MXPA97000618A - Electricame heated window - Google Patents

Abstract

The present invention relates to an electrically heated, laminated window of at least two folds or layers of a glass material and at least one fold of interlayer material, which extends between the folds of the glass material, this window includes: arrangement of thin wires, closely spaced, carried by one of the folds, elements of electrical connection, to connect the arrangement to an electrical supply, and to pass the current through the wires to heat the window, characterized because at least some of the wires extend along divergent lines, so that the array extends over substantially all of the transparent portion of the sale

Description

WINDOW HEATED ELECTRICALLY The present invention relates to an electrically heated window and, more particularly, but not exclusively, to a laminated window of a vehicle, comprising a number of folds or layers, this window includes an array of thin wires, closely spaced, which extend over one of the folds and which form a heating element, the heating effect results from the passage of the electric current through the wires. These windows can be installed as windshields, rear windows or other windows of a car or other vehicle, or as a window (especially the windshield) of a commercial, locomotive or airplane vehicle, or on a boat or ship. Electric heating is used to disperse the condensation or ice on the window surfaces and thus maintain good visibility through it. In its simplest form, a laminated window comprises an internal fold of interlayer material ("the interlayer"), disposed between two external folds of a rigid, transparent, glass sheet material, but the more sophisticated laminated windows comprise larger numbers of interlayer folds and glass material, for example, to give greater resistance to impact damage to the window, and reduce the risk of window penetration. The interlayer is usually a flexible plastic material, for example polyvinyl butyral, and the glass material may be glass or a rigid plastic material. Laminated windows are also known as comprising two or more folds, in which an exposed external fold is a fold of flexible plastic material, which can both increase the resistance to penetration as well as reduce the risk of injury by fragments of the material of Crystal during an impact. Such an external plastic fold normally forms the surface facing the interior of the window and is generally subjected to a surface treatment to increase the abrasion resistance. An electrically heated window, comprising an array of thin wires, closely spaced, is known from the patent of US Pat. No. 3,729,616. This document describes a laminated window having a pattern of shirred resistance wires, with the wrinkles oriented in a non-parallel random fashion, so as to reduce the brightness of the wires, when the window is used as a windshield. The heated area is generally rectangular and, since the windshield normally approximates the configuration of a trapezoid, there are generally triangular areas adjacent to each short edge of the windshield, which are not heated. Obviously, any condensation or ice in these unheated areas will remain in place, damaging visibility through the windshield. In the present specification the "trapeze" is used meaning a quadrilateral with only a pair of parallel sides. On modern windshields, the triangular areas in heating are substantial and may still include part of the area normally cleaned by windshield wipers (the "cleaned area"). The damage resulting from visibility is very inconvenient and can have serious consequences for safety. Also, when ice remains present in the cleaned area, damage to the cleaning sheets can occur as a result of scraping over the ice. A windshield of the prior art, showing such unheated areas, is illustrated in Figure 1 of the present application; It would be desirable to be able to heat these areas too. One possible solution is described in GB 1,365,785, which relates primarily to the problems of electrical discontinuity and the variation of resistance with path length, but also describes an arrangement which substantially heats up all of the two particular configurations of windows Two windows, in the shape of a rectangle and a trapeze, respectively, they are described, in which the wires go from one side to another, that is to say parallel to the two long, parallel edges. If the window is of a windshield, the wires, therefore, will be parallel to the top and bottom edges. The wires are arranged in a number of "elements", each with their own "collectors !, and these elements are connected in series so that the variable resistances of the elements are compensated and the same current flows through each element. The complexity of the circuit, however, makes it expensive to manufacture.Also, this arrangement does not solve the problem of extending the heated area in most modern vehicle windows, which have curved edges and are only approximately of the configuration of a Patent GB 1,365,785 only shows how to extend the heated area in windows of particular configurations and with wires of the particular orientations described, ie parallel to the long edges of a window In fact, when the window is a windshield, it is generally prefers to arrange the wires to go at right angles to the two long edges, generally parallel, that is, from the top to the bottom. This arrangement facilitates the heating of the entire viewing area (as defined in vehicle safety standards) and reduces optical interference to vision caused by the wires, especially when the windshields are installed at increased inclination angles. say wax to the horizontal. Therefore, a more general approach to the problem of extending the heated area of the vehicle's windows is necessary. Patent EP 32,139, which corresponds to the patent of E. U. A., No. 4,395,622, describes a solution to the secondary problem that part of the cleaned area is unheated. The wires are placed along circular arcs that extend in the direction of movement of the cleaner. The patent teaches that the heated area should be arranged to approximately coincide with the cleaned area; a substantial portion of the window, therefore, is left unheated, as in the patent of E. U. A., No. 3,729,616. The patent, therefore, does not address the problem of extending the heated area beyond the cleaned area. Patent GB 1,556,681, which corresponds to the US patent, No. 4,209,687, addresses the problem of the diffraction effects that occur as a result of the light passing through the thin wires, spaced closely, in an electrically heated window. . It is suggested that each wire is formed as a helix to alleviate such effects. Neighboring helices can be arranged in a parallel, trapezoid, sinuous or wavy relationship, according to the desired pattern. However, there is no indication of how to form the propellers, how they are arranged in the various relationships or why a particular pattern may be desired, and thus this document does not help an expert seeking to extend the heated area of a window . Accordingly, the need remains for an improved, electrically heated window, which is powered by an array of wires, which extend over substantially all of the transparent portion of the window, and which can be produced economically. It is also important to ensure that the heating effect does not vary excessively in intensity over an extended heating area, otherwise, the variation in time taken to freeze frost or condensation from different areas of the window would be unacceptable in practice. It has now been found, contrary to expectations, that it is possible to supply such a window by the arrangement of the