Abstract: The invention relates to a hydraulic striking mechanism including a cylinder, a percussion piston guided therein and a piston return device which is supported on the percussion piston and is displaceable independently thereof and can be connected on its side facing the percussion piston tip alternatingly to a pressure source or a pressure-free return conduit. The piston return device is configured as an annular piston which is freely displaceable along the percussion piston and the cylinder and forms therewith a piston chamber. The percussion piston has an abutment face at its end remote from the percussion piston tip which cooperates with the annular piston for moving percussion piston in the return stoke direction. The percussion piston, together with the cylinder, defines an oil chamber which axially follows the piston chamber in a spaced relationship. The percussion piston is provided with a cylindrical shoulder within the oil chamber which determines its end position during the return stroke.

Abstract: A hydraulic striking device (1) includes a percussion piston (3) which reciprocates in an operating cylinder (2) and strikes a bit (4). The reciprocation is governed by a control valve (10) which is connected to the operating cylinder by a control conduit (27). A holding valve (30) in the control conduit has three connections (27a, 27b, 31): one with the control valve, one with the operating cylinder, and one with the return conduit (17). The connections (27a, 31) which are connected with the operating cylinder and with the control conduit are axially aligned and form the outlets of a hollow cavity (53) in which a preferably spherical movable valve body (54) is disposed, the cross-sectional area of the valve body being smaller than that of the cavity. The connection (27b) with the control valve opens radially into the cavity.

Abstract: A hydraulically operable linear motor with a double-acting reciprocable piston in a cylinder, in which one side of the piston has connected thereto a piston rod so as to form with this one side an annular piston surface which is continuously exposed to a desired working pressure. The other side of the piston is by means of a hydraulically actuated control valve alternately exposed to the working pressure and to the pressure in an exhaust conduit. The pressure for actuating the valve spool of the control valve is generated in a conduit section which communicates with two annular grooves in the two cylinder sections separated from each other by the piston and adapted alternately to be closed off from the above mentioned conduit section. This conduit section communicates through throttles with the exhaust conduit.