US3283725A

US3283725A - Hydraulic machines

Info

Publication number: US3283725A
Application number: US415278A
Authority: US
Inventors: Scott George William Pearson; Montgomerie George Alan
Original assignee: Serck R&D Ltd
Current assignee: Serck R&D Ltd
Priority date: 1963-12-10
Filing date: 1964-12-02
Publication date: 1966-11-08
Anticipated expiration: 1983-11-08
Also published as: GB1089819A

Description

. 1966 G. w.- P. SCOTT ETAL 3,

HYDRAULIC MACHINES Filed Dec. 2, 1964 2 Sheets-Sheet IL NOV. 8, 1956 e. w. P. SCOTT ETAL 3,283,725

HYDRAULIC MACHINES 1 il l United States Patent 3,283,725 HYDRAULIC MACHINES George William Pearson Scott, Bowbridge, Stroud, and

George Alan Montgomerie, Leamington, England, assignors to Serck R & D Limited, Birmingham, England Filed Dec. 2, 1964, Ser. No. 415,278 Claims priority, application Great Britain, Dec. 10, 1963,

v 48,666/ 63 3 Claims. (Cl. 103162) This invention relates to hydraulic machines of the kind comprising a housing, a rotatable shaft mounted in the housing, a rotor drivingly connected to said shaft, said. rotor being formed with a plurality of passages, a pair of ports in one end of the housing arranged so that during rotation of the rotor said passages are brought successively into communication with ports, a plurality of pistons slideable respectively in the passages, and an inclined cam surface, at the end of the housing remote from the ports, against which the pistons bear so that rotary movement of the rotor is accompanied by axial movement of the pistons.

It is an object of the invention to provide an hydraulic machine of the kind specified in a convenient form.

According to the invention, in an hydraulic machine of the kind specified, each piston is hollow and is provided at its cam-engaging end with a slipper of cup-shaped form, the interior of the piston communicating with the interior of the slipper through a restricted bore and the slipper having and end face which is inclined to the axis of the slip-per at an angle substantially corresponding to the inclination of the cam surface.

Reference will now be made to the accompanying drawings in which FIGURE 1 is a longitudinal section of one example of a motor according to the invention and FIGURES 2, 3 and 4 are enlarged sections showing three different forms of piston for the motor shown in FIG- URE 1.

As shown in FIGURE 1 the motor includes a housing in which a shaft 11 is rotatably mounted. Also rotatably supported by hydrostatic bearings in the housing 10 is a rotor 12, which is drivingly connected to the shaft, by virtue of the non-circular section of its central passage 12a and the non-circular section of the associated part 11a of the shaft.

Formed in the rotor 12 are a series of axially extending passages in which pistons 13 are reciprocably mounted. These pistons project from one end of the rotor 12 and have slippers 14 bearing against an inclined cam surface 15 formed on a cylindrical block secured to the housing 10. It will thus be seen that rotation of the rotor 12 causes the pistons 13 to be reciprocated in their respective passages.

Formed in the port plate 16 which provides an end wall of the housing, are a pair of ports 17, 18 through which liquid enters and leaves the motor respectively. These ports are so disposed that the end of the passages in the rotor are brought successively into communication with the ports as the rotor is turned.

Referring now to FIGURE 2 the piston 13 shown therein has the slipper 14 formed integrally thereon. As shown the piston is formed at various positions along its length with circumferential oil retaining grooves 19. It will also be seen that the slipper 14 is of generally cup shaped form with its axis aligned with the axis of the piston 13. The end face 14a of the slipper is, however, inclined to the common axis of the piston and slipper at an angle corresponding to the inclination of the cam surface 15.

The interiors of the slipper 14 and. piston 13 are interconnected by a fine bore 20.

3,283,725 Patented Nov. 8, 1966 Thus, in use, when high pressure liquid is supplied to port 17 the interiors of the slippers will fill with pressurized liquid and will form an hydrostatic bearing between the slippers 14 and the cam surface 15. The spacing of face 14a from the surface 15 will regulate the rate at which liquid leaves the interior of the slipper and variation of flow through bore 20 will cause changes of pressure within the slipper as is known in hydrostatic bearings. 7

Turning now to FIGURE 3 (in which all reference numerals have been increased by the piston 113 and the slipper 114 are formed separately and are sealingly joined together. The end of piston 113 is closed by wall 1130 in which bore is formed. Also formed in the end wall 113a is a substantially hemispherical recess 11312. The periphery of the end of the piston is of somewhat reduced diameter and, in fact, may be of frusto-conical form as shown.

The slipper 114 is formed with a central hemispherical projection 114b which fits into the recess 113b, a large bore 113c being formed in this projection and communicating with the interior of the slipper 114. The slipper also has a cylindrical skirt portion 114d surrounding the reduced. end of the piston. The end face 1140 of the slipper is inclined as before.

The slipper 114 and piston 113 are joined together by means of a ring 121 of rubber or other elastomeric material. This ring is formed by treating the piston and slipper to form suitable keying surfaces, locating them together in the required relative position, injecting the raw elastomer into the space between the piston 113 and the skirt portion 114d and then curing the elastomer. Alternatively where the elastomer cannot be injected, a preformed ring of the raw elastomer may be inserted in the space during assembly. In either case when the elastomer is cured it becomes firmly bonded to the metal surfaces and forms a flexible but fully liquid-tight joint.

