US2383964A - Coating method and apparatus - Google Patents

Description

Sept l945.- w. F. GRUPE COATING METHOD AND APPARATUS Filed April 15, 1941 R WY 0 E fim m W 0 N w Is A W set of the Patented Sept. 4, 1945 UNIT-E STATES PATEN 2,388,964 COATING METHOD AND APBARATUS William F. Grupe, Lyndhurst, N. 3., assignor to Inter-chemical Corporation, New

corporation of Ohio York, N. E, a

Application April 15, 1941, Serial No. 388,573

.6 Claims.

This lnyention relates to the art of coating metal and aims to provide an improved method and apparatus by means of which metal, in the form of a thin continuous strip, may be effectively covered, preferably on both sides thereof, with a' throughout its length and width. Some of the unevenness in the stock may be caused by improper camber in the rolling mills; or if a particular strip which is to be coated has been cut from one of greater width, the edge or edges-which have been out are usually wavy or scalloped due to too deep a set of the slitter knives, the pitch of the waves or scallops varying with the depth of blade. Moreover, the cut edges are often blurred. When attempts are made to coat such strip metal with apparatus now available,

it is usually not possible to overcome the unevenness or tendency to twist with the tensions that are applied in normal coatin apparatus. This creates at least two important difliculties in the coating operation: first, it is not possible to obtain a uniform thickness of coat throughout the width of the strip: and second,.the scalloped and burred edge actually cuts into the usual resilient surfaced coating rollers, particularly when a reverse roll coater is employed. While this latter trouble is primarily one which involves the coating apparatus, it will be understood that any appreciable cutting into the coating rollers will ultimately alfect the coating operation. Furthermore, be-' cause of the relatively large diameters of the usual coating rollers, the coating tends to form streaks or ridges which are particularly pronounced when the coating material is pigmented. These and other difficulties have been of such a nature that there are not any available commercial machines or methods for properly coating thin strip metal,

coating is applied to both sides of the metal web,

two small diameter bars are employed and arranged so that the angle between the plane in which the strip is being fed and a plane passing through centers of the bars is between 3 and 30. The coated strip is first broken over one bar which levels and regulates the thickness of the layer on one side, .and is then bent back by breaking over the second bar which levels and regulates the thickness of the layer on the other side. By proceeding'in this manner, both sides of a wavy strip such as is used for manufacturing food containers and the like.

According to my invention, the strip metal to be coated and under suitable tension is covered on one side with an excess of the desired coating material and is then bent transversely at an angle of from about 3 .to 30 by breaking the strip over a bar of very smal diameter which is positioned along the line of the bend and is constructed and arranged so that the coating, throughout the entire width of the strip, is leveled to a uniform layer freeof ridges and all excess coating is re- 7 moved as the strip passe there'over. Where the coated on both sides thereof with desired coating material. Said of metal may be continuously coated throughout the width of the strip with a uniform and resulated layer of coating material free from all streaks, ridges or unevenness.

The above and other features and objects of the invention will become apparent on consideration of the following detailed description and the acc'ompanying drawing, in which;

Fig. 1 is a diagrammatic elevational view of an apparatus for continuously coating strip metal in which the apparatus features of my invention have been embodied; and

Fig. 2 is a fragmentary perspective detail view, with certain dimensions exaggerated for the sake of clarity, of one form of bar for bending a strip and leveling and upon one side thereof.

Referring now to the drawing, it will be observed that-a strip of thin gauge metal 5 is fed from a suitable supply reel or coil 6 upwardly over a feed or guide roll "i into a cleaning chambar 8. This cleaning chamber b may be of any conventional construction and contains some material, such as trlchlorethylene, for cleaning the strip 5 as it passes therethrough over a large glllding drum It and upwardly to a second guiding roller II. From the roller II, the strip passes downwardly and around a guide roller I 2 to a pair of brake rollers l3 and It. These rollers are of a rather large diameter and cause the strip to be flattened out somewhat in passing around them in the path shown in Fig. 1. The strip .is then fed in a substantially horizontal path through a coating apparatus, which is designated as a whole by the reference numeral it, where it is passed through a heating chamber It for drying the applied coating, a cooling chamber I1 and into a pull and feed apparatus which includes rollers It, 20, 2! and 22 that are driven and arranged to grip the metal sufficiently to feed or pull it through the entire apparatus. The web or strip 5; maybe passed from the uppermost roller 22 to regulating the coating applieda layer of anystrip is next a rewind reel 23, or it may be cut into sheets'in any conventional manner, if desired.

In one form of coating apparatus that has been tried, the strip 5 extends in a horizontal path from the upper brake roller M to the lowermost roller iii of the feed and pull apparatus and is substantially unsupported throughout this distance. The braking power of the rubber covered braking rollers 13 and i 4 is used to Provide a sufficient resistance for maintaining the supported strip taut and in a horizontal plane; and sumcient tension is provided to cause the strip to be in proper position for coating. However, due to the fact that the strip metal is usually not fiat, because of conditions'encountered in its manufacture, and has at least one sharp and scalloped edge, difficulties are encountered in the coating operation.

