EP0352406A1 - Countergravity casting apparatus and method using elastomeric sealing gasket and cooled vacuum chamber - Google Patents
Countergravity casting apparatus and method using elastomeric sealing gasket and cooled vacuum chamber Download PDFInfo
- Publication number
- EP0352406A1 EP0352406A1 EP89106902A EP89106902A EP0352406A1 EP 0352406 A1 EP0352406 A1 EP 0352406A1 EP 89106902 A EP89106902 A EP 89106902A EP 89106902 A EP89106902 A EP 89106902A EP 0352406 A1 EP0352406 A1 EP 0352406A1
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- European Patent Office
- Prior art keywords
- peripheral wall
- molten metal
- mold
- sealing gasket
- mold portion
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B22—CASTING; POWDER METALLURGY
- B22D—CASTING OF METALS; CASTING OF OTHER SUBSTANCES BY THE SAME PROCESSES OR DEVICES
- B22D18/00—Pressure casting; Vacuum casting
- B22D18/06—Vacuum casting, i.e. making use of vacuum to fill the mould
Definitions
- the invention relates to the countergravity casting of molten metal in a gas permeable mold and, more particularly, to means for prolonging the useful life of an elastomeric sealing gasket that seals successive molds to a vacuum chamber.
- a vacuum countergravity casting process using a gas permeable mold is described in such prior patents as the Chandley et al U.S. Patent Nos. 4,340,108 issued July 20, 1982, and 4,606,396 issued August 19, 1986.
- That countergravity casting process involves providing a mold having a porous, gas permeable upper mold member (cope) and a lower mold member (drag) engaged together, sealing the bottom lip of a peripheral wall of a vacuum chamber to the mold such that the vacuum chamber confronts the gas permeable upper mold member, submerging the bottom side of the lower mold member in an underlying molten metal pool and evacuating the chamber to draw the molten metal through one or more ingate passages in the lower mold member and into one or more mold cavities formed between the upper and lower mold members.
- the Voss U.S. Patent No. 4,616,691 issued October 14, 1986 discloses sealing the bottom lip of a peripheral wall of a vacuum chamber to a mold using a reusable elastomeric sealing gasket carried on the bottom lip.
- the elastomeric sealing gasket is thermally insulated, conduction wise, from the heat of the underlying molten metal pool by the mold- forming material of the drag and shielded from the radiant heat of the molten metal pool by a skirt depending from the peripheral wall of the vacuum chamber.
- the sealing gasket is insulated, conduction wise, from the pool by a substantially thickened upstanding ridge or shoulder formed on the drag and is sealed to the mold at a site atop the mold which is thermally remote from the molten metal pool.
- the invention contemplates an improved vacuum countergravity casting apparatus comprising a mold having a porous, gas permeable upper mold portion at least in part defining a mold cavity therein and a lower mold portion having an ingate for admitting molten metal into the mold cavity from an underlying molten metal pool, a sealing surface on the mold, a housing defining a vacuum chamber confronting the upper mold portion and including a thermally conductive peripheral wall with an open lower end defining a mouth of the vacuum chamber, an elastomeric sealing gasket sealingly engaged between the lower end of the peripheral wall and the sealing surface on the mold to seal the mold to the mouth of the vacuum chamber, and means for cooling the peripheral wall to maintain, by thermal conduction through the peripheral wall, the sealing gasket at a temperature where thermal degradation of the sealing gasket is reduced when the lower mold portion is immersed in the molten metal pool during casting, preferably at a temperature below the thermal degradation temperature of the sealing gasket.
- the sealing gasket is thereby protected from thermal damage during casting and its useful life in casting
- the elastomeric sealing gasket is secured on the lower end of the thermally conductive peripheral wall and the means for cooling the peripheral wall is disposed adjacent an upper end of the peripheral wall above and remote from the sealing gasket and the molten metal pool when the lower mold portion is immersed in the molten metal pool for casting.
- the means for cooling the pheripheral wall comprises an internal cooling channel adjacent an upper end of the pheripheral wall remote from the sealing gasket and the molten metal pool.
- a cooling fluid such as water, is supplied to the cooling channel to cool and maintain the lower end of the peripheral wall and the sealing gasket below the thermal degradation temperature of the sealing gasket when the lower mold portion is immersed in the underlying molten metal pool during casting.
- the means for cooling the pheripheral wall of the vacuum housing is located a selected distance above the lower end of the peripheral wall to preclude submersion of the cooling channel in the molten metal pool when the lower mold portion is immersed therein during casting.
- the means for cooling the pheripheral wall is disposed above the lower end of the peripheral wall a distance greater than the depth of the molten metal pool so that it is impossible to submerge the cooling means below the surface of the molten metal pool during casting.
- the invention also contemplates a method for the countergravity casting of molten metal into a mold having a gas permeable upper mold portion defining at least in part a mold cavity and having a lower mold portion with an ingate for admitting the molten metal into the mold cavity, wherein the method includes the steps of (a) enclosing the upper mold portion within a vacuum chamber having a mouth defined by a lower end of a depending, thermally conductive peripheral wall, (b) sealing the mold to the mouth of the vacuum chamber by sealingly engaging an elastomeric sealing gasket between the lower end and the mold, (c) immersing the lower mold portion in an underlying molten metal pool, including sufficiently evacuating the vacuum chamber to urge molten metal into the mold cavity through the ingate, and (d) cooling the pheripheral wall while the mold is immersed in the molten metal pool to maintain, by thermal conduction through the pheripheral wall, the sealing gasket at a temperature to reduce thermal degradation thereof during casting.
- Figs. 1-2 illustrate a vacuum countergravity casting apparatus in accordance with one embodiment of the invention.
- the apparatus includes a container 10 of molten metal 12 to be drawn up into the mold 14.
- the mold 14 includes a porous, gas permeable upper mold portion 16 and a lower mold portion 18, which may be gas permeable or impermeable.
- the upper and lower mold portions 16,18 may be adhesively secured together along juxtaposed surfaces that define a parting line or plane 20, although the upper and lower mold portions 16,18 can be held together by other means; e.g., by ambient pressure as illustrated in Fig. 3.
