| 摘要 |
Concrete pipes are usually manufactured by a pouring process. The outer mould (2) has an expansion for forming a joint at the end of the pipe, while the corresponding inner expansion is obtained by means of a so-called neck ring (6) which forms the core (4). The invention considerably increases the slipperiness of the neck ring by placing over the neck ring a thin covering shell or covering film (14, 11, 16) which acts as a slip-adjuvant. The neck ring can thus be tapped or withdrawn without damaging the pipe. The covering shell may even be embodied as a thicker shell which can be incorporated into the cast concrete to form a permanent, smooth, sealing lining on the pipe. |
