Patent GB-599916-A (GB)
Title: Improvements in and relating to gas fired ovens
IPC: A21B1/40
Filed: 1944-11-09
Abstract: 599,916. Gas-burning apparatus. GUNSTON, D., and BAKER YERKINS, Ltd. Nov. 9, 1944, No. 22085. [Classes 75 (i) and 75 (iii)] [Also in Group XXIX] A safety cut-off valve for the gas burners of ovens is adapted to be initially opened by the supply of gas to a pressure-responsive actuating member by a valve which also supplies gas to the pilot burner, the pressure of the main gas supply thereafter maintaining the valve open. As shown in Fig. 1, the safety cut-off valve comprises a valve member 6 carried by a diaphragm 7 and arranged in the supply pipe 1 leading to the burner 2. The diaphragm is loaded by weights 10 and also carries a throttling member 9 which regulates the outlet pressure during normal operation.. There is also provided in the pipe 1 a main gas valve 3, an electrically-actuated valve 4 and a final manually-operable valve 11. A pilot valve 13 controls the supply of gas from a pipe 15, connected to the pipe 1 on the supply side of valves 6 and 4, to a pilot burner 12 carried by the plug member of the valve 13 and also to the outlet side of the diaphragm valve 6 through a pipe 20. The plug member of the valve 13 has passages 18 and 19, Fig. 4, for the pilot burner and the pipe 20 respectively and these passages are so arranged that in the " off" position both are closed and in the " on " position gas is supplied to the burner only. In an intermediate position, however, which is determined by a thermal catch 22, Fig. 3, the passage 19 is opened and gas supplied to the diaphragm of valve 6, which is lifted off its seat provided the valve 11 to the burner is closed. On the pilot burner being lit the heat from the flame expands the thermal catch 22 to allow the valve 13 to be moved to the full " on " position in which the burner 12 is disposed adjacent the main burner and the supply to the pipe 20 is cut off although valve 6 remains in its open position. An additional valve 16 which is manually operated to open, but is then maintained open by the gas pressure is also provided in the pipe 15. The electricallyactuated valve 4 is in circuit with a fan motor for supplying air to the burner so that it is only opened when the fan motor is operating. A mercury switch 25 is also included in this circuit which is kept closed by the suction or pressure from the fan acting on a diaphragm 26 so that in the event of failure of the suction or pressure the circuit is broken and the valve 4 closes. The control of the fan motor circuit is effected through a rotary switch 29, Fig. 3, simultaneously with the operation of the pilot valve 13, gearing 30 being provided for this purpose. The switch starts the fan and maintains it running up to the intermediate position of the pilot valve and in the full " on " position of the valve the circuit of the electricallyactuated valve 4 is brought in. A damper (not shown) actuated by a lever 35 also controls a switch in the starting circuit of the fan so that this damper for clearing out residual unburnt gases must be opened before the fan can be started. This damper can be closed in a later position of the motor switch. A thermostatic control valve 37 may be provided between the valve 11 and the burner 2 to regulate the amount of gas flowing in accordance with a desired temperature condition at some point of the oven, a link 38, Fig. 2, also operating an air damper 40 proportionally. The manual control valve 11 also has a link 39 operating an air damper 41. Specification 599,917 is referred to.