Production of pistons having a cavity
First Claim
1. A method for producing a piston of a light alloy matrix metal having a cavity within its head by pressure casting, comprising the steps of:
- preforming a precursory member having the shape of said cavity from an extractable material which remains in solid state at room temperature and is convertible into a fluid at a heating temperature below the melting point of the matrix metal,disposing said precursory member in place in a pressure casting mold having a cavity corresponding to the shape of the piston, while covering said precursory member with a porous member stable to molten matrix metal,pouring molten matrix metal into the mold cavity and applying a pressure thereto to form a piston-shaped casting having said precursory member and said porous member embedded therein, andheating said casting at a temperature below the melting point of said matrix metal and above the fluidizing temperature of the material of said precursory member to convert the precursory member material into a fluid, and extracting said fluid from said casting, leaving a cavity at the location of said precursory member.
1 Assignment
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Accused Products
Abstract
A piston of a light alloy matrix material having a cavity for containing heat insulating air immediately below its head or a cavity for passing cooling oil inside the grooved side wall is manufactured by preforming a precursory member having the shape of the cavity from an extractable material which remains in solid state at room temperature and is convertible into a fluid, gas or liquid when heated at a temperature below the melting point of the matrix metal. The precursory member is disposed in place in a pressure casting mold having a cavity corresponding to the shape of the piston, and covered with a porous member stable to the molten matrix metal. A head member of heat resisting metal material to constitute at least a portion of the piston head may be disposed on the mold cavity bottom. Molten matrix metal is then cast into the mold cavity and a pressure is applied thereto to form a piston-shaped casting having precursory member and porous member embedded therein. Finally the casting is heated at a sufficient temperature to gasify or liquefy the extractable material of the precursory member material into fluid, which is extracted from the casting, leaving a cavity at the location of the precursory member. Alternatively, the precursory member may be formed from a composite material of a gasifiable material and a stable material whereby the cavity is given as a porous insert of the stable material which is left after the extraction of the gasifiable material by heating.
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Citations
24 Claims
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1. A method for producing a piston of a light alloy matrix metal having a cavity within its head by pressure casting, comprising the steps of:
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preforming a precursory member having the shape of said cavity from an extractable material which remains in solid state at room temperature and is convertible into a fluid at a heating temperature below the melting point of the matrix metal, disposing said precursory member in place in a pressure casting mold having a cavity corresponding to the shape of the piston, while covering said precursory member with a porous member stable to molten matrix metal, pouring molten matrix metal into the mold cavity and applying a pressure thereto to form a piston-shaped casting having said precursory member and said porous member embedded therein, and heating said casting at a temperature below the melting point of said matrix metal and above the fluidizing temperature of the material of said precursory member to convert the precursory member material into a fluid, and extracting said fluid from said casting, leaving a cavity at the location of said precursory member. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17)
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18. A method for producing a piston of a light alloy matrix metal having a cellular cavity within its head by pressure casting, comprising the steps of:
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preforming a precursory member having the shape of said cavity from a composite material comprising a normally solid material which remains in solid state at room temperature and is gasifiable at a heating temperature below the melting point of the matrix metal and a material integrated therewith and stable at least at the gasifying temperature of the normally solid material, disposing said precursory member in place in a pressure casting mold having a cavity corresponding to the shape of the piston, while covering said precursory member with a porous member stable to molten matrix metal, pouring molten matrix metal into the mold cavity and applying a pressure thereto to form a piston-shaped casting having a head member, said precursory member, and said porous member embedded therein, and heating said casting at a temperature below the melting point of said matrix metal and above the gasifying temperature of the normally solid material of said precursory member to gasify the normally solid material, and extracting the resulting gases from said casting, thereby converting said precursory member into the cellular cavity. - View Dependent Claims (19, 20, 21, 22, 23, 24)
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Specification