GB1079945A - Improvements in flame supervision devices for burners - Google Patents

Abstract

1,079,945. Photo-electric burner control. SATCHWELL CONTROL Ltd. July 23, 1965 [July 24, 1964], No.29767/64. Heading G1A. [Also in Division F4] A burner control system has two normally equal detectors irradiated by the burner flame which supply current to two relays, one relay receiving the sum of the two currents through the detectors and when operated indicates flame presence and the other relay receiving the difference in the two currents: the difference upon reaching a predetermined value indicates malfunctioning of one of the two detectors and the relay operates to shut down the system. As shown in Fig. 1 two detectors 8, 10 responsive to ultraviolet radiation are energized with A.C. from transformer 11 and a first relay FR1 is operated by the sum of the two currents in its coil 3 and a second relay FR2 operated when the unbalance between the currents in the two halves of the centre-tapped coil 7 exceeds the predetermined value. Upon starting up the system by closure of thermostat T, relay FR2 operates via normally closed contact 1 of relay FR1 and its second coil 6 to provide energizing circuits through contact 4 for the ignition device I, supplying sparks to the burner, and the series connection of heater 16 and 22 of bi-metallic strips 13 and 21. The current in heater 22 is as yet insufficient to bend strip 21 but with the additional heater 15 strip 13 bends to close contacts 17 and 19 to energize the fuel pump motor or valve M after which ignition should occur since sparks are being produced. Contact 19 provides a second energizing path for heater 22 completed via contact 4, which if closed would cause strip 21 to be heated sufficiently to bend it, so operating contact 23 to remove power from the system and shut down the burner. If meanwhile the burner has ignited normally, the detectors are irradiated and relay FR1 will have operated to open contact 1, de-energize relay FR2 and so prevent the strip 13 from bending and effecting shut down. Subsequent failure of the flame releases relay FR1 to operate FR2 so heating the strip 13 to effect shut down. Abnormal functioning of one of the detectors 8 and 10 results in unbalanced currents flowing in the two halves of coil 7 which operate relay FR2 and again cause strip 13 to be heated. The detectors and resistor 9 are contained in a probe head, the radiation being directed on to them by a lens or an angularly movable prism Figs. 2 and 3 (not shown).