PUMP ASSEMBLY

Abstract

A pump assembly comprising a housing, a support frame that can be attached to the housing, and a rotor that can rotate within the housing. The housing consists of resilient material and comprises an interior surface, an inlet portion including an inlet for fluid, an outlet portion including an outlet for the fluid, and a diaphragm portion. A housing-engaging surface area of the rotor will form a sealing interference contact with the interior surface, and a chamber-forming surface area of the rotor disposed radially inward from the housing-engaging surface area will form a chamber with the interior surface. When the rotor rotates within the housing as in use, the chamber can convey fluid from the inlet portion to the outlet portion. The diaphragm portion will bear against the chamber-forming surface as the chamber-forming surface travels from the outlet to the inlet, to prevent fluid passing from the outlet to the inlet and to expel the fluid from the chamber through the outlet portion. The support frame will be attached to spaced-apart portions of the housing, and will be sufficiently stiff to counter-balance the torque applied to the housing by the rotor.

Claims

1. A pump assembly for pumping fluid comprising: a housing, a support frame that can be attached to the housing, and a rotor that can rotate within the housing; the housing consisting of resilient material and comprising: an interior surface, an inlet portion including an inlet for the fluid, an outlet portion including an outlet for the fluid, and a diaphragm portion; in which the housing and rotor are cooperatively configured such that when assembled as in use: a housing-engaging surface area of the rotor will form a sealing interference contact with the interior surface, and a chamber-forming surface area of the rotor disposed radially inward from the housing-engaging surface area will form a chamber with the interior surface; and when the rotor rotates within the housing as in use: the chamber can convey fluid from the inlet portion to the outlet portion; the rotor will apply a torque to the housing in response to the housing-engaging surface area rotating against the interior surface; and as the chamber-forming surface travels from the outlet to the inlet, the diaphragm portion will bear against it, operative to prevent fluid passing from the outlet to the inlet, and to expel the fluid from the chamber through the outlet portion; and in which the support frame is configured such that when assembled as in use, it will be attached to a plurality of spaced-apart portions of the housing, at least partly enclose the housing, and will include respective ports for the inlet portion, the outlet portion and a rotor drive shaft, and be sufficiently stiff to counter-balance the torque applied to the housing by the rotor.

2. A pump assembly as claimed hi claim 1, in which the support frame is configured such that the diaphragm portion, or an area of the interior surface will be located between the spaced-apart portions.

3. The pump assembly as claimed in claim 1, in which the spaced-apart portions comprise the inlet, and outlet portions, respectively.

4. A The pump assembly as claimed in claim 1, in which the spaced-apart portions of the housing comprise the inlet and outlet portions, respectively, and there is a gap between a rotor port portion of the support frame and an external surface of the housing, in which the rotor port portion of the support frame is configured and arranged to accommodate the rotor shaft, so that in use, the rotor can be driven by an external drive mechanism to rotate.

5. The pump assembly as claimed in claim 1, in which the support frame will be attachable to a wall portion of the housing, between the inlet and outlet portions.

6. The pump assembly as claimed in claim 1, comprising a plurality of support frames, cooperatively configured with each other and the housing, such that when assembled as in use, different support frames will be attached to different portions of the housing.

7. The pump assembly as claimed in claim 1, in which the support frame is configured and is sufficiently stiff to substantially prevent the housing from being stretched or compressed in response to a force applied to the pump assembly by one or more fluid carrying devices attached to the housing.

8. The pump assembly as claimed in claim 1, in which the housing is configured such that it is not sufficiently stiff to resist being deformed and/or rotated about the axis of rotation of the rotor in response to the torque, when the inlet and outlet portions are connected to fluid carrying devices as in use.

9. The pump assembly as claimed in claim 1, in which the housing is configured such that it will reversibly distend in response to the sealing interference contact with the housing-engaging surface of the rotor.

10. The pump assembly as claimed in claim 1, in which the support frame comprises respective attachment mechanisms for attaching coupling mechanisms for coupling the inlet and outlet portions to respective fluid carrying devices; and/or the pump assembly includes at least one coupling mechanism for coupling the inlet and outlet portions to respective fluid carrying devices.

11. The pump assembly as claimed in claim 1, in which the support frame is configured such that when assembled as in use, it will be spaced apart from an unsupported external surface area of the housing, operative to allow deformation of the unsupported external surface area in response to the distending of the housing by the rotor and the rotation of the rotor.

12. The pump assembly as claimed in claim 1, comprising a resilient biasing mechanism for flexing the diaphragm against the housing-engaging and chamber-forming surface areas of the rotor, in response to the rotation of the rotor; in which a proximal side of the resilient biasing mechanism will bear against the diaphragm portion and reciprocate along a radial direction, and a distal side of the resilient biasing mechanism will be seated against the support frame and held stationary relative to the housing.

13. The pump assembly as claimed in claim 1, in which the support frame is configured such that when assembled as in use, it will contact a supported external surface area of the housing, operative to counter-balance reaction forces generated against the housing by the reciprocation of part of a resilient biasing mechanism in response to the rotation of the rotor.

14. The pump assembly as claimed in claim 1, in which the support frame comprises a groove configured for accommodating at least a portion of a resilient biasing mechanism for urging and flexing the diaphragm portion against the rotor in use.

15. The pump assembly as claimed in claim 1, in which the support frame comprises a slot for accommodating a wall portion of the housing that extends from adjacent the diaphragm portion.

16. A pump assembly as claimed in claim 15, in which the slot is configured operative to bear against the wall portion with sufficient force to contain fluid present within the housing.

17. The pump assembly as claimed in claim 1, in which the rotor comprises the rotor drive shaft.

18. The pump assembly as claimed in claim 1, in which the support frame comprises a driver attachment mechanism for attaching the support frame to a rotor driver mechanism.

