Patent ID: 6155353
Filing Date: 2000-12-05
Classification: B25D

Abstract:
An impact tool comprising:a body having a longitudinal axis, a central longitudinal passage, a striking end and a closed end;a striking tool reciprocably mounted in said passage;a hammer reciprocably mounted in said passage so disposed and arranged as to strike the striking tool in one direction of movement, said hammer having a lesser diameter nearer the striking tool and a larger diameter, there being a return shoulder joining them;a valving sleeve fixed in said passage, a portion of said hammer being reciprocably and sealing fitted in said valving sleeve, said sleeve including an orifice and an adjacent seal facing said hammer, and a seal facing away from said hammer, an axial channel extending along the outside of the sleeve from end to end;a seal on said hammer facing said adjacent seal on the valving sleeve;an axially reciprocable tubular valve having an outer wall spaced from the wall of the body;a piston slidably and sealingly fitted between the wall of the body and the outer wall of the piston, said piston including a skirt slidable on said valve;a stop on said outer wall of said valve disposed and arranged to be engaged by the said skirt;a lip and an adjacent seal on an end of said valve, said lip proportioned to enter said orifice leaving a gap around it, a pair of steps on the outer wall of said valve facing said piston and a notch in said piston facing one of said steps;an end cap closing said passage at its other end, said end cap together with said valve and piston forming a gas chamber to hold a charge of gas under elevated pressure;a drain plug fixed to said end cap extending into said passageway having an outer wall, and said end cap having an inner wall, said last-named walls forming a drain channel between them, said valve having a portion which enters said drain passage in some positions;a drain port through said end cap on the opposite side of the drain channel from the valve;a pressure port to admit oil under elevated pressure into an oil chamber on the opposite side of the sleeve from the hammer, the face of the piston away from the gas chamber facing into the oil chamber;whereas, gas under elevated pressure is charged into said gas chamber, pressing said valve against the sleeve to close the orifice, oil under pressure is admitted to the oil chamber to force the hammer against the surface on the sleeve, also to close the orifice;the piston is moved by oil pressure so the piston skirt strikes the stop on the valve and the valve is moved away from the orifice, thereby exposing the hammer to oil pressure, and driving the hammer toward the striking tool, while closing the drain channel, thereafter the piston returning the valve to the orifice, opening the drain channel and enabling the hammer to be returned and engage the sleeve seal.