PUMPS

Abstract

A rotary pump (200) comprises: a first fluid port (210) and a second fluid port (215); a housing (205) having an interior surface (220) defining a cavity in which a rotor (225) is located, the rotor comprising a housing engaging surface area (235) forming a sealing interference fit with the interior surface of the housing, and a surface recess (250) that forms with said interior surface of the housing a fluid-conveying chamber that, on rotation of the rotor, conveys fluid from the first fluid port to the second fluid port; a plurality of resiliently deformable diaphragms (255) providing part of the interior surface of the housing, each diaphragm comprising a rotor engaging surface (257) and a rear surface (260), the rotor engaging surface being urged into contact with the rotor by the action of a pressurising means (265) acting on the rear surface. The rotor comprises an elongate body that is substantially hollow, and a drive shaft (285), and comprises a first rotor cavity (270) and a second rotor cavity, the first rotor cavity (270) having an opening at a first end (240) of the rotor and the second rotor cavity having an opening at a second end (245) of the rotor. The rotor body further comprises a first opening between the first rotor cavity and the surface recess and a second opening between the surface recess and the second rotor cavity, the pump being arranged such that when the rotor body is located within the housing cavity, the first fluid port is in fluid flow communication with the first rotor cavity via the opening at the first end of the rotor, and the second fluid port is in fluid flow communication with the second rotor cavity via the opening at the second end of the rotor, and the pump being arranged such that the resiliently deformable diaphragm always bisects the first opening and the second opening on the rotor surface recess as the rotor rotates.

Claims

1. A pump comprising, a first fluid port and a second fluid port, a housing having an interior surface defining a cavity in which a rotor is located, a rotor, being rotatably mounted within the housing and having a longitudinal axis of rotation, and comprising, a housing engaging surface area forming a sealing interference fit with the interior surface of the housing, and a surface recess that forms with said interior surface of the housing a fluid-conveying chamber that, on rotation of the rotor, conveys fluid from the first fluid port to the second fluid port, a plurality of resiliently deformable diaphragms each providing part of the interior surface of the housing, each diaphragm comprising a rotor engaging surface and a rear surface opposite the rotor engaging surface, the rotor engaging surface of each diaphragm being urged into contact with the rotor by a pressurizing means acting on the rear surface of the diaphragm, the number of resiliently deformable diaphragms exceeding the number of surface recesses on the rotor, the rotor comprising an elongate body and a drive shaft, which body is substantially hollow and comprises separate first and second rotor cavities, the first rotor cavity having an opening at a first end of the rotor and the second rotor cavity having an opening at a second end of the rotor, the rotor further comprising a first opening between the first rotor cavity and the surface recess and a second opening between the surface recess and the second rotor cavity, the pump being arranged such that when the rotor is located within the cavity in the housing, the first fluid port is in fluid flow communication with the first rotor cavity via the opening at the first end of the rotor, and the second fluid port is in fluid flow communication with the second rotor cavity via the opening at the second end of the rotor, and the pump being arranged such that at least one of the resiliently deformable diaphragms always bisects the first opening and the second opening on the rotor surface recess as the rotor rotates.

2. A pump according to claim 1, comprising a plurality of surface recesses that form with the interior surface of the housing a corresponding number of fluid-conveying chambers.

3. A pump according to claim 1, wherein the rotor is twisted about the longitudinal axis of rotation thereof, such that the first end and the second end of the rotor are rotationally off-set relative to one another by at least 10 degrees, or by at least 15 degrees or by no more than 20 degrees.

4. A pump according to claim 1, wherein the housing comprises three resiliently deformable diaphragms and the rotor comprises two surface recesses forming two fluid-conveying chambers with the interior surface of the housing.

5. A pump according to claim 1, comprising a plurality of surface recesses, wherein each surface recess comprises a first opening between the first rotor cavity and the surface recess and a second opening between the surface recess and the second rotor cavity.

6. A pump according to claim 1, wherein each of the plurality of resiliently deformable diaphragms is urged into contact with the rotor by a separate pressurizing means acting on the rear surface of the diaphragm.

7. A pump according to claim 1, wherein each of the plurality of resiliently deformable diaphragms is urged into contact with the rotor by a common pressurizing means acting on the rear surface of all of the diaphragms.

