Bending mechanism and stereoscope using same

Abstract: A bending mechanism comprising a tubular body or linear body having a bending part, a movable part which can move in the lengthwise direction of said tubular body or linear body, two actuators formed to antagonize via said movable part, and a pull wire which extends in the lengthwise direction along the bending part, one end of the wire being fixed to one end side of the bending part and the other end of the wire being fixed to the movable part set at the other end side of the bending part, wherein at least one of the two actuators is a shape memory element, and a stereoscope. The bending mechanism of the present invention is free of displacement of movable part when bending action is not needed, since two actuators are used which antagonize each other via movable part, whereby buckling of the bending part can be prevented. The simple structure of activator unit of the present invention facilitates reduction of the size of the structure. The stereoscope of the present invention is free of buckling of image guide and the like, and angle of convergence can be adjusted easily and a desired three-dimensional view can be obtained easily.

Description: The present invention relates to a mechanism capable of bending a bending part by activating an actuator of a shape memory element, and further to a stereoscope utilizing said mechanism. A tip articulation mechanism has been conventionally used for bending a tip articulation endoscope used for observation of sites difficult to see by a normal technique, such as the inside of small tubes and human body. As such tip articulation endoscope, there has been developed one wherein the distal end portion of the endoscope and the operation end at the proximal side are connected by a pull wire, and an operator manipulates an operation nob attached to the above-mentioned operation end to pull the wire to cause articulation of the tip of the endoscope. This type of tip articulation endoscope requires highly skilled manipulation and is barely an ideal mechanism. Thus, a tip articulation endoscope has been proposed which aims at mechanical operation by the use of a shape memory alloy for the tip articulation mechanism. For example, there have been proposed one wherein the above-mentioned pull wire is made from such a shape memory alloy, and upon heating, the wire shrinks to bend the inserted tip of the endoscope, like pulling the tip by the wire as mentioned above; and one equipped with a shape memory alloy coil at the end portion of the above-mentioned pull wire, wherein, upon heating of the shape memory alloy coil, the shape memory alloy coil moves to pull the wire to bend the inserted tip of the endoscope. A specific example of the latter endoscope is shown in Fig. 12, which is a two direction articulation endoscope comprising an endoscope 5 set to a tip articulation mechanism. The tip articulation mechanism comprises shape memory alloy coils 2a and 2b, which memorized close coiling state of the coils and set, after stretching, in an outer tube 7 in parallel with the lengthwise direction of the tube, as well as pull wires 4a and 4b fixed, at one end thereof, to the end-most part of a tip articulation part 1b and, at the other end thereof, to the above-mentioned shape memory alloy coils 2a and 2b. The principle of this mechanism is disclosed in EP-A-0 533 050 as follows. That is, the tip articulation endoscope is bent toward the pull wire 4a side upon heating of the shape memory alloy coil 2a, which causes shrinking of the coil 2a to pull the wire 4a, as shown in Fig. 12. When heating is stopped, the shape memory alloy coil 2a undergoes reverse transformation to weaken the pull force to the same extent with the shape memory alloy coil 2b, where the pull force of shape memory alloy coils 2a and 2b are balanced, which means that the articulation part is not bent but linear now. At this point, elasticity (i.e., pull force) is the same for both shape memory alloy coils 2a and 2b when cooled, and the movement is balanced. However, the tip articulation part 1b is under application of force by the above-mentioned two shape memory alloy coils 2a and 2b. In addition, there has been proposed a stereoscope having two image guides, each guide having the above-mentioned tip articulation mechanism to individually change the angle of convergence of image guides. In this mechanism, since the angle of convergence is individually changed by each image guide, a desired stereoscopic image is difficult to obtain and a complicated three-dimensional target cannot be observed accurately. The above-mentioned tip articulation mechanism using the former type of shape memory alloy wire is not practical, since it requires a considerable length of said shape memory alloy wire to enable sufficient tip articulation. Those using the latter type of shape memory alloy coil are subject to buckling of the tip articulation part of the endoscope due to the pull force applied