GB2068261A - Electrical conductor wires insulated with varnish hardenable by ultraviolet radiation - Google Patents

Abstract

In order to coat an electrical conductor, such as a heavy gauge wire, with successive layers of insulative varnish hardenable by ultraviolet radiation, there is provided, one above the other, a varnish coating device 8, a stripper-calibrating device 12, and a hardening chamber 16, with guide rollers 9 at the top and bottom. The hardening chamber 16 has at least one pair of ultraviolet emitters disposed transverse to the direction of movement of the conductor and reflectors disposed behind the emitters. The hardening chamber 16 is provided for the passage of cooling gas, such as air. <IMAGE>

Description

SPECIFICATION Improvements in or relating to methods and devices for manufacturing electrical conductor wires insulated with varnish hardenable by ultraviolet radiation The invention relates to a method of and device for manufacturing conductor wires, such as profiled heavy gauge wires, insulated with varnish which may be hardened by ultraviolet radiation. Such a method, insulating varnish which may be hardened by radiation is continuously applied to the heated and possibly pre-treated wire, the thickness of the varnish coat is calibrated by stripping of the excess varnish, the varnish coat is then hardened by sufficient exposure to ultraviolet radiation, and the varnished wire produced in this way is lastly coiled.

In the conventional manufacture of varnished wires the method described above is used, in which, however, the insulating varnish applied to the conductor wire is hardened by the external action of heat. In this respect the solvent contained in the insulating varnishes used hitherto is evaporated together with cross-linking of the varnish film on the conductor as a result of a thermochemical reaction caused by the heat energy. The varnish film hardened in this way forms an insulation on the conductor surface which is suitably adhesive, sufficiently flexible and thermally and mechanically resistant, and whose particular properties, such as the increased heat resistance required in certain applications, may be determined within a wide range by a corresponding selection of the insulating varnish used in each case, as may be seen, for example, from the German Auslegeschrift 10 33 291.

Although this method of manufacture has given satisfactory results in respect of the quality of varnished wire produced in this way, it presents serious disadvantages which consist in particular in a considerable pollution of the environment as a result of the solvent vapours, which are damaging to health, released during the thermal hardening and, in addition, in the high power consumption required in this respect. The above in addition to the unavoidable loss of up to 70% of the quantity of the solvent containing the applied insulating varnish, which may not be recovered, causes high operating and manufacturing costs which are, in addition, considerably increased by the unavoidably high amount of scrap produced during starting of an apparatus designed for production of this type and including extended drying and hardening devices and by other factors.

The manufacturing costs of a device of this type are also very high as a result of the costly drying and hardening apparatus itself, as these are difficult to equip for the production of varnished wires of varying cross-section and impossible to equip for comparatively large diameters, for example for profiled heavy-gauge wires, or which reason the latter are insulated using the winding method.

On the other hand a method and a device for producing a protective layer of synthetic material on photoconductive fibres, in particular glass fibres, is known from the German Auslegeschrift 24 59 320, in which the coating is produced by means of a fluid polyester resin which may be hardened by ultraviolet radiation, and in which the thickness of the coating is maintained constant within predetermined limits by a stripper. The fibre coated in this way is then passed through a tubular ultraviolet radiator whose intensity of radiation is adapted to the required speed of manufacture in such a way that the coating is bubblefree, smooth and hardened after the radiation has stopped, it being possible to control the thickness of the coating by taking into account the viscosity of the fluid resin and other factors.The viscosity of the fluid resin and the elasticity of the hardened protective coating are adjusted in this respect by the addition of various resins which may be hardened by ultraviolet radiation.

The device known from this publication for carrying out the above method comprises a container tank for the polyester resin which is connected to a bath container via a level regulation, at the base of which is disposed an inlet opening for photoconductive fibre sealed by a capillary tube, and in whose further development there is disposed directly above the bath surface a stripper, one or several shutters against ultraviolet radiation and a tubular ultra-violet radiator.

The liquid coating agents used in accordance with this known method contain-in contrast to conventional insulating varnishes for conductor wires-photo-initiator systems, as a result of which they may be hardened and cross-linked solely by the comparatively low-power radiation with ultra-violet light. In this respect, there is no need for the separation by evaporation of solvents which are harmful to the environment and cause the high heat energy consumption of the conventional insulating varnish hardening processes.

