US2718474A

US2718474A - Metal coating method and apparatus

Info

Publication number: US2718474A
Application number: US396519A
Authority: US
Inventors: Ralph W Hodil; Jared L Holt
Original assignee: Individual
Current assignee: Individual
Priority date: 1953-12-07
Filing date: 1953-12-07
Publication date: 1955-09-20
Anticipated expiration: 1972-09-20

Description

METAL COATING METHOD AND APPARATUS Filed Dec. '7, 1955 (sheets-sheet 1 INVENTORS Ralph W.H0d i| JoredLHolt ATTORNEYS Sept. 20, 1955 R. w. HODIL ET AL 2,713,474

METAL COATING METHOD AND APPARATUS Filed Dec. '7, 1953 4 Sheets-Sheet 2 BY "(77? I 1/ I q f? i "11 J0 red LHoh f;

ATTORNEYS p 20, 1955 R. w. HODIL ET AL 2,718,474

METAL COATING METHOD AND APPARATUS Filed Dec. '7, 1955 4 Sheets-Sheet 3 I, 5 Ralph W.Hodil f. JaredLHoh BY Mvh ATTORNEYS R. W. HODIL ET AL METAL COATING METHOD AND APPARATUS 4 Sheets-Sheet 4 liFFd INVENTORS m WL d 6 mr 00 d BY $777M ATTORNEYS Sept. 20, 1955 Filed Dec. 7, 1955 United States Patent ()fiice 2,718,474 Patented Sept. 20, 1955 METAL COATING METHOD AND APPARATUS Ralph W, Hodil, Pittsburgh, and Jared L. Holt, Butler, Pa.

Application December 7, 1953, Serial No. 396,519

6 Claims, (Cl. 117-51) This invention relates to metal coating method and apparatus, and more particularly to a method and apparatus for coating tubular members, such as metal pipes.

The non-electrolytic coating of metal objects, such as iron pipes, with a galvanizing coating of zinc is a process which often involves many troublesome problems. The metal which is' to be coated must be raised to the proper galvanizing temperature which is in the range 850875 E. In order to offset the lowering in temperature due to the entry of the cold pipe or other object to be coated, the metal has to be heated to a higher temperature. However, if the zinc bath itself is heated to the higher temperature by the application of heat to the tank or kettle containing the zinc, a reaction occurs between the iron oi the kettle and the zinc bath which results in rapid deterioration of the kettle, thereby greatly shortening the life of the kettle and increasing formation of dross.

One method which has been proposed for overcoming the ditiiculty just mentioned is to preheat the metal pipe or other metal object to the proper galvanizing temperature by passing the object to be coated through a preheating bath of another metal, such as lead, which serves only as a preheating medium. This preheating step generally involves floating the zinc coating material on the lead preheating bath, both the lead and zinc being contained in the same tank or kettle. The metal object, such as the iron pipe, is drawn upwardly through the lead preheating bath and then through the upper floating layer of zinc.

The method just described has several serious objections. For example, a dross composed of a zinciron compound forms when the zinc coating is applied over an iron surface, and drops to the bottom of the floating layer of zinc, but remains above the preheating bath oflead. As a result, the metal pipe or other object being coated is drawn through the layer of dross before passing through the zinc bath. This results in imperfect coatings and poor appearance of the object being coated. Furthermore,-in this kind of lead-zinc process, the lead bath is in constant contact with the supply of zinc and picks up and holds about one per cent of zinc. This amount of zinc is sufiicient to cause the lead to have some aflinity for the iron or steel member being coated, with the result that the speed of passage of the work through the bath is limited due to the fact that globules of lead adhere to the work, damaging the coating and ruining its appearance. Also, due to the fact that the hot lead bath contains a certain percentage of zinc from its direct contact with the zinc layer, the machinery for moving the material to be coated, and the tank or kettle are chemically attacked to some degree by reaction with the zinc, although this reaction occurs to a lesser degree than if the bath were all zinc.

