GB2222205A

GB2222205A - Orbiting eccentric pumping device

Info

Publication number: GB2222205A
Application number: GB8813539A
Authority: GB
Inventors: Michael Joseph Egan
Original assignee: BARTON GORDON P
Current assignee: BARTON GORDON P
Priority date: 1988-06-08
Filing date: 1988-06-08
Publication date: 1990-02-28
Also published as: GB8813539D0

Abstract

A pumping device-comprises a housing 2 defining a cylindrical wall 3 within which is mounted a movable annular member 4 the longitudinal axis of which is eccentric relative to the axis of the wall 3 to define a pumping space 8 therebetween. Four seal members 11 each mounted in a holder 9 engage the movable member 4. The holders 9 each have a rectangular projection (26, Figs. 1 & 3) external to the pump and the projections (26) are coupled to the eccentric (25) coaxial with the crank pin 22 on which the movable member 4 is mounted such that the central longitudinal planes (27) of the projections (26) intersect on the axis of the eccentric (25). Accordingly as the crank shaft of the pump is rotated the seal holders 9 are rotated so that the seals 11 are always presented radially to the member 4. <IMAGE>

Description

ORBITING ECCENTRIC PUMPING DEVICE This invention relates to an orbiting eccentric pumping device, that is to say a pumping device having a body which defines a cylindrical wall and a movable cylindrical member mounted within the wall eccentric thereto, the movable member being mounted such that the axis thereof is forced, in use, to orbit about the axis of the cylindrical wall of the body to produce a cyclic variation in the spacing between each point on the cylindrical wall of the body and the adjacent part of the movable member. The movable member may, as a practical matter, rotate within the body as its axis orbits the axis of the cylindrical wall of the body, or it may simply move around the interior of the body without substantive rotation.

Heretofore, orbiting eccentric pumping devices have been furnished with vanes to divide the space defined between the body cylindrical wall and the movable member into a plurality of pumping chambers. Each chamber is furnished with inlet means for supplying fluid to the chamber as the volume of the chamber is increased during movement of the movable member, and outlet means for receiving fluid from each chamber as the volume of that chamber is decreased during movement of the movable member.

Such pumps are commonly known as "vane pumps". Known vane pumps suffer from the problem that it is difficult to achieve and to maintain in use adequate sealing between the vanes and both the body and the movable member.

According to one aspect of the present invention an orbiting eccentric pumping device comprises: a body defining a cylindrical wall; a member mounted within the body and movable relative thereto, the movable member having a cylindrical wall which faces the cylindrical wall of the body and is eccentric relative thereto to define a pumping space therebetween; a plurality of seal members mounted on the body, each seal member having a partcylindrical surface which engages the cylindrical surface of the movable member whereby the seal members divide the pumping space into a plurality of pumping chamber; means for moving the movable member so that the axis thereof orbits the axis of the cylindrical wall of the body whereby the volume of each pumping chamber is cyclically varied; and means for automatically changing the orientation of the seal members as the movable member moves within the body in use so that the axes of the cylindrical surfaces of the seal members always remain coincident with the axis of the movable member.

With such an arrangement, the seal members can be formed with a concave part-cylindrical surface which matches the corresponding cylindrical surface of the movable member. The seal member and movable member are accordingly in contact over a significant circumferential distance, ensuring a good fluid seal between the seal members and the movable member.

Preferably, each seal member is slidably mounted within a holder which is itself rotatably mounted in the body, and means bias each seal member radially inwardly into engagement with the cylindrical surface of the movable member. The biasing means can conveniently be provided by applying fluid pressure to the radially outer surface of each seal member. The fluid pressure can conveniently be provided from a suitable feed pump. Preferably, the fluid medium used to apply pressure to the seal members is the same medium as is to be pumped by the pumping device. In this case, passages for supplying fluid to each pumping chamber as the volume of the pumping chamber is increased in use of the pumping device are preferably formed in the seal members and extend from the radially outward face of each seal member to receive fluid therefrom.

