Abstract: A bent-axis type variable displacement hydraulic machine provided with one of a hydrostatic radial bearing and a hydrostatic thrust bearing to support hydraulic reaction forces exerted on a cylinder block. The hydraulic machine is adapted to draw out a high oil pressure corresponding to a tilt angle of the cylinder block through a variable throttle means or through a control valve, and to supply the pressure of the hydrostatic radial or thrust bearing to thereby impart a hydrostatic supporting capacity commensurate with a tilt angle of the cylinder block and stably support a rotational shaft while minimizing oil leaks.

Abstract: Described is a bent axis type variable displacement hydraulic machine which is provided with a hydrostatic radial bearing 23 and/or a hydrostatic thrust bearing 28 to support hydraulic reaction forces exerted on a cylinder block 8. The hydraulic machine is arranged to draw out a high oil pressure corresponding to the tilt angle of the cylinder block 8 through a variable throttle means 34, 37, 51 or 54 or through a control valve 77 or 78, and to supply the pressure to the hydrostatic radial or thrust bearing 23 or 28 thereby imparting to a hydrostatic supporting capacity commensurate with the tilt angle of the cylinder block 8 to support a rotational shaft stably while holding oil leaks to a minimum.

Abstract: A bent axis type variable displacement hydraulic machine employing hydrostatic radial bearings for supporting hydraulic reaction forces exerted on the cylinder block. In a hydraulic machine of this sort, the number of pistons which are located in the high pressure are varies with the rotation of the cylinder block, and the resultant force of hydraulic reaction forces has an acting point at a position off the axis of the rotational shaft. Therefore, the hydrostatic radial bearings are located in such positions as to balance the moment loads which occur about the rotational shaft in relation with the acting point of the resultant force of radial hydraulic reaction forces on the drive disc of the rotational shaft. As a result, it becomes possible to lead to suppression of oil leaks from the sliding surfaces to a minimal rate and to prevent abnormal abrasive wear of each of the sliding surfaces.

Abstract: A thrust hydrostatic bearing device for use in an axial piston machine includes a bearing sleeve fitted into a housing cover for rotatably supporting a drive shaft through a bearing and having a plurality of hydrostatic pads. The hydrostatic pads are disposed at locations which are symmetrical with respect to an axis lying in a cross-section taken perpendicular to the drive shaft, and these pads increase the performance and durability of the thrust hydrostatic bearing device for use in an axial piston machine.

Abstract: A direct drive type servo motor in which a spool is driven directly by a force motor, the force of the force motor being balanced by the reactional force generated by a resilient member to stabilize the position of the spool to control the flow of working fluid. The resilient member is constituted by a metallic cylindrical member having holes formed in the outer peripheral surface thereof. The holes are arranged such that, when the force is applied to the cylindrical member in the axial direction, the cylindrical member produces an axial reactional force. In consequence, the generation of force component which would act to press the spool against the sleeve is avoided to reduce the friction between the spool and the sleeve to permit a smooth movement of the spool, while allowing the resilient member to have a high spring constant to improve the response characteristic of the servo valve.

Abstract: A hydraulic operating apparatus including an actuating cylinder having a piston arranged therein and moved by a fluid under high pressure further includes a control valve having only one metallic seal whether the piston is at its upper or lower positions. The control valve is operative to apply the fluid under high pressure to a pressure receiving surface of the piston on the opposite side of a piston rod to move the piston in a direction in which the piston rod extends from the piston and to discharge the fluid existent on the opposite side of the piston rod from the actuating cylinder to move the piston in a direction opposite the direction in which the piston rod extends from the piston.