| 摘要 |
A screw cap of thermoplastic material, particularly intended for the closure of glass containers used in the food industry, is provided on the outer surface of its horizontal end wall (1) with a thin covering layer (13) of a composite laminated material which is adapted to form a barrier against the passage of gases through the wall. This composite, laminated material is constituted by a disc (13a) incorporated in the outer face of the horizontal end wall (1) of the cap during the injection moulding of the cap. The disc (13a) is permanently bonded to the horizontal end wall (1) of the cap and to a downwardly-curved wall (10) connecting the peripheral edge of the horizontal end wall (1) to a rounded anular shoulder (11) provided at the top of the cylindrical skirt (2) of the cap. The cap is made by a method in which the disc (13a) is inserted into the cavity of the matrix (19) of an injection mould (17, 18) and is held in place by frictional engagement of its peripheral edge with the ribs (23) of said matrix (19) which are intended to form vertical grooves (12) in the cylindrical skirt (2) of the cap. |