In respect of the advantages of the coating agent hardenable by ultraviolet radiation, its use for the production of insulated electrical conductor wires was attempted. It was however demonstrated that the transfer of the teaching of the above publication to this new use was not readily possible.

According to one aspect of the invention, there is provided a method of production of electrical conductors or wires insulated by varnish hardenable by ultra-violet radiation, in which insulating varnish which is capable of being hardened by radiation is continuously applied to the heated and possibly pretreated wire, the thickness of the coat of varnish is calibrated by stripping of the excess varnish, the varnish coat is then hardened by a sufficient quantity of ultra-violet radiation, and the varnished wire produced in this way is finally coiled, and in which, after hardening of the coat of varnish, one or more additional coats of insulating varnish are applied in a continuous sequence, the additional varnish coats being hardenable by radiation and having different properties in the hardened condition, and are hardened by ultra-violet radiation.

It is thus possible to provide a method of manufacturing insulated conductor wires, in particular profiled steel wires, provided with a varnish coating hardened by ultraviolet radiation which enables the latter wires to be produced with the same quality as the hitherto conventional varnished wires, but without pollution of the environment and with substantially lower costs than for the conventional wires. In a preferred method, at least one additional coat of varnish is applied and hardened by ultraviolet radiation in a continuous sequence after hardening of the first coat of varnish applied. Preferably coats of insulating varnish having different properties in the hardened condition and hardenable by ultraviolet radiation are applied in a continuous sequence to the wire to be insulated.

The production of the insulating varnish in several successively applied layers hardened by ultraviolet radiation ensures a quality which is at least as high as varnished wires with thermally hardened insulation and enables, in addition, an optimum, extremely fine, regulation of the differentiation of the properties of these varnished wires, in accordance with the proposed applications of these wires, This enables the attempted selection of varnishes having the required properties and their possible application in several coats, corresponding to the requirements in each case and the selection of the specific properties of the varnish of each of the layers so as to produce varnished wires with the most economical use of varnish and corresponding rationally therefore to different and varying quality requirements.

The known measure of determining the properties of the hardened coating by mixing various fluid coating agents which may be hardened by ultraviolet radiation is not sufficient to provide to the required extent the properties, which vary in many respects, required for the varnished wire insulation. The insulation of electrical conductor wires must not only possess good adhesiveness to the metallic conductor surface as well as elasticity and flexibility but in addition high electrical insulating properties, heat resistance and mechanical strength, and in particular must have a surface which is abrasion-proof and scratchor mar-resistant. All the above and further properties which may be additionally required at the same time may not be provided with a known coating agent of this type or by mixing of coating agents.

For this purpose in a preferred embodiment of the invention, at least one layer of a suitably adhesive varnish which is highly flexible is applied to the wire to be insulated, then at least one layer of a high-grade dielectric insulating varnish, then at least one layer of an insulating varnish which is heat-resistant in its final condition, and finally one layer of a mechanically resistant, in particular abrasionproof and mar-resistant, and sufficiently flexible insulating varnish is applied and hardened by ultraviolet radiation.For the manufacture of profiled, for example band-shaped, heavygauge wires which have a cross-section of more than 100 mm2, varnishes hardenable by ultraviolet radiation are applied, which have lower surface tensions in respect of the surfaces to be coated, for example metallic surfaces, in order to ensure the continuity of the coating with a substantially uniform varnish coat thickness even in the region of the edges of the profiled heavy-gauge conductor, having for example a rectangular cross-section of 4 x 20 mm.

Advantages of preferred methods lie in particular in an essentially more economical manufacture of varnished wire as a result of an energy consumption which is reduced to approximately one tenth of that used in conventional methods and the much lower comparative manufacturing costs of a device suitable in this respect of the same capacity. Further, such a method is not harmful to the environment and conductors insulated with varnish having large cross-sections of more than 100 mm2, and having profiled, for example rectangular, cross-sectional profiles may be manufactured in a rational way. As no varnish solvent and consequently no drying and evaporating devices are required in this case, envoronmental pollution by the separated solvent is avoided and the manufacturing conditions are more suitable for humans.

