Abstract: A feedback apparatus according to the present invention elastically interconnects the swashplate of a variable displacement hydraulic unit with the valve spool of a hydraulic unit displacement control, and is constructed such that a predetermined spring preload force is developed. A feedback spring extends along the valve spool and is surrounded by an elongated housing coupled with the swashplate. Axially movable spring guides are interposed between opposite ends of the spring and a flange formed at each end of the housing. A suitable spacer is positioned between the spring and at least one of the spring guides to compress the spring to a length representative of the desired preload.

Abstract: A manual displacement control is provided for varying the displacement of a hydraulic pump. The pump has a tiltable swashplate and is used in a hydraulic system which includes a control valve having an axially movable spool for metering control fluid to modulate the swashplate position. A displacement control linkage has a non-linear coupling element and a resilient override spring serially connected between the input lever and the valve spool. A torsional centering spring is connected between the input lever and the override spring to generate a feedback force which opposes a control force applied thereto and urges the input lever to a position representative of the no flow position of the pump swashplate. An adjustable connection is provided for centering the valve spool while maintaining a corresponding neutral position of the input lever and swashplate during assembly of the displacement control.