US1787175A - Apparatus for enameling metal articles - Google Patents

Description

Dec. 30, 1930. A. G. SHERMAN ET AL 1,737,175

APPARATUS FOR ENAMELING METAL ARTICLES Filed Feb. 26, 192'? fi 262;; M

Patented Dec. 30, 1930 UNITED STATES PATENT OFFIIZEV .ALVIN G. SHERMAN, OF GROSSE POIN'IE, AND ALBERT IVIEADOWS, OF DETROIT, MICHI- GAN, ASSIGNORS TO THE DETROIT VAPOR STOVE COMPANY, OF DETROIT, MICHIGAN,

A CORPORATION OF MICHIGAN APPARATUS FOR ENAMELING- METAL ARTICLES Application filed February 26, 1927. Serial No. 171,356.

the work has been conveyed on trucks in stacked relation to a diptank; the plates dipped and set upright without any relation to the subsequent firing or the preceding cleaning operations, and then stored on trucks preparatory to the firing operation. In the firing operation the enamel-coated articles have usually been placed on a suitable carriage in large gangs and fedinto a muffle furnace and heated until they are in a dull redhot condition. When the articles have been fired the proper length oftime, according to the individual operator, they are then removed from the muffle furnace and transferred to'racks or trucks and allowed to cool. This transferring of the pipes or articles to the racks: from the firing operation has been manual and entirely dependent upon the individual operator. After a cooling operation, the trucks are Wheeled to spraying booths preparatory to applying the finish enamel coats thereto and subsequently firing the same.

Recently a continuous enameling process and apparatus has been developed, such as is described in our copending application Serial No. 31,811, filed May 21, 1925, which has become Patent No. 1,681,441. In this recent process the articles are continuously worked in predetermined time periods, and synchronized from the time the process is first undertaken until it is finally finished. The various steps are coordinated in capacity, speed, and distance of; travel so that they all work together to apply the several coats of glass enamel to the article as it travels in the line of instrumentalities. The articles are fired in a rotary electric furnace and the dipping, drips with suchfiring furnace whereby the articles are in the proper physical and chemical conditions and are placed in the firing furnace at a predetermined time after thedripping and drying whereby to obtain'best results in the firing operation. The articles are progressively and uniformly heated in the rotary furnace, and are taken out at a point closely adjacent where they are placed into the rotary furnace. These articles, when taken out of the furnace, are at a dull red heat, according to the particular firing operation carried out, and it has been the prac' tice to place these articles, after being directly removed from'the rotary furnace, on a suitable straightening plate. It also has been the practice for an operator to remove such articles from the straightening plate and place the same on a suitable coolingconveyer preparatory to inspection and initial finish-- coat spraying. As this operation has been left entirely up to the particular operator, it has often resulted that the articles or plates were picked up too soon by the operator, with the result that a slight, or even a warpor sagging resulted. Furthern'iore, plates or articles placed in upright positions for'subsequentcooling have been subjected to still further warping or sagging, due to such vertically hanging, when transferred from the rotary furnace to the cooling conveyers too soon.

It is the object of the present invention to interpose a medium between the firing operations or after the. firing operations, where by the correct cooling and straightening of each and every article is positively insured. The apparatus comprises a suitable conyeyer moving horizontally and longitudinally, and provided with links or conveying surfaces which are fairly close together and of relatively heavy material. This conveyer is positioned betweenthe' rotary furnace and the cooling conveyers, the one end being positioned adjacent the removalpoint of the rotary furnace, and the conveyer being of sues hot articles being placed thereon will he properlystraightenedand cooled, and it will I be impossible for the operator to remove the tween the furnace and secondary cooling conveyers.

Fig. 2 is a fragmentary detail view, somewhat diagrammatic, of a oonveyer that may be used in carrying out this process.

It is believed that the invention Will best be explained by describing the stepsof operation leading up to the particular step forming the main basis for the presentinvention. Metal articles, particularly sheet metal articles, and even cast iron articles, have presented many diiiiculties in the glass enameling thereof, and a large majority of such difliculties, and a cause of the resulting imperfections, may be traced largely to the improper chemical and physical changes which arise between the various operations. WVhile the present invention may be utilized in various enameling systems other than the one described in applicants above mentioned pending uniformly perfect ware. Referring to Fig. 1, which is somewhat diagrammatic, the

- properly cleansed articles or plates may be dipped in the tank 1, which is known as the ground coat dipping tank. After the an ticles are properly dipped they are immediately transferred to the conveyer 2. The details of this conveyer are fully described and illustrated in applicants said copending application, but it will be sufficient for the present invention to state that it is atimed conveyer adapted to receive and position the articles vertically. i

A drying chamber is preferably provided for forcing the drying of the dipped articles, such drying chamber being designated 3. The conveyor for receiving the dipped articles is preferably positioned to run along closely adjacent the one wall of the drying chamber as at 4. the clipping tank to the drying chamber may be called the dripping run. This dripping run portion and conveyer are so p-osi-' tioned adjacent the drying chamber that the plates positioned on the conveyer will be subject to radiating heat from the drying chains.

ber,'so as to temporarily fix the depth of enamel coat at the proper time. a

The drying chamber 3 assists in forcing.

