Pressure control valve

A pressure control valve comprising a primary port for the supply of fluid, a pressure controlled secondary pressure port for connection with a load, a venting port and furthermore a valve operating means which is able to be positioned by means of a variable control pressure, obtaining in a control chamber, in different positions of control including a neutral setting, at least one supply setting and at least one venting setting, the secondary pressure port being in the neutral setting separated both from the primary pressure port and also from the venting port, whereas in the possible supply and venting settings it is connected either with the primary pressure port or with the venting port and simultaneously is separated from the respectively other port, wherein the valve operating device is so subjected to a mechanical spring device opposing the direction of action of the control pressure that if ambient pressure obtains in the control chamber it automatically assumes a basic setting, which is the same as a venting setting, further comprising a valve housing in which two transfer openings are defined connecting the secondary pressure port on the one hand with the primary pressure port and on the other hand with the venting port, such transfer openings being surrounded by a valve seat integral with the housing, the valve operating device comprising two independently moving closure members associated respectively with one of the valve seats and biased resiliently toward a closed setting closing the associated transfer opening, and furthermore a valve operating member which is adapted to serve for actuation of the closure members and is able to be moved linearly under the action of the control pressure, and wherein the more especially rod-like valve operating member is suspended using a flexible diaphragm in a moving manner on the valve housing, such diaphragm constituting a moving wall section of the control chamber, and further including means defining a counter-pressure chamber on the side of the diaphragm opposite to the control chamber, said counter-pressure chamber being in constant communication with the secondary pressure port.