US2496156A - Rotary-type burner for solid fuels - Google Patents

Description

N 0 T L U F M W ROTARY-TYPE BURNER FOR SOLID FUELS 6 Shee'ts-Sheet 1.

Filed July 27, 1944 w. M. umom ROTARY-TYPE BURNER FOR SOLID FUELS 6 Sheds-Sheet 2 Filed July 27, 1944 Jane M, R950 w. M. FULTON ROTARY-TYPE BURNER FOR SOLID FUELS 6 Sheets-Sheet 3 Filed July 27, 1944 Film July :27, 1944 6 Sheets-Sheet -11 N O T L U F M W ROTARY-TYPE BURNER FOR SOLID FUELS 6 Shets-Sheet 5 Filed July 27, 1944 W. M. FULTON ROTARY-TYPE BURNER FOR SOLID FUELS Jam. 3%, i1?

6 Sheets-Sheet 6 Filed July 27, 1944 l atented Jan. 31, 195( UNITED STATES PATENT OFFICE ROTARY-TYPE BURNER FOR SOLID FUELS Application July 27, 1944, Serial No. 546,771

19 Claims. 1

This invention relates to improvements in burners for solid fuels, particularly of the general type set forth in my prior copending applications, Serial No. 529,501, filed April 4, 1944, R- tary burner, now Patent No. 2,395,733, granted February 26, 1946; Serial No. 529,502, filed April 4, 1944, Fuel burners for boilers; Serial No. 529,- 503, filed April 4, 1944, Fuel burners, now Patent No. 2,444,985, granted July 13, 1948; and Serial No. 535,848, filed May 16, 1944, Burners for solid fuels, now Patent No. 2,427,596, granted September 16, 1947.

It has been proposed heretofore, to utilize revolving grates of different types for the burning of solid fuel, the grates being caused to rotate Within a cylindrical enclosure. One form thereof has provision for rotating both the grates and the enclosing drum, While another form rotates the grates while the enclosing drum remains stationary. In still another application of this principle, the grates are rotated intermittently at intervals and the enclosing drum remains stationary at all times.

In all of such prior devices, the grates while being enclosed within a drum or cylinder, are spaced away from the interior wall of the drum so that there is no appreciable contact between the interior cylindrical wall of the enclosure and the grates themselves. I have found that this makes them objectionable because the grates cannot dissipate heat to and through the walls of the enclosure with sufficient speed to prevent the grates from being heated to a temperature sufficiently high to cause ashes and clinkers to fuse upon the grates and adhere thereto. I have found also that it is necessary to maintain the temperature of the surface on which combustion takes place below the temperature of fusion of the ashes formed from the fuel being burned in order to prevent this objectionable condition.

One of the objects of this invention is to provide for holding the rotating grates in firm con tact with the inner wall of the enclosing drum 'or other cooling surface, so that the grates cannot become heated sufficiently to permit clinkers to 'adhere thereto.

It is well-known to combustion engineers that solid fuels may be classed as agitating, semiagitating and non-agitating. I have observed from varied and lengthy tests that during the process of combustion, some fuels, such for example, as bituminous coal, change from agitating to semi-agitating at successive stages of combustion. For example, when the coal is first fed into a rotating burner, it may be of the agitating type and hence require considerable agitation as it begins to burn. As combustion proceeds to the point where most, if not all, of the volatile content of the coal has been distilled off and burned, the remaining carbonaceous material comes within the class of semi-agitating fuel, and therefore, must be agitated to a lesser degree than the fuel introduced into the burner. Finally, it may reach the condition of non-agitating fuel and hence should not be agitated appreciably.

A further object of this invention is to provide different parts in a burner for rotation at speeds differing from each other, according to the different conditions of the fuel passing therethrough, and one part may be held stationary, if desired, to permit the combustion of the fuel when it reaches the non-agitating stage.

When rotating grates firmly contact the stationary inner wall of the enclosing drum, a substantial amount of friction results which resists the rotation of the grates to such an extent that a substantial amount of power is required for rotating the grates.

Yet another object of this invention is. to reduce to a minimum the friction incident to the rotating grates and render most effective the rotating power applied thereto, by an application of power with substantially equal force at two opposing points substantially diametrically on opposite sides of the center of the rotating grates around the periphery thereof.

In my experiments with rotary burners, I have found that radiant heat given off from the incandescent fuel in such a rotary burner, has a tendency to pre-ignite the incoming fuel and thus cause burning back into the fuel supply hopper. I have provided a means as set forth in my Patent No. 2,444,985, mentioned above, for preventing the occurrence of such burning back.

Still another object of this invention is to provide a further safeguard against this eventuality, by injecting a limited amount of cool air into the fuel inlet opening of the rotary burner.

I have shown a preferred embodiment of my invention, together with a modification thereof, in the accompanying drawings, in which:

Fig. 1 is a side elevation of the rotary burner applied to a furnace, with parts broken away and in section for clearness of illustration;

Fig. 2 is an end elevation of the burner thereof;

Fig. 3 is a longitudinal section through the burner substantially on the line 33 of Fig. 2;

Fig. 4 is a vertical cross-section through the burner on the line d4 of Fig. 3;

Fig. 5 is a perspective view of a portion of the grate structure with parts broken away and in section to clarify the illustration;

Fig. 6 is a side elevation of one of the grate bars detached;

Fig. 7 is an end elevation thereof;

Fig. 8 is a side view of one of the grate supporting ratchet wheels detached;

Fig. 9 is an edge view thereof; and

Fig. 10 is a diagrammatic plan view of :a rotary burner showinga modified form of driving mechanism for the grate structure.

