Stucco tower and method

Information

  • Patent Grant
  • 6503324
  • Patent Number
    6,503,324
  • Date Filed
    Thursday, July 27, 2000
    24 years ago
  • Date Issued
    Tuesday, January 7, 2003
    21 years ago
Abstract
Stucco tower and method for applying ceramic particulates to a ceramic slurry coated pattern involves positioning the ceramic slurry coated pattern in a chamber, discharging ceramic particulates downwardly onto the ceramic slurry coated pattern, and circulating air through air circulation plenums from a lower region of the chamber to an upper region thereof as the ceramic particulates are discharged. An air curtain is provided at an access opening to the chamber.
Description




FIELD OF THE INVENTION




The present invention relates to an apparatus and method for applying ceramic stucco particulates to a ceramic slurry coated fugitive pattern used in manufacture of investment casting ceramic shell molds for casting metals and alloys.




BACKGROUND OF THE INVENTION




In casting superalloy gas turbine engine blades and vanes using conventional equiaxed and directional solidification techniques, ceramic shell molds with or without a ceramic core therein are filled with molten metal or alloy that is solidified in the mold. The ceramic shell mold is made by the well known lost-wax process where a fugitive (e.g. wax) pattern of the blade, vane or other article to be cast is repeatedly dipped in a ceramic slurry, drained of excess slurry and covered (stuccoed) with a layer of relatively coarse ceramic particulates, such as ceramic sand or stucco, to build up the shell mold wall to a desired wall thickness. The pattern then is selectively removed from the shell mold by thermal or chemical dewaxing techniques, and the green mold is fired to develop adequate mold strength for casting. U.S. Pat. Nos. 5,335,717 and 5,975,188 describe a typical lost wax process sequence to make ceramic investment casting shell molds.




The ceramic stucco particulates are applied to the wet ceramic slurry on the pattern by positioning the slurry coated pattern in an internal chamber of a so-called stucco tower. The stucco tower includes a ceramic stucco hopper at the top of the internal chamber for gravity discharging loose, dry ceramic stucco particulates from the hopper downwardly onto the slurry coated pattern positioned in the chamber through a front access opening thereof. As the ceramic stucco particulates fall by gravity, they push air downwardly in the chamber, creating vortices, turbulence and non-uniform air flow patterns in the chamber and out of the access opening, expelling fine ceramic stucco particulates and dust into the ambient atmosphere. As a result of such irregular air flow, stucco towers used in the past have suffered from problems of uneven distribution of stucco particulates within the tower, resulting in uneven shell mold wall thickness as well as discharge of fine stucco particulates and dust out of the access opening of the tower. Dust collectors have been provided on the stucco tower to collect the fine stucco particulates and dust expelled from the access opening.




An object of the present invention is to provide a stucco tower or other apparatus to provide improved distribution of particulates discharged in a chamber.




Another object of the present invention is to provide a stucco tower or other apparatus that reduces emission of particulates and dust therefrom.




SUMMARY OF THE INVENTION




An illustrative embodiment of the present invention provides stucco tower apparatus that includes an internal chamber in which a ceramic slurry coated pattern is positioned and one or more air circulating plenums positioned for circulating air from a lower region toward an upper region of the chamber as stucco particulates are discharged from a hopper above the chamber and fall by gravity onto the ceramic slurry coated pattern. The apparatus preferably includes an air curtain at an access opening to the chamber to reduce emission of stucco particles and dust, especially when the stucco particles are initially released from the hopper before air circulation through the chamber and the air circulation plenums is fully established.




A method embodiment of the present invention involves applying stucco particulates onto ceramic slurry coated pattern, wherein the ceramic slurry coated pattern is positioned in a chamber, stucco particulates are discharged downwardly in the chamber onto the ceramic slurry coated pattern and create a downward air flow in the chamber, and air is circulated from a lower region of the chamber to an upper region of the chamber as the stucco particulates are discharged. An air curtain is formed at an access opening to the chamber to reduce emission of stucco particles and dust.




Although the invention will be described in detail and illustrated with respect to stucco tower apparatus for applying ceramic stucco particles onto a ceramic slurry coated pattern, the invention is not so limited and can comprise apparatus of other types and uses for discharging particulates from an upper region to a lower region in a chamber.




The above objects and advantages of the present invention will become more readily apparent from the following detailed description taken with the following drawings.











