Method for removing cores from castings

Information

  • Patent Grant
  • 6241000
  • Patent Number
    6,241,000
  • Date Filed
    Wednesday, June 7, 1995
    29 years ago
  • Date Issued
    Tuesday, June 5, 2001
    23 years ago
Abstract
Method for removing a ceramic core from a casting in a relatively rapid manner wherein the casting and a fluid spray nozzle are disposed in a manner to expose a region of the core to a core dissolving fluid discharge of the nozzle and a core dissolving fluid is discharged from the nozzle toward the core region to contact the core region and dissolve core material therefrom and progressively from further regions of the core within the casting as they become exposed as core material is progressively removed. The discharge of fluid from the nozzle can be interrupted periodically to allow dissolved core material and fluid to drain from inside the casting or, alternately, the casting and nozzle can be relatively moved so that the casting can drain and/or forced air can be directed at the casting to this same end at a location spaced apart form the nozzle.
Description




FIELD OF THE INVENTION




The present invention relates to the removal of a core, such as a ceramic core, from inside of a casting, such as an investment casting.




BACKGROUND OF THE INVENTION




In the manufacture of gas turbine engine components, such as gas turbine engine blades and vanes, an appropriate alloy, such as a nickel or cobalt based superalloy, is investment cast in a ceramic investment mold. One or more ceramic cores may be present in the ceramic investment mold in the event the cast component is to include one or more internal passages. For example, gas turbine blades and vanes for modern, high performance gas turbine engines typically include internal cooling passages extending through the airfoil and root portions and through which passages compressor bleed air is conducted to cool the airfoil portion during engine operation. In this event, the ceramic core positioned in the investment mold will have a configuration corresponding to the internal cooling passage(s) to be formed through the airfoil and root portions of the cast turbine blade or vane. The blade or vane component may be cast by well known techniques to have an equiaxed, columnar, or single crystal microstructure.




In the past, the ceramic core has been removed from the investment cast component by an autoclave technique or an open kettle technique. One autoclave technique involves immersing the cast component in an aqueous caustic solution (e.g. 45% KOH) at elevated pressure and temperature (e.g. 250 psi and 177° C.) for an appropriate time (e.g. 4-10 hour cycles) to dissolve the core from the casting. U.S. Pat. Nos. 4,134,777 and 4,141,781 disclose autoclave caustic leaching of yttria ceramic cores and beta alumina ceramic cores from directionally solidified superalloy castings. An exemplary open kettle technique involves immersing the cast component in a similar aqueous caustic solution at ambient pressure and elevated temperature (e.g. 132° C.) with agitation of the solution for a time (e.g. 90 hours) to dissolve the core from the casting. These core removal techniques are quite slow and time-consuming.




SUMMARY OF THE INVENTION




The present invention provides method and apparatus for removing a core from inside a casting in a relatively rapid manner as compared to the aforementioned autoclave and open kettle techniques. One embodiment of the method comprises disposing the casting and a fluid spray means, such as for example only a fluid spray nozzle, in a manner to expose a region of the core to a core dissolving fluid discharge of the fluid spray means, supplying a core dissolving fluid to the fluid spray means for discharge toward the exposed core region, and discharging the fluid from the fluid spray means to contact the core region and remove core material therefrom and progressively from further regions of the core within the casting as they become exposed as core material is progressively removed.




The discharge of fluid from the fluid spray means can be interrupted periodically to allow dissolved core material and spent fluid to drain from inside the casting or, alternately, the casting and fluid spray means can be relatively moved so that the casting can drain to this same end at a drain location apart from the fluid spray means. In a particular embodiment of the invention, the casting and a plurality of fluid spray nozzles are relatively moved so that the casting is moved from one fluid spray nozzle to the next to receive core dissolving fluid at each nozzle and to drain dissolved core material and spent fluid when moved to a drain location between the nozzles. A plurality of castings can be carried on a linearly movable carrier, such as a transport conveyor, or on a rotatable carrier, such as a carousel, past a plurality of fixed or stationary core dissolving fluid spray nozzles to remove the core from each casting.




In practicing the invention to remove a ceramic core from turbine blade or vane investment castings having an airfoil portion and root portion with the core exposed at the root portion, the castings and one or more core dissolving fluid spray means, such as fluid spray nozzles, are positioned so that a caustic solution (e.g. 45% KOH) at elevated temperature (e.g. 100 to 150° C.) and pressure (e.g. 50 to 450 psi) is supplied to the nozzles and discharged at the exposed core region at the root portion to dissolve the core from the root portion progressively through the airfoil portion in a relatively short time (e.g. typically 1 to about 10 hours) depending upon the configuration of the casting and core therein. One or more additional core dissolving fluid spray nozzles may be positioned to discharge core dissolving fluid at the blade or vane casting tips where another region of the core may be exposed at a tip plenum cavity of the castings.




The invention will be described in more detail by the following drawings and detailed description.











BRIEF DESCRIPTION OF THE DRAWINGS





FIG. 1

is a schematic perspective illustration of one embodiment of the invention for removing a ceramic core from inside each of a plurality of cast turbine blades.





FIG. 2

is a cross sectional view of an airfoil of a turbine blade casting.





