GB437327A - A relief valve device for maintaining constant pressure - Google Patents

Abstract

437,327. Relief valves. LAIDLAW, A. B. S., Calderwood Cottage, Lasswade, Midlothian. Jan. 21, 1935, No. 2011. [Class 135] A relief valve for oilburning and like fluidcirculating systems wherein a predetermined pressure is maintained, comprises two pistons 8, 12 of different area arranged in a common chamber 14 so as to act in opposition to one another through a spring or other resilient connection 13, the adjacent sides of the pistons being subject to a common pressure which is less than inlet pressure and the remote sides being maintained at inlet pressure. A shoulder 20 limits the displacement of the larger piston 12, the flow of fluid at inlet pressure to which is retarded by a needle valve 17 or other restriction. The valve member 7 formed on the piston 8 seats on a ported screw member 5. A passage 15 connects the chamber 14 to a bore 4 leading to the outlet. This passage may be dispensed with and the chamber 14 vented to the atmosphere. The initial compression of the spring 13 which determines the pressure at which the valve opens is adjustable by means of the screw 21 or the member 5. As fluid leaks past the valve 17 into the chamber 11, the compression of the spring 13 is increased, and hence also the pressure in the system, until the predetermined pressure is attained when the piston 12 abuts the shoulder 20. For fluids of great viscosity, the valve 17 may be replaced by a narrow clearance space between the upper part of the piston 12 and the wall of the chamber 11. This chamber may be connected by a pipe instead of the passage shown to the valve inlet, or alternatively directly to the discharge side of a pump in the system.