US2072060A - Wire coating process and apparatus - Google Patents

Description

ATTORNEY Feb. 23, 1937. R. w. scHuLTz WIRE CvOATING PRCESS AND APPARATUS 4 sheets-sheet 1 Filed Aug. 15, 1936 Feb. 23, 1937. R. w. sc HULTZ 2,072,060

WIRE COTING PROCESS -AND APPARATUS Filed Aug. 13. 1936 4 Sheets-Sheet 2 Ll iV WW BY M Feb. 23, 1937. R. w. scHULTZ l 2,072,060

WIRE COATING PROCESS AND APPARATUS INVEN TOR.

/Q ATTORNEY `Feb. 23, 1937. R. w. scHULTz WIRE COATING PROCESS AND APPARATUS Filed Aug. 13, 1956 4 Sheets-Sheet 4 Patented Feb. 23, 1937 UNITED STATES PATENT OFFICE Randall W. Schultz, Williamsport, Pa., assgnor to Metalloys Company, Williamsport, Pa., a corporation of Pennsylvania Application August 13, 1936, Serial No. 95,939

Claims.

In applying protective metallic coatings, such as zinc, lead, tin. cadmium, aluminum, etc., to other metal articles, such as wire, bars, strips, etc., it is very desirable to have the'coating as s pure as possible and unalloyed with the metal of the coated article. It is also desirable to control the thickness, or weight, of the coating. In some cases it is also desirable to have a coating that is very heavy, and this is practically impossible with 10 present commercial methods of applying protective coatings.

In the field of work to which my invention applies; namely, the coating of wire, rods, bars, strips, etc., the two most generally used processes l5 are electrical deposition and thehot dip process.

The former is used to only a very limited extent,

due to the slowness of the operation and the consequent cost of the process. The hot dip" process is the one most generally employed in commercial practice; but as this is performed at the present time, it has some very serious drawbacks.

It is impossible to obtain a relatively thick pure coating of one metal on another by the hot dip" process. This can be readily understood once this process is carefully analyzed. In any hot dip process the thickness, or weight, of the coating is a function of the time of immersion, and the temperature of the coating bath. The actual process of coating proceeds gradually and in no case is o the applied coating of pure metal throughout the entire thickness of the coating. Upon first entering a bath of coating metal, the article to be coated, for instance, a steel wire, is brought up to nearly the same temperature as the coating bath. As the outer surface of the Wire reaches the temperature of the coating both, the coating metal gradually penetrates and alloysA with the base or coated metal. As the temperature of the bath gradually penetrates into the metal which is be- 40 ing coated, the alloy penetration proceeds likewise, and the total depth of the penetration depends principally on the time the article being coated is submerged. Such a coating, analysis shows, is not of pure coating metal throughout the thickness of the coating, but is an alloy, ranging in composition gradually from base metal within to substantially pure coating metal without. The inner portion of the coating will be preponderantly of the base metal, but the composition will change gradually until, atrthe outer surface, the coating will be found to be a. skin" of practically pure coating metal.

In some cases, the coating applied by the hotdipprocess is very unsatisfactory. For instance,

where the coated article is subject to corrosion,

(Cl. .Z2-57.2)

because its resistance to chemical action is weakened by /the fact that the alloy will not withstand attack by corrosion as well as the pure coating metal. Again in some cases, where the coated article is continually being bent or twisted, as for instance in steel wire rope, the alloy formed by the hot dip process will spall or crack oi from the coated article, due to the fact that the alloy formed from the base metal and the coating metal is in all cases much harder and more brittle than the pure coating metal.

Numerous attempts have been made to improve the hot process method of applying protective coatings. Most of'these have used dies in one form or another to flow the coating metal on to the article being coated. These past attempts have not been entirely successful. In some cases,

lit hadbeen impossible to apply the coating uniformly and evenly, especially on round wire, as the wire could not be accurately centered in the coating die. However, the main reason for failure when using dies has been due to the coating metal oxidizing in the die. It is a well known fact that metals, such as tin, zinc, lead, etc., which are mostly used as protective coatings for other metals, oxidize and rapidly form dross at the temperature used. This accumulates on the dieand around the orifice thereof, and interferes with the coating by reducing the effective size of the orifice therein.

