Abstract:
The method and apparatus for reclaiming substantially pure sand from a heat treating furnace; wherein a casting with sand core and/or sand mold, comprising sand bound by a combustible binder, attached thereto is introduced into the heat treating furnace; or, wherein portions of sand core and/or sand mold that are not attached to a casting are introduced into the heat treating furnace. Wherein, the reclaiming within the furnace is carried out, in part, by a fluidizer that promotes binder combustion by one or more process of agitating, heating, and oxygenating. Wherein, the characteristics of the reclaimed sand are selectively controlled by controlling the dwell time of the sand within the heat treating furnace.

Description:
CROSS-REFERENCES TO RELATED APPLICATIONS  
       [0001]    This application is a continuation of application Ser. No. 08/419,372, filed Apr. 10, 1995, which is a continuation of application Ser. No. 08/283,958, filed Aug. 1, 1994, which is a continuation of application Ser. No. 08/272,153, filed Jul. 8, 1994, which is a continuation of Ser. No. 08/198,879, filed Feb. 18, 1994, U.S. Pat. No. 5,354,038, which is a continuation of application Ser. No. 07/930,193, filed Aug. 13, 1992, which is a continuation-in-part of application Ser. No. 07/705,626, filed May 24, 1991, which is a continuation-in-part of application Ser. No. 07/415,135, filed Sep. 29, 1989.  
     
    
     
       BACKGROUND OF THE INVENTION  
         [0002]    The present invention relates generally to the field of heat treating metal castings and the field of reclaiming sand from sand cores and sand molds used to make metal castings.  
           [0003]    Generally, prior art methods and apparatus require that two or three distinctly separate steps be taken in order to heat treat a metal casting formed by a permanent mold or sand mold with a sand core, and reclaim sufficiently pure sand from the sand mold or sand core. The present invention allows for heat treating and reclamation of sufficiently pure sand in a single step.  
           [0004]    Methods and apparatus for manufacturing metal castings are well known. Molds and cores are used to displace molten material so that when the molten material is solidified, a casting is formed that reflects the features of the mold and core. Molds have the exterior features of the casting formed on the interior walls of the mold and cores have the interior features of the casting formed on the exterior surface of the core. The cores are typically made from sand whereas the molds are sometimes made from sand. Sand molds and cores are typically pre-molded from a mixture of sand and a combustible binder. For simplicity, sand molds and sand cores are referred to hereafter as simply sand cores.  
           [0005]    In accordance with some of the prior art, once the casting is formed, three distinctly different steps are carried out in order to heat treat the metal casting and reclaim sufficiently pure sand from the sand core. The first step separates portions of sand core from the casting. The sand core is typically separated from the casting by one or a combination of means. For example, sand may be chiseled away from the casting or the casting may be physically shaken to break-up the sand core and remove the sand. Once the sand is removed from the casting, the second and third steps are carried out. In this typical, three-step prior art, the order in which the second and third steps are taken is not important, since the sand has already been separated from the casting. The second step consists of heat treating the casting. The casting is typically heat treated if it is desirable to strengthen or harden the casting. The third step consists of purifying the sand that was separated from the casting. The purification processes is typically carried out by one or a combination of means. These may include burning the binder that coats the sand, abrading the sand, and passing portions of the sand through screens. It is important that the reclaimed sand be sufficiently pure in order for it to be properly reused in the construction of new sand cores. It is also helpful if the reclaimed sand is rounded, at least to some degree, so as to assist in the casting of smooth surfaces and to assist in good bonding of the sand grains which causes strong cores. Therefore, portions of sand may be re-subjected to reclaiming processes until sufficiently pure sand is reclaimed.  
           [0006]    The purity of the reclaimed sand can be measured in terms of the quantity of unburned binder. The less unburned binder, the more pure the sand. While seeking increased purity, some sand is reduced to “fines”. Fines is the term used for sand particles smaller than a specified size. Fines are so small that they require excessive amounts of binder. These two measures (purity and fines) generally oppose each other in that the higher the measure of one, the lower the measure of the other. It is important to balance these measures; therefore, it is important that the sand reclaiming processes be capable of controlling these measures.  
           [0007]    In accordance with the present inventor&#39;s previous invention disclosure of U.S. application Ser. No. 07/705,626, only one step need be taken in order to heat treat metal castings formed by sand cores and reclaim sand from the sand cores. This is carried out by introducing the castings, with the sand cores attached thereto, into a furnace with an oxygenated atmosphere that is heated to at least the combustion temperature of the sand core binder material. This causes combustion of some of the binder of the sand core which, in combination with other means, causes the sand core to separate from the casting. The system disclosed in application Ser. No. 07/705,626 promotes more binder combustion than is required to separate the sand core from the casting. The system disclosed in application Ser. No. 07/705,626 ejects sand from the furnace in a sufficiently pure state for some applications; but, that system is not capable of combusting a sufficient amount of binder (or otherwise processing the sand core) so as to render sand that is sufficiently pure for certain other applications. Also, that system does not make provisions for varying the characteristics of the reclaimed sand; no selective control over sand roundness, amount of fines, or amount of unburned binder in the reclaimed sand is possible. Therefore, the sand reclaimed using the method and apparatus disclosed in application Ser. No. 07/705,626 may require further processing in order to obtain sand that is sufficiently pure for certain applications or sand that has certain characteristics. Therefore, previous sand reclaiming systems are inherently inefficient in that they require at least a two step process, carried out in two separate venues by separate, specialized equipment, in order to heat treat a metal casting formed by a sand core and reclaim sufficiently pure sand from the sand core.  
