Abstract: A hydraulic piston cylinder device comprising a cylinder, a piston dividing the cylinder into two cylinder spaces (A and B), and valve members between the cylinder spaces and respective pressure medium pipes. The problem is to achieve a hydraulic piston cylinder device in which the pressure or tractive force of the cylinder is maintained even if the external pressure led into the cylinder would stop. To solve this problem, an elastic material is interposed between two piston parts, and is elastically compressible by the external pressure applied to the cylinder; and the valve members are coupled to each other so that when one of the valve members is closed the other cannot be closed.

Abstract: A drill steel guiding and centralizing mechanism comprising a body (14) and a first and second jaw (1 and 6) connected to other ends of two-armed angled levers (2,3 and 7,8). The angled levers are turnably connected to the body (14) by joints (4 and 9) at the corner points between the arms (2 and 3; 7 and 8). The ends of the free arms (3 and 8) of the angled levers are connected to each other by a connecting road (11), the ends of which are connected to the ends of the arms (3 and 8) by swivel joints (12 and 13). The second angled lever (2,3) has an extension (16) which is affected by the power mechanism (15) substantially parallelly to the connecting rod (11). Thereby the jaws (1 and 6) can be opened and closed by the power mechanism (15) exactly centralized in relation to the drill steel.