US2109914A - Stoker mechanism - Google Patents

Description

March 1, 1938. G. VON HAASE STOKER MECHANISM Filed NOV. 18, 1935 5 Sheets-Sheet l fiat I IQ u lpl 7;

5 INVENTOR.

,4:- 650065 VM/rm:

.1 ATTORNEY;

March 1, 1938.

G. VON HAASE STOKER MECHANISM Filed Nov. 1a, 1955 5 Sheets-Sheet 2 GEO/96E l/a/v M .55 w, aaam M ATTORNEY? March 1, 1938. s. VON HAASE STOKER MECHANISM Filed NOV. 18, 1935 5 Sheets-Sheet 3 INVENTOR. GEORGE l/a/v HAAsE m, m M

ATTORNEYS March 1, 1938.

G. VON HAASE STOKER MECHANISM Filed Nov. 18, 1955 5 Sheets-Sheet 5 INVENTOR ATTORNEYS Patented Mar. 1, 1938 UNITED STATES PATENT OFFICE STOKER IVIECHANISM Application November 18, 1935, Serial No. 50,251

16 Claims.

This invention relates to improved apparatus for feeding and burning fuel, and more particularly to an improved stoker mechanism having novel fuel feeding means and novel grate actuating means.

An object of this invention is to provide improved apparatus of the type referred to, wherein the novel fuel feeding means comprises a relatively inclined feed tube having a correspondingly inclined reciprocable plate forming the bottom thereof.

Another object of this invention is to provide novel grate actuating mechanism wherein a releasable drive connection between one set of grate elements and a power shaft is rendered effective and ineffective by the action of releasable drive means between the shaft and another set of grate elements.

Still another object of the invention is to provide improved grate actuating mechanism wherein means for operating the grate elements in timed relation includes a member movable into and out of power transmitting cooperation with adjacent parts and wherein the movements of such member take place while it is not under load.

A further object of the invention is to provide novel grate actuating mechanism embodying means for operating grate elements in timed relation including members which are movable into and out of power transmitting cooperation and which are provided with a substantially dustproof casing.

Yet another object of this invention is to provide novel actuating mechanism for sets of grate elements, comprising an oscillating shaft having levers connected, respectively, with the sets of grate elements, and means for intermittently establishing a drive connection between said shaft and said levers.

Other objects and advantages of the invention will be apparent from the following description when taken in conjunction with the accompanying sheets of drawings, wherein- Fig. 1 is a partial front elevation showing a boiler to which my novel stoker mechanism has been applied.

Fig. 2 is a side elevation of the mechanism and boiler with portions of the latter broken away.

Fig. 3 is a partial elevational view from the opposite side of the apparatus but with parts broken away to show the fuel feeding means.

Fig. 4 is a plan view of the grate operating mechanism.

Fig. 5 is a front elevation thereof, and,

Figs. 6 to 9 inclusive are transverse sectional views taken through the grate actuating mechanism, as indicated by the corresponding section lines of Fig. 5.

In the accompanying drawings to which more 5 detailed reference will now be made, I have shown improved fuel feeding and grate operating mechanism which is more durable and reliable than apparatus of this character heretofore available. It will be understood, of course, that the novel combinations and features of my invention, hereinafter to be explained in detail, may be embodied in various other similar mechanisms and apparatus.

My improve-d stoker mechanism may be applied to various types of boilers, but is especially useful in connection with boilers of the Scotch or returntubular type. In Figs. 1 and 2 of the drawings I have shown my stoker mechanism applied to a boiler III which is a boiler of the latter type. As is usual in boilers of this type, a tubular corrugated furnace extends inwardly from the front head or tube sheet l2 of the boiler. The outer end of the furnace II is provided with a furnace front l3 which forms a support for the various furnace front fittings, such as the fire door M and ash pit door l5, and also provides a support for my stoker mechanism. As is well understood in this art, this furnace front may also embody an arrangement of air passages and dampers, and also provides a support for the outer ends of the grate bars or elements.

