Heating pane

Description of the invention

The subject of the invention is a heating window consisting of at least a rigid glass pane, at least two current busbars of different polarity arranged approximately parallel near the edge of the heating window at different distances from the edge, and linear heating resistances electrically connected thereto.

Such characteristics are known from the German utility model DE 29606071U1, which relates to a multilayer pane with electric heating, in which there are provided heating resistances electrically mounted in parallel and embedded in a thermoplastic intermediate layer in the area of ​​the rest position of the wipers. Also in the thermoplastic intermediate layer are embedded metal foil strips acting as busbars connected to the power lines and which are electrically connected to the heating resistances. The busbars are arranged very close to each other and the heating resistances are arranged as loops between the busbars. In an embodiment, the heating resistances are arranged in the form of U-shaped loops inserted into each other in the horizontal direction and soldered to two current busbars in the form of strips. The current busbars are very close to each other and parallel to each other in the area of ​​the side edge of the windscreen. The current busbar remote from the edge of the windshield is approximately twice as long as the current busbar directly adjacent to the side edge, this current busbar is connected to the upper halves of the wire loop, and the second current busbar is connected to the lower halves of the wire loop .

From EP 0 479 154 A1, an electrically heated windscreen is known which is provided with a flat heater with two current busbars arranged at opposite edges of the upper and lower pane. The lower current busbar is provided at its center with a current lead oriented perpendicular to the edge of the pane, so in the form of T. The upper current busbar is connected to two leads which are arranged along two side edges. The two leads also run along the edge of the lower pane under the lower current busbar. The first lead crosses, under electrical insulation, the perpendicular arm T and is electrically connected to the second lead. The second lead also points to the edge of the lower pane. Due to this arrangement, you only need two electrical connection lines in the middle of the lower edge of the windshield.

The object of the invention is to make another heating pane with current busbars arranged close to the edge of the pane.

According to the invention, this object is achieved in that the busbars run to the side of the heating resistances and the heating resistances are guided from the first current busbar so that they pass over the second current busbar and are insulated from it towards the surface. the shafts and form at least one loop towards and electrically connected to the second current busbar. The characteristics set out in the dependent claims reveal advantageous improvements to the presented solution.

According to the invention, the heating resistances extend from one current busbar remote from the edge towards the surface to be heated and are guided backwards in a loop form towards the second near-edge current busbar, crossing the current busbar remote from the edge. The current busbars close to and away from the edge are arranged in the area of ​​the same edge of the pane. To avoid a short circuit, the heating resistance is electrically isolated from the current busbar in the area of ​​the crossing. The heating resistances so arranged form a heating area which extends in the area defined by the heating panel and which is supplied with electrical energy by a pair of current busbars.

The invention is not limited to just one cooking zone on the glass pane. For example, it may be expedient to provide for several cooking zones, especially for the use of different heating powers in certain zones. It is also conceivable to arrange two or more cooking zones side by side on the glass surface. Corresponding pairs of current busbars, for example for two cooking zones, may be located on the same edge of the pane, the current leads run from the upper edge for the first upper cooking zone and from the lower edge for the second lower cooking zone. If the power leads are to depart from the same edge of the pane, there must be an insulated crossing with more than one current busbar. In another embodiment, the current busbar can be used as a common ground terminal for the two heating fields. It is also possible to arrange pairs of busbars for different bays

Heating elements on different side edges. The cooking zones thus cover areas of the heating pane that are arranged at a distance from one another, are adjacent to each other or even overlap.

In another embodiment of the heating panel, the heating resistances form multiple loops before current is applied to the second busbar. Thus, the heating resistances do not extend only from the busbar remote from the edge along the width of the heating field and back to the busbar near the edge, but are guided at least again through a second loop along the width of the heating field to the pair of busbars. The number of conducting loops is therefore always odd. For a specific heating resistance, which depends on the length of the conductor, the conductor cross-section and the resistance of the actual material used, the heating power per unit area can be adjusted by selecting the number of loops, regardless of the geometric dimensions of the heated surface. Using more loops has the added advantage that the number of electrical connections to be made by soldering is smaller than in a system where the heating resistances form one loop at a time. You can save on labor in this way.

The heating panes according to the invention can be monolithic panes in which the heating resistances are arranged on one basic surface. A known example of this type of glazing are car windows or toughened safety glass windows that are equipped with heating resistances made of conductive paint. Typically, for this purpose, a ceramic paste with a high proportion of conductive silver is applied to the surface of the pane by screen printing in the desired form of heating conductors and conductive rails and then fired. The conductive rail remote from the edge may be insulated from the conductor that crosses it by means of a dielectric paint. For this purpose, the operation of printing the heating resistances and busbars should be divided into two stages. In a first step, the current busbar remote from the edge is printed with the heating resistances, and the return arm of the heater loop terminates slightly in front of the current busbar remote from the edge. In a second step, where an insulating layer, for example a dielectric burn-in paint, is laid on the conductive rail. Finally, the current busbar close to the edge is printed while connecting wires are applied to the open ends of the heating wire loop. The connecting wires cross in an insulated manner with the busbar at a distance from the edge and complete the electric circuit of each individual heating resistance loop.

