Abstract:
Provided is a process/integrated furnace system that (i) receives and heat treats a casting, (ii) removes sand core materials from the casting, and (iii) actively reclaims sand from the sand core materials. The furnace system includes a heating chamber that receives and heat treats metal castings. During the heat treating process, sand core materials are dislodged and fall from the castings into a sand reclaiming region. A hot fluidized bed functions to reclaim sand from the fallen sand core materials within the heating chamber. The fallen sand core materials are not evenly distributed across the zones within the heating chamber. To compensate for the uneven distribution, sand discharge weirs and leveling bars divide the hot fluidized bed in to different bed zones having different dwell times.

Description:
CROSS-REFERENCE TO RELATED APPLICATION 
     This Application claims the benefit of priority to U.S. Provisional patent application Ser. No. 60/012,308, filed on Feb. 23, 1996. 
    
    
     CROSS-REFERENCE TO RELATED APPLICATION 
     This Application claims the benefit of priority to U.S. Provisional patent application Ser. No. 60/012,308, filed on Feb. 23, 1996. 
     BACKGROUND OF THE INVENTION 
     The present invention relates generally to the field of foundry processing, and more particularly to heat treating metal castings and reclaiming sand from sand cores and sand molds used in the manufacture of metal castings. 
     Many improvements have been made in the field of heat treating metal castings and reclaiming sand from sand cores and sand molds used in the manufacture of metal castings. Examples of some recent improvements are disclosed in U.S. Pat. Nos. 5,294,094 and 5,354,038, both of which are expressly incorporated herein by reference, in their entirety. Those patents disclose a unique three in one process/integrated system that (i) receives and heat treats a casting, (ii) removes sand core/sand mold materials from the casting, and (iii) very effectively reclaims sand from the sand core/sand mold materials removed from the casting. The sand core/sand mold materials (referred to hereafter as sand core materials) comprise sand that is held together by a binder material such as, but not limited to, a combustible organic resin binder. 
     Improvements such as those disclosed in the above-mentioned patents are driven, for example, by competition; increasing costs of raw materials, energy, labor, and waste disposal; and environmental regulations. Those factors continue to mandate improvements in the field of heat treating and sand reclamation. 
     SUMMARY OF THE INVENTION 
     Briefly described, a preferred embodiment of the present invention comprises a three-in-one process/integrated system that (i) receives and heat treats a casting, (ii) removes sand core materials from the casting, and (iii) actively reclaims sand from the sand core materials in a fluidized bed that is segregated into distinct zones. The distinct zones compensate for the varied manner in which sand core materials fall from castings into the fluidized bed. In accordance with the preferred embodiment, this compensation includes terracing the fluidized bed in a manner that seeks to insure that substantially all of the reclaimed sand has been subjected to generally the same amount of reclaiming and is therefore reclaimed to substantially the same degree. In accordance with one embodiment of the present invention, the process/integrated system does not heat treat the casting, but removes sand and reclaims sand similarly to the preferred embodiment. 
     In accordance with the preferred embodiment of the present invention, a furnace system is provided that has a heating chamber. The heating chamber receives and heat treats metal castings. During the heat treating process, sand core materials are dislodged and fall from the castings into a fluidized bed, which is disposed in the lower portion of the heating chamber. The sand core materials fall from castings as the castings pass sequentially through zones of the heating chamber. The fallen sand core materials are typically not evenly distributed across the zones. 
     In accordance with the preferred embodiment of the present invention, the fluidized bed is disposed within a trough. Fluidizing assemblies substantially cover the bottom of the trough. A weiring system includes sand discharge weirs that are sequentially arranged along the length of the trough. Reclaimed sand is discharged from the trough through each of the sand discharge weirs. The weiring system also includes leveling bars that span the trough. The weiring system accommodates for the uneven distribution of fallen sand core materials and provides control over the reclaiming of sand. The weiring system seeks to expose all portions of sand core material to generally the same amount of reclaiming within the fluidized bed by controlling dwell times and flattening top surfaces of the fluidized bed. 
