GB1601925A

GB1601925A - Production of filamentary material

Info

Publication number: GB1601925A
Application number: GB26086/77A
Authority: GB
Original assignee: Johnson & Nephew Ambergate Ltd
Current assignee: Johnson & Nephew Ambergate Ltd
Priority date: 1977-06-22
Filing date: 1977-06-22
Publication date: 1981-11-04
Also published as: AU519902B2; ZA783552B; ES475455A1; NO782136L; SE7807138L; BE868321A; IE781244L; CA1090527A; DE2827731A1; FI781985A; DK277378A; CH623495A5; IT1096799B; ES470985A1; LU79858A1; NL7806674A; IE46939B1; AU3741978A; PT68202A; FR2395090A1

Abstract

A vessel (20) has the shape of a sector of a right cylinder and pivots about a horizontal axis (25) coinciding with the top of this sector. The pivoting of the vessel is effected by means of a rack (27) and pinion (28). Removable heating means (30) are provided in order to maintain the temperature of the molten metal. During operation, the vessel (20) is filled with molten metal to a level (22a). The rotary extraction drum (21) is lowered inside. The pinion (28) is driven in rotation in the direction of the arrow (A), the surface of the metal (22a) is brought into contact with the drum (21) and the production of the metal filament (34) commences and continues until the quantity of metal contained in the vessel (20) is reduced to a critical level. The filament obtained is used for reinforcing concrete. <IMAGE>

Description

(54) IMPROVEMENTS IN OR RELATING TO THE PRODUCTION OF FILAMENTARY MATERIAL (71) We, JOHNSON & NEPHEW (AM- BERGATE) LIMITED, a British Company of Ambergate Wire Mills, Ambergate, Derby, DE5 2HE, do hereby declare the invention, for which we pray that a patent may be granted to us, and the method by which it is to be performed, to be particularly described in and by the following statement:- The present invention relates to a method and apparatus for producing metal filament, wire, strip, sheet, fibre or the like hereinafter referred to collectively as metal filament.

It is known to produce metal filament from molten metal by using extraction means forming the metal filament by contact with the surface of molten metal held in a vessel.

Examples of such an extraction means are a drum, disc or wheel, (preferably internally cooled) capable of rotating with a peripheral edge in contact with the molten metal so that the metal in contact with the edge is cooled and ejected as metal filament. This basic technique is illustrated in U.K. Patents Nos.

1,396,788, 1,448,494, 1,435,990 and 1,455,705.

The peripheral surface of the extraction means may be smooth or alternatively may be peripherally grooved to provide a plurality of edges for simultaneously producing a like plurality of metal filaments from the molten metal. Alternatively or additionally the edge may be notched so that staple filament is produced rather than a continuous length.

It has been found that solid material of substantially uniform cross section can be produced on a continuous or semi-continuous basis providing the depth of immersion of the extraction means can be maintained constant.

This has previously been achieved by lowering the extraction means into a furnace or crucible full of molten metal at a rate which maintains the immersion depth constant as the level of molten metal in the furance or crucible falls, or by raising the furance or crucible vertically at a similar rate towards the fixed extraction means. These methods can only produce filament or strip material so long as the path of the ejected fibres or strip does not strike the edge of the furnace or crucible.

Alternatively, it has been found possible to fix the relative position of the extraction means above a melting furnace in such a way that when the furnace is full the extraction device is immersed to the correct depth, and then to maintain the level of the metal in the furnace by continuously feeding solid elongate material of the desired composition at a rate equal to the rate of extraction of the extraction means. In this way, material may be extracted continuously for long periods limited only by the life of the furnace refractory lining, which suffers severe erosion in the region of the substantially constant level to which the furnace is charged.

This method suffers, however, from a number of disadvantages. Firstly the feed stock governs the composition of the product, and it is not possible to produce filaments or strip of a composition which is not available in elongated stock. Secondly, the rod must be melted in the furnace and the heating methods used to ensure this melting, e.g. induction heating, often create turbulence with results in a non-constant immersion depth for the extraction means and therefore adversely affects the quality of product produced.

It is therefore an object of the present invention to obviate or mitigate the abovementioned disadvantages.

According to a first aspect of the present invention there is provided apparatus for producing metal filament (as hereinbefore defined) comprising a pivotal vessel for holding molten metal, extraction means for producing metal filament by contact with the surface of molten metal held, in use of the apparatus, in the vessel, and means for pivotally moving the vessel to displace the surface of the molten metal towards the extraction means.