19. The pump, assembly as claimed in claim 1, in which the support frame comprises a plurality of frame members that can be assembled and disassembled.

20. The pump assembly as claimed in claim 1, comprising a plurality of support frames, each attachable to different external surface areas of the housing.

21. The pump assembly as claimed in claim 1, in which the support frame comprises material selected from the group consisting of polypropylene, polycarbonate, phenolic or epoxy resin, acetal, polyvinyl chloride (PVC), acrylonitrile butadiene styrene (ABS) or nylon material.

22. The pump assembly as claimed in claim 1, in which the diaphragm portion has a mean thickness of 0.1 to 3.0 mm.

23. The pump assembly as claimed in claim 1, in which the housing comprises a base wall portion that extends azimuthally between the inlet portion and the outlet portion, and radially from the interior surface to an external surface area of the housing; and the volume of the base wall portion is sufficiently great that pumped fluid having a pressure of up to 700 kPa can be contained within the chamber as the chamber rotates from the inlet portion to the outlet portion.

24. A pump assembly as claimed in claim 28, in which the base wall portion has a mean thickness of at least 4 times the mean thickness of the diaphragm portion.

25. The pump assembly as claimed in claim 1, in which the resilient material comprises elastomer material or thermoset material.

26. The pump assembly as claimed in claim 1, in which the resilient material comprises material selected from the group consisting of polyethylene, polypropylene, rubber modified polypropylene, plasticised polyvinyl chloride (PVC), or thermoplastic co-polyester elastomer, silicone rubber, butyl rubber, nitrile rubber, neoprene, ethylene propylene diene monomer (EPDM) rubber, or fluoroelastomer material.

27. The pump assembly as claimed in claim 1, in which the resilient material has a Young's, tensile and/or flexural modulus of 1 MPa to 1,500 MPa.

28. The pump assembly as claimed in claim 1, in which the resilient material has a nominal Shore D or Shore A hardness (durometer hardness) of 5 to 50; or a hardness of 50 Shore A to 90 Shore D.

29. The pump assembly as claimed in claim 1, in which at least part of the diaphragm portion will travel a radial distance of 0.2 to 6 mm from contacting the chamber-forming surface area to contacting the housing-engaging surface area of the rotor as the rotor rotates in use.

30. The pump assembly as claimed in claim 1, in which the chamber-forming surface of the rotor is configured such that it exhibits a concave cross-section in all planes including the axis of rotation, and a convex cross-section in all planes perpendicular to the axis of rotation.

31. The pump assembly as claimed in claim 1, in which the housing and the rotor are configured to be capable of pumping fluid at a rate of at most 0.5 millilitres per second (ml/s) when the rotor rotates at 10 revolutions per second (r.p.s.).

32. The pump assembly as claimed in claim 1, in which the rotor may comprise two or three chamber-forming surface areas, each configured to form a respective chamber (bolus) having a capacity of 1 to 10 microlitres (?l), the pump assembly capable of pumping fluid at a rate of about 0.02 to 0.3 millilitres per second at a rotor rotation rate of about 10 r.p.s.

33. The pump assembly as claimed in claim 1, in which the mean diameter of the cavity is 1 to 50 mm.

34. The pump assembly as claimed in claim 1, in which the mean diameter of the cavity is 1 to 10 mm and the resilient material has a Young's, tensile and/or flexural modulus of at most 200 MPa.

35. The pump assembly as claimed in claim 1, in which the pump is symmetrical about a plane between the inlet and the outlet portions, and including the axis of rotation of the rotor; and the rotor can be driven to rotate in either direction about the axis, operative to selectively pump fluid from the inlet to the outlet, or from the outlet to the inlet, in response to the direction of rotation of the rotor.

36. The pump assembly as claimed in claim 1, provided in kit form.

37. The part for a pump assembly as claimed in claim 1, the part comprising one or more of a housing, support frame, or member of a support frame assembly.

38. The fluid-carrier device configured for connection to a pump assembly as claimed in claim 1.

39. The fluid-conveyer assembly comprising a pump assembly as claimed in claim 1 and a fluid-carrier device configured for connection to the pump assembly.

40. A fluid-conveyor assembly as claimed in claim 39, in which the rotor comprises or can be coupled to a rotor drive shaft; the support frame comprises two, three or more interconnectable frame members; and the housing, support frame and rotor cooperatively configured such that when assembled as in use, the support frame will attach to the inlet and the outlet portions of the housing.

41. The fluid-conveyor assembly as claimed in claim 39, comprising: an inlet coupling mechanism and an outlet coupling mechanism; the inlet and outlet coupling mechanisms being cooperatively configured with the support frame and the housing, such that the inlet and outlet coupling mechanisms can be attached to the support frame adjacent the inlet and outlet ports, respectively, operable for fluid to flow through the inlet coupling mechanism and into the inlet portion of the housing, and for pumped fluid to flow from the outlet portion of the housing and through the outlet coupling mechanism.