FIG. 3

is a schematic perspective view of one embodiment of apparatus for practicing the invention for removing a ceramic core from each of a plurality of turbine blade castings.





FIG. 4

is a more detailed side elevation of apparatus of one embodiment of the invention with the cabinet partially broken away to reveal the spray manifold and a portion of the casting rotary carousel.





FIG. 4A

is an elevational view of the spray manifold.





FIG. 4B

is an end elevation of the spray manifold of FIG.


4


A.





FIG. 5

is a plan view of the apparatus of

FIG. 3

with the cabinet partially broken away to reveal the rotary carousel drive and turbine blade casting.





FIG. 6

is a side elevation of the cabinet.





FIG. 7

is a partial sectional view along lines


7





7


of FIG.


5


.





FIG. 8

is a partial sectional view along lines


8





8


of FIG.


6


.





FIG. 9

is partial sectional view along lines


9





9


of FIG.


4


.





FIG. 10

is a similar sectional view of another embodiment of the invention for fixturing a particular turbine blade on the rotary carousel for core removal.





FIG. 11

is an elevational view of a load bar of

FIG. 10

with turbine blades fixtured thereon.





FIG. 12

is an elevational view of a blade fixture of

FIG. 11

with the fixture open.





FIG. 13

is a sectional view similar to

FIG. 10

for fixturing a different turbine blade on the rotary carousel for core removal.





FIG. 14

is a schematic sectional view of the cabinet of another embodiment of apparatus of the invention for removing a core from a plurality of turbine blade castings fixtured on either a rotary carousel or a linear conveyor.





FIG. 15

is an elevational view of the linear conveyor of FIG.


14


.





FIG. 16

is a view along lines


16





16


of FIG.


15


.





FIG. 17

is a perspective view of another embodiment of apparatus of the invention.





FIG. 18

is a transverse sectional view of the double wall fluid manifold of FIG.


17


.





FIG. 19

is a perspective view of still another embodiment of apparatus of the invention.











DETAILED DESCRIPTION OF THE INVENTION




One embodiment of the present invention to remove a ceramic core from a plurality of turbine blade investment castings


10


is schematically illustrated in FIG.


1


. In particular, a plurality of cored turbine blade investment castings


10


are shown fixtured vertically in fixtures


12


on an annular fixture ring


16


that is rotated about a vertical axis by a variable speed rotor or other ring rotating motor (not shown). The turbine blade castings


10


can comprise equiaxed, columnar, or single crystal nickel base or cobalt base superalloy castings made by well known conventional investment or other casting processes. Although

FIG. 1

illustrates turbine blade investment castings


10


, this is only for purposes of illustration and not limitation. The invention is not limited to any particular casting technique or to any particular casting shape, casting metal, alloy or other material, or casting microstructure and can be practiced to remove a core from a wide variety of casting shapes, microstructures, and cast compositions produced by different casting processes.




The turbine blade castings


10


include an airfoil portion


10




a


, a root portion


10




b


, a platform portion


10




c


between the root and airfoil portions, and a tip portion


10




f


in conventional manner. Residing within each turbine blade casting


10


is a ceramic core


14


that is embedded in the casting by virtue of being present in the ceramic or other casting mold (not shown) and having alloy, metal or other melt material cast thereabout. The ceramic core


14


is configured to form an internal cooling air passage in the turbine airfoil and root portions


10




a


and


10




b


. The ceramic core


14


extends to the bottom of the root portion


10




b


where it is exposed or opens at core region


14




a


to an external root end surface


10




bb,



FIG. 2

, to communicate to the outside or ambient. The ceramic core also may be exposed at the tip


10




f


of the casting


10


at core region


14




b


externally to the outside to form a tip plenum cavity region


14




c


also for air cooling purposes.




The ceramic core


14


typically comprises an appropriate ceramic material selected in dependence on the metal, alloy or other material to be cast thereabout in the casting mold. For nickel base superalloys, such as Rene' 125, used in the manufacture of cast turbine blades and vanes as well as vane segments, the core


14


can comprise silica, zirconia, and alumina. For cobalt base superalloys, such as MAR-M509, also used in the manufacture of cast turbine blades and vanes as well as vane segments, the core


14


can comprise silica, zirconia, and alumina. Cores of different composition can be used depending on the particular metal, alloy or other material being cast and can be selected accordingly. The invention, however, is not limited to any particular core material and can be practiced to remove a core that is internal of a casting and is dissolvable in a suitable core dissolving fluid, such as, for example only, an aqueous caustic solution.




As shown in

FIG. 1

, the root portion


10




b


of each turbine blade casting


10


is received and held in a respective fixture or clamp


12


during core removal. The castings


10


are vertically located or oriented by the fixtures


12


with the root portions


10




b


lowermost and proximate core dissolving fluid spray means such as fluid spray nozzles


20


. Thus, the turbine blade castings


10


are fixtured in a manner to communicate a lowermost core region


14




a


exposed at the root end surface


10




bb


to a core dissolving fluid stream discharge DD of each fluid spray nozzle


20


.




