US3433171A - Peristaltic fluid pump - Google Patents

Description

M rc 8, 1969 E. R. CORNEIL 3,433,171

PERISTALTIC FLUID PUMP Filed Nov. 23, 1966 f 2 MW 02 BY. w M

March 18, 1969 E. R. CORNEIL PERISTALTIG FLUID PUMP Sheet 2 of2 Filed Nov. 23, 1966 United States Patent 3,433,171 PERISTALTIC FLUID PUMP Ernest R. Corneil, RR. 1, Thorold, Ontario, Canada Filed Nov. 23, 1966, Ser. No. 596,533 US. Cl. 103149 16 Claims Int. Cl. F041) 43/08, 17/02 ABSTRACT OF THE DISCLOSURE A peristaltic pump in which positive and negative pressures are produced by distortion of a resilient tube. One use of the pump may be to pump blood, for example, in such as artificial heart and lung machines.

In existing forms of peristaltic pumps resilient tubes or cylinders have been used, the resilience of the material forming the tube or cylinder creating the necessary negative pressure to draw in a fresh supply of fluid after fluid has been expelled by distortion of the tube or cylinder. Therefore it was essential that the tube be not only flexible but have the capability of recovering its undistorted shape after distortion. The recovery forces control the negative pressure obtained and set a limit to the rate at which fluid is drawn into the pump. An increase in recovery force, with a consequent increase in negative pressure, can be obtained by increasing the wall thickness of the tube or cylinder of the pump. However the increased thickness requires excessive power for distortion, creates undesirable heat and causes rapid deterioration of the tube materials. There results a limit to the practicability of the process to laboratory sized equipment.

Although resilient tubing is manufactured with given wall thicknesses and internal diameters, the tolerances are quite wide. Further, both the wall thickness and the internal diameter are subject to change under service conditions. The efliciency of the pumps is dependent upon the distortion, e.g., occlusion, of the tube, and overdistortion of the tube requires excessive power and limits tube life. It is, therefore, desirable to control the forces applied to the tube.

The positive pressure developed is limited by the strength, and thickness, of the resilinet tube walls and on occasion the walls balloon and burst. This limits pumps of this form to relatively low pressures. Also, it is desirable to match the wall thickness with the desired pressure to avoid using a greater wall thickness than necessary with the consequential increase in power requirements.

It is an object of the present invention to provide a fluid pump in which the positive and negative pressures are produced by the distortion and recovery of flexible tubes or cylinders, without relying on resilience of the tube or cylinder to cause recovery.

Another object is to provide a fluid pump using the distortion and recovery of a tube or cylinder for producing the necessary positive and negative pressures, in which the forces for distorting the tube or cylinder can be adjusted to produce a desired distortion independent of the thickness of the wall of the tube or cylinder.

Another object of the present invention is to provide an apparatus for converting rotary motion into a reciprocal motion for distorting the tube, and a further object is to provide means for controllably varying the cycle of operation whereby the distortion of the tube is nonuniform during the cycle, there being a dwell period at maximum distortion, and the production of a maximum pressure.

The invention will be readily understood by the following description of certain embodiments, by way of example, in conjunction with the accompanying drawings, in which:

3,433,171 Patented Mar. 18, 1969 ICC FIG. 1 is a longitudinal cross-section through one form of pump, on the line 11 of FIGURE 2;

FIGURE 2 is a cross-section on the line 2-2 of FIG- URE 1;

FIGURE 3 is a cross-section on the line 33 of FIG- URE 1, to a slightly reduced scale;

FIGURE 4 is an end view, partly in section, in the direction of arrow A in FIGURE 1;

FIGURE 5 is a side view of one form of tube for use in the pump;

FIGURE 6 is a cross-section on the line 6-6 of FIG- URE 5;

FIGURE 7 is a longitudinal cross-section of another form of tube for use in the pump; and

FIGURE 8 is a cross-section on the line 8-8 of FIG- URE 7.