In the form of the invention illustrated in the drawings, the burner comprises two main parts designated respectively at i and .2, each of which is constructed substantially of annular form and mounted in stationary position against rotation. The parts i and 2, being elongated horizontally, form .an enclosed hollow non-rotating shell extending about the rotating grates mounted therein.

The burner part i is formed with an outer wall 13 (see Figs. :3 and 4), an inner wall :3 and end walls :5 and .6, enclosing therebetween an annular :space or water chamber "i. This annular :space I is adapted to be filled with water or other cooling medium which may be supplied thereto by .convectional circulation from the boiler to which the burner is attached in a manher-similar .toxthatdescribed in my prior application on Fuel burners for boilers, Serial No. 529,502, filed .April 4, .1944, as hereinafter referred to -more'indetai1,

In a similar manner, the part 2 has an outer wall .8, an inner wall :9, and .end walls is and H, enclosing :an annular space !2 which is adapted to be filled with water in the same manner and from the same source described above in con- .nection with the burner part I.

While the burner parts .I and 2, each may be made in :a single piece, I prefer to construct each of them in a plurality of :sectionsgenerally in the manner well-known the manufacture [of cast iron heating boilers, .for the purpose of simplifying and reducing the cost of manufacture in production. The part i (see Fig. l) is :shown as composed of [end sections i3 and i4 and a plurality of intermediate sections 15. of :these sections is provided with inlet openings at its bottom and outlet openings at its top. These openings are connected together by means .of push nipples 56 (Fig. 3) which form a watertight joint with the sections around their outer circumferences but permit the free flow of water through their hollow interiors between the sections. This permits an open Water course through the space 9 formed in the part i. The burner par-t 2 is likewise formed of separate sections il' similarly constructed and connected together through nipples it, which form an open passageway therethrocgh in the space 12.

Each of the intermediate sections l5 has the water space therein narrowed in width throughout .a part of its circumference so that when the sections are assembled together, as shown in Fig.

3, air chambers i3 are formed between the sections at thenarrowed portions. These air chambers 18 are enclosed at opposite sides by walls Each an adjacent section to form a slot 20 into the periphery of each air chamber 18 through which air can be blown into this chamber for discharge into the burner. As shown in Fig. 3, the slots 29 are of different widths, being largest at the intake end of the burner and smallest at its outlet end. This arrangement :serves to admit the largest volume of air at the end of the burner where fresh fuel is being introduced, and the smallest amount at the end where ashes are being formed and discharged, the volume of admitted air decreasing progressively from the inlet end .to the discharge end.

Each of the sections ll of the burner part 2 is likewise narrowed along a part of its circumference so that when these sections ll are assembled together, an air chamber 22 is formed in the sections enclosed at opposite sides by ribs 23 and at its periphery by the outer wall 3 of the burner part 2. The outer wall has gaps in the portions thereof provided for the respective sections that :are :spaced apart to form a slot 24 into the periphery of the air chamber 222,, through which .air is blown into this chamber, thence into the burner, as indicated by the arrows in Fig. '3. This slot 24, corresponding with the slots 20 in the burner part -I is of smaller width than the latter slots so as to admit .a smaller amount of air for the purpose described above.

Mounted on aone side and near the bottom of the :burner, .as shown in Figs. 1 to 4, is a windbox 25 which extends throughout the major portion :of the length of the burner, including the parts .i and 2, enclosing therein the slots '25 and 25, as will be evident .from Figs. 1 and 3. The wind-Ibex .25 is adapted :to supply .air to these slots, :as indicated by the arrows in Figs. 3 and 4. An air duct '28 extends to the wind-box 25 from a blower 2] for supplying air, as needed, to the wind-box, which in turn directs it into the burner, as described.

At the interior of the burner part I is a series of grate-bars 28 (Figs. 4 to '7), the exact construc'tionof which is shown more clearly in Figs. -'5 and -'6. Each of the grate-bars is formed of slightly 'arcuate shape in-cross-section, as shown in Figs. 3,4 and 7, and has beveled opposite edges 29. Each grate-bar also has reduced opposite ends 30.

The grate-bars 2S are'mounted in and moved by driving rings '31, 32 "(see Figs. 5, 8 and 9). These rings 31, "32 are exact duplicates except that they are respectively of right and left design, intended to be in opposed cooperating relation. Each .ring is provided with an integral inwardly projecting rim '33 at its inner edge, and formed Withnotches 3'4 therein leaving projections 35 between .the notches which engage loosely with the reduced ends .30 .of the grate-bars 28 that are mounted in the notches 34. Each of the projecting ends 31) of the grate-bars is formed substantially .of keystone shape, and the notches ,34 are similarly shaped but of slightly larger size so as to receive the end-s loosely, although confining the grate-bars against dropping through the inner sides of the rings 3|, 32 for retaining them in place.