8. A pump according to claim 1, wherein the pressurizing means comprises a spring, a resilient member, and/or a fluid acting on the rear surface of the diaphragm.

9. A pump according claim 8, wherein the fluid acting on the rear surface of the diaphragm is the pumped fluid.

10. A pump according to claim 1, wherein one or each resiliently deformable diaphragm comprises a linear rib extending longitudinally along the length of the rear surface of the diaphragm.

11. A pump according to claim 1, wherein a linear rib acts on the rear surface of one or each resiliently deformable diaphragm extending longitudinally along the length of the diaphragm.

12. A pump according to claim 10, wherein the linear rib is angled relative to the longitudinal axis of rotation of the rotor by at least 10 degrees, or by at least 15 degrees or by at least 20 degrees.

13. A pump according to claim 1, comprising a rotor that is twisted about the longitudinal axis of rotation thereof, such that a first end and a second end of the rotor are rotationally off-set relative to one another by at least 10 degrees, wherein the rotor is twisted in the opposite direction to the linear rib on the resiliently deformable diaphragm.

14. A pump according to claim 1, wherein the rotor comprises a substantially cylindrical body in which one or more surface recesses are formed and the housing engaging surface area forming a sealing interference fit with the interior surface of the housing comprises the whole cylindrical surface of the rotor except the one or more surface recesses on the rotor.

15. A pump according to claim 14, wherein the housing engaging surface area of the rotor comprises a cylindrical area at each end of the rotor in which no surface recess is formed, which cylindrical areas are connected by elongate sections of the rotor surface separating a longitudinal extent of adjacent recesses.

16. A pump according to claim 4, wherein the two fluid-conveying chambers are separated from each other by a bulkhead extending within the hollow interior of the rotor.

17. A pump according to claim 1, wherein the first opening between the first rotor cavity and the surface recess and the second opening between the surface recess and the second rotor cavity are each provided by a slot in the rotor.

18. A pump according to claim 1, wherein the first opening between the first rotor cavity and the surface recess is located adjacent, and preferably contiguous with, an edge of the recess that would form a leading edge of the recess as the rotor rotates, and the second opening between the surface recess and the fluid-conveying chamber is located adjacent, and preferably contiguous with, an opposite edge of the recess that would form the following edge of the recess as the rotor rotates along the longitudinal axis.

19. A pump according to claim 1, wherein the first opening between the first rotor cavity and the surface recess extends along substantially the full axial length of the surface recess that overlies the first rotor cavity and the second opening between the surface recess and the second rotor cavity extends along substantially the full axial length of the surface recess that overlies the second rotor cavity.

20. A pump according to claim 19, wherein the first opening between the first rotor cavity and the surface recess extends along the full axial length of the surface recess that overlies the first rotor cavity and continues through at least one of the first end of the rotor the second opening between the surface recess and the second rotor cavity extends along the full axial length of the surface recess that overlies the second rotor cavity and through the second end of the rotor.

21. A pump according to claim 20, wherein the first opening and/or the second opening are tapered, opening outward to the widest part as the opening passes through the end of the rotor.

22. A pump according to claim 1, wherein the rotor comprises a first groove and a second groove in the surface of the rotor extending along substantially the full length of opposing longitudinal edges of the surface recess, wherein the first opening between the first rotor cavity and the surface recess extends along a portion of the first groove that overlies the first rotor cavity and the second opening between the surface recess and the second rotor cavity extends along a portion of the second groove that overlies the second rotor cavity.

