Control device for hydrostatic drive, especially for fork lift truck
AssigneeO&K Orenstein & Koppel Aktiengesellschaft
InventorFriedrich Hachmann
Life of this patent
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Abstract
A control device for a hydrostatic drive, especially for a fork lift truck, in which an engine drives a reversible variable delivery pump which supplies fluid to a fluid motor connected to the drive wheels of the lift truck. A reversible actuator is connected to a control element for the pump and is connected through a reversing valve with a further engine driven pump. The rate of movement of the actuator is controlled in the opposite directions of movement thereof. The truck includes a lift cylinder supplied by a still further engine driven pump, and when the lift cylinder is under pressure, the rate of movement of the actuator is controlled at a still slower speed of movement in at least one direction of movement.
Claims9
In a control system for a fork lift truck having a fluid operable lift cylinder and a fluid drive motor and a variable delivery reversible pump connected to the motor and a drive engine connected to drive the pump;
- said pump having a control element movable from a first position of maximum pump delivery in forward direction through a position of zero pump delivery to a second position of maximum pump delivery in reverse direction, a fluid operable reversible actuator connected to said control element and normally biased toward a center position in which said control element is in zero delivery position, a second pump and a reversing valve having an inlet connected to said second pump and a respective output connected to each side of said actuator, a third pump and a control valve connecting the third pump to the lift cylinder, both of said second and third pumps being driven by the engine, control means for controlling the rate of movement of said actuator at least toward said second position thereof in response to the supply of actuating fluid thereto from said reversing valve.
Dependencies are inferred from the claim text.