Hydraulic striking mechanism

A hydraulic striking mechanism, comprising:

• a cylinder including an interior surface having first and second oppositely facing annular faces;
• a percussion piston guided in said cylinder and being movable in said cylinder in one direction for performing a striking stroke and in an opposite direction for performing a return stroke, said percussion piston including a first end having a striking tip for striking an object during the striking stroke, and an opposite, second end presenting an axial abutment face and being charged with a compressible driving medium, said percussion piston defining, with said cylinder, an oil chamber and having a cylindrical shoulder disposed in said oil chamber and cooperating with the first annular face of said cylinder for fixing the end position of said percussion piston during the return stroke;
• a piston return device consisting of an annular piston having a first side which lies against said cylinder and a second side which lies against said percussion piston, said annular piston being freely displaceable, independently of said percussion piston and being configured for leading said percussion piston during the striking stroke, said annular piston cooperating with the axial abutment face of said percussion piston for moving said percussion piston in the direction of the return stroke, said annular piston having a third side facing the striking tip of said percussion piston which, together with the second annular face of said cylinder, defines axial limits of a piston chamber that is separated from the compressible drive medium and is located between said oil chamber and the second end of said percussion piston, the amount of movement of said annular piston relative to said percussion piston in the direction of the return stroke being limited by the abutment face of said percussion piston;
• and
• control means for alternatingly connecting said piston chamber with a pressure source of incompressible driving medium and a pressure-free return conduit, said control means connecting said oil chamber to the return conduit when the cylindrical shoulder of said percussion piston approaches the first annular face of said cylinder during the return stroke and connecting said piston chamber with the pressure source when said annular piston approaches the second annular face of said cylinder.