DESCRIPTION OF THE DRAWINGS





FIG. 1

is a schematic perspective view of a stucco tower in accordance with an embodiment of the invention where air circulation plenums are disposed on exterior side walls and a rear wall of the stucco tower. A front panel of the stucco tower apparatus is shown in exploded view to reveal a stucco collector.





FIG. 1A

is a sectional view of the stucco tower of

FIG. 1

along line


1


A—


1


A.





FIG. 2

is a schematic perspective view of a stucco tower of another embodiment of the invention where air circulation passages are disposed in the interior of the stucco tower.





FIG. 3

is a front elevational view of a stucco tower in accordance with a working embodiment of the invention.





FIG. 4

is a side elevational view of the stucco tower of

FIG. 3







FIG. 5

is an enlarged view of an air curtain nozzle.





FIG. 6

is a partial sectional view of a hopper fixed plate and movable plate.





FIG. 7

is a partial sectional view of the magnet assembly.











DETAILED DESCRIPTION OF THE INVENTION




Referring to

FIG. 1

, a stucco tower apparatus


10


in accordance with an embodiment of the invention is illustrated schematically for applying ceramic stucco particles to a wet ceramic slurry coated fugitive pattern P in practice of the well known “lost wax” process to buildup a refractory or ceramic investment shell mold on the pattern for use in casting molten metals and alloys. As discussed above, the lost wax process involves using a fugitive (e.g. wax) pattern of an article to be cast, repeatedly dipping the pattern in a ceramic slurry of fine ceramic powder or flour in a liquid, draining excess slurry from the pattern and then stuccoing the wet ceramic slurry layer with a layer of relatively coarse ceramic stucco particulates to build up the shell mold wall thickness to a desired value. The stucco particulates can comprise conventional ceramic sand particles, ceramic stucco particles and other ceramic particles used heretofore to stucco the wet slurry coated pattern in building up of the shell mold wall thickness. The pattern then is selectively removed from the shell mold by thermal or chemical dewaxing techniques, and the green mold is fired to develop adequate mold strength for casting. U.S. Pat. Nos. 5,335,717 and 5,975,188 describe a typical lost wax process sequence and materials to make ceramic investment casting shell molds.




The stucco tower apparatus


10


of

FIG. 1

is used to apply a layer of the ceramic stucco particulates to the previously ceramic slurry coated pattern P in the practice of the lost wax process. The stucco tower apparatus includes an internal chamber


12


in which the wet ceramic slurry coated pattern P is positioned and rotated by a conventional robotic arm


90


to expose exterior surfaces of the slurry coated pattern P to ceramic stucco particles. The robotic arm


90


holds the base B of the slurry coated pattern P, or a suitable fixture (not shown) holding the base B, and extends through an access opening


14


communicated to the internal chamber


12


and uses the wrist


92


of the robot arm


90


to rotate the slurry coated pattern P in the chamber


12


, the robot arm forming no part of the invention. Alternately, the slurry coated pattern P can be manually positioned and rotated in the chamber


12


.




The chamber


12


is defined by a tower front wall


20


having access opening


14


, a rear wall


22


, and first and second side walls


24


,


26


interconnecting the front wall and rear wall of the stucco tower apparatus. The walls


20


,


22


,


24


,


26


may comprise a single wall panel or a pair of spaced apart wall panels such as illustrated for rear wall


22


comprising inner and outer wall panels


22




a


,


22




b


. A bottom opening


28


of chamber


12


is open to a stucco reclamation collector


29


therebelow to collect ceramic stucco particles that do not fall on and form a stucco layer on the slurry coated pattern P. The walls


20


,


22


,


24


,


26


can comprise sheet metal, plastic, or other panels.




The top of the chamber


12


includes a stucco particulates hopper


32


that discharges the loose, dry ceramic stucco particulates for fall by gravity downwardly onto the wet ceramic slurry coated pattern P as it is rotated in the chamber


12


. The hopper


32


is of the type described in more detail below with respect to

FIGS. 3 and 4

. The ceramic stucco particles S are discharged from the hopper


32


to rain down upon the rotating ceramic slurry coated pattern P as illustrated in FIG.


1


and stick onto the wet ceramic slurry layer on the pattern P to form a stucco layer thereon.