23. A pump comprising, a first fluid port and a second fluid port, a housing having an interior surface defining a cavity in which a rotor is located, a rotor, being rotatably mounted within the housing and having a longitudinal axis of rotation, and comprising, a housing engaging surface area forming a sealing interference fit with the interior surface of the housing, and a surface recess that forms with said interior surface of the housing a fluid-conveying chamber that, on rotation of the rotor, conveys fluid from the first fluid port to the second fluid port, the rotor being twisted about the longitudinal axis of rotation thereof, such that a first end and a second end of the rotor are rotationally off-set relative to one another by at least 10 degrees, a resiliently deformable diaphragm providing part of the interior surface of the housing, the diaphragm comprising a rotor engaging surface and a rear surface opposite the rotor engaging surface, the rotor engaging surface of the diaphragm being urged into contact with the rotor by a pressurizing means acting on the rear surface of the diaphragm, the rotor comprising an elongate body and a drive shaft, which body is substantially hollow and comprises separate first and second rotor cavities, the first rotor cavity having an opening at a first end of the rotor and the second rotor cavity having an opening at a second end of the rotor, the rotor further comprising a first opening between the first rotor cavity and the surface recess and a second opening between the surface recess and the second rotor cavity, the pump being arranged such that when the rotor is located within the cavity in the housing, the first fluid port is in fluid flow communication with the first rotor cavity via the opening at the first end of the rotor, and the second fluid port is in fluid flow communication with the second rotor cavity via the opening at the second end of the rotor, and the pump being arranged such that the resiliently deformable diaphragm always bisects the first opening and the second opening on the rotor surface recess as the rotor rotates.

24. A pump comprising, a first fluid port and a second fluid port, a housing having an interior surface defining a cavity in which a rotor is located, a rotor, being rotatably mounted within the housing and having a longitudinal axis of rotation, and comprising, a housing engaging surface area forming a sealing interference fit with the interior surface of the housing, and a surface recess that forms with said interior surface of the housing a fluid-conveying chamber that, on rotation of the rotor, conveys fluid from the first fluid port to the second fluid port, a resiliently deformable diaphragm providing part of the interior surface of the housing, the diaphragm comprising a rotor engaging surface and a rear surface opposite the rotor engaging surface, the rotor engaging surface of the diaphragm being urged into contact with the rotor by a pressurizing means acting on the rear surface of the diaphragm, a linear rib either upstanding from either the rear surface of the resiliently deformable diaphragm or acting on the rear surface of the diaphragm, the linear rib being angled relative to the longitudinal axis of rotation of the rotor by at least 10 degrees, the rotor comprising an elongate body and a drive shaft, which body is substantially hollow and comprises separate first and second rotor cavities, the first rotor cavity having an opening at a first end of the rotor and the second rotor cavity having an opening at a second end of the rotor, the rotor further comprising a first opening between the first rotor cavity and the surface recess and a second opening between the surface recess and the second rotor cavity, the pump being arranged such that when the rotor is located within the cavity in the housing, the first fluid port is in fluid flow communication with the first rotor cavity via the opening at the first end of the rotor, and the second fluid port is in fluid flow communication with the second rotor cavity via the opening at the second end of the rotor, and the pump being arranged such that the resiliently deformable diaphragm always bisects the first opening and the second opening on the rotor surface recess as the rotor rotates.

25. A pump according to claim 24, wherein the rotor is twisted about the longitudinal axis of rotation thereof, such that a first end and a second end of the rotor are rotationally off-set relative to one another by at least 10 degrees, the rotor being twisted in the opposite direction to the angling of the rib.

26. A pump according to claim 24, comprising a plurality of resiliently deformable diaphragm.

27. A pump according to claim 24, comprising a rotor having a plurality of surface recesses that form with the interior surface of the housing a corresponding number of fluid-conveying chambers.

28. A pump according to claim 24, comprising an equal number of resiliently deformable diaphragms and surface recesses on the rotor.

Description

[0070] The following is a more detailed description of embodiments of the invention, provided by way of example only, reference being made to the accompanying drawings, in which:

[0071] FIG. 1 is a schematic partially cut-away of a rotor according to an embodiment of the first or third aspects of the invention;

[0072] FIG. 2 is a rotor according to an embodiment of the first or third aspects of the invention showing the fluid flow;

[0073] FIG. 3 is a schematic cross-sectional view through part of a pump comprising the rotor of FIGS. 1 and 2;

[0074] FIG. 4 is a schematic, partially cutaway view of a pump according to a second embodiment of first or third aspects of the invention;

[0075] FIG. 5 is a cross-sectional view of the pump of FIG. 4;

[0076] FIG. 6 is a schematic view of a rotor according to an embodiment of the second aspect of the invention;

