Patent ID: 7318386
Filing Date: 2008-01-15
Classification: B62D

Abstract:
1. A power assist apparatus for a hydraulic steering system, comprising: a directional control valve; a first valve port hydraulically connected to the control valve and being connectable to a first pump port of a manually operable steering pump; a second valve port hydraulically connected to the control valve and being connectable to a second pump port of the manually operable steering pump; a third valve port, a fourth valve port, a fifth valve port and a sixth valve port; a powered hydraulic pump having an input port and an output port, the input port and the output port being hydraulically connected to third and fourth ports of the control valve, respectively, the control valve having a member displaced in a first manner when hydraulic fluid flows into the apparatus through the first valve port, said member being displaced in a second manner when hydraulic fluid flows into the apparatus through the second valve port; a position sensor for detecting movement of the member; a controller for operating the powered hydraulic pump, said controller receiving signals from the sensor to operate the pump when hydraulic fluid flows into the apparatus through the first the valve port or the second valve port, the fifth and sixth valve ports being for hydraulic connection to a steering actuator, the control valve connecting the output port of the pump to the fifth valve port when hydraulic fluid flows into the apparatus through the first port and connecting the output port of the pump to the sixth valve port when hydraulic fluid flows into the apparatus through the second port.