Description

[0057] Example pump arrangements will be described with reference to the accompanying drawings, of which

[0058] FIG. 1A to FIG. 1E show various perspectives and aspects of an example pump assembly:

[0059] FIG. 1A shows a schematic external perspective view of an example pump assembly in assembled condition as in use;

[0060] FIG. 1B shows a schematic cross section view through the pump assembly in the plane A-A, which is perpendicular to the longitudinal axis about which the rotor will rotate in use (in other words, a radial or lateral plane);

[0061] FIG. 1C shows a schematic expanded view of a central area of the cross section view in FIG. 1B;

[0062] FIG. 1D shows a schematic cross section view through the pump assembly in the longitudinal plane B-B, which is parallel to the longitudinal axis about which the rotor will rotate in use;

[0063] FIG. 1E shows the view illustrated in FIG. 10, but without the rotor being present;

[0064] FIG. 2 shows a schematic expanded cross-section view of part of an example pump, the cross-section being perpendicular to the axis of rotation of the rotor

[0065] FIG. 3A shows a first schematic longitudinal cross-section perspective view of an example pump, the cross-section including a central cross-sectional plane of an example resilient biasing mechanism;

[0066] FIG. 3B shows a second schematic longitudinal cross-section perspective view A-A of the example pump of FIG. 3A, the cross-section being perpendicular to the first view;

[0067] FIG. 3C shows a schematic lateral cross-section perspective view B-B of the example pump of FIG. 3A (the cross-sections shown in FIG. 3A-3C are mutually orthogonal);

[0068] FIG. 4A shows three curves of example fluid flow rate F, in ml/s, versus diameter D, in mm, of a cylindrical rotor from just greater than 0 mm to 5 mm, in an example pump assembly in use, the three curves corresponding to rotor rotation frequencies of 1, 5 and 10 revolutions per second (r.p.s.), in which the length of the rotor is double its diameter; FIG. 4B shows similar curves for rotor diameters in the range of 5 mm to 15 mm; and FIG. 4C shows similar curves for rotor diameters in the range of 15 mm to 30 mm.

[0069] With reference to FIG. 1A to 1E, an example arrangement of a pump assembly in assembled condition (except in FIG. 1E, in which the rotor 300 is not shown), suitable for pumping liquid from a supply device (not shown) such as a tube into another device for conveying or containing fluid (not shown). A particular example pump assembly may comprise a housing 100 consisting of thermoplastic material such as polypropylene or plasticised PVC, and a support frame 200 consisting of polycarbonate or acetal material.

[0070] The housing 100 comprises a cylindrical cavity 120 defined by an interior surface and in fluid communication with the inlet of the inlet portion 102A on one side, and the outlet of the outlet portion 102B on the opposite side. The housing 100 also comprises a flexible diaphragm portion 110 disposed between the inlet and outlet portions 102A, 102B, and coterminous with the cavity 120. The diaphragm portion 110 is in the form of an elongate membrane having a substantially uniform thickness T and extending parallel to the longitudinal axis L. In the particular example shown, a pair of elongate side wall portions 114A, 114B of the housing 100 are adjacent the inlet and outlet portions 102A, 102B, respectively, and adjacent opposite respective side boundaries of the diaphragm portion 110. The side wall portions 114A, 114B are about four times thicker than the thickness T of the diaphragm portion 110 in order to support the side boundaries of diaphragm portion 110 and reduce movement when the rotor 300 rotates in use. A base wall portion 112 of the housing 100 extends azimuthally between the inlet and outlet portions 102A, 102B, and radially from the interior surface defining the cavity 120 and an external surface of the housing (an area of which is shown in contact with the support frame at 510).

[0071] In FIG. 1A, the inlet portion 102A of the housing 100 is visible and an outlet portion 102B is indicated on the opposite side of the pump assembly (not visible in FIG. 1A). In this example, the support frame 200 is generally cubic in shape and encases substantially the entire housing 100 within it (ends of the inlet and outlet portions 102A, 102B are visible). The inlet and outlet portions 102A, 102B are coaxial with each other, each including a tubular portion extending inwards from opposite sides of the pump assembly, each funnelling down to respective rectangular slits where they join the cavity 120, as shown in FIG. 1E. The inlet and outlet portions 102A, 102B are accommodated by respective cylindrical ports 202A, 202B provided in the support frame 200. The inner diameter of the ports 202A, 202B in the support frame 200 substantially matches the outer diameter of the inlet and outlet tubes 102A, 102B. Each of the ports 202A, 202B is mechanically attached to a respective inlet and outlet tube 102A, 102B, each of which fit coaxially within the respective rigid port 202A, 202B. Each of the ports 202A, 202B supports the respective inlet and outlet portion 102A, 102B, and enables it to be connected to the device for supplying or draining pumped fluid. Also visible in FIG. 1A is a splined mechanism 305 for driving a rotor 300, which will rotate in use in an anti-clockwise direction R about a longitudinal axis L that is perpendicular to the direction in which the fluid will be pumped from the inlet portion 102A to the outlet portion 102B. The support frame 200 comprises an attachment dock 202C for accommodating a rotor drive mechanism 305 for driving the rotor 300. The support frame 200 is sufficiently stiff to maintain the relative positions of the inlet portion 102A, the outlet portion 102B and the rotor drive mechanism 305 when the rotor 300 rotates as in use. The support body 200 in this example may consist of a pair of opposite members 200A, 200B, which may be similar but not necessarily identical, and which may be provided separately and attached to each other to substantially enclose the housing 100 and rotor 300. For example, the opposite halves 200A, 200B of the support body 200 may include a mechanical mechanism for snapping them together around the housing. It can be seen that this example pump is symmetrical about the plane B-B that passes between the inlet and outlet, and includes the axis of the rotor 300. In use, the direction of rotation R of the rotor 300 will be such that an area on its side surface will rotate past the diaphragm portion 110 as it travels from the outlet portion 102B to the inlet portion 102A (in other words, the inlet and outlet portions 102A, 102B can be identified solely by their positions in relation to the direction of rotation R or the rotor 300).

[0072] FIGS. 1B and 1C show schematic cross section views through the plane A-A indicated in FIG. 1A, parallel to the direction in which fluid will be pumped from the inlet device I to the outlet device O (I and O are indicated but not shown in FIG. 1B). The support frame 200 will fit around the housing 100, with the ports 202A, 202B mechanically attached to the respective inlet and outlet tubes 102A, 102B by means of respective ribs 204A, 204B projecting from the ports 202A, 202B into correspondingly configured circumferential depressions provided on the inlet and outlet tubes 102A, 102B.

