CONTROL CIRCUIT FOR VARIABLE DISPLACEMENT PUMPS WITH OVERRIDE VALVE

摘要

The variable displacement pump is used in a hydrostatic transmission in order to control the operating mechanism in a motor vehicle. The pump is controlled by a circuit containing fluid under pressure and the control may be over ridden selectively. A pump (11) with positive displacement is driven by a motor to provide a fluid under pressure in an inlet pipe (12) for a control circuit. The primary control comprises a control lever (14) which is displaced in a slot (15) by the user to set a three position value (16) to one of its positions. This controls selectively the operation and displacement of a variable displacement pump (P) driven by a motor (M). A pedal (27) allows the user to over ride the control by operation of a rotary valve (28) which allows the pump displacement to be modified.