US2319935A

US2319935A - Automatic stoker

Info

Publication number: US2319935A
Application number: US270619A
Authority: US
Inventors: Nathan M Lower
Original assignee: Individual
Current assignee: Individual
Priority date: 1939-04-28
Filing date: 1939-04-28
Publication date: 1943-05-25
Anticipated expiration: 1960-05-25

Description

May 25,1943?- N. M. LOWER 2,319,935

AUTOMATIC STOKER INVENTOR NATHAN M. LowEa 1. 'l ATTORNEYS N. M; LOWER AUTOMATIC STOKER Filed April 2e, 1959 May 25, 1943.

6 Sheets-Sheet 2 |NvENToR N N NATHAN M. LOWER H .i Y f 9M 5M". Q J/MMM' Y Nrw LI] /ATToJEYs May 25, 1943.

N. M. .OwER

AUTOMATIC STOKER.

Filed Apr'il 28, 1959 Y MLowgn' Wham/w ATTORNEYS 6 Sheets-Sheet 5 INVENTOR May 25, 1943. N. M. LOWER AUTOMATIC STOKER Filed April 2s, 1939` 6 Sheets-Sheet 4 INVENTOR NATHAN M.`I .owEx

ATIJ'ORIS May 25, 1943. VN. M. LOWER 2,319,935 i AUTOMATIC STOKER Filed April 2s, 1939 e sheets-sheet Fic-'1a.

Fcfl ISZJ /53 Z 164 )I6/I la? fw/ Furl?. o

IINVENTOR. [50 NATHAN M. LOWER BY gwwn//fmyr/MZL ATTORNEYS May 25 1943. N..M. LOWER 2,319,935

AUTOMATI C `STOKER Filed April 28, 19:59 6 sheets-sheet 6 H5 1 .1.2L Z0 1 l 1w 103 f 100 r :1 .l 1 123 :lA-f i f '14 INVENT OR. NATHAN M. LOWER ATTORNEYS Patented May 25, 1943 UNITED STATES PATEN' OFFICE AUTOMATIC STGKER Nathan M. Lower, Erie, Pa.

Application April'ZS, 1939, Serial No. 276,519

(Cl. llt-104) zt cranes.

This invention relates generally to mechanical stokers for delivering fuel from a source of supply to a furnace frebox, and more particularly to stokers of the type employing pneumatic fuel conveying means.

It is an object of the invention to provide a novel stoker, of the type in which fuel i's pneumatically conveyed, that is automatic in operation, easily installed, economical, and reliable in operation. i

Another object of the invention is to provide a novel stoker of the type described in which the fuel is preheated by a carrier fluid withdrawn from the furnace.

In such stokers difficulty has been experienced in the past in conveying Wet coal and particularly wet coal containing a large amount of slack Since even a very small percent of water in the coal gradually clogs the elbows in the fuel pipe and eventually the straight sections of the pipe. Local heat applied at the elbows will maintain thatl individual area clean but will not prevent eventual clogging of other sections of the pipe. It is consequently another object of my invention to provide an improved and simple stoker construction in which wet coal containing a considerable amount of slack can be pneumatically conveyed in a convenient and eiiicient manner.

Clogging of the fuel feed pipes is particularly troublesome where the bin is of necessity a conslderable distance from the furnace and it is a further object of my invention to provide a simple and efficient construction which will eliminate clogging where wet coal is pneumatically conveyed through a coal feed pipe of considerable length.

Another object of my invention is to provide simple and effective means for insuring a continuous supply of fuel from a fuel bin to a stoker trough disposed therebeneath, in which trough is provided conveying means for advancing the fuel therethrough. Coal will when slightly damp arch over the conveying means or in some cases a chasm will be formed above the conveying means, and the coal in the bin on either side of the conveying means willremain dormant. It is, therefore, an additional object of the invention to provide means that will render the fuel in the bin that is beyond the immediate zone of action of the conveyor available to the conveyor.

Still another object of the invention is to prO- vide in a stoker for conveying fuel from a fuel bin to a furnace, means eliminating dust in the fuel bln and. leakage of dust from the stoker.

Another object of the invention is to provide novel means automatically interrupting the operation of the motor for the mechanical fuel conveying means of the stoker when a clog occurs and to provide means signalling cessation of the stoker conveying means.

Another object of the invention is to provide means for automatically interrupting the operation of the motor for the fan of a pneumatic fuel conveying mechanism when a clog occurs in the fuel feed piping.

Still another object of the invention is to p'rovide a novel combination and arrangement of elements for automatically operating a stoker intermittently.

Another object of the invention is to provide a novel aperiodically operated stoker of the type in which fuel is pneumatically conveyed, that will eiciently Vconvey wet fuel without clogging of the fuel tube.

Another object of the invention is to provide a novel coal feeding pipe, having a movable section arranged to be swung out of axial alineme'nt with the stationary sections of the coal feeding pipe and having means eliminating leakage of coal dust between the adjacent ends of the movable coal pipe section and the stationary sections of the coal pipe.

Other and further objects and advantages of the invention, residing in the construction of parts, the combination and relation of 'elements will become apparent from the following description when read in connection with th'e accompanying drawings, in which Figure 1 is a View in elevation of a furnace and fuel bin showing the novel stoker applied thereto, parts being broken away and shown in section;

Figure 2 is a plan view of a portion of the stoker fuel feed tube and the pipe for withdrawing het gases from the furnace, parts being broken away;

Figure 3 is an isometric View of a portion of the stoker fuel tube provided with a movable section and including a novel arrangement for elimina-ting leakage of fuel dust;

Figure 'i is a sectional plan View of the fuel bin and stoker taken on the irregular line fl-fl of Figure l Figure 5 is a sectional View taken en the line 5-5 of Figure 4;

Figure 6 is a sectional view taken on the irregular line 6 6 of Figure 4, parts thereof being shown in elevation;

Figure '7 is a sectional view taken on the line 1 -1 of Figure 4;

Figure 8 is a sectional view on the line 8-8 of Figure 4, parts thereof, being shown in elevation;

Figure 9 is a sectional view taken on the line 3--8 of Figure 8, parts being shown in elevation;

Figure 10 is a fragmentary sectional view of the construction shown in Figure 9 in a different phase of its operation;

Figure 11 is a sectional view taken on the line II-II of Figure 4;

Figure 12 is a sectional view taken on the line I2-I2 of Figure 4;

Figure 13 is a sectional enlarged view of the stoker clog control mechanism shown on Fig- Figure 14 is a sectional view on the line I4-I4 of Figure 13 with the electrical connections to a motor shown diagrammatically;

Figure 15 is a view of the control mechanism shown in Figure 13 in a different phase of its operation;

Figure 16 is a fragmentary sectional plan view of a modified form of the stoker drive mechanism shown in the preferred form of the invention; and

Figure 17 is a sectional view taken on line I 'I-I I of Figure 16 showing the drive mechanism in detail and a control mechanism therefor, the electrical connections being shown diagrammatically.

