| 摘要 |
PURPOSE:To shorten the working time, to improve the pipe quality, and to extend the roll life, by retreating the mandrel while the pusher is advancing. CONSTITUTION:If the pusher 2 approaches the plug 3' of the mandrel 3 when the piercing work is to be finished, the mandrel fixer 5 is retreated while the pusher 2 is still advancing; and the mandrel 3 together with the bottomed cylindrical pipe blank P in one body are sent out to the delivery side by the rolling force. The timing of releasing the mandrel fixer 5 may be the time that the unpierced part's length C becomes the specified length, that is the usual bottom thickness in case of manufacturing the bottomed cylindrical pipe blank. The position of releasing the mandrel fixer 5 is mechanically or electrically detected by the releasing position detector using the photoelectric tube, for example, when the front end of the pusher 2, or the rear end of the polygonal section bloom B, or other detection terminal, arrives at the specified position. |
