Combination conduction/convection furnace

Information

  • Patent Grant
  • 6336809
  • Patent Number
    6,336,809
  • Date Filed
    Wednesday, December 15, 1999
    24 years ago
  • Date Issued
    Tuesday, January 8, 2002
    22 years ago
Abstract
A single furnace system integrates, in combination, two or more distinct heating environments (which in the preferred embodiments include a conduction heating environment and a convection heating environment) integrated such that the multiple environments define a continuous heating chamber through which a moving workpiece (such as a casting) transitions from one heating environment to the other without being exposed to the atmosphere. In accordance with the preferred methods, the transitioning of the casting from one environment to the other is accomplished with no meaningful change in temperature.
Description




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 changes have been made in the field of heat treating of metal castings and reclaiming sand from sand cores and sand molds used in the manufacture of metal castings. Examples of some recent disclosures which address the heat treating of castings, removal of sand cores, and further reclaiming of sand are found in U.S. Pat. Nos. 5,294,094, 5,354,038, 5,423,370, and 5,829,509 (hereinafter sometimes referred to collectively as the “Reference Patents”), each of which is expressly incorporated herein by reference, in their entirety. Those patents disclose a 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) reclaims sand from the sand core/sand mold materials removed from the casting; the '094 and '038 patents embodying a convection furnace species, the '370 patent embodying a conduction furnace species, and the '509 patent alternately embodying either a conduction furnace species or a convection furnace species (and adding an integrated cooling chamber). 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.




Technology such as that 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, the present invention provides a single furnace system which integrates, in combination, a plurality of distinct heating environments (which in the preferred embodiments include two heating environments comprising a conduction heating environment and a convection heating environment) integrated such that the plurality of environments define a continuous heating chamber through which a moving workpiece (such as a casting) transitions from one heating environment to the other without being exposed to the atmosphere. In accordance with the preferred methods, the transitioning of the casting from one environment to the other is accomplished with no meaningful change in temperature.




In accordance with a second aspect of the invention, improved species embodiments of a 3-in-1 processing system of the genus described in the above identified prior patent specifications are provided. These species embodiments of the present invention disclose a system apparatus and method for processing a casting which perform the integrated processes of core removal, sand reclaiming and heat treatment in a combination conduction and convection furnace system.




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





FIG. 1

is a schematic, side cut-away view of a combination conduction/convection furnace, in accordance with the preferred embodiment of the present invention.





Fig. 1A

is an isolated view of hoist and rail components of one embodiment of a transport system utilized in the furnace of the present invention.





FIG. 2

is a schematic, side cut-away view of a combination conduction/convection furnace, in accordance with an alternate embodiment of the present invention.





FIG. 3

is a schematic, side cut-away view of a combination conduction/convection furnace, in accordance with a second alternate embodiment of the present invention.





FIGS. 4-6

are schematic, side cut-away views of alternate embodiments of multiple heating environments comprising an integrated continuous heating chamber of a furnace system in accordance with the present invention.





FIG. 7

is a schematic side cut away view of an alternate embodiment of the convection heating segment including a casting rotary mechanism.











DETAILED DESCRIPTION OF THE DRAWINGS




Referring now to the drawings in which like numerals represent like components throughout the several views,

FIG. 1

depicts in schematic representation a combination conduction/convection furnace


10


in accordance with a preferred embodiment of the present invention. The combination furnace


10


is seen as comprising a frame structure


12


which defines an enclosed heating chamber


14


and includes insulated walls


15


surrounding the heating chamber, an entrance portal


16


outfitted with a selectively closable insulated inlet door


17


and an exit portal


18


outfitted with a selectively closable insulated outlet door


19


. The heating chamber


14


is seen as divided into two major heating chamber segments


23


,


24


which together comprise the continuous heating chamber


14


and are interconnected by a transitional passage


25


. In accordance with the preferred embodiments of the present invention, the transitional passage


25


is of sufficient size and orientation to allow for the easy movement from the first heating chamber segment


23


to the second heating chamber segment


24


of a work piece, such as a casting, as well as the free movement of heat, gases, dust, and the like from one chamber segment to the other chamber segment. An integrated transportation system


26


transports the castings from the entrance portal


16


, through the first heating chamber


23


, into and through the second heating chamber


24


, to the exit portal


18


.