Pursuant to an embodiment of the invention, a first air circulation plenum


40


is provided adjacent and outboard (exterior) of the first side wall


24


and a second air circulation plenum


42


is provided adjacent and outboard (exterior) of the second side wall


26


,

FIG. 1. A

third air circulation plenum


44


is provided adjacent and outboard (exterior) of the rear wall


22


, FIG.


1


A. The first air circulation plenum


40


is communicated by a lower opening


41


to the chamber


12


at the lower region thereof proximate bottom opening


28


and by a similar upper opening


43


at the upper region thereof below the hopper. The second air circulation plenum


42


is communicated by a lower opening


41


to the chamber


12


at the lower region thereof proximate the bottom opening


28


and by a similar upper opening


43


at the upper region thereof below the hopper. The third air circulation plenum


44


is communicated by a similar lower opening


41


to the plenum


12


at the lower region thereof proximate the bottom opening


28


and by a similar upper opening (not shown) at the upper region thereof below the hopper. As the ceramic stucco particles fall by gravity from the hopper


32


in the chamber


12


, they create a relatively lower pressure at the upper region of the chamber


12


below the hopper


32


and a relatively higher pressure at the lower region of the chamber


12


proximate bottom opening


28


and push air through the air circulation plenums


40


,


42


,


44


for flow upwardly to the upper region of the chamber


12


below the hopper


32


.




The air circulated back to the upper region of the chamber


12


is carried downwardly by the falling ceramic stucco particles S to establish air flow from the upper region to the lower region of the chamber


12


and from the lower opening


41


toward the upper opening


43


in the circulation plenums


40


,


42


,


44


as illustrated with the arrows. This air flow provides a more uniform air flow distribution from top to bottom in the chamber


12


to improve distribution of ceramic stucco particles falling therein and depositing on the ceramic slurry coated pattern P. The distribution of stucco particles on the slurry coated pattern and thus the uniformity of thickness of the shell mold wall thereby are improved.




The air circulation plenums


40


,


42


,


44


typically are formed as conventional sheet metal and/or plastic panel passages or ducts in the configurations shown for connection on the exterior of the stucco tower


10


. The cross-sectional size and locations of the openings


41


,


43


and the plenums


40


,


42


,


44


are chosen to provide uniform air flow downwardly from top to bottom in the chamber


12


with vortices and turbulence substantially reduced or eliminated to, in turn, provide a more uniform top-to-bottom stucco particulate flow in chamber


12


.




Although air circulation plenums


40


,


42


,


44


are shown adjacent opposite side walls


24


,


26


and rear wall


22


, the invention is not a so limited as fewer or additional air circulation plenums may be used. For example only, air circulation plenums


40


,


42


can be provided adjacent side walls


24


,


26


while air circulation plenum


44


can be omitted. One or more air circulation plenums can be provided adjacent any one or more of the front and rear walls


20


,


22


and side walls


24


,


26


.




The access opening


14


to the chamber


12


preferably includes an air curtain device


50


operably associated therewith. The air curtain device


50


comprises a compressed air conduit


52


that is disposed on the exterior of the front wall


20


and across the extent of the access opening


14


at its upper extent. The conduit


52


is connected to a source SA of filtered shop compressed air and includes a downwardly facing air discharge slot nozzle


54


to discharge a curtain of compressed air (designated by arrows A) downwardly toward the lower extent of the access opening


14


to confine stucco particles and dust in the chamber


12


. The slot nozzle


54


may be oriented to discharge the air curtain at a slight angle inwardly toward the chamber


12


(e.g. 5 degrees relative to the vertical plane defined by the front wall


20


). The compressed air can be supplied to the conduit


52


at


80


psi for example only to create the desired air curtain effect. Much of the stucco particles and dust that are pushed by air flow in chamber


12


toward the access opening


14


are deflected by the air curtain back toward the chamber


12


for entrainment in the air flow circulating in the chamber and the air circulation plenums


40


,


42


,


44


. Dust collection ducts shown in

FIGS. 3 and 4

can be provided to collect any fine stucco particles and dust that may escape from the access opening.




The air curtain device


50


can comprise a plurality of air discharge nozzles spaced laterally apart along the length of the conduit


52


, rather than a single slot nozzle as illustrated in FIG


1


. The air discharge nozzles will be arranged such that the air streams discharged therefrom collectively form an air curtain directed downwardly and preferably inwardly toward the chamber


12


to reduce emissions of ceramic stucco and dust from the access opening


14


during stuccoing of a wet ceramic slurry coated pattern in the chamber


12


.




