WO1998055252A1

WO1998055252A1 - Gold casting device

Info

Publication number: WO1998055252A1
Application number: PCT/SE1998/001061
Authority: WO
Inventors: Jouko JANNÉ
Original assignee: Jouko Janne
Priority date: 1997-06-03
Filing date: 1998-06-03
Publication date: 1998-12-10
Also published as: FI972350A; AU8047098A; FI972350A0

Abstract

The invention relates to a melting apparatus for gold, comprising a gold melting mould (1) with a bottom orifice, and a chilling mould (2) linked therewith for chilling the gold melted in the mould and possible additives, said chilling mould (2) having a discharge orifice which matches the diameter of a shaft extracted from the apparatus, and said chilling mould being provided with a pull rod (4) extending all the way to the melting mould (1) and one end thereof extending all the way to drive rollers (5) of the apparatus. The pull rod (4) is divided in two sections, whereof a section (9) extending into the melting mould (1) consists of gold or an alloy thereof and its end protruding from the chilling mould (2) is by way of a link element (8) connected to the pull rod section (4), which can be some base metal or the like and which is in contact with the drive rollers (5).

Description

Gold Casting Device.

The present invention relates to a melting apparatus for gold, comprising a gold melting mould with a bottom orifice, and a chilling mould linked therewith for chilling the gold melted in the mould and possible alloying materials, said chilling mould having a discharge orifice which matches the diameter of a shaft extracted from the apparatus, and said chilling mould being provided with a pull rod extending all the way to the melting mould and one end thereof extending all the way to drive rollers of the apparatus.

Initially, in this type of prior art apparatus, there is a rod extending to the molten gold, normally a rod of some non-precious metal, for example iron or steel, the end of which extends into the melting mould and melts away and thus adheres to molten metal present in the melting chamber. A slow withdrawal of the outer end of the pull rod results in the fact that the pull rod adhered to molten metal pulls the molten metal along. Upon transferring into a chilling mould placed below the melting mould, the metal sets and produces a continuous shaft, having a cross-section which matches in shape the discharge orifice of the melting mould. The melting mould and chilling mould are made of graphite, a material resistant to high temperatures, yet incapable of resisting mechanical stresses. For this reason, the drive rollers associated with the pull rod are located a fair distance away from the mould in order to cause as little flexure, torsion, and vibration as possible. The melting process is finished when the melting mould is nearly exhausted. For the next melting operation it is necessary to leave a small amount of metal in the mould for a withdrawal in the next melting.

The metal shaft emerging from the chilling mould is severed below the traction rollers whereby, after the melting, there will be a relatively large piece of pull rod left in the apparatus, i.e. a piece of rod extending from the melting furnace to the chilling mould and that extending beyond the drive rollers and guide rollers set therebelow. This is a drawback, especially when dealing with precious metals with a considerable price per kilogram. Thus, even more than two kilograms of metal may remain in the apparatus to wait for the next melting, which may not happen till after a long time, even months.

An object of the present invention is to propose a solution that would enable avoiding needless unproductive non-use of such precious metals.

The invention is characterized in that the pull rod is divided in two sections, whereof a section extending into the melting mould consists of gold or an alloy thereof and its end protruding from the chilling mould is by way of a link ele- ment connected to the pull rod section, which can be some base metal or the like and which is in contact with the drive rollers.

In a preferred embodiment of the invention, the pull rod element is cruciform in cross-section and around the central circumference of the drive rollers extends a groove, having a depth which is at least equal to the height of the arm of the pull rod element.

The invention will now be described in more detail with reference made to the accompanying drawings, in which

figs. 1 and 2 illustrate the structural and operating principle of a prior known apparatus.

Fig. 3 shows a corresponding structural and operating principle, and

fig. 4 shows a detail along a line IV-IV in fig. 3.

The gold melting apparatus depicted in fig. 1 comprises a bowl-shaped melting mould 1 , provided for example with induction heating (heating elements and regulating equipment therefor not shown). The melting mould 1 has its bottom provided with an orifice, in which is fitted a chilling mould 2. The chilling mould includes a channel, whose discharge end matches in shape the cross-section of a rod emerging from the mould. At a distance from the chilling mould 2, the pull rod 4 is provided on either side thereof with pairs of drive rollers 5, a metal shaft emerging from the mould being advanced through said pairs, and said rollers 5 pulling the shaft slowly downwards. The circumferential surfaces of the drive rollers are roughened for an improved engagement with the emerging rod 4. Below the drive rollers 5, likewise on either side of the pull rod 4, are mounted pairs of guide rollers 6 for guiding the emerging rod or shaft in such a way that the rod is driven steadily downwards. This is important since both the melting mould 1 and the chilling mould 2 are made of graphite, which is capable of withstanding high temperatures but not mechanical torsion.

Prior to commencing a melting process in such prior known apparatus, a metal rod is pushed into the mould 1 through the chilling mould 2 in such a way that the end of the rod 4 extends into the melting chamber. This rod, which for reasons of costs is usually made of some base metal, has such a length that it extends from the melting mould 1 across the chilling mould 2 through the drive rollers 5 and likewise through the guide rollers 6 therebelow. The distance between the opposite pairs of drive rollers 5 is adjusted in such a manner that the rollers take a firm grip on the pull rod 4.

The melting chamber 1 is supplied with metal to be melted, which consists of gold and possibly some other material to be alloyed therewith. The metal is melted in the melting chamber 1 , whereby the end of a metal rod extending into molten metal 3 melts away and this way adheres to the molten gold alloy 3 present in the melting chamber 1.

