US1893590A - Method of insulating wire - Google Patents

Description

Jan, 10, 1933; E. A. MAU ET AL METHOD OF INSULATING WIRE Original Filed Nov. 29, 1922 Patented Jan. 10, 1933 UNITED STATES PATENT OFFICE EDWARD A. MAU, OF ARLINGTON, NEW JERSEY, AND

ORRIN F. HUTCHINSON,

NEW HAVEN, CONNECTICUT METHOD or INSULATING wmn Original application filed November 29, 1922, Serial No. 604,022. Patent No. 1,885,889, dated September 25,

1928. Divided and this application filed December 6, 1927. Serial No.

This invention relates to insulated conductors and more particularly to the method of making conductors of the class shown in our pending application No. 604,022, filed November 29, 1922, which has matured into Patent N 0. 1,685,369, issued Sept. 25, 1928, of which this application is a division, especially those which have insulated coverings of such small thickness as to fall Within the class of magnet Wires.

The invention is directed to the method of making an insulated conductor which is distinguished by the uniformity and reliability of the covering with respect to its electrical insulating properties,

sulating covering Which is a necessary attribute of magnet Wire and the adaptability of the insulating covering to rapid manufacture of the Wire at low cost, using inexpensive short fibres Which are not suitable for general use.

Magnet Wire as commonly made heretofore has been of two types, that in which the insulating covering is a composition applied to the Wire in a liquid or plastic state and hardened, and that in which the covering is made of fibrous material and is applied to the Wire by Wrapping it thereon. The object of this invention is to provide a magnet Wire which is superior to these, superior to the film-coated Wire with respect to reliability and uniformity of the covering as an electrical insulator and superior to the Wrapped Wire in that equally W ll insulated Wire may be manufactured at much less cost. ll lagnet Wire having the film or composition coating is deficient in the reliability of its electrical insulating ropei'ties for the reason that the coating lacks the necessary uniformity and is subject to cracking under ilexure, peeling, ucling burrs, and so forth, so of exposure of the conductor or weakening or: the insulation at one or more points is always present. l Vith Wrapped fibre coatng, on the other hand, While the uesired uniformi't and reliability of the coating a: an insulation may secured, the cost oi production is relatively high as the manufacturing operation proceeds slowly and relatively expensive longfibred staples must be pin-holes, pron that the dange the thinness of the inemployed in the production of the wra ping The insulated conductor made accor ing to the method of the present invention consists of a wire having thereon a coating of unspun fibres, preferably cotton fibres, interentangled and densely'compaoted and having ample flexibility and a smooth, hard, moistureproof surface, the coating being very thin as is required of the insulating coating of magnet wire, but nevertheless of such thickness that at every point the Wire is overlayed by a number of fibres. Such a coating may be made to adhere to the wire with great tenacity by the employment of a suitable adhesive in which the innermost fibres are embedded, and it is exceedingly tough and amply flexible. Because of thesecharacteristics, there is no danger of the coatihgpeeling from the Wire or cracking as a result of repeated fiexure of the Wire, Also, in making such a coating, it is permissible to use shortfibre staple which is inexpensive because ct its limited utility for other purposes. Fun therrnore, it is possible to apply such a coating to a Wire by a continuous and comparatively rapid process, much more rapid than any Wrapping operation, with the result that the completed conductor may be produced at low manufacturing cost. The fibre may be supplied to the Wire in continuous sliver which is brought into contact "with the Wire after the latter has been coated an achesive, then the sliver may be subjected to a suitable rub motion whereby it is caused to enclose the Wire and adhere to it; and then as the Wire is -ted along, it is subjected to rapidly rotating pressure devices which serve to compact the nbrous coa to a great density and give it a hard, glazed and preferably water-proofed surface While retaining its toughness and ilexibi it has been proposed heretoi re to insulate electrical conductors with an insulating coating of interentanglecl fibres, such -for instance as cotton or asbestos, but this has been done only in connection With the manufacture of so-called fixture Wire which the thickness of the insulating coating is matter of ii importance, mechanical stren th to stand blows and strains incident to I applying the fibres to the wire dling of the fixture being the important consideration. So far as we are aware, a magnet wire with a thin, dense, tough, flexible and uniform coating of unspun interentangled fibres has never been produced heretofore successfully.