A grate ll extends into the furnace substantially at the transverse mid-plane thereof and divides the interior of the furnace into a fire box l8 and an ash pit IS. The grate may comprise sets of reciprocable elements such as the sets and 2| of grate bars, the individual bars of the set 2|] being disposed between the individual bars of the set 2|. The grate bars comprising the set 20 may be supported at their outer end upon a transversely extending bridge or arch 22, which is rockably mounted in the furnace front. The outer ends of the bars of the set 2| may be supported upon a similar transverse rocking bridge or arch 23. The inner ends of both sets of grate bars may be slidably supported upon a transverse bar 24 which is provided in the furnace adjacent the inner end thereof. The outer ends of the bars of the sets 20 and 2| may be prevented from becoming disengaged from the rocking arches 22 and 23 by providing the bars of the sets with notches 25 in which the respective arches engage. Reciprocating movement is imparted to the sets of grate bars by rocking the 55 arches 22 and 23 and, as will be explained hereinafter, this reciprocating of the grate bars takes place in timed relation, such that fuel supplied to the outer end of the grate will travel slowly inwardly along the grate while combustion is taking place. As is well understood in the art, the ashes from the fuel will either drop through the spaces between the grate bars or be discharged over the inclined inner ends 28 thereof to drop into the ash pit l9.

Fuel may be supplied to the grate either through the opening closed by the fire door 14, or preferably by means of my novel fuel feeding means. This fuel feeding means comprises a hopper 28 which is suitably supported on the furnace front above the fire door l4 and communicates with a downwardly inclined feed tube 29. This feed tube communicates with or extends through an opening 30 of the furnacevfront above the fire door l4, so that fuel fed through the tube may be deposited upon the outer end of the grate. A correspondingly inclined reciprocable plate 3! forms the bottom of the feed tube which, supplemented by the action of gravity, causes the fuel to be advanced in the tube. Reciprocation may be imparted to the inclined plate 31, as by means of a rock shaft 32 and levers 33 carried by the rock shaft and operably engaging the outer end of the plate. The rock shaft 32 may be oscillated by any suitable means such as by motion transmitted through the connecting rod 34 and the lever 35. If desired, the inclined plate 3i may be provided with one or more transverse shoulders 35 arranged to assist the feeding of fuel along the tube.

From the arrangement of fuel feeding means just described it will be seen, that when a quantity of fuel is placed in the hopper 28 it will be supported in part by the plate 3| forming the bottom of the feed tube. The inclination of the feed tube and the reciprocation of the plate 3! will cause the fuel to travel along the feed tube at a desired rate and substantially without clogging or obstruction and to be supplied to the outer end of the grate.

To supply power for the operation of the grate I! and the feed plate 31 I may employ an electric motor or other suitable power means. The motor employed in this instance is drivingly connected with a speed reducing mechanism 4! by means of a belt 42. The reduction gear 4! is provided with a crank 43 which is connected with an oscillating grate-operating shaft 44 by means of a. connecting rod 45 and a lever 46 mounted upon the adjacent end of the oscillating shaft. As shown in Figs. 1 and 2, the oscillating shaft 44 extends transversely of the furnace front just outwardly of the ends of the grate bars and may be supported upon the furnace front by suitable laterally spaced bearings 4! and 48. Motion is transmitted from the oscillating shaft 44 to the sets of grate bars by mechanism 49 which will presently be described in detail.

Before describing in detail the construction and operation of the grate actuating mechanism 49, I wish to explain briefly that the timed oper-- ation of the sets of grate bars consists in imparting movement to these elements such that both sets of grate bars move inwardly substantially simultaneously to move the fuel toward the inner end of the furnace and then the sets of grate bars are retracted independently of each other at spaced timed intervals preparatory to both sets of grate bars being again moved inwardly substantially simultaneously. LIIn the retracting movement of the sets of grate bars the set 20 is retracted first and the set 2! is retracted at a later interval. The set 20 is, therefore, referred to as the leading set and the set 2i as the fol-- lowing set.

As best shown in Figs. 5 to 8 inclusive the grate actuating mechanism 49 includes levers 5i and 52 which may be arranged on the transverse oscillating shaft 44 and which may, by means hereinafter to be described, be intermittently connected with the shaft to be driven or swung thereby. Each of these levers is constructed with an enlarged upper head part 53 through which the transverse shaft 44 extends and with spaced depending parts providing a pair of arms 54. The pairs of arms 54 are provided with openings accommodating transverse pins 55. The lever 51 is o-perably connected with the rocking arch 22, for the operation of the leading set of grate bars 20, by suitable means such as a connecting rod 5? having one end pivoted to the arch and its other end mounted on the pin Since the lever 5! is connected with and operates the leading set of grate bars 28 it may be referred to as the leading lever. The lever 52 is operably connected with the arch 23 by means of a similar suitable connecting rod 58 and since this level; is connected with the following set of grate bars it may be referred to as the following lever.

