US20090162228A1

US20090162228A1 - Guide element for a peristaltic pump

Info

Publication number: US20090162228A1
Application number: US12/003,000
Authority: US
Inventors: James E. Nelson; Faez J. Shukur; Robert R. Voltenburg, JR.
Original assignee: Individual
Current assignee: Delphi Technologies Inc
Priority date: 2007-12-19
Filing date: 2007-12-19
Publication date: 2009-06-25

Abstract

A guide element for a peristaltic pump includes a base and a plurality of spindles established on a surface of the base. The spindles are positioned substantially normal to the surface of the base and project outward from the surface. The spindles are also configured to locate a journal formed in a respective one of a plurality of rollers. The guide element is configured to guide the rollers when the rollers are rotating.

Description

BACKGROUND

The present disclosure relates generally to peristaltic pumps, and more particularly to a guide element for a peristaltic pump.
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. The rollers revolve together in the cassette when rotationally driven by a drive shaft. A flexible tubing is disposed around a portion of the assembly of rollers and exerts a force against the rollers in contact therewith to generally 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.
In some instances, a roller may not directly contact the tubing. In this case, the roller(s) may undesirably move or shift and lose proper contact with the drive shaft, and/or a roller may undesirably contact an adjacent roller. These occurrences may cause errors in various pumping operations, thereby potentially diminishing the overall performance of the pump.

SUMMARY

A guide element for a peristaltic pump including a plurality of rollers is disclosed. The guide element includes a base and a plurality of spindles established on a surface of the base. The plurality of spindles is positioned substantially normal to the surface of the base and projects outward from the surface of the base. Each of the plurality of spindles is configured to locate a journal formed in a respective one of the plurality of rollers.

BRIEF DESCRIPTION OF THE DRAWINGS

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.

FIG. 1 is a semi-schematic perspective view of an exemplary rotary-style peristaltic infusion pump for use in the present disclosure;

FIG. 2 is a semi-schematic top view of a disposable pump cassette including a configuration of an assembly of rollers received within a cavity formed in the cassette;

FIG. 2A is a semi-schematic top view of the disposable pump cassette including another configuration of the assembly of rollers received within a cavity formed in the cassette;

FIG. 3 is a perspective, top view of a guide element according to an embodiment of the present disclosure;

FIG. 4 is a perspective, bottom view of the guide element of FIG. 3; and

FIG. 5 is a cutaway top view showing an example of a guide element assembled to the peristaltic pump of FIG. 1.

