Metal founding – Means to shape metallic material – Including ladle or crucible type melt receptacle
Reexamination Certificate
2000-11-22
2002-11-26
Elve, M. Alexandra (Department: 1725)
Metal founding
Means to shape metallic material
Including ladle or crucible type melt receptacle
C164S054000, C249S086000
Reexamination Certificate
active
06484792
ABSTRACT:
BACKGROUND OF THE INVENTION
The present invention relates to a single use transportable reaction crucible for a metallothermic, especially aluminothermic, welding portion and includes a crucible shell having a cylindrical casing and a flat floor and a lid and in the crucible shell a refractory lining that receives the welding portion and that is provided in its base with an opening that can melt open.
Such a reaction crucible is known from DE 197 02 410 C1. In the known reaction crucible, the actual reaction crucible is stamped or riveted into a metal crucible shell in the form of a lining made of a sand mixture. For this reason the shell must be made from a high-strength, metallic, heavy material. A lighter and less expensive material such as cardboard, plastic, or the like cannot be used. Since the lining has a flat floor corresponding to the flat floor of the crucible shell, it does not facilitate the flow of the molten metal to the bottom opening. In the lining the welding portion is either fed into a conventional can or into a conventional plastic sack or into another container. When the reaction crucible is used, the lid is removed and the welding portion is ignited using an ignition rod, whereupon the lid is replaced. The metal crucible shell requires a separate removal from the application site.
SUMMARY OF THE INVENTION
The object of the present invention is to provide a reaction crucible of the aforementioned type in which less expensive materials can be used for the crucible shell and the actual reaction crucible is securely maintained in the crucible shell and has an inclined floor.
This object is achieved in that placed on the flat floor of the crucible shell, which is made of a non-metal material, is the flat underside of a support disc made of a refractory material and adapted to the interior diameter of the casing, the top surface of which forms a cone in the direction of a central opening, and in that the refractory lining is a specially produced cylindrical reaction vessel that has been inserted into the casing, the floor of which is configured in the shape of a cone to correspond to the top surface of the support disc and is placed on the disc and engages the central opening of the support disc with a hollow guide projection.
Since the crucible shell does not simultaneously have to serve as the exterior profile for the reaction vessel, it can be produced from a non-metallic material such as cardboard, laminated paper, plastic, or the like. At least the cylindrical casing and the floor of the crucible shell comprise preferably cardboard, plastic, or the like. Cardboard is particularly preferred for the material. The reaction vessel, which is produced as a separate component, is provided with a conical floor. The support disc ensures that the reaction vessel is securely supported and centered in the crucible shell.
Production tolerances during the manufacture of the reaction vessel and/or the construction of the overall wall thickness required for the melting reaction can be compensated in a preferred manner in that the outer diameter of the reaction vessel is smaller by a pre-specified amount than the inner diameter of the casing and the annular intermediate space is filled with a refractory material, preferably in the form of small particles.
There are a plurality of options for the design of the crucible shell. For instance, it is possible that the cylindrical casing and the floor of the crucible shell and at least one lid of the reaction crucible, the lid preferably being provided with an opening, are made of cardboard, laminated paper, or the like. The lid of the reaction crucible is thus made from the same material as the crucible shell. On the other hand, it is also possible that at least one lid of the reaction crucible, the lid preferably being provided with an opening, comprises a refractory material. In addition, it can be useful to use a double-lidded system in which an exterior lid made from one of the other materials cited in the foregoing is placed on an interior lid made of a refractory material.
In order to maintain the lid securely in place, it is advantageous when the cylindrical casing of the crucible shell extends beyond the free edge of the reaction vessel and at least one of the lids rests upon the free edge of the reaction vessel and is maintained by the overhanging section of the casing.
In order to ensure that the closure remains air-tight and/or moisture-tight, it is useful that, in addition to the lid or lids, a film is provided on the exterior side thereof as a protective and/or sealing protecting element, said film preferably covering the upper edge of the crucible shell casing.
It is thereby also possible that the parts of the crucible shell that are made of cardboard, plastic, or the like are protected from the penetration of moisture in that, e.g. if cardboard is used for the crucible cover, the cardboard is lined on its interior side with a metal film or the cardboard is provided with a film on the interior.
The guide projection can be embodied integrally with the reaction vessel or as a separate component. Embodying it separately facilitates inserting the melting seal into the guide projection that defines the floor opening of the reaction vessel.
At many sites where the metallothermic welding process is used, e.g. tunnels, it is desirable that dust be removed from gases exiting the reaction crucible. Therefore, it is useful when the opening in the lid is provided with a filter made of a refractory nonwoven web. It can be useful when an additional ignition opening is provided in the lid when the filter is joined securely to the lid over the exhaust opening.
A particularly stable construction of the crucible shell results when the floor of the crucible shell is provided with a circular flange and is glued into the casing such that the free edges of the casing and flange lie in the same plane.
Preferably a different refractory material is used for the support disc than is used for the reaction vessel, since the support disc undergoes less thermal stress when the crucible is used than does the reaction vessel. The filler material for the annular gap between casing and reaction vessel also undergoes less thermal stress than the reaction vessel and can therefore also be different.
In the reaction crucible in accordance with the invention, the welding portion is preferably introduced into the reaction vessel as free fill and the lid or lids are sealed air-tight and/or moisture-tight.
REFERENCES:
patent: 3860062 (1975-01-01), McMurray et al.
patent: 4063720 (1977-12-01), Boutet et al.
patent: 4149704 (1979-04-01), de Savigny
patent: 4522322 (1985-06-01), Guntermann et al.
patent: 5151202 (1992-09-01), Bommart
patent: 5215139 (1993-06-01), Swartz et al.
patent: 5715886 (1998-02-01), Fuchs
patent: 5829510 (1998-11-01), Fuchs
patent: 0 007 055 (1980-01-01), None
patent: 197 02 410 (1998-03-01), None
Becker R W
Elve M. Alexandra
Kerns Kevin P.
R W Becker & Associates
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