GB1228129A - - Google Patents

Abstract

1,228,129. Valves. ANDERSON, GREENWOOD & CO. 20 March, 1969, No. 14828/69. Heading F2V. [Also in Division G3] In a valve having an inlet duct A, a working duct B and a vent duct V, the flow of fluid between ducts A and B takes place through a valve seat 60 and is controlled by a valve member 62, and the flow of fluid between ducts B and V takes place through a seat 30 and is controlled by a valve member 28, the two valve members 62 and 28 being biased towards their seats by respective springs 66 and 36, and having extending therebetween a spacer 64 whose cross-sectional shape is square over substantially the whole of its length. The separation between seats 30 and 60 can be adjusted by appropriate manipulation of a knob 50 to which the latter seat is screw-threaded. In use, (Fig. 1, not shown), the valve P performs the function of a pilot valve which controls the operative state of a pressure relieving valve (R) associated with a tank (T), with the duct A being connected to the inlet line of the relief valve (R), duct B being connected to an actuating means of the relief valve and duct V being open to atmosphere. In operation, when the pressure within the tank (T) is below a certain level, valve member 28 remains seated and flow from duct A, and hence the tank (T), takes place to duct B with such flow tending, via the actuating means, to maintain the relief valve closed. Upon the tank pressure exceeding the level, the pressure in duct A rapidly unseats valve member 28 and seats valve member 62 such that the operating means is placed in communication with the vent duct V and the relief valve (R) is allowed to open. The rapid change of state of the pilot valve is ensured by forming closure member 28 with a skirt which surrounds the member seat 30. The time delay between the tank pressure returning to the certain level and the valve members returning to the positions shown, is_ determined by the spacing of the two valve seats 30 and 60, the larger the spacing the smaller the compression of spring 36 upon valve member 28 becoming unseated, and hence the smaller the force tending to re-seat member 28 subsequent to the relief of pressure and its return to the certain level.