Multiple passage of the same wire through the ultraviolet radiation hardening area of the device after each application of varnish provides an optimum use of the latter and high delivery speeds with, in each case, only short dwell periods or periods of exposure to the ultraviolet radiation of a few seconds or even fractions of seconds, in accordance with the composition of the insulating varnish used, the thickness of the varnish coat involved and- the radiation intensity. For example with a radiation output of only 20 W/cm a varnish coat of approximately 25 p may be hardened in 3 sec., i.e. three passages of one second each.This hardening or dwell period may however also be a multiple or only a fraction of this value, in accordance with the properties required of this coat of varnish and the corresponding composition of the varnish used in each case, in the case of a preferred delivery speed of, for example, 20 m/min. In this respect, the number of passages, leaving aside the delivery speed, is dependent on the length of the ultraviolet radiation area available and the hardening time of the varnish used in each case and the thickness of the coat of varnish involved. This thickness is preferably between 5 and 25 IL whereby thicker layers may be obtained by a plurality of applications with subsequent ultraviolet hardening of the same varnish.

According to another aspect of the invention, t there is provided a device for performing the method of the invention, comprising, disposed substantially vertically above one another on a common platform with a support frame, a varnish coating device, which comprises a plurality of separate baths disposed for the regulation of the level of their content and having openings for the passage of the conductor to be coated, a stripper-calibrating device, a hardening chamber, and, both under the coating device and above the hardening chamber, a plurality of guide rollers, with which unwinding and re-winding devices are associated, the baths being disposed adjacent to one another in a series of groups and in lateral and/or vertically staggered groups, a respective one of the stripper-calibrating devices being separately associated with each of the baths, the hardening chamber being provided with at least one pair of ultra-violet emitters disposed transverse to the direction of movement of the wire through the chamber and with reflectors located behind the emitters and with a plurality of plane reflectors at regular distances between the individual wire lines and directed substantially perpendicular to the ultraviolet emitters, the hardening chamber being arranged for the passage of a cooling gas.

In a preferred embodiment of this device, pairs of ultraviolet radiators of varying radiation intensities are disposed in the box-like hardening chamber, for example a pair of lowpressure radiators upstream of a pair of highpressure radiators.

In contrast to the prior art this device has no tubular, i.e. hollow cylindrical, ultraviolet radiator, through whose longitudinally extending cavity a longitudinally extending article provided with the coating to be hardened is to be passed, but rather pairs of rod-shaped ultraviolet radiators disposed opposite to one another in a housing, the radiation emission of these radiators taking place, as a result of the reflectors located behind and in between, on the varnish coated wires passing through the centre on all sides to a substantially uniform extent.

The rod-shaped ultraviolet radiators, for example metal vapour beams, high-pressure or low-pressure lamps, such as mercury vapour lamps, ultraviolet radiation lamps may be readily obtained commercially in varying lengths. As a result of the arrangement in pair sequences of these lamps, for example HTQ or HOK and TL/05 radiators of the firm Philips GmbH, in the hardening chamber, an optimum use of space and power is provided in that a plurality of coated wires guided parallel to one another or coated wire sections guided in the same way may be passed through this hardening chamber and subjected to the radiation energy. The hardening chamber may be designed in such a way that the coated wires to be hardened are guided with a small spacing approximately centrally between the pairs of lamps and between the reflectors disposed in between intersecting these planes at right angles.A spacing of the wires of only 5 mm with respect to the reflectors and 200 mm from their radiation surfaces ensures the optimum radiation intensity without the danger of coming into contact with the lamps and/or the reflectors.

The actual operation of the ultraviolet radiator is temperature dependent, as optimum radiation emission takes place at a comparatively high temperature, which should not be exceeded however, as the radiation flow stops and the radiator is extinguished. It is therefore important to maintain the radiator temperature constant by means of a flow of cooling gas, for example a flow of air, so as not to disturb the operation of the hardening chamber of this device, whose gas or air cooling is carried out and controlled by apparatus which is described in more detail below.

