| 摘要 |
The starting point is synthetic acrylonitrile rubber (NBR) of formula <IMAGE> Before vulcanising it, 3-10% of di-2-ethylhexyl sebacate [C8H16(COOC8H17)2] are added to it and this mixture is poured into a mould having the shape of the mounting 12. The addition made to the NBR has the effect of reducing, on a long-term basis, the coefficient of friction at rest of the mounting. Once in place, the latter centres the encircling bezel 10 round the bezel 11 of the casing and makes it possible for the bezel 10 to rotate without difficulty even through very small angles, which facilitates the adjustment of this bezel in very precise orientations. <IMAGE>
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