Sheet of glass material for a chimney or furnace insert-type device

ES 2 837 802 T3

DESCRIPTION

Chimney or stove with a glass ceramic panel and method of manufacturing said panel

The present invention relates to a heating device in the form of an insert for fireplaces or stoves.

Apart from open hearth fireplaces, new types of heating appliances have been developed over the last decades that have a practically aesthetic and / or functional character, such as fireplace inserts or cassettes, or new types of stoves that are easy to install and maintain, which meet many requirements especially in terms of comfort and safety. To benefit from the pleasure associated with the appearance of homes with these devices, they are generally equipped with a window on the front of the device, normally incorporated in a door that allows access to the home and conventionally made of a glass material; In an open hearth fireplace, the protection provided by this window or door can be ensured at the same time by a fire protection screen that can also be made of glass material.

In insert fittings for stoves or fireplaces in particular, for reasons of safety or ease of use, it is also becoming more common to replace conventional wood-burning heating systems with more sophisticated heating systems that incorporate ducts or circuits for the supply. fuel and / or air circulation; however, these conduits and circuits can appear somewhat unappealing when not hidden by flames when these devices are not in operation.

Therefore, the aim of the present invention is to propose a heating device in the form of an insert for fireplaces or stoves that is both aesthetically attractive and functional while meeting the existing requirements in this field.

In particular, the present invention has developed a plate made of a glass material that is suitable for use on the front of this type of device and meets the objectives defined in this way, in particular by making it possible to preserve the visual appearance. attractiveness of the homes of these devices while masking any unattractive internal structures of such homes when they are not burning, being the difficulty of implementing this type of product especially associated with the rigorous resistance requirements, particularly resistance to temperature, of this type of product and also a priori with those that are applied to combine materials with different properties subjected to those particular conditions. strict.

This objective has been achieved by the device of claim 1.

The reader is reminded that a glass-ceramic is originally a glass, called precursor glass, the specific chemical composition of which makes it possible to induce controlled crystallization by means of "ceramicization" heat treatments. This specific partially crystallized structure provides the unique properties of glass-ceramics. However, it is very difficult to make modifications to these plates and / or their manufacturing process without the risk of adversely affecting the desired properties; in particular, it has never been envisaged to add a reflective coating to this type of material in the type of application currently envisaged, in particular due to the risks of degradation of said coating, in particular taking into account the different coefficients of expansion of these types of materials and the risk of cracking due to the frequency of expected thermal shocks.

Surprisingly, the present invention has shown that this combination is possible and advantageous.

The present invention relates to a heating device in the form of an insert for fireplaces or stoves, said device comprising at least one plate formed of at least one glass-ceramic substrate comprising at least one reflective coating on the surface intended to be directed out of the heating device; said plate having a light reflectance value (luminous reflectance value - LRV) of between 20% and 80%; the coating being formed by a stack of thin layers made of alternating dielectric materials between high and low refractive indices comprising the alternation of the following oxide layers: TiO2 / SiO2 / TiO2.

This plate is preferably located on the front face of the device, for example, incorporated in a door that allows access to the hearth, or incorporated in the structure as a window, or optionally removable, especially in the case of a plate coupled to the home as a protective screen.

The present invention also refers to a method for manufacturing said plate, which includes a step of deposition of at least one reflective coating on the glass-ceramic substrate.

ES 2 837 802 T3

The term "glass-ceramic plate" means, from now on, not only plates made of our own glass-ceramic but also plates made of any other similar material resistant to high temperatures and having a coefficient of expansion of zero or almost zero (for example, less than 15.10-7K^-1). However, it is preferred that it be your own glass ceramic hob.

The combination of the reflective coating with the glass-ceramic substrate has the advantage of more or less hiding the fireplace when it is not burning while allowing the fire to be seen when it is in operation. The plate according to the invention also meets the requirements that are demanded in this type of application; in particular, it has a temperature resistance (in particular, without degradation or delamination) of at least 500 ° C, preferably at least 600 ° C, particularly preferably at least 650 ° C, or even 700 ° C depending on the coating selected . The plate according to the invention also has good resistance to the risks of scratches or impacts.

The coating is on the outer face of the plate, that is, the face designed to be directed towards the outside of the heating device; this face is not in direct contact with the fire during the operation of the device.

The plate of the heating device according to the invention (having the reflective coating as defined) has a light reflectance value (LRV) (in the visible wavelength range - between 0.38 pm and 0, 78 pm - with an illuminant D65) of between 20% and 80%, with special preference between 30% (or even 40%) and 70%. It also preferably has a visible transmittance (visible transmittance -VT) of between 10% and 78% (in the visible wavelength range - between 0.38 pm and 0.78 pm - with an illuminant D65).

Preferably, the substrate forming the plate is transparent and especially has at least a visible transmittance (visible transmittance - VT) greater than 70%, particularly preferably greater than 80%. Optionally, it can be molded with color or decorated, for example, with enamel. The use of what is called a translucent substrate, or even an opaque substrate, can also be contemplated; however, in this case the visibility of the combustion fire may be reduced.

The coating may be in the form of a multilayer stack. Advantageously, the cell comprises at least one layer of the metallic type and / or at least one layer made of a dielectric material.

According to the invention, the coating is formed from a stack of thin layers made of dielectric materials that alternate between high refractive indices (preferably above 1.8 or even 1.95, or even 2, as explained above) and low (preferably below 1.65), especially made of metal oxide material (or metal nitride or oxy-fluoride), such as TiO2, SO2, the layer, if any, being deposited last and, therefore the one that is placed on the external face of the plate, a layer with a high refractive index.