In the drawings, referring to Figure 1, a furnace is shown at F, which for purpose of illustration is shown with a pair of redoors II and I I; and a pair of downcomer coal delivery pipes I2 and I2; entering the furnace above the level of the doors II and II; respectively. As the description proceeds it will become apparent that the invention is equally applicable to a furnace having one, or more than two separate fuel entrances, or to a battery of furnaces. A fuel bin is shown at B, from which the novel stoker S delivers fuel to the furnace F.

The bin B may be of any desirable shape, that shown in the drawings being by preference, cylindrical. The bottom I3 of the bin is preferably disposed above the level of the furnace room fioor Ill, thereby making certain mechanism on the underside of the/bottom I3, hereinafter described in detail, freely accessible. Preferably the bin bottom I3 is in the form of an iron casting, since an iron casting is cheap to make and does not rust. It is provided with'a depending elongated trough I4 integrally formed therewith. The

trough I4 is arranged to receive coal from the' bin B and as best shown in Figure 4 is disposed to one side of the center of the bin bottom I3. It is obvious, of course, that the trough I4 could if desired be formed as a separate casting or as a fabricated member and be secured in any suitable manner to the bin bottom I3.

For convenience in description and denite orientation of parts, the terms forward and front, and rearward and rear will be used Yrelative to the direction of travel of the coal from the bin to the furnace. The trough I4 is open at its forward end and registers with an opening I5 in the upright wall I6 of the bin B, as best shown in Fig. 6. Embracing the opening I5 is a compartment or box Il which is secured in any suitable manner to the outer surface of the upright wall I6 of the fuel bin B. The wall of the compartment I1 opposite the opening I5 is provided with an opening I8 arranged to receive one F end of a conduit I3. The conduit I9 extends forwardly from the compartment I'I in axial alinement with the trough I4 and is supported at its forward end in any suitable manner on the furnace room floor I5 and at its rearward end on a platform 20 secured to the compartment Il. The supports for the respective ends of the conduit I9 are preferably provided with the vibration dampers 2l. A dust tight seal 22 of any suitable form is provided at the point of entrance of the conduit I9 into the compartment I'I.

Coal entering the trough I4 is conveyed forwardly therethrough into the compartment I'I by a screw conveyor 23 mounted in the trough I4 and extending through the opening I5 into the compartment I'l. A screw conveyor 24, of larger diameter than the screw conveyor 23, is spliced to the forward end of the screw conveyor 23 as at 25 and conveys the fuel from the compartment I1 forwardly through the conduit I9 to a discharge opening 26 near the forward end of the conduit I9. rIhe screw conveyor 24 is provided at its foiward end between the discharge opening 25 of the conduit I9 and its forward end with a reverse flight 2T, best shown in Fig. 7. The reverse flight 21 loosens the coal, preventing packing thereof at the forward end of the conduit I9 and aids in urging the coal through the discharge opening 26.

The coal screw conveying system, comprising the spliced screw conveyors 23 and 24, is driven from its forward end through gearing housed in the gear casing 28, which casing is rigidly secured to the forward end of the conduit I9. dust seal 29, of any suitable design, is provided in the forward end of the conduit I9 between the end of the reverse flight 2'I and the gear casing 28 to prevent coal dust from entering the gearing. The gearing includes a gear 30 splined on a short shaft 3|, which in turn is operatively connected with the hub of the screw conveyor 24.

The bin B is provided with means operatively connected with the rearward end of the screw conveyor 23 for insuring a continuous supply of coal to the trough` I4 and for completely emptying the bin. Goal, particularly when it contains an appreciable amount of slack, will not when damp flow freely into the trough I4. The coal arches over the screw conveyor or in some instances a chasm will be formed in the coal above the screw conveyor. In the novel construction shown in the drawings, reference being had particularly to Figs. 4 and 6, the bin bottom I3 is provided centrally thereof with a vertically extending bearing 32 in which is rotatably mounted a shaft 33 extending above and below the bin bottom I3.

Secured to the shaft 33 within the bin B are a number of laterally extending arms spaced a little distance above the bin bottom I3. Four arms, numbered 34, 35, 36, and 31, at right angles to each other extending successively greater distances away from the shaft 33, are shown in the drawings. The revolving

arms

34, 35, 36, and 31 prevent the formation of an arch or chasm in the coal, permitting it to fall freely into the trough I4 and also push coal that rests on the bin bottom into the trough. The screw conveyor 23 takes more coal away from the rearward por#- tion of the bin B than from its forward portion, so that another purpose of the

arms

34, 35, 36 and 37 is ,to continuously push coal from the forward portion of the bin to the rearward portion thereof preventing depletion of coal in the rearward portion of the bin. For purpose of illustration, four rotating arms have been shown, however, where the moisture content of the coal is not excessive, fewer arms will function satisfactorily and less power is required to operate them,

In order to effect a continuous delivery of coal to the trough I4 it is only necessary that the

arms

34, 35 and 3i revolve very slowly and for this purpose the drive mechanism from the screw conveyor 23 to the shaft 33 includes speed reduc- .ing mechanism, best shown in Figs. 4, 6 and 12. The screw conveyor 23I is provided with an extended shait portion 33 mounted in a bearing 39 formed with the rear wall of the trough I4 and projects rearwardly therethrough. Secured to the projecting portion of the shaft extension 38 is a crank arm 4!) having a pin 4I projecting rearwardly from its free end and on which pin is loosely mounted a block 42. One end 43 of a transversely extending rod 44 is attached to the block 42 so that reciprocating movement is transmitted to the rod 44 by the screw conveyor 23 through the medium of the shaft extension 38, crank arm and block 42.

