US1685369A - Insulated wire - Google Patents

Description

Sept. 25, 1928. 1,685,369

E. A. MAU ET AL INSULATED WI-RE Original Filed Ndv. 29. 1922 71 .1 I ig/ Patented Sept. 25, 1928.

EDWARD A. MAU AND ORRIN F. HUTCEINSON,

CORPORATION OF MASSACHUSETTS.

01 NEW HAVEN, CONNECTICUT, AS-

SIGNORS, BY MESNE ASSIGNMENTS, TO ROCKBESTOS PRODUCTS CORPORATION, A

INSULATED WIRE.

Application filed November 29, 1922, Serial No. 604,022. Renewed October 21, 1987.

This invention relates to insulated conductors and more particularly to conductors which have insulated coverings of such small thickness as to fall within the class of magnet 45 wires.

The invention is directed to the provision of an insulated conductor which 1s distinguished by the uniformity and reliability of the covering with respect to its electrical insulating properties, the thinness of the insulating 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 i5 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 to is superior to these, superior to the film-coatcd wire with respect to reliability and uniformity of the covering as an electrical insulator and superior to the wrapped wire in that equally well insulated wire may be manufactured at much less cost. Magnet wire having the film or composition coating is deficient in the reliability of its electrical insulating roperties for the reason that the coating ElCkS the necessary uniformity and is subject to cracking under flexure, pea-ling, pin-holes, protruding burrs, and soforth, so that the danger of exposure of the conductor or weakening of the insulation at one or more points is always present. With the wrapped fibre coating, on the other hand, while the desired uniformity and reliability of the coating as an insulation may be secured, the cost of production is relatively high as the manufacturing operation proceeds slowly and relatively 46 expensive long-fibered staple must be employed in the production of the wrapping.

The insulated conductor constituting the present invention consists of a wire having thereon a coating of unspun fibres, preferably cotton fibres, interentangled and densely compacted and having ample flexibility anda smooth, hard, moisture-proof surface, the coating being very thin as is required of the insulating coating of magnet wire, but never theless of such thickness that at every int the wire is overlaid by a number of Such a coat-ing may be made to adhere to the wire with eat tenacity by the employment of a suitab e adhesive in which the innermost fibres are embedded, and it is exceedingly tough and amply flexible. Because of these characteristics, there is no danger of the coating pealing from the wire or cracking as a result of repeated flexure of the wire. Also, 1n making such'a coating, it is permissibleto use short-fibre staple which is inexpensive because of its limited utility for other urposes. Furthermore, it is possible to app y such a coating to a wire by a continuous and comparatively rapid process, much more rapid than any wrapping operation, Withthe result that the completed conductor may be produced at low manufacturing cost. The fibre may be supplied to the wire in a continuous sliver'which is brought into contact with the wire after the latter has been coated with an adhesive; then the sliver may be subected to a suitable rub motion whereby it is caused to enclose the wire and adhere to it; and then as the Wire is fed along, it is subjected to rapidly rotating pressure devices which serve to compact the fibrous coating to a great density and give it a hard, glazed and preferably water-proofed' surface while retalnlng its toughness and flexibility.

It has been proposed heretofore to insulate electrical conductors with an insulating coating of interentangled fibres, such for instance as cotton or asbestos, but this has been done only in connection-with the manufacture of so-called fixture wire in which the thickness of the insulatin coating is a matter of little importance, mechanical strength to withstand blows and strains 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 characterincident to the handling of.

istic is made more certain by so applying the fibres to the wire 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 tov thewire are arran ed generally parallel to the length of the wlre, whereas the fibres further from the wire are arrangedin 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 employement of a rub motion apparatus, this should not be so operated as to result in rolling of the wire back and forth upon itself ashas 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 impaired at all.

The invention will be better understood by reference to the following description taken in connection with the accompanying drawings which illustrate the conductor and also the apparatus which may be employed in making it.

