US1776116A - Enameled sheet steel - Google Patents

Description

SePt- 16, 1930. H. c. HARVEY 1,776,116

ENAMELED SHEET STEEL Filed Jan. 1i, 192s Wl- Wifi-E f d @0000009 'd @AGM L W I TN ESS INVENTOR ATTORNEYS Patented Sept. 16, 1930 UNITED STATES PATENT OFFICE HAROLD G. HARVEY, 0F TRENTON, NEW JERSEY, ASSIGNOR TO THE AGASOTE MILL- -BOARD COMPANY, OF EWING TOWNSHIP, NEW JERSEY, A CORPORATION OF NEW JERSEY i ENAMELED SHEET STEEL Application led January 11, 1928. Serial No. 246,068.A

My invention relates to sheets of enameled steel of such size, relative to their thickness, that they will ordinarily assume a curved shape during the manufacture thereof, and has for its object the provision of certain means for overcoming in whole, or to a large part, the tendency to assume such curved shape. Enameled steel treated in accordance with my invention ma be used for many purposes, for instance, airies',bathrooms, kitchens, pantries, restaurants, the lining of rail-v road cars, tunnels, etc.

Enameled sheet steel is well known in the art of steel treatment. As is known to those skilled in the art, steels of a special type are used for this purpose which are ysubjected to x a stretching operation and a preliminary surfacing operation (ground coating). The enamel powder is then placedupon the steel so treated and fused thereon in a kiln or furnace heated to a temperature suficient for this purpose, usually in the neighborhood of 2500 F. When the steel is thereafter cooled it is obtained in a distorted form, if it is of such size that its inherent strength is insuicient t'o overcome the tendency to become distorted. Comparatively small sheets even of relatively thin steel, and sheets of larger size, but thicker steel, will not be distorted to any substantial degree. But a sheet, for'instance, ten feet long, four feet wide, and of a thickness indicated by gauges 18 to 4() will assume a curved form during the process of manufacture. It is this type of sheet that I refer to in m yclaim as enameled steel of the kind w ose normal shape is curved, and whose treatment I` describe below. If the sheet is oblong it will take a curve along its minor axis, the major axis lying substantially in a straight line, while if it is square or very nearly so it will generally curve into dish form.

My invention'involves the step of so-shaping certain portions of the steel sheet prior to the application of the enamel and the subsequent heat treatment, and in such a manner and along such lines that such portions con-f bracing means I designate in my claim as integral bracing means. Just where such bracing means must be applied can easily be determined by a study of the curved steel and ifnecessary by the empirical method of sucv cessively supplying bracing means until the desired degree of stiness in the enameled sheet is attained. In practice, however, I prefer to use such bracing means not only for their mechanical effect but also for their ornamental effect and may therefore apply more of suchmeans than might be necessary fori attaining the desired mechanical eect on y.

In the accompanying drawing illustrating several forms of my invention, Fig. 1 shows a plan view of a sheet of enameled steel having formed integrally therewith longitudinal and transverse bracing means to resist the bending stresses in said steel in accordance with my invention; Figs. 2, 3 and 4 are views similar to Fig. 1 but illustrating a number of different ornamental effects ,that may be attained in addition to the mechanical effect by the practice of my invention; Fig. 5 shows an oblong plate having bracing means embodied therein designed primarily to prevent distortion of the sheet; Fig. 6 is a sectional view taken along the line 6-6 of Fig. 1.

Referring to the drawings, a represents a sheet ofenameled steel of any desired shape, but generally square or oblong, the letter b indicating the base plate of steel and c the enamel coating thereon.` Bracing means d, which may be in the form of corrugations or ribs or other compressed and shaped sect-ions, are formed integral with the body of the steel sheet, and extend in such directions and are formed in such number as to overcome partially or entirely, as desired, any tendency of the sheet of enameled steel to curve in any direction ldue to stresses `set up during the manufacturing operations.

The form of indentations or ribs shown is that produced by a shallow arcuate groove or trough, but it is obvious that dierent depths of ribsmay be employed and that other shapes of integral strengthening ribs will suggest themselves to those skilled in the art.

I shall now describe the preferred manner of practising my invention for use in making a sheet of enameled steel having a substantially fiat form.

From among a batch of steel sheets or plates which are to receive a coating of enamel, and which are preferably of substantially the same gauge, shape and chemical composition and which have been produced under substantially similar conditions, so as to react similarly to the various treatments to which they are subjected prior, during and after the enameling operation, I take a sample sheet and give it the necessary preliminary treatment such as stretching, ground coating, etc. which are well known to those skilled in the art of enameling steel, and after applying the enamel powder thereto, subject it in a furnace or oven to a sufficiently high temperature to fuse the enamel thereon to form a smooth homogeneous coating. The sheet is then cooled, after which it is carefully examined to determine the extent of the distortion of the enameled sheet. The number, location, sharpness (i. e. curvature) and direction of the curves are noted.