           [0008]    There is a need, therefore, for a more efficient method, and associated apparatus, that allows for more efficient heat treatment, sand core removal, and reclamation of sufficiently pure sand from the sand core.  
         SUMMARY OF THE INVENTION  
         [0009]    Briefly described, the present invention provides an improved method and apparatus for heat treating metal castings that are manufactured using sand cores and for reclaiming sand from the sand cores. More specifically, the present invention provides an improved method and apparatus for collecting sand within a heat treating furnace, purifying the sand, and ejecting the sand from the furnace. The present invention can reclaim sand that is more pure than that typically extracted from heat treating furnaces. The method and apparatus of the present invention also allows for selective control over the amount of binder and fines in the sand ejected from the furnace.  
           [0010]    The preferred embodiment of the present invention includes, associated with a furnace, apparatus for agitating sand which has been collected within the furnace. In the preferred embodiment, this agitation apparatus utilizes pressurized air to accomplish the agitating function through a process of “fluidization”, and shall be referred to herein as a fluidizer. This fluidization process passes air, from a pressurized source, through sand collected in the furnace causing portions of the sand to be suspended and act like a turbulent fluid. The fluidizer, in conjunction with other components in the furnace, causes the binder portion of sand cores to sufficiently combust within the furnace so that sufficiently pure sand is reclaimed. In this embodiment, the sand cores, from which binder is combusted, are attached to the castings that are transported into the furnace. A preferred furnace embodiment, and some of the elements within the furnace are disclosed in application Ser. No. 07/705,626. The fluidizer and some of the elements associated with it are disclosed for the first time in this application.  
           [0011]    The fluidizer of the preferred embodiment of the present invention causes the fluidization of sand that has collected within the furnace hopper. The fluidizing causes portions of sand to abrade against one another, and in at least one embodiment, to also abrade against a metal target, in a manner that exposes the binder. The exposed binder then combusts. The process is repeated until a sufficient amount of binder has been combusted to satisfy the user as to the purity of the sand.  
           [0012]    In the preferred embodiment of the present invention, the fluidizer adds oxygen to the furnace hopper so as to promote binder combustion. In one preferred embodiment of the present invention, the fluidizer is supplied with preheated air from a secondary heat source so as to further promote binder combustion. In an alternate, preferred embodiment, the air of the fluidizer is not pre-heated. In accordance with one aspect of the present invention, multiple fluidizers are employed, and, in such embodiment, appropriate fluidizer embodiments are chosen and selectively placed along a multiple zoned furnace.  
           [0013]    The present invention further includes methods and apparatus for discharging reclaimed sand from the furnace. In the preferred embodiment of the present invention, this discharging is controlled so as to control the volume of sand contained in the furnace. This affects the amount of time that sand is subjected to the fluidizing, thus effecting a control over the characteristics of the reclaimed sand.  
           [0014]    An alternate embodiment of the present invention includes a supplemental sand reclamation unit (the “SSRU”). The supplemental sand reclamation unit, which functions in conjunction with the furnace heat source and in conjunction with the fluidizer and other components in the furnace, provides supplemental reclamation of sand previously reclaimed from casting cores. For example, sand collected from prior art shakers and sand discharged from the troughs of the furnace of Ser. No. 07/705,626 is reprocessed by the supplemental sand reclamation unit. The supplemental sand reclamation unit includes a bin that is outside of the furnace. A tube is connected to a bin outlet and passes into the furnace. The tube passes, within the furnace, in close proximity to furnace heaters and terminates toward the furnace hopper. Collected sand is deposited into the bin where it is heated to above the binder combustion temperature and exposed to an oxygen-rich atmosphere; this causes an initial binder combustion. The sand then enters the tube. While passing through the tube, the sand is heated by the furnace heaters and further binder combustion occurs. When the sand exits the tube it falls into the furnace where it is, preferably, further purified by the in-furnace sand reclamation unit of the present invention.  
           [0015]    It is, therefore, an object of the present invention to provide an improved method and apparatus for heat treating castings, with sand core material attached thereto, and reclaiming sand from the sand core material.  
           [0016]    Another object 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.  
           [0017]    Another object of the present invention is to provide a method and apparatus for reclaiming, within a furnace, sand from portions of sand-core that are separated from castings within the furnace.  
           [0018]    Another object of the present invention is to provide a method and apparatus for agitating, within a furnace, sand that is collected within the furnace.  
           [0019]    Another object of the present invention is to provide a method and apparatus for fluidizing, within a furnace, sand that is collected within the furnace.  
           [0020]    Another object of the present invention is to provide a method and apparatus for enhancing combustion, within a heat treating furnace, of binder that coats sand that is collected in the furnace.  
           [0021]    Another object of the present invention is to provide a method and apparatus for heating, from a secondary source, sand that is collected within a furnace.  
           [0022]    Another object of the present invention is to provide a method and apparatus for providing oxygen to the area in which sand is collected within a furnace.  
           [0023]    Another object of the present invention is to provide a method and apparatus for reclaiming sand outside of the furnace, and purifying the reclaimed sand within a furnace.  
           [0024]    Yet another object of the present invention is to provide a method and apparatus for controlling the amount of time that sand core material is exposed to sand reclamation processing within a furnace so that the characteristics of the reclaimed sand can be controlled.  
           [0025]    Other objects, features and advantages of the present invention will become apparent upon reading and understanding this specification, taken in conjunction with the accompanying drawings. 
       
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0026]    [0026]FIG. 1 is a cut-away view of a combination heat treating furnace and In-furnace sand reclamation unit, in accordance with the preferred embodiment of the present invention.  
