Classifications

• • H—ELECTRICITY
  • H01—ELECTRIC ELEMENTS
  • H01F—MAGNETS; INDUCTANCES; TRANSFORMERS; SELECTION OF MATERIALS FOR THEIR MAGNETIC PROPERTIES
  • H01F41/00—Apparatus or processes specially adapted for manufacturing or assembling magnets, inductances or transformers; Apparatus or processes specially adapted for manufacturing materials characterised by their magnetic properties
  • H01F41/02—Apparatus or processes specially adapted for manufacturing or assembling magnets, inductances or transformers; Apparatus or processes specially adapted for manufacturing materials characterised by their magnetic properties for manufacturing cores, coils, or magnets
  • H01F41/04—Apparatus or processes specially adapted for manufacturing or assembling magnets, inductances or transformers; Apparatus or processes specially adapted for manufacturing materials characterised by their magnetic properties for manufacturing cores, coils, or magnets for manufacturing coils
  • H01F41/12—Insulating of windings
  • H01F41/122—Insulating between turns or between winding layers
• • C—CHEMISTRY; METALLURGY
  • C25—ELECTROLYTIC OR ELECTROPHORETIC PROCESSES; APPARATUS THEREFOR
  • C25D—PROCESSES FOR THE ELECTROLYTIC OR ELECTROPHORETIC PRODUCTION OF COATINGS; ELECTROFORMING; APPARATUS THEREFOR
  • C25D11/00—Electrolytic coating by surface reaction, i.e. forming conversion layers
  • C25D11/02—Anodisation
  • C25D11/04—Anodisation of aluminium or alloys based thereon
• • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
  • Y10—TECHNICAL SUBJECTS COVERED BY FORMER USPC
  • Y10T—TECHNICAL SUBJECTS COVERED BY FORMER US CLASSIFICATION
  • Y10T29/00—Metal working
  • Y10T29/43—Electric condenser making
  • Y10T29/435—Solid dielectric type
• • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
  • Y10—TECHNICAL SUBJECTS COVERED BY FORMER USPC
  • Y10T—TECHNICAL SUBJECTS COVERED BY FORMER US CLASSIFICATION
  • Y10T29/00—Metal working
  • Y10T29/49—Method of mechanical manufacture
  • Y10T29/49002—Electrical device making
  • Y10T29/4902—Electromagnet, transformer or inductor
  • Y10T29/49071—Electromagnet, transformer or inductor by winding or coiling