The rings 3|, 32 are mounted to rotate freely within opposite ends of the burner part I, which .serve as :bearings therefor, there being sufficient play provided between the rings and the hearings to :allow for expansion and contraction resulting from wide changes in temperature. The reduced ends. :of the gratebars 2.8 set-suffic'iently loosely ate-$631 56 in the notches 34 to permit the grate-bars to have substantial movement towards and away from the axis of rotation of the rings 3|, 32, although as pointed out above, this movement is restricted to prevent the ends 30 from becoming disengaged by the projections 35 by which the grate-bars are moved, as will be evident from Figs. 4 and 5. Furthermore, these parts are so proportioned that the grate-bars are spaced in relation to each other so as to leave longitudinal slots or openings 36 therebetween, formed by the adjacent beveled edges 29 of the grate-bars which are so disposed as to provide substantially a tangential arrangement of the openings 36 relative to the interior of the burner, as shown in Fig. 4.

Each of the driving rings 3|, 32 has on its peripheral portion thereof, ratchet teeth 31 in this form of the invention, as a means of driving the rings and thereby the grate-bars, as hereinafter described. The ratchet teeth on both of the driving rings 3!, 32, of course, are of the same pitch.

The burner part 2 is provided with a driving ring 39 which is similar to the rings 3| and 32, except that it extends continuously throughout the width of theburner part 2 and has an inwardly disposed annular rib 40 at the inner end of the burner. Furthermore, the driving ring 39 has ratchet teeth ll on its peripheral rim portion but of shorter pitch than the ratchet teeth 31 so as to provide for finer stepping adjustment of the driving ring 39 than of the driving rings 3|, 32.

The driving ring 39 has rectangular openings 42 arranged at intervals around its circumference and loosely receiving therein, grate-bars 43. These openings and grate-bars taper inwardly, as shown in Fig. 5. Each grate-bar is suniciently smaller than its co-acting opening so as to provide longitudinal spaces or slots between an edge of the grate-bar and the adjacent edge of its opening 42, as indicated at 44 in Fig. 5. These openings or slots 44 are likewise disposed generally in a tangential direction relative to the cylindrical wall of the burner. The loose fit of the grate-bars 43 in the openings 42, permits the grate-bars to have substantial movement toward and away from the axis of rotation of the ring 39. One purpose of this, is to allow for expansion and contraction between the grate-bars and their openings, due to wide changes in temperature, often unevenly distributed between the bars and the openings. Another purpose, is to provide the spaces 44 through which air can pass into the discharge end of the burner to support combustion, as indicated by the arrows in Fig. 3.

At the fuel inlet end of the burner is a stationary burner head 45 (Fig. 3), which forms an enclosure for the cylindrical burner structure. The burner head 45 is hollow to provide a water space .46 therein, and having inlet and outlet water connections at its bottom and top respectively, each of which is provided with a push nipple, one being shown at 48 at the top, as a means of connecting the burner head with the burner part I. These connections permit free circulation of water between the water chamber 46 in the burner head and the water chambers I and I2 in the burner parts I and 2 in a manner usually em- .ployed in the construction of cast iron boilers.

One end of the cylindrical burner is supported by means of the burner head 45. which is carried by legs 49 on a base 53, preferably bolted thereto.

The opposite end of the burner may be supported in any convenient manner, but I prefer that it be V the enclosure is mounted.

seated in a fire-brick wall 5| (Fig. 1) which con? nects the outlet end of the burner with a heating boiler 52. The fire-brick wall 5| has a chamber 53 therein, receiving the products of combustion from the burner and having a fire-brick face in opposed relation to the open end of the burner,

generally as described in connection with my prior application, SerialNo. 529,502.

When all of the sections of the burner parts I and 2 are assembled together with the burner head 35, they constitute an integral non-rotating enclosure for the rotating grates. this enclosure is connected with the furnace structure including the fire-brick wall on which Hence, it is only necessary to support separately the opposite end of the structure. It is not required that the respective sections be supported intermediate their ends since these two points of support at the respective opposite ends, will be sufficient.

The burner head is provided also with the fuel inlet 54 opening into the inner side of the burner at a point preferably located at the vertical longitudinal plane through the axis of the burner, and preferably above the axis. This fuel inlet is preferably in the form of a zigzag conduit through which the fuel may be directed into the outer end of the burner from a suitable source of fuel supply, such as a hopper, as described in my prior application, Serial No. 529,502.

Referring to Figs. 1 and 2, the rotor of the blower 27 is keyed on the armature shaft 55 of an electric motor 55, which is attached to the base 55 by means of bolts 5?. This motor 56 also drives the operating parts of the burner.

The opposite end of the armature shaft 55 has a pulley 55 keyed thereon and connected by a V-belt 59 with a pulley 53, which is keyed to the drive shaft 6! of a speed reducer 62 that is mounted on the base 59 adjacent the motor 56.

The speed reducer 62 has a reduced speed power output shaft 63 on which is mounted a crank 5 for turning movement thereby. A linkarm 55 has one end pivoted to the crank 64 and its opposite end pivotally connected with the lower end of a swinging lever-arm 55. The lower end of the lever-arm 55 is bifurcated to receive therein the adjacent end of the link-arm 65.

