristics due to the compression alone. When a circular tube is compressed to the point that its internal opening is completely closed, the inner and outer peripheries are subjected to extreme and damaging compression and tension, respectively. Thus, the sides of the circular tube are quickly weakened and fractured.

Although there are peristaltic pumps of the prior art which do provide intermittent kneading action, either fluid back flow is permitted through the tube; or alternatively, complicated valving mechanisms are required to prevent the back flow. Even in these pumps having intermittent kneading action, no means are provided to permanently position the tube in the pump and at the same time reduce the wear due to scuffing.

It is, therefore, a general object of this invention to provide an improved peristaltic pump.

It is a more particular object of this invention to provide a peristaltic pump wherein means are provided to reduce the wear of the pump tubes.

It is another object of this invention to provide a peristaltic pump having the aforementioned characteristics which may be economically constructed and which provides an accurate pumping action.

It is still another object of this invention to provide a peristaltic pump wherein the tubes are alternately kneaded and released whereby tube scuffing is avoided.

It is a further object of this invention to provide a peristaltic pump having the aforementioned characteristics wherein means are provided for selectively varying the stroke of the pumping action.

Another object of this invention is to provide a peristaltic pump having the aforementioned characteristics wherein a plurality of the tubes are employed.

It is another object of this invention to provide a tube for use in a peristaltic pump, which tube includes a novel cross-section for reducing the wear thereof.

It is still a further object of this invention to provide a peristaltic pump having the aforementioned characteristics and which employs a tube having a novel crosssection.

It is still another object of this invention to provide a peristaltic pump having intermittent action wherein means are provided to compensate the load on the prime mover of the pump.

It is a further object of this invention to provide a

peristaltic pump having the aforementioned characteristics wherein simple valve means are provided to prevent back flow of the fluid. The aforementioned objects are accomplished gener

5 ally by employing a frame upon which are pivoted a plurality of arms. A plurality of tubes are retained on the arms with at least a portion of each tube slidable with respect to its associated arm. Eccentric rotating means are provided for intermittently compressing the

10 tubes while urging the arms about their pivot point against a resilient force. When the tubes are not being compressed by the eccentric rotating means, the resilient force urges the arms toward a stop which collapses the tubes to prevent back flow.

15 Upon review of the following description in conjunction with the accompanying drawing, the aforementioned objects as well as other objects and features of the invention will become apparent. Referring to the drawing:

20 FIGURE 1 is a front elevational view of a peristaltic pump in accordance with the invention;

FIGURE 2 is a sectional view taken along the lines 2—2 of FIGURE 1;

FIGURE 3 is a partial sectional view taken along the

25 line 2—2 of FIGURE 1 wherein the operation of the pumping action is shown;

FIGURE 4 is a view taken along the line 4—4 of FIGURE 3;

FIGURE 5 is a cross-section of one embodiment of a 30 resilient tube used in accordance with the invention;

FIGURE 6 is a cross-section of another embodiment of a resilient tube used in accordance with the invention; and

FIGURE 7 is a cross-section of the tube shown in

35 FIGURE 6 in its normal partially compressed state as used in accordance with the invention.

Referring to FIGURES 1 and 2, it is seen that the pump includes a frame having a base member 11 and a pair of upright members 13 and 15 secured thereto.

40 The upright members 13 and 15 may be held in spaced relationship by a cross bar 17, by a tube retaining bar 19, and by an arm shaft 21.

A plurality of arms 23 are rotatably mounted on the shaft 21 and are separated from each other by spacers

45 25. The straight underside 29 of each of the arms 23 includes a channel 27 and a tube 31 is retained in each of the channels 27. A portion of each tube, for instance, that as shown in the area 33, is firmly secured in the channel 27 to prevent longitudinal movement of that

50 portion while allowing longitudinal stretch and contrac. tion of the remainder of the tube. As shown in FIGURE 4, segments 35 of the channel walls are forced inwardly into the tube 31 at the area 33 to provide the locking action. Thus, the tube along the straight edge of the

55 arm 23 may be easily stretched to and away from the lock portion 33, but its overall position is maintained.

