US1981947A - Combustion apparatus - Google Patents

Description

Nov. 27, 1934. L CORBETT 1,981,947

COMBUSTION APPARATUS Filed Dec. 4, 1928 4 Sheets-Sheet 1 @J. .P/MA, 0 m

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COMBUSTI ON APPARATUS Filed Dec. 4, 1928 4 Sheets-Sheet 4 Patented Nov. 27, 1934 UNITED STATES PATENT OFFICE COMBUSTION APPARATUS Doble, Hingham, Mass.

Application December 4, 1928, Serial No. 323,687

1 Claim.

This invention relates to combustion apparatus for burning solid fuel.

One object of the invention is to provide novel and improved combustion apparatus which is reliable in operation, requires minimum attention,

and may be substantially automatic in operation, and one which may be successfully operated utilizing any of the different grades of solid fuel.

A further and more specific object of the invention is to provide novel combustion apparatus capable of successful use as an automatic stoker in heating apparatus, and whose construction is such as to insure efiicient combustion of solid fuel in an automatic manner requiring minimum attention.

With these objects in view, and such others as may hereinafter appear, the invention consists in the combustion apparatus and in the structures, arrangements and combinations of parts hereinafter described and particularly defined in the claim at the end of this specification.

In the drawings the different features of the invention are illustrated as embodied in a domestic heating apparatus wherein Fig. 1 is a side elevation of the apparatus with portions in section; Fig. 2 is a plan view, with portions in section, of the apparatus shown in Fig. 1,; Fig. 3 is an end elevation of the apparatus viewed from the right in Fig. 1; and Figs. 4 and 5 are details to be referred to.

In general, the present invention contemplates combustion apparatus for the successful and economical combustion of the solid fuels such as the different grades of bituminous and anthracite coal and coke and which a bed of the fuel is maintained during combustion upon an inclined grate operatively supported within a combustion chamber, by the supply of succeeding amounts of the fuel to the upper portion of the grate. Provision is made for imparting movement to the bed of fuel during combustion preferably by antomatic movement of the grate member. Provisicn is also made for forcing the primary supply of air through the fuel bed to maintain the combustion and also preferably an additional supply of air over the fuel bed in order to complete the combustion. The grate member may and preferably will be constructed of conical shape and the fuel fed from below the grate member upwardly through an opening in the apex portion of the cone to be thereby deposited upon the upper portion of the conical grate member. During combustion the movement of the gn'ate member together with gravity causes the progressive movement of the fire and ash down the inclined grate, and provision is preferably made for automatically removing the ash as the latter accumulates at the lower portion of the grate.

Referring now to the drawings which illustrate the invention as embodied in a domestic heating apparatus such as a hot water or steam heater, represents the heater whose general construction and operation may, except as to details to be hereinafter pointed out, comprise that of the ordinary hot water or steam heater at present used for domestic heating purposes. The heater 10 is provided with the usual combustion chamber 12 Within which a novel grate member 14 is operatively supported upon standards 15, as illustrated in Fig. 1. The grate member 14 comprises a movable portion 17 preferably of conical shape, as illustrated in Fig. 1, and which is operatively supported to be capable of rotary movement about its vertical axis upon ball bearing members 20 supported within a raceway formed by cooperating portions 21 in the underside of a supporting web 22 of the movable conical grate member, and an upstanding rim portion 23 of a stationary grate member 24, as shown in Fig. 1. The stationary grate member 24 is arranged to surround the conical grate member and is provided with a flaring rim portion 28 which serves, as will be described, to support the lower portion of the fuel bed and to deflect the ashes from the lower portion of the conical grate member down into an annular trough 29 in the stationary grate memher.

In order to maintain a bed of the solid fuel upon the conical grate member 14, as herein shown, provision is made for feeding a stream of the solid fuel from a storage hopper 30 through a fuel supply conduit or pipe 32, the latter being extended upwardly through an opening 34 in the apex portion of the conical grate member. The movement of the solid fuel from the hopper 30 is effected by a reciprocatory plunger or piston 36 working in the end portion of the fuel supply pipe 32. The fuel supply hopper 36 is preferably constructed with a downwardly inclined bottom wall 38 which insures flow of the solid fuel by gravity through an outlet or discharge opening into the end portion of the fuel supply pipe and in advance of the piston 36. The piston 36 is arranged to be reciprocated. by a crank 40 and connecting rod 42, the crank being secured to a transversely extended shaft 44, and the latter is arranged to be rotated by means of a crank 46, link 47 and pawl arm 48. The pawl arm 48 carries a pawl 49 which is arranged to cooperate with the teeth of a ratchet 54 secured upon said shaft 44. The amount that the ratchet 54 and shaft 44 is rotated at each throw of the pawl is variably controlled by a spring finger or member 106 mounted upon an operating arm 108 loosely mounted upon the shaft 44 and arranged to cooperate with the pawl 49 to control the number of teeth that the pawl will pick up and advance the ratchet at each throw of the pawl. The operating arm 108 may and preferably will be connected with the air supply as will be described. The crank 46 is driven from an electric motor 56 through gearing connections indicated diagrammatically at 58.

