Patent Application
20050095404
1. Field of the Invention
The present invention relates to a method for making a knobbed plate from glass or a glass ceramic material, the knobbed plate made thereby and a tool used for that purpose. The knobbed plate can be used in a baking oven for thermal decoupling of the heated inner chamber from the colder exterior region (kitchen), and also for killing germs in air conditioning units.
2. Description of the Related Art
Different methods are available in the prior art for providing a glass plate with holes or cavities. It is possible to provide a glass plate with holes with conventional drills using a diamond drill bit.
Ultrasonic lapping is a generally known method for introducing only holes or cavities into a glass plate, which have a size of at maximum 25.4 cm (10 inches). The cavity size is very limited in this lapping method.
Generally sand blasting can introduce holes or cavities into a glass plate. Similarly laser methods can be used to produce individual holes of small diameter in glass.
It is an object of the present invention to provide a method for rapidly manufacturing a glass or glass ceramic plate with a large number of holes or cavities of any arbitrarily selected shape.
It is also an object of the present invention to provide a knobbed glass plate and a method of making it.
It is an additional object of the present invention to provide a forming tool from making the knobbed glass plate according to the invention.
According to the present invention the technical problems related to providing the method for rapidly manufacturing the glass or glass ceramic plate of the above-described type are solved by a method comprising:
The making of the plate occurs by placing the plate on a planar or flat support and by heating the support and plate to a sufficiently high temperature so that a plastic deformation of the plate occurs. If the support has knob-shaped elevations or projections, glass or glass ceramic material fills the spatial regions between the elevations or projections by viscous flow. Alternatively if the support has knob-shaped depressions or cavities, the glass or glass ceramic material heated to a sufficiently high temperature flows into these depressions or cavities. The surface of the support is mapped on the plate in this way. In this sense the support acts like a photographic negative and the plate as the positive (the photo).
The flat support has knob-like elevations or projections or depressions or cavities. The plate is provided with knobs at the positions on the support where the elevations/projections or depressions/cavities are located.
The term “knob” in the sense of the present invention means a displacement of material in a direction substantially perpendicular to the surface of the plate, which is hump-shaped. An observer would view the displacement of material as an elevation or projection with a generally arbitrarily shaped surface when viewing the plate from one side of the plate and as a cavity or recess from the other side of the plate.
To obtain exact knob geometry in the glass or glass ceramic plate the support itself should experience no temperature-related deformation. In other words, it should be sufficiently form stable at high temperature. Moreover the glass should experience only slight adherence to the support, so that the plate can be released from the support. A chromium-nickel steel, especially that with material number 1.4122 and carbon content between 0.20 and 0.25%, has proven satisfactory in this sense. Best results are obtained with additional tempering of the chromium-nickel-steel to 800 to 1000 N/m2.
In order to guarantee slight adherence of the plate on the support, a separating agent can be used. Good results are obtained using boron nitride BN A 01 as separating agent for, among others, chromium-nickel steel.
It suffices or the method when the plate and the support are jointly heated so that they both exceed the transformation temperature. It is sufficient when the plate in a still heated state is placed on the support so that they can be subsequently heated jointly over the transformation temperature.
The speed of the manufacturing method generally is limited by the condition that not only the plate but also the support must be heated. For this reason the method is more rapid when the plate is placed on a pre-heated support.
In order to improve the filling of all spatial regions of the support between the knob-shaped elevations or the flowing of material into the knob-shaped depressions, a waiting time until cooling can be maintained after exceeding a set temperature above the transformation temperature. The glass needs a certain time in order to reach all depressions between knob-shaped elevations/projections or depressions/cavities. The maintaining of a waiting time improves the exact mapping of the support structure on the glass or glass ceramic plate.
In order to guarantee an exact shaping of the glass or glass ceramic plate by the support surface it is important that the glass or glass ceramic completely fill all spatial regions of the support between the knob-shaped elevations. In order to improve the filling of these regions of the support they can be acted on with suction or vacuum. The low pressure in these regions can be in a range of about 0.4 bar to about 0.6 bar. A suction or vacuum can act on the depressions In the case of knob-shaped depressions. In this case the plate material is the glass or glass ceramic material of the plate will be drawn into the depressions.
The low pressure can be produced in the support by equipping the support with through-going openings that connect the regions between the knob-shaped elevations or the knob-shaped depressions on one side of the plate with the other side of the plate and by producing a low pressure on the other side of the plate. In this way the glass or glass ceramic material will be drawn into the depressions or the regions between the elevations by the suction or low pressure on the rear or other side of the plate. In this way the material experiences a force in the direction of the support between the knob-shaped elevations or into the knob-shaped depressions, which leads to an improved filling of these regions with the glass or glass ceramic material.
In order to guarantee the exact mapping of the glass or glass ceramic material with the support surface additionally the plate can be acted on with a pressure. In this way the plate material is forced into regions between the knob-shaped elevations or into the depressions of the support.
