Pump with conveying chamber formed in outer rotor surface
A pump is formed by a housing (10) having an inlet (11) for connection to a source of fluid and an outlet (12) for pumped fluid. A rotor (15) is rotatable within the housing and the inlet (11) and the outlet (12) are spaced apart around the path of the rotor (15) in the housing. The rotor (15) has surfaces (16a, 16b, 16c, 16d) that form, with the housing (10), closed chambers (18a, 18b, 18c, 18d) which travel around the housing (10) to convey fluid from the inlet (11) to the outlet (12). The housing (10) carries a seal (14) that is located between the inlet (11) and the outlet (12) in the direction of travel of the rotor (15). The seal (14) co-operates with the rotor surfaces (16a, 16b, 16c, 16d) as the surfaces (16a, 16b, 16c, 16d) pass between the outlet (12) and the inlet (11) to prevent the formation of a chamber during said passage and so prevent fluid flow from the outlet (12) to the inlet (11). Such a pump is easily and cheaply produced and is particularly useful in medical applications.
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1. Field of the Invention
The invention relates to pumps.
2. Background to the Invention
A known form of pump comprises a housing with an inlet for connection to a source of fluid and an outlet for pumped fluid with the inlet and the outlet being spaced apart around a path of a rotor within the housing. The rotor includes at least one surface forming, with the housing, a closed chamber travelling around the housing to convey fluid around the housing.
In such pumps, a problem is the prevention of direct communication between the outlet and inlet. In JP-A-60240890, a flexible film is fixed to a partition wall between the outlet and the inlet and engages partitioning pieces on the rotor. In GB-A-482750, the rotor carries sections that seal against an arcuate surface of the housing. In U.S. Pat. No. 3,282,496 slidable elements are forced by pressure against the chamber-forming surfaces of the rotor. In JP-A-60111078, the rotor carries movable seals formed by various deformable bodies that seal against the housing between the outlet and the inlet. In GB-A-1109374, the rotor carries seals that seal against the housing between the inlet and the outlet
SUMMARY OF THE INVENTIONAccording to the invention, there is provided pump comprising a housing, a rotor path defined within the housing, an inlet formed in the housing at a first position on said rotor path, an outlet formed in the housing at a second position on said rotor path spaced from said first position, a rotor rotatable in said housing, at least two apices formed on the rotor and sealing against said rotor path, at least one surface formed on said rotor between said at least two apices, a chamber formed by said at least one rotor surface between the at least two apices and the housing and travelling around said rotor path on rotation of the rotor to convey fluid around the housing, a resilient seal carried by the housing located on said rotor path and extending between the outlet and the inlet in the direction of rotation of said rotor that each apex seals with, and resiliently deforms, the seal, as each apex passes between the outlet and the inlet to prevent fluid flow from said outlet to said inlet past the seal.
The following is a more detailed description of some embodiments of the invention, by way of example, reference being made to the accompanying drawings in which:—
Referring first to
The housing 10 contains a rotor 15. The rotor 15 may be formed of stainless steel or as a precision injection moulded plastics part formed from a resin such as acetal. As seen in the Figures, the rotor 15 is generally of circular cross-section and includes four recessed surfaces 16a, 16b, 16c and 16d of equal length equiangularly spaced around the rotor and interconnected by apices 17a, 17b, 17c and 17d formed by unrelieved portions of the rotor 15. Accordingly, each apex is rounded with a curvature that matches the curvature of the cylindrical housing surface 13 so that the rotor 15 is an interference fit within the cylindrical housing surface 13. As a result, each recessed surface 16a, 16b, 16c and 16d forms a respective chamber 18a, 18b, 18c and 18d with the cylindrical housing surface 13 as each surface 16a, 16b, 16c, 16d travels around that housing surface 13. If the housing 10 is formed from a resilient plastics material that deforms under load, the rotor 15 may be arranged to distend slightly the housing 10, so ensuring a fluid-tight seal around each surface 16a, 16b. 16c. 16d.