Still another problem which occurs in the method just described is the danger of entrapment of dross in the interior of the pipe, requiring blowing at high pressure to make sure that there is no plugging of the pipe by such dross.

Another problem which is often encountered in gale vanizing processes in accordance with the prior art is the oxidation which occurs if the zinc coating is applied in an open atmosphere. An outer layer of oxidized zinc forms in the zinc bath and has to be skimmed off, resulting in considerable waste. In fact, a substantial percentage of the molten zinc used in accordance with prior methods of zinc coating is lost insofar as the galvanizing process is concerned, due to reaction either with the atmosphere or with the kettle or tank in which the galvanizing process takes place.

Accordingly, it is an object of this invention to provide an apparatus and method for applying a galvanizing coating of zinc to metal objects'in accordance-with which the galvanizing coating material is heated to not in excess of the galvanizing temperature, and wherein the object to be coated is heated in a separate preheating bath.

it is another object of this invention to provide a method and apparatus for applying a coating of zinc to an iron or steel member which greatly reduces chemical reaction between the zinc coating material and its containing kettle, thereby greatly prolonging the life of the kettle;

It is another object of this invention to provide a method and apparatus for applying a coating of zinc to an iron or steel member in which a purer coating of zinc is obtained than is possible using methods and apparatus of the prior art.

Still anotherobject of this invention is to provide an apparatus and method for applying a zinc galvanizing coating to a metal object, such as a tubular pipe, in which the zinc galvanizing bath is maintained out of contact with the preheating bath, such as a lead preheating bath.

Still another object of this invention is to provide an apparatus and method for applying a galvanizing coating to a metal object in which the galvanizing process occurs in an atmosphere which is inert to the galvanizing material, Such as zinc.

Still another object of the invention is to provide a simple and uncomplicated galvanizing apparatus which expeditiously and efljciently moves the object to be galvanized, such as an iron or steel pipe, successively through a flu bath. a prehe a h. and a lvan zing a h n th r bj t t e ti n is't P v e n pparatus and method for coating metal pipes with zinc in, accordance with which production of dross is greatly e d an he p u in Qt P p by dross is su a a ly eliminated.

A still further object of the invention is to provide an apparatus and method for galvanizing metal pipes which permits a much higher output than is possible using the apparatus and methods of the prior art.

In achievement of these objectives, this invention provides an apparatus and method in which metal pipes to, be galvanized are carried by a conveyor system first, through a flux or acid bath to remove oxidation, then through a preheating bath of hot lead to heat the pipes to the galvanizing temperature, and then through a' gal. vanizing bath of zinc. 'Each of the baths is contained in a separate tank, and each tank is provided with a separate rotary conveyor which carries the pipes in a circular path first downwardly and then upwardly through the given bath. The successive tanks are connected by inclined guide-ways or ramps down which the pipes roll to be picked up by the conveyor of the succeeding bath. The galvanizing bath tank, the preheating bath tank and part of the flux bath tankare enclosed in a substantially. airtight structure which is filled above the levels of the respective baths. with an atmosphere of a gas inert to the galvanizing material, such as zinc. The pipes to be coated enter and leave the various baths at an angle inclined to the horizontal so that the liquids drain from the interior of the pipes upon leaving the baths. Furthermore, the structure is so arranged that the air inside the pipes to be coated is purged as it enters the flux bath and is filled with the inert gas as it emerges from the flux bath. 'This prevents any air contained in the interior of the pipes from being carried into the preheating and galvanizing tanks in such manner as to contaminate the inert atmosphere in those tanks.

