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Hartmann Controls, Inc.

Donald G Bethke

A control arrangement controls a position of a swashplate in an axial piston pump between a no-stroke position and a maximum stroke position. The control arrangement includes a servo spool mounted for limited sliding movement in a compensator piston cylinder. A solenoid coil is configured to provide a coil force to move the servo spool. A compensator piston is mounted in the compensator piston cylinder in response to movement of the servo spool. A spring between the servo spool and the compensator piston provides a spring force in response to the coil force applied to the servo spool. The control arrangement defines a feedback system configured to maintain a balancing relationship between the spring and coil forces to enable infinite control of the swashplate position.

Electro-hydraulic swashplate control arrangement for an axial piston pump

An axial piston pump includes a housing with a cover plate assembly, a rotor with reciprocable pistons rotatably mounted with a drive shaft and a swashplate assembly tiltably mounted relative to the drive shaft and engaged with outer ends of the pistons. A holddown spring is incorporated within the swashplate assembly and positioned outside the rotor such that the holddown spring tilts with the swashplate assembly and does not rotate with the drive shaft. The holddown spring applies a force holding the piston outer ends against the swashplate assembly and the rotor against the cover plate assembly.

Holddown system for an axial piston pump

An axial piston pump assembly includes a housing having an outer wall defining a generally cylindrical interior and an end wall. A drive shaft extends through the end wall is rotatably mounted in the housing for rotation on the axis of the cylindrical interior, and the rotor is attached to the drive shaft for rotation therewith. A plurality of circumferentially spaced, axially disposed cylinders is positioned in the rotor, and a series of axially reciprocable pistons is disposed in the cylinders. A swashplate surrounds the drive shaft and is mounted in the housing for tilting movement on a tilt axis transverse to the drive shaft axis. A planar reaction surface on the swashplate is engaged by the outer ends of the pistons. A biasing arrangement is provided for urging the piston ends into engagement with the reaction surface, and a control arrangement is supplied for tilting the swashplate on its axis to maintain the reaction surface angularly disposed with respect to the axis of the drive shaft. A pair of inboard trunnion blocks is adjustably attached to the interior of the housing end wall on opposite sides of the drive shaft and supports the swashplate on a rear surface opposite the reaction surface for tilting movement thereon. The control arrangement resides in a cooperating piston arrangement acting in opposed relationship against the reaction surface and the rear surface of the swashplate to eliminate the bending moments induced by the axially reciprocable pistons and biasing means about the tilt axis of the swashplate.

Swashplate control system for an axial piston pump

A radial piston pump includes a pair of inboard trunions which provide tilting bearing support for the swashplate. The trunion blocks may be made from sections of ordinary cold rolled steel bar stock and attached to the end wall of the pump housing with externally accessible bolted connections which allow final precise alignment of the trunion blocks in the assembled pump. The swashplate includes a concave cylindrical bearing surface which rides on the trunion blocks and, to enable precision finishing and machining of the concave bearing surface in a simple manner. Two swashplates are made from a single metal casting in which a full cylindrical through bore can be accurately cut and finished, and the casting subsequently cut in two to provide two swashplates. The swashplate is mounted with its transverse tilt axis offset from the axis of the pump drive shaft in a direction providing a net imbalance in piston spring biasing force to urge the swashplate on-stroke to enhance start-up operation.

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Hartland, WI, United States of America

Donald G Bethke