The rotor 15 is rotated in a clockwise direction in
The seal 14 is formed by a block of elastomeric material that is compliant, flexible and resilient such as that sold under the trade mark Hytrel. The seal 14 is connected to the housing 10 to prevent fluid passing between the seal 14 and the housing 10. This may be by use of an adhesive. Alternatively, the seal 14 could be moulded with the housing 10 in a 2-shot injection moulding process. In this latter case, the material of the seal 14 must be such that it welds to the housing to prevent leakage. The seal 14 has a first axial edge 19 adjacent the inlet 11 and a second axial edge 20 adjacent the outlet 12. The seal 14 has a rotor engaging surface 21 that has a length between the first and second edges 19, 20 that is generally equal to the length of each of the recessed surfaces 16a, 16b, 16c and 16d between the associated apices 17a, 17b, 17c, 17d and is shaped to match the shape of each recessed surface 16a, 16b, 16c, 16d. The axial extent of the seal 14 is that at least the same as the axial extent of the recessed surfaces 16a, 16b, 16c, 16d. The seal 14 projects into the space defined by an imaginary cylinder described by a continuation of the cylindrical surface 13 between the inlet 11 and the outlet 12. The seal 14 may be flexed between the first and second axial edges 19, 20 so that it bows outwardly relatively to the seal 14 towards the axis of the rotor 15 where the recessed surfaces 16a, 16b, 16c, 16d are concave.
The natural resilience of the material will tend to return the seal 14 to the undistorted disposition after distortion by the rotor 15 and this may be assisted by a spring (not shown) acting on the radially outer end of the seal 14.
The operation of the pump described above with reference to
Referring next to
Referring next to
The rotor 15 then moves to a position equivalent to the position shown in
It will be appreciated that the rate of flow of liquid is proportional to the rate of rotation of the rotor 15 and the volumes of the chambers 18a, 18b, 18c and 18d. Although the rotor 15 is shown as having four surfaces 16a, 16b, 16c, 16d, it could have any number of surfaces such as one or two or three surfaces or more than four surfaces. The surfaces 16a, 16b, 16c, 16d may be planar, or may be, for example, convexly or concavely curved. Preferably they are shaped as indentations formed by the intersection with the rotor 15 of an imaginary cylinder having its axis at 90° to the axis of the rotor and offset to one side of the rotor axis. As described above, the rotor engaging surface 21 of the seal 14 may be shaped to compliment the shape of the surfaces 16a, 16b, 16c, 16d.
At all times, the seal 14 acts to prevent the formation of a chamber between the outlet 12 and the inlet 11 in the direction of the rotor 15. The resilience of the seal 14 allows it always to fill the space between the inlet 11 and the outlet 12 and the portion of the rotor 15 in this region. As the pressure differential between the inlet 11 or the outlet 12 increases, there is an increased tendency for fluid to pass between the seal 14 and the rotor 15. The use of a spring acting on the seal 14, as described above, will decrease that tendency and so allow the pump to operate at higher pressures. Thus, the force applied by the spring determines the maximum pump pressure. Pumps are known in which the outlet and the inlet are separated by a thin vane extending from the housing and contacting the rotor. In such pumps, there is a volume of fluid between the outlet and the inlet and a large pressure gradient across the vane that will increase as the speed of rotation of the rotor. As a result, there is an increased liability to leakage across the vane. In the pump described above with reference to the drawings, although there is a pressure differential between the inlet and the outlet, there is a much more gradual gradient as the fluid is gradually squeezed out of the chambers 18a, 18b, 18c and 18d into the outlet 12 and then, after further rotation of the rotor 15, gradually introduced into a chamber 18a, 18b, 18c and 18d on the inlet side. This reduces the possibility of leakage and allows the pump to provide an accurate metered flow. The seal 14 acts as a displacer displacing the fluid between the inlet 11 and the outlet 12.
Referring next to
In this embodiment, the rotor 15 is formed in two parts; an outer cylindrical sleeve 25 and an inner rod 26. The rod 26 is provided with a radially extending pin 27 that engages a helical slot 28 provided in the sleeve 25.
The sleeve 25 is provided with a first set of surfaces 16a, 16b, 16c, 16d as described above with reference to
In addition, however, the sleeve 25 is also provided with a second set of recessed surfaces 29a, 29b, 29c, 29d at a position on the sleeve 25 axially spaced relative to the first mentioned surfaces 16a, 16b, 16c, 16d. These second surfaces 29a, 29b, 29c, 29d have a smaller circumferential extent than the first-mentioned surfaces 16a, 16b, 16c, 16d. In addition, the sleeve 25 is also formed with a circumferential groove 30 spaced axially from the first mentioned surfaces 16a, 16b, 16c, 16d and the other side of the surfaces 16a, 16b, 16c, 16d from the second surfaces 29a, 29b, 29c, 29d.