by elasticity which pulls the wire not only during heating but also cooling, thus necessitating another member to prevent such buckling. Such additional member leads to a greater force needed for the bending action, which in turn creates the need to enlarge said shape memory alloy coils, so that the endoscope cannot be made smaller in diameter. When the same, conventional shape memory alloy coil is used, the degree of tip articulation becomes smaller to cause a different problem. When the above-mentioned tip articulation mechanism is applied to a stereoscope, two image guides are respectively associated with the problem of buckling. In addition, the two image guides which function individually make their control difficult and a desired stereovision cannot be obtained with ease. It is therefore an object of the present invention to provide an improved bending mechanism for an endoscope and a stereoscope. The bending mechanism of the present invention comprises a tubular body or linear body having a bending part, a movable part which can move in the lengthwise direction of said tubular body or linear body, two actuators formed such that they antagonize via said movable part, and a pull wire which extends in the lengthwise direction along the bending part wherein one end of the wire is fixed to one end side of the bending part and the other end of the wire is fixed to the movable part set at the other end side of the bending part, wherein at least one of the two actuators is a shape memory element. The two actuators are subject to no particular limitation as long as at least one of them is a shape memory element and they antagonize via the movable part. The both actuators are preferably shape memory elements, since quick responses in, for example, recovering the movable part to the original position (elimination of bending) can be attained as a result of independent activation of the actuators. It is also beneficial to use the same shape memory element for the both actuators, because it facilitates designing of the bending mechanism and control of bending. The above-mentioned antagonization means that the two actuators are activated in the directions that balance the force of each actuator. The bending mechanism of the present invention is more beneficial when the two actuators are shape memory elements, and two pull wires are used where one actuator pulls one wire and the other actuator pulls the other wire, thus enabling bending in two directions. When bending in two directions is desired, the pull wire only need to be pulled toward the proximal end of the bending mechanism by the action of the above-mentioned actuator. As shown in Fig. 2, for example, either end of the pull wire (e.g., 4a) is extended along the bending part and the other end thereof is fixed to the movable part, and either end of the pull wire (e.g., 4b) is extended along the bending part and the other end thereof is fixed to the movable part via a pulley formed on the proximal end side of the tubular body outside the movable range of the movable part; or at least either one of the above-mentioned pull wires is wound around a pinion working with a rack (movable part in this example). When bending in a number of directions is desired, two or more pull wires of shape memory alloy coils are used which can be heated individually. When the shape memory alloy coil is heated, the coil comes to have a greater spring constant than an unheated coil. As a result, when actuator is activated to draw a pull wire, the coil shows smaller elongation, and the pull wire of shape memory alloy coil having a smaller elongation becomes shorter than other pull wires to cause bending in the direction of the shorter wire side. Thus, the shape memory alloy coil to be heated should be appropriately determined to attain bending in a desired direction. This design is simple in construction as compared to an embodiment where plural activator units are contained as described later, and suitable for miniaturization. The present invention is advantageous in that the bending part can be bent to numerous directions by forming plural actuator units wherein one actuator unit comprises two actuators, a movable part and a pull wire, one end of each pull wire of the plural actuator units being extended at a predetermined circumferential position of the bending part, and the other end thereof being fixed to each movable part of the actuator units, whereby the bending part can be beneficially bent in many directions. For forming plural actuator units to allow bending in a number of directions, for example, two actuator units are disposed in the radial direction of the tubular body as shown in Fig. 5, and the pull wires of the aforementioned two actuator units are set at the predetermined circumferential positions and extend in the direction of the above-mentioned bending part, which positions corresponding to desired bending directions (180° opposite positions in Fig. 5). Alternatively, as shown