EP2532824A2

EP2532824A2 - Fabric shield for double-glazing units and the like

Info

Publication number: EP2532824A2
Application number: EP12171249A
Authority: EP
Inventors: Massimo Gentili; Giovanni Nicolosi
Original assignee: Pellini SpA
Current assignee: Pellini SpA
Priority date: 2011-06-08
Filing date: 2012-06-08
Publication date: 2012-12-12
Also published as: EP2532824A3; ITBO20110328A1

Abstract

A fabric shield for double-glazing units and the like, of the type comprising at least a portion of fabric coated with a metal film at least partially covered with an interference filter with high reflectivity in the visible spectrum; the interference filter comprises at least a double layer of metal oxides made by using a PVD sputtering type apparatus.

Description

TECHNICAL FIELD OF THE INVENTION

The present invention concerns a fabric shield for double-glazing units and the like.

STATE OF THE ART

It is known that in double-glazing units used, for example, for making building facades, there are problems when managing and controlling the heat load which is developed in the inner chamber containing the shield.
The problems are, in particular, related to the absorption of the incident solar radiation.
The temperatures inside of the chamber defined by the double layer of glass can indeed reach very high levels, which in some cases can even reach 100°C.
In the case in which it is desired to insert a roller blind or pleated blind inside the double-glazing, these high temperatures can create conditions which could jeopardise the correct operation of the unit.
In particular, phenomena of vapour release can be activated by the fibres forming the fabric, which, following the cooling of the glass, can then condensate on the surface generating undesired effects, such as the creation of misted spots or other similar phenomena, generally known in the field as fogging phenomena.
It is clear that, since the double-glazing is sealed, the removal of such misted spots is in fact impossible, therefore the formation thereof must be absolutely avoided: it is known that these phenomena do not occur when the temperature inside the double-glazing is well below 100°C, in particular lower than 80°C, above which it has been observed that the emission of vapour from the synthetic material forming the fibres of the fabric does indeed become highly relevant.
Both experimentally, for example with the aid of measuring systems with thermocouples to measure the temperature on the glass and on the blind, and through simulation systems in which the parameters in inlet can be, for example, the type of glass, the physical dimensions of the double-glazing, the type of materials and the thickness of the blind, it has been detected that, for the same type of glass, an increase in the reflectivity of the blind in the visible spectrum allows a considerable reduction of the temperature both on the surface of the blind itself and on the glass. Indeed, in such a way, the quantity of incident solar energy converted into heat, i.e. absorbed in the visible spectrum and re-emitted in the infrared, is decreased.
Therefore, in the field, solutions have been devised in which the surface of the fabric is treated with a suitable coating which makes it possible for there to be a certain reflection of the incident radiation in particular in the visible spectrum.
In some of the known solutions, the technical fabrics are coated with metal films, for example aluminium, deposited through physical vaporization or through suitable chemical treatments; in other solutions the shield is made through metallization of a thin continuous plastic film, the specular appearance of which however, generates a dazzling effect which is not suitable for use in double-glazing units.
Aluminium is selected since the general theory of reflectivity of metals indicates it as the metal material with the best reflection properties in the wide range from ultraviolet to infrared.
In other known types of solutions, the metal coating film is made from steel. The results are however worse than those which can be obtained with the aluminium coating, which is due to the lower reflectivity in the spectral bands of visible light and the near infrared of steel with respect to aluminium.
The aluminium coating, which indeed forms the best solution available in this field, makes it possible to obtain results which are not however satisfactory in terms of overcoming the aforementioned drawbacks, and mainly the problems of fogging up inside of the double-glazing: indeed, the simulation carried out related to this type of solution indicates a temperature on the blind of around 94°, wherein such data is also confirmed experimentally.
In addition to the problem mentioned above it is known that, particularly in the case of double-glazing units with roller blinds, there are manufacturing limitations related to the surfaces which can be obtained. Indeed, for double-glazing with large surfaces, the low rigidity of the technical fabric used causes there to be irregularities in the flatness of the blind when the roller is completely unwound.
Indeed, in these cases, it is possible to see a greater or a smaller undulation in the opened up blind, which compromises the appearance of the unit as well as its functionality.
This drawback could be overcome by using, for blinds, particularly rigid fabrics.
Rigid fabrics, however, have a greater thickness: since they must always be inserted inside the double-glazing, there are of course limitations in the maximum diameters of the rollers. Consequently, blinds made from rigid fabric cannot exceed a certain maximum length.