In use, rotation of the rotor 15 in a direction shown in
It will be appreciated that, since the pump is symmetrical about a plane including the rotor axis and midway between the inlet 11 and the outlet 12, the pump would operate on reverse rotation of the rotor 15 to draw fluid from the outlet 12 and deliver it to the inlet 11. It will also be appreciated that the surfaces 16a, 16b, 16c and 16d will need to have a curvature that is similar to a corresponding portion of the curvature on the seal 14 however because the surfaces are smaller the seal with have a permanently bowed disposition.
The end 32 of the sleeve 25 remote from the rotor drive projects from the housing 10. It is possible manually to push this end 32 so moving the sleeve 25 into the housing 10 until a groove 30 is aligned with the inlet 11 and the outlet 12. When in this position, as shown in
An alternative proposal is shown in
In the embodiments described above with reference to the drawings the rotor 15 is shown as a solid cylinder with the recessed surfaces 16a, 16b, 16c and 16d formed in that surface. This need not be so. As shown in
In
This is shown in
The pumps described above with reference to the drawings can be used for pumping any fluid preferably containing no particulates. Such pumps may, however, find particular application in the pumping of medical fluids and may be used with intravenous administration sets. Such pumps allow aseptic pumping and metering of fluid to high volumetric accuracies. In this case, the inlet 11 and the outlet 12 may be connected in line before the housing 10 and the rotor 15 assembly are connected to a drive. The housing 10 and rotor assembly 15 may be supplied with the inlet 11 and the outlet 12 aligned with the groove 30 so that a delivery tube of the set is in a free flow condition and able to be primed as soon as the housing 10 and rotor 15 assembly is connected in-line. When the rotor 15 is connected to the drive, the making of the connection moves the rotor 15 to a position in which the rotor surfaces 16a, 16b, 16c, 16d are aligned with the inlet 11 and the outlet 12 so that the pump 10 is ready for metered operation. It is thus mechanically impossible for the rotor 15 to be in the free flow position when connected to the drive so that, should the drive fail, free flow is not possible.
Referring next to
In the arrangement shown in
In this embodiment, the seal 14 is formed by a membrane 37 that extends between the first and second axial edges 19, 20 of the housing 10 and between the outlet 12 and the inlet 11. The membrane 37 is supported by a member 38 that applies a resilient force to the membrane 37. This member 38 can have a number of forms. Some examples of this are shown in
The membrane 37 has a low coefficient of friction with the rotor 15 but is sufficiently stretched to prevent the formation of wrinkles when deformed outwardly by the apices 17. The membrane 37 seals closely against the rotor 15 to displace fluid in the chambers 18 and prevent leakage between the outlet 12 and the inlet 11.
The problem of communication between an outlet and an adjacent inlet is not confined to the case disclosed above where a single inlet and a single outlet are provided with fluid being conveyed between the single inlet and the single outlet. It is possible to have two or more inlets and two or more outlets spaced around the housing 10. In this case, the problem will still exist of preventing fluid communication between an outlet and a succeeding inlet, in the direction of rotation of the rotor, but the outlet and the inlet will not be associated with the same flow paths. An example of this will now be described with reference to
Referring next to
In use, as the rotor 15 rotates, starting from the rotor position shown in
It will be appreciated that, in this configuration, the seals formed by the membranes 37, 37a act to prevent fluid flow not between the inlet 11 and the associated outlet 12 and between the second inlet 11a and the associated second outlet 12a, but between the first outlet 12 and the second inlet 11a and between the second outlet 12a and the first inlet 11. The problem overcome is, however, the same as described above with reference to
It will be appreciated that the pump described above with reference to
It will be appreciated that any of the pumps described above with reference to the drawings may have more or less than four chambers 18a, 18b, 18c, 18d. A single chamber is possible but will only give an output once per rotation of the rotor 15. A number of smaller chambers having a total volume of one large chamber may provide a smoother (less pulsed) output flow per revolution. In relation to the embodiment of
It will be appreciated, that the pumps described above with reference to the drawings are formed from few parts—effectively, the housing 10, a rotor 15 and a seal 14. It is possible to form the housing 10 and seal 14 in a two-shot injection moulding process. Alternatively all three elements can be produced in a single assembly injection moulding process in which the rotor 15 is moulded first with the housing 10 then being moulded around the rotor 15 and finally the seal 14 moulded into the housing. The use of such a moulding process allows a pump to be manufactured cheaply and simply to an extent that may allow the pump to be used as a disposable pump.
