Patent ID: 6823669
Filing Date: 2004-11-30
Classification: F15B

Abstract:
A hydraulic transfer valve system for coupling one of primary and secondary hydraulic systems, each having a source and a return, to a hydraulic load having an input and a return, the hydraulic transfer valve system comprising:a first valve; a second valve; and a passageway coupling the first valve to the second valve and having first and second ports at said first and second valves, respectively, the first valve having: a first condition in which the first valve: provides communication between the primary hydraulic system source and the hydraulic load input; provides communication between the primary hydraulic system return and the hydraulic load return; blocks communication between the secondary hydraulic system source and the hydraulic load input; provides communication between the secondary hydraulic system return and the hydraulic load return; and blocks the passageway first port; and a second condition in which the first valve: provides communication between the secondary hydraulic system source and the hydraulic load input; provides communication between the secondary hydraulic system return and the hydraulic load return; blocks communication between the primary hydraulic system source and the hydraulic load input; provides communication between the primary hydraulic system return and the hydraulic load return; and does not block the passageway first port; and the second valve having; a first condition in which the second valve blocks the passageway second port; and a second condition in which the second valve does not block the passageway second port and wherein with the first valve in its second condition, the passageway permits a flow from the primary hydraulic system source to the primary hydraulic system return.