US3584983A - Continuous output pump - Google Patents

Abstract

A pump for delivering a continuous or uniform i.e., not pulsating, flow of liquid through a flexible tubing. A pump body is provided with an annular recess open at one axial end face thereof, and the body is rotatably mounted on a drive shaft. A sleeve is rotatably connected on axially adjacent camming elements on the drive shaft, and one sleeve axial end face extends into the pump body annular recess. A flexible tubing enters the annular recess and extends therearound for a length greater than one circumferential length of the recess, in particular exiting from the body through the same opening through which it enters. One end of the tubing is connected to a source, for example a reservoir of anticoagulant liquid, and the other end to a load, such as a catheter inserted into the arm of a patient and operatively connected to a pressure transducer.

Description

United States Patent [72] Inventors Daniel T. Hindman Kenmore; Karl A. Baake, Angola, both of, N.Y. [211 App]. No. 873,244 [22] Filed Nov. 3, 1969 [45] Patented June 15, 1971 [73] Assignee Menneu-Greatbatch Electronics, Inc.

Clarance, N.Y.

[54] CONTINUOUS OUTPUT PUMP 6 Claims, 13 Drawing Figs.

[52] US. Cl. 417/476, 128/214 [51] Int. Cl ..F04b 43/08, F04b 43/12, A61m S/00 [50] Field of Search 417/476, 474, 475, 477; 418/45 [56] References Cited UNITED STATES PATENTS 2,002,862 5/1935 Moran 417/476 2,249,806 7/1941 Bogoslowsky 418/45 2,789,514 4/1957 Hill 417/476 2,818,815 1/1958 Corneil 418/45 FOREIGN PATENTS 484,479 5/1938 Great Britain 417/476 Primary Examiner-Carlton R. Croyle Assistant ExaminerR. E. Gluch Att0rney-Christel and Bean ABSTRACT: A pump for delivering a continuous or uniform i.e., not pulsating, flow of liquid through a flexible tubing. A pump body is provided with an annular recess open at one axial end face thereof, and the body is rotatably mounted on a drive shaft. A sleeve is rotatably connected on axially adjacent camming elements on the drive shaft, and one sleeve axial end face extends into the pump body annular recess. A flexible tubing enters the annular recess and extends therearound for a length greater than one circumferential length of the recess, in particular exiting from the body through the same opening through which it enters. One end of the tubing is connected to a source, for example a reservoir of anticoagulant liquid, and the other end to a load, such as a catheter inserted into the arm of a patient and operatively connected to a pressure transducer.

PATENTEUJUMSIQYI 3584.983

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CONTINUOUS OUTPUT PUMP BACKGROUND OF THE INVENTION This invention relates generally to the pump art, and more particularly to a new and useful pump of the type wherein the material being pumped is transferred through a resilient tubing by a nutating member applying compressive pressure to the tubing.

Pumps of this general type are well established and the use of resilient tubing has many advantages in the transfer of liquids. The relatively easy removal of the tubing from the pump assembly for sterilization orreplacement is of great importance in the medical field and wherever contamination must be prevented. Since the liquids do not come into contact with metal parts, particular attention to the corrosive tendencies of these parts is unnecessary and ordinary, low cost materials can be used in the assembly.

A characteristic of pumps of this type heretofore available is a pulsating delivery, from the pump, of the material being transferred through the tubing. There are, however, applications in which there is needed a pump of this general type but which will deliver a constant or uniform output flow. One such application is in the medical procedure of heartbeat monitoring wherein the pump would be employed to supply saline solution to a catheter inserted into the patient and to which catheter a pressure transducer is connected for operating an electrical indicating or display instrument. If the pump output were not continuous but instead pulsating, the pulsations in the flow caused by the pump would give rise to electrical signals which can distort or add confusion to the signals indicative of true heartbeat.

