US2194025A - Underfeed stoker for hot air furnaces - Google Patents

Description

March 19, 1940. 1.. LEE

I UNDERFEED STOKER FOR HOT AIR FURNACES Filed July 30, 1955 5 Sheets-Sheet 1 m w M M W? m 6/ L [W W I IM March 19, 1940. LEE 2,194,025

UNDERFEED STOIIER FOR HOT AIR FURNACES Filed July 30, 1936 5 Sheets-Sheet 2 Y 0 Q 4Q; ATTORNEY firs H M i h 19, 1940. LEE 1 UNDERFEED STOKERDFOR HOT AIR FURNACES Filed July so, 1936 5 Sheets-Sheet 3 ATTORNEY March 19, 1940. I L. LEE 2,194,025

UNDERFEED STOKER FOR HOT AIR FURNACES Filed July 50; 1936 5 Sheets-Sheet 4 ATTORNEY Lew- L-E'E v March 19, 1940. LEE 2,194,025

UNDERFEED STOKER FOR HOT AIR FURNACES Filed July 30, 1936 5 Sheets-Sheet 5 w IINVENTOR,

L'El 'F L'E'E K K BY 2 ATTORNEY Patented Mar. 19, 1940 NlTED STATES PATENT OFFICE illeii Lee, Youngstown, Ohio; Halfdan Lee, executor of the Estate of said Leif Lee, deceased Application .luly 3t), 1936, Serial No. 93,513 i illaims. (en. rec-r) The present invention relates to an air heating furnace and more particularly to a furnace utilizing automatic stoker means for burning coke or other solid fuel.

i The primary object of the invention is to provide an emcient air heating furnace which is inexpensive to construct, economical in operation, and which may be operated with a minimum of attention.

More specifically an object of this invention is to provide an air heating turnace which relies principally on radiation for its heating efiect and in which the counterfiow principle is used and applied between the incoming cold air and the i outgoing heated air and between the flow of flue gases and the flow of the air being heated.

Another object of the invention is to provide a novel stolzer mechanism which is simple in design and which is operative to under feed coke or other solid fuel to a heel of live coals, to agitate the bed and to dispose of the ashes.

Another object of the invention is to provide a novel combination of a furnace, air ducts associated therewith and automatic stoker means to 5 form a highly eficient self-contained heating unit operable with a minimum oi attention.

A further object of this invention is to provide novel means to regulate the flow of secondary air above the grates automatically in response to the a pressure of the primary air below the grates or manually in such a manner that the primary air supply must be at its maximum before any secondary air is allowed to enter the combustion chamber.

5 These and other objects and advantages of the invention will become apparent from a consideration oi the drawings and the following specification.

In the drawings:

Figure l is a side elevation of the assembled furnace with parts broken away and other parts in section.

Figure 2 is a part cross-sectional view taken along the linen-A of Figure 1, looking in the direction of the arrows.

Figure 3 is a cross-sectional view taken along the line BB oi Figure 1, looking in the direction of the arrows. 7 s

Figure 4 is a cross sectional view taken along a the line -C of Figure 1, looking in the direction of the arrows.

the line D-D oi Figure l,,loohing in the direction oi the arrows. l p

g Figure 8 is a c-sectional view similar to 5 is a cross-sectional view tairen along Figure 3 but showing a modified means for supplying air for combustion. v

Figure 7 is a top view of the air controlling means of Figure 6.

The heater and stoker assembly is supported on d a floor plate Ill which in the illustrated embodi-- extending along the lower portion of their outside walls for communication with the space within the combustion chamber. A wall 'l t of refractory material is supported by and extends along the top of each duct it. The refractory material is preferably light in weight so that it will not store a large amount of heat.

Extending transversely of the ducts at the ends thereof are the two supporting plates ii and it which constitute spaced supporting means for the grate bars i9. The grate bars are preferably tour in number, although any number may be and as shown they are provided witha plurality of perforations for supplying air to the fuel placed on the grates. The grate bars it are longitudinally oscillatable and are placed adjacent each W other for a purpose to be'later' described.

[inv outer casing supported on floor plate it encloses the entire assembly including the furnace, stoirer and hopper. An intermediate casing 21 is housed within but spaced from the outer casing cs- 2t and is spaced from but followsthe general contour of the arch-shaped casing ii of the combustion chamber. At its lower end the intermediate casing 277 is flanged outwardly at 20 to engage against the inner surface of the side wall of the outer casing 2h. The spaces between the outer casing and the intermediate casing constitute ducts for the passage of cold incoming air while the spaces between the arch-shaped casing ii and the intermediate casing 21 constitute ducts for the passage oi air being heated by the combustion of fuel within the casing l I.

Positioned forwardly of the combustion chamher and on either side thereof is a circulating fan housed in the fan casing 25 having its inlet faced toward the center of the assembly. A fuel hopper having slanting side walls H is positioned above and between the two fan casings and a portion of the lower surface of the walls 2| constitutes a portion of the side walls of-the ducts connecting the 5 s 1 5 with coal or coke dust emitted by the operation of the stoker mechanism.