[0073] In this example, the rotor 300 comprises a pair of opposite ends through the centres of which the longitudinal axis L of rotation passes, the ends being connected by a side surface that is coaxial with the longitudinal axis L. The side surface comprises a radially outer housing-engaging surface area 310 and a chamber-forming surface area 320 radially inward from the housing-engaging surface 310. In the illustrated example, the entire housing engaging surface area 310 is at a uniform radial distance from the axis (in other words, the housing-engaging surface area 310 would lie on a cylindrical surface), and the chamber-forming surface areas 320 describe a geometrically more complex profiled shape, which may be referred to as saddle-shaped.

[0074] FIGS. 1B and 1C show cross sections through the central radial plane A-A, showing the shape profiles of the housing-engaging 310 and chamber-forming 320 surface areas of the rotor in this plane A-A. In the example illustrated, the rotor 300 comprises three azimuthally equidistant chamber-forming surface areas 320, azimuthally spaced apart by three housing-engaging surface areas 310. In this example, the housing-engaging surface areas 310 form a contiguous housing-engaging surface, which surrounds each of the three chamber-forming surface areas 320, as can be seen from the orthogonal views shown in FIG. 1C and FIG. 1D. FIG. 1D shows the cross section view in the plane B-B, through the longitudinal axis L, showing a longitudinal shape profile of the housing-engaging 310 and chamber-forming 320 surface areas in this plane B-B. When viewed in central lateral cross section A-A, the chamber-forming surface area 320 has a convex profile, the mean tangential radius of which is substantially less than that of the housing-engaging surface area 310. When viewed in central axial cross section B-B, the chamber-forming surface area 320 has a concave profile.

[0075] The pump assembly includes a resilient biasing mechanism in the form of a generally elongate U-shaped member 400 consisting of elastomer material and extending along an axis parallel to the longitudinal axis L. A proximal side of the biasing member 400 comprises an elongate central rib 410, and will bear against the diaphragm portion 110, and a distal side will bear against a seat portion 210 of the support frame 200. The seat portion 210 comprises a pair of parallel, longitudinally extending slots for accommodating the feet of the biasing member 400, and the seat portion 210 is configured to hold the distal side of the biasing member 400 substantially stationary relative to the adjacent side wall portions 114A, 114B when the rotor rotates as in use. The proximal portion of the biasing member 400 will be free to reciprocate radially in response to the rotor 300 rotating against a central region of the diaphragm portion 210 in use. The biasing member 400 will apply a radial force to the diaphragm portion 210 to flex it against the side surface of the rotor 300 with sufficient force that fluid cannot pass between the diaphragm portion 210 and the surface of the rotor 300 in use.

[0076] In the illustrated example, the support frame 200 contacts the external surface of the housing 100 adjacent the ends of the inlet and outlet portions 102A, 102B, at the side walls 114A, 114B, and at a supported external surface area 510 diametrically opposite the biasing mechanism 400. The support frame 200 is spaced apart from other areas of the external surface of the housing 200 to allow the unsupported surface area to distend freely within an air gap 500 in response to the rotation of the rotor 300. In FIGS. 1D and 1E, air gaps 500A, 500D are shown at opposite axial ends of the pump. The support frame 200 abuts the supported external surface area 510 to apply a counter-balancing reaction force to the housing 100, in response to the reciprocation of the proximal side resilient biasing means 400.

[0077] Each of the three chamber-forming surface areas 320 is spaced apart from the interior surface of the housing 100, which defines the cavity 120, except for the diaphragm portion 120, which will be pressed against the chamber-forming surface area 320 rotating past it. The chamber-forming surfaces 320 will thus form respective chambers 122 with the interior surface, which can contain a volume of liquid (if the liquid contains medication to be delivered to a patient, each volume may be referred to as a bolus). Since the housing-engaging surface area 310 surrounding the chamber-forming surface areas 320 will form a seal against the interior surface of the housing 100, each volume of liquid will be contained within each chamber 122 as it is conveyed about the cavity 120 from the inlet portion 102A to the outlet portion 102B, on rotation of the rotor 300. The biasing member 400 will urge the diaphragm portion 110 against the housing-engaging and chamber-forming surface areas 310, 320 of the rotor 300 as it rotates. The diaphragm portion 110 will thus be variably flexed between the resilient biasing member 400 and the rotor 300, both of which bear against it, on opposite sides. The maximum pressure of fluid within the outlet portion 102B is regulated by the pressure applied to the diaphragm portion 110 by the biasing member 400. Since the shape profile of the chamber-forming surface areas 320 may be complex and constantly changing in use as the rotor 300 rotates, the diaphragm portion 110 will need to be sufficiently flexible for its shape to be change continually. The radial contact force between the diaphragm portion 110 and the housing-engaging and chamber-forming surface areas 310, 320 of the rotor 300 will be sufficiently great along its entire length to prevent the pumped fluid at a desired pressure from passing between the diaphragm portion 210 and the rotor 300.