In a conductor having an insulating coating of this nature, it is of the utmost importance to insure that the conductor shall be overlayed by a substantial number of fibres at every point, and this requisite must not be sacrificed to any appreciable extent in order to secure thinness of the coating, for thorough electrical insulation is a primary requisite. The attainment of this desirable characteristic is made more certain by so that they will be arranged more or less in accordance with a prescribed order. Very desirable results with respect to uniformity of the coating may be obtained by so applying the fibrous covering to the wire that the fibres close to the wire are arranged generally parallel to the length of the wire, whereas the fibres further from the wire are arranged in some other manner, as for instance, in a generally circumferential relation. This form of covering presents two important advantages,

first, it results in the attainment of a greater degree of uniformity in the dielectric strength of the insulation, and second, it permits of the use of simple and inexpensive manufacturing expedients.

Another consideration of importance is that the electrical characteristics of the wire must not be deteriorated by the application of the covering to the wire. If the process employed be such that the wire is worked to any considerable extent it will become fatigued and its conductivity will be lowered. For instance, if the application of the fibrous covering to the wire be effected by the employment of a rub motion apparatus, this should not be so operated as to result in rolling of the wire back and forth upon itself as has been the case with apparatus of this character heretofore proposed. The best results are attained when the process and apparatus for applying the insulating covering are such that the wire passes through the apparatus with the minimum of bending and no movement about its axis, with the result that its electrical conductivity is not imparied at all.

The invention will be better understood by reference ,to the following description taken in connection with the accompanying drawing which illustrates the conductor and also the apparatus which may be employed in making it according to our preferred metho Referring to the drawing, Fig. 1 is a view on an enlarged scale of a short length of magnet wire embodying the invention; Fig.

1A is a similar View many times enlarged;

Fig. 2 is a transverse section of the wire shown in Fig. 1A; Fig. 3 is a View in elevation of apparatus for producing the wire; Figs. 4c and 5 are similar views of apparatus employed in later stages of the process; Figs. 6 and 6A are sections on lines 6-6 and 6A6A of Fig. 4; and Figs. 7 and 8 are detail views of wiping and polishing devices, being sections on lines 7--7 and 8-8 respectively of Fig. 5.

Figs. 1, 1A and 2 show the insulated wire embodying the invention, the wire being indicated at 10 and the insulating covering at 11. The wire itself may be of any size and of any material. The insulated covering 11 on the wire is a highly compacted, uniform, tough and flexible coatingof unspun interentangled fibres snugly adhering to the wire and having a smooth, water-proofed surface. Preferably this coating is so formed that the fibres therein are arranged more or less in accordance with a prescribed order; the fibres at the interior of the covering and close to the wire are arranged generally parallel to the length of the wire and are adhered to the wire by being imbedded in a suitable adhesive whereas the fibres in the outer portion of the covering are arranged generally circumferentially.

In Fig. 1A, the reference 11 indicates the inner portion of the insulating covering in which the fibres are arranged generally parallel to the length of the wire. The fibres of the outer portion of the covering are considerably inter-entangled but their arrangement is generally circumferential. This arrangement of the fibres of the covering conduces to uniformity of dielectric strength, flexibility and insurance against weakening of the insulation by fiexure of the wire.

