US1936994A

US1936994A - Rubber insulated electrical conductor

Info

Publication number: US1936994A
Application number: US555209A
Authority: US
Inventors: Harold D Rice
Original assignee: NAT INDIA RUBBER CO
Current assignee: NAT INDIA RUBBER CO; NATIONAL INDIA RUBBER Co
Priority date: 1931-08-05
Filing date: 1931-08-05
Publication date: 1933-11-28
Anticipated expiration: 1950-11-28

Description

Nov. 28, 1933, H. D. RICE 1,93 994 RUBBER INSULATED ELECTRICAL CONDUCTOR Filed Aug. 5, 1931 INV ENTOR HAROLD 0. RIC

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"Nrrso STA Al'EN'l orrice masses RUBBER WSULATED ELECTRICAL CGN'DUCTDR Harold D. Rice, Bristol, R. IL, assignor to National India Lubber Company, Bristol, R. L,

a corporation of Rhode Island Application August 5, 1931. Serial No. 555,209

' eclaimo. (01.173-264) This invention relates to, rubber insulated electrical conductors and methods oi. manufacturing the same.

This is a continuation, as to all common subject matter therein, 01' application No. 388,036

filed August 23, 1929.

Heretofore it has been the practice to apply rubber insulation to electrical conductors byv either extruding the rubber onto the conductor,

or by forming the rubber in sheet form, cutting the sheets into strips-and wrapping the strips,

up in parallel, or twisting, with or without a braid, and finally covering if desired with silk, rayon, or cotton braids, or the like, or reinsu= lating with a rubber compound.

It is the object of this invention to provide a rubber insulation for conductors which is or" a 5 grainless texture, is unmilled, and which is tough, flexible, durable and has a high resistance to abrasion.

It is also the object of this invention to apply a suitable rubber insulation to a conductor directly from latex or other aqueous dispersions of rubber.

I It is the further object of this invention to provide an insulation for an electrical conductor from an aqueous dispersion of rubber that has high electrical insulating properties especially when wet.

It is also the object of the invention to pro vide improved constructions of various types of electrical conductors. V

Uther objects and advantages of. the present invention will appear front the following description.

In the drawing is shown various embodiments of the invention; in which Figure 1 illustrates a solid conductor, insulated, and braided single;

Fig. 2 illustrates a stranded conductor, insu lated, layed up .in parallel, and braided double;

Fig. 3 illustrates another construction stranded conductor; insulated, layed up in parallel, and braided double;

Fig. 4 illustrates an insulated solid conductor such as code wire;

5 Fig. 5 illustrates a stranded conductor, insulated, twisted double, and with an overall reinsulation of rubber; and

Fig. 6 illustrates a stranded conductor, insulated, twisted double with a filler, and with an overall reinsulation of rubber.

The conductor to be insulated is brought to size on wire drawing machinery if a solid con-. ductor, or made in stranded form if of a flexible construction, in a manner well known in the art. The conductormay be tinned, paper wrapped, or provided with a serving of cotton or other fibrous material prior to the application of the rubber insulation thereon. Such a covering, as is well known, protects the wire from the action 'of free sulphur contained in the rubber composition which otherwise would migrate into contact with the copper of'the wire to produce an undesirable reaction.

The conductor preferably tinned, or served with cotton or other fibrous material, or both it tinned and served with fibrous material may then be conducted into and through a bath of aqueous dispersion of rubber which preferably takes the form of la ex which. has been purified and compounded mitt; lca'nizing ingredients and if desired also filler ingredients. As the con duster emerges from the coating bath, it is pref 'erably passed through a drying chamber to co= need be employed and the vulcanization may be completed by a subsequent heating operation. $5 The rubber in the disperson may, if desired, be in vulcanized condition, and in such case, a low or temperature and smaller drying chamber may be used than when vulcanization is also effected. The dipping and drying o'r dipping and coagulat= ing operations may be repeated until a-sumcient thickness of rubber has been formed on the who to provides. layer having the desired electrical insulation properties.

