Casting Procedure, Particularly for an Engine Cylinder Head

Abstract

Cast parts having internal cavities or passages are produced by using a main core and one or more secondary cores. The secondary cores are associated with the main core by coating the secondary cores with a material which dissolves on contact with mold metal. The cores to be coated can also be formed by hollow inserts made of a heat resistant material, filled with sand polymerized resin.

1 . A method for casting an engine cylinder head from molten metal, said method comprising steps of: 
 forming a core from sand or other material, said core having a conical end towards a combustion chamber;    providing a die for coating said core with a layer of a material suitable for dissolving upon contact with said molten metal;    providing at least one valve seat having conical internal and external surfaces, wherein the tapering of the internal surfaces corresponds to the tapering of said conical end of the core;    placing said valve seat in a respective reference provided in said die;    placing said core in said die in such a way that the conical end of the core mates with said valve seat internal surface; and    coating said core with said layer of material in such a way that said material envelops said valve seat around the external surface thereof.    
   
   
       2 . A method according to  claim 1 , further comprising a step of forming at least one seat for a valve guide, before said step of coating at least one core with a layer of a material adapted to dissolve in contact with the casting metal.  
   
   
       3 . A method according to  claim 1 , wherein said coating is applied to the core only in the zones and by the thickness of the casting shape.  
   
   
       4 . A method according to  claim 3 , wherein the coating is performed by injection molding on the core to be coated.  
   
   
       5 . A method according to  claim 1 , wherein a main core, which is the water jacket core intended to form the coolant circulation passages, and secondary cores, which mainly are ducts cores for the intake and exhaust ducts, are provided.  
   
   
       6 . A method according to  claim 5 , wherein the main core is formed into a special core box, along with one or more secondary cores intended to be associated to said main core, and further comprising steps of: 
 coating at least one secondary core, only in the zones and by the shaped thickness, with a layer of material intended to dissolve in contact with the molten metal;    inserting the group consisting of at least one secondary core and of at least one valve seat, all coated with said layer of material intended to dissolve in contact with the molten metal into the main core box yet to be molded;    molding the main core box; and    inserting the monolithic group comprising the water jacket core, the secondary cores, the at least one valve seat, the layer of material intended to dissolve in contact with the molten metal that keeps them firmly connected, into the mold or chill intended to receive the molten metal.    
   
   
       7 . A method of an engine cylinder head according to  claim 6 , wherein the secondary cores include cores of the intake and exhaust ducts, wherein said duct cores are laid into a single die to be coated with the coating material layer so as to form a single body to be laid into the special water jacket core box.  
   
   
       8 . A method according to  claim 7 , wherein valve seats for the intake and exhaust ducts are first laid into the die, the injected material enveloping said valve seats on the outer diameter.  
   
   
       9 . A method according to  claim 1 , wherein prior to assembly monolithic group into the mold or chill, at least one valve guide for the intake and/or exhaust valve is inserted into the monolithic group comprising the main core and the secondary coated cores.  
   
   
       10 . A method according to  claim 1 , wherein the cores to be coated comprise hollow inserts made of a heat resistant material, wherein the cavity represents the shape according to the drawing.  
   
   
       11 . A method according to  claim 1 , wherein the cores to be coated comprise a hollow insert for the shaped zones only, made of a heat resistant material filled with sand and polymerized resin to form prints and prevent metal infiltrations.  
   
   
       12 . A method according to  claim 1 , wherein the coating material of the sand and polymerized resin cores or of the inserts is a foamed material.  
   
   
       13 . A method according to  claim 12 , wherein the foamed material is polystyrene.  
   
   
       14 . A main core box for the method according to  claim 5 , said box consisting of only two portions intended to be closed onto one another, and being free from undercuts and moving parts, and having seats and negative prints for receiving and blocking into position the secondary cores pre-coated with the coating material.  
   
   
       15 . A die for coating the intake and exhaust duct cores in an engine cylinder head casting process according to  claim 5 , said die comprising cylindrical mobile pins intended to form at least one seat into the coating material for the valve guides of the intake and/or exhaust valves.  
   
   
       16 . A die for coating the intake and exhaust duct cores in an engine cylinder head casting process according to  claim 5 , wherein the die is configured to receive at least one valve seat for the intake and/or exhaust valves.  
   
   
       17 . An engine cylinder head having embedded therein at least one embedded hollow insert made of metal or other heat resistant material, whose interior forms the design of the corresponding intake and exhaust duct.  
   
   
       18 . An engine cylinder head casting, having at least one embedded valve seat or valve guide.  
   
   
       19 . A method of casting parts having internal cavities or holes, said method comprising steps of 
 laying into a mold or chill intended to receive the molten metal one or more cores made of sand or other material, wherein each core is formed separately into a proper core box, and, before laying into the mold or chill,    coating at least one core with a layer of a material adapted to dissolve in contact with the casting metal, and further comprising, before said coating step,    forming at least one seat for a valve guide.    
   
   
       20 . A method for casting an engine cylinder head, wherein said cylinder head has at least one water jacket for the engine coolant circulation at least an intake and/or exhaust duct, and at least one valve seat for the intake and/or exhaust valve, said method comprising steps of 
 laying into a mold or chill intended to receive the molten metal one or more cores made of sand or other material and provided separately into proper core boxes, at least the core of the duct being coated with a layer of a material adapted to dissolve in contact with the casting metal before being laid into the mold or chill, and    embedding said at least one valve seat guide into said layer of a material adapted to dissolve in contact with the casting metal, in such a way that during the casting, the molten metal will dissolve and replace the layer of a material adapted to dissolve in contact with the casting metal, determining the required thickness and embedding said valve seat or guide.    
   
   
       21 . Apparatus for casting an engine cylinder head, wherein said cylinder head presents at least a water jacket for the engine coolant circulation, at least an intake and/or exhaust duct, at least one valve guide for the intake and/or exhaust valve, wherein said water jacket and duct are obtained by 
 laying into a mold or chill intended to receive the molten metal one or more cores made of sand or other material and formed separately into proper core boxes, and wherein at least the core of the duct is coated with a layer of a material adapted to dissolve in contact with the casting metal before being laid into the mold or chill, and further comprising    embedding said at least one valve guide into said layer of material in such a way that during the casting, the molten metal will dissolve and replace said layer of material, determining the required thickness and embedding said valve guide.    
   
   
       22 . Apparatus for casting an engine cylinder head, wherein said cylinder head presents at least an intake and/or exhaust duct, at least one valve seat or valve guide for the intake and/or exhaust valve, wherein said duct is obtained with one or more cores made of sand or other material, and wherein at least the core of the duct is coated with a layer of a material adapted to dissolve in contact with the casting metal, and further comprising 
 means for embedding said at least one valve seat or guide into said layer of a material adapted to dissolve in contact with the casting metal, in such a way that during the casting, the molten metal will dissolve and replace the layer of a material adapted to dissolve in contact with the casting metal, determining the required thickness and embedding said valve seat or guide.