Retractable treatment instrument for endoscope

1. A retractable treatment instrument for an endoscope, comprising:

a flexible sheath comprising at least a tip portion thereof formed of a flexible tube;

an operation wire inserted in the flexible sheath, the operation wire configured to move in an axial direction within the flexible sheath; and

a front-end treatment member attached to a tip of the operation wire, a tip portion of the front-end treatment member comprises a flat rod, and a flat shape of the flat rod being oriented along the axial direction of the flexible sheath,

wherein the front-end treatment member is configured to move back and forth—along the axial direction with respect to a tip of the flexible sheath,

the front-end treatment member having a wide part elongated in a radial direction of the flexible tube, wherein the wide part is configured to press and broaden the flexible tube from an inside of the flexible tube,

the wide part being formed integrally with a base portion of the front-end treatment member,

corner portions of the wide part being cut away such that each edge of the wide part bends at a predetermined degree,

wherein the flexible sheath has at least one expanded part in which the wide part of the front-end treatment member is configured to fit, the at least one expanded part being located at a part of the flexible sheath comprising the flexible tube, and

wherein the at least one expanded part is formed by pressing a part of the flexible tube from both sides of the flexible tube so that the part of the flexible tube is expanded in a direction perpendicular to a pressing direction in which the flexible tube is pressed.

2. The retractable treatment instrument according to claim 1 , further comprising an operation unit attached to a base of the flexible sheath,

wherein the operation unit has a movable hook connected to a base of the operation wire, wherein the movable hook is configured to move the operation wire back and forth in the axial direction, and wherein the movable hook comprises a recess provided on an outer circumferential surface of the movable hook.

3. The retractable treatment instrument according to claim 1 ,

wherein the operation wire is configured to rotate about a central axis of the operation wire and rotate relative to the flexible sheath.

4. The retractable treatment instrument according to claim 3 ,

further comprising a holding ring attached to a base portion of the flexible sheath, wherein the holding ring is configured to rotate the operation wire about the central axis.

5. The retractable treatment instrument according to claim 1 ,

wherein an extension of the tip of the operation wire coincides with a center axis of the wide part.

6. The retractable treatment instrument according to claim 1 , wherein a pad-like part is provided at a tip portion of the front-end treatment member by elongating the flat shape of the flat rod at the tip portion of the front-end treatment member.

7. The retractable treatment instrument according to claim 1 ,

wherein when the wide part of the front-end treatment member is positioned within the at least one expanded part of the flexible sheath, the front-end treatment member is fully retracted into the flexible sheath.

8. The retractable treatment instrument according to claim 1 , wherein:

the at least one expanded part comprises a plurality of expanded parts; and

the plurality of expanded parts are arranged along an axial direction of the flexible sheath.

9. The retractable treatment instrument according to claim 8 , wherein:

when the wide part of the front-end treatment member is positioned within a rear end expanded part of the plurality of expanded parts nearest to a base of the flexible sheath, the front-end treatment member is fully retracted into the flexible sheath; and

when the wide part of the front-end treatment member is positioned within one of the plurality of expanded parts other than the rear end expanded part, the front-end treatment member protrudes from the tip of the flexible sheath by a predetermined length.

10. The retractable treatment instrument according to claim 1 ,

wherein the expanded part is formed by expanding the flexible tube uniformly in a radial direction of the flexible tube.

11. The retractable treatment instrument according to claim 1 ,

wherein the flexible tube has a cut off part which is formed by cutting off a part of the at least one expanded part projected outward from an outside diameter the flexible tube.

12. The retractable treatment instrument according to claim 1 ,

wherein the retractable treatment instrument satisfies a condition:

1.07d≦W≦1.26d

where W represents a width of the wide part in an elongated direction, and d represents an internal diameter of the flexible sheath.