An example of a layer material with a high refractive index is TiO2, others being SnO2, SÍ3N4, SnxZnyOz, TiZnOx or SixTiyOz, ZnO, ZrO2, Nb2Os, etc. An example of a layer material with a low refractive index is SO, others being a silicon oxynitride and / or silicon oxycarbide, or a mixture of silicon and aluminum oxide, or a fluorinated compound, e.g. eg, of type MgF2 or AIF3, etc.

According to the invention, the stack comprises at least three layers, the desired reflection taking place by the combined action of the various layers of the stack, the layer closest to the substrate being a layer with a high refractive index, the intermediate layer being a layer with a low refractive index, and the outer layer being a layer with a high refractive index. The cell comprises the following alternation of oxide layers: (substrate) TiO2 / SiO2 / TiO2.

Preferably, the (geometric) thickness of the coating is between 20nm and 1000nm (the thickness of the substrate being generally a few millimeters, especially between 3mm and 6mm, and usually about 4mm in the case of a glass-ceramic substrate ). In the case of a coating formed of several layers (generally in the form of a stack of layers), the thickness of each of the layers can vary between 5 nm and 160 nm, generally between 20 nm and 150 nm.

According to a first embodiment, the thickness of these layers is a few tens of nanometers (for example around 60-80 nm) for each of the respective layers of TiO2 and SiO2, the coating in this case having a silver appearance, and in In a second embodiment the thicknesses of the TiO2 layers are of the same order as the previous ones but the thickness of the SiO2 layer is more than double (for example around 130-150 nm), the coating in this case having a golden appearance.

The plate can also be provided with a coating that has another type of functionality, possibly coupled with the desired one according to the invention (without this additional functionality being detrimental to the desired properties) but more generally on the opposite face, such as a coating with a low emissivity function (for example made from a doped metal oxide such as SnO2: F or tin and ITO doped indium oxide, or aluminum and

ES 2 837 802 T3 zinc oxide doped Al: ZnO), favoring the pyrolysis of soot that can be deposited inside the fireplace, or a coating made of SO2 forming a barrier against the sulfur contained in the combustion exhaust gases.

The plate can be surrounded by a frame and / or have free edges that are generally shaped (rounded, beveled, etc.). It is usually flat but can also be curved, warped, or bent.

The object of the invention is also a method for manufacturing a plate of the device according to the invention. As a reminder, the manufacture of glass ceramic hobs generally takes place in the following way: the glass of the composition chosen to form the glass ceramic is melted in a melting furnace, the molten glass is then laminated into a standard tape or sheet causing the Molten glass passes between laminating rollers and the glass tape is cut to the desired dimensions. The plates cut in this way are subjected to a known ceramicization method, the ceramicization consisting of firing the plates according to the selected thermal profile to convert the glass into the polycrystalline material called "glass-ceramic", which has a zero or almost zero coefficient of expansion. and that withstands a thermal shock of up to 700 ° C. Ceramming generally comprises a step of progressively raising the temperature to the nucleation range, which is generally close to the glass transformation range, a step of passing for several minutes through the nucleation range, a new step of progressively raising the temperature up to the holding temperature of the ceramics, maintaining the holding temperature of the ceramics for several minutes, followed by rapid cooling to room temperature.

Optionally, the method may also comprise a step of shaping the plate (possibly carried out at various times during the aforementioned procedure, provided that the material constituting the plate is at a high enough temperature to allow its plastic deformation), consisting, for example, of a casting, molding or pressing operation (by rolling or other operation) or bending operation, ceramicization of the plate generally taking place after the shaping operation.

The method generally includes a cutting operation, for example using water jets, optionally followed by a shaping operation (grinding, chamfering, etc.). The plate can also undergo other operations during its manufacture (for example, screen printing for aesthetic or indicated reasons, the screen printing taking place, preferably, before ceramicization, to allow, where appropriate, the firing of the enamel during said ceramicization, etc. .), and can be provided with added elements, such as handles, etc.

The coating is applied to the plate generally after ceramming, in line with it, or as an extension (for example after the plate has been cut and / or shaped). The coating can be applied in particular by pyrolysis (of a powder, liquid or gas), by evaporation or by sputtering. Preferably, the coating is deposited by a sputtering and / or vacuum deposition method, optionally enhanced with plasma; in particular the method of depositing the layer (s) by sputtering (for example magnetron sputtering), especially magnetically intensified sputtering (and with a DC or AC current) is used, the oxides or nitrides being deposited from one or more Suitable metal or alloy or silicon or ceramic targets, if necessary under oxidizing or nitriding conditions (argon / oxygen or argon / nitrogen mixtures, if applicable). It is also possible, for example, to deposit the oxide layers by reactive sputtering of the metal in question in the presence of oxygen and the nitride layers in the presence of nitrogen. To produce SiO2 or Si3N4, a silicon target can be used that is lightly doped with a metal such as aluminum to make it sufficiently conductive. The layer (s) selected according to the invention condense on the substrate in a particularly uniform manner, without any separation or delamination taking place.

In general, the coating is a continuous coating, however, adding an additional aesthetic effect by adding the coating in the form of a discontinuous coating, for example in the form of a grid or a pattern (preferably with a high open aperture ratio) is not excluded. , especially one greater than 50% or greater than 75%), using suitable masks, for example, made of perforated sheet metal. If the coating comprises several layers, the layers are deposited in succession, one after the other.

The plates of the device according to the invention can be used, in particular, with the advantage of creating a new range of insert accessories for hearths or fireplaces.