From these data, the length, direction, location and depth or strength of the bracing ribs to be formed on the steel sheets prior to the enameling operations so as to overcome the bending stresses set up in the steel sheets during the enameling and cooling operations, can be approximately determined by inspection. The bracing means should generally run in a direction substantially at right angles to the axes of the curved surfaces noted on the sample sheet and should preferably extend completely across the surfaces indicated by the sample sheet as certain'to be curved after said enameling and cooling operations. If the curved surface is bounded by a more or less plane or flat surface the rib or other bracing means should preferably extend at least partially across said plane surface to insure more effective stiffening of the plate or sheet. Where the curvature is smaller (i. e. the radius of the curve is large), shallower or fewer ribs will be necessary, whereas where the curve is sharper (i. e. the radius is small), deeper or more ribs will be necessary to prevent curving of the sheet.

Having thus determined from a st-udy of the distortion of the sample sheet approximately the minimum amount of bracing necessary to insure that the finally cooled enameled sheet shall be of a substantially fiat form, I take a second sample sheet and preferably before the. ground coating treatment, but after the stretching operation if such preliminary treatment is employed, form in the body thereof, as by stamping or pressing,

bracing ribs or corrugations of a length, depth and direction determined by such study of the first sample sheet. I then ground coat and finally enamel and cool the said second sample sheet in the well-known manner. If this latter sheet emerges in substantially Hat form from the cooling apparatus, it will be clear that it has been braced either just suiiiciently or too much to overcome the bending stresses in the steel. If an excess in the number or depth or length of the ribs is not objectionable then no further study and trial need be made and the rest of the batch of plates can be stamped or pressed and enameled in the same way as the second sample sheet.

If, however, it is desirable to have as few ribs or as short or as shallow ribs as possible,

then it may be assumed that the said second sample sheet has been given too much bracing, and a third sheet may then be taken and given the same treatment except that the ribs may be made shallower, and/or shorter and/or fewer in number. If the finally finished cooled sheet is still flat in shape, a fourth sample sheet may be employed and similarly treated but given weaker stitl'ening means and this trial method continued until a safe minimum of bracing ribs, allowing for possible variations in the steel plates, is found.

Of course, instead of making these trials one at a time, a number of sample sheets may be treated simultaneously, being given stiftening means of different degrees of strength, the safe minimum beingdetermined from a study of the finally cooled sheets.

If the second sample sheet, above referred to, instead of being held flat by its bracing ribs, is still curved, other sample sheets are taken and similarly treated but given stiflfening means of increasing strength until a safe minimum is determined.

For many of the uses to which my enamin the form of geometrical designs, though other designs will occur to those skilled in the art of ornamentation. In Fig. 1 I show longitudinal and transverse ribs intersecting to form rectangles. In a sheet of this oblong form, the longitudinal strengthening ribs are not quite as necessary as the transverse ribs because the sheet, when enameled and cooled, tends to curve along its minor axis. In Fig. 2 I have therefore weakened tl'ese longitudinal ribs to obtain the more decorative tile effect. Fig. 3 shows a sheet having ribs intersecting and forming squares, there being more longitudinal and transverse ribs than are necessary to insure flatness. In Fig. 4 I have weakened the longitudinal and transverse.

components of the ribs by impressing them into the sheet at an angle to the latters axes thereby producing the ornamental diamondshape design. Fig. 5 shows a design that may be followed When a minimum amount of bracing is desired.

If desired the enamel covering the indentations or ribs may be of a different color :from that of the rest of the sheet in order to in# crease the ornamental efect.

My invention may also be employed to obtain sheets of enameled steel having a definite' curvature of larger radius than that of normal curvature of the unbraced sheet. In the practice of this form of my invention, the sheets are stifened by means of ribs or corrugations which are insuicient to overcome completely the bending stresses created during the cooling operation.- The exact length, depth, direction and location of these stiieningr means which Will permit the sheet to remain somewhat curved, may be determined by the empirical method outlined above in connection with the production of flat sheets of enameled steel.

It will be obvious, that where a sheet curves along more than one arc, as Where a sheet leaves the cooling apparatus in dished, shape, and it is desired to retain the curvature along one arc, the strengthening ribs may be so directed and located (as may be determined empirically) as to overcome the tendency to curve along all arcs but the desired one.

I Wish it to be understood that where in the claim I employ the expression substantially at I mean to y'include thereby all shapes which are substantially nearer the flat condition than is the normal shape of the unbraced sheet of enameled steel.

When I refer in my claim to steel, I desire i it to be understood that such term includes not only steel but any other metallic material, such as iron, which has a curved form after enameling, whether or not it has been subjected to the particular treatment of stretching and scribed.

I claim:

ground coating hereinabove de- The method of making a substantially flat i sheet of enameled steel Which consists in applying to a sheet of steel of such dimensions that during the process of baking enamel thereon it would assume, and thereafter retain, the form of a curve, indentations constituting integral bracing means crossing the lines which would form the axes of such curve, and then baking a coating of enamel thereon. f

HAROLD C. HARVEY.

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