wires extending along divergent lines. While it has apparently been the belief in the past that the arrangement of the wires to extend along non-parallel lines is not feasible in practice, it has now been found possible, surprisingly, to modify, in a relatively simple manner, as described above, one of the known types of wire laying apparatus, in order to arrange them along divergent lines in a practical and economical manner. Also, ways have been found to control the intensity of the heating effect within acceptable limits of variation over the entire heated heated area. According to the present invention there is provided an electrically heated, laminated window of at least two folds of glass material and at least one fold of interlayer material, which extends between the folds of the glass material, this window includes: arrangement of thin wires, closely spaced, carried by one of the folds, - elements of electrical connection, to connect the arrangement to an electrical supply, so as to pass the current through the wires and heat the window, characterized because at least some of the wires extend along divergent lines, so that the array extends over substantially all of the transparent portion of the window. Divergent lines can be straight or curved. By the term "electrical connection elements", the skilled person will understand in the present context any of the products generally used in such windows to connect the array of wires, which include busbars; drivers; adjuncts; plugs, swords and their corresponding caps. The lines along which the wires extend are imaginary in the sense that, until the wires are actually laid along the lines, during the manufacture of the window, the position of the lines can not be determined by an inspection. The wires themselves may be corrugated or otherwise folded crazily in a repeated, regular or irregular manner, to alleviate the inconvenient optical effects, as will be described in more detail below, and therefore it will be imprecise to define the present invention by the definition that the wires themselves diverge, because, if examined more closely, it will be seen that the undulated wires may in fact diverge and converge repeatedly over their length. The present invention relates primarily to the configuration and orientation of the wires through a window as a whole and secondarily with the smaller scale configuration, for example the corrugation, of the wires. It will be appreciated that it is possible to place any corrugated or non-corrugated wire along the lines, as defined by the present invention. In a preferred embodiment of the invention, the array of wires comprises one or more groups of wires extending along substantially parallel straight lines and wires adjacent to the groups extending along diverging lines. This embodiment has the advantage that with most devices it is faster to place the wires in a piece of the interlayer in this way (which will be described later) and the programming of the apparatus is simplified. In another embodiment of the invention, substantially all wires are comprised in the array extending along diverging lines. This modality has the advantage of being very flexible in terms of the variety of window configurations that can be wired. This is because there is a limit on the angle of divergence between the line along which a wire extends, and the line along which an adjacent wire extends (if the angle is too large, it is leaves an unheated area), but if each line diverges from the previous one, it is possible that the total angle between opposite sides of the wired area becomes relatively large and thus accommodate extreme window configurations increasingly. Preferably, at least some of the lines, along which the wires extend, are substantially parallel to an edge of the window. A window, according to the invention, can have at least one pair of opposite, non-parallel sides. Such a window is especially suitable for use as a vehicle windshield, since the heated area can be extended to the work pillars of the body on the windshield sides, known in the automotive industry as the A poles, which are generally inclined each other, just like towards the back of the vehicle. Normally, the window is of an approximate configuration of a trapezoid, but with the curved edges and at least some of the wires extending along diverging lines in directions from the shorter of the two substantially parallel edges of the trapezoid towards the more along the two substantially parallel edges. For the manufacture of the embodiments of the invention, mentioned above, it has been found necessary to improve the known processes and apparatuses, used in the manufacture of conventional electrically heated windows. In particular, the apparatus that in the past has been used to assemble the array of wires for incorporation as part of the heating element (commonly referred to as a wiring machine) has been found unsatisfactory when the windows are manufactured in accordance with the invention. A known apparatus is described in the patent of E. U. A., No. 3,795,472 (divisional patent of the patent of E. U. A., No. 3,729,616, which was mentioned above). A wiring machine is provided comprising a drum, rotatably mounted, with a wire supply device on one side. A sheet of the interlayer to be wired joins the drum and rotates, while the wire is supplied from the supply device thereof. This device is gradually moved in a direction parallel to the axis of rotation of the drum, so as to deposit the successive turns of the wire on the interlayer, each turn of the wire being in a spaced relation to the previous one, to produce a helical spiral wound around the drum. The spiral is cut and opened along an axial line on the surface of the drum, in the gap between two adjacent edges of the interlayer, and the sheet of the interlayer is removed from the drum and placed in one of the folds of the glass material for assembly in a laminated window. This apparatus supplies a product in which the wires are arranged along parallel straight lines, although in a close inspection, it will not be necessary to describe the wires themselves as parallel, due to the randomly oriented wrinkles. It is not possible to manufacture the wired products improved, mentioned above, in this apparatus. Another wiring machine, which includes a drum, is described in patent EP 443,691. While several improvements in the machine of the US patent, No. 3,795,472, are described, they are not related to the orientation of the lines along which the wires are deposited, which are still arranged in a finished window. long straight and parallel lines.

A different type of wiring machine is described in EP 32,139. This comprises a flat table on which an interlayer sheet is placed, a sliding bridge arranged above the table and there extends, a wire laying element, slidably mounted on the bridge and joined to a connecting rod, the which pivots around a vertical axis. The wire laying element slides back and forth on the bridge, in a reciprocal manner, but, because the bridge itself is also "free to slide in a reciprocal manner, and the wire laying element is restricting by the connecting rod, the net movement is along a circular path.The wires can only be placed along divergent lines, with this apparatus placing successive wires along non-concentric circular curves. This machine is not suitable for placing wires in the arrangements extending over substantially all the transparent portion of a window of a configuration used in a modern vehicle.None of these known wiring machines, therefore, has been found suitable for its use in the manufacture of the improved wired products, mentioned above.