'Other objects and advantages of the present invention will become more apparent from the following detailed description taken in conjunction with the attached drawings in which:

Fig. 1 is a top plan view of a galvanizing apparatus in accordance with the invention;

Fig. 2 is a view in section along line 2-2 of Fig. 1;

Fig. 3 is a view in section along line 33 of Fig. 4 showing details of the sealing doors between the flux bath and the preheating lead bath;

Fig. 4 is a view in section along line 44 of Fig. 1; Fig. 5 is an enlarged detail view, partially cut away, showing the support and lifting arrangement for the box girders which, in turn, support the conveying mechanism. within the respective baths;

Fig. 6 is an enlarged sectional detail view showing the supporting and sealing arrangement for the removable covers of the galvanizing apparatus; and

Fig. 7 is an enlarged detail view of one of the tanks, showing the manner in which the pipe conveying mechanisms and cover are lifted;

Referring now to the drawings, the galvanizing apparatus comprises three

tanks

10, 12 and 14 which extend parallel to each other, but in spaced relation, tank being supported by a suitable concrete foundation 16, as shown, while the other tanks are supported on brick work 16a. Tank 10 serves as a receptacle for a bath of an acid, such as muriatic acid, which removes all traces of dirt and oxide on the surfaces of the pipes to be galvanized, to thereby provide the pipes with a surface to which the galvanizing solution will readily adhere. Tank 12 serves as a receptacle for a bath of hot lead, which serves as a preheating medium to raise the pipes to the galvanizing temperature of 850875 F. Tank 14 serves as a receptacle for the zinc bath which provides the galvanizing coating for the pipes.

A heating chamber 18 surrounds the side walls of the lead bath tank 12, and includes openings 20 through which a gas fired heating means extends on either side of the side walls of the tank 12 in order to raise the temperature of the lead bath to the required range. Similarly, a heating chamber 22 extends longitudinally on either side of the tank 14 which contains the zinc bath, and electrical heating elements 24 serve to heat the chamber 22 and the contents of the tank 14 to the desired temperature range.

The pipes to be coated are delivered to the flux bath tank 10 by means of a conveyor 26, as will best be seen in Fig. 4. The pipes are automatically delivered to the conveyor 26 from a water tank in which they are placed after a pickling process. pleted the galvanizing process, they are delivered to a water bath 28, shown at the left of Fig. 4, by means of an inclined guideway 30, the pipes then being carried out of the water bath by an upwardly moving conveyor 32.

To serve as a support for the enclosing cover which is to be later described, and also as a support for the con veying mechanism within each tank,

box girders

34, 36 and 38 extend above each of the

respective tanks

10, 12 and 14. Each of the

box girders

34, 36, 38 is supported at its opposite ends by the oppositely disposed cantilever beam members 40 and 42 (Figs. 1 and 2). The

beams

40 and 42 in turn are supported at their outer ends by the pillars or walls 44.

As will best be seen in Figs. 2 and 5, the

box girders

34, 36, 38 are provided at each end with a stepped portion 50, which is supported by a mating stepped portion 52 of the

respective beams

40 and 42.

In order to permit detachable engagement of the After the pipes have com box girders with the supporting beams, each end of the

girders

34, 36 and 38 is provided with an upstanding bracket member 53 having rigidly attached thereto and extending therefrom a pair of apertured guide elements 54 which engage the vertical post 56, see Fig. 5, extending from each of the

respective beam members

40 and 42.

Each

box girder

34, 36, 38 serves as a support for the conveying mechanism within one of the

respective tanks

10, 12, 14. Within each of the tanks, a plurality of large serrated disk members 60, see Fig. 4, are rigidly attached to a rotatable shaft 62 which extends longitudinally within each of the respective tanks. The disks are spaced along the shaft 62, as can best be seen in the view of Fig. 2. The shaft 62 in any one tank is supported by a plurality of spaced bearing brackets 64 which extend downwardly from the respective one of the

beams

34, 36, 38 which extends above the given tank. Cooperating with each of the serrated disks 60 is a guide plate 66 which is supported by the base of the tank and which has an arcuate cut-away portion of just slightly smaller peripheral extent than the periphery defined by the teeth of the respective disks 6%). The guide plate 66 serves to retain the outer surface of the pipes as they are fed through the bath by the rotating serrated disk 60. Cooperating with the guide plates for this purpose are the auxiliary plates 66a located adjacent to the tops of the disks 60, on the rising sides thereof, as shown in Fig. 4.