DETAILED DESCRIPTION

Example(s) of the guide element and the method of guiding a plurality of rollers for a peristaltic pump including the guide element as disclosed herein advantageously guide and/or locate a plurality of rollers during rotational movement of a drive shaft to thereby maintain contact of the rollers with the drive shaft, and/or prevent a roller from contacting an adjacent roller. The guide element may also improve the overall performance of the peristaltic pump and enable the pump to achieve higher precision in fluid volume delivery. The guide element is also advantageously simple to fabricate and to incorporate into the pump assembly. Further, unlike previous guide elements where the guide element is attached to the drive shaft and is the only part that carries the rollers around, the guide element of the present disclosure is actually carried around by the rollers, which in turn are moved by the drive shaft. As such, the guide element of the present disclosure generally only carries a roller when a roller loses contact with the drive shaft (e.g., when a roller is not in contact with the tubing, such as in or adjacent to the 6 o'clock position).
With reference now to the drawings, FIG. 1 provides a rotary-style peristaltic infusion pump 10 including a disposable pump cassette 12 supported within a cassette receiving cavity (not shown) formed into a pump housing 14. A pump motor 16, disposed within the pump housing 14, drives rotational movement of a drive shaft 18. The drive shaft 18 extends through a bore (not shown) formed in the pump housing 14, through the cassette receiving cavity, and through a bore (not shown) formed in the cassette 12.
As shown in FIG. 2, the cassette 12 includes a base 22 and a wall 24, thereby defining a generally cylindrically-shaped cavity 26 therein. A flexible or otherwise compressible tubing 28 is disposed through an inlet 30 of the cassette 12, around a substantial portion of an inner surface 32 of the wall 24, and through an outlet 34. The tubing 28 is generally disposable and is often made of a polymeric material, non-limiting examples of which include silicones, AUTOPRENE (an opaque thermoplastic rubber with high wear resistance derived from SANTOPRENE, commercially available from Advanced Elastomer Systems, a subsidiary of ExxonMobil Chemical located in Houston, Tex.), VITON (a black fluoroelastomer with resistance to concentrated acids, solvents, ozone, radiation and temperatures up to 200° C. with good chemical compatibility, commercially available from DuPont Performance Elastomers located in Wilmington, Del.), TYGON (good chemical resistance with a clear finish, commercially available from Saint-Gobain Performance Plastics Corporation located in Akron, Ohio), PROTHANE II (a transparent, blue, polyester, polyurethane tubing with good chemical resistance, commercially available from Randolph Austin Company located in Manchaca, Tex.), and/or the like, and/or combinations thereof. The inner diameter of the tube 28 may be selected based on the desirable flow rates and the desirable viscosities of the fluid that will flow therethrough.
An assembly 36 of satellite rollers 38 is received within the cavity 26 of the cassette 12 and abuts a substantial portion of the tubing 28. Each roller 38 includes a generally cylindrically-shaped body 42 including an outer surface 40 and an inner surface 41, a cavity 44 defined by the inner surface 41, and opposed generally cylindrically-shaped ends. At least a portion of the outer surface, 40 of the roller 38 may be contoured (as best shown in FIG. 4). In an embodiment, one of the opposed ends 46 is open, and the other opposed end 47 is closed. However, it is to be understood that both opposed ends 46, 47 may be open if desired. It is to be understood that the rollers 38 rotate both individually and rotate as an assembly inside the cavity 26 of the cassette 12.
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 FIG. 2, the rollers 38 are also arranged in parallel configuration with respect to the drive shaft 18 and the journal 48 of each roller 38. It is to be understood that the journal 48 may extend through, or partially into the respective roller 38, as desired. In an embodiment, the rollers 38 are made from a polymeric material such as, for example, acetal, polytetrafluoroethylene (e.g., Teflon® manufactured by E.I. du Pont de Nemours and Company, Wilmington, Del.), or the like, or combinations thereof. However, it is to be understood that any suitable material may be used, as desired.
In an embodiment, e.g., as shown in FIG. 4, the rollers 38 may include a radial flange 49 formed on one or both cylindrically- shaped ends 46, 47, where the radial flange 49 protrudes radially outwardly from the periphery of the ends 46, 47.
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 upon rotation of the drive shaft 18. The roller assembly (e.g., a spider roller assembly) 36 (i.e., the rollers 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 when the roller assembly 36 and the individual rollers 38 are all rotating. Fluid is trapped in the tubing 28 between two points of occlusion (i.e., from one roller 38 to an adjacent roller 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.
In every revolution of the roller assembly 36, each roller 38 disengages the tube 28 generally between the five o'clock and the seven o'clock positions (e.g., as shown in FIG. 2).
As shown in FIG. 2A, a roller 38′ is located at the six o'clock position (i.e., a position between the five o'clock and the seven o'clock positions). Since (in this position) the tubing 28 is not generating a radially inward force against the roller 38′ to thereby hold the roller 38′ against the drive shaft 18, the roller 38′ may shift or slightly move within the cavity 26. As such, the roller 38′ may lose desirable contact with the drive shaft 18 and may slip when the drive shaft 18 rotates. This situation may, in some instances, cause the rollers 38 to slip when the drive shaft 18 rotates.
When the rollers 38, 38′ lose frictional contact with the drive shaft 18, the rollers 38, 38′ may also contact one another. Contact between two rollers 38, 38′ may lead to jamming of the rollers 38, 38′. In either situation (i.e., slipping or jamming), the overall performance of the peristaltic pump 10 may be deleteriously affected.
In accordance with the present disclosure, jamming or slipping of the rollers 38, 38′ may be corrected or lessened by including a guide element 50 into the cassette 12.