         [0027]    [0027]FIG. 2 is a cut-away view of selected elements of the sand reclamation unit of FIG. 1.  
         [0028]    [0028]FIG. 3 is a cut-away top view of selected elements of the sand reclamation unit of FIG. 1, showing some of the elements that are cut-away in FIG. 1.  
         [0029]    [0029]FIG. 4 is a cut-away top view of selected elements of the sand reclamation unit of FIG. 1, showing some of the elements that are cut-away in FIG. 1.  
         [0030]    [0030]FIG. 5 is a cut-away side view of the discharge valve assembly of FIG. 1.  
         [0031]    [0031]FIG. 6 is a cut-away top view of a portion of an in-furnace sand reclamation unit, in accordance with an alternate, preferred embodiment of the present invention.  
         [0032]    [0032]FIG. 7 is a cut-away side view of a portion of the apparatus of FIG. 6.  
         [0033]    [0033]FIG. 8 is a cross-sectional view of the fluidizer conduit of FIG. 6, taken along line  8 - 8  of FIG. 7.  
         [0034]    [0034]FIG. 9 is a side view of an in-furnace sand reclamation unit, in accordance with an alternate, preferred embodiment of the present invention.  
         [0035]    [0035]FIG. 10 is a detailed perspective view of the fluidizing ring of FIG. 9.  
         [0036]    [0036]FIG. 11 is a cross-sectional view of the fluidizing ring of FIG. 9, taken along line  11 - 11  of FIG. 10.  
         [0037]    [0037]FIG. 12 is a cross-sectional view of the fluidizing ring of FIG. 9, taken along line  12 - 12  of FIG. 11.  
         [0038]    [0038]FIG. 13 is a cut-away view of a portion of an in-furnace sand reclamation unit, in accordance with an alternate embodiment of the present invention.  
         [0039]    [0039]FIG. 14 is a cut-away view of a multi-zone embodiment of the heat treating furnace and in-furnace sand reclamation system, in accordance with the present invention.  
         [0040]    [0040]FIG. 15 is an isolated side view of a supplemental sand reclamation unit which is part of an alternate embodiment of the present invention.  
         [0041]    [0041]FIG. 16 is a cut-away, side view of the supplemental sand reclamation unit of FIG. 15 mounted on top of the combination heat treating furnace and in-furnace sand reclamation unit.  
         [0042]    [0042]FIG. 17 is a cut-away view of the reclaimer hopper of FIG. 15. 
     
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT  
       [0043]    This section of the specification consists of two parts. The first part introduces components and describes their orientation and interconnections. The second part describes the operation of the components and provides some examples of acceptable components.  
         [0044]    Referring now in greater detail to the drawings, in which like numerals represent like components throughout the several views, FIG. 1 shows a partially cut-away view of a combination heat treating furnace  19  and in-furnace sand reclamation unit  20 , in accordance with the preferred embodiment of the present invention. The in-furnace sand reclamation unit  20  includes a hopper  30  which has a hopper wall  31  and defines a hopper inlet  33  and a hopper outlet  35 . A portion of the hopper wall  31  and other elements are cut-away in FIG. 1 so that elements shown can be clearly seen. The in-furnace sand reclamation unit  20  further includes a fluidizer  40 , guidance tube  80 , abrasion disk  90  and a discharge valve assembly  100 . The fluidizer  40  is shown passing through the hopper wall  31 . The guidance tube  80  is shown oriented above the fluidizer within the hopper  30 . The abrasion disk  90  is shown oriented above the guidance tube  80  within the hopper  30 . The discharge valve assembly  100  is shown connected to the hopper outlet  35 . In the preferred embodiment of the present invention, the hopper  30  of the in-furnace sand reclamation unit  20  doubles as the hopper  30  of the heat treating furnace  19 . An appropriate heat treating furnace  19  is disclosed in application Ser. No. 07/705,626. The specification of U.S. patent application Ser. No. 07/705,626 is hereby incorporated herein by reference. The discharge valve assembly  100  provides a path to the outside of the furnace.  
         [0045]    [0045]FIG. 2, which is a cut-away side view of selected elements of FIG. 1, shows the fluidizer  40  of the preferred embodiment of the present invention, in greater detail. Sand  25  is also shown, in representative form, collected at the hopper outlet  35 . The fluidizer  40  is seen as including a fluidizer conduit  41 ; the fluidizer conduit  41  has a fluidizing end  42  that is within the hopper  30  and a source end  43  that is outside of the hopper  30 . A portion of the fluidizer conduit  41  has been cut-away to expose a conduit interior  44  which is defined by the fluidizing conduit  41 . The source end  43  of the fluidizer conduit  41  is sealed by an end plate.  47 . The end plate  47  is attached to the source end  43  in a manner that would be understood by those reasonably skilled in the industry; for example, by welding. A portion of the end plate  47  is cut away in FIG. 2, to fully expose a heater  60 . The heater  60  is secured through the end plate  47  in a manner that facilitates removal for repair or replacement with a different type of heater. The heater  60  has an exhaust end  61  located within the conduit interior  44  and an intake end  62  outside of the fluidizer conduit  41 . Pressurized air is supplied into the intake end  62  of the heater  60  through an air intake  65 . In the preferred embodiment of the present invention, the heater  60  is a high pressure gas burner. In an alternate embodiment of the present invention, the heater  60  consists of an electric heating element. Other heater types are acceptable.  