The other end 45 of the rod 44 is attached to L a block 45 which is mounted on the free end oi an arm 41 of the pivotally mounted bell crank lever 48. The bell crank lever 48 is mounted for rotation on the vertical shaft 49 which is supported in a sleeve 5G depending from the under side of the bin bottom I 3. A rod 5I is pivotally attached at one end to the free end of the other arm 52 of the bell crank lever 48. The free end of the rod 5I carries a pin 53 engaging the teeth of a large ratchet Wheel 54 fastened to the shaft 33, and a spring 55 holds the free end of the rod 5| against the ratchet wheel 54. Thus, reciprocating movement of the rod 44 oscillates the bell crank lever 43 which in turn transmits reciproeating movement to the rod 5I. The reciprocatingr movement of the rod 5I causes the ratchet wheel 54 to turn a fraction of a revolution which in turn through the shaft 53 causes the arms 3'4, 35, 35 and 3'! to turn a small part of one revolution.

Coal is discharged by the screw conveyor 24 through the discharge opening 26 of the conduit I9 into an upturned arm of a duct 56 leading from a fan casing 51. From the duct 55, the coal is pneumatically conveyed through a coal tube 53, by means hereinafter described in detail, to the branch fitting 59 where the stream of coal is divided and delivered to the downcomers I2 and I2. The branch fitting 59 is provided with a pivotally mounted vane 6U arranged for convenient adjustment by a handle 6I to vary the relative amounts of fuel delivered to the downcorners I2 and I2.

Since the coal is pneumatically conveyed through the coal tube 58, there is a tendency for some of the carrier fluid to blow through the opening 26 and the conduit I9 and raise considerable dust in the bin. This is of course objectionable and the stolzer is therefore designed to prevent this condition. The screw conveyor 23 can yhe made somewhat smaller in diameter than the screw conveyor 24, for example in a ratio of 3 to since the screw conveyor 23 is working in a body of coal and will convey a greater quan tity than its rated capacity. A plate 62, the lower edge of which is formed on an arc, is mounted against the inside surface of the upright wall of the bin B above the screw conveyor 23 for vertical adjustment to permit regulation of the size of the opening I5. The size of the opening I5 is regulated to keep the portions oi the screw conveyors 23 and Z4 within the cornpartinent I1 completely filled with coal. With the opening I5 adjusted as described and with the backward slipping of the coal down the inclined .'f casing 64 into the mixing box 59.

flight of the screw conveyor 24 the conduit IS is filled with coal and forms an effective seal against the blowing back of the carrier iiuid through the conduit I9.

For convenient installation of the Stoker it may be necessary to provide bends such as at B3 in the coal tube 58 and downcomer pipes I2 and I2. In the preferred installation overhead piping is shown through which the coal is pneumatically conveyed, however, it will be apparent that the piping can be made to extend beneath the furnace room floor to the furnace, il desired.

In the past difficulty has been experienced in pneumatically conveying wet coal and particularly wet coal containing a large amount of slack, since even a very small percent of water in the coal gradually clogs the elbows in the fuel pipe and eventually the straight sections of the pipe. This diculty has been eliminated Iby convenient and efficient means in the presont construction. A substantial portion of the coal tube 58 at that end receiving coal from the conduit I is enclosed by a casing $4 which communicates with the pipe l65 leading from the breeching 55 of the furnace F. An elbow 57 swivelly mounted on the casing 54 for movement about the vertical shaft 68 provides communication between the casing 54 and the pipe 55.

The lower end of the casing S4 communicates with a mixing box 69 through a |passage It, and a passage 1I provides communication between the mixing box 59 and an intake port of a small or auxiliary fan 12 which is operated by a small motor 73. The discharge port of the fan 'I2 communicates through a passage 'I4 with the intake port of a larger or main fan 'i5 housed in the fan casing 57 and operated by a large motor` 15. The small or auxiliary fan 'I2 is not essential to successful operation of the stolier and could be omitted, however, the advantages thereof will be hereinafter explained.

The fans i2 and i5 draw hot stack gases from the breeching 55 through the pipe 65 and the In traversing the casing 64, the hot stack gases heat the coal tube 58 thereby drying the wet coal passinsT through the coal tube 58 and preventing clogging of the coal therein.

The bottom of the mixing box 8S is open to atmosphere as shown at l?, and the fans 'l2 and i5 draw air into the mixing box E3 where they are mixed with the hot stack gases, the mixed gases then are drawn through the fans f2 and 'i5 and discharged from the fan l5 into the duct 56. The mixture of stack gas and air blown through the duct 55 pneumatically conveys the coal entering the duct 55 through the opening 25 upwardly into the coal tube 53 and thence to the furnace. Thus, when wet coal is being delivered from the conduit I 3, the heated mixture of air and stack gas dries the coal preventing adherence to the coal tube 58 and eventual clogging thereof.

The mixing box B9 is provided with a horizontal partition i8 extending partially across the mixing box between the hot stack gas and cold air admission ports. A vane iii, rigidly secured to a horizontal shaft Si) extending through the Opposite Upright side walls of the mixing box, is arranged for adjustment to any desired position about a horizontal axis by turning the hand wheel 8i. By adjusting the vane 19, hot stack gases and cold air can be admitted to the fan 12 in any desired proportions to obtain the de'- sired temperature.

The screw conveying system, consisting of thc screw conveyors 23 and 24|, as stated before, is operatively connected to gearing housed in the gear casing 28. The motive power for operating the screw conveying system is supplied by the motor 16 which also operates the fan 15. The drive connections between the motor 1S and the gear 35 in the gear casing 28, including means for sounding an alarm if the screw conveying system should stall, will now be described in detail, reference .being had particularly to Figs. 4, '1, 8, 9 and 10.

