MEDICAL APPARATUS

1 . A medical apparatus comprising:

a bendably deformable portion;

a deforming-force-transmitting mechanism that is connected to a part of the bendably deformable portion; and

an operation portion that applies a deforming force or a shape retaining force to the bendably deformable portion by controlling a tension applied to the deforming-force-transmitting mechanism,

wherein the deforming-force-transmitting mechanism includes a tension reducing mechanism.

2 . The medical apparatus according to claim 1 , wherein the tension reducing mechanism changes a distance between the bendably deformable portion and the operation portion by opening a part of the deforming-force-transmitting mechanism when a tension at a predetermined value or higher is applied to the deforming-force-transmitting mechanism.

3 . The medical apparatus according to claim 2 ,

wherein the deforming-force-transmitting mechanism includes

a first deforming-force-transmitting path; and

a second deforming-force-transmitting path that is longer than the first deforming-force-transmitting path,

wherein, when the part of the deforming-force-transmitting mechanism is closed, the deforming force or the shape retaining force from the operation portion is transmitted to the bendably deformable portion through the first deforming-force-transmitting path,

wherein, when the tension at the predetermined value or higher is applied to the first deforming-force-transmitting path, a part of the first transmitting path opens, and

wherein, after the part of the first transmitting path is open, the deforming force or the shape retaining force from the operation portion is transmitted to the bendably deformable portion through the second transmitting path.

4 . The medical apparatus according to claim 3 ,

wherein the first transmitting path includes a shared part that is shared with a part of the second transmitting path, and

wherein, when the tension at the predetermined value or higher is applied to the first deforming-force-transmitting path, a part of the first transmitting path other than the shared part opens.

5 . The medical apparatus according to claim 1 , wherein the deforming-force-transmitting mechanism is positioned in such a manner as to deviate from the center of a cross section of the bendably deformable portion.

6 . The medical apparatus according to claim 2 , further comprising a mechanism that detects the opening of the part of the deforming-force-transmitting mechanism.

7 . The medical apparatus according to claim 6 , further comprising a mechanism that notifies a user of the opening of the part of the deforming-force-transmitting mechanism.

8 . A medical apparatus comprising:

a bendably deformable portion;

a deforming-force-transmitting mechanism that is connected to a part of the bendably deformable portion; and

an operation portion that controls a tension applied to the deforming-force-transmitting mechanism,

wherein the deforming-force-transmitting mechanism includes

a first portion including a wire or a group of wires that are connected in parallel;

a second portion including a group of wires that are connected in parallel; and

a third portion including a wire or a group of wires that are connected in parallel,

wherein the first portion, the second portion, and the third portion are connected in series,

wherein at least one of the wires of the second portion has a different length from the others, and

wherein at least a shortest one of the wires of the second portion includes a part having a smaller tensile breaking strength than all of the other wires included in the deforming-force-transmitting mechanism.

9 . A medical apparatus comprising:

a bendably deformable portion;

a deforming-force-transmitting mechanism that is connected to a part of the bendably deformable portion; and

an operation portion that controls a tension applied to the deforming-force-transmitting mechanism,

wherein the deforming-force-transmitting mechanism includes

a first portion including a wire or a group of wires that are connected in parallel;

a second portion including a wire or a group of wires that are connected in parallel; and

a third portion including a wire or a group of wires that are connected in parallel,

wherein the first portion, the second portion, and the third portion are connected in series,

wherein all of the wires included in the second portion each have a part having a smaller tensile breaking strength than all of the wires included in the first portion and the third portion,

wherein the medical apparatus further includes a tension maintaining member, and

wherein, if all of the wires included in the second portion are broken, the tension maintaining member maintains a tension applied to the first portion and a tension applied to the third portion at substantially the same values as those obtained before the breakage.

10 . The medical apparatus according to claim 8 , wherein the wires included in the first portion are positioned in such a manner as to deviate from the center of a cross section of the bendably deformable portion.

11 . The medical apparatus according to claim 8 ,

wherein the wires included in the deforming-force-transmitting mechanism include

at least one driving wire that is deformable with the bendably deformable portion;

at least one controlling wire that controls a force of pulling the driving wire; and

at least one breaker wire that breaks when the force of pulling the driving wire reaches a predetermined value or larger,

wherein the driving wire is held by a driving wire holder, and

wherein the driving wire holder has graduations that indicate a length of travel of the driving wire holder.

12 . The medical apparatus according to claim 11 , further comprising an impact absorbing member that absorbs an impact on the driving wire holder when the breaker wire is broken.