| 摘要 |
To mould a helical gear, the same injection jet (16, 10) gives a co-injection action for two thermoplastic materials of different mechanical characteristics. The first thermoplastic material (19) has a long performance life, passing first through the injector (16, 10) to give the mantle shrouding structure for the helical gear, including the axial drive section (20) and the outer tooth formation (6). The other thermoplastic material (21) is injected in a second stage within the shrouding of the first material before it has set. The second material (21) takes up vibrations, and is softer than the first material. Also claimed is a helical gear with an outer material for the external teeth (6) and the central and axial drive section (20). The outer material is strengthened with glass fibres and the inner core material is of a softer material (21) to take up vibrations. |
