Patent GB-627554-A (GB)
Title: Improvements in furnaces
IPC: F23K3/00
Filed: 1943-10-28
Abstract: 627,554. Solid-fuel furnaces. ARMSTRONG, J. J. V. (Sandebond Patents, Inc.). Oct. 28, 1943, No. 31447/45. Divided out of 627,544. [Class 51 (i)] [Also. in Groups XXX and XXXV] In a furnace for burning solid fuel, the latter is fed to a firepot by a reciprocating pusher the drive of which is influenced by two control devices respectively operative to feed a predetermined number of charges in a given time for maximum combustion and a predetermined less number of charges in the same time for idling operation, means responsive to heat demand being provided for automatically rendering one or other of the control devices effective. As shown, the firepot 10 is of rectangular section with its side walls 11 diverging in the direction of fuel travel, the discharge end being fitted with an inclined counterweighted ash door 18 ; the firepot base 13 slopes downwardly towards the discharge end and is formed with staggered air ports directed in the direction of fuel travel and covered by hoods 16. The air for combustion is supplied by a fan 60 and before reaching the ports 15 is heated in a partitioned jacket 64 surrounding the firepot ; a portion of the air is diverted through a pipe 67, Fig. 2, and delivered as secondary air through passages 69 in an arcn 39 which extends downwardly to just above the level of the fuel bed. The arch 39 co-operates with a dome 38 to form a chamber in which the gases arising from the fresh fuel circulate before passing through the narrow passage 40 below the arch into the chamber 32 communicating with the flue 37. Fuel is fed from a hopper 45 by a slide 43 to the space in front of a pusher 24 arranged at the charging end of the firepot, the passage of lumps being facilitated by the provision of depending spring fingers 50 protected from the heat of the furnace by a hanging plate 51. The pusher 24 and slide 43 are reciprocated by cranks 75, 76 on a crank-shaft 71 driven by a motor 73 the cranks being connected by links 81, 86 to pivoted levers 78, 83 having bifurcated upper ends to engage pins on the pusher and slide rods 30, 55. The lever 83 has a lost-motion pivot connection at its lower end comprising a slot 84 which is adjustable in length by a screw 84b so that, while the forward limit of travel of the slide 42 remains constant, the rearward limit may be varied. The pusher rod 30 carries a collar 87 having oppositely extending arms 88 for actuating, by engagement with rods 101, two timing switches arranged in the control circuit of the motor 73, viz :-a fast timer 89 and a slow timer 90. Each of these switches incorporates a spring escapement mechanism for imparting a slow return movement to the rods 101 and is preferably set so that the pusher 24 is always stopped in its most advanced position and the slide 42 in its fully retracted position. Movement of the ash-discharge door 18 effects operation of two control switches 111 which are so connected in the circuit that they exercise an overriding control to permit continuous reciprocation of the pusher and slide when a fire is being built or when rapid combustion produces a void in the fuel bed resulting in a complete closure of the door 18. Separate control circuits for the motor 73 are described for use respectively with anthracite and fuel other than anthracite, in both cases a thermostat being disposed in a bypass around the slow timer 90 so as to render either the slow timer or the fast timer operative in accordance with the heat demand. The position of the thermostat is determined by the purpose for which the furnace is to be used, e.g. in a system for heating by hot water the thermostat may be located either in the hot water tank or in the house or apartment being heated. When the furnace is incorporated in a steam generator, either a thermostat subject to steam temperature, or a device responsive to steam pressure may be used to render either the fast or slow timer effective. The motor 61 driving the air supply fan 60 is connected in the control circuit so that air is continuously supplied during the fast timer control but only intermittently when the stoker motor 73 is in operation during the slow timer control. When anthracite is being used an additional timer may be provided by which during the idling operation of the furnace the motor 61 is intermittently operated independently of the stoker motor 73. Specification 627,544 is referred to.