Patent GB-556720-A (GB)
Title: Improvements in or relating to automatic mechanical stokers
IPC: F23K3/14
Filed: 1942-04-18
Abstract: 556,720. Mechanical stokers. WARD, F. H., ALLMAN, April 18, 1942, No. 5183. [Class 78 (i)] An automatic stoker comprises a fuel bunker or hopper 1,a screw or other conveyer mechanism 7 for delivering the fuel to the grate 12, and a feeder mechanism 2 interposed between the hopper and the conveyer with means for varying the motions of the feeder mechanism relatively to those of the conveyer mechanism whereby the fuel may be measured-out to the said conveyer. The feeder device may screen the fuel. Where a screw conveyer 7 is used this is preferably run at such a speed that is does not run full and friction is thereby reduced. In the construction shown in Figs. 1 and 3 the feeder comprises a member 2 oscillated about a pivot 3 and provided with screening slots 4 at its ends, so that small fuel falls through the slots into an opening 5 in the casing of the conveyer 7, while oversize pieces bridge the slots and finally are thrown out over the ends. The conveyer 7 is driven by a motor 8 and worm gear 10, 11, and the feeder 2 is driven from the worm-wheel 11 by a crank-pin 14, link 13, and bell-crank 16, 18 pivoted at 17. The lever arm 18 is connected by a pin 19 to one end of a balanced lever 20 pivoted at 21 on the feeder 2, and the other end of the lever is connected to an arm 24 of a thermostat 25. As the arm 24 moves in response to boiler temperature the lever 20 is rocked and the pin 19 moves up or down the arm 18 thus altering the stroke of the feeder. Alternatively, the lever 20 may be controlled by boiler pressure or manually. In order to prevent arching of the fuel in the hopper, a hammer 50, Fig. 4, may be operated by the feeder when the latter is at full stroke. As the feeder oscillates a catch 51 theron raises the hammer away from the side of the hopper and, if the stroke of the feeder is sufficiently great, releases it suddenly due to the difference in the pivotal positions of the feeder and the hammer. A plate 47 extending across the width of the feeder may be fixed to the hopper mouth, and the distance between the hopper mouth and the feeder may be adjusted by means of a sleeve or telescopic pipe 49 set at any desired height. Agitators 48 rocked by links 52 may be projected through the screen slots 4 to assist in screening the fuel. Other feeding devices of known kinds may be used instead of the oscillating member 2 and are described in connection with the following Figures. Fig. 5 (not shown) shows a screw conveyer used as a feeder; Fig. 6 (not shown) shows a rotary drum mounted on a horizontal axis; Fig. 7 (not shown) shows a horizontal rotary disc provided with a stationary scraper blade; Figs. 8, 9 and 15 (not shown) show endless band or like conveyers; Figs. 10 and 11 (not shown) show a stationary table above which a suspended scraper blade or blades is or are oscillated ; Figs. 12, 13 and 14 (not shown) show oscillating or jigging tables mounted below the hopper. In order to prevent blow-back of fume or smoke along the conveyer 7 its casing 6 may be connected at 26 through a filter 28 to a reduced-pressure point such as a smoke flue or an ejector 27.