In accordance with the preferred embodiments of the present invention, each of the first heating chamber segment


23


and second heating chamber segment


24


is equipped to heat a casting within the respective chamber segment by a furnace heating process which is of a process distinct from the furnace heating process with which the other chamber segment is equipped.




The herein depicted, preferred embodiments of

FIGS. 1-3

are equipped with a conduction furnace heating process, in the form of a fluidized bed furnace, in the first heating chamber segment


23


and are equipped with a convection type heating furnace in the second heating chamber segment


24


. The heating environment provided in the first heating chamber segment


23


is, thus, an environment as is created by a conduction type furnace (such as a fluidized bed furnace) and the heating environment of the second heating chamber segment


24


is, thus, an environment as is created by a convection type furnace. As depicted in the drawings, a bed


27


of particles (the fluidizing medium) mostly fills the first heating chamber segment


23


, and conduit


28


for the introduction of fluidizing gases are provided. A heating source (not shown) provides heated fluidizing gases to the conduit


28


. In this heating chamber segment


23


, castings are immersed within the fluidized bed


27


where heat is transferred to the castings from surrounding heated bed particles by conduction, and where the castings are heated to an appropriate temperature for an appropriate period of time to accomplish one or more (full or partial) desired casting processing steps (an example of which is expressed below). The convection heating chamber segment


24


includes heating sources (not shown) which heat the air inside the heating chamber segment such that the heat transfers by convection to a casting contained within the convection heating chamber segment and such that the castings are heated to an appropriate temperature for an appropriate period of time to accomplish one or more (full or partial) desired casting processing steps (an example of which is expressed below).




Referring again, generally, to

FIG. 1

(and FIGS.


2


and


3


), the combination furnace


10


is seen as also including a loading station


40


outside the furnace structure


12


and, an entry zone


41


inside the furnace structure


12


. The entry zone


41


, of the herein depicted embodiments of

FIGS. 1 and 2

, occupies a portion of the heating chamber


14


positioned above the fluidized bed segment


23


and receives rising heat, thus exposing castings in the entry zone to initial chamber heat. The integrated transport system


26


, of the herein depicted embodiments is comprised of a combination of a charge transport mechanism (depicted by arrow


43


) and entry transport mechanism


44


(depicted in

FIG. 1

, for example, as a hoist), a first chamber transport mechanism


45


(depicted in

FIG. 1

, for example, as a ram/push device


39


and including an elongated fixed rail assembly


42


(see FIG.


1


A)), a transitional transport mechanism


46


(depicted in

FIG. 1

as, for example, another hoist mechanism), a second transitional transport mechanism


47


(depicted herein as, for example, a ram/push device), and a second chamber transport mechanism


48


(depicted as, for example, a roller conveyor). With reference to

FIG. 1A

, an example of a hoist type entry transport mechanism


44


is depicted, together with a representative fixed rail assembly


42


of the first chamber transport mechanism


45


. The entry transport mechanism


44


includes a movable pallet


70


(formed of two spaced apart lateral rails


71


(one shown) and two, spaced apart transverse beams


72


) and a four cornered support frame


73


supported from above by cabling


74


connected to a drive mechanism (not shown). A hoist type first transition transport mechanism


46


is of similar construction. The construction and operation of the depicted integrated transport system


26


is deemed readily understood by those skilled in the art upon reference to this specification. Movement of the casting through the various chambers is not limited to those particular mechanisms depicted herein and alternate transporting mechanisms will be apparent to those skilled in the art.