The enlarged head portions 53 of the levers 5! and 52 are of hollow construction so that each lever provides a substantially dust-proof chamber or casing 68 for certain cooperating power transmitting members. For the lever 5! these power transmitting members comprise a ratchet 62 which is nonrotatably mounted on the transverse shaft 44 and a pawl 63 which is pivoted on the lever for cooperation with the ratchet. The pivot for the pawl 63 is formed by a shaft G4 which projects outwardly of the casing or cham-- ber 60 so that the pawl may be actuated from the exterior of the casing. For the lever 52 the power transmitting members operable in its casing 60 comprise a ratchet 66 which is non-rotatably mounted upon the shaft 44 and a pawl 61 which is pivoted by being mounted upon a shaft 68 which extends exteriorly of the casing. In the casing of the lever 5| an abutment B9 is provided at a point spaced from the pawl E23, so that upon rotation of the shaft 44 in one direction the ratchet 62 will engage this abutment, and upon rotation of the shaft in the opposite direction the ratchet will engage the pawl 63. Similarly, an abutment 10 is provided in the casing of the lever 52 such that upon rotation of the shaft 44 in one direction the ratchet 66 will engage this abutment, and upon rotation of the shaft in the opposite direction the ratchet will engage the pawl 61. The levers 5i and 52 are preferably not mounted directly upon the shaft 44, but are journaled upon laterally extending sleeve portions of the respective ratchets E32 and so that oscillation of the shaft 44 may take place without imparting movement to the levers until the ratchets thereof engage either the abutments or the pawls, whereupon driving connection from the shaft to the levers is established.

The ends of the pawl shaft 64 of the lever 5| project outwardly at opposite sides of the casing (ill, and upon these ends are mounted the levers 12 and 13 for operation. of the pawl from the exterior of the casing. A tension spring '54 having one end anchored to the casing 68 and the other end connected to the lever 12 urges the latter in a direction to swing the pawl 63 into the path of movement of the ratchet 62. The lever 13, as shown in Fig. 5, is provided with a laterally projecting lug 15 which extends into the path of movement of a cam 16 provided on the exterior of the casing of the lever 52. One end of the pawl shaft 68 projects outwardly from the casing of the lever 52 and upon this projecting end is mounted a lever TI. A tension spring 18 (see Fig. 8) having one end anchored to the casing is connected with the lever 11 and normally urges the same in a direction to swing the pawl 61 into the path of movement of the ratchet 66.

Assuming now that the parts of the grate actuating mechanism 49 are in the relative positions shown in Figs. 6 and 7 and that the shaft 44 is oscillated or rotated in a counter-clockwise direction, it will be seen that the ratchets 62 and 66 will engage, respectively, the pawl 63 and theabutment 10. This action will result in both levers 5| and 52 being swung in a direction to transmit pushing force to the connecting rods 51 and 58 and will cause simultaneous inward movement of the sets of grate bars 20 and 2|. It is desirable that while this movement is taking place the pawl 61 be swung out of the path of movement of the ratchet 66, and for this purpose, I provide means whereby the movement of the pawl 61 into and out of power transmitting position is caused by the action of the other lever 5|. To this end I provide a countershaft 80 which may be rockably mounted in bracket plates 8| and 82 and extends in spaced substantially parallel relation with the shaft 44. A lever 83 mounted on the countershaft is connected with the lever 5| by a link 84, so that movement imparted to the lever 5| by the shaft 44 will cause oscillation of the countershaft 80. Another lever 85, mounted on the countershaft 80 (see Fig. 8) is connected with a member 86 so that oscillations imparted to the countershaft will cause reciprocation of the latter member. The member 86 is in the form of a lever having a cam part 81 at its free end for cooperation with a pin 88 projecting from the lever 11. The member 86 may be supported and guided in any suitable manner, such as by providing the same with a fork portion 89 which slidably straddles an auxiliary shaft 90. From the arrangement just described it will be seen that while the lever 5| is being swung in a counter-clockwise direction motion is transmitted through the countershaft 80 and the member 86 to cause the cam portion 81 to engage the pin 88 of the lever 11. This causes the lever 11 to swing in a direction to lift the pawl 61 out of the path of movement of the ratchet 66.

