Abstract:
An automatic coal stoker is provided with internal means to increase the sensible heal outflow from the operating stoker, which means comprises a modified stoker housing that provides a first combustion chamber and an abutting second chamber for induced air heat exchange with the hot combustion gases. A tubular means is disposed in the second chamber which intakes the combustion gases to be vented and extracts much of their sensible heat, and then directs by forced convection, the heated air useful to the stoker environment, while venting the spent combustion gases to the standard flue means.

Description:
CROSS-REFERENCE TO OTHER APPLICATIONS 
     None. This is an examinable patent specification submitted for a filing receipt under Code Section 111( a ). 
    
    
     BACKGROUND OF THE INVENTION 
     In an automatic coal stoker of Potts (U.S. Pat. No. 4,662,290 of May 5, 1987) employs the pusher assembly, operated by a cam assembly  24 , which reciprocally shifts step-like protuberance  58  and provides an enshrouded pusher which is resistant to attacks of such coal acids. The intermittent pusher assembly of the Potts patent, and incorporated by reference here, is an ancillary feature of the present invention. The state of the art in the Potts device (1987) includes long established perforations  32  for fire grate  30 , which grate may be an integral member, as depicted, or may be composed of two more grate modules that aid in loading of the device. 
     It is axiomatic with coal stoker type furnaces that much of the sensible heat provided by this exothermic coal combustion is wasted as it escapes the ambient area being warmed by the flue conduit gases venting to the outside. This has been confirmed by measured combustion gas temperatures in the flue of the Potts—290 patent, ranging as high as 350 degrees F. It would be useful to capture more of the furnace generated heat that is now vented with combustion gases, provided that the efficiency of coal combustion, and the isolation of the toxic gases from the environment, can be maintained with an introduction of augmented sensible heat extraction means. 
     It is a principal object of the invention to provide a separate heat exchange means within stoker housing which efficiently extracts appreciably more sensible heat from the combustion gases just prior to their safe dispersal via the flue conduit, augmenting substantially the established radiant heating benefit. 
     It is a major object of the invention to provide a heat exchanger means disposed within a discrete second chamber that is hermetically sealed from the combustion-loaded gases flowing from of the first chamber. 
     It is still another object of the invention to draw toxic gases more uniformly from the combustion first chamber to a means for extracting much of their sensible heat normally being vented to the atmosphere for user safety. 
     A further object of the invention is to burn with a deeper fire bed, extracting greater sensible heat from the coal and producing ashes of a more powder-like consistency. 
     A still further object of the invention is to provide an ancillary induced air cooling means that reduces the surface temperature of the glassed access door and which further inhibits glass smudging by continuous air stream washing. 
     A further object of the invention is to provide a coal stoker serving as a mini-furnace whereby the extra sensible heat being generated in the improved stoker can also be funneled from the heat venting chamber via a separate conduit to another area, the heated air flow being within the power of the stoker convection blower means. 
     Other objects and advantages and features of the invention will be apparent to those skilled in the art from the following description taken in conjunction with the accompanying drawings and specification. 
    
    
     DESCRIPTION OF THE DRAWING 
     FIG. 1 is a front face, perspective view of the automatic stoker of the present invention; 
     FIG. 2 is a rear face, perspective view of the stoker of the present invention; 
     FIG. 3 is a front face, perspective view of the stoker with certain outer elements seen in phantom; 
     FIG. 4 is a rear face, perspective view also with certain outer elements seen in phantom; 
     FIG. 5 is a front face, elevation view with the access doors closed; 
     FIG. 6 is a bottom up plan view of the stoker, depicting the opposing air inlet ports of the front face vertical air inlet conduits; 
     FIG. 7 is a vertical sectional view of the stoker (enlarged), taken along lines  7 - 7 ′ of the stoker of FIG. 5; 
     FIG. 7A is a broken out, side elevation of an alternate embodiment. 