As the hardening reaction takes place optimally at a temperature above 1 00 C, preferably between 1 50 and 1 80 C, it is advantageous if an infrared radiation area is disposed before the hardening chamber, the effect of which brings the coat of varnish to be hardened quickly to the required reaction temperature. In the same way the arrangement in pair sequences of different ultraviolet radiator pairs contributes to controlling the operating temperature in the hardening chamber, independently of the above-mentioned radiator cooling.It is therefore recommended to dispose low-pressure radiator pairs in the lower region of the hardening chamber, where the wires with the coating to hardened enter, these lowpressure radiators also emitting a considerable proportion of infrared radiation and therefore also heating the coatint to be hardened. However the operating temperature increases towards the upper area of the hardening chamber within the given limits, whilst the coated wires are subjected to exposure to intensive ultraviolet radiation from the pairs of the highpressure radiators.

The invention will be further described, by way of example, with reference to the accompanying diagrammatic drawings, in which: Figure 1 shows a cross-section through a varnished wire produced in by a method con stituting a preferred embodiment of the invention; Figure 2 shows a front view of a device constituting a preferred embodiment of the invention; Figure 3 shows a vertical section through a hardening chamber of the device of Fig. 2, with associated devices for applying the varnish and for the varnish calibrating stripper; Figure 4 shows a horizontal section through the hardening chamber of Fig. 2 with associated devices for cooling the radiator; and Figure 5 shows a section through an embodiment of the stripper and calibrating device of Fig. 2.

The varnished wire shown in Fig. 1 comprises an electrical conductor 1, for example copper wire, which is insulated with a plurality of varnish coats 2, 3, 4, 5 applied concentrically on top of one another and hardened after each application by exposure to ultraviolet radiation. Each of these varnish coats is formed from the multiple application and subsequent hardening of an insulating varnish of the same type in order to obtain the required total thickness of the coat.In the case of the varnished wire illustrated, in accordance with the method described above, a blank, heated and possibly pre-treated conductor 1 received the application of an innermost layer 2 of an insulating varnish suitable for the permanent adhesion to the metallic surface of the conductor both in the fluid and the hardened condition on all sides, and possibly on the edges, fo followed by an additional varnish coat 3 with predominantly insulating properties which was in turn covered by a particularly heat resistant varnish coat 4 and then by a concentric, outermost covering coat 5 which was mechanically resistant, in particular abrasion-proof and scratch-resistant in the hardened condition.It is also possible to produce heavy-gauge wires insulated with varnish having a conductor 1 of any cross-sectional shape for example rectangular or quadratic, and having a cross-sectional area of up to more than 100 mm2, which are provided in the same way with an insulating coating of this type, and in which the number and thickness of the individual coats are dependent on the purpose for which the varnished wire produced in this way is designed. It is however recommended in the case of conductors 1 having corners in cross-sectional profile to use an insulating varnish at least for the innermost layer 2 which has a lower surface tension than the conductor surface which it coats so that it surrounds the corners optimally, and covers them with a uniform coat thickness.

It has proved to be particularly advantageous to apply each varnish coat at a thickness of at least 5lib, preferably 1 5 to 20it, subject it to a relatively short exposure to radiation and finally harden it by at least one further, short, ultraviolet radiation, and in which the same wire may be subjected for a successive number of times to the ultraviolet radiation by corresponding deflection. As coat thicknesses of more than 20,u only harden with difficulty even if passed through several times, whereas coat thicknesses of below 5 EL do not ensure a completely homogeneous coat, it is preferred to form each different varnish coat 2, 3, 4 or 5 from several individual varnish coats.

After each application the coated conductor wire 1 is subjected to ultraviolet radiation at a temperature of more than 1 00 C, preferably between 1 50 and 1 80 C, for a period of less than 25 sec., preferably between 3 and 1 5 sec. This may take place in a corresponding radiation area in one passage or as preferred for rational use of the hardening chamber-in several passages. Insulating varnishes of high reactivity which are, however, only suitable for quite specific special purposes, may be hardened by shorter periods of exposure to ultraviolet radiation, for example 0.2 to 0.3 secs.Deflection for returning the conductor wire provided with partially hardened coating is advantageously carried out at a varnish temperature of less than 1 00 C in order to avoid plastic deformations of the varnish coat. For many purposes varnishes hardenable by ultraviolet radiation must be applied and/or hardened under an inert protective gas, for example nitrogen, in order to produce the required properties in the hardened condition or because varnishes having specific predominant properties may only be hardened in this way.