- each ingate passage 24 extends from the bottom 18a of the lower mold portion to a respective mold cavity 22 that is formed at least in part in the upper mold portion 16.
- the number, size and spacing of the mold cavities 22 and the ingate passages 24 will vary with the type of part to be cast and the particular metal to be cast as explained in U.S. Patent 4,340,108, the teachings of which are incorporated herein by reference.
- Upper and lower mold portions 16,18 can be made of resin-bonded sand in accordance with known mold practice wherein a mixture of sand or equivalent particles and bonding material is formed to shape and cured or hardened against a contoured pattern (not shown) having the desired complementary contour or profile for the parting surfaces and the mold cavities in the upper and lower mold portions.
- the invention is not so limited and may be used with other types of gas permeable molds including unitary investment molds of the high temperatures ceramic type illustrated in the Chandley et al U.S. Patent Nos. 3,863,706 and 3,900,064.
- the mold 14 is sealing received in the mouth 30 of a housing 32 that defines a vacuum chamber 34 confronting the gas permeable, upper mold portion 16, Fig. 1.
- the vacuum chamber 34 is communicated to a vacuum source 36 through a conduit 38 sealingly connected to the upper end wall 40 of the housing 32 so that the mold cavities 22 can be evacuated through the gas permeable upper mold portion 16 to draw the molten metal 12 through the bottom ingate passages 24 when the lower mold portion 18 is immersed in the molten pool 13.
- the housing 32 includes the upper end wall 40 typically made of steel and an annular, peripheral wall 42 fastened to the upper end wall 40 by suitable means and made of a highly thermally conductive material, such as preferably copper.
- the peripheral wall 42 depends from the upper end wall 40 and terminates in a lower end 44.
- the lower end 44 includes an annular bottom lip 46 that defines the mouth 30 of the vacuum chamber 34.
- a continuous, annular groove 48 is formed in the bottom lip 46 and extends upwardly therefrom.
- the groove 48 is shown having a rectangular cross-section but other cross-sectional shapes may be used.
- An annular, elastomeric sealing gasket 50 (e.g., silicone rubber or fluoroelastomeric rubber) is received and secured (by glue or press fit) in the groove 48 in the bottom lip 46 so as to be carried with the housing 32 for repeated use in casting successive molds 14.
- the sealing gasket 50 is shown having a rectangular cross-section to this end but other cross-sectional shapes can be employed. Moreover, the sealing gasket 50 may be secured to the inner side 42a or the outer side 42b of the lower end 44 of the peripheral wall 42 instead of to the bottom lip 46.
- the sealing gasket 50 extends from the groove 48 below the bottom lip 46 of the peripheral wall 42 to sealingly engage an annular, upwardly facing sealing surface 60 on the lower mold portion 18.
- the sealing gasket 50 is sealingly engaged and compressed between the bottom lip 46 of the thermally conductive peripheral wall 42 and the sealing surface 60 by securing the mold 14 and the housing 32 together using, for example, multiple conventional clamps 70 (only one shown) spaced around the periphery of the housing 32.
- Each clamp 70 includes a fluid cylinder 72 mounted on the upper end wall 40 of the housing 32, a plunger 74 actuated by the cylinder 72 and a clamp arm 76 pivotable about pivot pin 78. Extension of the plunger 74 causes the clamp end 80 on the clamp arm 76 to grip the lower mold portion 18 to secure it against the housing 32 and to sealingly compress the sealing gasket 50. Other means may be used to hold the mold 14 and the metal housing 32 together with the sealing gasket 50 compressed between the bottom lip 46 of the peripheral wall 42 and the sealing surface 60 on the mold 14.
- Fig. 4 illustrates a preferred embodiment of the invention (wherein like reference numerals represent like features or components of Figs. 1-2) differing from the embodiment of Figs. 1-2 in that the sealing gasket 50 is compressed substantially into the groove 48 and in that the bottom lip 46 of the peripheral wall 42 bottoms out (engages) against the sealing surface 60 on the lower mold portion 18 when the mold 14 and the metal housing 32 are held together.
- the lowermost portion of the sealing gasket 50 sealingly engages the sealing surface 60.
- the groove 48 is suitably configured to accommodate compression of the sealing gasket 50 therein when the mold 14 and metal housing 32 are held together.
- the cooled inner and outer sides 42a,42b of the peripheral wall 42 also protect the sealing gasket 50 from radiant heat from the molten metal 12 when the lower mold portion 18 is immersed therein as will be explained hereinbelow.
- the sealing gasket 50 is brought in close proximity to the surface 13a of the molten metal pool 13 and is exposed to significant heat that radiates from the pool and that may be conducted through the lower mold portion 18. If during the casting of successive molds 14 the sealing gasket 50 repeatedly reaches temperatures above its thermal degradation temperature (e.g., about 600°F for silicone rubber and about 450°F for fluroelastomeric rubber), the sealing gasket 50 can be thermally degraded (thermal degradation typically being characterized by flattening, hardening and cracking of the sealing gasket) and lose its effectiveness as a vacuum seal.
- thermal degradation temperature e.g., about 600°F for silicone rubber and about 450°F for fluroelastomeric rubber
- the thermally conductive peripheral wall 42 includes an internal, annular cooling channel 90 adjacent an upper end 43 of the peripheral wall.
- the cooling channel 90 is spaced above and remote from the sealing gasket 50 and the molten metal pool 13 during casting.
- An inlet fitting 92 is provided on the upper end 43 of the peripheral wall 42 on one side of an internal dividing wall 93 in the cooling channel 90 to supply a cooling fluid, such as water, to the cooling channel 90 from a coolant source 94.
- An outlet fitting 96 is also provided on the upper end 43 of the peripheral wall 42 on the opposite side of the dividing wall 93 to exhaust the cooling fluid from the cooling channel 90 after the cooling fluid absorbs heat from the peripheral wall 42 to cool same.
- the exhausted cooling fluid may be passed through a heat exchanger device (not shown) to cool the fluid for return to the coolant source 94 for recirculation to the cooling channel 90.
- Various cooling fluids may find use in the invention.