The pump illustrated in FIGURES 1 and 2 comprises a housing 1 having an end cover 2. A camshaft 3 is rotatably supported in the end 4 of the housing 1 and in the cover 2 by bearings 5. The camshaft has a series of pairs of cams 6 and 7. The cams 6 and 7 forming a pair are displaced to each other and each pair is displaced relative to adjacent pairs, so that successive pairs are equally spaced around a circular locus. In the particular example illustrated there are twelve pairs of cams 6 and 7, each pair displaced 30 relative to the adjacent pair.

Mounted on the cams 6 and 7 are movable plates 10 and 11, respectively. Each plate 10 has a cam slot 12 within which turns the cam 6, and also has a leg 13 extending through one wall 14 of the housing 1. Each plate 11 also has a cam slot 15 within which turns cam 7 and a leg 16 extending through the wall 14 of the housing. The legs 13 and 16 are supported for reciprocal movement by a bearing strip or support 17. The bearing strip or support is rotatably supported in the wall 14 for a purpose explained below. It is readily inserted in a slot in the wall 14 from the end when the cover 2 is removed.

The slots 12 and 15 are mirror images of each other and the pair of plates 10 and 11 for each pair of cams 6 and 7 are immediately adjacent and reciprocate in opposite directions. The form of cam slot 15 in plate 11 is readily seen in FIGURE 2, and the form of cam slot 12 in plate 10 is seen in FIGURE 3.

Each plate 10 and 11 has a slot 18 in its lower end. A rotatable bar 19 passes through all the slots 18 in the plates. The bar 19 is supported in the end 4 of the housing 1, and in the cover 2, by bearing sections 20 which are eccentric to the main portion of the bar. A control lever 22 is attached to the end of the bar which extends through the cover 2, the lever attached to the bar by a pin 23.

The bar 19 acts in cooperation with the bearing strip or support 17 to guide the plates 10 and 11 in their reciprocal movement. The control lever 22 can rotate the bar 19 for a purpose which will be described later.

Legs 13 and 16 carry at their ends, remote from the related plate, pressure bars 24 and 25 respectively. As will be seen in FIGURE 1, pressure bars 24 on legs 13 are on the remote side of pressure bars 25 on legs 16, relative to the housing 1.

The pumping member comprises a flexible tube 30 having two radially extending fins 31 and 32. The fins 31 and 32 are diametrically opposite each other and in a plane parallel to a plane passing through the axis of the camshaft 3. A series of holes 33 are formed in the fins 31 and 32 for the reception of the pressure bars 24 and 25. The ends 34 are attached to inlet and outlet conduits 35 and 36.

As the camshaft 3 is rotated, the cams 6 and 7 rotate within the cam slots 12 and 15 causing the plates 12 and 16 to reciprocate, moving the pressure bars 24 and 25 towards and away from each other. As the pressure bars move towards each other they press upon the tube to distort it, whilst movement away from each other positively returns the tube to its original cross-sectional shape. The distortion of the tube is progressive along the tube, in the manner of a travelling wave. The positive action to re turn the tube to its undistorted cross-section improves the operation of the pump as there is no reliance on the resilience of the tubing material. The thickness of the tube wall has only to be sufficient to withstand the maximum positive pressure produced during pumping. The negative pressure, or suction, produced by the return of the tube to its undistorted cross-section is independent of the tube resilience and can be positively controlled. Any variation in the physical properties of the tube material will not affect the pressure produced.

In the operative position as shown in FIGURE 1, the pressure bars 24, 25 at the left of the figure are at their closest position while the pressure bars in the centre are at their maximum spacing. As the pump operates, by rotation of the camshaft 3, the pressure bars to the right of the centre will move apart while the pressure bars to the left will move towards each other. Thus the volume of fluid within the tube is moved to the right. Simultaneously, the pressure bars at the extreme left will be moving apart creating a low pressure area into which fluid is drawn.

FIGURE 2 shows the tube 30 distorted to a condition where the gap between the opposed walls is almost at a minimum. This gap width will occur at this phase position for each revolution, as long as the plates reciprocate in the plane set by the bearing strip or support -17 and the bar 19 as they are positioned in FIGURE 2. The gap width between the opposed walls of the tube and the gap width between opposed pressure bars 24 and 25 can be varied by the control lever 22.

