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, the unwinding bobbin and the winding bobbin being configured to convey a tubular material from the unwinding bobbin to the winding bobbin and the unwinding bobbin being configured to unwind the tubular material having a structure of a linear grooved tube having a plurality of straight grooves formed on an inner surface of the linear grooved tube along a longitudinal direction;
• 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 material, and to revolve the tubular material around the floating frame as being supported by the rotary shaft;
• and
• first and second drawing dies positioned on a front stage and a rear stage of the revolving flyer, respectively, in the tube route of the tubular material, wherein
• the first and second drawing dies are configured to reduce a diameter of the tubular material in conjunction with the revolving flyer being configured to impart twist associated with a rotation of the revolving flyer to the tubular material to form the inner spiral grooved tube.