Metal founding – Process – Shaping liquid metal against a forming surface
Utility Patent
1998-09-08
2001-01-02
Lin, Kuang Y. (Department: 1722)
Metal founding
Process
Shaping liquid metal against a forming surface
C164S066100, C164S130000, C164S324000, C164S430000, C164S475000
Utility Patent
active
06167944
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates to an improved method and system for ingot mould casting of metals. More particularly, the present invention relates to an apparatus for casting metal ingots, a mould for use in the apparatus, a method which utilises the apparatus, and metal cast by the method.
BACKGROUND OF THE INVENTION
The use of an ingot mould to cast molten metals is common practice. Casting of metals under an inert or protective gas atmosphere also is well known and is essential in the case of some metals such as magnesium.
In casting metals in ingot moulds, a system which is frequently used has a series of moulds mounted along an endless conveyor by which the moulds are presented in turn to a molten metal supply or distribution device. The conveyor, which may comprise endless chains or belts, passes around longitudinally spaced cogs, sprockets or the like, by which drive is imparted to the conveyor. The series of moulds is mounted on the conveyor so as to be in an upright orientation when presented to the supply or distribution device on an upper run of the conveyor. Typically the moulds are inverted in turn as each passes around a cog, sprocket or the like at a discharge end of the conveyor, such that the then sufficiently solidified ingot therein is able to drop from its mould.
With such a conventional conveyor system, it is difficult to restrict adequately the amount of air ingress to the atmosphere above the moulds and/or the amount of inert or protective gas atmosphere that leaks between moulds or otherwise is lost. Of course, it is possible to house the entire system in a leakproof enclosure, and to have the molten metal supply or distribution device within the enclosure. However, this substantially increases overall capital costs, and gives rises to several practical difficulties in operation, not the least of which is difficulty of access to the system in the event of a malfunction, particularly where the inert or protective gas is toxic.
SUMMARY OF THE INVENTION
In a first aspect, the present invention provides an apparatus for casting metal ingots comprising:
a series of ingot moulds mounted along an endless conveyor which is arranged to be driven around spaced apart rotatable members;
a molten metal supplying device having a discharge member for supplying molten metal to empty moulds moving along an upper run of the conveyor from a supply end to a discharge end of the upper run of the conveyor;.
a casting hood overlying at least a portion of the moulds on the upper run of the conveyor and being in slideable sealing engagement with the portion of the moulds, adjacent moulds of the portion of moulds being closely contiguous during passage beneath the casting hood whereby passage of gas between said adjacent moulds is minimised, the casting hood and the portion of moulds forming a substantially gas tight enclosure above the portion of moulds, the enclosure housing the discharge member of the molten metal supplying device; and
gas introduction means for introducing gas into the enclosure.
In a second aspect, the present invention provides a method for casting molten metal utilising an apparatus according to the first aspect of the present invention, the method comprising the steps of driving the series of ingot moulds around the spaced apart rotatable members, introducing gas into the enclosure to establish and maintain an atmosphere of the gas within the enclosure, and supplying molten metal from the discharge member to successive moulds moving below the casting hood.
In a third aspect, the present invention provides a metal cast by a method according to the second aspect of the present invention.
Preferably, the spaced apart rotatable members comprise longitudinally spaced cogs, sprockets or the like. Preferably, sides of said adjacent moulds are substantially normal to the direction of movement of the moulds along the upper run of the conveyor. Preferably, the casting hood is mounted above, and extends along, the upper run and along each side of the conveyor.
The moulds may be of rectangular form in plan view. While this is not necessarily the case, particularly in relation to the cavity of each for casting an ingot, such form will be assumed for ease of description. In line with that assumption, it will be further assumed that each mould is of similar form and dimensions and that each has a rectangular open top bounded by substantially parallel sides which are substantially perpendicular to the length of the conveyor, and a respective end which extends along each side of the conveyor. However, it is to be noted that these further assumptions also do not necessarily apply.
On the upper run of the conveyor, successive moulds may be closely contiguous along adjacent sides of the open top of each. The arrangement may be such that the adjacent sides simply abut at opposed surfaces thereof. Alternatively, the adjacent sides may interfit or interlock. In each case, the adjacent sides preferably conform to close tolerances, so as to minimise the gap between the successive moulds and, hence, the extent to which inert or protective gas atmosphere provided above the moulds is able to escape during movement of the moulds along the upper run. However, whether abutting, interfitting or interlocking, it is necessary that successive moulds are closely contiguous on the upper run of the conveyor in a manner which enables their separation as each mould reaches and moves around the discharge end of the conveyor.
In accordance with a fourth aspect of the present invention, a mould may comprise a substantially rectangular base, a pair of end walls and first and second side walls, the end walls and side walls extending upwardly and outwardly from the base, the side walls being longer than the end walls and the first side wall being taller than the second side wall, the first side wall having an outwardly extending first side wall lip having a concave underside and the second side wall having an outwardly extending second side wall lip having a convex upperside, the first and second side wall lips being arranged such that when two of the moulds are placed horizontally beside one another the concave underside of the first side wall lip of a first of the two moulds sits atop the convex upperside of the second side wall lip of a second of the two moulds whereby passage of gas between the first side wall of the first mould and the second side wall of the second mould is minimised.
In one arrangement, each side of the open top of each mould is defined by an outwardly turned lip, one of which is slightly higher than the other. The higher lip of one of successive moulds, for example the leading lip in the direction of movement along the upper run, can overlap the lower lip of the other of the successive moulds. The lips may be arcuate in sections parallel to that direction, such that a convex upper surface of the lower lip is received under a concave lower surface of the upper lip. Where of such arcuate form, the lips may have a radius of curvature which facilitates separation of the leading one of the successive moulds when it reaches the discharge end of the conveyor. Also, in that arrangement, the higher lip preferably is at substantially the same height as the ends of the open top such that, in being received over the lower lip of the next successive mould, it is neatly received between the ends of the open top of that next mould.
The casting hood may be of elongate form in plan view. Also, it may have a respective side structure along each side of the conveyor by which it is in slideable sealing engagement with at least a plurality of successive moulds on the upper run, and a cover which extends between the side structures, above these moulds. That sealing engagement may be provided along ends of the open top of each of the moulds, and preferably is of a tongue and groove type. In one form, each of those ends has a groove therein into which an edge of the respective side structure is received. Each groove preferably is defined in an upper surface of its end. Howev
Baker Phillip Wilmott
Ricketts Nigel Jeffrie
Commonwealth Scientific and Industrial Research Organisation
Lin Kuang Y.
Rodman & Rodman
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