Within a sleeve 82, extending laterally from the gear casing 2S, is mounted a shaft 83 carrying a worm 84 meshing with the gear 3U. A portion of the shaft 83 projects beyond the sleeve 82 and on the projecting portion is loosely mounted a pulley 85 whichxis rotated by a belt 85 from the motor 15. Also mounted on the projecting portion of the shaft 83 and keyed thereon, as at 81 in Figure 9, is a disc 88. The disc 88 is provided with a pin 89 extending laterally from a side face of the disc near the periphery thereof, on which pin is rotatably mounted a hook 98. The hook 88 engages a pin 9| extending laterally from the pulley 55 between the periphery and the center thereof so that the pin 9| revolves with the |pulley 85 about the axis of the latter. Rotation of the pulley 85 causes, through engagement of the pin 9| b-y the hook 98, rotation of the disc 88, which in turn, through being keyed to the shaft 83, rotates the latter, and rotation of the shaft 83 is transmitted through the gearing in the gear casing 26 to the screw conveyor 24.

The depth of engagement of the .pin 9| and hook 90 is such that any load short of stalling of the conveying system, 4will not cause disengagement of the pin 9| and hook 98. The depth of engagement, however, is such that when the conveying system stalls, consequently stopping the disc 88, the pin 9| is forced from engagement with the hook 95 permitting the pulley 85 to idle on the shaft 83 and thereby preventing the motor from burning out.

In connection with the safety release mechanism just described, an alarm device is provided warning the attendant that the coal conveying screw has been disconnected from the motor. The attendant, after releasing the clog in the coal conveying screw, can manually reengage the pin 9| and hook 88 whereupon the coal conveying screw is again in operative re lation with the motor 16.

The alarm device, referring particularly to Figures 8, 9 and 10, includes a lever 92, pivotally attached between its ends to the hook 9U, and having an arm 93 and a hammer arm 94. The lever 92 is normally held in position relative to the hook 98, as shown in full lines in Figures 9 and 10, by a spring 95 which holds the lever arm S3 in contact with the stop member 96 of the hook Si), When, by reason of the stalling of the coal conveying screw, the pin 9| is disengaged from the hook 88, as described before, a spring 91 pulls the hook 88 about'its pivot 89 from its normal position to the position shown in Figure 10 and as also shown in dot and dash in Figure 9, against the stop member 98 of the disc 88. With the hook 99 in this latter position, the lever arm 93 lies in the path of the pin 9| which is still free to revolve with the pulley 85. In its travel, the pin 9| depresses the lever arm 93 against the tension of the spring 55 thereby raising the hammer arm 94. After the pin 9| has passed over lever arm 93, the spring 95 returns the lever 92 to its original position causing the hammer arm 84 to strike the bell plate 99. Thus, each revolution of the pin 8| will cause the bell plate 99 to sound, warning the attendant that the coal conveyor screw has stalled. After removing the clog in the coal conveyor, the attendant can reset the alarm device manually.

As fully explained above, the stoker is designed to prevent clogging of the fuel feed tube 58 when wet coal is pneumatically conveyed. However,

'should a clog occur for some reason when very wet coal is being conveyed, or in starting the st'oker when the coal tube is cold, the stoker is designed to automatically take care of such emergencies in the manner now to be described.

A clog control mechanism |82 is secured in any convenient place, it being shown secured to the casing 64 in the drawings, see Figure 1. The clog control mechanism, referring particularly to Figs. 13, le and 15, includes a casing |83 having a port |84. A pipe |85, see Fig. 1, connects the port |84 with the fan casing 51 providing communication therebetween. Normally the clog control mechanism is in the position shown in Fig. 13, however, when a clog occurs in the coal tube 58, pressure builds up in the casing 51 of the fan 15, which is communicated through the pipe |85 to the casing |83 of the clog control mechanism |92, and the clog control mechanism will assume the position shown in` Fig. 15. Increase in pressure in thecasing |83 raises the flexible diaphragm |86, causing the member |81 to raise the forked lever |88 about its pivots |88. The free end of the forked lever |08 carries a contact bar ||l normally connecting the contacts and i2 in the motor circuit I3. A spring |4 causes the forked lever |88 to snap rapidly upward upon being raised by the member |81 thereby preventing sparking between the Contact bar Il] and contacts and ||2. Raising of the contact bar I8 of the forked lever |08 due to increase in pressure against the flexible diaphragm |06 breaks the motor circuit |3 causing the motor 16 to stop, thereby interrupting operation of the main fan 'l5 and the coal conveying screws 23 and 24.

Upward movement of the member |01 raises a stem |55 which is provided with a piston ||6 working in a cylinder ||1. When the member |01 drops back to the position shown in Fig. 13 due to the pressure against the under side of the diaphragm |85 being relieved, the spring I8 acting against the piston ||B forces the stern ||5 down, the stern ||5 in turn forcing the forked lever |88 down against the tension of the spring |l4, so that the motor circuit ||3 will again be closed. The piston ||i working in the cylinder lil, in conjunction with the ball check |88 prevents too rapid descent of the stem 5.

When the motor 15 stops, thereby stopping the fan 15, the pressure in the fan casing 51 will be rapidly dissipated, even before the clog in the coal pipe 58 has been relieved, so that the forked lever |88 would be forced down, closing the motor circuit I I3 and starting the fan 15 and the screw conveyors ":3 and 24 before the clog is relieved. The clog control mechanism is therefore provided with Ineans preventing the intermittent starting and stopping of the motor 1S while the coal tube 58 remains clogged.

This means includes a pawl ||5 arranged to engage a notch |28 in the portion of the Stem projecting through the top wall of the clog control casing |63. When the stem I I5 is raised due to pressure against the under side of the diaphragm |05, the pawl IIS will engage the notch |20, thereby holding the stem in its raised position even though the pressure against the diaphragm Hit is subsequently relieved, and thereby also preventing downward movement of the forked contact lever |53 and closing of the motor circuit IIS.

In the event of a clog in the coal tube 58, the cessation of operation of the main fan I5 andthe screw conveyors 23 and 24, by the clog control mechanism just described, does not aiect the running of the auxiliary fan l2 which is operated by the separate motor 13. The auxiliary fan 'I2 continues to discharge hot stack gases which after a time dry out the coal tube 58 and the plastered coal scales orf and is blown into the furnace.

