Patent GB-841724-A (GB)
Title: Improvements in control devices for oil-fired heating systems
IPC: F23N5/22
Filed: 1958-06-26
Abstract: 841,724. Photo-electric control systems. HESSELGREN, T., and SVENSKA NU-WAY A. B. June 26, 1958. [July 1, 1957], No. 20473/58. Class 40(3). [Also in Group Xl] A flame responsive control and ignition system for oil burners comprises cams A-H for actuating electrical contacts, an exhaust fan F, an ignition device 1G, a burner motor (not shown), an oil valve OV, a modulation motor MM, a motor M for driving the cams, a room thermostat- TH a photo-cell PH responsive to the burner flame and a resilient lever I co-operating with an arm G2 on the cam shaft and with the cam G1 to actuate electrical contacts g1-g7. When the thermostat TH closes its contacts the motor M driving the cams is energized through contacts MS, g5-g6, the coil KS of a contactor, contact f1 of a relay FS in series with the photo-cell PH and contacts bl-b3. The current through coil KS is not sufficient to actuate the contactor. A transformer TR supplying a rectifier. L for the photo-cell is also energized. Cam A closes contact a1 to energize the fan F and cam B closes contacts b1, b2 so that the motor M is energized through contacts h1, h2. After a time cam Cl closes contact cl to energize the igniter IG in parallel with the motor M. After a further time cam D closes contact dl to energize the coil KS which closes contacts k1-k5. Contact k5 keeps coil KS energized when cam D again opens contact d1; Contacts k1, k2, k3 connect the three phases of a supply to the burner motor (not shown); Contact k4 shunts contact cl which is opened by cam C2 as soon as soon as the contactor KS has operated. The free end of rotating arm G2 strikes a roller N carried by the lever I to cause the free end of the lever I to move into contact with an electromagnet GM. At the same time the cam E closes contacts el, e2 to energize the electromagnet GM from the rectifier L. The lever 1 istherefore held against the electromagnet after the arm G2 has disengaged from the roller N. The lever 1 closes contacts g 1, g2, to energize the oil valve OV. After a time the cam E opens the contacts el, e2 energizing the electromagnet GM and closes contacts e2, e3. If the burner is now lighted the photo-cell current energizes the relay FS which closesthe contacts f2 to energize the electromagnet GM through contacts e2, e3. After a further time the cam H opens contacts h1, h2 to stop the motor M and closes contacts h2, h3 to start the modulation motor MM. When the room temperature rises sufficiently to open the contacts of thermostat TH the transformer TR is de-energized so that the electromagnet. GM releases the lever I whichtherefore returns to open contacts g1, g3 supplying the oil valve OV and to close contacts g2, g<SP>3</SP> to restart the motor M. The latter rotates until it reaches the initial position when it is de-energized by cam B opening contacts b1, b2 and closing contacts b2, b3. If the burner does not ignite the relay FS is not energized and the electromagnet GM is deenergized at contacts f2 when contacts e2, e3 close. The lever I is therefore released by the electromagnet and is moved by a spring Y to cause the roller N to contact the cam G1. Contacts g2-g3 again close so that when contacts h1-h2 are opened the motor M continues to run to complete a revolution of the cams and then to repeat the starting operation. During the first revolution of the cam G 1 the roller N is prevented from. entering a recess P in the cam by a projection T on the end of a spring mounted tongue U having a projection S engaging the outside of a flange R on the cam G1. When however the projection T has bridged the recess P the projection S passes through an opening RA in the flange R and if ignition also fails on the second rotation of the cams the projection T is unable to support the roller N at the recess P whereupon the roller enters the recess and the lever I opens contacts g5-g6 to de-energize the control circuits. This is a lock out condition. The motor is again energized by pushing a button TK to restore the lever I to the position in which the contacts g5-g6 are again closed. If the second attempt to ignite is successful the lever I is held by the electromagnet GM and pulls on the tongue U so that the projection S slides out through the opening RA just before the motor M is stopped by the opening of the contacts hl-h2. In order to prevent the roller N from entering the recess P in consequence of an interruption to the current supply the electromagnet is constructed to release slowly and a pivoted arm V is pushed by the armature K of the contactor KS to engage the lever I and hold it against the electromagnet. A device MF short circuits terminals 14, 15 when the burner is set for minimum flame.