- the cooling fluid is circulated through the cooling channel 90 as the mold 14 is advanced toward the molten metal pool 13, immersed therein for casting and then withdrawn away from the molten metal pool 13 after casting.
- the cooling fluid flowing through the cooling channel 90 absorbs heat from the highly thermally conductive peripheral wall 42 to maintain the lower end 44 of the peripheral wall and the sealing gasket 50 received in the lower end 44 at a temperature below the thermal degradation temperature of the sealing gasket 50. Heat is conducted from the lower end 44 of the peripheral wall 42 and from the sealing gasket 50 to the cooled upper end 43 of the peripheral wall 42 and establishes a thermal gradient along the peripheral wall 42 to protect the thermally-degradeable sealing gasket 50 from thermal damage when the lower mold portion 18 is immersed in the molten metal 12 during casting.
- the particular cooling fluid used as well as its temperature and flow rate through the cooling channel 90 and the size, shape, number and location of the cooling channels 90 are selected to this end. Thermal degradation of the sealing gasket 50 is thereby significantly reduced and its useful life in casting successive molds 14 is increased.
- the cooling channel 90 is spaced above the bottom lip 46 of the peripheral wall 42 and the lower mold portion 18 is a distance D1 selected to preclude immersion of the cooling channel 90 in the molten metal 12 when the lower mold portion 18 is immersed therein for casting.
- the distance D1 is greater than the depth D2 of the molten metal pool 13 whereby it is impossible to immerse the cooling channel 90 below the surface of the molten metal pool 13 as a result of excessive movement of the mold 14 downwardly into the molten metal pool 13 during casting.
- the cooling channel 90 may be provided in the upper end wall of the housing 32 provided that the lower end 44 of the peripheral wall 42 and the sealing gasket 50 are sufficiently cooled by thermal conduction through the peripheral wall 42 to maintain the sealing gasket 50 at a reduced temperature to minimize thermal degradation thereof during casting.
- a separate cooling annulus (not shown) may be secured in thermally conducting relation on the housing 32; e.g. on the peripheral wall 42, to maintain the sealing gasket 50 at the desired reduced temperature by thermal conduction through the peripheral wall 42.
- Fig. 3 illustrates still another embodiment of the invention wherein like reference numerals are used for like features or components of Fig. 1 and different reference numerals are used only when the Figures differ from one another.
- the vacuum housing 32 differs from that shown in Fig. 1 in that the housing 32 comprises a central, gas impermeable, upper end member 41 overlying and following the contour of the upper surface 16a of the upper mold portion 16.
- a plurality of standoffs 33 are spaced apart on the inner or lower side of the sheet metal member 41 and extend toward and into engagement with the upper surface 16a to provide a plurality of spaced apart contact regions 25 between the upper end member 41 and the upper surface 16a.
- the plurality of standoffs 33 establish a vacuum chamber 35 between the upper end member 41 and the upper surface 16a.
- a vacuum conduit 38 is sealingly attached to the upper end member 41.
- the vacuum chamber 35 is communicated through the conduit 38 to a vacuum source 36 to evacuate the mold cavities 22 through the porous, gas permeable upper mold portion 16.
- the housing 32 further includes a flexible, annular sealing member 39 sealingly secured between the upper side 41a of the upper end member 41 and a highly thermally conductive (copper), annular, peripheral wall 42 of housing 32.
- Annular attachment rings 51,53 are fastened to the upper end member 41 and the peripheral wall 42, respectively, to secure the flexible sealing member 39 thereto.
- the thermally conductive peripheral wall 42 includes an internal cooling channel 90 formed in the upper end 43 thereof.
- an annular groove 91 is formed in the upper end of the peripheral wall 42 and is closed by an annular end cap 45 secured by suitable means to the peripheral wall 42 to form the cooling channel 90 therein.
- Inlet and outlet fittings are secured on the peripheral wall 42 to supply cooling fluid to the cooling channel 90 and to exhaust cooling fluid therefrom in the same manner described hereinabove for Figs. 1-2.
- the peripheral wall 42 terminates in a lower end 44 that includes a bottom lip 46.
- the bottom lip 46 includes an upstanding, annular groove 48 in which an annular, elastomeric sealing gasket 50 is received and secured.
- the sealing gasket 50 extends below the bottom lip 46 to sealingly engage an annular, upwardly facing sealing surface 60 on the lower mold portion 18.
- Cooling fluid such as water
- Cooling fluid is circulated through the cooling channel 90 to maintain, by thermal conduction through the peripheral wall 42, the sealing gasket 50 at a temperature below its thermal degradation temperature when the lower mold portion 18 is immersed in the underlying molten metal pool 13 during casting, as shown in Fig. 3, with the mold cavities 22 evacuated by the vacuum source 36 through the upper mold portion 16 to urge the molten metal 12 into the mold cavities 22.
- Ambient pressure above the upper end member 41 is transmitted to the upper mold portion 16 by the standoffs 33 in opposition to ambient pressure transmitted to the bottom 18a of the mold portion 18 through the molten metal 12.
- the upper mold portion 16 and lower mold portion 18 are held or engaged together by ambient pressure without the need for adhesive, as described in copending U.S.
- the present invention is further advantageous from the standpoint that there is no need to increase the thickness t (Fig. 1) of the lower mold portion 18 to provide enhanced thermal insulation of the sealing gasket 50 from heat conduction through the mold-forming material of the lower mold portion 18 and further no need to completely shield the sealing gasket 50 from radiant heat of the molten metal pool 13 during casting.
- Cooling of the peripheral wall 42 as described hereinabove is effective to remove sufficient heat from the lower end 44 thereof to maintain the temperature of the sealing gasket 50 below its thermal degradation temperature during casting in spite of the conductive heat input through the lower mold portion 18 and the radiant heat input from the molten metal pool 13 during casting.
- the invention can be practiced in combination with these other thermal protection techniques (i.e., enhanced thermal insulation and/or radiant shielding as shown in Fig. 4).
