Metal founding – Process – Shaping a forming surface
Patent
1986-01-21
1987-09-15
Crosby, Gene P.
Metal founding
Process
Shaping a forming surface
164119, B22C 904, B22C 908, B22D 1804
Patent
active
046932925
DESCRIPTION:
BRIEF SUMMARY
BACKGROUND OF THE INVENTION
1. Field of the Invention
This invention relates to the casting of metal articles. More particularly, it relates to the casting of metal articles in which molten metal is poured into a mould cavity formed in particulate material by destroying a pattern in situ.
2. Description of the Prior Art
One well known example of such a casting method comprises embedding a pattern of foam plastics material, e.g. expanded polystyrene, in binder-free foundry sand, consolidating the sand to form a mould, pouring molten metal into the mould to destroy the pattern by burning or vaporising the pattern so that the metal replaces the pattern and an article corresponding to the original shape of the pattern is cast in the mould cavity previously occupied by the pattern.
Such a method has a number of advantages which include:
1. the ability to produce castings without joint lines and thus with reduced flash thereby requiring less fettling than with conventional moulds comprising cope and drag parts;
2. the process is relatively easy to automate since moulding involves simple filling of particulate material around the pattern using dry binder-free particulate material such as foundry sand;
3. knock-out and de-coring are easy since the unbonded particulate material simply runs off and out of the casting.
However, it suffers from the disadvantage of sporadic filling defects which are unacceptable in castings which are safety critical, such as suspension and steering components for automobiles.
SUMMARY OF THE INVENTION
It is accordingly an object of the present invention to provide a method of casting metal articles whereby the above mentioned problem is overcome or is reduced.
According to the broadest aspect of the present invention I provide a method of casting metal articles comprising the steps of feeding molten metal generally upwardly against the force of gravity from a source of molten metal into a mould cavity, permitting the metal to solidify within the cavity, interrupting the feed of said metal and removing the casting from the mould.
According to a first more specific aspect of the invention, the method may include the step of embedding an in situ destroyable pattern in particulate moulding material to form a mould cavity therein.
The pattern may be destroyed in situ by the heat of the metal as it is fed into the mould cavity.
Alternatively the pattern may be destroyed in situ prior to feeding the metal into the mould cavity.
The pattern may comprise a casting part to provide a casting portion of the cavity and an ingate part to provide a casting ingate portion of the cavity.
The pattern may also be provided with a runner system part to provide a runner system portion of the cavity and a runner ingate part to provide a runner ingate portion of the cavity.
Metal may be fed from the source into the mould through an orifice in a mould base on which the mould is supported.
The casting ingate part of the pattern may be disposed in casting relationship with the orifice in the mould base and then the particulate material is introduced around the casting part and casting ingate part to embed the pattern within the particulate material.
The runner ingate part of the pattern may be disposed in casting relationship with an orifice in the mould base and then the particulate material is introduced around the casting part and runner system and runner ingate parts to embed the pattern within the particulate material.
The pattern may be disposed within a peripheral wall extending upwardly from a mould base to provide a mould box into which the particulate material is introduced to embed the pattern therein.
The pattern may be coated with one or more washes, for example an aqueous ceramic slurry, to support the mould during the casting process, followed by drying.
The particulate material in which the pattern is embedded may be compacted by vibration or the application of a vacuum, or by other means, or by a combination of such means.
According to either the broadest aspect of the invention or the first
REFERENCES:
patent: 3259949 (1966-07-01), Moore
patent: 3532154 (1970-10-01), Balevski et al.
patent: 3635791 (1972-01-01), Bly et al.
patent: 3727674 (1973-04-01), Chatourel et al.
patent: 3771588 (1973-11-01), Cavanagh
patent: 4003424 (1977-01-01), Hetke et al.
patent: 4222429 (1980-09-01), Kemp
Batten, Jr. J. Reed
Cosworth Research and Development Limited
Crosby Gene P.
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