A cross duct 3| utilizing a portion of the lower surface of the slanting wall 2| of the hopper as a wall and a portion of the outer casing 20 as an- 1 other wall interconnects the inlet ducts of the two fans. The purpose of this duct is to equalize the pressure .existing in the inlet ducts of the fans. This results in an equal volume of air passing through each fan and over each side of the heatingsurface II and consequently uniform and more eflicient heating of the air.

The fans 25 discharge into the space between the casing II and the outer casing at the bottom of the furnace below the flange 28. The,

20 air passes upwardly in intimate contact with the corrugated surface of casing ll within the intermediate casing 21 and out through the outlet at the top of the furnace. The path of travel of the incoming and outgoing air is indicated throughout the drawings by arrows which show the application of the counterflow principle.

The products of combustion pass upwardly from the space between the refractory walls l6 and into the dome of the arch-shaped casing II from where they are drawn downwardly in contact with the inner surface of corrugated sheet H be tween the sheet and the outer surface of wall I 6. Since the inlet openings'l5 of conduits l4 are near the bottom of the furnace, the. flue gases are required to travel substantially to the bottom of casing ll before they escape from adjacent the surface of the casing I I. It can thus be seen that the flue gases are directed downwardly along the inner surface of casing ll whereas'the fan dis- 0. charged air is caused to flow upwardly along the outer surface of easing ll.

Conduitsdl are connected at one end with a header 23, a box-like duct one wall of which is the lower portion of end wall I 2. The duct 23 43 discharges into the longitudinally extending duct 24 which in turn discharges into the cross duct 26 which may be connected with a stack at either.

end thereof.

As shown in Figures 1, 3 and 4, a small trans- 0 versely extending duct 32 is positioned along the top of header 23 and under the grate bars IS. The duct is open at its ends and is in communication with the discharge of the fans. The center portion of the rear wall of the duct is cut away at 33 to allow air coming into the ends of the duct to flow beneath the grate bars l9 to supply primary air for combustion.

Longitudinally-spaced from the end wall l2 of the combustion chamber is the parallel plate 22 which forms the rear wall of the hopper and the front, end of the space between the inner casing II and the intermediate casing 21. Plates l2 and 22 are provided with aligned openings to accommodate the grate bars I! and passage of 55 fuel from the hopper into the combustion chamber. Plates 34 connect the side edges of the openings for a portion of their length, a small opening 36 being left at the top on either side thereof. A bent strip 35 is positioned between the plates 70 I2 and 22 and seals the space between the plates l2 and, 22 from communicatioi with the combustion chamber. The plates I2, 22 and 34 and the strip 35 form conduits for the entry of secondaryair for combustion. The inlets of these 1 conduits are in communication with the discharge of the fans 25 and are controlled by pressure responsive valves 31 which are normally held closed by springs 38 but which are adapted to open and admit air above the grate bars I! when the fan has attained a predetermined discharge pressure, the extent of opening being governed by the pressure attained.

A gate 39 having a rearwardly bent lower end 40 extending into the aligned opening in plates [2 and 22 is slidably supported on the front surface of plate 22 by straps 4| which may be adjustably anchored in lugs 42 by pins 43 passing through an eye in the upper end of straps 4|. The bent end 40 of gate 39 supports an L-shaped block 44 of refractory material which extends the width of the aligned openings in plates l2 and 22. As shown, one side of the block 44 engages the inner surface of plate l2 and the block 44 is provided with an enlarged lower portion 45 to engage and be supported by the portion 4| of gate The inclined surface of portion 45 of the refractory block 44 is provided with a plurality of spaced parallel grooves 46 therein which in conjunction with the plate 40 form a plurality of secondary air conducting orifices directed towards the grate bars l9 and into the furnace. As shown, the orifices are in communication with the secondary air conduit formed by the strip 35.

The grate bars I! are arranged to oscillate longitudinally out of phase with each other and they may either be moved manually or be power driven. I have shown a preferred. arrangement whereby the grate bars are power driven and in which the connecting rods 48 are utilized to connect the ends of the bars with the cranks of the crankshaft 50. The connecting rods 48 are pivotally connected with the grate bars by the pins 49. Crankshaft 50 is slowly driven by a pawl and ratchet mechanism 5253 operated by an arm 54 oscillated by the crank 56 through an arm 55. A variable speed electric motor 58 is adapted to drive crank 56 through suitable reduction gear ing 51. As shown, the cranks of the crankshaft 50 are angularly spaced 90 from each other. The purpose of this arrangement is to insure relativemovement between adjacent bars and movement in opposite directions of adjacent bars at least during part of one revolution-of the crankshaft and this results in agitating the bed of live coals on the grate bars and causes coals or lumps of solid fuel lying on the grate bars to be angularly oscillated.