Along with providing a constant or uniform output flow, the pump when used in heartbeat monitoring procedures should be capable of operating over a reasonably large pressure range. This is because the equipment will be used to sense arterial pressure at one time and veneous pressure at another which pressures are ofcourse significantly different.

In addition to satisfying these two specific requirements, a pump of this general type, no matter what its particular use or construction, should be designed to prevent drag by the nutating member on the flexible tubing. Otherwise such frictional dragging will destructively wear the tubing and will cause the tubing to crawl or creep during the pumping operation, to an extent such that the tubing often will become separated from the pump assembly. The design for preventing destruction wear and creeping" nevertheless should allow easy removal and replacement of the tubing, especially when the pump is to be used in medical procedures.

SUMMARY OF THE INVENTION It is therefore a primary object of the present invention to provide a pump for delivering a continuous output flow and of the type wherein the material being pumped is transferred through a resilient tubing by a nutating member applying compressive pressure to the tubing.

It is a further object of this invention to provide such a pump wherein destructive wear and creeping" of the flexible tubing is prevented in a manner allowing easy manual replacement and removal of the tubing.

The present invention provides a pump having a stationary body with an annular recess therein and a nutating member having an annular end face which extends into the recess thereby defining an annular region. A single length of flexible tubing enters the region, and the length of tubing in the annular region is greater than one circumferential length of the region by an amount such that during one complete rotation of the pump drive shaft, a portion of the length of tubing in the region always will be compressed by an amount sufficient to prevent any reverse flow. The nutating member is rotatably connected to the pump drive shaft whereby destructive wearing of the tubing is minimized and creeping" thereof is prevented.

The foregoing and other advantages and characterizing features of the present invention will become clearly apparent from the ensuing detailed description of a preferred embodiment thereof taken in conjunction with the included drawing wherein:

BRIEF DESCRIPTION OF THE DRAWING FIGURES FIG. 1 is a schematic diagram showing a pump of the present invention as it would appear in use in one illustrative application;

FIG. 2 is an elevational view of the pump of the present invention;

FIG. 3 is an end view thereof taken about on line 3-3 in FIG. 2;

FIG. 4 is a longitudinal sectional view taken about on line 4-4 in FIG. 2;

FIG. 5 is an end view thereof taken about on line 5-5 in FIG. 4;

FIGS. 6 and 7 are end and side elevational views, respectively, of one part of the drive shaft of the pump of the present invention;

FIG. 8 is a fragmentary view, partly in section, taken about on line 8-8 in FIG. 2 but on an enlarged scale and with flexible tubing assembled in the pump;

FIG. 9 is an enlarged, fragmentary sectional view illustrating the nutating movement of a component of the pump of the present invention;

FIGS. 10:: and 10b, taken about on line 10-10 in FIG. 8, are fragmentary views, partly in section, showing release and compression, respectively, of flexible tubing by the pump of the present invention; and

FIGS. 11a and 11b show schematically the manner of assembling flexible tubing in prior art pumps and in the pump of the present invention, respectively.

DETAILED DESCRIPTION OF THE ILLUSTRATED EMBODIMENT FIG. I shows schematically a pump 10 constructed in accordance with the present invention as it would appear in use, for example in combination with heartbeat monitoring equipment. The detailed structure of pump 10 will be described further on in the specification. Suffice it to say at the present time, and referring to both FIGS. 1 and 2, that pump 10 comprises a generally cylindrical body portion 11 provided with an annular recess 12 open at one axial end face thereof and provided with an opening 13 through the wall thereof communicating with annular recess 12. Pump 10 further comprises a drive shaft 14 rotatably mounted in pump body 11 by means of a bearing and disposed so that the axis thereof is coincident with the axis of body 11. In addition, pump 10 includes a sleeve 16 mounted on drive shaft 14 for nutating movement about the axis of shaft 14 and at an axial position thereon such that one end of sleeve 16 extends partially into annular recess 12 so as to define an annular region therein. By virtue of this arrangement, upon rotation of drive shaft 14 sleeve 16 is nutated about the axis thereof with the result that the volume of the annular region thus defined is varied from a maximum to a minimum in a direction around the circumferential length thereof. Pump 10 also comprises a single length of flexible tubing 17 extending through opening 13 in the wall of pump body 11 and around the annular region therein. The length of tubing 17 in the annular region is greater than one circumferential length of the region by an amount such that during one complete rotation of drive shaft 14, a portion of the length of tubing 17 in the region always will be compressed by an amount sufficient to prevent any reverse flow through tubing 17. By way of specific example as shown in FIG. 1, tubing 17 extends twice around the annular region and thus both enters and leaves pump body 11 through the single opening 13. Pump body 11 is fixedly positioned by a supporting framework, designated generally at 18 in FIG. I, r by other suitable means, and drive shaft 14 can be driven by an electric motor 19 operatively connected thereto and energized by a suitable power supply indicated generally at 20.

