GB650708A - Improvements relating to pressure-relief valves for pressure cooking vessels or the like - Google Patents

Abstract

650,708. Pressure gauges. KELLER, M. Dec. 31, 1947, No. 35232. Convention date, May 18, 1946. [Class 106 (ii)] [Also in Group XXIX] A pressure-relief valve device, suitable for a pressure cooker, includes visual and acoustic warning signals and a throttling device, the arrangement being such that, on increase of pressure in the vessel, first the visual signal is operated, then the acoustic signal, and finally the relief valve is opened, but the escaping steam is throttled by the throttling device during the initial actuation of the relief valve. In an embodiment, the valve comprises an open-ended casing 23 screwed into the vessel and covered at its outer end by a screwed cap 6, and a piston 2 and sleeve valve 1 project through, and can slide in, an aperture in the cap. Normally, the piston occupies the dotted-line position, but as the steam pressure increases, it is lifted to the full-line position when a mark 9 on the stem of the piston becomes visible. On further increase of pressure, the piston contacts the lower end of the sleeve valve 1 and lifts it so that a small flow of steam takes place up the outside of the sleeve, past a shoulder 14 which constitutes a throttle, and then through coincident grooves 15, 19 and ports in the sleeve and piston, respectively, into the interior of the piston, and so past a whistle 21. At still higher pressures, groove 15 starts to coincide with the exhaust ports 17 in the casing and a throttled downward escape of steam is permitted, the amount escaping increasing as the sleeve is moved further upwards. The piston carries heatresisting lubricant in a groove 13.