Method of producing inner spiral grooved tube and apparatus for producing inner spiral grooved tube

An apparatus for producing an inner spiral grooved tube, the apparatus comprising:

• first and second bobbins, one of which is an unwinding bobbin and the other of which is a winding bobbin, a tubular material being conveyed from the unwinding bobbin to the winding bobbin and the tubular material unwound from the unwinding bobbin being a liner grooved tube;
• a floating frame that supports a shaft of the first bobbin;
• a rotary shaft that supports the floating frame though bearings and rotates in a direction perpendicular to an axis of a bobbin in the floating frame;
• a revolving flyer configured to invert a tube route of the tubular material between the first bobbin and the second bobbin, to convey the linear grooved tube, and to revolve the linear grooved tube around the floating frame as being supported by the rotary shaft;
• and
• first and second drawing dice positioned on a front stage and a rear stage of the revolving flyer, respectively, in the tube route of the tubular material,
• wherein
• a plurality of straight grooves is formed on an inner surface of the linear grooved tube along a longitudinal direction, and
• the inner spiral grooved tube is formed by reducing a diameter of the tubular material by the first and second drawing dice in conjunction with imparting twist associated with the rotation of the revolving flyer to the tubular material.