in Fig. 6, the movable part is divided in the circumferential direction of the tubular body (divided into four in Fig. 6), and two actuators and pull wires are set on each of the divided movable parts to give plural actuator units, wherein one end of the pull wires in the actuator unit is set at the predetermined circumferential position and extend in the direction of the above-mentioned bending part, which position corresponding to desired bending directions (in four directions different by 90° in Fig. 6). The shape memory element of the actuator is not particularly limited in terms of material and shape, and shape memory alloys and shape memory polymers can be used, and the mode thereof may be coil, linear materials, plate materials, and the like. Preferred is a shape memory alloy coil, since the actuator can be made smaller and thin with ease by using such a coil which can increase displacement of the movable part without significant decrease in driving force (shape recovery force) as compared to linear materials and plate materials. It is also preferable to form plural shape memory elements in an actuator, because the size of one shape memory element can be reduced. For example, when the movable part is a ring, smaller shape memory elements can be disposed at about same intervals in the circumferential direction of a tubular body, and when the movable part is square, they may be disposed at corners. When they are formed in this manner, the force of the shape memory elements can be uniformly transmitted to the movable part. The plural shape memory elements are preferably heated by application of a current, since serial electric connection thereof for this end makes it possible to decrease the size of the tubular body or linear body and the current for activation. The movable part is subject to no particular limitation as long as it can move in the lengthwise direction of the scope and can be determined as appropriate in terms of shape. Preferred shape thereof is a ring. By mounting the actuators 2a and 2b, and movable part 3 on a tubular body 1, the diameter of the tubular body can be reduced and a greater inside space can be secured. For example, one or more working channels can be formed, in which laser guide optical fiber, pressure sensor, tactile sensor, PH sensor and the like are inserted to additionally impart laser irradiation function and various sensor functions, whereby a multi-functional endoscope can be provided. When a control means is formed on a power supplying means of the actuator of the bending mechanism, the bending angle can be optionally determined. Specifically, for example, when the actuator is a shape memory alloy and the mechanism is activated upon heating by a current, the current is pulsed, so that the amount of current can be varied by pulsing to control heating of the shape memory alloy. As a result, shape recovery deflection (driving amount), namely, pull amount of the pull wire can be controlled to adjust the bending angle. The stereoscope of the present invention comprises two image guides, each having a bending part, which are disposed at a certain distance, a movable part capable of freely moving in the lengthwise direction of the image guide, two actuators formed to antagonize each other via said movable part, and a pull wire with one end thereof formed along the bending part and the other end fixed to the movable part, wherein at least one of the two actuators is a shape memory alloy element, and operation of the pull wire activates the bending parts of the two image guides to make them approach each other. Inasmuch as the two image guides can be co-activated by a coupling wire connecting the two image guides at the distal end portion thereof, with one end of the pull wire connected to the coupling wire and the other end to a movable part, the angle of convergence can be adjusted and controlled to obtain a desired image of three-dimensional targets. By the angle of convergence is meant the angle formed by the axial direction of the image guide before pulling and the axial direction after pulling. When two pull wires are used with the end portion of each one of them connected to the end portion of the two image guides and the other end connected to the movable part, a space can be formed between the two image guides, and various functions can be established using said space. In addition, a stopper to limit displacement of the movable part obviates contact of the two image guides when angle of convergence is changed, which in turn decreases a potential for failure of a scope. The stopper may comprise, for example, a displacement limiting control rod which is attached to the movable part in such a manner that it penetrates through a control window formed therein, so that the displacement occurs only in the region of the opening of the control window. Fig. 1 is a cross section partially broken away of one embodiment of a bending endoscope using the bending mechanism of the present