The air curtain device


50


is useful to prevent emission of stucco particles and dust from the chamber


12


when the ceramic stucco particulates are initially released from the hopper


32


before air circulation through the chamber


12


and air circulation plenums


40


,


42


,


44


is fully established.




The invention is not limited to provision of air circulation plenums


40


,


42


,


44


on the exterior of the stucco tower apparatus. For example, the invention can be practiced using air circulation passages formed interiorly within the stucco tower


10


′ as illustrated schematically in FIG.


2


. In particular, interior side walls


24


′,


26


′ are disposed in the stucco tower


10


′ adjacent and inwardly of exterior side walls


60


′,


62


′ of the stucco tower. Air circulation passages or plenums


40


′,


42


′ are thereby formed between the inner side wall


24


′ and exterior tower side wall


60


′ and inner side wall


26


′ and exterior tower side wall


62


′. The air circulation plenums


40


′,


42


′ communicate with the chamber


12


′ at a lower region proximate bottom opening


28


′ via lower opening


41


′ and at an upper region below hopper


32


′ via upper opening


43


′. The air circulation plenums


40


′,


42


′ circulate air from the lower region of the chamber


12


′ to the upper region thereof beneath the hopper


32


′ as described for the embodiment of

FIG. 1

when stucco particulates are discharged from the hopper. The air circulated back to the upper region of the chamber


12


′ is pushed downwardly by the falling ceramic stucco particles from the hopper


32


′ to establish air flow from the top to bottom in the chamber


12


′ and from bottom to top in the circulation plenums


40


′,


42


′ as illustrated with the arrows. An air curtain


50


′ is provided with a conduit


52


′ to supply compressed air to slot nozzle


54


′ to form an air curtain directed downwardly across the access opening


14


′ in front tower wall


20


′ as indicated by arrows A′ as described in FIG.


1


.




In operation of the stucco towers of

FIGS. 1 and 2

pursuant to the invention to apply ceramic stucco particulates to the wet ceramic slurry coated pattern P, the ceramic slurry coated pattern P is placed in the chamber


12


(


12


′) via access opening


14


(


14


′) and rotated by the robotic arm. The ceramic stucco particulates S then are released from the hopper


32


(


32


′) to fall by gravity downwardly onto the ceramic slurry coated pattern to form a layer of ceramic stucco on the wet slurry layer. As ceramic stucco particulates are discharged from the hopper, air in the chamber


12


(


12


′) is circulated by plenums


40


,


42


,


44


(


40


′,


42


′) from the lower region of the chamber


12


(


12


′) adjacent the bottom opening


28


(


28


′) upwardly to the upper region of the chamber


12


(


12


′) below the hopper


32


(


32


′) as illustrated by the arrows. Concurrently, the air curtain generated across access opening


14


(


14


′) by air curtain device


50


(


50


′) reduces discharge of ceramic stucco particles and dust to the atmosphere outside the stucco tower. The slurry coated pattern is rotated in the chamber


12


(


12


′) for a predetermined time to deposit a layer of stucco particles on the wet ceramic slurry layer previously applied to the pattern. The improved more uniform air flow distribution in chamber


12


(


12


′) pursuant to the invention provides more uniform downward stucco flow to build up a more uniform shell mold wall thickness on the pattern.




Referring to

FIGS. 3 and 4

, stucco tower apparatus


100


is shown having internal chamber


112


defined by a front wall


120


, rear wall


122


and first and second interior side walls


124


,


126


and a bottom opening similar to opening


28


′ of FIG.


2


. The side walls


124


,


126


are spaced inwardly from exterior stucco tower side walls


160


,


162


in a manner similar to

FIG. 2

to define interior air circulation plenums


140


,


142


that are each communicated to the lower region of the chamber


112


proximate bottom chamber opening by lower openings


141


and to the upper region of the chamber


112


below the hopper


132


by upper openings


143


to provide the air flow circulation pattern indicated by arrows AA in

FIG. 3

pursuant to the invention. The chamber walls can comprise sheet metal panels mounted on structural frame members F or on the tower walls, although side walls


124


,


160


and


126


,


162


can comprise transparent plastic material, such as Plexiglass material to allow viewing of the chamber


112


.




