A pressure regulator whose initial pressure can be set by manually setting the initial stress of a control spring has a double-seated valve with an inner and outer valve seat and a valve closing element. The valve closing element divides a supply pressure chamber from a control pressure chamber and the latter from a pressure-relief chamber. The inner valve seat is arranged on a control piston which is loaded by the control spring. In order to set a higher initial pressure, the initial stress of the control spring is increased, in order to reduce pressure, the initial stress of the spring is diminished. During this process, the outer or inner valve seat lifts off temporarily from the valve closing element until equilibrium is reestablished by a corresponding pressure chamber and the double-seated valve closes. In order to compensate the hysteresis occurring here, a lifting device is provided which, when the initial stress of the control spring is reduced, briefly lifts off the inner valve seat from the valve closing element and then becomes inactive again. The superproportional pressure drop associated with this in the control pressure chamber has the effect that the equilibrium of forces for closing the double-seated valve is always produced after the outer valve seat is opened by the pressure increase.
A pressure regulating valve having secondary venting measures. It comprises a control member for the control of the fluid connection between a primary duct and a secondary duct. The position of the control member is able to be influenced by a venting aperture also under the control of the control member and serving for venting the secondary duct. The venting opening is so arranged on the setting member that it is located outside the comparison chamber and in this respect either directly in the secondary duct or in a region in communication with the secondary duct.
