Abstract: A hand-held hammer drill has a housing and an electric drive motor arranged in the housing. A tool spindle is arranged in the housing and configured to receive a tool. The tool spindle can be driven in rotation by the electric drive motor. The tool spindle has a longitudinal axis and is oscillatingly moveable in a direction of the longitudinal axis. A hammer mechanism is provided to move the tool spindle oscillatingly in the direction of the longitudinal axis. A hydraulic drive is arranged in the housing and configured to drive the hammer mechanism. The hydraulic drive has a hydraulic pump generating a hydraulic pressure for driving the hammer mechanism.

Abstract: A water driven hammer device has a machine housing and a hammer piston movable to-and-fro in the machine housing. The hammer piston is guided in the machine housing in two guides separated from each other. The guides are formed from two parts each having different inner diameters, and the parts with the largest inner diameters on the guide are turned towards each other. A room between the guides is pressurized and chambers on the other side of the guides are kept at a lower pressure, resulting in fluid flow through the guides for centering the hammer piston in the machine housing to avoid seizure of the hammer piston.

Abstract: Liquid driven hammer machine with a machine housing (1) and a hammer piston (2) moveable to-and-fro in guides (4,5) in the machine housing. The guides are made with an intermediate section (6) and end sections (7,8) on either sides thereof. The slot between the intermediate section and the hammer piston is less than, preferably one half of, the slot between the end section and the hammer piston at the end of the end section turned away from the intermediate section. The intermediate section has according to an advantageous embodiment an ax/al extension which is approximately one third of the length of the guide.