Abstract: An electrohydraulic switching device adapted to supply electric control signals in dependence on pressure signals received includes a first piston adapted to be acted upon by the input pressure and spring-loaded in opposition to the input pressure, and a second piston positively engaged with the first piston to activate an electric switching element. The first and second pistons are axially slidable relative to each other by a predetermined distance. A retaining element engages the second piston to provide for a switch hysteresis. To avoid an impact on the limit values as a result of fluid temperature and viscosity variations, the second piston is carried in the retaining element by several circumferentially spaced contact points in that the retention element is an elastic, substantially annular body with open ends.

Abstract: The disclosed valve device includes first, second and third user ports. A pressure accumulator connects with the first user port. With the accumulator fully charged, a pressure port connected to a pump communicates with the second user port. With the accumulator evacuated, the pressure port communicates with the first user port. In the event of a fluid demand at the third user port, the pressure port will be connected to the third user via a control valve. The control valve is a non-return valve in a channel connecting the first user port to the third user port, which opens under influence of a pressure in the first user port.