Percussion device, drilling machine including such a percussion device and method for controlling such a percussion device

A percussion device including, inside a machine housing, a reciprocally moveable percussive piston, the movement of which being controllable through a control valve, which is arranged to alternatively connect a chamber to a pressure source and to low pressure in dependence of a signal describing the axial position of the percussive piston, wherein inside said chamber a drive face on the percussive piston is received, wherein a plurality of axially separated control channels for transmitting said signal have openings in a cylinder space for the percussive piston in order to co-operate with a control edge on the percussive piston, and wherein valve means are arranged to allow adjustment of in which axial position of the percussive piston said signal is transmitted, through respectively opening and blocking of connection between one or a plural of said control channels and the control valve, wherein—said valve means includes a first valve element, which is controllable between a first positions, wherein it is arranged to block a first portion or portions of a respective connection between a first subset of control channels and the control valve and a second position, wherein it is arranged to open said first portion or portions, and wherein said valve means also includes a second valve element which is controllable between a first position, wherein it is arranged to open said first portion or portions, and wherein said valve means also includes a second valve element which is controllable between a first position, wherein it is arranged to block a second portion or portions of a respective connection between a second subset of the control channels and the control valve and a second position, wherein it is arranged to open said second portion or portions, wherein the valve elements are circular cylindrical, and wherein the second valve element is arranged concentrically inside the first valve element and has recesses co-operating with channel portions, which extend radially through the material of the first valve element for opening and blocking respectively of said connection portions.

A method for controlling a percussion device including, inside a machine housing, a reciprocally moveable percussion piston, the movement of which being controlled by a control valve, which in dependence of a signal transmitting the axial position of the percussive piston alternatively connects a chamber to a pressure source and to low pressure, wherein inside said chamber, a drive face of the percussive piston is positioned, wherein a plurality of axially separated control channels for transmitting said signal have openings in a cylinder space receiving the percussive piston for co-operation with a control edge on the percussive piston, and wherein valve means are provided to control the position of the control valve and are arranged in order to allow adjustment of in which axial position of the percussive piston said signal is transmitted, by respective opening and blocking of connection between one or a plurality of said control channels and the control valve, said valve means being disposed between each of said control channels and said control valve, wherein—said valve means includes a first valve element, which is controlled between a first position, in which it blocks a first portion or portions (F2) of a respective connection between a first subset of the control channels and the control valve, and a second position, wherein it opens said first portion or portions, and

• wherein said valve means also includes a second valve element, which is controlled between a first position, wherein it blocks a second portion or portions (F2) of a respective connection between a second subset of the control channels and control valve and a second position, wherein it opens said second portion or portions, said first and second valve elements arranged to be movable relative to each other.