Pressure control valves

Claim 1

A fluid flow controlling valve comprising, in combination, a valve body, a first chamber defined in the body, said body having an inlet and an outlet communicating with the first chamber, a valve housing provided in the first chamber, said housing being of cup shaped form having a closed end and an open end, said open end being directed towards said outlet, a piston slidable within the housing, said piston having a head and a skirt portion, said skirt portion extending into said outlet, said skirt portion having an aperture with the aperture being exposed beyond said valve housing to permit flow of fluid between the inlet and outlet as the piston is moved towards the outlet, a second chamber defined by the piston head and the closed end of the housing, and means for controlling the pressure in said second chamber whereby the pressure in said outlet can be controlled, said controlling means comprising a seating in communication with the inlet, a valve control surface co-operating with the seating to determine the fluid pressure in the second chamber, a movable part, said part having a second surface which is exposed to the pressure within said second chamber, resilient means for opposing movement of the movable part due to the force created by the fluid pressure acting on said second surface, the movement of said part determining the relative setting of said valve control surface and the seating, and electromagnetic means for influencing the relative setting of the valve control surface and the seating.