If the seal members are slidably mounted in holders as described above, the orientation-of the seal members can conveniently be changed by changing the orientation of the holders. To this end, each holder preferably extends to the exterior of the body and is coupled to a suitable driving device for automatically varying the orientation of the holders as the movable member moves. The driving device can conveniently comprise an eccentric mounted on the drive shaft of the movable member, the eccentric being coaxial with the axis of the movable member. The seal member housings are then coupled to thc eccentric to tilt the seal member housings as the movable member and eccentric move together, maintaining the desired relationship between the seal members and the movable member.

Conveniently, each seal member housing can be formed with a rectangular projection which slides in a mating slot formed in a coupling device. The longitudinal axes of the slots are arranged to intersect at the axis of the eccentric and the coupling device is connected to the housing so that the point of interception of the longitudinal axes of the slots is free to move as the eccentric rotates, to maintain the point of intersection of the axes of the slots coincident with the axis of the eccentric.

Preferably, the means for moving the movable member comprises a rotatable input member having an eccentric on which the movable member is mounted. If the body is fixed against rotation, the torque required to turn the rotatable input member will of course depend on the extent to which the output from the pumping chambers is restricted. By providing progressive restriction for the output from the pumping chambers from a state in which there is substantially no restriction to a state in which there is substantially no flow, the input torque required to turn the rotatable input member will vary from substantially nothing, to an extremely high value. This characteristic can conveniently be used to form a variable ratio drive coupling, the transmission ratio of which can be determined by varying the restriction imposed on fluid flowing from the pumping device.

In particular, the rotatable input member can be the ring gear of an epicyclic gear set. Drive from an input shaft can then be used to drive a cage containing the planetary gears of the epicyclic gear set, and the sun gear of the epicyclic gear set can be used to drive an output shaft. With such an arrangement, when there is substantially no restriction to fluid leaving the pumping chambers the ring gear will be able freely to rotate. If there is no load on the output shaft the planet gears will tend to carry the ring gear and the sun gear around with them as a unit and the rotational speed of the output shaft will be substantially the same as the rotational speed of the input shaft. If the output shaft is loaded it will remain stationary, and if it is driven at a speed different from that of the input shaft, the speed differential will be accommodated by rotation of the ring gear If, however, a load is imposed on the pump by restricting the outlet from the pumping chambers, the ring gear will in effect be braked and the rotating planet gears, driven from the input shaft, will tend to rotate the sun gear and with it the output shaft at a speed higher than the speed of rotation of the input shaft.

Accordingly, the pumping device can be used to form a variable ratio drive coupling.

The invention will be better understood from the following description of a preferred embodiment thereof, given by way of example only, reference being had to the accompanying drawings wherein: Figure 1 is an axial cross-sectional view of one embodiment of the invention, taken on the line I-I of Figure 2; Figure 2 is a radial cross-section of the embodiment of Figure 1, taken on the line II-II of Figure 1; Figure 3 is a radial cross-section on the line III-III of Figure 1; and Figure 4 is an exploded view of various of the components of the embodiment of Figures 1 to 3.

- e orbiting eccentric pumping device 1 shown in the drawings comprises a housing 2 which defines a right circular cylindrical wall 3 within which is mounted a movable member 4 in the form of an annulus defining a right circular cylindrical wall 5 which faces the cylindrical wall 3 of the housing. The longitudinal axis 6 of the movable member 4 is eccentric relative to the longitudinal axis 7 of the wall 3 whereby a pumping space 8 is defined between the walls 3 and 5.

Four seal assemblies 9 are mounted on the housing 2. Each seal assembly comprises a holder 10 which is rotatably mounted in the housing and a seal member 11 slidably mounted in the holder. Each seal member 11 has a part cylindrical surface 12 complementary to the wall 5, and in engagement therewith. Accordingly, the seal members 11 divide the pumping space 8 into four pumping chambers 13-16.

