Abstract: A bridging coupling is actuated by an annular piston to which the converter's internal pressure is applied on one side thereof in an opening direction and a closing pressure is applied in the closing direction. The closing pressure is controlled by a precontrolled regulating valve depending on the output pressure of the converter and on a control pressure that depends upon further operating parameters. With the coupling open, the closing pressure in the closing pressure chamber remains below the internal pressure of the converter by a specified value. This ensures that the bridging coupling responds quickly and can be precisely regulated within narrow tolerances. In addition, only relatively little power is needed for the regulation.

Abstract: A hydraulic pressure-control device, specially for powershift transmissions of motor vehicles, comprises a fluid pump (1) and a main valve for regulating the pressure in at least one high-pressure consumer device (6), which is attached to a pressure pipe (3) between the fluid pump (1) and the main pressure valve. The main pressure valve is designed as pressure-relief valve. In the main pressure valve is integrated the operation of a second pressure-relief valve. Two different pressure limits can be adjusted in the pressure pipe (3) by a valve piston (21) through two compression springs (17, 18) connected in parallel of which one compression spring (18) is bound.

Abstract: A hydraulic control device for the pressurization of a clutch or the like for a transmission operable under load comprises a spool-type valve displaceable in one direction to pressurize the clutch and in the opposite direction to vent the same. The valve spool operates with a damping piston which receives the clutch pressure buildup and acts against a control piston which, in turn, is displaced by an operative valve. According to the invention, the pressure head is maintained substantially constant by providing a sleeve or bushing within the damping piston chamber which bears against the spool by a spring and which can be biased by a spring between the damping piston and the sleeve.