Patent GB-189904704-A (GB)
Title: Improvements in Furnaces.
Inventor: MCCLAVE WILLIAM
Filed: 1899-03-03
Granted: 1899-06-17
Abstract: 4704. McClave, W. March 3. Mechanical stoking; firebars and grates; deadplates; firebridges ; ashpits; footplates.-Relates to furnaces with inclined grates composed of rocking firebars. The fuel hopper 2, which is preferably of the full width of the furnace, is fitted with a curved pusher 5 suspended on rocking arms at the side and centre, the arms being enclosed in hollow pockets in the side walls and central partition of the hopper. The forward edges of the pusher are slotted so as to allow free expansion. The pusher is fitted with loose packing-pieces bearing on an extension of the dead-plate 8. The front plate 18 of the hopper is formed in two or more sections which are hinged to give access to the furnace, packing-pieces, bearing on the top of the pusher, being fitted in the edges of the plates. The discharge opening has sliding gates 35, with slotted lower edges. These gates are raised and lowered by means of a series of bell-crank levers. The pusher shaft 6 is actuated from a parallel rocking shaft 4 by slotted crank arms embracing adjustable sliding blocks in two parts pinned together. These shafts, in a series of furnaces, are preferably driven from a single main shaft, rotating or rocking. In the latter case, an easilydetachable connecting-link is provided, and a spring clutch with inclined teeth is interposed to prevent injury from any obstruction. The inclined grate, which is preferably in two sections side by side, is composed of transverse rocking bars 77, preferably coupled together in sets of two or more. They may be all rocked together, and to the same extent ; but preferably the operating- mechanism is so arranged that the upper bars, or sets of bars, may be rocked through a variable angle, which is usually smaller, but which may be greater, than that through which the lower bars are rocked. When such variable motion is required, each set of bars, or each bar, is separately linked to a rocking frame 81, the points of connection to the frame being adjustable to vary the throw, except in the case of the bottom bars. The frame 81 is composed of a number of rocking- bars on which sliding-blocks are simultaneously adjusted, after the manner of a steam-engine link .motion, by rack-and-pinion gearing. The teeth of the pinions are curved to allow the motion of the frame while the pinions remain in gear, the points of contact being in the axis of oscillation of the frame. The handle of the adjusting-gear is provided with a locking-device, and an indicator is fitted, consisting of a graduated sliding rack. The frame 81, or a simple rocking-shaft when variable motion is not required, is rocked to an adjustable extent by connection to an adjustable block in a yoke or slotted arm 125 on the shaft 4. The construction of the various links and connections is described and illustrated in the Specification. By rocking all the bars to the full extent, ashes, clinker, or the fire itself, may be dumped. The firebars are supported on inclined bearers which engage with supports at top and bottom and are connected together by specially-formed cross-bars at their lower ends. Each bar is formed of removable transverse pieces 160 as shown in the detached view, Fig. 10. These pieces have stems fitting in sockets in the main web 158, and they are formed with teeth, preferably curved as shown, on each side. The front edges of the upper bars, or of all of them, may consist of hinged pieces 67 so as to be always in contact with the dead-plate, or with the next bar above, to prevent the passage of fine fuel. The dead-plate 8 is composed of a series of plates supported, side by side, on a frame of special construction. The space between the lower end of the grate and the bridge wall is closed by a bar 180, similar in construction to the fire bars, which may be rocked with the firebars to remove clinker and ashes. Its upper surface is mainly cylindrical, but it is formed with a recess into which ashes &c. drop when it is moved back sufficiently. The mechanism for operating the bar 180 may be provided with a gab connection 203 for throwing it out of gear ; and this may be disconnected automatically at stated intervals by means of a cam 209 which is slowly rotated by ratchet gear. In forced-draught furnaces, the rods for actuating the grate may pass through sliding plates on the furnace front, so as to prevent leakage while allowing free motion. The plate 155 supporting the bridge wall is formed with a series of slots to break the edge presented to the heat of the fire. The ashpit is made in the form of a hopper delivering into a horizontal duct 231 in which is a reciprocating pusher or scraper 236 with hinged blades by which the ashes are drawn out and discharged into a truck 252 below. This truck may be run on to a transversely-travelling truck 255 in a tunnel extending below the fronts of a series of furnaces. The reciprocating scraper runs on wheels, and is operated by means of links and levers from the rocking- shaft 4 ; and the operating-mechanism may be automatically thrown in and out of gear at intervals by means of a gab connection 271, and cam and ratchet gear, in the same way as the mechanism operating the bar 180. The cam and ratchet mechanism may be itself thrown out of gear by lowering a hand-rod 289 with a special retaining-pawl 291. The ash-discharging apparatus may be modified to deliver the ashes at the back of the duct 231. The front part of the footplate may be hinged so as to be capable of being brought in line with the inclined front 229 of the ashpit, which is then at a lower level. By this means ashes may be raked up by hand on to the footplate. This arrangement may be applied alone, or as supplementary to the duct and reciprocating scraper. The various modified and alternative arrangements, and the construction of the various details, are described at great length and illustrated in the Specification.