As a means for supporting the lever-arm 66, the burner head 615 has integral therewith, a shelf 6? on which is supported a knifeedge pivot block 58 held in position by a screw 69 and adjustable transversely of the shelf 6'5 by a screw 1!), which is threaded through an upstanding portion of the shelf. Opposite from the shelf 671 is a knife-edge pivot member H integral with the burnerhead 45. The lever-arm 66 has V- cavities T2 in opposite sides of its upper end which receive the knife-edge pivot members 68 and ii thereby forming a frictionless knifeedge hearing about which the lever-arm 63 can oscillate freely.

I prefer this type of bearing for the lever-arm because it does not require lubrication. The heat from the burner head 45 conducted through a bearing support connected thereto, would render the lubrication satisfactorily of a pin-pivot or journal bearing difficult. Any of the pinpivots of the oscillating parts of the mechanism, may be replaced by knife-edge pivots, similar to that here described, if desired.

The lever-arm 53 is also bifurcated at its middle portion, as shown at T3 in Fig. 1, thereby providing an open space in which is located a walking beam 34, pivoted at 15 intermediate its ends to One end of the lever-arm .58. The opposite ends :Of the walking "beam member 14, carry links .16 and E?! pivoted thereto. These links '55 and 'I'! extend transversely of the burner head -45 in opposite directions, :and have their outer lends pivotally connectedat 18, 29, respectively, with-crankearms 85, 8I, keyed to shafts 82, 83 journaled to turn freely in bearings 84, 85, respectively, integral with the burner part I. Also keyed to the shafts 82, 83 are short crank-arms 86, 31., two crankarms being provided on each shaft, which crankarms carry pawls 88, 89., held .in engagement with the teeth 3lof the driving rings 3|, 32 by means of springs 90, S I. On the outer ends of the shafts 82, 33, are keyed crank-arms 92, 93, which .carry pawls M, 05, held in operating engagement with the teeth H of the driving ring 30 by means of springs 95, 97; Crank-arms 02, 93 are shorter than the crank-arms 85, 87 so as to provide for smaller throw. of the pawls .54, 95 than of the pawls S8, 89, consistant with the smaller size of the teeth 4i than the teeth 37. The crank-arms 80, BI, as well as the crank-arms 85, 8! and 92, 93, are respectively of equal length at opposite sides of the (burner. This insures the application of equal force at substantially diametrically gapposite points on the driving rings 3I, 32 and The two bearings 34, 85 nearest the inlet end of the burner are provided with brackets 08, 90, in which are threaded set screws I00, lilI in the path of swinging movement of the crankarms 86, 81, for limiting the extent of movement of these crank-arms in one direction. This would likewise limit the movement of the arms 92, 93,, which are keyed to the same shafts 8?, 83.

A pipe I02 connects the housing of the blower 21 with the fuel inlet 54, having a nozzle I02 directed along the central axis of the lower pipe section so that air discharged therefrom will be directed downward through the inlet 54 into the interior of the burner. Thus, when the blower 2'! is operated to supply air through the duct 26 into the wind-box 25, and thence through the slots and the grate-bar openings 38 and 44 into the fuel bed inside the burner, air will be supplied also through the nozzle I02 in the fuel inlet 54.

One or more inlet connections are provided at I03 in the stationary burner grate enclosure (Fig. 2), and similar outlet connections I04, leading respectively to the bottom and top portions of the steam or hot water boiler 52. Thus water from the bottom of the boiler will be directed into the water passages of the burner enclosure through the connection I03 where it will be heated and returned to the boiler through the top connection I04, as described more in detail in my co-pending application, Serial No. 529,502.

Referring to Figs. 3 and 4, the burner head 45 has integral therewith, a hollow member I05 which is in open communication with the chamber 45 of the burner head so that water can circulate .freely therebetween. The member I05 extends throughout the entire length of the interior of the burner, as shown in Fig. 3, and is crescent-shaped in cross-section, as shown in Fig. 4. This member I05 is spaced from the interior wall 4 of the grate enclosure to permit the grates 28 and 43 to slide freely through the space between the Wall 4 and the member I05. The member I05 preferably is not concentric with the wall 4 of the grate enclosure, the eccentricity being sufiicient to make the space between the is. it

two increasesomewhat as the grates'passaround in the direction of the arrow in Fig. 4.

The member I05 has integral with its terminal edges, two channels I06 extending lengthwise thereof, and have channels I-01 at opposite ends thereof, in whichchannels I06, H11 rest the edges of a fire-clay baffle I08. The purpose of this bafile is similar to that described in my Patent No. 2,427,596, for Burners for solid fuels. The baffle I08 .is preferably spaced somewhat from the member I05, as indicated at I09 to reduce the heat exchange therebetween.

The member I05, forming a water cooled 'baflle, used alone or in connection with the refractory bafile I08, is claimed in a copending application of Weston M. Fulton and Sidney R. Galyon for Rotary grate burners, Ser. No. 546,770, filed July 27., 1944, now Patent No. 2,426,348, granted August 26, 1947.

