EP2410244B1

EP2410244B1 - Fireplace with heat-resistant glass and transparent supporting edge

Info

Publication number: EP2410244B1
Application number: EP11005931.8A
Authority: EP
Inventors: Karl De Baenst
Original assignee: Debatra bvba
Current assignee: Debatra bvba
Priority date: 2010-07-23
Filing date: 2011-07-20
Publication date: 2018-09-12
Anticipated expiration: 2031-07-20
Also published as: SI2410244T1; EP2410244A1; BE1019430A5

Description

The present invention relates to a built-in gas fireplace, comprising a combustion chamber which is formed in a housing and which can be sealed off by a removable sealing element. The invention relates in particular to a decorative fireplace, comprising a combustion chamber which is formed in a housing and which can be sealed off virtually hermetically by means of a removable sealing element. The invention relates more particularly to a built-in gas fireplace of the closed or hermetic type.
Originally, all decorative fireplaces were open fireplaces which are very attractive due to the fact that they are open. However, as a result of the increase in energy prices and their limited efficiency, decorative fireplaces had to become more economical and efficient, which has resulted in fireplaces which can be sealed off by means of a closure element becoming increasingly popular. Usually, a sealing element made from heat-resistant glass is chosen which is attached to or clamped in a metal frame, also referred to as a window frame or frame.
There are hundreds of models which are commercially available on the market, using wood, coal or gas as fuel. In connection with the discharge of flue gas, decorative fireplaces using wood or coal are always provided with a chimney. Gas-fired built-in fireplaces may optionally be provided with a chimney, but can also be designed as a hermetic unit. In the latter case, no combustion air is removed from the room. A hermetic unit is provided with a duct for the supply of fresh air and a duct for the discharge of flue gases. Such a system is referred to and known as a balanced flue system. Such systems are compulsory in newly built dwellings with mechanical ventilation. As a result thereof, it is important that the sealing element seals off the combustion chamber perfectly.
A large number of the known devices are provided with a windowed door which use a frame as a sealing element and which are installed to be flush with the wall. Some are installed in such a manner that the windowed door is recessed. The sealing element, in particular the windowed door, has a frame or edge which serves to change the position of the closure of the combustion chamber from an open to a closed position and vice versa, mainly so that the rear of the windowed door can be cleaned. In this case, the known devices can be provided with a means which makes it possible, on the one hand, to open the windowed door outwards, for example by fitting hinges on the side so that the windowed doors can be swung open to the left or to the right or, on the other hand, to push the windowed door upwards, for example by providing a lift system or a combination of both systems.
For aesthetic reasons, modern architecture, on the one hand, wants to create as large a fire as possible for the user and at the same time strives to keep the resulting assembly simple and sleek. In this context, the presence or visibility of the frame is regarded as being annoying. The Applicant has already filed a patent application BE 1 015 920 in which the frame is no longer visible due to the fact that the window frame is attached on the inside of the fireplace. These fireplaces are commercially available under the brand names Cosyflame Invento and Cosyflame Rotario. With these embodiments, the window frame is obviously larger than the opening of the fireplace, as a result of which this solution has its limitations.
Such a fireplace in which the window glass is pressed (fitted) against the peripheral edges of a metal frame is described, inter alia, in German patent publication DE 34 08 483 A1 . This patent publication describes a decorative fireplace for burning solid fuels in which the window glass can be moved up and down in the window frame in order thus to create an adjustable opening on the bottom side via which air can enter the combustion chamber and thus to control the burning of the wood. In order to prevent too much air from entering the combustion chamber via the top side during the up and down movement, a plate of metal or transparent material is provided at the location of the top side of the decorative fireplace which slightly restricts the influx of air at the top.
Recently, fireplaces have been introduced which are provided with sealing elements, one or more sides of which have no frame and which therefore only consist of glass. In this case, use is made of strong glass with polished edges. However, this solution is only feasible for gas-fired devices, where the sealing element has to be opened for maintenance only on sporadic occasions. With such fireplaces, the glass is pressed against the peripheral edges of the housing in various mechanical ways, often with a seal in between, in order to seal the assembly virtually hermetically. This solution produces a satisfactory result, but the seal and/or the peripheral edges of the housing remain visible through the glass. To this end, a more or less non-transparent, dark strip (screening) will often be printed on the outer edges of the glass, which is less aesthetically pleasing. Various ways have been developed to hide the window frame or the dark strip on one or more sides, but there remains at least one side where this cannot be achieved as it has to be possible to remove the glass for maintenance purposes.
It is an object of the present invention to provide a decorative fireplace in which the frame (border) around the glass or the mounting of the glass is no longer visible and in which it is still possible to remove the sealing element in a relatively simple manner from the decorative fireplace. Such decorative fireplaces are known as frameless decorative fireplaces.
The object of the invention is achieved by providing a decorative fireplace, comprising a combustion chamber which is formed in a housing and can be sealed by a removable sealing element in which at least one of the peripheral edges of said housing comprises a transparent supporting edge against which the sealing element is pressed. Preferably, at least two of the peripheral edges of said housing comprise a transparent supporting edge against which the sealing element is pressed. In particular, both upright (vertical) peripheral edges of the housing comprise such a transparent supporting edge. Said sealing element is made from heat-resistant glass.
Said decorative fireplace is a built-in gas fireplace of the closed type.
Due to the fact that the supporting edge, against which the sealing element is pressed (bears), is also made from a transparent material, preferably heat-resistant glass or a similar material, this supporting edge is completely inconspicuous and this makes it possible to install a decorative fireplace in a very 'minimalistic' or 'sleek' way. With a decorative fireplace which is designed in such a manner, virtually only the flames will be visible and no annoying edges and/or frames will distract the eye.
In a preferred embodiment of the decorative fireplace according to the invention, the right-hand and the left-hand peripheral edge comprise a transparent supporting edge against which the sealing element is pressed. More preferably, the top and bottom peripheral edge also comprise such a transparent supporting edge.
According to a first preferred embodiment, the transparent supporting edge is mechanically connected to the housing. The mechanical connection is preferably achieved by clamping profiles or a bolt/nut connection.
With devices of the hermetic type, it is very important that the combustion chamber is properly sealed and therefore, said supporting edge can be moved counter to a spring force in another preferred embodiment of the decorative fireplace according to the invention. In this way, uneven structures can be absorbed by the sealing element (glass plates are hardly ever perfectly flat) and thus it becomes possible to hermetically seal the combustion chamber by means of the sealing element even more effectively. In a preferred embodiment, a rubber seal is provided between the transparent supporting edge and the housing in order to arrange the supporting edge in a resilient manner.
The abovementioned supporting edge preferably has a width of between 15 and 100 mm and a thickness of between 3 and 8 mm. In particular, a supporting edge having a width of 25 mm and a thickness of 5 mm is preferred.
In a particular embodiment of the decorative fireplace according to the invention, said decorative fireplace comprises a clamping means in order to clamp the sealing element against the transparent supporting edge. The sealing element can be (resiliently) pressed against the one or more transparent supporting edges in different ways. For example by means of:

a metal profile provided with tightening screws or another clamping means;
a sealing strip made from fibreglass or other heat-resistant fibre;
a hollow or solid rubber profile.

In a more particular embodiment of the decorative fireplace according to the invention, said decorative fireplace furthermore comprises a supporting profile, as a result of which a receiving space is formed for the edge of the sealing element. Preferably, such a supporting profile is provided on two or three sides of the periphery of the housing, so that a respective receiving space is provided for two or three edges of the sealing element, in particular the top edge and the two side edges.
According to an advantageous embodiment of the decorative fireplace according to the invention, said receiving space is designed such that the sealing element is displaceable therein when the sealing element is being installed or removed. Not every receiving space is designed in this way, as a great deal depends on the number of supporting edges for the sealing element and the configuration thereof.
In a more advantageous embodiment of the decorative fireplace, said clamping means is resilient and provided in said receiving space in order to press the sealing element against the glass support edge with a force which can be moved counter to a spring force. To this end, the clamping means comprises a preferably resilient core material provided with a woven or knitted heat-resistant casing. The core material may, for example, be made of spring steel or resilient expanded metal.
A more detailed description of the built-in fireplace according to the invention is given below in order to further explain the properties of the present invention and to indicate the additional advantages and features thereof. It will be clear that nothing in the following description can be interpreted as a limitation of the scope of the present invention which is defined in the claims.
Reference numerals are used in this description to refer to the attached drawings, in which:

- Fig. 1 shows a view of a decorative fireplace according to the invention in which both upright peripheral edges of the housing are provided with a glass supporting edge;
- Fig. 2 shows a view of a decorative fireplace according to the invention in which all peripheral edges of the housing are provided with a glass supporting edge;
- Fig. 3 shows a perspective view of a non-fitted decorative fireplace according to the invention in which both upright peripheral edges of the housing are provided with a glass supporting edge;
- Fig. 4 shows a view of the decorative fireplace from Fig. 3 fitted in a mantelpiece with depth frame;
- Fig. 5 shows a decorative fireplace according to the invention provided with only one glass supporting edge, with Fig. 5 . 1 showing a detail view of the bottom peripheral edge of the housing, Fig. 5 . 2 showing a detail view of the top peripheral edge of the housing which is provided with the glass supporting edge, and Fig. 5 . 3 showing a detail view of an upright peripheral edge of the housing;
- Fig. 6 shows how a sealing element is inserted in the decorative fireplace shown in Fig. 5 ;
- Fig. 7 shows how the sealing element is clamped against a glass supporting edge by means of a resilient rubber profile;
- Fig. 8 shows how the sealing element is clamped against a glass supporting edge by means of a clamping means comprising a resilient core material provided with a woven heat-resistant casing;
- Fig. 9 shows a decorative fireplace according to the invention in which both upright peripheral edges are provided with a glass supporting edge, with Fig. 9 . 1 showing a detail view of the bottom peripheral edge of the housing, Fig. 9 . 2 showing a detail view of the top peripheral edge of the housing, and Fig. 9 . 3 showing a detail view of an upright peripheral edge of the housing which is provided with the glass supporting edge;
- Fig. 10 shows how a sealing element is inserted in the decorative fireplace shown in Fig. 9 ;
- Fig. 11 shows a decorative fireplace according to the invention in which both upright peripheral edges and the top peripheral edge are provided with a glass supporting edge, with Fig. 11 . 1 showing a detail view of the bottom peripheral edge of the housing, Fig. 11 . 2 showing a detail view of an upright peripheral edge of the housing which is provided with the glass supporting edge, and Fig. 11 . 3 showing a detail view of the top peripheral edge of the housing which is provided with the glass supporting edge;
- Fig. 12 shows how a sealing element is inserted in the decorative fireplace shown in Fig. 11 ;
- Fig. 13 shows a detail view of both upright peripheral edges of a housing of a specific embodiment of a decorative fireplace according to the invention in which the glass supporting edge is arranged so that it can be displaced counter to a spring force.

The present invention relates to a decorative fireplace (1) which comprises a combustion chamber (3) which is formed in a housing (2) and which can be hermetically sealed by a removable sealing element (4). The sealing element (4) is made from heat-resistant glass which is adapted to the size of the opening of the fireplace. The glass from which the sealing element (4) is made has a standard thickness of 4 to 5 mm, but other values are also possible.
The present invention makes it possible to install such a decorative fireplace (1) in a very 'minimalistic' or 'sleek' manner. With a decorative fireplace which is designed in this way, virtually only the flames will be visible and no annoying edges and/or frames will distract the eye.
As is shown in Figs. 1 and 2, this is achieved by providing at least one of the upright peripheral edges of the housing (2) with a transparent supporting edge (5). Due to the fact that the sealing element (4) is pressed against a transparent supporting edge (5), this support is hardly visible to someone who is looking at the decorative fireplace (1); virtually only the flames are visible and no annoying edges and/or frames will distract the eye, as can be seen in Fig. 4. Fig. 4 illustrates the decorative fireplace (1) shown in Fig. 3, with both upright peripheral edges of the housing (2) being provided with a transparent (glass) supporting edge (5), fitted into a mantelpiece (14) with depth frame. As can be seen from this figure, no edges or parts of the frame are visible anymore.
In order to offer sufficient support for the sealing element (4), each peripheral edge (see for example Fig. 2) is preferably provided with a transparent supporting edge (5). However, providing only the two upright peripheral edges (see for example Fig. 1), three or only one peripheral edge with such a transparent supporting edge (5) also falls within the scope of protection of this patent application.
The transparent supporting edge (5) is preferably made from heat-resistant glass or a similar material and is attached to the inside of the housing (2), at the location of the peripheral edge, via a mechanical connecting means, such as for example screws, bolts and nuts.
The transparent supporting edge (5) has a standard width of approximately 25 mm and a thickness of approximately 5 mm. Obviously, these values can be changed depending on the size of the opening of the fireplace.
The sealing element (4) is pressed against one or more supporting edges (5), either with or without a transparent seal in between.
Due to the fact that the sealing element (4) and the supporting edge (5) are both sufficiently flat, they will fit tightly against each other and the seal without a sealing in between suffices for use in a gas fireplace, as a gas fireplace has to be airtight and not watertight. Tests carried out by the patent proprietor and the testing body Technigaz have shown that, at a pressure of 10 Pascal, the leakage rate is negligible and well within the permitted values, provided that both elements (4 and 5) are firmly pressed against each other.
In order to press (clamp) both elements, in particular the sealing element (4) and the transparent supporting edge (5), firmly against one another, said decorative fireplace (1) comprises a so-called clamping means (6) which is designed to clamp (press) the sealing element (4) against the transparent supporting edge (5).
The sealing element (4) can be pressed against the one or more supporting edges (5), and any metal peripheral edges which may be present in various ways, for example by means of:

a metal profile with tightening screws or other pressure means;
a sealing strip made of glass fibre or another heat-resistant fibre;
a hollow or solid rubber profile;
some form of coiled spring or other spring, with or without a casing;
a tubular annular spring made of spring steel or woven bronze, with or without a casing.

Preferably, however, use is made of a clamping means (6) which comprises a resilient core material (9) provided with a woven heat-resistant casing (10) (see Fig. 8). The clamping means (6) is resilient and is partly provided in a receiving space (8), formed between a supporting profile (7) and the sealing element (4). The supporting profile (7) is attached to the housing (2) as can be seen from the attached Figs. 5, 9 and 11.
By inserting the resilient clamping means into the receiving space (8), the sealing element (4) is pressed against the transparent supporting edge (5) with a force which can be displaced counter to a spring force.
In order to enable the user to remove the sealing element (4) from the decorative fireplace (1), for example in order to clean it, said receiving space (8) is designed in such a manner that the sealing element (4) is displaceable therein when the sealing element (4) is being installed or removed.
A more detailed description of a number of possible embodiments of the decorative fireplace (1) according to the invention is given below with reference to Figs. 5 to 11, in particular a decorative fireplace (1) provided with one supporting edge (5) (Fig. 5), a decorative fireplace (1) provided with two supporting edges (5) (Fig. 9) and a decorative fireplace (1) with three supporting edges (5) (Fig. 11) in transparent glass. The description is in each case supplemented by an explanation of the way in which the sealing element (4) can be inserted.
Fig. 5 shows a decorative fireplace (1) provided with only one glass supporting edge (5), with Fig. 5.1 showing a detail view of the bottom peripheral edge of the housing (2), Fig. 5.2 showing a detail view of the top peripheral edge of the housing (2) which is provided with the glass supporting edge (5), and Fig. 5.3 showing a detail view of an upright peripheral edge of the housing (2).
Just like the decorative fireplace (1) shown in Figs. 9 and 11, the decorative fireplace shown in Fig. 5 comprises a housing (2) which is provided with a first supporting profile (7) along its periphery. These supporting profiles (7) can be attached to the housing (2) of the decorative fireplace (1), if desired resiliently or with adjustable spacers.
In the version illustrated in Fig. 5, only one peripheral edge, in particular the top peripheral edge (see Fig. 5.2) is provided with a transparent supporting edge (5) against which the sealing element (4) is pressed. The upright edges are provided with a second supporting profile (11). In this way, a receiving space (8) is formed for the edges of the sealing element (4), between the glass supporting edge (5) and the first supporting profile (7) (see Fig. 5.2), or between the first (7) and second (11) supporting profile (see Fig. 5.3) or between the housing (2) and the first supporting profile (7) (see Fig. 5.1).
In order to clamp the sealing element (4) against the metal parts of the decorative fireplace, in particular the first supporting profile (7) or the second supporting profile (11) and achieve a good sealing, the decorative fireplace (1) is provided with a sealing profile (16) which is fixedly connected to the housing at the location of the bottom peripheral edge and is made from rubber which can withstand high temperatures. This rubber sealing profile (16) is in principle only fitted (provided) on the sides of the periphery where there is no glass supporting edge (5) in the formed receiving space (8) and where the sealing element (4) would otherwise bear against a metal part. This sealing profile (16) is secured in the bottom peripheral edge by means of a securing plate (12). The decorative fireplace (1) furthermore comprises a support (13) for the sealing element (4) in its bottom peripheral edge, which support (13) is made from fibre material.
The sealing element (4) of the decorative fireplace (1) according to the invention can be fitted on the fireplace in a simple manner and can also be readily removed therefrom. Thus, the sealing element (4) of the decorative fireplace (1) shown in Fig. 5 is inserted in the following way (see Fig. 6). To this end, the receiving space of one of the upright peripheral edges is designed in such a manner that a groove is provided in which the sealing element (4) can move. The following steps have to be followed in order to insert the sealing element:

place a suction cup (not shown) on the sealing element;
position the sealing element against the right-hand edge and above the bottom edge and slide it to the right into the groove;
turn the sealing element slightly until it touches the fireplace on the left-hand side and slide the sealing element to the left;
slide the sealing element down into the bottom receiving space;
fit a resilient clamping means (6) in the receiving space on the side where the glass supporting edge (5) is situated and also in the receiving space at the location of the upright peripheral edges.

It is important that the decorative fireplace (1) is sealed properly after the sealing element (4) has been fitted, particularly on the peripheral edges where a supporting edge (5) is provided. This is achieved by means of a clamping means (6) placed in the receiving space (8). As is illustrated in Fig. 7, the clamping means (6) can be designed as a resilient tubular rubber sealing profile. Preferably, however, use is made of a clamping means (6) which consists of a resilient tubular metal core (9) surrounded by a knitted sleeve (10) of glass fibre (see Fig. 8). The diameter of this clamping means is slightly larger than the receiving space, as a result of which it is compressed into an oval shape, thus fitting tightly and pressing against the sealing element.
In the version shown in Fig. 9, the two upright peripheral edges (see Fig. 9.3) are provided with a transparent supporting edge (5) against which the sealing element (4) is pressed. The upright edges are also provided with a second supporting profile (11) which offers support to the transparent supporting edge (5). In this case, the receiving space for the lateral edges of the sealing element (4) is formed between the transparent supporting edge (5) and the first supporting profile (7). An additional reinforcing profile (15) is provided between the housing (2) and the first supporting profile (7) (just as in the embodiments shown in Figs. 5 and 11) for reinforcement purposes.
As has been described above, a rubber sealing profile (16) which can withstand high temperatures is provided at the location of the peripheral edges where there is no supporting edge (bottom and top peripheral edge). This sealing profile (16) is held securely in the bottom and top peripheral edge by means of a securing plate (12) (see Figs. 9.1 and 9.2). The decorative fireplace (1) furthermore comprises, along its bottom peripheral edge, a support (13) made from fibre material for the sealing element (4). The decorative fireplace is provided with a removable clamping means (6) in order to press the sealing element (4) against the supporting edges (5), as is shown in Fig. 8.
The sealing element (4) of the decorative fireplace (1) shown in Fig. 9 is then inserted in the following way (see Fig. 10). To this end, the receiving space of one of the upright peripheral edges is designed in such a manner that a groove is present in which the sealing element (4) can be displaced.
The following steps have to be carried out in order to insert the sealing element:

place a suction cup (not shown) on the sealing element;
position the sealing element against the top edge and slide it upwards into the groove;
turn the sealing element slightly until it touches the fireplace at the bottom;
slide the sealing element down into the bottom receiving space;
fit a resilient clamping means in the receiving spaces on the two sides with the glass supporting edges.

In the version shown in Fig. 11, the upright peripheral edges (see Fig. 11.2) and the top peripheral edge (see Fig. 11.3) are provided with a transparent supporting edge (5) against which the sealing element (4) is pressed. The upright edges are also provided with a second supporting profile (11) which offers support to the transparent supporting edge (5). In this case, the receiving space for the lateral edges of the sealing element (4) is formed between the transparent supporting edge (5) and the first supporting profile (7).
Just as described above, a rubber sealing profile (16) which can withstand high temperatures is provided at the location of the peripheral edges where there is no supporting edge (bottom peripheral edge). This sealing profile (16) is held securely in the bottom peripheral edge by means of a securing plate (12) (see Fig. 11.1). At its bottom peripheral edge, the decorative fireplace (1) furthermore comprises a support (13) made of fibre material for the sealing element (4). The decorative fireplace is provided with a removable clamping means (6) in order to press the sealing element (4) against the supporting edges (5), as shown in Fig. 8.
The sealing element (4) of the decorative fireplace (1) shown in Fig. 11 is then inserted in the following way (see Fig. 12). For this purpose, the receiving space of one of the upright peripheral edges is designed in such a manner that a groove is provided in which the sealing element (4) can be displaced.
The following steps have to be carried out in order to insert the sealing element:

place a suction cup (not shown) on the sealing element;
position the sealing element against the bottom edge and slide it downwards into the groove;
turn the sealing element slightly until it touches the fireplace at the top;
fit the clamping means in the receiving spaces on the three sides with glass supporting edges.

As it is very important with devices of the hermetic type to properly seal the combustion chamber, in a more preferred embodiment of the decorative fireplace (1) according to the invention said supporting edge can be moved counter to a spring force, as can be seen in Fig. 13. Fig. 13 shows a detail view of the two upright (vertical) peripheral edges of a decorative fireplace according to the invention, with only these upright edges being provided with a transparent supporting edge for the sealing element.
By making the supporting edges displaceable counter to a spring force, uneven structures in the sealing element can be absorbed (glass plates are virtually never perfectly flat) and thus it becomes possible to seal the combustion chamber by means of the sealing element even more hermetically. In order to resiliently mount the supporting edge, a rubber seal (17) (in practice a hollow rubber profile) is situated between the transparent supporting edge and the housing, preferably between the supporting edge (5) and the supporting profile (11) which provides support to the transparent supporting edge (5).

Claims

Built-in gas fireplace of the closed type (1), comprising a combustion chamber (3) which is formed in a housing (2) and which can be sealed off by a removable sealing element (4) made from heat-resistant glass, characterized in that at least one of the peripheral edges of said housing (2) comprises a transparent supporting edge (5) against which the sealing element (4) is pressed.
Built-in gas fireplace of the closed type (1) according to Claim 1, characterized in that at least two of the peripheral edges of said housing (2) comprise a transparent supporting edge (5) against which the sealing element (4) is pressed.
Built-in gas fireplace of the closed type (1) according to Claim 1 or 2, characterized in that the right-hand and the left-hand upright peripheral edge comprise a transparent supporting edge (5) against which the sealing element (4) is pressed.
Built-in gas fireplace of the closed type (1) according to one of the preceding claims, characterized in that the transparent supporting edge (5) is mechanically connected to the housing (2).
Built-in gas fireplace of the closed type (1) according to one of the Claims 1 to 3, characterized in that said supporting edge (5) can be moved counter to a spring force.
Built-in gas fireplace of the closed type (1) according to Claim 5, characterized in that a rubber seal (17) is provided between said transparent supporting edge (5) and the housing.
Built-in gas fireplace of the closed type (1) according to one of the preceding claims, characterized in that said supporting edge (5) has a width of between 15 and 100 mm, and a thickness of between 3 and 8 mm.
Built-in gas fireplace of the closed type (1) according to one of the preceding claims, characterized in that said fireplace (1) comprises a clamping means (6) in order to clamp the sealing element (4) against the transparent supporting edge (5).
Built-in gas fireplace of the closed type (1) according to Claim 8, characterized in that said fireplace (1) furthermore comprises a supporting profile (7) as a result of which a receiving space (8) is formed for the edge of the sealing element (4).
Built-in gas fireplace of the closed type (1) according to Claim 9, characterized in that said receiving space (8) is designed such that the sealing element (4) is displaceable therein when the sealing element (4) is being installed or removed.
Built-in gas fireplace of the closed type (1) according to Claim 9 or 10, characterized in that said clamping means (6) is resilient and is provided in said receiving space (8) in order to press the sealing element (4) against the transparent supporting edge (5) with a force which can be moved counter to a spring force.
Built-in gas fireplace of the closed type (1) according to one of Claims 8 to 11, characterized in that said clamping means (6) comprises a resilient core material (9) provided with a woven or knitted heat-resistant casing (10).
Built-in gas fireplace of the closed type (1) according to one of the preceding claims, characterized in that said transparent supporting edge (5) is made from heat-resistant glass.