         [0046]    A signal generating pressure gauge  70  is connected to the fluidizer conduit  41  by a gauge conduit  71 . This connection is such that the signal generating pressure gauge  70  is in communication with the conduit interior  44  and can sense the pressure within the fluidizer conduit  41 . A signal adjuster  74  is associated with the signal generating pressure gauge  70 . The signal generating pressure gauge  70  is connected to an electric power supply by a gauge power cable  72 . The signal generating pressure gauge  70  is connected by a signal cable  73  to the discharge valve assembly  100 , which is not shown in FIG. 2.  
         [0047]    The fluidizer end  42  of the fluidizer conduit  41  is turned upward in FIG. 2 toward a the guidance tube  80  and the abrasion disk  90 . The guidance tube  80 , part of which is cut away in FIG. 2, has a tube wall  81  and defines a tube passage  82 . The abrasion disk  90 , part of which is cut away in FIG. 2, has disk back  92  and a concave disk face  91 .  
         [0048]    [0048]FIG. 3 is a top view of the apparatus of FIG. 2 in greater detail and with the abrasion disk  90  removed. As shown in FIG. 3, the guidance tube  80  is connected to tube support rods  85   a,b  which are connected to the hopper wall  31 . These connections are made in a manner as would be understood by those reasonably skilled in the industry; for example, by welding or bolting. The guidance tube  80  is positioned such that the guidance tube  80  is oriented above the fluidizer end  42  of the fluidizer conduit  41  and the tube passage  82  is in-line with the conduit interior  44  at the fluidizer end  42 .  
         [0049]    [0049]FIG. 4 is a top view of the apparatus of FIG. 2 in greater detail. In FIG. 4 the disk face  91  of the abrasion disk  90  is oriented toward the fluidizer end  42  and is therefore not seen. As seen in FIGS. 2 and 4, the abrasion disk  90  is connected to disk support cables  95  which are attached to the hopper wall  31 . The cables  95  have a disk end  96 , a hook end  97 , and a turnbuckle  98  disposed between the disk end  96  and the hook end  97 . The disk ends  96  of the cables  95  are attached to the abrasion disk  90  in a manner that would be understood by those reasonably skilled in the industry; for example, by welding or bolting. The hook end  97  of each cable  95  is attached to the inner hopper wall  31  by an eyehook  99 ; the hook ends  97  are hooked to eyehooks  99 . The eyehooks  99  are connected to the hopper wall  31  in a manner that would be understood by those reasonably skilled in the industry; for example, by welding or bolting. There are a plurality of eyehooks  99 , each of which is oriented so that the height of the abrasion disk  90  above the fluidizer end  42  is capable of being adjusted, as will be explained below. The fluidizer end  42 , conduit interior  44 , and guidance tube  80  are not seen in FIG. 4 because they are concealed by the abrasion disk  90 .  
         [0050]    [0050]FIG. 5 is a cut-away side view of the discharge valve assembly shown in FIG. 1. The discharge valve assembly  100  includes a double dump valve  110  and a pneumatic valve operator  130 . The double dump valve  110  has a valve inlet  111  and a valve outlet  112 . The valve inlet  111  is connected to the hopper outlet  35  (see FIG. 1) in a manner that would be understood by those reasonably skilled in the industry; for example, by welding or bolting. The valve outlet  112  is located outside of the heat treating furnace  19  such that the double dump valve  110  provides a path from within the hopper  30  to the outside of the furnace  19 . A portion of the double dump valve  110  is cut away in FIG. 5 to expose a first disk  116 , a second disk  117 , a first seat  118 , and a second seat  119 . The pneumatic valve operator  130  is connected to the double dump valve  110 , in a manner that is understood by those reasonably skilled in the art, such that the pneumatic valve operator  130  controls the operation of the double dump valve  110 . The pneumatic valve operator  130  is connected to a pneumatic supply line  131  and the signal cable  73 . In an alternate embodiment of the present invention, the pneumatic valve operator  130  is replaced with an electric, motorized valve operator; hydraulic valve operator; or some other type of valve operator.  
         [0051]    [0051]FIG. 6 and FIG. 7 show an alternate, preferred embodiment of the present invention. FIG. 6 is a cut away top view of portions of the present invention in accordance with the alternate embodiment. This alternate embodiment does not include the guidance tube  80  or abrasion disk  90 . This alternate embodiment does include a fluidizer  40 ′ which is somewhat similar to the fluidizer  40  of the preferred embodiment. However, the fluidizer  40 ′ has a fluidizer conduit  41 ′ that splits into three fluidizer conduits  41 ′ a,b,c,  each of which pass through the hopper wall  31 . The fluidizer conduits  41 ′ a,b,c  originate from a conduit header  55 . The conduit header  55  originates from the source end  43  of the fluidizer conduit  41 ′. Also, the fluidizer ends  43 ′ a,b,c  are sealed in a manner that would be understood by those reasonably skilled in the industry; for example, with a plug  50 . Also, as is indicated by FIG. 7, which is a side view of the fluidizer  40 ′ showing a portion of the hopper  30 , each fluidizer conduit  41 ′ a,b,c  defines a plurality of fluidizing holes  51  that are oriented toward the hopper outlet  35 . (In FIG. 7, two of the fluidizer conduits  41 ′ b,c  are concealed by one of the fluidizer conduits  41 ′ a. ) FIG. 8 is a cross-sectional view taken along line  8 - 8  in FIG. 7; only one fluidizer conduit  41 ′ a  is shown for simplicity; the other conduits  41 ′ b,c  being similarly constructed. As seen in FIG. 8, the fluidizing holes are in communication with the conduit interior  44 ′. Also, in the embodiment shown in FIGS. 7 and 8, the fluidizing holes  51  are spaced linearly and radially along the portion of the fluidizer conduit  41 ′ a  that faces the hopper outlet  35 . Preferably, the angle between the center-lines  52  defined by two fluidizing holes  51  that are radially positioned with respect to one another is ninety degrees. In alternate embodiments of the present invention, the fluidizing holes  51  are spaced in a different manner.  
