MEDICAL APPARATUS

To prevent a medical apparatus such as an endoscope or an electrophysiological catheter that includes an insertion portion to be inserted into the body of a patient from breaking at any unexpected positions. A medical apparatus includes 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. The deforming-force-transmitting mechanism includes a tension reducing mechanism.

TECHNICAL FIELD

The present invention relates to a bendable medical apparatus.

BACKGROUND ART

Medical apparatuses such as endoscopes and electrophysiological catheters that access target sites through internal body structures such as coeloms include insertion portions that are to be inserted into the bodies of patients. The insertion portions of some of such medical apparatuses include bendable portions, with which the insertion portions can move along internal body structures. The medical apparatuses are guided to various sites of human bodies by such bendable functions. As a result, the success rate of examination and treatment is improved, and the pain or side effects experienced by patients, the use or risk of painkillers, and so forth are reduced.

Exemplary medical apparatuses have bendable structures equipped with operation wires. Such a medical apparatus is bendable by pulling the operation wires with a driving unit. PTL 1 discloses a medical apparatus that is capable of retaining a desired bent shape during a treatment even if any operation wires are broken. In this technology, the shape of the apparatus is retained by securing or releasing the operation wires even if any operation wires are broken on a side of the driving unit with respect to a securing/releasing unit.

In the medical apparatus disclosed by PTL 1, the wires may be broken at unexpected positions while the wires are released.

CITATION LIST

Patent Literature

SUMMARY OF INVENTION

According to an aspect of the present invention, a medical apparatus includes 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. The deforming-force-transmitting mechanism includes a tension reducing mechanism.

DESCRIPTION OF EMBODIMENTS

Embodiments of the medical apparatus according to the present invention are summarized as follows when considered from one aspect.

A medical apparatus according to each of embodiments of the present invention includes 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. The deforming-force-transmitting mechanism includes a tension reducing mechanism.

The bendably deformable portion is a structure or material a part or the entirety of which is bendable. The part or the entirety of the bendably deformable portion may be inserted into a human body. In such a case, the bendably deformable portion is desired to be deformable while being inside the human body. Typically, the bendably deformable portion has a long side and a short side. The bendably deformable portion is desired to be bendable more easily in a short-side direction than being deformed in a long-side direction.

The deforming-force-transmitting mechanism is connected to a part of the bendably deformable portion. Typically, the deforming-force-transmitting mechanism has a long side and a short side. Typically, one end (one long-side end in many cases) of the deforming-force-transmitting mechanism is connected to the part of the bendably deformable portion. The bendably deformable portion deforms when receiving a force from the deforming-force-transmitting mechanism.

The operation portion applies a deforming force or a shape retaining force to the bendably deformable portion by controlling the tension applied to the deforming-force-transmitting mechanism. For example, in a configuration where one part of the deforming-force-transmitting mechanism and one part of the bendably deformable portion are connected to each other while another part of the deforming-force-transmitting mechanism and the operation portion are connected to each other, the operation portion controls the tension applied to a point between the one part and the other part of the deforming-force-transmitting mechanism. The above connections are not limited to mechanical connections and may be connections utilizing magnetic force or the like.

The tension reducing mechanism may change 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. The expression “opening a part of the deforming-force-transmitting mechanism” means that a part of the deforming-force-transmitting mechanism that forms a path through which the deforming force or the shape retaining force is transmitted to the bendably deformable portion opens, disabling the transmission of the deforming force or the shape retaining force to the bendably deformable portion through that path solely. According to an embodiment of the present invention, instead of the open part, a new path (a path having a different length from the path provided before the opening) is provided by another part of the deforming-force-transmitting mechanism. Hence, the deforming force or the shape retaining force continues to be transmitted to the bendably deformable portion.

In an exemplary case where the distance between the bendably deformable portion and the operation portion is changed, the deforming-force-transmitting mechanism may include a first deforming-force-transmitting path, and a second deforming-force-transmitting path that is longer than the first deforming-force-transmitting path. In such a case, 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. Furthermore, 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. 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. The first transmitting path may include a shared part that is shared with a part of the second transmitting path. In such a case, 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.

The medical apparatus according to the above aspect of the present invention may further include a mechanism that detects the opening of the part of the deforming-force-transmitting mechanism. The medical apparatus according to the above aspect of the present invention may further include a mechanism that notifies a user of the opening of the part of the deforming-force-transmitting mechanism.