An improved process and apparatus for manufacturing the aforesaid improved wired products have now been developed; the underlying advance is to provide an extra degree of freedom of movement to the supply and placement device of the wire (the "wiring head"), together with an associated control element, to control the extra movement. In accordance with these aspects of the invention, a process for the manufacture of an electrically heated window is first supplied, as claimed in claim 1, part of the process being carried out in an apparatus, which includes an endless support surface, which can rotate about an axis, to support the interlayer material, and a wiring head to supply the wire and place it on the interlayer material, the supporting surface and the wiring head being movable in mutual relation, in a direction parallel to the shaft, and the process includes the steps of: - securing a piece of the interlayer in a position on the support surface, - causing the support surface to rotate, - placing the wire in contact with the interlayer material by means of of the wiring head, while rotating the support surface, so that successive turns of the wire are placed on the interlayer material, - stop the rotation On the surface of the support, when the desired number of turns of wire has been placed, the process is characterized by: cutting the spiral in a direction parallel to the axis, so that it can be opened as an array of wires, generally flat, - remove the wire piece from the interlayer from the support surface and provide the wire arrangement with electrical connections and - assemble the piece of interlayer material in a laminated window. in that, while the wire is placed, the process includes: moving the supporting surface and the wiring head back and forth in mutual relation, in a reciprocal manner, in the direction parallel to the axis, and in coordination with the rotation of the wire; the support surface, to provide an array of wires over the interlayer material, in which at least one of the wires extends along diverging lines. Clearly, the relative movement between the support surface and the wiring head can be provided as a result of the movement of the support surface alone, or of the wiring head alone, or both together. Secondarily, an apparatus for forming an array of wires in a piece of interlayer material during the manufacture of an electrically heated window is also provided, the apparatus includes an endless support surface, mounted for rotation about an axis, to support the interlayer material, and a wiring head for supplying the wire and placing it on the interlayer material, the supporting surface and the wiring head are arranged for relative movement in one direction parallel to the axis, characterized by a pulse element, to cause the support surface and the wiring head to reciprocally move relative to each other in the direction, and a control element, to control the pulse element to coordinate the reciprocal movement with the rotation of the supporting surface, so that the wiring head places the wire along diverging lines. Preferably, the wiring head is movably mounted on an elongated element, which extends parallel to the axis, and is propelled along the elongate element in a reciprocal manner by the drive element. The invention will now be illustrated by the following non-limiting description of particular embodiments, with reference to the accompanying drawings, in which like reference numerals denote similar elements throughout the various figures. In the drawings: Figure 1 is a general view of a known electrically heated window, seen in a direction approximately normal to the surface of the window; Figure 2 is a general view of a first embodiment of the electrically heated window, according to the invention, seen in a direction corresponding to Figure 1; Figure 3 is a cross-sectional view, greatly enlarged, of a small marginal portion of the window of Figure 2, taken on line III-III of Figure 2; Figure 4 is a general view of a second embodiment of the electrically heated window, again seen in a direction corresponding to Figures 1 and 2; Figures 5a and 5b are greatly enlarged views of the heating wires in versions of the windows in which the wires are arranged differently in different portions of the window; Figure 6 is a perspective view of an apparatus for positioning the heating wires for manufacturing a window according to the invention, including an endless support surface, in the form of a cylindrical drum; Figure 7a is a diagram showing the cylindrical support surface of the drum of Figure 6, as a flat rectangle, so that the entire support surface can be seen at the same moment, schematically showing how the wires can be placed when manufacturing two prior art windows, of the type shown in Figure 1; Figure 7b is a diagram similar to Figure 7a, schematically showing how the wires can be placed when making two windows according to the first embodiment of the invention (Figure 2). Figure 1 shows a known window 1, electrically heated, suitable for use as the windshield of a vehicle. It comprises an area 2 heated by an array of thin wires 3, spaced closely. The wires are arranged in two heating elements, 4 and 5, which extend between respective bus bars 6, by means of which the electric current is supplied to the two elements independently. It will be appreciated that as the heating wires are placed very close to each other, in the heated windows of the type described in this specification, it is not possible to represent in the drawings all the wires, which are actually present in these windows. Consequently it will be understood that only a portion of the heating wires is shown in the drawings of this specification, and that they are shown further apart than they really are. Also, to avoid excessive repetition of the drawer, when the area covered by wires is relatively large, no wires have been drawn over that part of the area. Instead, dotted lines and dashes have been used to indicate the extent of the area covered by the wires. The window 1 is generally in the shape of a trapezoid, with generally parallel edges 8 and 9 and non-parallel edges 10 and 11. All edges are slightly curved. The result of supplying a heated area 2, comprising wires extending along parallel straight lines, is that the heated area is rectangular and thus two areas 7, generally triangular, remain unheated. Unfortunately, it is not possible to simply continue the straight, parallel wires through the areas 7, because the strength, and thus the length, of each wire 3 should not vary excessively to obtain a satisfactory performance (i.e., a warming moderately uniform). References in this specification to the shape of a line along which a heating wire extends (eg, "straight") and references to the shape of the line when the interlayer material piece is placed on a flat surface. When a piece of the interlayer material comprises wires extending along the straight lines it is assembled in a curved window, and placed between curved folds of glass material, the lines will obviously adopt the curvature of the glass material and only appear absolutely straight at a particular point of the window, when they look in a direction normal to the surface of the window at that point. A window having heating wires that extend along parallel straight lines (as shown in Figure 1), can be obtained using the prior art apparatus, known from EP 443 691, to place the wires of heating. Figure 2 shows an electrically heated window, according to a first embodiment of the invention. This window 20 is suitable for use as