From the description thus far and from an inspection of Fig. 1 it will be apparent that in the operation of the combustion apparatus, as the solid fuel is fed upwardly through the fuel supply pipe 32 it emerges from the open upper end thereof and overflows onto the conical grate. In this manner a bed of fuel of substantial thickness, depending upon the rate of the fuel feed, is maintained upon the conical grate surface, the bed being supported at its lower end by the rim section of the stationary grate member 24.

Provision is made for forcing the primary supply' of air for maintaining the combustion through the bed of fuel as the latter is supported upon the conical grate, and as herein shown I than the inlet end thereof, thereby overcoming J any tendency of dust and ash to gravitate into the opening and to clog the same. Air under pressure is preferably suppliedto within the' conical grate from a fan or blower 64 connected to the motor 66 to be driven thereby and whose discharge pipe 65 is connected by a conduit 66 to an opening formed in the supporting web 22 of the conical grate member, as illustrated in Fig. 1. For convenience the conduit 66 may be arranged to surround the fuel feed pipe 32 for that portion of the length of the same within the heater, and in this manner an annular air passage is provided between the conduits 32 and 66.

Provision is also preferably made for supplying additional air to above the bed of fuel during the combustion thereof in order that the volatiles within the coal or other fuel which may have been distilled may be burned as well as'in order to complete the combustion of the fuel gases themselves. As herein shown, the additional air is distributed over the fire from two end of the fuel supply pipe 32 and the movable conical grate 14. In order to deflect the air as it passes through such annular opening in a direction downwardly over the surface of the fire to distribute the air through the mass of fuel gases, it is preferred to provide the downwardly extended lip '76 upon the upper end of the fuel supply pipe 32. In order that the combustion may approach completion it is desirable that approximately one-half of the total air should be admitted over the fire through the openings 70 and the opening between the fuel tube and the movable grate previously described. In addition some additional air may find its way into I the combustion chamber through the lower rows of primary air openings 60 inasmuch as during combustion the extreme lowest portion of the grate will be covered with material consisting mostly of ash so that the air passing therethrough is not consumed. The mass of coal or other fuel within the upper end of the fuel supply pipe ,serves as a diffuser for the additional air passing therethrough, producing many small stream of air projected in random directions,

al'air in that inherent control of the additional air is attained by control of the quantity of the primary air and by properly proportioning the size and number of the various openings described, the proper amount of additional air will be supplied at all of the different rates. of combustion.

Provision is also preferably made in the illustrated apparatus for controlling the volume of both the primary and additional air in accordance with the amount of fuel being fed, and as herein shown the rate of fuel feed is controlled by regulating the position of a spring finger 106 (see Fig. 4) mounted upon an operating arm 108 provided with a handle 110 so that the pawl 49 will pick up a variable number of teeth of the ratchet wheel 54 according to the particular position into which the operating arm and handle are moved. The operating arm is connected by the linkage illustrated in Fig. 4 and indicated generally therein at 112 to a damper 114 in the discharge pipe leading from the blower 64, so that as the rate of fuel feed is increased, the volume of primary air and consequently the additional air is proportionately increased.

The rotary movement above described is preferably imparted to the conical grate member 14 by mechanism designed to provide rotation of the conical grate member upon its supporting bearings 20, and as herein shown this movement is produced by the cooperation of a bevel pinion gear 83 with a ring gear 84 formed in the under side of the supporting web 22 of the grate member. The pinion gear 83 is mounted upon the end of a drive shaft 43 and is driven through mechanism including bevel gears 86, 87, a counter shaft 88, sprockets 89, 90, and a sprocket chain 91, as best illustrated in Figs. 1 and 2. The rotary movement of the conical grate member 14 is preferably utilized to effect the automatic removal of the ash as the latter accumulates in the trough 29 at the bottom of the conical grate member, and as herein shown scrapers 94 formed as lugs on the lower portion of the grate member are arranged to extend to near the bottom of the trough 29 in a position such that as the grate member rotates, each scraper 94 operates to scrape a portion of the ash into a position over an ash receiving opening 96 formed in the supporting web 22 of the grate member. As the ash drops through the opening 96, it falls into an ash discharge pipe 97 having a driven worm conveyor 98 therein which operates to move the ash through the discharge pipe 97. From the discharge pipe 97 the ash is raised by a driven endless conveyor of any usual or preferred form in; dicated generally at 100 through the inclined conduit 102 to be discharged into an ash receptacle 104, the latter preferably being provided with a cover at its upper end to reduce dust to a minimum.

