Bending tube, insertion appliance, and manufacturing method of bending tube

An insertion appliance, comprising:

• an insertion section including a bending tube,
• wherein the bending tube includes:
• a first region including a first plurality of slits;
• a second region including a second plurality of slits, the second region separated from the first region along a longitudinal axis of the bending tube;
• a first guiding surface on an inner circumferential surface of the bending tube, the first guiding surface extending in a circumferential direction of the bending tube and including a first channel;
• and
• a first wire slidably housed in the first channel, the first wire configured for bending the bending tube,
• wherein each slit of the first plurality of slits is at a different position in the circumferential direction of the bending tube, and is at a different position in a longitudinal direction of the bending tube than another of the first plurality of slits,
• wherein each slit of the second plurality of slits is at a different position in the circumferential direction of the bending tube, and is at a different position in the longitudinal direction of the bending tube than another slit of the second plurality of slits,
• wherein the first plurality of slits is distributed over a first angle in the circumferential direction of the bending tube, the second plurality of slits is distributed over a second angle in the circumferential direction of the bending tube, and the second angle is less than the first angle,
• wherein the bending tube further includes a second guiding surface including a second channel, a third guiding surface including a third channel, a second wire slidably housed in the second channel, and a third wire slidably housed in the third channel,
• wherein the first plurality of slits includes a first slit, a second slit, a third slit, and a fourth slit,
• wherein, relative to a longitudinal axis of the insertion section, the first slit and the third slit are positioned opposite each other and the second slit and the fourth slit are positioned opposite each other,
• wherein:
• when the first wire is pulled by a first pulling distance and the third wire is pulled by a second pulling distance, the first region bends in a first direction,
• when the first wire and the second wire are pulled, the first region bends in a second direction,
• when the second wire and the third wire are pulled, the first region bends in a third direction, and
• when the first wire is pulled by a third pulling distance and the third wire is pulled by a fourth pulling distance, the first region bends in a fourth direction, and
• wherein a ratio between the first pulling distance and the second pulling distance is different from a ratio between the third pulling distance and the fourth pulling distance.

A manufacturing method of a bending tube of an insertion appliance, the manufacturing method comprising:

• providing a first guiding surface, a second guiding surface, and a third guiding surface on an inner circumferential surface of the bending tube, wherein the first guiding surface, the second guiding surface, and the third guiding surface, are distributed in a circumferential direction of the bending tube, and wherein the first guiding surface includes a first channel configured to slidably house a first wire for bending the bending tube the second guiding surface includes a second channel configured to slidably house a second wire for bending the bending tube, and the third guiding surface includes a third channel configured to slidably house a third wire for bending the bending tube;
• providing, in a first region of the bending tube, a first plurality of slits, wherein each slit of the first plurality of slits at different positions in the circumferential direction of the bending tube, and at different positions in a longitudinal direction of the bending tube than another of the first plurality of slits;
• and
• providing, in a second region, a second plurality of slits, wherein each slit of the second plurality of slits is at different positions in the circumferential direction of the bending tube, and at different positions in the longitudinal direction of the bending tube than another of the second plurality of slits,
• wherein the second region is provided proximally relative to the first region,
• wherein the first plurality of slits is distributed over a first angle in the circumferential direction of the bending tube, the second plurality of slits is distributed over a second angle in the circumferential direction of the bending tube, and the second angle is less than the first angle,
• wherein the first plurality of slits includes a first slit including a first center position, a second slit including a second center position, a third slit including a third center position, and a fourth slit including a fourth center position, and
• wherein, in the circumferential direction, the first guiding surface, the second guiding surface, and the third quiding surface are at positions different from the first center position, the second center position, the third center position, and the fourth center position.