Claims
1. A pump comprising:
- a housing formed of a resilient material,
- a rotor path defined within the housing,
- an a first inlet formed in the housing at a first position on said rotor path,
- an a first outlet formed in the housing at a second position on said rotor path spaced from said first position,
- a rotor rotatable in said housing around an axis, the rotor having an outer rotor surface which seals against contacts said rotor path and resiliently distends said rotor path housing to provide a fluid-tight seal between the rotor and the rotor path, and at least one first chamber-forming concavity inwardly formed from said outer rotor surface, said first concavity a) having a first concave surface which is concave in planes including the rotor axis, b) being surrounded by said outer rotor surface, and c) solely forming a first conveying chamber travelling around said rotor path on rotation of the rotor to convey fluid around the housing; and
- a first resilient seal carried by the housing, located on said rotor path and extending between the first outlet and the first inlet in the direction of rotation of said rotor, said first resilient seal being adapted to seal with and be resiliently deformed by said outer rotor surface surrounding said first concavity to prevent fluid flow from said first outlet to said first inlet past the first seal, and to seal with said first concave surface of said first concavity, as said first concavity passes between the first outlet and the first inlet to squeeze fluid from the first chamber into the first outlet, and
- wherein the housing includes a second inlet and a second outlet spaced axially along the rotor from the first inlet and the first outlet,
- wherein the rotor includes at least one second chamber-forming concavity forming, with the housing, a second conveying chamber travelling around the housing between the second inlet and the second outlet to convey fluid from said second inlet to said second outlet,
- wherein the housing between the second outlet and the second inlet in the direction of rotation of the rotor includes a second resilient seal adapted to seal with and be resiliently deformed by the outer rotor surface of said second concavity to prevent fluid flow from said second outlet to said second inlet past said second seal, and to seal with a second concave surface of said second concavity, as said second concavity passes between the second outlet and the second inlet to squeeze fluid from the second chamber into the second outlet,
- wherein the rotor is movable axially between a) the above described position which aligns the first concavity with the first inlet and the first outlet and the second concavity with the second inlet and second outlet, and b) an alternative position of which aligns the second concavity with the first inlet and the first outlet while closing the second inlet and the second outlet.
2. A pump according to claim 1, wherein the first seal has a rotor-engaging surface having an axial and angular extent generally the same as the axial and angular extent of the at least one first chamber-forming concavity of the rotor.
3. A pump according to claim 1, wherein the housing includes a generally cylindrical interior surface co-operating with the rotor to form said first conveying chamber.
4. A pump according to claim 3, wherein the first seal interrupts said cylindrical interior surface, extending axially and circumferentially relative to said cylindrical interior surface.
5. A pump according to claim 4, wherein the first seal projects radially inwardly of the cylinder defined by said cylindrical interior surface.
6. A pump according to claim 1, wherein the first seal has angularly spaced first and second ends around the path of the rotor, the first outlet being formed adjacent said first end.
7. A pump according to claim 6, wherein the housing includes a generally cylindrical interior surface forming said rotor path and co-operating with the rotor to form said first conveying chamber, the first inlet and the first outlet being formed in said cylindrical interior surface of the housing.
8. A pump according to claim 6, wherein the first inlet and the first outlet are formed in said first seal.
9. A pump according to claim 1, wherein the first seal has angularly spaced first and second ends around the path of the rotor, the first inlet being formed adjacent said second end.
10. A pump according to claim 1, wherein the first seal is formed by a block of resilient material.
11. A pump according to claim 1, wherein the first seal is formed by a membrane and a member resiliently supporting the membrane, the membrane sealing against the rotor.