[0077] FIG. 7 is a schematic illustration of a rotor according to a second embodiment of the second aspect of the invention;

[0078] FIG. 8 is a schematic illustration or a rotor according to a third embodiment of the second aspect of the invention;

[0079] FIG. 9 is a schematic, partially cut-away illustration of part of a pump according to an embodiment of the third aspect of the invention;

[0080] FIG. 10 is a schematic, partially cut-away illustration of part of a pump according to an alternative embodiment of the third aspect of the invention;

[0081] FIG. 11 is a schematic cross-sectional view of a pump according to an embodiment of the first aspect of the invention;

[0082] FIG. 12 is a schematic view of a rotor according to an alternative embodiment of the first or third aspects of the invention;

[0083] FIG. 13 is a schematic, partially cut-away view of the rotor of FIG. 12.

[0084] It can be seen from FIG. 1 that the rotor 10 has a generally cylindrical shape. Rotor 10 has two surface recesses 20, which extend along the longitudinal extent of the rotor 10, generally parallel to the longitudinal axis of rotation 15 of the rotor. The surface recesses 20 are provided by concave sections of the rotor. The rotor comprises a housing engaging surface area 25 at each end of the rotor and between adjacent surface recesses 20.

[0085] The rotor is hollow and comprises a first rotor cavity 30 and a second rotor cavity 35 arranged consecutively within the rotor 10. The rotor comprises a drive shaft 40 that extends within and is attached to the hollow interior of the rotor 10.

[0086] Each end 45, 50 of the rotor 10 is open to provide fluid access into the first and second fluid cavities 30, 35, respectively.

[0087] In the embodiment shown in FIG. 1, the rotor 10 further comprises a first groove 52 and a second groove 53 extending along opposing longitudinal edges of the surface recess 20.

[0088] Slots 55, 60 provide the opening between the first rotor cavity 30 and the surface recess 20 and the second rotor cavity 35 and the surface recess 20, respectively. Each slot 55, 60 is essentially linear and extends along a longitudinal edge of the recess 20 and is essentially parallel to the longitudinal axis of rotation of the rotor 15. However, slot 55 providing the first opening is located in the first groove 52 and the slot 60 providing the second opening is located in the second groove 53, the slots 55 and 60 are parallel but adjacent opposite sides of the land 25 extending between the recesses 20. For each of the two surface recesses 20 in the embodiment shown in FIG. 1, there is a slot 55 providing a first opening between the first rotor cavity 30 and the surface recess 20, and a slot 60 providing a second opening between the second rotor cavity 35 and the surface recess 20. The slots 55 and 60 are on opposite sides and opposite ends of the recess 20. The view shown in FIG. 1, shows only 30 one slot 55, 60 of each recess 20.

[0089] In the embodiment shown in FIG. 1, both of the slots 55 providing an opening between the first rotor cavity 30 and the surface recesses 20, to allow fluid to flow from the first rotor cavity 35 into the chamber formed by each surface recess 20. Likewise, both of slots 60 will allow fluid to flow from the chamber formed by each surface recess 20 into the second rotor cavity 35.

[0090] FIG. 2 illustrates an alternative embodiment of the rotor of FIG. 1, without the grooves 52, 53 to locate the slots 55 and 60, but like features are referred to by like reference numerals. FIG. 2 also illustrates, for a given direction of rotation of the rotor, the direction of fluid flow into the first rotor cavity 30 through the openings in the end 45 of the rotor 10 and from the first rotor cavity out through the slot 55 into the chamber (not shown) formed by the surface recess 20. FIG. 2 also shows fluid from the adjacent chamber (not shown) formed by the adjacent surface recess 20 flowing into the slot 60 into the second rotor cavity 35 and out through the open end 50 of the rotor 10. This fluid flow will apply equally to the embodiment of FIG. 1 and FIG. 2.

[0091] FIG. 3 shows a rotor 105 similar to the rotor 10 of FIGS. 1 and 2 in a housing 100. The cross-sectional view of FIG. 3 shows the arrangement of the first rotor cavity 30 and the second rotor cavity 35 more clearly. It also shows the bulkhead 70 which separates the first and second rotor cavities 30, 35. FIG. 3 also illustrates more clearly how the drive shaft 40, which is attached to or unitary with the rotor, extends from the interior of hollow the rotor 10. Only one slot 60 is shown in this view, which is the opening between the second rotor cavity 35 and the surface recess (not shown). This view illustrates the housing engaging surface area 25 at each end of the rotor and between adjacent surface recesses. (not shown).

