Abstract: A superconducting magnet coil is produced by winding a superconducting wire to form a coil; impregnating the coil with a curable resin composition of low viscosity which contains for example at least one epoxy resin selected from the group consisting of diglycidyl ether of bisphenol A, diglycidyl ether of bisphenol F and diglycidyl ether of bisphenol AF, all having a number-average molecular weight of 350-1,000, a flexibilizer and a curing catalyst, to obtain a curable-resin composition-impregnated coil; and heating the curable-resin-composition-impregnated coil to cure the composition.

Abstract: A stock material for winding into a magnet coil includes a running length of conductive aluminum metal having a cross section that has first and second long sides and two short sides. The long sides and short sides meet at corners which are substantially free of jagged edges and sharp corners. An insulating epoxy polymer coating uniformly about 0.001 inches (25 microns) thick covers the first long side and the short sides, with the second long side being substantially free of the insulating coating. A heat-activatable adhesive is arrayed non-continuously on one of the long sides.

Abstract: An improved electrical insulation structure is provided for a motor driven fluid apparatus having the compression and drive mechanisms within a hermetically sealed housing. The drive mechanism comprises a drive shaft operatively connected to the compression mechanism and a motor for rotating the drive shaft. The motor comprises a rotor fixedly surrounding the drive shaft and a stator assembly surrounding the rotor with a small radial air gap therebetween. The stator assembly comprises an annular magnetic core fixedly secured to the housing. The core has a plurality of axially extending slots and a plurality of windings, each having a plurality of coils formed by multiple turns of an enamel-coated conductor. The multiple turns of the conductor have side turn portions which are disposed within the axially extending slots and end turn portions which axially project from the slots and are generally disposed about the axial end surfaces of the core.

Abstract: A monolithic magnetic device having a plurality of transformer elements having single turn primaries and single turn secondaries fabricated on a plate of ferrite which has the outline of a ceramic leadless chip carrier. Each of the magnetic elements has a primary winding formed from a copper via plated on the ferrite. Each element's secondary is another copper via plated over an insulating layer formed over the first layer of copper. The elements' primaries are interconnected on the first copper layer and the elements' secondaries are interconnected on the second copper layer. The configuration and turns ratio of the transformer are determined by the series and or parallel interconnections of the primary and secondaries. Some of the interconnections can be provided by the next higher assembly level through the circuit card, with the same magnetic device providing many turns ratio combinations or values of inductors.

Abstract: There is disclosed a method and apparatus for coating an electromagnetic coil, particularly stator coils for an electric motor, with an insulating catalyzed resin material. The catalyzed resin material is a two component material comprising an epoxy resin and a catalyst. The catalyzed resin material is a free flowing liquid at a first temperature and begins to cure rapidly at a second elevated temperature. The stator coils are first heated by supplying current to the stator coils to raise the temperature of the stator coils to the first temperature. The free flowing liquid catalyzed resin material is dispensed through nozzles onto the stator coils as the stator coils and the nozzles move relative to each other. After the liquid catalyzed resin material has been dispensed in a predetermined amount, at predetermined locations, for predetermined times, the catalyzed resin material is allowed to penetrate the stator coils.

Abstract: The invention concerns a compressible prepreg based on flat substrates impregnated with thermosetting synthetic resins, characterized in that it comprises a first, C stage synthetic-resin layer directly deposited on the substrate and a second, B stage synthetic-resin layer deposited on the first synthetic-resin layer.

Abstract: Process for fixing wound items made from electrically conductive materials by impregnation with radically polymerisable compositions and thermal curing characterised in that the wound items are impregnated by immersion impregnation, flow coating, vacuum impregnation, vacuum pressure impregnation or trickle impregnation and that simultaneously with or after thermal curing the wound articles are cured by high-energy radiation. The process operates with low energy requirements and low emissions of volatile substances. Radically curable compositions are also described.

Abstract: A dry type transformer has an iron core, high voltage windings embedded in cast resin, and low voltage windings resin encapsulated. The low voltage winding is constructed with flexible sheet conductors coincident with layer insulation sheets that extend beyond the edge of the sheet conductor. Cooling air ducts are fabricated in the low voltage windings as it is wound. To prevent the extension of the layer insulation sheets from collapsing over the formed air ducts during a vacuum and pressure resin impregnation process, reinforcing means are added to the extensions to prevent them from collapsing.

