US3753762A

US3753762A - Method of galvanizing

Info

Publication number: US3753762A
Application number: US00255806A
Authority: US
Inventors: W Garrison
Original assignee: American Spin-A-Batch Co
Current assignee: American Spin-A-Batch Co
Priority date: 1972-05-22
Filing date: 1972-05-22
Publication date: 1973-08-21
Anticipated expiration: 1990-08-21

Abstract

A method of galvanizing batches of articles wherein the articles are placed in a perforate basket which is suspended from a rail above a workpath. The thusly suspended articles are first dunked in pickling, rinsing and fluxing solutions and then into a zinc bath where the basket and articles are spun to remove flux. The basket is then removed from the bath, moved directly to a position over a quench tank and again spun so that spelter falls into the tank for removal as shot. The basket and articles are also spun while being lowered into the quench tank; after the quenching step; and during certain of the other above described steps so as to result in varying degrees of product improvement.

Description

United States Patent 1191 Garrison Aug. 21, 1973 METHOD OF GALVANIZING 1,119,934 10/1930 Giblin 111/101 Inventor: William HGl I RichmondVa' 2,273,250 2/1942 Charlton 117/101 F El N ATEN S PPL AT NS [73] Asslgneez American Spln-A-Batch Company, 1 3 3 5 G T IC I0 118 54 Richmond Va reat rttam [221 Filed 1972 im??? smi" '#R Rh..$-, 111 1 211 App] N 255 0 AJtqmey-B. Franklin Grifiin, Alan E. J. Branigan e a Related US. Application Data [63] Continuation of Ser. No. 111, Jan. 5, 1910, [57] AESTRACT abandoned A method of galvanizing batches of articles wherein the articles are placed in a perforate basket which is sus- [52] Cl 117/51 1 5 pended from a rail above a workpath. The thusly sus- 51 I t Cl 3 pended articles are first dunked in pickling, rinsing and d c fluxing solutions and then into a zinc bath where the l 1 e 71?; C 4 4 11 basket and articles are spun to remove flux. The basket l 4 is then removed from the bath, moved directly to a position over a quench tank and again spun so that spelter [561 References (med falls into the tank for removal as shot. The basket and UNITED STATES PATENTS articles are also spun while being lowered into the 1,140,068 5/1915 Roberts 118/54 quench tank; 'after the quenching step; and during cerl,252.005 1/1918 Hess 117/101 X tain of the other above described steps so as to result Kelley 1. in varying degrees of product i provernent 1,748,363 2/1930 Peirce, Jr 118/54 16 Claims, 5 Drawing: Figures SPIN SPIN COAT QUENCH PRE-COATING PAIEmwww ma 3.753762 saw 1 022 FIG.

Hf/Ol? ART l6 [-IZ 14 I87 PICKLE, RINSE a COAT QUENCH FLUX FIG. 2

SPIN SPIN COAT QUENCH PRE-coAT|Ne- FIG. 3

juvsmon WILLIAM H. GARRISON BY .Bram'qan m ATTORNEYS PATENIEmncm um I 3.753762 SHEEI 2 OF 2 FIG. 4

mvsmon WILLIAM H. GARRISON y g ffl'mjraniqan MHZ/ Mus ATTORNEYS METHOD OF GALVANIZING This is a continuation, division, of application Ser. No. 771, filed 5 Jan. 1970, now abandoned.

GALVANIZING METHOD AND APPARATUS Conventional methods of galvanizing batches of articles usually include a spinning step to throw off surplus molten zinc or spelter. In this respect, as described in US. Pat. No. 1,324,228 to Watrous, after certain surface preparation steps, the articles to be galvanized are dipped in a kettle or tank of molten zinc. The articles are then removed and usually placed in a floor mounted centrifuge to remove the spelter which strikes the side of the centrifuge for subsequent removal. The articles are then removed from the centrifuge while they are still hot, and dipped in a quench tank. The thusly coated articles are then removed from the quench tank.