This is followed by starting the drive rollers 5, which rotate in opposite directions, thus pulling the rod 4 slowly downwards. The pulling speed is worked out to match the cooling capacity of the chilling mould 2. The pulling is continued and gradually an actual gold shaft 7 emerges from the melting mould 2. At the same time, a junction 8 between the iron rod 4 and the gold shaft 7 has traveled past the drive and guide rollers 5, 6.

When the melting process is about to be stopped, a small amount of gold alloy must be left in the melting mould. The emerged gold shaft 7 is severed below the guide rollers 6 and, in addition to this, the metal rod section 4 is of course also severed for producing a pure staff of gold or gold alloy. Thus, following the melting and cutting of the rod, the melting apparatus is left with a gold bar extending from the melting mould 1 to below the guide rollers 6, which bar or shaft, depending on the shape thereof, may be relatively long and contain even up to two kilograms of gold or gold alloy. Furthermore, an iron rod extending into a molten gold alloy contaminates the gold alloy, the estimation of accurate gold content is difficult beforehand, even though, in principle, the content of a melted gold bar emerging from the apparatus is predeterminable. However, the iron dissolving and melting from an iron rod makes this determination inaccu- rate.

According to the invention, a solution is now proposed to this problem, such that there will be no need to leave large amounts of precious metal in the apparatus, which is a major drawback, particularly when melting cycles are infre- quent. In addition, the apparatus of the invention does not produce iron or like impurities at all.

An apparatus of the invention is shown in fig. 3, which in principle corresponds to the prior known equipment depicted in figs. 1 and 2. A difference in the apparatus of the invention is, however, the fact that the pull rod 4 is divided in two sections, whereof the top section, i.e. the one that penetrates into the gold melting mould, comprises a gold rod or staff. Such a staff, which is relatively short, is easy to manufacture beforehand. It can be manufactured for stock or individually for each initial melting and it does not contain very large amounts of gold, i.e. about 0,7 kilograms.

A gold staff 9 extends into a gold melting mould 1 through a chilling mould 2. Its end protruding from the chilling mould 2 is connected for example by means of a bolt 8 to a pull rod 4, made from a non-precious metal, for example steel or iron, and driven by way of drive rollers 5 and guide rollers 6 steadily from the mould 1 , 2 downwards.

The operation of an apparatus of the invention is similar to that of the prior known apparatus, i.e. as soon as the solid metal in the melting mould 1 has melted, the drive rollers 5 are started for moving the gold staff 9 and the pull rod 4 coupled therewith by means of the junction 8 slowly downwards, carrying molten metal 3 along from the melting mould into the chilling mould 2.

Being made of graphite, the melting mould 1 and the chilling mould 2 are not able to withstand mechanical stresses. For this reason, the pull rod 4 is designed to be cruciform in cross-section and, respectively, the drive rollers 5 are designed to be slot- or groove-shaped 11 in terms of the central periphery thereof. The groove 11 has a depth which is at least equal to the height of the arm of the pull rod 4. The guide rollers 6 are designed in a corresponding fashion. In terms of its shape, the emerging gold shaft corresponds primarily to the opposite pairs of arms of the pull rod 4, such that the pull rod 5 adheres also to the gold shaft.

When the melting process in an apparatus of the invention is completed, the pull rod protruding from the melting mould is severed by means of a hydraulic cutter immediately below the chilling mould. Thus, only a small section of the gold shaft will be left in the apparatus, i.e. the section which extends from the bottom of the melting mould 1 to below the chilling mould 2. When the subse- quent melting cycle is commenced, the end of the shaft protruding from the melting mould 1 is drilled to form a hole for the fastening bolt 8 of the pull rod 4. The pull rod 4 is set in its position through the drive rollers 5 and the guide rollers 6 and secured to the gold shaft 9 present in the apparatus. In preparation for drilling the shaft, a backing block (not shown) is placed behind the shaft, such that the graphite moulds 1 and 2 do not experience any torsion during the course of drilling, which might damage the moulds. When the pull rod is secured, the melting process can be initiated by supplying the melting mould with material to be melted, which may comprise previously weighed gold, pieces of gold, residual gold, pieces of residual gold, alloying materials, e.g. copper, platinum, silver etc.

Thus, the apparatus of the invention is capable of achieving an accurately predetermined gold content for a gold bar or shaft, in addition to which the section of gold shaft left in the apparatus is relatively small, its length being about 15 cm (or about 700 g of gold), while in the prior known apparatus, the length of a gold shaft left in the apparatus can be 50 cm, which is equivalent to as much as two kilograms of gold. Leaving such an amount of material in the apparatus is uneconomical due to high costs, particularly when is used infrequently.

Claims

1. A melting apparatus for gold, comprising a gold melting mould (1) with a bottom orifice, and a chilling mould (2) linked therewith for chilling the gold melted in the mould and possible additives, said chilling mould (2) having a discharge orifice which matches the diameter of a shaft extracted from the apparatus, and said chilling mould being provided with a pull rod (4) extending all the way to the melting mould (1) and one end thereof extending all the way to drive rollers (5) of the apparatus, characterized in that the pull rod (4) is divided in two sections, whereof a section (9) extending into the melting mould (1) consists of gold or an alloy thereof and its end protruding from the chilling mould (2) is by way of a link element (8) connected to the pull rod section, which can be some base metal or the like and which is in contact with the drive rollers (5).

2. A melting apparatus as set forth in claim 1, characterized in that the pull rod element (4) is cruciform in cross-section and around the central circumference of the drive rollers (5) extends a groove (11), having a depth which is at least equal to the height of the arm of the pull rod element.