In use, each seal member 11 is biased into engagement with the movable member 4 by pressurizing the chamber formed between the radially outer surface of the seal member and the associated holder 10. For this purpose, fluid from a suitable feed pump is supplied via ports 17 in the housing and ports 18 in the holders 9. The fluid supplied for biasing the seal members is the same fluid as t6 be pumped by the pumping device, and feed passages 1 9 extend through each seal member from the radially outer surface thereof to one of the pumping chambers for supplying fluid to that pumping chamber as the volume of the pumping chamber is increased by movement of the movable member in use.A suitable non-return valve is provided for preventing the expulsion of fluid through each passage 19 as the volume of the associated pumping chamber is reduced by movement of the movable member.

Outlet ports 20, furnished with appropriate nonreturn valves, are formed in the housing to permit fluid to be discharged from each pumping chamber as the volume of that pumping chamber decreases due to movement of the movable member 4.

The movable member 4 is mounted via a bearing 21 on the crank pin 22 of a crankshaft 23. The crankshaft is connected to a ring gear 24 which constitutes a rotary input member for the pumping device whereby rotation of the ring gear 24 relative to the housing 2 causes rotation of the crankshaft 23 forcing the axis 6 of the movable member to orbit the axis 7 of the housing thereby cyclically varying the volume of each pumping chamber.

Externally of the housing 2 an eccentric 25 is keyed to the crankshaft 23. The external surface of the eccentric 25 lies on a common right circular cylinder with the surface of the crank pin 22 whereby as the crankshaft rotates in use the position of the surface of the eccentric 25 external of the housing at all times corresponds to the position of the surface of the crank pin 22 within the housing.

Each seal assembly holder 9 extends through the end wall of the housing and terminates in a rectangular projection 26 which has a central longitudinal plane 27 coincident with the central longitudinal plane of the associated seal member 11. The rectangular projections 26 are coupled to the eccentric 25 such that as the eccentric 25 rotates in use the longitudinal planes 27 intersect on the axis of the eccentric 25. Because of the connection of the projections 26 to the seal members 11 on the one hand, an of the eccentric 25 to the crank pin 22 on the other hand, the effect of this arrangement is that as the crankshaft rotates the orientation of the seals 11 is automatically changed so that the axes of the cylindrical surfaces 12 of the seal members always remain coincident with the axis 6 of the movable member.It will accordingly be appreciated that the seal members 11 remain in full-face contact with the surface 5 and accordingly provide a high quality seal between adjacent pumping chambers. It will be further noted that in general, the movable member 5 will not rotate in use, but will merely orbit about the pumping chamber. In the circumstances, there will be very little relative movement between the surfaces 12 of the seal members and the contacting surface of the movable member, and very little wear in use a this point will be experienced.

The projections 26 may conveniently be coupled to the eccentric 25 by a coupling device 32 comprising a body 33 having a circular aperture 34 in which the eccentric is received, the body 33 being connected to the housing 2 by means of small crankshafts 35 which permit the coupling device 32 to orbit with the eccentric 25, but prevent rotational movement of the coupling device relative to the housing. Each projection 26 is connected to the coupling device body 33 by a slotted member 36 whereby as the coupling device orbits with the eccentric 25 the orientation of each projection 26 is changed to maintain the intersection of the planes 27 coincident with the axis of the eccentric.

In use, fluid to be pumped is supplied to the ports 17 from a suitable feed pump at an appropriate pressure, for example approximately 1034kPa (150psi). The crankshaft 23 is rotated, causing the movable member 4 to orbit around the interior of the housing, whereby the volume of each pumping chamber is in turn increased to receive fluid via the associated passage 19, and then decreased to expel fluid via the associated port 20.