A wire having these properties may be made by the employment of the method and apparatus indicated in Figs. 3 to 8 inclusive of the drawing. In Fig. 3, 12 indicates the doifer roll of a finishing card provided with a comb 13 which acts to strip slivers of carded cotton or like fibres from the usual rings of the dofier roll of a carding machine. The sliver is shown at 1 and as is usual after being carded the-fibres thereof while somewhat interentangled are arranged generally parallel to the length of the sliver. After the sliver 1 leaves the roll 12 it is sustained by a belt or conveyor 14. The stock employed in making the sliver may be any grade of cotton or other fibre, well ginned and cleaned; the grade of cotton fibre commonly known as combings maybe employed to advantage. One of the valuable characteristics of the wire of this invention is that high insulating properties may be attained in an insulating covering made of short fibre staple which is very inexpensive because its field of utility is so limited.

The conductor to to be applied is shown at which the insulation is 15. It is guided by nsaa eeo lelisru. for coaclziou Wioil slivers l which are clofil roin T l? s, pnralleiisrn.

2 consiscs of a suitsolvent ii-1e arrang ile ins the Wire 15 be? one solveni will considerable enleni and n m 4 line Liclbesi v l T"-- KY sole gum uissl cc.

Wire is so 6 centrally bowie i is lo the sliver. overliengs the 1 Wire leave cubed in close f 'ibese rub -u y progressmob-on, Tnis Wrens llie AL 11.

mus o0 sncl no". 01' obese i motion belts applies one liver w re eniirely around blue Wire causes e substsnti purl-ion oi u e sliver be in blue adhesive m and obese encls accomplished without (lis- 'iur lie of the distribution of e fibres len 'u 153 of the sliver As a reeeves Elie rub motion bells i i one manner molested in 6.6L Willi the suit the proclucc y Within a substantial- Wire enclosed cen" ly circular bres which are more or less condensed and in which the fibres at the i e imbeu'clecl in the so u arranged generally 1 belts the product (levies or licker 19 which pair springs adopted 13o engage opposite sioles of the Wire and to be misled by suiouble means not shown, as

passes to u Wioin soi substantially concentric with the periphery thereof and reduce it to upproximslely size requ red gauge, although the pressure exerted by the Wiper is relatively low compared to that exerted byvche polishing device.

The wire is blien carried through moisiureprooling medium 22 which may be in a receptacle 20 having a pulley 21 mounted ilicrcin around which the Wire passes. A compound of nitrocellulose is Well adapted for use us the moisture-prooling medium as a coating of that subsiience not only pro'teczhs blic insulaiing covering from moisture but also serves lo cement do; n the fibres of the insulating body and hold. them permanently in close contact.

From the receptacle 20 the Wire posses to s wiper 23 which is of the some general nature us inc licker 19 This Wig/er serves no remove excess solution from the fibre body and furbber condense she lute-er prcperetory to the polishing operationw The polishing may be performed by a. suituble (lie 2% which may be locstecl in close proximity to the Wiper 23. This polishing device may consist e pair of polishing blocks 25 shown in detail in Fig. 8. These blocks have opposing smooth polishing surfaces between which the Wire passes, While the blocks are rapidly Pointed theresboui". The SiJZUCiHiG of these blocks is such that the portions of the which are in engagement with the covering are drawn together and press sgsinst the covering by centrifugal force.

The urincipel function of the polishing" olev ce is in condense the fibres of the covering in a high degree sncl moi them to bring the covered wire to the required gauge encl to compact the fibrous insulating covering to dicsirea'l density.

By the employment of such a process and upper-mus, e Wire may be provided Wii-b an insulating; covering which is 01 the thinness of magnet Wire insulu bion and which is or pronounced uniformity of thickness sncl (lielocicric strength and of such toughness and elasticity that it will not be broken or weakened by repealed iilexure of the Wire. Tbs

