US2086166A - Method of producing articles from sheet material - Google Patents

Description

y A.- KRQNQUEST 2,086,166

METHOD OF PRODUCING ARTICLES FROM SHEET MATERIAL Filed Jul 24, 195

Patented July 6, 1937 METHOD OF PRODUCING ARTICLES snnn'r MATERIAL FROMl -Alfred L. Kronquest, Syracuse. N. asslgnor to Continental Can Company, Inc., New

N. Y., a corporation Application f July 24,

2 Claims.

The invention relates to new and usefuI im provements in a. method of producing articles from metal coated sheet steel and the product produced thereby.

An object of the invention is to provide a method of producing articles from metal coated sheets wherein the metal coating on the finished article is continuous .and unbroken throughou the entire surface of the article.

A further object of the invention is to provide a method of healing or closing cracks or scratches formed in the metal coating on a sheet during the die-drawing of the same to shape the article.

A still further object of the invention is to provide an article produced by drawing a metal coated sheet, which article has a continuous u'nbroken metal coating throughout the entire surface thereof.

These and other objects will in part be obvious 0 and will in part be hereinafter more fully disclosed.

' In the drawing which shows by way of illustration one form of article exemplifying the inventiona coated metal sheet indicating in'broken lines the blanks which are to be cut therefrom and shaped into a can end;

Fig. 21s a' plan view of a can 'end'cut from the sheet and shaped preparatory to applying the same to the can body for double seaming; Fig. 3 is a vertical sectional view diametrically of the can end, on an enlarged scale, and

Fig. 4 is a view showing a portion of a can ,end double seemed to a can body.

It has been a common practice to coat steel sheets with metal such as tin, for the purpose of protecting the steel andpreventing the same from oxidizing and deteriorating. Ithas also been a common practice to out such metal coated is strained to a point where it ruptures and separates, thus exposing the steel plate to the attack of the oxygen of the air. The purpose of the.

present invention is to produce a product and the method of ma ng the same wherein these spaces or cracks incident to the drawing operation are healed or closed, and whereby this closing of the cracks may be accomplished without applying any further coating to the shaped article. Tin has a much lower melting point than steel. Applicant has discovered that it is pos- Figure l is a perspective viewof a portion of York, of New York 1935, Serial-No. 32,937

sible to subject the finished article to the influence of heat and thus render the metal coating on the sheet steel fluid so that it will flow and close up the cracks in the coating produced during the die-drawing without in any way disturb- .ing the sheet steel which gives shape and form to the article.

It is thought that the invention will be better understood by a' more detail-description of the specific article and the method of making the same. The article illustrated in the drawing is a can end which is produced from tin-coated sheet steel. The sheet steel is indicated at I and the tin coatings thereon are indicated at 2 and 3, both surfaces preferably being coated. The sheet of steel is coated with tin while in the flat. Blanks are cut from this sheet of steel and are die-shaped into can ends. The broken lines a, a (Fig. 1) indicate the line of cutting of the sheet to form the blanks, each blank forming a can 6 end. In Figures 2 and 3 of the drawing, the finished can end is indicated at l. The blank die-shaped to produce the can end. The metal is drawn so as to provide a central panel surrounding which is 'a raised annular rib 5. This is for the purpose of giving strength to the panel and preventing the same from curving.

one way or the other, due to a differential in pressure on the opposite sides of the end when the receptacle is sealed. The can end is shaped so as to provide a wall 6. This wall is substantially atright angles to the plane of the can end. The purpose of producing this wall is to enable the endto be joined to the body of the can by a double, seam. In Fig. 4 of the drawing, the can end is indicated at I, and itis noted that this wall 6 extends down into the can end so that a chuck placed in the recess formed in the outer face of the can end will contact with this wall 6. The flanged portion 1 of the can end is then curled in a well known manner into-the double seam 8. This forming of the wall 6 produces a severe strain on the metal coating covering the surface of the steel sheet. This metal surface, particularly in the region indicated at 9 in the drawing, is so severely strained that it often breaks and separates, forming a crack or a space where the sheet steel is exposed.v There are other portions of the can end wherein the-metal coating is also under severestrain.

which is likely to fracture the metal coating.

but this particular place referred to will be sum cient to illustrate thepurpose of the present invention. This portion'of the end indicated at 9 is on the inner face of the end when it is attached to the can body, and as a. consequence, the exposed portion of the steel is likely to be contacted, not only with the gases in the head space of the can, but the contents of the can 5 itself. Injurious effects upon the food product and also upon the steel forming the end occur from these fractures of the metal coating incident to die-drawing.

