| 摘要 |
A peripheral edge of the hole in the mat is folded towards the well cylindrical wall (3) against which it is secured by a clamp ring. To obviate problems of adequate seal between the mat and the well, (2-4), a ring-shaped flat ring provided with adhesive on both sides is positioned between them. - It is so positioned that one surface of it locates both against the well peripheral flange (2), and the cylindrical wall (3). To ensure a good fit of the folded mat edge, a cutting tool is used to provide a circular hole edge. |