The object of my invention is to coat objects of the character specified by casting the coating metal in a die around the wire, bar, strip, or other form, either directly or by means of an intermediate coating; the coating being effected under such condition that oxidation, and the consequent formation of dross is practically or entirely avoided. l This invention involves a method or process for accomplishing the result stated; and a mechanism or apparatus for carrying out the method or process. Broadly stated, the method involves the removal of air from about the casting die, and the drawing of the metal through the die around the article being coated, thus making impossible the oxidization referred to, and at the same time producing an easier and more uniform ow of metal through the casting die than is possible with any pressure system of casting. 'I'he machine or apparatus comprises means by which the suction, and consequent removal of air from around the die, and iiow of the coating metal, is effected.

I have illustrated the best means for practicing my invention, as it would be applied to the coating of round wires, but the invention is not limited to the coating of wires, and the character of the dies and other features will be determined` Fig. 5 is a plan view of the coating machine..

likewise partly broken away.

Fig. 6 is an enlarged partial sectional view on the line 6 6, Fig. 5, looking in the direction of the arrows.

Fig. '1 is Aa partial sectional view on the line 1 1, Fig. 6, and showing particularly the valves by which the flow of molten metal to the casting dies is controlled.

Fig. 8 is a sectional view on the line 8 8Flg. 6, and looking in the direction of the arrows.

Fig. 9 is a sectional view on the line 9 9, Fig. 8, and showing the ejector in section.

Fig. 10 is a sectional view onL the line III-III, Fig. 7,'and showing the die holder in section.

Fig. 11 is an enlarged view of the die holder, dies and associated parts of Fig. 10.

Fig. 12 is a detail view o! the pump used to supply the ejector.

Generally speaking, the wire, or the other object to be coated, is iirst thoroughly cleansed, then passed through a preheating and preliminary coating bath, and then, while still hot, passed directly to the die casting devices, at which point the iinal coating metal is applied around the moving wire. 'I'he coated wire is then immediately cooled and wound on spools or otherwise disposed of.

As here disclosed, the suction or vacuum forming device is an ejector, through which oil, water or other suitable uid is forced around the die.

'This notonly removes the air from around the die, and produces the necessary vacuum, but also cools the coated wire as it emerges from the die. Of course, any other suitable vacuum producing means may be used.

As here illustrated, the mechanism or apparatus is provided with means for simultaneously coating four separate wires; but since each set of elements is a. duplicate of the others, a description of one will suffice forl all.

In the accompanying drawings, to which reference is here made, the wire or other shape t`o be coated I is taken from any suitable source as a reel (not shown). It is first passed through a fluxing bath II, Fig. l, beneath a roller or other guide I2, beneath a wiper guide I3 and then between rollers I4. As the wire passes through the iiux, the surface is cleansed and prepared for further operations.

From this fluxing bath, in the apparatus here disclosed, the wire is passed through an opening I into a bath I 6 of some preliminary coating metal and out through a similar opening I5'. This bath may be the same metal as that which forms the nal coating, as lead, where the iinal coating is of that metal ;\or it may be some metal which will form a true alloying bond between the wire and the metal of the iinal coating. This bath I6 is contained in asuitable tank I1, which is thoroughly heat insulated, as by the same nonheat-conducting body I8, which -in turn is retained in some suitable casing I9. This bath is heated in any suitable way, as by electric heating units 20, Fig. v2. Any suiiicient number of these heaters may be used.

Each of the several tanks I1 is provided with'a cover 2I Fig. 2, hinged in any suitable manner, as to the casing I9. These covers 2I are shown best in Fig. 2, where the one on the left is illustrated as raised andthe others as closed. Withinv the several tanks I1, the wires I 0 to be coated pass through suitable guides 22 and 23. Of these, in the apparatus here shown, 22 are stationary, while 23 are carried by the covers 2|, and are adapted to be raised and lowered with the raising and lowering of the covers. When in the lower position, the wires are held depressed i'n the molten metal. Any suitable arrangement of guides may be used, it merely being important that the wires shall be held down in the mass of molten metal.