According to a second aspect of the invention there is provided a method of producing metal filament (as hereinbefore defined) with an extraction means forming metal filament by contact with the surface of molten metal held in a vessel wherein the vessel is pivotally moved to maintain the contact between the molten metal surface and the extraction means.

The invention is applicable particularly to the use of rotary extraction means such as an internally cooled disc, drum or wheel of the type described above which produces metal filament having a thickness dependent on the immersion depth of the extraction means.

Whatever the nature of the extraction means used the important feature of the invention is the pivotally movable molten metal holding vessel. This vessel is such that pivotal movement thereof causes molten metal to be displaced towards the extraction means so that said extraction means may continue to produce metal filament whilst the molten metal charge in the vessel is depleted due to the production of metal filament. The shape of the vessel, and the positioning of the extraction means, should be such that the metal filament may be continuously thrown externally of the vessel without hindrance from the vessel walls.

The vessel itself it preferably of such configuration that, when it is in a position in which it is capable of holding a full charge of molten metal, the inner surface of its base is inclined with respect to the horizontal in a direction which is downwardly and away from the axis about which the vessel pivots.

For such a vessel the extraction means will be located proximate the pivot axis so that upward pivotal movement of the vessel ensures that the extraction means are continuously supplied with molten metal. Preferably the wall of the vessel at the deeper end thereof is arcuate in a vertical section and the pivot axis substantially coincides with the center of curvature of the wall. An example of such a vessel is an open-topped vessel having the form of a segment of a right circuit cylinder and having a horizontal pivot axis which substantially coincides with the apex of the segment. Such a vessel may, if desired, be depended at its pivoted end without detriment, in which case it is still preferred that pivotal movement of the vessel is centred at the centre of radius of the curved surface remote from the pivot.

The vessels described above are of such geometric design that pivotal movement thereof at a constant rate displaces molten metal at a constant rate to the extraction means. Alternatively if the vessel is not so geometrically designed the rate of pivotal movement may be varied so that there is still a constant rate of displacement of molten metal towards the extraction means.

The extraction means are preferably movable away from the vessel to facilitate filling thereof with molten metal. Preferably also auxiliary heating means are provided for the vessel for ensuring that the melt is maintained at a suitable constant temperature for production of filament. The heating means, which are also preferably movable to facilitate charging of the vessel, may be, for example, carbon electrodes for striking an arc onto the surface of the melt, electrodes for striking a heating arc above the melt, an electric plasma heating device, an induction coil built into a refractory lining of the vessel, or conventional burners.

During the method of producing the metal filament, the vessel is progressively depleted of molten metal and the pivotal movement, and extraction operation, is continued until shortly before the vessel is completely emptied. The operation or arresting the pivotal movement may be effected either manually by an operator or by a suitable automatic limit switch.

In order to refill the vessel, the extraction means (and auxiliary heating means if fitted) may be removed, the vessel returned to the starting position, and subsequently filled either by positioning it below the pouring spout of any conventional melting furnace or crucible or by means of a ladle supplied by a melting unit feeding several vessels.

The invention will be further described by way of example with reference to the accompanying drawings in which: Figs. la--e diagrammatically illustrate the method in accordance with the invention; Fig. 2 is a sectional side view of one embodiment of apparatus in accordance with the invention.

Referring to Figs. la--c, an apparatus for producing metal filament comprises a vessel 1, which is open-topped and in the form of a segment of a right circular cylinder pivoted about an axis 2 at the apex of the segment, and a rotary extraction wheel 3 for producing metal filament the thickness of which is dependent on the depth of immersion of the wheel 3 in molten metal 4.

Fig. la shows the vessel 1 substantially completely charged with molten metal 4 and the extraction wheel 3 producing filament 5 therefrom.

As the extraction operation continues, the vessel 1 is pivoted at a controlled rate in the direction of arrow 6 so that the extraction wheel 3 continues to be immersed to the same depth in the molten metal 4, thereby producing filament of substantially constant cross-section. Fig. lb shows an intermediate position of the vessel 1, in which approximately one half the original metal charge has been used and Fig. lc shows the vessel 1 practically depleted of metal. It is near the stage shown in Fig. lc that the extraction operation would be discontinued and the vessel would be recharged.