After the end has been shaped by die-drawing,

it is submerged in a heated bath of liquid having a boiling point substantially higher than the melting point of tin. The liquid used for the bath is preferably one which is water soluble and has a fiuxing re-action. Glycerine is found to be verysuitable for this purpose. It has a boiling point of approximately 554? F., which is approximately 112 above the melting point of tin. This is still far below the melting point of steel. Therefore, the die-shaped article may be submerged in the glycerine bath heated to a temperature considerably below its boiling point. A good workable temperature is 470 F. When the article is submerged in the heated bath from ten to twenty seconds, the tin coating will become fiuid. The glycerine will flux the exposed steel surface between the separated edges of the -tin coating and the metal will flow so as to complete- 1y heal or close up the crack and thus produce a continuous unbroken tin surface covering the entire surface of the article. Glycerine is water soluble and can easily be removed from the surface of the article when it is taken from the.

bath. In order to activate this fluxing reaction, two to three percent each of ammonium chloride and zinc chloride is preferably added to the glycerine bath.

Liquids other than glycerine may be used. For

example, diethylene glycol, the boiling point ofwhich is approximately 482 E, which is well above the melting point of tin. Any fatty acid,

such as palm oil, oleic acid, stearic acid, and mixtures of these with other oils having'high bolling points could be used. If, however, fatty acids are used then a hydrocarbon solvent would be necessary to clean the article after treatment. It

contact of the dies with the metal coating and the excessive strain exerted upon the metal coating din-ing the shaping of the sharp angular portions of the article.

While the invention is described in connection with the making of cans ends, it lsyunderstood, .of course, that it may be used in connection with other articles which are shaped by die-drawing metal coated sheets of steel. While sheet is described as coated with tin, it may be the metal coated with other metals having a melting point considerably below'that of the steel so that it may be dipped in the bath and the metal coating rendered fluid for the purpose described above. In describing the invention and the article, the sheet steel is stated to be coated with a metal on both faces. It will be understood, of course, that only the face of the metal may be coated which it is desired to protect. For example, in a can end, it might be desirable to coat with metal the inner face of the end only, and therefore, the invention is not limited 'to the coating of both faces of the sheet steel, but is directed more particularly to the healing or closing of cracks in a metal coating produced by die-drawing. While sheet steel is referred to as the base metal which gives shape and form to the article, it will be under- I stood that other metals may be used for this purpose, but it is essential to the carrying out F of the method that the base metal shall be of a higher melting point than the coating metal applied to and covering the surfaces thereof.

From the above it will be noted that the improved method produces an article from a coated metal sheet by die-drawing wherein the finished article has a continuous unbroken metal coating extending throughout the entire surfaces thereof and this is accomplished without any further application of the coating material to the shaped article. It is obvious that many changes may be made in the application of the invention and in the details of the method described and the product produced without departing from the spirit of the metal coating fluid, causing the same to flow and thereby closing all cracks and bare spots in the metal-coated surface.

2. The method of producing an article from sheet material consisting in coating a sheet of steel with tin, cutting the sheet to form a blank, die-shaping the blank to form the article, heating the shaped article in a bath of glycerine to which has been added a chloride flux, which bath is raised to a temperature above the melting point of the tin and below the melting point of the steel, rendering the metal coating fluid, causing the same to flow and thereby closing all cracks and bare spots in the metal-coated surface.

ALFRED L. KRONQUEST.

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