| 摘要 |
A screw cap of plastics material for sealing PET bottles having a mouth diameter of 28 mm has an annular shoulder (9) between the top wall (2) and the annular skirt (3) of the cap. The annular shoulder (9) includes an annular rib (10) and forms a continuous annular recess (11) engaged by the rim of a seal (14) which is compression-moulded in situ. The depth (Y) of the annular rib (10) is about 0.62 mm and the distance (X) between the downwardly-facing surface (9a) of the shoulder (9) and the internal surface of the top wall (2) is about 1.87 mm. The annular recess (11) comprises a first, upwardly-diverging, frusto-conical portion (12) with an inclination (Z) of about 60 DEG and a second portion constituted by a groove (13) having, in section, a circular profile with a radius of curvature (R) of about 1.76 mm. The weight of the drop which is intended to form the seal (14) is about 0.16 g.
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