[0078] In use, the rotor 300 will be inserted into the housing 100 and driven by a drive mechanism (not shown) to rotate in the direction R about its longitudinal axis L. The inlet portion 102A supported by the respective port 202A of the support frame 200 will be connected to a fluid conveying device, such as a tube, from which fluid will flow into the inlet portion 102A. The chamber 122 can receive fluid from the inlet portion 102A when the rotor 300 is oriented such that a chamber 122 is in fluid communication with the inlet portion 102A; and when the chamber 122 comes into fluid communication with the outlet portion 102B, the volume of fluid within it will be discharged from the chamber 122 as the rotor 300 rotates and the fluid is prevented from passing between the diaphragm portion 110 and the rotor 300 under the action of the resilient biasing member 400 which ensures that the diaphragm portion 110 seals against the surface of the rotor 300 along its entire longitudinal extent. In other words, the volume of fluid in the chamber 122 will be squeezed out of the chamber 122 as the latter is rotated past the outlet portion 102B. The outlet portion 102B supported by the respective port 202B of the support frame 200 will be connected to another fluid conveying device into which fluid will flow from the outlet portion 102B. In this way, relatively accurate discrete doses of the fluid can be pumped, the total dose pumped depending on the volumes of the chambers 122, the number of chambers 122 (there are three chambers in this particular example), the number of revolutions of the rotor 300, and the rotational speed of the rotor 300.

[0079] In a particular example pump assembly, the rotor 300 may have a circumscribed diameter of about 3 mm (which would also be the approximate diameter of the cavity 120), the diaphragm portion 110 may have a substantially uniform thickness of about 0.25 mm and a base wall portion 112 may have a thickness of about 3.0 mm (the ratio of thickness of the base wall portion 112 to the thickness T of the diaphragm portion may be 12:1). In another example, the thickness T of the diaphragm portion 110 may be about 0.1 mm, and so the ratio of thickness of the base wall portion 112 to the thickness T of the diaphragm portion may be 30:1. In some examples, the thickness T of the diaphragm portion 110 may be about 1.0 mm, or in the range 0.1 to 1.0 mm. In general, the thickness T of the diaphragm portion 110 and that of the base wall portion 112 may both vary such that the ratio of the former to the latter is at least about 1:50 or at least about 1:20, and at most about 1:4. A relatively thin diaphragm portion 110 may exhibit greater flexibility in use, but may require that the side and base wall portions 114A, 114B, 112 is sufficiently thick to support it and hold its side boundaries in place during use.

[0080] In some examples, the housing 100 may consist of polypropylene, the thickness T of the diaphragm 110 may be about 0.1 mm, and the base wall portion 112 may be about 1.5 mm thick; and in some examples in which the resilient material may consist of rubber having a substantially lower Young's modulus, the thickness T of the diaphragm portion 110 may be about 0.5 mm and that of the base wall portion 112 may be 5 mm.

[0081] FIG. 2 shows a schematic expanded cross-section view of a central region of an example pump. This example pump comprises many of the same features as that described with reference to FIG. 1A to FIG. 1E. However, the diaphragm portion 110 includes an aperture 116 through it. The aperture 116 places the outlet portion 102B in fluid communication with a cavity volume 118 that is coterminous with the side of the diaphragm portion 110 against which the biasing member 400 bears (which may be referred to as the underside of the diaphragm portion). This example arrangement would result in the presence of pumped fluid within the cavity volume 118, the pressure of the fluid being the same as that in the outlet portion 102B. Therefore, the diaphragm portion 110 would be urged against the rotor 300 by both the biasing member 400 and fluid at the pressure of pumped fluid. This arrangement may have the aspect of increasing the pressure of the fluid that can be pumped into the outlet portion 102B without passing between the diaphragm portion 110 and the rotor, from the outlet portion 1028 to the inlet portion 102A.

[0082] In this example arrangement shown in FIG. 2, the support frame 200 comprises a seat portion 210 configured for receiving a pair of feet on the distal side of an elongate U-shaped biasing member 400 (the proximal side of which includes a projecting rib 410 that will bear against the diaphragm portion 110). The seat portion 210 comprises a pair of grooves 211 for receiving the feet, and a pair of slots 212 for receiving elongate side wall portions 114 of the housing 100 proximate the diaphragm portion 110. The slots 212 for each side wall portion 114 is defined by a pair of substantially parallel or aligned respective walls 214, 216 formed on the support frame 200. Each of the distal feet of the biasing member 400 will thus be spaced apart from a respective side wall portion 114 by a wall-like projection 216 of the support frame 200. The side wall portions 114 may be laterally supported by the wall-like projections 214 of the support frame 200. When this example pump is assembled, each of the two side wall portions 114 of the housing 100 would be inserted into a respective slot 212; and the distal feet of the biasing member 400 would be inserted into the adjacent groove 211. In other examples, there may be a single side wall portion 114, which may be circular, elliptical or rectilinear when viewed in a plan view. The distal side of the biasing member 400 will thus be held substantially statically in relation to the side wall portions 114 as the proximal side reciprocates against the diaphragm portion 110 in use, to flex it and urge it against the rotor 300 as the rotor 300 rotates.

[0083] FIG. 3A-3C show different perspective and cross-section views of an example pump, in which the same reference numbers refer to the same general features in FIG. 1A-FIG. 2. In this example, the support frame 200 is attached to the inlet and outlet portions 102A, 102B of the housing 100, and a pair of fitting 600A, 600B are attached to respective portions 202A, 202B of the support frame 200. In this example, the inlet and outlet portions 102A, 102B are coaxial and project from opposite ends of the housing 100. The support frame 200 consists of a pair of opposing fame members 200A, 200B, which can be attached to each other (by a mechanical clip mechanism, for example) enclose most of the housing 100. In this example, each fitting 600A, 6006 comprises male coupling mechanism for mating with a corresponding female coupling mechanism that will be attached to or formed as part of a fluid carrying device (not shown) such as a tube. The portions 202A, 202B of the support frame attached circumferentially about the inlet and outlet portions 102A, 102B, respectively, comprises an attachment mechanism for attaching the fittings 600A, 600B.