         [0052]    Another alternate embodiment of the present invention, which is not shown, is similar to the previously disclosed alternate embodiment of FIGS.  6 - 8 , except that the fluidizer conduit  40  splits into six fluidizer conduits. Three of the six fluidizer conduits penetrate one furnace hopper  30  and the other three of the six fluidizer conduits penetrate a different furnace hopper  30 . Actually, there are a variety of alternate embodiments of the present invention that are variations upon those just disclosed. Although not shown in FIGS. 6 and 7, the signal generating pressure gauge  70 , with all of its associated elements, is included in these alternate embodiments of the present invention.  
         [0053]    [0053]FIG. 9 shows an alternate, preferred embodiment of the present invention which does not include the guidance tube  80  or the abrasion disk  90 . In this alternate embodiment, a fluidizing ring  140  is disposed between the hopper outlet  35  and the valve inlet  111 . The fluidizing ring  140  is connected to the hopper outlet  35  and the valve inlet  111  in a manner that would be understood by those reasonably skilled in the industry; for example, by welding or bolting. Also shown in FIG. 9 is a fluidizer conduit  41 ″. The fluidizer conduit  41 ″ defines a conduit interior  44 ″ (not shown). The fluidizer conduit  41 ″ has a fluidizing end  42 ″, which is connected to the fluidizing ring  140 , and a source end  43 ″, into which pressurized air is supplied.  
         [0054]    [0054]FIG. 10 is a detailed perspective view of the fluidizing ring  140  of FIG. 9. The fluidizing ring  140  includes a hollow ring frame  141  which defines a ring interior  142  (see FIG. 11). The fluidizing ring  140  bounds an open area  145  that is in communication with the ring interior  142  by way of a plurality of fluidizing holes  146  that are defined by the ring frame  141 . Only two of the fluidizing holes are labeled in FIG. 10 for simplicity. The ring frame  141  further defines a conduit connection hole  147 . The ring frame  141  is connected at the conduit connector hole  147  to the fluidizing end  42 ″ of the fluidizer conduit  41 ″ such that the conduit interior  44 ″ is in communication with the ring interior  142 . This connection is made in a manner that would be understood by those reasonably skilled in the industry; for example, by welding.  
         [0055]    [0055]FIG. 11 is a cross-sectional view taken along line  11 - 11  in FIG. 10. FIG. 11 shows the ring interior  142 . FIG. 12 is a cross sectional view taken along line  12 - 12  in FIG. 11. FIG. 12 shows one of the plurality of fluidizing holes  146  defined by the ring frame  141 . The fluidizing holes  146  are angled steeply enough so that portions of sand core which pass through the open area  145  defined by the ring frame  141  cannot easily migrate up, through the fluidizing holes  146 , into the ring interior  142 .  
         [0056]    In an alternate embodiment of the present invention, no signal generating pressure gauge  70  is included. As shown in FIG. 13, which is a cut-away view, this alternate embodiment of the present invention includes signal generating sensors  170   a,b,c  that are mounted within the hopper  30 , to the hopper wall  31 . The sensors  170   a,b,c  are mounted such that they detect a predetermined level of sand core in the hopper  30 . Each signal generating sensor  170   a,b,c  is connected by signal cable  73 ′ to the discharge valve assembly  100  (not shown in FIG. 13). A selector  171  is associated with the signal generating sensors  170   a,b,c.  In the preferred embodiment of this alternate embodiment, the signal generating sensors  170   a,b,c  are electric probes.  
         [0057]    [0057]FIG. 14 shows a multi-zone embodiment of the present invention, which includes a multi-zone furnace  211  employing several embodiments of the in-furnace sand reclamation unit  20 . An example of furnace  211  is disclosed in application Ser. No. 07/705,626. As disclosed, in FIG. 14 hereof, the furnace  211  includes: a work chamber  215 ; zones  216 A-H; furnace heaters  218 ; a pre-heat chamber  224 ; a furnace input door  225 ; a furnace upper end  226 ; a furnace discharge door  227 ; a furnace lower end  228 ; a roller hearth  234 ; rollers  236 ; baskets  240 , for transporting castings; axial fans  244 ; a furnace top  245 ; screens  252 ; baffles  253 ; a sand conveyor  259 ; and a central collection bin  260 . For a clear understanding of the furnace  211 , please refer to application Ser. No. 07/705,626, which has been incorporated into this specification. The furnace  211  further includes hoppers  30  and discharge valve assemblies  100 . Zones  216 A,B are equipped with the fluidizer  40  (see FIGS. 1, 2,  3 , and  4 ) guidance tube  80 , and abrasion disk  60 . The pre-heat chamber and Zone  216 E are equipped with the fluidizer  40 ′ (see FIGS. 6, 7, and  8 ), and Zones  216 F,G,H are equipped with the fluidizer  40 ″ (see FIGS. 9, 10,  11 , and  12 ). Sand  25  is shown, in representative form, collected at the hopper outlet  35 .  
