Hydraulic door operating system
AssigneeApplied Power Inc.
InventorsXudong Yu, Eric N. Griesbach, Douglas C. Blotz
Life of this patent
Estimating the term…
Abstract
A hydraulic system for opening and/or closing the rear lift gate of a vehicle uses a double or single acting gas charged hydraulic cylinder. If double acting, a second piston separates the head side of the cylinder into hydraulic and gas chambers. A unidirectional (for the single acting cylinder) or a bidirectional (for the double acting cylinder) drives a pump to operate the cylinder. A solenoid actuated on-off valve selectively communicates the ports of the cylinder with tank pressure. A gas charge accumulator may also be provided. In the double acting embodiment, a two way ball shuttle valve which is vented in the center provides alternating communication between the two cylinder ports.
Claims11
In a hydraulic door operating system having a linear hydraulic actuator for opening or closing a door, said actuator having a cylinder defining a chamber with a rod piston within said chamber and a rod extending from said rod piston out a rod side end of said cylinder, said rod piston dividing said chamber into a rod side on the side of said rod piston from which the rod extends and a head side opposite from said rod side, and said actuator having a rod side port opening into said rod side of said chamber, a hydraulic pump for supplying hydraulic fluid under pressure and means for communicating said hydraulic fluid from said pump to said rod side port, the improvement wherein said head side of said chamber is charged with a gas under super-atmospheric pressure which biases said rod to an extended position.
Dependencies are inferred from the claim text.