US2011135A - Method of coating - Google Patents

Description

Aug. 13, 1935.

A. o. AUSTIN METHOD OF COATING Filed Jul 24, 1951 2' Sheets-Sheet 1 0 OH R N 0 R T 0 m T V n T m A Aug. 13, 19 35.

A. O. AUSTIN METHOD OF COATING Filed July 24, 1931 2 Sheets-Sheet 2 INVENTOR F, Arf/rur 0. flasvf/n 9-6 62%},47 ATTORN Y Patented Aug. 13, 1935 Jersey METHOD OF COATING Arthur 0. Austin, near Barber-ton, Ohio, asslgnor,

by mesne assignments, to The Ohio Brass Company, Mansfield, Ohio, a corporation of New Application July 24, 1931, Serial No. 552,815

7 Claims. (0191-) This invention relates to a process of galvanizing various forms of articles, especially rods, bars and structural shapes that are elongated in form.

One of the objects of the invention is to provide a galvanizing process which will conserve the coating material.

Another object is to provide a coating process in which the coating will be uniformly and thoroughly applied to the surface of the coated arti-. cle.

A further object is to provide a coating process which may be operated continuously. I

A further object is to provide a process by which the coating may be easily,'conveniently and effectively applied to articles which have heretofore been diflicult to coat.

Other objects and. advantages will appear from the following description.

The invention is exemplified by the steps of the process described in the following specification and by the apparatus shown in the accompanying drawings for performing'these steps. The invention is more particularly pointed out in the appended claims.

In the drawings:

Fig. 1 is a somewhat diagrammatic plan view sf one form of apparatus for practicing the invenion.

Fig. 2 is a transverse section on line 2-2 of Fig. 1.

Fig. 3 is an elevation of a modified form of one portion of the apparatus.

Fig. 4 is a modified form of another portion of the apparatus.

Fig. 5 is an elevation of one, form of apparatus for performing a somewhat modified process.

.Fi 6 is a view similar to Fig.5 showing still another form of apparatus.

Fig. 7 is a section on line 'I--'| of Fig 6.

Fig. 8 is an elevation on line 8-8 of Fig. 5.

In galvanizing structural steel shapes, reinforce ing rods, fence posts, and guy or anchor rods, it is frequently very difficult to galvanize the parts economically unless large volumes of material are used. This is due to the fact that a very large or long galvanizing pot for holding the melted spel: ter is required; The present invention applies to any process for coating the article with a fusible metal, such as zinc, lead or tin. The method is particularly applicable to structural or other shapes which cannot be bent so as to deflect them into a galvanizingpot, but it may be used for wire, rods or cable which could normally be deflected into a pot but which it is desired to galvanize in a straight position.

With my improved method, it is possible to galvanize structural shapes of large dimensions with a very small amount of melted coating material.

Since the amount of coating material required is rather small, the loss due to dressing, which is effected to a very considerable extent by material dissolved from the large melting pot, is greatly reduced. In fact, in some cases, it is possible to use a continuous method so that the iron content in the melted zinc bath does not require drossing, thereby resulting in a material saving for a given thickness of coating or weather-proofing.

Where a large pot is used to galvanize a few pieces, as has heretofore been the practice, the iron content of the molten zinc tending to cause dross. is influenced more by the iron or steel dissolved from the pot than it is from the piece being galvanized; This is frequently a serious factor in the cost of galvanizing, particularly where the temperatures of the bath are high.

The present invention comprises the steps of cleaning and fiuxing the object to be coated and then driving the object through a stream of molten coating material. Following the coating of the article, the amount of coating material adhering thereto is reduced by a super-heated air or gas jet, by rubbing means, or by a fiame and blast jet which will maintain the piece at a fusing temperature while the excess material is being taken off.

Figure 1 shows one form of apparatus for practicing the invention in which a long object I ll is to be coated or galvanized. The object is placed upon suitable rollers H for supporting it during the coating process'and for driving it through the coating bath. After passing through the" coating bath, the object is picked up by rolls I2 or other suitable conveyor.

The object is first cleaned and pickled, or, if desired, it may pass through a sandblast hood l3 and then through a pickling or fiuxing chamber II. It then passes through a drying chamber i5 or it may pass directlyinto the coating chamber l6. When the object goes into the coating chamber l6, one or more revolving bucket or paddle wheels l'l rotated by a shaft [8 causes the melted coating material I 9 to flow or be sprayed over the object to be coated. The metal IS in the tank is heated by jets 20, or electrically, or in any convenient way.

In order that all sides of the object l0 may be coated, it is rotated during its passage through the coating chamber by suitable driving mechanism 2| and 22. In many cases, the rotating mechanism is not necessary as the placing of the rolls II and I2 at an angle or the spiral twist in the work, as in the case of reinforcing rods, will cause the object to rotate as it passes through. This rotation may be at acontinuous rate or may be intermittent, or vary in degree, so as to permit coating and the throwing oil of excess material. In large pieces, such as angles, I beams and channels, it may be necessary to control the speed of rotation in order that proper coating can be effected.

