In a wire galvanization apparatus, metallic wires are drawn through a molten metal bath, such as a molten zinc, zinc alloy or aluminum bath, in order to form a metal coating on the surface of the wire. As the surface of the molten metal bath is in contact with air, a thick tough stringy oxide skin forms thereupon.

Besides, metal dross and dirt float upon the surface of the molten metal bath.

Hence, one of the difficulties of galvanization is to prevent entrainment of oxides, zinc dross or dirt with the molten metal coating on the wire; which would result in so-called lumps or other irregularities in the metal coating.

Australian Pat. 11,542/70 discloses a process and apparatus for hot dip coating of a ferrous base wire with a metallic coating. The wire is pulled upwardly and emerges from the molten metal bath into a vertical tube partially submerged in the molten metal bath. The upper portion of the tube has an annular groove communicating with the interior of the tube by means of a plurality of radially spaced, downwardly angled passages. A non-oxidizing gas is blown into the tube through these passages in the tube, where it prevents the oxidation of the surface of the molten metal bath and of the molten metal coating on the wire.

US Pat. No. 4,287,238 relates to a protective atmosphere gas wiping apparatus.

A wire drawn from a molten metal bath is enclosed in a gas hood as it passes from the molten metal bath to a gas wiping die connected to the gas hood. The gas hood is supplied with an inert or effectively inert gas, which serves to protect the surface of the molten metal coating from oxidation until it reaches the wiping die. A portion of the surface of the molten metal bath is also enclosed within the hood to prevent the formation of an oxide skin or scum upon the surface of the molten metal.

The above mentioned protective chambers, i. e. the tube and gas hoods, provide a fair protection of the emerging wire against oxides and dross or other dirt floating on the surface of the bath for the emerging wire, but are complex and space consuming. In production conditions, a row of protective chambers has to be installed over the bath, in order to coat a series of wires simultaneously from the same molten zinc bath. Each wire is consequently individually drawn in its respective protective chamber. It is clear that the row of protective chambers is rather complex and space consuming. Indeed, each protective chamber has to be attached to a support. Furthermore, a certain clearance is required between two consecutive protective chambers in order to allow maintenance. It follows that the lack of compactness of these protective chambers is responsible for wide galvanization lines, with respect to the number of wires drawn.

Object of the invention Consequently, there is a strong need for a more compact wire coating appara- tus for simultaneously coating several wires from a same molten metal bath, wherein the wires drawn from the bath are nevertheless protected against entrainment of oxide skin and dross floating on the surface of the molten metal bath. According to the present invention, this is achieved by an apparatus according to claim 1.

General description of the invention In accordance with the present invention, a wire coating apparatus comprises a molten metal bath and means for drawing n (n22) wires in parallel through said molten metal bath. According to an important aspect of the invention, a massive block, partially submerged in the molten metal bath, has at least n channels therein, each wire being drawn out of said molten metal bath through one of said channels.

A massive block comprising n channels simplifies the structure of former installations using protective chambers such as the above mentioned gas hoods or tubes. Therefore, the apparatus of the invention provides a compact, but

nevertheless efficient, protection against entrainment of oxides, dross and other dirt floating on the surface of the molten metal, for wires being drawn simultaneously from the same molten metal bath. The channels can be very close to each other, without requiring any individual supporting means. The distance between two consecutive wires no longer depends on the necessary clearance distance needed for maintenance. If the distance between two consecutive wires can be reduced, the number of wires coated per bath can be increased. Therefore, the compactness of the apparatus of the invention permits to draw a great number of wires simultaneously from the same molten zinc bath. Moreover, for a given width of a molten metal bath, a greater number of wires can be drawn than with the former protective chambers; hence in- creasing productivity. Another advantage of the invention is the simplicity of its installation, since a massive block having several channels therein is easier to install than a series of individual protective chambers.

It will be noted that the cross-section of a channel is several times larger than the cross-section of the wire passing therethrough. It follows that there is sufficient clearance to avoid contact between the wire and the channel walls, and that the molten metal level will not rise in the channel. In other words, the molten metal level in the channel is substantially the same as outside, in the molten metal bath.