invention. Fig. 2 is a cross section partially broken away of another embodiment of a bending endoscope using the bending mechanism of the present invention. Fig. 3 is a cross section partially broken away of still another embodiment of a bending endoscope using the bending mechanism of the present invention. Fig. 4 is a perspective view showing an actuator unit of the bending mechanism of the present invention. Fig. 5 is a perspective view showing another actuator unit of the bending mechanism of the present invention. Fig. 6 is a perspective view showing still another actuator unit of the bending mechanism of the present invention. Fig. 7 is a perspective view showing still another actuator unit of the bending mechanism of the present invention. Fig. 8 is a lengthwise cross section of the stereoscope of the present invention. Fig. 9 is a lengthwise cross section of another embodiment of the stereoscope of the present invention. Fig. 10 is a cross section of Fig. 9 along A-A. Fig. 11 is a lengthwise cross section of still another embodiment of the stereoscope of the present invention. Fig. 12 is a lengthwise cross section of an articulation endoscope using a conventional articulation mechanism. The present invention is described in more detail in the following. Fig. 1 shows one embodiment of the bending mechanism of the present invention. In this Figure, 1 is a tubular body consisting of a main body 1a and a bending part 1b formed on the distal end of the body. At the end of the main body 1a, a movable part 3 is set which is capable of moving in the lengthwise direction of the tubular body 1, and an actuator 2a of a shape memory alloy coil and an actuator 2b of the same shape memory alloy coil are installed to antagonize each other via said movable part 3. A pull wire 4 extends in the lengthwise direction along the bending part 1b wherein one end of the wire is fixed to one end side of the bending part and the other end of the wire is fixed to the movable part 3. According to this construction, the activation forces of actuators 2a and 2b are balanced by antagonization, and are not transmitted to the movable part 3 in a normal state when actuators are not in operation. Thus, pull force is not applied to the pull wire 4 fixed to the movable part 3. As a result, bending part 1b is not subject to a force and is free of buckling. When this part is to be bent, the actuator 2a is activated by making the shape memory alloy coil in the present embodiment recover to the original shape thereof to alter the balance between the actuators 2a and 2b, thereby to move the movable part 3. Thus, a pull force is applied to the pull wire 4 to cause bending of 1b. In the bending mechanism of the present invention, the tubular or linear body only need to comprise a flexible bending part 1b, and may be exemplified by a tubular or linear body having flexibility in the entirety thereof, an inflexible tubular or linear body connected with a flexible member as a bending part, and the like. The actuators 2a and 2b only need to be able to antagonize via the movable part, and may be disposed serially or in a parallel relationship in the lengthwise direction of the tubular body via the movable part. The former serially disposed actuators are easily fabricated and suitable for small size scopes. The latter parallel actuators are suitable when heating by light is intended, since both actuators can be heated easily. When heating by light is applied, the actuators may be tapered in the lengthwise direction, so that the entire actuators in the lengthwise direction can be heated, which is preferable for materials with poor thermal conduction, such as TiNi shape memory alloy and the like. The movable part 3 is not particularly limited, and is optionally designed according to the mode of use. When a shape memory alloy coil is used for actuator and the actuator is heated by a current, for example, a conductive material is preferably used for easy connection with a lead wire. When a shape memory alloy coil is heated by a current, however, an insulating material should be used to connect the shape memory alloy coil dynamically in parallel and electrically in series, when plural shape memory alloy coils are used in a single actuator. The movable part 3 and two actuators 2a and 2b may be prepared from a single shape memory alloy coil. That is, one shape memory alloy coil is placed in the lengthwise direction of a tubular body, a pull wire 4 and a lead wire for earthing are fixed to the center portion in the lengthwise direction of the shape memory alloy coil, and lead wires are connected to the both ends of the shape memory alloy coil to enable separate heating of the distal end side and the proximal end side divided by the center portion in the lengthwise direction of the shape memory alloy coil. Consequently, the center portion in the lengthwise direction of the shape memory alloy coil functions as a movable part, and the distal end side and the proximal end side