Referring to these drawings, Fig. 1 is a view on an enlarged scale of a short length of magnet wire embodying the invention; Fig. 1 is a similar view many times enlarged;

, Fig. 2 is a transverse section of the wire shown in Fig. 1; Fig. 3 is a view in elevation of ap paratus for producing the wire; Figs. 4 and 5 are similar views of apparatus employed in later stages of the process; Figs. 6 and 6 are sections on lines 6-6 and 6**6 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, 1 and 2 show the insulated wire embodying the invention, the wire'being indicated at 10 andthe 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 coating of unspun interentangled fibres snugly adhering to the wire and having a smooth, water-proofed surface.

wire by being imbedded in a suitable adhesive 7 whereas the fibres. in the outer portion of the covering are arranged generally circumferentially.

In Fig. 1*, the reference 11' indicates the innerportion of the insulatingcovering 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 interentangled 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 drawings. In Fig. 3, 12 indicates the doifer roll of a finishing cardprovided with a comb 13 which acts to strip slivers of carded cotton or like fibres from the usual rings of the dofi'er roll. The sliveris' shown'at 1 and after it leaves the roll 12 it is sustained by a belt or conveyor 14 having transversely disposed ribs 16 thereon. 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 may be 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 which the insulation is to be applied is shown at 15. It is guided by suitable rolls through a bath of adhesive 2 and then passes up beside the roll 12 to the upper surface of the belt 14 where it comes in contact with the under side of the sliver 1 and travels along upon the surface of the belt 14 with the sliver. Of course, a plurality of wires may be treated at the same time, these being arranged in parallelism for coaction with slivers 1 which are dofi'ed from the roller 12 in parallelism.

diameter of the wire to be covered and the wire is so guided and sustained that it is centrally located with respect to the sliver. As shown in Fig. 6, the sllver overhangs the wire at the sides as the sliver and wire leave the belt 14. From the belt 14 the sliver and wirepass to ether at the same speed between rub motion elts 17 and 18 located in close proximity to the transfer belt 14. These rub motion belts have a longitudinally progressing and laterally reciprocating motion. This reciprocating motion produces a rolling or twisting of the sliver about the core but care is exercised in so positioning the belts that in rollin the sliver upon the wire they will not roll the wire upon itself. Such rolling ofthe wire is exceedingly detrimental to the wire 'for it has the effect of hardening it and therebydecreasing its electrical conductivity. The action of these rub motion belts applies. the sliver to the wire entirely around the wire and causes a substantial portion of the fibres of the sliver to be imbedded in the adhesive and these-ends are accomplished without disturbing the uniformity of the distribution of the fibres lengthwise of the sliver. As a result, the product leaves the rub motion belts in the manner indicated in Fig. 6 with the wire enclosed centrally Within a substantially circular body of fibres which are more or less condensed and in which the fibres at the interior of the body are imbedded in the adhesive on the wire.

While we have shown and described above,

certain operations and apparatus by the use of which a sliver or body of fibres is caused to be first applied to a conductor-or core member and distributed substantially uniformly thereabout without disturbing the general lengthwise or substantially parallel arrange ment of the fibres adjacent the wire or core, after Which subsequent steps are performed, as described, we do not limit ourselves to these specific preliminary operations as described or to the form of apparatus as specifically shown. Other operations and other forms of apparatus may be employed, provided suitable means are supplied whereby the fibres will first be substantially uniformly distributed about and generally parallel to the wire or core member adjacent the surface thereof, and provided the fibres adjacent the surface of the wire or core member are maintained generally parallel thereto or lengthwise thereof during the subsequent operations during which the remaining or outer fibres of the covering are indiscriminately entangled or are inter-entangled and arranged generally circumferent-ially of the wire.

From the rub motion belts the product passes to a wiping device or licker 19 which may consist of a pair of flat springs adapted to engage opposite sides of the wire and to be rotated by suitable means, not shown, as the The wire is then carried through a mois- I ture-proofing medium 22 which may be in a receptacle 20 having a pulley 2lvmounted therein around which the wire passes. A compound of nitrocellulose is well adapted for use as the moisture-proofing medium as a coating of that substance not only protects the insulating covering from moisture but also serves to cement down the fibres of the insulating body and hold them permanently in close contact.