         [0058]    [0058]FIG. 15 shows a supplemental sand reclamation unit  180  which is part of an alternate embodiment of the present invention. The supplemental sand reclaiming unit  180  includes a reclaimer hopper  181  which has a reclaimer inlet  182 , a reclaimer outlet  183 , and a reclaimer wall  184 . The supplemental sand reclamation unit  180  further includes a discharger  190  that has a discharger inlet  191  and a discharger outlet  192 . In the preferred, alternate embodiment, the discharger  190  is a screw auger. The discharger inlet  191  is connected to the hopper outlet  183  in a manner that would be understood by those reasonably skilled in the industry, for example, by welding or bolting. The supplemental sand reclamation unit  180  further includes a delivery tube  195  that defines a tube interior  199 . The delivery tube  195  also has a tube inlet  196 , a tube outlet  197 , and an oxygen supply line  198  that is in communication with the tube interior  199 . The tube inlet  196  is connected to the discharger outlet  192  in a manner that would be understood by those reasonably skilled in the industry; for example, by welding or bolting.  
         [0059]    [0059]FIG. 16 is a cut-away view of the supplemental sand reclamation unit  180  of FIG. 15 mounted on top of the combination heat treating furnace  19  and in-furnace sand reclamation unit  20  in accordance with an alternate embodiment of the present invention. The reclaimer hopper  181  and discharger  190  are located outside of the heat treating furnace  19 . The delivery tube  195  penetrates the heat treating furnace  19  and is in close proximity to u-tube furnace heaters  218 ′. The tube outlet  197  is oriented toward the hopper inlet  33 .  
         [0060]    [0060]FIG. 17 is a cut-away view of the reclaimer hopper  181  of FIG. 15. A portion of the reclaimer wall  184  is cut-away to show a reclaimer interior  185  that is defined by the reclaimer wall  184 . Included within the reclaimer interior  185  are heaters  186 , oxygen suppliers  187  and a level indicator  188 . The reclaimer hopper  181  also includes a recycle exhaust duct  189  that exhausts into the heat treating furnace  19  and a baghouse exhaust duct  198 .  
       Operation  
       [0061]    Referring back to FIGS. 1 and 14, as the casting, with sand core attached thereto, is acted upon in accordance with the method and apparatus disclosed in application Ser. No. 07/705,626, portions of sand and sand core fall through the hopper inlet  33  and sand collects within the hopper  30  toward the hopper outlet. Before a defined level of sand accumulates in the hopper  30 , the first disk  116  and second disk  117  within the double dump valve  110  are maintained in contact with the first seat  118  and second seat  119 , respectively. Therefore, as portions of sand and sand core continue to fall through the hopper inlet  33 , the level of sand core within the hopper  30  increases.  
         [0062]    [0062]FIGS. 1, 2,  3 , and  4  disclose the first, preferred embodiment of the present invention. The equipment and process that are at the heart of the first, preferred embodiment are referred to as “high temperature fluidization with a target”. In this embodiment, pressurized air is supplied through the air intake  65 . Oxygenated and heated exhaust from the heater  60  discharges from the fluidizer end  42  of the fluidizer conduit  41 . As the level of sand rises above the level of the fluidizer end  42 , fluidization begins; the oxygenated and heated exhaust fluidizes portions of sand core that are above the fluidizer end  42 . That is, the exhaust passes up through the sand, causing the sand to be suspended and act like a turbulent fluid. The fluidization further propels portions of sand through the guidance tube passage  82  where the trajectory of the entrained portions of sand is oriented toward the disk face  91  of the abrasion disk  90 . Portions of sand contact the abrasion disk  90  and fall back toward the fluidizer end  42  where they are further fluidized. The portions of sand that are fluidized abrade against each other and the disk face  91 . The abrasion caused by this process knocks away ash that is adhered to the sand. This exposes unburned binder and thus promotes binder combustion. In addition to promoting binder combustion by exposing unburned binder, the fluidizer  40  promotes combustion by providing a hot and oxygenated environment. Thus, the exposed binder combusts to promote purification of the sand reclaimed from the sand core. Since the “high temperature fluidization with a target” incorporates a variety of techniques to reclaim sand (which include, at least, fluidization, fluidization in combination with an abrasion disk, heating to promote combustion, and oxygenating to promote combustion) it has a relatively high capacity as compared the processes referred to below.  
         [0063]    Some alternate embodiments of the present invention, one of which is shown in FIGS. 6, 7, and  8 , are referred to as “hot fluidization”. “Hot fluidization” does not propel portions of sand core toward a target. However, “hot fluidization” is otherwise similar to “hot fluidization with a target”. Pressurized air is supplied through the air intake  65 . oxygenated and heated exhaust from the heater  60  discharges from the fluidizer holes  51 . As the level of sand approaches the level of the fluidizing holes  51 , fluidization begins. Fluidization is promoted and enhanced by the placement and orientation of the fluidizing holes  51 . The portions of sand that are fluidized abrade against each other. The abrasion caused by this process knocks away ash that is adhered to the sand. This exposes unburned binder and thus promotes binder combustion. In addition to promoting binder combustion by exposing unburned binder, the fluidizer  40 ′ promotes combustion by providing a hot and oxygenated environment. Thus, the exposed binder combusts to promote purification of the sand reclaimed from the sand core. Since “hot fluidization” does not utilize a target, it does not typically cause as much abrasion as “hot fluidization with a target”. Thus, “hot fluidization” typically exposes less binder than and therefore causes less combustion than “hot fluidization with a target”. Therefore, “hot fluidization” typically has less capacity than “hot fluidization with a target”. Thus, “hot fluidization with a target” is used where relatively large portions of sand and sand core fall through the hopper inlet  33  and “hot fluidization” is used where relatively moderate portions of sand and sand core fall through the hopper inlet  33 .  