There are many drawbacks to the above described conventional galvanizing process, but it has been used for years with only minor modifications being made from time to time. One of the major drawbacks of the conventional process has been the need for transferring the coated articles to the centrifuge. This has been required, however, because such centrifuges are large and highly specialized pieces of equipment which, for purposes of stability, must be securely mounted to the floor. Hence, it is an object of this invention to provide a method which does not require the coated articles to be transferred to a centrifuge.

In addition, as a practical matter, conventional centrifuging methods are limited to use in connection with the coating of relatively small articles having a maximum length of about 24 inches or so because the cost of larger centrifuges is almost prohibitive. Consequently, it is another object of the invention to provide a more practical and economical method and apparatus for galvanizing articles which range in size from about a half-inch all the way up to about 48 inches in length or larger. In this respect, it has been quite difficult to satisfactorily galvanize large batches of small articles such as wood screws, for example. Among other reasons, this is because the flux in the zinc bath has a tendency to lodge in the recesses of the coated articles. In the case of batch dipped wood screws, for example, the slots in the head become clogged and the thusly coated threads are often too shallow. This not only produces an inferior product, but also wastes zinc. Other objects of the invention, therefore, are to provide a galvanizing method which uses less zinc and produces a higher quality galvanized product. In this respect, it should be noted that the invention not only provides a more economical method, but also produces a superior quality galvanized product having a wider range of sizes than those of the prior art. It should be similarly noted that in conventional galvanizing methods some of the excess zinc appears as spurs" on the surfaces of the galvanized articles. But my method substantially eliminates those spurs so as to result in much safer product.

Articles galvanized by conventional centrifugal methods have also been plagued with water staining or white rust which occurs after the quenching step. Hence, it is another object of this invention to produce a high quality galvanized articles that is free of water stains.

Finally, it is an object of the invention to provide a simple, easily maintainable apparatus for practicing the method of the invention so as to produce higher quality galvanized articles in less time than has previously been required.

SUMMARY OF THE INVENTION In accordance with the broader aspects of my inventive method, the articles to be galvanized are first placed in a spinable perforate container or basket that is hung so as to be freely suspended above a workpath comprised of a series of vats or tanks used during the process. The basket and its contents are first sequentially dipped in suitable pre-coating tanks containing pickling, rinsing, and flux solutions. The'basket and its thusly prepared articles are then dipped into a molten zinc bath where they are galvanized. While the arti cles are still suspended in the galvanizing basket, they are next moved over the quench tank where the basket and articles are spun while suspended above the quench tank to remove the excess molten zinc or spelter which drops into the quench tank for subsequent removal in the form of shot. Next, while still spinning, the basket and articles are lowered into the quench tank for quenching. This is followed by removal and drying. Significantly, the thusly galvanized articles are suspended during the entire process of the invention. Hence, it is not necessary to perform the previously required steps of transferring the articles into a separate centrifuge or again transferring them back to the quench tank after they are spun.

In addition, the apparatus of my invention permits the articles to be spun during any of the above noted process steps. In this respect, I have found that the pickling process is both faster and more adequate when the basket and articles are spun while they are in the pickling tanks. They can also be spun dry after pickling so as to obtain the benefits of such a drying step without applying heat as has been required in the past. Similarly, when they are spun while in the zinc bath, flux is more completely and uniformly removed which, as noted above, results in a superior product, particularly for small articles such as wood screws which have many relatively small recesses and depressions where flux tends to lodge. Also similarly, objectionable zinc spurs are substantially eliminated when the basket and parts are spun as they are dunked in the quench tank; the coating has a more uniform hardness when the basket is spun during the quench step; and when a spinning step is added after quenching the resulting product is substantially free from white rus or water staining. Consequently, it will be appreciated by those skilled in the art that my apparatus not only results in an economical process, but provides a product that is superior to that of the prior art.

Insofar as the apparatus aspects of my invention are concerned, a means is provided for moving the suspended perforate basket horizontally above the various tanks and selectively raising and lowering the basket vertically to dunk the articles. A means is also provided for selectively spinning the basket at controlled speeds so that the method of the invention can be practiced as described above.