[0084] The support frame 200 comprises an attachment dock 202C for a rotor drive mechanism to couple with a splined mechanism 305 attached to the rotor 300, to rotate the rotor 300 in use. The support frame 200 thus holds the inlet and outlet portions 102A, 102B (and the pair of fitting 600A, 600B) firmly in place relative to one another, and relative to the rotor drive mechanism to which it can be secured, and which can be held stationary in use relative to the inlet and outlet fluid carrying devices (not shown). Thus, the support frame 200 can rigidly connect the inlet and outlet portions 102A, 102B with the rotor drive mechanism, and will remain stationary as the rotor 300 rotates in use because it is stiff enough to counter-balance the torque applied by the rotor 300 onto the housing 100.

[0085] With reference to the cross-section views shown in FIGS. 3B and 3C, an annular side wall portion 114 of the housing 100 projects outward from the adjacent the diaphragm portion 110 (coaxial with an axis that is perpendicular to the rotor axis) and is accommodated by an annular slot 212 formed by the support frame 200. A seat portion 210 of the support frame 200 abuts a distal side of a resilient biasing member 400 in the general form of an elongate U-shape, a proximal side of which bears against the diaphragm portion 110. In this example, the side wall portion 114 projects outwardly beyond the seat portion 210. The support frame 200 is thus configured to substantially prevent the side wall portion 114 from moving laterally relative to the distal side of the biasing member 200, and indirectly provides support for the side boundaries of the diaphragm portion 110, to which the side wall 114 is adjacent. The support frame 200 contacts an external surface area of the housing at 510 on the opposite side of the housing 100 to the diaphragm portion 110, to counter-balance the forces arising from reciprocation of the proximal side of the biasing member 400 in response to the rotation of the rotor 300 in use. However, the support frame is spaced apart from the external surface of the housing 100 at various places 500, 500A, 500B, 500C (and other locations) wherever contact is not advantageous for balancing forces. For example, the circular side wall portion 114 can reciprocate somewhat within the slot 212 formed by the support frame 200, owing to gaps 500C. This allows for the housing 100 to distend cyclically in use wherever possible and reduces the dimensional tolerances required for manufacturing the support frame 200. However, the support frame 200 does not provide gaps that would allow the housing 100 to move or distort azimuthally about the rotor axis in use.

[0086] The graphs in FIGS. 4A, 4B and 4C show example curves of flow rates F (in millilitres per second, ml.Math.s.sup.?1) of pumped fluid versus the diameter D (in millimetres, mm) of example rotors (in other words, the diameters of circles that will circumscribe the rotor in the radial plane), for each of the rotor rotation speeds of 1, 5 and 10 revolutions per second (r.p.s.). In general and all else being equal, the pumped flow rate will be proportional to the rotation rate of the rotor. These curves correspond to pump assemblies having substantially the configuration described with reference to FIG. 1A to FIG. 1E. These example curves may represent lower limits of the potential performance of example pump assemblies, and the flow rates F may be substantially higher, for example up to about 50% higher in practice. In the example pump assemblies for which the curves are shown, the cavity is generally cylindrical (and the rotor can be circumscribed by a cylinder), and the length of the axial length of the chamber-forming surface area of the rotor is double the diameter D. In other examples, the diameter D may be half of L to ten times L (? L to 10 L).

[0087] In some examples, the diameter of the cavity 120 may be about 1 mm, about 3 mm or about 5 mm. In certain examples in which the diameter of the cavity 120 may be about 5 mm, the thickness T diaphragm portion may be about 3 mm, supported by an base wall portion 112 having thickness of at least about 12 mm. In some examples of small pumps, in which the cavity 120 has a diameter of about 1 to 3 mm, the resilient material may consist of soft rubber having Young's modulus of as low as about 4 MPa, and/or have about 70 Shore A hardness at low strain. In some examples, the mean diameter of the cavity may be about 3 mm and the elastic, tensile or flexural modulus may be about 150 MPa.

[0088] In order for the diaphragm portion to be flexible enough to follow the contour of the surface areas of the rotor as it rotates, the diaphragm portion can be moulded with a very thin wall section. By careful processing using temperature and pressure feedback sensors and local venting to eliminate gassing it is possible to achieve diaphragm portions with a wall thickness of about 0.1 to 0.3 mm. In an example process, a sliding portion of an injection moulding tool that will create the outer surface of the diaphragm portion may be controlled independently or as a consequence of the tool opening and closing. In some examples, molten plastic may be injected into the tool by an injection screw, the diaphragm portion wall thickness being approximately twice the desired thickness in order to allow for some of the molten material to flow across the diaphragm portion. In some examples, the sliding portion of the tool may be advanced at the desired time within the injection cycle to create the desired diaphragm portion wall thickness without knit lines and creating sufficient packing pressure at the same time. The use of a single shot moulding process may exhibit the aspects (separately or in combinations) of reducing the number of manufacturing processes, having a faster cycle time, requiring simpler mould tools and mould machinery and leading to higher manufacturing yield and lower production costs than a two-shot process. Pumps formed in a single-shot moulding process may have the aspect of having a longer operational life.

[0089] In some examples, the diaphragm portion and the rest of the housing may comprise or consist of elastomeric material by a process including a single shot injection moulding process. The diaphragm portion and the rest of the housing may comprise or consist of thermoplastic material. For example, the housing material may comprise or consist of polyethylene, polypropylene, rubber modified polypropylene, plasticised polyvinyl chloride (PVC), or thermoplastic co-polyester elastomer such as Hytrel? (commercially available from DuPont?).