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Abstract
A vacuum countergravity casting apparatus includes a vacuum chamber (34) having a thermally conductive peripheral wall (42) and a gas permeable mold (14) sealed to the lower end (44) of the peripheral wall (42) by an elastomeric sealing gasket (50) engaged therebetween. The peripheral wall (42) is cooled at a location (90) above and remote from the sealing gasket and an underlying molten metal pool (13) when the mold is immersed in the pool (13) during casting to maintain, by thermal conduction through the peripheral wall (42), the sealing gasket (50) at a temperature to reduce thermal degradation thereof during casting; e.g., at a temperature below the gasket's (50) thermal degradation temperature. Reduced thermal degradation of the sealing gasket (50) during casting prolongs its useful life in casting successive molds.
Description
- The invention relates to the countergravity casting of molten metal in a gas permeable mold and, more particularly, to means for prolonging the useful life of an elastomeric sealing gasket that seals successive molds to a vacuum chamber.
- A vacuum countergravity casting process using a gas permeable mold is described in such prior patents as the Chandley et al U.S. Patent Nos. 4,340,108 issued July 20, 1982, and 4,606,396 issued August 19, 1986. That countergravity casting process involves providing a mold having a porous, gas permeable upper mold member (cope) and a lower mold member (drag) engaged together, sealing the bottom lip of a peripheral wall of a vacuum chamber to the mold such that the vacuum chamber confronts the gas permeable upper mold member, submerging the bottom side of the lower mold member in an underlying molten metal pool and evacuating the chamber to draw the molten metal through one or more ingate passages in the lower mold member and into one or more mold cavities formed between the upper and lower mold members.
- The Voss U.S. Patent No. 4,616,691 issued October 14, 1986, discloses sealing the bottom lip of a peripheral wall of a vacuum chamber to a mold using a reusable elastomeric sealing gasket carried on the bottom lip. During casting when the mold is immersed in an underlying molten pool, the elastomeric sealing gasket is thermally insulated, conduction wise, from the heat of the underlying molten metal pool by the mold- forming material of the drag and shielded from the radiant heat of the molten metal pool by a skirt depending from the peripheral wall of the vacuum chamber. The sealing gasket is insulated, conduction wise, from the pool by a substantially thickened upstanding ridge or shoulder formed on the drag and is sealed to the mold at a site atop the mold which is thermally remote from the molten metal pool.
- It is an object of the present invention to provide an improved vacuum countergravity casting apparatus and process wherein a vacuum chamber includes a cooled, thermally conductive peripheral wall having a lower end sealed to the mold by an elastomeric sealing gasket engaged therebetween and wherein cooling of the thermally conductive peripheral wall maintains the sealing gasket at a temperature where thermal degradation thereof is reduced during casting, thereby prolonging the useful life of the sealing gasket in the casting of successive molds.
- The invention contemplates an improved vacuum countergravity casting apparatus comprising a mold having a porous, gas permeable upper mold portion at least in part defining a mold cavity therein and a lower mold portion having an ingate for admitting molten metal into the mold cavity from an underlying molten metal pool, a sealing surface on the mold, a housing defining a vacuum chamber confronting the upper mold portion and including a thermally conductive peripheral wall with an open lower end defining a mouth of the vacuum chamber, an elastomeric sealing gasket sealingly engaged between the lower end of the peripheral wall and the sealing surface on the mold to seal the mold to the mouth of the vacuum chamber, and means for cooling the peripheral wall to maintain, by thermal conduction through the peripheral wall, the sealing gasket at a temperature where thermal degradation of the sealing gasket is reduced when the lower mold portion is immersed in the molten metal pool during casting, preferably at a temperature below the thermal degradation temperature of the sealing gasket. The sealing gasket is thereby protected from thermal damage during casting and its useful life in casting successive molds is extended.
- In one embodiment of the invention, the elastomeric sealing gasket is secured on the lower end of the thermally conductive peripheral wall and the means for cooling the peripheral wall is disposed adjacent an upper end of the peripheral wall above and remote from the sealing gasket and the molten metal pool when the lower mold portion is immersed in the molten metal pool for casting.
- In another embodiment of the present invention, the means for cooling the pheripheral wall comprises an internal cooling channel adjacent an upper end of the pheripheral wall remote from the sealing gasket and the molten metal pool. A cooling fluid, such as water, is supplied to the cooling channel to cool and maintain the lower end of the peripheral wall and the sealing gasket below the thermal degradation temperature of the sealing gasket when the lower mold portion is immersed in the underlying molten metal pool during casting.
- In still another embodiment of the invention, the means for cooling the pheripheral wall of the vacuum housing is located a selected distance above the lower end of the peripheral wall to preclude submersion of the cooling channel in the molten metal pool when the lower mold portion is immersed therein during casting. In particular, the means for cooling the pheripheral wall is disposed above the lower end of the peripheral wall a distance greater than the depth of the molten metal pool so that it is impossible to submerge the cooling means below the surface of the molten metal pool during casting.
- The invention also contemplates a method for the countergravity casting of molten metal into a mold having a gas permeable upper mold portion defining at least in part a mold cavity and having a lower mold portion with an ingate for admitting the molten metal into the mold cavity, wherein the method includes the steps of (a) enclosing the upper mold portion within a vacuum chamber having a mouth defined by a lower end of a depending, thermally conductive peripheral wall, (b) sealing the mold to the mouth of the vacuum chamber by sealingly engaging an elastomeric sealing gasket between the lower end and the mold, (c) immersing the lower mold portion in an underlying molten metal pool, including sufficiently evacuating the vacuum chamber to urge molten metal into the mold cavity through the ingate, and (d) cooling the pheripheral wall while the mold is immersed in the molten metal pool to maintain, by thermal conduction through the pheripheral wall, the sealing gasket at a temperature to reduce thermal degradation thereof during casting.
- The invention may be understood better when considered in light of the following detailed description of certain specific embodiments thereof which are given hereafter in conjunction with the following drawings.
- Figure 1 is a side sectional view through one embodiment of a vacuum countergravity metal casting apparatus in accordance with the present invention.
- Figure 2 is a plan view of the embodiment of Fig. 1.
- Figure 3 is a side sectional view through another embodiment of a vacuum countergravity metal casting apparatus in accordance with the invention.
- Figure 4 is a side sectional view through still another embodiment of a vacuum countergravity metal casting apparatus in accordance with the invention.
