GB808769A - Improvements relating to valves for mixing fluids at different temperatures - Google Patents

Abstract

808,769. Mixing fluids in flow. TACCHI, P. G. Aug. 13, 1956 [Jan. 12, 1956], No. 1042/56. Class 86 [Also in Group XXIX] A steam and cold water mixing valve to produce hot water, comprises a valve body 10 having steam and cold water inlets 12, 13 respectively, a mixing chamber 11 having a hot water outlet 18 and a piston 27 slidable in the mixing chamber and on a tube 19 connecting the steam inlet and the mixing chamber. The piston 27 is subjected on its lower face to cold water pressure and on it upper face to mixing chamber pressure and the loading of a spring 44 and carries a valve member 22 urged by an adjustable loading spring 46 to close the tube outlet. Cold water is admitted to the mixing chamber through a resilient nozzle 31 (or nozzles) in the base 30 of the piston. The piston is provided with a cap 24 having a clearance fit between it and the mixing chamber so that leakage past the cap dampens piston movement. The amount of adjustment of the valve loading spring 46 is limited by a web 47 carried by a knob 37 and a peg 48 mounted on a closure cap 42 to limit the maximum and minimum operating temperatures of the valve. When hot water it drawn off through the outlet 18 pressure in the chamber 11 falls so that the piston rises to open the valve 22 to admit more steam to the mixing chamber and at the same time the nozzle 31 expands to admit more cold water thereto. If foreign matter between the valve 22 and its seat prevents the former from properly closing, steam issuing through the partly open valve will collapse the nozzle 31 so that pressure builds up above the piston to assist the spring 44 to close the valve and dislodge the obstruction. The nozzle (or nozzles) may be replaced by holes through the piston base which co-operate with loose ball valves. The balls being carried on spring arms fixed to the valve body beneath the piston so that in the lowermost position of the piston the holes are closed. The steam inlet and tube 19 may be heat insulated internally and also if desired externally to avoid overheating of residual water in the mixing chamber. Where sudden fluctuations in steam supply are likely to occur, the cap 24 of the piston is equipped with a sealing ring and a body passage connects the upperside of the cap to the steam inlet so that steam pressure assists in holding the valve closed and thus when a sudden increase in steam pressure occurs the valve 22 is prevented from opening.