a heated vehicle windshield, and is heated by a heating element, which extends over substantially the entire transparent portion of the window. The window has long edges, 29 and 30, and short edges, 31 and 32, the long edges are substantially parallel so that the window has a general configuration of a trapezoid, allowing the curvature of the edges. When the window is installed in the orientation which is usual for a windshield, the long edge 29 forms the upper edge, the long edge 30 forms the bottom edge, and the short edges, 31 and 32, form the windshield sides. Figure 3 is a cross section of the window 20, taken along the line III-III of Figure 2. The window comprises two folds of sheet glass material, which can be cured, the fold forming the surface external 44 of the window 20 is designated by the outer fold 40, and the fold forming the inner surface 47 of the window (ie, the surface of the window which, after the glass, faces the interior of the object, example a vehicle, which is to be glazed by the window) is designated the inner fold 41. While the folds 40, 41 can be composed of any transparent and rigid sheet glass material (for example various plastics), a preferred material It is glass. The folds also have surfaces 45, 46 which are joined together to form a laminate, by a fold of the interlayer material 42, which is transparent in the finished product, and extends between the folds of the glass material. The interlayer is generally composed of a plastic material with suitable physical and chemical properties, to join the folds of the glass material together, and to confer the product with the performance required for its application, for example in terms of safety, optical realization , etc. A suitable interlayer material is polvi-nil-butyral ("pvb"), but other interlayer materials can be used. As mentioned before, other laminated window constructions exist, which involve more or less folds. Still referring to Figure 3, a band 43, substantially opaque (known in the vehicle glass industry as a darkening band) is arranged around the periphery on one side of one of the folds, preferably the inner side 45 of the outer fold 40. The darkening band 43 may be in the form of a printed coating, composed of a ceramic ink (based on frit). This darkening band serves to conceal the receiving rim of the bodywork of the vehicle when the windshield is encristala in position; and when the window is adhesively glazed, the band not only hides but also protects the adhesive and / or light sealant, especially its ultra-violet component. In this specification, references to a transparent portion of the window are references to the portion not obscured by the darkening band. In Figure 3, the imaginary line ZZ is shown dividing the opaque portion 48 of the transparent portion 49. Preferably, the darkening band 43 is disposed on the inner face 45 of the outer fold 40, because in this position the band is additionally capable of hiding from the external view components, for example the bus bars, located on the peripheral surface of the interlayer fold 42. For this reason, the darkening band has been omitted from Figure 2 in order to show the busbars. If the darkening band is arranged on a different surface, for example the surface 47, it is possible to apply an organic sizing to the inner face 45 instead of it, so that the components located on the peripheral surface of the inner layer fold are still hidden. Referring again to Figure 2, the window 20 is heated by heating elements, comprising an array 21 of thin wires 22, closely spaced, arranged on a surface of one of the folds, preferably on the inner side of the material fold interlayer, although it is entirely possible to carry out the invention with the wires arranged on the outer face of the interlayer material fold, or in the middle of the fold, especially if it is a composite fold. Indeed, the invention also includes windows in which the wires are disposed on one side of one of the other folds, as long as they are adequately protected. The arrangement may comprise two or more heating elements 23, 24, each element having its own power supply. This arrangement is preferable for large windows, since they, when supplied with power from a standard 12 volt vehicle nominal supply, provide a substantial current. The division of the arrangement into independently supplied elements reduces the load on the various electrical connection elements, which supply current to each element; clearly, the number of elements may vary according to the size of the windshield. In the window of Figure 2, the elements 23 and 24 extend between the electrical connection element in the form of respective busbars. There are two bus bars, 25, 26, which extend along the upper edge 29 of the windshield, and two bus bars 27, 28 that extend along the bottom edge 30. The bus bars are made from a conductive strip electrically, usually a strip of metal, for example, copper strips of 3-6 mm wide, preferably 6 mm wide and about 0.04 to 0.08 mm thick. The strips are preferably tinned with a surface layer of tin, or a tin: lead alloy (Sn: Pb ratio of 60:40), to protect the copper from oxidation. In this windshield, the bus bars, 25, 26, extend around the upper corners and below the windshield sides 31, 32. These bus bars 25, 26, 27, 28 can be connected to the flight conductors 33 by welding, possibly by means of a small connector fitting of known design, for cleaning (not shown) and the conductors have appropriately terminated 34 for the connection to a voltage supply. Alternatively, conventional sword connectors can be welded to the ends of the busbars and the conductors attached to the swords. These conductors, attachments, terminations and connectors also constitute elements of electrical connection. The wires 22 are preferably joined to the strip forming the bus bars 25., 26, 27, 28 by the use of a further collector strip piece (not shown) to form a sandwich with the wires between the two strips, one face of at least one of the bar strips is provided with a surface layer of low melting point solder, so that this solder fuses in an autoclave to provide good electrical contact between the bus bar strip and the wires. Such a technique is known from patent EP 385 791. The wires 22 are preferably composed of tungsten and preferably have a thickness of 10 to 30 μm for a nominal operating voltage of 12 volts.; Typically, the array 21 of wires for a windshield can include between 300 and 900 wires, in accordance with the size of the windshield and the used spacings of the wires. These wires are arranged to extend along divergent lines, so that the array extends over substantially all of the transparent portion 49 (as indicated in Figure 3) of the window. With this window configuration, the wires extend along lines diverging in one direction from one long edge (upper edge 29) to the other generally parallel long edge (bottom edge 30). The wires may be fan-shaped and as a result the wires adjacent the short edges, 31 and 32, are substantially parallel to those respective edges. Clearly, this array of wires can also be described as converging in one direction from the bottom edge 30 to the top edge 29. In this embodiment, substantially all the wires comprised in the array 21 extend along divergent lines and, as mentioned earlier, this arrangement provides greater flexibility in terms of windshield configurations, which can be wired satisfactorily. While in most windshields the angle between the sides 31 and 32 is between 5 and 20 degrees, with this arrangement it is possible to wire windshields of more