Abstract: A laminated coil for motor having heat resistance and capable of voluminous production at a moderate cost, in which a conductive pattern 116 for coil is formed on a glass substrate 111, a glass coating 112 is applied on the conductive pattern 116 for oil, and further another conductive pattern 117 for coil is formed again on this glass coating 112. In a similar manner a glass coating 113, a conductive pattern 118 for coil, glass coating 114, and a conductive pattern 119 for coil are repetitively formed thereon, and finally a glass coating 115 is applied as a top coating, thereby making coils by thus laminating glass which have a high heat resistance and reliability for use under various environmental conditions. Furthermore, since, unlike a ceramic material, no baking as one body is required, there will never take place a disadvantage as the relation between the basing temperature of the ceramic and the melting point of the conductor for oil, thereby enabling enhancing the yield of coil production.

Abstract: A method of making a thin film magnetic head having multi-layer coils wherein a raised insulative photoresist spiral pattern having undercut sidewalls is formed. Two layers of coils are fabricated simultaneously by evaporating metal onto the upper surface of the spiral pattern and in spaces between the pattern. The cross-section of the bottom coil decreases in width with an increase in height. The coils are insulated from each other with a layer of insulative photoresist.

Abstract: a thin film printed circuit inductive element exhibiting low Q wherein a conductive spiral is deposited on an insulating substrate and resistive links are connected between adjacent turns of the spiral. Inherent resonance is thereby damped out.

Abstract: A composition for the copper armature coil of a electric motor which can withstand crack generation due to great temperature differentials by setting the coefficient of thermal expansion of the composition to a value between the coefficients of thermal expansion of both iron and copper.

Abstract: A passive transformer which can be formed in an MMIC having a plurality of first-layer wirings formed on a substrate so that each of the first-layer wirings intersects a desired virtual line on the substrate; an insulating film for covering a substrate surface on which the first-layer wirings are formed; and a plurality of second-layer wirings formed on the insulating film so that each of the second-layer wirings intersects the virtual line and has opposite ends respectively connected to different ends of the first-layer wirings through contact holes. An inductor element having a spiral structure along the virtual line constitutes the first-layer wirings the contact holes and the second-layer wirings. The opposite ends of the inductor element are primary electrodes, and one end and a desired intermediate point of the inductor element are secondary electrodes. Because the transformer has such a structure, a three-dimensional coil can be formed on the substrate so that the transformer can be formed in an MMIC.

Abstract: A method of impregnating a winding assembly of an electrical equipment with varnish, the winding assembly including a core and one or more windings wound on the core, the method comprising steps of enclosing the winding assembly in a bag, pouring a predetermined amount of varnish into the bag enclosing the winding assembly, reducing an atmospheric pressure in the bag and thereafter, maintaining the bag in the air-tightly closed state so that the winding of the winding assembly is impregnated with the varnish poured into the bag, and drying the winding assembly after completion of the step of impregnating the winding with the varnish.

Abstract: A high accuracy surface mount inductor device is comprised of first and second parallel planar spiral conductive patterns mounted over a rectangular substrate. The outermost conductive traces of the respective patterns extend to opposite edges of the device and are contacted by terminations extending over the ends of the device. The terminations are U-shaped and include legs extending over parts of the upper and lower surfaces adjacent the ends. The legs overlie the outermost traces and preferably terminate at a position coincident with or not extending inwardly beyond the innermost portions of the outermost traces.

Abstract: The present invention is directed to a method of imparting moisture resistance to epoxies. Moisture resistant epoxy compositions are formed from epoxies and alkenylsuccinic anhydride (ASA) such as tripropenylsuccinic anhydride (TSA). The epoxy compositions, following cure, show surprisingly improved moisture resistance and retention of properties when exposed to warm, humid environments.

Abstract: A thin film printed circuit inductive element exhibiting low Q wherein a conductive spiral is deposited on an insulating substrate and resistive links are connected between adjacent turns of the spiral. Inherent resonance is thereby damped out.

Abstract: A process of forming an LC composite part. The process includes the steps of: forming a substrate having a capacitor section by laminating ceramic sheets having a plurality of capacitor electrodes formed thereon such that the ceramic sheets and electrode layers alternate, sintering the substrate, forming a plurality of coil sections on the sintered substrate, cutting the substrate into composite parts, and electrically connecting the capacitor electrode layers with the coil section.

