Peristaltic pump assembly
A peristaltic pump assembly includes a cassette configured to be operatively engaged with a pump housing. A roller assembly is operatively disposed within a cavity formed into the cassette. The roller assembly includes a plurality of rollers that may be arranged in a planetary configuration around a drive shaft. At least one guide element is disposed about the periphery of the roller assembly and in engagement with at least a portion of an outer surface of each of the plurality of rollers. The guide element is configured to guide the plurality of rollers when the plurality of rollers is rotating.
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The present disclosure relates generally to peristaltic pumps and, more particularly, to a peristaltic pump assembly.
Rotary-style peristaltic infusion pumps are often used to deliver fluid in a very controlled manner such as, for example, the intravenous delivery of medicine to a patient. These peristaltic pumps typically include a disposable pumping cassette and an assembly of radially arranged rollers received within a cavity of the cassette, wherein the rollers revolve together when rotationally driven by a drive shaft operated by a pump motor. A flexible tubing is disposed around a portion of the assembly of rollers and generally exerts a force against the rollers in contact therewith to thereby hold the rollers against the drive shaft.
In response to rotational movement of the rollers, portions of the flexible tube that are in contact with the rollers compress or otherwise occlude against a wall of the cassette. As a result, fluid traveling through the tube is temporarily trapped in the tube between the occluded points. The trapped fluid is released from the tube when the occlusion force on the tube is released. In this manner, fluid is urged through the tube via peristaltic wave action.
Sometimes a roller may not directly contact the tubing. In this instance, the roller(s) may undesirably move or shift and lose proper contact with the drive shaft. This could cause errors in various pumping operations, which may diminish the overall performance of the pump.
SUMMARYDisclosed herein is a peristaltic pump assembly including a cassette configured to be operatively engaged with a pump housing. A roller assembly is operatively disposed within a cavity of the cassette and includes a plurality of rollers that may be arranged in a planetary configuration around a drive shaft. At least one guide element is disposed about the periphery of the roller assembly and in engagement with at least a portion of an outer surface of each of the plurality of rollers.
Features and advantages of embodiment(s) of the present disclosure will become apparent by reference to the following detailed description and drawings, in which like reference numerals correspond to similar, though perhaps not identical components. Reference numerals having a previously described function may or may not be described in connection with other drawings in which they appear.
Embodiment(s) of the peristaltic pump assembly as disclosed herein advantageously guide and/or locate a plurality of rollers of a roller assembly in response to rotational movement of a drive shaft to thereby maintain contact of the rollers with the drive shaft. The guide element may also improve the overall performance of the peristaltic pump by, for example, enabling the pump to achieve higher precision in fluid volume delivery. The guide element is also relatively simple to incorporate into the pump assembly.
With reference now to the drawings,
As shown in
Referring also to
The rollers 38 are radially arranged in the cavity 26 around the drive shaft 18 that protrudes into the cavity 26 through the bore (not shown) formed into the base 22 of the cassette 12. As shown in
In an embodiment, e.g., as shown in
The drive shaft 18 is generally knurled, roughened, and/or etched, or otherwise configured to frictionally engage the outer surface 40 of each roller 38, 38′ upon rotation of the drive shaft 18. The roller assembly 36 (i.e., the rollers 38, 38′ operating as a single unit) thus rotates in response to rotational movement of the drive shaft 18.
When the pump 10 is operating, rotational movement of the roller assembly 36 pumps the liquid through the tubing 28 to create a pressurized flow thereof. The tubing 28 compresses or otherwise occludes at a number of points in contact with the rollers 38, 38′ when the roller assembly 36 and the individual rollers 38, 38′ are all rotating. Fluid is trapped in the tubing 28 between two points of occlusion (i.e., from one roller 38, 38′ to an adjacent roller 38, 38′). The trapped fluid is passed or moved through the tubing 28 via peristaltic wave action at a flow rate determined by the rotational rate (rpm) of the drive shaft 18, and released when the tubing 28 is no longer occluded by the rollers 38, 38′.
In every revolution of the roller assembly 36, each roller 38, 38′ disengages the tubing 28 generally between the five o'clock and the seven o'clock positions (e.g., as shown in
As shown in
Referring now to
The guide element 50 may be described as a continuous member that surrounds the entire periphery of the roller assembly 36. In an embodiment, the guide element 50 may be two bands (e.g., O-rings), each band having a substantially circular cross section (though it is to be understood that any suitable cross-sectional shape may be used, if desired), with a diameter ranging from about 0.5 mm to about 0.7 mm (though, similarly, it is to be understood that any suitable cross-sectional size may be used, if desired). As shown, guide elements 50 may be received within the annular notch(es) 51, if desired, to further aid in retaining the guide element(s) 50 in a desirable position. Although two guide elements 50 are shown in
The guide element 50 may be fabricated from any suitable elastomeric material. In a non-limiting embodiment, the guide element 50 is formed from polymeric materials, e.g., silicones, natural or synthetic rubbers, and/or the like, and/or combinations thereof. The polymeric materials are generally flexible.