Referring to Fig. 2 an apparatus for producing metal filament comprises a pivotally mounted vessel 20 and a rotary extraction drum 21 for producing metal filament from molten metal 22 held by the vessel 20.

The vessel 20, which comprises an outer steel shell 23 lined with a refractory material 24, has a front wall 20a, a rear wall 20b and two side walls 20c (only one shown). The front wall 20a is of lesser height than the rear wall 20b and, as shown in Fig. 2, the inner surface of the base of the vessel slopes downwardly away from the front wall 20a to the rear wall 20b when the vessel is in a position for receiving a full charge of molten metal. Additionally the inner surface of the rear wall 20b is arcuate in vertical section with a radius R,.

The vessel 20 is pivotally mounted by means of two axles 25 (only one shown) which are positioned such that pivotal movement of the vessel 20 is centred, or nearly so, at the centre of radius of the inner surface of the rear wall 20b. The axles 25 are supported on bearers 26 (only one shown).

The external surface of the rear wall is provided with a rack 27, having a radius of curvature R2, and a pinion 28 is provided for engagement with the rack 27 to effect pivotal movement of the vessel 20. The pinion 28 may be supported at the required height, e.g.

by means of bearers 29.

A removable auxiliary heating device 30 is provided over the vessel 20 and comprises two graphite electrodes 31 (only one shown) carried in electrode holders 32. The electrodes 31 are used for direct arc heating to maintain the molten metal charge at the required temperature and the heating device 30 includes a hood 33 for minimising heat loss.

In operation the vessel 20 is filled with molten metal 22 to level 22a. The rotating extraction drum 21 is lowered into any suitable position which may be fractionally above the molten surface 22a but must be nearer to the axle 25 than to the radiussed end of the vessel 20. Once the vessel 20 is filled and pinion 28 is rotated at a controlled rate in the direction of arrow A, the metal surface 22a will be brought into contact with the rotating drum 21 and extraction to produce metal filament 34 will commence and continue (provided the pinion 28 is rotated) until the amount of metal in the vessel 20 is reduced to a critically low level.

However, emptying the vessel below the level represented by the radius joining the pivot axis to the base of the lowermost portion of the arcuate rear wall 20b of radius R, (i.e. point B in Fig. 2) will result in nonuniform displacement of the metal for a constant rate of deflection of the vessel giving a consequent thinning of the filament. In the drawing, this critical level is that represented by the illustrated radius R2.

Once the metal charge has been reduced to the desired minimum level, the vessel 20 may be returned to the starting position and, after removal of the drum 21 and heating device 30, be recharged with molten metal.

The invention has the advantage that batches of filament of any desired composition may be produced semi-continuously without the need for accurately moving the extraction device or raising a complicated and heavy furnace.

Additionally, the metal stock to be melted for producing the filament need not be excessively cleaned since any impurities may be slagged-off in the melting furnace before the melt is transferred to the extraction vessel.

WHAT WE CLAIM IS: 1. Apparatus for producing metal filament (as hereinbefore defined) comprising a pivotal vessel for holding molten metal, extraction means for producing metal filament by contact with the surface of molten metal held, in use of the apparatus, in the vessel, and means for pivotally moving the vessel to displace the surface of the molten metal towards the extraction means.

2. Apparatus as claimed in claim 1 wherein the extraction means is a rotary extraction means.

3. Apparatus as claimed in claim 2 wherein the rotary extraction means is an internally cooled drum, disc or wheel.

4. Apparatus as claimed in any on of claims 1 to 3 wherein the vessel is such that pivotal movement thereof at a constant rate will effect a substantially constant rate of displacement of molten metal surface to the extraction means.

5. Apparatus as claimed in any one of claims I to 4 wherein the vessel has a wall which is arcuate in vertical section, and the centre of curvature of the wall substantially coincides with the axis about which the vessel pivots.

6. Apparatus as claimed in claim 5 wherein the vessel is an open-toppped vessel in the form of a sector of a right circular cylinder and the pivot axis of the vessel substantially coincides with the axis of the apex of the sector.

7. Apparatus as claimed in any one claims 1 to 6 wherein the means for pivotally moving the vessel is a rack and pinion arrangement.

8. Apparatus as claimed in any one of claims 1 to 7 wherein heating means are provided for maintaining the temperature of molten held, in use of the apparatus, in the vessel.