A distinguishing characteristic of pump provided by the present invention is that it delivers a continuous or uniform i.e., not pulsating, flow in tubing 17. One particularly ad vantageous use of the present invention is in medical heartbeat monitoring procedures. Such procedures include the insertion of a catheter into an artery or vein of a patient and the utilization ofa pressure transducer in communication with the catheter to transform blood pressure variations indicative of heartbeats into electrical signals which, in turn, are displayed or recorded by readout equipment operatively connected to the transducer. A problem frequently arising during these procedures is coagulation of blood in the catheter which, of course, makes further monitoring impossible with the catheter in that condition. In order to prevent coagulation, the conventional procedure has been for a doctor or nurse to inject periodically a quantity of saline solution into the catheter, the solution serving as an anticoagulant. This procedure, of course, requires time which can be considerable when a large number of patients are being monitored over an extended period.

FIG. 1 shows pump 10 provided by the present invention as it is used to deliver a continuous flow of anticoagulant liquid to the catheter and thus obviate the need for hospital personnel to periodically attend the catheter. The portion of tubing 17 which provides an input to pump 10 is connected to a tank or reservoir 21 filled with saline solution or other anticoagulant liquid. The remaining portion of tubing 17 which delivers the output of pump 10 is in fluid communication with a catheter 22 inserted in a patients arm. Catheter 22 is operatively connected to a pressure transducer indicated schematically at 23 which, in turn, is operatively connected through line 24 to conventional readout equipment designated generally at 25. Transducer 23 typically is ofthe type wherein a pressure sensitive diaphragm changes the electrical resistance of a bridge network. Readout equipment 25 can include, for example, an oscilloscope display.

Pump 10 is driven by motor 19, which preferably is a variable speed DC motor and brushless for the purpose of avoiding noise, at a speed sufficient to follow a pressure in the patients blood stream corresponding to one milliliter of mercury. If the patients blood pressure increases, pump 10 has the capability of following that pressure. Actually, pump 10 can be constructed so as to follow a pressure up to about that equivalent to I000 milliliters of mercury which is well beyond pressures encountered in both veneous and arterial pressure sensing. In particular, veneous pressure is known to be equivalent to about I milliliter of mercury and arterial pressure to about 250 milliliters of mercury. Because of the fact that pump 10 follows the patients pressure but does not exceed it, there is no need for the provision of any additional pressure balancing arrangements.

In the system shown in FIG. 1, pump 10 functions to deliver a continuous or constant flow of saline solution from reservoir 21 through tubing 17 to catheter 22 at the rate of about l2 milliliters per hour. It is important to note that the flow is continuous, not pulsating. A pulsating flow would activate transducer 23 periodically in addition to the activation provided by the heartbeats of the patient. This, in turn, would give rise to additional electrical signals either added to or interspersed between signals produced in response to the patients heartbeat with the result that the indication from readout equipment 24 would become confused and distorted. Pump 10 of the present invention, by virtue of its delivery ofa continuous, nonpulsating output, prevents any confusion or distortion in the indication of the patients heartbeat. Furthermore, any reverse flow of saline solution, i.e. in a direction from catheter 22 to pump 10, is prevented by the structural relationship between tubing 17 and pump 10.