In the illustrated embodiment of the invention drive for the pump is derived from a gear 28 which is rotated from any suitable external power source. The gear 28 has rigidly mounted thereon a cage carrying a plurality of planetary gears 29. The planetary gears 29 are in mesh with the ring gear 24 and a sun gear 30 formed on the end of an output shaft 31. In use, the gear 28 is rotated to drive che planetary gears around the sun gear 30. If hlere is substantially no resistance to output from the pump, very little torque will be required to turn the ring gear 24, and accordingly the ring gear will tend to rotate as a unit with the planetary gears, sun gear, and input gear 28.

The output shaft 31 will accordingly turn at substantially the same rotational speed as the input gear 28.

If, however, output from the pumping device is restricted, for example by an appropriate pressure control valve, the torque required to turn the ring gear 24 will be increased, and the planetary gears 29 will be forced to rotate about their own axes as they orbit the sun gear.

This in turn will cause the sun gear to rotate faster than the input gear 28. In the extreme case, if output from the pumping device is totally prevented, the ring gear 24 will remain substantially stationary relative to the housing, and the planetary gears will rotate the sun gear and output shaft 31 at a speed ratio relative to the speed of the input gear determined by the ratio of the number of teeth on the ring gear to the number of teeth on the star gear.

When used as a variable ratio drive coupling the invention may conveniently be used as part of a steering mechanism, e.g. for heavy civil engineering machines. This is done by incorporating a variable ratio drive coupling in the final drive to each driven wheel or track sprocket. By controlling the output of the drive couplings differential rotation of the driven wheels or track sprockets can be obtained to effect steering of the machine.

Claims

1. An orbiting eccentric pumping device comprises: a body defining a cylindrical wall; a member mounted within the body and movable relative thereto, the movable member having a cylindrical wall which faces the cylindrical wall of the body and is eccentric relative thereto to define a pumping space therebetween; a plurality of seal members mounted on the body, each seal member having a partcylindrical surface which engages the cylindrical surface of the movable member whereby the seal members divide the pumping space into a plurality of pumping chamber; means for moving the movable member so that the axis thereof orbits the axis of the cylindrical wall of the body whereby the volume of each pumping chamber is cyclically varied; and means for automatically changing the orientation of the seal members as the movable member moves within the body in use so that the axes of the cylindrical surfaces of the seal members always remain coincident with the axis of the movable member.

2. A pumping device according to claim 1 wherein the seal members are each formed with a concave partcylindrical surface which matches the corresponding cylindrical surface of the movable member.

3. A pumping device according to claim 1 or claim 2 wherein each seal member is slidably mounted within a holder which is itself rotatably mounted in the body, means being provided to bias each seal radially inwardly into engagement with the cylindrical surface of the movable member.

4. A pumping device according to claim 3 wherein the biasing means comprises fluid pressure applied to the radially outer surface of each seal member.

5. A pumping device according to claim 4 wherein the fluid pressure is provided by a feed pump and the fluid medium used to apply the fluid pressure to the seal members is the medium to be pumped by the pumping device.

6. A pumping device according to claim 5 wherein each seal member has a passage formed therein for supplying fluid from the radially outer surface thereof to a pumping chamber.

7. A pumping device according to any of claims 3 to 6 wherein the orientation of the seal members is changed by changing the orientation of the holders.

8. A pumping device according to claim 7 wherein each holder extends to the exterior of the body and is coupled to means for automatically varying the orientation of the holders as the movable member moves.

9. A pumping device according to claim 8 wherein the means for automatically varying the orientation of the holders comprises an eccentric mounted on the drive shaft of the movable member coaxial with the axis of the movable member, and means coupling the seal member housings to the eccentric to tilt the seal member housings as the movable member and the eccentric move together.

10. A pumping device according to any preceding claim wherein the means for moving the movable member comprises a rotatable input member having an eccentric on which the movable member is mounted; the body is mounted in a manner which permits rotation of the body; and means are provided for controlling the outlet pressure from the pumping device to vary selectively the amount of torque transmitted from the rotatable input member to the body.

11. A pumping device substantially as hereinbefore described with reference to the accompanying drawing.