As will best be seen in Fig. 2, each of the respective guide plates 66 is ofiset longitudinally of the tank a short distance from the plane of the respective disk member 60 with which it cooperates to permit a slight overlapping between the outer periphery of the disk 60 and the inner periphery of the guide plate 66.

Mounted above and adjacent the serrated disks 60 in each of the respective tanks are a plurality of star wheels 68. In the embodiment shown, a star wheel is positioned adjacent every other disk 69, see Fig. 2. The star wheels 68 are mounted on a shaft 70 which, in turn, is supported by the same bearing brackets 64 which support the shaft 62. The star wheels 68 serve to pick up the pipes from the disks 60 after the pipes have completed their rotation through the given bath.

In order that the pipes which are carried by the conveyor system enter and leave the various baths at an inclination to the horizontal in order to permit drainage of the liquid from the pipes as they emerge from the bath, and also to permit purging of air from the pipes in the flux bath of tank 18*, the

shafts

62 and 70 which support the serrated disks 60 and star wheels 68 are so mounted as to be inclined at a predetermined angle with respect to the horizontal, as can best be seen in the view of Fig. 2. Thus, for example, the

shafts

62 and 70 may be inclined from the horizontal by 4 inch per foot of length.

The

shafts

62 and 70 in each of the respective tanks is driven by a vertical drive shaft 72 having worm threads 74 which cooperate with worm wheels '76 on the respective shafts 62 and '70. At its upper end, each of the respective vertical shafts 72 is provided with one of a pair of mating offset bevel gears 77 which are driven from a horizontally extending auxiliary drive shaft 78 through a suitable clutching device 80. Each of the auxiliary drive shafts 78 is connected through a gearing and clutch arrangement generally indicated at 82 to a main drive shaft 84 which is driven by a suitable power source generally indicated at 86.

An important feature of the invention is the provision of an air tight enclosure means over the galvanizing tank 14, the lead bath tank 12, and part of the flux tank 10. This enclosure means serves to insure that the galvanizing process is conducted in an inert atmosphere which prevents harmful oxidation of the zinc galvanizing material.

The enclosure means over the tanks includes, as shown in Fig. 4, the cover sections 99, 92., 93 and 94, the cover portions 96 and 98 attached to the upper surfaces of the respective box girders 36 and 38, the longitudinally extending walls 184 and 186, the laterally extending walls 108, and the sealing Walls or bafiles 109 and 11 which depend downwardly from the

respective box girders

34 and 36 into tanks and 12 respectively. The

cover sections

90, 98, 92, 96, 93 and 94 all lie in the same horizontal plane and together form the top cover for the galvanizing apparatus. The cover sections are removable and are each provided with a sealing means comprising downwardly extending fins or vanes 10% which seat in liquid recesses 102, see Figs. 4 and 7, attached to the sides of the box girders and of the various walls which the cover sections engage, to provide an air tight enclosure. Thus, the end wall 184, shown at the left of Fig. 4, the intermediate wall 106 between the tanks 10 and 12, and the transversely extending walls 108 (Fig. 6), as well as each of the

box girders

34, 36, 38 are provided with the liquid filled recesses 102 which engage the downwardly depending vanes 160 of the various cover sections to provide an air tight seal.

The enclosure is further sealed by flexible sealing means 107 (Fig. 6) which connect the underneath edges of the transversely extending walls 108 to their supporting foundation- 115. When the cover sections are in place, the atmosphere above the zinc bath in tank 14, above the hot lead bath in tank 12, and above part of the flux bath in tank 10 is substantially enclosed and sealed from the exterior atmosphere. The longitudinally extending wall portion 111 which depends downwardly from box girder 36 to slightly below the level of the bath in tank 12 serves as a means which tends to isolate the atmosphere to the left of the Wall 111, With respect to the view shown in Fig. 4, from the atmosphere to the right of the wall 111. In a similar manner, the sealing wall 109 which depends downwardly from the box girder 34 tends to isolate the atmosphere to the left of wall 109 from that to the right of wall 169, with respect to the view shown in Fig. 4. The entire enclosed space from end wall 104 to sealing wall 109 is filled with a protective atmosphere which is inert to the zinc coating material and may be, for example, a mixture which is 96 /2 percent nitrogen (N2) and 3 /2 percent hydrogen (H2).

