US3455021A

US3455021A - Method of making electrically insulated copper strip conductors

Info

Publication number: US3455021A
Application number: US644036A
Authority: US
Inventors: Emil H Olson
Original assignee: Anaconda Wire and Cable Co
Current assignee: ANAMAG Inc A CORP OF DE; Chase Commercial Corp
Priority date: 1964-09-14
Filing date: 1967-03-06
Publication date: 1969-07-15
Anticipated expiration: 1986-07-15

Description

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July 15, 1969 E. H. OLSON 3,455,021

METHOD OF MAKING ELECTRICALLY INSULATED COPPER STRIP CONDUCTORS Original Filed Sept. 14, 1964 I I A 1 I L.

United States Patent 3,455,021 METHOD OF MAKING ELECTRICALLY INSU- LATED COPPER STRIP CONDUCTORS Emil H. Olson, Muskegon, Mich., assignor to Anaconda Wire and Cable Company, a corporation of Delaware Original application Sept. 14, 1964, Ser. No. 396,087, now Patent No. 3,317,876, dated May 2, 1967. Divided and this application Mar. 6, 1967, Ser. No. 644,036

Int. Cl. H01f /06; C23b 5/58 US. Cl. 29-605 15 Claims ABSTRACT OF THE DISCLOSURE A method of making electrically insulated copper strip conductors by applying metallic aluminum to the side edges of the copper strip, then treating the metallic aluminum on the side edges to form a continuous oxidic dielectric film thereon and finally coating at least one of the flat surfaces of the strip with an electrically insulated film.

This i a division of copending application Ser. No. 396,087, filled Sept. 14, 1964 and now Patent No. 3,317,876.

The invention relates to electrically insulated copper strip conductors for use in the manufacture of electrical coils. More particularly, it is directed to a method of manufacturing electrically insulated copper strip conduc tors which are characterized by metallic aluminum along the side edges of the strip and have a dielectric oxidic coating on the metallic aluminum.

In the manufacture of insulated copper magnet strip conductor which are most commonly used for the manufacture of electrical coils, it is essential that the insulating coatings which are applied to the copper strip be free from discontinuities which might cause short circuits in their electrical application. The most common source of these discontinuities in the insulating coating has-been found to occur along the side edges of the strip conductor.

These side edges are the most common source of failings both because they are so diflicult to coat properly with insulating varnishes or lacquers and also because they present such a relatively sharp edge that the insulating coatings either do not adhere properly or they become scraped off during handling, such as the winding operation required to form electrical coils.

In forming the narrow copper strips in the fabrication of the strip conductors, the method almost universally followed is to cut the narrow copper strip from a much wider copper strip. When this wide copper strip is cut longitudinally into narrower strips the cutting operation always exposes the side edge portions of the narrower strips and leaves them rough with slivers and burrs. Thus, even if the wider copper strips are coated with a dielectric insulating coating before the cutting operation, the flat surfaces may be adequately insulated but the side edge portions must be covered over with a suitable insulation or they would surely be the source of a short circuit particularly in their use of electrical coils.

It is an object of the invention to provide continuous methods for the manufacture of these electrically insulated strip conductors.

The method is one for making an electrically insulated copper strip conductor in which a relatively wide strip of copper i cut into a plurality relatively narrow strips which are each bare of any coating at their side edges. According to the invention, the side edges of the narrow strips are cleaned and deburred and metallic aluminum is applied to the side edges. The strip is then treated to form a continuous oxidic dielectric film on the metallic aluminum along the side edges to cover and insulate the side edges of the strip. An electrical insulating film coating is also provided on at least one of the flat surfaces of the strip. It is clear that by the method of the invention in which the side edges of metallic aluminum are first coated, the subsequent formation of an oxidic dielectric film is easily made to the metallic aluminum and a strong and continuous insulating film along the side edge portions of the strip conductor is assured. The coating of the flat surfaces of the strip conductor can be made either before the strip conductor has been longitudinally cut from a wider copper strip or it can be made subsequent to the formation of the dielectric oxidic film along the side edges of the strip.

