Abstract: A flexible tube includes a helical tube having a first sparsely wound region, a closely wound region, a change region, and a second sparsely wound region. In a state where the change region is arranged between the closely wound region and the second sparsely wound region, the change region changes an unbendability such that the unbendability of the distal end portion of the third flexible portion is closer to the unbendability of the second flexible portion and the unbendability of the proximal end portion of the third flexible portion is closer to the unbendability of the fourth flexible portion.

Abstract: A flexible tube includes a first outer layer covering an outer side of a closely-wound region; a second outer layer forming a second flexible portion which is more difficult to bend than the first flexible portion; a third outer layer covering an outer side of the sparsely-wound region, and forming a third flexible portion which is as difficult to bend as the second flexible portion, or more difficult to bend than the second flexible portion; and a fourth outer layer arranged consecutively between the second and third outer layers to cover the outer side of a boundary position of the closely-wound region and the sparsely-wound region, and reducing a difference in bending difficulty/bending easiness at the boundary position.

Abstract: A flexible tube includes an envelope, a spiral tube and a built-in component. The spiral tube includes a first area portion and a second area portion. The spiral tube is under an initial tension throughout the overall length, and the built-in component includes a supplement area portion which supplements the elasticity of the spiral tube.

Abstract: A flexible tube includes a helical tube including a closely-wound region and a sparsely-wound region, and an outer tube covering an outer side of the helical tube. The closely-wound region includes a closely-wound portion to which a tight contact force is applied, the tight contact force allowing adjacent parts of a wire member adjacent along the longitudinal axis to become a tight contact state, a sparsely-wound portion which is arranged at a proximal side of the closely-wound portion, and a change portion which is arranged at a proximal side of the sparsely-wound portion and, has the tight contact force between the adjacent parts on the proximal side rather than the distal side along the longitudinal axis reduced more than the tight contact force of the closely-wound portion.

Abstract: A flexible tube for an endoscope includes a helical tube, a cover, and an inhibition mechanism. The inhibition mechanism enables movement of a densely wound portion to the cover in a direction of a central axis of the helical tube and inhibits movement of a loosely wound portion to the cover in the central axis direction of the helical tube.

Abstract: A flexible tube includes a first outer layer covering an outer side of a closely-wound region; a second outer layer forming a second flexible portion which is more difficult to bend than the first flexible portion; a third outer layer covering an outer side of the sparsely-wound region, and forming a third flexible portion which is as difficult to bend as the second flexible portion, or more difficult to bend than the second flexible portion; and a fourth outer layer arranged consecutively between the second and third outer layers to cover the outer side of a boundary position of the closely-wound region and the sparsely-wound region, and reducing a difference in bending difficulty/bending easiness at the boundary position.

Abstract: A flexible tube includes a helical tube including a closely-wound region and a sparsely-wound region, and an outer tube covering an outer side of the helical tube. The closely-wound region includes a closely-wound portion to which a tight contact force is applied, the tight contact force allowing adjacent parts of a wire member adjacent along the longitudinal axis to become a tight contact state, a sparsely-wound portion which is arranged at a proximal side of the closely-wound portion, and a change portion which is arranged at a proximal side of the sparsely-wound portion and, has the tight contact force between the adjacent parts on the proximal side rather than the distal side along the longitudinal axis reduced more than the tight contact force of the closely-wound portion.

Abstract: A flexible tube includes an envelope, a spiral tube and a built-in component. The spiral tube includes a first area portion and a second area portion. The spiral tube is under an initial tension throughout the overall length, and the built-in component includes a supplement area portion which supplements the elasticity of the spiral tube.

Abstract: A flexible tube includes a helical tube having a first sparsely wound region, a closely wound region, a change region, and a second sparsely wound region. In a state where the change region is arranged between the closely wound region and the second sparsely wound region, the change region changes an unbendability such that the unbendability of the distal end portion of the third flexible portion is closer to the unbendability of the second flexible portion and the unbendability of the proximal end portion of the third flexible portion is closer to the unbendability of the fourth flexible portion.

Abstract: A flexible tube for an endoscope includes a helical tube, a cover, and an inhibition mechanism. The inhibition mechanism enables movement of a densely wound portion to the cover in a direction of a central axis of the helical tube and inhibits movement of a loosely wound portion to the cover in the central axis direction of the helical tube.