U.S. Pat. No. 3,310,027 to Lindemann is pertinent to these apparatus aspects of my invention, but the Lindemann structure is not suited for the practice of my method. Firstly, Lindemann does not describe a galvanizing apparatus and has no structure such as my perforate basket for spinning large batches of articles. Se-

condly, my structure permits the basket to be spun during any or all parts of its horizontal and vertical travel; whereas Lindemanns apparatus can only spin individual articles at two specific locations; and thirdly, the motion of Lindemanns coated article is confined to a fixed closed path, so that it does not have the flexibility required for galvanizing apparatus which use different sizes and locations of tanks depending on the type of articles being galvanized.

In addition to fulfilling the above objects, my invention also has certain other advantages. For example, when the basket is spun in the zinc bath to dislodge undesired flux, the zinc is also more evenly distributed on each article and the incidence of undesired occlusions is greatly reduced if not substantially eliminated. Also, when the spelter is spun out of the basket over the quench tank, it falls into the tank so that it can be easily removed as shot and returned to the zinc bath. But when conventional floor mounted centrifuges are employed, the spelter is far more difficult to recover. It should also be noted that because of the short time lag between removal of the basket from the zinc bath and the spin step over the quench tank, my method produces a more uniform coating without the hills and valleys which occur when floor mounted centrifuges are employed.

BRIEF DESCRIPTION OF THE DRAWINGS The foregoing and other objects, features, and advantages of the invention will be apparent from the following more particular description of preferred embodiments of the invention as is illustrated in the accompanying drawings, wherein reference characters refer to the same parts throughout the different views. The drawings are not necessarily drawn to scale. Instead, they are merely presented so as to illustrate the principles of the invention in a clear manner.

FIG. 1 is a schematic representation of a prior art process for galvanizing metal;

FIG. 2 is a schematic representation of the method of the invention;

FIG. 3 is a pictorial representation of certain apparatus of the invention including control means therefor;

FIG. 4 illustrates an air motor and mechanical coupling (partially broken-away) for spinning a suspended perforate galvanizing basket; and,

FIG. 5 is a sectional view taken along the lines 5-5 in FIG. 3.

DETAILED DESCRIPTION As noted above, conventional methods of galvanizing batches of articles include the steps of dipping the articles in a series of pre-coating tanks of pickling, rinsing, and fluxing solutions. These tanks are located along a given work path and are schematically illustrated in FIG. 1 by a single tank 12. The articles to be coated are then conventionally placed in a tank such as 14 containing a molten zinc bath covered with flux. Next, the flux is swept back and the parts are removed to be placed in a centrifuge 16 where they are spun toremove excess zinc. The parts are then quenched in a suitable quenching solution located in tank 18.

In accordance with the method of the instant invention, the parts to be coated are placed in a perforate basket 20 in FIG. 2 which is freely suspended above the workpath and adapted to undergo horizontal and vertical motion in the direction of the

arrows

22 and 24 respectively in other words, the basket is portable along the above the workpath without a need to remove the articles to be coated. The basket 20 is also adapted to be selectively spun as indicated by arrow 26 at controlled speeds of up to about 725 rpm in a preferred embodiment of the invention. In this manner, the basket and the parts to be coated can be spun at selected speeds in any of the baskets various positions.

In practicing the method of my invention, the parts to be coated are first placed in the suspended basket which is then sequentially dunked into the various pickling, rinsing, and fluxing solutions. In this respect, I prefer to first dunk in an alkali bath comprised of a caustic soda solution. Next, the articles are rinsed in a water bath before being placed in a sulfuric acid pickling solution and then water rinsed again. The articles are then dipped in either a muriatic acid flux solution or one of the commercial fluxes such as that sold by Du- Pont under the Trademark ZACLON. It should be noted that at this point I have found the pickling, rinsing and fluxing steps to be both more rapid and more adequate when the basket is spun at a speed of up to about rpm while it is in the various schematically illustrated tanks 28.