In order that the ian 'IS and the screw conveyors 23 and 2A may not remain idle for an extended period after the auxiliary fan I2 has dried out the coal tube and relieved the clog, means is provided that periodically, as for example every 30 minutes, attempts to start` the moto-r iii. This means includes a time interval contactoi` 42|. The details of the time interval contactor |2i are not shown or described since such devices are well known, it being suiiicient to state that this device functions to close an electric circuit |22 at periodic intervals, as for example every 30 minutes. At the stated periodic intervals, the contact arm |23 of the time interval contacter B2i closes the circuit |22 operating a solenoid IM, which raises a lever |25 releasing the pawl H9 from the notch |2 in stern |I5. Release of the pawl IIS permits the stem ||5 to descend, thereby forcing the forked contact arm |03 down, in turn closing the motor circuit II3 and placing the fan 'I5 and the screw conveyors 23 and 2li operation. If the clog has not been relieved by the auxiliary fan 12, pressure will again build up beneath the flexible diaphragm Hit, raising the stem ||5 and causingv re-engagement of the pawl IIE! in the notch IZB. The Stoker will then again be inoperative, except for the auxiliary fan "I2, until the contact arm |23 again closes the circuit |22.

In many cases it is not necessary to operate the stoker continuously, sufficient fuel being delivered to the furnace by operating the stoker for a predetermined length of time at periodic intervals. To accomplish this, operation of the motor 'I6 may be controlled through a circuit arranged to be opened and closed through another contact arm on the time interval contactor I2I. As stated before, when the motor I6 is cut out of operation, thereby stopping the main fan l5 and the coal conveying screws 23 and 24, the auxiliary ian 12, operated by the rnoto1` "i3, continues to function.

With control mechanism, such as that;v described, Ior intermittently operating the Stoker, it is evident that the auxiliary fan 'I2 maintains va circulation of hot stack gases through the coal tube 53 during the "oiT periods of the Stoker, thereby preventing cooling of the coaltube 58 and consequent adherence of wet coal thereto when the Stoker is again placed in operation. It is apparent, therefore, that the present invention greatly minimizes the possibility of` clogs in the coal tube when the stoker is operated intermittently. It is also apparent that the device will function in the same manner with other well known types of controls that can be arranged to cause intermittent operation of the motor l5.

The invention has been described in connection with the pneumatic conveying of wet coal since it is particularly adapted to successfully convey such coal. When dry coal is being conveyed the tendency for coal to clog in the coal tube 58 is very remote so that it is not essential to utilize the hot stack gases as a carrying fluid for the coal. In such cases the vane or valve T9 in the mixing box (i9 can be adjusted to a vertical position thereby interrupting the passage of hot stack gases through the mixing box 59 to the ian i2. When conveying dry coal, the motor I3 which runs the auxiliary' fan l2 can be out out of operation, since there is no tendency for the coal to clog in the coal tube 58 and there is, therefore, no necessity for maintaining a circulation of hot stack gases through the coal tube at any time Whether the large fan I5 is in operation or is rendered inoperative by reason of the intermittent operation of the Stoker. When the auxiliary fan 'l2 is cut out of operation, the large fan 'I5 draws in carrier luid from the mixing box 69 through the blades of the auxiliary fan 72.

When conveying dry coal, it is not essential, as explained in the preceding paragraph', to utilize the hot stack gases as a carrier uid. It is, however, advantageous to do so, since the hot stack gases preheat the coal, sol that the nner particles are in a condition for instantaneous combustion upon entering the furnace, thereby greatly minimizingstack loss. The temperature of the carrying uid can be regulated by adjusting the Vane 'I9 in the mixing box The carrying iuid has in practice attained a temperature of about 400 F. and as is well known preheating of coal produces changes in the physical structure of the coa-l rendering it in a better condition for cornbustion.

Since in my novel stoker, coal is pneumatically conveyed, provision has been made against escape of coal dust to the atmosphere at such places where leakage is apt to occur. A pipe |25 leads from the compartment or dust box Il to the intake side of the fan T2, thus maintaining a suction inthe dust box II and withdrawing the coal dustv therefrom through the pipe |26. This coal dust mixes with the air and hot gases that are drawn through the Stoker by the fans 'I2 and i5 and is discharged therewith into the coal tube 58 and thence into the furnace. A pipe |21 leads from the dust sealV 2'9- to the dust box and another pipe |28 leads from thel dust seal |23, disposed about the shaft |36A of the motor i6 where it enters the casing 5l of the fan l5, to the dust boxl AV clean out door iSI is provided in the duct through which foreign material in the coa-l' that is too heavy to be pneumatically conveyedcan be removed.

The suction in the casing 04 will withdraw any coal dust that works its way into the grooves |44 and |45 atthe adjacent ends of the tube portion |32 and the coal tube 50.

In Figures 16 and 17 is shown a modification` of a portion of the preferred form of the stoker. in the preferred form of the invention, it will be recalled, when the screw conveyors 23 and 24 stall, the mechanism shown in Figs. 8, 9 and 10 l clutches out the screw conveyors and sounds an alarm, the motor i6 and consequently fan l5, however, continue to run. In the modified form of the invention, when the coal conveyor screws stall, the motor |50, corresponding t0 motor i6 of the preferred construction, is cut out of operation thereby shutting of the main fan as well as the coal conveying screws. As in the preferred `construction, a belt |5l runs from the motor |50 to a pulley |52. The pulley |52 is keyed to' the transversely extending shaft |53, the end of the shaft |53 remote from lthe pulley |52 extending into a gear casing |54, corresponding to the gear casing 28 of the preferred construction.

When the coal conveying screws stall, thereby stopping the gear |56, the worm |55 will continue to turn and thread itself along the teeth of the gear |56 causing the shaft |53 to move toward the left against the pressure of the spring |6|. This movement of the shaft |53 is communicated to a contact member |63 through the pivoted levers |64 and |65 breaking a control 'circuit |60 to the motor and causing it to stop. The contact member |63 thereupon closes a circuit |51 ringing a bell |68, signifying that a clog in the coal conveying screws has caused the stoker to shut down. The spring |61 is of sufficient strength to prevent the worm from threading itself along the teeth of the gear |56 during nor- -mal operation of the stoker.