FIGS. 2-11 show in detail the specific structure of pump 10 of the present invention. Pump body 11, as shown in FIGS. 2-4, is generally cylindrical in shape and can be formed from any suitable material such as aluminum. A plurality of internally threaded bores 29 can be provided in one axial end face of body 11 for the purpose of attachment to a suitable support such as that designated 18 in FIG. 1. A relatively large diameter, central bore 30 is provided through this same end face for the purpose of receiving a bearing 31, and drive shaft 14 is journaled therein as seen in FIG. 4. The opposite axial end of body 11, in which annular recess 12 is formed, is provided with a hublike portion 32 extending from the innermost wall of recess 12 in an axial direction slightly beyond the point of termination of the outer wall of body 11. A bore 33 is provided in the axial end face of hub 32 through which drive shaft 14 extends. Referring back to FIG. 2, opening 13 includes a first portion 13a which is slightly elongated in a direction perpendicular to the axis of body 11 and a second portion 13b disposed parallel to the axis of body 11 and extending from portion 13a to the axial end face of the outer wall of body 11. In other words, the length or extent of opening 13 in a direction parallel to the axis of body 11 is about equal to the axial length of recess 12.

Sleeve 16 likewise is formed from any suitable material, for example aluminum, and has an outer diameter slightly less than the diameter of the outer surface of annular recess 12 provided in body 11. Sleeve 16 has an axial end face 34, shown in FIG. 4, of a radial width or thickness slightly less than the radial width of annular recess 12 in pump body 11. The wall of sleeve 16 defining end face 34 is of constant width to a point about midway along the axial length of sleeve 16 whereupon it meets a wall 35 disposed perpendicular with respect to the axis of sleeve 16 and provided with a central bore 36 therein through which pump drive shaft 14 extends. The sleeve wall extending from wall 35 through the remaining axial length of sleeve 16 has a slightly smaller radial width and defines therein a region or chamber 37 which receives a bearing 38 for the purpose of mounting drive shaft 14. The edges of sleeve end face 34 should be smoothed so as to prevent destructive wear of flexible tubing 17 with which it comes in contact.

Pump drive shaft 14 comprises two parts or sections connected together as shown most clearly in FIG. 4. The drive shaft part which enters pump body 11 from the left-hand side in FIG. 4 includes a rod 42 provided with threads 43 at one end thereof and connected at the other end in a hollow cylindrical member 44 which is provided with a notch 45 in the end thereof opposite the end in which rod 42 is connected. Notch 45, which is disposed perpendicular to the axis of rod 42, facilitates connection of shaft part 40 to the output shaft of a drive means such as motor 19 shown in FIG. 1.

The part of drive shaft 14 which enters sleeve 16 from the right-hand side in FIG. 4 is shown in more detail in FIGS. 6 and 7 and includes four sections along an axis 50 and having a common axial bore 51 therethrough. A first section comprises a knurled knob 52 which is disc-shaped and concentric with respect to axis 50. A second section comprises a camming element 54 in the form of a generally cylindrical member having end faces 55 and 56. The cylinder wall is concentric with respect to axis 50, and end face 55, which abuts an end face of knob 52, is disposed in a plane perpendicular with respect to axis 50. The opposite axial end face 56 is disposed in a plane which, in turn, is disposed at a slight acute angle, depending upon the degree of nutation required, with respect to a plane perpendicular to axis 50. The degree of nutation required is dependent upon the diameter of flexible tubing 17 and desired flow rate. In the particular example of FIG. 1 with a desired flow rate of l milliliter per hour and with tubing 17 having a diameter of one-eighth inch, end face 56 lies in a plane disposed at an angle of 2 with respect to a plane perpendicular to axis 50.