The device illustrated comprises, on a common platform 6 with a support frame 7, and above one another, a varnish coating device 8, a combined stripper and calibrating device 12 and a hardening chamber 16. Between the stripper device 1 2 and the hardening chamber 1 6 there is disposed a reflecting diaphragm 1 3 traversed by the coated varnished wires, which shields the above devices from the effect of the radiation in order to prevent an undesirable preliminary varnish hardening and to prevent radiation losses. For the same reason a light trap 10 is disposed above the hardening chamber 1 6.

In the upper and lower region of this device a number of guide rollers 9 are disposed in such a way that a blank wire to be insulated is drawn off an unwinder (not shown), preferably disposed on the same platform 6, associated with one of the rollers, passed via the guide rollers 9, possibly several times, through the coating and stripper device 8 and 1 2 and the hardening chamber 1 6 to the related upper guide roller 9, deflected on this and may be returned to the relevant lower guide roller 9 outside the device. It may be guided via the latter for repeated passages through the device for further varnish applications or varnish hardening in accordance with the required number of applications and varnish coats, and finally drawn off as a finished varnished wire provided with hardened varnish insulation and wound onto a spool.

In order to ensure that no problems arise in the application of the insulating varnish to the blank conductor wire 1 or the varnished wire already provided with the hardened coats 2, 3 or 4, the varnish coating device 8 is disposed under the hardening chamber 1 6 and the stripper-calibration device 1 2 is disposed between the coating device and the diaphragm 1 3. The coating device comprises a number of separate baths 1 4 oriented for the regulation of their level having inlet openings 34 for the wire to be coated 1, in which the baths 14 are disposed adjacent to one another in group sequences and laterally and/or vertically offset groups and in which each bath is separately associated with a stripper-calibration device 1 2. This arrangement enables both the concentric application of varnish and the hardening of several layers on top of one another as well as in reverse--the repeated subsequent hardening of a single coat of the insulating varnish. The coated conductor 1 returned in this way can in this respect be guided by correspondingly offset rollers 9 or in the case of coaxial, equal rollers 9through baths containing no varnish for specific manufacturing purposes for further hardening.

In a preferred embodiment the baths 14 and groups of baths possible separated by dividing walls of the varnish coating device 8 are trough-shaped with a lateral wall 32 projecting downwards and inclined or bent inwardly, from which vertical slits 34 open outwardly are taken as inlet openings. In this respect capture troughs 1 5 are provided under the baths 14 for the varnish escaping from these slits and comprise a device 11 for continuously returning the varnish to the baths 14. The capture troughs 1 5 are disposed slightly backwardly spaced in one of the backwardly projecting lower edges corresponding to the baths 1 4 and opposite one of the vertical wire guide planes intersecting one of the slits 34.This enables a continuous circulation of the insulating varnish to be applied from the capture troughs 1 5 to the coating baths 14, where it is partially applied to the wire 1 to be insulated, whereas the rest runs through the slot 34 and along the inclined or bent lateral wall 32 and therefore into the capture trough located below. In this way the level of the coating baths 14 is mained constant, whilst the resupply of the insulating varnish used may take place at certain spacings of time.

In order to carry out in a successful and rational manner the above method the special formation of the hardening chamber 1 6 is of importance. This is formed with a box-shaped housing having lateral walls 24 and 25 and end walls 27 and 28, as shown in Figs. 3 and 4. The height of the hardening chamber corresponds approximately to the length of the hardening area provided, in the circuit of which the coatings are subjected to ultraviolet radiation. A number of rod-shaped ultraviolet radiators are disposed opposite to one another in pairs above each other on the lateral walls 24 and 25 of the hardening chamber. The spacing between the individual pairs is selected in accordance with the radiation intensity of the respective radiator in such a way that their areas of emission intersect.In the illustrated embodiment of the hardening chamber 16, four pairs of high-pressure ultraviolet radiators 1 7 are disposed with a spacing of 200 mm each over two pairs of lowpressure ultraviolet radiators 1 8 in such a way that the spacing remaining between the radiators of each pair is not more than 50 mm, preferably 40 mm.In this way the coated wire which is passed centrally therebetween is subjected to radiation which is as intensive as possible without the risk of coming into contact, this radiation being intensified and relected by preferably concavely bent reflectors 21 disposed behind each radiator 17 and 18 and by plane reflectors 20 disposed between the pairs of radiators in planes intersecting their axes perpendicularly in such a way that they have a substantially uniform effect on all sides of the coating to be hardened.