12. A pump according to claim 11, wherein the resilient member is formed by a container of fluid or gas under pressure.
13. A pump according to claim 11, wherein the resilient member is formed by a spring.
14. A pump according claim 1, wherein two or more first chamber-forming concavities are provided on said rotor at axially aligned angularly spaced positions around the rotor, each first chamber-forming concavity co-operating with said first seal as the first concave surface passes from said first outlet to said first inlet in the direction of rotation of the rotor.
15. A pump according claim 1,
- wherein the housing includes a second inlet and a second outlet spaced axially along the rotor from first-mentioned inlet and outlet,
- wherein the rotor includes at least one second chamber-forming concavity forming, with the housing, a second conveying chamber travelling around the housing between the second inlet and the second outlet to convey fluid from said second inlet to said second outlet,
- wherein the housing between the second outlet and the second inlet in the direction of rotation of the rotor includes a second resilient seal adapted to seal with and be resiliently deformed by the outer surface of said at least one second chamber-forming concavity to prevent fluid flow from said second outlet to said second inlet past said second seal, and to seal with a concave surface of said second concavity, as said second concavity passes between the second outlet and the second inlet to squeeze fluid from the second chamber into the second outlet.
16. A pump according to claim 15, wherein the rotor is:
- movable axially in one direction to align the first-mentioned at least one chamber-forming concavity and the second inlet and second outlet while closing the first-mentioned inlet and the first-mentioned outlet, and
- moveable axially in an opposite direction to align the at least one chamber-forming concavity with the first inlet-mentioned and the first-mentioned outlet while closing the second inlet and the second outlet.
17. A pump according to claim 16, wherein the housing is formed of a resilient material, the rotor engaging and resiliently distending the housing to provide a fluid-tight seal between the housing and housing-contacting portions of the rotor.
18. A pump according to claim 17 1,
- wherein the housing has a generally cylindrical interior surface,
- wherein the rotor has a co-operating generally cylindrical exterior surface sealing against said interior surface, and
- wherein said at least one first chamber-forming concavity is formed in said generally cylindrical exterior surface.
19. A pump according to claim 18, wherein said exterior surface is formed by a land on the rotor, the land having axially spaced ends and the rotor being provided with radially relieved portions at said ends.
20. A pump according to claim 18, wherein a circumferential rib is formed on each relieved portion, each rib sealing resiliently against the interior surface of said housing.
21. A pump according to claim 1, wherein only a single first inlet and a single first outlet are provided, the rotor conveying fluid from said first inlet to said first outlet.
22. A pump according to claim 1,
- further including a second another first inlet and a second another first outlet spaced circumferentially around the housing from the first mentioned inlet and first outlet,
- the rotor further including a plurality of chamber-forming concavities conveying fluid from the first mentioned inlet to the first mentioned outlet and from the second another first inlet to the second another first outlet, and
- wherein the first mentioned seal is located between the second another first inlet and the first mentioned outlet and a second another first seal is provided between the first mentioned outlet and the second another first inlet.
23. A pump according to claim 22, wherein the rotor has at least four first chamber-forming concavities.
24. A pump according to claim 1, wherein the rotation of the rotor is reversible to pump fluid from the first outlet to the first inlet.
25. A pump according to claim 1, further including a drive for rotating the rotor.
26. A pump according to claim 1, wherein the housing and first seal are a unit including of an insert moulding, an over-moulding or a dual shot moulding.
27. A pump according to claim 1, wherein the housing, first seal and rotor are a single injection moulding.
28. A pump comprising:
- a housing,
- a rotor path defined within the housing,
- an inlet formed in the housing at a first position on said rotor path,
- an outlet formed in the housing at a second position on said rotor path spaced from said first position,
- a rotor rotatable in said housing, the rotor having at least two apices formed on the rotor and sealing against said rotor path, at least one first surface formed on said rotor between said at least two apices, and a chamber formed in said at least one first surface between the at least two apices and the housing, and travelling around said rotor path on rotation of the rotor to convey fluid around the housing,
- a resilient seal carried by the housing located on said rotor path and so extending between the outlet and the inlet in the direction of rotation of said rotor that each apex seals with, and resiliently deforms, the seal, as each apex passes between the outlet and the inlet to prevent fluid flow from said outlet to said inlet past the seal;
- in which the rotor is movable axially relative to the housing between a first axial position and a second axial position, and
- the rotor further including at least one second chamber-forming surface spaced axially from said at least one first chamber-forming surface, the at least one first chamber-forming surface forming a chamber with the housing in said first axial position of the rotor and the at least one second chamber-forming surface forming a chamber with the housing in said second axial position of the rotor.