     The weiring system segregates the fluidized bed into bed zones. Bed zones into which greater amounts of sand core material are expected to fall (the &#34;higher volume zones&#34;) define greater volumes and have greater dwell times, while bed zones into which lesser amounts of sand core material are expected to fall (the &#34;lower volume zones&#34;) define lesser volumes and have lesser dwell times. In accordance with the preferred embodiment of the present invention, it is the variations in dwell time that compensate for the varied distribution of fallen sand core portions. 
     In accordance with the preferred embodiment of the present invention, variations in volume and dwell time are achieved by the fact that different bed zones define different heights. The sand discharge weirs cooperate with the leveling bars to define the different heights. Higher sand discharge weirs are employed where greater amounts of sand core materials are expected to fall into the fluidized bed and lower sand discharge weirs are employed where lesser amounts of sand core materials are expected to fall into the fluidized bed. The leveling bars span the trough such that a leveling bar is disposed between adjacent sand discharge weirs. The upper edges of the leveling bars are higher in areas of higher volume zones and lower in lower volume zones. 
     It is, therefore, an object of the present invention to increase the efficiency of heat treating and sand reclamation processes. 
     Yet another object of the present of the present invention is to provide an improved method and apparatus for removing sand core material from a casting and reclaiming sand from the sand core material. 
     Still another object of the present invention is to provide a single system that provides for substantially complete sand reclamation. 
     Still another object of the present invention is to provide control over the characteristics of reclaimed sand. 
     Still another object of the present invention is to compensate for the uneven distribution of sand core materials within a fluidized bed. 
     Other objects, features, and advantages of the present invention will become apparent upon reading and understanding this specification, when taken in conjunction with the accompanying drawings. 
    
    
     BRIEF DESCRIPTION OF THE DRAWING 
     FIG. 1 is a schematic, side cut-away view of a furnace system in accordance with a preferred embodiment of the present invention. 
     FIG. 2 is an isolated, schematic, perspective view of a collection trough of the furnace system of FIG. 1. 
     FIG. 3 is a perspective, schematic, cut-away view of the collection trough and a weir of the furnace system of FIG. 1. 
     FIG. 4 is a schematic, cut-away, cross-sectional view of a portion of the furnace system of FIG. 1 taken along line 4--4 of FIG. 3. Substantial portions of the furnace system have been cut-away, and cross-sectioned fluidizing tubes are shown in FIG. 4. 
     FIG. 5 is an isolated, schematic, side cut-away view of the collection trough, sand discharge weirs, leveling bars, and fluidized bed of FIG. 1. 
     FIG. 6 is a schematic, cut-away, perspective view of portions of the collection trough and a few of the sand discharge weirs and leveling bars of FIG. 1. 
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     Referring to the drawings in which like numerals represent like components throughout the several views, FIG. 1 is a schematic, side cutaway view of a furnace system 20 in accordance with a preferred embodiment. The furnace system 20 includes a heating chamber 22 that receives and heat treats castings (that are acceptably transported through the heating chamber 22 in baskets 26a,b), dislodges sand core materials 28 from the castings, and actively reclaims sand 30 from the sand core materials 28. The reclaiming is carried out, at least in part, in a hot fluidized bed 32 that is preferably disposed within the heating chamber 22. The furnace system 20 includes a plurality of sand discharge weirs 84a-i through which reclaimed sand exits the fluidized bed 32 and the heated chamber 22. In FIG. 1, portions of the sand discharge weirs 84a-i are hidden from view behind a sub-header assembly 76 portion of a fluidizing assembly 68 that creates the fluidized bed 32. The weirs 84 cooperate with a plurality of leveling bars 158a-g to terrace the fluidized bed 32 so that it defines distinct zones that compensate for the varied manner in which sand core materials 28 fall from castings into the fluidized bed 32. 