In

FIG. 1

, the fluid spray nozzles


20


are spaced apart in a circular array that is beneath and aligned with the path of movement of the castings


10


so that the exposed core regions


14




a


pass over and communicate with the discharge ends


20




a


of the fluid spray nozzles


20


as they are moved by the fixture ring


16


. Between the fluid spray nozzles


20


are defined drain positions DP where dissolved core material and spent core dissolving fluid residing in passage regions formed in the castings


10


by removal of core regions can drain by gravity and/or by forced (compressed) air (e.g. 90 psi compressed air or other gas) directed upwardly in

FIG. 1

at the castings


10


by underlying compressed air discharge nozzles CN (one shown) positioned in alternating sequence between the spray nozzles


20


to this end. The castings


10


typically are moved in stepped or intermittent manner so as to reside at each fluid spray nozzle


20


and drain position DP a selected period of time to this end. Alternately, the castings


10


typically can be moved at a constant speed relative to the spray nozzles


20


and drain positions DP and/or compressed air nozzles CN with the speed adjusted to be slow enough for adequate fluid removal from internal of the castings


10


by gravity drainage and/or as forced by compressed air.




The fluid spray nozzles


20


are disposed on a stationary annular, tubular fluid manifold


24


(partially shown) that receives core dissolving fluid at elevated temperature and pressure from high pressure pumps to be described herebelow. The manifold


24


and thus the fluid spray nozzles


20


are disposed in fixed relation or position relative to the rotatable fixture ring


16


, although the invention is not so limited and can be practiced with the fluid spray nozzles


20


movable relative to the stationary castings


10


, or with both the fluid spray nozzles


20


and castings


10


movable. Still further, in another embodiment of the invention described herebelow, the fluid spray nozzles


20


and the castings


10


are not moved relative to one another. Such embodiment is useful, although not limited, for removing ceramic core material from large industrial gas turbine engine vanes and blades.




The fluid manifold


24


includes a plurality of spaced apart apertures that receive a respective fluid spray nozzle


20


by, for example, threading of the nozzle body in each manifold aperture. The fluid spray nozzles


20


include a passage


20




b


that receives the core dissolving fluid from the manifold


24


at the inner nozzle end


20




c


and directs the core dissolving fluid to the outer nozzle discharge end


20




a


toward the exposed core region


14




a


that is located in registry and in communication with the nozzle discharge end


20




a


therebelow. The fluid spray nozzles


20


are sized to provide a selected core dissolving fluid flow rate (gallons per minute) at a given fluid pressure toward the core region


14




a


registered therewith. The spray nozzles


20


shown are available under designation Washjet solid stream 0° (zero degree) nozzles from Spraying Systems Co., North Ave., Wheaton, Ill. 60188.




Although the discharge ends


20




a


of the fluid spray nozzles


20


are shown spaced from the exposed core region


14




a


, they can be spaced closely to the root end surface


10




bb


provided clearance is present for relative movement of the nozzles


20


and castings


10


and depending on the relative spray size of the nozzles


20


and the area of the exposed core region


14




a.






The core dissolving fluid is selected so as to be capable of dissolving the ceramic material of the core


14


residing in the castings


10


. For the ceramic cores described hereabove used in the manufacture of nickel based and cobalt based superalloy castings, a suitable core dissolving fluid comprises an aqueous caustic solution at elevated temperature and pressure. For example, an aqueous caustic solution comprising from 35% to 50% by weight KOH or higher can be used at a temperature between 220 and 280° C. or higher and pressure of 50 to 450 psi and higher depending on pump capability available. Alternately, an aqueous caustic solution comprising 27 to 50% by weight NaOH and higher at the temperatures and pressures just described can be used as the core dissolving fluid. These core dissolving fluids are offered for purposes of illustration only, the invention not being limited to these core dissolving fluids. The invention can be practiced with other fluids that are capable of dissolving a particular core material involved in the manufacture of a particular casting.




In practicing a method embodiment of the invention, the fixture ring


16


is intermittently rotated to move each casting


10


sequentially past the first (#1), second (#2), third (#3), etc. fluid spray nozzles


20


arranged in series and the intervening drain positions DP to remove core material at the exposed core region


14




a


at the root portion


10




b


and progressively from further regions of the core within the airfoil portion


10




a


of the castings


10


as they become exposed as core material is progressively removed. The elevated temperature and pressure core dissolving fluid discharged from the fluid spray nozzles


20


is effective to dissolve and mechanically flush core material from the core regions until eventually most or all of the core


14


is removed from each casting


10


. The core dissolving fluid can be continuously discharged from the nozzles


20


or can be discharged periodically as a casting


10


is positioned thereabove. The number of fluid spray nozzles


20


employed and the temperature and pressure of the core dissolving fluid, flow rate and concentration of core dissolving fluid, as well as the residence time of the castings above each nozzle


20


(i.e. speed of transport of castings via fixture ring


16


) are selected accordingly.




