Patent GB-470469-A (GB)
Abstract: 470,469. Gas valves. FAIRBROTHER, H. (Merker & Cie Akt.-Ges.) Feb. 13, 1936, No. 4412. [Class 135] In a combined safety cut-off device and gas pressure regulator for water heaters, gas passes from the inlet 38 of the main gas valve to a chamber 32 below the valve-actuating diaphragm 31 and to a permanently open nozzle 21a in the pilot burner head 21 when an ignition valve 26 is opened and when the pilor flame is ignited, a valve is carried by a metallic strip 23 operated by the pilot flame closes a second nozzle 29a so that pressure builds up below the diaphragm 31 and the main valve opens. On allowing the ignition valve to close, gas continues to pass to the pilot flame and the chamber 32 from the outlet 34 of the main valve. If the pilot flame is extinguished, the valve 20 opens so as to vent the chamber 32 and allow the main valve to close under its own weight. The safety gas cut-off valve 37, Fig. 7, has an extension 35 acting as a pressure regulating valve. When an ignition valve 26 is pressed open, gas from the inlet 38 flows through conduits 27, 24, and an aperture in the bimetallic strip 23 where it is ignited. A passage 29 connects the nozzle 29<a> with the chamber 32 and communicates through a restricted bore 30 with the outlet 34. Gas passes into the outlet 34 and hence into the chamber 32 by a passage 33 when the ignition valve is open. The valve 37 initially opens to the full and the extension 35 which has ridges 36 thereon is raised to its seat. Due to a gap in the inner ridge a restricted pilot supply is maintained through the passage 33. If a water-actuated valve 3 on the outlet side of the valve 37 is now opened, the pressure falls in the chambers 34, 32 and the extension 35 descends to admit more gas until finally a steady position is reached in which the pressure under the diaphragm balances the weight of the valve parts. The pressure of the gas passing to the burner is thus subtantially constant and hence the water temperature may be controlled entirely by controlling the water flow. The main burner B cannot be ignited unless the pilot supply is ignited before the water is turned on, since with the valve 3 open, no pressure could build up in the chambers 34, 32. The water-actuated cut-off valve 3 is shown in Fig. 1. It is opened against a spring 2 by means of pins 6, 10 due to the difference in water pressure on opposite sides of a diaphragm 18. The pressures in the two diaphragm chambers 15, 16 are equal when the tap 1 is turned off, but when the water flows a reduced pressure is created in the chamber 15 due to its connection with the throat of a nozzle 14. The chamber 15 may be drained for repair purposes by a normally-closed aperture 11. Fig. 11 shows a modified form having a safety cut-off valve 40 with a pressure regulating extension 59 and also having a gas cock 44 on its outlet side. When the cock is in a position for igniting the pilot supply, peripheral grooves on it permit gas to pass from the supply chamber 41 to the ignition valve 48 and back into the outlet chamber 52 by a passage 51. In this position also, the orifice 54 is open to the chamber 52 and as the main passage through the cock is closed, pressure builds in the chamber 52 and in a diaphragm chamber 56 after the valve 20 is closed. When the main gas passage 53 is opened as shown in Fig. 11, the regulating extension 59 descends to an intermediate position to control the supply pressure. Specification 423,776 is referred to.