The sequence of the conductive and insulating layers is known from DE 39 11 178 C2. In this case, the output conductor of the antenna is made in the shape of a pseudo coaxial conductor with strong shielding.

In addition to monolithic heating panes, the invention also includes laminated glass heating panes which consist of at least two rigid panes joined together by gluing using an interlayer. In this case, the heating resistances are preferably made of wires which are embedded in the intermediate layer. It is, however, also possible to make a multilayer heating pane according to the invention by using the monolithic heating pane described above to make an individual pane. The surface with heating resistances can be placed both on the inside and outside of the multi-layer pane. Individual panes can be made of glass or plastic. The laminated panes may be composed of two or more panes of identical or different materials. Typically, an individual thermoplastic adhesive film, for example made of polyvinyl butyral, is used as an intermediate layer connecting the two panes.

Current busbars in laminated glass panes, which can be heated by means of heating resistances embedded in an intermediate layer, are usually made of flat tinned copper foil. There are also versions which are furthermore equipped with a polyimide insulation jacket. With such a foil strip as the current busbar spaced to the edge, the multi-layer pane according to the invention can be easily made and the insulation removed only where the heating resistances should be electrically connected to the current busbar. The current busbar close to the edge can be placed without an insulating cover or, in the case of using insulated metal foil tape, the insulation can also be removed at the points of connection to the heating resistances.

In order to ensure the visibility disturbed as little as possible by the multi-layer pane, the heating wires should have a relatively small diameter of about 20 μm to 100 μm. Tungsten heating wires have proved to be suitable for this purpose. However, copper wires, which may be provided with a layer of dark matt paint to avoid metal glare, may also be used in the multi-layer glazing of the present invention. Multi-layer conductors are also known which have a mechanically strong core surrounded by good metal

A conductor and / or easy to solder. The choice of wire material and / or wire diameter is made depending on the mechanical and electrical requirements of the desired heating field.

When the wires are straight and parallel with a small distance between them, diffraction of the incident light can occur under unfavorable circumstances. These phenomena can be avoided by providing some irregularity in the alignment of the heating wires, for example a kind of wave on the heating wires.

When the current busbars are arranged only close to one side edge, the multi-layer glazing can be used, for example, as a multi-layer heating window with free edges, so for example as a side window that can be opened in a car. The current busbars can be placed inside the door channels and masked by the bodywork or sealing elements.

Other details and advantages of the invention will be disclosed in the following detailed description when combined with the accompanying drawings of a non-limiting embodiment of the invention.

The drawings are simplified, not to scale.

Figure 1 shows a multi-layer pane according to the invention as a side window for a motor vehicle in a front view;

Figure 2 shows a section of the side pane of Figure 1 along line II.

The multi-layer pane 1 of FIG. 1 is provided with black lacquered copper heating wires 2 which are arranged inside the multi-layer pane 1 and whose diameter is approximately 85 µm. The heating wires extend in the form of a loop between the lower edge of the side pane 1 in the installed position and its upper edge. For power supply, a first end of each loop is connected to the current busbar 3 and the other end of the loop is connected to the current busbar 4. On the way to the current busbar 4, the heating wires 2 should cross the current busbar 3 in areas 31. In these areas 31, the heating wires 2 are electrically insulated with respect to the current busbar 3. The two current busbars 3 and 4 are as heating wires 2, arranged inside the multi-layer pane 1 and connected to the two poles of the on-board electrical network. There is therefore usually a voltage of 12 V between the current busbars. The supplied current corresponds to the required heating power per unit area, so the electrical resistance of the heating wires 2 as well as the distances between them must be taken into account. For a homogeneous distribution of the heating power on the surface of the multi-layer pane 1, the lengths of the wires of the individual loops should be equal, with the remaining properties of the wires being the same. For the multi-layer glazing shown in Fig. 1, where some of the lengths lie in the sloped edge area, so at a lower height, there are five changes of direction in the loop, while the other lengths of the wire only change direction three times.

The current busbars 3 and 4 are led outside the multi-layer pane 1 to the side and connected in a manner known per se to the on-board network. For the vehicle side window shown here, a portion adjacent to the lower edge of the window that houses the current busbars is positioned inside the door channel and is masked by the car body. The masking normally used for current busbars with a layer of opaque paint is not needed in this case.

Figure 2 shows a section of the side pane of Figure 1 along line II. The multi-layer pane 1 consists of two individual panes 11 and 12 with a thickness of about 2.1 mm, which are connected to each other in a known manner by gluing by means of a thermoplastic intermediate layer 13 made of polyvinyl butyral. Before the assembly operation, the heating wires 2 and the current busbars 3 and 4 are embedded in the surface of the intermediate layer 13 using a process also known.

The current busbar 4 is made of tin-plated copper foil and is mechanically and electrically connected to the heating conductor 2 by soldering. However, for the current busbar 3, the tin-plated copper foil 32 is surrounded on all sides by a polyimide insulating sheath 33, the heating conductor 2 can therefore safely cross the current busbar 3, not without electrical contact therewith. At the points where the heating conductor 2 is electrically connected to the current busbar 3, the insulating sheath should be removed before being placed in the thermoplastic intermediate layer.