Patent ID: 6334495
Filing Date: 2002-01-01
Classification: B25D

Abstract:
A fluid-operated percussion device comprising:a percussive piston that moves in a work cylinder and strikes a tool, said percussive piston having two opposed piston end surfaces of different sizes, with a smaller of the piston end surfaces, which is effective in the direction of a return stroke, being continuously connected to a pressure line that is acted upon by a work pressure, and a larger of the two piston end surfaces, which is effective in the direction of a work stroke, being alternately connected via a pilot valve to the pressure line and to a pressure-less return line; a control having a slide valve that moves in a pilot valve, said slide valve having two valve surfaces that are of different sizes and are effective in opposite directions of movement, with a smaller of the valve surfaces of the slide valve, which smaller valve surface acts on the slide valve in the direction of the return-stroke position of the slide valve, being continuously connected to the pressure line, and a larger of the valve surfaces of the slide valve being alternately connected temporarily to said pressure line and to said return line via a circumferential groove disposed on the piston surface between the piston end surfaces; the interior of the work cylinder additionally has a no-load-strike opening, which opening is enabled, in the direction of the interior, by a front piston collar of the percussive piston, with the front piston collar having the smaller piston surface, after the percussive piston has overshot an extended position occurring in normal operation, by a predetermined distance in the work-stroke direction to assume a no-load-strike position; a safety element, which can be switched between a first inoperative end position and a second operative end position and whose input side is connected to the pressure line, is disposed upstream of the no-load-strike opening, with the safety element acting on the no-load-strike opening with the work pressure originating from the safety element in the second operative end position, and with the safety element breaking the connection between the pressure line and the no-load-strike opening in the first inoperative end position; and when the safety element assumes the second operative end position and the percussive piston reaches the no-load-strike position, the work pressure applied to the no-load-strike opening acts on the control via the circumferential groove such that the slide valve of the control is blocked in the work-stroke position.