Pressure operated{13 positive displacement shuttle valve

Claim 1

A shuttle valve adapted to permit the control of a fluidpressure-operated utilization device from either one of two separate fluid-pressure-supplying control units comprising: a. a body member having a longitudinally extending axial bore therein, and a transversely extending second bore passing through the bottom surface of the body member, intersecting said axial bore, and extending into the outer wall at the top of said body member providing a partial bore therein; b. a balance plate positioned in said partial bore and having a polished surface on the side thereof facing the interior of the body member; c. a seal plate positioned in the portion of said second bore extending through the bottom portion of said body member, said seal plate having an axial bore extending therethrough from the bottom surface of said seal plate and communicating with the axial bore in said body member, said seal plate having a polished surface in the side thereof facing the interior of the body member; d. piston means positioned in said axial bore in the body member and adapted for movement therein between a first end position in which the piston means is positioned in a first furthermost position at one end of said body member and a second end position in which the piston means is positioned in a second furthermost position at the opposite end of the body member, said piston means having a central portion having first and second bores extending transversely completely therethrough from the top to the bottom thereof, said piston means also having first and second arm portions extending longitudinally from said central portion, said first arm portion having an axial bore extending therethrough from the end surface thereof and communicating with said first transversely extending bore in the central portion, said second arm portion having an axial bore extending therethrough from the end surface thereof and communicating with said second transversely extending bore in the central portion, said piston means being positioned so that, in said first end position, said first bore in the central portion thereof is in communication with the bore in said seal plate, and, in said second end position, said second bore in the central portion thereof is in communication with said bore in the seal plate; e. seal means positioned at each end of each of said bores extending through the central portion of said piston means, each of said seals having a polished surface on the exterior portion thereof that abuts upon the polished surfaces of said balance plate aNd said seal plate; f. spring means to maintain said seal means in contact with the polished surfaces of said balance plate and said seal plate; g. first input conduit means for providing fluid communication between a first control unit and the axial bore in said first arm portion of the piston means; h. second input conduit means for providing fluid communication between a second control unit and the axial bore in said second arm portion of the piston means; i. output conduit means providing fluid communication between the axial bore in said seal plate and the fluid-pressureoperated utilization device to be controlled, whereby when said first control units is operative, fluid flows through said first input conduit means to the axial bore in the first arm portion of the piston means, the fluid pressure therein being transmitted to said first bore in the central portion of said piston means, the polished surfaces of the balance plate, the seal plate and said sealing means permitting the shuttle valve to slide to its first end position in which said first bore communicates with the bore in the seal plate, thereby establishing fluid communication to the utilization device, whereas when said first control unit is inoperative and said second control unit is operative, the piston means is caused to slide to its second end position so as to establish fluid communication from the second control unit through the axial bore in said second arm portion, said second bore in the central portion and said bore in the sealing plate to the utilization device, the positive fluid pressure required to cause said piston means to slide between the first and second end positions being operative at relatively low flow rates, the flow rate only affecting the response time of the valve in switching from said first to said second end positions.