Valving means is provided in the form of a stationary bar or stop 37 extending between the upright members 13 and 15. A plurality of springs 39, one spring associ

60 ated with each of the arms 23, is connected between the individual arms 23 and to the cross bar 17. Thus, the arms 23 are resiliently urged in a counterclockwise direction as viewed in FIGURE 2, and when so rotated, the tube 31 is urged against the stop 37 and is consequently

65 closed.

An elliptically shaped cam 41 is pivotally secured to the upright member 13 and a similar cam 42 may be secured to the upright member 15 in a position directly opposite the cam 41. The cams are preferably rotatable 70 about the intersection of their major and minor elliptical axes. A pair of rollers 43 and 45 extend across the pump as seen in FIGURE 1 and are rotatably secured 4

on one side to the cam 41 and on the other side to the cam 42. The rollers 43 and 45 are preferably secured to the cams 41 and 42 along the minor axis thereof and are equally spaced on opposite sides of the point of cam rotation. It is observed that upon rotation, the roll- g ers 43 and 45 pivotally contact the tube 31 urging the arm 23 in a clockwise rotation against the force of the spring 39. During the contact, as seen in FIGURE 3, tube 31 is compressed in a longitudinally progressing manner whereby fluid will be forced therethrough. As io rollers 43 and 45 urge the arm 23 in a clockwise direction, the tube 33 is retracted from the stationary valve or stop 37 whereby the passage through the tube is open except for the longitudinally progressing pressure caused by the rollers. 15

A cam follower 47 is secured to an arm 49 which is pivoted about a bearing 51 and resiliency urged in the clockwise direction by a spring 53. It is seen that during a portion of the cycle of cam 41, the rotation is resisted by the force of the springs 39 as applied to the 20 arms 23. When the rollers 43 and 45 are not in contact with the tube 31, the rotation of the cam 41 is resisted by the resilient action of the spring 53. Thus, the motive means for rotating the cam 41 is subjected to a substantially constant load despite the intermittent contact be- 25 tween the rollers 43 and 45 against the tubes 31 on the arms 33.

As seen more clearly in FIGURE 1, rotative motive power is applied to the cam 41 from the motor 55 through a coupler 57, and gear train enclosed by a gear 30 box 59. Any type of gear train may be employed in the box 59. However, a worm gear is preferable due to the minimum play and back lash thus attained. The output of the gear train is applied to rotate the cam 41 which, in turn, rotates the cam 42 through the eccentrically 35 pivoted rollers 43 and 45.

It is apparent that, if desired, motive power may be applied to both cams 41 and 42. Moreover, it is apparent that a substantially constant load may be applied to . the motive means with a single cam 41. In such an 40 instance, the cam 42 may be replaced by a plate which receives the eccentrically located rollers 43 and 45.

Referring to FIGURE 1, it is noted that on the left-hand side of the bar 37 an adjustable plate 61 is secured. The plate 61, in the embodiment shown, underlies four of ^5 the arms 23 and serves to alter the pumping stroke of the tube associated with the four overlying arms 23. It is obvious that the amount the plate 51 is raised may be sufficient to clear the tubes 31 associated therewith above the rotating rollers 43 and 45 during the complete cycle 5q of rotation of the cam 41. With the plate 61 in this high position, no fluid will be pumped through the tubes 41 overlying the plate 61. It is equally obvious that the stroke may be adjusted at any point from this extreme high position downward to the level of the bar 37. Al- 55 tentatively, the plate 61 may completely replace the bar 37 whereby the stroke of the particular arms overlying the plate 61 may be adjusted to provide any stroke variation between complete non-contact to continuous contact with the rollers 43 and 45. 60