The metallic aluminum can be applied to the side edges of the strip either by passing the strip continuously through an aluminum coating operation or the copper strip can be wound into a roll and coated with aluminum along its side edges in a batch process. For the formation of the dielectric oxidic film on the aluminum along the side edges, however, it is preferred first to wind the copper strip into roll form with a sealant between the turns of the roll and then immerse the roll into an aqueous electrolytic oxidation bath to form an anodic dielectric film on the metallic aluminum which is contained on the side edges of the copper strip. Once the copper strip conductor has been coated on its side edges with the oxidic dielectric film, and provided at least one of the fiat surfaces is coated with an electric insulating film, the electrically insulated copper strip conductor can be unwound from the roll and then wound into an electrical coil.

A preferred embodiment of the invention described hereinbelow with reference to the drawing wherein:

FIG. 1 is a side elevation, partly schematic, of a first method of forming electric strip conductors;

FIG. 2 is a side elevation, partly schematic, of a second method of forming electric strip conductors; and

FIG. 3 is a section of a copper strip conductor formed according to the methods in FIGS. 1 and 2.

As shown in FIG. 1 a coil 10 comprising a multiplicity "of turns of a fiat strip of copper 11, which has been cut from a wider copper strip, is being fed to a first cleaning and deburring station 12 where the side edge portions 13 of the strip 11 are being cleaned of slivers and burrs by means of vertical rolls 14 and horizontal rolls 15. By these mechanical means or their equivalent, the sharp cutting edges of the strip 11 are rounded and relatively smooth side edges are prepared by this mechanical treatment and with the assistance of a chemical treatment if required. The cleaned and deburred copper strip 11 is then passed to a chamber 16 where metallic aluminum is disposed only on the side edges of the copper strip. Protective plates 17 and 18 are positioned substantially against the flat surfaces of the strip 11 to protect these flat surfaces from aluminum deposition. These protective plates should be of a material such as plastic, wood or fiber. In applying the aluminum coating 19 on the side edges of the strip of the coating generally disposed not only along the side edge portions of the strip but also along a small marginal edge portion of the flat surfaces of the strip as will be seen in FIG. 3. Thus, in FIG. 1 as the copper strip 11 emerges from the aluminum coating chamber 16 the strip 11 appears to have a greatly enlarged thickness and this has been done to illustrate that an aluminum coating 19 has been disposed on the side edges of the strip and on a small marginal portion of the fiat surfaces of the strip.

The copper strip with the aluminum disposed on its side edges is then passed to a coating station 20 where an organic insulating film such as epoxy, Formvar, polyester, polyurethane, polyamide, polyirnide, polyamidepolyimide, or any of the standard materials now used for coating magnet conductors, is applied to the fiat surfaces of the strip 11 between the aluminum deposit 19 on the side edges thereof.

The thus coated strip conductor is then wound into a roll While a thin plastic sheet 21 is simultaneously fed with the strip conductor 11 so that the roll is interleaved with this thin plastic sheet 21 between successive turns. Polyethylene sheets have been used with success for this operation and it has been found that the rolls can also be interleaved with another sealant such as a heavy liquid like kerosene.

The roll 22 and others like it are then taken to anodizing equipment Where they are lowered into an electrolytic bath 23 which may be chromic, sulfuric, oxalic or other acid or it may be a caustic alkaline bath. Low voltage direct current is then passed through the bath with each of the rolls therein serving as the anode. A lead stainless steel or other conducting electrode is employed as the cathode. A film of aluminum oxide is thereby formed on any aluminum surface exposed to the electrolyte and thus all exposed aluminum edges defining the flat sides of the rolls are covered with an even and continuous insulating anodic film.

The plastic sheet 21 which is interleaved between the turns of the roll serves as a sealant to prevent the electrolyte from penetrating between the turns of the roll by capillary action where if it remains it might corrode the copper if it were to contact the metal or it would attack the organic coating which has previously been applied to the flat surfaces of the strip conductor. After the anodizing has been completed the batch of rolls are lifted from the bath, rinsed and dried and the strip conductor is then prepared to be rewound from the roll into electrical coils to which leads may be attached.