- Figs. 1-2 illustrate a vacuum countergravity casting apparatus in accordance with one embodiment of the invention. The apparatus includes a
container 10 ofmolten metal 12 to be drawn up into themold 14. Themold 14 includes a porous, gas permeableupper mold portion 16 and alower mold portion 18, which may be gas permeable or impermeable. The upper andlower mold portions plane 20, although the upper andlower mold portions - Defined between the upper and
lower mold portions molten metal pool 13 in thecontainer 10 throughrespective ingate passages 24 on the underside or bottom 18a oflower mold portion 18 when the mold cavities are evacuated with the bottom 18a submerged in themolten metal pool 13. To this end, eachingate passage 24 extends from the bottom 18a of the lower mold portion to arespective mold cavity 22 that is formed at least in part in theupper mold portion 16. The number, size and spacing of themold cavities 22 and theingate passages 24 will vary with the type of part to be cast and the particular metal to be cast as explained in U.S. Patent 4,340,108, the teachings of which are incorporated herein by reference. - Upper and
lower mold portions - The
mold 14 is sealing received in themouth 30 of ahousing 32 that defines avacuum chamber 34 confronting the gas permeable,upper mold portion 16, Fig. 1. Thevacuum chamber 34 is communicated to avacuum source 36 through aconduit 38 sealingly connected to theupper end wall 40 of thehousing 32 so that themold cavities 22 can be evacuated through the gas permeableupper mold portion 16 to draw themolten metal 12 through thebottom ingate passages 24 when thelower mold portion 18 is immersed in themolten pool 13. - The
housing 32 includes theupper end wall 40 typically made of steel and an annular,peripheral wall 42 fastened to theupper end wall 40 by suitable means and made of a highly thermally conductive material, such as preferably copper. Theperipheral wall 42 depends from theupper end wall 40 and terminates in alower end 44. Thelower end 44 includes anannular bottom lip 46 that defines themouth 30 of thevacuum chamber 34. A continuous,annular groove 48 is formed in thebottom lip 46 and extends upwardly therefrom. Thegroove 48 is shown having a rectangular cross-section but other cross-sectional shapes may be used. - An annular, elastomeric sealing gasket 50 (e.g., silicone rubber or fluoroelastomeric rubber) is received and secured (by glue or press fit) in the
groove 48 in thebottom lip 46 so as to be carried with thehousing 32 for repeated use in castingsuccessive molds 14. The sealinggasket 50 is shown having a rectangular cross-section to this end but other cross-sectional shapes can be employed. Moreover, the sealinggasket 50 may be secured to theinner side 42a or theouter side 42b of thelower end 44 of theperipheral wall 42 instead of to thebottom lip 46. - As shown in Fig. 1, the sealing
gasket 50 extends from thegroove 48 below thebottom lip 46 of theperipheral wall 42 to sealingly engage an annular, upwardly facingsealing surface 60 on thelower mold portion 18. The sealinggasket 50 is sealingly engaged and compressed between thebottom lip 46 of the thermally conductiveperipheral wall 42 and the sealingsurface 60 by securing themold 14 and thehousing 32 together using, for example, multiple conventional clamps 70 (only one shown) spaced around the periphery of thehousing 32. - Each
clamp 70 includes afluid cylinder 72 mounted on theupper end wall 40 of thehousing 32, aplunger 74 actuated by thecylinder 72 and aclamp arm 76 pivotable aboutpivot pin 78. Extension of theplunger 74 causes theclamp end 80 on theclamp arm 76 to grip thelower mold portion 18 to secure it against thehousing 32 and to sealingly compress the sealinggasket 50. Other means may be used to hold themold 14 and themetal housing 32 together with the sealinggasket 50 compressed between thebottom lip 46 of theperipheral wall 42 and the sealingsurface 60 on themold 14. - Fig. 4 illustrates a preferred embodiment of the invention (wherein like reference numerals represent like features or components of Figs. 1-2) differing from the embodiment of Figs. 1-2 in that the sealing
gasket 50 is compressed substantially into thegroove 48 and in that thebottom lip 46 of theperipheral wall 42 bottoms out (engages) against thesealing surface 60 on thelower mold portion 18 when themold 14 and themetal housing 32 are held together. When compressed into thegroove 48, the lowermost portion of the sealinggasket 50 sealingly engages the sealingsurface 60. Thegroove 48 is suitably configured to accommodate compression of the sealinggasket 50 therein when themold 14 andmetal housing 32 are held together. In this embodiment of the invention, the cooled inner andouter sides peripheral wall 42 also protect the sealinggasket 50 from radiant heat from themolten metal 12 when thelower mold portion 18 is immersed therein as will be explained hereinbelow. - As is apparent in Fig. 1, during casting when the
lower mold portion 18 is immersed in themolten metal pool 13, the sealinggasket 50 is brought in close proximity to thesurface 13a of themolten metal pool 13 and is exposed to significant heat that radiates from the pool and that may be conducted through thelower mold portion 18. If during the casting ofsuccessive molds 14 the sealinggasket 50 repeatedly reaches temperatures above its thermal degradation temperature (e.g., about 600°F for silicone rubber and about 450°F for fluroelastomeric rubber), the sealinggasket 50 can be thermally degraded (thermal degradation typically being characterized by flattening, hardening and cracking of the sealing gasket) and lose its effectiveness as a vacuum seal. - In accordance with the present invention, the useful life of the sealing
gasket 50 in casting successive molds is extended by minimizing thermal degradation of the sealing gasket during casting. In particular, the thermally conductiveperipheral wall 42 includes an internal,annular cooling channel 90 adjacent anupper end 43 of the peripheral wall. Thecooling channel 90 is spaced above and remote from the sealinggasket 50 and themolten metal pool 13 during casting. Aninlet fitting 92 is provided on theupper end 43 of theperipheral wall 42 on one side of an internal dividingwall 93 in thecooling channel 90 to supply a cooling fluid, such as water, to thecooling channel 90 from acoolant source 94. Anoutlet fitting 96 is also provided on theupper end 43 of theperipheral wall 42 on the opposite side of the dividingwall 93 to exhaust the cooling fluid from thecooling channel 90 after the cooling fluid absorbs heat from theperipheral wall 42 to cool same. The exhausted cooling fluid may be passed through a heat exchanger device (not shown) to cool the fluid for return to thecoolant source 94 for recirculation to thecooling channel 90. Various cooling fluids may find use in the invention. - Typically, the cooling fluid is circulated through the
cooling channel 90 as themold 14 is advanced toward themolten metal pool 13, immersed therein for casting and then withdrawn away from themolten metal pool 13 after casting. - The cooling fluid flowing through the