The object "I as it passes through the coating chamber, is subjected to one or more streams of coating material, either in the form of drops or in a steady stream, or, if desired, more than one coating chamber may be used, as shown at 2|. In general, however,it is preferable to have the first coating applied with as low a temperature as possible in order that amalgamation be started with a minimum amount of oxidation. Following this, ahigher temperature coating may be applied which will make the coating material more fluid and thereby make it possible to use a thinner and more even coating, saving material and providing a finer finish. To secure this result, the temperature may be'kept relatively low in chamber l6 and higher in chamber 2|.

Where the temperature of the bath is not very high, a flux, such as ammonium chloride or zinc chloride is used to flux the piece. Where the work is enclosed, this may be sprayed on as indicated at M, without serious difficulty as to spattering, the fluxing medium tending to insure a good uniform coating and a smooth surface. The work is subjected to a second fiuxing in the chamber 22 before it enters the second coating chamber 2|. fine, light spray or as dry powder spray, so that the work will not be wet when it enters the chamber 2| or, of course, a second drying chamber like I! can be interposed between the chamber 22 and 2|.

Where it is desired to provide a thin coating, the object is subjected to blast nozzles 23 which tend to drive off excess material as the rod or bar advances through the pot. Where a thin coating is desired, the blast nozzles are provided with super-heated air or with a flame, preferably at high velocity, or, at least, a portion at high velocity. Unless the air is super-heated, the expansion of the air lowers the temperature and tends to cause the coating to become solid. The addition of the gas flame, however, makes it possible to maintain the temperature, even though a supply of air or gas at normal temperature is used for the blast.

With pre-heated air, it is possible to use the supply of air over and over to conserve some of the heat of the blast and, what may be even more important, to maintain a neutral or inert atmosphere about the work to be galvanized or coated, thereby eliminating the eiIects of oxidation. In this case, the supplyv of air is taken out through the opening 24, goes to a compressor and then back through the nozzles 23.

The chamber is provided with bailles 25 which prevent the splashing of the material out, particularly where the coating material is fed with some considerable force. It is understood that the coating material may be applied, either as a steady or smooth flow, or, by splashing the molten material on the object.

Any convenient way may be used to establish the easy fiow of material, such as a small paddle wheel for raising the material from .a lowerlevel to a higher level, after which it will flow over the piece. Another form of device, shown in Fig. 4, includes connected pots for holding the molten material above the work, the pots being pivotally mounted to tilt about the work and alternately lifted, elevating the material which passes over the work from one pot to the other. The material may also be lifted by a conveyor, or by a suitable centrifugal pump, or other means,

In this chamber the flux is applied in a.

Of course, it is necessary that all material used for handling the spelter in molten condition, be maintained at a temperature which will prevent it from solidifying. These parts may be'heated, if desired, or may be maintained at temperature by the volume of molten material passing through. Where the material is elevated by a conveyor to a melting pot, it is not necessary that the material be in molten condition when elevated.

In general, the hood of the coating chamber for a continuous process is preferably maintained at a temperature which will cause the material splashing or falling on the sides to melt, so it may get back into the bath and be immediately re-used, or so it will flow into the conveying equipment.

As the work advances and is cleaned, it is usually necessary and advisable to solidify the coating before it touches any object. Unless this is done, bare spots are likely to result. An air blast 21 maybe used to congeal the material on the surface. On large objects, however, it will be found that while the surface is chilled, the heat from the interior will cause melting of the coating a little later so it will easily damage. This is particularly true where the advance of the work is rather rapid so that the cooling eifect is of short duration. In order to prevent trouble of this nature, it is necessary to lower the temperature sufliciently so that thecoated object will not be damaged in the later handling. In some cases, a series of cooling jets 21 or a water spray may be used.

Preferably, all cooling equipment should be placed in advance of apparatus coming in contact for translating or rotating the object being coated. In some cases, it may be necessary to cool thr pieces gradually by jets at the same time holding the material in position to prevent warping. In this case, the rolls must hold the pieces in position and the cooling on the diiferent faces may be regulated by the jets so as to reduce the tendency to warp to a minimum.

The object to be galvanized may be placed in a horizontal position or inclined downward or upward as it passes through the coating chamber. Each type has special advantages. When the path is downward, the cleaning jet may blow the coating material back into the coating chamber and the fact that the article is inclined downward as it enters the coating chamber, any flow of material over same will tend to be returned to the pot. This may be of great advantage, particularly where the part has longitudinal grooves or pockets which tend to retain quantities of the coating material.

If it is desired to omit the blast or means for regulating the thickness of the coating or for removing excess material, the work may be inclined upwardly'as it leaves the coating chamber. For this condition, it may be necessary to rotate the object to be coated sufllciently to throw oif material so it will not run out of the coatingchamber, or to provide a long coating chamber or one with a sufficiently long entrance to prevent the falling of the material outside of the pot or chamber, or .it may be necessary to use a blast which will prevent the material fiowingout along the piece where it enters the chamber. In this case, the blast may be placed on the entering side in place of the exit, or, if desired, blasts may be placed on each side.

