Patent GB-357666-A (GB)
Title: Improvements relating to a control for an electrically operated fluid fuel burner mechanism
IPC: F23N1/00
Filed: 1930-07-08
Abstract: 357,666. Electrically - controlled burner systems. McCABE, I. E., 546, West Adams Street, Chicago, U.S.A. July 8, 1930, No. 20642. [Class 75 (i).] In a fuel burning system for domestic heating purposes the closing of the room thermostat switch R completes the circuit from the mains 17, 31 through a boiler control C and an ignition switch 14 to the primary coil 6 of a constant current transformer having a rectangular core 2, and the current from the terminals 8, 7 of the secondary coil 5 passes through an ignition device W and a bifurcated bimetallic member T. The ignition switch 14 is carried by a carrier plate 45 pivoted on the baseplate 12 and is held in the closed position with a latch member 58 pressing against an adjustable abutment when the burner is not operating by the engagement of a roller on a spring-pressed lever 50 with the upper of two oppositely sloping surfaces on the plate 45 as shown in Fig. 1. The lever 50 is pivoted to a plate 52 which is pivoted at 53 to the baseplate 12 and has a pin-and-slot connection 55, 56 with a link 54 pivoted to the thermal member T, the pin being normally maintained at the left of the slot by a spring 57. The motor switch 15 is carried by a pivoted plate 48, the end 61 of which engages an arm 63 on the plate 52 when the burner is not operating so as to hold the switch in the open position. The energization of the transformer causes the primary coil 6 to float above the secondary coil 5 and releases a yoke 9 which is slidable vertically on the back of the panel 1 and has bent legs 10 entering between the coils 5, 6. The yoke 9 is attached by a pin 64 to a lever 66 which is attached by a spring 74 to another lever 71 having a pin 69 engaging in a slot 68 in the yoke. The spring has a greater leverage on the lever 66 than on the lever 71 so that the tension of the spring causes the yoke to rise when the coil 6 floats until the pins 64, 69 engage the tops of apertures 65, 70 on the baseplate 12. On the bimetallic member T becoming sufficiently heated by the transformer current its upper end turns the plate 52 to allow the motor switch 15 to close and later to open the ignition switch 14 by the passage of the roller on the lever 50 past the nose between the oppositely sloping surfaces on the plate 45, as shown in Fig. 3. The interval between the closing of the ignition and motor circuits is varied by adjusting at 54a the length of the link 54. An electrically operated fuel valve O may be arranged in circuit with the motor M. If ignition of the fuel occurs before the ignition switch is opened the heat of the flame closes a stack switch S in series with the room thermostat switch R and boiler control C to energize an electromagnet E having a pivoted armature 75 which operates a bell-crank lever 80 carrying a latch 81 and thereby locks the plate 45 with the motor switch 15 in the closed position and the yoke 9 in the raised position. When the thermostat switch R opens, the lever 80 is released and the parts assume the starting position shown in Fig. 1. If ignition of the fuel fails, the opening of the ignition switch allows the descent of the coil 6 and the yoke 9, and a stud 73 on the lever 71 operates the plate 45 to open the switch 15. The lever 80, not having been operated, engages a shoulder 82 on the plate 52 and prevents the return of the ignition switch to its closed position until the apparatus is manually reset by pressure on a knob 83 operating the armature 75. A plate 86 pivoted to the baseplate engages a pin 88 on the lever 80 and prevents the lever from engaging the shoulder 82 when the burner ceases to operate on the opening of the circuit of the electromagnet E. A pawl 90 pivoted to the lever 71 is formed with stops 92 adapted to engage the pin 79, a stud 93 adapted to engage the arm 80 and a projection 94 adapted to engage a stud 96 on a plate 95 the weight of which tends to tilt the ignition switch to its closed position. If the current supply is interrupted during starting up or during normal operation the pawl 90 acts to cause the control to recycle upon the resumption of the current supply without manual resetting, the cycle including an opening of the motor switch to shut down the burner to allow time for the combustion chamber to be freed from unburned fuel vapours.