The purpose of lifting the pawl 61 out of the path of the ratchet 66 is to render the drive connection between the shaft 44 and the lever 52 ineffective during the next succeeding oscillation of the shaft 44, so that the following set of grate bars 2| will remain stationary while the leading set of grate bars 26 is being retracted. Following the counter-clockwise rotation of the shaft 44 mentioned above, this shaft is rotated in a clockwise direction, and since the pawl 61 has been moved out of the path of the ratchet 66 no drive connection for the lever 52 is established at this time. However, the clockwise rotation of the shaft 44 causes the ratchet 62 to engage the abutment 69 of the lever 5| and thereby cause the lever to be swung in a direction to exert a pulling force on the connecting rod 51 to retract the leading set of grate bars 28.

It is desirable that during the retracting movement of the grate bars 26 the pawl 63 be lifted out of the path of the ratchet 62, so that during the next succeeding oscillation of the shaft 44 there will be no driving connection to the lever 5|. For thus moving the pawl 63 out of the path of the ratchet 62 I have provided the cam 16 on the head portion of the lever 52. It will thus be seen that by this means I utilize the action of the lever 52 to cause the pawl 63 for the other lever 5| to be moved into and out of power transmitting position. While the lever 5| is being swung by the action of the ratchet on the abutment 69 to thereby retract the grate bars 20, the lever 52 remains stationary because of the pawl 61 having been lifted out of the path of the ratchet 66, as explained above, and the lug 15 of the lever 13 rides up on the cam 16 and thereby causes the shaft 64 to be rotated in a direction to lift the pawl 63 out of the path of the ratchet 62.

This same movement of the lever 5|, which causes the lug 15 to ride up on the cam 16, also causes the countershaft 80 to be rotated in a direction to cause the cam 8'1 to be retracted. The retracting of the cam 8! allows the tension spring '58 toact upon the lever 11, but at this time the ratchet 66 is beneath the pawl 61 which prevents the lever from being swung. However, upon the next succeeding oscillation of the shaft 44 which is a counter-clockwise rotation thereof, the ratchet 66 is moved out from beneath the pawl 61, allowing the spring 78 to cause the pawl to be moved inwardly behind the ratchet into the path of movement thereof. This last mentioned counter-clockwise oscillation of the shaft 44 is an idle stroke, because at this time both pawls 63 and 61 are being retained in their outer or lifted positions and the ratchets are then spaced angularly from the abutments 69 and 16.

The next succeeding oscillation of the shaft 44 is a clockwise rotation, and since the pawl 67 has been moved back into the path of the ratchet 66, it is immediately engaged thereby and a drive connection from the shaft to the lever 52 is thus established. The lever 52 is thereupon swung in a direction to exert a pulling force on the connecting rod 58 which causes the following set of grate bars 2| to be retracted. The clockwise rotation of the shaft 44 which results in the grate bars 2| being retracted, as just explained, does not impart any movement to the lever 5| because at this time the ratchet 62 is being moved back toward the abutment 69. The next succeeding oscillation of the shaft 44 is the counter-clockwise rotation first referred to above, which causes both sets of grate bars to be moved inwardly substantially simultaneously in the manner already explained.

Because of the frictional drag and possibly other factors, there is a tendency for the grate bars 2| to be retracted at the same time that the grate bars 20 are being retracted, and also for the lever 5| to swing in a counter-clockwise direction during the retracting of the grate bars 2|. It is, therefore, desirable to provide hold-back means for preventing such untimely retracting of the grate bars 2| and swinging of the lever 5|. For the lever 5| this hold-back means may be in the form of a bar 92 which is straddled by the arms 54 of this lever. Laterally extending abutments or stops 93 may be provided adjacent the outer end of this bar to be engaged by the parts 94 of the arms 54 upon the completion of the retracting movement of the grate bars 20. This engagement of the arms 54 with these abutments prevents the lever 5| from being rotated farther in a counter-clockwise direction during the retracting oscillation of the lever 52.

