| 摘要 |
<p>An apparatus (10) for injection molding an opening device (3) on a multilayer sheet packaging material (2) provided with a hole (9) having an axis (B), formed through a first layer (4) and sealed by a cover portion (11) of a second layer (5, 6); the apparatus (10) comprises a mold cavity (31) coaxially housing the cover portion (11) and in turn comprising a first confetti-shaped chamber (32) adapted to be filled with molten plastic material on a first side (11a) of the cover portion (11), and a second tubular chamber (33) projecting along the axis (B) from the first chamber (32) and adapted to be filled with the molten plastic material coming from the first chamber (32) through an annular peripheral portion of the cover portion (11) to form, on a second side (11b) of the cover portion (11), a spout (13) of the opening device (3); the apparatus (10) further comprises an annular rib (41) delimiting a narrow-section passage (42) connecting the first and second chamber (32, 33) and defining, when filled with the plastic material, an annular tearable membrane connection portion (19) between the spout (13) and the plastic material covering the cover portion; the annular rib (41) is bounded, on the first chamber side, by a first annular surface (43), which is parallel to the axis (B) and forms a sharp edge (46) against which the cover portion (11) is stretched by the pressure of the plastic material.</p> |