cooling channel 90 absorbs heat from the highly thermally conductiveperipheral wall 42 to maintain thelower end 44 of the peripheral wall and the sealinggasket 50 received in thelower end 44 at a temperature below the thermal degradation temperature of the sealinggasket 50. Heat is conducted from thelower end 44 of theperipheral wall 42 and from the sealinggasket 50 to the cooledupper end 43 of theperipheral wall 42 and establishes a thermal gradient along theperipheral wall 42 to protect the thermally-degradeable sealing gasket 50 from thermal damage when thelower mold portion 18 is immersed in themolten metal 12 during casting. The particular cooling fluid used as well as its temperature and flow rate through the coolingchannel 90 and the size, shape, number and location of thecooling channels 90 are selected to this end. Thermal degradation of the sealinggasket 50 is thereby significantly reduced and its useful life in castingsuccessive molds 14 is increased. - The cooling
channel 90 is spaced above thebottom lip 46 of theperipheral wall 42 and thelower mold portion 18 is a distance D1 selected to preclude immersion of the coolingchannel 90 in themolten metal 12 when thelower mold portion 18 is immersed therein for casting. In particular, the distance D1 is greater than the depth D2 of themolten metal pool 13 whereby it is impossible to immerse the coolingchannel 90 below the surface of themolten metal pool 13 as a result of excessive movement of themold 14 downwardly into themolten metal pool 13 during casting. - The cooling
channel 90 may be provided in the upper end wall of thehousing 32 provided that thelower end 44 of theperipheral wall 42 and the sealinggasket 50 are sufficiently cooled by thermal conduction through theperipheral wall 42 to maintain the sealinggasket 50 at a reduced temperature to minimize thermal degradation thereof during casting. Furthermore, a separate cooling annulus (not shown) may be secured in thermally conducting relation on thehousing 32; e.g. on theperipheral wall 42, to maintain the sealinggasket 50 at the desired reduced temperature by thermal conduction through theperipheral wall 42. - Fig. 3 illustrates still another embodiment of the invention wherein like reference numerals are used for like features or components of Fig. 1 and different reference numerals are used only when the Figures differ from one another. In particular, the
vacuum housing 32 differs from that shown in Fig. 1 in that thehousing 32 comprises a central, gas impermeable,upper end member 41 overlying and following the contour of the upper surface 16a of theupper mold portion 16. A plurality ofstandoffs 33 are spaced apart on the inner or lower side of thesheet metal member 41 and extend toward and into engagement with the upper surface 16a to provide a plurality of spaced apartcontact regions 25 between theupper end member 41 and the upper surface 16a. The plurality ofstandoffs 33 establish avacuum chamber 35 between theupper end member 41 and the upper surface 16a. Avacuum conduit 38 is sealingly attached to theupper end member 41. Thevacuum chamber 35 is communicated through theconduit 38 to avacuum source 36 to evacuate themold cavities 22 through the porous, gas permeableupper mold portion 16. - The
housing 32 further includes a flexible, annular sealingmember 39 sealingly secured between theupper side 41a of theupper end member 41 and a highly thermally conductive (copper), annular,peripheral wall 42 ofhousing 32. Annular attachment rings 51,53 are fastened to theupper end member 41 and theperipheral wall 42, respectively, to secure theflexible sealing member 39 thereto. - The thermally conductive
peripheral wall 42 includes aninternal cooling channel 90 formed in theupper end 43 thereof. In particular, an annular groove 91 is formed in the upper end of theperipheral wall 42 and is closed by anannular end cap 45 secured by suitable means to theperipheral wall 42 to form the coolingchannel 90 therein. Inlet and outlet fittings (not shown) are secured on theperipheral wall 42 to supply cooling fluid to the coolingchannel 90 and to exhaust cooling fluid therefrom in the same manner described hereinabove for Figs. 1-2. - The
peripheral wall 42 terminates in alower end 44 that includes abottom lip 46. Thebottom lip 46 includes an upstanding,annular groove 48 in which an annular,elastomeric sealing gasket 50 is received and secured. The sealinggasket 50 extends below thebottom lip 46 to sealingly engage an annular, upwardly facing sealingsurface 60 on thelower mold portion 18. - Cooling fluid, such as water, is circulated through the cooling
channel 90 to maintain, by thermal conduction through theperipheral wall 42, the sealinggasket 50 at a temperature below its thermal degradation temperature when thelower mold portion 18 is immersed in the underlyingmolten metal pool 13 during casting, as shown in Fig. 3, with themold cavities 22 evacuated by thevacuum source 36 through theupper mold portion 16 to urge themolten metal 12 into themold cavities 22. Ambient pressure above theupper end member 41 is transmitted to theupper mold portion 16 by thestandoffs 33 in opposition to ambient pressure transmitted to the bottom 18a of themold portion 18 through themolten metal 12. As a result, theupper mold portion 16 andlower mold portion 18 are held or engaged together by ambient pressure without the need for adhesive, as described in copending U.S. patent application Serial No. 198,229 entitled "Countergravity Casting Apparatus And Method" filed in the name of George D. Chandley as inventor and assigned to the assignee of the present invention. A gas permeable member (not shown) may be used in lieu of the gasimpermeable member 41 in Fig. 3 as taught in the aforesaid copending application Serial No. 198,229. - In addition to extending the useful life of the sealing
gasket 50 by reducing thermal degradation thereof during casting, the present invention is further advantageous from the standpoint that there is no need to increase the thickness t (Fig. 1) of thelower mold portion 18 to provide enhanced thermal insulation of the sealinggasket 50 from heat conduction through the mold-forming material of thelower mold portion 18 and further no need to completely shield the sealinggasket 50 from radiant heat of themolten metal pool 13 during casting. Cooling of theperipheral wall 42 as described hereinabove is effective to remove sufficient heat from thelower end 44 thereof to maintain the temperature of the sealinggasket 50 below its thermal degradation temperature during casting in spite of the conductive heat input through thelower mold portion 18 and the radiant heat input from themolten metal pool 13 during casting. However, the invention can be practiced in combination with these other thermal protection techniques (i.e., enhanced thermal insulation and/or radiant shielding as shown in Fig. 4). - While the invention has been described in terms of specific embodiments thereof, it is not intended to be limited thereto but rather only to the extent set forth hereafter in the claims which follow.