Another feature of the invention is provision of means to prevent permanent seating of the tubes 31 against the stop 37 or plate 61 when the pump is not in use and thus avoid a permanent set in the tubes. To this end, guides 63 having slots 64 are provided on each of the 65 upright members 13 and 15. Each of the slots 64 includes an enlarged portion 65. A plate 67 (FIGURES 2 and 3) has a pair of rivet-like members along the upper edge thereof. The rivet-like members include an enlarged head portion of a diameter only slightly smaller 70 than the enlargements 65 in the guide 63 and a neck portion having a diameter slightly smaller than the slot 64 itself. Near the lower end of the plate 67 is another pair of rivet-like members having an enlarged head portion slightly smaller than the enlarged section 65 on 75

the slot 64. The rivet-like members at the lower portion of the plate 67 have a neck larger than the slot 64 but smaller than the head portion of the rivets. Thus, the rivets at the top of the plate may first be inserted in the enlargement 65, and the entire plate raised until the heads of those rivets at the lower portion of the plate can be inserted through the enlargement 65. The plate is then released; the neck portions of the rivets along the lower edge of the plate will retain the plate from downward excursion. The portion of the slot 64 below the enlargements 65 may be employed to store the plate while the pump is in use by retaining merely the rivet-like members near the upper edge of the plate.

The uppermost edge 69 of the plate 67 cooperates with the underside 71 of the channel 27. The underside 71 of the channel 27 completely encloses the tube 31 whereby pressure applied thereto is not transferred to the tube itself. The dimension of the plate is such that when the rivet-like members along the lower edge are locked into the enlargement 65 of the guides 63, the tubes 31 are held away from the stop 37. After positioning the plate 67, the rollers 43 and 45 are then rotated into position shown in FIGURE 2 and the tube 31 is completely free of any pressure. Consequently, the tube 31 does not receive a permanent set from the rollers 43 and 45, nor the stop 37 when the pump is not in use.

Referring to FIGURE 5, a cross-section is shown of the tube 31 in accordance with one embodiment of the invention. Here, it is noted that the cross-section is externally rectangular or square. The internal orifice 73 of the tube, however, is lip-shaped in cross-section and has convergent corners 75 and 77. Preferably, the convergent corners 75 and 77 lie in a plane substantially parallel to the surface of the arm 23 against which the tube is retained. Thus, when the upper and lower edges of the tube are progressively squeezed, the lip-shaped orifice 73 tends to become completely closed without undue stress on the side walls of the tube.

The cross-section of another embodiment of the tube is shown in FIGURES 6 and 7. Here, the tube is designated by the reference numeral 31' and is similar to that as shown in FIGURE 5 but includes a membrane 79 which extends between the convergent corners 75 and 77. In use, the embodiment of the tube shown in FIGURE 6 is normally held partially compressed as shown in FIGURE 7. In partial compression, it is noted that the convergent lips 75 and 77 are spread outwardly, and consequently the membrane 79 is placed in a slight tension. Thus, with even the slightest compression increase beyond normal, the membrane 79 will have sufficient tension to cause the corners 75 and 77 to be drawn together and the tube will expand in the vertical direction to the conditions shown in FIGURE 7.

Referring to FIGURES 2 and 3, the general operation of the pump may be explained. The left-hand portions of the tubes 31 may be placed in communication with a source of fluid to be pumped and the right-hand portions of the tubes are connected to a suitable apparatus for receiving the fluid pumped. The plate 67 is lowered so that the arms 23 are resiliently urged against either the stop means 37 or one of the rollers 43 or 45. The motor 55 is started and the rollers 43 and 45 are rotated in a clockwise direction about the axis of the cams 41 and 42. As seen more clearly in FIGURE 3, when the rollers reach the position as shown therein, the tubes 31 are contacted and the arms 23 are urged in a clockwise direction about the shaft 21. Since the resilient action of the springs 39 is greater than the resilient force of the tube 31, the tube is progressively compressed from left to right to provide the desired pumping action.

As the rollers 43 and 45 compress the tube from left to right, it is apparent that the tube is likewise urged in the same direction. However, due to the clamping action 33, the overall position of the tube is retained. When the rollers are retracted from a tube, as shown in FIG