Referring now to FIG. 2 a second embodiment of the method of the invention is shown schematically. A roll 25 of bare copper strip conductor which has been cut from a wider copper strip but has had no prior treatment is interleaved with a sealant, either a thin plastic sheet or a heavy liquid. The roll 25 is immersed into an etching solution in bath 26 to clean the edges and remove burrs, slivers and sharp corners along the side edges of the narrow copper strip. The sealant will prevent the solution in the bath from being drawn between the turns of the roll by capillary action and will maintain the flat surfaces free from this etching opertaiou. The etched roll 25 is then removed from the bath 26 and is moved to a chamber 27 where the roll 25 is placed and the side edges of the entire interleaved coil for metallic aluminum deposit thereon by any of the presently known methods such as vapor deposition, plating, cladding or perhaps an electrochemical process. The roll 25 is then passed to an anodizing bath 28 where the aluminum coated side edges can be anodized to form an anodic dielectric film on the aluminum side edges by immersing the roll 25 into the electrolyte in a similar operation as that described in relation to FIG. 1. A copper strip conductor 29 is then unwound from the roll 25 and is passed through a coating die 30 where any of the organic insulating films mentioned above are coated either on one flat surface of the strip conductor, both flat surfaces, or on the entire conductor.

The conductor 29 is then passed to a coil winding operation where the extended length of copper strip conductor is wound into a multilayer coil with the organic electric insulating film disposed within succesive layers of the coil, and then suitable leads are attached.

It is also proposed that the copper strip conductor can be formed by coating the entire copper strip with metallic aluminum coating and then anodizing the entire aluminum coated copper strip.

As shown in FIG. 3 the electrically insulated copper strip conductor consists of a copper strip 31 which has a top flat surface 32 and a bottom flat surface 33 and fiat

side edge portions

34 and 35. A metallic aluminum coating is deposited on the

flat side edges

34 and 35 and extends continuously beyond the side edges and covers the

marginal edge portions

36, 36, 37 and 37' on both of the fiat surfaces up to about 10 percent of the flat surface area. A thin organic insulating

film

38 and 39 is deposited on the fiat surface of the copper strip conductor between the aluminum

side edge deposits

36, 36, 37 and 37.

I claim:

1. A method of making an electrically insulated copper strip conductor in which a relatively wide strip of copper is cut into a plurality of relatively narrow strips which are each bare of any coating at their side edges comprising:

(a) cleaning and deburring the side edges of said narrow strip,

(b) applying metallic aluminum to said side edges,

(c) treating the metallic aluminum on the side edges to form a continuous oxidic dielectric film thereon to cover and insulate the side edges of the strip, and

(d) coating at least one of the fiat surfaces of the strip with an electrical insulating film.

2. A method of making strip electrical coils from an electrically insulated copper strip in which a relatively wide strip of copper is cut into a plurality of relatively narrow strips which are each bare of any coating at their side edges comprising:

(a) cleaning and deburring the side edges of said narrow strip,

(b) applying metallic aluminum to said side edges,

(c) treating the metallic aluminum on the side edges to form a continuous oxidic dielectric film thereon to cover and insulate the side edges of the strip,

(d) coating at least the fiat surfaces of the strip with an electrical insulating film, and

(e) winding the resulting insulated copper strip into an electrical coil.

3. A method of making an electrically insulated copper strip conductor in which a relatively wide strip of copper is cut into a plurality of relatively narrow strips which are each bare of any coating at their side edges comprising:

(a) cleaning and deburring the side edges of said narrow strip,

(b) applying metallic aluminum to said side edges,

(c) treating the aluminum coating on the side edges by subjecting the strip to anodic oxidation to form a continuous anodic dielectric film on the aluminum metal to cover and insulate the side edges of the strip, and

(d) coating at least one of the flat surfaces of the strip with an electric insulating film.

