US2533788A - Screen with baked enamel coating - Google Patents

Description

Dem 1950 F. J. GEYER 2,533,,78

SCREEN WITH BAKED ENAMEL COATING Filed Oct. 26, 194a 2 Sheets-Smart l k/w g/ W DEM: 12, 1950 GEYER 2,533,788

SCREEN WITH BAKED ENAMEL COATING Filed Oct. 26, 1948 2 Sheets- Sheet 2 Mlllll u IIIE Z 126 2??? J a;

ings becoming jammed in the apertures.

Patented Dec. 12, 1950 UNITED STATES PATENT OFFICE SCREEN WITH BAKED ENAMEL COATING Fred J. Geyer, East Chicago, Ind.

Application October 26, 1948, Serial No. 56,614

6 Claims. (Cl. 209-401) This invention relates to an enameled screen. and more particularly to an enameled vibrating screen for use in screening wet material.

This application is a continuation-in-part of my copending applications Serial No. 581,850, filed March 9, 1945, now abandoned and Serial No, 643,591, filed January 26, 1946, now abandoned.

Considerable difficulty has been experienced in the past in the screening of wet materials such as coal, coke, slag, limestone and the like. The apparatus generally employed is a vibrating machine for vibrating a wire screen. The material undergoing screening often contains moisture and when the moisture range of the material is between 12 and 25%, a problem known as "blinding arises.

Blinding occurs at a much slower rate where the free moisture content of the material undergoing screening is less than 12% or more than 25%, and extremely wet material will often wash through the screen without any blind- .ing.

Blinding is the gradual closing of the underside of the screen openings by fine particles of the material being screened. In this respect, it

should not be confused with plugging which is caused by particles larger than the screen open- Plugging always occurs on the top of the screen and is rarely more than any annoyance. Blinding, however. will in time completely block the underside of the screen. When screening coal, for example, the ordinary screen made of uncoated carbon steel wires becomes'completely blinded in a matter of 24 to 36 hours. At the end of this time, the openings between the wires will substantially all be closed. To remove the accumulated material, it then becomes necessary to remove the screen from the machine and break loose the blinding particles. This is generally accomplished by placing the screen upon a firm support and striking it repeatedly with a sledge. The effect of the blows generally breaks a number of wires in the screen, particularly at points where they are intermeshed, and as a consequence the ordinary screen became useless in a very short period of time.

Attempts have been made in the past to overcome the blinding tendency of screens by making them of stainless steel wires rather than carbon steel. Such stainless steel screen, while not subject to blinding, is very expensive and its use therefore has been greatly limited.

The wires of the screen are rod-like in that they are substantially rigid as compared with the wires in a household screen and therefore should have a diameter of at least inch. For heavy work the diameter may be greater so'that the screen may be capable of supporting the weight of the material as it is being screened. With; a

mesh whose minimum opening is greater than inch blinding is not a seriousproblem and'li'ttle difiiculty arises. Accordingly, my invention: is directed primarily toward producing a vibratory screen consisting of wires having diameters of at least inch and woven into a cloth having a mesh size up to inch. Accordingly, there are not more than four wires to the inch across the screen in any direction and, with inch wire, not less than 1 wires, on; the average, in at least one direction. My preferredscreen has a mesh whose smallest opening is from inch to inch.

I have found that by applying a hard baked enamel coating to the wires of the screen, I can prevent blinding during the entire life of the screen. The enamel coating must be sufliciently hard so as tohave no residual elasticity. Softer coatings, such as paint, are not satisfactory as minute particles of the screened material become embedded in the coating and permit blinding of the wires to proceed at approximately the same rate as if no coating existed. The coating must also be non-porous so as to prevent even minute particles of the moisture-filled material undergoing screening from reaching the metal comprising the wires. For this reason, galvanized Wires are unsatisfactory as a galvanized coating contains minute pores.

