Pistons for hydraulic piston type pumps and motors

Claim 2

A piston slipper for a hydraulic pump or motor of the kind comprising a body, said body being provided with a cam surface, a rotor rotatably mounted in the body, a pluralitY of pistons mounted in respective bores in the rotor, the pistons, at their ends, carrying respective slippers which engage with the cam surface, the improvement being that each slipper includes a main portion and an insert for the main portion, said main portion and insert being formed from different materials, the insert being located on the main portion at one end of the slipper, a layer of adhesive material securing the insert to the main portion, the insert providing a running surface of the slipper, the insert, in the running surface thereof having a conical recess communicating at its apex with a bore in the slipper through which lubricant passing through the piston can enter the recess, and the outer edge of the conical recess terminating at an annular step, with the conical recess, during operation, serving to minimize erosion of the running surface of the insert across which the flow of lubricant occurs.

Claim 3

The piston slipper as claimed in claim 1 in which the annular step is perpendicular to the running surface of the insert.

Claim 4

The piston slipper as claimed in claim 2 in which the edge of the annular step, at the inner edge of the surrounding annular end surface of the insert, is rounded.

Claim 5

The piston slipper as claimed in claim 1 in which the main portion of the slipper is formed from cast iron and the insert is formed from lead-bronze.

Claim 6

An hydraulic pump or motor of the kind comprising a body, said body being provided with a cam surface, a rotor rotatably mounted in the body, a plurality of pistons mounted in respective bores in the rotor, the pistons, at their ends, carrying respective slippers which engage with the cam surface, the improvement being that the slippers on the pistons each comprises a main portion and an insert, said main portion and insert being formed from different materials, the insert being located on the main portion at one end of the slipped, a layer of adhesive material securing the insert to the main portion, the insert providing a running surface of the slipper, the insert, in the running surface thereof having a conical recess communicating at its apex with a bore in the slipper through which lubricant passing through the piston can enter the recess, and the outer edge of the conical recess terminating at an annular step, with the conical recess, during operation, serving to minimize erosion of the running surface of the insert across which the flow of lubricant occurs.

Claim 7

An hydraulic pump or motor of the kind comprising a body, said body being provided with a cam surface, a rotor rotatably mounted in the body, a plurality of pistons mounted in respective bores in the rotor, the pistons, at their ends, carrying respective slippers which engage with the cam surface, the improvement being that the slippers on the pistons each comprises a main portion and an insert, said main portion and insert being formed from different materials, the insert being located on the main portion at one end of the slipped, a layer of adhesive material securing the insert to the main portion, the insert providing a running surface of the slipper, the insert, in the running surface thereof having a conical recess communicating at its apex with a bore in the slipper through which lubricant passing through the piston can enter the recess, and the outer edge of the conical recess terminating at an annular step, with the conical recess, during operation, serving to minimize erosion of the running surface of the insert across which the flow of lubricant occurs.

Claim 8

A piston slipper for a hydraulic pump or motor of the type comprising a body, said body being provided with a cam surface, a rotor rotatably mounted in the body, a plurality of pistons mounted in respective bores in the rotor, the pistons, at their ends having a part spherical head carrying respective slippers which engage with the cam surface, the improvement being that each slipper includes a main portion having a part spherical recess receiving the part spherical head of the piston, said main portion being provided with a shallow cylindrical recess in its end remote from the piston head, a circular insert positioned in the cylindrical recess and having a running surface protruding beyond the end surface of the main portion, said main portion and insert being of different materials, a layer of adhesive material securing the insert within the cylindrical recess of the main portion, the insert providing a running surface of the slipper, said main portion having an axial passage leading at one end to the cylindrical recess and at the other end to a cavity, the running surface of the insert being provided with a conical recess communicating at its apex with the passage in the main portion, the outer edge of the cylindrical recess terminating in a short annular step perpendicular to the running surface of the insert, the piston head having a flat surface located opposite the cavity in the main portion of the slipper and an axial bore terminating at the center of the flat surface whereby lubricant passing through the piston can flow through the axial bore to the conIcal recess in the insert via the cavity, axial passage in the main portion of the slipper, and the bore in the insert, with the conical recess, during operation, serving to minimize errosion of the running surface of the insert across which the flow of lubricant occurs.

Claim 9

A piston slipper for a hydraulic pump or motor of the type comprising a body, said body being provided with a cam surface, a rotor rotatably mounted in the body, a plurality of pistons mounted in respective bores in the rotor, the pistons, at their ends having a part spherical head carrying respective slippers which engage with the cam surface, the improvement being that each slipper includes a main portion having a part spherical recess receiving the part spherical head of the piston, said main portion being provided with a shallow cylindrical recess in its end remote from the piston head, a circular insert positioned in the cylindrical recess and having a running surface protruding beyond the end surface of the main portion, said main portion and insert being of different materials, a layer of adhesive material securing the insert within the cylindrical recess of the main portion, the insert providing a running surface of the slipper, said main portion having an axial passage leading at one end to the cylindrical recess and at the other end to a cavity, the running surface of the insert being provided with a conical recess communicating at its apex with the passage in the main portion, the outer edge of the cylindrical recess terminating in a short annular step perpendicular to the running surface of the insert, the piston head having a flat surface located opposite the cavity in the main portion of the slipper and an axial bore terminating at the center of the flat surface whereby lubricant passing through the piston can flow through the axial bore to the conIcal recess in the insert via the cavity, axial passage in the main portion of the slipper, and the bore in the insert, with the conical recess, during operation, serving to minimize errosion of the running surface of the insert across which the flow of lubricant occurs.