It will be noted that while the interiors of the galvanizing tank 14 and of the lead bath tank 12 are completely covered by means of the

cover members

90, 96, 92,. 98, and 93, the flux bath tank 10 into which the pipes are first introduced is only partially covered by the cover member 94. The box girder 34 is positioned laterally inwardly a short distance from the outer wall of the tank 10 and the wall or baffle member 1439 extends vertically downwardly from the underneath surface of the box girder 34 to a distance somewhat below the level normally maintained by the liquid in tank 10. The wall or baffie member 109 is suitably apertured to permit passage therethrough of the bearing bracket 64 which supports the

shafts

62 and 70 and is also apertured or slit to permit rotation therethrough of the serrated disk members as they move through the flux bath in tank 10, the slit formation closely cooperating with the disk member to prevent loss of the protective atmosphere or contamination thereof.

An inclined guide-way or ramp 110 extends between the discharge end of the tank 10 and the inlet end of the tank 12. The guide-way is inclined in such manner that the pipes delivered to the upper end of the guideway within the chamber 10 roll by gravity to the lower end of the guide-way, where they pass to downwardly inclined guide-way 112 in tank 14, where they are picked up by the disks 60 within the tank 12. A series of normally closed hinged doors 114 are positioned at spaced apart intervals along the downwardly inclined guide-way 110. As each pipe rolls down guide-way 110, it forces Pen the successive doors 114 which return to their normally closed position as soon as the pipe has passed through the door. In the embodiment shown, five doors 114 are provided. These doors serve as seals which tend to prevent loss of large quantities of the inert or protective atmosphere from the

tanks

12 and 14, and further tend to isolate the atmosphere or

tanks

14 and 12 from that of tank 10.

The lead bath tank 12 and the galvanizing tank or kettle 14 are connected by a ramp or inclined guideway 116 so that pipes which are discharged from tank 12 roll downwardly due to the force of gravity and are delivered by guide-way 118 into the tank 14 where they are picked up by the rotating serrated disks in tank 14.

An inclined guide-way 118 permits pipes which are discharged from the tank 14 to pass downwardly to the discharge end of the apparatus Where they pass through a normally closed hinged door 120 which is forced open by the passage of the pipe but which returns to its normally closed position after the pipe has passed through.

To facilitate removal of the cover members, lifting lugs 122 are provided on each of the

respective cover sections

90, 92, 93 and 94.

The box girders 96 and 98 are each provided with a lifting lug 124 which is inclined at an angle away from the vertical in order that the point of attachment of the lifting hook will be over the center of gravity of the rig attached to the respective box girders, which includes the disks 60, the star wheels 68 and their supporting shafts.

As most clearly illustrated in Fig. 7, when it is desired to remove the cover sections for any reason, such as to periodically remove the dross which settles at the bottom of the galvanizing kettle or tank 14 due to the reaction of the zinc with the iron pipes or other metal object being coated, the covers may be lifted by attaching a hoist hook 125 to the lifting lugs 122. After the cover sections have been removed, the box girders may be removed by attaching the hoist hook to the lifting lugs 124, thereby causing the conveying mechanism, including the disks 60, the star wheels 68., and their supporting shafts to be raised out of the respective tank in which they are located.

