The present invention relates to a glass-ceramic panel providing a cooking surface with at least one cooking zone, which is associated with a heating element with an annular or ring-shaped lighting device and which is marked off by an optical structured cooking zone indicating device visible on the cooking surface.
The present invention also relates to a method of making the glass-ceramic panel providing the cooking surface with the at least one cooking zone, which is associated with the heating element and provided with the structured cooking zone indicating device.
Glass-ceramic panels providing cooking surfaces with individual cooking zones are established parts of modern kitchen equipment. The cooking zones typically are part of the glass-ceramic panel. However they can also be formed by separate ceramic or metallic parts, which are inserted in openings in the glass-ceramic panel. The cooking zones on the cooking surface are marked off optically in order to make the manipulations of placing cooking or roasting vessels on the respective cooking zones easier and for optimum usage of heat energy.
A number of methods have been used in order to produce this sort of cooking zone marking off device, which is designated in the following as a cooking zone indicating device.
For example, it is possible to make it by providing a suitable pattern on the cooking surface that has a different appearance than the remaining surface of the glass-ceramic panel by means of a suitable treatment during the course of the manufacture of the glass-ceramic panel.
In order to guarantee a uniform appearance for the cooking surface portions that do not operate as cooking areas, numerous optical arrangements are known for producing the cooking zone indicating device under the glass-ceramic panel. They typically have lighting elements connected with light guides in different configurations, in order both to produce a through-going and also point-illuminating cooking zone indicating device, if necessary, in combination with a residual heat indicator.
These optical display elements are associated directly with the heating element arranged under the cooking zone, which typically is formed by a radiating heated body, but can also be embodied by an inductively acting heating element. For example, EP 0 540 876 A2 describes an externally lighted glass ring formed as a light conductor, which is integrated in an insulating ring of the heating element. This illuminated glass ring indicates the circular cooking zone inside of the ring and can be used also as a residual heat indicator.
An annular region marked off on the cooking surface acting as cooking zone indicating device is described in DE 40 04 309 A1. This cooking zone indicating device marks off this annular region in contrast to other parts of the cooking surface even more strongly by design elements.
DE 197 00 551 A1 discloses an annular state indicating device in the form of a lighted ring, which is arranged around a conventional heated cooking plate embedded in a glass-ceramic panel. An annular transparent region of the glass-ceramic panel is formed by a suitable annular interruption in a non-transparent cover layer on the underside of the glass-ceramic panel.
No structure is provided in the annular indicating regions in both these known cooking zone indicating devices.
A structured lighted cooking zone indicating device is described in EP 0 746 179 A2, which is equivalent to U.S. Pat. No. 5,750,959. In this cooking zone indicating device the previously described illuminated glass ring is covered by a light-blocking or light-impermeable heat-resistant foil provided with holes and arranged between the insulating wall for the heating element and the glass-ceramic underside, in order to provide a structured cooking zone indicating device. Since this foil is preferably mica and is only structured by a comparatively difficult cutting method, e.g. laser cutting methods, this method of providing a structured lighted cooking zone indicating device is comparatively expensive.
Further correct placement of this cooking zone indicating device during assembly in the cooking area is very troublesome, time-consuming and expensive.
Structured cooking zone indicating devices are currently in fashion in comparison to through-going cooking zone indicating devices and are frequently demanded by customers.
It is an object of the present invention to provide a glass-ceramic panel of the above-described type that provides a cooking surface with at least one cooking zone, which is associated with a heating element with an annular lighting device and which is marked off optically by a structured cooking zone indicating device on the cooking surface by means of the annular lighting device, by simple means, which is more economical and faster to make than the corresponding known mica mask and which guarantees easier handling during assembly.
It is also an object of the present invention to provide a method of making the above-described glass-ceramic panel providing a cooking surface with at least one cooking zone, which is associated with a heating element having an annular lighting device and which is marked off optically by a structured cooking zone indicating device by means of the lighting device, wherein this method is more economical and faster than the current method and which guarantees easier handling during assembly.
These objects, and others that will be made more apparent hereinafter, are attained in a glass-ceramic panel providing a cooking surface with at least one cooking zone, which is associated with a heating element having an annular lighting device and which is marked off optically by a structured cooking zone indicating device by means of the annular lighting device.
According to the invention a structured light-blocking or light-impenetrable covering layer is applied directly to the underside of the glass-ceramic panel and provided with transparent regions within the structured cooking zone indicating device corresponding to or according to a desired predetermined pattern or structure for the cooking zone indicating device.
The application of the coating layer with the structured light-permeable regions on the underside of the glass-ceramic panel can occur economically and faster than the production of a mica mask. Since the structure fixed to the underside of the glass-ceramic panel corresponds to the later position of the heating element in the cooking area, the assembly of the glass-ceramic panel requires no special handling in regard to the cooking zone indicating device. Since these known predetermined light-permeable regions are provided by application of the structure pattern, the light from the annular lighting device, preferably in the form of a lighted glass ring, passes through these holes or openings in the coating layer, thus forming the cooking zone indicating device.
The method of making the glass-ceramic panel providing the cooking surface with the at least one cooking zone, which is associated with the heating body and which has the structured cooking zone indicating device, includes the steps of:
printing the coating layer made from heat-resistant light-impermeable material provided with transparent regions corresponding to the desired or predetermined structure or pattern within the cooking zone indicating device directly on the underside of the glass-ceramic panel by means of screen printing; and
drying the resulting printed glass-ceramic panel.
This screen printing technique guarantees an economical and fast application of the structured coating layer on the underside of the glass-ceramic panel with a minimum of time consumed.
Glass-ceramic cooking surfaces are known, which are light-impermeable in an unheated region from the underside. The inner regions of the cooking area are covered by illumination from the outside. For that purpose a smooth or flat organic light-impermeable enamel coating is applied to the underside of the glass-ceramic cooking surface in the appropriate regions by means of screen printing.
In the known embodiment the flat underside coating only serves for covering the unheated regions. There is no disclosure in the prior art that suggests the structured coating for designating the heated cooking zone and for conveying information regarding it to a user.