Abstract: A hydraulic device for driving piles including a casing accommodating a striker with an anvil block, a hydraulic power cylinder, having a rod connected to the striker and a hydraulic directional control selector. A control unit is separated from the directional control selector and is secured on a housing of the power cylinder coaxially with the striker. The hydraulic directional control selector comprises two valves, each of which is provided with two pilot chambers, communication pairwise with each other. The first valve puts the head end of the power cylinder in communication with the rod end, and the second valve establishes communication between the head end and the return flow line.

Abstract: The impact hammer comprises a working piston (22) which is displaceable within a working cylinder (21) and controlled by a control means (40,41) in such a manner that it exerts impacts onto an anvil surface (23) of an adapter (24) which can be connected to the object to be advanced. When retracting the object, a return impact piston (51) exerts impacts onto the adapter (24) in opposite direction. Thereby, it is achieved that the object can be better released from the drill hole.

Abstract: Apparatus comprising a striking piston driven hydraulically in a reciprocating fashion by an incompressible fluid inside a cylinder and striking against a tool, of the type in which the piston slides in a cylinder having two concentric piston bearing surfaces of different sections, of which that situated on the tool side has a section smaller than that remote from the tool, the piston and the cylinder delimiting two antagonistic chambers, an annular bottom chamber and a top chamber of larger section.According to the invention the interior of the top chamber is permanently at a regulated pressure of a value intermediate between the inlet or high pressure and the outlet or low pressure, and the annular bottom chamber is connected alternately by a distributor to the high pressure supply circuit during the upward phase of the piston and to the top chamber during the accelerated downward phase of the piston.