In the operation of the apparatus, when it is desired to galvanize metal pipes, the lead bath in tank 12 is heated to the required temperature range of 850875 F. and the zinc plating solution is heated to its required temperature. The disks 60 in each of the respective tanks and the star wheels 68 are caused to rotate by energizing the prime mover 86, the main drive shaft 84, the auxiliary drive shafts 78 and the vertical drive shafts 72. This causes rotation of the

shafts

62 and 70 which respectively carry the serrated disks 60 and the star wheels 68. The pipes which are to be metal plated are then delivered by conveyor 26 down the inclined guide-way 27 into the flux bath of tank 10 where they are picked up by the teeth of the plurality of serrated disks 60. The pipe P is supported at an inclination to the horizontal due to the inclination of the shaft 62.

As the disks 60 rotate, one end of the pipe passes into the flux solution first and causes any-air in the interior of the pipe to be purged from the pipe as the pipe passes down into the solution. The pipe is then rotated through the solution, being guided by the guide plates 66. After completing its circular path of rotation in the tank 10, and having had dirt and oxidation removed from its outer surface, the pipe is picked up by the star wheels 68 in tank 10 and delivered to the ramp or inclined guide-way 110;. The atmosphere above the portion of tank 10 where the pipes emerge from the flux or muriatic acid bath is a substantially inert atmosphere, since the interior of tank It) is to a large extent sealed by the sealing wall or bafiie 108. Hence, the pipes have been purged of air as they enter the muriatic acid bath and are filled with the inert atmosphere as they emerge from the bath at the time of their delivery to the ramp 110. The pipe rolls down the ramp 110 and passes through each of the successive sealing doors 114, each door 114 closing as the pipe passes by it. This prevents excessive escape of the inert atmosphere from tank 12.

At the end of the guide-way 110, the pipe is picked up by the guideway 112 and delivered to the rotating serrated disks 60 in tank 12. These disks carry the pipe through the bath of hot lead which raises the temperature of the pipe to the temperature of the lead bath, which is the same as the temperature required for the metal coating step. After having completed its rotary path of motion in tank 12, the pipe is picked up by the star wheels 68 and delivered to the ramp or inclined guide-way 116. The pipe rolls down guide-way 116 due to the force of gravity and passes down inclined guide-way 118 in tank 14, where it is picked up by the rotating disks 60 of that tank. The disks 60 carry the pipe through the zinc bath and the coating of zinc is deposited on the outer and inner surfaces of the pipe. After completing its path of motion through the zinc bath, the pipe is picked up by the star wheels 68 and delivered to the inclined ramp or guide-way 118, rolls down guide-way 118 due to the force of gravity and passes out through the normally closed door 120 which is opened due to the force of the rolling pipe striking it. The door 120 closes as soon as the pipe has passed through. After passing through the door 120, the pipe rolls down the inclined guide-way into the water bath 28 and is carried out of the water bath by the conveyor 32.

It can be seen from the foregoing that there is provided in accordance with this invention an improved method and apparatus for applying metal coatings, such as zinc coatings, to metal pipes. The invention provides a method in accordance with which the metal coating process occurs in an atmosphere which is inert to the zinc, thereby preventing oxidation of the zinc. Furthermore, the invention provides an apparatus which permits the pipes to be preheated to the required galvanizing temperature in a lead bath which is entirely out of contact with the zinc bath, thereby avoiding injurious chemical reactions which occur when the zinc bath itself is heated to the galvanizing temperature. The apparatus of the invention permits pipes to be efficiently conveyed through the flux bath, the lead preheating bath and the zinc bath in succession, resulting in much faster production of metal plated pipes than is possible using the methods and apparatus heretofore known. Furthermore, the amount of dross formed in the Zinc plating tank is substantially reduced as compared to the amount of dross normally obtained. As a result, a much purer and more uniform zinc coating is obtained than is possible using conventional apparatus and methods, and plugging of pipes by dross is substantially eliminated.

