A hydrostatic piston machine has an adjustment element that is adjustable for varying a displacement volume, and a rotating cylinder part having a plurality of cylinder bores with pistons that are supported on the adjustment element and delimit a displacement chamber. Each displacement chamber is moved in an alternating manner by a connecting opening to overlap a low-pressure control opening situated on a low-pressure side of a stationary control part and a high-pressure control opening situated on a high-pressure side of the control part. Two switching regions are situated between the low-pressure control opening and the high-pressure control opening, the pistons changing direction at a dead center within the switching regions. The position of the adjustment element is determined from a pressure profile which is a function of the variable size of the displacement chambers in a switching region, the variable size depending on the position of the adjustment element.

A variable displacement axial piston pump including a cylinder block defining a plurality of cylinder bores, each receiving a piston. A swash plate having a piston-supporting surface is pivotally supported relative to the cylinder block. A port block defines first and second pumping ports arranged in fluid communication with the plurality of cylinder bores such that, during operation of the pump, one of the first and second pumping ports is configured to supply fluid to the cylinder bores for pumping, and the other of the first and second pumping ports is configured to receive fluid pumped from the plurality of cylinder bores. The swash plate partially defines at least one variable volume control chamber, and the swash plate is operable to tilt with respect to the port block in response to a fluid pressure change in the at least one control chamber.

A cylinder block including plurality of piston chambers formed at intervals in circumferential direction; plurality of pistons fitted in respective piston chambers movable in expanding and contracting directions to reciprocate in the expanding and contracting directions; a valve plate in contact with the cylinder block rear end surface and including first and second ports communicating with piston chambers. A portion of each ports is close to a top dead center switching land formed between first and second ports as a portion having a narrow opening width in a rotation radial direction of the cylinder block. An auxiliary port is formed at the valve plate switching land. Auxiliary port pressure is maintained lower than pressure of a side port that is the first or second port. When the piston chamber lacks communication with the side port (first or second port), the piston chamber and auxiliary port communicate with each other.

In a piston pump assembly, cradle bearings support a swash plate on an inner surface of a housing assembly. The cradle bearing and/or the corresponding portion of the housing inner surface may have undercut portions allowing deflection of an inward portion of the cradle bearing when the swash plate is subjected to pressure forces from hydraulic fluid compressed within pump cylinders by the pump pistons. Deflection of the cradle bearings allows increased contact pressure to be further distributed across the engaging surfaces of the swash plates and the cradle bearings.

In a piston pump assembly, cradle bearings support a swash plate on an inner surface of a housing assembly. The cradle bearing and/or the corresponding portion of the housing inner surface may have undercut portions allowing deflection of an inward portion of the cradle bearing when the swash plate is subjected to pressure forces from hydraulic fluid compressed within pump cylinders by the pump pistons. Deflection of the cradle bearings allows increased contact pressure to be further distributed across the engaging surfaces of the swash plates and the cradle bearings.

A swash-plate type piston pump includes a cylinder block configured to be rotated with rotation of a driving shaft, a plurality of pistons accommodated in a plurality of cylinders provided in the cylinder block, a swash plate configured to reciprocate the piston so that a volume chamber of the cylinder is expanded/contracted with the rotation of the cylinder block, an biasing mechanism configured to bias the swash plate in a direction where a tilting angle is made larger, a control pin configured to drive the swash plate in a direction where the tilting angle is made smaller in accordance with a rise in a load pressure of a pressure chamber, and a discharge channel configured to discharge the load pressure of the pressure chamber.

A device, system, and process for turning hydraulic pressure into rotational force and for turning rotational motion into hydraulic pressure. An example of the device/system for performing the process comprises actuators, rotationally positioned between two thrust plates that are fixed in a housing at an angle to a rotational axis and in parallel to each other.

A device, system, and process for turning hydraulic pressure into rotational force and for turning rotational motion into hydraulic pressure. An example of the device/system for performing the process comprises actuators, rotationally positioned between two thrust plates that are fixed in a housing at an angle to a rotational axis and in parallel to each other.

A power end frame includes a housing and a face plate secured to the housing. During use, components of the power end frame, including the housing and the face plate, are subjected to large tensile stresses. This disclosure describes a method of imparting compressive stresses in the power end frame to resist these large tensile stresses.

An electro-hydraulic piston pump system comprising an electric motor (16), first and second hydraulic piston pumps (30,60), a first hydraulic actuator (90) having a first port (93) connected directly to a first port (48) of the first pump and a second port (94) connected directly to a second port (49) of the first pump, a second hydraulic actuator (100) having a third port (103) connected directly to a third port (78) of the second pump and a fourth port (104) connected directly to a fourth port (79) of the second piston pump, wherein an external force applied to the first hydraulic actuator (90) that provides a negative pressure differential to the first pump applies an assistive torque to a common motor shaft (18) driving both the first pump (30) and the second pump (60), and an external force applied to the first and second actuators (90,100) that provides a summed negative pressure differential to the first and second pumps (30,60) recharges a power supply for the motor (16).