GB2056576A

GB2056576A - Piston pumps and motors

Info

Publication number: GB2056576A
Application number: GB7936405A
Authority: GB
Original assignee: Commercial Shearing Inc
Current assignee: Commercial Shearing Inc
Priority date: 1979-08-20
Filing date: 1979-10-19
Publication date: 1981-03-18
Also published as: FR2463862A1; SE8000132L; CH634632A5; AT373367B; AU5461680A; BE880598A; FR2463863A1; BR7907640A; DE2946333A1; ATA2780A; ZA795822B; IT1126888B; IT8047578A0; JPS5632080A

Abstract

A piston pump or motor has a port plate assembly which corrects for tilt in the rotating cylinder block during operation and comprises a generally annular port plate 50 having on one side a flat generally planar face bearing against the cylinder block 21 and on the other side a generally spherical surface and a bearing member 40 having a corresponding mating spherical surface against which the spherical surface of the port plate bears, both the port plate and bearing member having aligned port openings communicating from the cylinder block to the inlet and outlet ports, whereby the port plate moves on the mating spherical surfaces to follow any tilt of the cylinder block. <IMAGE>

Description

SPECIFICATION Piston pumps Field ofinvention The invention relates to piston pumps and particularly to port plates for such pumps. Whilst the invention is described in terms of pumps receiving a motive input-and having a high pressure hydraulic output, the invention can also be described and applied analogously to motors receiving a hydraulic high pressure input and having a motive output.

Background of invention Over center and one side of center piston pumps have been used to provide hydraulic fluid under pressure in any of a great variety of systems. These pumps are operated by rotating a plurality of pistons on sliding shoes over a tilted swash plate which causes the pistons to reciprocate in cylinders in a rotating cylinder block or piston carrier passing across a port plate. As the pumping speed increases a tilt effect may occur on the rotating cylinder block, increasing wear and misalignment of the port plate to the cylinder block. This effect may be reduced by providing the cylinder block with a stub shaft on the end opposite the drive shaft and coaxially of the drive shaft. This stub shaft is mounted in a bushing in the end of the motor housing. However, even with this added stub shaft uneven wear may occur.

Maintaining the necessary manufacturing tolerances in the journals may also be expensive and difficult because of the criticality of the port plate fit.

The invention aims to solve or reduce these problems by providing a port plate made in two pieces having mating spherical bearing surfaces between them which permit relative movement between the two pieces and permit one face of the plate to tilt following the tilt of the cylinder block. The problem of misalignment and the wear and manufacturing problems associated can be overcome to a considerable extent.

Summary of Invention The invention provides an over center or one side of center pump having a housing, a rotating cylinder block in said housing with cylinder openings spaced around a center axis, pistons reciprocable in said openings, a drive shaft rotating said cylinder block at one end of said central axis, a stub shaft on said cylinder block at the other end of said central axis and journalled in said housing, a tiltable swash plate in the housing engaging said pistons for regulating their reciprócating motion in the cylinder block, means in the housing for adjusting the tilt of said swash plate, spaced inlet and outlet ports in the housing and a port plate of generally annular shape between said ports and the cylinder block and surrounding the stub shaft, said plate having on one side a flat, planarface bearing against the cylinder block around the stub shaft, port openings communicating through said plate from the cylinder block to said ports in the housing and on the other side a generally spherical surface and bearing member on the housing have a corresponding spherical surface against which the spherical surface of the port plate bears and corresponding port openings whereby said port'plate may move around said spherical surface to follow the tilt of the cylinder block in operation.Preferably the port plate and bearing member are separate pieces whose combined thickness corresponds to a standard unitary port plate used in over center piston pump assemblies and thus can be used in any conventional over center or one side of center or swash plate piston pump without changing the pump; however, the bearing member could be formed with the housing as a part of the port end cover. Preferably the port plate is provided with annular and radial oil slots through which oil flows to lubricate the wear surfaces.

Drawings Figure 1 is a section through a typical over cen;er piston pump assembly incorporating a port plate according to this invention; Figure 2 is a plan view of the bearing member portion of a port plate assembly used in Figure 1; Figure 3 is a section on the line Ill-Ill of Figure 2; Figure 4 is a plan view of the port plate portion of a port plate assembly used in Figure 1;- Figure 5 is a section on the line V-V of Figure 4;Figure 6 is an enlarged section through the- combined assembled bearing and port plate of this invention; Figure 7 is a plan view of the bearing member portion of a port plate for a one side of center pump; Figure 8 is a section on the line VIll-VIll of Figure 7; Figure 9 is a plan view of the port plate portion of a port plate assembly; and Figure 70 is a section on the line X-X of Figure 9.

Specific description Referring to the drawings there is iilustrated an over center piston pump having an outer pump housing 10 having a drive shaft 11 journalled in bearings 12 and one end. The other end of housing 10 is closed by port end cover 13 sealed to housing by seal ring 14 and held in place by bolts not shown.

Atiltable swash plate 15 is pivoted at one side 16 on shaft- 17 and is pivotally connected at the diametrically opposite side 18 to actuating piston 19 through link 20. A cylindrical cylinder block 21 is keyed to drive shaft 11 within housing 10 and has upper and lower stub shafts 22 and 23 journalled in bearings 24 and 25 in housing 10 and port end cover 13 respectively. Pistons 26 are reciprocably movable in cylinder openings 27 in cylinder block 21 by sliding shoes 28 connected to ball ends 29 on the lower end of each piston 26. The sliding shoes 28 ride on bearing plate 30 carried by swash plate 15 and are held in place by a thrust ring 31. The reciprocating movement of pistons 26 in cylinder openings 27 is thus controlled by the tilt position of swash plate 15.