[0092] FIG. 3 further illustrates parts of two diaphragm chambers 150 each surrounding the rear surface of a diaphragm 120. The diaphragm being urged into contact with the rotor 10 by pressurising means (not shown).

[0093] FIGS. 4 and 5 show a pump 200 having a housing 205, a first fluid port 210 providing a fluid inlet and a second fluid port 215 providing a fluid outlet. The housing having an interior surface 220 defining a cavity in which the rotor 225 is located. The rotor 225 has a longitudinal axis of rotation indicated by dashed line 230. The rotor 225 having surfaces 235 at each end thereof and the lands extending between recesses on the surface thereof together providing a housing engaging surface area of the rotor. The rotor shown in FIGS. 4 and 5 is twisted about the longitudinal axis of rotation 230, such that the first end 240 and the second end 245 are offset relative to one another. The rotor 225 has two surface recesses 250 provided by concave areas of the rotor surface. A resiliently deformable diaphragm 255 is formed by a thinner section of the housing providing the cavity in which the rotor 225 is located. The resiliently deformable diaphragm 255 has a rotor engaging surface 257 and a rear surface 260. Pressurising means in the form of a spring 265 is in contact with the rear surface 260 of the diaphragm 255. It can be seen from FIGS. 4 and 5 that the rotor 225 comprises an elongate body that is substantially hollow, comprising a first rotor cavity 270 and a second rotor cavity (not shown). The first rotor cavity 270 has openings at the first end 240 of the rotor and the second rotor cavity (not shown) has openings (not shown) at the second end 245 of the rotor. The first rotor cavity 270 and the second rotor cavity (not shown) are separated from each other by a bulkhead 280 that extends across the full interior of the hollow rotor, to prevent fluid flowing along the full internal length of the rotor. The drive shaft 285 extends from the bulkhead 280. The rotor comprises a first opening 290 extending between the first rotor cavity 270 and the surface recess 250 of the rotor. It can be seen from FIG. 4 that the first opening 290 has a tapered shape and extends along a longitudinal edge of a section of the surface recess 250 overlying the first rotor cavity 270 and continues across the land 235 at the first end 240 of the rotor, making an opening in the housing engaging surface provided by the land 235 at the first end 240 of the rotor. The rotor also comprises a similarly arranged second opening (not shown) extending between the second rotor cavity (not shown) and the surface recess 250. The second opening will by locating on the opposite longitudinal edge of the recess 250 and at the opposite end of the rotor 225, such that it overlies the second rotor cavity (not shown). It can be seen from FIG. 4, in particular, that the pressurising means 265 urges the resiliently deformable diaphragm 255 into contact with the surface recess 250 and is located such that the contact line between the diaphragm 255 and the surface recess 250 bisects the first opening 290 and the second opening (not shown) because the second opening (not shown) is located on the opposite longitudinal edge of the recess 250.

[0094] There are three resiliently deformable diaphragm 255 (not all shown) equidistantly spaced about the circumference of the rotor and a spring 265 providing pressurising means acts on the rear surface of each diaphragm.

[0095] Each of the two surface recesses 250 has a first opening 290 and a second opening at opposite ends of the rotor and extending along opposite longitudinal edges of each recess 250.

[0096] In use of the pump 200, the rotor 225 is rotated by the action of a motor connected to the drive shaft 285, fluid flows into the first fluid port 210 and then into the first rotor cavity 270 through the open first end 245 of the rotor 225. The fluid flows from the first rotor cavity 270 through each first opening 290 into the fluid-conveying cavity provided between the surface recesses 250 and the interior surface 220 of the housing. The resiliently deformable diaphragm 255 is urged into contact with the surface of the rotor as it rotates by the action of the spring 265. The action of the diaphragm 255 on the surface of the rotor 225 displaces the fluid from the fluid-conveying cavity as the rotor rotates and the fluid flows through the second openings into the second rotor cavity (not shown). From there, the fluid flows out of the pump though the second fluid port 215.