     As depicted in FIG. 1, the outlet ends of the weirs 84a-i are equipped with valves 82a-i which are normally open so that reclaimed sand 30 flows from the fluidized bed 32, through the weirs 84, to a and conveying assembly 34. The sand 30 exits the heating chamber 22 as it passes through the weirs 84. The sand 30 falls from the weirs 84 to the sand conveying assembly 34. The sand conveying assembly 34 is acceptably in the form of one or more vibratory conveyers that transport the reclaimed sand 30 to a hopper 120. The sand in the hopper 120 is substantially ready for reuse. 
     A front 35 and a rear 37 are defined. The heating chamber 22 includes insulated walls 36, an insulated inlet door 38 toward the front 35, and an insulated outlet door 40 toward the rear 37. In FIG. 1, only the walls 36 and doors 38,40 have been partially cut-away/cross-sectioned. The walls 36 and doors 38,40 bound and define the heated work chamber 22. An upper conveyer assembly 42a (e.g., a roller hearth) and a lower conveyer assembly 42b (e.g., a roller hearth) extend through the heating chamber 22 from the inlet door 38 to the outlet door 40. The conveyer assemblies 42 each receive and transport the castings (which are preferably disposed within baskets 26) through the heating chamber 22 in a direction defined from the inlet door 38 toward the outlet door 40. A casting quench facility (not shown) is preferably proximate to the outlet door 40 such that castings can be immediately quenched upon removal from the heating chamber 22. The baskets 26 are of open construction to permit sand core materials 28 dislodged from the castings to fall freely out of the baskets 26. Similarly, the conveyer assemblies 42 are constructed so that dislodged sand core materials 28 pass through the conveyer assemblies 42. 
     The heating chamber 22 can be characterized as including multiple zones through which the baskets 26 pass sequentially. For example, in FIG. 1 a different zone extends with and beneath each of the fans 44a-f. While only six fans 44 are shown in FIG. 1, heating chambers 22 with more or less than six fans 44 or zones are within the scope of this disclosure. The fans 44 function to circulate the atmosphere within the heating chamber 22. Heaters 46 heat the atmosphere in the heating chamber 22 to a processing temperature, in the preferred embodiment, sufficient to both heat treat castings and to combust (and pyrolize in regions of castings lacking oxygen) binder that binds the sand of the core material 28, whereby core materials 28 fall from the castings. Preferably a plurality of heaters 46 are employed within the heating chamber 22. A single heater 46 is schematically illustrated in FIG. 1 as including a burner 48 within a U-shaped tube 50. The U-shaped tube 50 isolates the burner 48 from the atmosphere within the heating chamber 22. Alternatively, the burner 48 is exposed to the atmosphere within the heating chamber 22. A variety of different types of heaters 46 can acceptably be employed within the heating chamber 22. 
     The heaters 46 are capable of heating the atmosphere within the heating chamber 22 to a temperature sufficient to both heat treat the castings and dislodge sand core materials 28 from cavities within the castings. The sand core materials 28 preferably comprise sand that is bound by a combustible binder material such as, but not limited to, an organic resin binder. Thus, the heaters 46 heat the heating chamber 22 to above the combustion temperature of the organic resin binder. The heating chamber 22 is preferably heated to a temperature of approximately 850 to 1000 degrees Fahrenheit. The fans 44a-f are preferably constructed to circulate the atmosphere in a manner that aids in the dislodging of core materials 28 from the castings subsequent to binder combustion. 
     A plurality of screens 52, such as but not limited to one-quarter inch screens, are positioned beneath the conveyer assembly 42b in at least some of the earlier zones of the heating chamber 22. The screens 52 extend above the trough 54 (discussed below) in a manner such that the screens 52 capture substantially all of the clumps of sand core material 28 larger than one-quarter inch which are dislodged from the castings. The clumps of core material 28 collected on the screens 52 will continue to be suspended within and exposed to the heated and oxygen-rich airflow within the heating chamber 22 until a substantial portion of the binder associated with the clumps has burned off, at which time the clumps will disintegrate. When the clumps have disintegrated to a size smaller than one-quarter inch, the disintegrated clumps fall through the screens 52. The screens 52 are preferably situated in the earlier and middle zones because that is where a majority of the core materials 28 are expected to be dislodged and fall from the castings. In accordance with certain embodiments, the screens 52 extend for the entire length of the heating chamber 22. 