A wiper 2l, one for each tank, removes excess molten metal from the wire as it passes out of the tank through the oulet I5 to the iinal coat ing devices.

The purpose of this bath is to bring the wire I0 to the temperature necessary for the iinal coating; and also in some cases, to coat the surface of the wire with an intermediate coating of metal, which metal may be a mere preliminary coating of the metalused for the nal coating, or a bonding metal which will alloy with both the base and the nal coating. So far, the practice is that usuallyvfollowed in the "hot dip process of coating.

Final coating The metal to be applied as the iinal coating is contained in a pot or kettle 25, Fig. 4, which is heated to the desired temperature in any suitable way, as by one or more electric heating elements 26, Fig. 5. This type of heater is immersed directly in the metal being heated; and is supplied with current through suitable connections, as by terminals 21, Fig. 5. The pot or ,kettle 25 is provided with an opening 28 in the bottom thereof, Fig. 5, through which the coating metal can ow to the casting dies. As here shown, the molten metal flows into the pipe or tube 29, Fig. 4, and thence into a horizontal manifold 30, Fig. 4, to the die casting blocks 3|, one of which is provided for each wire to be coated. One or more electric heaters 26'. having terminals 21 extend through the manifold 3 0 so as to keep the metal therein in fluid condition.

The melting pot 25 is suiliciently elevated above could be supplied for each die head 3I if desired. f

Casting devices-Each die head 3| is provided with a passage 35, Fig. 7, leading to a valve charnber 3B. This passage is controlled by valve 31, which cooperates with a valve seat 38. This valve may be operated in any suitable manner, as by handle 39 on the valve stem Unthreaded' into e Cn . shall be of uniform thickness.

a nut 4| which compresses paf 'ing 42 around the valve stem. The flow of metal from the manifold to the valve chamber 38 is controlled by opening and closing this valve.

A casting die proper 44 having an oriiice 46 together with its cooperating elements, is mounted in each die head 3|. Each head is bored to form a recess 43 threaded at 46, and shouldered at 41, Fig. 10. Within this recess is mounted a plug 48 threaded to cooperate with the threads 46 of the die head 3|, and provided with a ledge to rest on the shoulder 41 of the die head. The plug 48 is provided with a tapered opening 49 in which a die holder 50 is positioned. rIfhis opening 49 is closed by a cap 5| having an opening 52 which is threaded into the upper end thereof.

In order that liquid metal may pass from the valve chamber 36 to the casting die 44, the bore 43 in the head 3l is arranged so as to intersect the valve chamber 36 at the point 53, thus forming a communicating passage at this point. The plug 481s provided with an outer -annular channel 54, which registers with this opening 53, and an inner annular channel 55 communicating with the outer channel 54 through passages B between them.

The plug 48 is threaded and is screwed into the recess 43. This threaded connection forms a suificiently tight seal at this point, and the ledge at the lower end of the plug rests on the seat 41, thus forming a seal at this point.

As before stated, the die 44 applies the outer coating to the wire. The wire to be coated must be kept central of this die, so that he coating complish this, centering guides or dies are employed. In the apparatus here shown, two such dies are used, an upper one 51 having an oriiice 58, and a lower one 59. This die has an elonga# tion or projection on its underside in which the oriiice 60 is located, thus making it possible to bring this opening close to and directly above the center of the casting die 44, Figs. and l1.