     FIG. 8 is an exploded perspective view of all of the operative elements of the stoker and hopper still attached to the stoker unit; 
     FIG. 9 is a schematic perspective view of the operative elements in situ, depicting the directional flow path of the heatable air through the stoker to area outflow. 
    
    
     SUMMARY OF THE INVENTION 
     According to the present invention, there is provided in a motorized coal stoker housing including a coal feed hopper with a lower forward passage, a base box forming an ash pit, a rearward ramp adapted to receive coal from the bottom of the hopper, and a pusher assembly disposed in the lower forward passage, eccentric movement means operably connected to the pusher assembly for causing reciprocating action, and a forward fire grate for receiving particulate coal incrementally from the pusher means, the improvements comprising: the stoker housing further comprising a larger and forward first chamber and a hermetically sealed smaller and rearward second chamber; a first chamber having closed sidewalls, a closed top wall, a front facing vertical panel perforated for intermittent user access, and a vertical inner back wall adapted to receive a coal stoker and coal firebox assembly; an exit portal means proximal the inner back wall adapted to conduct coal combustion gases from the first chamber to: (ii) a tubular first means disposed in the second chamber and operatively interconnecting between the exit portal means and a flue conduit for cooled combustion gases, the first means serving to exchange the sensible heat of the combustion gases with a contained forced air flow entering the second to chamber, thereby to provide a heated forced air outflow proximal the uppermost end of the stoker housing serving to warm the housing environment; and, (ii) a first blower means to introduce forced air flow proximal to the bottom of the second chamber and to allow flow therethrough, so as to vent heated forced air proximal to the upper and forward end of the second chamber and outwardly into the ambient surroundings. 
     In a second embodiment wherein the coal stoker has a glass insert frontal door, a washing and cleaning assembly is provided adjacent the frontal panel of the stoker housing comprising: a second pair of tubular conduits, one in each front corner of the front panel, each conduit having their lower longitudinal end open to the ambient atmosphere, and with their upper longitudinal ends connecting to a horizontal second manifold positioned intermediate of the heated air vent point and the upper sill of the fire box exit door; and, the lower surface of the second manifold being provided with ports that direct the induced air flow along the lateral peripheries of the fire box access door for cooling and cleaning purposes. 
     In a third embodiment of the coal stoker, the first conduit means for heat exchange comprises a first pair of opposing conduit members disposed in the second chamber separately connecting at the lower ends thereof with the bottom of the first chamber and jointly connecting the upper ends thereof with a first manifold located in the upper section of the second chamber, which first manifold is functionally connected to a combustion gases exhaust flue conduit, such that venting combustion gases are precluded from leaking into the second chamber, while substantially useful sensible heat is extracted. 
     DETAILED DESCRIPTION OF THE INVENTION 
     Referring now to the drawing, and to FIG. 1 in particular, there is provided a coal-fired, automatic stoker  12  having the improved air circulation system of the present invention. It comprises an upright, rectangular box  14 , floor offset on raised upright corner legs  16 A/D, and a conventional, top surface, mounted vertical chimney or flue  18 . The upper front section of the stove presents a hinged, transparent door  20 , which give user access for clearing of the fire grate (not seen), and a second hinged lower imperforate door  22 , for accessing an ash box (not seen) to effect periodic dumping of collected ash. The chimney  18  is preferably located proximal to the rearward linear edge of the stoker. 
