| 摘要 |
PURPOSE:To extend the life of a plug device and to prevent generation of flaws on the inside surface of a stock pipe by providing a roller holder to the front end of a plug bar to be inserted to the stock pipe to be pierced and disposing a roller plug freely rotatably to the roller holder. CONSTITUTION:The attachable and detachable roller holder 15 is provided in the front end of the plug bar 14 and the roller plug 17 which is freely rotatably held by upper and lower holding parts 16 of the holder 15 is disposed. A passage 19 for force-feeding a lubricating agent is provided to the plug bar 14 and roller holder 15 of the plug device 13. Lubricating agent discharge ports 20, 22 are respectively disposed to the front ends of the holding part 16 and the holder 15. The plug 17 makes rolling contact with the inside surface of the stock pipe 11 right under rolling rolls 12 and the contact parts 23, 24 of the plug 17, the holder 15 and the stock pipe 11 are lubricated. The life of the plug device 13 is, therefore, extended and the generation of flaws on the inside surface of the pipe 11 is prevented. |
