Abstract: A hydraulic piston unit including a rotational group for driving or being driven by a driving shaft, and having a tiltable displacement element for adjusting the displacement volume of the rotational group between a minimum or a maximum displacement, wherein, on t valve segment between a kidney-shaped inlet port and a kidney-shaped outlet port at respective dead end positions of reciprocally moveable working pistons first and second control ports are located in fluid connection with cylinder bores in the cylinder block, for controlling the position of the displacement element. The hydraulic piston unit further includes a control valve with a shiftable control valve spool fluidly connected via a high pressure port to a high pressure side of the hydraulic piston unit. The control valve spool is configured to conduct hydraulic fluid from the high pressure side to one of the first or the second control port.

Abstract: A hydraulic piston unit including a rotational group for driving or being driven by a driving shaft, and having a tiltable displacement element for adjusting the displacement volume of the rotational group between a minimum or a maximum displacement, wherein, on t valve segment between a kidney-shaped inlet port and a kidney-shaped outlet port at respective dead end positions of reciprocally moveable working pistons first and second control ports are located in fluid connection with cylinder bores in the cylinder block, for controlling the position of the displacement element. The hydraulic piston unit further includes a control valve with a shiftable control valve spool fluidly connected via a high pressure port to a high pressure side of the hydraulic piston unit. The control valve spool is configured to conduct hydraulic fluid from the high pressure side to one of the first or the second control port.

Abstract: A bearing attachment system for a pump product having a seal carrier and a cover plate. The attachment system is configured to produce a force deflection curve that provides a clamping force on a pair of tapered roller bearings such that a tight bearing endplay on the tapered roller bearings is maintained through a full range of manufacturing tolerances. The geometric shape of the cover plate and the top surface of the seal carrier provide the desired deflection characteristics.

Abstract: A bearing attachment system for a pump product having a seal carrier and a cover plate. The attachment system is configured to produce a force deflection curve that provides a clamping force on a pair of tapered roller bearings such that a tight bearing endplay on the tapered roller bearings is maintained through a full range of manufacturing tolerances. The geometric shape of the cover plate and the top surface of the seal carrier provide the desired deflection characteristics.

Abstract: A hydraulic piston unit including a rotational group for driving or being driven by a driving shaft, and having a tiltable displacement element for adjusting the displacement volume of the rotational group between a minimum or a maximum displacement, wherein, on t valve segment between a kidney-shaped inlet port and a kidney-shaped outlet port at respective dead end positions of reciprocally moveable working pistons first and second control ports are located in fluid connection with cylinder bores in the cylinder block, for controlling the position of the displacement element. The hydraulic piston unit further includes a control valve with a shiftable control valve spool fluidly connected via a high pressure port to a high pressure side of the hydraulic piston unit. The control valve spool is configured to conduct hydraulic fluid from the high pressure side to one of the first or the second control port.

Abstract: A servo piston assembly having a servo piston body mounted within a servo piston cylinder. A pair of bushings are mounted within each end of the servo piston body. An elongated bore extends through the servo piston body and receives a guide rod that extends out of the servo piston body and is received within the servo piston cylinder.

Abstract: An integrated wheel hub assembly includes a hydrostatic spindle assembly that has a spindle with a hydrostatic rotational power unit and integral high-pressure passageways therein, a wheel hub rotatably supported by the spindle assembly, and an axle shaft extending through the spindle for transmitting power from the hydrostatic unit to the wheel hub through a planetary gear set reducer. For radial compactness, the swashplate of the hydrostatic power unit resides outside the wheel hub.

Abstract: The neutral override circuit of this invention includes a variable displacement pump controlled by a servo fluidly connected to a displacement control that is biased to a neutral position. A charge pump is connected to the pump and the displacement control. A solenoid-operated neutral override brake control valve is connected to the charge circuit upstream of the displacement control valve and is normally biased to an open position. However, the solenoid urges the valve to a closed position in a response to a signal indicating that the brake has been released. In the open position, the valve dumps charge flow to the pump case until the supply pressure to the displacement control is inadequate to overcome the centering bias of the displacement control. The characteristics of the brake control valve can be set so that some minimum charge pressure and lubricating flow are still provided to the rotating elements of the pump.

Abstract: An integrated wheel hub assembly includes a hydrostatic spindle assembly that has a spindle with a hydrostatic rotational power unit and integral high-pressure passageways therein, a wheel hub rotatably supported by the spindle assembly, and an axle shaft extending through the spindle for transmitting power from the hydrostatic unit to the wheel hub through a planetary gear set reducer. For radial compactness, the swashplate of the hydrostatic power unit resides outside the wheel hub.

Abstract: The neutral override circuit of this invention includes a variable displacement pump controlled by a servo fluidly connected to a displacement control that is biased to a neutral position. A charge pump is connected to the pump and the displacement control. A solenoid-operated neutral override brake control valve is connected to the charge circuit upstream of the displacement control valve and is normally biased to an open position. However, the solenoid urges the valve to a closed position in a response to a signal indicating that the brake has been released. In the open position, the valve dumps charge flow to the pump case until the supply pressure to the displacement control is inadequate to overcome the centering bias of the displacement control. The characteristics of the brake control valve can be set so that some minimum charge pressure and lubricating flow are still provided to the rotating elements of the pump.

Abstract: A hydraulic slipper includes a slipper body having first and second ends and a central portion therebetween. The first end terminates in a spherical-shaped head. The second end terminates in a round base portion with a hub protruding outwardly therefrom in the direction away from the head. The hub terminates in a planar surface and has a diameter less than the diameter of the round base portion. The slipper includes a washer element having a center opening extending around the hub and having first and second opposite planar surfaces. The first surface engages the base portion, and the second surface extends beyond the planar surface of the hub to create a running face for the slipper. The washer element can be a bi-metal ring formed of steel and bronze.

Abstract: A holddown pin mechanism for hydraulic power units has a cylindrical flat base washer having a central opening and opposite sides, a plurality of spaced elongated holddown pins have one end rigidly secured to one side of said base washer and an outer end. The pins extend outwardly at right angles from the side of said washer to which they are secured. The holddown pin mechanism is placed in a hydraulic cylinder block having a center bore, with the pins extending into holes in the block. A guide member on a shaft extending through the block engages the free ends of the pins.