Pressure control valve

In a control device for controlling the pressure in a pressure line connected to a load, comprising a pressure control valve receiving pressurized fluid from said pressure line when a predetermined pressure in the pressure line is reached, said pressure control valve including a closure member, and a pilot valve to adjust the closure member of said pressure control valve, the improvement wherein said pilot valve comprises a solenoid valve having three defined positions, said pressure control valve further comprising a control chamber for pressure fluid for biassing the closure member, a piston to which the pressure in said control chamber is applied, and which in turn applies the pressure in the control chamber to said closure member, said control chamber of the pressure control valve in one of said positions of the solenoid valve being isolated, in a second of said positions being supplied with pressure fluid and in a third position being released of pressure fluid, said solenoid valve including a solenoid which determines said three positions of said solenoid valve and an electrical three point switch means for controlling said solenoid to set the position of the solenoid valve selectively to one of said three positions, sensing means connected to said pressure control valve for producing an output signal related to the pressure in the pressure chamber, and comparator means receiving the output signal from the sensing means for comparing said output signal with a predetermined signal to produce a control signal, said comparator means being connected to said three point switch means for supplying said control signal thereto to operate said three point switch means to produce an output signal therefrom to set the position of the solenoid valve selectively to one of said three positions.