PURPOSES OF THE INVENTION

The technical task of the present invention is therefore that of improving the state of the art, by devising a fabric shield for double-glazing units and the like which makes it possible to limit the temperatures inside the double-glazing itself within the desired levels, so as to not generate vapour and other undesired phenomena.
In such a technical task, one purpose of the present invention is to make a fabric shield for double-glazing units and the like that is also characterized by high rigidity, so as to overcome the productive limitations - in terms of obtainable surface - due to the undulation effect which is usually generated in the opened up blind.
This task and this purpose are achieved with the fabric shield for double-glazing units and the like according to the attached claim 1.
According to one aspect of the present invention, the presence of an interference filter deposited on the film of aluminium which in turn coats the fabric forming the shield substantially increases the reflectivity of the fabric in the visible area, thus limiting in a decisive manner the conversion of incident solar energy into thermal energy and thus limiting the temperature of the glass and of the shield within the desired limits.
According to another aspect of the present invention, the presence of an interference filter deposited on the metal film coating the fabric of the shield increases the rigidity of the fabric itself in a considerable manner, eliminating or at least drastically minimizing undulation phenomena which characterise the shield when it is in the completely opened up configuration. Further advantageous characteristics are described in the dependent claims.

BRIEF DESCRIPTION OF THE DRAWINGS.

The characteristics of the invention shall become clearer to any man skilled in the art from the following description and from the attached table of drawings, given as a non limiting example, in which:

figure 1 is an exploded axonometric view of a double-glazing unit with a fabric shield according to the present invention;
figure 2 is a diagram showing the trend of the percentage reflectivity of a fabric shield according to the invention compared to a shield of the conventional type, according to the wavelength of the incident radiation and in the range from 300 nm to 2500 nm.

EMBODIMENTS OF THE INVENTION.