The control lever 22 has a screw 40 extending through the end remote from the bar 19. The tip of the screw enters indents in a boss 43 formed on the cover 2. By loosening the screw 40 to withdraw the tip from indent 44, the control level 22 can be moved to rotate bar 19 relative to the housing 1. As the bar is supported eccentrically by the bearing section 20, rotation of the bar 19 shifts the plane in which the plates and 11 reciprocate. Shifting the plane of reciprocation also alters the relative positions of the cams 6 and 7 in the cam slots 12 and 15. When the control lever 22 is moved to the extreme right, as seen in FIGURE4, the pressure bars 24 and 25 approach closer to each other in the one extreme position. Thus the gap width between the opposed walls of the tube is reduced. In addition, or alternatively, to varying the minimum gap between the opposed walls of the tube, variation in the minimum distance between pressure bars 24 and 25 can be used to compensate for variation in the wall thickness of different tubes. The variation in the plane of reciprocation of the plates 10 and 11, and thus of legs 13 and 16, is accomodated in the bearing strip 17 by the strip being rotatably supported in the 'wall 14.

The displacement of the point of contact between each cam and its associated cam slot, relative to the rotational axis of the camshaft 3', does not follow a linear curve. The reciprocation of the plates 10' an 11 slows down as the displacement of the cams approaches maximum. There is thus produced a considerable mechanical advantage and the force applied to the tube increases substantially as the gap between the pressure bars approaches the minimum. In addition there is a dwell period at the position where the tube walls are closest together, improving the action of the pump.

FIGURES 7 and 8 illustrate a modified form of tube 50 which has a lining 51 compatible with the fluid being pumped. The tube may also include reinforcing material, such as a synthetic fibre braid, indicated at 52. This enables the tube to withstand higher pumping pressures without making the wall of the tube very thick. The

4 reinforced tube will also withstand more arduous working conditions.

As stated above, as the return of the tube from its distorted condition to its undistorted cross-section is positively produced by the reciprocating action of the pressure bars 24 and 25, the resilience of the material forming the tube is not a pertinent feature. Tubes of material having little or no resilience can be used, and may be preferred as the power requirement for distortion of the tube is reduced.

It will be appreciated that a pump according to the present invention is particularly useful as a peristalic pump for pumping blood, for example, such as in artiiicial heart and lung machines.

A further and very important advantage of the present invention is that it is very quick and easy to replace the actual pumping member, the tube. Both in medical and in other practices it is often necesary to sterilizethe tube. In certain circumstances the tube may become contaminated with undesirable or dangerous materials. It will be seen that the pumping member is very quickly and easily removed, providing ready disposal, or decontamination or sterilization, as the case may be. Also, pumping members of differing materials can readily be interchanged for the pumping of different materials.

I claim: 1. A fluid pump comprising: a flexible tube; a series of pairs of opposed action reciprocable pressure members positioned along said tube at spaced apart locations, one of each pair of members on one side of the tube and the other of each pair of members on the other side of the tube; means attaching said members to the wall of the tube; means for reciprocating successively the pairs of pressure members to progressively distort the tube to an occluded condition and to progressively restore the tube to an undistorted cross-section, said means comprising a rotatable cam member having a series of pairs of opposed cam surfaces on said member, the pairs of cam surfaces progressively displaced about the axis of rotation of the cam member, a series of reciprocating members, one for each pressure member, and means on each reciprocating member for engagement with a related cam surface;

each reciprocating member including; a first extension extending in a direction from said cam member toward said tube, a pressure member attached to the end of each said first extension; and a second extension extending in a direction opposed to said first extension and having at least one guide surface extending generally in the same direction as said second extension; and

guide means extending parallel to said cam member,

said guide surfaces on said second extensions cooperating with said guide means.

2. A pump as claimed in claim 1, including radially extending fins on said tube, diametrically opposed and extending parallel to the longitudinal axis of the tube.