I The invention comprises the steps of subjecting the'object to be coated to a flow of coating material and giving the object a movement with respect to the coating bath. The object may be inclinedto regulate the flo'w and amount of coating or coatings of different temperatures may be used to facilitate the operating and control the thickness of coating.

To facilitate the work, cleaning jets are provided, as well .as chilling means. The object is cleaned and fluxed during the operation or separately. If desired, the object may be subjected to fluxing means between baths or in the coating chamber itself. Instead of nozzles 21, a circular pipe may encircle the work I0, having inner perforations for directing the jets against the work.

l The method is particularly applicable to galvanizing pipe, large cylinders and containers, particularly where it is desired to coat one side only. Fig. 5 shows one form of apparatus for pplying the invention to a large sized pipe in which a cylinder or pipe 30 is to be coated on the inside. Mechanism 3| is provided for rotating the pipe or cylinder. The molten material is allowed to flow in at the upper end through a spout 32 and discharge at the lower end at 33. The cylinder may be handled in any enclosure which is heated in any convenient way, or where there is suflicient volume of material, the heating may be accomplished by the flow of material itself. If desired, the blast cleaning system may be used on the coated surface, or the surface may be heated on the outside by a series of jets. In this case, the coating is accomplished over a small zone, the rotation of the member advancing the zone being coated untilthe object is completed Another method is to supply the molten material through a channel or duct system 36, as shown in Fig. 6. The coating material feeds back as the object is advanced and rotated. This method can be used for blind chambers or tanks, or may be used for open end equipment, if desired, where a longitudinal heated zone might tend to cause unnecessary warping. In this method, the coating zone is in the form of a spiral, making it possible to use much smaller cleaning blasts than where the long coating zone is used. The fact that a certain amount of material runs down over the surface and congeals in advance of the hot zone, can be used to advantage in obtaining an amalgamation or adherence of the coating before oxidation takes place.

If desired, some forms of work may be heated after passing through the coating chamber, either by passing through a chamber which has a suflicient temperature, or by the flow of electric current through the article which will cause it to be heated.

I claim:

1. The process of coating an article with molten metal which will adhere to the surface of the article, the article being adapted for rotation, said process comprising the steps of feeding the article relative to a, coating station, flowing molten metal by gravity over the outer surface of the article at the coating station and rotating the article about an axis extending in the direction in which it is fed to present different portions of the article to 1 with molten metal which will adhere to the surface of said article, said process comprising the steps of feeding the article forwardly in the direction of the length thereof, causing molten coating metal outer surface of the article as the article is fed forwardly and rotating the article about an axis extending in the direction of the length thereof, to present various faces of the article to the stream of coating material. 1

3. The process of coating an elongated article of definite length and adapted for rotation about a longitudinal axis, said process comprising the steps of causing liquid coating material to flow by gravity over a limited portion of the article, feeding the article forwardly to present successive portionsthereof to the bath of coating material, rotating the article to present different faces thereof to the coating bath and directing a blast or jet against the coated surface, to wipe said surface and regulate thacoating material thereon.

4. The method of coating an elongated article of definite length and irregular cross sectional contour comprising the steps of subjecting a limited portion of the article at a time to a bath of liquid coating material, feeding the article in the direction of its length through said bath to present successive portions of the article to the coating bath, rotating the article about an axis extending in the direction of the length thereof, to insure the application of the coating to different faces of the article and directing a wiping jet or blast against the surface of the article'as it moves away from the coating bath, to regulate the coating of material on the surface of the article.

5. The method of coating the surface of an elongated article of definite length and adapted for rotation about a longitudinal axis, said method comprising-the steps of feeding the article in a substantially straight path through successive stations positioned in the path of the moving article, spraying the article with fluxing material at one of the said stations, causing liquidcoating material to flow over said article at a subsequent station, rotating the article about an axis extending in the direction of said path to subject all sides thereof to the flowing stream of coating material and directing a wiping blast or jet against the surface of said article at still another station.

6. The method of coating an elongated article of definite length and adapted for rotation about cleaning blast upon the article at one station, spraying the article with fluxing material at a subsequent station, causing coating material to flow over the article at another station, rotating the article about an axis extending in the direc-' tion of said path to subject all sides thereof to the flowing stream of coating material, directing a -wiping blast or jet against the surface of said article as it leaves the coating station and cooling thecoated surface before it comes in contact with any solid object after it has been subjected to said wiping blast or jet.

7. The method of coating an article comprising the steps of applying liquid coating material to the article, directing a gaseous jet or blast against the coated surface, collecting the gas from said jet or blast, after it strikes the article, and again using the collected gas for said jet or blast.

. ARTHUR 0. AUSTIN.

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