In some embodiments the knobs of the cooled plate can be partially ground or sanded. In this way a knob with a through-going opening or a hole is produced. The grinding or sanding can take place by means of a grinding plate, diamond grinding disk, CNC-grinding machine with a diamond tool, or by means of a laser. When the grinding process is performed parallel to the plate surface openings with identical edge- shape or contour are produced in equal knobs.
A glass or glass ceramic plate with knobs is produced by the method according to the invention and is part of the present invention. The knobs are provided with arbitrary surfaces in their basic form and are hollow. However the knobs can have an open structure on both side. In this latter case the knobs have a through-going opening. The shape of the opening depends on the geometric shape of the knob and on the manner in which the top parts of the knobs are ground off. In the grinding process a part of the knob is abraded or ground off. Different shaped knobs, if necessary with different opening shapes, can be provided in a plate.
The glass or glass ceramic plates that can be equipped with knobs have a thickness of about 0.5 mm to about 60 mm. Good results were obtained when the knob-shaped elevations were slightly greater than the plate thickness, for example by about {fraction (1/10)} mm.
The openings produced by grinding or abrading away a part of the knobs have a diameter of about 0.5 mm to 100 mm. The spatial form of the knobs can be such that they have a variable height. The knobs can have a circular or polygonal edge contour when the plate is observed. The knobs can further be polyhedral or truncated cone-shaped. In the case of truncated cone-shaped knobs it has proven suitable that the outer surface of knob is inclined at an angle from about 20° to about 85° relative to the base surface. For larger angles the surface area of an elevation of the support increases, which makes release of the glass or glass ceramic material from the support increasingly difficult.
From the foregoing disclosure it would seem that the glass or glass ceramic plate that is provided with the knobs should be planar in its basic form. However it is also possible to provide curved glass or glass ceramic plates with these sorts of knobs.
The support must be made from a material that has a stable form at high temperature in order to make the knobbed glass or glass ceramic plate. Materials which are suitable include chromium-nickel steel. The flat or planar tool is provided with through-going openings between the knob-shaped elevations to guarantee an exactly shaped mapping surface of the support.
In the method according to the invention a large number of openings can be provided in a comparatively short time, for example 1000 openings in a large plate of for example 1500 mm×1500 mm in size. The time required to provide the openings in a plate is only about 50 min.
Furthermore the knobbed plate can be coated, for example by means of a sputtering method with a metal oxide layer (e.g. such as a gold, chromium or titanium layer). On account of its large glass surface area the plate can then be provide with a suitable germ killing coating of the type for cleaning air in an air conditioner.
The objects, features and advantages of the invention will now be illustrated in more detail with the aid of the following description of the preferred embodiments, with reference to the accompanying figures in which:
a is a side view of the portion of the knobbed glass plate shown in
b is a top plan view of the portion of knobbed glass plate with the tops ground off the knobs, as shown in
A support plate 2 for use in the method of making the knobbed glass or glass ceramic plate P is shown in
In the method of making the knobbed glass plate a 2 mm thick and planar soda lime glass plate or panel with a transformation temperature of 630° C. is placed in a cold state on a support plate 2 made from chromium-nickel steel, which has been pre-heated to a temperature of 450° C. The support has truncated cone-shaped knobs with a height of 5 mm and a cone angle of 45°. The support and plate are introduced into an oven together and brought to a final temperature of 740° C. Then they are left in the oven for about 10 minutes. Subsequently a pre-defined cooling process takes place, in order to reduce thermal stresses in the glass.
The knobbed soda lime glass plate P made with the support 2 by this method is shown in a side view in
The round or circular edge contour of the openings O is clearly shown in the top plan view of
The knobbed glass plate is suitable for use in a baking oven for thermal decoupling of hot and less hot spatial regions, especially for decoupling the hot interior region of the oven from a kitchen area outside of the oven.
The disclosure in German Patent Application 103 51 718.9-45 of Oct. 31, 2003 is incorporated here by reference. This German Patent Application describes the invention described hereinabove and claimed in the claims appended hereinbelow and provides the basis for a claim of priority for the instant invention under 35 U.S.C. 119.
While the invention has been illustrated and described as embodied in a method of making a knobbed glass or glass ceramic plate, knobbed plate made thereby and tool for making the plate, it is not intended to be limited to the details shown, since various modifications and changes may be made without departing in any way from the spirit of the present invention.
Without further analysis, the foregoing will so fully reveal the gist of the present invention that others can, by applying current knowledge, readily adapt it for various applications without omitting features that, from the standpoint of prior art, fairly constitute essential characteristics of the generic or specific aspects of this invention.
What is claimed is new and is set forth in the following appended claims.
| Number | Date | Country | Kind |
|---|---|---|---|
| 103 51 718.9 | Oct 2003 | DE | national |