The hold-back means for the lever 52, may be in the form of a pivoted lever or pawl 95, a portion of which is adapted to be straddled by the arms 54 of the lever 52. The lever 95 is provided adjacent the outer end thereof with laterally extending shoulders or abutments 96 adapted to be engaged by the parts 91 of the arms 54 when the lever has been swung upwardly into the path of movement of these arms. The lever 95 is acted upon by a counterweight 98, or the equivalent, tending to swing the same upwardly to bring the abutments 96 into the path of the arms 54. During a part of the cycle of operation, however,- the lever 95 is held against such upward swinging movement by the engagement of the arcuate portions 99 thereof with the end faces I of the arms 54. When the lever 52 has been swung in a counterclockwise direction to a position such that the faces I00 clear the arcuate portions 99 of the lever 95, the latter swings upwardly under the influence of the counterweight 98 to bring the abutments 95 into the path of the parts 91. Upon return movement of the lever 52 the parts 9'! engage the abutments 96 and the lever 52 is thereby held against further swinging movement while the grate bars 20 are being retractd. The extent to which the lever 95 may be swung upwardly may be limited by lugs IOI which are provided thereon to engage the end faces I00 of the arms 54.

To permit swinging of the lever 52 to retract the grate bars H at the proper time after the retraction of the grate bars 20, it is necessary to swing the lever downwardly to move the abutments 96 out of the path of the arms 54 and for this purpose I provide a member I03 which is pivotally connected to, and actuated by, a lever I04 (see Fig. 8) having driving connection with the shaft 44. The lower end of the member I03 is provided with a fork-like part Hi5 which engages a laterally projecting pin I05 of the lever 95 to move the latter downwardly to the inoperative position mentioned above. It will be seen from the arrangement just described that the movement of the lever 95 to inoperative position is caused by a counter-clockwise oscillation of the shaft 44. It is desirable, however, that the lever 95 be moved to its inoperative position by the member I 03 only during the above-mentioned idle counter-clockwise oscillation of the power shaft 44, and therefore, I construct and arrange the parts such that the forked part !05 will enage the lug I 06 while the latter is in its elevated position as represented by the broken lines of Fig. 8, but will not engage this lug while it is in its lower position as shown in full lines in Fig. 8. To obtain this result I provide a laterally projecting lug I01 on the member 06 and a cam part I08 on the member I03. During the time that both sets of grate bars are being moved inwardly simultaneously the member E03 is being moved downwardly by the lever I04, but at this same time the member 86 is being actuated from the countershaft 00 to lift the pawl. 61. The lug I01 engaging the member I03 causes the latter to be swung toward the right, as seen in Fig. 8, so that the forked part I05 will miss the lug I05. The passage of the forked part I05 clear of the lug I06 in this manner may be facilitated by making the arm I09 of the forked part relatively short and by providing this arm with an inclined end face IIO. If desired, a tension spring III may be connected to the member I03 to normally hold the same against the lug I01.

Since, during the simultaneous inward movement of both sets of grate bars, the forked part I05 misses the lug I01 as just explained, the lever 95 will swing upwardly as soon as the arm portions 91 of the lever 52 clear the abutments 95. During the succeeding clockwise rotation of the shaft 44 which retracts the grate bars 20, the lever 95 will hold the lever 52 against retracting movement, and at this time the lever I04 lifts the member I03. The lifting of the forked part I05 and the action of the spring I I I cause the arm I09 to ratchet over the lug I05 which is then in its upper position. On the next counter-clockwise oscillation of shaft 44, which is the above-mentioned idle oscillation, the member I03 is again moved downwardly but at this time the lug I05 engages in the forked part I05 and the lever 95 is therefore now moved downwardly to its inoperative position preparatory to retracting of the grate bars 2| during the succeeding clockwise oscillation of shaft 44.