     A receptacle such as, but not limited to, a trough 54 is defined in the bottom of the heating chamber 22. FIG. 2 is a isolated perspective view of the trough 54 from the front 35. The trough 54 includes a bottom 56 and side walls 58,60 extending upward from side edges of the bottom 56 in a divergent manner such that obtuse angles are defined between the side walls 58,60 and the bottom 56. Walls 62,64 extend upward from the other edges of the bottom 56. The bottom 56 of the trough 54 defines openings 80a-i therethrough (opening 80a is not seen in FIG. 2). The sand discharge weirs 84a-i (FIG. 1) extend through the openings 80a-i, respectively. 
     Referring to FIG. 1, the fluidizing assembly 68 is closely associated with the bottom 56 of the trough 54. The fluidizing assembly 68 includes a blower 70 that forces a fluidizing medium through a conduit 72 that separates into headers 74a,b that feed a sub-header assembly 76. In accordance with the preferred embodiments, the sub-header assembly 76 includes a multiplicity of fluidizing tubes (i.e., the sub-header assembly 76 is preferably a sparger or perforated pipe distributor). A variety of conventional sub-header assemblies 76 are capable of being acceptably incorporated into the disclosed embodiments. In accordance with an alternate embodiment, a sub-header assembly 76 is not employed and the bottom 56 of the trough 54 functions as part of the fluidizing assembly 68. That is, the bottom 56 is perforated and a fluidizing medium is forced through the perforations of the bottom 56. 
     In accordance with the preferred embodiment, the conduit 72 cooperates with a heater assembly 73 that heats the fluidizing medium to a temperature in excess of the combustion temperature of the binder of the core material 28. The heating of the fluidizing medium above the combustion temperature of the binder of the core material 28 causes binder to combust within the hot fluidized bed 32. In the preferred embodiment, the heater assembly 73 includes a high pressure gas burner (not shown) that is preferably operated such that the burner does not consume all of the oxygen passing through the heater assembly 73, as discussed in greater detail below. In accordance with alternate embodiments, the heater assembly 73 incorporates an electric heating element or other type of heater. In accordance with other alternate embodiments, a heater assembly 73 is not employed. In that alternate embodiment, the heating chamber 22 is sufficiently heated such that binder materials combust within the fluidized bed 32. The heating chamber 22 controllably vents to the atmosphere through an exhaust conduit 99 that communicates with an incinerator 101. 
     FIG. 3 is a schematic, cut-away, perspective view of a portion of the trough 54 and the sand discharge weir 84i from the front 35 (FIG. 1). The weir 84i fits over or through the opening 80i (FIG. 2) such that the opening 80i is hidden from view in FIG. 3. Except for the fact that the weirs 84a-i (FIG. 1) define different heights, weir 84i is representative of the weirs 84a-h. That is, in accordance with the preferred embodiment, each of the discharge weirs 84a-i is identical, except for variations in height, as discussed below. The weir 84i extends upward from the opening 80i (FIG. 2) and includes walls 86, 88, 90, 92 that are joined at their edges such that the weir 84i is in the form of an elongated conduit that is generally in the shape of a square in a top plan view thereof. The walls 86, 88, 90, 92 bound a passage 94 that is open at the upper end of the weir 84 within the trough 54. At the lower end of the weir 84i, the passage 94 is open to discharge reclaimed sand 30 (FIG. 1) to the conveyor assembly 34 (FIG. 1) when the valve 82i is open. 
     FIG. 4 is a schematic, cut-away, cross-sectional view of the furnace system 20 (FIG. 1), taken along line 4--4 of FIG. 3. The valve 82i is not shown and substantial portions of the furnace system 20, including portions of the trough 54 and sub-header 76, are cut away in FIG. 4. Additionally, in FIG. 4, the sub-headers 76 are depicted in the form of fluidizing tubes 78, only several of which are specifically identified in FIG. 4. The fluidizing tubes 78 are cross-sectioned transverse to their length in FIG. 4. The fluidizing tubes 78 preferably define a plurality of apertures (not shown) through the sidewalls thereof. The fluidizing medium passes through the apertures in the side walls of the fluidizing tubes 78. The apertures are preferably oriented downward in a manner that seeks to keep sand 30 and sand core materials 28 from entering the fluidizing tubes 78. 