In order to aline these guiding dies with the casting die 44 and hold them in position with re- H spect to each other, they are allenclosed in a sleeve 50, before referred to, tapered to fit more or less closely the tapered opening 49 of plug 48. This die sleeve has formed in its upper portion a series of slots 62 extending from at or near the top to near the bottom thereof; and the lower part of this sleeve is shaped to fit closely into the bottom of the tapered opening 49, and rests on a seat 63, in the bottom thereof, which is cut away at 64. As here shown, the casting die 44 is placed in the bottom of the sleeve, and rests upon the annular ledge 65. In the lower part of the sleeve, directly above the die 44, a spacing ring 66 is inserted. The lower guiding die 59 rests upon the spacing ring 66. Directly above the die 59 is another spacing ring 68, which is somewhat longer than the lower spacing ring 66; and directly above this second spacing ring 68 is another guiding die 51 having therein an orifice 58. These elements are all enclosed in the die holder 48, the casting die 44 resting on the ledge 65 in the bottom thereof, the lower spacing ring 66 resting on the die 44, the lower guiding die 59 resting on the lower spacer 66, and the second and longer spacing ring 68 resting on the guiding die 59 and the upper guiding die 51 resting on the spacer 68. The upper guiding die I 51 is seated in the screw cap 5|, which cap contains a ledge 10. By turning down this cap 5|, the ledge 10 will press on the top of the upper guiding die 51. and pressure will thus be transmitted In order to acthrough the spacer 88, lower centering die Il.

and lower spacing ring Il. to the casting' die 44,

which is thereby forced to its seat 65. Thisv arrangement forms a construction which is quick- 1y assembled, and easily disassembled for inspection, replacement of parts, or repair.

In practice, it is desirable that the wire to be coated shall pass through the coating metal, and also that coating metal shall be supplied directly above the casting die. To supply the molten metal freely, the upper spacing ring 68, is provided with slots 1|, through which molten metal can ow to the interior of the die holder and the lower spacing ring 66 with slots 12 through which molten metal can iiow directly to the casting die 44.

This arrangement of dies, and means for supplying molten metal thereto, has certain important advantages over the prior art. 'I'he guiding die 59 in effect divides the die chamber into two parts, one above the die 59 through which the wire passes for a relatively long distance through the molten metal, and one between the guiding die 59 and the casting die 44, which is relatively short.. From the casting die 44 the coated wire ypasses directly to the cooling or quenching position to be hereafter described. This arrangement gives the coating time to be thoroughly allofed with the surface of the wire while passing through the uid metal above the die 59, but gives very little time for this alloy to mix with the final coating metal as it is applied by the die 44. The result is a particularly pure iinal coating of the coating metal.

'I'his long upper chamber in the ring or sleeve 68 also tends to permit the temperature of the wire to be raised to the temperature of the coating metal, as it passes therethrough, thus causing the final coating from die 44 to flow more freely around the wire.

In or'der to maintain the casting die and its associated elements at sufficient temperature to maintain the casting metal liquid, each die head is provided with a heating means. Such aheater is shown at 15, Figs. 6 and l0. As there illustrated these heaters are electrical resistance units of ring form, which rest, `one in a recess 16 in each die head 3|. Each heater is enclosed by a heat insulating ring 11, which ring is retained in pace by other heat insulating rings 18 and 19, which are secured to the die head by suitable screws 80, or by any other suitable means. Suitable leads 8|, only onefof which is shown, Fig. 6, are used to conduct current to these heaters.

Supported on or adjacent to each of the die heads 3| is a grooved wheel 85, having its upper face in line with the outlet I5' of the preheating or` preliminary coating chamber, and its vertical face in line with the orifice in the guiding die 51, Fig. 6. This wheel is mounted for rotation in any suitable way,'as by support 86 bolted to an extension 81 of the die head. A protective casing 88 covers the wheel, and protects the wire and prevents undue radiation. The wire will thus be directed from the preheating or preliminary coating tank Ydirectly to the center of the upper guiding die 51. And since the support for the Wheel is mounted directly on the die head, the parts will not be subjected to displacement due to expansion and contraction of the parts.