In a first preferred embodiment, as depicted in

FIG. 1

, the convection heating chamber segment


24


is comprised of an upper open air portion through which the casting moves and is heated and a lower portion formed, for example, as a hopper (or hoppers)


33


into which falls and is collected (and, preferably, is further processed) any sand core materials which may fall from the casting in this segment of the heating chamber. In the embodiment of

FIG. 1

, the convection segment


24


is shown outfitted with an air re-circulating system


52


which stirs air within the convection heating chamber segment


24


to assist in acquiring temperature uniformity, throughout the convection heating chamber segment (including at the vicinity of the transitional passage


25


), as would be understood by those skilled in the art. The herein depicted re-circulating system includes a re-circulating fan


53


and related ductwork


54


, though other re-circulating systems will be readily identified by those skilled in the art. In the embodiment of

FIG. 1

, the convection segment


24


is provided with sand reclaiming features such as screens


55


and in-hopper fluidization


56


. The structure and operation of these reclaiming features will be understood by reference to the Reference Patents, especially U.S. Pat. Nos. 5,294,094 and 5,345,038. In the alternate embodiment of the combination furnace


10


′ of

FIG. 2

, the convection segment


24


′ includes a furnace chamber with a trough


58


with fluidized, migrating bed


59


, discharge weir


60


, and integrated cooling chamber


61


similar to the embodiment of

FIG. 1A

of Reference Patent U.S. Pat. Nos. 5,829,509, and the structure and operation of the furnace chamber segment


24


′ and related reclaiming will be understood by reference to that Patent. The embodiments of

FIGS. 1 and 2

are also seen as including a weir or spillway


37


by which sand or other particles accumulating within the fluidized bed furnace is allowed to spill into the hopper


33


or trough


58


, respectively, of the convection chamber


24


,


24


′, thus controlling the depth of the bed


27


of the fluidized bed segment


23


, and, preferably, controlling the dwell time of any sand core particles within the fluidized bed


27


.




Each of the conduction heating segment


23


and the convection heating segment


24


,


24


′ of the depicted embodiments will have additional structure and will operate in a manner all of which will be clearly understood by those skilled in the art after review of this entire specification, aided with reference to the specifications of the “Reference Patents” cited previously herein. As such, no further description is deemed necessary to enable the functionality mentioned throughout this specification.




In operation, and in accordance with one preferred method of the present invention, a casting (not seen), typically laden with outer molds and/or inner sand cores (collectively referred to herein as “sand cores”) is positioned at the loading station


40


(“P1”). The casting is, for example, carried within a wire basket or like transport container


50


which contains the casting yet allows for access to the casting by the fluidizing medium of the bed


27


and also allows for the discharge from the container of sand core material which falls from the casting. The basket and casting are moved, for example, by being pushed by the charge transport mechanism


43


through the temporarily open inlet door


17


to the entry segment


41


(at position “P2”), where the basket rests on, for example, a hoist pallet


70


. The entry transport mechanism


44


lowers the pallet


70


with the basket


50


and casting into the conduction heating chamber segment


23


until the casting is fully immersed within the fluidized bed


27


and the lateral rails


71


align with the fixed rails


42


. The fluidized bed


27


is, preferably, comprised of refinery sand similar in nature to that sand of which the sand cores of the casting are created. Preferably, the fluidized bed has been preheated to an initial temperature prior to receiving the casting. The fluidized bed


27


is heated to a temperature sufficient to perform the particular casting processing steps desired to be carried out within the fluidized bed. For example, the bed


27


is heated to a temperature sufficient enough to conduct heat to the casting of a temperature sufficient to dislodged sand core materials from cavities within castings. The core materials preferably comprise sand that is bound by a thermally degradable material such as, but not limited to, an organic resin binder. Thus, in at least the preferred embodiments, the fluidized bed is heated to above the combustion temperature of the organic resin binder. In preferred embodiments, the processing steps desired to be performed in the fluidized bed segment


23


are, at least, the process of removing sand cores from the casting and the process of reclaiming sand from the core material which exists in the castings while in the fluidized bed furnace. To that end, the techniques of heating the sand core to a sufficiently high temperature as well as the techniques of retaining the discharged sand core within the fluidized bed


27


for sufficient dwell time to substantially reclaim the sand are employed as would be understood by those skilled in the art, especially with reference to the “Reference Patents”. It is not required that all moldings and sand core be removed from the casting in the fluidized bed since a certain amount of core removal and sand reclamation is provided for and acceptable within the convection segment


24


, though in preferred embodiments a meaningful amount of core removal and sand reclamation is preferred within the conduction segment


23


. A certain amount of heat treatment of the casting within the fluidized bed heating chamber segment


23


is anticipated.