Referring to Figs. 3 and '5, the driving rings 3 I, '32 have recesses I H], II 1 into which are placed flexible expanding packing rings I I2, II3. These rings are collapsed slightly before being put into place, and their resilience causes them to tend to expand circumferentially. The outer edge of each of the recesses III), III is beveled at the point where the packing rings H2, H3 press. This pressure produces a wedging action which tends to cause the ring Hz to press the driving ring 3| to the right in Figs. 3 and 5, thereby maintaining a tight joint between the driving ring 31 and the end wall 5 of the burner part "I. In like manner, the packing ring II2 seals the joint between the burner head 45 and the driving ring 3i. Similarly, the packing ring II3 tends to force the driving rings 32, 30 apart causing them to make tight joints respectively with the end wall 6 of the burner part I, and with the end wall It of the burner part 2. Also the packing ring II3 seals the joint between the driving rings 32, '39.

In order to safeguard further against the possible escape of very fine ashes from these joints, I have provided flanges H1, H8 (Figs. 1 and '3) integral with the burner parts I and 2 respectively, which flanges enclose the driving rings 32, 39 throughout the lower half of their circum- Terence, thereby forming a catch basin II9, into which any escaping ashes may fall. Likewise, flanges are formed on the burner part I and burner head 45 to enclose catch basin I20 extending about the lower circumference of the driving ring 3| for any particles that may escape about this ring.

These catch basins terminate at their bottoms in pockets I2I, I22, respectively (Fig. l), which are connected together by a conveyor pipe I23, carrying a small conveyor screw 1-24. The pipe 123 also includes short sections that extend from the pockets to the ends of the burner. The screw I24 is driven by a ratchet wheel I25 on the shaft thereof, and engaged by a pawl pivoted in the bifurcation of an oscillating arm I26 journaled on the screw shaft, and which is moved back and .forth by means of a pin I21 projecting from a side of the swinging lever-arm 66. Thus the screw I24 will be operated upon the operation of the mechanism of the burner, whereby any slight particles caught in the pockets Ii2l, I22, are conveyed to the open end of the pipe .123 and there discharged into the ash-pit or other ash disposal means, along with the ashes from the burner, at the bottom of the chamber 53, as

shown in .Fig. 1.

" Operation In the operation of the burner, fuel iscfed through the inlet 54 by any suitable means, preferably mechanical stoker mechanism of the character set forth in my priorapplication, Serial No. 529,502. In the meantime, the motor 56 drives the speed reducer 52 and through the crank 64 and link-arm 55. causes the swinging. lever-arm 66 to oscillate back and forth from right .to left, as viewed in Fig. 2, carrying with it the. walking beam member M. This oscillating movement of the lever-arm 66 will cause oscillation ofthe crank arms 80, ill and steppingmovement of the pawls $3, 39 and 9d, 95, acting respectively. on the teeth 3? and M to-rotate the-driving rings 3i, 32 and 39 in thedirectionindicated bythe arrow in Fig. 5.

S nce the crank arms.92, 93 areshorter than the arms. 85, 87, the pawls 94, 95 will move through a shorter distance than the nawls B8,. 89. The teeth ll of the driving ring 39 are. made shorter than the teeth 37 to correspond with the shorter movement of their driving pawls. Therefore, it is evi ent that the ring 39 will be driven at a slower rate than the rin s 3L. 32. By selecting the pro er len ths for the crank arms, it is ev dent that any-desired difference in speed of rota ion can be obtained. for the driving rings.

Si ce the alking beam member 1A is pivoted midway of its opposite ends, force will be ap plied equa lv by t e driving pawls which are located at substant ally diametrically opposite poi ts on the circumference of the driving rings. This is important for practical results. because if the driving forceis not ap lied eoually in this' manner. these dr ving rin s SI, 32 and 39 would offer undue resistance to .the driving. force.

As the rings 3!. 32 are thus caused to rotate in the direction indicated by the arrows in. the drawings, themcarrv with them the -grate-bars 21'! along with the burning fuel-that lies on these grate-bars. As pointed outabovegtheopposite edges of the proiections 35 "are disposedat an acute an le relative to the-radius of the driving rings. Like ise. the opposite edges of the-re duced ends 3!! of the grate-bars are shaped at correspondin angles of a-keysto'oe. Therefore, when the driving force is ap lied in a direction tangent to the c rcle of rotat onythere is aresulta t component of force tending to 'push the bars outward y from thezaxis of rotation. Hence it these bars beingfree to move outward, are urged by their own weight; plus the weight of superimposed fuel, plus the component of force mentioned, to'bearagainst. the inner wall 4 of the water-cooled enclosure. In this manner, they are maintained in firm contact with this cooled surface throughoutthe rentire length while they are passing throughthe region covered by the major portion of -the fuelsbed, as indicated at B in Fig. 4, in the lower segment of the :burner. It is in this region that the grate-bars arecsubjected to the most intense-heat, andtherefore,

require the maximum degree of protection.