         [0064]    Other alternate embodiments of the present invention, one of which is shown in FIGS. 9, 10,  11 , and  12 , are referred to as “cool fluidization”. “Cool fluidization” is somewhat similar to “hot fluidization” except that it does not incorporate heating. Pressurized air is supplied to the source end  43 ″ of the fluidizer conduit  41 ″. The pressurized air passes into the ring interior  142  by way of the fluidizer end  42 ″ of the fluidizer conduit  41 ″ and the conduit connection hole  147 . The pressurized air then escapes from the fluidizing ring  140  through the fluidizing holes  146 . As the level of sand rises above the fluidizing holes  146 , fluidization begins. The portions of sand that are fluidized abrade against each other. The abrasion caused by this process knocks away ash that is adhered to the sand. This exposes unburned binder and thus promotes binder combustion. In addition to promoting binder combustion by exposing unburned binder, the fluidizer  40 ″ promotes combustion by providing added oxygen to the environment (the heat necessary for combustion is provided by the heat treating furnace  19 ). Thus, the exposed binder combusts to promote purification of the sand reclaimed from the sand core. Since “cool fluidization” does not add heat to promote combustion, it does not typically cause as much combustion as “hot fluidization”. Therefore, “cool fluidization” typically has less capacity than “hot fluidization”. Thus, “cool fluidization” is used where relatively small portions of relatively clean sand fall through the hopper inlet  33 . “Cool fluidization”, in addition to reclaiming sand, cools portions of sand before they pass through the double dump valve  110 . This protects the double dump valve  110  from heat related stress and strain and allows for the use of a less expensive double dump valve  110 .  
         [0065]    As specified above, the different embodiments of the present invention have different capacities. As specified in application Ser. No. 07/705,626, different zones  216  (see FIG. 14) within a continuous-process furnace  211  have different capacities for loosening sand core from castings. Therefore, it is necessary to reclaim more sand in some zones  216  and less from others. In accordance with one multi-zone embodiment of the present invention, as shown in FIG. 14, higher capacity embodiments of the in-furnace sand reclamation unit  20  (for example FIGS.  1 - 4 ) are employed in high capacity zones  216 A,B; moderate capacity embodiments of the in-furnace sand reclamation unit  20  (for example FIGS.  6 - 8 ) are employed in the pre-heat chamber  224  and moderate capacity zones  216 E; and lower capacity embodiments of the in-furnace sand reclamation unit  20  (for example FIGS.  9 - 12 ) are employed in lower capacity zones  216 F,G,H of the furnace  211 . Likewise, it is preferred to employ higher capacity embodiments of the present invention in higher capacity batch-type furnaces and lower capacity embodiments of the present invention in lower capacity batch-type furnaces.  
         [0066]    In several embodiments of the present invention, the signal generating pressure gauge  70  and the equipment associated with it, serves to provide positive control over the level, and therefore the volume, of sand that accumulates within the hopper  30  (refer to FIGS. 2 and 9). As portions of sand continue to fall through the hopper inlet  33 , the level of sand within the hopper  30  increases. As the level increases there is more resistance to the flow of air from the fluidizer end of the conduit  42  and the back-pressure in the fluidizer conduit  41  increases. The signal adjuster  74  associated with the signal generating pressure gauge  70  is set such that when a certain back-pressure is detected within the conduit interior  44  by the signal generating pressure gauge  70 , a “high level” signal is generated. The pneumatic valve operator  140  receives the “high level” signal by way of the signal cable  73 . While the pneumatic valve operator  140  receives the signal it operates the double dump valve  120 . The double dump valve  120  is operated such that the first disk  126  and second disk  127  alternately move away from and then return to the first seat  118  and second seat  119 , respectively. This operation is such that while the first disk  116  is not in contact with the first seat  118 , the second disk  117  is in contact with the second seat  119 , and visa-versa. Thus, while the double dump valve  110  is operating and sand is flowing from within the hopper  30  to outside of the heat treating furnace  19  by way of the double dump valve  110 , back-pressure is maintained at the hopper outlet  35  such that fluidization is not disrupted. It is important that back-pressure is maintained at the hopper outlet  35  because the pressurized air that is being supplied through the fluidizer conduit  41  will take the path of least resistance. If both the first disk  116  and the second disk  117  where off of their seats, and there was a level of sand within the hopper, the path of least resistance would be through the doubled dump valve  110  to the atmosphere outside of the furnace. Therefore, the pressurized air would flow through the double dump valve  110  rather than forcing its way up through the sand accumulated in the hopper. In an alternate embodiment of the present invention, the double dump valve  110  is replaced with a star valve or screw auger, or another type of device that performs a discharging and a sealing function.  
         [0067]    In alternate embodiments of the present invention, signal generating sensors  170 , mounted to the hopper wall  31  (see FIG. 13), serve to provide positive control over the level, and therefore the volume, of sand that accumulates within the hopper  30 . In one embodiment the signal generating sensors  170  consist of electric capacitance probes. An electric capacitance probe is mounted to the hopper wall at each position that corresponds to a level at which it is desired to operate the double dump valve  110 . The particular level at which the double dump valve will operate is established by operating the selector  171  which establishes which electric probe is controlling. As the level of sand increases and comes into contact with the controlling electric probe, a “high level” signal is generated. The pneumatic valve operator  140  receives the “high level” signal by way of the signal cable  73 ′. When the pneumatic valve operator  140  receives the signal it operates the double dump valve  110  as is disclosed above.  