3. A fluid pump as claimed in claim 2 wherein holes are formed in said fins, said pressure members extending through said holes.

4. A fluid pump as claimed in claim 3, said fins laterally displaceable on said pressure members for removal from and replacement on said members.

5. A fluid pump as claimed in claim 1 wherein the rotatable cam member comprises a rotatable camshaft provided with a pair of cams for each pair of pressure members, the cams in a pair displaced substantially about the axis of rotation of the camshaft, and each pair of cams successively displaced about the rotational axis of the camshaft.

6. A fluid pump as claimed in claim 5 wherein the tube extends in line with and is spaced parallel to the camshaft.

7. A fluid pump as claimed in claim 1 wherein said reciprocating member comprises a plate member, said plate member defining a cam slot for cooperation with a cam.

S. A fluid pump as claimed in claim 1 wherein said guide means is a rotatable bar, mounted for eccentric rotation, said bar extending in line with and parallel to said cam means, rotation of said bar varying the angular disposition of said reciprocable pressure members relative to said cam means.

9. A fluid pump as claimed in claim 8 including further guide means for said first extension on said reciprocable members.

10. A fluid pump comprising an elongated hollow housing, said housing having side and end walls and closed at one end with a cover; a camshaft extending through said housing and mounted for rotation in said end wall and said cover; a series of pairs of cams on said camshaft, the cams forming a pair displaced substantially 180, the pairs of cams positioned at spaced apart intervals and progressively angularly displaced along the camshaft; a series of reciprocable members mounted one on each cam for reciprocation thereby; a support positioned in a side wall of the housing and extending longitudinally in the housing in line with said camshaft; a series of guide holes in said support; a first extension on each of said reciprocating members, said extensions extending through said guide holes; a pressure member at the end of each said first extension and extending normal thereto, said pressure members spaced apart on either side of a plane parallel to the axis of rotation of said camshaft for the reception of a flexible tube therebetween; a second extension on each of said reciprocating members, said second extensions extending in a direction opposed to said first extensions, and at least one guide surface on each said second extension extending generally in the direction of the second extension; guide means in said housing for cooperation with said guide surfaces on said second extensions; a flexible tube supported between said pressure members and having means for connecting one end of said tube to a fluid source and the other end to a fluid supply and means for connecting said pressure members to said tube, whereby on rotation of said camshaft the tube is progressively distorted to occlude the tube bore and progressively restored to an undistorted cross-section.

11. A fluid pump as claimed in claim 10 wherein said guide means comprises a bar mounted for eccentric rotation in said end wall and said cover; each said second extension defining a slot for cooperation with said bar; and means for rotating said bar; whereby the angular disposition of said reciprocating members relative to said camshaft is varied.

12. A fluid pump as claimed in claim 11 wherein each said reciprocating member comprises a plate, said plate defining a slot for cooperation with the related cam.

13. A fluid pump as claimed in claim 10 wherein said tube has two diametrically opposed fins extending radially in the same plane and longitudinally of the tube, said fins defining holes therein for the reception of said pressure members.

14. A fluid pump as claimed in claim 13, said fins laterally displaceable on said pressure members for removal from and replacement on said members.

15. A fluid pump as claimed in claim 10 wherein said tube has a lining of material which differs from the material of the tube.

16. A fluid pump as claimed in claim 10 wherein the tube is reinforced by fibrous material in the wall of the tube.

References Cited UNITED STATES PATENTS 1,922,196 8/1933 Butler l03--152 2,105,200 1/ 1938 Phelps 103--l49 2,546,852 3/1951 Comeil 103--148 2,689,530 9/1954 Harvey 103-148 2,877,714 3/1959 Sorg et al 103-149 3,083,647 4/1963 Muller 103-148 3,176,622 4/1965 Pfeitfer 103149 FOREIGN PATENTS 961,579 5/ 1950 France. 836,006 4/ 1952 Germany.

DONLEY J. STOCKING, Primary Examiner.

LEONARD H. GERIN, Assistant Examiner.

US. Cl. X.R. l03l52

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