operation of applying this coating to the Wire an inexpensive one because she insulating the Wire proceeds with far greater rapi lity than any braiding or Wrapping operation and bbe cosi'; of the completed; Wire is furl-her reduced by the fact that this form of insulation permits of the use of short fibre sis pie conductor by rub motion which is inexpensive. Also, the nature of the operation is such that the electrical properties of the wire are-not altered by the operation of applying the coating to the wire as they would be if the wire were rolled back and forth upon itself as an incident to applying the fibrous coveri g to it uniformly for such rolling motion of the wire would cause the wire to become fatigued and its electrical conductivity would be substantially reduced. The high insulating properties of this form of covering together with the toughness, elasticity and uniformity of the covering are due to the employment of unspun interentangled fibres so as to produce a coating having a thickness of a plurality of fibres at every point over the surface of the wire. Good 1nsulating characteristics are obtained with a covering of such a thickness that there are approximately 7 fibres one on top of another at every point over the surface of the wire, these fibres being criss-crossed and interentangled more or less indiscriminately but being disposed generally or as entities according to the order or arrangement above described. When the conductor is flexed the fibres running more. or less in the direction of the length of the wire are particularly effective in maintaining the integrity of the covering. Thus, fibres which lie adjacent to the wire are arranged generally parallel to the length of the wire; this is due primarily tothe fact that the fibres in the sliver 1 are initially arranged insubstantial parallelism by the carding machine and the fibres close to the wire become imbedded in the adhesive more or less before the wire and sliver arrive between the rub motion belts. The action of these belts causes a greater imbedding of the fibres in the adhesive and wraps the sliver entirely around the wire. In the later operations, particularly those of the licker 19 and of the polishing device 24, the body of fibres is compacted and as an incident to that the fibres which are not securely imbedded in the adhesive are given a generally circumferential direction about the wire. I

From the above it will be obvious that we have provided an eflicient and inexpensive method ofinsulating a conductor wherein a sliver of fibres is applied to the conductor by the cooperation of comb 13 and dofier roll 12, with the fibres directed generally parallel to the conductor, and is then wrapped about the belts 17 and 18 to embed the fibres adjacent the conductor and which are generally parallel thereto in the. adhesive thereon, said belts acting to further entangle the unengaged fibres while slightly condensing the fibrous body. The covere conductor is then directed downwardly into the wiper or licker 19 which further compresses the body of fibres, and due to the rapid rotation of said licker disposes the outer fibres generally circumferentially about aseaeeo the conductor. From the licker 19, the cov ered conductor passes through compoun applicator 20 and is then upwardly d1rected to the polishing and smoothing device 24 where 7 by the body of fibres is further compacte and smoothed and any loose or pro ectin ends of fibres circumferentially disposed an embedded. 1

While we have shown and described a preferred form of 'our invention, it is to be understood that the same is not to be limited hereto in all of its details, as many modifications and variations may be possible which will lie within the spirit of this invention and scope of the appended claims.

What we claim is:

1. The method of making an insulated electrical conductor, which comprises drawing a conductor through an adhesive mixture,

disposing it beneath a sliver of fibrous material and then with the fibrous sliverbetween a' pair of cooperating forwardly moving and transversely agitating belts causing the fibres ad'acent the conductor to be embedded in the ad esive thereon, then passing the fibre covered conductor between fibres together, then passing the same through a bath of fibre binding compound and then passing the same between a pair of cooperating rotating olishing members to further compress the bres of the. covering.

2. The method of making an insulated electrical conductor, which comprises continuously drawing a conductor through a series of insulation applying and finishing devices and thereby successively, face of the conductor with an adhesive, applying a sliver of generally parallel and entangled fibres to the surface of the conductor,

folding and compressing the sliver about the conductor without substantially disturbing the parallel arrangement thereof, compressing and wiping the fibres adjacent the outer surface about the conductor into a generally circumferential position, impregnating the fibres with a fibre binding compound, and then compressing the compound filled fibrous covering while smoothing the outer surface thereof. v I

p 8. The method of applying an insulating covering to an electrical conductor, which comprises covering the surface of the conductor with an adhesive, applying a sliver of entangled and generally parallely disposed fibres to the adhesive covered surface, fol ing the sliver about the conductor, compressing thevfibrous covering while turning the fibres adjacent the surface generally circumd ferentially, impregnating the covering with a fibre binding compound, and smoothing the surface of the covering while further compressing the same. 1

4. The method of applying an insulating covering to an electrical conductor, which covering the sur-1 comprises applying an adhesive to the surface of the conductor, applying a sliver of fibres generally arallel ductor an in en agement therewith, folding and entanglingt e fibres of the fibrous sliver about the conductor without disturbing the generally parallel disposition thereof, compressing the fibrous covering and disturbing the parallel arrangement of the fibres adjacent the outer surface, impregnating the covering with a fibre binding compound, and smoothing the surface of the covering while further compressing the same.

