| 摘要 |
1,221,285. Laminated vehicle windscreens. COMPAGNIE DE SAINT-GOBAIN. 29 Jan., 1969 [29 Jan., 1968; 7 Feb., 1968; 3 May, 1968; 15 July, 1968], No. 4930/69. Heading B5N. [Also in Division B7] A laminated safety windscreen for a vehicle comprises an intermediate layer of plastics material sandwiched between an inner sheet of transparent material and an outer sheet of glass, both the inner sheet and intermediate layer having smaller dimensions than the outer sheet, which is the only part held by its peripheral portion by the windscreen frame. The intermediate layer and/or the inner sheet has a resistance at least sufficient to withstand without perforation the impact of a spherical body of 20 Kg with an impact speed of 50 Km/hr. at right angles to the surface of the windscreen at impact point, the outer sheet having less resistance so that upon such an impact it breaks at least around the peripheral portion. The intermediate layer is preferably polyvinyl butyral of a thickness between 0À7 and 1 mm. and the inner sheet may be glass, glass strengthened, e.g. by ion exchange, and of high bending strength or a thermoplastic substance which, in the temperature range -20‹ to + 40‹ C. exhibits a shear shock strength of at least 5 Kg/cm.<SP>2</SP> and a tensile strength (measured by a specified test) of over 200 Kg/cm.<SP>2</SP>. Suitable materials are ethylene glycol polyterephthalic ester (0À25 mm.), thermoplastic polycarbonates of dihydroxy aromatic compounds e.g. bisphenol alkane (1 mm.), amorphous polyamides of aromatic dicarboxylic acids, e.g. terephthalic acid and substituted alkyl aliphatic diamines (0À25 mm.) or 0À5 mm. unplasticized P.V.C. If the outer sheet is of unhardened glass, it may be provided with a rupture- or score-line e.g. in the form of a groove in the surrounding peripheral portion. |
