Dilator

1 . A dilator comprising:

a distal end side coil part comprising:

a first coil having a hollow shape and comprising a first wire wound in a first winding direction; and

a second coil provided around an outer periphery of the first coil and comprising a second wire wound in a second winding direction that is opposite to the first winding direction; and

a proximal end side coil part located at a proximal end side of the distal end side coil part and having a distal end portion connected to a proximal end portion of the distal end side coil part, the proximal end side coil part comprising:

a third coil having a hollow shape and comprising a third wire wound in the second winding direction; and

a fourth coil provided around an outer periphery of the third coil and comprising a fourth wire wound in the first winding direction.

2 . The dilator according to claim 1 , wherein:

the first winding direction is a direction of S-winding, and

the second winding direction is a direction of Z-winding.

3 . The dilator according to claim 1 , wherein a weld connecting the distal end side coil part and the proximal end side coil part is formed between an entire periphery of the proximal end portion of the distal end side coil part and an entire periphery of the distal end portion of the proximal end side coil part.

4 . The dilator according to claim 1 , wherein:

the first wire and the third wire are different wires from each other, and

the second wire and the fourth wire are different wires from each other.

5 . The dilator according to claim 1 , wherein:

in the distal end side coil part, the first coil is an innermost coil and the second coil is an outermost coil, and

in the proximal end side coil part, the third coil is an innermost coil and the fourth coil is an outermost coil.

6 . A dilator comprising:

a distal end side coil part comprising:

a first coil having a hollow shape and comprising a first wire wound in a first winding direction; and

a second coil provided around an outer periphery of the first coil and comprising a second wire wound in a second winding direction that is opposite to the first winding direction; and

a proximal end side coil part located at a proximal end side of the distal end side coil part and having a distal end portion connected to a proximal end portion of the distal end side coil part, the proximal end side coil part comprising:

a third coil having a hollow shape and comprising a third wire wound in the second winding direction; and

a fourth coil provided around an outer periphery of the third coil and comprising a fourth wire wound in the first winding direction,

wherein a weld connecting the distal end side coil part and the proximal end side coil part is formed between an entire periphery of the proximal end portion of the distal end side coil part and an entire periphery of the distal end portion of the proximal end side coil part,

wherein a lumen of the first coil and a lumen of the third coil are in communication with each other.

7 . The dilator according to claim 6 , wherein:

the first winding direction is a direction of S-winding, and

the second winding direction is a direction of Z-winding.

8 . The dilator according to claim 6 , wherein:

the first wire and the third wire are different wires from each other, and the second wire and the fourth wire are different wires from each other.

9 . The dilator according to claim 6 , wherein:

the diameter of the wires forming the fourth coil is larger than the diameter of the wires forming the third coil.