This flexible joint enables the slipper 114 to move slightly relative to the piston 113. Such movement is, however, restricted to turning of the slipper about the centre of the mating spherical surfaces. Thrust and journal loads on the slippers are transmitted directly to the piston without much effect on the ring 121. The movement of the slipper enables it to follow any irregularities in the cam surface and to allow for the bending of the pistons that occurs under load without any undue loss of pressure within the slippers.

Referring now to FIG. 4 (in which reference numerals have again been increased by 100) the piston 213 is formed with a convex part spherical end 213a which fits against a complementary surface within the skirt portion 214d of slipper 214. The bore 220 is, in this case, formed in the slipper 214. The piston 213 and the slipper 214 are again bonded together by a ring 221.

In this case the piston receives directly any thrust on the inclined slipper face 214a, but journal loads are taken by the ring 221.

In the embodiments shown in FIGURES 3 and 4 the

ring

121 or 221 cured in situ may be replaced by a ring already cured and bonded in position using any suitable adhesive. Moreover (although not shown) a flexible metal bellows may be employed to form the flexible and sealed connection between the piston and the slipper. Once again the piston and the slipper would preferably be interengaged so that the bellows do not have to transmit thrust and journal loads.

The invention may be applied in like manner to hydraulic pumps and couplings.

Having thus described our invention what we claim as new and desire to secure by Letters Patent is:

1. An hydraulic machine comprising the combination of a rigid housing, a shaft rotatable within the housing,

a rigid cam block rigidly secured within the housing and providing a cam face extending in a plane inclined to the shaft axis, a rotor enclosed within the housing and drivingly coupled to the shaft, said rotor being formed with a plurality of passages, a pair of ports in one end of the housing arranged so that during rotation of the rotor the passages therein are brought successively into communication with the ports, a plurality of pistons slidable respectively in the passages and projecting from one end of the rotor towards the cam face, a plurality of cup-shaped slippers mounted respectively on the pistons where these project from the rotor, each slipper including a skirt portion encircling the piston, a cupped end face remote from the skirt portion and inclined to the axis of the skirt portion at an angle equal to the inclination of the cam face to the shaft axis and a portion engaged directly against the end of the associated piston, and a plurality of elastomeric rings coupling the respective slippers to the pistons, each ring being sealingly bonded to the interior of the associated skirt portion and to the piston and each piston/ slipper combination having a restricted bore connecting the interior of the associated passage to the interior of the slipper to form between each slipper and the cam face, a hydrostatic bearing.

References Cited by the Examiner UNITED STATES PATENTS 2,847,938 8/1958 Gondek 103162 2,901,979 9/1959 Henrichsen 103-462 3,095,221 6/1963 Kaup 287-21 3,120,816 2/1964 Firth et al 103162 3,221,564 12/1965 Raymond 103162 X MARTIN P. SCHWADRON, Primary Examiner.

I. C. COHEN, Assistant Examiner.

Claims

1. AN HYDRAULIC MACHINE COMPRISING THE COMBINATION OF A RIGHT HOUSING, A SHAFT ROTATABLY WITHIN THE HOUSING A RIGID CAM BLOCK RIGIDLY SECURED WITHIN THE HOUSING AND PROVIDING A CAM FACE EXTENDING IN A PLANE INCLINED TTO THE SHAFT AXIS, A ROTOR ENCLOSURE WITHIN THE HOUSING AND DRIVINGLY COUPLED TO THE SHAFT, SAID ROTOR BEING FORMED WITH A PLURALITY OF PASSAGES, A PAIR OF PORTS IN ONE END OF THE HOUSING ARRANGED SO THAT DURING ROTATION OF THE ROTOR THE PASSAGES THEREIN ARE BROUGHT SUCCESSIVELY INTO COMMUNICATION WITH THE PORTS, A PLURALITY OF PISTONS SLIDABLE RESPECTIVELY IN THE PASSAGES AND PROJECTING FROM ONE END OF THE ROTOR TOWARDS THE CAM FACE, A PLURALITY OF CUP-SHAPED SLIPPERS MOUNTED RESPECTIVELY ON THE PISTONS WHERE THESE PROJECT FROM THE ROTOR, EACH SLIPPER INCLUDING A SKIRT PORTION ENCIRCLING THE PISTON, A CUPPED END FACE REMOTE FROM THE SKIRT PORTION AND INCLINED TO THE AXIS OF THE SKIRT PORTION AT AN ANGLE EQUAL TO THE INCLINATION OF THE CAM FACE TO THE SHAFT AXIS AND A PORTION ENGAGED DIRECTLY AGAINST THE END OF THE ASSOCIATED PISTON, AND A PLURALITY OF ELASTOMERIC RINGS COUPLING THE RESPECTIVE SLIPPERS TO THE PISTONS, EACH RING BEING SEALINGLY BONDED TO THE INTERIOR OF THE ASSOCIATED SKIRT PORTION AND TO THE PISTON AND EACH PISTON/SLIPPER COMBINATION HAVING A RESTRICTED BORE CONNECTING THE INTERIOR OF THE ASSOCIATED PASSAGE TO THE INTERIOR OF THE SLIPPER TO FORM BETWEEN EACH SLIPPER AND THE CAM FACE, A HYDROSTATIC BEARING.