Abstract: An electrolyte dispensing ampule for deferred action batteries comprises a spring having means at both ends thereof for forming a closed, generally cylindrical space inside the spring and a metal layer covering the spring to hermetically seal the space. An electrolyte solution is contained in the spring and is dispersed to activate the battery when set-back forces extend the spring and break the sealing layer.

Abstract: A method and apparatus for impregnating the superconductors on a superconductor winding with epoxy such that a vacuum/pressure containment vessel, in which the winding is placed, allows epoxy to be introduced into the vessel whereby the epoxy eventually impregnates the superconductors through the application of various evacuating, pressuring and epoxy transporting steps.

Abstract: A thin film magnetic read/write head is manufactured using Al.sub.2 O.sub.3 dams. The Al.sub.2 O.sub.3 dams are formed using a sacrificial layer which is deposited upon a bottom pole layer. An Al.sub.2 O.sub.3 layer is deposited over the sacrificial layer. When the sacrificial layer is removed, the Al.sub.2 O.sub.3 layer forms dams between which a top pole piece is deposited. The sacrificial layer is removed using lapping and a selected chemical etch; partial lapping or chemical etch followed by chemical etch of the sacrificial layer which lifts-off overlying Al.sub.2 O.sub.3 ; depositing photoresist dams and chemically etching the encapsulation layer and the sacrificial layer; or removal through physical or thermal shock of the Al.sub.2 O.sub.3 layer sputtered at zero bias followed by a selective chemical etch of the sacrificial layer.

Abstract: The helix (10) of the slow wave structure of a travelling wave tube is formed on a steel mandrel (12) by depositing the metal (44) of the helix on the mandrel and then coating the deposited metal with a photo resist (46). A laser light beam (24,26), having a cross section in the form of a short line, is focused upon the resist and moved linearly along the axis of the mandrel while the mandrel is rotated. The resulting helical exposure pattern on the photo resist is developed and the remainder of the undeveloped resist is then removed to expose a helical pattern (50,52) of deposited helix metal (44). The latter is subjected to etching processes so as to remove the deposited metal between the turns of the helical resist pattern (54,56), leaving a helix (44) of deposited metal on the mandrel underneath the resist. The resist is then removed and the mandrel etched away to leave the completed helix.

Abstract: A rectangular parallelepiped having a width of approximately 1 micron and a height of several microns and they are separated by an amagnetic spacer.

Abstract: This invention provides a heat-resistant voice coil of H class in heat-resistance standard, which is characterized in that an electrically insulated adhesive paint applied onto both a bobbin and conductor wire is mainly consisted of a mixture comprising all aromatic polyamide resin and a hardening agent composed of aromatic polyamic acid. This invention further provides a method of manufacturing such a heat-resistant voice coil, wherein the conductor wire coated with the paint is wound around the bobbin preliminarily coated with the paint in a semihardened state, while applying a non-water polar solvent onto the bobbin.

Abstract: The present invention relates to a reaction resin composition comprising a mixture of polyisocyanates, epoxides, and amine catalysts of the formula ##STR1## wherein A is independently alkylene, alkenylene, alkynylene, alkylidene, cycloalkylene, or aralkenylene; m is an integer of from 0 to 30; R.sup.1, R.sup.2 and R.sup.3 are independently optionally substituted aralkyl or polyaralkyl; and R.sup.4 is alkyl, alkenyl, alkynyl, cycloalkyl, or optionally substituted aralkyl or polyaryalkyl.

Abstract: A method of manufacturing the pole pieces and the gap of magnetic heads in thin layers for computer, audio and video applications, starting from a silicon substrate, includes formation of an insulator layer on a silicon substrate followed by deposition of a metal layer on the insulator layer and of a masking resin layer on the metal layer. The substrate covered with the insulator layer and the metal layer is etched to form wells bordering a bar of a determined width and the left-over portion of the metal layer etched is removed. The etched substrate is thermally oxidized to develop a silicon oxide layer enabling the bar to be adjusted to obtain the desired gap. A conductive layer is deposited at the bottom of the wells followed by the electrolytic deposition of a magnetic material in the wells and the removal of the left-over portion of the insulator layer initially deposited on the substrate.

Abstract: The invention provides a mounting method by which a flat coil formed by winding an insulator layer and a metal foil sheet in layers can be mounted readily and with certainty on a circuit board. In mounting a flat coil on a circuit board, at first a pair of terminal portions each composed of a layer of solder are formed at a first end portion and a last end portion of the flat coil such that they extend in an axial direction of the coil, and then the coil is disposed on the circuit board such that the terminal portions thereof may be opposed in a perpendicular relationship to connecting faces of a conductor pattern on the circuit board. After then, the coil and the circuit board are heat processed to cause solder material applied to the connecting portions of the conductor pattern to adhere to faces of the terminal portions over the full extent of the axial length of the flat coil to interconnect the connecting faces of the conductor pattern and the terminal portions of the flat coil.