Another embodiment of the invention similar to that described hereabove can be practiced with as few as one (1) fluid spray nozzle


20


wherein each casting


10


is positioned above the single nozzle


20


for a time as needed to remove the core


14


therefrom. Additional nozzles


20


can be used with each casting


10


residing at the a respective nozzle


20


for the entire time needed for core removal; i.e. there is no relative movement between each nozzle


20


and the associated casting


10


therewith for core removal. In this embodiment, the discharge of core dissolving fluid from each nozzle


20


is interrupted periodically to allow dissolved core material and spent fluid to drain from inside the casting


10


while it is positioned above the respective nozzle


20


. Otherwise, removal of the core


14


from the casting


10


is effected in similar manner.




For purposes of illustration rather than limitation, the invention can be practiced to remove a silica based ceramic core from a conventional turbine blade investment casting (first stage blade for V2500 gas turbine engine made by Pratt & Whitney Aircraft) having an airfoil portion and root portion with the core exposed at the root portion. Core dissolving fluids used were 35%, 40%, 45%, and 50% by weight KOH and 50% NaOH aqueous solutions. The caustic solution was supplied to a single fluid spray nozzle (Washjet solid stream 0° nozzle from Spraying Systems Co.) as described hereabove with respect to the alternative embodiment where each casting is positioned above the nozzle without movement for the entire time to remove the core therefrom. The caustic solution was supplied at different temperatures in the range of 220 to 280° C. and a manifold pressure of 400 psi to provide a solution flow rate of 19 gallons per minute through the nozzle. The flow of caustic solution to the nozzle was interrupted every 0.17 minutes for 0.17 minute intervals to allow drainage of dissolved core material and spent caustic solution from the casting. The time required to remove the cores from the castings ranged from 1 to 10 hours. Core removal in 4 hours was achieved at 121° C. and 400 psi using an aqueous caustic solution comprising 45% by weight KOH.




One or more additional core dissolving fluid spray nozzles


21


may be positioned as shown in

FIG. 1

for discharging core dissolving fluid at the casting tips


10




f


where another region


14




b


of the core may be exposed at a tip plenum cavity


14




c


of the castings


10


.




Referring to

FIGS. 3-9

, one embodiment of apparatus for practicing the invention for removing a ceramic core from each of a plurality of turbine blade castings is illustrated wherein a plurality of turbine blade castings


10


are fixtured and carried on a rotatable carrier, such as a rotary carousel


125


, past a plurality of stationary core dissolving fluid spray nozzles


120


. The core dissolving fluid spray nozzles


120


are disposed on a stationary central fluid manifold


124


located at the rotational axis of the carousel


125


.




The rotary carousel


125


is rotatably mounted in a stainless steel cabinet


126


(schematically shown) having a hinged access door


127


openable to permit the castings


10


to be fixtured on the carousel. The cabinet


126


is supported on a structural member support base B. The door


127


includes hinges


127




a


and handles


127




b.






The carousel


125


is supported at a free end by a plurality (


3


shown) of wheel assemblies


128


engaging a carrier ring


129


as shown best in

FIGS. 4

,


5


, and


6


. The wheel assemblies


128


each include a rotatable wheel


128




a


having a concave V-shaped profile (

FIG. 8

) for riding on a convex V-shaped periphery of the carrier ring


129


. The wheel assemblies


128


are mounted on cabinet


126


. The carrier ring


129


is mounted (bolted) on the carousel


125


. The rotary carousel


125


is thereby rotatably supported in the cabinet


126


at one end by the wheel assemblies


128


and carrier ring


129


and at the other end by the carousel drive arrangement described in the next paragraph.




The rotary carousel


125


is rotated by a drive shaft


130


that is coupled to an electric or other suitable drive motor


131


by a gear reducer


132


. The shaft


130


is coupled to a drive spindle


132




a


,

FIGS. 4-5

and


7


, that extends through a hub


126




a


of the cabinet wall


126




b


and through a gear reducer mounting plate


132




a


, pass-through plate


134


on the cabinet wall hub


126




a


, and through a fluoropolymer flange bearing


135


. The flange bearing


135


is sealed on the inside of the cabinet


126


by a shaft baffle ring


136


held on the shaft by the set screw shown and a baffle ring


137


fastened (bolted) to the cabinet wall hub


126




a


as shown in FIG.


7


. Rotation of the shaft


130


by the drive motor


131


through the gear reducer


132


is thereby transmitted to the drive spindle


132




a


and the carousel


125


on which the castings


10


are fixtured.




The drive shaft


130


and drive spindle


132


are coaxially aligned with the fluid manifold


124


shown best in

FIGS. 4A

,


4


B as having a plurality of threaded apertures


124




a


in an annular array at spaced apart axial locations along the manifold to threadably receive the core dissolving fluid spray nozzles


120


of the type described hereabove (0 degree spray nozzles). The manifold


124


includes a central passage


124




b


for receiving the pressurized, hot caustic fluid from the pumps P


1


, P


2


. The fluid flows through the passage


124




b


and then through spray nozzles


120


threaded into the apertures


124




a


for discharge toward the castings


10


in the manner described hereabove.




The fluid manifold


124


is mounted (bolted) via a manifold flange


124




c


on a manifold pass-through plate


137


fastened (bloted) on the cabinet wall


126




g


opposite to the cabinet wall


126




b


. A flange


140




a


of a caustic feed conduit or pipe


140


is bolted to the pass-through plate


137


to communicate the manifold passage


124




b


and the feed pipe


140


conveying the pressurized, hot caustic fluid from the pumps P


1


, P


2


.




