GB897134A - Improvements in and relating to gas control means - Google Patents

Abstract

897,134. Fluid-pressure servomotor-control systems. RADIATION Ltd. July 20, 1960 [Aug. 12, 1959], No. 27591/59. Class 135. Gas control means embodies a gas inlet 6, a valve 2 controlling the flow of gas through the inlet, a diaphragm 3 controlling the valve, a nozzle 12 supplied with gas from the inlet, and a Venturi throat 15 into which the nozzle discharges, one side of the diaphragm being in communication with the throat whereby the diaphragm may be subjected to reduced pressure caused by the flow of gas through the throat. When the main gas tap (not shown) is turned on gas passes through pipes 13, 16, the nozzle 12 and throat 15 to a pilot burner 10 creating, through a pipe 11, a small negative pressure in a space 8 between the diaphragm 3 and a smaller diaphragm 4 which also serves as a gland. The underside of the diaphragm 3 communicates with the atmosphere through an orifice 7, but the difference in pressure remains insufficient to open the valve 2 until a burner 10 is ignited to close a bi-metallically-operated valve 18 at the end of a branch pipe 17a. The leak through this pipe into the throat 15 is thus stopped to cause a further decrease in pressure in the space 8 to open the valve 2. Deliberate or accidental extinction of the burner 10 or the opening of thermostatically and time-controlled valves 19 and 20 respectively cause the valve 2 to close again by admitting air to the throat 15. The pipes 11 and 13 may be replaced by passages in the housing for the valve 2.