     In the rearward perspective view of FIG. 2 are depicted the box-like coal hopper  24 , underlying, box-like, air intake manifold,  26 , and the associated convection air blower  28 , which is typically a 265 CFM squirrel cage motor. Overlying is second intake air blower  30  of 50 CFM capacity. This smaller blower force feeds air to the firebox (not seen) at variable speeds to regulate combustion rate and heat output. Hopper  24  is spaced apart from manifold  26 , and has its upper perimeter flush with the stoker top horizontal panel. the phantom modified perspective view of FIG. 3, is depicted an underlying ash box  32 , resting on housing bottom panel  34 , and within is normally closed (during coal combustion) hinged door  20 . At the lower rear comer  36  of forward chamber  38  is a portal  40 L (one of two), which receives combustion gases from the main chamber  38 , which are directed to the lower longitudinal end of partially obscured tubular member  40 L. This conduit member is located in a hermetically sealed rearward smaller chamber  44 . A separate dividing member which defines the inner first and second chambers,  38  and  44 , respectively, is an L-shaped bridging rigid panel  46 , extending from the floor  34  of the housing along its lower linear edge  48  to the upper front panel  52  at its upper an leading linear edge. The configuration of the first and second chambers will be later described in detail. 
     As to rear chamber  44 , the tubular members,  40 L/R, each connect at their upper end with combustion gas collection manifold  54 , (FIG. 4) which manifold, in turn, supports the lower end of combustion gases flue conduit  18 . 
     The rear perspective view of FIG. 4 better depicts the air flow blowers  28 / 30 , the paired inverted Y-shaped tubular members,  40 L/R, the gases collection manifold  54 , and the spent gases flue  18 . 
     The perspective views of FIG.  3 / 4  also reveal certain of the internal components, like ash box  32 , resting on planar bottom plate  34 , and chimney  18 , operatably connected to the upper surface of internal manifold  54 . The transverse internal baffling panel, substantially an L-shaped configuration, is also adapted to receive coal stoker  64  in its vertical segment  46 V, and overlies fire box  38 . 
     In the front side, phantom perspective view of FIG. 3 are a pair of internal, upright tubular  56 L/R, which connect functionally with front bridge box-like, elongate manifold  58 , as will be described. 
     Upper air blower  30  is located intermediate of the opposing tubular pair,  40 L/R, and forces air to the undersurface of fire box stoker unit  76  (FIG.  7 ). The upper segment  46 H of planar baffling plate  46  is sloped upwardly from rearward to frontward, forming an elongate horizontal passage  45  (FIG. 7) slot with planar top panel  47 , which top panel supports the bridge manifold  54 , and upwardly projecting chimney  18 . The feet of the converged tubular members,  40 L/R, are in open connection with the niches, ports  50 L/R, located at the rearward two opposing back comers of the stove  12 . 
     The front elevational view of FIG. 5 depicts the stove  12  as it presents to the user, being oriented for operation with central flue  18  positioned and connected (not seen) to vent the heat-spent coal combustion gases. The bottom upward plan view of FIG. 6 depicts bottom plate  34 , comer legs  16 A/D, and front air intake ports,  56 L/R. Blower  28  and its front handle on lower door  20  are seen. Coal hopper  24  and fire box  26  overlie blower  28 . (FIG. 7) 
     In the vertical cross section view of FIG. 7 are shown all of the operative components in their functional juxtapositions, including flue  18  mounted on horizontal manifold  54 ; sensible heat outflow passage  45 ; elongate vent  52 ; front bridge box  58 ; and sloped tubular members,  40 L/R, front face, tubular members,  56 L/R, to horizontal tube  58 ; ash box  32 , upper blower  30 , and forced air passage  76  to the underside of firebox  64 . Fire grate  78  projects horizontally into combustion chamber  38 , receiving forced air flow from manifold  26 . This innovation is described in my copending application, USSN 10/038,444, filed Jan. 7, 2002. 
     Regarding underside inlet ports,  57 L/R, of FIG. 6 associated with front face conduits  56 L/R of FIG. 3, these provide a washing and cleaning feature for combustion chamber glassed door  20 . These conduits each have their lower longitudinal ends open to the ambient atmosphere, and draw in cooler ambient air to collect in bridging manifold  58 . Manifold  58  is provided with a bottom side linear vent  62  (FIG.  9 ), which directs air flow laterally about glassed door  20 , as is depicted in the flow lines of FIG.  9 . Fire grate  78  is horizontally aligned, along with coal hopper  24 , and vertical mounting plate is at right angles with  46 V. 