Where the strip metal is to be used in the manufacture of containers, it is desirable to provide a thin coat of protective material that is entirely continuous, free of porosity, and of uniform protective value over the entire surface of the metal. Such coated stock is then formed into cans or containers and during fabrication may be bent either in easy turns or sharply in crimping and closing the side seams for the containers; or it may be shaped and drawn, as in making the can ends when sharp draws are made which actually distort the metal. Some of the fabricating operations cause the strip to be bent 180. Because of. these strenuous fabricating operations, it is essential that the coating applied to the strip be uniform and of a minimum thickness so as to provide proper protection. I If the coating is uneven or heavy, it will crack, or lose its bond at the sharp ends so as to expose the metalto corrosion.

, The thinner the coating is applied, the more economical is the operation and the easier it is to make the necessary bends during fabrication without undue stretching of the outer surface of the coating, thus avoiding any break in the coatedsurface.

At the present time, all metal coating is done with roller coaters in which the rollers are of rather large diameter ranging from to ,14 inches. These rollers usually have a resilient surface of some gelatine or rubber compound. Due

to the rather large diameter of the-rollers, there is a long surface contact between the roller and the metal surface, and the coating contacting the metal and the roller is gradually split as the roller revolves. For a roller 10 inches in diameter, this surface contact is always at least one inch in length. Depending upon the viscosity and the amount of coating material applied, it has a tendency to gather in streaks as it approaches the breaking point. This results in rather high inch, the surface contact is reduced to a minimum ridges which run longitudinally of the strip and may be spaced at distances from 3 5 of an inch in low viscosity material. to A or of an inch in the heavier and more viscous materials; these coating streaks or ridges not only destroy th protective value of the coating or final beauty or finish of the material, but obviously create an undesirable waste of coating material. j

In accordance with my invention, strip steel that is not flat and may be twisted, scalloped or burred, is coated with a thin and uniform layer of the desired coating material by applying an excess of the coating to one-or both sides thereof and then bending the strip transversely art s-n angle of from about 3 to 30.by breaking the strip over a bar of very small diameter which is positioned along the line ofthe bend and is conand the coating streaks or ridges referred to above are entirely eliminated. I have found that with a $4; inch bar the surface contact does not exceed V8 inch, and in most cases the coating is split in a distance of a. of an inch beyond the line of contact. With such a short rapid break, there is no noticeable streak formation.

The coating apparatus i5 comprises an upper resilient surface coating roller 25 which receives coating material from a feed or distributing roller 26 and cooperating fountain roller 21, the latter of which is arranged to rotate in a bath 28 of the coating material. This upper surface coater is of conventional construction and the setting of the rollers 25, 28 and 21 is such that a layer of the coating material will be applied upon the upper surface of the strip 5 as it passes beneath and in contact with the coatingroller 25. A supporting and guiding roller 30 is positioned on the lower side of the web or strip 6 between the coating roller 25 and a second coating roller 3| which is supplied with coating material in the desired excess quantities by means of a fountain roller 32 rotating in a bath 33 of the coating material. The strip 5 is shown as maintained in a substan.- tially horizontal position in passing from the braking roller hi through the parts of the coating apparatus thus far described and is thus coated on both sides thereof with a slight excess of the coating material. All of the parts of the coating apparatus are positioned as closely together as possible; and the intermediate supporting roller is of extreme importance in insuring a suitable flat contact with the coating rollers 25 and 3| and in avoiding such twisting of the strip as would render the apparatus inoperative.

Upon passing beyond the coating roller 3|, the strip 5 is bent upwardly through an angle of from 3 to 30, depending primarily upon the thickness thereof. In passing a web over such a bar, it will act to regulate the thickness of the coating material due to the provision of the grooves 35; and the windings provide a, spiral surface which, when rotated, create a feeding action that serves to carry any undesirable foreign matter over the edge of the strip where it may be caught in a suitable pan. However, when the wire 35 is omitted the bar still functions satisfactorily but provides an even thinner layer. As mentioned above, it is the small diameter and resulting short surface contact which I have found to be particularly important in eliminating the undesirable streaks and ridges in the applied coating.