from said center portion function as two actuators. This construction simplifies the structure by obviating the connection between the movable part and actuators, which is suitable for miniaturization and easy fabrication. While the pull wire 4 is not particularly limited, a material with less elongation is preferably used. This is because pull wire 4 is preferably devoid of stretching by pulling, so that a stable operation can be secured during bending and repetitive bending. When an image guide is placed in the inside of the tubular body, a bending endoscope can be easily fabricated. The image guide is not subject to any particular limitation as long as it is flexible, and silica fibers and multi-component fibers can be used. The image guide may be used alone or in combination with a light guide to give an image scope. While the above-mentioned embodiments concern a tubular body having a bending part at a distal end, the bending mechanism of the present invention is not limited to this structure. For example, plural bending mechanisms may be serially formed on a tubular body to allow bending of the tubular body in multiple degrees of freedom. Moreover, the tubular body may be a linear body. Fig. 8 shows one embodiment of the stereoscope of the present invention. Following the Figure, a movable part 3 is movably formed on the scope in the lengthwise direction, and two actuators 2a and 2b of shape memory elements are disposed on both sides of said movable part to allow their antagonistic action. Image scopes 5, 5 are installed in a parallel relationship to interpose movable part 3 and actuators 2a and 2b, and are supported by support plates 16, 16 which also fix actuators 2a and 2b and support image scopes 5, 5. The image scopes 5, 5 can be bent, as bending parts, at the distal portion from the distal support plate 16. The actuators 2a and 2b are fixed, at one end thereof, to the support plates 16, 16, and pull wires 4, 4 are fixed, at one end thereof, to movable part 3 and to the end portion of image scopes 5, 5 at the other end. According to this construction, the movable part 3 moves downward in the Figure when the shape memory element 2a is heated to recover to its original shape, thereby pulling the wires 4, 4. In consequence, the bending part of the image scopes 5, 5 is bent as in the above-mentioned bending mechanism to change angle of convergence and obtain a three-dimensional image. The present invention is not limited to the above-mentioned embodiments as regards movable part, actuator, pull wire, image guide and the like of the stereoscope, and those similar to the foregoing various modes described with respect to bending mechanism can be also used. Example 1 The present invention is described in detail by way of specific examples in the following. In this Example, a bending endoscope as shown in Fig. 1 was fabricated. A tubular body 1 comprising a main body 1a (outer diameter 1.0 mm) of a stainless pipe (inner diameter 0.7 mm, outer diameter 0.8 mm) coated with polyimide for insulation, and a stainless close coiling bending part 1b (outer diameter 1.3 mm, strand diameter 0.15 mm) was used. On the periphery thereof, a first actuator 2a of a TiNi shape memory alloy coil spring which was close coiled at strand diameter 0.25 mm, outer diameter 1.6 mm and length 6 mm and made to store this coiling state, and a second actuator 2b of the same shape memory alloy coil spring were serially set in the lengthwise direction of the tubular body 1 in such a manner that the length of the each coil spring became 20 mm. A movable stainless ring 3 (inner diameter 1.3 mm, outer diameter 1.4 mm) was set between the two coil springs 2a and 2b to which the end portions of the two springs were attached. Stainless actuator fixing members 6, 6 (inner diameter 1.0 mm, outer diameter 1.2 mm) were set at the other end portions of the coil springs. The actuator fixing members 6, 6 were fixed to the main body 1a. A 0.08 mm diameter stainless pull wire 4 was fixed to the distal end of the bending part 1b at one end thereof, and the other end thereof was fixed to the movable ring 3 through the bending part 1b. An image scope 5 (outer diameter 0.4 mm) was set in the tubular body 1, and a polyurethane outer tube 7 (inner diameter 1.8 mm, outer diameter 2.0 mm) was applied. In this Example, the outer tube 7 in combination with bending part 1b functioned as a guide wire for pull wire 4. The above bending endoscope was fabricated as in the following. The shape memory-treated coil springs 2a and 2b were fixed to movable stainless ring 3 at one end of the springs and to actuator fixing members 6, 6 at the other end thereof. These were inserted into the main body 1a with the first actuator coil spring 2a at the proximal side, and actuator fixing member 6 at the second actuator coil spring 2b side was fixed to one side of the main body 1a, leaving the part to be fixed to the bending part 1b. The coil springs 2a and 2b were each stretched to 20 mm, and