[0097] FIG. 6 shows an alternative rotor 300. The rotor is twisted about the longitudinal axis of rotation 315 of the rotor 300, such that opposing ends 310,320 of the rotor are off-set relative to one another.

[0098] It can be seen that the result of twisting the rotor is to distort the shape of the surface recesses 330, 335. Since the first slot 340 providing the opening between the first rotor cavity 350 and the surface recess 330 and the second slot 345 providing the opening between the second rotor cavity 355 and the surface recess 335 extend along opposing edges of the recesses 330, 335, the twisting of the rotor also causes the slots 340, 345 to become angled relative to the longitudinal axis of rotation 315 of the rotor 300. FIG. 4 also illustrates that twisting the rotor also angles the land 360 between adjacent recesses 330, 335, which becomes angled relative to the longitudinal axis of rotation 315 of the rotor 300.

[0099] FIG. 7 shows a rotor 400 which is a variation of the rotor 300 of FIG. 5. In this embodiment, the first slot 440 providing the opening between the first rotor cavity 450 and the surface recess 430 and continues through the first end 410 of the rotor. The second slot 445 providing the opening between the second rotor cavity 455 and the surface recess 435, continues through the second end 420 of the rotor. It can be seen that the first slot 440 and the second slot 445 extend through housing engaging surface area 460 at each end of the rotor.

[0100] The dashed lines 465 illustrate the location of the bulkhead extending across the interior of the rotor 400, separating the first rotor cavity 450 and the second rotor cavity 455.

[0101] This arrangement of the first and second slots is not limited to a twisted rotor as illustrated in FIGS. 4 and 7. In the rotor of FIGS. 1 and 2 the slots 55, 60 could also extend through the first and second ends 45 50, respectively and through the surface engaging surface area 25.

[0102] FIG. 8 shows a rotor 500 which is a variation of the rotor 400 of FIG. 6. In this embodiment, the first slot 540 providing the opening between the first rotor cavity 550 and the surface recess 530. The slot is open at the first end 510 of the rotor. The second slot 545 providing the opening between the second rotor cavity 555 and the surface recess 535.

[0103] The slot is open at the second end 520 of the rotor. It can be seen that the first slot 540 and the second slot 545 extend through housing engaging surface area 560 at each end of the rotor. In the embodiment of FIG. 8 the first slot 540 and the second slot 545 are tapered with the widest part forming the opening in the first end 510 and the second end 520 of the rotor respectively.

[0104] The dashed lines 565 illustrate the location of the bulkhead extending across the interior of the rotor 500, separating the first rotor cavity 550 and the second rotor cavity 555.

[0105] This arrangement of the first and second slots is not limited to a twisted rotor. In the rotor of FIGS. 1 and 2 the slots 55, 60 could also be tapered and extend through the first and second ends 45 50, respectively and through the surface engaging surface area 25.

[0106] FIG. 9 shows part of a pump 600 having a housing 605, a first fluid port 610 providing a fluid inlet and a second fluid port (not shown) providing a fluid outlet. The housing having an interior surface 620 defining a cavity in which the rotor 625 is located. The rotor 625 has a longitudinal axis of rotation indicated by dashed line 630. The rotor 625 having lands 635 at each end thereof and between recesses on the surface thereof together providing a housing engaging surface area of the rotor. The rotor 625 has two surface recesses 650 provided by concave areas of the rotor surface. A resiliently deformable diaphragm 655 is formed by a thinner section of the housing providing the cavity in which the rotor 625 is located. The resiliently deformable diaphragm 655 has a rotor engaging surface 657 and a rear surface 660. The resiliently deformable diaphragm 655 has a linear rib 665 protruding from the rear surface 660 of the diaphragm 655. The linear rib 665 is angled relative to the longitudinal axis of rotation 630 of the rotor. It can be seen from FIG. 9 that the rotor 625 comprises an elongate body that is substantially hollow, comprising a first rotor cavity 670 and a second rotor cavity (not shown) at the opposite end of the rotor 625. The first rotor cavity 670 has openings at a first end 675 of the rotor and the second rotor cavity (not shown) has openings (not shown) at a second end of the rotor (not shown). The first rotor cavity 670 and the second rotor cavity (not shown) are separated from each other by a bulkhead (not shown) that extends across the full interior of the hollow rotor, to prevent fluid flowing along the full internal length of the rotor. The rotor 625 comprises a first opening 690 extending between the first rotor cavity 670 and the surface recess 650 of the rotor. The first opening 690 has a linear shape and extends along a longitudinal edge of a section of the surface recess 650 overlying the first rotor cavity 670. The rotor also comprises a similarly arranged second opening (not shown) extending between the second rotor cavity (not shown) and the surface recess 650. The second opening is located on the opposite longitudinal edge of the recess 650 and at the opposite end of the rotor 625, such that it overlies the second rotor cavity (not shown). Each surface recess 650 has a first opening 690 and a second opening arranged at opposite ends of the rotor and on opposite sides of the recess.

