US1845041A

US1845041A - Insulated electric conductor

Info

Publication number: US1845041A
Application number: US219908A
Authority: US
Inventors: Boving Henrik
Original assignee: Bell Telephone Laboratories Inc
Current assignee: AT&T Corp
Priority date: 1927-09-16
Filing date: 1927-09-16
Publication date: 1932-02-16
Anticipated expiration: 1949-02-16

Description

522320 1%, 19:32. BOVENG 345,041

INSULATED ELECTRIC CONDUCTOR Filed Sept. 16, 1927 Arron/var Patented Feb. 16, 1932 UNITED STATES PATENT OFFICE HENRIK BOVIN G, 01 NEW YORK, N. Y., ASSIGNOR TO TELEPHONE LABORATORIES, INCORPORATED, OF NEW YORK, N. Y., A CORPORATION OF NEW YORK INSULATED ELECTRIC CONDUCTOR Application filed September 18, 1927. SeriaLNo. 219,908.

This invention relates'to the insulation for electrical conductors. One application of it is in insulating wire and more particularly to the insulating of copper wire of the type 5 having a coating of baked enamel.

When the usual types of enamels, such as black compound and varnish enamels, are applied and baked directly on tinned copper wires, the enamel adheres so firmly to the wire that it is dilficult to removeunless it is baked very soft or very hard. Either the very soft or the very hard baking of the enamel coating is undesirable because in the I very soft state the coating is susceptible to mechanical injury and in the very hard state it becomes brittle and will not stand handling or bending without flaking. Furthermore, in the case of tinnedcopper wire the baking incident to producing a very hard enamel coating causes the tin to partly alloy with the copper, thereby producing a surface which is difficult to solder.

The invention in one aspect consists of means between the enamel insulation and the conductor for facilitating the removal of the insulation.

In a more specific aspect, the invention comprises applying to. a tinned wire a priming coating of adhesive/material, such as a varnish containing a phenolic condensation product, or a varnish composed of a metallic soap dissolved in a volatile solvent, baking the coating to form an adherent layer, applyingv to the riming coating a coating of insulating enamel and baking the double coating at 1 a higher temperature than the baking temperature of the priming coating, to change the priming coating to a substantially nonadherent layer and form an insulation having the necessary qualities of flexibility, inertness to solvents and freedom from embrittling 'upon aging. The thin priming coating has the property of beingmore adherent to the insulating enamel than to the surface of the wire so that the insulation may be easily and completely removed by stripping, by mechanical means, thus leaving the tinned wire in suitable condition for soldering purposes.

A more detailed description of the invention follows and is illustrated in the accompanying drawings.

Fig. 1 illustrates a conductor having a thin priming coating of material which is substantially non-adherent and an outer coating of elastic insulating enamel.

F ig'. 2 is a cross-sectional view of Fig. 1.

Referring to the drawings, Fig. 1 shows an electrical conductor 10, of copper, having a thin coating of tin to form a surface which is easy to solder. The amount of tin in the coating is necessarily small being approximately from one to six milligrams per square inch of conductor surface. Heavy tin 'coatings are not'suitable for subsequent enameling because the enamel coating is usually baked at a temperature above the melting point of tin, and heavy coatings roduce a suflicient amountof liquid tin in the enamel baking process so that the tin collects in droplets under the enamel applied to the conductor. A thin priming coating 11 is applied to the tinned conductor or wire 10 and is preferably of an adhesive material which can be baked to a hard non-adherent state at a 75 temperature not greater than that used for producing the usual type of enamel coating in-the adherent flexible state.

It has been found that varnishes containing a condensation product of the phenol group, such as bakelite varnishes, or a varnish or enamel prepared by dissolving metallic soaps in boiled vegetable oils are suitable for the-priming coat. By diluting the varnish or enamel with a suitable volatile solvent, the thickness of the priming coating may be varied from .0002 of an inch to .00005 enameling process. When the priming coating consists of a varnish containing a phenolic condensation product, the baking temperature should be approximately 400 F., while the baking temperature of the metallic soap varnish should be approximately 500 F. This preliminary baking temperature can be changed, however, depending upon the type of varnish used in the priming coat since the object of this baking is to dry the varnish and .produce sufiicient adherence of the varnish to the conductor during subsequent operations. The conductor is passed through a bath containing an enamel in any suitable manner to form a layer or a plurality of layers of protective insulation and finally baked at a suitable temperature from approximately 500 to 600 F. The enameling and baking may be performed in a continuous operation in an ovenstructurev such as is disclosed in the Holmes and l larris Patent 1,101,281, dated June 23, 1914. a

The final baking temperature which is higher than the baking temperature of the priming coating changes the priming coating from a flexible adherent layer to a substantially non-adherent coating on the conductor surface. The priming coating is of a fragile character but due to its adherence to the enamel insulation the two coatings may be easily stripped from the conductor by mechanical means, such as pliers, and the tinned conductor will be in clean condition to soldering operations.