Advantageously, the surface of the massive block in the channel is designed so as to be not wetted, or only slightly, by the molten metal. This means that the adhesion between the molten metal and the channel walls is extremely poor.

Hence, the coating process is not influenced by the presence of the channel walls.

Means for generating a gas flow of a preferably inert gas in the channel are advantageously provided. The gas flow creates a protective atmosphere for the emerging wire and the surface of the molten metal bath in the channel.

The massive block is preferably provided with a slot for each of the channels, which is partially submerged in the molten metal bath and opens from the exterior of the massive block into the channel. The gas flow introduced into the

channel impinges on the molten metal surface and creates a surface flow of molten metal from the channel to the exterior of the massive block through the slot. Should oxide be formed in the channel upon the surface of the bath, it would be carried away with the surface flow of molten metal. As the slot is partially submerged in the molten metal bath, the surface flow of molten metal is insured for normal, production-related level variations in the molten metal bath.

Advantageously, the slot extends over the whole height of the block, so that the wire can be introduced laterally through the slot into the channel. Thus, a wire can be introduced very easily through this slot ; this saves time when introducing a new wire into the coating apparatus.

Preferably, the means for generating a gas flow comprises a gas wiping nozzle partially introduced in the channel. The gas wiping nozzle is firstly used to wipe the wire coated with molten metal in order to control the thickness and surface aspect of the molten metal coating. Secondly, the gas blown in the gas wiping nozzle fills the channel and thereby provides a gas flow of non-oxidizing gas for a protective atmosphere surrounding the emerging wire and the molten metal bath in the channel. Finally, the gas flow issuing from the gas wiping nozzle impinges on the surface of the molten metal bath and creates a surface flow of molten metal from the interior of the channel to the exterior of the massive block.

If the molten metal coating bath consists predominantly of zinc, then the massive block may be made e. g. of AI203, which is slightly wetted by molten zinc.

Advantageously, a support is installe above the block in such a way that buoyancy presses the massive block against the support.

Detailed description with respect to the figures The present invention will be more apparent from the following description of a not limiting embodiment with reference to the attached drawings, wherein Fig. 1: is a front-view of a preferred embodiment of a wire coating apparatus ;

Fig. 2: is a section AA of the apparatus of Fig. 1 ; Fig. 3: is a top view of a channel; Fig. 4: is a section BB of the apparatus of Fig. 1.

In the figures, the same reference signs indicate identical or similar elements.

Fig. 1 shows a preferred embodiment of a wire coating apparatus 10 according to the invention. A horizontal dot-dashed line 12 represents the level of a molten zinc bath 14, which could as well be another molten metal bath, such as e. g. molten zinc alloy or aluminum. Four wires 16, identified by their axes (vertical dot-dashed lines), are drawn from the molten zinc bath 14 by schematically represented drawing means 18. Each wire 16 is pulled upwardly, emerging from the molten zinc bath 14 in a massive block 20, which is partially submerged in the molten zinc bath 14. As can be seen from Fig. 1,2 and 4, the massive block 20 is a rectangular parallelepiped.

Fig. 4 shows a section BB of the apparatus of Fig. 1. The massive block 20 has four vertical channels 22, each of the wires 16 being drawn out of the molten zinc bath 14 through one channel 22. It will be understood that only a portion of the massive block 20 is shown, and that there can be more than four wires 16 and thence more than four channels 22. This view clearly shows that two channels 22 can be very close to each other. This is possible as the channels 22 are in a same structure, i. e. the massive block 20, and that they don't require individual supporting means to be installed over the molten zinc bath 14. Each channel 22 also has a partially submerged vertical slot 24, which extends over the whole height of the massive block 20 and opens from the exterior of the massive block 20 into the channel 22.

Fig. 2 illustrates a section AA of the apparatus of Fig. 1. A wire 16, represented by its axis, is drawn from the molten zinc bath 14 through one channel 22.