[0107] In use of the pump 600, the rotor 625 is rotated by the action of a motor connected to the drive shaft 685, fluid flows into the first fluid port 610 and then into the first rotor cavity 670 through the open first end 675 of the rotor 625. The fluid flows from the first rotor cavity 670 through each first opening 690 into the fluid-conveying cavity provided between the surface recesses 650 and the interior surface 620 of the housing. The resiliently deformable diaphragm 655 is urged into contact with the surface of the rotor as it rotates by the action of pressurising means (not shown). The action of the diaphragm 655 on the surface of the rotor 625 displaces the fluid from the fluid-conveying cavity as the rotor rotates and the fluid flows through the second openings (not shown) into the second rotor cavity (not shown). From there, the fluid flows out of the pump though the second fluid port (not shown).

[0108] FIG. 10 shows part of a pump 700 having a housing 705, a first fluid port 710 providing a fluid inlet and a second fluid port (not shown) providing a fluid outlet. The housing having an interior surface 720 defining a cavity in which the rotor 725 is located. The rotor 725 has a longitudinal axis of rotation indicated by dashed line 730. The rotor 725 having lands 735 at each end thereof and between recesses on the surface thereof together providing a housing engaging surface area of the rotor. The rotor 725 has two surface recesses 750 provided by concave areas of the rotor surface. A resiliently deformable diaphragm 755 is formed by a thinner section of the housing providing the cavity in which the rotor 725 is located. The resiliently deformable diaphragm 755 has a rotor engaging surface 757 and a rear surface 760. The resiliently deformable diaphragm 755 has a linear rib 765 protruding from the rear surface 760 of the diaphragm 755. The linear rib 765 is angled relative to the longitudinal axis of rotation 730 of the rotor. It can be seen from FIG. 10 that the rotor 725 comprises an elongate body that is substantially hollow, comprising a first rotor cavity 770 and a second rotor cavity (not shown) at the opposite end of the rotor 725. The rotor 725 is twisted about the longitudinal axis of rotation 730, such that opposite ends of the rotor 725 are offset relative to one another. The rotor 725 is twisted in the opposite direction to the direction that the rib 765 is angled relative to the longitudinal axis of rotation 730 of the rotor. The first rotor cavity 770 has openings at a first end 775 of the rotor and the second rotor cavity (not shown) has openings (not shown) at a second end of the rotor (not shown). The first rotor cavity 770 and the second rotor cavity (not shown) are separated from each other by a bulkhead (not shown) that extends across the full interior of the hollow rotor, to prevent fluid flowing along the full internal length of the rotor. The rotor 725 comprises a first opening 790 extending between the first rotor cavity 770 and the surface recess 750 of the rotor. The first opening 790 has a has a tapered shape and extends along a longitudinal edge of a section of the surface recess 750 overlying the first rotor cavity 770 and continues across the land 735 at the first end 775 of the rotor, making an opening in the housing engaging surface provided by the land 735 at the first end 775 of the rotor. The rotor also comprises a similarly arranged second opening (not shown) extending between the second rotor cavity (not shown) and the surface recess 750. The second opening is located on the opposite longitudinal edge of the recess 750 and at the opposite end of the rotor 725, such that it overlies the second rotor cavity (not shown). Each surface recess 750 has a first opening and a second opening arranged at opposite ends of the rotor and on opposite sides of the recess.