For the above reasons the low-pressure ultraviolet radiators 18, whose emission also contains a substantial infrared component, are arranged in the lower area of the hardening chamber 16. Infrared radiators 19 may be disposed before the lower region of the hardening chamber 16 on both sides as an additional device for rapidly heating the coatings to be hardened to the reaction temperature. In this way the reaction temperature of the respective outermost coat is very rapidly attained without any noteworthy heating of the conductor 1 or of the already hardened coatings, this being a substantial contribution to the low power requirement.As also mentioned above, for efficient operation of the ultraviolet radiators 1 7 and 18 a comparatively high operating temperature of the latter which is as constant as possible and normally more than 400"C should be observed, which should not, however, exceed the limit value of 500"C, as otherwise operational disturbances may arise as a result of radiator cut-out.

Therefore the hardening chamber 1 6 is provided in the region of all the radiators with efficient gas cooling, preferably air cooling.

For this purpose gas ducts 22 are provided at the front of the hardening chamber 1 6 and in their region towards the ends of the radiators 17, 1 8 open inlets 23 of the end walls 27 and 28 of the hardening chamber 1 6 are provided together with, on both side walls 24 and 25 of the latter, inwardly oriented cooling gas baffle plates 26 which are oriented in a direction parallel to the axes of the ultraviolet radiators 1 7 and 1 8 and between the radiators. For simple air cooling, gas ducts 22 arranged on one of the end walls 27, 28 of the hardening chamber 1 6 are sufficient, these being connected via corresponding piping 29 with an exhauster 30, whilst inlets 23 are recessed on the opposite end wall 27 at the height of each radiator.For reasons of uniform production of hardening and to provide chamber housings with a convenient use of space for connecting the latter to the gas supply pipes 29 and also for the purposes of a simple equipment of the hardening chamber 1 6 for operation under air seal, the gas ducts are preferably provided on both end walls 27, 28.

In the case of simple air cooling; the connection openings of the gas ducts 22 which are not connected to an exhaustor 30 remain open or are connected to piping (not shown) and possibly an air filter, for the supply of fresh air from outside the housing. In all cases the air stream is essentially guided only over the area of the radiators 17, 1 8 as a result of these devices, and, as a result of the cooling gas baffle plates 26 engaging therebetween, parallel to these in their longitudinal direction.

In order to maintain the radiator temperature constant, the amount of the cooling gas passed through in this way may be controlled by thermostat sensors dependent on the end region of the radiators and disposed in the gas duct 22 by means of a throughput amount control device 21, e.g. a pivotable flap, at 1 least one of which is provided in the piping 29. This cooling system may be readily adapted to operation with protective gas, in that the outlet of the exhauster 30 may be connected via corresponding piping with a gas storage device, preferably with the inclusion of a recooling device, and in that this is connected with the input openings of the gas ducts 22 of the opposite end wall 27 of the hardening chamber 16, with according fastening to the latter.

The stripper-calibration device 1 2 arranged between the varnish coating device 8 and the diaphragm 1 3 is of importance for determining the thickness of each individual varnish coat. In this respect the or each stripper calibration device is formed in accordance with the profile of the wire 1 to be coated and comprises in a guideway 35, possibly laterally movable parts 36 which move to and away from one another and which are held together by resilient force. The stripper and calibration device shown in Fig. 5 is provided for round conductors and is formed in such a way that it strips by means of its stripper components 37, 38 in a self-centering manner, the excess varnish adhering to the coated wire up to the predetermined t thickness of the layer.

For each layer thickness, corresponding stripper components are provided with exactly adapted dimensions of their bore or aperture.

For the calibration in particular of the varnish cost on the surface of profiled heavy gauge wires, the stripper device 1 2 has guide components having a cross-sectional shape of an H or a double T, in whose recesses segment or block shaped stripper components 37, 38 having serrated stripper surfaces are guided, the serrations of these stripper surfaces having a depth corresponding to the required thickness of the varnish coat. These are held facing one another by means of spring tension in such a way that they slide with their calibrating surfaces onto the coat surface and strip the excess varnish. In this respect however, according to the dimensions of these serrations, there remains on the surface of the wire to be coated enough varnish to be distributed as a result of its powers of cohesion and adhesion to form a uniform film of the required thickness specified for the relevant varnish coat and for which the stripper components used are intended.