The ends of the grate bars l9 extend beneath the outlet of the hopper and are each provided with a transverse shoulder 60 which propel solid fuel from the hopper along the path of travel of the grate bars. The fuel is prevented from returning in the direction of the hopper by pressure exerted by fuel sliding down the inclined wall 2| of the hopper. If desired, the inner surface of wall 2| may be lined with glazed tile or other smooth surfaced material to lessen friction between the fuel and the plate 2| and to prevent abrasion of the metal plate 2|.

Extending across'the rear end of the furnace above and to'the rear of the grate bars is the member 6| which has a depending lip the rounded lower surface of which is positioned slightly above the upper surface of the grate bars and slightly to'the rear of the end of the bars when the bars are in retracted position. This allows a small space between the edge of the grate bar and the lip when'the grate bar is in retracted position to provide a passage for ashes but which prevents the falling-of unburnt pieces of coal or coke by arresting their further movement. The ashes are shoved oif the plate H by the ends of the grate bars and fall into the pan. 63 which pan may be removed through door 62.

It can thus be seen that the grate bars perform a plurality of functions, i. e., support the fire bed admit air thereto, agitate-the bed, feed fuel tion.

thereto and dispose of the ashes. The operation is such that the fuel is caused to be moved along the surface of the bars and thus under feed the fire. The lumps of fuel move into the fire zone with an erratic motion due to the relative movement of adjacent grate bars. The motion may be described as composed of linear, rotation and angular oscillation movements. An important result achieved by this feature is that the fire bed is agitated and a normally adequate supply of primary air for combustion is insured. Another result is that clinkers do not form as the relative erratic movement of the pieces of fuel effectively prevent amalgamation orfusion of the pieces which is the chief cause of clinker forma- The operation of the device is obvious. A door 64 is provided whereby access may be had to the combustion chamber for the purpose of starting the fire. Fuel is fed from the hopper in the man- --ner heretofore described. The quantity of fuel consumed and consequently the rate of heat delivery is determined by the vertical position of gate 39 and the speed of motor 58 which drives the grate bars I 9 and the fans, the fans bein mounted on shaft 65 driven bymotor 58 through pulleys 66 and 61 and belt 68. Within certain limits of operation the automatic dampers 31 controlling the supply of secondary air for combustion remain closed but for higher rates of operation when the permeability of the grate bars and bed of live coals is such that an insufficient supply of primary air can reach the points of combustion the dampers 31 open in response to an increase of pressure from the fans and allowsecondary air to flow to the bed of coals along the path previously described. The result is an intensification of the combustion with a consequent increase in the heat output.

Figures 6 and 7 illustrate a modification of the invention wherein primary and secondary air for combustion is taken directly from the atmosphere and natural draft is relied on-to supply such air. The conduit 32 instead of being in communication with the discharge-of the fans is connected with the atmosphere by means of a conduit 14 communicating with an opening II in the side wall of the outer casing 20. Another opening 12 in the outer casing is provided directly above'the opening H and allows secondary 'air to pass from the atmosphere to the conduit formed by strip35 through a duct I3. The openingsflll'and I2 are controlled by a valve 15 which is cylindrical in shape to rotatably fit within the curved indentation of the sidewall at the openings II and "I2.

The cylindrically shaped valve is rotatably sup- 15 so that the upper opening 12 cannot be opened when the lower opening H is closed. The arrangement is such that the lower opening must be completely open before any portion of the upper opening may be uncovered. This means that the maximum supply'of primary air must be furnished before any secondary air can be admitted.

If desired, the chain ILmay be coupled with means controlling the speed of operation of the motor 58 whereby when the'motor is controlled to run at a predetermined speed, either the opening II or both openings II and 12 may be uncovered.

While I have shown but one valve 15 it is obvious that another may also be employed-positioned on the opposite side of the furnace.

Having thus described my invention what I claim is:

1. An air heating furnace comprising a casing constituting a fuel supporting and combustion chamber, a pair of spaced ducts arranged longitudinally in the lower portion of said casing and spaced from the side walls of said casing, a refractory wall supported on each of said ducts, a grate structure between said walls, each of said ducts having openings in its outer side wall opposite the adjacent side wall of the casing, means connecting said ducts with a flue, and means to supply air to the space beneath the grate structure. v

2. An air heating furnace comprising a casing, a plurality of longitudinally mov ble grate bars extending longitudinally into'sai casing. a hopper positioned at one end of saidasing, the outer ends of said bars positioned belo the outlet of said hopper andprovided with means to propel fuel from said hopper into said casing, a pair of ducts arranged longitudinally within the lower portion of said casing on either side of said bars, a refractory wall supported on each of said ducts and spaced from the adjacent side wall of the casing, means positioned beneath said hopper to connect said duets with a fiue and means to supply air to the space beneath said bars.

3. An air heating furnace comprising a casing forming a combustion chamber, fuel supporting means in said casing, a fuel hopper. adjacent one end of said casing, said fuel supporting means being movable and operative to move fuel from the hopper into the casing, a flue duct in the lower beneathsaid hopper, an air circulating device on either side of said duct arranged to circulate air in heat exchanging relation with the outer surfaces of said casing, and means positioned beneath said hopper and between said air circulating devices to operate the fuel supporting and moving means.

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