When the coal conveyor screws stall and the motor |50 has been shut off by the mechanism ljust described, the attendant may remove the clog. The clog having been removed, the spring |6I forces the shaft |53 back toward the right, and the spring |60 will force the contact member |63 to again close the circuit |66 and operation of the motor |50 will be resumed.

I claim:

l. A Stoker for a furnace including a fuel tube extending from a source of fuel supply t0 the said furnace, a conduit leading from a source of hot gases, said conduit enclosing a substantial portion of the length of said fuel tube, and means for creating a Icurrent of hot gases through the enclosing portion of said conduit from said source of supply and discharging all of said hot gases into said fuel tube for pneumatically conveying the fuel through said enclosed portion of said tube to the furnace.

2. A stoker for a furnace including a fuel tube extending from a source of fuel supply to the said furnace, a conduit leading from a source of hot combustion gases produced in said furnace, said conduit enclosing a substantial portion of the length of said fuel tube, and pressure fluid generating means having an intake port communicating with said conduit for producing a current of hot gases through the enclosing portion of said conduit from said source of supply and a discharge port communicating with and discharging all of said hot gases into said fuel tube for pneumatically conveying the fuel through said enclosed portion of said tube to the furnace.

3. A stoker for delivering fuel from a source of supply to a furnace including means for mechanically conveying fuel from said source of supply to a point remote therefrom, a fuel tube communicating at one end with said mechanical fuel conveying means and at its opposite end with said furnace, a conduit leading from a source of lio-t gases, pressure fluid generating means having an intake port communicating with said conduit for withdrawing hot gases from said source of supply and la discharge port communicating with said fuel tube for pneumatically conveying rthe fuel delivered thereto by said mechanical conveying means to -said furnace, a common motor for operating said pressure fiuid generating means and said mechanical conveying means, and means for automatically disconnecting said mechanical conveying means from said motor when said mechanical conveying means stalls Without interrupting operation of said pressure fluid generating means.

4. A stoker for a furnace including a fuel tube extending from a source of fuelsupply to the said furnace, a conduit leading from a source of hot gases, said con-duit enclosing .a substantial portion -of said fuel tube, pressure uid generating means including a main generator and an auxiliary generator, said pressure fluid generating means having intake ports communicating with said conduit for withdrawing hot gases from said source of supply and discharge ports communicating with said fuel tube for pneumatically conveying fuel through -'the enclosed portion of said tube to the furnace, and means for independently operating said main and lauxiliary generators, said auxiliary generator constituting a booster generator for said main generator when both said generators are in operation and effecting a continued current Iof hot gases through the enclosing portion of said conduit for heating the enclosed portion of said fuel tube when said main generator is out of operation.

5. A stoker for delivering fuel from a source of supply to a furnace including means for mechanically conveying fuel from said source of supply to a point remote therefrom, a fuel tube communicating at one end with said mechanical fuel conveying means and at its opposite end with said furnace, a conduit leading from a source of hot gases, saidl conduit enclosing a substantial portion of said fuel tube, fan means including a main fan and an auxiliary fan connec'ted in series, said fan means having intake ports communicating with said conduit for withdrawing hot gases from said source of supply and discharge ports communicating with -said fuel tube for pneumatically conveyingr the fuel delivered thereto by said mechanical conveying means through the enclosed porti-on of said fuel tube to said furnace, a common motor for operating said main fan and said mechanical conveying means, `and a motor for operating said auxiliary fan independently of said main fan and said mechanical conveying means, said auxiliary fan effecting la continued current of hot gases through the enclosing portion of said conduit for heating the enclosed portion of said fuel tube when `said main fan and mechanical conveying means are out of operation.

6. A stoker for delivering fuel from a source of supply to a furnace including means for mechanically conveying fuel from said source of supply to a point remote therefrom, a fuel tube communicating at one end with said mechanical fuel conveying means and at its opposite end with said furnace, a conduit leading from a source of hot gases, fan means including 'a main fan and an auxiliary fan connected in ser-ies, said fan means having an intake port communicating with said conduit for withdrawing hot gases from said source of supply and a discharge port communicating with said fuel tube for pneumatically convey-ing the fuel delivered thereto by said mechanical conveying means to said furnace, a common motor for operating said main fan and said mechanical conveying means, means for automatically disconnecting said mechanical convey-ing means from said motor when said mechanical conveying means stalls, and a motor for operating said auxiliary fan independently of said main fan.

7. A stoker for a furnace including a fuel tube extending from a source of fuel supply to said furnace, fanmeans having an intake port and a discharge port, means forming a passage from a source of hot combustion gases to the intake port ofsaid fan means, said passage forming means enclosing a substantial portion of the length of said fuel tube, said passage forming means having an. air admission opening, said fan means withdrawing commingled -hot furnace gases and air from said passage forming means through said intake port, and said ldischarge port communicating with said fuel tube for pneumatically conveying the fuel through said enclosed portion of said tube by said commingled hot furnace gasesand air to the furnace.

8. A stoker for a furnace including a fuel tube extending from a source of fuel supply to the said furnace, pressure fluid generating means having an intake 4port and a discharge port, `means forming a passage from a source of hot gases to the intake port of said pressure fluid generating means, said passage for-ming means enclosing a substantial portion of the `length of said fuel tube, said passage forming means having an air admission opening, said pressure fluid generating means. withdrawing commingled hot gases and air from said passage forming means through said intake port, and valvular means in said passage forming means, said valvular means being adjustable to control the relative volume of hot gases passing through said passage forming means and the volume of air entering said passage forrning means through said air admissionopening, said discharge port communicating with said enclosed portion of said fuel tube for pneumatically conveying the fuel .through said tube by said commingled hot gases Iand air to the furnace.

