GB979015A - Improvements in or relating to fluid pressure control valves - Google Patents

Abstract

979,015. Electromagnets. BRAKESHOE INTERNATIONAL S.A. Aug. 16, 1961, No. 29522/61. Heading H1P. [Also in Division G3] An electromagnet for loading a pilot valve is disposed in the upper part of the valve housing accommodating a core 61 for the coil 43 of an electromagnet, and a thermistor 44; the core 61 is cupshaped and is provided with a centre post 63. The armature includes a disc 66 with a hollow depending member 68 of non- magnetic material which freely extends through the post 63 whilst the tube 60 is axially slidable within the member 68 and is secured thereto by an adjusting screw 69. The disc 66, member 68, tube 60 and rod 57 are supported against lateral motion by non-magnetic diaphragm 72 having a rim and hub portions connected by curved flexible spokes. A pin 80 prevents rotation of the diaphragm 72, washer 79, and core 61. The air gap between the disc 66 and the poles 62, 63 is made large enough by using a washer 79 so that the forces acting on the armature will remain constant for any given excitation of the coil. The thermistor 44 adjusts the current in accordance with temperature. Operation.-When the electromagnet seats the pilot closure 54 the fluid pressure forces acting in the opposite surfaces of the piston 27 are equal and the main closure is seated by the spring 33; when the -pilot closure 54 allows fluid to enter the chamber 45 from bore 37 the fluid from chamber 45 flows to the port 18 via the external groove in the insert 49, the balancing piston 31 and the bore 30. The coil 43 is permanently excited so that when the fluid pressure in the passage 20, hence in bore 37 has risen sufficiently to unseat the pilot closure 54 against the electromagnetic action of the coil 43, the main closure is unseated due to the pressure drop across the orifice 38 by an amount proportional to that drop; the pilot closure will open to a position wherein the fluid and electromagnetic forces are in balance. The quantity of electricity supplied to the coil 43 is proportional to the pressure which will be maintained in the passage 20; this pressure may be regulated by a potentiometer in the coil supply circuit.