US2388805A - Fuel stoker - Google Patents

Description

D. R. STAHL Nov. 13,1945.

FUEL STOKER Filed Sept. 15. 1944 I 4%; 2 flII/IIIIIIIIIIIIIIIIIIII), k 6' A TTORAIEYS.

atenied ov. 13, 15

s'rrss Metal Specialties 00., Inc., corporation of Wisconsin Milwaukee, Wis., a

Application September 15, 1944, Serial No. 554,183 6 Claims. (oi. 110-109) improvements in the construction and operationof mechanical stokers for feeding fuel such as coal to furnaces or the like.

The primary object of my invention is to provide a new and useful fuel stoker which is simple and compact in construction, and which is moreover automatic and highly eficient in operation.

Many different types of automatic Or mechanical stokers have heretofore been proposed and used with varying degrees of success and for various purposes; and the prior fuel stoking devices most extensively employed, were either of the reciprocating plunger or of the rotary screw type. In the reciprocating plunger type of stoker, a piston or plunger is caused to reciprocate beneath the lower outlet opening of a fuel supply bin or hopper so a to positively force successive batches of the fuel which are delivered by gravity past the hopper outlet, through a feed pipe leading into the combustion chamber. This plunger type has heretofore been utilized principally for commercial boiler installations, and considerable difilculty has been experienced in causing the plunger to advance properly beneath the open hopper outlet when the hopper was laden with an abundant supply of fuel. In the rotary screw type of stoker, an elongated screw is caused to revolve in the feed pipe leading from the bottom of the supply bin to the combustion chamber so as to constantly advance a stream of fuel through the straight feed pipe. This screw type has heretofore been employed primarily for household or domestic heating service, and its construction is such that the feed screw must be disposed near the combustion chamber since the available power will not readily permit feeding from a remote zone through curved or irregular feed pipes. Both of these prior types of stoking devices were also relatively complicated and costly to install and to maintain in operating condition, and were also otherwise objectionable.

It is therefore a more specific object of the present invention to provide a simplified and more efficient plunger type of stoker which may be utilized for either domestic or commercial purposes, and which i adapted to feed the fuel for a considerable distance through irregular feed pamages with minimum power consumption.

Another specific object. of the invention is to provide an exceedingly compact and durable automatic fuel stoker which will effectively advance the fuel at any desired rate through a curved or straight feed pipe from a fuel supply bin to a furnace or other combustion device located remote from the source of fuel supply.

Still another specific object of my invention is to provide a simple mechanical stoker for fuel such as low grade coal, which. may be manufactured and sold at moderate cost, and which is safe and reliable in operation and easily installed.

These and other specific objects and advantages of the invention will be apparent from the following detailed description.

A clear conception of the features constituting my present improvement, and of the construction and operation of a typical installation embodying the invention, may be had by referring to the drawing accompanying and forming a part of this specification wherein like reference char acters designate the same or similar parts in the various views.

Fig. 1 is a somewhat diagrammatic part sectional top view of a typical stoker installation embodying my improvements, showing a fragment of a fuel supply bin or hopper;

Fig. 2 is a similar part sectional side elevation of the installation disclosed in Fig. 1, showing the fuel feeding plunger advanced forwardly-beyond the supply bin outlet opening;

Fig. 3 is a. view similar to that of Fig. 2, but showing the fuel feeding plunger retracted rearwardly beyond the supply bin outlet opening;

Fig. 4 is a diagrammatic perspective view showing the improved fuelstoker embodied in a typical domestic heating installation; and

Fig. 5 is a fragmentary transverse vertical section through the supply bin outlet, fuel feed pipe, feeding plunger and cut-ofi slide.

While the invention has been shown and described herein as having been embodied in a reciprocating plunger type of stoker installation especially adapted for domestic or household heating purposes, it is not my desire or intention to thereby unnecessarily restrict the scope or the utility of the improvement.

Referring to the drawing, the typical fuel stoker shown therein by way of illustration, comprises in general a fuel supply hopper Gr bin a normally containing an abundant supply of fuel such as coal 1 and having a lower outlet opening 8 adapted to deliver successive batches of the coal 7 by gravity, into the inlet end ofan elongated fuel feed conduit or pipe 9; a fuel feeding piston or plunge l8 reciprocable within the pipe 9 beneath the bin outlet opening 8; a fuel cut-ofi gate or slide ll movable back and forth in a space between the outlet opening 8 and the plunger III;"a worm wheel I2 and a driving worm I3 therefor, both journalled in a housing or casing I4 disposed beyond the rear end of the pipe I; a crank I 5 secured to one side of the worm wheel I2 and being connected to the plunger It by means of a piston rod I6; another crank I'I secured to the opposite side of the worm wheel I2 and being connected to the slide I l by means of a gate rod I3; and means such as a V.-belt drive I9 fordriving the worm I3 at any suitable speed.

