The invention provides a shoe for a hydraulic apparatus and manufacturing method thereof, by which production cost can be lowered without making a sliding-contact surface uneven by a welding process. The shoe comprises a main body (10) provided on one side (10a) thereof with a concave spherical surface (12) to which a sphere is slidably engaged, and on the opposite side (10b) thereof with a locking portion (14) and a sliding-contact plate (11) provided with an engaging portion (20) by which to be engaged with the locking portion (14) to make contact with the opposite side (10b), wherein the sliding-contact plate (11) comprises a first layer (18) to make contact with the opposite side (10b) and a second layer (19) laminated on a region of the first layer (18) leaving uncovered welding portion (21) so that its surface serves as a sliding-contact surface (19a), and the first layer (18) is welded to the main body (10) at the welding portion (21). The locking portion (14) is a protruding portion located at a central portion of the opposite side (10b) of the main body (10), and the engaging portion (20) is a bore portion by which to be engaged with the protruding portion.

In a refrigerant compressor unit of a type in which the reciprocating movement of pistons is caused by the nutation of a non-rotatably but nutatably supported wobble plate driven by a cam rotor. The wobble plate includes a ring member and a bevel gear member. The bevel gear member is provided with a plurality of axial grooves in the peripheral side surface thereof. The gear member is fitted into a counterbore formed in the ring member and secured by caulking the peripheral edge of the counterbore to the ring member. The material of the ring member is moved into the grooves and valleys between the teeth of the gear by the caulking operation so that relative rotation and axial movement of the ring member and gear member is prevented. The wobble plate is supported on a ball bearing so as to be able to nutate about the ball center but is prevented from rotation by engagement of the bevel gear with another bevel gear fixedly supported on the cylinder block.

A swash plate pump or motor is provided having a swivel plate surrounding the slippers and a positive hold down ring connected to the swash plate and bearing on said swivel plate to maintain it at a fixed distance from the slipper plate, said hold down ring having a series of successive controlled wedge angles on the face bearing on the swivel plate and oil feed means connected to each wedge angle whereby a hydrodynamic force is created holding the swivel plate and hold down ring apart.

A hydrostatic piston machine has a housing, a rotor, a plurality of pistons rotatable with the rotor, and a displacing element operative for effecting reciprocation of the pistons and having a surface which is in sliding contact with the latter. Means is provided for reducing friction between the surface of the displacing element and the pistons during the sliding contact. This means includes a recess formed in the surface of the displacing element and communicating with a space which is under pressure so that a cushion of pressure fluid develops between the surface and the piston. The space under pressure may be constituted by a low pressure zone of the machine or by the low pressure and a high pressure zone of the machine.

A motor or processing machine, such as a lowspeed radial piston motor, having a piston with a socket formed therein operatively contacting a ball formed on one end of a piston rod, to form a ball-and-socket joint with articulated movement, and a shoe on the other end of the piston rod, adapted to glide on a rotating element of the machine, such as a crankshaft eccentric, in which the entire piston rod is formed from a bronze-base bearing metal, such as steel bronze. At least the shoe of the piston rod may be coated with a thin, soft run-in layer, such as tin, and a pocket may be formed in the shoe of the piston rod to provide hydrostatic relief.