Endoscope treatment tool

1. An endoscope treatment tool comprising:

a tubular sheath member that can be inserted into a channel of an endoscope;

a wire that is inserted into an interior of the sheath member in such a manner that the wire can be advanced/retracted in a longitudinal direction of the sheath member; and

a basket that is provided at a distal end of the wire, the basket being formed to protrude from and to be pulled into a distal-end opening in the sheath member by advancing and retracting the wire, the basket comprising a plurality of elastic wires bundled into a basket shape, the plurality of wires being expanded in a state in which the basket is made to protrude from the sheath member and being contracted by being pulled into the sheath member,

wherein the sheath member is configured having a two-layer structure in which a metal coil and a resin tube are layered in a radial direction and secured to each other at least at both end parts in the longitudinal direction thereof,

in the metal coil, lateral cross-sectional shapes of portions of a strand that are adjacent to each other in the longitudinal direction have a complementary depression and protrusion that are brought into tight contact with each other,

the resin tube has a flexural rigidity that is greater than that of the metal coil, and

the strand of the metal coil has a lateral cross-sectional shape in which at least a part of the protrusion on one side in the longitudinal direction is arc shaped and at least a part of the depression on the other side thereof is arc shaped.

2. An endoscope treatment tool according to claim 1 , wherein the resin tube is disposed on an inner circumferential side of the metal coil.

3. An endoscope treatment tool according to claim 2 , wherein

a thickness of the metal coil in a radial direction and a thickness of the resin tube in a radial direction have a relationship described below:

t 1< t 2,

where t 1 is the thickness of the metal coil in the radial direction, and t 2 is the thickness of the resin tube in the radial direction.

4. An endoscope treatment tool according to claim 1 , wherein a thickness of the metal coil in a radial direction and a thickness of the resin tube in a radial direction have a relationship described below:

t 1< t 2,

where t 1 is the thickness of the metal coil in the radial direction, and t 2 is the thickness of the resin tube in the radial direction.

5. An endo scope treatment tool according to claim 1 , wherein the resin tube is disposed on an outer circumferential side of the metal coil.

6. An endoscope treatment tool according to claim 5 ,

wherein the sheath member is provided with, at a distal end thereof in the longitudinal direction, a cylindrical distal-end member that secures at least the metal coil and that has substantially the same inner diameter as that of the metal coil, and

wherein a thickness of the metal coil in a radial direction, a thickness of the resin tube in a radial direction, and a thickness of the distal-end member in a radial direction have a relationship described below:

t 3> t 1+ t 2,

where t 1 is the thickness of the metal coil in the radial direction, t 2 is the thickness of the resin tube in the radial direction, and t 3 is the thickness of the distal-end member in the radial direction.

7. An endoscope treatment tool according to claim 1 , wherein the metal coil and the resin tube are secured to each other at the both end parts so that surface contact between the depression and the protrusion is maintained.

8. An endoscope treatment tool according to claim 7 , wherein

a thickness of the metal coil in a radial direction and a thickness of the resin tube in a radial direction have a relationship described below:

t 1< t 2,

where t 1 is the thickness of the metal coil in the radial direction, and t 2 is the thickness of the resin tube in the radial direction.