Embodiments of the present invention are also summarized as the following two typical general embodiments when considered from other aspects.

According to a first general embodiment of the present invention, a medical apparatus includes 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. 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. The first portion, the second portion, and the third portion are connected in series. At least one of the wires of the second portion has a different length from the others. 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.

According to a second general embodiment of the present invention, a medical apparatus includes 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. 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. The first portion, the second portion, and the third portion are connected in series. 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. The medical apparatus further includes a tension maintaining member. 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.

The wires may be connected to one another directly or via other members.

The term “wire” represents, in short, a long bendable member and is a concept that encompasses materials that are commonly called thread, cord, wire, and the like.

Typically, the “part having a smaller tensile breaking strength” can be determined on the basis of comparison in terms of the cross sections of the wires. In a case where the tension applied to the deforming-force-transmitting mechanism is experimentally increased, the part that breaks first is determined as the “part having a smaller tensile breaking strength”.

The general embodiments, mainly, the first general embodiment, will now be described more specifically, including modifications thereof. A medical apparatus according to the first general embodiment is configured as illustrated inFIGS. 1A and 1B.FIG. 1Ais a side view of the medical apparatus according to the first general embodiment and illustrates the relationship among elements included in the medical apparatus. The medical apparatus according to the first general embodiment includes an insertion portion1as the bendably deformable portion. The insertion portion1is insertable into a narrow space such as a coelom. The distal end of the insertion portion1corresponds to point A. The insertion portion1has a round columnar shape whose long-side direction corresponds to a virtual line connecting point A and point B and whose short-side direction is perpendicular to the long-side direction. Hereinafter, a side of the insertion portion1that is nearer to point A is referred to as distal side, and the other side of the insertion portion1that is nearer to point B is referred to as proximal side. If an image pickup device, an illumination device, and so forth are provided at the distal end A of the insertion portion1, the medical apparatus functions as an endoscope. If an electrode is provided at the distal end A of the insertion portion1, the medical apparatus functions as an electrophysiological catheter. The medical apparatus according to the first general embodiment further includes, as the deforming-force-transmitting mechanism, a series of a driving wire8, a breaker portion6including a wire, a redundant path7including a wire, and a controlling wire4that are connected to one another. As illustrated inFIGS. 1A and 1B, the wire forming the breaker portion6and the wire forming the redundant path7are connected in parallel as a block. The controlling wire4and the driving wire8are connected in series with the block. The controlling wire4is on the distal side and the driving wire8is on the proximal side with respect to the block. The block including the wire forming the breaker portion6and the wire forming the redundant path7that are connected in parallel corresponds to the second portion. The controlling wire4and the driving wire8correspond to the first portion and the third portion, respectively. One end of the controlling wire4is secured at the distal end A, and the other end of the controlling wire4is connected to point B. The controlling wire4is a bendable wire capable of transmitting tension and extends through the insertion portion1as illustrated by the dotted line inFIG. 1A. The insertion portion1has a guide hole (not illustrated) that allows a part of the controlling wire4illustrated by the dotted line to move in the long-side direction of the controlling wire4. The controlling wire4passes through the insertion portion1at a position deviating from the center of a cross section of the insertion portion1, the cross section being taken in a direction perpendicular to the long-side direction. The breaker portion6and the redundant path7that are connected in parallel extend between point B and point C. The driving wire8is connected to point C and to a driving pulley9. The driving wire8and the driving pulley9in combination function as a driving unit2. The driving pulley9is connected to a power source (not illustrated). A combination of the driving pulley9and the power source corresponds to the operation portion. A pulling force generated by the power source is transmitted to the driving unit2, the breaker portion6(or the redundant path7), and the controlling wire4in that order.FIG. 1Aillustrates a state where the breaker portion6is not broken, that is, the breaker portion6is continuous. In the state where the breaker portion6is continuous, the breaker portion6transmits the pulling force to the controlling wire4. If the breaker portion6is broken in such a manner as to be described below, the redundant path7transmits the pulling force to the controlling wire4.

The insertion portion (bendably deformable portion)1includes a bendable portion3that is bendable and an unbendable portion5that is substantially unbendable. The bendable portion3is bendable by pulling the controlling wire4. The unbendable portion5does not substantially bend even by pulling the controlling wire4. As illustrated inFIGS. 1A and 1B, the bendable portion3and the unbendable portion5are provided on the distal side and the proximal side, respectively, of the insertion portion1. The unbendable portion5is a stiff portion that does not substantially bend or a flexible portion that has a higher stiffness in the bending direction than the bendable portion3. The expression “substantially unbendable” used herein means that the stiffness in the bending direction is about 100 times or greater than that of the bendable portion3.

