| 摘要 |
The frame consists of a U-section bar (10) with side-pieces (18) attached to either end by hinges (16), and a lens mount (20) in the form of two surrounds (23) connected by a central nose bridge (22), and lenses of optical of filtering glass. The bar has its opening facing downwards and shaped to receive the upper edge of the lens mount. The bar can be made from a moulded synthetic material, reinforced with carbon or glass fibres, while the lens mount can be cut from a pre-coloured sheet of cellulose acetate or injection-moulded from a synthetic material.The upper edge of the lens mount can engage with the bar by means of matching tapering surfaces or by a system of projections and recesses which lock them together. ADVANTAGE - Permits easy exchange of lens mounts e.g. for near or distant viewing, sunglasses or a change of style.
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