During the time that the casting is immersed within the fluidized bed, basket


50


, with the casting, is moved by the first chamber transport mechanism


45


longitudinally through the conduction heating chamber segment


23


from its entry position at “P3” to a final bed position “PF” adjacent the convection heating chamber segment


24


. Various techniques understood in the art are acceptably used for moving the basket


50


and casting through the fluidized bed, including, for example, the ram/push device


39


and rail assembly


42


depicted. The push device


39


, in the exemplary embodiments, pushes the basket


50


laterally off the rails


71


of the movable pallet


70


onto the fixed rails


42


, through the fluidized bed chamber segment


23


, to a resting position on the rails


71




a


of the movable pallet


70




a


of the first transitional transport mechanism


46


(position PF). From position PF, the movable pallet


70




a


, with the basket


50


and casting, is raised by the transitional transport mechanism


46


(for example, by a hoist) through the transitional passage


25


to a position in the convection heating chamber segment


24


adjacent the second chamber transport mechanism


48


. From this position the basket


50


is moved longitudinally off the pallet rails


71




a


and then through the convection heating chamber segment


24


, first by the second transitional transport mechanism


47


and then by the second chamber transport mechanism


48


. Again, movement of the casting through the various chambers is not limited to those particular mechanisms depicted herein and alternate transporting mechanisms will be apparent to those skilled in the art. For example, in one embodiment (not shown) the casting is acceptably transported through the entire chamber


14


by a basket supported overhead by a cable extending from a shuttle moving longitudinally over the frame structure


12


on an overhead rail. The shuttle selectively spools and unspools the cable to raise and lower the basket at appropriate times.




It is the intention of the present invention that heat generated in the conduction heating chamber segment


23


will pass freely through the transitional passage


25


into the convection heating chamber segment


24


and, thereby, provide preheat to the convection segment and assist in effecting a continuing casting heating process from the conduction heating environment to the convection heating environment without meaningful change in temperature. As the casting is moved through the convection heating chamber segment


24


, the chamber segment is heated to sufficient temperature to perform the casting processing steps desired for this chamber segment. For example, preferably, heat treatment of the casting is performed and completed during the casting's containment within the convection heating chamber segment


24


.




Simultaneously with the heat treating, it is desired that any remaining sand core is removed from the casting and the sand is substantially reclaimed from the remaining sand core portions. Accordingly, for assisting in removal of any remaining sand of the core of the casting, hot air can be directed toward the casting in one or more directions so as to bombard the casting on different sides as the casting is moved through the convection heating chamber segment to remove any remaining sand out of the casting. Alternatively or in conjunction with the application of hot air against the casting, the casting further can be quenched by directing air toward the casting in one or more directions. This quenching air tends to cool down the casting and force any remaining sand of the core out of the casting. Any sand that is removed from the casting in such a manner will tend to fall through the second chamber transport mechanism


48


for collection by the reclaiming sand hoppers


33


. Further, as the casting is moved through convection heating chamber segment


24


toward the exit portal


18


, the castings can further be subjected to a vibrating mechanism or other similar mechanism that vibrates or shakes the castings to further assist in the removal of any remaining sand from the castings. Any remaining sand removed or vibrated out of the castings will be collected in the reclaiming sand hoppers


33


for reclamation and discharge. It is possible that any of these steps of applying hot air, applying cool air to quench the casting, and/or vibrating the casting as it is moved through the convection heating chamber segment


24


can be used separately or in conjunction with the heating and reclamation process of the invention to further assist in removal of any remaining sand of the sand core from the castings. Upon completion of the appropriate processing, the basket and casting are conveyed out of the exit portal


18


.





FIG. 2

depicts a third embodiment of the combination furnace


10


″ which does not include a hopper or a trough for retention of fallen sand core materials but, rather, includes a sand return


62


by which sand core collected in the convection heating segment


24


″ is conveyed back to the fluidized bed segment


23


where it is further processed for reclaiming of sand. A discharge weir


64


within the fluidized bed segment


23


″ is provided in order to discharge reclaimed sand from the fluidized bed segment, and the depth of the bed


27


is established or regulated to provide proper dwell time for reclamation. The weir


64


acceptably discharges to a cooling chamber


61


″ as will be understood by reference to the embodiment of

FIG. 113

of the U.S. Pat. No. 5,829,509 patent.