As described above, the driving unit2includes the driving wire8and the driving pulley9. The driving pulley9is connected to the power source. When the driving pulley9rotates, the driving wire8is wound up around the driving pulley9and is pulled. The driving wire8is made of a material that transmits the pulling force, or a bendable wire material that transmits tension. The driving unit2may alternatively have another configuration that transmits the pulling force generated by the power source. For example, the driving unit2may be a pushable/pullable columnar member.

A bending movement of the medical apparatus according to the first general embodiment will now be described with reference toFIG. 1B. The driving pulley9winds up the driving wire8in a direction of arrow E, whereby the breaker portion6and the controlling wire4are pulled. The controlling wire4is secured at the distal end A of the insertion portion1and passes through a position deviating from the cross-sectional center of the insertion portion1. Hence, the tension produced by the pulling of the controlling wire4acts as a torque that bends the bendable portion3in a direction of arrow D. With such a bending torque, the bendable portion3bends as illustrated inFIG. 1B. If the length of the driving wire8to be wound around the driving pulley9is adjusted, the magnitude of the bending torque is adjusted correspondingly. In this manner, the bending movement of the bendable portion3is controlled.

Behaviors of the breaker portion6and the redundant path7will now be described with reference toFIGS. 2A and 2B, which illustrate a state where the breaker portion6is continuous and a state where the breaker portion6is broken, respectively. The state illustrated inFIG. 2Ais a normal use state. As illustrated inFIG. 2A, when the controlling wire4is pulled in the direction of arrow E, the controlling wire4undergoes the bending movement in the direction of arrow D. In this state, an environment11such as body tissues is in contact with the distal end A. If the controlling wire4in this state is further pulled in the direction of arrow E, the distal end A is strongly pressed against the environment11. Moreover, since a high tension is applied to the elements forming the deforming-force-transmitting mechanism, the elements may be broken. Such a situation is avoidable with the medical apparatus according to the first general embodiment if the breaking strength of the breaker portion6is set appropriately. The breaking strength of the breaker portion6is set to a value smaller than the breaking strength of the controlling wire4. Hence, the breaker portion6breaks before the tension reaches the breaking strength of the controlling wire4. Thus, breakage of the deforming-force-transmitting mechanism at an unexpected position is avoided.

If the stress that is allowable by the environment11is smaller than the breaking strength of the controlling wire4, the breaking strength of the breaker portion6may be set to a value that does not exceed the allowable stress. In such a case, the influence upon the environment11is reduced.

The breaker portion6is allowed to be broken at any position between point B and point C. That is, the breaker portion6may be broken at point B or point C. For example, the driving wire8, the redundant path7, and the controlling wire4may be provided as a piece of wire, in parallel with which the breaker portion6may be connected. In such a configuration, the breaker portion6tends to be broken at point B or point C.

FIG. 2Billustrates a state where the breaker portion6is broken. If a tension that exceeds the breaking strength of the breaker portion6is applied to the breaker portion6, the breaker portion6breaks. Once the breaker portion6is broken, the redundant path7transmits the tension from the driving wire8to the controlling wire4as illustrated inFIG. 2B. The redundant path7may be made of a bendable wire material that transmits tension, as with the controlling wire4. In the state illustrated inFIG. 2A, the redundant path7is connected to point B and point C with some slack. In the state illustrated inFIG. 2B, the redundant path7between point B and point C is stretched with a tension applied thereto so as to transmit the pulling force. When the breaker portion6is continuous, the distance between the controlling wire4and the driving wire8is B′-C. When the breaker portion6is broken, the distance between the controlling wire4and the driving wire8is B-C. The difference between the distance B-C and the distance B′-C is hereinafter referred to as avoiding distance10. As described above, when the breaker portion6breaks, the controlling wire4automatically moves in a direction of arrow G by the avoiding distance10. With the movement of the controlling wire4in the direction of arrow G, the distal end A undergoes an avoiding movement from point A′ to point A (in a direction of arrow F), avoiding the application of a large pressing force to the environment11. The avoiding distance10is set to a value shorter than a length by which the bendable portion3moves so as to return to its natural position (the position taken before the controlling wire4is pulled). Therefore, if another environment11such as body tissues is present on a side toward which the bendable portion3undergoes the avoiding movement (in the direction of arrow F), the application of a large pressing force to the other environment11is also avoided. In this manner, at the moment the breaker portion6breaks, the distal end A automatically undergoes the avoiding movement. After the distal end A undergoes the avoiding movement, the redundant path7in replacement transmits the pulling force transmitted from the driving wire8. Therefore, the bendable portion3remains controllable in the same manner as in the state where the breaker portion6is continuous, and the bendable portion3is easily removable from the human body.