With reference now to FIGS. 3-5, the guide element 50 includes a base 52 and a plurality of spindles 54 projecting substantially outward or away from a first surface 56 of the base 52, wherein each spindle 54 is configured to locate the cavity 44/journal 48 of a respective roller 38, 38′. The guide element 50 may also be referred to as a spider assembly, a carrier, or a planetary carrier.
The base 52 of the guide element 50 may be a plate or disc including the first surface 56 (as shown in FIG. 4) and a second surface 58 (as shown in FIG. 3). The first surface 56 may be generally flat and includes the plurality of spindles 54 formed or otherwise established thereon, wherein the spindles 54 may blend into the surface 56. The second surface 58 may also be generally flat, though alternative shapes or configurations may be employed. As a non-limiting example, the surface 58 may include contours that would complement the inner surface of a cover (not shown) that may be placed over and secured to the cavity 26 of the cassette 12.
The base 52 also includes an outer edge 60 and an inner edge 62, wherein the inner edge 62 defines a bore 64. It is to be understood that the bore 64 is not essential to the operative function of the guide element 50. In an embodiment, the bore 64 simply provides clearance for the drive shaft 18, as the drive shaft 18 may project higher than the rollers 38, 38′ and, thus, a spacing or bore 64 is necessary to accommodate the length of the drive shaft 18. In another non-limiting example, the guide element 50 does not include a bore 64.
The edge 60 of the base 52 may be formed in any geometric shape so that the guide element 50 can suitably be received within the cassette 12, and the spindles 54 can be arranged on the base 22 in any configuration to be operatively received within the cavity 44 of its respective roller 38, 38′. As a non-limiting example, and as shown in FIGS. 3-5, the edge 60 of the base 52 generally includes a rounded or circular shape.
The thickness of the base 52 includes any thickness that will suitably allow the guide element 50 to function properly when the pump 10 is operating. The base 52, however, should also be thin enough to fit within the cassette 12 and to provide suitable clearance between the guide element 50 and the cover of the cassette 12. If the cover touches the guide element 50, then the guide element 50 as well as the pump 10 may not work properly if such contact creates undesirable dragging, catching, or substantial amounts of friction. In an embodiment, the base 52 may have a thickness ranging from about 0.5 mm to about 1.5 mm.
The spindles 54 are established on the base 52 and radially distributed around the bore 64. The number of spindles 54 is determined based on the number of rollers 38, 38′ used in the cassette 12. As shown in FIG. 5, three rollers 38, 38′ are provided and, thus, the guide element 50 includes three spindles 54, where a single spindle corresponds to a respective single roller 38, 38′. It is to be understood that any number and/or configuration of spindles 54 may be established on the base 52 of the guide element 50 depending on the number and/or configuration of the rollers 38, 38′ used in the cassette 12.
The spindles 54 are generally provided as projections positioned substantially normal to the first surface 56 of the base 52, and extend outwardly from the first surface 56. Spindles 54 may have a length about equal to or less than the length of the cylindrical body 42 of the rollers 38, 38′. As a non-limiting example, the spindles 54 may have a length ranging from about 4 mm to about 6 mm.
As shown in FIG. 4, the spindles 54 include an outer surface 66, an inner surface 68 and an end 70. The shape of the outer surface 66 generally conforms to the shape of the inner surface 41 (which surface 41 forms the journal 48) of the rollers 38, 38′ such that the spindles 54 will slidingly engage the rollers 38, 38′. As shown in FIG. 2, the inner surface 41 of the rollers 38, 38′ is rounded and, thus, the outer surface 66 of the spindles 54 (as shown in FIG. 4) is also rounded. The complementary shapes of the two surfaces 41, 66 facilitate easy rotation of the rollers 38, 38′ when the guide element 50 is placed in the cassette 12, where the rounded surfaces 41, 66 will “slide” when the surfaces 41, 66 are in contact. In an embodiment, the outer surface 66 may be substantially smooth (although some roughness may be acceptable, for example resulting from molding processes) to facilitate desirable sliding engagement with the rollers 38, 38′.
The inner surface 68 of the spindle 54 has any suitable shape that will facilitate easy operation of the guide element 50 while operatively placed in the cassette 12. As shown in FIG. 4, the inner surface 68 of the spindle 54 may be generally concave.
The guide element 50 may be integrally formed. Such integral forming may be accomplished by any suitable molding techniques such as, for example, injection molding, machining or the like. The guide element 50 may also be formed from any suitable polymeric material, non-limiting examples of which include engineered polymeric materials (e.g., ABS), thermoplastic materials, or thermoset materials. In an embodiment, guide element 50 may be formed from polytetrafluoroethylene (PTFE), acetal, polypropylenes, and/or the like, and/or combinations thereof.
With reference now to FIG. 5, an example assembly of the guide element 50 with the peristaltic pump 10 is shown. The drive shaft 18 protrudes through a bore formed into the pump housing 14 and through the cavity 26 of the cassette 12. In the cassette 12, the tubing 28 is fed through the inlet 30, around the inner surface 32 of the wall 24, and through the outlet 34. The plurality of rollers 38, 38′ are radially arranged within the cavity 26 of the cassette 12 around and in frictional engagement with the drive shaft 18 and also abutting a portion of the tubing 28. The guide element 50 is disposed over the rollers 38, 38′, where each spindle 54 of the guide element 50 is received within a respective journal 48 of the rollers 38, 38′. A cover (not shown) may be disposed over the guide element 50 and may be latched or otherwise fixed to the wall 24 of the cassette 12.
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 guide element for a peristaltic pump including a plurality of rollers each having a journal formed therein, the guide element comprising:

a base; and

a plurality of spindles established on a first surface of the base and positioned substantially normal to the first surface, the plurality of spindles projecting outwardly from the first surface, each of the plurality of spindles configured to locate the journal of a respective one of the plurality of rollers.

2. The guide element as defined in claim 1 wherein the guide element is a spider assembly.

3. The guide element as defined in claim 1 wherein the base has a thickness ranging from about 0.5 to about 1.5 mm.

4. The guide element as defined in claim 1 wherein the base further includes a second surface opposed to the first surface, wherein the second surface is substantially flat or contoured.

5. The guide element as defined in claim 1 wherein the base further includes a first edge having a substantially rounded shape and a second edge defining a bore in the base, wherein the plurality of spindles are radially distributed around the bore.

6. The guide element as defined in claim 1 wherein each of the plurality of spindles further includes a length substantially equal to or less than a length of each of the plurality of rollers.

7. The guide element as defined in claim 1 wherein the plurality of spindles projects substantially perpendicularly from the first surface of the base.

8. The guide element as defined in claim 1 wherein each of the plurality of spindles further includes a surface configured to slidingly engage the journal of a respective one of the plurality of rollers.

9. The guide element as defined in claim 1 wherein the base and the plurality of spindles are integrally formed by injection molding.

10. The guide element as defined in claim 1 wherein the guide element is formed from one of engineered polymeric materials, thermoplastic materials, thermoset materials, or combinations thereof.

11. The guide element as defined in claim 1 wherein the guide element is configured to guide the plurality of rollers when the plurality of rollers is rotating.

12. A method of guiding a plurality of rollers for a peristaltic pump, wherein the peristaltic pump includes a drive shaft, the method comprising:

arranging the plurality of rollers around the drive shaft;

placing a guide element on the plurality of rollers, wherein the guide element includes a base and a plurality of spindles established on a first surface of the base, wherein each of the plurality of spindles is positioned substantially normal to the first surface and projects outward from the first surface, and wherein each of the plurality of spindles is configured to locate a journal formed in a respective one of the plurality of rollers; and

rotating the drive shaft to impart rotational movement to the plurality of rollers.

13. The method as defined in claim 12, further comprising guiding the plurality of rollers with the guide element when the plurality of rollers is rotating.

14. The method as defined in claim 12, further comprising separating each of the plurality of rollers from an adjacent roller.

15. The method as defined in claim 12, further comprising maintaining rotational movement about the drive shaft of a roller not in frictional contact with the drive shaft.

16. 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 plurality of rollers operatively disposed within the cavity of the cassette and arranged around a drive shaft; and

a guide element including a base and a plurality of spindles established on a first surface of the base, wherein the plurality of spindles are positioned substantially normal to the first surface and project outward from the first surface, each of the plurality of spindles being configured to locate a journal formed in a respective one of the plurality of rollers.

17. The assembly as defined in claim 16 wherein the base of the guide element further comprises a second surface opposed to the first surface, wherein the second surface is substantially flat or contoured.

18. The assembly as defined in claim 16 wherein the base of the guide element further includes a first edge having a substantially rounded shape and a second edge defining a bore in the base, wherein the plurality of spindles established on the base is radially distributed around the bore.

19. The assembly as defined in claim 16 wherein the plurality of spindles of the guide element projects substantially perpendicularly from the first surface of the base.

20. The assembly as defined in claim 16 wherein the plurality of spindles of the guide element further includes a surface configured to slidingly engage the journal of a respective one of the plurality of rollers.