Abstract: A method of operating apparatus to treat with a hardenable liquid adhesive material a plurality of cores each having a winding means with a pair of opposite end turn groupings thereon. An endless conveyor is operable with discrete intermittent movement to dispose a plurality of spindles for carrying the cores in a plurality of preselected indexed positions. In some of these indexed positions, the liquid adhesive material is dispensed onto the opposite end turns of the winding means on the cores carried by the spindles which are rotated while in the some preselected indexed positions.

Abstract: A thin film recording head which utilizes polyimide as the coil encapsulant. The polyimide encapsulant is self planarizing and lends itself to processing of the coil vias, magnetic shunt vias and apex tapers. Methods of fabricating a thin film recording head and forming coil vias, magnetic shunt vias and apex tapers are also disclosed. In general, an insulating material is deposited on a bottom magnetic yoke. A first layer of polyimide is then deposited of the insulating material. Then, a three layer photoresist structure is deposited on the first layer of polyimide, which includes a transfer layer deposited between two layers of photoresist. The top layer of photoresist is developed and the transfer layer is etched. The first layer of photoresist is then etched into the polyimide layer to form troughs therein. The coil material is then deposited into the etched troughs. The coil material comprises a layer of metal having a relatively thin passivation layer deposited thereover.

Abstract: A method of producing a thin film magnetic head by successively depositing on a substrate a first magnetic material, a gap material, an electrically conductive material consisting of a coil, an insulating film, a second magnetic material and a protecting film, wherein the improvement comprises a step for forming a recessed portion in the insulating film at a portion corresponding to a gap portion on the air bearing surface side, the bottom surface of said recessed portion serving as an exposed portion on the upper surface of the gap material and the side surfaces of said recessed portion being tapered, a step for forming a recessed portion in the gap material by etching using the insulating film with the recessed portion as a mask and making the thickness thereof equal to the gap length, and a step for depositing a second magnetic material on the whole surface, so that the recessed portion formed in the gap material will have a rectangular shape with its one side being equal to a gap depth and its another sid

Abstract: A method of treating a core for a dynamoelectric machine with a hardenable liquid adhesive material. The core includes winding receiving slots, a plurality of layers of a dielectric material associated in overlaying relation in each slot, a plurality of apertures in each layer arranged in non-aligning relation, and a plurality of non-apertured sections in each layer disposed in overlaying relation with the apertures in adjacent layers. In this method, the liquid adhesive material is passed by capillary action through the aperture in one of the layers in the slots and channeled by capillary action past the non-apertured sections in the one layer and another layer interposed between the one layers and the slot. The liquid adhesive material is then flowed through the apertures in the another layers into communication with the slots.A method of assembling a core, a core, a slot liner, and a method of assembling a slot liner are also disclosed.

Abstract: A process for fabricating a thin film magnetic head to achieve improved dimensions and tolerances of the pole tip portion of the head. A lower thin film magnetic layer comprising the lower pole tip is first formed followed by a thin layer defining the gap of the head. A thin film magnetic layer is then deposited only in the vicinity of the pole tip to define the upper pole of the head. Following this, successive layers of insulation and coils are deposited. Finally, a top thin film magnetic layer is deposited. This top layer contacts the already formed layer comprising the top pole piece.

Abstract: A method of applying solventless varnish to stator windings in electrical machinery. A magnetic core having a plurality of stator windings disposed in the slots of the core is positioned above a tank containing a solventless varnish, and the tank is then raised to immerse the end turns of the windings on one end of the core into the varnish. The windings are energized to heat them and the varnish which adheres to the end turns to reduce the viscosity of the varnish. The tank is then lowered and the stator and windings are inverted so that a portion of the reduced viscosity varnish which adheres to the end turns flows downwardly through the slots of the stator. This is repeated until varnish begins to flow freely through the slots to the other end, thereby indicating that good coating of the winding within the slots has been accomplished.