Definitions

• This invention relates to the manufacture of electrically insulated aluminum strip. More particularly, it is directed to a method wherein a strip of aluminum covered on one or both sides with a dielectric material is cut into narrow strips which are wound into rolls and oxidized so that the edge portions thereof are insulated with an oxidic dielectric film.
• the invention provides a novel method for sealing the turns of the wound rolls to prevent penetration by the electrolyte into the rolls during formation of the oxidic dielectric film.
• the invention relates also to strip produced by the method of the invention, and to electrical coils made from such strip.
• Electrical coils are often made up of a plurality of turns of flat aluminum strip with a continuous coating of dielectric material disposed between the turns of the coil to electrically insulate them from one another.
• Leaves of thin paper or a film of insulating enamel, varnish or lacquer are generally used as the dielectric coating between the turns of the strip.
• a deposit of aluminum oxide frequently serves the purpose.
• the method comprises the steps of first applying a continuous dielectric coating to at least one side of a relatively wide strip of aluminum.
• a dielectric coating is advantageously a dielectric organic material such as varnish or lacquer, or it may be an inorganic such as an anodic film.
• This wide coated strip is then cut into a plurality of relatively narrow strips which are each bare of the coating at their edge portions. Then, at least one of the narrower strips is wound into a roll in which the bared edges of the strip are exposed at the side faces of the roll.
• the side faces of the roll are treated to form a continuous oxidic dielectric film deposited on the bared edge portions of the strip.
• this oxidizing step is carried out by anodizing the rolled-up strip in an electrolytic bath.
• the strip thus formed which is itself part of the invention, comprises an aluminum strip having a continuous dielectric coating composition adherent to at least one face, and further having a dielectric oxidic layer covering and insulating it side edges.
• the invention also provides applying 'a sealing compound to at least the edge portions of the strip on at least one side thereof and leaving bare the edges of the strip, whereby the compound is disposed between and seals the turns of the roll.
• the hot cleaning solutions or the electrolyte cannot penetrate between the turns to plasticize the organic coating and blocking is prevented.
• no residual deposits of electrolyte can remain between the turns to corrode or otherwise attack the metal.
• the sealing compound need not extend entirely across the strip between the turns since it usually sufiices only to seal the edge portions, but if it is likely that the entire roll will be heated to the plasticizing temperatures of the organic coating then it is preferable to cover the strip edge-to-edge with the sealing com-pound.
• the invention also provides a novel electrical coil.
• the coil comprises an extended length of aluminum strip wound into a multi-layer coil.
• the strip has a continuous film of dielectric coating composition adherent to at least one face thereof disposed between successive layers of the coil.
• the strip further has a dielectric oxidic layer covering and insulating its edge portions the composition being separated from the dielectric layer.
• the dielectric oxide in an anodizing operation wherein an acidic electrolyte is employed, a considerable amount of the burrs and slivers on the edges of the strip are removed by chemical attack when the roll or coil is submerged in the electrolyte.
• the oxidic insulation also does not overlap onto the previously applied dielectric material covering the flat sides of the strip as is the case when additional oragnic material is applied to the strip edge portions.
• a rela tively wide aluminum strip of say .003 inch thickness is run over one or more applicator rolls carrying a liquid organic dielectric coating composition, for example a polyvinyl acetal or a silicone insulating enamel, whereby a layer of such composition of uniform thickness is transferred to the surface of the advancing aluminum strip.
• a liquid organic dielectric coating composition for example a polyvinyl acetal or a silicone insulating enamel
• the strip may be coated on only one side or on both sides, as desired.
• the coating composition Upon emerging from this coating apparatus, the coating composition is dried to a hardened condition.
• the wide strip may be covered by an inorganic dielectric coating, such as an anodic film, in which case the later-applied anodic edge-coating is still separate from insulation on the broad surface of the strip.
• the coated wide strip is then directed through continuous cutting apparatus where it is divided longitudinally into a plurality of narrow strips, each the width of a roll.
• any type of cutter used in this step bares the aluminum base metal and leaves a certain amount of slivers, burrs or other irregularities on the edges of the narrow strip. Also, the cutters often flake off small amounts of dried varnish from portions of the flat sides of the narrow strips adjoining their newly cut edges.
• the narrow strips exiting from the cutting apparatus are then directed into winding apparatus where they are formed into rolls of a multiplicity of turns about suitable cores.
• the cores preferably are made either of aluminum, or of an electrically non-conducting material which is resistant to attack in the subsequent anodizing operation.
• Aluminum cores, although conducting, soon become insulated by becoming coated with a non-conducting anodic film in the anodizing operation and so are equivalent to non-conducting cores for purposes of this invention.
• Both flat ends of the cylindrical rolls so wound are defined, of course, by the exposed edges of the aluminum strip which are in ragged condition as a result of the cutting operation.
• Small flakes of varnish may be missing between edge portions of the successive turns so that in addition to their roughness the strip edges defining the sides of the roll also have small gaps between them.
• rolls are taken in batches to anodizing equipment where they are subjected to conventional cleaning operations and then are lowered into an electrolytic bath which may advantageously be chromic, sulphuric, oxalic or other acid, or it may be a caustic alkaline bath.
• Low-voltage direct current (or sometimes alternating current) is 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 surface exposed to the electrolyte and the particularly small slivers and burrs on the strip edges are removed. Thus all exposed edges of the narrow strips defining the flat sides of the rolls are covered with an even and continuous insulating anodic film.
• the roll core When the roll core is aluminum, it too becomes anodized and thus electrically insulated. Insulated or nonconducting cores are desirable to minimize the tendency for the anodizing current to by-pass interior turns of the roll in cases where the core is supported in the anodizing equipment on a supporting element which is anodically charged.
• the batch of rolls is lifted from the bath, rinsed and dried.
• Thev resulting rolls each comprises a multiplicity of turns of aluminum strip which is electrically insulated on one or both flat faces by the coating composition, and at both side edges by the oxidic anodized film.
• Suchstrip is eminently suited for being rewound from the roll into electrical coils, to which suitable leads may be attached.
• leads may be attached to the strip when it is first wound into rolls directly after slitting, and such rolls after having their side edges anodized in the manner described may be employed without further preparation as electrical coils.
• a sealing compound as described previously is warranted if the organic dielectric coating disposed between the edges of the strip is likely to plasticize after the roll is wound.
• rolls of aluminum strip formed in accordance with the invention are normally subjected to a cleaning process wherein the strips are immersed in a mild caustic (for example, a 3-5 percent sodium hydroxide) solution before they are wound and the finished rolls are later submerged in a hot water rinse (near 212 F.) after anodizing.
• a hot water rinse near 212 F.
• suitable organic dielectric coatings which will plasticize at temperatures below that of the hot water rinse and become tacky. Vinyl dielectrics, for instance, soften at about F. When this happens, the turns of the wound roll stick together and it is difiicult to unwind the strip in use.
• electrolyte used in the anodizing step should be prevented from penetrating the turns of the wound rolls.
• One of the more common electrolytes is an aqueous 15 percent sulfuric acid solution which is readily drawn between unsealed turns. of a roll by capillary action where it remains and later corrodes the metal or attacks the organic coating. Phosphoric and sulfamic acid electrolytes are also likely to penetrate a roll and chemically attack the metal or organic coating.
• the sealing compound can be applied in at least two ways. It may be wiped over the flat sides of the strips before they are wound and thereby cover the strips edge-toedge, or it may be drawn between the turns of a wound roll by impressing both end faces of a roll against a pad saturated with the compound, in which case edge-to-edge sealing between the turns is a possible but not necessary result.
• the sealing compound may be chosen solely for its sealing properties, Whereas in the second manner of application the compound should also be sufficiently low in viscosity to penetrate readily by capillary action between the turns.
• a clear pure mineral oil (such as a white refined hydrocarbon oil) has been found satisfactory for wiping the strips before they are wound and kerosene has proven to be advantageous for impregnation between the turns of a wound coil.
• These two examples of sealing compounds are by no means conclusive, however, since virtually any compound resistant to the'electrolytes now used may be suitable. Generally, the best sealing compounds will be found among hydrophobic liquids.
• the penetration of the compound between the turns of a wound coil is the better method of application because less of the compound is used.
• the compound is wiped over the sides of a strip before winding, much of it squeezes out from between the turns as the roll is formed. This can be somewhat messy for production purposes.
• Films of sealing compound so deposited between the turns of a wound roll of electrically insulated strip serve to prevent penetration between the turns by the electrolyte or other liquids to which the roll is exposed. Thus, corrosion or other attack by those liquids is prevented.
• the sealing compound serves as a release agent which prevents the organic dielectric coating on the strip from adhering the turns of a roll together when such coating is heated above its plasticizing temperature.
• the sealing compound should be disposed as far in toward the center of the strip as the over-heating is likely to progress. If necessary, the strip should be covered entirely from one edge to the other.
• the term aluminum is intended to cover both commercially pure aluminum and any aluminum-base alloys which are suitable for use in electrical coils. Also, in those claims reciting the use of the sealing compound, it is to be understood that the step of applying the compound can be carried out either before or after the winding of the roll, unless otherwise indicated.
• a roll of aluminum strip formed for rewinding into electric coils comprising an extended length of aluminum strip wound into a multi-layer roll, said strip having a continuous film of dielectric coating composition adherent to at least one face thereof which is disposed between successive layers of the roll, side edges on said strip which are free from said composition, a sealing compound disposed between and sealing the turns of the roll on at least the marginal edge portions of the strip on at least one side thereof with the side edges of the strip being free from said compound, and a distinct dielectric oxidic layer covering and insulating said side edges of the strip, said roll being wound with the successive lay'ers formed by adjacent turns of the strip being free from blocking and separable from each other so that rewinding into electric coils is permitted.
• a roll of aluminum strip formed for rewinding into electric coils comprising an extended length of aluminum strip wound into a mutli-lay-er roll, said strip having a continuous film of dielectric coating composition adherent to at least one face thereof which is disposed between successive layers of the roll, side edges on said strip which are free from said composition, a sealing compound disposed between and sealing the turns of the roll on at least the marginal edge portions of the strip on both sides thereof with the side edges of the strip being free from said compound, and a distinct dielectric oXidic layer covering and insulating said side edges of the strip, said roll being wound with the successive layers formed by adjacent turns of the strip being free from blocking and separable from each other so that rewinding into electric coils is permitted.
• a roll according to claim 1 wherein said sealing compound is a hydrocarbon oil.