This run of the conveyer from the drying of the articles, and is so designed and operated that the articles, after being dipped and having the proper coatingenamel, are dried to have the proper chemical and physical properties upon issuing from the drying chamber, thus eliminating all chances of damage to the coated surfaces due to the humidity of the air and dust or other particles. .The properly dried articles continuously and successively issue from the drying chamber and are presented by the conveyer to a position 5 closely adjacent the feeding port of a firing furnace, which may be generally designated 6.

As such properly coated and dried articles are continuously and successively presented, they must be removed by the workmen, and immediately placed in the firing oven. Each piece is therefore uniform with respect to physical and chemical characteristics at the time it is to be fired, and each piece is there fore also fired at just the proper time after drying.

The rotary furnace 6 is diagrammatically illustrated in Fig. 1, and it is of the type described. in applicants said above mentioned copending application. It comprises an electric furnace of circular design, the heating portion of which comprises an annular small passageway extending around the furnace. Inthis'annular passageway is adapted to rotate a suitable table provided with prongs for receiving the articles to be fired. Suitable electric resistance elements'are placed in the furnace at the desired point whereby the articles are progressively brought upto the desired fusing temperature, maintained at such temperature for the correct amount of time and then progressively cooled until they reach a position to be removed from the furnace. As this firing operation is uniform and continuous, each separate article fired will, at the time of its removal from the furnace, be of approximately the same temperature. In practice, such articles as are removed from the rotary furnace, are of cherry red in color, and are of such a temperature that they very easily warp and sag, particularly if the articles are large and have broad faces. The articles are taken from their horizontal position on the supporting prongs in the furnace by means of forks which are designed to evenly support the articles at all points.

However, this is not always possible, and it is therefore sometimes desirable to lay the hot articles on a fiat surface whereby they will straighten, due to the inherent heat in the article, and thus be in a condition to handle properly when cool. It may be that even if the article warps the warped part may be brought into shape by subsequent firing operations, but this is not always true and it usu- In order to positively prevent the article from being picked up too soon after it is removed from the firing furnace, a straightening conveyer is provided, which may be designated '7. This conveyer is supported at the ends by means of suitable gears or rotors 8, whereby the conveyer is continuously moved in a closed path at a desired speed. The length of this conveyer 7 is proportioned according to the firing temperature maintained in the furnace 6, one end of the conveyer being positioned closely adjacent the take-out aperture of the furnace, and the other end of the conveyer being positioned closely adjacent a conveyer 9, which may be termed a secondary cooling conveyer.

The articles, when they are removed from the furnace in their cherry red condition, are then placed fiatly upon the straightening conveyer 7. This conveyer is provided with a plurality of heavy, fiat, shoes or slats 10 which present a continuous flat surface between the rotors 8. As the hot articles are positioned flatly on this conveyer, they will gradually straighten out, due to their inherent weight and temperature, and also gradually cool. The separate articles are maintained in this flat condition the length of the conveyer and the conveyer is of such length that when said articles reach the end of the conveyer, they will have cooled to such an extent that they will not be affected in the least by the removal from the conveyer table by the operator.

This positively eliminates all sagging and warping of the hot articles due to any operator picking them up too soon, and it automatically insures straightening of all the articles.

When the articles are removed from the straightening and cooling conveyer they are placed in upright position on the secondary cooling conveyer 9 and are conveyed back and forth whereby they are completely cooled, so as to be initially inspected and then conducted through the spray booth.

After the articles are sprayed they are immediately dried and fired, and then sprayed, dried and fired again for the finishing operation. It will be understood that between the second and third firing operations a similar conveyer 7 may be utilized for positively effecting straightening and cooling of the articles. The same is true after the final firing operation when the finally finished articles are stored or placed upon racks. After this final firing operation, the article may be placed directly on a cooling and straightening conveyer, just as is shown in Fig. 1, and therefore insuring positive straightening and the correct amount of cooling before being picked up and stored or transported.

It will be understood that the conveyer elements 10 are preferably heavy, whereby, in case any extra heavy sheet or article is fired and is slightly warped when placed upon the straightening conveyer, that suitable weight ing means may be utilized when effecting straightening of the article.

It will be also understood that this interposition of the straightening and cooling conveyer between the first and second firing operations cooperates directly with the spraying and subsequent firing operation, in that the articles are insured to be evenly and uniformly sprayed, as otherwise if the article were as to the firing of the enamel and the contour of the surface.

Claims:

1. In an enameling mill of the type having a rotary furnace for consecutively firing metal articles at a relatively high heat and means for receiving the fired articles, the combination with said firing furnace and said receiving means of a conveyer positioned therebes tween, one end of the conveyer being adjacent the outlet of the furnace and the other end adjacent said receiving means, the surface of said conveyer being relatively flat whereby to receive the hot fired articles and to straighten the same, the length of the conveyer between said furnace and saidreceiving mean-s being such as to insure cooling and fixing of the straightened articles whereby to insure that the articles will not be afiected when transferred from the straight ening conveyer to the receiving means.

2. In an enameling mill for metal articles, the combination of firingmeans for firing and delivering metal articles at a relatively high heat, means positioned adjacent said delivering point for receiving and supporting said articles whereby they are straightened due to saidsupporting surface, mean-s for moving said supporting means whereby movement of the supporting surface will simultaneously cool said article or articles thereon at or during the straightening step, and a secondary cooling means positioned adjacent saidsupporting means at such a distance from the delivering point of the hot articles to insure cooling and fixation of the articles before being transferred to said secondary cooling means.

In testimony whereof we aifix our signatures.

ALVIN G. SHERMAN. ALBERT MEADOWS.

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