| 摘要 |
The device, which is used for fastening a sealing film (3) to a material of low intrinsic strength (2), has a base body (5) with an external thread and a head (6). The external thread is divided into a conical preforming section (A), a cylindrical centre section (B) and a conical pressure section (C). When the device is screwed into materials (2) of great thickness, the cylindrical shape of the centre section (B) reduces the force requirement, since the centre section (B) does not itself displace any material. <IMAGE> |