9. A Stoker for a furnace including a fuel tube extending from a source of fuel supply tothe said furnace, pressure fluid generating means having an intake port and a discharge port, means forming a passage fro-m a source of hot gases to the intake port of said pressure fluid generating means, said passage forming means enclosing a substantial portion of the length of said fuel tube between said pressure fluid generating means and said furnace, said passage forming means having an air admission opening, said pressure fluid generating means withdrawing commingled hot gases and air from said passage forming means through said intake port, and sai-d discharge port communicating with said fuel tube for pneumati-cally conveying the fuel through said tube by said commingled hot gases and air to the furnace.

10. A stoker for a furnace including a fuel tube extending from a source of fuel supply to the said furnace, pressure fluid generating means having an intake vport and a discharge port, means forming a passage from a source of hot gases to the intake port of said pressure fluid generating means, said passage forming means enclosing a substantial portion of the length of said fuel tube, said passage forming means having an air admission opening, said pressure fluid generating means withdrawing commingled hot gases and air from said passage forming means through said intake port, and valvular means in said passage forming means, said valvular means being adjustable to control the relative volume of hot gases passing through said passage forming means and the volume of` air entering said passage forming means through said air admission opening, said discharge port communicating with said fuel tube for pneumatically conveying the fuel through said enclosed portion of said tube by said commingled hot gases and air to the furnace.

l1. A Stoker for a furnace including a fuel tube extending from a source of fuel supply to the said furnace, a conduit leading from a source of hot combustion gases produced in said furnace, said conduit enclosing a substantial portion of the length of said fuel tube, fan means having an intake port and a discharge port, and a compartment between and communicating with said intake port and said conduit, said compartment having an opening to atmosphere, said fan means withdrawing commingled hot furnace gases and air from said compartment through said intake port, and said discharge port communicating with said fuel tube for pneumatically conveying the fuel through said enclosed portion of said tube by said commingled hot furnace gases and air to the furnace.

12. A stolzer for a furnace including a fuel tube extending from a source of fuel supply to the said furnace, a conduit leading from a source of hot combustion gases produced in said furnace, said conduit enclosingy a substantialr portion of the length of said fuel tube, fan means having an intake port and a discharge port, and a compartment between and communicating with said intake port and said conduit, said compartment having an opening to atmosphere, said fan means withdrawing commingled hot furnace gases and air from said compartment through said intake port, and valvular means in said compartment, said valvular means being adjustable to control the relative volume of hot furnace gases and air admitted to said fan means, said discharge port communicating with said fuel tube for pneumatically conveying the fuel through said enclosed portion of said tube by said commingled hot furnace gases and air to the furnace.

13. A stoker for a furnace including a fuel tube extending from a source of supply to the furnace, a conduit leading from a source of hot gases, pressure fluid generating means having an intake port communicating with said conduit for withdrawing hot gases from said source of supply and a discharge port communicating with said fuel tube for pneumatically conveying the fuel through said tube to the furnace, a motor for operating said pressure fluid generating means and means responsive to the pressure built up by said pressure fluid generating means, when a clog occurs in said fuel tube, for cutting said motor out of operation,

14. A stoker for a furnace including a fuel tube extending from a source of supply to the furnace, a conduit leading from a source of hot combustion gases produced in said furnace, fan means having an intake port communicating with said conduit for withdrawing hot gases from said source of supply and a discharge port communicating with said fuel tube for pneumatically conveying the fuel through said tube to the furnace, a motor for operating said fan and means responsive to the pressure built up by said fan means, when a clog occurs in said fuel tube, for cutting said motor out of operation.

15. A stoker for a furnace including a fuel tube extending from a source of supply to the furnace, a conduit leading from a source of hot combustion gases produced in said furnace, said conduit enclosing a substantial portion of the length of said fuel tube, fan means having an intake port communicating with said conduit for withdrawing hot gases from said source of supply and a discharge port communicating with said fuel tube for pneumatically conveying the fuel through said tube to the furnace, a, motor for operating said fan and means responsive to the pressure built up by said fan means, when a clog occurs in said fuel tube, for cutting said motor out of operation.

16. A stoker for delivering fuel from Va source of supply to a furnace including means for mechanically conveying fuel from said source of supply to a point remote therefrom, a fuel tube communicating at one end with said mechanical fuel conveying means and at its opposite end with said furnace, a conduit leading from a source of hot gas, fan means having an intake port communicating with said conduit for withdrawing hot gases from said source of supply and a discharge port communicating with said fuel tube for pneumatically conveying the fuel delivered thereto by said mechanical conveying means to said furnace, means for operating said fan means and said mechanical conveying means, and means responsive to the pressure built up by said fan means. when a clog occurs in said Afuel tube, for cutting said fan means and said mechanical conveying means out of operation.

17. A stoker for delivering fuel from a source of supply to a furnace including means for mechanically conveying fuel from said source of supply to a point remote therefrom, a fuel tube communieating at one end with said mechanical fuel conveying means and at its opposite end with said furnace, a conduit leading from a source of hot gas, said conduit enclosing a substantial -portion of the length of said fuel tube, fan means having an intake port communicating with said conduit for withdrawing hot gases from said source of supply and a discharge port communicating with said fuel tube for pneumatically conveying the fuel delivered thereto by said mechanical conveying means to said furnace, a common motor for operating said fan means and said mechanical conveying means, and means responsive to the pressure built up by said fan means, when a clog occurs in said fuel tube, for cutting said motor out of operation.

18. A stoker for delivering fuel from a source of supply to a furnace including means for mechanically conveying fuel from said source of supply to a point remote therefrom, a fuel tube communicating at one end with said mechanical fuel conveying means and at its opposite end with said furnace, a conduit leading from a source of hot gas, fan means including a main fan and an auxiliary fan connected in series, said fan means having an intake port communicating with said conduit for withdrawing hot gases from said source of supply and a discharge port communicating with said fuel tube for pneumatically conveying the fuel delivered thereto by said mechanical conveying means to said furnace, a common motor for operating said main fan and said mechanical conveying means, means responsive to the pressure built up by said main fan, when a clog occurs in said fuel tube, for cutting said motor out of operation, and a motor for operating said auxiliary fan independently of said main fan.