The pump P


1


comprises a relatively low pressure feed pump (e.g. 75 psi), while the pump P


2


comprises a high pressure pump (e.g. 400 psi) for pumping via the feed pump P


1


hot caustic fluid from the heated sump


143


of the cabinet


126


via a suction pipe


144


. The suction pipe is communciated to an inlet box disposed at the bottom of the sump


143


. The sump


143


receives caustic solution from the cabinet via a return trough


143




a


therebetween. The pump arrangement is similar to that shown in

FIG. 14

for another embodiment of the invention. The inlet box


145


includes an upper filter screen (not shown) for preventing ceramic debris of a certain size from being sucked through the suction pipe


144


. A filter screen size of 60 mesh providing an 0.0092 inch by 0.0092 inch square opening can be used to this end.




A serpentine heat exchanger


150


(see

FIG. 14

) is disposed in the sump


143


and is heated by a gas-fired burner (not shown) disposed proximate the sump


143


such that burner gases flow through the serpentine heat exchanger. The serpentine heat exchanger


150


is submerged in the caustic fluid and heats the caustic fluid (e.g. 45% by weight KOH) to elevated temperature, such as about 100 to about 150 degrees C. Make-up caustic solution is supplied to the sump


143


by a valve and make-up fluid tank (not shown) to counter losses by evaporation. The level of the caustic fluid in the sump


143


is sensed by a float or other similar device and provides a signal to add make-up caustic fluid when the fluid level in the sump


143


drops below a predetermined level.




The rotary carousel


125


includes opposite end plates


125




a


,


125




b


joined together by fixture tie bars


152


bolted or otherwise fastened to the end plates


125




a


,


125




b


at circumferentially spaced apart intervals. Only some of the tie bars


152


are shown in

FIGS. 3



4


, and


5


for convenience. Each tie bar


152


supports a load bar


154


bolted or otherwise fastened thereto. Each load bar


154


in turn has fastened thereto by mounting plates


156


clamping fixtures F that engage and hold the root portion of the turbine blade castings


10


,

FIGS. 11-12

.




In

FIG. 9

, straight-line action toggle clamps C are shown for holding the load bar


154


to the carousel bar


152


. The clamping fixtures F are bolted to the load bar


154


, FIG.


11


. The clamping fixtures F are shown in detail in

FIGS. 10-12

as comprising a pair of mounting blocks


156


by which the fixture is fastened (bolted) to a respective load bar


154


. The mounting blocks


156


are in turn fastened (bolted) to a lower stainless steel fixture bar


162


to which is screwed a Teflon or other resilient pad


164


thereon to avoid localized grain recrystallization when single crystal (SC) and/or columnar grain directionally solidified (DS) castings are heat treated. An upper stainless steel fixture bar


166


carrying a Teflon or other resilient pad


168


is mounted on the lower fixture bar


162


by a pair of threaded rods


170


and nuts


172


. Fixtures for use in treating equiaxed castings wherein grain recrystallization is not a concern can be made of all stainless steel.




The Teflon pads


164


,


168


for SC/DS castings


10


are brought into clamping engagement with the root portions of the castings


10


by lowering the upper fixture bar


166


on the threaded rods


170


and tightening the nuts


172


as shown best in FIG.


10


. The pads


164


,


168


which are configured complementary to the root profile to this end as shown in

FIG. 10

to engage the root portions


10




b


of the castings


10


(e.g. 3 castings in FIGS.


11


-


12


).




Referring to

FIG. 13

, fixturing for clamping different equiaxed turbine blade castings


10


′ (i.e. differently shaped castings) is shown for illustration. In these like features of

FIGS. 10-12

are represented by like reference numerals primed. In the fixture F shown in

FIG. 13

, the upper fixture bar


166


of

FIGS. 11-12

is omitted since the castings


10


are equiaxed grain castings.




In practicing another method embodiment of the invention, the rotary carousel


125


is intermittently rotated by drive motor


131


to move the castings


10


sequentially past the first (#1), second (#2), third (#3), etc. fluid spray nozzles


120


arranged in circumferential arrays on the fluid manifold


124


,

FIG. 10

, and intervening drain positions DP and/or compressed air blow off positions where compressed air nozzles (not shown) are disposed to remove core material at the exposed core region at the root portion


10




b


and progressively from further regions of the core within the airfoil portion


10




a


of the castings


10


as they become exposed as core material is progressively removed. The elevated temperature and pressure core dissolving fluid discharged from the fluid spray nozzles


120


is effective to dissolve and mechanically flush core material from the core regions until eventually most or all of the core


14


is removed from each casting


10


. The core dissolving fluid can be continuously discharged from the nozzles


20


or can be discharged periodically as a casting


10


is positioned in registry therewith. The number of fluid spray nozzles


120


employed and the temperature and pressure of the core dissolving fluid, flow rate and concentration of core dissolving fluid, as well as the residence time of the castings with each nozzle


120


(i.e. speed of transport of castings via the carousel


125


) are selected accordingly.




