Patent GB-911723-A (GB)
Title: Gas safety device
IPC: F23N1/02
Filed: 1960-04-05
Abstract: 911,723. Controlling burners. ZIMMERMANN & JANSEN G.m.b.H. April 5, 1960 [March 12, 1960], No. 12049/60. Class 75 (1). The gas supply to the burner of a hot blast stove is controlled by a regulating valve SBV which is opened by electrical control means but is adapted to close automatically by means of bias when the electrical control means is deenergized. The valve SBV comprises a disc 32 fixed to a shaft 34 connected by an hydraulic, pneumatic or magnetic coupling C to the shaft 46 of a reversible electric low-speed motor SBVDU. When the magnetic coupling C is deenergized a weight 42 on the end of the valve shaft 34 returns the disc 32 to its closed position. The burner is supplied with air by a fan 30 and an air regulating valve ARBV. At starting a burner shut-off valve BV and a gas shut-off valve GV are opened and the burner shut-off valve closes contacts 1, 11 of a switch BVLS-O and causes the operation of the fan 30 and the opening of the air valve ARBV. If the temperature of the wall of the stove is above the ignition temperature of the burner, further contacts 1, 11 are held in closed condition by a pyrometer WTC. A delay relay SBVTR is therefore energized and closes contacts 1, 11 in line bb, Fig. 2, to energiza magnetic coupling relay MCR. The latter opens contacts 1, 11 in line e, closes contacts 2, 12 in line ea, closes contacts 3, 13 in line f, closes contacts 4, 14 in line b and closes contacts 5, 15 in line d. Magnetic coupling C in line d is therefore energized so that the two shafts 34, 46 are connected together. The opening of the air valve ARBV closes contacts 1, 11 of a switch SBVIS in line b so that the opening of contacts 1, 11 in line bb of delay relay SBVTR, after a predetermined time does not de-energize the relay MCR. A manometer switch SBVPS in line a, responsive to the air pressure in the air main AM or a centrifugal switch responsive to the fan opens its contacts 1, 11 to de-energize a relay SBVAR in line a so that its contacts 2, 12 in line b are maintained closed to prevent de-energizing of relay MCR. Push-button PB-O is now pushed to close its contacts 1, 11 in line f so that a starter relay GBV-O is energized and causes the electric motor SBVDU to rotate in a direction to open the gas-regulating valve SBV. When the valve is open by the desired amount the contacts 1; 11 of the push-button PBO are allowed to open and the motor stops. Under automatic operation contacts 2, 12 of a switch A/M in line fu are closed and contacts 4, 14 of switch A/M in line f are opened and the starter relay GBV-O is then energized for a time determined by an automatic regulator GR. The gas valve SBV is prevented from opening beyond a maximum position by a limit switch LSBVDU-O in line f. The initial movement of the electric motor SBVDU closes a further limit switch LSBVDU-C in line e to enable a starter relay GBV-C in line e for rotating the motor in reverse direction to be energized at will by means of a further push-button PB-C in line ea or by the automatic regulator GR. When the gas valve is open contacts 2, 12 of switch SBVLS-O in line g are closed to energize a signal lamp SBVSL. In the event of power failure whilst the burner is operating the coupling C becomes de-energized and the gas valve closes under the action of the weight 42. On restoration of power, starter relay GBV-C is energized through line e and returns the motor to the starting position. In the event of a failure of air pressure from the fan, manometer switch SBVPS in line a closes its contacts 1, 11 to energize relay SBVAR which opens its contacts 2, 12 in line b to de-energize coupling relay MCR. Coupling C is consequently deenergized and the gas valve closes under gravity. Since line e is completed by closure of contacts 1, 11 of coupling relay MCR starter relay GBV-C is again energized and returns the motor to the starting position. In a modified arrangement the unit SBVDU driving the gas valve is driven by a fluid and a pair of solenoid valves control the direction of the flow of fluid to open and close the regulating valve SBV. The fully open and fully closed positions of the valve are controlled by a piston in the drive unit SBVDU so that the limit switches LSBVDU-C and LSBVDU-O are not required. The switch WTC, which is reponsive to. the temperature of the wall of the blast stove, so that its contacts open if the temperature is too low, may have a further pair of contacts which close in response to low temperature and energize a relay which energizes a gas valve, an air valve and a spark igniter. The gas and air valves supply a gas/air mixture to an auxiliary burner projecting into the blast stove and the igniter ignites the mixture. The auxiliary burner continues to burn for a predetermined period after the wall temperature has risen to the change-over temperature of the switch WTC. Specification 883,508 is referred to.