An enamel coating, however, which is baked on at elevated temperatures provides a coating sufficiently hard and non-porous as to prevent blinding during the life of the screen. As the screen is vibrated at a comparatively rapid rate, abrasion takes place at the upper side of the wires and the coating on the upper side is rapidly worn off. This does not affect the non-blinding qualities of the screen, however, and the screen can be used until the wires are substantially completely worn away by abrasion. It is therefore unnecessary that the entire surface of the wire be coated, it being sufllcient merely to coat the underside of the wires. As vitreous enameling is generally carried on by dipping the screen into a bath of the enamel, it is impractical to attempt to coat the underside of the wires only. If the enamel is an organic enamel, for example a phenolformaldehyde resin such as described in Hempel U. S. Patent 2,198,939, issued 'April 30, 1940, and Hempel U. S. Patent 2,253,235,

assans perature of the order of 1300 to 1400 F. The

effect of subjecting the steel in the wires to such temperatures is to anneal the wires and soften the steel. However, organic resins of the type mentioned above may be baked on at temperatures as low as 140 F., and therefore do not affect the quality of the steel in the wires. Accordingly, I prefer to use an organic resin enamel, although both are equally satisfactory in preventing blinding of the screen. As shown by Hempel Patent No. 2,253,235 these resins may contain an inorganic non-fibrous filler.

A particular form of screen is shown in the accompanying drawings in which:

Fig. 1 is an end elevation of a vibratory screening machine;

Fig. 2 is a top plan view of the machine of Fi Fig. 3 is an enlarged view of a portion of the screen shown in Fig. 2;

Fig. 4 is an end view of the screen of Fig. 3;

Fig. 5 is a cross section through one of the wires of the screen showing the baked enamel coating thereon; and

Fig. 6 is a cross section through one of the wires of the screen showing its appearance after use in the vibrating machine.

Referring now to the drawings, 10 indicates a vibratory screener having three screens, H, I! and I3, thereon. The screens are carried by a frame I which extends upwardly along the sides of the screens and which is mounted for horizontal movement upon a base IS. A drive wheel I6 is provided with an eccentric l'i whereby rota-' tion of the drive wheel is adapted to vibrate the scr ens. Each screen is provided at opposite ends with metal retaining flanges l0 and is to prevent material und r oing screening from dropping off the ends of the screen. The flanges general type used for screening coke and coal.

When the screening is used for screening limestone, a inch square mesh is preferred. It is obvious that the size of the m sh is determined by the particular use to which the screen is to be put. For example,'my screen has been used for sizing and grading of soy beans in which 29 diilerent sizes of mesh are used.

Baked on the outside of each wire 20 and 2| of the screen is a coating of enamel 22. Ordinarily this coating has a thickness of about .009 inch. Such thickness is sumcient effectively to prevent blinding of the screen when used for screening wet material.

After several hours of use for the screening of hard materials, the enamel coating is entirely worn on the upper surfaces of the wires and thereafter the wires themselves are abraded away to the condition shown in Fig. 6. Even though no coating exists upon the upper portion of the wire when it has reached this condition, blinding of the screen will not occur and the screen may continue in use until the wires are too thin to support the weight of the material on the screen.

By the use of my screen, it is now possible to remove fines from coal by employing fewer vibratory machines than was heretofore necessary. For example, a coal screening plant which previously kept three vibratory machines in as continuous operation as was possible with uncoated carbon steel screens was able to halt the operation of two of those machines when an enameled screen of the type described in this application was installed in the third machine. The amount of coal screened by the third machine was greater than the amount screened by the three machines operated together with ordinary carbon steel screens.

I have also found that with the use of my screen it .is now feasible to screen and grade slag, the common by-product of steel mills. Properly screened and graded slag has been found to be especially well adapted for use as a road building material, but heretofore, due to the tendency of slag rapidly to blind any screen on which it was graded, it has been economically unsound to attempt such operations.

While I have shown and described my invention in a preferred embodiment, it is to be understood that it is capable of many modifications. Changes therefore in the construction and arrangement may be made without departing from the spirit and scope of the invention as disclosed in the appended claims.

