Stock material or miscellaneous articles – Structurally defined web or sheet – Including components having same physical characteristic in...
Reexamination Certificate
1997-06-25
2001-07-24
Nakarani, D. S. (Department: 1773)
Stock material or miscellaneous articles
Structurally defined web or sheet
Including components having same physical characteristic in...
C156S102000, C156S104000, C156S106000, C428S214000, C428S215000, C428S412000, C428S425600, C428S430000, C428S441000, C428S442000
Reexamination Certificate
active
06265054
ABSTRACT:
The present invention relates to a composite glazing material made of glass and plastic, usable especially in the automobile industry for producing windshields and side windowpanes.
It is known that glazing materials for automobile vehicles must have at the same time good optical properties, such as transparency and nonscratchability and good mechanical properties such as the resistance to impacts and a low weight.
A composite glazing material according to the preamble of claim
1
is known from Patent WO 96/12604. However, because of their very small thickness, the glass layers employed are incapable of giving the glazing material the resistance to impacts and the flexural rigidity which are required by glazing materials for automobile vehicles. The only part played by the glass layers is that of protecting the plastic interlayer against scratches.
U.S. Pat. No. 4,600,640 relates to a composite glazing material made up of a layer of polycarbonate, of an adhesive layer and of a thin sheet of glass which has a thickness of the order of 0.1 mm. Here too the objective sought after is that of protecting the layer of plastic against scratches. The glazing material is therefore not suitable for producing windshields of automobile vehicles. In addition, this patent gives no information on the thickness of the adhesive layer. And yet, the adhesive layer runs the risk of appreciably perturbing the rigidity, all the more so since, as the coefficient of expansion of the glass is seven times smaller than that of the polycarbonate, a considerable thickness of adhesive, capable of taking up the differences in expansion, would have to be employed, and this adhesive of considerable thickness will impair the rigidity of the glazing material and its mechanical performance characteristics.
Patent GB 1 184 042, for its part, also describes a composite glazing material including two extremely thin layers of glass which have an antiscratch function. These glass layers are incapable of imparting the least rigidity to the glazing material.
Patents CH 427 234 and DE 94 03 934 both relate to a composite glazing material which has two glass layers markedly thicker than in the preceding glazing materials, but here too there is no search for mechanical performance.
The present invention aims to remedy the disadvantages of the glazing materials of the prior art and its subject matter is therefore a glass and plastic composite glazing material which has good mechanical performance characteristics such as a good flexural strength and a low mass per unit area.
To this end the invention relates to a composite glazing material according to the characterizing part of claim
1
.
In the glazing material according to the invention the glass sheets are sufficiently thick to create, on association with the plastic, a beam effect which gives the glazing material a good flexural strength.
Another subject matter of the invention is a composite glazing material such that, when the glass sheets break up following an impact, the glass debris remain adhesively bonded to the plastic interlayer and do not escape from the glazing flange in which the glazing material is secured. The glazing material will thus be able to retain its rigidity and prevent the passengers from being ejected through it.
To facilitate or strengthen the adhesion of the plastic to the glass sheets it is possible to employ an adhesiveness promoter which is deposited onto the glass or introduced into the plastic.
Experience has shown that the adhesion between glass and plastic must be such that the resistance to tearing out is at least 20 N/cm for a strip 1 cm in width. In some cases this resistance can be obtained without any adhesiveness promoter; in other cases an adhesiveness promoter deposited on the glass and/or introduced into the plastic will be resorted to.
The invention also relates, by way of new industrial product, to units incorporating the glazing material described above, for example bodywork units, such as tailgates or panels including a transparent zone consisting of a glazing material according to the invention and zones which are not necessarily transparent, painted or raw from demolding, made from the same plastic as that forming part of the composition of the glazing material or from another plastic and optionally possessing other properties, especially transparency and optionally greater rigidity. These other zones external to the glazing material zone may be produced during the same molding operation that allows the glazing material to be manufactured, and in the same mold, or, on the contrary, a two-step molding operation may be involved, either in the same mold or by reprocessing in a second mold.
It is also possible to produce a unit including essentially the glazing material, the latter being simply equipped at its periphery with rims, of a frame particularly thus forming a glazing material which is encapsulated, or various appendages.
These components can be made of injection-molded plastic, but can also include additions or inserts, such as embellishers, accessories intended to fulfill various functions (optical signaling block, third stoplight combined with the rear window of the vehicle, passages for electric cables, piping especially for a window-washer, profiled component for improving the aerodynamics, lock housing, and the like).
Before the injection molding of the plastic the inserts are placed between the two glass sheets and the additions with their projecting appendages are received in housings provided for this purpose in the mold. The inserts and appendages will thus be incorporated into the bulk of the glazing material or of the unit comprising a transparent zone forming a glazing material without there being any need to drill through or to machine the glazing material.
The present invention also relates to a process which makes it possible to determine the optimal geometric parameters of the composite glazing material in order that it may have a minimum mass per unit area while retaining a good mechanical behavior with regard to impacts.
It is known, in fact, that the trend is to restrict the emissions of polluting gases and consequently to design components that are lightened in weight. It has been found, in fact, that a 1% lightening in the weight of the vehicle reduces the emission of carbon dioxide by 0.3%, everything else being otherwise equal. This trend also applies to glazing materials.
However, the search for a lightening in the weight of the glazing material at any cost can be accompanied by a deterioration in its flexural rigidity and consequently can entail a decrease in the rigidity of the vehicle.
It is found, in fact, that purely and simply replacing sheets of glass with sheets of polymers of low weight, such as polycarbonates, methacrylates, polyethylene ionomers or polyurethanes, with retention of a sufficient rigidity to meet the criteria of good mechanical behavior on impacts, is not reflected in a lightening in weight. This is due to the fact that the saving in the specific mass of the plastics (which is of the order of half that of the glass) is more than compensated for by the loss in Young's modulus of these plastics.
The Applicant Company has been interested in the problem of the systematic investigation of glass and plastic composite glazing materials with a view to determining those which have the smallest mass per unit area at a given flexural rigidity.
Where glazing material for the automobile industry is concerned, there is already known the composite glazing material including an interlayer thickness of polyvinylbutyral (PVB) included between two sheets of glass. However, it has been found that, to obtain a satisfactory flexural rigidity with such a glazing material, it is necessary to employ a very large thickness of PVB, and this, despite the low specific weight of this material, results in a glazing material that is markedly heavier than a glazing material made of monolithic glass which has the same flexural rigidity. This is due to the fact that, because of its low compressi
Bravet Jean-Louis
Bureau Bernard
Morin Claude
Padoy Christian
Vidal Boris
Nakarani D. S.
Saint-Gobain Vitrage
Scully Scott Murphy & Presser
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