GB762000A - Improved safety device for apparatus using fuel gases - Google Patents

Abstract

762.000. Supplying gas to burners. POURSIN, L. Dec. 22, 1953 [Dec. 23, 1952], No. 35634/53. Class 75(1) [Also in Group XXIX] A safety control assembly for gas fired heating apparatus comprises operatively interconnected first and second valves 5, 31 arranged in series in the gas supply line to a main burner (not shown), the first valve 5 being adapted to be opened and closed as required and to effect opening and closing of the second valve 31 but to remain closed if the second valve has not closed after closure of the first valve, the second valve being actuated by a thermally responsive element 37 and being capable of opening only when the first valve is open, and a lock-out device 21 for closing the second valve if both valves remain open when the gas supply should be cut off. The first valve 5 is secured to a diaphragm 8 and co-operates with two concentric seats 6, 7. Gas is supplied to the underside of the diaphragm by a small orifice 9 by-passing the valve, and the space above the diaphragm is connected to the gas supply pipe 1 by a pipe 13 and a second small orifice 12 and to the feed pipe 23 of a continuously burning burner 22 by a pipe 27 containing a thermostatically 'operated valve 26 which opens when the temperature of water heated by the main burner is below a desired tmeperature. The second valve 31 is secured to a diaphragm 32. The space above the diaphragm 32 is connected to the space below the diaphragm by a small orifice 33 and tc the feed pipe 23 of the continuously burning burner 22 by a pipe 35 containing a valve 36 controlled by the thermally responsive element 37. The latter is heated by a burner 18 supplied with gas by a pipe 20 from an outlet between the two concentric seats 6, 7 of the first valve 5. In operation when a main valve 3 is opened gas passes through orifices 9, 12 to both sides of the diaphragm 8 of the first valve. If the thermostatically operated valve 26 is open the pressure above the diaphragm 8 rises only slightly above atmospheric and since the second valve 31 is closed the pressure below the diaphragm 8 rises sufficiently to open the first valve. Gas is then supplied from between the two concentric seats 6, 7 to the burner 18 which is ignited by the continuously burning burner 22 and heats the thermal element 37 to open the valve 36. The pressure of the gas admitted to thespace above the diaphragm 32 of the second valve by the small orifice 33 is thereby reduced to almost atmospheric and consequently the gas pressure under the diaphragm opens the second valve. The lock-out device 21 controls the gas supply to the burner 18 and comprises a mass of metal of low melting point which fuses to block a gas passage when the temperature of the water being heated rises above an upper limit In a modification the second valve 31 is not secured to a diaphragm but instead is mounted on the end of a rod attached to a heat sensitive element treated by the burner 18. In the embodiment shown in Fig. 3 the first and second valves 42, 46 are electromagnetically operated. The second valve 46 makes electrical contact with the valve body when closed but is insulated therefrom when open by. an insulating bush 47. The first valve 42 makes electrical contact when open with a contact 44 insulated from the valve body: On closing switch 56 the electromagnet 43 of the first valve 42 is energized through an electrical thermostat 49, the second valve 46 and the valve body so that the first valve 42 opens and engages insulated contact 44 to energize the electromagnet 43 independently of the second valve 46. Gas is -then supplied through a pipe 55 containing a lock-out device 53 to a burner 51 which heats a heat sensitive element 50 to close contacts to energize the electromagnet 48 of the second valve 46 which accordingly opens