After pickling, the basket is spun until dry and then moved above a tank 30 containing the molten zinc bath 32 covered by a flux such as ZALCON. The basket is then lowered into the zinc bath. Next, the zinc baths flux is skimmed back in a conventional manner and the basket is spun at a speed of about 100 rpm and preferably about 50 rpm while suspended in the bath. As this occurs the flux can be observed leaving the coated articles and rising to the surface of the otherwise skimmed bath. This spinning step is continued until the flux stops rising at which time there is no longer any appreciable amount of flux lodged in the recesses of the galvanized articles. In this manner, the articles are not only free of flux, but the zinc coating has fewer high spots than in the past so as to result in a saving of zinc even though the galvanized product is of an overall higher quality.

After coating, the flux is again skimmed from the bath, and the basket is removed to be suspended over a quench tank 34 which is surrounded on at least one side by shields 36 which have been partially broken away in FIG. 2. Once the basket is located above the quench tank 34 it is spun at a relatively high speed such as about 725 rpm in the preferred embodiment noted above. When the basket is spun in this manner, the spelter is spun out of the baskets perforations to either fall into the quench tank 34 or strike the shields 36 which direct the spelter into the quench tank. In either event, the spelter collects in the bottom of the quench tank in the fonn of shot which can be subsequently easily removed so that it can be either used to replenish the zinc bath or otherwise reclaimed.

While the basket is still spinning it is next lowered into the quenching solution for cooling. Spinning at this time prevents the formation of spurs. The basket is then removed from the quench tank and air dried while it is again spun. In this manner, the familiar water staining or white rust is prevented.

From the above discussion, it will be appreciated that the method of the invention is not only simple, but eliminates the previous requirement for a separate centrifuge; permits the coated articles to be quenched while they are at a higher temperature to prevent them from sticking together, and eliminates the need for separately transferring the coated articles into a centrifuge and then out again into a quench tank. In this respect, it should be noted that the time between the zinc bath and quench is much less than in conventional methods so as to result in less build up of zinc on parts such as threaded bolts or the like. In addition, the method of the invention generally results in a superior product that is evenly coated, bright, and free of both water staining and flux clogging as well as being substantially spurless.

Having described the method of the invention, the apparatus thereof will now be described with reference to FIG. 3.

The basket is perforated throughout its surface and has a sturdy eye 38 on a handle 40 for accommodating a hook 42 extending out of the bottom of a drive linkage housing 44 of a spin air motor housing 46. The basket also has a tubular center column 49 (FIG. 5) which extends upwardly to or above the baskets rim. This center column functions to keep the baskets load more evenly distributed during spinning so as to prevent eccentric loads from causing the basket to walk about during the various spinning steps.

Another eye 48 is affixed to the top of the spin motor housing and receives a second hook 50 extending from a hoist-pulley assembly 52. A cable 54 extends from a drum (not shown) on a reversible drive air motor 56 under control of a vertical control throttle valve 58 which is connected to the vertical drive motor 56 by means of an air supply tube 60. The other end of the cable 54 is affixed to a point not shown on a second reversible-drive air motor assembly 62. In this respect, both of the

drive motors

56 and 62 are mounted on a horizontal rail 64 corresponding to the arrow 22 in FIG. 2. Consequently, as air power is directed to drive motor 62 by means of a horizontal drive motor throttle control 66 and a second air supply tube 68, the two drive motors and a connecting arm 70 are selectively moved back and forth across the rail 64. In this manner, the basket 20 is suspended above the work bath for selective motion to its various process positions in the manner described in connection with the inventions method.

The spin motor located in the spin motor housing 46 receives air pressure from a pipe 72, see sketch FIG. 3, through a spin control throttle 76. In this respect, as is illustrated in more detail in FIG. 4, the spin air motor is rigidly affixed within the housing 46 by bolts 47 and has a square ended output shaft 78 which, under control of throttle 76, spins freely within a support tube 80 having

flanges

82 and 84 on either end thereof. The upper flange 82 is bolted to the spin motor housing 46 as shown in FIG. 4 and the flange 84 is bolted to a lower cover member 86, also as shown.

The hook 42 has a square female socket 88 affixed to a collar 90 at the upper end thereof. As illustrated, the female socket 88 engages the square output shaft 78 of the spin motor so that rotation of the spin motor is transmitted to the hook 42 which is supported and journaled for rotation within

bearings

92 and 94 which are suitably press flt into shoulders on the lower cover It should be particularly noted and appreciated that the weight of the basket 20 and its contents is transmitted from the collar 90 on the hook 42 to the upper bearing assembly 92, the lower cover 86, the doubly flanged tube 80 and the spin motor housing 46 to the upper eye 48. In this manner, none of the baskets weight is placed on the spin motor so that it is protected and insured of a longer life.