. In the present instance, the bar 34 is mounted in a suitable bearing 31 and provided at one end thereof with a driving gear or sprocket 38 which may be connected up to any convenient source of 'powerso as to rotate the bar 34 continuously during the coating operation. The bar is rotated in width of the strip which thus contacts the bar uniformly throughout its width and accurately regulates and levels the coating material that has been applied to the upper surface of the strip 5 by the coating roller 25. In any case, the tension provided by the feedand pull unit and the braking rollers should be suflicient to cause the strip to be properly bent along a straight line in passing over the bar 84. For strip steel of 0.010 inch thickness, this tension maybe about 50 pounds per lineal inch of width of the strip. I

Similarly, the coating material applied to the lower part ,of the strip is regulated and leveled into a uniform layer free of streaks or ridges by bending said strip back to a substantially horizontal plane, i. e., bending it through an angle of from 3 to 30. This'is accomplished by breaking the strip 5 over a small diameter bar t mounted for rotation in a suitable bearing ti. This second leveling bar performs the same action on the coating material applied tothe lower side of the web and is substantially identical in construction and operationwith the bar 3!.

With both sides of the strip 6 thus coated with a very thin and uniform layer of coating material,

said strip is thus passed through the heater it,

where the coating, due to its uniformity and regulated thickness, is quickly and eifectively dried; and the strip may then be cooled and rewound as described above.

From the foregoing description, it will be understood that, by the present invention, I have provided an improved method and apparatus by means of which strip metal may be continuously coated on one or both-sides with a thin and uniform layer of any desired coating material free from streaks or ridges and accurately regulated throughout the entire width'of the strip. Various changes may be made in the construction and method described and certain features or steps thereof may be employed without others, without departing from my invention or of its advantages.

What I claim is:

1. A method-of continuously coating a side of a travelingstrip of metal with a thin and uniform layer of a coating material, which comprises maintaining said strip under tension; covering one side of said strip with an excess of the coating material; and bending said strip transversely through an angle of from 3 to 30 by breaking the strip and drawing it over a small diameter bar with the coated side in contact with said bar.

the amount of tension and the angle of bend being sumcient to cause said strip to become entirely fiat along the line of bend, so as to obtain complete contact between said strip and said bar throughout the width of said strip, but insuflicient to cause a permanent deformation of said strip.

2. A method of continuously coating a side of a traveling strip of metal with form layer of a coating material,

which comprises maintaining said strip under tension covering one side of said strip with an excess of the coating material; and bending said strip transversely through an angle of from 3 to 30 b breaking the strip and drawing it over a bar rotating in the direction of movement of the strip and having such asmall diameter that said strip has no greater than A; inch lineal surface contact therewith, the amount of tension and the angle of bend being suflicient to cause said strip to become entirely flat along the line of bend, so as to obtain complete contact between said strip and said bar throughout the width of said strip, but insuflicient to cause a permanent deformation of said strip.

3. A method of continuously coating both sides of a traveling strip of sheet metal with a thin and uniform layer of a coating material, which comprises maintaining said strip under tension;

sacrificing any v sides of a thinand unip covering both sides of said strip with an excess of coating material; bending said strip transversely through an angle of from 3 to 30 by breaking the strip and drawing it over a small diameter bar with one surface thereof incontact with said bar; and bending said strip transversely through an angleof from 3 to 30 by breaking the strip and drawing it over a small diameter bar with the other surface in contact with said bar, the amount of tension and the angle of bend in each instance being suiiicient to cause said strip to become entirely fiat along the line of bend, so as to obtain complete contact between said strip and said bar throughout the width of said strip, but insuflicient to cause a permanent deformation of saidstrip.

4. A method of continuously coating 9, side of a traveling strip of metal with a thin and uniform layer of a coating material, which comprises maintaining said strip under tension; covering one side of said strip with an excess of the coat ing material; and bending said strip transversely through a predetermined angle by breaking the strip and drawing it over a small diameter bar with the coated side in contact with said bar,

the amount of tension and the angle of bend being suificient to cause said strip to become entirely flat along the line of bend, so as to obtain complete contact between said strip and said bar throughout the width of said strip, but insuillcient other side of said strip with an excess of thecoating material; a first bar of from 1%; to posed in the path of said strip so that one side will contact therewith; a second regulating'and leveling bar of from s to of an inch in diameter arranged beyond said bar so that the other side of said strip will contact therewith, the arrangement of said bars being such that said strip regulating and leveling will be'bent through an angle of from 3 to 30- in passing over each of them; and means arranged between said covering means for sup-. porting said strip in its traveling movement between them.

6. Apparatus for continuously coating both a traveling strip of sheet metal with a thin and uniform layer of a coating material, which comprises meansior maintaining said strip under tension in its traveling movement, said .of {*1 inch in diameter dis- 4- asssper tension being equivalent to a tension of 50 pounds per lineal inch of width for a metal strip 0.010

inch thick; means for covering one side of said strip with an excess of the coating material; means tor covering the other side of said strip with an excess of the coatingmaterial; a first regulating and leveling bar of from f to of an inch in diameter disposed in the path of said strip so that one side will contact therewith; a

second regulating and leveling bar of from v to of an inch in diameter arranged beyond

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