extreme configurations (such as the windshields of racing cars), in which the angle is greater than 50 degrees. The limit also depends on the relative proportions of a window and thus different values can be applied to other types of windows, in addition to windshields. Those skilled in the art know that when a bright light from a point source, such as one of the headlights of a coming vehicle, shines through a windshield having an array of thin, closely spaced wires, effects may occur. inconvenient secondary optics (believed to be due to reflections of the wires) that alter the vision of the vehicle operator through the windshield. As is common practice in the art, the wires 22 of the window 20 normally have corrugations to alleviate these effects, for example, they undulate in a sinusoidal pattern. Other patterns may be used, such as in zigzag, or a helical spiral, or in fact the undulations may be random in nature. Figure 4 shows a second embodiment of an electrically heated window, according to the invention, in which some of the wires extend along diverging lines, while other wires extend along straight lines substantially parallel. This embodiment is also particularly suitable for use as a windshield of a vehicle. Many aspects of this window 50 are the same, or equivalent, to the corresponding aspects of the window 20, described in relation to the first embodiment (Figures 2 and 3) and thus these aspects will not be described here further. Such aspects include the composition of the window, i.e. the folds of glass material and the interlayer material; the use and details of any darkening band; and the materials used for the wires, busbars and their connection. The window 50 also comprises an array 51 of thin wires 22, closely spaced, but the array differs from that of the window 20, shown in Figure 2, in that, in the preferred embodiment of the embodiment illustrated, it comprises a central group 55. of wires that extend along straight lines that are substantially parallel. Adjacent to this group 55 of wire and on either side thereof, are other groups of wires, designated 56 and 57, respectively, which extend along divergent lines, so that array 51 extends over substantially all the transparent portion of the window. The advantage of using wires that extend along straight lines for part of the window, where its configuration allows it, is related to the time taken to manufacture the window and will be explained in relation to Figure 6 below. In Figure 4, the array 51 is also divided into two heating elements 53 and 54. In both embodiments described above, it is important to ensure that the particular array of diverging wires, selected for the window, provides at least a moderately warm heating effect. uniform (as measured, for example, in terms of the density of heating energy) over the heated area. It is preferred that the ratio of the maximum heating energy density to the minimum heating energy density in different locations in the window should be less than 2.0, more preferably less than 1.5, and especially preferred less than 1.3. Assuming that the voltage supply is fixed, the density of the heating energy in the wire resistance (which itself depends on its thickness and length), the spacing of the wires and is also affected by the degree to which it is the wires ripple. For satisfactory performance, the maximum spacing of most wires in the transparent portion of a windshield must not exceed 10 mm, preferably less than 5 mm and may conveniently maintain a spacing of 3 mm or less, especially in critical areas. -cas, such as the primary vision area. The adjacent wires should not touch each other, so that the minimum spacing is governed by the accuracy with which the wires can be placed during their laying, and the degree of corrugation in use. The number of wires to be included in the arrangement for a particular windshield is selected with respect to the desired spacing of the wires; clearly, the spacing will tend to be greater towards the bottom of the windshield than towards its upper part, as a result of the divergence of the wires. Therefore, there is a corresponding tendency to reduce the density of heating energy towards the bottom corners of the windshield. The variation in the heating effect is also used by the variation in the length (and thus the resistance) of the wires. One of the advantages of the specific embodiments of the invention is that, owing to the reduced separation of the busbars, the wires are shorter (and thus in the operation are warmer) in the areas adjacent to the sides 31, 32 of the window, where the maximum spacing tends to be greater. The effects of the variation in spacing and length, therefore, compensate each other to some extent in this case. Preferably, the strength of the shorter wires is at least 50% of that of the longer wires, more preferably at least 70% and, in cases where the particular uniformity of the heating is required, is at least 80%. %. However, the placement of the busbars in a window is also affected by the configuration of the window, and the position in which the electrical connections will be made. For this reason, and also to ensure a moderately uniform heating effect in the extreme configuration windshield, it is desirable to have other techniques available with which the effect of wire spacing on the heating energy density is compensated. In the course of the development of the present invention, it was found that by varying the degree of corrugation in the wires such a technique is provided. While the presence of a small degree of undulation is desirable to alleviate adverse optical effects, the degree of undulation may be varied above this minimum level, apparently without further optical effect. This discovery can be exploited in several ways; for example, it can be used to increase the strength of a wire that would otherwise get too hot. By rolling a wire more densely, its actual length is increased, although it extends over the same separation of the busbar. Also, the degree of corrugation can be used to orient the heat output of a wire to one end, although the current flow of the wire, of course, is constant for its length. If the wire undulates more densely towards one end only, for example where there is a greater spacing from the adjacent wire, as a result of the divergence, the heat output will be correspondingly greater towards that end.

Figures 5a and 5b illustrate possible ways in which the degree of corrugation can be varied. In Figure 5a, a circular area 60 of a wire array is enlarged more than the actual size. The wires 62 extend along the divergent lines 61 which are spaced apart at intervals denoted by the arrow M and densely undulate. Area 60 may be from a bottom corner of a windshield, for example, where the wires are at a greater spacing, as a result of divergence. In Figure 5b, which is amplified to the same extent as Figure 5a, a different circular area 63 of wires is shown. Area 63 is from a different part of the arrangement, and may, for example, be the upper corner of a windshield. In Figure 5b, the wires 65 extend along diverging lines 64 and spaced at smaller intervals, denoted by the arrow N and ripple only slightly. Despite the difference in the spacing of the wire, the heating energy density in the two areas may be approximately the same as a result of the denser crimping in the area 60. In fact, the wires 65 and 62 may just be the they are represented at different points along their length, in which case these figures show how the degree of corrugation can vary by the length of the individual wires.

