Casting methods with composite molded core assembly

Claim 3

A method according to claim 1 wherein said step of molding a destructible layer comprises inserting said first core into a corebox, applying thermoplastic resinous pellets around said first core and expanding said pellets around said first core.

Claim 4

A method according to claim 2 wherein said step of applying resinous pellets comprises applying pre-expanded polystyrene pellets.

Claim 7

A method according to claim 4 wherein said step of molding a destructible layer comprises inserting said first core into a corebox, applying thermoplastic resinous pellets around said first core and expanding said pellets around said first core.

Claim 8

A method according to claim 5 wherein said step of applying resinous pellets comprises applying pre-expanded polystyrene pellets.

Claim 9

A coring assembly for use in casting a cylinder head for an internal combustion engine, comprising: a port core having a base and port-defining extensions projecting generally laterally and downwardly from said base in generally parallel relationship; said port-defining extensions having irregular outer surface portions; said base and port-defining extensions terminating downwardly in essentially coplanar positioning members; a molded-in-place destructible layer of cellular plastic material disposed in encompassing relation around a substantial portion of said port-defining extensions of said port core; said plastic layer including a plurality of spaced upstanding posts for forming cast-in-place valve guide bosses of the engine and forming an irregular outer surface portion of said plastic layer; said plastic layer including an inner surface which intimately contacts and conforms to the irregular outer surface portion of said port core to interlock said port core and said plastic layer together; a molded-in-place cooling jacket core disposed in encompassing relation around a substantial portion of said plastic layer including said upstanding posts; said cooling jacket core terminating downwardly in a positioning portion and including an inner surface which intimately contacts and conforms to the irregular outer surface portion of said plastic layer to interlock said cooling jacket core and said plastic layer together, the outer surface of said cooling jacket core being of nonconforming shape relative to the outer surface of said plastic layer.

Claim 10

A coring assembly for use in casting a cylinder head for an internal combustion engine, comprising: a port core having a base and port-defining extensions projecting generally laterally and downwardly from said base in generally parallel relationship; said port-defining extensions having irregular outer surface portions; said base and port-defining extensions terminating downwardly in essentially coplanar positioning members; a molded-in-place destructible layer of cellular plastic material disposed in encompassing relation around a substantial portion of said port-defining extensions of said port core; said plastic layer including a plurality of spaced upstanding posts for forming cast-in-place valve guide bosses of the engine and forming an irregular outer surface portion of said plastic layer; said plastic layer including an inner surface which intimately contacts and conforms to the irregular outer surface portion of said port core to interlock said port core and said plastic layer together; a molded-in-place cooling jacket core disposed in encompassing relation around a substantial portion of said plastic layer including said upstanding posts; said cooling jacket core terminating downwardly in a positioning portion and including an inner surface which intimately contacts and conforms to the irregular outer surface portion of said plastic layer to interlock said cooling jacket core and said plastic layer together, the outer surface of said cooling jacket core being of nonconforming shape relative to the outer surface of said plastic layer.

Claim 11

A core assembly according to claim 7 wherein said destructible layer comprises a thermoplastic resinous material.

Claim 12

A core assembly according to claim 8 wherein said thermoplastic resinous material is polystyrene. .Iadd.10. A method of casting metal castings comprising the steps of: fabricating a composite core assembly by molding a destructible layer of cellular plastic material such that a surface of said plastic layer includes an irregular surface portion; and forming a core in encompassing relation around said irregular surface portion of said plastic layer by blowing a mixture of sand and binder around said surface portion, such that a surface of said core intimately contacts and conforms to the configuration of the irregular surface portion of said plastic layer to interlock said core and said plastic layer together; forming a mold cavity within a pair of mold sections; inserting said core assembly as an integral unit within one of said mold sections; securing said mold sections together; and introducing molten metal into said cavity to destroy said plastic layer and

Claim 13

form said casting..Iaddend..Iadd. 11. A method according to claim 10, wherein said step of molding a plastic layer comprises fabricating an initial core having an irregular surface portion, inserting said initial core into a corebox, applying thermoplastic resinous pellets around said initial core, and expanding said pellets around said initial core such that a surface of said plastic layer intimately contacts and conforms to said irregular surface portion of said initial core..Iaddend..Iadd. 12. A method according to claim 11, wherein said step of applying resinous pellets comprises applying pre-expanded polystyrene pellets. .Iaddend. .Iadd. 13. A core assembly for use in metal casting operations, comprising: a first core having an irregular outer surface, a mold-in-place, destructible layer of plastic cellular material disposed around at least a portion of said outer surface of said first core, with an inner surface of said plastic layer intimately contacting and conforming to the irregular configuration of said first core to interlock said first core and plastic layer such that removal of said plastic layer from said first core in any direction is prevented; said first core and said plastic layer forming a composite core subassembly; and a formed-in-place second core encompassing a portion but not all of said subassembly in overlying relation to said plastic layer and in non-engagement with said first core; an inner surface of said second core intimately contacting and conforming to an irregular surface portion of said plastic layer to interlock said second core and said plastic layer..Iaddend. .Iadd. 14. A core assembly according to claim 13, wherein said second core comprises sand and binder. .Iaddend..Iadd. 15. A core assembly according to claim 13, wherein said plastic layer comprises a thermoplastic resinous layer..Iaddend..Iadd. 16. A core assembly according to claim 15, wherein said resinous material is polystyrene.