The device described enables the production of high-quality, varnish insulated conductor wires of any cross-section, possibly even having corners in cross-section, in an extremely rational and environmentally safe manner in the above-described way.

Claims (5)

1. A method of production of electrical conductors or wires insulated by varnish hardenable by ultra-violet radiation, in which insulating varnish which is capable of being hardened by radiation is continuously applied to the heated and possibly pre-treated wire, the thickness of the coat of varnish is calibrated by stripping of the excess varnish, the varnish coat is then hardened by a sufficient quantity of ultra-violet radiation, and the varnished wire produced in this way is finally coiled, and in which, after hardening of the coat of varnish, one or more additional coats of insulating varnish are applied in a continuous sequence, the additional varnish coats being hardenable by radiation and having different properties in the hardened condition, and are hardened by ultra-violet radiation.

2. A method as claimed in claim 1, in which the wire to be insulated has applied to it a layer of a suitably adhesive varnish of high flexibility, followed by at least one layer of a high-grade dielectric insulating varnish, followed by at least one layer of an insulating varnish which is heat-resistant in its final condition, and finally followed by a layer of an insulating varnish which is mechanically resistant, in particular abrasion-proof and scratchresistant and sufficiently flexible in its final condition.

3. A method as claimed in claim 1 or 2, in which hardenable varnishes are applied to profiled heavy gauge wires in a continuous sequence and are hardened by ultraviolet radi ation, of which at least the varnish of the innermost layer has a lower surface tension in the viscous state in respect of the surface to be coated, and in which the coat of varnish is applied to a thickness of at least 5 IL.

4. A method as claimed in any one of claims 1 to 3, in which the coated conductor wire is subjected to ultra-violet radiation at least after each respective application of varnish for a period of less than 25 sec at a temperature of more than 100"C and in which the respective outermost coat of varnish is pre-hardened as a result of the effect of relatively short exposure to ultra-violet radiation and is hardened lastly by at least one further exposure to ultra-violet radiation of a higher intensity.

4. A method as claimed in claim 3, in which the innermost varnish layer is applied to a thickness of between 1 5 and 20 is and is then pre-treated with infrared radiation and directly after this is treated with ultra-violet radiation of different intensity.

5. A method as claimed in any one of claims 1 to 4, in which the coated conductor wire is subjected to ultra-violet radiation at least after each respective application of varnish for a period of less than 25 sec at a temperature of more than 100"C and in which the respective outermost coat of varnish is pre-hardened as a result of the effect of relatively short exposure to ultra-violet radiation and is hardened lastly by at least one further exposure to ultra-violet radiation of a higher intensity.

6. A method as claimed in claim 5, in which the period of ultra-violet radiation is between 3 and 1 5 seconds at a temperature between 150 and 180"C.

7. A method as claimed in claim 6, in which the conductor wire provided in each case with a pre-or partially hardened coat of varnish after re-cooling of the outermost coat of varnish to below 1 00'C is returned twice in order to pass through the ultra-violet radiation area again in the same direction of movement and, after hardening of the coat in question, for the purposes of the subsequent application of varnish.

8. A method as claimed in any one of claims 1 to 7, in which at least one of the coats of varnish is applied and/or hardened under an air seal or under protective gas.

9. A device for carrying out the method of claim 1, comprising, disposed substantially vertically above one another on a common platform with a support frame, a varnish coat-j ing device, which comprises a plurality of separate baths disposed for the regulation of the level of their content and having openings for the passage of the conductor to be coated, a stripper-calibrating device, a hardening chamber, and, both under the coating device and above the hardening chamber, a plurality of guide rollers, with which unwinding and rewinding devices are associated, the baths being disposed adjacent to one another in a series of groups and in lateral and/or vertically staggered groups, a respective one of the stripper-calibrating devices being separately associated with each of the baths, the hardening chamber being provided with at least one pair of ultra-violet emitters disposed transverse to the direction of movement of the wire through the chamber and with reflectors located behind the emitters and with a plurality of plane reflectors at regular distances between the individual wire lines and directed substantially perpendicular to the ultraviolet emitters, the hardening chamber being arranged for the passage of a cooling gas.