The drive shaft part includes a third section in the form of camming element 57 which likewise is generally cylindrical, having a wall'and end faces 59, 60. To provide the required described, the wall axis is disposed at an angle of two degrees with respect to axis 50. End face 59 is coincident with end face 56 of camming element 54 and this is disposed in a plane extending at an angle of 2 with respect to a plane perpendicular to axis 50. End face 60 is disposed in a plane perpendicular with respect to axis 50. The drive shaft part is completed by a fourth section in the form of cylinder 61 which is concentric with respect to axis 50. Internal threads are provided along the portion of bore 51 common to knob 52 and camming element 54 for engagement with corresponding threads on rod 42 when the two parts of drive shaft 14 are connected together.

Pump of the present invention is assembled in the following manner. The part of drive shaft 14 located at the left-hand side in FIG. 4, in particular rod 42, is rotatably positioned in bearing 31 which, in turn, is fixedly mounted in bore 30 of pump body 11. A form of bearing found to be suitable is commercially available under the designation NICE I6l5DS. This shaft part is oriented relative to body 11 so that rod 42 extends through bore 33 in hub 32 so as to expose threads 43. The part of drive shaft 14 shown at the right in FIG. 4 is rotatably mounted in sleeve 16 by means of bearing 38 which, in turn, is fixedly mounted in region or chamber 37 of sleeve 16. A form of bearing 38 found particularly suitable is commercially available under the designation NICE I623DE. In particular, camming element 57 is rotatably mounted in bearing 38, and camming element 54 and knob 52 extend axially outward from the axial end face of sleeve 16. Bore 51 of the drive shaft part is in communication with bore 36 of sleeve 16.

Pump body would be fixedly mounted to a suitable support such as that designated 18 in FIG. 1, and cylindrical member 44 of drive shaft 14 is connected to the output shaft ofa suitable drive means, for example motor 19 in FIG. 1. With sleeve 16 and the part of drive shaft 14 rotatably mounted therein disconnected from pump body 11 and the other part of drive shaft 14, tubing 17 can be assembled .by hand in pump 10 in the following manner. A portion of tubing 17 is grasped by hand so that the longitudinal axis thereof is in a plane generally perpendicular with respect to the axis of pump body 11. This portion is moved by hand in a direction parallel to the axis of body 11 into portion 13b and then portion 13a of the opening 13. The tubing is positioned around recess 12 in pump body 11 and is wound twice around body 11 and then manipulated further by hand so as to leave pump body 11 from portion 13a of opening 13.

The manner in which tubing 17 is placed in pump body 11 may be understood. more clearly by referring to FIG. 8 which shows tubing 17 in final assembled condition in pump body 11. It will be noted from an inspection of FIG. 8 that opposite edges of opening portion 13a are disposed at a slight angle, for example l5, to a line perpendicular to the axis of pump body 11 and to the plane of opening 13. By virtue of this arrangement, tubing 17 is subjected to a more gradual bend as it enters and leaves pump body 11 than would be the case if opening 13 included entirely right angle junctions with the inner surface of recess 12.

When tubing 17 has been placed in pump body 11, pump 10 is assembled further into completed form in the following manner. Sleeve 16 is grasped and moved toward pump body to a position where the threads 43 of rod 42 are ready for engagement with the threads in bore 51. A simple manual rotation of knob 52 then moves sleeve 16 and the drive shaft part carried thereby axially toward pump body 11 by virtue of the engagement between the corresponding threads ofrod 42 and bore 51. The extent of axial movement is sufficient so that axial end face 34 of sleeve 16 extends partially into recess 12 thereby defining an annular region which contains tubing 17.

Pump 10 of the present invention operates in the following manner. In response to rotation of drive shaft 14, sleeve 16 is nutated about the axis of shaft 14, as shown in FIG. 9. The angle of nutation, which in this particular example is 2, is determined by the degree of inclination of the particular end faces of camming elements 54 and 57 as previously described. As a result, the annular region definedby'recess 12 in pump body 11 and axial end face-of sleeve 16 is varied in volume from a maximum to a minimum in a direction around the circumference thereof. This, in turn, causes a corresponding release and compression of flexible tubing 17 positioned in the annular region as illustrated further in FIGS. 10a and 10b.

