Galvanizing Apparatus

Abstract

Means raise, lower, spin and translate a perforated basket to, into and through a sequence of treating stations whereby to galvanize articles supported in the basket. A separate motor effects spinning of the basket. This motor is independent of any means to raise, lower, translate or support the weight of such basket.

Parent Case Text

This is a division of U.S. Pat. application Ser. No. 771, filed Jan. 5, 1970, and now abandoned.

Description

An apparatus is described. In this respect, the perforate basket has a central vertical column to prevent load unbalance. Air motors and controls are used to both selectively spin the basket and provide it with selective vertical and horizontal motion. The basket itself is hung from a hook that is rotatably suspended from the rail above the workpath so that the weight of the basket and articles is transmitted to the rail. The hook also has a socket for engaging a mating output shaft on the spin motor which is free to rotate at a selected speed. In this manner the spin motor is adapter to spin the basket without being subjected to its weight.

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 U.S. 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 an apparatus to obviate the requirement that the coated articles a centrifuge.

In addition, as a practicle 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 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 produce 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 apparatus 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 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 invention, 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 articles 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 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, the 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"p167 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 rust" 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. Secondly, my structure permits the basket to be spun during any or all parts of its horizontal and vertical travel; whereas Lindemann's apparatus can only spin individual articles at two specific locations; and thirdly, the motion of Lindemann's 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 undersired 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 to remove 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. 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 basket's various positions.

In utilizing the apparatus 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 alkalai 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 DuPont 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 100 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 bath's flux is skimmed back in a conventional manner and the basket is spun at a speed of about 100 rpm and preferably about 5 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 clading 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 basket's 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 form 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 apparatus 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, 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.

The invention will now be described with reference to FIG. 3.

The basket 20 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 basket's rim. This center column functions to keep the basket's 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 at 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.

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 fit into shoulders on the lower cover 86.

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 basket's 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 4 inch diameter pipe.

No. 1 No. 2 No. 3 No. 4 __________________________________________________________________________ Diameter, Inches 16 22 33 20 Depth, Inches 22 30 36 48 Metal Thickness 3/16" 3/8" 3/8" 3/8" Perforation hole sizes 1/8" 3/8" 3/8" 3/8" Hole Spacing (centers) 3/8" 3/4" 3/4" 3/4" __________________________________________________________________________

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 throttle valves 58, 66, and 76, it will also be appreciated that the movements of the suspended basket and its spin speed are susceptible to being automatically controlled. As still another modification, it will be appreciated that separate spinning means can be located 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.

Claims

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

1. An apparatus for hot dip, spin galvanizing articles comprising:

a tank containing a molten metal;

a tank containing a quenching solution; and,

a portable, freely suspended centrifuge, said portable, freely suspended centrifuge comprising:

a motor having a rotatable shaft;

article support means for supporting articles to be galvanized about a substantially vertical axis;

support means mounted between said motor and said article support means for supporting the weight of said article support means and said motor in a manner such that said motor is free to rotate said article support means, the shaft of said motor being loosely connected, in driving fashion, to said article support means;

raising and lowering means mounted above said motor, said article support means and said said support means and attached to said support means for selectively vertically raising and lowering said motor, said article support means and said support means; and,

movement means adapted to horizontally move said motor, said article support means and said support means from a position above said tank containing a molten metal to a position above said tank containing a quenching solution.

2. An apparatus for hot dip, spin galvanizing articles as claimed in claimed 1 wherein said article support means comprises a perforate container including a central vertical column for preventing articles supported in said container from becoming unbalanced when said perforate container is selectively rotated about said substantially vertical axis, the longitudinal axis of said central vertical column coinciding with said substantially vertical axis.

3. An apparatus for hot dip, spin galvanizing articles as claimed in claim 2 wherein said support means comprises:

a motor housing suitable for housing said motor, said housing being attached to said raising and lowering means;

A drive linkage housing attached to said motor housing; and,

a drive linkage mounted in said drive linkage housing and rotatably connected between the shaft of said motor and said perforate container.

4. An apparatus for hot dip, spin galvanizing articles as claimed in claim 3 wherein said drive linkage comprises:

a hook shaped element, said perforate container being hung from the hook shaped end of said hook shaped element, the other end of said hook shaped element being mechanically connected to the shaft of said motor; and,

a thrust bearing mounted in said drive linkage housing and surrounding said hook shaped element in a manner such that said hook shaped element is free to rotate.

5. An apparatus for hot dip, spin galvanizing articles as claimed in claim 4 wherein said motor is a first air motor and including means for selectively applying air pressure to said first air motor in order to control the velocity at which said first air motor selectively rotates said perforate container.

6. An apparatus for hot dip, spin galvanizing articles as claimed in claim 5 wherein said rasing and lowering means includes a second air motor and means for selectively applying air pressure to said second air motor.

7. An apparatus for hot dip, spin galvanizing articles as claimed in claim 6 including a cable attached between said second air motor and said motor housing in a manner such that increasing and decreasing the length of said cable raises and lowers said motor housing, said first air motor and said perforate container, said increase and decrease in the length of said cable being caused by the selective application of air to said second air motor.