     Lower blower  28  provides forced air flow to backward chamber  44 , which air flows therethrough in heat exchange with sealed combustion gas conduits,  40 L/R, disposed vertically in that chamber. The heated intake air is adapted to flow upwardly and outwardly through converging horizontal passage  45  and so to vent usefully to the environment of the stoker  12  via port  52 . 
     In the exploded vertical view of FIG. 8, all of the stoker elements are depicted, including rear sidewall, central continuous cutouts, adapted to receive the firebox  64  projection into the operative stove body, and the downwardly sloped edge  63  of top panel  47  which serve to direct heated air from the stoker body into the ambient space. 
     On the forward facade of stove  12  is seen the cooler-washer subassembly,  58 / 56 , and the front panel cutouts  64  and  68 , which operatively connect to access doors,  20  and  22 , respectively. Heat exchange, conduit assembly,  40 L/R and  54 , are disposed vertically between inner plate  44 V that defines the first and second chambers,  38  and  44 , respectively, and the back panel  70  provided with cutouts,  71  and  72 , which accommodates fixedly stoker unit  24  and lower blower  28 , respectively. The cutout  74  on vertical plate  44 V receives the body of firebox  64  within larger chamber  38 . Coal hopper  24  is mounted on the external surface of stove firebox  64 . Underlying passage  76  feeds forced air to the fire grate  78  of firebox  64 . Stoker housing  10  comprises three conjoining upstanding panels, with the front panel  65 , adapted by cutouts to access the firebox and ash pan respectively. 
     Averting now to the opened-up perspective view of FIG. 9, the two forced air flows to the housing are graphically shown: of the combustion gases; of the induced convection air for enhanced sensible heat generation; and of the ancillary front panel, glassed, access door element, all of which are dynamically depicted. Combustion gases arising from firebox  64  are drawn as they cool somewhat, to the lowermost area of main chamber  38 . They are then drawn through corner niches,  50 L/R into combustion gas outflow conduits  40 L and  40 R, flowing upwardly to gas collection manifold  54 , also set in back chamber  44 , and then away from the inhabited area of the stoker via flue conduit  18 . 
     Concurrently, the to-be-heated, but cooler air, indrawn via blower  28 , flows directly to the lower section of back chamber  44 , wherein that air effects a substantial heat exchange with combustion gases conduits disposed therein,  40 L/R. Much sensibly heated air rises, and is drawn via lateral passage  45  of chamber  44  to outflow of the stoker housing itself, via slot vent  52 , thereby providing added sensible heat to the room that has been newly extracted from the normally quite hot combustion gases that are continuously being vented. Typically, the flue gas temperature is reduced on the order of 100 degrees F. by the use of the present invention. 
     As to the ancillary, front panel cooling feature, ambient air is drawn upwardly at intake ports,  57 L/R, (FIG. 6) into vertical conduits,  56 L/R, and is combined in collection elongate manifold  58 . The collected cooler air is vented downwardly via manifold bottom slot  62 , along the lateral edges of upper door  20 , cooling and air washing that access door to the combustion chamber. This feature minimizes any searing inadvertent contact of user with the hot glass element of the upper door, and also facilitates needed peaks at the firebox to confirm ongoing combustion of the automatic hopper deposited coal bed. 
     In a partial sectional view of FIGS. 7A, an alternative embodiment for sensible heat rerouting from outflow chamber  45 A is depicted. All of the other elements are unchanged, but top plate  47 A is modified to provide an outlet port  70  upon which is mounted fixedly, a heated air conduit  72 . This alternate outlet serves to conduct a portion of the sensible heat air flow to another area to be warmed (not shown), while the mini-furnace is being operated at its maximum flow capacity. At lower air flow rates, intended only to warm the stoker immediate environment, an outlet port cover underlying the outflow conduit (not seen) can be rotated to shut off this outflow.