19. A stoker for delivering fuel from a source of supply to a furnace including means for mechanically conveying fuel from said source of supply to a point remote therefrom, a fuel tube communicating at one end with said mechanical fuel conveying means and at its opposite end with saifl furnace, a conduit leading from a source of hot combustion gases produced in said furnace, said conduit enclosing a substantial portion of the length of said fuel tube, fan means including a main fan and an auxiliary fan connected in series, said fan means having an intake port communieating with said conduit for withdrawing hot gases from said furnace and a discharge port communicating with said fuel tube for pneumatically conveying the fuel delivered by said mechanical conveying means to said furnace, a common motor for operating said main fan and said mechanical conveying means, means responsive to the pressure built up by said main fan, when a clog occurs in said fuel tube, for cutting said motor out of operation, and a motor for operating said auxiliary fan independently of said main fan.

20. A stoker for delivering fuel from a source 'of supply to a furnace including means for mechanically conveying fuel from said source of supply to a point remote therefrom, a fuel tube communicating at one end with said mechanical fuel conveying means and at its opposite end with said furnace, a conduit leading from a source of hot gas, fan means having an intake port communi` cating with said conduit for withdrawing hot gases from said source of supply and a discharge port communicating with said fuel tube for pneumatically conveying the fuel delivered thereto by said mechanical conveying means to said furnace, a common motor for operating said fan means said mechanical conveying means, means for disconnecting said mechanical conveying means from said motor when the conveying means stalls, and alarm means associated With said disconnecting means arranged to be set in operation upon functioning of said disconnecting means.

21. A stoker for delivering fuel from a source of supply to a furnace including means for mechanically conveying fuel from said source of supply to a point remote therefrom, a fuel tube communicating at one end with said mechanical fuel conveying means and at its opposite end with said furnace, a conduit leading from a source of hot combustion gases produced in said furnace, said conduit enclosing a substantial portion of the length of said fuel tube, fan means having an intake port communicating with said conduit for withdrawing hot gases from said furnace and a discharge port communicating with said fuel tube for pneumatically conveying the fuel delivered -thereto by said mechanical conveying means to said furnace, a common motor for operating said fan means and said mechanical conveying means, means for disconnecting said mechanical conveying means from said motor when the conveying means stalls, and alarm means associated with said disconnecting means arranged to be set in operation upon functioning of said disconnecting means.

22. A Stoker for delivering fuel from a source of supply to a furnace including means for mechanically conveying fuel from said source of supply to a point remote therefrom, a fuel tube communicating at one end with said mechanical fuel conveying means and at its opposite end with said furnace, a conduit leading from a source of hot gases, pressure fluid generating means having an intake port communicating With said conduit for withdrawing hot gases from said source of supply and a discharge port communicating with said fuel tube for pneumatically conveying the fuel delivered thereto by said mechanical conveying means to said furnace, power means for operating said pressure fluid generating means and said mechanical conveying means, means for automatically interrupting the application of power to said mechanical conveying means by said power means when said mechanical conveying means stalls and means, responsive to the pressure built up by said pressure fluid generating means When a clog occurs in said fuel tube, for rendering said mechanical conveying means and said pressure fluid generating means automatically inoperative.

23. A stoker for delivering fuel from a source of supply to a furnace including means for mechanically conveying fuel from said source of supply to a point remote therefrom, a fuel tube communicating at one end with said mechanical fuel conveying means and at its opposite end with said furnace, a conduit leading from a source of hot gases, pressure fluid generating means having an intake port communicating with said conduit for withdrawing hot gases from said source of supply and a discharge port communicating with said fuel tube for pneumatically conveyingr the fuel delivered thereto bv said mechanical conveying means to said furnace, a common motor for operating said pressure uid generating means and said mechanical conveying means, means for automatically disconnecting said mechanical conveying means from said motor when said mechanical conveying means stalls and means, responsive to the pressure built up by said pressure fluid generating means when a clog occurs in said fuel tube, for automatically cutting said motor out of operation.

24. A stoker for a furnace including a fuel tube extending from a source of fuel supply to the said furnace, said fuel tube including a bend between its ends, a conduit leading from a source of hot gases, said conduit enclosing the bend in said fuel tube, and means creating a current of hot gasesfrcm said source of supply through the portion of said conduit enclosing said bend and discharging all of said hot gases into said fuel tube for pneumatically conveying the fuel through said enclosed portion of said tube to the furnace.

25. A stoker for delivering fuel from a source of supply to a furnace including means for mechanically conveying fuel from said source of supply to a point remote therefrom, a fuel tube communicating at one .end with said mechanical fuel conveying means and at its opposite end with said furnace, a conduit leading from a source of hot gases, fan means including a main fan and an auxiliary fan connected in series, said fan means having an intake port communicating with said conduit for withdrawing hot gases from said source of supply and a discharge port communicating with said fuel tube for pneumatically conveying the fuel delivered thereto by said mechanical conveying means to said furnace, power means for operating said main fan and said mechanical conveying means, means for automatically interrupting the application of power to said mechanical conveying means by said power means when said mechanical conveying means stalls, and means for operating said auxiliary fan independently of said main fan.

26. A stoker for a furnace including a fuel tube extending from a source of fuel supply to the said furnace, a conduit leading from a source of hot gases, said conduit enclosing a substantial portion of the length of said fuel tube between the fuel receiving and fuel discharging ends of said fuel tube, and means for effecting a current of hot gases flowing through the said enclosing portion of said conduit from said source of hot gas supply to the fuel receiving end of said fuel tube and discharging said hot gases into said fuel tube for pneumatically conveying the fuel through said enclosed portion of said tube to the furnace 27. A stoker for a furnace including a fuel tube extending from a source of fuel supply tothe said furnace, said fuel tube including a bend between its fuel receiving and fuel discharging ends, a conduit leading from a source of hot gases, said conduit enclosing the bend in said fuel tube, and means for eifecting a current of hot gases flowing through the said enclosing portion of said conduit from said source of hot gas supply to the fuel receiving end of said fuel tube and discharging said hot gases into said fuel tube for pneumatically conveying the fuel through said enclosed portion, of said tube to the furnace.

NATHAN M. LOWER.