Patent GB-614390-A (GB)
Abstract: 614,390. Furnaces. DAVIDSON, T. M. Sept. 4, 1944, No. 16836. [Class 51 (i)] In a furnace, as described in Specification 357,955, comprising refractory bricks mounted in longitudinally channelled reciprocating grate bars, the bricks are shaped to overhang and rest upon the upper faces of the lateral walls of the channels to protect them from the heat and to prevent entry of fuel to the channel. As shown, the bricks 11-16, e.g. of silicon carbide, are formed with sloping shoulders 22 which rest upon similarly inclined faces on the walls of the grate bars 10. The undersides of the bricks are hollowed out at 23 to form a continuous air channel when the bricks are assembled in the grate bar. Grooves 24, of semi-circular section in the faces of the bricks, lead to transverse grooves 25, the upper half of the wall of each groove 25 being plane and set at an angle of 45 deg., the two ends of the groove 25 being flared outwardly. When assembled, the grooves 24, 25 in adjacent bricks come together to form air supply passages, but the bricks are provided with grooves 24, 25 of different diameter and are arranged so that the areas of the passages vary according to the quantities of air required at the various points of the grate and the air pressure prevailing underneath these points. The bricks are, with the exception of the foremost bricks 11 which are provided with air passages on one face only, made of greater depth at the rear than at the front faces, so that when the bricks are assembled a stepped fuel-supporting surface is formed. The bricks have transversely convex upper faces 26 and the rear faces have flanges 27 which overlap and fit the front ends of the next bricks. The bricks are laid in the channelled bar 10 without cement, or with spots of cement at spaced positions, to permit combustion air to pass between the bricks and the walls of the channel. The sides and bottoms of the bricks or the inner faces of the channel walls may be ribbed or provided with projections to facilitate this passage of air. Slots are provided in the bottoms of the channels to admit air to the bricks and also to provide an outlet for ash. The opposed faces of the bricks may be provided with small recesses to receive cement or the like for locking the bricks together. The bars 10 are reciprocated by arms 32 on shafts 33 which are geared together, one shaft being fitted with a crank arm 34 connected by an adjustable rod 37 to an eccentric on a shaft 40 which is intermittently rotated by a ratchet mechanism driven by a motor 46 through reduction gearing rotating a crank pin 49 connected by a rod 50 to the oscillating frame carrying the ratchet pawl. The effective stroke of the ratchet is controlled by a shroud which is regulable by a hand wheel 52. The arms 32 engage links 21 secured to box-like extensions 19 of the grate bars 10 which are accommodated between the forward frame member 7 and a rectangular hollow furnace door fitting 29 closed by a door 30 having an aperture 31 either for observation or for reception of an oil or like burner. The fuel is fed from a hopper 54, through an opening controlled by a gate 56 adjustable by a rack-wheel 60, over a reciprocating apron 61 operated by arms 62 secured to the extensions 19 of the reciprocating grate bars 10. The ash discharge opening between the rear frame member 8 and the wall 2 is closable by a member 64 which is slidable on longitudinally supports 3 by a rod 65 which extends through the front of the furnace. Ash is discharged by a scraper 69 which is slidable over the bottom of the flue tube 1 by a rod 70 passing through the furnace front. Stops 71 on the rods 65, 70 limit their movements. The rod 70 is cleaned by a scraper 72. The ash hopper 67 has a hinged door 75 supported in closed position by a lever 76, and the air supply is through a conduit opening into the side of the hopper 67.