US 4,318,437 A · Metal casting system

Abstract

A metal casting system including novel process and apparatus wherein the shape of the casting is defined by a thin thermal degrading film supported by a particulate bed. A pattern having the shape of the desired casting is surrounded by the tight fitting film with one end of the pattern exposed. A particulate bed is tightly packed about the film-surrounded pattern. A reduced fluid pressure is established within the particulate bed relative to the pattern so that the surrounding film is tightly held by atmospheric pressure against the particulate bed and slightly released from the pattern. The pattern is removed from the surrounding film and leaves therein a cavity bounded by the film with the shape of the desired casting. The cavity is filled with molten metal for forming the desired casting simultaneously with the vaporization of the film. The present metal casting system is especially useful for the casting of cylindrical shapes using unique molds and a novel flask is provided for such a casting process.

Claims40

Dependent claims

A process for the manufacture of a cylindrical metal casting using a pattern having the shape of the casting comprising:

(a) providing a pattern of a porous rigid material having the shape of the desired casting,
(b) forming a tubular sleeve of tight-fitting, thermally degradable film of relative thinness so as to be non-self-supporting about and enclosing all the surfaces of the pattern except one end of the pattern being exposed by an opening in said surrounding film and subject to a source of subatmospheric pressure,
(c) inserting the film surrounded pattern into a fluidized particulate bed and terminating fluidization of said particulate bed while yet subjecting said patterns to subatmospheric pressure with said film surrounded pattern standing upright therein,
(d) tightly packing said particulate bed about the film-surrounded pattern which stands upright therein and only the exposed end of the film surrounded pattern being accessible in the top surface of said particulate bed,
(e) providing a reduced fluid pressure within said particulate bed relative to the pattern and its exposed end now subject to the atmosphere whereby said surrounding film is tightly held against said particulate bed and slightly released from the pattern,
(f) removing manually the pattern upwardly by its exposed end from the surrounding film and leaving therein a cavity with an open top bounded by the film with the shape of the desired casting, and
(g) filling through the open top of the cavity defined by the film with molten metal for forming the casting simultaneously with thermal degration of the film.

4 more elements

A process for the manufacture of a metal casting having a tubular shape comprising:

(a) providing a pattern of a porous rigid material having the tubular shape of the desired casting,
(b) placing a tubular thermoplastic film about the exterior of the pattern and returning one end of the film through the central opening of the pattern whereby the free ends of the film extend beyond the pattern forming an exposed annular end therebetween,
(c) heating the film sufficiently to soften same and applying a vacuum at said exposed annular end of the pattern and to the annulus between the free ends of the film whereby the film is form fitted about the exterior and interior surfaces of the pattern,
(d) cooling the film surrounding the pattern to harden the film thereabout,
(e) tightly packing a particulate bed about the film surrounding the pattern which stands upright therein,
(f) sealing the free ends of the film to an enclosure containing the particulate bed with said exposed annular end and the annulus exposed to atmospheric pressure and applying a vacuum to the particulate bed whereby atmospheric pressure holds the film tightly against the surrounding particulate bed,
(g) removing the pattern upwardly from the surrounding film and leaving therein a cavity with an open top bounded by the film having the shape of the desired casting, and
(h) filling through the open top of the cavity within the film with molten metal for forming the casting.

5 more elements

A process for the manufacture of a metal casting having a tubular shape as a right circular cylinder with an axial opening comprising:

(a) providing a pattern having the tubular shape of the desired casting from a porous rigid material,
(b) sliding a tubular sleeve of thermoplastic film about the exterior surface and along its interior surface through the axial opening of the pattern, said sleeve having free ends projecting beyond one annular end of the pattern forming an annulus,
(c) placing an annular riser member coaxially on the pattern within the annulus formed by the free ends of said sleeves,
(d) heating and vacuum forming the sleeve tightly about the pattern and the riser member,
(e) tightly packing a particulate bed about the pattern and the riser member standing upright therein but with the riser member exposed in said particulate bed to receive a charge of molten metal,
(f) establishing a pressure gradient across the pattern and the particulate bed whereby the sleeve is held tightly by fluid pressure against the surrounding particulate bed,
(g) removing the pattern and riser member upwardly from the surrounding sleeve leaving a cavity with an open top bounded exteriorly and interiorly by film within the particulate bed and the cavity having the shape of the desired casting,
(h) filling through the open top of the cavity in the particulate bed with molten metal for forming the casting.

5 more elements

Dependencies are inferred from the claim text.

Metal casting system

Life of this patent

Metal casting system

Life of this patent

Abstract

Claims40