As the grate-bars 28 are carried forward in the direction indicated by'the arrows, they enter the space between the water cooled member 535 and the outer enclosure. As the bars approach the region vertically above the center of rotation,

they are free to drop down by gravity onto the peripheral surface of the'member 'illi' Here it will be noted that'the' action of gravity graduallyshifts the grate-bars away'from the Watercooled 'enclosuretowards the member lllt. Also -therebetween increases from the point where the .the barsgare relieved of the weight of fuel as they rise above the fuel bed, and hence the driving force is reduced to a minimum, .the component of force tending to deflect the grate-bars outwardly is likewise reduced. Consequently,- the bars, upon entering the space between the member Hi5 and the water-cooled enclosure, soon drop of their own weight down onto the periphery of the member Hi5 and bear thereon in their movement over the upper portion of said member. These bars are then carried around on this member to where they emerge from the space mentioned, and in so :doing, reach a region where all of the forces previously mentioned begin to .come into. play, and thus force the bars outwardly these forces be yielding, as opposed to rigid means, in order to provide for the expansion and contraction of the grates and other parts, [due to wide variations in temperature, and also to be self-adiusting for wear.

Since the curvature of the member Hi5 is eccentric to that of the enclosure wall, the space grates enter this space to the point where :they leave it. The object of this-arrangement is to prevent any possibility of the grates becoming clogged by any-foreign matter which may; accidentally exist in'the -fuel,:andwhich may1ad- 'here to the bars and be 'carriedby them into this space.

It will be evident. from Fig. 4 that any particles smallenough to be carried bythe grates through the restricted entrance to this a non circular'orbit, and thus free the air spaces 36between them from small pieces of fuel which ma drop therein. It is evident that as each forward moving grate-bar drops down ontothe member Hi5, the space between it and the next adjacent grate-bar, is enlarged somewhat, thus freeing allparticles contained in this space.

Furthermore, asthe grate-bars move to the'exit side of this space, they again change relationships, and finally their relationship is changed for a thirdtime as they move into and through the fuel be'd B, as shown in Fig. 4. This constant shifting action makes the grate-bars self-cleaning and has proven frompractical tests of the construction to possess great merit.

As fuel is fed into the burner at the fuel inlet 5%, it drops onto'the grates or lower edge portion of the fuel bed and is carried around by 'the grate-bars through the fuelbed. It is there supplied with'air from the wind-box 25 through the slots 28 and air chambers i8, thence through the openings or slots 36 between the grates into the bed of burning fuel, as indicated by the arrows in Figs. 3 and 4. Since the slots 20 gradually decrease in size toward the discharge end of the burner, the amount of air admitted to the fuel will be decreasedcorrespondingly at successive points. When fuel 'first' enters the burner, itgives up its volatile-content at'the fast- 'bon. decreases as the fuel is shifted toward the out- 11 est rate, and hence a large volume of air is required to burn these volatile gases in addition to the amount required to burn the fixed car- Obviously, this demand for air gradually let end of the burner.

As pointed out above, many fuels which are properly classed as "agitating fuels become semi-agitating fuels as combustion proceeds. The burner part 2 will take care of this eventuality. As the fuel moves through the burner from the inlet to the outlet end thereof, it leaves the burner part I and enters the burner part 2. Since the burner part 2 is driven at a slower speed of rotation than the burner part I, the degree of agitation is reduced accordingly. Here the grate-bars 43, being free to move about in the openings 42, shift in the same manner as the grate-bars 28 with respect to the burner part I, thus possessing the same self-cleaning and other advantageous features described above. Since the fuel steadily decreases in volume as it passes through the burner due to its consumption by combustion, the burner part 2 is not ordinarily required to have the same volumetric capacity as the burner part I, and hence its length may be appreciably less than the burner part I.

I have found by experience that a limited amount of air blown downward through the fuel feed inlet 54 b the nozzle I632, aids the cooling of this entrance and also reduces the intensity of radiant heat emitted upward through this entrance from the burning fuel in the burner. Since air is highly diathermic, the air itself probably does not intercept any large portion of the radiant heat. However. it is my opinion that very fine particles of fuel which would otherwise loiter by flotation in th s fuel inlet passageway are caught by this stream of incoming air and carried quickly into the combustion chamber, whereby, they are prevented from absorbing an excessive amount of radiant heat. and becoming preignited therefrom. Evidently, all of the heat which is absorbed by these fine particles is qu ckly carried by them, back into the combustion chamber by the air injected in the fuel inlet by the air jet I82. It is also my opinion that these fine particles, which constitute the very substantial part of most commercial grades of coal, and which are h ghly athermanous. do intercept a very substantial percentage of the radiant heat emitted from the combustion chamber. Since this air jet I52 prevents these particles from loitering enroute to the burner, they are not allowed to collect heat. Furthermore, this air jet impinges against the surface of the burning fuel at the very point from which heat is emitted into the fuel passage. Th s incoming air being relatively much cooler than the burning fuel reduces the temperature of the latter at its immediate radiating surface, and thereby reduces the intensity of radiation in proportion.

It will be evident from the foregoing that this improved burner construction accomplishes the several desired results pointed out, and is a material improvement in burners that utilize revol'ving grates.

