Adhesive bonding and miscellaneous chemical manufacture – Methods – Surface bonding and/or assembly therefor
Reexamination Certificate
2001-03-20
2002-12-03
Loney, Donald J. (Department: 1772)
Adhesive bonding and miscellaneous chemical manufacture
Methods
Surface bonding and/or assembly therefor
C156S277000
Reexamination Certificate
active
06488796
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The invention relates to a method for producing a vacuum between two sheets of glass and insulating glazing thus produced.
The method according to the invention, although it is not limited to the production of insulating glazing, will be described more particularly by reference to this application.
2. Discussion of the Background
It is usual, in order to obtain thermal and/or acoustic insulation, to produce insulating glazing including two sheets of glass separated from one another by a relatively thick air gap. Such glazing provides thermal insulation which is judged to be insufficient for certain occasions. To remedy that, it is known to produce glazing including three sheets of glass and one of the air gaps can be replaced by a gas, for example krypton. This glazing has markedly enhanced thermal insulation properties, but is so thick that it is not always easy to use it.
Moreover, current demand from the users is turning towards thermal insulation of glazing equivalent to that of solid walls. Insulating glazing had already been proposed, particularly in Patent No. WO-91/02878, consisting of two sheets of glass separated from one another by a space in which a vacuum has been produced.
This glazing, due to the vacuum, achieves very good insulation but it is very difficult to produce. On the one hand, the slight thickness between the two sheets of glass, which is of tenths of a millimeter, has to be constant over the whole region where the sheets of glass are face-to-face.
Moreover, a perfectly leaktight seal has to be formed between the two sheets of glass.
Patent No. WO-91/02878 describes a technique consisting in placing studs a few tenths of a millimeter thick on one of the sheets of glass, which are distributed over the whole surface, and, at the same time, a joint which will allow the two sheets of glass to be sealed. These studs and this seal are produced in the same material, which is a glass-making composition. It is apparent that this glazing is difficult to produce due to these simultaneous operations which require intricate handling.
Moreover, the sealing joint has a number of bubbles which can impair the leaktightness and the aesthetics.
This patent also describes a method for forming the vacuum between the two sheets of glass. It particularly proposes inserting a tube between the two sheets of glass before sealing, to which a connection is made in order to pump out the air. Another embodiment consists in piercing a hole through one of the sheets of glass and in pumping out the air through this orifice.
In the first case, it is necessary to seal the tube in a leaktight fashion at the same time as the sheets of glass, which makes the operations difficult. Moreover, it is necessary, after having formed the vacuum, to seal the end of the tube, then to protect this end in order to avoid breaking.
In the second case, the vacuum is formed by means of a tube previously sealed around the hole. Then, after having formed the vacuum, this tube is melted so as to seal its end. The disadvantage of these embodiments is that the insulating glazing provided has a fragile point either on the periphery or on one surface. In the second case, part of the tube remains outside the glazing, which increases the risks of damage.
SUMMARY OF THE INVENTION
The object of the invention is a method for producing a vacuum between two sheets of glass, which is simple to produce, with the glazing produced advantageously having no fragile point.
This object is achieved according to the invention by a method for producing a vacuum between two sheets of glass capable, in particular, of constituting insulating glazing, one of the sheets of glass including a hole pierced through its thickness, consisting, after having deposited spacers between the two sheets of glass, in forming a sealing joint at the periphery of the sheets of glass, in forming the vacuum and in stopping the hole, the spacers being fixed on to a sheet of glass by bonding with an inorganic compound covering at least the bonding areas on the sheet of glass, the second sheet of glass being deposited on the spacers and on the peripheral sealing joint, and bonding with the inorganic compound being carried out simultaneously with the peripheral sealing.
According to a first embodiment, the inorganic compound is sodium silicate in aqueous solutions. This compound advantageously coats the spacers and is dried before they are deposited on the sheet of glass. This drying allows easy handling of the spacers. Bonding of the spacers to the sheet of glass is achieved by remoistening the inorganic compound, then drying them.
According to another embodiment, the inorganic compound is an enamel.
In particular, this second embodiment according to the invention is, on the one hand, simplified because the second sheet of glass can simply come to rest on the spacers which are integral with the first sheet of glass. This technique allows precise depositing of the second sheet of glass, which is less strict than according to the known techniques, the deposition being able to be slightly corrected, for example by sliding. Moreover, at this stage of the method, the enamel has not yet been fired, but the usual enamel pastes exhibit sufficient viscosity to hold the spacers in place, more particularly after the enamel paste has dried, during the phase of putting in place and positioning the sheet of glass. Moreover, a variant can provide for the sealing joint advantageously to be put in place after the second sheet of glass, still in order to facilitate the positioning thereof.
Moreover, the method makes provision to carry out the sealing and the firing of the bonding enamel simultaneously, which limits the number of stages of the method. For preference, the bonding enamel is identical to the sealing joint; otherwise the firing temperatures are advantageously chosen to be similar.
According to a first embodiment of the invention, the bonding of the spacers is carried out by successive depositions of dots of inorganic bonding compound, for example by screen printing, then depositions of the spacers by a suction tool pierced with holes which are smaller than the spacers, at the same pitch as the dots obtained.
The dots of inorganic bonding compound can be deposited by any type of device known to a person skilled in the art, making it possible to form dots with a diameter of the order of 0.5 mm and with a thickness of a few tens of microns and to arrange them very precisely with a regular pitch. Such a pitch particularly allows a number of dots lying advantageously between 600 and 1500 per square meter, and preferably equal to 1000 per square meter.
For preference, the suction tool picks up and transports the spacers previously arranged on a plate and deposits them on the dots of inorganic compound by stopping the suction and possibly by blowing.
The spacers according to the invention advantageously have a parallel-face, bi-truncated spherical shape. Such a shape makes it possible to place all the spacers on a plate in the same position, for example by causing the plate to vibrate; this occurs because the bulging part of the spacers has a tendency to bring them on to one of the parallel faces. Moreover, the previously described shape associated with the suction tool allows good gripping of the spacers and precise deposition thereof, one of the flat faces ensuring good stability, including before firing the bonding enamel. Such spacers advantageously have a distance between the parallel faces of between 0.1 and 0.3 millimeter and a diameter, in the region of the bulging part, of less than 0.5 millimeters.
According to a second embodiment of the method according to the invention, the bonding of the spacers is carried out by depositing the spacers on the surface of a sheet of glass, said spacers previously being covered, over the area coming into contact with the glass, with the inorganic bonding compound.
For preference, the spacers are transported by a suction tool which, during transport, moistens the relevant
Bezzel Eik
Bredsdorff Mikael
Demars Yves
Margerand Stephane
Moltke Ivar
Loney Donald J.
Saint-Gobain Glass France
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