The fuel supply bin 6 may be a hopper located either closely adjacent to or remote from a combustion chamber or fire pot 20 disposed within a heater or furnace 2|; and while the portion of the fuel feed pipe 8 within which the plunger I reciprocates should be straight, that portion of the pipe 9 beyond the limits of movement of the plunger I0 may be straight, or curved, or of any other irregular shape but should preferably have approximately uniform transverse cross-sectional area. The bin 6 may therefore be located a consider distance away from the furnace 2|, near a window or coal chute, and may be connected to the fire pct 20 by a long gradually curved or straight pipe 9 disposed either above or below the intervening floor, and the stoker installation may also be provided with a fan 22 and combustion air supply duct 23 as illustrated in Fig. 4.

The top of the fuel feed pipe 9 is provide with an elongated slot 24 extending both forwardly and rearwardly beyond the hopper outlet 8; and the portion of this slot which extends forwardly beyond the hopper 6, is provided with a readily removable cover 25 for permitting quick access to the interior of the feed pipe 9 in order to remove pieces of wood or other large obstructions which may he accidentally deposited within the supply bin. The piston or plunger III is preferably cylindrical in shape and should snugly en age the interior of the cylindrical feed pipe 9, and the cut-off plate or slide II is movable in the slot 24 and is curved to conform with the contour of the pip-e 9 and plunger I0 as clearly shown in Fig. 5. While the slide I I is never movable rearwardly beyond the hopper outlet opening 8, it is movable forwardly beneath the cover 25, and the front end of the slide II is preferably bevelled or chamfered as indicated in Figs.

2 and 3, so that the advancing plate will cut or sever the mass of coal I.

The housing or casing i4 may be formed of several rigidly but detachably united sections readily mounted upon a suitable base 25, and the cranks I5, II have alined outer bearing portions 21, 28 respectively, which are disposed coaxial with the worm wheel I2 and provide rotary supports for this main gear Wheel. The driving worm I3 which coacts with the worm wheel I2 within a lower lubricant confining pocket in the casing I4, is rotatably supported in alined bearings 28 carried by the housing; and the belt drive l9 which is associated with the outer end of the worm shaft 30 may be disposed in any desired direction and connected in any suitable manner to a driving motoror the like, which may also be utilized to propel the fan 22. The specific disposition and mode of driving the belt drive I9 constitutes no essential part of the present improvement, and may be varied to suit different conditions.

The inner eccentric end of the lunger reciprocating crank I is provided with a crank pin H which is rigidly and fixedly attached to the adjacent side of the worm wheel I 2, and the piston rod I3 has one end engaging the crank pin II while its opposite end is pivotally attached to the plunger III by means of a pin 32. The inner eccentric end of the slide moving crank I1 is provided with a crank pin 33 which is also rigidly but adjustably attached to the opposite side of the worm wheel I2, and the gate rod I8 has an end engaging the crank pin 32 while its opposite end is pivotally attached to the cut-ofi slide II by means of another pin 34. In order' to permit adjustment of the crank pin 33 relative to the worm wheel I2 and crank pin 3| so as to insure proper timing of the motion of the sliding cuteoff gate relative to the feed plunger III, the pin 33 may be made adjustable, but should be firmly locked in adjusted position. As shown, the worm wheel I2 is provided with an arcuate slot 35 through which the slightly reduced end of the crank pin 33 projects, and a washer 36 and screw 31 are also provided in order to lock the pin 33 in any desired position of adjustment within the slot 35. This pin look? ing assemblag must be so constructed that it will efiect locking of the crank pin 33 to the worm wheel I2 without clamping the gate rod I8 and without interfering with the normal movement of the piston rod I6; and these rods I8, I8 may be bent or off-set to provide proper clearance and to avoid interfering with each other, and are substantially concealed within the housing casing I4 and pipe 9 at all times.

During normal operation of the improved fuel stoker, the fuel supply hopper 6 should be constantly provided with an abundant supply of coal I, and the worm I3 should be either continuously or intermittently rotated so as to revolve the worm wheel I2 in the direction of the arcuate arrows, whenever fuel feeding is desired. When the feed plunger I0 is in its extreme forward position as in Fig. 2, it has just completed a feeding stroke and is about to be withdrawn from beneath the hopper outlet 8, and the cut-off slide and slide will be positioned as shown in Fig. 3

with the plunger I0 fully retracted and the slide II partially advanced and moving forwardly as indicated by the straight arrow again located thereabove. The slide II actually begins its cutoff stroke before the plunger III has been fully retracted, due to the angular location of the crank pins 3|, 33 relative to. the central axis of the worm wheel I2, and while the top of, the plunger I0 is slightly exposed to the coal I within the hopper 6 during its return stroke, this slight exposure is not objectionable.