By regulating the thickness of the priming coating, enamel coatings may be produced varying from the condition of being very ads" herent and therefore diflicult to remove, to the condition of being quite non-adherent, easy to 395 171, filed September 25, 1929.

I The invention is not limited to the specific materials entioned for the priming coating since other materials may be employed which would become non-adherent continuous priming layers after the insulating coating has been applied and treated as described above.

Furthermore, the invention is not limited to the particular method of baking since the coatings may be treated by other media to cause the priming coating to become nonadherent to the conductor.

What is claimed is:

1. The method of forming a coating of insulation on an electric conductor which comprises, applying to the conductor a coating of adhesive material, applying thereto a coating of insulation, and treating the insulated conductor to render the inner coating non-adherent.

2. The method of forming a coating of insulation on an electric conductor which comprises, applying to the conductor a coating of adhesive material, applying thereto a coat ing of. insulation, and applying heat to the insulated conductor to render the innercoating non-adherent.

3. The method of forming a coating of insulation on an electric conductor which coniprises, applying to the conductor a coating of varnish, applying thereto a coating of insulation, and treating theinsulated conductor to render the inner coating non-adherent.

4. The method of forming a coating of insulation on an electric conductor which comprises, applying to the conductor a coating of varnish, applying thereto a coating of insulation, and applying heat to the insulated conductor to render the inner coating non-adherent.

5. The method of forming a coating-of insulation on an electricaL conductor which comprises, applying to the conductor a coating of adhesive material, applying thereto a coating of. insulating enamel, and treating the insulated conductor to render theinner coating non-adherent. v

6. A method of-forming a coating of insulation on an electrical conductor which com prises, applying to the conductor a coating of adhesive material, applying thereto a coating of insulating enamel, and applying heat ios dried and becomes non-adherent when heated a sufiieient, amount, applying a second coat- "ing of a different insulating material, and

heating the two coatings to render the priming coating non-adherent. z 9. The method of forming a coating of insulation on a conductor which comprises, ap-

plying a coating of varnish having properties which change within a certain range of temperatures, baking the coating at temperatures etween 300 and 500 F., applying a finishing coating of elastic material, and baking the two coatings at temperatures between 500 and 600 F.

10. The method of forming a coating of insulation on a conductor which comprises, applying a varnish containing a phenolic condensation product, baking the varnish at a temperature of approximately 400 F., applying an insulating enamel to said varnish, and baking the varnish and enamel at a temperature ofapproximately 600 F.

11. An electric conductor insulated with baked enamel, comprising. a layer in contact with the conductor for spacing the insulation from the conductor, said layer being non-adherent to the conductor.

12. An electric conductor insulated with baked enamel, comprising a layer of fra ile varnish between the enamel and the cond uctor for facilitating the removal of the insulation.

V 13. An electric conductor insulated with baked enamel, comprising a phenolic condensation varnish between the insulation and the conductor for preventing the latter adhering firmly to the former.

14. An electric conductor insulated with baked en amel, comprising a-layer of varnish containing an einbrittling agent between the enamel and the conductor for preventing the adherence of the enamel to the conductor.

15. An insulated conductor having a plurality of coatings of insulating material thereon, the innermost coating consisting of a thin priming layer of varnish, said layer being substantially non-adherent to the surface of the conductor and firmly adherent to the adjacent coating of insulating material.

16. An insulated conductor compris' a central wire having a non-adherent riming layer of varnish containing a. pheno ie condensation product, and an outer coating of insulating enamel firmly adherent to said non-adherent primin layer.

17; The method 0 forming a coating of insulation on a conductor which comprises applying a varnish to the conductor containing a material which is non-adherent when heated to a certain temperature, baking the coating at a temperature to dry the varnish on the conductor, applying an insulating enamel to said coating, and baking the varnish and enamel at a temperature of approximatel 600 F. I

18. he method of forming a coating of insulation ona conductor which comprises applying to the conductor a riming coating 0 insulating material which changes from an adherent to anon-adherent state within a certain ran a oftemperatures, baking the priming coating at a temperature below the insulation on a conductor w perature, whereby the varnish coatin said layers being capable of being transition temfi'perature, applying a second coating of a di erent insulating material, and baking the two coatings at a temperature higher than the transition temperature of said priming coating.

19. The method of formin a coating of ich comprises applying a coating of varnish erties which change at high temperatures, baking the coating to form an adherent layer,

applying a finishing coating of elastic material, and baking the two coatin at a higher temperature than the first baking teraheres to the finishing coating more rmly than to the conductor.

20. In an insulated conductor, a layer of insulating varnish adjacent to the bare conductor composed of material which is substantially non-adherent thereto, and a la er of insulating enamel adherent to said varnish, easily stripped from the conductor.

In witness whereof, I hereunto subscribe my name this 8th day of September, A. D.

HENRIK BOVING.

having prop-