Hydraulically powered impact device

摘要

A hydraulic impact device has a hammer member carrying a piston which is reciprocally disposed in a cylinder chamber to form an expansible chamber. When the expansible chamber is pressurized, the hammer is retracted against an air spring or other energy storage device by the high pressure. A sleeve valve is reciprocally disposed in the cylinder chamber between the piston and the energy storage device and is held against the piston by an imbalanced fluid pressure as the hammer is retracted against the spring. When the piston and sleeve valve have been retracted to a predetermined position, high pressure fluid is ported between the sleeve valve and piston to hydraulically separate the two members. The chamber pressure is then equalized on both sides of the piston at the return line pressure so that the air spring can accelerate the hammer to deliver an impact blow to an anvil and thence a tool with minimum resistance to movement of the piston by the hydraulic fluid as the chamber pressure is reduced to return line pressure. The sleeve valve is then again moved downwardly against the piston member by an imbalanced pressure condition. When the sleeve valve moves downwardly and seats against the piston, the piston and sleeve are again retracted by the high pressure and the cycle is repeated. The chamber wall is shaped to provide a hydraulic cushion for the hammer near the end of its impact stroke and to provide a seat for the piston apart from the sleeve valve so that high pressure fluid is bypassed to reservoir until a predetermined load is placed on the hammer.