The degree of undulation in a particular wire can be conveniently quantified by expressing it as the difference between the length of the wire when it is straight (ie, before the ripple) and the (shorter) length over which it extends before the ripple, divided by the last length and indicating the relationship as a percentage, that is: length without corrugation - corrugated length x 100% wavy length Expressed in these terms, the degree of undulation can vary between a minimum notable level, for example 1%, or possibly a higher level, such as 3 or 5%, and a maximum, which, in practice, is determined for the ability to control the corrugated wire densely during the laying of the wire, for example 100%, preferably 50% and certainly 30%. Figure 6 shows an apparatus 90 for positioning the heating wires by straight or divergent lines in various configurations, so that, in the finished window, the array of wires extends over substantially all of the transparent portion of a window, as It was described before. The apparatus comprises a base 105, a wiring head 95 and an endless support surface 91 for one or more pieces of intercalary material 92 ("the interlayer"). The support surface 91 is provided by the curved surface of a cylindrical drum 93, which can rotate in the direction of the arrow Y about an axis of rotation, represented by the dashed line X-X. The drum 93 is driven by the belt 106 from a motor (not shown) within the base 105. The support surface 91 may be perforated and the internal air pressure of the drum 93 may be reduced to retain the interlayer in contact therewith. . The interior of the drum can, for example, be connected to an external suction element. The preferred way of providing the relative movement between the support surface 91 and the head 95 of the wiring is to mount the latter for sliding movement along one or more elongated elements, which extend in a direction parallel to the X-X axis. As shown in Figure 5, the elongated element is in the form of two rails 94, which extend parallel to the axis XX and move to one side of the drum 93. Other arrangements provide the translation movement of the wiring head They're possible. The wiring head 95 comprises devices for supplying the wire and for placing it on the interlayer 92. The wire is supplied from a reel of the same 99, which can additionally be provided with elements for unwinding the wire, by means of wire guiding elements, such as pulleys or eyelets 100 and placing them in contact with the interlayer by means of a traction roller 96. The spool and the wire guide elements are arranged to impart a slight tension to the wire, which helps in keeping the wire properly threaded and under control. Preferably, the wiring head also comprises elements for imparting corrugations to the wire for use when the interlayer for a windshield is wired, for example pinion gears or bevel gears 101, 102, through which the wire is fed to thereby undulate it. The wire guide, corrugating gears and traction rollers are mounted on an arm 107, the corrugating gears are mounted on the arm by means of an auxiliary frame 108, and the traction roller by means of a pivot hinge 109. Different ripple gears with different tooth sizes can be used to obtain different ripple levels. Also, as the wire is also preferably maintained under slight tension as it passes from the wiring head onto the drum, some of the ripple can be pulled out of the wire, varying the tension, the degree of ripple can thus be varied in operation. A preferred way of ensuring that the wire adheres to the interlayer after coming in contact with it is to heat the wire, since the interlayer becomes sticky when heated, so that the hot wire tends to adhere to the interlayer. . A preferred method of heating the wire is to pass an electric current through it, preferably the wiring head includes an element for applying a voltage across the length of the wire near where it is brought into contact with the interlayer. A convenient way to achieve this is to apply a voltage between the traction roller 96 and the corrugating gears 101, 102, by means of electrical conductors 103, 104 attached to a voltage source (not shown). The laying roller 96 can rotate about an axis 110 passing through its center, so that it can roll over the interlayer as it presses the hot wire on the surface of this interlayer. In order to accommodate changes in the direction of the diverging lines along which the wire is placed, the laying roller and part of the arm 107 may also oscillate about a second axis, substantially at right angles to the axis of the wire. rotation of the laying roller. This second axis is shown by line V-V in Figure 5, and the arrow shows the direction of oscillation. The axis VV around which the roller, articulation and arm can be rotated, is preferably oriented at substantially right angles to a tangent to the support surface 91, taken at the point at which the laying roller 96 makes contact therewith. (or with the interlayer). As an alternative to the rotation of the laying roller and part or all of the wiring head 95, just the laying roller 96 and its mounting hinge 109 can rotate by themselves. In this case, the axis of rotation is transferred to the laying roller to thus pass through the point of contact between the laying roller and the interlayer on the support surface, and the second wire guide element (not shown) it can be provided adjacent to the laying roller to assist in keeping the wire in place on the laying roller, when the last one turns. The wiring head 95 also includes the drive element 97, for example an electric motor, for propelling the wiring head back and forth along the rails 94, in a reciprocatingly sliding manner, as indicted by the arrow U. This reciprocal movement is in addition to a forward movement, indicated by the arrow T, in other words, the impulse element is capable of advancing the wiring head from one end of the drum to the other, as well as causing their reciprocal movement during the course of such advancement. The various movements that the impulse movement 97 is capable of carrying out are controlled by the control element 98, which is preferably an NC control element (numerical control) and which coordinates the reciprocal movement of the wiring head with the rotation of the drum. . Further details of the known aspects of this apparatus are available from EP 443 691. Although only one piece of the interlayer 92 is visible in Figure 5, it is convenient to be able to wiring two or more pieces at a time. Figure 7 shows two ways to do this; in Figure 7a, an arrangement is shown for wiring two pieces of interlayer 12 to obtain the prior art window of Figure 1, while in Figure 7b, an arrangement for obtaining the window of Figure 2 is shown. In each case, the endless support surface 91 of the drum has been represented as a rectangle, as if the surface had been cut, opened and flattened. When the prior art windows are manufactured (as shown in Figure 1), an important consideration is to save space on the surface of the drum, and thus the interlayer pieces 12 are placed on the drum with the curvature of all the long edges 8, 9, generally parallel, face in the same way. This allows the pieces of the interlayer to be placed as closely together as possible, enabling the size of the interlayer pieces to be wired in pairs in a given drum, to be maximized. However, this inter-layer arrangement of