What is claimed is:

1. Apparatus for the treatment and coating of tubular elements comprising first tank means for containing flux solution, second tank means for containing molten metal for preheating the tubular elements, and third tank means for containing the molten coating metal, conveyor means for conveying the tubular elements through each of said tank means, and protective enclosure means for said second and third tank means and at least part of said first tank means for enclosing above the contents of each tank means a protective atmosphere, said conveyor means including fixed plates each having a cutaway portion providing an edge over which the tubular elements are moved, rotatably mounted cooperative members provided with tubular element-receiving surface portions predeterminately disposed relative to said fixed plates so as to spacedly hold said tubular elements, said cooperative members having driving means for moving said elementreceiving surface portions relative to said plates, said fixed plates being disposed in successively stepped relation and the cooperative members being mounted on an inclined axis so as to convey the tubular elements in slightly inclined relationship, and said protective enclosure means including a depending sealing wall projecting into the first tank means below the level of its contents and in spaced relation to one end wall thereof so that upon entry of the tubular elements into the contents of the first tank means between such one end wall and the sealing wall the air is purged from the tubular elements and upon exit from said first tank means the tubular elements fill with protective atmosphere for passage into the second tank means.

2. Apparatus for the treatment and coating of tubular elements comprising first tank means for containing flux solution, second tank means for containing molten metal for preheating the tubular elements, and third tank means for containing the molten coating metal, conveyor means for conveying the tubular elements through each of said tank means, and protective enclosure means for said second and third tank means and at least part of said first tank means for enclosing above the contents of each tank means a protective atmosphere, said conveyor means including fixed plates each having a cutaway portion providing an edge over which the tubular elements are moved, rotatably mounted cooperative members provided with tubular element-receiving surface portions predeterminately disposed relative to said fixed plates so as to spaccdiy hold said tubular elements, said cooperative members having driving means for moving said elementreceiving surface portions relative to said plates, said fixed plates being disposed in successively stepped relation and the cooperative members being mounted on an inclined axis so as to convey the tubular elements in slightly inclined relationship, and said protective enclosure means including a depending sealing wall projecting into the first tank means below the level of its contents and in spaced relation to one end wall thereof so that upon entry of the tubular elements into the contents of the first tank means between such one end wall and the sealing wall the air is purged from the tubular elements and upon exit from said first tank means the tubular elements fill with protective atmosphere for passage into the second tank means, said protective enclosure means having plural normally closed doors between said first and second tank means through which doors the tubular elements successively pass.

3. Apparatus for the treatment and coating of tubular elements comprising first tank means for containing flux solution, second tank means for containing molten metal for preheating the tubular elements, third tank means for containing the molten coating metal, conveyor means for conveying the tubular elements through each of said tank means, and removable protective enclosure means for at least said second and third tank means for containing a protective atmosphere, said conveyor means including first ."neans disposed within each of said tank means for conveying the tubular elements through the contents of the respective tanks, and second means for consecutively transferring the tubular elements between the tank means, and common means supporting the first and second means from said removable protective enclosure means.

4. Apparatus for the treatment and coating of tubular elements comprising first tank means for containing flux solution, second tank means for containing molten metal for preheating the tubular elements, and third tank means for containing the molten coating metal, conveyor means for conveying the tubular elements through each of said tank means, said conveyor means including a plurality of plates fixed Within each of said tank means and each having a cut-away portion providing an edge over which the tubular elements are moved, a serrated disc rotatably mounted adjacent each of said fixed plates and all of the serrated discs within each tank means being connected for common rotation, a plurality of star wheels mounted for common rotation within each tank means above said serrated discs, and inclined elements disposed between the tank means for receiving tubular elements discharged from the star wheels, protective enclosure means for at least the second and third tank means for containing a protective atmosphere, said protective enclosure means including cover sections removably sealingly associated with the several tank means, means for individually removing said cover sections, and means connecting certain of said cover sections over respective tank means with said serrated discs and said star wheels whereby the serrated discs and star wheels are removable with such cover sections.

5. The method of applying a galvanizing coating of zinc on ferrous tubular elements which comprises passing the tubular elements through a flux solution, passing the tubular elements through a separate preheating bath approximately in the galvanizing temperature range and containing a molten metal having substantially no afiinity for the ferrous tubular elements, and passing the tubular elements through a separate body of molten galvanizing metal the temperature of which is within the galvanizing temperature range.

