GB924144A - A flame controller - Google Patents

Abstract

924,144. Photo-electric control of oil burners. A. ARGAMAKOFF. April 10, 1959 [April 10, 1958], No. 12151/59. Class 40 (3). [Also in Group XI] In a flame controller for an oil burner incorporating a photo-conductive cell 1 to observe the flame, the cell is connected in series with a thermistor 2 to form a voltage divider from the junction point of which a control potential is derived, the thermistor being located in the vicinity of the cell and having the same heat dependent charcteristic whereby it compensates for the effect of heat radiation on the cell and the control potential is determined solely by light radiation emanating from the burner flame. The control potential is applied to operate a relay 2 by way of a transistor 31. The controller operation is initiated by a thermostat 12 (which may be connected as shown in either the primary or secondary of the main supply transformer 16 for the controller) and the timing of the controller operation is determined by three bimetallic elements 6, 7, 8 which are heated by resistive elements 17, 18, 19 and operate in the sequence 6, 7, 8. The first, after an interval to allow the escape of gases from any previous combustion, energizes ignition element 24, the second, after an interval to allow the ignition element to become clean, completes the circuit for the burner supply motor 10, and the third, after an interval to allow for combustion, switches off the system unless flame has appeared in which case photo-electric cell 1 operates relay 2 and at contact 4 provides a holding circuit for the motor. Contact 3 interrupts the circuit to the resistance elements 17, 18, 19. If during operations the flame fails, the controller automatically initiates a further sequence of operations to re-start the burner. Bi-metallic elements 8 may be re-operated by manual means 54 to initiate a sequence of operations following an unsuccessful attempt to start the burner. In two other embodiments, Figs. 2 and 3 (not shown), the D.C. supply to the photo-electric cell, transistor and relay circuit (which is derived from the main supply transformer 16 by rectifier circuit 29, 30) is completed via a contact which is closed when bi-metallic element 7 operates, a holding connection being provided by a contact of relay 2 to allow for the subsequent release of the bi-metallic elements. In Fig. 1, photo-electric cell 1 is chosen to be substantially insensitive to infra-red radiation, a cadmium sulphide being suggested as suitable. In other embodiments, Figs. 3 and 4 (not shown), the cell is chosen to be infra-red responsive so as to be influenced by the fluctuating component of the light output of the flame. The cell output is applied to control the relay through capacitive coupling circuits so as to eliminate the signal due to the steady component of the flame. In Fig. 4, a transistor amplifier precedes the transistor which controls the relay. Leadsulphide, germanium and silicon cells are suggested as suitable infra-red sensitive cells.