[0109] In use of the pump 700, the rotor 725 is rotated by the action of a motor connected to the drive shaft 785, fluid flows into the first fluid port 710 and then into the first rotor cavity 770 through the open first end 775 of the rotor 725. The fluid flows from the first rotor cavity 770 through each first opening 790 into the fluid-conveying cavity provided between the surface recesses 750 and the interior surface 720 of the housing. The resiliently deformable diaphragm 755 is urged into contact with the surface of the rotor as it rotates by the action of pressurising means (not shown). The action of the diaphragm 755 on the surface of the rotor 725 displaces the fluid from the fluid-conveying cavity as the rotor rotates and the fluid flows through the second openings into the second rotor cavity (not shown). From there, the fluid flows out of the pump though the second fluid port (not shown).

[0110] FIG. 11 illustrates a cross-sectional view though part of a pump according to an embodiment of this invention. This figure illustrates the action of a plurality of diaphragm on the surface of a rotor comprising a plurality of recesses. In particular, FIG. 11 shows a housing 910 comprising three resiliently deformable diaphragm 920 each formed as a unit with the housing as provided by a thinner section of the housing. The section of housing providing the diaphragms being sufficiently thin to make the diaphragms resiliently deformable. The three diaphragms 920 are equidistantly spaced about the circumference of the rotor 930.

[0111] The rotor 930 comprises two surface recesses 940, which form, with the interior surface 945 of the housing, two fluid-conveying chambers 950.

[0112] Each diaphragm 920 is urged into contact with the surface of the rotor 930 by spring means 955 located within a diaphragm chamber 960. The spring means 955 ensure that each resiliently deformable diaphragm 920 remains in contact with the surface of the rotor 930 as it rotates and the surface profile of the rotor 930 varies. As can be seen from FIG. 11, each spring means 955 comprises a rib acting on the rear surface of the diaphragm 920.

[0113] FIGS. 12 and 13 illustrate an example of a rotor 1000, comprising an elongate body, which body is substantially hollow and comprises a first rotor cavity 1010 and second rotor cavity 1015. The first and second rotor cavities extend longitudinally along the length of the rotor and extend at least partially alongside one another. The first rotor cavity 1010 and the second rotor cavity 1015 are separated from each other by a bulkhead 1020. The bulkhead is staggered and separates the first and second rotor cavities 1010, 1015 such that the first rotor cavity 1010 and the second rotor cavity 1015 are not in direct fluid communication. The rotor further comprises two recesses 1025 and 1030. Each recess comprises a first opening 1035 between the first rotor cavity 1010 and the recess 1025, 1030 and a second opening 1040 between the recesses 1025 and 1030 and the second rotor cavity 1015. In FIGS. 13 and 14 only the second opening 1040 of recess 1030 is illustrated and only first opening 1035 of recess 1025 is illustrated. The first openings 1035 and the second openings 1040 in the rotor 1000 extend along a major portion of opposing longitudinal edges of each recess 1025, 1030. However, the arrangement of the first and second openings 1035, 1040 and the bulkhead 1020 are such that the first openings 1035 only open into first rotor cavity 1010 and the second openings 1040 only open into the second rotor cavity 1015. It can further be seen from FIGS. 12 and 13 that the first rotor cavity is open at only a first end 1045 of the rotor and the second rotor cavity 1015 is open only at a second end 1050 of the rotor.

[0114] The arrows indicate the direction of fluid flow, in one direction of rotation, when the rotor 1000 is in use in a pump according to any aspect of the present invention. It can be seen from FIG. 13 that fluid flow into the first rotor cavity 1010 through the end first end 1045, from there fluid flows through the first openings 1035 into the recesses 1025, 1030. As the pump operates and the rotor rotates in the given direction the fluid in the recesses 1025, 1030 is displaced by the pressurising means (not shown) through the second openings 1040 and into the second rotor cavity 1015 and out through the open second end 1050 of the rotor 1000. If the direction of rotation of the rotor is reversed, the direction of fluid flow will be reversed.