     The walls 86,88,90,92 (also see FIG. 3) of the weir 84i preferably each extend to the same height above the bottom 56 of the trough 54. Therefore, the upper edges of the walls 86,88,90,92 together function as a weir edge 100 over which the sand 30 (FIG. 1) flows into the passage 94 to pass through the weir 84i. The weir edge 100 and the opening defined by the weir edge 100 preferably define a generally horizontal plane. As seen in FIG. 4, the lower edges of the walls 86,88,90,92 (also see FIG. 3) of the weir 84i preferably extend through the bottom 56 of the trough 54. A flange 98 preferably bounds the opening 80i and is attached to the bottom of the trough 54, for example by welding. The lower edges of the weir 84i are preferably attached to the flange 98, for example by welding. 
     As depicted in FIG. 1, inverted V-shaped baffles 96a-i are positioned above the upper opening to the passage 94 (FIG. 4) of each weir 84a-i, respectively. The baffles 96 do not interfere with the flow of sand 30 from the hot fluidized bed 32 into the passages 94 of the weirs 84. The baffles 96 are broad enough to substantially keep any sand core materials 28 from falling directly into the weirs 84 from above the hot fluidized bed 32. That is, the baffles 96 deflect sand core materials 28 such that the sand core materials fall into the hot fluidized bed 32. 
     Referring to FIG. 1, the valves 82a-i function to open and close the passages 94 (FIGS. 3 and 4) defined through the weirs 80a-i, respectively. The valves 82a-i are represented schematically in FIG. 1. The valves 82a-i are open during normal operation. The valves 82a-i may be closed in the case of an emergency. The valves 82a-i are preferably manual gate or dump valves, or vibratory feeder valves, or stone-box type valves. 
     FIG. 5 is a, schematic, side cut-away view of the trough 54 fitted with the sand discharge weirs 84a-i, the leveling bars 158a-g (e.g., partitions), the inverted V-shaped baffles 96a-i, and containing the fluidized bed 32, in accordance with the preferred embodiment of the present invention. The sub-header assembly 76 is not depicted in FIG. 5 in an effort to clarify the view. FIG. 6 is a, schematic, perspective, partially cut-away view from the rear 37 (FIG. 1) of the trough 54 fitted with a few of the sand discharge weirs 84 and leveling bars 158, in accordance with the preferred embodiment. 
     Referring primarily to FIG. 6 and leveling bar 158b for example, in accordance with the preferred embodiment, each leveling bar 158 is an elongated generally flat slab having opposite ends 160, 162 that are connected to the opposite side walls 58,60 of the trough 54. Each leveling bar extends generally perpendicular to the length of the trough 54. Additionally, each leveling bar 158 includes an upper edge 164 and a lower edge 166 that extend generally horizontally and are disposed above the bottom 56 of the trough 54. 
     Referring to FIG. 5, certain of the weirs 84 define different weir heights. The weir height of each weir 84 is defined as the distance between the respective weir edge 100 (FIG. 4) and the bottom 56 of the trough 54. As an example, the dimension &#34;H&#34; identified with respect to the weir 84d represents the weir height of the weir 84d. Similarly, the upper edge 164 (FIG. 6) and lower edge 166 (FIG. 6) of each leveling bar 158 define an upper height and a lower height, respectively, above the bottom 56 of the trough. As an example, the dimension &#34;U&#34; identified with respect to the leveling bar 158d represents the upper height of the leveling bar 158d. Similarly, the dimension &#34;L&#34; identified with respect to the leveling bar 158d represents the lower height of the leveling bar 158d. 
