Electric heating – Heating devices – Combined with diverse-type art device
Reexamination Certificate
2002-01-18
2003-12-09
Jeffery, John A. (Department: 3742)
Electric heating
Heating devices
Combined with diverse-type art device
C052S171200, C219S522000, C219S486000
Reexamination Certificate
active
06660968
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention concerns an electrically heated glass pane, in particular for a motor vehicle.
2. Discussion of Background
The heated glass panes used in motor vehicles are generally composed of at least a glass sheet provided on one of its faces with a heating network consisting of strips of resistance connected in parallel. This network generally enables the deicing or demisting of the glass pane. The strips of resistance may have a constant cross section, but it is also known to have their width vary from one end to the other of the glass pane in order to have intensified heating areas and preferential fields of view. In all these glass panes, the same nominal power is applied to all the resistance strips for the duration necessary for deicing or demisting the glass pane.
The heating network of such glass panes may also include several heating areas operating sequentially and in cycles (see U.S. Pat. No. 3,982,092). The heating of each area is controlled by means of a differential thermostat functioning over a narrow temperature range, for example 10 to 30° C. With this type of glass pane, we cannot, however, adapt the duration or power of heating to outside conditions such as temperature, the thickness of the ice or the amount of mist. What happens is that the first area is heated as soon as the outside temperature is less than the lower temperature (10° C.) of the thermostat, and the heating of this area stops, to pass on to the next area, only when the temperature reaches the upper temperature (30° C.) of the thermostat.
SUMMARY OF THE INVENTION
In the motor vehicle sector, the tendency is towards the multiplication of powered devices of all kinds (seat adjustment, door locks, electric windows, wing mirrors, etc.). For this purpose, we seek to reduce the energy consumption of electrically heated glass panes by reducing the power consumed or the duration of heating without affecting the efficiency of the deicing or demisting.
In order to achieve this one can, as it is disclosed in U.S. Pat. No. 5,496,986, provide the glass pane with an electronic device which permits to control the external temperature and to apply the minimal power necessary to heat the glass surface.
The purpose of the present invention is therefore to propose an economic heated glass pane, especially a heated glass pane that can be used advantageously as a rear window in a motor vehicle, said glass pane being used for demisting or efficient deicing with a reduced duration of heating and/or a gain in the power consumed.
This purpose is achieved by the glass pane according to the invention comprising at least a glass sheet provided with heating strips powered by collectors, the heating strips being divided in groups, the power supply to the different groups being provided sequentially, each group being powered once per sequence, the supply being provided by a device equipped with means enabling it to measure the outside temperature and the temperature of the outer surface of the glass, to determine a minimum heating time for each group according to said outside temperature, and to maintain the heating in said group as long as the outer surface temperature of the glass opposite said group is not higher than the melting point of ice.
The glass pane according to the invention is preferentially a motor vehicle rear window, but it can also be a windscreen or any other glass pane for the motor vehicle or a glass pane used in applications other than a motor vehicle. This glass pane may comprise one or more sheets of glass and possibly one or more plastic sheets. In most cases, it is a monolithic glass pane comprising a tempered sheet of glass or, possibly, it is a laminated glass pane comprising at least two sheets of glass generated by a plastic insert or an armored glass pane further comprising at least a sheet having the required armoring properties. The glass pane may also be convex. The heating strips are located on at least one face (and generally only on one face) of a sheet of glass the glass pane and/or, where appropriate, are located on or are embedded in a plastic insert of the glass pane.
The heating strips are generally electrically conductive transparent layers with a suitable resistance (generally in the region of 0.1 &OHgr; and capable of going up to 200 &OHgr;), for example a layer containing a metal oxide such as tin oxide, or are metal conductor wires of suitable resistivity, for example thin tungsten wires, or are wires with an electrically conductive composition (generally enamel) also with a suitable resistivity (i.e. generally in the region of a few &mgr;&OHgr;. cm, able to go up to 50 &mgr;&OHgr;.cm in the present invention). The conductive compositions used are generally in the form of a suspension of metallic silver and glass frit in an organic binder, and are generally deposited by screen printing or any other equivalent technique before being dried and baked at high temperature (for example during glass bending or tempering treatment) on the glass pane. Such wires may also be reinforced subsequently, by an electrolytic process or by metal deposition not using electrical current to achieve the resistance value wanted. Preferably screen-printed wires are used for glass panes formed of a tempered sheet of glass and for laminated glass panes, and tungsten wires are used for laminated glass panes.
The heating strips may be wavy or straight and are preferably narrow strips, for example approximately 10 mm in the motor vehicle sector and up to 100 mm for glass panes used in building for the conductive layers, in the region of 0.2 to 0.8 mm for screen-printed wires and in the region of 25 to 50 &mgr;m for tungsten wires. Also preferably, the strips are arranged with a gap between neighboring strips that may attain several centimeters. Advantageously, these strips are also arranged horizontally (generally along the larger dimension of the glass pane) in the position of use of the glass pane, especially for a rear window, and are isoresistant, i.e. they have constant resistivity over their whole length. For example, the strips are transparent layers or screen-printed wires uniform both in terms of conductive composition and thickness, or are metal wires of constant cross section.
The heating strips, at the two lateral edges of the glass pane, are connected by electrical connection elements to the current supply cables, these elements being called connectors or current supply terminals or collector strips or “busbars”. In the present invention, these elements are referred to hereafter more simply as “collectors”. These collectors may come, for example, in the form of metal strips or sections (for example in the form of tinned copper tabs) attached for example by welding onto the glass pane. Each separately powered group has its own collectors. These may be obtained by splitting the normal collecting strips into several parts separated by insulators or several collectors may be used, the number of collectors or separate parts in the collectors depending on the number of groups to be powered.
According to the definition of the invention, power is supplied sequentially, each group being powered by its own collectors and each group being powered only once per sequence. “Sequence” here is understood to mean the operation consisting in heating each group of heating strips just once in a specified order with a view to achieving the deicing and/or demisting of the glass pane. The sequential power supply of the groups is controlled by a device equipped with means for establishing the power supply sequence, i.e. the order in which the different groups are powered one after the other, and for determining the duration of heating of each of these groups. For this purpose, an electronic control box or a control device may be used connected to the collectors comprising means of measuring the outside temperature and the surface temperature of the glass, the control box or device being programmed to associate a heating time or minimum power supply tim
Letemps Bernard
Mottelet Beatrice
Jeffery John A.
Oblon & Spivak, McClelland, Maier & Neustadt P.C.
Saint-Gobain Glass France
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