GB1378546A - Fluid pressure machines - Google Patents

Abstract

1378546 Fluid pressure motors and pumps HYDROSTATIC TRANSMISSIONS Ltd 12 June 1973 [20 June 1972] 28765/72 Headings F1A, F1M, and F1N A dual capacity hydraulic, or gas motor or pump includes a cylinder block rotatably mounted on a cylindrical surface eccentric to a shaft, a housing coaxial with the shaft and surrounding the block, radial cylinders in the block which in use communicate sequentially with inlet and outlet ports located on opposite sides of the cylindrical surface, each cylinder having a sleeve and an inner piston, and control valves for controlling the cylinder capacity whereby either the inner pistons or the inner pistons and sleeves reciprocate and co-operate with respective thrust pads on the housing to drive the machine. The housing and cylinder block maybe stationary and the shaft rotate or vice versa. In one embodiment Fig. 1, a motor 10 comprises a shaft 11 rotatably mounted in a casing 14 and having an eccentric 12, a cylinder block 15, a ring 17 forming part of the housing and coaxial with the shaft 11 and a thrust pad 20 secured to the ring 17 to co-operate with a respective cylinder. The block has five cylinders, each containing a sleeve 21 and inner piston 22 which has an axial passage between its ends for fluid pressure communication therebetween and thereby reduce adverse mechanical or fluid loadings. Working spaces 31 and 38 under the inner face of each piston and sleeve are separated by a seal 32 having a conical seating surface 34 against which a peripheral edge 29 of the sleeve 21 abuts when inoperative. The seals 32 each have openings 36, 37 communicating with the spaces 31 and 38 respectively. Pressure liquid can be circulated through the spaces 38 from ports 39, 40 via grooves 41, 42, passages 43, 44, 45, 46 and grooves 47, 48 in the surface of the eccentric 12, and thence by openings 36. The grooves 47, 48 extend over parts of the eccentric's surface so that liquid is supplied and exhausted sequentially from the cylinders as the block 15 rotates relative to the eccentric 12. Control valve spools 55, 56 control a path (not shown) from the passages 43, 44 to grooves 64, 69 respectively, the grooves 64, 69 being similarly arranged as the grooves 47, 48 and so sequentially communicating with working spaces 38 via openings 37. When the spools 55, 56 abut seats 60, 61 the spaces 38 are vented to a sumphole 78 so that the sleeves 21 are inoperative and are held against the seals 32 by liquid pressure in the spaces 31 acting on lips 30 of the sleeves. When the spools 55, 56 abut seats 62, 63, the spaces 38 communicate with the liquid and the sleeves 21 move with their respective inner pistons 22. The direction of liquid circulation determines the direction of rotation of the shaft 11 or casing 14 depending upon which is held stationary. Alternatively the motor may be used as a pump by way of the shaft or casing and the casing or shaft is held stationary. In modifications of this machine (not shown), the sleeves 21 have a bore for pressure communication between the inner and outer ends to improve their response between their operative and inoperative positions and a recess in their outer faces accomodates a lipped outer end of an inner piston. Alternatively open ended tubes maybe fitted for liquid communication between the grooves 47, 48 and the spaces 31 and the axial passages in the inner pistons may have larger diameters at their inner than outer ends. In an alternative machine embodiment Figs. 7, 8 (not shown), a five cylinder block is mounted for rotation on a stub shaft which is eccentric to the shaft 11 which is fixed to a housing which provides a counterpart to the ring 17. The housing and shaft 11 is supported by bearings in a casing which is coaxial with the shaft 11 and is fixed to the stub shaft. When the machine is supplied with pressure liquid, the inner pistons or the inner pistons and sleeves co-operate with the housing to rotate the casing, the machine including similar hydraulic circuits to that already described.