Abstract: A method of assembling a core for a dynamoelectric machine with the core including a pair of opposite end faces, a wall in the core defining a winding receiving slot intersecting the end faces, and a plurality of layers of a generally thin dielectric material with each layer having a plurality of apertures extending therethrough in a preselected pattern. The layers are associated in overlaying relation, and the apertures in the layers are arranged in non-aligning relation with the apertures in each layer communicating with a non-apertured section of an adjacent layer, respectively. The layers in their overlaying relation are positioned in the slot, and one of the layers is interposed between another of the layers and the wall of the slot.A method of assembling a slot liner is also disclosed.

Abstract: Heat-curable hot-melt enamels, a process for their preparation, and the production of highly heat-resistant wire windings. These heat-curable hot-melt enamels are solutions of a nylon in organic solvents, which contain, as the nylon, a nylon possessing functional amino groups and additionally contain a blocked di- or polyisocyanate. They are useful for the production of highly heat-resistant wire windings.

Abstract: A method of insulating electrical conductors wherein a tape of porous mica paper and of glass felt or cloth or plastic material film is wound round the conductors, wherein the tape is impregnated with a varnish comprising a polymerizable liquid resin, and wherein the impregnated tape is polymerized by heat treatment, the method including the improvement whereby an adhesive powder is initially added to the tape to provide adhesion between the porous mica paper and the glass felt or cloth or the plastic material film, said adhesive powder comprising a polymer having chains of oxazolidone groups containing groups with epoxy terminations, and whereby the polymerizable liquid resin of the varnish essentially contains isocyanate groups which are transformed into isocyanurate groups during polymerization.

Abstract: A method and apparatus are disclosed for producing rolls or coils of film of insulating material which has been conductively coated, in a vacuum, by vaporizing conductive material in direct electron beam bombardment and condensing the vapor on the film surface. According to the invention, the film is subjected to a plasma treatment after coating and before the film is wound in a coil.

Abstract: A process for producing a coil for a magnetic recording head and the coil obtained by this process. An insulating film which covers a support is etched in order to give it the shape of a first spiral. The support is then etched by using the insulating film as a mask, forming a groove in the form of a second spiral, which is complementary to the first spiral. A thin metal layer is then deposited on the insulating film used as the mask and simultaneously on the bottom of the etched groove, producing two conductors in the form of complementary spirals which are located in two different planes.

Abstract: There provides a process for preparing a coil type thin film magnetic head having high density record by planarization differences in level caused by an electroconductive coil holded between upper and lower magnetic cores.

Abstract: A method for making an electrical inductive device for use in hermetic atmospheres which incorporate refrigerants such as halogenated methane compositions, for example refrigerant R-22, monochlorodifluoromethane. The device may be a wound coil device formed of magnet wire, the enamel coating of which has resistance to blistering when exposed to refrigerants under saturated conditions at temperatures up to about 200.degree. or 210.degree. C. and above. The enamel coating composition or wire enamel is formed as the reaction product of 1,2,3,4-butanetetracarboxylic dianhydride, optionally with an aromatic dianhydride, and a diamine such as p,p'-methylenedianiline or p,p'-oxydianiline, in an organic solvent such as N-methyl-2-pyrrolidone.

Abstract: A method for manufacturing a molded transformer comprises the steps of forming a coil by winding concentric layers of a conductor with insulating layers interposed between the adjacent layers of the conductor and provided with insulating end members at both ends of the respective layers of the conductor, providing insulating layers on the inner and outer surfaces of a resultant structure, applying a curing accelerator to the insulating layers on the inner and outer peripheral surfaces and the insulating end members at one end of the coil, assembling a wound core in the coil to form a core-coil assembly, immersing the assembly in resin with said one end of the coil directed downward, taking out the assembly when the resin starts to gel due to the action of the curing accelerator, and then setting the resin in the coil and on the wound core.

Abstract: A thermosetting synthetic resin composition consisting mainly of, for example, an epoxy resin is melted at a temperature of 70.degree. to 130.degree. C. After adding a filler to the resin composition, the resultant mixture is kneaded and rapidly cooled. The composition consists of a thixotropy agent, a leveling agent, etc., in addition to the epoxy resin and a curing agent for the epoxy resin. Aluminum as the filler is added in the amount of 30 wt % to 100 wt % of the mixture. The mixture of the composition with the filler is kneaded and rapidly cooled and is then pulverized to prepare a powder. The powder coating thus obtained is coated on a coil and is cured to provide a heat radiating insulator.