Prior efforts to apply protective coatings to wire by the use of casting dies have involved difliculties. These troubles have been two-fold. First, where hydrostatic pressure alone, such as that caused by elevating the coating metalsupply, is used to cause a flow through the casting die, the coating is apparently affected by the friction and eddies of the coating metal in the ducts leading to the die opening, such as the manifold 30 and passage 35, in the drawings of this application. The flow of coating metal through such passages apparently is not continuous and uniform, and this results in thinspots, or rings, in the coating on the wire. The second trouble has been the oxidizing of the coating metal on the outgoing face of the coating die. Such oxidizing is particularly true where lead is used as the coating metal. This oxide, accumulating on the surface of the die, as for instance on the lower face of the die 44, nally protrudes over the opening in the die through which the wire passes, thus in effect reducing the size of such opening. When this happens the thickness of the coating being applied is reduced. Eventually this oxide accumulation will close off the opening in the die, and act as a wipe on the wire, -thus preventing any coating from being appliedz In my early experiments, attempts were .made to solve these difficulties; first, by the use of increased hydrostatic pressures, and, second, by the use of a non-oxidizing agent around the casting die, or by a combination of the two. None of these means were successful. The use of a reduced atmosphere, or other non-oxidizing agent, around the casting die will prevent an accumulation of oxide, and thus allow long use of the cast- `ing die without reduction in thickness of the coating on the wire, but even in such cases, and where relatively high hydrostatic pressures were used, the thin spots, or rings, were still apparent. These thin spots, or rings, which appear on the wire at very regular and uniform distances apart, are apparently due to the fact that the pressure on the coating metal applied above the die causes eddy currents in the ow, especially where the coating metal, in flowing to the die opening, passes sharp corners or bends in the manifolds. While the above is believed the cause of the im'- perfections noted, it is to be understood that the effect may have been produced in other ways.

In my invention, I overcome these difficulties by means to be now described. It is a well-known fact that flow of a fluid caused by induction is much more steady and uniform than a forced flow. This principle has been applied and used in my invention. This is done by creating a vacuum or partial vacuum at the outer face of the casting die which accomplishes two things: first, by reducing the atmospheric pressure on the outer face of die 44, the coating metal is induced to now through the opening 45, and, second, by creating a vacuum at this point, the formation of oxide is automatically prevented.

My experiments have definitely proved that the flow of coating metal through the coating die and around the wire, caused by creating a vacuum at the outer surface of die 44, is much smoother and more uniform than a flow from hydrostatic pressure alone, and that the thin spots, or rings, disappear when this method is used. `Further than this, the ,fact that oxide formation is effectively prevented, allows the coating to be applied continuously, evenly, and uniformly for long periods of time.

While any suitable means for producing a vacuum may be used, that here shown is of the ejector type; that is, the type in which streams of water, oil or other liquid or gas, are caused to converge in a restricted passage and entrain the surrounding air thus producing a vacuum, or at least a partial vacuum, around the die and within the die holder. This particular type is well suited for this use as -the stream of liquid, or gas, fioW- ing through the difusor part ||3 is used as the cooling or quenching medium to quench the coating applied to the wire by the casting die.

While some hydrostatic pressure is used in the form of my invention here disclosed to create a flow of coating metal from pot 25, to and through opening 45 in die 44, such pressure is not necessary, as flow of coating metal can be induced by the vacuum means alone.

'Ihe speed at which coatings can be applied to wire is related tof the pressure used on the coating metal, within certain limits; the higher the pressure on the coating metal, the'faster the wire can be passed through the casting die. In order to relieve the ejector of the necessity of inducing the flow through the different passages and manifolds, sufficient hydrostatic head is used to force the coating metal through these passages and up to the opening 45 in die 44. This allows the vacuum produced to work more effectively in smoothing out the flow, and also secures a higher speed of operation, without having the vacuum means unduly large.

Some flexibility in the apparatus is desirable. 'I'he delivery of coating metal to the casting die is dependent upon the static head of the metal and the vacuum produced by the suction device. As it is more practical to vary the vacuum than it is to vary the head of molten metal, I have provided means for varying the flow of the coating metal by varying the vacuum produced by the ejector. By increasing the flow of liquid through the ejector, the vacuum is raised and the flow of coating metal increased; by decreasing the flow, the vacuum is lowered and the flow decreased. Therefore, the amount of vacuum produced may be varied at will by varying the flow of fluid to the ejector.

