Patent ID: 6966240
Filing Date: 2005-11-22
Classification: B25B,F15B

Abstract:
1. A hydraulic circuit including: a hydraulic ratchet wrench having a double-action hydraulic cylinder with a piston that is displaceable in the hydraulic cylinder, a piston rod actuating said ratchet, a working stroke chamber in the hydraulic cylinder having a high-pressure chamber on one piston side and a low-pressure return stroke chamber on the other piston side with the piston rod, a hydraulic pump arrangement with a gear pump and a piston pump connected via hydraulic controls to the working stroke chamber and the return stroke chamber to drive said wrench in alternating work strokes and return strokes, wherein said circuit comprises: a gear pump connected to said working stroke chamber by a working stroke oil line and connected by a return stroke oil line to said return stroke chamber; said working stroke oil line connected to an oil reservoir by a first suction port; said return stroke oil line connected to said oil reservoir by a second suction port; an oil backflow line connected to said working stroke oil line and said oil reservoir, and a blocking valve arranged in said backflow line to selectively deliver an oil flow from said working stroke oil line; said piston pump connected to said oil reservoir by a piston pump suction line and to said working stroke chamber by said working stroke oil line; a pump control actuating said gear pump in one direction of rotation for delivering oil through said working stroke oil line to said working stroke chamber, and actuating said gear pump in an opposite direction for delivering oil through said return stroke oil line to said return chamber; a working stroke flow valve arrangement in communication with said working stroke oil line to direct a flow of working oil to said work stroke chamber during said work stroke; a return stroke flow valve arrangement in communication with said return working stroke oil line and said oil backflow line to direct a flow of oil back to said oil reservoir during said return stroke; and said working stroke and return stroke valve arrangements operating automatically in response to flow conditions in one or more of said working stroke oil line, return stroke oil line, and backflow oil line caused by operating said gear pump in opposite directions.