In accordance with the most preferred methods of the present invention, the combination furnace


10


is utilized to perform the three-in-one processes of casting processing known as core removal, in furnace sand reclamation, and heat treatment. However, it should be understood that the combination furnace


10


of the present invention is acceptably utilized to perform one or more of the mentioned processes or other processes associated with the processing of castings using heat. In alternate embodiments where it is planned that no core removal will take place within the combination furnace (for example, when all sand core molds are removed, perhaps by vibration techniques, prior to delivery of the casting to the furnace), then the sand reclaiming features of the furnace, such as, the spillway


37


, screens


55


, and fluidizers


56


are acceptably removed.




The present invention is seen as relating to the integration of a plurality of (two or more) heating environments in such a manner as to effect a continuous heating chamber, and, in accordance with the present invention, at least two adjacent heating environments within the continuous heating chamber are distinct from one another. In the herein described embodiment, the distinct environments are disclosed as one being a fluidized bed conduction furnace and the other a convection furnace.




It is clear and understood that the combination heating environment expressed in

FIGS. 1-3

herein is acceptably two segments of a larger heating chamber comprised of other heating chamber segments, including other heating environments. Such an expanded heating chamber


14


′,


14


″ is schematically represented in

FIGS. 4 and 6

. For example, in one alternate embodiment (see FIG.


6


), another segment


80


comprising a fluidized bed furnace type of heating environment follows the convection segment


24


of FIG.


1


. Following the spirit of the present invention, in such embodiment, a heat channeling transitional zone


81


is provided between the convection segment


24


and the additional conduction heating chamber segment


80


of FIG.


6


.




By way of further example, in another embodiment (not specifically shown, but inferentially seen in FIG.


4


), a convection type heating segment is added to the front of the fluidized bed conduction segment


23


of

FIG. 1

, with a heat channeling transitional zone in between. In still other embodiments (not shown), a duplicate of the combination fluidized bed and convection system of

FIG. 1

is “piggy-backed” to the front or back (or both) of the system shown in FIG.


1


. In such latter embodiments, the invention again includes a heat channeling transitional zone provided between each adjacent heating environment segment.




Furthermore, the present invention is not limited by the order of the respective heating environments. Rather, for example (as schematically represented by FIG.


5


), should a particular processing technique favor the placement of a convection heating environment prior to a fluidized bed conduction environment, then the order of the heating environments as shown in

FIG. 1

is acceptably reversed.

FIG. 5

schematically shows a convection heating environment as the first heating segment


23


′″ and a fluidized bed conduction environment as the second heating segment


24


′″.




As illustrated in

FIG. 7

, in a further alternative embodiment of the second, convection heating segment


24


″″, a rotating mechanism


80


is provided along the second chamber transport mechanism


48


″″, positioned at an intermnediate point along the length of the second heating chamber segment


24


″″. The rotating mechanism can comprise a pair of pivoting rails, such as indicated by dashed lines


81


, or similar mechanism to engage and lift the castings, so as to cause the castings to be reoriented on the transport mechanism


48


″″ as illustrated in FIG.


7


. The reorienting of the casting on the transport mechanism helps to enable a higher percentage of sand to be dislodged or shaken loose and thus removed from the castings so as to be collected in the sand reclamation hoppers. The rotating mechanism


80


can further be used separately or in conjunction with a further application of hot air or cooling air being directed against the castings from one or more directions in order to heat or quench the castings to further assist in the removal of sand from castings, or in conjunction with the vibrating mechanism, as discussed above, so as to further insure a substantially complete removal of sand from the sand cores from within the castings.




Whereas the disclosed embodiments have been explained using the fluidized bed conduction heating environment and the convection furnace heating environment as adjacent heating environments, it is clearly within the scope of the invention to incorporate any distinct heating environments as the at least two adjacent distinct heating environments. Such heating environments might acceptably include any heating environment known and understood currently or in the future by those skilled in the art, including, without limitation, conduction, convection, and radiant heating environments.




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 and without departing from the spirit and scope of the claims.