With reference to the attached figure 1, reference numeral 1 wholly indicates a fabric shield for double-glazing units and the like according to the present invention.
The double-glazing unit represented exploded in figure 1, is wholly indicated with reference numeral 2 and, purely as an example and not for limiting purposes, comprises a quadrangular frame 3 comprising four open metal window channels 4 that are reciprocally connected with L-bars 5, for example made from plastic.
At one of the upper corners of the frame 3 a motor group 6 for actuating the shield 1, is installed.
The shield 1 is wrapped around a roller 7 rotatably supported at a section bar 8 mounted below the upper window channel 4.
All of this is closed by two sheets of glass, not represented in the figure but of the known type, which define an airtight chamber in which the shield 1 is mobile.
A bottom 9, fixed to the lower edge of the shield 1, places the latter under the right tension when it is partially or completely unwound.
Alternatively, the shield 1 according to the invention can also be pleated, or of yet another type, without any limitation: in such a case it is clear that there will not be a roller 7 inside the double-glazing, but there will be other devices suitable for supporting other types of blinds.
The shield 1, according to the present invention, has shape and dimensions that can vary in relation to the specific application requirements.
The shield 1 is made, for example, from a fabric comprising a polyester fibre; alternatively, it can be made from a fabric comprising any other suitable material for this type of application.
At least a portion of the fabric with which the shield is made is coated with a metal film.
More in detail, the aforementioned metal film comprises aluminium.
In other embodiments of the shield 1 according to the present invention, the metal film with which the fabric is coated could comprise other types of metals, for example steel or yet others, without particular limitations.
In one embodiment of the shield 1 according to the invention, substantially the entire surface of the fabric with which it is made, is coated with the aforementioned metal film, so as to obtain the maximum reflectivity of the incident radiation in the visible spectrum.
Indeed, out of the various metal materials, aluminium is provided with the best properties of reflectivity of the incident radiation in the visible spectrum. According to one aspect of the present invention, the aforementioned metal film is at least partially covered with an interference filter having high reflectivity in the visible spectrum.
This solution makes it possible to drastically reduce the phenomenon of converting the incident solar energy into heat, or rather the phenomenon of absorption in the visible spectrum and of re-emission in the infrared, as shall become clearer in the rest of the description.
In one embodiment of the shield 1 according to the present invention, substantially the entire surface of the metal film is covered with an interference filter having high reflectivity in the visible spectrum.
The interference filter comprises at least one double layer of metal oxides.
In one embodiment of the shield 1 according to the invention, the interference filter comprises four layers of metal oxides.
More in detail, the aforementioned four layers are made from two types of metal oxides, arranged alternated on one another.
One of the types of metal oxides, with which the four layers of the interference filter are made, comprises silicon dioxide (SiO₂).
Such a material has a refractive index of 1.46.
Another type of metal oxide with which the four layers of the interference filter are made, comprises niobium pentoxide (Nb₂O₅).
This other material has a refractive index of 2.4.
In particular, one of the layers of silicon dioxide (SiO₂) is deposited, as the first innermost layer, directly on the metal film, whereas the other layers are arranged alternated above the first layer.
The selection of such materials, mainly dictated by their refractive indexes, and also according to other types of considerations, together with a suitable dimensioning of the thickness of the layers, makes it possible to minimise the radiation passing through the filter and that is thus absorbed by the fabric. Consequently, the radiation that, on the other hand, is reflected by the filter itself in the visible spectrum is maximised, and therefore it does not generate an increase in the temperature on the fabric and inside the double-glazing.
Purely as an example, the thickness of the two layers of silicon dioxide is of around 85-86 nm.
The thickness of the two layers of niobium pentoxide is, on the other hand, of around 51-52 nm.
It is worth underlining that these parameters are purely indicative, provided only as an example, and can be modified and optimised in relation to the different requirements of use.
In terms of productiveness, the layers of metal oxides which constitute the interference filter of the shield 1 according to the present invention are made by using a PVD sputtering apparatus, i.e. an apparatus, of the per se known type, which carries out the depositing of the layers by means of physical evaporation.
The invention thus conceived makes it possible to obtain important technical advantages.
As mentioned, the reflectivity of the incident solar radiation on the shield in the visible spectrum is considerably increased, and consequently the phenomena of absorption and of re-emission in the infrared, which are responsible of the rising of the temperature inside of the double-glazing and therefore of the shield 1, are reduced.
Figure 2 compares the trend of the reflectivity of the fabric before and after the deposition of the interference filter, as a function of the wavelength of the incident radiation.
In particular, in the diagram of figure 2 the curve A is relative to the fabric with interference filter, whereas the curve B is relative to the fabric without interference filter, i.e. a fabric of the known and conventional type.
As can be clearly seen, the presence of the interference filter - curve A - substantially increases the reflectivity of the fabric in the visible spectrum, defined by two broken vertical lines, with the advantages which have already been described.
This result therefore makes it possible to keep the temperature of the shield 1 and of the double-glazing below the desired limits, eliminating or minimising fogging phenomena of the fabric forming the shield 1. Another important result achieved with the shield 1 according to the present invention consists of increasing the rigidity of the fabric constituting the shield following the depositing of the metal oxide layers which constitute the interference filter.
Purely as an example, it should be considered that experiments carried out, in standard environmental conditions, on one fabric provided with interference filter and on one without a filter have shown a substantially equal result in terms of bending hysteresis, whereas the bending rigidity was of around 66.502 mN x mq/m in the case of fabric with interference filter and of around 38.696 mN x mq/m in the case of fabric without a filter, respectively, with an increase, therefore, which is above 70%.
This result makes it possible to substantially reduce undulation phenomena which normally occur in conventional types of fabric shields when they are partially or completely spread out.
It has thus been seen how the invention achieves the proposed purposes.
The present invention has been described according to preferred embodiments, but equivalent variants can be conceived without departing from the scope of protection offered by the following claims.

Claims

Fabric shield for double-glazing units and the like, of the type comprising at least a fabric portion coated with a metal film, said metal film being at least partially covered by an interference filter with high reflectivity in the visible spectrum, characterised in that said interference filter comprises at least at least one double layer of metal oxides made by using a PVD sputtering apparatus.
Shield according to claim 1, wherein said interference filter comprises four layers of metal oxides.
Shield according to the previous claim, wherein said four layers are made of two types of metal oxides, arranged alternately one above the other.
Shield according to claim 3, wherein one of said types of metal oxides comprises silicon dioxide (SiO₂).
Shield according to claim 3, wherein one of said metal oxides comprises niobium pentoxide (Nb₂O₅).
Shield according to claim 4, wherein one of said layers of silicon dioxide (SiO₂) is directly deposited on said metal film.
Shield according to claim 1, wherein said metal film comprises aluminium.
Method for the production of a fabric shield for double-glazing units and the like, characterised in that it comprises the following steps:
providing at least a fabric portion coated with a metal film;

covering, by using a PVD sputtering apparatus, at least a portion of said metal film with an interference filter with high reflectivity in the visible spectrum constituted by at least one double layer of metal oxides.