During the return stroke of the plunger ID, by virtue of the fact that the slide II has been simultaneously withdrawn from beneath the hopper outlet 8, a charge of coal I gravitates freely through the open slot 24 into the pipe-9, and the batch of coal thus delivered by gravity substan-' outlet 8 and will move into the portion of the slot 24 beneath the cover 25; and the forwardly advancing plunger l will then force the previously deposited batch of coal 1 which is thus confined within the pipe 9 by the slide II, forwardly through this pipe without permitting the coal to escape or return into the hopper 8. This feeding cycle is constantly repeated as long as the rotation of the worm wheel l2 continues, and the successive batches of coal I delivered by gravity from the hopper 6 into the pipe 9 are forced forwardly so as to provide a uniformly advancing stream of coal at the combustion chamber or grate 20.

From the foregoing detailed description it will be apparent that my present invention provides an improved fuel stoker which besides being extremely simple, compact and durablein construction, is also highly efficient in operation and may be utilized to feed a stream of fuel through either a straight or a circuitous conduit for considerable distances. The improved stoker assemblage is not subject to ready clogging and abnormal obstructions may be quickly removed through the forward end of the slot 24 by merely removing the cover 25. The plunger I0 is constantly protested against excessive wear and. is freely reciprocable within the feed pipe 9 by virtue of the fact that the cut-ofi plate I I relieves the plunger Ill from excessive weight of material within the hopper 6, during the feeding stroke of the plunger.

.This cut-off plate II also prevents the successive batches of coal I from being returned to the hopper 6 during the feeding stroke of the plunger, and the adjustability of the crank pin 33 enables the operator to properly time the movement of the slide II so as to insure most efllcient operation of the unit. The provision of the worm gear drive, besides providing for operation at a desirably low speed, also insures sufficient power for reciprocation of the plunger l0 and slide I I, and this gear assemblage furthermore reduces the mechanism to relatively simple form. All parts of the improved apparatus are obviously well protested against damage and against possible injury to attendants, and the various parts should of course be maintained properlylubricated in order to prolong the life of the apparatus to a maximum. The improved stoker unit can obviously be manufactured and sold at moderate cost, and readily installed in conjunction with various types of heating equipment, and may also be conveniently located relative to the source of fuel supply.

It should be understood that it is not desired to limit this invention to the exact details of construction, or to the precise mode of use, herein shown and described, for various modifications within the scope of the appended claims may ocour to persons skilled in the art.

Iclaim:

1. In a stoker, a fuel supply hopper having a lower outlet, 9. fuel feed pipe leading away from said hopper outlet and having an elongated slot spanning the outlet,- a plunger movable within said pipe directly beneath said slot, a slide reciprocable within said slot directly between said hopper outlet and said plunger, a member rotatable about an axis disposed transversely of the direction of movement of said plunger and said slide and having crank pins operatively associated with the opposite sides thereof, and driving connections interposed between said pins and said plunger and slide respectively for independently reciprocating the plunger and slide.

2. In a stoker, a fuel supply hopper having a lower outlet, a fuel feed pipe leading away from said hopper outlet and having an elongated slot spanning and extending forwardly beyond the outlet, a plunger reciprocable within said pipe beneath said outlet and said slot, a cut-off plate slidable back and forth beneath said outlet and within said slot directly adjacent to said plunger, a gear rotatable beyond, the rear end of said .pipe about an axis disposed transversely of the said outlet to substantially fill said slot and to relieve said plunger from the weight of fuel within said hopperwhen saidplunger is moving forwardly, means for simultaneously reciprocating said plunger and moving said plate, and means for varying the timing of said plate movement.

4. In a stoker, a fuel supply hopper having a lower outlet, a fuel feed pipe extending away from said outlet and having an elongated slot spanning and extending forwardly beyond the outlet, a plunger reciprocable within said pipe directly beneath said slot, a cut-off plate slidable within said slot and-directly between said plunger and said outlet to substantially fill said slot and to prevent return of fuel from said pipe to said plunger andsaid outlet to substantially fill the slot, a worm wheel rotatable in the plane of reciprocation of said plunger, a crank pin at one side of said wheel and being drivingly connected to said plunger, and another crank pin at the other side of said wheel and being drivingly connected to said cut-off plate 6. In a stoker, a fuel supply hopper having a lower outlet, a fuel conducting pipe having a straight portion provided with an elongated slot extending across and beyond said outlet, a

plunger reciprocable within said straight pipe portion directly beneath said slot, a cut-off plate reciprocable within said slot between said plunger and said outlet, a worm wheel rotatable in the plane of reciprocation of said plunger, a crank pin at one side of said wheel and being drivingly connected to said plunger, another crank pin at the other side of said wheel and being drivingly connected to said slide, and means for varying the relative positions of said crank pins with respect to each other and to said wheel.

DONALD R. S TAHL.

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