I claim:

1. A vibratory screen for screening moisturecontaining material comprising a screen woven of high carbon steel wires having a diameter of at least A; inch, said screen having a mesh whose shortest opening is not substantially less than inch and not substantially greater than inch, and a coating on at least the underneath side of each of. the wires, said coating being a hard. *baked, substantially non-porous enamel coating having no residual elasticity.

2. A vibratory screen for screening moisturecontaining material comprising a woven wire screen with the wires being of high carbon steel and having a diameter of at least inch, said screen having a mesh of between A; inch and inch and each of said wires having a bakedhard, substantially non-porous, organic enamel coating thereon, said wires having the tensile strength and temper of uncoated, high carbon steel wires.

3. A vibratory screen for screening moisturecontaining material comprising a woven wire screen with the wires being of high carbon steel and having a diameter of at least inch, said screen having a mesh whose shortest opening is not substantially less than inch and not substantially greater than inch, each of said wires having a baked hard, substantially non-elastic and non-porous, heat-set resin coating thereon.

4. A vibratory screen for screening moisturecontaining material comprising a woven wire screen with the wires being of high carbon steel and having a diameter of at least ,4; inch, said screen having a mesh whose shortest opening is not substantially less than inch and not substantially greater than inch, each of said wires having a phenol formaldehyde resin coating thereon.

. 5. A vibratory screen for screening moisturecontaining material comprising a woven wire screen with the wires being of high carbon steel and having a diameter of at least $4; inch, said 5 screen having a mesh whose shortest opening is not substantially less than inch and not substantially greater than inch, each of said wires having a hairedmn coating comprising phenol formaldehyde resin and inorganic non-fibrous filler.

6. A vibratory screen for screening moisturecontaining material comprising a screen woven of steel wires having the tensile strength and temper of non-annealed high carbon steel, said wires having a diameter of at least inch and said screen having a mesh whose shortest opening is not substantially less than fi inch and not substantially greater than inch, and a heatset organic enamel coating on at least the underneath side of each of the wires, said coating in its permanent applied state being baked hard. substantially non-porous, and being capable of assuming its permanent applied state at temperatures below those annealing high carbon steel.

FRED J. GJEWER.

REFERENCES CITED The following references are of record in the file of this patent: I

5 UNITED STATES PATENTS Number Name Date 1,220,232 Jackson Mar. 27, 1917 1,693,130 Anderson Nov. 27, 1928 1,713,144 Overstrom May 14, 1929 1,718,386 Sherwood June 25, 1929 2,198,939 Hempel Apr. 30, 1940 2,334,707 Johnson Nov. 23, 1943 2,371,665 Wulfi Mar. 20, 1945 FOREIGN PATENTS Number Country Date 150,824 Australia Sept. 25, 1937 OTHER REFERENCES 20 land, Ohio, copyright 1938, pp. 5, 6 and 19.

The Making, Shaping, and Treating of Steel, 5th ed. Div. 3, by J. M. Camp and C. B. Francis, 1940, DD. 1087, 1252 and 1246, 1125 and p. 1115.

Claims (1)

1. A VIBRATORY SCREEN FOR SCREENING MOISTURECONTAINING MATERIAL COMPRISING A SCHRREN WOVEN OF HIGH VARBON STEEL WIRES HAVING A DIAMETER OF AT LEAST 1/8 INCH, SAID SCREEN HAVING A MESH WHOSE SHORTEST OPENING IS NOT SUBSTANTIALLY LESS THAN 3/16 INCH AND NOT SUBSTANTIALLLY GREATER THAN 5/8 INCH, AND A COATING ON AT LEAST THE UNDERNEATH SIDE OF EACH OF TGHE WIRES, SAID COATING BEING A HARD,BAKED, SUBSTANTIALY NON-POROUS ENAMEL COATING HAVING NO RESIDUAL ELASTICITY.

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