The ejectors as a whole are indicated by the character 90, Figs. 4 and 6, and the pump for supplying the liquid thereto by 9| Fig. 1. Only one pump is here used, but of course there is one ejector for each die, and there may be a pump and ejector for each die. A pipe 92 having therein an accumulating reservoir 92' leads from the pump to the several ejectors, and the water or lother fluid which passes through the ejectors is received in any suitable reservoir as 93, whence it is returned to the pump.

The pump 9| is provided with a relief valve |06 actuated by spring |01. Pressure on this spring is supplied by nut |08, which screws into the extended portion |09 of pump 9|. This construction is standard commercial practice and needs no further description.

The structure of the ejectors is shown in connection with the other elements of the apparatus in Figs. 4 and 6. The ejector may be attached to its casting head 3| in any convenient way. As here shown, it is attached directly to the heat insulating ring 19, Fig. l0, by means of a metallic ring 94, which in turn is secured to the insulating ring 19 by means of screws 95. This ring 94 is internally threaded at 96, Fig. 9, and the body 91 of the ejector is threaded at its upper end and engages with the thread 96 of the plate 94. A seal between the casing 91 and the ring 94 is effected by the edge 98 on the body 91 engaging with the inner surface of ring 94.

The body 91 of the ejector is provided with two chambers, an upper one 99 in the form of an annulus, which communicates with the supply pipe 92, and a lower and larger one |00, which communicates with the die chamber through openings IOI, and the openings in the rings 18 and 19, Figs. 8 and 9. A cone-shaped member |02, connects the two chambers 99 and |00, and through the body of this cone is bored a series of holes |03 at an angle to the vertical, so that they converge at a point a short distance below the lower end of the cone.

The top of the chamber 99 is closed by a plug |03 having a screw threaded extension |04, by which itengages with a cooperating threaded portion of the nozzle |02. A flange extends over the top of the upper chamber 99 and rests upon the top of a casing 91, so that when the plug is screwed into its seat it will close the top of the chamber 99 with a tight t. The two chambers 99 and |00, are connected only by the holes |03 in the cone |02.

Secured to the ejector body 91, and forming one of the essential parts of ejector, is a diffuser or nozzle. This diffuser consists of an upper funnel-shaped member III, a middle screw threaded section I I2, and a lower flaring member II3. The screw threaded portion III is adapted to be threaded into the opening H4 of the body 91, a flange I I5 serving to form a tight joint with the bottom of the body 91. The upper funnelshaped member I|I partly surrounds the cone |02, and the lower flaring member II3 joins with the funnel at a constricted point or throat IIB. This construction forms two channels through the ejector; one through II1 in the plug |03, and down .through the central passage in the cone |02; the other from the die chamber, through the openings IOI, into chamber |00, and through the channel I I8 between the cone |02 and the funnel III.

The wire which is being coated passes from the coating die 50, directly down through the opening I I1 in the plug |03, and on through the throat` I I6 of the ejector, and out through the nozzle I I3.

At the throat |I6 lthe wire is caught in the stream of water or other liquid that is now flowing through the diagonal openings |03, and is quenched or cooled at this point. From here it passes out to suitable winding mechanism, illustrated diagrammatically in Fig. 2, where the wire is shown passing under a guide wheel I2I, to winding drums |22, driven by any suitable means, as by a motor |23 and gearing |24.

Operation 'I'he general operation of the several features has been given in describing the various parts of the machine or apparatus, but a general review of the complete operation may be helpful. The wire is here shown as first passing through the cleansing bath II, and then through the preheating and preliminary coating bath I6. In this bath the wire is heated to approximately the temperature of the coating medium. While in this heated condition it passes directly to the coating die. However, it is to be understood that previously coated wire may be used and be passed directly to the coating dies; or an uncoated wire may be passed directly thereto, as the circumstances justify. But whatever the condition of the wire, it is desirable to have the temperature raised to approximately that of the coating metal before it passes through the coating die.

Assuming that the coating metal has been raised to the proper temperature, and that the die heads have been properly heated, the valves 36 for as many of the dies as are to be used are opened, and the die head and die chamber filled with liquid metal.