Claims (32)
1. Apparatus for the countergravity casting of molten metal, comprising:
(a) a mold having a porous, gas permeable upper mold portion at least in part defining a mold cavity and having a lower mold portion with an ingate for admitting molten metal into said mold cavity from an underlying molten metal pool,
(b) a sealing surface on said mold,
(c) a housing defining a vacuum chamber confronting the upper mold portion for evacuating said mold cavity through said upper mold portion, said housing having a thermally conductive peripheral wall with an open lower end defining a mouth of said chamber,
(d) an elastomeric sealing gasket sealingly engaged between the sealing surface and the lower end of the peripheral wall for sealing said mold to the mouth of said chamber, and
(e) means for cooling the thermally conductive peripheral wall to maintain, by thermal conduction through said peripheral wall, the sealing gasket engaged therewith at a temperature to reduce thermal degradation thereof when the lower mold portion is immersed in the molten metal pool to admit said molten metal into said mold cavity.
2. The apparatus of claim 1 wherein the sealing surface is disposed on an upper surface of the lower mold portion.
3. The apparatus of claim 1 wherein the means for cooling the peripheral wall is disposed on said housing above and remote from the sealing gasket and the molten metal pool when the lower mold portion is immersed therein.
4. The apparatus of claim 3 wherein the means for cooling the peripheral wall comprises an internal cooling channel adjacent an upper end of the peripheral wall and means for supplying cooling fluid to the internal cooling channel.
5. The apparatus of claim 3 wherein said means for supplying cooling fluid comprises a cooling water inlet to said internal cooling channel.
6. The apparatus of claim 5 wherein said internal cooling channel is disposed above the lower end of the peripheral wall higher than the depth of the molten metal pool.
7. The apparatus of claim 1 wherein said means for cooling the peripheral wall maintains the sealing gasket below its thermal degradation temperature.
8. The apparatus of claim 1 wherein the thermally conductive peripheral wall comprises copper.
9. The apparatus of claim 1 wherein the sealing gasket is secured on the lower end of the peripheral wall.
10. The apparatus of claim 9 wherein the lower end of the peripheral wall terminates in a bottom lip that defines the mouth of the vacuum chamber, said bottom lip including a continuous, upstanding groove in which a portion of the sealing gasket is received.
11. Apparatus for the countergravity casting of the molten metal, comprising:
(a) a mold having a porous, gas permeable upper mold portion at least in part defining a mold cavity and having a lower mold portion with an ingate for admitting molten metal into said mold cavity from an underlying molten metal pool,
(b) a sealing surface on said mold,
(c) a housing defining a vacuum chamber confronting the upper mold portion for evacuating said mold cavity through said upper mold portion, said housing having a thermally conductive peripheral wall with an open lower end defining a mouth of said chamber,
(d) an elastomeric sealing gasket sealingly engaged between the sealing surface and the lower end of the peripheral wall for sealing said mold to the mouth of said chamber, and
(e) means disposed on the peripheral wall above the sealing gasket for cooling the peripheral wall to maintain, by thermal conduction through said peripheral wall, the sealing gasket engaged therewith at a temperature to reduce thermal degradation thereof when the lower mold portion is immersed in the molten metal pool to admit said molten metal into said mold cavity.
12. The apparatus of claim 11 wherein the sealing surface is disposed on an upper surface of the lower mold portion.
13. The apparatus of claim 11 wherein the means for cooling the peripheral wall is disposed on said peripheral wall above and remote from the sealing gasket and the molten metal pool when the lower mold portion is immersed therein.
14. The apparatus of claim 13 wherein the means for cooling the peripheral wall comprises an internal cooling channel adjacent an upper end of the peripheral wall and means for supplying cooling fluid to the internal cooling channel.
15. The apparatus of claim 13 wherein said means for supplying cooling fluid comprises a cooling water inlet to said internal cooling channel.
16. The apparatus of claim 13 wherein said internal cooling channel is disposed above the lower end of the peripheral wall higher than the depth of the molten metal pool.
17. The apparatus of claim 11 wherein said means for cooling the peripheral wall maintains the sealing gasket below its thermal degradation temperature.
18. The apparatus of claim 11 wherein the thermally conductive peripheral wall comprises copper.
19. The apparatus of claim 11 wherein the sealing gasket is secured on the lower end of the peripheral wall.
20. The apparatus of claim 19 wherein the lower end of the peripheral wall terminates in a bottom lip that defines the mouth of the vacuum chamber, said bottom lip including a continuous, upstanding groove in which a portion of the sealing gasket is received.
21. Apparatus for the countergravity casting of molten metal, comprising:
(a) a mold having a porous, gas permeable upper mold portion at least in part defining a mold cavity and having a lower mold portion with a bottom ingate for admitting molten metal into said mold cavity from an underlying molten metal pool,
(b) an upwardly facing sealing surface on said mold,
(c) a housing defining a vacuum chamber confronting the upper mold portion for evacuating said mold cavity through said upper mold portion, said housing having a thermally conductive peripheral wall that terminates in a bottom lip defining a mouth of said chamber,
(d) an elastomeric sealing gasket secured on the bottom lip for sealingly engaging said sealing surface to seal said mold to the mouth of said chamber, and
(e) cooling channel means in the peripheral wall disposed above the sealing gasket for cooling the thermally conductive peripheral wall and maintaining, by thermal conduction through said peripheral wall, the sealing gasket at a temperature to reduce thermal degradation thereof when the lower mold portion is immersed in the molten mold pool to admit said molten metal into said mold cavity.