     In accordance with the preferred embodiment, a leveling bar 158 is disposed between two adjacent weirs 84, and the upper and lower heights of the leveling bars 158 are coordinated with the weir heights of the adjacent weirs 84. Where adjacent weirs 84 define different weir heights, the upper height of the leveling bar 158 interposed between the adjacent weirs 84 is generally equal to the highest weir height of the adjacent weirs 84. Similarly, the lower height of that leveling bar 158 is generally equal to the lowest weir height of the adjacent weirs 84. Where adjacent weirs 84 define generally the same weir heights, the upper height of the leveling bar 158 interposed between the adjacent weirs 84 is generally equal to the weir heights of the adjacent weirs 84. The lower heights of all of the leveling bars 158 are preferably high enough to allow the fluidized bed 32 to readily flow beneath the leveling bars 158. 
     The leveling bars 158 function to restrict flow of the fluidized bed 32 proximate to the upper surface of the fluidized bed 32. The upper heights of the leveling bars 158 function to separate the upper surface of the fluidized bed 32 into bed zones 168a-i. A first bed zone 168a is defined between the leveling bar 158a and the wall 64 of the trough 54, a second bed zone 168b is defined between the leveling bar 158a and the leveling bar 158b, a third bed zone 168c is defined between the leveling bar 158b and the leveling bar 158c, a fourth bed zone 168d is defined between the leveling bar 158c and the leveling bar 158d, a fifth bed zone 168e is defined between the leveling bar 158d and a leveling bar that is not shown in FIG. 6, a sixth bed zone 168f is defined between the leveling bar that is not shown in FIG. 6 and the leveling bar 158e, a seventh bed zone 168g is defined between the leveling bar 158e and the leveling bar 158f, an eighth bed zone 168h is defined between the leveling bar 158f and the leveling bar 158g, and a ninth bed zone 168i is defined between the leveling bar 158g and the wall 62 of the trough 54. In accordance with the preferred embodiment, the amount of the sub header assembly 76 (FIG. 1 ) disposed within each of the bed zones 168 is generally equivalent, whereby in theory each bed zone 168 receives generally the same amount of fluidizing medium. Reclaimed sand 30 (FIG. 1) exits the bed zones 168a-i through the sand discharge weirs 84a-i, respectively. 
     The leveling bars 158 and the sand discharge weirs 84 cooperate such that the fluidized bed 32 has a generally planar and generally horizontally extending upper surface in each bed zone 168a-i. The surface height of the fluidized bed 32 above the bottom 56 of the trough 54 is preferably different in different bed zones 168. The height of the surface of the fluidized bed 32 in a particular bed zone 168 corresponds generally to the weir height of the weir 84 that is central to that bed zone. Therefore, the hot fluidized bed 32 is terraced. In accordance with one acceptable example, the weir 84a and the portion of the hot fluidized bed 32 around the weir 84a (i.e., the portion of the hot fluidized bed 32 in the first bed zone 168a) define a height of approximately one hundred and fifty millimeters; the weir 84b and the portion of the hot fluidized bed 32 around the weir 84b (i.e., the portion of the hot fluidized bed 32 in the second bed zone 168b) define a height of approximately two hundred millimeters; and the weir 84c and the portion of the hot fluidized bed 32 around the weir 84c (i.e., the portion of the hot fluidized bed 32 in the third bed zone 168c) define a height of approximately three hundred millimeters. 
     In accordance with the preferred embodiment, the volume of an individual bed zone 168 (which correlates to the quantity of sand core materials 28 within that individual bed zone) is proportional to the height of the fluidized bed 32 within that individual bed zone 168. The height of the fluidized bed 32 within an individual bed zone 168 corresponds generally to the weir height of the weir 84 within that individual bed zone. In accordance with the preferred embodiment, each bed zone 168a-i is similar in construction such that, if each bed zone 168a-i contained the same height of sand core materials 28 therein (which is not the case in accordance with the preferred embodiment), each bed zone 168a-i would contain the same quantity or volume of sand core materials 28. 