An air manifold conduit


152


connected to source SA of filtered shop compressed air at a pressure of, for example only,


80


psi is mounted on the front wall


120


and includes a plurality of air discharge nozzles


154


to discharge flat planar air streams that collectively form an air curtain directed downwardly across the access opening


114


in the front wall. The nozzles


154


are oriented on the conduit


152


to create an air curtain that is directed inwardly toward the chamber


112


, FIG.


5


. For example, the air curtain can be oriented inwardly at about 5 degrees relative to a vertical plane of the front wall


120


. Suitable air nozzles are available as model MEG nozzles from Industrial Spray Products, PO Box 7900, Wheaton, Ill. 60189-7900.




The stucco tower


100


includes a stucco hopper


132


at the top for discharging loose, dry ceramic stucco particles downwardly into the chamber


112


. The hopper


132


includes a fixed plate


133


and movable plate


135


that slides on a plurality of pairs of wheels


137


mounted on the hopper sides


132




a


. As illustrated in

FIG. 6

, the fixed plate


133


includes a plurality of holes


133




a


, while the movable plate


135


includes a plurality of holes


135




a


that are aligned by movement with the holes


133




a


of the plate


133


to allow stucco particles to be discharged at a controlled rate from the hopper


132


into the chamber


112


. Stucco particles are deflected by rods


138


aligned with the stucco stream, directly below stucco discharge holes


135




a


. The movable plate


135


is moved relative to the fixed plate


133


by a fluid (e.g. air) actuator


139


(e.g. an air or hydraulic cylinder) via its plunger


139




a


moving a cross-shaft


141


on the movable plate


135


to release the ceramic stucco particles from the hopper


132


to fall by gravity into the chamber


112


onto the ceramic slurry coated pattern therein (not shown in FIGS.


3


and


4


). The ceramic stucco particles in the hopper


132


can comprise conventional ceramic stucco or sand particles having a particle size of


14


mesh to


120


mesh (US standard sieve) for purposes of illustration only. The hopper includes a top closure wall


132




w


with access covers


132




o


through which ceramic stucco particles can be introduced to the hopper.




Ceramic stucco particles that do not stick to the wet ceramic slurry on the wet ceramic slurry coated pattern fall into a stucco collector


129


at the bottom opening of the chamber


112


. An apertured grate


127


optionally can be provided in the bottom opening of the chamber


112


above the collector


129


to catch large stucco particles and/or drips of ceramic slurry/stucco that might fall off of the pattern. The collector


129


includes walls sloped in a direction to direct the collected ceramic stucco particles to a funnel


131


that supplies the collected ceramic stucco particles to a lowermost particle collection chamber


172


of a pick-up elevator


170


.




A wire mesh-covered trough


129




a


is provided at the lower extent of the access opening


114


exteriorly on the front wall


120


to catch any stucco particles falling off the pattern when it is removed from the chamber


112


. The trough


129




a


communicates to the collector


129


so that the stucco particles that fall into the trough


129




a


then fall into the collector


129


.




The pick-up elevator


170


includes a plurality of pick-up buckets


171


disposed on a conventional endless chain


174


disposed behind the stucco tower. The endless chain


174


moves the buckets


171


downwardly to scoop the ceramic stucco particles in collection chamber


172


into the buckets


171


and then upwardly to a discharge chute


176


where the buckets are moved to invert them in a manner to discharge the ceramic stucco particles into the chute


176


. The endless chain


174


includes a tension adjustment screw


174




a


. The collection chamber


172


can include a porous stone or ceramic plate


177


disposed at the bottom of the chamber


172


and connected to a source S


1


of compressed air at


40


psi for example only. The compressed air is supplied to the porous stone or ceramic plate


177


and is discharged into the collected ceramic stucco particles in the chamber


172


to fluidize them to facilitate pick-up by buckets


171


. The endless chain


174


is driven by an electric motor


178


with gear reducer box


178




a


via a belt


180


between pulleys


182




a


,


182




b


. The elevator


170


includes an upstanding metal tunnel enclosure


173


that includes access panel


173




a


and panel toggle clamps


173




b


and is supported by brackets


175


connected to frame members F on the rear of the stucco tower.