22. Apparatus for the countergravity casting of molten metal comprising:
(a) a mold having a porous, gas permeable upper mold portion at least in part defining a mold cavity and having a lower mold portion with an ingate for admitting molten metal into said mold cavity from an underlying pool of molten metal,
(b) a sealing surface on said mold,
(c) a housing defining a vacuum chamber confronting the upper mold portion for evacuating said mold cavity through said upper mold portion, said housing having a thermally conductive peripheral wall with an open lower end defining a mouth of said chamber,
(d) an elastomeric sealing gasket sealingly engaged between the sealing surface and the lower end of the peripheral wall for sealing said mold to the mouth of said chamber,
(e) said thermally conductive peripheral wall being cooled at a location above and remote from the sealing gasket and the underlying molten metal pool when the lower mold portion is immersed therein during casting to maintain, by thermal conduction through said peripheral wall, the sealing gasket below its thermal degradation temperature during casting.
23. In vacuum countergravity casting molten metal into a mold having a gas permeable upper mold portion defining at least in part a mold cavity and having a lower mold portion with an ingate for admitting the molten metal into the mold cavity, for steps of:
(a) enclosing the upper mold portion within a vacuum chamber having a mouth defined by a lower end on a depending, thermally conductive peripheral wall,
(b) sealing the mold to the mouth by sealingly engaging an elastomeric sealingly gasket between the lower end and the mold,
(c) immersing the lower mold portion in an underlying molten metal pool including evacuating the vacuum chamber to urge molten metal into the mold cavity through the ingate, and
(d) cooling the thermally conductive peripheral wall while the mold is immersed in the molten metal pool to maintain the sealing gasket at a temperature to reduce thermal degradation thereof during casting.
24. The method of claim 23 wherein the peripheral wall is cooled by cooling fluid flowing internally of the peripheral wall above the sealing gasket.
25. The method of claim 24 wherein the cooling fluid is water.
26. The method of claim 23 including securing the sealing gasket to the lower end of the peripheral wall.
27. The method of claim 23 wherein the sealing gasket is maintained below its thermal degradation temperature when the mold is immersed in the molten metal pool.
28. In vacuum countergravity casting molten metal into a mold having a gas permeable upper mold portion defining at least in part a mold cavity and having a lower mold portion with an ingate for admitting the molten metal into the mold cavity, the steps of:
(a) enclosing the upper mold portion within a vacuum chamber having a mouth defined by a bottom lip on a depending, thermally conductive peripheral wall,
(b) sealing the mold to the mouth of the vacuum chamber by sealingly engaging an elastomeric sealing gasket between the bottom lip and the mold,
(c) immersing the lower mold portion in an underlying molten metal pool including evacuating the vacuum chamber to urge molten metal into the mold cavity through the ingate, and
(d) cooling the thermally conductive peripheral wall at a location above and remote from the sealing gasket and the molten metal pool while the lower mold portion is immersed in the molten metal pool to maintain, by thermal conduction through said peripheral wall, the sealing gasket at a temperature to reduce thermal degradation thereof during casting.
29. The method of claim 28 wherein the peripheral wall is cooled by cooling fluid flowing internally of the peripheral wall.
30. The method of claim 28 wherein the cooling fluid is water.
31. The method of claim 28 including securing the sealing gasket to the bottom lip of the peripheral wall.
32. The method of claim 28 wherein the sealing gasket is maintained below its thermal degradation temperature when the mold is immersed in the molten metal pool.
Applications Claiming Priority (2)
Application Number | Priority Date | Filing Date | Title |
---|---|---|---|
US21946088A | 1988-07-15 | 1988-07-15 | |
US219460 | 1988-07-15 |
Publications (1)
Publication Number | Publication Date |
---|---|
EP0352406A1 true EP0352406A1 (en) | 1990-01-31 |
Family
ID=22819352
Family Applications (1)
Application Number | Title | Priority Date | Filing Date |
---|---|---|---|
EP89106902A Withdrawn EP0352406A1 (en) | 1988-07-15 | 1989-04-18 | Countergravity casting apparatus and method using elastomeric sealing gasket and cooled vacuum chamber |
Country Status (3)
Country | Link |
---|---|
EP (1) | EP0352406A1 (en) |
JP (1) | JPH0263667A (en) |
BR (1) | BR8903427A (en) |
Cited By (1)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
EP0415091A2 (en) * | 1989-08-28 | 1991-03-06 | General Motors Corporation | Countergravity casting using particulate filled vacuum chambers |
Citations (3)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
US2637882A (en) * | 1944-02-17 | 1953-05-12 | Atomic Energy Commission | Vacuum die-casting |
DE953191C (en) * | 1942-04-13 | 1956-11-29 | Philips Nv | Method and device for casting objects by sucking them into a vented mold |
US4658880A (en) * | 1985-12-09 | 1987-04-21 | General Motors Corporation | Countergravity casting apparatus |
-
1989
- 1989-04-18 EP EP89106902A patent/EP0352406A1/en not_active Withdrawn
- 1989-07-06 JP JP17316089A patent/JPH0263667A/en active Pending
- 1989-07-12 BR BR8903427A patent/BR8903427A/en unknown
Patent Citations (3)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
DE953191C (en) * | 1942-04-13 | 1956-11-29 | Philips Nv | Method and device for casting objects by sucking them into a vented mold |
US2637882A (en) * | 1944-02-17 | 1953-05-12 | Atomic Energy Commission | Vacuum die-casting |
US4658880A (en) * | 1985-12-09 | 1987-04-21 | General Motors Corporation | Countergravity casting apparatus |
Cited By (2)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
EP0415091A2 (en) * | 1989-08-28 | 1991-03-06 | General Motors Corporation | Countergravity casting using particulate filled vacuum chambers |
EP0415091A3 (en) * | 1989-08-28 | 1992-06-10 | General Motors Corporation | Countergravity casting using particulate filled vacuum chambers |
Also Published As
Publication number | Publication date |
---|---|
BR8903427A (en) | 1990-02-13 |
JPH0263667A (en) | 1990-03-02 |
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