Boost valve device

Claim 1

A hydraulic fluid pressure control device for controlling the operation of a hydraulic cylinder having a piston and a rod affixed to the piston, the piston dividing the cylinder into an upper chamber and a lower chamber, a hydraulic fluid supply including a hydraulic fluid tank, a pump connected to the tank for receiving hydraulic fluid therefrom, fluid conduit means between the pump and the cylinder, the conduit means comprising a first conduit leading to the upper chamber, a second conduit leading to the lower chamber and a return leading to the tank, a directional control valve mounted in the conduit means and having respective ports communicating with the first and second conduits, the valve being operable between a first position wherein the pump is connected to the first conduit to supply hydraulic fluid to the upper cylinder chamber and the second conduit is connected to the return conduit, and a second position wherein the pump is connected to the second conduit to supply hydraulic fluid to the lower cylinder chamber and the first conduit is connected to the return circuit, a boost valve body assembled in abutting engagement with the directional control valve and having two opposite surfaces, the surfaces defining a plurality of ports, respective ones of the ports in the directional control valve being in fluid-tight assembly with the ports in one of the surfaces of the boost valve body, and a manifold assembled in abutting engagement with the boost valve body, the manifold having a plurality of ports in fluid-tight assembly with the ports in the oppisite surface of the boost valve body, one of the manifold ports being connected to the pump, the boost valve body defining between respective ports in the opposite surfaces thereof three fluid flow passages permitting fluid flow from the second conduit through the passages controlled solely by a respective check valve in each of the passages, each check valve comprising a ball and a spring biasing the ball into a normally closed position, a first one of the passages connecting the second conduit to the pump, second and third ones of the passages connecting the second conduit to the control valve, first and second ones of the check valves in the first and second passages, respectively, being spring-biased in the direction of the second conduit, the second check valve being biased under a pressure exceeding the biasing pressure of the first check valve, and the third check valve in the third passage being spring-biased in the direction of the control valve, whereby hydraulic fluid flowing out of the lower cylinder chamber through the second conduit in the first position of the control valve flows through the first passage and opens the first check valve to continue flow towards the pump, this hydraulic fluid flow being added to the hydraulic fluid being delivered by the pump to the first conduit to boost the fluid supply to the upper cylinder chamber and thus to accelerate the piston velocity.