The guide element 50, formed from the selected elastomeric material(s), is stretched around the rollers 38, 38′, and generally provides a force that pushes the rollers 38, 38′ into suitable contact with the drive shaft 18. The guide element 50 is generally useful when the rollers 38, 38′ are not in contact with the tubing 28 (e.g., at about the “6 o'clock” position) and may lose contact with the drive shaft 18. This is the position at which the rollers 38, 38′ (if they did not have guide element 50 therearound) may stall and may then cause a jam when the roller 38, 38′ behind the stalled one tries to push it along. Thus, the guide element 50 generally engages the outer surface 40 of the rollers 38, 38′, wherein any friction between the outer surface 40 and the guide element 50 is overcome by driving forces of the drive shaft 18. The guide element(s) 50 also rotate as the rollers 38, 38′ rotate, similar to a belt in a pulley.
In an embodiment, the guide element 50 is formed from an elastomeric polymeric material wherein the material is configured to stretch a predetermined amount beyond its relaxed state so as to minimize the normal force created. In contrast, higher normal forces created by stretching the material more than the predetermined amount may in some instances require an undesirable amount of power to drive the rollers, which may in turn undesirably reduce the battery life. In an embodiment, the predetermined amount is about 5% beyond the material's relaxed state.
Still referring to
In other embodiments, as mentioned above, one, or more than one guide element 50 may be placed or otherwise disposed about the periphery of the roller assembly 36. The one or a plurality of guide elements 50 may be situated in any position against the outer surface 40 of the rollers 38, 38′; however, the guide element(s) 50 should generally not be in a position where the tubing 28 comes into contact with the rollers 38, 38′.
With reference now to
While several embodiments have been described in detail, it will be apparent to those skilled in the art that the disclosed embodiments may be modified. Therefore, the foregoing description is to be considered exemplary rather than limiting.
Claims
1. A peristaltic pump assembly, comprising:
- a cassette configured to be operatively engaged with a pump housing, wherein the cassette includes a cavity formed therein;
- a roller assembly operatively disposed within the cavity of the cassette, the roller assembly including a plurality of rollers arranged around a drive shaft, wherein each of the plurality of rollers includes an outer surface; and
- at least one guide element disposed about at least a portion of a periphery of the roller assembly and in engagement with at least a portion of the outer surface of each of the plurality of rollers.
2. The assembly as defined in claim 1 wherein the at least one guide element is a continuous member.
3. The assembly as defined in claim 1 wherein the at least one guide element surrounds the entire periphery of the roller assembly.
4. The assembly as defined in claim 1 wherein the at least one guide element is one of a ring or a washer.
5. The assembly as defined in claim 1 wherein the at least one guide element is fabricated from elastomeric materials.
6. The assembly as defined in claim 1, wherein the at least one guide element is fabricated from an elastomeric material configured to stretch a predetermined amount beyond its relaxed state so as to minimize the normal force created.
7. The assembly as defined in claim 6 wherein the predetermined amount is about 5%.
8. The assembly as defined in claim 5 wherein the elastomeric materials are polymeric materials selected from silicones, natural or synthetic rubbers, and combinations thereof.
9. The assembly as defined in claim 1 wherein the roller assembly rotates as a single unit while the at least one guide element is disposed about the periphery thereof.
10. The assembly as defined in claim 1 wherein each of the plurality of rollers includes an axis of rotation such that each roller rotates individually while the at least one guide element is disposed about the periphery of the roller assembly.
11. The peristaltic pump assembly as defined in claim 1 wherein the outer surface of each of the plurality of rollers is configured to retain the at least one guide element.
12. The assembly as defined in claim 1 wherein the at least one guide element is configured to guide the plurality of rollers when the plurality of rollers is rotating, and wherein the at least one guide element is an O-ring.
13. The assembly as defined in claim 1 wherein each of the plurality of rollers has two opposed ends and at least one radial flange protruding outwardly from at least one of the two opposed ends, and wherein the at least one radial flange is configured to retain the at least one guide element.
14. The assembly as defined in claim 1 wherein each of the plurality of rollers has two opposed ends and at least one annular notch defined in each of the rollers substantially adjacent at least one of the two opposed ends, and wherein the at least one annular notch is configured to retain the at least one guide element.
15. A method for guiding a plurality of rollers for a peristaltic pump, the peristaltic pump including a drive shaft, the method comprising:
- arranging the plurality of rollers around the drive shaft, wherein each of the plurality of rollers includes an outer surface;
- disposing at least one guide element about a periphery of the arranged plurality of rollers and in engagement with at least a portion of the outer surface of each of the plurality of rollers; and
- rotating the drive shaft to impart rotational movement to the roller assembly.
16. The method as defined in claim 15, further comprising configuring the outer surface of each of the plurality of rollers to retain the at least one guide element.
17. The method as defined in claim 15, further comprising guiding the plurality of rollers when the plurality of rollers is rotating, wherein the at least one guide element is an O-ring.
18. The method as defined in claim 15, further comprising maintaining frictional contact between the plurality of rollers and the drive shaft.
19. The method as defined in claim 15, further comprising:
- rotating the roller assembly as a single unit while the at least one guide element is disposed about the periphery thereof; and
- rotating the plurality of rollers individually while the at least one guide element is disposed about the periphery of the roller assembly.
20. The method as defined in claim 18 wherein frictional contact between the plurality of rollers and the drive shaft is maintained by the guiding of the plurality of rollers.
Type: Application
Filed: Dec 19, 2007
Publication Date: Jun 25, 2009
Applicants: , ,
Inventors: Faez J. Shukur (Gurnee, IL), James E. Nelson (North Branch, MI), Robert R. Voltenburg, JR. (Davison, MI)
Application Number: 12/002,999
International Classification: F04B 43/08 (20060101);