8. An apparatus for hot dip, spin galvanizing articles as claimed in claim 7 wherein said movement means comprises:

a horizontally supported rail mounted above said tank containing a molten metal and said tank containing a quenching solution;

a third air motor mounted on said rail for movement along said rail; and,

means for selectively applying air pressure to said third air motor, said application causing the selective horizontal movement of said first, second and third air motors, and said perforate container.

9. An apparatus for hot dip, spin galvanizing articles as claimed in claim 1 wherein said motor is a first air motor and including means for selectively applying air pressure to said first air motor in order to control the velocity at which said first air motor selectively rotates said article support means.

10. An apparatus for hot dip, spin galvanizing articles as claimed in claim 9 wherein said raising and lowering means includes a second air motor and means for selectively applying air pressure to said second air motor.

11. An apparatus for hot dip, spin galvanizing articles as claimed in claim 10 including a cable attached between said second air motor and said first air motor in a manner such that increasing and decreasing the length of said cable raises and lowers said first air motor and said article support means, said increase and decrease in the length of said cable being caused by the selective application of air to said second air motor.

12. An apparatus for hot dip, spin galvanizing articles as claimed in claim 11 wherein said movement means includes:

a horizontally supported rail mounted above said tank containing a molten metal and said tank containing a quenching solution;

a third air motor mounted on said rail for movement along said rail; and,

means for selectively apply air pressure to said third air motor, said application causing the selective horizontal movement of said first, second and third air motors, and said article support means.

13. An apparatus for hot dip, spin galvanizing articles comprising:

a tank containing a molten metal;

a tank containing a quenching solution; and,

a portable, freely suspended centrifuge, said portable, freely suspended centrifuge comprising:

a motor having a rotatable shaft;

article support means for supporting articles to be galvanized about a substantially vertical axis;

support means mounted between said motor and said article support means for supporting the weight of said article support means and said motor in a manner such that said motor is free to rotate said article support means without the shaft of said motor bearing the weight of said article support means, the shaft of said motor being loosely connected, in driving fashion, to said article support means;

raising and lowering means including at least one cable attached to said support means for selectively vertically raising and lowering said motor, said article support means and said support means; and

movement means adapted to horizontally move said motor, said article support means and said support means from a position above said tank containing a molten metal to a position above said tank containing a quenching solution.

14. An apparatus for hot dip, spin galvanizing articles as claimed in claim 13 wherein said motor is a first air motor and including means for selectively applying air pressure to said first air motor in order to control the velocity at which said first air motor selectively rotates said article support means.

15. An apparatus for hot dip, spin galvanizing articles as claimed in claim 14 wherein said raising and lowering means includes a second air motor and means for selectively applying air pressure to said second air motor.

16. An apparatus for hot dip, spin galvanizing articles as claimed in claim 15 wherein said cable is attached between said second air motor and said first air motor in a manner such that increasing and decreasing the length of said cable raises and lowers said first air motor and said article support means, said increase and decrease in the length of said cable being caused by the selective application of air to said second air motor.

17. An apparatus for hot dip, spin galvanizing articles as claimed in claim 16 wherein said movement means includes:

a horizontally supported rail mounted above said tank containing a molten metal and said tank containing a quenching solution;

a third air motor mounted on said rail for movement along said rail; and,

means for selectively apply air pressure to said third air motor, said application causing the selective horizontal movement of said first, second and third air motors, and said article support means.

18. A portable, freely suspended centrifuge comprising:

article support means for supporting articles about a substantially vertical axis;

a first air motor having a rotatable shaft;

support means mounted between said first air motor and said article support means for supporting the weight of said article support means in a manner such that said first air motor is free to rotate said article support means without the shaft of said first air motor bearing the weight of said article support means, the shaft of said first air motor being loosely connected, in driving fashion, to said article support means to rotate said article support means in a centrifuge manner about said substantially vertical axis;

raising and lowering means including at least one cable attached to said support means for selectively vertically raising and lowering said first air motor, said article support means and said support means as the length of said cable is selectively increased and decreased; and,

movement means attached to said raising and lowering means, said first air motor, said article support means and said support means for horizontally moving said raising and lowering means, said first air motor, said article support means and said support means.

19. A portable suspended centrifuge as claimed in claim 18 wherein said raising and lowering means includes a second air motor and means for selectively applying air pressure to said second air motor.

20. A portable suspended centrifuge as claimed in claim 19 wherein said cable is attached between said second air motor, and first air motor and said article support means in a manner such that increasing and decreasing the length of said cable raises and lowers said first air motor and said article support means, said increase and decrease in the length of said cable being caused by the selective application of air to said second air motor.

21. A portable suspended centrifuge as claimed in claim 20 wherein said movement means includes a horizontally supported rail and a third air motor mounted on said rail for movement along said rail, and further including means for selectively applying air pressure to said third air motor, said application causing the selective horizontal movement of said first, second and third air motors, and said article support means.