     Operation 
     Referring to FIG. 1, in accordance with the preferred embodiment, the furnace system 20 (i) receives and heat treats castings, (ii) removes sand core materials 28 from the castings, and (iii) actively reclaims sand 30 from the sand core materials 28. Initially, metal castings such as, but not limited to, aluminum castings are placed into baskets 26. The castings preferably have at least some sand core materials 28 attached thereto. The sand core materials 28 preferably comprise sand bound by a binder material such as, but not limited to, a combustible organic resin binder. Most preferably the castings are aluminum castings that define cavities and have substantially intact sand cores (comprising sand bound by a combustible binder) therein. In accordance with an alternate embodiment, sand core materials 28 are introduced into the heating chamber 22 separate from the castings. 
     The inlet door 38 is temporarily opened and a basket 26 is placed upon one of the conveyer assemblies 42. Alternatively the castings may be placed directly upon the conveyer assemblies 42. As the castings are conveyed through the heating chamber 22 at least a portion of the binder of the sand cores combusts (or, in appropriate condition, pyrolize) such that sand core materials 28 fall from the castings and the conveyer assemblies 42. The castings are preferably maintained within the heating chamber 22 for a sufficient period such that the castings are heat treated for at least several hours and the sand cores are substantially totally removed from the castings. Oxygen is introduced into the heating chamber 22 to enhance the combustion. Oxygen is preferably supplied with the fluidizing medium (i.e. air) into the bottom of the heating chamber 22 by way of the fluidizing assembly 68. Oxygen (e.g., air) can also be introduced by other means such as by exposing the burner 48 to the atmosphere within the heating chamber 22 and by providing an excess amount of oxygen (e.g., air) to the burner 48. The screens 52 are preferably quarter inch screens so that any lumps of core material 28 larger than a quarter inch are suspended upon the screens 52. While lumps of sand core materials 28 are suspended on the screens 52, further binder combustion occurs such that the lumps disintegrate and fall from the screens 52 into the hot fluidized bed 32. 
     The sand core materials 28 that fall into the hot fluidized bed 32 are suspended and agitated within the heated and oxygenated environment of the hot fluidized bed 32 such that the binder material associated with the sand core materials 28 is combusted and sand 30 is reclaimed that is substantially ready for reuse. Stated differently, in accordance with the preferred embodiment, calcination occurs within the hot fluidized bed 32 (i.e., the binder material is decomposed). In addition to being heated by the heater assembly 73, the hot fluidized bed 32 is heated due to its proximity to the heater 46 and the heated environment within the heating chamber 22. 
     In accordance with the preferred embodiment, the reclaimed sand 30 within the hot fluidized bed 32 flows toward the sand discharge weirs 84a-i due to the action of the fluidizing assembly 68 and the fact that weirs 84a-i are an outlet from the heating chamber 22. During normal operation the valves 82a-i are open and the reclaimed sand flows through the weirs 84 and falls onto the sand conveyor 34. The valves 82a-i may be closed automatically if such closure would aid in minimizing the negative impacts of certain types of equipment malfunctions. Similarly, the valves 82a-i may be operated for maintenance purposes. 
     In accordance with the preferred embodiments, as castings are transported thought the heating chamber 22, sand core materials 28 fall from the castings in varying amounts. The amount of sand core material 28 that falls from the casting is generally a function of the amount of time that a castings has been disposed within the heating chamber 22. For example, it takes some time for the castings and sand core materials 28 attached to the casting to reach the combustion temperature of the binder that binds the sand core materials 28. Because the castings are preferably transported through the heating chamber 28, the amount of sand core material 28 that falls from the castings is generally a function of the position of the castings along the length of the heating chamber 22. 
     Based on experience and in accordance with the preferred embodiment, greater amounts of sand core materials 28 are dislodged from castings toward the middle of the heating chamber 22 and lesser amounts of sand core materials 28 are dislodged toward the front 35 and rear 37 ends of the heating chamber 22. Stated differently, in accordance with one exemplary embodiment, the distribution of fallen sand core materials 28 can be represented by a graph or geometric picture generally in the form of a bell-shaped curve. The present invention compensates for the above-described varied distribution of sand core materials 28 to provide a system and process that insures that substantially all of the reclaimed sand 30 has been subjected to generally the same amount of reclaiming and therefore is reclaimed to substantially the same degree. 
