Patent GB-810725-A (GB)
Title: Improved means for supervising flames more especially non-iuminous flames
IPC: F23Q9/12
Filed: 1955-03-30
Abstract: 810,725. Controlling gas burners. LANDIS & GYR A.G. March 30, 1955 [March 31, 1954], No. 9261/55. Class 75(1) In a flame supervisory device utilizing the rectifying action of the flame 2 and comprising a delay action relay 29, a safety switch 33, a polarized relay 18 having a polarizing winding 17, and two glow discharge lamps 14, 15 connected in series across a D.C. voltage provided, for instance, by a transformer 5, at rectifier 9 and a reservior condenser 10, the polarizing winding 17 of the polarized relay 18 is connected across the D.C. voltage and the control winding 23 of the polarized relay is connected between a point 22 between the two discharge lamps 14, 15 and a point 21 between a condenser 20 and a resistance 19 connected in series across the D.C. voltage. The polarized relay 18 operates two change over contactors 24, 48 and is such that when the polarizing winding 17 is energized the direction of the current in the control winding 23 determines whether the contactors close the upper contacts 26 and 49 or the lower contacts 25 and 51. If the control current ceases the contactors 24, 48 remain stationary but if the polarizing current ceases the contactors move to close the upper contacts 26, 49. The safety switch 33 is a thermal switch comprising a bimetallic strip 32 heated by a winding 27 and supporting, when cold. a movable contact 33 in contact with a fixed contact 34. Forty five seconds energization of the heating winding 27 causes the upper end of the bimetallic strip 32 to move to the left so that the movable contact 33 falls away from the fixed contact 34. The delay relay 29 comprises an armature 40 and a bimetallic strip 39 which, when cold, prevents movement of the armature 40 but which, after seven seconds energization of cheating winding 28, bends to the right to release the armature. The armature actuates contacts 41 for de-energizing the heating winding 28, contacts 42 for energizing a pilot gas valve 47 and contacts 43 for energizing a main gas valve 52. The two heating windings 27, 28 and the delay relay 29 are energized in series from the upper contact 26 of the contactor 24, but the delay relay 29 can also be energized through a condenser 31 connected to the lower contact 25 of the contactor 24. On closing a main switch 36 the transformer 5 5 is energized through the safety switch 33, a room thermostat 44 and a  maximum thermostat 45. The polarizing winding 17 of the polarized relay 18 is thus energized and the condenser 20 charges up through the resistance 19. Initially the voltage across the resistance 19 is sufficient to ignite the glow lamp 15 and current passes in the direction a through the control winding 23 of the polarized relay. The contactors 24, 48 then move to close the lower contacts 25, 51 but as the contacts 42, 43 are still open the pilot and main gas valves 47, 52 remain closed. As the condenser 20 charges the voltage across the resistance 19 reduces until eventually the glow lamp 15 extinguishes: The voltage on the condenser 20 then reaches the ignition voltage of the glow lamp 14 which therefore ignites and discharges the condenser through the control coil 23, the current now flowing in the direction z and causing the contactors 24, 48 to close their upper contacts 26, 49. When the glow lamp 14 extinguishes the partially discharged condenser is charged again through the resistance 19 until the glow lamp 14 again ignites. The frequency of ignition of the glow lamp 14 is about 1 cycle per sec. The contactors 24, 48 remain in their upper positions. After seven seconds the relay 29 closes the contacts 41, 42, 43 and the pilot gas valve 47 opens to supply gas to the pilot burner 6 which is ignited by means of an ignition transformer 50 energized by the contactor 48. In the presence of a pilot flame a rectified current passes from the electrode 1 to the earthed burner 6 and then through the resistance 19 back to the transformer 5. This current increases the voltage across the resistance 19 and causes a corresponding decrease in the voltage across the condenser 20 and in consequence the glow lamp 14 fails to ignite and the other glow lamp 15 ignites. Current again passes in the direction a through the control winding 23 and the contactors 24, 48 change over to close the contacts 25, 51. Contact 25 energizes the relay 29 through the condenser 31 and contact 51 energizes the main gas valve 52 which supplies a main burner (not shown). As the condenser 20 charges through the glow lamp 15 the voltage across the resistance 19 decreases until the glow lamp 15 extinguishes. The condenser 20 then discharges through a resistance 16, the polarizing winding 17 and the resistance 19, and as it discharges the voltage on the resistance 19 increases until the glow lamp 15 again ignites. The frequency of ignition of the glow lamp 15 varies between 1 and 10 cycles per sec. If the pilot flame fails to ignite, the contactor 24 remains in contact with its upper contact 26 thus energizing the heating winding 27 so that after forty five seconds a a safety switch 33 deenergizes the transformer and the pilot gas valve 47 and energizes a warning lamp 38. The safety switch 33 is reset manually. If during normal working the pilot burner extinguishes the voltage developed across the resistance 19 becomes insufficient to ignite the glow lamp 15 but instead the voltage developed on the condenser 20 is sufficient to ignite the other glow lamp 14. Current therefore flows intermittently through the control winding 23 in the direction z and the contactors 24, 48 close their upper contacts 26, 49. The ignition transformer 50 is again energized but if a flame does not appear at the pilot burner within forty five seconds the safety switch 33 operates to close down the installation. Instead of using the burner 6 itself as an electrode a second electrode may be disposed in the flame and connected to the point 21 which in this case is not earthed.