It will be understood also that the drawings are intended to be merely illustrative of the principal embodiment of the invention, and that changes in mechanical forms may be made without departing from m invention. For instance, while Furthermore, one of the burner parts, at the outlet end of the burner, may be non-rotating in the manner described in my Patent No. 2,427,596. In this event, the flanged portion 40 of the ring 39 would be replaced by a helical edge of the type described in my said application. This would enable me to utilize fuel which passes successively through stages from agitating to semi-agitating and then to non-agitating.

It is also evident, that while this burner construction is shown as applied to the heating of steam or hot water, it may be used as well for other types of furnaces, such as hot air furnaces. In this event, air instead of water is circulated through the passageways of the enclosure, which may be provided somewhat larger and more spacious for this purpose than is necessary for water passages. Such air circulation may be accomplished in any of the ways set forth in my aforesaid corresponding patents, No. 2,395,733 and No.

furnishes a relatively cool surface for them to rest upon while moving through the upper portion of their path of rotation. While either of these members I05 or I 08 may be used alone without the other, in some installations, especially where other means are available to prevent pre-cooling of the gaseous products of combustion, I prefer ,to use both bafiles, for general purposes.

While I have shown, and prefer to employ, the arrangement set forth above for insuring uniformly distributed power at two diametrically opposite points on the driving rings, I may employ other mechanical means for this purpose, if desired. Another example thereof is shown in Fig. 10, in which a rotating burner part is shown at I4I, provided with driving rings I42, I43, which driving rings have gear teeth provided at their peripheries, instead of the ratchet teeth referred to above. Also. these driving rings are rotated by p nions I44, I45 mounted respectively on shafts I 46, I 41. These shafts are mounted at diametrically opposite sides of the burner part I 4| so as to apply equal driving forces to the driving rings and on opposite sides thereof.

The shafts I46, I41 may be driven in any suitabe manner, but for purpose of illustration, I have shown them operated by worm gear speed reducers I28, I29, which in turn are operated by cross-stub shafts I30, I3I from a differential I32. The differential I32 is operated by a drive shaft I33, carrying a driving gear I34, which may be operated by a pinion I35 mounted on the armature shaft of an electric motor. This form of driving mechanism also obtains an equalization of power in the driving of the burner part or parts, generally with the results pointed out above.

I claim:

1. In a burner of the character described, the combination of an annular structure extending about an approximately horizontal axis and includ ng an inner surface and having means for circulating a cooling medium in heat exchange relation with said inner surface, rotary grates extending lengthwise of the axis of said annular structure throughout the major portion of the length thereof and mounted for movement through an orbit for supporting the fuel bed on the grates in the lower portion of the orbit, and

means for turning said grates in bearing relation with said inner surface.

2. In a burner of the character described, the combination of an enclosing structure having an annular inner surface with means for circulating a cooling medium in heat exchange relation with said inner surface, rotary grates, and means for rotating said grates in yieldable bearing relation 'with said inner surface.

3. In a burner of the character described, the combination of an enclosing structure extending about an approximately horizontal axis and including an inner wall surface and means for confining a heat exchange medium in heat excrange relation with the periphery of the wall surface for cooling said surface by dissipating heat therefrom, grates mounted in peripheral bearing relation against said inner wall surface and extending lengthwise of the axis of said inner wall surface throughout the maior portion of the length thereof and movable in an orbit wall surface.

5. In a burner of the character described, the combination of a tubular burner structure mounted approximately on a horizontal axis and including an inner wall surface and means for confining a heat exchange medium in peripheral bearing relation with said wall surface for dissipating heat therefrom, cylindrical grate structures having side surfaces thereof mounted on peripheral bearing relation against said inner wall surface, said grate structures extending lengthwise of the inner wall surface throughout the major portion of the length thereof and movable through an orbit in bearing relation therewith for supporting a fuel bed on the grate structures in the lower portion of the orbit, and means for turning said grates in said peripheral bearing relation.

6. In a burner of the character described, the combination of a tubular burner structure mounted approximately on a horizontal axis and including an inner wall surface and means for confining a heat exchange medium in peripheral bearing relation with said wall surface for dissipating heat therefrom, cylindrical grate structures having side surfaces thereof mounted in peripheral bearing relation against said inner wall surface, and means for turning said grates in said peripheral bearing relation, said turning means having a loose connection with the grates for yielding movement of the grates inwardly relative to the wall surface while maintaining the driving connection with the grates.

'7. In a burner of the character described, the combination of a burner structure including outer and inner walls spaced apart for confining a cooling medium therebetween in heat exchange relation with the inner wall, said inner wall being substantially cylindrical and having an approxiinately horizontal axis, grate-bars mounted in peripheral bearing relation against the inner surface of said inner wall for turning movement in contact therewith throughout a substantial portion of the circumference of said inner wall, said grate-bars extending lengthwise of said inner surface throughout the major portion of the length thereof and movable relative thereto through an orbit for supporting a fuel bed on the grate-bars in the lower portion of the orbit, and means for turning said grate-bars about the axis of said inner wall.

8. In a burner of the character described, the

combination of an enclosing structure including an inner wall surface and means for confining a heat exchange medium about said wall surface in heat exchange relation therewith, grate-bars having cylindrical surfaces in peripheral bearing relation against said inner wall surface, rings mounted at opposite ends of the grate-bars and having driving connections therewith, said driving connections being sufiiciently loose for inward. yielding movement of the grate-bars relative to the rings.