By virtue of the above described structure, the basket is adapted to undergo selective vertical motion under control of vertical throttle control 58; and selective horizontal motion under control of horizontal throttle control 66. At the same time the speed at which the basket is spun at any given time is under control of the spin control valve 76.

It is apparent that larger articles to be galvanized require larger baskets; and in this respect, the invention has been employed with several types of baskets. It should be noted however, that it has been found more satisfactory to use different perforation sizes and spacings for different basket sizes. The following table sets forth some of the dimensional parameters for baskets which have been found to operate satisfactorily in the practice of the invention. In each case the center column 49 was comprised of a 4 inch diameter pipe.

No. I No. 2 No. 3 No. 4 Diameter, inches 16 22 33 20 Depth, inches 22 30 36 48 Metal thickness 3/16" Perforation hole sizes a" #6" 46" $6" Hole Spacing (centers) 56" W 56" As noted above, it has been found satisfactory to use a spin motor having a spin speed variation of from 0 to about 725 rpm. In some specific applications it might be desirable to employ a higher speed air motor, but generally speaking 725 rpm is an adequate maximum. One air motor having that speed range consumed air at the rate of 48 cubic feet per minute at 90 lbs. per square inch input pressure.

In terms of production capacity, the method and apparatus of the invention provides startling results. For example, prior art structures, as. a practical matter, have had maximum batch weights of about 250 lbs. per load so as to result in an hourly maximum galvanizing capacity of about 3,000 lbs. per hour. When the above described invention is employed, however, 2,000 lbs. per load can be easily accommodated and the hourly output capacity is 24,000 lbs. or more. Moreover, and perhaps most significantly, use of the invention has cut overall production costs to less than one third of those of current methods; and labor costs have been reduced to almost one fourth of those of current methods. Consequently, when these startling cost reductions are coupled with a realization that my invention also results in a superior product, it will be appreciated that the invention has wide application and use.

While the invention has been particularly shown and described with reference to preferred embodiments thereof, it will be understood by those skilled in the art that various changes in form and detail may be made therein without departing from the spirit and scope of the invention. For example, the various pneumatic elements can be replaced by suitable electrical motors and switches. In fact, the rail and motor structure illustrated in FIG. 3 can be replaced by a vertically moveable swinging boom. Similarly, although the invention has been described in terms of manual control by means of above each work station so that the suspended perforate basket and its contents can be selectively sequentially moved by a crane or the like from one work station to another.

The embodiments of the invention in which an exclusive property or privilege is claimed are defined as follows:

l. A suspended centrifuge method of spin galvanizing articles comprising the steps of:

freely suspending said articles from above a workpath so that said articles are adapted to be selectively spun about a substantially vertical axis at selected locations along the workpath;

lowering said suspended articles into a molten zinc bath to coat said articles with zinc;

raising said suspended articles from said zinc bath;

promptly spinning said suspended articles about said vertical axis while said articles remain suspended to remove excess zinc therefrom before undesired zinc build-up occurs; and

lowering said suspended articles into a quench tank promptly after said zinc removal step while said articles are spinning and still at a sufficiently high temperature that the articles do not stick together.

2. The method of claim 1 wherein the excess zinc removal spinning step occurs while said articles are suspended over said quench tank whereby spelter is permitted to fall into said quench tank.

3. The method of claim 2 including the step of removing said spelter from said quench tank.

4. The method of claim 1 including the step of removing said suspended articles from said quench tank; and,

drying said suspended articles by spinning after removal from said quench tank.

5. The method of claim 1 wherein the step of freely suspending said articles includes placing said articles in a spinable perforate container.

6. The method of claim 1 including the step of immersing the suspended articles in a pre-coating solution prior to immersion of said articles in said molten zinc bath.

7. The method of claim 6 including the step of spinning said suspened articles while immersed in said precoating solution.