parts, while optimizing the use of the support surface area, is more difficult to wire with the wires extending along divergent lines that are generally parallel to the short edges. , 32 of the pieces, because the wire will have to turn two sharp corners in the area between the two pieces of the interlayer that will be realigned to the next piece. Thus, a different arrangement of the interlayer parts can be adopted, which allows the wiring to be carried out more quickly and reliably, although efficient use of space is not made on the supporting surface, one may initially be reluctant to consider it. . Figure 7b shows an arrangement of parts 92 of the interlayer on the support surface 91, which can be adopted when the parts are for the manufacture of a windshield, as illustrated in Figure 2. The longer edges 30 of the two edges Parallels of each of the two interlayer pieces are placed adjacent to each other, so that the two pieces are in an opposite relationship with a substantial mirror symmetry around a line extending halfway between the two longer edges . As seen in Figure 7b, the lines along which the wires 22 are placed are between the pieces of the interlayer, making it possible for the wire head 95 to cross directly from one piece of the interlayer onto the other , without turning any sharp corner. The same arrangement can be used to obtain the window of Figure 4. Clearly, if the support surface is sufficiently large, the number of pieces can be increased to four, or even more. The manufacture of a heated window, according to the invention, which includes the operation of the wiring apparatus 90, will now be described with particular emphasis on the novel aspects. A piece of interlayer cut to the appropriate size and configuration for the window to be manufactured, is placed on a horizontal surface in a clean environment. The lengths of the tinned copper strip are placed in position on the interlayer to serve as part of the bus bars and secured in place. The interlayer part is then transferred to the endless support surface 91 of the wiring apparatus 90, and secured in place by known conventional means, as in patent EP 443 691. A second interlayer piece can be similarly placed. on the drum, as explained above, During the laying of the wire, the drum 93 rotates and the wire head 95 advances along the rails 94, as is known from patent EP 443 691. Additionally, the reciprocal movement of the wiring head along the rails 94 coordinates with the rotation of the drum. The head can realize an integral number of reciprocal movements for each revolution of the drum, so that after each complete revolution of the drum, the wire head almost returns to its starting position, but not completely, the difference being equal to the spacing of successive turns of the wire on the drum. When the drum retains two parts of the interlayer for a windshield, as shown in Figure 7b, the movement of the wiring head is synchronized with the rotation of the drum, so that this wiring head performs a reciprocal movement for each revolution of the drum. The combination of the rotation of the drum and the movement of the wiring head results in the wire being placed along diverging lines in the interlayer part, so that, in the finished window, the arrangement extends over substantially the entire transparent portion of the window. A wire spiral is formed on the drum, but unlike the process of the prior art, it is not a helical spiral, since each turn of the spiral is distorted by the reciprocal movement of the wiring head. The amplitude of the reciprocal movement is varied according to the position of the wiring head 95 along the rails 94. For a windshield, the amplitude is greater when the wiring head is at either end of its travel along the the rails, and it's smaller at the midpoint. In fact, if the windshield is to have one or more wires placed along a straight line, such as by or parallel to its center line (ie its axis of mirror symmetry), then during the layer formation of these wires, the wiring head does not move at all reciprocally; it merely moves forward as if to space the wires. Such wires are placed substantially parallel to the edges of the drum, allowing a slight inclination due to the advance of the wiring head. the wiring head does not reciprocate during the laying of the parallel wires in the second embodiment of the invention (as shown in Figure 4) ie the wires in the central group 55. The reciprocal movement only occurs during the laying of the wires. the wires in groups 56 and 57, which are placed along diverging lines. It is possible to operate the wiring machine faster (ie a higher number of revolutions of the drum per minute) when the wiring head does not move reciprocally and thus the embodiment of Figure 4 has the advantage that can be obtained more quickly. If a window to be obtained includes several groups of wires, which extend along parallel straight lines, with other groups of wires placed along diverging lines between or adjacent to the straight wire groups, then it will be necessary that the wiring head moves reciprocally during the laying of all the wires, except those substantially parallel to the edges of the drum. However, when the total number of differently oriented lines, along which the wires are stretched, is still reduced compared to the window of Figure 2, in which each line is oriented differently, the programming of the control element It is simplified. The speed with which the wiring head slides along the shaped rails moves reciprocally during the wiring of an interlayer part varies according to the amplitude of the reciprocal movement, for a given rate of revolution of the drum. When the amplitude is greater, the wiring head has to travel a greater distance along the rails by reciprocal movement and thus slides at a correspondingly higher speed. One of the advantages of this process is that it is possible to wire pieces of the interlayer quickly and economically. Although the precise times will vary, for example according to the number of wires in the window being manufactured, the time taken to wiring one or more pieces of the interlayer (i.e. the number of pieces that can be placed on the supporting surface together) is less than 3 hours and may be less than 2 hours, or even less than 1 hour.

When the wiring is completed, the pieces of the interlayer are removed from the drum and placed flat again on a horizontal surface. The further lengths of tinned copper strips are placed on the upper part of the previously placed strips, where the wires cross, and are welded in position so that the busbar is of two-layered construction or "sandwich", as taught in patent EP 385 791, in the region where the wires make contact with the busbars. The window is completed by executing the steps that are known, and thus described only briefly. The additional electric connection elements (eg flight conductors, connectors, etc.) are joined and the wired piece of the interlayer is placed between complementary curved folds of glass material. The air is then removed from the assembly and subjected to high temperature and pressure in an autoclave, so that the material of the interlayer binds the folds of the glass material together. If the low melting point solder was previously applied to the lengths of the bus bar strip, then it melts in the autoclave and ensures a good electrical connection between the wires and the busbar.

