| 摘要 |
A smooth end ring 6 is arranged in a folded metal pipe 5 which serves for interconnecting smooth pipes 1, 2 to form a ventilation duct. This ring extends a little way into the folded pipe 5 and is mounted so as to press against the inside of the folded pipe 5. The end ring 6 engages, with a portion 7, around the edge portion 8 of the folded pipe 5. When an extension pipe 3 provided with a sealing ring 4 is inserted into the folded pipe 5, the sealing ring 4 is intended to bear sealingly against the smooth inside of the end ring 6. <IMAGE> |