**WARNING** end of DESC field may overlap start of CLMS **.

Claims

**WARNING** start of CLMS field may overlap end of DESC **. stage shown in Fig. lc that the extraction operation would be discontinued and the vessel would be recharged. Referring to Fig. 2 an apparatus for producing metal filament comprises a pivotally mounted vessel 20 and a rotary extraction drum 21 for producing metal filament from molten metal 22 held by the vessel 20. The vessel 20, which comprises an outer steel shell 23 lined with a refractory material 24, has a front wall 20a, a rear wall 20b and two side walls 20c (only one shown). The front wall 20a is of lesser height than the rear wall 20b and, as shown in Fig. 2, the inner surface of the base of the vessel slopes downwardly away from the front wall 20a to the rear wall 20b when the vessel is in a position for receiving a full charge of molten metal. Additionally the inner surface of the rear wall 20b is arcuate in vertical section with a radius R,. The vessel 20 is pivotally mounted by means of two axles 25 (only one shown) which are positioned such that pivotal movement of the vessel 20 is centred, or nearly so, at the centre of radius of the inner surface of the rear wall 20b. The axles 25 are supported on bearers 26 (only one shown). The external surface of the rear wall is provided with a rack 27, having a radius of curvature R2, and a pinion 28 is provided for engagement with the rack 27 to effect pivotal movement of the vessel 20. The pinion 28 may be supported at the required height, e.g. by means of bearers 29. A removable auxiliary heating device 30 is provided over the vessel 20 and comprises two graphite electrodes 31 (only one shown) carried in electrode holders 32. The electrodes 31 are used for direct arc heating to maintain the molten metal charge at the required temperature and the heating device 30 includes a hood 33 for minimising heat loss. In operation the vessel 20 is filled with molten metal 22 to level 22a. The rotating extraction drum 21 is lowered into any suitable position which may be fractionally above the molten surface 22a but must be nearer to the axle 25 than to the radiussed end of the vessel 20. Once the vessel 20 is filled and pinion 28 is rotated at a controlled rate in the direction of arrow A, the metal surface 22a will be brought into contact with the rotating drum 21 and extraction to produce metal filament 34 will commence and continue (provided the pinion 28 is rotated) until the amount of metal in the vessel 20 is reduced to a critically low level. However, emptying the vessel below the level represented by the radius joining the pivot axis to the base of the lowermost portion of the arcuate rear wall 20b of radius R, (i.e. point B in Fig. 2) will result in nonuniform displacement of the metal for a constant rate of deflection of the vessel giving a consequent thinning of the filament. In the drawing, this critical level is that represented by the illustrated radius R2. Once the metal charge has been reduced to the desired minimum level, the vessel 20 may be returned to the starting position and, after removal of the drum 21 and heating device 30, be recharged with molten metal. The invention has the advantage that batches of filament of any desired composition may be produced semi-continuously without the need for accurately moving the extraction device or raising a complicated and heavy furnace. Additionally, the metal stock to be melted for producing the filament need not be excessively cleaned since any impurities may be slagged-off in the melting furnace before the melt is transferred to the extraction vessel. WHAT WE CLAIM IS:

1. Apparatus for producing metal filament (as hereinbefore defined) comprising a pivotal vessel for holding molten metal, extraction means for producing metal filament by contact with the surface of molten metal held, in use of the apparatus, in the vessel, and means for pivotally moving the vessel to displace the surface of the molten metal towards the extraction means.

9. Apparatus as claimed in any one of

claims I to 8 wherein the extraction means is located proximate the axis about which the vessel is pivotal.

10. A method of producing metal filament (as herein before defined) with an extraction means forming metal filament by contact with the surface of molten metal held in a vessel wherein the vessel is pivotally moved to maintain the contact between the molten metal surface and the extraction means.

11. A method as claimed in claim 10 wherein the extraction means is a drum, disc or wheel rotating about a substantially horizontal axis with its lower most peripherial edge partially immersed in the molten metal surface, and the vessel is pivotally moved at a rate such that the immersion depth of said edge is maintained substantially constant thereby to produce filament of substantially constant cross-section.

12. Apparatus for producing metal filament (as hereinbefore defined) substantially as hereinbefore described with reference to Fig. 1 or Fig. 2 of the accompanying drawings.

13. A method of producing metal filament (as hereinbefore defined) substantially as hereinbefore described with reference to Fig. 1 or Fig. 2 of the accompanying drawings.