From the receptacle 20 the wire passes to a wiper 23 which is of the same general nature as the licker 19. This wiper serves to remove excess solution from the fibre body and further condense the later preparatory to the polishing operation.

The polishing may be performed by a suitable die 24 which may be located in close proximity to'the wiper 23. This polishing device may consist of a pair of polishing blocks 25 shown in detail in Fig. 8. These blocks have opposing smooth polishing surfaces between which the wire passes. The function of the polishing device is to condense the fibres of the covering to a high degree and further entangle and mat them to bring the covered wire to the required gauge and compact the fibrous insulating covering to the desired density.

By the employment of such a process and apparatus, a wire may be provided with an insulating covering which is of the thinness of magnet wire insulation and which is of pronounced uniformity of thickness and dielectric strength and of such toughness and elasticity that it will not be broken or Weakcned by repeated flexure of the Wire. The operation of applying this coating to the wire is an inexpensive one because the insulating of the wire proceeds with far greater rapidity than any braiding or wrapping operation and the cost of the completed wire is further reduced by the fact that this form of insulation permits of the use of short fibre staple 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 covering to it uniformly for such rolling motion of the wire would covered are approximately 7 fibres one 'on top of an other at every point over the surface of the wire, these fibres being cries-crossed and interentangled more or less indiscriminately.

When the conductor is flexed the fibres running more or less in the direction of the length of the wire are particularly effective in maintainin the integrity of the covering. Thus, fibres w ch lie adjacent to the wire are arranged generally parallel tothe length of the wire; t the fibres in the sliver 1 areinitially arranged in substantial parallelism 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 adhesvie and carries the sliver entirely around the wire. In the later operations, particularly that of the polishin device 24, the body of fibres is compacte 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.

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

We do not claim herein the method of insulating wire as described and claimed in our copending application, Serial No. 238,178, filed December 6, 1927, nor the apparatus for insulating wire as described and claimed in our copending application, Serial No. 238,179, filed December 6, 1927.

We claim:

1'. An insulated electrical conductor comprising a wire and an insulating sheath for the wire consisting of a tough, flexible cover ing of densely compacted fibres, the fibres of the covering adjacent to the wire being generally parallel to the length of the wire and is is due primarily to the fact that entangled fibres, the fibres the remaining fibres being indiscriminately entan led.

insulated electrical conductor com- .prismg a mm and an insulatifi sheath for the wire consisting of a tough, exible covering of densely compacted bres, the fibres of t e coverin adjacent to the wire being generally para el to the length of the wire and the remaining fibres belng interentanled and arranged generally circumferentialy of the wire.

insulated electrical conductor comprising a wire in a substantially unfatigued condition and an insulating covering for the wire comprising a highly compacted,uniform,

.tough, flexible and moisture-proofed coating of fibres, the fibres at the interior of the covermg being generall parallel to the length of the. wire and imbe dad in an adhesive on the wire and the remaining fibres being inter- I entanlgled but arranged generally circumferentia y of the wire.

4. An insulated electrical conductor, comprising a core member and an insulating sheath for said core member, comprising a densely compacted mass of fibres, the fibres directly adjacent the core member bein directed generally parallel to the length thereof, the remaining fibres being indiscriminately intermingled, and all the fibres of the covering being interentangled with each other, and means to bind all of the fibres together.

5. In an electrical conductor, the combination of a core member and a covering therefor, comprising a densely com acted mass of entangled fibres, the fibres being directed generally parallel to the length of said core member adjacent the same, and turned to a position wherein they are generally directedcircu'mferentially of the core member at the outer surface of the covering, and means to bind said covering to said core member.

6. In an electrical conductor, the combination of a core member and a coveringtherefor, comprising a densely com acted mass of bein directly generally parallel to the length 0 said core member adjacent the same, and gradually turned to a position wherein they are gen erally directed circumferentially of the core member at the outer surface of the covering, means to bind said coverin to said core member, and means to bind a l of the fibres together.

In testimony whereof we afiix our signatures.

- EDWARD A. MAU.

ORRIN F. *HUTGHINSON.

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