29. A pump according to claim 28, wherein the volume of the chamber formed by the at least one first chamber-forming surface is different from the volume of the chamber formed by the at least one second chamber-forming surface.
30. A pump according to claim 29, wherein the volume of the chamber formed by the at least one first chamber-forming surface is greater than the volume of the chamber formed by the at least one second chamber-forming surface.
31. A pump according to claim 28, wherein a device is provided for moving said rotor axially between said first and second axial positions.
32. A pump according to claim 31,
- in which rotation of said rotor in one direction acts to convey fluid from the inlet to the outlet with the rotor in the first axial position,
- in which rotation of said rotor in an opposite direction will move said rotor axially between said first and second axial positions,
- in which a reversal of rotation from the opposite direction to the one direction with the rotor in the second axial position will move the rotor back to the first axial position, and
- in which rotation in said opposite direction acts to convey fluid from the outlet to the inlet by said at least one second chamber-forming surface.
33. A pump according to claim 32, wherein said device includes a mechanism acting between the housing and the rotor for moving the rotor axially between the first and second axial positions relative to the housing depending on rotation of said rotor in the one or the opposite direction.
34. A pump according to claim 33, wherein said mechanism comprises a pin member and a helical slot member, one member being on the rotor and the other member being on the housing, rotation of the rotor between the one direction and the opposite direction moving the pin in a helical path along said slot to move the rotor axially between the first and second axial positions.
35. A pump comprising:
- a housing,
- a rotor path defined within the housing,
- an inlet formed in the housing at a first position on said rotor path,
- an outlet formed in the housing at a second position on said rotor path spaced from said first position,
- a rotor rotatable in said housing, the rotor having at least two apices formed on the rotor and sealing against said rotor path, at least one surface formed on said rotor between said at least two apices, and a chamber formed by said at least one surface between the at least two apices and the housing, and travelling around said rotor path on rotation of the rotor to convey fluid around the housing,
- a resilient seal carried by the housing located on said rotor path and so extending between the outlet and the inlet in the direction of rotation of said rotor that each apex seals with, and resiliently deforms, the seal, as each apex passes between the outlet and the inlet to prevent fluid flow from said outlet to said inlet past the seal; and
- in which the rotor is movable axially relative to the housing between a first axial position in which the at least one chamber-forming surface forms a chamber with the housing and a second axial position in which the rotor cooperates with the housing to provide a direct communication between the inlet and the outlet.
36. A pump according to claim 35, wherein a device is provided for moving said rotor axially between said first and second axial positions.
37. A pump according to claim 36,
- in which rotation of said rotor in one direction acts to convey fluid from the inlet to the outlet with the rotor in the first axial position,
- in which rotation of said rotor in an opposite direction will move said rotor axially between said first and second axial positions, and
- in which a reversal of rotation from the opposite direction to the one direction with the rotor in the second axial position will move the rotor back to the first axial position.
38. A pump according to claim 37, wherein said device includes a mechanism acting between the housing and the rotor for moving the rotor axially between the first and second axial positions relative to the housing depending on rotation of said rotor in the one or the opposite direction.
39. A pump according to claim 38, wherein said mechanism comprises a pin member and a helical slot member, one member being on the rotor and the other member being on the housing, rotation of the rotor between the one direction and the opposite direction moving the pin in a helical path along said slot to move the rotor axially between the first and second axial positions.
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Type: Grant
Filed: Apr 18, 2012
Date of Patent: Apr 15, 2014
Assignee: Quantex Patents Limited (London)
Inventors: Richard P. Hayes-Pankhurst (London), Graham K. Lacy (London), Christopher E. Nightingale (London)
Primary Examiner: Mary A Davis
Application Number: 13/449,985
International Classification: F01C 19/02 (20060101); F01C 20/20 (20060101);