US1633576A - Protective coating - Google Patents

Description

June' 7 c. H. FRANKs PROTECTIVE COATING Filed ADE. 26. 1925 Patented June 28, 1927.

UNITED STATES i, 1,633,576 PATENT OFFICE.

OLEI H. FRANXB, l' LA GRANGE, ILLINOIS, ABBIGNOB T0 WESTERN ELECTRIC COM- PANY, INCORPORATED, OF YORK, N. Y., A. CORPORATION 0F NEW YORK.

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Appunti mea aan se, .1925. semi no. 52,697.

This invention relates to a protective coating and a method of producing such a coating. Y

The .principal object of this invention is to produce an improved protective coating which is tough but relativel flexible, in an efficient, reliable and expeditious manner.

In order to obtainy this object in accordance with one embodiment of the invention, a cellulose derivative in fiber or strand form, arranged in any manner, may be subjected to a solvent to dissolve portions thereof, thereby causing the .adjacent fibers or strands to coalesce thus forming an imperforate film or coating reinforced by theundissolved portions of the fibers or strands. The strands may also be composed of natural fibers and impregnated with a cellulose derivative and arranged in unwoven warp formation before subjection to the solvent for the cellulose derivative. In order to prevent undue shrinkage upon the evaporation of the solvent, the fibers or strands may be impregnated with an agent which retards or prevents the hardening of the cellulose derlvative. A coating formed in either manner may be employed to advantage in making protective and insulating covers or envelopes for electrical coils.

These and other features of the inventlon will be clearly comprehended from the following description taken in connection with the accompanying drawings, in which- Fig. 1 is a view in elevation of an electrical coil having a coating embodying the invention and prgduced according to the improved method,"part of the coil being broken away to more clearly illustrate the details of the structure; e

Fig. 2 is a vertical section taken on the line 2-2 of Fig. 1 looking in the direction of the arrows;

Fig. 3 is an enlarged fragmentary view in elevation of the coil shown in Fig. 1, illustratin schematically one of the steps of the metho;

Fig. 4 is a plan view of a plurality of interwoven strands before and after treatment with the solvent to produce a coating; and

Fig. 5 is a vertical section taken on the line 5-5 of Fig. 4 looking in the4 direction of the arrows.

When practicing the invention it is apparent that the process divides itself quite naturally into two main divisions: first, the

preparation and arrangement of the fibers or strands, and secondly, the treatment therey of to form an imperforate sheet. In order to slmplllfy the description these two divisions of t e process, each including a plurality ofl steps, will now be described in the order in which they were enumerated.

The ty e of fiber or strand em loyed may be any fi er or strand of a cellulose nature, such as the cellulose derivatives, which in a manner to be described later, may be treated with a solvent to produce the effect desired. Examples of such materials are the strands of artificial silk which are made up of a plurality of synthetic filaments or ends. These strands may be employed for practicing the invention without any additional treatment. Strands of natural vegetable or animal fibers, suchas cotton or silk threads, may be employed but they must be impregnated with a cellulose derivative, such as nitro-cellulose or `cellulose acetate, before they are in con-A dition for use.

When the type of strand to be used has been selected lengths thereof may be arranged in an unwoven manner, such as solely 1n an unwoven warp formation, inthe form of a web or in whatever other form is de-` sired and which will permit the successful. treatment by the second division of the process. When employed to form a waterproof and insulatin cover for an electrical conductive winding 10 of an electrical coil Figs. 1, 2 and 3), designated generally by t e numeral 11 having a core 20 and end pieces or spool heads 21, the strand is preferably arranged in a series of adjacent helices 12. As an alternative a plurality of strands may be interwoven as indicated in that portion of Figs. 4 and 5 indicated by the numeral 13.

The fibers or strand having been selected and arranged in a suitable manner as indi cated in the preceding paragraph, the next division of the process may be performed. This includes the subjection of the assembled fibers or lengths of strand to a solvent for the cellulose derivative, to produce an imperforate sheet. The solvent may be applied in a number of Ways depending upon the specific arrangement of the fibers or strands and the results desired. As an example, they may be sprayed with a solvent or sub- 'ected to the vapor of a solvent durin the boiling thereof. When the associated bers 110 or strands are subjected to the solvent, particularly in vapor form, they become partiall dissolvedor fused in a manner which mig t be termed autogenous agglutination. The closely associated ,individual fibers or strands thus coalesce or adhere to each other, and after beinndried to evaporate all of the solvent, the 'shed imperforate coating resents the appearance as shown at l5 in ig. 3 or at 16 1n Figs. 4 and 5. The coating when completed is homogeneous and shin on one surface where the solvent action has en applied to the strands, but on the opposite portion of the covering the strands will still be found to retain their original individual character.