Referring to

FIGS. 14-16

, apparatus in accordance with another embodiment of the invention is shown in schematic manner. The apparatus includes a rotary carousel


125


″ like that described hereabove in detail with respect to

FIGS. 3-15

wherein like features are represented by like reference numeral double primed. The carousel


125


″ is shown optionally rotated by a drive motor


131




a


″ via a drive chain


131




b


″ about a pulley


131




c


″ fastened to the carousel


125


″. This optional carousel drive is illustrated schematically to simply show an alternative carousel drive mechanism.




The apparatus also includes a linear conveyor


200


″ disposed in the cabinet


126


″ below the carousel


125


″. A valve


202


″ controls flow of pressurized, hot fluid from the sump


143


″ through either the feed pipe


140


″ to the fluid manifold


124




a


″ of the carousel


125


″ or to the fluid manifold


140




a


″ of the linear conveyor


200


″.




The linear conveyor


200


″ comprises endless conveyor chains


210


″ that convey fixture bars


211


″ in a linear motion manner. The fixture bars


211


″ hold cored vane segment castings


10


″ and transport them past a plurality of core dissolving fluid spray nozzles


120


″ arranged in linear array as the chains are driven by sprockets


214


″. The direction of movement of the conveyor and the castings


10


″ thereon is parallel with the linear array of nozzles


120


″. The fixture bars


211


″ are retained in position by retainers


215


″ that are fastened on conveyor


200


′. The nozzles


120


″ are communicated to a respective fluid branch manifolds


140




aa″


extending from main manifold


140




a


″. The vane segment castings


10


″ are fixtured on the fixture bars


211


″ so that exposed core regions at the lower portion


10




b


″ are removed by the discharge of fluid from the nozzles


120


″ in the manner described hereabove and progressively from further regions of the core within the airfoil portion


10




a


″ of the castings


10


″ as they become exposed as core material is progressively removed. A ceramic debris collector conveyor (not shown) may be disposed beneath the linear conveyor to collect and discharge and solid ceramic debris that may fall from the castings.




Referring to

FIG. 17

, apparatus in accordance with still another embodiment of the invention is shown. A cleaning cabinet


326


includes a hinged access door


327


that is openable via the handle shown to permit castings


10


′″ fixtured on load bars


354


to be mounted on tie bars


352


in a manner described hereabove with respect to previous figures of a rotary carousel


325


. The carousel


325


includes two carousel sections disposed in end-to-end relation in the internal chamber defined by the cabinet and closed door about a stationary, constant diameter fluid manifold


324


. The rotary carousel


325


is otherwise similar to those described hereabove with respect to previous figures. The door


327


includes latches


327




a


that cooperate with latches plates


326




a


of the cabinet for door closing. A door locking plate


327




b


cooperates with cabinet locking device


326




b


to lock the door and prevent door opening during the core removal operation. The door includes a seal S to seal on the cabinet when the door is closed and locked. A limit switch SL is used with a switch trip ST on the door to detect door closure in order to proceed with the core removal operation. A drip tray T is provided at the front of the cabinet to catch dripping liquid when the door is opened.




As shown in

FIG. 18

, the fluid manifold


324


includes a double wall construction having an inner core dissolving fluid chamber


324




a


and outer compressed air chamber


324




b


defined by inner wall


324




c


of the manifold


324


, both chambers having a constant diameter. Core dissolving fluid spray nozzles


320


are fastened to the inner wall


324




c


so as to communicate with core dissolving fluid chamber


324




a


. Air blow off (discharge) orifices


321


(diameter of 0.060 inch) are drilled in the outer manifold wall so as to communicate with the compressed air chamber


324




b


. The core dissolving fluid spray nozzles


320


(schematically shown) and air blow off orifices


321


(schematically shown-diameter 0.060 inch) are spaced circumferentially around the manifold in alternating manner in common planes along the length of the manifold such that each turbine blade casting


10


′″ fixtured on the carousels


325


(turbine blade castings shown fixtured only on a portion of the right-hand carousel in

FIG. 17

for convenience) is aligned with a core dissolving fluid spray nozzle


320


and then an air blow off orifice


321


in repeated sequence as the carousels are rotated relative to the fluid manifold


324


. At the nozzles


320


, core dissolving fluid of the type described hereabove is sprayed under pressure at an exposed region of a core (not shown but like the core described hereabove), and at the air blow off orifices


321


, compressed air is discharged at the same region of the castings


10


′″ to assist drainage of fluid and debris from the castings


10


′″.




The carousel


325


includes carrier rings


329


at each end and at an intermediate region with each carrier ring


329


supported for rotation in

FIG. 17

by a wheeled carousel support frame


328


(only one end and intermediate support frame section shown) disposed on the cabinet. The support frame


328


has wheels


328




a


spaced apart for engaging the carousel carrier rings


329


at circumferential ring locations. The rotary carousel


325


is directly driven to rotate by a drive shaft


330


of a gear reducer


332


coupled to a servo drive motor


331


, the gear reducer and motor being disposed external of the cabinet


326


as shown.