in Figures 1 and 2 are illustrated examples of conductors made according to the present in vention. Figure 1 illustrates a conductor in which 1 represents a solid core, 2 a cottonservlug there over, 3 a layer of rubber deposited from an aqua out dispersion of rubber over-the serving, and a 11 a rlnal braid over the insulation on the single conductor. Figure 2 illustrates a pair of parallel stranded conductors such as may be used for lamp cord, in which 5 represents the stranded cores, 6 a cotton serving over the cores, '1 a layer of rubber deposited from an aqueous dispersion of rubber over the serving, and 8 an overall braiding over the two conductors made of fibrous material, such as cotton or rayon, or the like. Conductors insulated with rubber from an aqueous dispersion of rubber may be finished in a variety of ways. For single conductors, they may be finished with a braid as shown in Figure 1. For multiple conductors, a plurality of the rubber insulated wires, either with or without a braid over each wire, may be finished by braiding overall, as shown in Figure 2.

For still heavier insulations, and where even a greater toughness, durability, and resistance to abrasion is desired, the single conductors insulated and braided may again be passed through a rubber dispersion and dried or otherwise coagulated. As before this may be repeated any number of times, depending upon the thickness or the layer of insulation desired. This dipping in the dispersion again after the wire has been coated with a film of rubber and a braid has been provided over the rubber, impregnates the braid and also sufiicient dispersion passes through the braid so that on subsequent drying, and vulcanization, the new film of rubber over the braid is bonded through the braid to the inner rubber film. Such a novel construction of a rubber film over the braid which also provides a bond with "the inner rubber film through the braid, provides an exceptional insulation. Conductors formed in this manner may be finished in the same manner as the conductors with one layer of rubber insulation above, either by braiding 'i'or single conductor, or braiding overall a plurality of conductors with or without a braid over the single wires, or by reinsulating overallwith a rubber compound. Figure 3 illustrates as one form of such construction a pair of parallel stranded .conductors such as may be used for lampcord, in which 9 represents the stranded cores, 10 a cotton serving over the cores, 11 a layer of rubber deposited from an aqueous dispersion of rubber over the serving, 12 a braid 0t fibrous material, for example, cotton over said film. Over this braid 12 another film 13 of rubber bonded to the first film 11 through the braid 12, is deposited from an aqueous dispersion of rubber, and 14 represents an overall braiding over the two conductors made or a fibrous material, such as cotton, rayon, or the like.

Figure 4 illustrates a solid conductor such as code wire in which 15 represents the usual tinned solid conductor and 16 a layer of rubber deposited Irom an aqueous dispersion of rubber over they core.

Figures 5 and 6 illustrate conductors which are twisted in pairs and have an overall reinsulation of rubber deposited from an aqueous dispersion of rubber. Figure 5 illustrates a pair of twisted stranded conductors in which ll represents the stranded cores, 18 a cotton serving over the cores, 19 a layer of rubber deposited from an aqueous dispersion oi. rubber over the serving and 20 dispersion of rubber over the serving, 24 a pair of fillers made of twisted cotton threads, 25 a coarse net like overall braid of cotton and 26 an overall reinsulation over the twisted conductors and fillers of rubber deposited from an aqueous dispersion of rubber. 0! course, the

reinsulations

20 and 26 may, if desired, be tubed, if desired from a solid rubber composition in the usual manner.

Insulation deposited from normal latex or other aqueous dispersions of rubber which contain a high percentage of water soluble non-rubber ingredients have inferior electrical insulating properties, especially when moist. I have found that a purification of the latex such as a reduction of the amount of non-rubber ingredients in the latex composition by purification processes such as disclosed and claimed in the Hopkinson and Gibbons Patent Reissue 16,874, by dialysis or electrodialysis, or by creaming processes such as with the aid of creaming'agents and/or centrifuging provides a latex from which insulation may be made which has high electrical insulating properties, even when wet. As an example, I may use a latex twice creamed with pectin or alginates or Irish moss or other suitable creaming agents, forming a creamed latex of 50-60% solids.

