Bending device and endoscope

1. A bending device comprising:

a bendable bending section in which a plurality of bending pieces are coupled;

a wire, a distal end of the wire being fixed to the bending section, the wire being towed to bend the bending section;

a plurality of wire receivers provided on an inner circumferential surface of the bending section, the wire being inserted through the wire receivers in an advanceable and retractable manner;

an inner coil sheath, a distal end of the inner coil sheath being fixed to a cap, the cap being interposed between the bending pieces in an intermediate section of the bending section, the inner coil sheath being inserted through the plurality of wire receivers that are closer to a proximal end of the bending section than the cap and the inner coil sheath extending toward the proximal end of the bending section;

an outer coil sheath, the inner coil sheath being inserted through the outer coil sheath, the outer coil sheath being arranged proximally relative to the cap;

a cover that covers an entirety of a region of the inner coil sheath inserted through the plurality of wire receivers on an outer circumference of the inner coil sheath between the cap and the outer coil sheath in a longitudinal axis direction of the wire, the cover being inserted through the wire receivers with the wire, the cover having stretchability in the longitudinal axis direction of the wire, and the cover being advanceable and retractable in the longitudinal axis direction in the bending section between the cap and the outer coil sheath;

wherein a distal end of the cover abuts a proximal end portion of the cap when the cover advances and retracts in the bending section; and

a proximal end of the cover abuts a distal end portion of the outer coil sheath when the cover advances and retracts in the bending section.

2. The bending device according to claim 1 , wherein the cover is configured from a sparsely wound coil.

3. The bending device according to claim 1 , wherein the cover has a constant stretching ratio over an entire length in the longitudinal axis direction.

4. The bending device according to claim 1 , wherein the cover is formed, regardless of the covers advancing/retracting with respect to the wire receiver in the longitudinal axis direction of the cover involved in the bending of the bending section, in a length in the longitudinal axis direction for covering the entirety of the region.

5. The bending device according to claim 1 , wherein the cover is covered on the outer circumference of the wire such that the distal end of the cover is located to be proximally separated in the longitudinal axis direction by a set interval relative to the distal end of the wire.

6. The bending device according to claim 1 , wherein

the bending section is configured from a first bending section that is concatenated to a distal end side of the cap and independently bends according to the towing of the wire and a second bending section that is concatenated to a proximal end side of the cap and bends with the first bending section according to the towing of the wire,

the distal end of the wire is fixed to a distal end in the longitudinal axis direction of the first bending section,

a proximal end in the longitudinal axis direction of the inner coil sheath is configured such that a fixed state and an unfixed state can be switched,

when the proximal end of the inner coil sheath is in the fixed state, only the first bending section bends according to the towing of the wire and, when the proximal end of the inner coil sheath is in the unfixed state, the first bending section and the second bending section bend according to the towing of the wire, and

the cover is covered on an outer circumference of the inner coil sheath in the second bending section.

7. An endoscope comprising the bending device according to claim 1 .