Behaviors of the breaker portion6and the redundant path7in another configuration will now be described with reference toFIGS. 3A and 3B, which illustrate a state where a breaker portion6B is continuous and a state where the breaker portion6B is broken, respectively. In the configuration illustrated inFIGS. 3A and 3B, two independent systems are provided each including a controlling wire4A or4B, a breaker portion6A or6B, a redundant path7A or7B, a driving wire8A or8B, and a driving pulley9A or9B. In this configuration, the bendable portion3is bendable in two opposite directions including the direction illustrated inFIGS. 3A and 3B. InFIG. 3B, the system including the controlling wire4A, the breaker portion6A, the redundant path7A, the driving wire8A, and the driving pulley9A is not illustrated.

To prevent the controlling wires4A and4B from slacking during the operation of the medical apparatus, the same pre-tension is applied to the controlling wires4A and4B before bending is performed.FIG. 3Aillustrates a state where the bendable portion3has been bent by pulling the controlling wire4A and is retained in that bent state. That is, the driving pulleys9A and9B are fixed at the respective positions illustrated inFIG. 3A.

InFIG. 3A, the environment11that is moving has come into contact with the distal end A. Such a movement of the environment11may occur with, for example, an unexpected deformation of body tissues. That is, the distal end A may be pushed in a direction of arrow H by the environment11. In the case illustrated inFIG. 3Aalso, the environment11may be influenced or the controlling wire4B may break with an excessive load. In the configuration illustrated inFIG. 3A, the controlling wires4A and4B each include a corresponding one of the breaker portions6A and6B and a corresponding one of the redundant paths7A and7B. In the state illustrated inFIG. 3A, the tension applied to the controlling wire4B increases, and the breaker portion6B breaks. InFIG. 3B, the breaker portion6B is broken. When the breaker portion6B breaks, the controlling wire4B automatically moves in a direction of arrow J by the avoiding distance10. Hence, even if the environment11continues to move in a direction of arrow I, the application of a large stress to the distal end A is avoided while the distal end A is moving from point A′ to point A. In this manner, even if the distal end A is pushed by the environment11, the breaker portion6B prevents the occurrence of a large load that may be applied to the controlling wire4B. Furthermore, the redundant path7B allows the bendable portion3to undergo the avoiding movement that prevents the moving environment11from being influenced.

FIG. 4illustrates another medical apparatus according to the first general embodiment. As with the configuration illustrated inFIGS. 3A and 3B, the configuration illustrated inFIG. 4includes two independent systems each including a controlling wire4A or4B, a breaker portion6A or6B, a redundant path7A or7B, a driving wire8A or8B, and a driving pulley9A or9B. In addition, the insertion portion1includes two bendable portions3A and3B. The controlling wire4A is secured at point L and is capable of bending the bendable portion3B. The controlling wire4B is secured at point K and is capable of bending both of the bendable portions3A and3B. Thus, the bendable portions3A and3B are bendable by desired amounts, respectively, by adjusting the tensions applied to the respective controlling wires4A and4B. Therefore, as illustrated inFIG. 4, the bendable portions3A and3B are simultaneously bendable in opposite directions, respectively. In this configuration also, the medical apparatus can undergo the avoiding movement in the situation described above referring toFIGS. 2A to 3B. Particularly, the controlling wires4A and4B in this configuration are provided for the different bendable portions3A and3B, and loads allowable by the controlling wires4A and4B are different. Therefore, if the breaking strengths of the breaker portions6A and6B (not illustrated but connected in parallel with the redundant paths7A and7B, respectively) are adjusted, the breaker portions6A and6B can be made to function with respective desired loads.

The relationship between the length of pulling the controlling wire4and the length of travel of the distal end (point K) also differs between the controlling wires4A and4B. Therefore, if the lengths of the redundant paths7A and7B are adjusted, the avoiding distance10and the displacement of the distal end K resulting from the avoiding movement can be set to desired values, respectively.

