Casting mold with constricting device

Abstract

A stricture is formed between riser and cast article in a conventional metal mold casting process to facilitate clean removal of the riser after casting by interposing thin-walled frangible constriction means between riser cavity and casting cavity prior to pouring molten metal; the flow of metal into casting cavity is also regulated thereby.

We claim: 
     
       1. In a mold assembly for casting having an upper portion and a lower portion and a casting cavity defined by said upper and lower portions in which a casting is to be formed, said upper and lower portions mating along an interface plane, said casting cavity communicating with a riser cavity in which a riser is formed for feeding molten material to the casting cavity as the casting solidifies, means for forming a stricture between the riser cavity and casting cavity and for regulating the flow of molten metal from the riser cavity into the casting cavity, said means including a constriction device .Iadd.formed from a fired ceramic material and .Iaddend.having aperture means therein, .Iadd.a thin wall of about one-eighth inch in thickness, and a thickened ribbed peripheral portion, said aperture means being an aperture defined by a rounded edge of the thin wall and of a size sufficient in inhibiting the flow of molten metal from the riser cavity into the casting cavity to maintain the level of molten metal within the riser cavity about said aperture means, .Iaddend.said device being interposed between the casting cavity and the riser cavity at the point of communication thereof, and .Iadd.said thickened ribbed peripheral portion of .Iaddend.said device simultaneously engaging both said upper and lower portion of said mold when said portions are in mating engagement along said interface plane. .[.2. The invention of claim 1 wherein said constriction device comprises a frangible thin-walled member defining an aperture therethrough and further having a 
     
     
        thickened ribbed peripheral portion..]. .[.3.  The invention of claim 1, 
     
     
        wherein said constricting device is comprised of ceramic material..]. 4. The invention of claim 2, wherein the thin wall of the constriction device is between about one-sixteenth inch and one-fourth inch thickness. .[.5. The invention of claim 1, wherein said aperture means is an aperture of a size sufficient for inhibiting the flow of molten metal from the riser cavity into the casting cavity to maintain the level of molten metal 
     
     
        within the riser cavity above said aperture means..]. 6. .[.The invention of claim 1, wherein the.]. .Iadd.In a mold assembly for casting having an upper portion and a lower portion and a casting cavity defined by said upper and lower portions in which a casting is to be formed, said upper and lower portions mating along an interface plane, said casting cavity communicating with a riser cavity in which a riser is formed for feeding molten material to the casting cavity as the casting solidifies, means for forming a stricture between the riser cavity and casting cavity and for regulating the flow of molten metal from the riser cavity into the casting cavity, said means including a constriction device having a thin wall and .Iaddend.aperture means .[.is.]. defined by a rounded edge of the thin wall.Iadd., said thin wall being of sufficient thinness with respect to the thermal conductivity of the wall material to prevent premature cooling and hardening of the molten material thereat said device being interposed between the casting cavity and the riser cavity at the point of communication thereof, and said device simultaneously engaging both said upper and lower portion of said mold when said portions are in mating engagement along said interface plane.Iaddend.. .[.7. The invention of claim 2 wherein said constriction device is fabricated from high refractory insulating material. .]. .[.8. The invention of claim 7 wherein said constriction device is fabricated from ceramic material..].