Abstract: A device for varying the opening and closing times of gas exchange valves of an internal combustion engine, comprising a drive unit (2) which is in driving relationship with a crankshaft through a traction element and a driven unit (14) connected to an intake or exhaust camshaft, there being arranged within the device (1), a coupling element (18) by which a rotationally fixed, force-transmitting connection can be established between the drive unit (2) and the driven unit (14) when the pressure of the hydraulic medium falls below a level required for the displacement of the adjusting piston (9), the coupling element (18) being configured as a locking piston (19) which can be displaced on the one hand by hydraulic pressure and on the other hand by an auxiliary energy and comprises on an end face (26) a number of concentrically arranged extensions (27) which are associated to complementary recesses (35) of a locking ring (34) in the housing (6) to avoid noise generation on starting of the internal combustion eng

Abstract: The invention concerns a valve arrangement installed in a hydraulic system including a housing (17a, 17b) which is provided with two connections (22, 23) and includes a closing element (14) which lies in a neutral position on a valve seat (6). In accordance with the invention, a valve element (11) is provided which has two step valves (15a, 15b), arranged at a distance, each being associated with one flow direction, whose the closing elements (14) are acted upon by a spring force.