         [0068]    The characteristics of reclaimed sand are controlled by controlling the dwell time of portions of sand within the hopper  30 . The longer the dwell time, the longer the amount of time that the portions of sand are fluidized. When portions of binder coated sand are fluidized for a relatively longer period of time, less binder is contained in the reclaimed sand but more fines are contained in the reclaimed sand. When portions of binder coated sand are fluidized for a relatively shorter period of time, more binder is contained in the reclaimed sand but less fines are contained in the reclaimed sand. The dwell time is controlled by controlling the volume of sand that is allowed to accumulate in the hopper  30 . The greater the volume of sand allowed to accumulate in the hopper  30 , the greater the dwell time (assuming a constant input of sand). The volume of sand that is allowed to accumulate in the hopper  30  is selected by adjusting the signal adjuster  74  in the one disclosed preferred embodiment of the present invention or by adjusting the selector  171  in the second disclosed embodiment of the present invention. In the embodiment which includes the signal generating pressure gauge  70 , a larger volume of sand accumulates in the hopper  30  when the signal adjuster  74  is adjusted so that the signal generating pressure gauge  70  emits a “high level” signal at a higher pressure. A smaller volume of sand accumulates in the hopper  30  when the signal adjuster  74  is adjusted so that the signal generating pressure gauge  70  emits a “high level” signal at a lower pressure. In the embodiment which includes signal generating sensors  170  a larger or smaller volume of sand is allowed to accumulate in the hopper  30  by adjusting the selector  171  to select the signal generating sensor  170  that is mounted at the level that corresponds to the desired volume.  
         [0069]    Referring back to FIGS. 2 and 4, the characteristics of the reclaimed sand are also controlled, in the preferred embodiment of the present invention, by adjusting the height of the abrasion disk  90  above the fluidizer end  42  of the fluidizer conduit  41 . The height is adjusted by loosening the turnbuckles  98 , unhooking the hook ends  97  from the eyehooks  99 , hooking the hook ends  97  to the appropriate eyehooks  99 , and tightening the turnbuckles  98 . These components can be accessed by entering the hopper  30  through the furnace  19  or through trap doors in the hopper wall  31 . Generally, when the height of the abrasion disk  90  is decreased more abrasion occurs because propelled portions of sand impact the abrasion disk  90  with more force; therefore, less binder is contained in the reclaimed sand and more fines are contained in the reclaimed sand. Generally, when the height is increased less abrasion occurs because propelled portions of sand impact the abrasion disk  90  with less force; therefore, more binder is contained in the reclaimed sand and less fines are contained in the reclaimed sand.  
         [0070]    Referring back to FIGS.  15 - 17 , the supplemental sand reclamation unit  180  is used, in conjunction with the fluidizer  40  and other components in the heat treating furnace  19 , to further purify sand that has already been reclaimed by some other process, and to reclaim sand from portions of sand core initially reclaimed by another process. The portions of sand core and coated sand that are introduced into the supplemental sand reclamation unit  180  are not adhered to castings. For example only, if a core was accidentally molded into the wrong shape such that it could not be used for casting, it could be crushed and the portions thereof could be introduced into the supplemental sand reclamation unit  180 . Portions of sand core and coated sand are introduced into the supplemental sand reclamation unit  180  through the reclaimer inlet  182 . The heaters  186  and oxygen suppliers  187  maintain an atmosphere within the reclaimer interior  185  that causes some of the binder associated with the introduced sand and portions sand core to combust such that sand is reclaimed within the reclaimer hopper  181 . The reclaimed sand is transferred from the reclaimer hopper  181  to the delivery tube  195  by the discharger  190 , The sand within the delivery tube  195  is drawn by gravity from the tube inlet  196  toward the tube outlet  197 . The sand in the delivery tube  195  is heated due to the fact that the delivery tube  195  is in close proximity to u-tube furnace heaters  218 ′. The sand in the delivery tube  195  is also exposed to oxygen that is supplied through the oxygen supply line  198 . Therefore, at least some exposed binder that passes through the delivery tube  195  is combusted. As sand passes from the tube outlet  197  it falls into the hopper  30  where it is further purified by fluidization, as is discussed above.  
         [0071]    The embodiments of the present invention can be constructed from a variety of materials and include a variety of components. The following is offered for example only. The hopper  30 , guidance tube  80 , and abrasion disk could be made out of various abrasion resistant alloys. More specifically, the hopper  30  and guidance tube  80  could be made out of  4130 ,  4140  or  1020  steel, and the abrasion disk  90  could be made out of a cast high manganese alloy. The fluidizing ring  140  could be constructed of A 36  structural steel square tubing. The high pressure burner, which serves as the heater  60  in one embodiment of the present invention, could be an Eclipse brand. The signal generating pressure gauge  70  could be a Dwyer brand photoelectric gauge. The electric capacitance probes, that serve as the signal generating sensors  170  in one embodiment of the present invention, and the level indicator  188  could be an Endress Hauser brand, LSC 1110 Series capacitance probe. A low voltage is applied to these probes, and when the probe comes into contact with some material (for example sand) current flows into the material and the probe senses the current flow. The double dump valve  110  could be a Ni-Hard and nickel chrome alloy high temperature double dump valve made by Plattco Corporation. The Fluidizer conduit  41  can be constructed from stainless steel. The heater  186  could be a National brand silicon carbide heating element.  
         [0072]    Whereas this invention has been described in detail with particular reference to preferred embodiments and alternate embodiments thereof, it will be understood that variations and modifications can be effected within the spirit and scope of the invention, as described herein before and as defined in the appended claims.