As described above, each of the above medical apparatuses according to the first general embodiment of the present invention includes the breaker portion6and the redundant path7. Therefore, the controlling wire4is prevented from breaking, and the influence upon the environment11such as peripheral tissues is reduced. Even if the controlling wire4includes a plurality of wires, the breaker portion6and the redundant path7can be provided for each of the controlling wires4independently. Hence, the loads allowable by the respective controlling wires4and the length of avoiding movement of the distal end A or K can be set for the individual breaker portions6and the individual redundant paths7.

EXEMPLARY EMBODIMENTS

More specific embodiments of the present invention will now be described. The following exemplary embodiments do not limit the present invention in any way.

First Exemplary Embodiment

A first exemplary embodiment of the present invention will now be described with reference toFIGS. 5A and 5B. The first exemplary embodiment corresponds to the first general embodiment described above. More specifically,FIGS. 5A and 5Billustrate elements according to the first exemplary embodiment that correspond to the breaker portion6and the redundant path7illustrated inFIGS. 1A to 4.FIG. 5Aillustrates a state where an element corresponding to the breaker portion6is continuous.FIG. 5Billustrates a state where the element corresponding to the breaker portion6is broken.

The controlling wire4is secured by a controlling wire anchor15, which is also referred to as controlling wire holder. The driving wire8is secured by a driving wire anchor14, which is also referred to as driving wire holder. Points B and C illustrated inFIGS. 5A and 5Bcorrespond to points B and C illustrated inFIGS. 1A and 1B. The driving wire anchor14and the controlling wire anchor15are connected to each other with a breaker wire16, which corresponds to the breaker portion6. The breaker wire16has a smaller diameter than the controlling wire4and the driving wire8. Therefore, the breaker wire16has a low breaking strength than the controlling wire4and the driving wire8.

The driving wire anchor14and the controlling wire anchor15are connected to each other also with redundant wires12and redundant wire anchors13, which correspond to the redundant path7. The redundant wire anchors13are also referred to as redundant wire holders. The redundant wires12each have some slack and are horizontally symmetrical to each other in the state illustrated inFIG. 5A. In the first exemplary embodiment, the controlling wire4is made of a superelastic titanium-nickel alloy, and the driving wire8and the breaker wire16are made of stainless steel.

Referring toFIG. 5B, when the breaker wire16breaks, the redundant wires12each having some slack are stretched. Hence, the controlling wire4moves in a direction away from point C by the avoiding distance10. In this manner, with the breaking strength of the breaker wire16being as a threshold, the avoiding movement is realized without any overload on the controlling wire4. Thereafter, the redundant wires12allow the pulling force transmitted from the driving wire8to be transmitted to the controlling wire4. Hence, the bendable portion3continues to be operable and is removable from the human body.

The presence of the driving wire anchor14and the controlling wire anchor15makes it possible to exchange the breaker wire16solely. Therefore, even if the insertion portion1has an overload, the medical apparatus can be repaired easily. Furthermore, the redundant wire anchors13may be detachable from the driving wire anchor14and the controlling wire anchor15via screws, hooks or the like. Such a configuration facilitates exchanging of the redundant wires12and changing of the avoiding distance10.

The elements corresponding to the breaker portion6and the redundant path7are all wires and are therefore bendable freely. Hence, the path from the controlling wire4to the driving pulley9can be set freely. Particularly, in a case where the outside diameter of the insertion portion1is small and the gap between adjacent ones of a plurality of driving pulleys9is larger than the gap between adjacent ones of a plurality of controlling wires4provided in correspondence with the driving pulleys9, the freedom in setting the above path is advantageous.

The controlling wire anchor15may have optical or magnetic reference marks or graduations. By optically or magnetically reading the positions of such marks (or graduations), the length by which the controlling wire4has been pulled can be detected. Furthermore, any breakage of the breaker wire16can be detected, whereby the application of a load exceeding the allowable stress can be detected.

Second Exemplary Embodiment

A second exemplary embodiment of the present invention will now be described with reference toFIGS. 6A,6B,7A, and7B. The second exemplary embodiment corresponds to the second general embodiment described above. Elements having the same functions as those described in the first exemplary embodiment are denoted by the corresponding reference numerals, and description thereof is thus omitted.