If desired, a manually operable control may be provided for rendering the grate operating mechanism inoperative. This control may be in the form of a hand crank I I2 which is mounted upon, and drivingly connected with, an extension of the shaft 90 so that by swinging the hand crank the shaft 90 may be oscillated. A curved lever H3 is carried by the shaft 90, as shown in Fig. 8, and is adapted to be swung thereby to engage the lug 88 of the lever TI to lift the pawl 61 out of the path of the ratchet 66. The bracket plate 82 may, if desired, be provided with arcuately spaced openings H4 in which a slidable locking pin II5 of the crank handle II6 may engage. It is desirable to prevent operation of the manual control at a time when movement of the pawl 61 into or out of the path of the ratchet 66 would cause incorrect operation or damage to the apparatus, and for this purpose I provide suitable inhibiting means for preventing manual operation of the control at such times. This inhibiting means may comprise a laterally projecting lug II! on the crank H2, and a stop II8 carried by the shaft 44 and shaped to be engaged by the lug I I1 during such part of the operating cycle when the pawl 61 is not to be manually engaged or disengaged.

I have referred above to the connecting rod 34 of the fuel feeding means being operated from any suitable source of power and, if desired, this member may have operative connection with the oscillating shaft 44, so that the fuel feeding means will be operated in timed relation to the actuation of the sets of grate bars. For this purpose I may provide the shaft 44 with a lever I20 with which the connecting rod 34 has adjustable connection. This adjustable connection may comprise a screw I2I mounted on the lever I20 and a nut I22 operable along the screw and to which the rod 34 is connected. By rotation of the screw I2I the position of the nut I22 relative to the axis of the shaft 44 may be varied to thereby vary the length of the stroke of the connecting rod 34 and thereby vary the rate of fuel feed.

Without attempting to summarize all of the advantages and novel features of my stoker mechanism, I wish to call attention to the fact that in the operation of the grate operating mechanism, as explained above, the movement of the pawls 63 and 6'! into and out of power transmitting cooperation with the ratchets takes place only while the pawls are not under load. This is an'important advantage, because it minimizes wear on the cooperating parts and thereby enables the apparatus to render prolonged efficient service. Further in this connection, it should be noted that the casings provided on the levers and 52 exclude ashes and other gritty foreign matter from the cooperating power transmitting parts and thus eliminate the destructive abrading action heretofore present in devices of this character. I

While I have illustrated and described the stoker mechanism of my invention in a somewhat detailed manner, it will be understood, of course, that I do not wish to be limited to these precise details of construction and arrangements of parts, but regard my invention as including such changes and modifications as do not constitute a departure from the spirit and scope of the invention herein disclosed.

Having thus described my invention I claim:

1. In combination, a plurality of sets of grate bars, a power shaft, a plurality of members journaled to rock about said shaft and corresponding in number with said sets of bars, said members each havinga chambered hub portion and a projecting arm, means connecting the arms of said members with the respective sets of bars, and means housed in said chambered hub portions and operable therein for intermittently establishing a driving connection between said shaft and said members.

2. In combination, a pair of sets of longitudinally extending grate bars, a transverse power shaft mounted for rocking about its own axis, a pair of members journaled to rock about said shaft, said members each having a chambered hub portion and a projecting arm, means connecting the arms of said members with said sets of grate bars, means for actuating said shaft, and means for intermittently establishing a driving connection between said shaft and said members including cooperating parts contained in said chambered hub portions.

3. In combination a plurality of sets of grate bars, a, power shaft mounted to rock about its axis, a plurality of members mounted to oscillate about said shaft and corresponding in number with said sets of bars, said members each having a chambered hub portion and a lever portion, means connecting the lever portions of said members with the respective sets of bars, means for oscillating said shaft, and means for intermittently establishing a driving connection between said shaft and said members including a pair of abutment elements contained in the hub chamber of each member and ratchet elements on the shaft and extending into the hub chambers for cooperation with the abutment elements therein.

4. In apparatus of the character described the combination of a grate comprising a pair of sets of longitudinally movable grate bars, a transverse shaft adjacent one end of the grate and mounted to rock about its axis, means for oscillating said shaft, a pair of levers each having an opening through which said shaft extends and a chamber therein adjacent the shaft opening, means operably connecting said levers with said sets of bars, and means adapted to intermittently establish connections for causing oscillation of said levers by said shaft including cooperating parts carried respectively by the shaft and the levers and operable in the chambers of the latter.

5. In a grate operating mechanism, a grate, an operating shaft, a member oscillatable on said shaft and operably connected with said grate, means for intermittently connecting said member for actuation by said shaft, and easing means carried by said member in surrounding relation to the connecting means and adapted to exclude foreign matter from said connecting means.