The chute


176


includes a magnet assembly


178




FIG. 7

, of permanent magnets


184


(e.g. cylindrical, rectangular, square and any other cross-section permanent magnets) disposed in the chute in the path of the ceramic stucco particles to remove any magnetic metallic particles or shavings that may be present in the ceramic stucco particles. The permanent magnets


184


are shown as cylindrical in shape. Each magnet


184


includes a removable tubular sleeve


185


made of non-magnetic material, such as aluminum, austenitic stainless steel and the like. The assembly


178


′ has a plate


183


that is clamped to the chute


176


by conventional toggle clamps


189


to position the permanent magnets


184


in the path of the ceramic stucco particles in the chute. The toggle clamps can be periodically released so that the magnet assembly can be removed from the chute


176


using handle H to clean off accumulated magnetic metallic particles and shavings. In particular, after the magnet assembly is removed from the chute, the sleeves


185


are removed from the magnets


184


by removing nuts


186


from threaded shafts


190


and removing plate


187


. The metallic particles and shavings fall off the non-magnetic sleeves


185


when they are removed from the magnets


184


. The sleeves then are reinstalled on the magnets


184


for return of the magnet assembly to inside the chute


176


. The magnets


184


can be tubular with the shafts


190


extending therethrough or solid with shafts


190


connected at opposite ends of the magnets.




The ceramic stucco particles are supplied from the chute


176


to a rotating wire mesh screen drum


192


of a drum separator


190


located above the hopper


132


. The drum


192


receives the stucco particles from the chute


176


and functions to allow stucco particles of the proper size to pass through the drum wire mesh screen to the hopper


132


. The drum


192


is inclined upwardly such that ceramic stucco particles that are too large migrate down the drum


192


for discharge through a discharge end


192




d


to a collection container (not shown). The drum


192


is driven to rotate on drum shafts


192




a


,


192




b


by a conventional rotary electric motor


194


and gear reducer


195


connected to drum shaft


192




b


via a coupling


196


.




A duct collection duct


200


is disposed on each side wall


160


,


162


and functions to collect any fine stucco particles and dust that may escape from the access opening


114


. To this end, each dust collection duct


200


includes an intake slot


200




a


disposed along a respective vertical side of the access opening


114


such that the intake slot


200




a


of one collection duct


200


faces the intake slot


200




a


of the opposing collection duct


200


. The collection ducts


200


include connection ports


200




b


that are connected to a dust collection blower (not shown) that generates a suction in the ducts


200


to suck or draw any fine stucco particles and dust escaping from the access opening


114


through the intake slots


200




a


and into the ducts


200


where the particles and dust are filtered out of the air stream in conventional manner and forming no part of the invention. Although the invention has been described in detail and illustrated with respect to stucco tower apparatus for applying ceramic stucco particles onto a ceramic slurry coated pattern, the invention is not so limited and can comprise apparatus of other types and uses for discharging particulates downwardly from an upper region to a lower region in a plenum.




Although the invention has been described with respect to certain specific embodiments thereof, those skilled in the art will appreciate that the invention is not limited to these embodiments and that various changes, additions, omissions, and the like can be made therein without departing from the scope of the invention as set forth in the appended claims.



Claims
  • 1. Apparatus, comprising:a chamber, means for discharging particulates downwardly from an upper region to a lower region of said chamber, and an air circulation plenum communicated by a lower opening to said lower region of said chamber and by an upper opening to said upper region of said chamber to circulate air from said lower region to said upper region as said particulates are discharged downwardly in said chamber.
  • 2. The apparatus of claim 1 wherein said chamber is defined by a front wall, a rear wall, and first and second side walls interconnecting said front wall and rear wall.
  • 3. The apparatus of claim 2 including a first air circulation plenum adjacent said first side wall and a second air circulation plenum adjacent said second side wall.
  • 4. The apparatus of claim 1 wherein said upper opening is disposed below said means for discharging particulates.
  • 5. The apparatus of claim 2 including an access opening to said chamber and an air curtain disposed at said access opening.
  • 6. The apparatus of claim 5 wherein said air curtain includes a plurality of air discharge nozzles proximate an upper extent of said access opening for discharging air downwardly.
  • 7. The apparatus of claim 6 wherein said nozzles are angled toward a wall having said access opening therein.
  • 8. The apparatus of claim 1 including a collection chamber for the ceramic particulates and means for fluidizing the particulates in the collection chamber.
  • 9. The apparatus of claim 4 wherein said means for discharging particulates comprises a hopper.
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