Claims (25)

1. CLAIMS 1. An electrically heated, laminated window of at least two folds or layers of a glass material and at least one fold of interlayer material, extending between the folds of the glass material, this window includes: - an arrangement of fine wires, spaced tightly, carried by one of the folds, - electrical connection elements, to connect the arrangement to an electrical supply, and thus pass the current through the wires to heat the window, characterized because at least some of the wires extend along divergent lines, so that the array extends over substantially all of the transparent porcipn of the window. A window, as claimed in claim 1, wherein the array of wires comprises one or more groups of wires extending along straight lines, substantially parallel, and the wires adjacent to one or more groups extend along divergent lines. 3. A window, as per > claims in claim 1, in which substantially all the wires comprised in the array extend along divergent lines. 4. A window, as claimed in any of the preceding claims, in which the ratio of the maximum density of the heating energy to the minimum density of heating energy, measured in different locations on the window, is less than 2.0. 5. A window, as claimed in claim 4, wherein the ratio is less than 1.5. 6. A window, as claimed in any of the preceding claims, wherein the spacing of adjacent wires is less than 10 mm. 7. A window, as claimed in claim 6, wherein the spacing is less than 5 mm. A window, as claimed in any of the preceding claims, in which at least some of the wires are corrugated, and the degree of corrugation varies. 9. A window, as claimed in claim 8, wherein the degree of corrugation (expressed as the difference between the length of the wire when it is straight and when it is undulated, divided by the length when it is undulated, and expressed as a percentage ) varies between 1 and 100%. 10. A window, as claimed in claim 8 or claim 9, wherein the degree of corrugation is increased in a portion of the window, where the spacing of the wires is greater. A window, as claimed in any of the preceding claims, in which some of the lines, along which the wires extend, are substantially parallel to an edge of the window. A window, as claimed in any of the preceding claims, in which this window has the approximate configuration of a trapezoid, but with curved edges, and at least some of the wires extend along diverging lines in directions from the shorter of the two substantially parallel edges of the trapezoid to the longer of the two substantially parallel edges. 13. A process for manufacturing the electrically heated window, according to claim 1, part of the process is executed in an apparatus which includes an endless support surface, which can be rotated about an axis, to support the material of the interlayer, and a wiring head for supplying the wire and placing it on the interlayer material, the supporting surface and the wiring head can be moved in mutual relation, in a direction parallel to the axis, where the process includes the steps of: - securing a piece of the interlayer in a position on the support surface, - causing the support surface to rotate, - placing the wire in contact with the interlayer material by means of the wiring head, while rotating the surface of support, so that successive turns of the wire are placed on the material of the interlayer, - stop the rotation of the support surface, when the desired number of turns of wire has been placed, the process is characterized by: - cutting the spiral in a direction parallel to the axis, so that it can be opened as an arrangement of wires, generally flat, - remove the wire piece from the interlayer from the support surface and provide the wire arrangement with electrical connections and - assemble the piece of interlayer material in a laminated window. in that, while the wire is being placed, the process includes: moving the supporting surface and the wiring head back and forth in mutual relation, in a reciprocal manner, in the direction parallel to the axis, and in co-ordination with the rotation of the support surface, to provide an array of wires on the interlayer material, wherein at least one of the wires extends along diverging lines. 14. A process, as claimed in claim 13, in which the number of reciprocal movements that the wiring head performs, for each revolution of the support surface, is an integer 15. A process, as claimed in Claim 14, in which the relative reciprocal movement of the wiring head and the supporting surface are synchronized, so that the wiring head performs a reciprocal movement for each revolution of the supporting surface. 16. A process, as claimed in claim 15, wherein the piece of the interlayer material is of the approximate configuration of a trapezoid, whereby it has two generally parallel edges and two of these pieces are placed on the supporting surface , with the largest of the parallel edges, of each piece, adjacent to each other, so that they are in an opposite mirror-like relationship. 17. A process, as claimed in any of claims 13 to 16, wherein the amplitude of the reciprocal movement of the wiring head varies with its position, along the line parallel to the axis. 18. A process, as claimed in claim 17, wherein the amplitude is greater when the wiring head is at either end of its travel, relative to the interlayer material, and the amplitude is smaller when the wiring head is at the midpoint of your trip, in relation to the interlayer material. 19. A process, as claimed in any of claims 13 to 18, wherein the support surface and the wiring head move in mutual relation, so as to place the wire in a variable spacing of less than 10 mm. 20. A process, as claimed in claim 19, wherein the spacing is less than 5 mm. 21. A process, as claimed in any of claims 13 to 20, which includes crimping the wire and arranging for the variation of the degree of the corrugation in the wire placed on the interlayer material. 22. A process, as claimed in claim 21, wherein the degree of corrugation (expressed as the difference between the length of the wire when it is straight and when it is undulated, divided by its length when corrugated, and expressed as a percentage) in the wire placed on the interlayer material, varies between 1 and 50%. 23. An apparatus for forming an array of wires on a piece of interlayer material, during the manufacture of an electrically heated window, this apparatus includes an endless support surface, mounted for rotation about an axis, to support the interlayer material , and a wiring head, for supplying the wire and placing it on the interlayer material, the supporting surface and the wiring head are arranged for relative movement in a direction parallel to the axis, characterized by a pulse element, to cause that the support surface and the wiring head move reciprocally in mutual relation in said direction, and a control element, to control the impulse element to coordinate the reciprocal movement with the rotation of the support surface, so that the wiring head places the wire along diverging lines. 24. An apparatus, as claimed in claim 23, in which the wiring head is movably mounted on an elongated element ", which extends parallel to the axis, and is propelled along the elongate element of the elongated element. in a reciprocal manner by the pulse element 25. An apparatus, as claimed in claim 23 or claim 24, wherein the wiring head includes a positioning roller, which can be rotated about a first axis, to be placed contact the wire with the interlayer material, this roller is mounted for rotary movement around a second axis perpendicular to the first axis, so that the roller can rotate to follow a divergent line along which the wire is placed.