Speedup device for hydraulic control circuit systems

摘要

A speedup device or valve means comprises a check-valve disposed in an oil passage connected with the rod-end chamber of a double-acting cylinder for preventing working oil from returning toward a tank only, a circulation valve provided in the upstream of said check valve, said circulation valve being usually urged by a spring to block communication between the oil passages connected with the rod-end and the piston-end chambers, respectively, said circulation valve being designed to move against the spring so as to connect the oil passages with each other in response to the pressure rise in the return oil from the rod-end chamber when said double-acting cylinder is in its rod-extending motion, causing the return oil from the rod-end chamber to shift into the piston-end chamber through a variable restriction, and a circuit set up in a portion of said circulation valve for allowing a portion of the return oil from the rod-end chamber to return to the tank through a variable restriction and a restriction passage.