[0090] In general, the smaller the housing, the softer should be the resilient material of which the housing is formed. In some examples, the housing material may have nominal Shore D hardness (durometer hardness) of at most about 50, at most about 40 or at most about 30 as measured using the ISO 868 standard method (15 s). The housing material may have nominal Shore D hardness of at least about 5. In some examples, the housing material may have nominal Shore A hardness (durometer hardness) of at most about 50, at most about 40 or at most about 30. The housing material may have nominal Shore D hardness of at least about 10, or at least about 20. For example, depending on the size of the pump (the diameter of the cavity) and the fluid pressure, the material may have a hardness of 60 Shore A to 90 Shore D. In some examples, the housing material may have nominal Shore 00 hardness (durometer hardness) of at most about 80, at most about 60 or at most about 50. The housing material may have nominal Shore 00 hardness of at least about 5, at least about 10, or at least about 20.

[0091] General aspects of example disclosed pumps and pump assemblies will be explained below.

[0092] The sealing interference contact between the housing-engaging surface area and the interior surface will be able to contain the fluid within the chamber at the operating pressure. As the rotor rotates, so will the sealing interference contact, which will apply a torque onto the housing. In addition, the interference contact will induce hoop stress in the housing, and the housing may (reversibly) distend to some extent. The magnitude of the hoop stress that can be sustained by the housing will depend on the elastic modulus of the resilient material and the volume of the housing surrounding the cavity. In general, the higher the elastic modulus and the thicker wall of the housing, the greater the hoop stress that can be sustained, and the higher the pressure of the fluid that can be delivered by the pump.

[0093] The resilient material will have mechanical properties such that the diaphragm portion can be sufficiently flexed and deformed in use to maintain an effective seal against both the housing-engaging and the chamber-forming surface areas of the rotor as these surfaces rotate against the diaphragm portion. In some examples, the shape of the chamber-forming surface may be compound, and may include both concave and convex components (when viewed on different cross-sectional planes). Therefore, for a given thickness, length and width of the diaphragm portion, the resilient material will be selected to permit the degree of dynamic deformation required to prevent the pumped fluid from passing between it and the rotor (and thus to expel fluid from chamber into the outlet portion). In particular, the resilient material may be sufficiently soft and have a sufficiently low elastic or flexural modulus for the diaphragm portion to be reliably and repeatedly flexed in use, given its dimensions. Given the intrinsic mechanical properties of the resilient material, the configuration and volume of the housing (for example, the thickness of a base wall portion at least partly enclosing the cavity) will make it sufficiently stiff to maintain the sealing interference contact with the housing-engaging surface area of the rotor. In addition, movement of side boundaries of the diaphragm portion relative to the rotor axis may be resisted or substantially prevented as the diaphragm portion is dynamically flexed in use. However, to avoid the housing being undesirably large, its volume and stiffness may not be sufficient to counter-balance the torque applied by the rotor in use.

[0094] The flexibility of the diaphragm portion will likely be influenced by its shape and size, and the resilient material. In general, the thinner and wider the diaphragm portion, the greater its flexibility (all else being equal); also the softer the resilient material, or the lower its elastic, tensile or flexural modulus, the more flexible the diaphragm portion will likely be (all else being equal). In practice, there may be a technical or practical limitation to the lower limit of the mean thickness of the diaphragm, which may determine an upper limit to the elastic, tensile or flexural modulus, or the hardness of the resilient material that may be selected (all else being equal; for example, for a given fluid pumping rate). The selection of the resilient material will likely be especially important for relatively small pumps, particularly if a relatively high pumping rate is desired. The support frame may be particularly, but not exclusively, helpful for relatively small pumps, in order to avoid the need to make the housing volume undesirably large to achieve the stiffness required for effective operation.

[0095] To the extent that the minimum thickness of the diaphragm portion is limited by practical or technical considerations, the intrinsic flexibility of the resilient material will be adequately great for the extrinsic flexibility of the diaphragm portion to be sufficiently high. For example, it will have a suitably low elastic (e.g. Young's, flexural) modulus and/or hardness to provide a sufficiently flexible diaphragm portion. In certain examples, a lower limit of the thickness of the diaphragm portion may be set by the manufacturing method or apparatus used to mould the housing, or by a need to reduce the risk of the diaphragm portion tearing in use. If the diaphragm portion is too thin, then it may tend to distend excessively (which may be likened to a ballooning effect in extreme cases), and even if the pump continues to pump effectively, the accuracy of the volume of fluid pumped may be reduced. The volume of the housing (in particular, the thickness of its wall portions) may depend on the desired operating pressure of the fluid in the outlet portion, and may be calculated based on the hoop stress that will need to be sustained, given the elastic modulus of the resilient material of the housing.

[0096] In general and all else being equal, a diaphragm portion on a relatively small housing will likely be less flexible than a wider diaphragm portion of the same thickness on a relatively larger pump. Given the size of the pump (for example, as indicated by the diameter of the cavity, the rotor, the volume of the chamber), the resilient material may be selected in view of the lowest practical thickness of the diaphragm portion that can be injection or compression moulded, the required strength of the diaphragm portion and the required pressure that the diaphragm portion will need to sustain when it is urged against the rotor by the resilient biasing mechanism in use, which will depend on the pressure on the fluid being pumped into the outlet portion.

[0097] In some examples, there may be advantages for forming the inlet, outlet and diaphragm portions as portions of a single unit. For example, it may be technically easier or more efficient to form the housing by injection moulding.

[0098] On the one hand, the interference contact pressure between the interior surface of the housing and the housing-engaging surface area of the rotor will be sufficient to contain the pumped fluid within the chamber at the desired pressure; and on the other hand, the greater the contact force, the greater will be the power required to rotate the rotor at the desired rate, and the greater will be the torque applied by the rotor onto the housing. The use of the support frame as disclosed may have the aspect of reducing the volume of the housing that would be required to sustain the torque without rotating or being excessively distorted about the rotor axis. The interior surface may be reversibly impressed by the housing-engaging surface area, and a wall portion of the housing adjacent the interior surface may tend to expand radially to some degree, owing to its resilience. The support body may have the aspect of adequately maintaining the positions of the inlet, outlet and diaphragm portions in relation to the rotor axis and to each other, so that certain examples of the pump can operate effectively.

