Caterpillar Inc.

Thomas A Watts

Wayne E Fritz

Phillip J Wenger

An axial piston hydraulic unit has a valve plate assembly positioned between a head and a rotatable cylinder barrel. The assembly includes a pair of valve plates stacked together to function as a single valve plate. The valve plate assembly defines a restricted flow path for providing initial communication between an approaching piston bore of the rotatable barrel and an intake port and a discharge port extending through the pair of plates. A first portion of the flow path is defined in the valve plate adjoining the head and a second portion of the flow path is defined in the valve plate adjacent the barrel. The stacked valve plates are hydraulically held together by a pair of pressure balancing devices.

Hydraulic axial piston unit with multiple valve plates

A variable displacement axial piston hydraulic unit includes first and second control pockets individually disposed between first and second arcuate shaped fluid passages, a first electrohydraulic valve for controlling fluid flow between the first control pocket and the first fluid passage and a second electrohydraulic valve for controlling fluid flow between the second passage and the second control pocket. A controller outputs first and second control signals to the first and second electrohydraulic valves in response to receiving a command signal so that the tilt angle of a swashplate is controlled to obtain a desired operating parameter. An angle detector, a pressure detector, and a speed detector provide feedback signals to the controller for determining when the desired operating parameter has been obtained.

Variable displacement axial piston hydraulic unit

An axial piston hydraulic device includes a holddown device for maintaining the slippers swivably connected to pistons in sliding contacting with a cam surface of a swashplate. The holddown device also includes a nested wave spring disposed to resiliently urge a holddown sleeve away from a cylinder barrel for biasing a holddown plate engaging the slippers toward the cam surface.

Slipper holddown device for an axial piston pump

A follow up mechanism for maintaining a timed positional relationship between a bearing cage of an arcuate roller bearing assembly and a swashplate supported by the bearing assembly includes a flexural elastic link pivotally connected to the bearing cage and having first and second ends slidably disposed within a first bore in a pump housing and a second bore in the swashplate, respectively. The bores are in axial alignment with each other when the swashplate is in the equivalent of its centered position thereby allowing blind assembly of the follow up mechanism thereby eliminating the need for an access opening in the side of the pump housing and the associated cover, gasket and bolts.

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Ottawa, IL, United States of America

Thomas A Watts