6. The method of applying a galvanizing coating of zinc on ferrous tubular elements which comprises passing the tubular elements through a flux solution, purging the tubular elements of the air contained therein, filling the tubular elements with protective atmosphere, passing the tubular elements through a separate preheated bath 10 approximately in the galvanizing temperature range which bath consists of a molten metal having substantially no affinity for the ferrous tubular elements and which is protectively covered with a protective atmosphere, and passing the tubular elements through a protectively covered, separate body of molten galvanizing metal the temperature of which is within the galvanizing temperature range.

References Cited in the file of this patent UNITED STATES PATENTS 2,111,826 Waltman et al. Mar. 22, 1938 2,135,387 Dellgren Nov. 1, 1938 2,159,297 Shover May 23, 1939 2,166,250 Herman July 18, 1939 2,197,622 Sendzimir Apr. 16, 1940 2,276,232 Gilbert Mar. 10, 1942 2,405,221 Mann Aug. 6, 1946 FOREIGN PATENTS Germany Apr. 15, 1939

Claims

1. APPARATUS FOR THE TREATMENT AND COATING OF TUBULAR ELEMENTS COMPRISING FIRST TANK MEANS FOR CONTAINING FLUX SOLUTION, SECOND TANK MEANS FOR CONTAINING MOLTEN METAL FOR PREHEATING THE TUBULAR ELEMENTS, AND THIRD TANK MEANS FOR CONTAINING THE MOLTEN COATING METAL, CONVEYOR MEANS FOR CONVEYING THE TUBULAR ELEMENTS THROUGH EACH SAID TANK MEANS, AND PROTECTIVE ENCLOSURE MEANS FOR SAID SECOND AND THIRD TANK MEANS AND AT LEAST PART OF SAID FIRST TANK MEANS FOR ENCLOSING ABOVE THE CONTENTS OF EACH TANK MEANS A PROTECTIVE ATMOSPHERE, SAID CONVEYOR MEANS INCLUDING FIXED PLATES EACH HAVING A CUTAWAY PORTION PROVIDING AN EDGE OVER WHICH THE TUBULAR ELEMENTS ARE MOVED, ROTATABLY MOUNTED COOPERATIVE MEMBERS PROVIDED WITH TUBULAR ELEMENT-RECEIVING SURFCE PORTIONS PREDETERMINATELY DISPOSED RELATIVE TO SAID FIXED PLATES SO AS TO SPECEDLY HOLD SAID TUBULAR ELEMENTS, SAID COOPERATIVE MEMBERS HAVING DRIVING MEANS FOR MOVING SAID ELEMENTRECEIVING SURFACE PORTIONS RELATIVE TO SAID PLATES, SAID FIXED PLATES BEING DISPOSED IN SUCCESSIVELY STEPPED RELATION AND THE COOPERATIVE MEMBERS BEING MOUNTED ON AN INCLINED AXIS SO AS TO CONVEY THE TUBULAR ELEMENTS IN SLIGHTLY INCLINED RELATIONSHIP, AND SAID PROTECTIVE ENCLOSURE MEANS INCLUDING A DEPENDING SEALING WALL PROJECTING INTO THE FIRST TANK MEANS BELOW THE LEVEL OF ITS CONTENTS OF THE FIRST SPACED RELATION TO ONE END WALL THEREOF SO THAT UPON ENTRY OF THE TUBULAR ELEMENTS INTO THE CONTANTS OF THE FIRST TANK MEANS BETWEEN SUCH ONE END WALL AND THE SEALING WALL THE AIR IS PURGED FROM THE TUBULAR ELEMENTS AND UPON EXIT FROM SAID FIRST TANK MEANS THE TUBULAR ELEMENTS FILL WITH PROTECTIVE ATMOSPHERE FOR PASSAGE INTO THE SECOND TANK MEANS.