Abstract: A tube cutting apparatus includes an inner blade, a drive shaft, a coupling shaft, a planetary gear, and a ring gear. The outer blade has an inner peripheral surface which contacts an entire circumference of an outer periphery of a work W so as to cover a predetermined axial range of the outer periphery. The drive shaft is rotatably supported inside the work W coaxially with the work W and defines a bore therethrough at a position decentered by a predetermined amount within the drive shaft. The coupling shaft is rotatably supported in the bore. The inner blade is rotatably retained on an eccentric shaft decentered at a front end portion of the coupling shaft and is positioned inside the work W. The planetary gear is positioned outside the work W and fitted on a rear end portion of the coupling shaft coaxially and meshes with the ring gear.

Abstract: The motor (50) transmits its rotation to the main shaft (1) through the first transmission gear train (9) while transmitting rotation at a rotating speed ¾ as high as the rotating speed of the main shaft (1) to the eccentric shaft (2) through the second transmission gear train (10) and the offset shaft coupling (7). As the motor (50) is driven, an eccentric axis (30) moves on a circle decentered by a predetermined length L while the inner blade (3) moves in the same direction on a circle further decentered by the predetermined length L from the eccentric axis (30). The inner blade (3) rotates and moves while exposing part of its outer peripheral surface exteriorly of a tube (W) at plural positions on the outer periphery of the tube (W).

Abstract: A tube forming apparatus performs a forwardly rotating step in which a main roll is rotated forwardly with a pair of subsidiary rolls in a forming position during a move of a contact position between the main roll and a work from a first end of the work to a central portion of the work, a feeding step in which the main roll is rotated forwardly with the pair of subsidiary rolls in a retracted position during a move of the contact position between the main roll and the work from the central portion of the work to a second end of the work, and a reversely rotating step in which the main roll is rotated reversely during a move of the contact position between the main roll and the work from the second end of the work to the central portion of the work.

Abstract: The motor (50) transmits its rotation to the main shaft (1) through the first transmission gear train (9) while transmitting rotation at a rotating speed ¾ as high as the rotating speed of the main shaft (1) to the eccentric shaft (2) through the second transmission gear train (10) and the offset shaft coupling (7). As the motor (50) is driven, an eccentric axis (30) moves on a circle decentered by a predetermined length L while the inner blade (3) moves in the same direction on a circle further decentered by the predetermined length L from the eccentric axis (30). The inner blade (3) rotates and moves while exposing part of its outer peripheral surface exteriorly of a tube (W) at plural positions on the outer periphery of the tube (W).