8. The method of claim 6 including the step of spinning said articles after removal from said pre-coating solution and prior to immersion in said molten zinc bath.

9. A suspended centrifuge method of spin galvanizing articles comprising the steps of:

spinning said articles while said articles are immersed in said zinc bath so that undesired flux is removed from the surface of said articles while said articles are in said zinc bath;

raising said suspended articles from said zinc bath;

promptly spinning said suspended articles about said vertical axis while said articles remain suspended to remove excess zinc therefrom before undesired zinc build up occurs; and

lowering said suspended articles into a quench tank promptly after said zinc removal step while said articles are still at a sufficiently high temperature that the articles do not stick together.

10. The method of claim 9 wherein said articles are coated with a fluxing agent prior to immersion in said molten zinc bath; and said spinning of said articles while immersed in said zinc bath is terminated and said articles are raised from said zinc bath when said fluxing agent ceases to float to the top of said zinc bath during said spinning in said zinc bath.

11. The method of claim 9 wherein said articles are spun while being lowered into said quench tank.

12. The method of claim 9 wherein the excess zinc removal spinning step occurs while said articles are suspended over said quench tank whereby spelter is permitted to fall into said quench tank.

13. The method of claim 12 including the step of removing said spelter from said quench tank.

14. The method of claim 9 including the step of removing said suspended articles from said quench tank; and,

drying said suspended articles by spinning after removal from said'quench tank.

15. The method of claim 9 wherein the step of freely suspending said articles includes placing said articles in a spinable perforate container.

16. The method of claim 9 including the step of spinning said articles while said articles are immersed in said quench tank.

Claims

2. The method of claim 1 wherein the excess zinc removal spinning step occurs while said articles are suspended over said quench tank whereby spelter is permitted to fall into said quench tank.
3. The method of claim 2 including the step of removing said spelter from said quench tank.
4. The method of claim 1 including the step of removing said suspended articles from said quench tank; and, drying said suspended articles by spinning after removal from said quench tank.
5. The method of claim 1 wherein the step of freely suspending said articles includes placing said articles in a spinable perforate container.
6. The method of claim 1 including the step of immersing the suspended articles in a pre-coating solution prior to immersion of said articles in said molten zinc bath.
7. The method of claim 6 including the step of spinning said suspened articles while immersed in said pre-coating solution.
8. The method of claim 6 including the step of spinning said articles after removal from said pre-coating solution and prior to immersion in said molten zinc bath.
9. A suspended centrifuge method of spin galvanizing articles comprising the steps of: freely suspending said articles from above a work-path so that said articles are adapted to be selectively spun about a substantially vertical axis at selected locations along the workpath; lowering said suspended articles into a molten zinc bath to coat said articles with zinc; spinning said articles while said articles are immersed in said zinc bath so that undesired flux is removed from the surface of said articles while said articles are in said zinc bath; raising said suspended articles from said zinc bath; promptly spinning said suspended articles about said vertical axis while said articles remain suspended to remove excess zinc therefrom before undesired zinc build up occurs; and lowering said suspended articles into a quench tank promptly after said zinc removal step while said articles are still at a sufficiently high temperature that the articles do not stick together.
10. The method of claim 9 wherein said articles are coated with a fluxing agent prior to immersion in said molten zinc bath; and said spinning of said articles while immersed in said zinc bath is terminated and said articles are raised from said zinc bath when said fluxing agent ceases to float to the top of said zinc bath during said spinning in said zinc bath.
11. The method of claim 9 wherein said articles are spun while being lowered into said quench tank.
12. The method of claim 9 wherein the excess zinc removal spinning step occurs while said articles are suspended over said quench tank whereby spelter is permitted to fall into said quench tank.
13. The method of claim 12 including the step of removing said spelter from said quench tank.
14. The method of claim 9 including the step of removing said suspended articles from said quench tank; and, drying said suspended articles by spinning after removal from said quench tank.
15. The method of claim 9 wherein the step of freely suspending said articles includes placing said articles in a spinable perforate container.
16. The method of claim 9 including the step of spinning said articles while said articles are immersed in said quench tank.