The fluid manifold


324


is mounted on the cabinet wall in a manner described in previous figures to communicate to a caustic feed conduit or pipe that supplies hot caustic solution to the inner manifold chamber


324




a


from high pressure pump P


2


(e.g. 400 psi). A relatively low pressure pump P


1


(e.g. 75 psi) draws hot caustic solution through a pump suction pipe from a sump


343


in the bottom of the cabinet and supplies it to the high pressure pump P


2


. The caustic solution is drawn from a filter tank or box


345


in the sump


343


wherein the filter box includes filter screens


345




a


to prevent harmful debris from entering the pumps. The sump


343


receives caustic solution sprayed from the cabinet after spraying at the castings


10


′″ via floor filter screen


347


disposed below the carousels


325


as shown in FIG.


17


. The outer compressed air chamber


324




b


of the manifold


324


receives compressed air via a manifold fitting proximate the caustic feed pipe to receive filtered, dried compressed air from a conventional source, such as shop air (not shown).




A serpentine heat exchanger (not shown but like that shown in

FIG. 14

) is disposed in the sump


343


submerged in the caustic solution therein and is heated by a gas-fired burner (not shown) disposed adjacent a side of the sump such that burner gases flow through the serpentine heat exchanger to heat the caustic solution to a suitable elevated temperature described hereabove. The heat exchanger vents combustion gases through a vent


350




a


in the top of the cabinet. The sump


343


has a main drain


343




b


for draining caustic solution and sludge or other debris therefrom. A cabinet wash manifold


349


is provided and extends into the sump


343


to introduce rinse water to flush out caustic solution and sludge or other debris from the sump. Other sump components, such as solution make-up valves and conduits, caustic solution level sensor (not shown), caustic solution temperature sensor S


1


, are provided to control the concentration and temperature of the caustic solution in the sump within selected operational ranges. An ambient vent V with a blower (not shown) is disposed on the top of the cabinet above and communicating with the internal chamber to provide a negative pressure therein relative to ambient to prevent steam from escaping the cabinet.




The apparatus of

FIG. 17

functions in similar manner as apparatus described hereabove to remove core material from internal of the turbine blade castings


10


′″. That is, the castings


10


′″ are rotated by carousel


325


in sequence past the circumferentially spaced apart core dissolving fluid spray nozzles


320


and then the air blow off orifices


321


on the stationary manifold


324


to progressively remove core material from internal of the castings. The castings


10


′″ can be rotated by carousels


325


continuously or intermittently relative to the fluid nozzles


320


and air blow off orifices


321


to this end as described hereabove.




In the embodiment of

FIG. 19

, the carousel support frame


328


can be mounted on rails


425


that extend into the cleaning cabinet


326


through a side access opening


326




a


of the cabinet. The carousel support frame


328


includes rollers


328




a


′ that allow the carousel


325


thereon to be rolled into/out of the cabinet relative to the fixed fluid manifold


324


and a fixed end panel


328




b


that functions to close off the opening


326




a


when the carousel


325


is positioned in the cabinet


326


about the fluid manifold


324


for the core removal operation. A set of pneumatic or other clamps


427


are operative to engage the end panel


328




b


to lock and seal the end panel relative to the cabinet opening


326




a


. A rotary table RT is disposed proximate the cabinet opening


326




a


and includes two stations S


1


, S


2


having a frame F supporting a pair of rails


429


that can be aligned with the rails


425


that are disposed inside and outside the cabinet by rotation of the table by a rotary motor M (shown schematically) in order to allow the carousel


325


to be rolled into/out of the cabinet


326


on the aligned rails. Each station S


1


, S


2


can receive a carousel


325


/frame


328


such that one carousel can be loaded with castings outside the cabinet


325


, while the other, already loaded carousel/support frame is positioned in the cabinet. A ball screw drive


430


is mounted on the table frame F at each station S


1


, S


2


with one ball screw end


430




a


connected to the respective end panel


328




a


via a ball nut


431


and bracket


433


and the other ball screw end


430




b


connected to the table frame. A motor (not shown) is provided proximate and connected to the ball screw end


430




a


to rotate the ball screw to move the respective carousel


325


into/out of the cabinet.




The carousel


325


positioned in the cabinet about the fixed fluid manifold


324


is rotated by the motor


331


and gear reducer


332


disposed adjacent the respective end panel


328




b


on the carousel support frame


328


.




The other features of the cabinet are similar to those described hereabove in FIG.


17


and bear like reference numerals.




Although the invention has been described with respect to certain specific embodiments thereof, those skilled in the art will recognize that these embodiments were offered for purposes of illustration rather than limitation and that the invention is not limited thereto but rather only as set forth in the appended claims.