The manner whereby pump 10 of the present invention delivers a uniform or continuous, not pulsating, output flow is illustrated in FIGS. 11A and 11B by means of a comparison with prior methods of positioning flexible tubing in a pump of this general type. FIG. 11A shows schematically a length of flexible tubing 70 extending around the annular region in a pump body 71 of this general type for about only one circumferential length of the region. Arrow 72 indicates the direction along which tubing 70 is compressed in response to nutating movement of the pump member. It will be noted that a discontinuity or open space is present along tubing 70 between bends 70a and 70b which correspond to the exit and entry points, respectively, of tubing 70 in the pump body. More particularly, as tubing 70 is compressed along the direction indicated by the arrow in FIG. 11A by means of the nutating pump member, the portion of tubing 70 near bend 70a is compressed flrst while the portion near bend 70b is in its normally open or relaxed condition. Further travel of the tube contacting portion of the nutating member is across the gap or space toward the tube portion atbend 70b whereupon that portion is compressed and the portion near bend 70a is released. Because of the gap or space between bends 70a and 70b, the tube portion near bend 70a can open from its previously compressed condition before the tube portion near bend 70b is compressed. This, in turn, allows a flow through tubing 70 in a reverse direction, i.e. from load to source, relative to the direction desired. The periodic flow reversal causes the pump to deliver a pulsating or nonuniform flow.

FIG. 118 shows schematically the manner in which flexible tubing 17 is positioned in the pump 10 of the present invention whereby a continuous, nonpulsating output flow is delivered. Flexible tubing 17 is in a single length and extends through opening 13 in pump body 11 and around the annular region therein. The length of tubing 17 in the annular region is greater than one circumferential length of the region by an amount such that during one complete rotation of the pump shaft, a portion of the length of tubing 17 in the region always will be compressed by an amount sufficient to prevent any reverse flow. In other words, tubing 17 enters pump body 11, extends around pump body 11 for a length greater than one circumferential length of the annular region therein, passing the point of entry, and exits from pump body 11 at a point positioned circumferentially beyond the point of entry. As shown in FIG. 11B, tubing 17 preferably is wound around nearly two circumferential lengths of the annular region in the pump body thus permitting entry and exit of the tubing through the same opening in the pump body. As the nutating member, specifically pump sleeve 16, moves in the direction of the arrow in FIG. 118, the portion of tubing 17 near bend 17a can open from its previously compressed condition before the tube portion near bend 17b is fully compressed. But, the portion of the length of tubing 17 which extends along the circumferential length of the annular region between the bends 17a and 17b prevents any reverse flow. This is because portion 17c will be compressed by sleeve 16 as it travels across the gap or space between the bends 17a and 17b in tubing 17. As a result, a portion of tubing 17 always will be compressed during each rotation of the pump shaft thereby preventing any reverse flow of fluid through tubing 17.

In addition to a uniform or continuous output flow, there are several other significant advantages provided by the construction of pump 10 of the present invention. It will be recalled that sleeve 16, the end face 34 of which contacts and compresses tubing 17, is rotatably mounted on pump drive shaft 14. In particular, cam element 57 is journaled in bearing 38 which is fixed in region 37 of sleeve 16. The rotatable mounting of sleeve 16 on pump drive shaft 14 minimizes the frictional drag between sleeve end face 34 and tubing 17 which otherwise would be ofa large amount if sleeve 16 were fixedly mounted on shaft 14. This, in turn, prevents any destructive wear of tubing 17.

The rotatable mounting of sleeve 16 on shaft 14 also prevents "creeping" of tubing 17, in other words movement of tubing 17 along the annular region in pump body 11. This is because frictional drag between sleeve end face 34 and tubing 17 is minimized. By virtue of this arrangement creeping" is prevented without the need to anchor tubing 17 in pump 10 which would otherwise complicate removal and insertion of tubing 17 in pump 10.

