GB626619A - Improvements in or relating to thermostatic mixing valves - Google Patents

Abstract

626,619. Thermally-actuated valves. BIRCHFIELD, P. A. Aug. 14, 1945, No. 20847. Convention date, Aug. 14, 1944. [Class 135] A thermostatic mixing valve for two liquids at different temperatures comprises a casing having inlets 25, 31, respectively for the hot and cold liquids, a spool valve member 38 for controlling the inlets and forming a mixing chamber 40 with the casing, an outlet 35, a valve 46 carried by the valve member for closing the outlet, and means, enclosed within the valve member, responsive to the temperature of the mixed liquids in the mixing chamber for maintaining the mixture at a predetermined temperature. The spool is hollow and filled with a volatile liquid, the opening 47 at one end being closed by a metal bellows 48 carrying a block 49 supported on the manually adjustable screwed stem 16 by which the mixture temperature is selected. On turning the stem the valve 46 is opened and the liquids flow into the mixing chamber through the ports 22, 23 and flow to the outlet through slots 33, port chambers and ports 37 in the casing. If the temperature of the mixed liquids rises above that set by the position of the end of the stem, the thermosensitive liquid expands so that the bellows contracts and the spool moves downwards against the spring 53 so that its end 42 closes the port 22 and the other end 43 opens the port 23. If the mixture temperature falls, the bellows elongates and the spool rises. If the temperature fall is excessive, the flow is stopped by the end 43 covering the slot 33. In a modification, the spring is dispensed with, the spool moves in a liner and, in order to prevent strain on the bellows when the valve 46 is closed due to excessive rise in temperature, the stem 16 can move outwardly against a spring.