4. A method of making an electrically insulated copper strip conductor in which a relatively wide strip of copper is cut into a plurality of relatively narrow strips which are each bare of any coating at their side edges comprising:

(a) etching the side edges of the strip to clean and deburr it,

(b) applying metallic aluminum only to substantially the side edge portions of the strip and leaving the flat surfaces of the strip free from metal aluminum except along the marginal edge portions thereof,

(c) immersing the copper strip coated at its side edges with metal aluminum into an aqueous electrolytic oxidation bath to form a continuous anodic dielectric film on the aluminum metal to cover and insulate the side edges of the strip, and

5. A method of making an electrically insulated copper strip conductor in which a relatively wide strip of copper is cut into a plurality of relatively narrow strips which are each bare of any coating at their side edges comprising:

(a) cleaning and deburring the side edges of the narrow strip,

(b) continuously applying metallic aluminum to the side edges of said narrow strip,

(c) winding the strip into a roll with a sealant between turns thereof in which the aluminum side edges of the narrow strip are exposed at the end faces of the roll,

(d) treating the end faces of the roll to form a continuous oxidic dielectric film on said aluminum edges, and

(e) coating at least one of the fiat surfaces of the strip with an electric insulating film.

6. A method according to claim 5 wherein said fiat surfaces of the strip are protected during application of aluminum metal so that the metal aluminum is formed on the side edges thereof.

7. A method according to claim 5 wherein said sealant is a plastic film.

8. A method according to claim 5 wherein said sealant is a heavy liquid.

9. A method according to claim 5 wherein the roll is immersed into an aqueous electrolytic oxidation bath to form a continuous anodic dielectric film on the aluminum metal to cover and insulate the side edges of the strip.

10. A method of making strip electrical coils from an electrically insulated copper strip in which a relatively wide strip of copper is cut into a plurality of relatively narrow strips which are each bare of any coating at their side edges comprising:

(a) cleaning and deburring the side edges of the narrow strip,

(d) treating the end faces of the roll to form a continuous oxidic dielectric fihn on said aluminum edges,

(e) coating at least the flat surfaces of the strip with an electric insulating film, and

(f) winding the resulting insulated copper strip into an electrical coil.

11. A method of making an electrically insulated copper strip conductor in which a relatively wide strip of copper is cut into a plurality of relatively narrow strips which are each bare of any coating at their side edges comprising:

(a) winding the strip into a roll with a sealant between turns thereof in which the bare edges of the narrow strip are exposed at the end faces of the roll,

(b) cleaning and deburring the bare edges of the roll,

(c) applying metallic aluminum to the bare edges at the end faces of the roll,

(e) coating at least one of the fiat surfaces of the strip with an organic electric insulating film.

12. A method according to claim 11 wherein said sealant is a plastic film.

13. A method according to claim 11 wherein said sealant is a heavy liquid.

14. A method according to claim 11 wherein the roll is immersed into an aqueous electrolytic oxidation bath to form a continuous anodic dielectric film on the aluminum metalv to cover and insulate the side edges of the strip.

15. A method of making strip electrical coils from an electrically insulated copper strip in which a relatively wide strip of copper is cut into a plurality of relatively narrow strips which are each bare of any coating at their side edges comprising:

(b) cleaning and deburring the bare edges of the roll,

(c) applying metallic aluminum to the bare edges at the end faces of the roll,

((1) treating the end faces of the roll to form a continuous oxidic dielectric film on said aluminum edges,

(e) unwinding the edge insulated strip from the roll,

(f) coating at least one of the fiat surfaces of the strip with an organic electric insulating film, and

(g) winding the resulting insulated copper strip.

References Cited UNITED STATES PATENTS 2,974,097 3/1961 Ramirez et al 204-28 3,061,527 10/ 1962 Karner et al. 204-15 3,223,896 12/1965 Smith l74-119 3,270,401 9/1966 Staley et al 29-605 FOREIGN PATENTS 908,330 10/ 1962 Great Britain.

JOHN H. MACK, Primary Examiner T. TUFARIELLO, Assistant Examiner U.S. Cl. X.R. Z04-15, 28