Claims
  • 1. A furnace system comprising, in combination, a plurality of distinct heating environments integrated and in open communication with one another, and a transitional passage defined between said heating environments, such that said distinct environments define a continous heating chamber through which a moving workpiece transitions from one distinct heating environment to another with no meaningful change in temperature of the workpiece.
  • 2. The furnace system of claim 1 and wherein at least one of said distinct heating environments includes a fluidized medium in which the workpiece is received for heating.
  • 3. The furnace system of claim 1 and wherein one of said distinct heating environments comprises a conduction furnace.
  • 4. The furnace system of claim 1 and wherein one of said distinct heating environments comprises a convection furnace.
  • 5. The furnace system of claim 1 and further including a transport system extending through said heating environements.
  • 6. A furnace system comprising a transport system and a plurality of distinct heating environments in communication with one another so as to define a continous heating chamber through which a workpiece is transitioned from one distinct heating environment to another with no meaningful change in temperature of the workpiece, and wherein said transport system further comprises an entry transport mechanism, a first chamber transport mechanism within a first one of said heating environments, a transitional transport mechanism, and a second chamber transport mechanism within a second one of said heating environments.
  • 7. The furnace system of claim 6 and wherein at least one of said distinct heating environments includes a fluidized medium in which the workpiece is received for heating.
  • 8. The method of claim 7 and further including initially exposing the castings to heat at an entry zone for the heating chamber.
  • 9. The method of claim 7 and further including the step of heating the dislodged core portions within the first heating environment at a temperature and for a dwell time sufficient to reclaim sand from the dislodged core portions.
  • 10. The method of claim 7 and further including preheating the second heating environment with heat from the first heating environment.
  • 11. The method of claim 7 and wherein the step of moving the castings through a heating chamber comprises placing the castings in transport containers and conveying the transport conveyors through the first and second heating segments of the heating chamber.
  • 12. The method of claim 7 and further comprising collecting sand dislodged from the castings.
  • 13. The method of claim 12 and further comprising heating the sand collected from the castings for a time and at a temperature sufficient to reclaim the sand.
  • 14. The method of claim 7 and wherein the step of moving the castings comprises moving the castings along a transitional passage between the first and second heating environments to move the castings from the first to the second heating environment with no meaningful change in temperature.
  • 15. A furnace system comprising:a substantially continuous heating chamber having a plurality of distinct heating environments integrated with and in communication with one another so as to enable free passage of heat from one heating environment to another; a transitional passage defined between said distinct heating environments to enable passage of workpieces and heat from one distinct heating environment to another with no exposure to atmosphere and with no meaningful change in temperature of the workpieces as the workpieces move from one distinct heating environment to another.
CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a continuation-in-part of U.S. application Ser. No. 09/313,111, filed May 17, 1999. This application also claims the benefit of U.S. provisional application Ser. No. 60/112,400, filed Dec. 15, 1998.

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Entry
Economical Used Energy Type Continuing Heat Treating Furnace For Aluminum Castings Dogyo—Kanetsu vol. 21 No. 2 pp. 29-36—Mar. 1984.
Brochures describing Beardsley & Pipe PNEU-RECLAIM Sand Reclamination Units Prior to Aug. 13, 1992.
Brochure describing Fataluminum Sand Reclamination Units—Prior to Aug. 13, 1992.
Paul M. Crafton—Heat Treating Aging System Also Permits Core Sand Removal—Reprinted from Sep. 1989 Modern Castings magazine.
Sales brochure describing Thermfire Brand Sand Reclamation, Gudgeon Bros., Ltd. believed to be known to others prior to Sep. 1989.
Sales brochure describing Simplicity/Richards Gas-Fired Thermal Reclamation System Simplicity Engineering, Inc.—believed to be known to others prior to Sep. 1989.
Sales brochure describing AirTrac Brand Fluidizing Conveyor, Air Trac Systems Corp., believed to be known to others prior to Sep. 1989.
Sales brochure describing Fluid Bed Calcifer Thermal Sand Reclamation Systems, Dependable Foundry Equipment Co.—Believed to be known to others prior to Sep. 1989.
Provisional Applications (1)
Number Date Country
60/112400 Dec 1998 US
Continuation in Parts (1)
Number Date Country
Parent 09/313111 May 1999 US
Child 09/464229 US