It is therefore apparent that the present invention accomplishes its intended objects. While a single specific embodiment of the present invention has been described in detail, this has been done by way of illustration without thought oflimitation.

We claim:

1. A pump for delivering a continuous output flow comprismg:

a. a generally cylindrical pump body provided with an annular recess open at one axial end face thereof and with an opening through the wall of said body communicating with said annular recess;

b. a drive shaft rotatably mounted in said pump body and disposed so that the axis thereof is coincident with the axis of said annular recess;

c. a sleeve having an outer diameter slightly less than the diameter of the outer surface of said annular recess in said pump body and having an axial end face of a radial width less than the radial width of said annular recess, said sleeve being mounted for nutating movement about the axis of said drive shaft and at an axial position thereon so that said sleeve extends partially into said annular recess in said pump body so as to define an annular region therein;

d. whereby upon rotation of said shaft said sleeve is nutated about the axis of said shaft; and

e. a single length of flexible tubing extending through said opening in the wall of said pump body so as to enter said annular region therein, said tubing extending around said annular region for a length greater than one circumferential length of said annular region by an amount such that during one complete rotation of said shaft a portion of the length of said tubing in said annular region always will be compressed by said sleeve sufficiently to prevent any reverse flow.

2. A pump as defined in claim 1 wherein the point of exit of said tubing from said pump body is positioned circumferentially beyond the point of entry of said tubing into said pump body.

3. A pump as defined in claim 1 wherein said flexible tubing leaves the annular region in said pump body through the same opening in the wall of said body through which it enters.

4. A pump as defined in claim 1 wherein said sleeve is rotatably mounted on said drive shaft.

5. A pump as defined in claim 1 wherein said drive shaft comprises:

a. a first part rotatably mounted in said pump body; and

b. a second part rotatably mounted in said sleeve and having first and second axially adjacent camming elements on which said sleeve is connected for nutating movement.

6. A pump as defined in claim 5 wherein said first and second drive shaft parts are threadably connected together.

Claims (6)

1. A pump for delivering a continuous output flow comprising: a. a generally cylindrical pump body provided with an annular recess open at one axial end face thereof and with an opening through the wall of said body communicating with said annular recess; b. a drive shaft rotatably mounted in said pump body and disposed so that the axis thereof is coincident with the axis of said annular recess; c. a sleeve having an outer diameter slightLy less than the diameter of the outer surface of said annular recess in said pump body and having an axial end face of a radial width less than the radial width of said annular recess, said sleeve being mounted for nutating movement about the axis of said drive shaft and at an axial position thereon so that said sleeve extends partially into said annular recess in said pump body so as to define an annular region therein; d. whereby upon rotation of said shaft said sleeve is nutated about the axis of said shaft; and e. a single length of flexible tubing extending through said opening in the wall of said pump body so as to enter said annular region therein, said tubing extending around said annular region for a length greater than one circumferential length of said annular region by an amount such that during one complete rotation of said shaft a portion of the length of said tubing in said annular region always will be compressed by said sleeve sufficiently to prevent any reverse flow.

2. A pump as defined in claim 1 wherein the point of exit of said tubing from said pump body is positioned circumferentially beyond the point of entry of said tubing into said pump body.

3. A pump as defined in claim 1 wherein said flexible tubing leaves the annular region in said pump body through the same opening in the wall of said body through which it enters.

4. A pump as defined in claim 1 wherein said sleeve is rotatably mounted on said drive shaft.

5. A pump as defined in claim 1 wherein said drive shaft comprises: a. a first part rotatably mounted in said pump body; and b. a second part rotatably mounted in said sleeve and having first and second axially adjacent camming elements on which said sleeve is connected for nutating movement.

6. A pump as defined in claim 5 wherein said first and second drive shaft parts are threadably connected together.

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