6. In a grate operating mechanism, a grate, an operating shaft, a dust-proof hollow casing into which said shaft extends, means operably connected with said grate and with said casing at a point eccentric to said shaft for transmitting motion to the grate, means for driving said shaft, and means in said casing for intermittently connecting the same with said shaft.

7. In a grate operating mechanism, a grate comprising a pair of sets of grate bars, an operating shaft, a pair of hollow casings into which said shaft extends, means mounting said casings side by side to swing in substantially parallel planes about said shaft, means connecting said sets of bars with the respective casings at a point eccentric to the axis of said shaft, and means in each casing adapted to releasably connect the same for actuation by said shaft.

8. In combination, a grate comprising a pair of sets of movable grate bars, a power shaft, means associated with each set of bars and providing a releasable drive between the same and said shaft, and means actuated by the drive means for one set of bars for rendering the drive means for the other set of bars effective and ineffective as an operating connection between said shaft and said other set of bars.

9. In combination, a grate comprising a pair of sets of movable grate bars, an oscillating power shaft, means providing a releasable driving connection between one set of bars and said shaft, and means providing a releasable driving connection between the other set of bars and said shaft, the driving means for one set of bars being rendered effective and ineffective as an operating mechanism between said shaft and said one set of bars by action of the driving means for the other set of bars whereby said sets of bars are actuated in timed relation to each other.

10. In combination, a pair of sets of grate ele ments, an oscillating power shaft, a pair of levers on said shaft connected respectively with said sets of grate elements for actuating the latter, each of said levers having a chamber and a pair of spaced abutments thereon in such chamher, and ratchet-like means on said shaft extending into the chambers and between the abutments on each lever and adapted to drivingly engage one abutment upon rotation of the shaft in one direction and to drivingly engage the other abutment upon rotation of the shaft in the opposite direction.

11. In combination, a movable grate structure, an oscillating shaft, a lever on said shaft, said lever being provided with a chamber adjacent the shaft, means connecting said grate structure for actuation by said lever, a pair of abutments on said lever in the chamber thereof, and ratchet-like means on said shaft and extending into said chamber for driving engagement with one abutment on rotation of the shaft in one direction and for driving engagement with the other abutment on rotation of the shaft in the opposite direction, one of said abutments being movable into and out of position to be engaged by the driving means of the shaft.

12. In apparatus of the character described the combination of a pair of sets of movable grate elements, an oscillating shaft, a pair of levers connected respectively with said sets of grate elements, and means associated with each lever for providing a releasable driving connection between the same and said shaft, each lever being provided with a substantially dust-tight chamber formed as an integral part of the lever and in which its releasable driving means is disposed.

13. In apparatus of the character described the combination of a pair of sets of movable grate elements, an oscillating shaft, a pair of levers connected respectively with said sets of grate elements and each being provided with a chamber, means on said shaft extending into the chambers of said levers for transmitting motion to the levers from the shaft, and abutments in said chambers adapted to be engaged by the last mentioned means including pawls movable into and out of position to be engaged by said means.

14. In apparatus of the character described the combination of a pair of sets of movable grate elements, an oscillating shaft, a pair of levers on said shaft connected respectively with said sets of grate elements and each being provided with a chamber, means on said shaft extending into the chambers of said levers for transmitting motion to the levers from the shaft, abutments in said chambers adapted to be engaged by the last mentioned means including pawls movable into and out of position to be engaged by said means, and means arranged to be actuated by movement of each lever for actuating the pawl of the other lever.

15. In apparatus of the character described the combination of a plurality of sets of reciprocable grate elements, said sets being arranged for substantially simultaneous forward movement and individual retracting movement, an oscillating power shaft, a pair of levers on said shaft and having connection with the respective sets of grate elements, each of said levers being provided with a chamber, means housed in the chambers of the levers and operable for intermittently establishing a drive connection between the shaft and said levers for causing forward and retracting movement of the sets of grate elements in timed relation, and means for preventing retracting movement of one or said levers during the retracting movement of the other.

16. In apparatus of the character described the combination of a movable grate structure, an oscillating power shaft, means for transmitting motion from said shaft to said grate structure including a pawl, manual means for causing movement of said pawl into or out of operative position, and means carried by said shaft and movable thereby into position for rendering said manual means inoperative during a portion of the operating movement of said shaft.

GEORGE VON HAASE.

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