The solvent employed may be any of the well known solvents for the cellulose derivatives. Acetone, however, is preferred because this material is a good solvent for both cellulose acetate and cellulose nitrate and is easily handled. Other solvents, however, which may be employed are a mixture of ether and alcohol, tetrachloralethane, ethylacetate, diacetone alcohol, methyl'ethyleketon or benzol acetate. ln addition to true solvents, partial solvents or so-called plasticisers may be employed, such as furfural.

ln the protection and insulation of electrical coils, other cellulose material may also be employed with the waterproof Coating described above, to form a protective coating or envelope entirely surrounding the turns of the coil. In providin this form of coatin a core portion of ce lulose material 25 @gigs l and 2) may be formed around the core 20, and end pieces 26 of the same material formed adjacent to the spool heads 21, and made integral with the core portion 25. The turns or windings 10 of the electrical coil may then be applied around the core ortion 25 and between the end pieces 26. hereafter the windings may be covered with helices l2 of cellulose material in strand form (Fig. 3), the entire coil subjected to the action of a 'solvent preferably in vapor form. The strand covering is thus formed into an imperforate sheet, as described hereinbefore, and imperforately connected, cemented or coalesced with the end pieces 26, thus producing a continuous imperforate waterproof coating, entirely surrounding the turns or windings of the coil.

The portion 25 and end pieces 26 may be formed in a variety of ways. For example, they may be formed of sheet cellulose material treated with a solvent to dissolve or fuse adjacent portions thereof; or the cellulose material may be dissolved in a suitable solvent to form a varnish or paint, which is sprayed, painted or in some other suitable manner applied to the core and spool heads of the coil. Another method is to apply cellulose material in strand form to the core and spool heads, and then subject the associated strands to a solvent there for either before or after the electrical conductor is applled, in the manner described above for producing the exterior portion or the covering.

Where the process embodying the invention is employed for the purpose of covering coils wound on headed spools, it is essentialthat all of the windings thereof. be covered and the coveringl material closely abut the ends of the spool heads or the cellulose end pieces, as the case may be, in order to exclude moisture and the like from the windings of the coil. In order to prevent all shrinkage of the coverin and the possibility of the covering pulling away from the spool heads or the end pieces, the strands may be given a simple treatment before they are applied to the coil. This treatment consists in impregnating the strand with an agent which retards or prevents the hardening of the cellulose derivative upon the evaporation of the solvent. An oil, a dye o'f coal tar derivation or similar substances may be used. Preferably castor oilis employed in which one part of castor oil is dissolved in about four parts of alcohol and the strands are then soaked vin this mixture until they are thoroughly impregnated. The strands are then removed from the alcohol-castor oil solution and thoroughly dried, after which they are applied to form a covering in the manner described above.

The term cellulose material is used in the appended claims-to refer either to fibers or strands composed entirely or partially of synthetic filaments or to natural fibers or strands impregnated with a cellulose derivative, and the term solvent as employed in the appended claims is intended to include plasticisers7 as well as true solvents.

What is claimed is:

1. A protective coatin for a body consisting of a film of a cell ose derivative reinforced by bers of a cellulose derivative.

2. A protective coating for a body consisting of coalesced fibers of a cellulose derivative.

3. A protective coating for a body consisting of coalesced unwoven cellulose fibers.

4. A protective coating for a body consisting of a plurality of helices of cellulose material surrounding the body, adjacent helices being coalesced.

5. A protective coating for an electrical coil consisting of a plurality of coalesced fibers of a cellulose derivative surrounding the coiled conductor.

6. A protective coating for an electrical coil consist-ing of a plurality of coalesced helices of cellulose material surrounding the coiled conductor.

7. A protective coating for an electrical coil consisting of a plurality of coalesced helices of a cellulose derivative surrounding the coiled conductor.

8. A protective coating for an electrical coil consisting of an imperforate envelope of coalesced cellulose material extending through the coil and entirely surrounding the coiled conductor. Y

9. A method of producing a protective coating, which consists in arranging in un- Woven Warp formation a plurality of lengths of cellulose material in strand form, subjecting the assembled lengths to a solvent to dissolve portions thereof and thereby coalesce the adjacent lengths, and evaporating the solvent. A

10. A method of producing a lprotective coating, which consists in arranging cellulose material in strandform in a plurality of adjacent helices, subjecting the helically arranged material to a solvent to dissolve portions thereof and thereby coalesce the adjacent helices, and evaporating the solvent.

11. A method of roducing a protective coating for an electrical coil, which consists in positioning portions of cellulose material around and extending through the coil to completely surround the coiled conductor, subjecting the positioned material to a solvent to coalesce the adjacent portions of the material to form an imperforate coating completely enveloping the coiled conductor,

and evaporating the solvent.

12. A method of producing a rotective coating for an electrical coil, Whic consists in applying a cellulose derivative in strand form around the coil in a plurality of helices,

subjecting the applied strand to a solvent to dissolve portions thereof and thereby coalesce the adjacent helices, and evaporating the solvent.

13. A method of forming a protective coating, which consists in .impregnating cellulose derivative fibers with an agent for retarding the hardening thereof, assembling the impregnated fibers, subjecting the assembled fibers to a solvent for the cellulose derivative to coalesce the adjacent libers, and evaporating the solvent.

14. An article of manufacture comprising a body and a covering of coalesced cellulose material therefor.

15. An article of manufacture comprising a body and an envelope therefor composed of coalesced fibers of a cellulose derivative.

16. An article of manufacture comprising an electrical coil and an imperforate covering .therefor consisting of coalesced fibers of cellulose material reinforced by untreated fibers.

In Witness whereof, I hereunto subscribe my name this 14th day of August A. D., 1925.

CLEM H. FRANKS.

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