Claims
  • 1. A method of removing a ceramic core from inside a metallic casting, comprising:disposing the casting and a fluid spray means in a manner that an exposed region of the core is contacted by a caustic core dissolving fluid discharged from said fluid spray means, discharging the core dissolving fluid from said fluid spray means at the exposed core region to contact the exposed core region and remove core material therefrom and expose further regions of the core residing within the casting, and discharging the core dissolving fluid to contact the further regions of the core residing within the casting to remove core material therefrom as they become exposed to the core dissolving fluid as core material is removed.
  • 2. The method of claim 1 wherein the discharge of core dissolving fluid from said means is interrupted periodically to allow dissolved core material and spent fluid to drain from the casting.
  • 3. The method of claim 1 wherein said casting and said fluid spray means are relatively moved so that said core dissolving fluid can drain at a drain location spaced from said means.
  • 4. The method of claim 1 wherein said casting is moved relative to a gas discharge means directed at said casting to force core dissolving fluid out of said casting.
  • 5. The method of claim 1 wherein the casting and a plurality of fluid spray nozzles are relatively moved so that the casting is moved from one fluid spray nozzle to the next to contact the core with core dissolving fluid at each nozzle and to drain dissolved core material and spent fluid from the casting when it is moved to a drain location between the means.
  • 6. The method of claim 5 wherein a plurality of said castings are carried on a linearly movable carrier past a plurality of stationary core dissolving fluid spray means to remove the core from each casting.
  • 7. The method of claim 5 wherein a plurality of said castings are carried on a rotatable carrier past a plurality of stationary core dissolving fluid spray nozzles.
  • 8. The method of claim 7 wherein said plurality of said castings are carried on a carousel past a plurality of core dissolving fluid spray nozzles disposed on a stationary central manifold located at the rotational axis of said carousel.
  • 9. The method of claim 8 wherein the caustic solution is at a temperature of 100 to 150° C. and pressure of 50 to 450 psi.
  • 10. The method of claim 1 wherein the core dissolving fluid comprises a caustic solution at elevated temperature and pressure.
  • 11. A method of removing a ceramic core from inside a metallic turbine blade or vane casting having an airfoil portion and root portion with a region of the core exposed at the root portion, comprising:disposing the casting and fluid spray means in a manner that the exposed region of the ceramic core at the root portion is contacted by a caustic core dissolving fluid discharged from said fluid spray means, discharging the core dissolving fluid from said fluid spray means at the exposed core region to contact the exposed core region and remove core material therefrom at the root portion and expose further regions of the core residing within the airfoil portion, and discharging the core dissolving fluid to contact the further regions of the core residing within the casting at the airfoil portion to remove core material therefrom as they become exposed to the core dissolving fluid as core material is removed.
  • 12. The method of claim 11 wherein the discharge of core dissolving fluid from said means is interrupted periodically to allow dissolved core material and spent fluid to drain from the casting.
  • 13. The method of claim 11 wherein said casting and said fluid spray means are relatively moved so that said casting can drain at a drain location apart from said means.
  • 14. The method of claim 1 wherein said casting is moved relative to a gas discharge means directed at said casting to force core dissolving fluid out of said casting.
  • 15. The method of claim 11 wherein the casting and a plurality of fluid spray nozzles are relatively moved so that the casting is moved from one fluid spray nozzle to the next to contact the core with core dissolving fluid at each nozzle and to drain dissolved core material and spent fluid from the casting when it is moved to a drain location between the nozzles.
  • 16. The method of claim 15 wherein a plurality of said castings are carried on a linearly movable carrier past a plurality of stationary core dissolving fluid spray nozzles to remove the core from each casting.
  • 17. The method of claim 16 wherein a plurality of said castings are carried on a rotatable carrier past a plurality of stationary core dissolving fluid spray nozzles.
  • 18. The method of claim 17 wherein said plurality of said castings are carried on a carousel past a plurality of core dissolving fluid spray nozzles disposed on a stationary central manifold located at the rotational axis of said carousel.
  • 19. The method of claim 11 wherein the core dissolving fluid comprises a caustic solution at a temperature of 100 to 150° C. and pressure of 50 to 450 psi.
  • 20. The method of claim 11 wherein an additional core dissolving fluid spray nozzle is positioned for discharging core dissolving fluid at a casting tip where another region of the core may be exposed at a tip plenum cavity of said casting.
US Referenced Citations (16)
Number Name Date Kind
2638645 Olson May 1953
2644472 Ward Jul 1953
2786480 Hofer Mar 1957
3070104 Faust et al. Dec 1962
3486938 Dubitsky Dec 1969
3590863 Faust et al. Jul 1971
3645791 Sadwith Feb 1972
3799178 Anderson et al. Mar 1974
4134777 Borom Jan 1979
4141781 Greskovich et al. Feb 1979
4569384 Mills Feb 1986
4708153 Hambleton et al. Nov 1987
4741351 Minkin May 1988
4836268 Devendra Jun 1989
5332023 Mills Jul 1994
5507306 Irvines et al. Apr 1996
Foreign Referenced Citations (12)
Number Date Country
1 271 910 Jul 1968 DE
24 14 167 Oct 1975 DE
27 46 405 Apr 1979 DE
2316024 Jan 1977 FR
1549220 Jul 1979 GB
2171932 Sep 1986 GB
2266677 Nov 1993 GB
63-256239 Oct 1988 JP
470365 Jul 1975 SU
872024 Oct 1981 SU
997975 Feb 1983 SU
1320016 Jun 1987 SU
Non-Patent Literature Citations (2)
Entry
Das Reingen von Druckgub in Wäbrigen Lösungenals Altermativr zur Reingung mit Lösemittein H. D. Heidenblutt, Glesserei 75, pp. 110-113, 1988.
Hochdruck-Nabentkernungs maschine für Glesserei 73, pp. 515-516, 1986.