PRODUCTION METHOD AND PRODUCTION DEVICE FOR TUBE WITH SPIRALLY GROOVED INNER SURFACE
A method in accordance with the present application includes sending a raw tube from a drum to an unwinding side capstan while the raw tube is rotated around a central axis perpendicular to a winding shaft of the drum by rotating the drum and the unwinding side capstan about the central axis concurrently with unwinding of the raw tube from the drum holding the raw tube, on an inner surface of which multiple straight grooves along a longitudinal direction of the raw tube are formed with an interval in a circumferential direction, in a coil shape, to wind the raw tube around the unwinding side capstan, and drawing in which the unwound raw tube is drawn while the diameter of the raw tube is reduced, and then the raw tube is wound around the drawing side capstan to twist the raw tube and obtain an inner spiral grooved tube.
1 . A method for producing an inner spiral grooved tube comprising the steps of:
twisting and drawing an unwound raw tube, which has grooves or fins on an inner surface, by introducing twist to the unwound raw tube while a diameter of the unwound raw tube is reduced by being passed through a drawing die, to obtain an inner spiral grooved tube, the unwound raw tube being wound up on an unwinding side capstan; and
winding up the inner spiral grooved tube, wherein
the unwinding side capstan rotates in such a way that: a post-unwound-pre-diameter-reduction raw tube from having been unwound from the unwinding side capstan to reaching to the drawing die rotates about a central axis of the post-unwound-pre-diameter-reduction raw tube; and the raw tube before being wound up on the unwinding side capstan rotates in synchronization with the raw tube being wound up on the unwinding side capstan.
2 . The method for producing an inner spiral grooved tube according to claim 1 , wherein a diameter reduction ratio of the drawing die is 5% to 40%.
3 . The method for producing an inner spiral grooved tube according to claim 1 , wherein a foremost location, on which the raw tube is wound around the unwinding side capstan; and a foremost location, on which the raw tube is sent from the unwinding side capstan to a side of the drawing die, are displaced in a direction parallel to a rotation axis of the unwinding side capstan for an interspace between the unwinding side capstan and the drawing die to be a twist processing zone of the raw tube.
4 . The method for producing an inner spiral grooved tube according to claim 1 , wherein forward and backward tension are introduced in the raw tube during reducing the diameter of the raw tube with twisting by passing the raw tube through the drawing die.
5 . The method for producing an inner spiral grooved tube according to claim 1 , wherein the inner spiral grooved tube passing through the drawing die is wound around a drawing side capstan.
6 . The method for producing an inner spiral grooved tube according to claim 5 , wherein the inner spiral grooved tube unwound from the drawing side capstan is shaped into a form with a second drawing die.
7 . The method for producing an inner spiral grooved tube according to claim 1 , wherein the raw tube unwound from the drum is shaped into a perfect circle shape with the drawing die before the raw tube reaches to the unwinding side capstan.
8 . The method for producing an inner spiral grooved tube according to claim 1 , wherein the raw tube is an extruded raw tube made of aluminum or aluminum alloy.