Different parts of the massive block 20 are graphically distinguished: the patterned part 26 is in the cutting plane; next to this patterned part is the channel 22, which is a cylindrical surface; and then is another plane, slightly in the back compared to the patterned part, which indicates the vertical slot 24. As can be seen, the level 12 of molten zinc in the channel 22 is substantially the

same as in the molten zinc bath 14. This is firstly due to the fact that the channel 22 has a diameter which is several times the diameter of the wire 16 which is drawn from the molten zinc bath 14. Secondly, the massive block 20 is made of Al203, and is therefore only slightly wetted by molten zinc; disrupting phenomena on the surface of the molten metal bath 14, due to adhesion on the channel 22 walls, and resulting in uneven molten zinc coating on the emerging wire 16 are thereby avoided.

The massive block 20 is installe under a support comprising a vertical shaft 28 (partially shown), and a horizontal arm 30, adjacent to the surface of the molten zinc bath 14, connected to the lower end of the shaft 28. Since the massive block 20 is partially submerged in the molten metal bath 14, it is pressed against the arm 30 due to buoyancy. Reference 32 generally indicates a gas wiping nozzle having a circular throat 34 with an annular gas slit 36 therein. A gas duct 38 is installe in the arm 30 and supplies nitrogen to a distribution chamber 40 in the gas wiping nozzle 32; the nitrogen then circulates in the distribution chamber 40 and is blown in the throat 34 through the annular gas slit 36. As for the channels 22, one gas wiping nozzle 32 is provided for each wire 16. The gas wiping nozzles 32 are installe in the arm 30, through vertical holes prolonging the channels 22 in the support. The gaz wiping nozzles 32 protrude into the channels 22, thus stopping the massive block 20 from lateral shifting. In other words, due to the protruding lower part of the gas wiping nozzle 32 and to buoyancy, the massive block 20 is immobilized without any attachment means.

In operation, a wire 16 is drawn upwardly from the molten metal bath 14 and emerges through the channel 22; then the wire 16 enters the throat 34 of the gas wiping nozzle 32, where the metal coating is wiped by the nitrogen blown through the annular gas slit 36, thereby controlling the thickness and surface aspect of the coating; before the wire 16 finally exits the throat 34 of the gas wiping nozzle 32. Fig. 3 is a topview of a channel 22, which shows the interior of the channel 22 in operation. It shall be noted that the gas blown in the gas wiping nozzle 32 passes at least partially in the channel 22, where this nitrogen gas flow serves as protective atmosphere. The gas flow issuing from the gas

wiping nozzle 32 also impinges on the surface of the molten metal bath 14 in the channel 22, and thereby creates a surface flow of molten metal from the interior of the channel 22 to the exterior of the massive block 20, through the slot 24; this is illustrated by the arrows 42. The surface flow of molten metal is even more easily obtained due to the fact that Api203 is a material which is only slightly wetted by molten zinc, hence offering a poor adhesion to molten zinc onto the walls of the channel 22. This renewal of the molten zinc surface in the channel 22 is of great advantage since the molten zinc on the surface is thereby always fresh, of a fluid consistence, and oxide-free. Should any oxide or zinc dross particle be in the channel 22, it would readily be evacuated out of the channel 22 by the surface flow of molten zinc created by the gas flow. This is illustrated in Fig. 3, where zinc dross particles 44 are carried out of the channel 22 by the surface flow of molten zinc.

Turning now to Fig. 1, it should be noted that the massive block 20 is herein used with a vertical slot 24 extending over the whole height of the massive block 20. One could also use a shorter slot, which is partially submerged in the molten metal bath 14 but does not extend to the whole height of the massive block 20. Indeed, a partially submerged slot 24 is of great interest since the surface flow of molten metal can thereby be guaranteed, even when the level in the molten metal bath 14 varies. However, the vertical slot 24 represented on Fig. 1 is also very handy for inserting the wire 16 into the channel 22. As showed, the arm 30 also has a vertical slot 46, prolonging the slot 24; it is thereby possible to readily introduce a wire 16 into both massive block 20 and support.

It should be noted that it is possible to apply a non-wetting lining on the channel 22 walls instead of manufacturing the massive block 20 from a material which is not wetted by the molten zinc bath 14.