9. In a burner of the character described, the combination of a supporting structure, a plurality of rotating grate-bars adapted for turning movement about an approximately horizontal axis, driving rings having interfitting connections with the grate-bars for rotating said grate-bars in an orbital movement, said interfitting connections being loose relative to the grate-bars for yielding movement of the grate-bars inwardly relative to the rings.

10. In a burner of the character described, the combination of a supporting structure, a plurality of rotating grate-bars adapted for turning movesides of said driving rings for turning said rings.

11. In a burner of the character described, the combination of an inner wall, grates mounted for rotating movement in peripheral bearing relation with said well, turning means operatively connected with the grates for rotating said grates through an orbit, and means for applying power equally at approximately diametrically opposite points to the turning means causing movement of said turning means and the grates.

12. In a burner of the character described, the combination of a plurality of grate members, and means mounting said grate members for turning movement through a non-circular orbit, said grate members being constructed for supporting a fuel bed thereon with the orbit.

13. In a burner of the character described, the combination of an enclosing structure, grates mounted within the enclosing structure and constructed of sections spaced lengthwise of said structure, each of said grate sections including a plurality of bars spaced about the circumference of the enclosing structure, and one or more driving rings for each grate section and having interfitting driving connection with the gratebars to move said grate-bars through an orbit upon rotation of said ring.

14. In a burner of the character described, the combination of an enclosing structure, grates mounted within the enclosing structure and con .of the enclosing structure, and oneor more driving rings for each grate section and having interfitting driving connection with the gratebars to move said grate-bars through an orbit upon rotation of said ring, and means having driving connections with the respective rings for I rotating the grate sections.

15. In a burner of the character described, the combination of an enclosing structure, grates mounted within the enclosing structure and constructed of sections spaced lengthwise of said structur each of said grate sections including a plurality of bar spaced about the circumference of the enclosing structure, and one or more driving rings for each gratesection and having interfitting driving connection with the grate-bars -to move said grate-bars through an orbit upon rotation of said ring, ash-receiving means beneath the rings, and means for removing ashes from said ash-receiving means.

16. In a burner of the character described, the combination of a tubular structure, a plurality of grates, means mounting said grates for turning movement through an orbit relative to the supporting structure, said mounting means supporting the grates in spaced relation and free for bodily shifting movement relative to each other during movement through the orbit, and means for admitting air to support combustion through the spaces between the grates.

17. In a burner of the character described, the combination of an approximately horizontal tubular structure adapted to support a fuel bed in the lower portion thereof, grates mounted in the tubular structure for bodily turning movement through an orbit relative thereto, and a fire baiile mounted in the supporting structure inwardly of at least a portion of the orbit of movement of the grates to shield the grates from the heat of combustion in the burner during a portion of their rotation.

18. In a burner of the character described, the

combination of a plurality of grate members,

means mounting said grate members for turning movement through a non-circular orbit, said grate members being constructed for supporting a fuel bed thereon Within the orbit, and means for feeding solid fuel to said fuel bed at the inner side of the orbit.

19. In a burner of the character described, the

combination of an annular structure extending about, an approximately horizontal axis and including an inner surface and having means for circulating a cooling medium in heat exchange relation with said inner surface, movable grates extending lengthwise of the axis of said annular structure throughout the major portion of the length thereof and mounted for movement through an orbit for supporting a fuel bed on the grates in the lower portion of the orbit, and means for moving said grates in bearing relation with said inner surface.

WESTON M. FULTON.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PA I E N I S Number Name Date 592,616 Sanderson Oct. 26, 1897 737,306, Wilson Aug. 25, 1903 745,247 Shontz Nov. 24, 1903 901,938 Poppenhusen Oct. 13, 1908 1,079,151 Smallwood Nov. 18, 1913 1,102,662 Hobbs July 7, 1914 1,295,685 Brown et a Feb. 25, 1919 1,304,380 Santmyer May 20, 1919 1,318,375 Goff Oct. 14, 1919 1,344,666 Westerberg June 29, 1920 1,393,979 Skelly Oct. 18, 1921 1,406,883 Miller Feb. 14, 1922 1,496,913 Warford June 10, 1924 1,575,350 McEWen Mar. 2, 1926 1,672,563 Fox June 5, 1928 1,698,113 Van Brunt Jan. 8, 1929 1,828,270 Anderson Oct. 20, 1931 1,832,459 I-Ianiman Nov. 17, 1931 1,837,535 Van Deventer Dec. 22, 1931 2,019,942 Valentine Nov. 5, 1935 2 020,950 Pehrson et a1 Nov. 12, 1935 2,124,661 White July 26, 1938 2,160,481 Lockwood- May 30, 1939 2 238,161 Drew et al Apr. 15, 1941 2,321,389 Julyan et a1. June 8, 1943 2,359,445 Schweickart et a1. Oct. 3, 1944 FOREIGN PATENTS Number Country Date 255,753 Great Britain July 29, 1926 293,461 Great Britain Sept. 5, 1929 372,429 Great Britain May 12, 1932 420,589 Germany Oct. 20, 1925

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