PURPOSE: To automatically and continuously control a pressure at high speed in applying a sealing pressure of the tube end of inner tube at the pressure increased higher in fixed range than expanding pressure continuously varying in producing a metal double tube by hydraulic pressure expanding.
CONSTITUTION: When a double tube is produced by using two kinds of metal tubes having different elastic deformation property for an inner tube 2 and outer tube 4 and by pressure Joining with a hydraulic pressure expanding device by which expanding force is applied from the inner side of inner tube 2 while sealing the tube end side parts of inner tube 2 with a tube end sealing device 6, the sealing pressure applied to the sealing device 6 is continuously detected. Further, the expanding pressure at hydraulic expanding is continuously detected, based on these two pressure detected values, the pressurized fluid constantly higher than the expanding pressure is supplied from a sealing pressure cylinder 30 to the sealing device 6, the applied sealing pressure is controlled to the pressure in a prescribed range higher than the expanding pressure.
NISHIKAWA MAMORU
WATANABE TOSHIHIKO
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