Abstract: A method for insulating a coil of a rotary electric machine resulting in improved insulating properties at critical coil ends. A mica sheet or mica tape is wound around a part of each coil to be inserted into a slot cut in an iron core of the rotary electric machine to thus form a first insulating layer. The coils thus treated are inserted into respective slots and are connected together and to external terminals as required. Each coil end is then covered in its entirety with a thermosetting resin. The thermosetting resin is hardened by heating to form a second insulating layer.

Abstract: A method of consolidating a magnetic core which contains amorphous metal, including the step of thermal spraying an electrically non-conductive material on the edges of the laminations which make up the magnetic core.

Abstract: The invention relates to a heat-hardened molded material produced from a resin mixture of a polyfunctional epoxide, a polyfunctional isocyanate and a reaction accelerator, which optionally contains additives and/or fillers. The objective is to make a resin mixture which permits the manufacture of a highly heat-resistant molded material, and which has at the same time a high-temperature cycle resistance and good mechanical properties. For this purpose, the polyfunctional epoxide of the resin includes a polyoxyalkylene glycol polyglycidyl ether.

Abstract: This invention provides reaction resin molded materials (OX/ICR molded materials) containing oxazolidinone and isocyanurate rings prepared from reaction resin mixtures of polyepoxides and polyisocyanates (EP/IC resins) in the presence of a hardening catalyst and has as an object to provide a simple manufacturing method for heat resistant OX/ICR molded materials with improved mechanical properties. According to this invention, EP/IC resins which are capable of casting and impregnating and which are free from solvents are provided. These resins have a formula mole ratio of EP:IC of about 1 to 5 and a viscosity of up to 7,000 mPa sec at 25.degree. C. and are cross-linked by means of tertiary amine or imidazole hardening catalysts at gelling temperatures of up to 130.degree. C. and post-hardening temperatures of 130.degree. to 200.degree. C. to produce OX/ICR molded materials with a mole ratio OX:ICR greater than 1, wherein the reaction of the epoxy and isocyanate groups is above 90% after the hardening.

Abstract: A hardenable liquid adhesive material is dispensed onto opposite end turn portions of coils in winding means of a loose wound core with a greater amount of the liquid adhesive material flowing therefrom generally along one of the opposite side turn portions of the coils into the slots of a generally loose lamination stack of the loose wound core in which the one opposite side turn portion of the coils are received in response to the rotation of the loose wound core in one direction and with a greater amount of the liquid adhesive material flowing generally along the other of the opposite side turn portions of the coils into the slots of the loose lamination stack in which the other opposite side turn portions of the coils are received in response to the rotation of the loose wound core in another direction opposite the one direction thereby to generally equalize the liquid adhesive material fill of the slots.

Abstract: A highly fluid, solventless heat curable resin is formulated from an admixture comprising a polyglycidyl aromatic amine, a polycarboxylic acid anhydride curing agent, and a curing accelerator. The heat curable formulation exhibits low viscosity and is useful as an encapsulant and insulation for electrical members exposed to high electrical stress. Magnetic coils encapsulated with the cured formulation resist corona discharge at electrical stresses in excess of 2100 volts per mil.

Abstract: Methods of constructing a void-free, cellulose-free electrical winding insulated with a solid resinous insulation. The method includes forming a plurality of conductor turns on a substrate, with each conductor turn being immersed in liquid resinous insulation as it is formed, to provide a void-free intermediate structure. The void-free aspect of the intermediate structure is maintained up to and including the final step of the method by building solid insulation, thin layer upon thin layer, from the liquid resinous insulation, while the conductor turns are being formed, with the solid insulation, as it is formed, providing a solid substrate for the continued application of liquid resinous insulation and subsequent conductor turns of the winding.

Abstract: Insulation process by impregnation of electric leads using isocyanate and oxazolidone cycle resins in which a glass cloth and porous mica paper tape is wound around the leads, the tape is impregnated with a quaternary ammonium salt, catalyzing condensation of isocyanate and epoxy derivatives in isocyanurate and oxazolidone cycles and with a varnish comprising a liquid epoxy resin and an isocyanate derivative, then the impregnated tape undergoes a heat treatment for polymerization of the varnish.As quaternary ammonium salt, is used a benzyltrialkylammonium halide with alkyl chain containing at most 3 carbon atoms, the tape is first impregnated with benzyltrialkylammonium halide and liquid epoxy resin, it is dried at a temperature equal to 135.degree. C. at maximum and then it is impregnated with isocyanate derivative based varnish before undergoing the polymerizing heat treatment.