Composite Foundar Core and Casting Method Using Said Core

Abstract

A foundry shell core includes an outer shell made of a polymerised sand and resin mixture suitable for withstanding the heat and metallostatic pressure produced by molten metal during casting, and of an inner core body made of a material suitable for being thermally dissolved before using the shell core forming an inner cavity inside the core itself that facilitates the intake of smoke and gases produced during the casting. Alternatively, the inner core body is dissolved after the solidification of the casting. The shell cores are obtained by injection with the use of a conventional core box into which the core bodies, previously obtained by a die, have been inserted.

1 - 17 . (canceled) 
   
   
       18 . A foundry core for obtaining a cavity or an inner or outer surface of a casting, comprising an outer shell made of a polymerized sand and resin mixture and an inner core body made of a material having a specific weight lower than that of said mixture and suitable for being dissolved before using the core or after casting solidification, the thickness of said outer shell being selected so as to at least withstand metallostatic pressure produced by the molten metal during casting. 
   
   
       19 . A core according to  claim 18 , wherein the thickness of the outer shell is selected so as to prevent transmission of heat generated by the molten metal to the inner core body, for preventing thermal collapsing of said inner core body, when it has not been dissolved prior to the casting of the molten metal. 
   
   
       20 . A core according to  claim 18 , wherein the outer shell has an uneven thickness according to the different metallostatic pressure it is subject to. 
   
   
       21 . A core according to  claim 18 , wherein the material forming the inner core body is suitable for being thermally dissolved before or after its use. 
   
   
       22 . A core according to  claim 21 , wherein the material forming the inner core body is foamed polystyrene. 
   
   
       23 . A core according to  claim 22 , wherein the material forming the core body is a water-soluble foamed material. 
   
   
       24 . A core according to  claim 18 , wherein the inner core body has at least one through hole for the passage of the material of the outer shell consisting of sand and resin mixture so as to facilitate the inner core body sheathing operation. 
   
   
       25 . A method of making a core according to  claim 18 , comprising the steps of:
 arranging a core box having a cavity corresponding to the shape of the cavity or surface of the casting to be obtained with the core;   molding the inner core body so that it has a smaller volume than that of said cavity of the core boxes;   arranging the inner core body into the cavity of the core box;   injecting a mixture of sand and resin into the air space between the inner surface of the cavity of the core box and the core body; and   carrying out the polymerization of the sand and resin mixture.   
   
   
       26 . A method according to  claim 25 , wherein the shape of the inner core body is selected so as to obtain a thickness of the outer shell suitable for withstanding the metallostatic pressure the core is subject to. 
   
   
       27 . A casting method, comprising the steps of:
 making at least one core according to the method of  claim 25 ;   laying the core in a container suitable for receiving the molten metal;   casting the molten metal;   removing any cores from the casting obtained at the previous step.   
   
   
       28 . A casting method according to  claim 27 , wherein after carrying out the casting of the molten metal, the inner core body is dissolved. 
   
   
       29 . A casting method according to  claim 27 , wherein before positioning the core in the container suitable for receiving the molten metal, the inner core body is dissolved. 
   
   
       30 . A casting method according to  claim 27 , wherein the core shell protects the inner core body from any contact with the molten metal. 
   
   
       31 . A casting method according to  claim 27 , wherein, before laying the at least one composite core into the container suitable for receiving the molten metal, said core is incorporated in a pattern of foamed polystyrene representing the casting for a lost foam casting process. 
   
   
       32 . A container for carrying out the method according to  claim 27 , wherein in the core print zones intended to contact the inner core body of a core, said container has inserts of an insulating material suitable for preventing the degradation of the material of said inner core body. 
   
   
       33 . A die for carrying out the casting method according to  claim 31 , wherein the die is constructed only with the external shapes of the pattern corresponding to the molten cast, in that it has seats suitable for seating the core prints of all the cores making up the internal shape of said pattern.