Electromagnetic control valve responsive to positive and negative pressures

An electromagnetic control valve comprising a coil housing, a valve housing having a connector for inlet therein of a medium whose pressure which is to be controlled, said valve housing having a chamber connected to ambient atmosphere and a valve means controlling communication between said chamber and the medium introduced into said valve housing for opening when the medium exceeds a predetermined positive pressure, a by-pass channel connected to ambient atmosphere, and a suction valve controlling communication between said by-pass channel and the medium introduced into said valve housing when the medium is at a negative pressure which exceeds a predetermined negative pressure, said valve means comprising a valve plate facing a valve seat in said valve housing for selectively opening and closing an opening in said valve seat to respectively connect and disconnect the medium introduced into the valve housing from said chamber, a basket slidably supporting said valve plate, and a spring between said basket and said valve plate to urge the valve plate against a stop means provided on said basket, an electromagnet in said coil housing including an armature acting on said basket to displace the basket when said electromagnet is energized to apply said valve plate against said valve seat and cause said valve plate to be lifted off said stop means, said valve plate then being subject on one side thereof to which for positive pressures said medium tends to displace said valve plate off said seat and on the other side of said spring urging said valve plate against said seat whereby when said medium has a positive pressure above said predetermined value of positive pressure said valve plate will be forced off said seat to relieve said positive pressure, and when said medium has a negative pressure below said predetermined value of negative pressure said suction valve will open and the pressure will increase.