-A bearing member 40 and port plate 50 are placed between the cylinder block 21 and port end cover 13.

The bearing member 40 has a flat face 42 on one side and a generally spherical convex face 43 on the other side. The port plate 50 has a flat bearing face 52 which bears on the end of cylinder block 21 and a spherical concave face 53 which matches and bears on face 43. In normal position faces 42 and 52 are parallel; however, in operation if cylinder block 21 assumes a slight tilt at high pump speed, then bearing member 40 and port plate 50 move relatively to one another on mating faces 42 and 52 to maintain face 53 in uniform contact 'Atith the top of cylinder block 21 and face 43 in contact with port end cover 13. Each of bearing member 40 and port plate 50 are provided with a series of interconnected aligned transverse ports 44,45 and 54, 55 on opposite sides of the member 40 and plate 50.These ports communicate through the member 40 and plate 50 from the top end of cylinder block 21 to an inlet port and an outlet port (not shown, but conventional) in the port end cover 13. The plate 50 is provided on its flat bearing face 52 with an annular groove 56 between the ports 54, 55 and the outer periphery and with radial grooves 57 extending from the annular groove 56 to the outer periphery. The bearing member 40 is similarly provided on flat face 42 with an annular groove 46 between ports 44,45 and the outer periphery and with radial grooves 47 from the annular groove 46 to the outer periphery.

These grooves act as lubricant and seal channels.

The port plate assembly used in a one side of center pump is illustrated in Figures 7 through 10.

This assembly is basically the same as in the over center pump port plate assembly except for the porting and like ports will be given like numbers with a prime sign. A bearing member 40' and port plate 50' make up the assembly to be placed between the cylinder block and port end cover. Bearing member 40' has a flat face 42' on one side and a generally spherical convex face 43' on the other side. The port plate 50' has a flat bearing face 52' and a spherical concave face 53' which matches and bears on convex face 43'. Each of bearing member 40' and port plate 50' are provided with a series of interconnected aligned transverse ports 60, 61, 62 on one side and 63 on the other side ofa diametric line as in a conventional port plate for such a pump. Plate 50' is provided with an annular groove 56' and radial grooves 57' and member 40' is provided with annular groove 46' and radial grooves 47' which act as lubricant and seal channels.

Claims

1. A piston pump comprising a housing, a rotating cylinder block in said housing with cylinder openings spaced around a central axis, pistons reciprocable in said openings, a drive shaft rotating said cylinder block around said central axis, a tiltable swash plate in the housing engaging said pistons for regulating their reciprocating motion in the cylinder openings, means in the housing adjusting the tilt of said swash plate, spaced inlet and outlet ports in the housing, a generally annular port plate betwen the ports and the cylinder block around said central axis, the plate having on one side a flat generally planar face bearing against the cylinder block with port openings communicating through said plate from the cylinder block to said ports and on the other side a generally spherical surface and a bearing member on the housing having a corresponding mating spherical surface against which the spherical surface of the port plate bears and having corresponding port openings communicating with the port opening of the port plate whereby the port plate may move around said spherical surface to follow the tilt of the cylinder block in operation.

2. A piston pump as claimed in claim 1 wherein the cylinder block has stub shafts at each end journalled in the housing.

3. A piston pump as claimed in claim 1 or claim 2 wherein the port plate and bearing member are separate annular members having mating concave and convex spherical surfaces and opposite spaced flat bearing faces.

4. A piston pump as claimed in any of the preceding claims wherein the bearing member has a convex spherical surface and the port plate has a mating concave spherical surface.

5. A piston pump as claimed in claim 3 or claim 4 wherein the flat faces of each of the bearing member and the port plate are provided with annular grooves between the port openings and the periphery and with radial grooves extending from the annular groove to said periphery.

6. A piston pump as claimed in any of the preceding claims wherein the combined thickness of the separate bearing member and port plate are substantially equal in thickness to a standard one piece port plate for the pump.

7. A port plate and bearing member assembly for use between a port end cover and a rotating cylinder block of a piston pump comprising an annular bearing member and an annular port plate having mating concave and convex spherical surfaces and opposite spaced flat bearing faces, said bearing member and port plate have spaced aligned port openings extending through both for communicating from the cylinder block to the port end cover whereby the port plate and bearing member move spherically relative to oneanotherto permit the port plate to follow any tilt of the cylinder block in operation.

8. A port plate and bearing member assembly as claimed in claim 7 wherein the bearing member has a convex spherical surface and the port plate has a mating concave spherical surface.

9. A port plate and bearing member assembly as claimed in claim 7 or claim 8 wherein the flat faces of each of the bearing member and port plate are provided with annular grooves between the port openings and the periphery and with radial grooves extending from the annular groove to said periphery.

10. A port plate and bearing member assembly as claimed in any of claims 7 to 9 wherein the combined thickness of the separate bearing member and plate are substantially equal in thickness to a standard one piece port plate for said pump.

11. A piston pump substantially as shown herein and as described with reference to Figures 1 and 2 to 6 or Figure 1 and 7 to 10.