5. The method of applying an insulating covering to an electrical conductor, which comprises applying an adhesive to the surface of the conductor, arran in a sliver of fibres generally parallel with tile length of the conductor in enga ement therewith, folding the fibrous sliver a out the conductor, and

embedding the fibres adjacent the conductor into the adhesive thereon without disturbing the generally parallel disposition thereof, compressing the fibrous covering and disposing vthe outer fibres thereof generally circumfercntially with res set to the conductor, impregnating the covering with a fibre binding compound, and smoothing the surface of the covering while further compressing the same.

6. The method of making an insulatin sheath for an electrical conductor, whic comprises applying a sliver of entangled bres to a conductor, with the fibres adjacent the conductor generally parallel to the length thereof, and disposing the remaining fibres generally circumferentially about the conductor, then filling the fibrous mass with a fibre bindin compound, and then compressing the fi res and smoothin the outer surface of the covering so formed.

7. The method of making an insulated electrical conductor which comprises continuously drawing a conductor through a series of insulation applying and finishing devices and thereby successlvely, covering the surface of the conductor with an adhesive applying a sliver of generally parallel and entangled fibres to the adhesive covered surface of the conductor and parallel thereto, compressing the body of fibres and wi ing the fibres adjacent the outer surface 0 the body of fibres about the conductor into a generally circumferential position in respect thereto impregnating the body of fibres with a fibre-binding com ound and then compressing the compoun -filled fibrous covering while smoothing the outersurface thereof.

8. The method of making'aninsulated electrical conductor which comprises applying an adhesive to the conductor, disposlng it beneath and parallel to a thin flat sliver of fibrous material, then pressing the fibres of the sliver into the adhesive and folding the 65 sliver completely about theconductor so that with the length of the confib it encircles the same and forms thereon a closely adhering covering of interentagled res, passing the fibre-covered conductor through a wiping device to compact the covering of fibres, and then applying a suitable impregnant to-the covering.

9. The method of making an insulated electrical conductor which comprises appl ing an adhesive to the conductor, passing t e conductor and a fibrous sliver arranged parallelly between a pair of cooperatin belts to embed the fibres of the sliver in t e adhesive and fold the sliver about the conductor, then passing the conductor'through a wiping device to compact the fibres, and then impregnating the covering.

10. The method of making an insulated electrical conductor which comprises applyin an adhesive to the conductor, disposin su stantially parallel to the adhesive-coats conductor a thin flat sliver whose fibres are generally longitudinally disposed, embedding the fibres at one face of the sliver in the adhesive on the conductor, folding the sliver circumferentially completely about the conductor to encircle the same and form thereon a closely adhering covering of interentangled fibres, then impre nating the fibrous overing, and finally su jecting the covering to a circumferential pressing operation to condense the same.

11. The method of making an insulated electrical conductor which comprises applyin an adhesive to the conductor, disposing su stantially parallel to the conductor and in me close proximity thereto a thin flat sliver whose fibres are generally longitudinally disposed, embedding the fibres at one face of the sliver in the adhesive on the conductor and folding the sliver about the conductor so 105 that the latter is completely encircled and coated with interentangled fibres, compacting the fibres, and impregnating the fibrous coverm In witness whereof, I, EDWARD A. MAU, 110 have set my hand this 29th day of November, 1927, and I, Ounm F. Hmomnson', have set my hand this 3rd day of December, 1927.

EDWARD A. MAU. ORRIN F. HUTOHINSON.

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