10. A device as claimed in claim 9, in which the reflectors located behind the emitters are concavely bent.

11. A device as claimed in claim 9 or 10, in which pairs of ultraviolet emitters of varying intensities of radiation are disposed in the hardening chamber, which has the shape of a box, the lower intensity emitters being disposed upstream of the higher intensity emitter, an infrared radiation stage being disposed upstream of the hardening chamber.

1 2. A device as claimed in any one of claims 9 to 11, in which the hardening chamber has means for the passage of cooling gases at the ends of opposite uptraviolet radiators or radiator groups comprising on each side associated gas ducts and in the region thereof facing the ultraviolet radiators open outlets of end walls of the hardening chamber there being provided on both lateral walls of the hardening chamber cooling gas baffle plates orientated parallel to the axes of and between the ultraviolet radiators.

1 3. A device as claimed in claim 12, in which, in the case of cooling with air, the gas ducts and outlets of one end wall communicate with the atmosphere and are open to the surrounding air, the gas ducts of the opposite end wall being connected to at least one exhauster by tubing, in whose circuit there is, provided at least one control device for controlling the throughflow amount of cooling air in a temperature-dependent manner.

14. A device as claimed in any one of claims 9 to 13, in which the baths or groups of baths separated by dividing walls of the varnish coating device are trough-shaped and are formed with a downwardly projecting, inwardly inclined or bent lateral wall from which outwardly opening vertical slots extend to provide wire inlet openings, captive troughs being provided below the projecting lower edge of the baths for the varnish esceping from the baths, troughs having devices for continuously returning the varnish to the baths disposed in a slightly spaced backwardly offset position in respect of one of the wire guide planes intersecting the slots.

1

5. A device as claimed in any one of claims 9 to 14, in which the or each strippercalibration device comprises movable parts arranged to correspond to the profile of the wire to be coated and movable in a guideway laterally towards and away from each other, the movable parts being held together by resilient force.

16. A device as claimed in claim 15, in which the stripper device comprises two guide components having the cross-section of an H or a double T, in whoch recesses segment or board shaped stripper components with ser rated stripper surfaces are guided, and whose serrations have a depth corresponding to the thickness of the varnish coat required.

17. A method of producing varnish-coated electrical conductors, substantiallyaas hereinbefore described with reference to the accompanying drawings.

1 8. A device for producing varnish-coated electrical conductors, substantially as hereinbefore described with reference to and as illustrated in the accompanying drawings.

1 9. A varnish-coated conductor produced by a method as claimed in any one of claims 1 to 8 and 17, or in an apparatus as claimed in any one of claims 9 to 16 and 18.

CLAIMS (14 Oct 1980)

1. A method of production of an electrical conductor or wire insulated by varnish hardenable by ultra-violet radiation, comprising applying ina continuous sequence a plurality of varnish layers to the heated and possibly pretreated conductor or wire, each varnish application comprising the steps of continuously applying insulating varnish which is capable of being hardened by radiation to the conductor or wire, calibrating the thickness of the coat of varnish by stripping of the excess varnish, and hardening the varnish coat by a sufficient quantity of ultra-violet radiation, the finished varnished conductor or wire produced in this way finally being coiled, in which the first layer if a suitably adhesive varnish of high flexibility, followed by at least one layer of a high-grade dielectric insulating varnish which is heat-resistant in its final condition, and finally followed by a layer of an insulating varnish which is abrasion proof and scratchresistant and sufficiently flexible in its final condition

2. A method as claimed in claim 1, in which the varnishes are successively applied to profiled heavy gauge wires, of which at least the varnish of the innernist layer has a lower surface tension in the viscous state with respect to the metal surface to be coated and each subsequent layer of varnish has a surface tension which is lower than the varnished surface to which it is applied, and in which each coat of varnish is applied to a thickness of at least 5 ju, is then pre-treated with infrared radiation and directly after this is treated with ultra-violet radiation of differing intensity.

3. A method as claimed in claim 2, in which each varnish payer is applied to a thickness of between 1 5 and 20 IL