The valves 26 having been opened, the pumpv 9| started, the oil or water therefrom is discharged through the openings |03 in the cone |02. These liquid streams converge in the throat IIB of the ejector, and out of the nozzles II3, to the receiving tank 93, from whence it is returned to the pump.

The passage of the liquid through the ejector entraps the air in the die chamber and removes some of the same therefrom. The ejector thus produces a vacuum, or at least greatly lowers the air pressure. in the die chamber and prevents the introduction of new air thereto; and this effectively prevents the formation of oxide on the face of, and the vicinity of the die, thus making the formation of objectionable oxide impossible.

The formation of the vacuum at this point causes the liquid coating metal to flow from the melting pot, through the channels, around the dies, and finally through the casting die itself. The coating metal, as it is drawn through the die 44, unites with the wire or with the preliminary coating on the wire, and solidies around the wire now moving through the ejector. And as the heated metal reaches the point where the liquid streams unite, it is quenched and cooled. The wire with coating now cast thereon then passes out of the machine to be disposed of as desired; it is here shown as received on spools or drums 22.

What I claim as my invention is:

1. The process of coating an elongated metal article of uniform cross section with a protective coating of another metal which comprises, moving the article to be coated through a casting die, simultaneously drawing molten coating metal through the die around the article to be coated by reduci-ng the atmospheric pressure beneath the die, and quenching the coated article.

2. The process of coating an elongated metal article of uniform cross section with a protective coating of another metal which comprises, moving the article to be coated through a casting die, removing the air from around the casting die to prevent oxidation and reducing the atmospheric pressure beneath the die so as to draw molten coating metal through the die around the article being coated.

3. The process of coating an elongated metal article of uniform cross section withV a protective coating of another metal which comprises moving the article to be coated through a casting die, drawing molten coating metal through the die around the article being coated, and simultaneously removing the air from around the die tc prevent oxidation by means of a partial vacuum beneath the die, and quenching the article being coated in the vacuum producing means.

4. In a machine for coating elongated metal articles of uniform cross section, the combination of a casting die, means for moving the article to be coated through the die, a source of molten metal, vacuum producing means for drawing the air from beneath rthe casting die and for drawing the molten metal through the die around the article to be coated, and means for passing the coated article through the vacuum producing means to quench and cool the same.

5. In a wire coating machine, a die chamber, a casting die therein, means for supplying molten metal thereto, guides for keeping the wire central of the casting die, a fluid ejector conhected to the die chamber for withdrawing air from around the casting die and to simultaneously draw the molten metal through the naat-` ing die, and means for passing the coated wire through the fluid of the elector to cool the same.

6. In a wire coating machine, the combination of a. die chamber, a casting die therein, a source of molten metal to supply the casting die, a uid actuated ejector for drawing air from around the `casting die so as to prevent oxidation of the ing air from the die chamber and from around' the casting die and for drawing molten metal through the die around the wire, and means for drawing the coated wire through the liquid which operates the ejector to quench and cool the freshly coated wire.

8. In a wire coating machine, the combination of a die chamber, a ldie holder in the die chamber, a casting die in the lower part of the die holder,l a guiding and centering die in the die holder dividing the same into an upper chamber of considerable length and a relatively short lower chamber, means for supplying molten metal to both chambers, and means for passing a wire to be coated iirst through the upper and longer chamber and "then through the relatively short chamber and through the casting die.

9. In a wire coating machine, the combination oi' a die chamber, a die holder in the die chamber, a casting die inthe lower part of the die holder, a guiding and centering die in the die holder dividing the die holder into an upper alloying chamber and a lower, casting chamber.

10. In a wire coating machine, a die assembly comprising a die plug having an opening therein, a die holder in yfthe plug, va casting die in the lower part of the dievholder, a guiding diek spaced from the casting die, a ring spacer resting on the guiding die, an entering guide resting on the ring spacer. a cap resting on the entering guide and cooperating with the opening in the die plug to hold the other elements oi the die assembly in position.

RANDALL W. SCHULTZ.

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