     Referring to FIG. 5, the different heights of the weirs 84a-i and the leveling bars 158a-g compensate for the variation in the amounts of sand core materials 28 that fall into the fluidized bed 32. The weirs 84a-i and the leveling bars 158a-g function to generally maintain a level surface of the fluidized bed 32 in individual bed zones 168a-i. By maintaining level surfaces of the fluidized bed 32 in individual bed zones 168a-i, control is maintained over the reclaiming of sand 30. When a level surface is maintained in an individual bed zone 168, the sand core materials 28 within that individual bed zone 168 tend to experience a generally equivalent amount of exposure to the reclaiming effects of the fluidized bed 32. 
     The weirs 84a-i and the leveling bars 158a-g also seek to vary the dwell time of the sand core materials 28 within the fluidized bed 32. The variation of dwell times is established between bed zones 168 and seeks to subject all sand core materials 28 to the same amount of reclaiming irrespective of the bed zone 168 into which the sand core materials 28 fall. This seeks to provide reclaimed sand 30 having uniform properties. That is, in accordance with the preferred embodiment, reclaiming within the bed zones 168 is varied to compensate for varied distribution of fallen sand core materials 28 such that generally all of the reclaimed sand is reclaimed to generally the same degree. In accordance with the preferred embodiment, the bed zones 168 into which greater quantities of sand core materials 28 fall (e.g., bed zones 168c-f) hold greater quantities of sand core materials 28 than do the bed zones 168 into which lesser quantities of sand core materials 28 fall (e.g., bed zones 168a-b,g-i). Stated differently, the bed zones 168 into which greater quantities of sand core materials 28 fall define greater volumes than do the bed zones 168 into which lesser quantities of sand core materials fall. Individual pieces of core material 28 tend to have a greater dwell times in bed zones 168 having greater volumes. 
     This paragraph presents one example of the preferred embodiment. In accordance with this example, the first bed zone 168a defines a height of approximately one hundred and fifty millimeters and the third bed zone 168c defines a height of approximately three hundred millimeters. Since the bed zone 168c has approximately twice the height of the bed zone 168a, the bed zone 168c has approximately twice the volume of the bed zone 168a. Since the bed zone 168c has approximately twice the volume of the bed zone 168a, the bed zone 168c has approximately twice the dwell time of the bed zone 168a. In accordance with the preferred embodiment, approximately the same amount of fluidizing medium is supplied to each bed zone 168, so variations in dwell time compensate for variations in the quantity of sand core material 28 between bed zones 168. For example, statistically and theoretically, the sand core materials 28 disposed within the bed zone 168a will be exposed to substantially the same amount of reclaiming. (i.e., have the same dwell time) as the sand core materials 28 disposed within the bed zone 168c such that the sand 30 reclaimed in the bed, zone 168a will be substantially similar to the sand 30 reclaimed in the bed zone 168c. 
     In accordance with an alternate embodiment, variations in dwell time are not employed in an effort to equalize the reclamation of the sand 30. Rather, equalized reclaiming between bed zones 168 is established by varying the fluidizing action between individual bed zones 168. In accordance with this alternate embodiment, the fluidizing action is more intense in the zones 168 into which greater quantities of sand core material 28 fall, and the fluidizing action is less intense in the zones 168 into which lesser quantities of sand core material 28 fall. Variations in intensity can be accomplished, for example and not limitation, by varying the quantity of fluidizing medium injected into a bed zone 168. Alternately, a combination of variations in dwell time and variations in fluidizing flow (e.g., variations in the flow of fluidizing medium) are employed. 
     While the embodiments which have been disclosed herein are the preferred forms, other embodiments will suggest themselves to persons skilled in the art in view of this disclosure. Any relationships and dimensions shown on the drawings are given as the preferred relative relationships, but the scope of this disclosure is not to be limited thereby.