FIGS. 6A and 6Bare a sectional view and a top view, respectively, of elements according to the second exemplary embodiment that correspond to the breaker portion6and the redundant path7.FIG. 6Ais taken along line VIA-VIA illustrated inFIG. 6B.FIG. 6Bis taken along line VIB-VIB illustrated inFIG. 6A.

The second exemplary embodiment differs from the first exemplary embodiment in elements corresponding to the redundant path7. In the second exemplary embodiment, the elements corresponding to the redundant path7include a link portion17and a stopper portion18, which in combination correspond to the tension maintaining member described above.

The driving wire anchor14is secured to the link portion17. The stopper portion18is secured to the link portion17. The link portion17and the stopper portion18are made of highly stiff materials. In the second exemplary embodiment, the link portion17and the stopper portion18are made of stainless steel.

The controlling wire4extends through the stopper portion18. The controlling wire4is movable with respect to the stopper portion18. The controlling wire anchor15is provided above the link portion17. A cover20is provided as illustrated inFIGS. 6A and 6Band guides the controlling wire anchor15to be movable only along a virtual line passing through point C and point B.

Behaviors of the above elements according to the second exemplary embodiment will now be described with reference toFIGS. 7A and 7B.FIGS. 7A and 7Bare sectional views both taken along line VII-VII illustrated inFIG. 6Aand illustrate a state where the breaker wire16is continuous and a state where the breaker wire16is broken, respectively. As illustrated inFIG. 7A, when the breaker wire16is continuous, the controlling wire anchor15is spaced apart from the stopper portion18by the avoiding distance10. As illustrated inFIG. 7B, when the breaker wire16is broken, there is no gap between the controlling wire anchor15and the stopper portion18and the space between the controlling wire anchor15and the driving wire anchor14increases by the avoiding distance10. In this manner, the controlling wire4is movable by the avoiding distance10as illustrated inFIGS. 7A and 7B. In the state illustrated inFIG. 7Bwhere the breaker wire16is broken, the controlling wire anchor15is stopped by the stopper portion18. Hence, the pulling force transmitted from the driving wire8is transmitted to the controlling wire4.

Since the link portion17and the stopper portion18are highly stiff, the avoiding distance10is determined accurately. Particularly, the amount of deformation of the stopper portion18that occurs when the controlling wire anchor15collides with the stopper portion18is negligibly small compared with the avoiding distance10. Therefore, the avoiding distance10is determined accurately.

Since the link portion17and the cover20cover the breaker wire16, the breaker wire16is prevented from breaking with an unexpected external force. For example, an unintentional touch on the breaker wire16during disassembling work, adjusting work, or the like is prevented. In addition, in the state where the breaker wire16is continuous, foreign matter is prevented from unexpectedly getting caught between the stopper portion18and the controlling wire anchor15. Hence, the avoiding movement is assuredly realized in response to the breakage of the breaker wire16.

A modification of the second exemplary embodiment will now be described with reference toFIGS. 8A and 8B.FIGS. 8A and 8Billustrate the modification in which a damper member19is added to the configuration illustrated inFIGS. 7A and 7B. The damper member19is also a part of the tension maintaining member described above.FIGS. 8A and 8Billustrate a state where the breaker wire16is continuous and a state where the breaker wire16is broken, respectively. As illustrated inFIG. 8A, the damper member19is provided between the controlling wire anchor15and the stopper portion18. In this modification, the damper member19is secured to the stopper portion18. The damper member19is in a form similar to the stopper portion18. The controlling wire4is movable with respect to the damper member19. The damper member19may be made of an elastomer based on nylon, urethane, or the like. In this modification, the damper member19is made of urethane elastomer.

When the breaker wire16breaks, the damper member19is sandwiched between the controlling wire anchor15and the stopper portion18as illustrated inFIG. 8B. In this state, the damper member19absorbs the impact of collision of the controlling wire anchor15against the stopper portion18. Thus, the rate of change in the pulling force that occurs at the collision of the controlling wire anchor15against the stopper portion18is reduced. Furthermore, in a case where the rate of change in the pulling force is nearly the same as or greater than the frequency of vibration in any of various resonance modes generated in the bendable portion3, unnecessary excitation of resonance that may occur in the insertion portion1is suppressed.

This application claims the benefit of Japanese Patent Application No. 2012-124499, filed May 31, 2012, which is hereby incorporated by reference herein in its entirety.

REFERENCE SIGNS LIST

ADVANTAGEOUS EFFECTS OF INVENTION

According to the present invention, breakage of any wires at unexpected positions is prevented with a simple mechanism.