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• Engineering & Computer Science (AREA)
• Power Engineering (AREA)
• Chemical & Material Sciences (AREA)
• Materials Engineering (AREA)
• Chemical Kinetics & Catalysis (AREA)
• Electrochemistry (AREA)
• Manufacturing & Machinery (AREA)
• Metallurgy (AREA)
• Organic Chemistry (AREA)
• Laminated Bodies (AREA)
• Insulating Of Coils (AREA)
• Fixed Capacitors And Capacitor Manufacturing Machines (AREA)
• Winding, Rewinding, Material Storage Devices (AREA)
• Chemical Treatment Of Metals (AREA)

Priority Applications (6)

Applications Claiming Priority (3)

Publications (1)

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ID=27359317

Family Applications (2)

Family Applications After (1)

Country Status (3)

Cited By (7)

Citations (9)

Family Cites Families (4)

• 1961
  • 1961-01-04 US US80546A patent/US3223896A/en not_active Expired - Lifetime
  • 1961-02-10 GB GB5033/61A patent/GB908330A/en not_active Expired
  • 1961-02-22 DE DE19611414682 patent/DE1414682B2/de active Pending
• 1968
  • 1968-01-24 US US723963*A patent/US3456337A/en not_active Expired - Lifetime

Patent Citations (9)

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