From the description thus far it will be apparent that the present construction of combustion apparatus operates upon a principle analogous to the overfeed type of stoker which has been successfully used in industrial Work and which has been found to be suitable for the efficient combustion of all different types'of coals. The ordinary underfeed stoker, particularly the type which has heretofore been proposed for use in domestic heating apparatus, has not been satisfactory With coals of either low fusion point ash, or coals of high ash content, for the reason that during the operation of the stoker the coal is fed and the ash removed in such manner that the ash is in contact with a highly incandescent fuel bed and is fused into clinkers. The present construction of conical grate serves to keep the burning fuel and the ash moving toward the point of ash discharge, and furthermore as the concentration of ash increases, the ash is moved into a region of lower temperature, thereby avoiding a tendency toward the formation of clinkers. This is an important advantage in a domestic heating apparatus, particularly in that it enables the operation of such domestic heating apparatus to be made substantially automatic.

By reference to Fig. 1 it will be observed that during the operation of the present combustion apparatus the movement of the fuel bed tends to overcome any caking which may occur as the coal leaves the fuel tube in the region of lower temperature surrounding the coal tube. Any caking which may take place is broken up by the movement of the fire with the conical grate. In

addition to its eifect in preventing caking and thereby enabling caking and bituminous coals to be successfully burned in the present combustion apparatus, the moving rate in combination with its inclined position and particularly with its conical shape assists the travel of the fire down the sides of the cone. With relation to the intermediate movable conical grate member 14, both the fuel entering from the feed tube and the circular stationary grate 24 are stationary and as a result during operation, the fuel bed between these two stationary elements is moved by the grate and the interaction tends to loosen the fire causing it to slide down the grate. A further result of this action is that the agitation of the fire causes the ash to fall downwardly toward the grate itself and into a region of lower temperature, thus contributing to the prevention of the formation of clinker.

By feeding the fuel in the manner described at the upper end of the grate, the combustion occuring in the area surrounding the fuel tube will be very slight, and as a result during operation a region of low temperature will prevail at this point so that the volatile portions of the fuel will be distilled at a low temperature avoiding cracking with the formation of soot and. at the same time enabling the volatiles to be mixed with an excess of oxygen, thus insuring their complete combustion. The construction of the present combustion apparatus facilitates the installation of it in small size units such as in the domestic heaters, in that all tubes and mechanism entering the furnace may do so through one opening enabling the apparatus to be readily installed in existing heaters, and the fact that the fuel may be successfully fed from below the grate, lowers the storage hopper, thus reducing the height to which the fuel must be lifted in charging the hopper.

While in the preferred and illustrated embodiment of the invention it is preferred to utilize a forced draft for effecting movement of the air through the fuel bed and for supplying the additional air to the combustion chamber above the fuel bed, nevertheless it is to be understood that in some instances if found desirable a natural draft, as by a chimney, may be utilized for effecting such air movement and air supply, and furthermore it is to be understood that while it is preferred to rotate the conical grate member as above described, nevertheless if found of advantage other forms of motion may be imparted to said grate member including oscillatory motion.

For the combustion of certain kinds of fuel such as certain finely divided bituminous coals which exhibit a tendency toward packing, it may be desirable to provide a mechanical feed for the fuel through the fuel supply tube 32, such a construction being illustrated in detail in Fig. 5. Referring to Fig. 5 the fuel supply tube is provided with a screw conveyor 130 driven from the shaft 44 through a pair of bevel gears 132, 133. The upper end of the fuel supply tube 32 is preferably arranged to taper, as illustrated, in order to diminish any tendency which may exist for the fuel to pack as it is forced up through the end of the tube.

While the preferred form of the invention has been illustrated and described, it will be understood that the same may be embodied in other forms within the scope of the following claim.

Having thus described the invention, what is claimed is:-

In a combustion apparatus, in combination, a combustion chamber, a burner unit in the chamber comprising an annular stationary grate member provided with an upwardly and outwardly flaring rim portion and an inwardly extending flange forming a trough within said rim portion, a conical gratemember rotatably mounted upon and supported by the flange of said stationary grate member and provided with a plurality of openings in and distributed around the surface thereof for permitting the passage of a primary air supply through a conical bed of fuel supported on the grate member, means for rotating the conical grate member, scraper means carried by said conical grate member for assisting in the removal of ash accumulating in the aforesaid trough, means for supplying air under pressure to within the conical grate member, and means for supplying fuel to the upper portion of the conical grate member and maintaining a conical bed of fuel thereon.

LAWRENCE W. CORBET'I'.

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