[0099] Some example pump assemblies may have the aspect that the presence of the support frame may reduce the risk of fluid leakage from the connection mechanisms by which the inlet and outlet portions can be coupled to respective fluid carrying devices.

[0100] In certain applications, it may be desired for the pump assembly to be as small as possible whilst the maximum pumping rate is as high as possible. In particular, the shaped chamber-forming surface area or areas may be radially deep into the rotor. A need for the rate of rotation of the rotor to be relatively high may require the diaphragm portion to be flexed in a complex way at relatively high frequency. Although making the diaphragm portion thinner will likely increase its flexibility for this purpose, there will likely be a practical limitation to the lower limit of its thickness, which may result from the method used to mould the diaphragm portion and the rest of the housing as a single, integral unit, and/or from risk of the diaphragm portion tearing. An approach may be to form the diaphragm portion from a softer material, and/or a material having a lower elastic modulus. However, the rest of the housing will be formed of the same material and there will likely be practical limitations to the flexibility of the housing, which will need to distend or distort slightly in response to the rotor surface contacting it in use, but which will need to be sufficiently stiff to sustain the hoop stress caused by the rotating rotor. The more flexible the housing, the greater the challenge of coupling the inlet and outlet portions to inlet and outlet devices such as tubes, especially if the pump is relatively small. In disclosed examples, this can be ameliorated by using a sufficiently stiff support frame or casing. In use, the housing may be significantly deformable and the frame may function as an external skeleton accommodating it and securing it to the inlet and outlet devices.

[0101] Certain terms and concepts used herein will be briefly explained below.

[0102] As used herein, in example arrangements of pumps or parts of pumps that have a generally cylindrical or conical shape, and therefore having a degree of cylindrical symmetry, the use of terminology associated with a cylindrical coordinate system may be helpful for describing the spatial relationship between features. In particular, a cylindrical or longitudinal axis may be said to pass through the centres of each of a pair of opposite ends and the body or a part of it may have a degree of rotational symmetry about this axis. Planes perpendicular to the longitudinal axis may be referred to as lateral or radial planes and the distances of points on the lateral plane from the longitudinal axis may be referred to as radial distances, radial positions or the like. Directions towards or away from the longitudinal axis on a lateral plane may be referred to as radial directions. The term azimuthal will refer to directions or positions on a lateral plane, circumferentially about the longitudinal axis.

[0103] As used herein, a bolus is a depression or cavity formed in a rotor of a pump, which can transfer fluid from an inlet to an outlet. The maximum mass of the fluid that can be transferred in a single full rotation of the rotor will be determined by the number and volume of the bolus or boluses in the rotor, as well as the density of the fluid. Where a pump is used to deliver fluid for medical purposes, such as for infusion into a patient, the bolus is the smallest precise dosage of the fluid that can be delivered in practice. For example, the pump may be used to administer a specific amount of medication or other drug in fluid form to increase the level of a drug in a patient's blood.

[0104] Durometer or Shore hardness is one of several measures of the hardness of a material, particularly of polymer, elastomer and rubber materials. Hardness may be defined as a material's resistance to permanent indentation. There are various scales of Shore hardness, for example Shore OO, Shore A and Shore D, although there is no direct conversion among different scales.

[0105] As used herein, plastics may be referred to as synthetic resins and grouped as thermosetting resins and thermoplastic resins. Thermosetting resins include phenolic resin, polyamide resin, epoxy resin, silicone resin and melamine resin, which are thermally hardened and never become soft again. Thermoplastic resins include PVC (which may also be referred to as vinyl), polyethylene, polystyrene and polypropylene, which can be re-softened by heating. PVC is a thermoplastic comprising chlorine and carbon. Elastomer material is polymer material that exhibits both relatively high viscosity and elasticity, and generally has relatively low Young's modulus and high failure strain. Rubber is an example of elastomer material. At ambient temperatures (about 20? C. to 25? C.), elastomer materials are thus relatively soft and deformable.

[0106] As used herein, the stiffness of an object (which may also be referred to as its rigidity) is the extent to which it resists deformation in response to an applied force. An object described as stiff will deform relatively little when a given force is applied to it, and an object described as flexible or pliable will deform to a relatively greater degree under the force. Stiffness (and flexibility) is a property of an object and not a material as such; it will generally depend on the material or materials of which the object is comprised, as well as the object's shape and volume. Stiffness is an example of an extrinsic property. Properties of a material as such, for example as elastic modulus and hardness, are called intrinsic properties.

[0107] As used herein, a material, object or mechanism that is described as resilient will return to its original shape or configuration once a deforming force is no longer applied to it; it will exhibit elastic-like or spring-like behaviour and be reversibly deformable over a range of forces. When applied to a material, resilience is an intrinsic property of the material as such, and a resilient material will exhibit elastic properties within a range of forces applied to it. As used herein, a resilient material may consist of a mixture of materials, provided that the resultant effect of the mixture is to provide material that is resilient.

[0108] As used herein, the torsional deformation or simply torsion of an object is its twisting response to a torque applied to it.

[0109] As used herein, fluoroelastomer materials that may be commercially available under the brand name of Viton? include synthetic rubber and fluoropolymer elastomer materials, categorized under the ASTM D1418 and ISO 1629 designation of FKM. These include copolymers of hexafluoropropylene (HFP) and vinylidene fluoride (VDF or VF2), terpolymers of tetrafluoroethylene (TFE), vinylidene fluoride (VDF) and hexafluoropropylene (HFP) as well as certain perfluoromethylvinylether (PMVE). The fluorine content of the fluoroelastomer material may be 66% to 70%.