Whereas a normal latex contains about 11 or 12% of solid non-rubber constituents which includes soaps, resins, proteins, salts quebrachitol and smaller amounts of other maerials, and concentrated latex even a greater percentage, a once creamed-latex contains approximately but 4-5% of solid non-rubber constituents and a twice creamed latex contains from 2 /2-3% non-rubber constituents, and if the creaming process is continued the amount of non-rubber constituents may be even further decreased. On the other hand, the best known types of crude rubber have anywhere from '7 to 8% solid non-rubber constituents. In order to form the best electrical insulation from an aqueous dispersion oi. rubber, the amount of solid non-rubber constituents should be kept as low as possible. The removal of practically all of the water soluble constituents contained in the latex, as by creaming, renders the rubber dispersion most satisfactory for use in forming rubber insulation.

The following examples of insulation compositions are merely included as illustrations and are not intended to be construed in any way as limitations of the invention:

Example 1 Parts Rubber as creamed latex 100 Zinc oxide--- 4 Su1phur Whiting Zinc dimethyl amino dithiocarbamate ,5 Ammonium stearate 1 Sodium undecylenate (25% solution) 2 Example 2 iii ea set Example 3 Parts Rubber as creamed latex Mid Zinc oxide l Sulphur it Zinc dimethyl amino dithiocarbamate A Ammonium stearate 1 Examples 1 and 2 illustrate latices creamed once or more times as desired, containing vui canizing ingredientsand also filler materials. Example 3 illustrates a latex, creamed once or more times as desired, containing vulcanizing ingredients and no compounds other than are necessary for vulcanization purposes. The zinc dimethyl amino dithiocarbamate is an accelerator of vulcanization. The ammonium stearate acts as a stabilizer of the dispersion and increases the penetrating power of the rubber dispersion. and thus enables it better to wet the materials such as the cotton service etc. with which it comes in contact. The sodium undecylenate in Example 1 is a stabilizer. The various ingredients may be added dry, in solution, or in suspension in a manner well known in the art. The asphalt in Example 2 is preferably added in the form of an emulsion. The above formula: may be cut with water to any desired solids content. I have found a latex composition compounded. to about 40% solids content very satisfactory to apply. Other accelerators and compolmding ingredients may be used, if desired. The propoi ions and nature of the compounding ingredients may obviously be varied to suit the purposes to which the conductor is to be put as will be evident to one skilled in the art. The latices, as described above, may be purified in other ways than by creaming, if desired.

While the invention has been described more or less in detail, it is not intended thereby to so limit the invention inasmuch as the examples herein set forth are merely illustrative thereof and various modifications may be made without departing from the invention, the scope of which is indicated in the following claims.

Having thus described my invention, what I.

claim and desire to protect by Letters Patent is:

1. An electrical conductor comprising a core of conducting material and an insulation thereon of vulcanized and srainless unmilled rubber composition containing not more than 5% of natural non-rubber constituents.

2. An electrical conductor comprising a core of conducting material and an insulation thereon oi vulcanized and grainless unmilled rubber. composition substantially free from water-soluble constituents.

3. An electrical conductor comprising a core of conducting material and an insulation there= on of vulcanized and grainless unmilled rubber composition substantially free from water-soluble constituents and containing not more than 3% natural non-rubber constituents.

4. an electrical conductor comprising a core of conducting material and an insulation there= on oi vulcanized and grainless unmilled rubber composition containing not more than 3% natu= ral non-rubber constituents based on the rubber content.

5. An electrical conductor comprising a core of conducting material. and an. insulation there= on of vulcanized and grainless rubber com-= position deposited directly from a creamed rub ber latex.

d. An electrical conductor comprising a core of conducting material and an insulation there on of vulcanized and grainless rubber composi tion deposited directly from a rubber latex from which has been removed the major proportion of natural non-rubber constituents.

"Z. An electrical conductor comprising a core of conducting materialand an insulation thereon of vulcanized and grainless rubber composi tion deposited directly from rubber latex, said I latex containing not more than 5% natural nonrubber constituents on a dry rubber basis.

8. An electrical conductor comprising a core of conducting material and an insulation there on of vulcanized and grainless rubber composttion deposited directly from rubber latex, said latex being substantially free from natural ,watcr soluble constituents.

9.1m electrical conductor comprising a core of conducting material and an insulation there on of vulcanized and grainless rubber composi tion deposited directly from rubber latex, said latex containing not more than 3% natural nonrubber constituents on a dry rubber basis and being substantially free from natural water-soluble constituents.

HAROLD D. RICE.