the other actuator fixing member 6 was fixed to the main body 1a. In this Example, the two coil springs were the same and either coil could be inserted into the main body 1a first. Then, the end portion of the stainless bending coil 1b was fixed to the above-mentioned part of the stainless pipe of the main body 1a, and a stainless end ring 8 (inner diameter 1.3 mm, outer diameter 1.6 mm) was fixed to the other end of the stainless coil. In doing so, the portion of the stainless coil which was not fixed was 30 mm in the bending part. One end of pull wire 4 was fixed to the above-mentioned movable ring 3, and the other end was fixed to end ring 8. Lead wires 9, 9, 9 were connected, at one end thereof, to movable ring 3, and actuator fixing members 6, 6, respectively. Outer tube 7 was applied, and image scope 5 was inserted into tubular body 1, which was followed by fixing to give an endoscope. The prepared endoscope functioned according to the following principle. The first actuator shape memory coil spring 2a was heated by a current from a power source not shown. The coil spring 2a recovered its original shape of close coiling state to cause displacement of movable ring 3 to the proximal side, whereby pull wire 4 was pulled to cause bending of bending part. In this Example, a shape memory coil spring 2b was used for the second actuator, and heating of coil spring 2b enabled quick recovery of the initial state (without bending) after bending of the tip. Example 2 A two direction bending endoscope as shown in Fig. 2 was fabricated. The common parts with Example 1 were prepared in the same manner as in Example 1 using the same materials. The members used only in this Example were a second pull wire 4b different from the pull wire used in Example 1 only in length, pulley 10 of a stainless pipe (inner diameter 1.3 mm, outer diameter 1.4 mm) and a pulley support tube 11 of a stainless pipe (inner diameter 1.7 mm, outer diameter 1.8 mm) to support the above pulley 10 and the main body 1a. The two direction bending endoscope was fabricated as in the following. A hole was formed in each of the pulley support tube 11 and the main body 1a at the proximal side from the actuator fixing member 6 attaching to one end of the first actuator shape memory coil spring 2a, and the pulley 10 was fitted into both holes. In the same manner as in Example 1, coil springs 2a and 2b, movable ring 3 and actuator fixing member 6 were assembled, fixed to the main body 1a, and bending part 1b and end ring 8 were fixed. Then, the first pull wire 4a was set in the same manner as in Example 1, and one end of the second pull wire 4b was fixed to the end portion of the bending part 1b at the opposite position from the first pull wire 4a, and the other end thereof was fixed to movable ring 3 via pulley 10 through the bending part 1b. Lead wires 9, 9, 9 were connected to movable ring 3 and actuator fixing members 6, 6, respectively, at one end. Outer tube 7 was applied, and image scope 5 was inserted into the tubular body 1, which was followed by fixing to give an endoscope. While the principle of action of the two direction bending endoscope was the same as in Example 1, when the second actuator shape memory coil spring 2b was heated by a current, the second pull wire 4b was pulled toward the distal end at the portion fixed to the movable ring 3 and, being reversed by the pulley 10, drawn to the proximal end at the bending part 1b. Therefore, the bending part 1b bent to a direction opposite from the bending direction when the first actuator shape memory coil spring 2a was heated. Example 3 This Example relates to a multi-direction bending endoscope using a shape memory alloy coil for a pull wire as shown in Fig. 3. In addition to the structure of Example 1, three shape memory alloy coils (strand diameter 0.03 mm, outer diameter 0.09 mm) were used as pull wires which were placed in the circumferential direction at equal intervals. Respective pull wires 14, 24 and 34 were fixed to the distal end of the bending part 1b at one end thereof and to the movable ring 3 at the other end thereof. The shape memory alloy coils were each connected to lead wires (not shown) and could be heated separately. The actuator shape memory alloy coils 2a and 2b were close-coiled at strand diameter 0.3 mm, outer diameter 1.6 mm, length 9 mm and made to store this coiling state. The coils were stretched to 24 mm and attached. The structure other than the pull wires and actuators were the same as in Example 1. The prepared multi-direction endoscope functioned according to the following principle. As in Example 1, the actuator shape memory coil spring 2a was heated by a current from a power source not shown. The coil spring 2a recovered its original close coiling state to cause displacement of movable ring 3 to the proximal side, whereby pull wires 14, 24 and 34 were pulled. Of these shape memory pull wires 14, 24 and 34, for example, only pull wire 14 was heated. Thus, the heated wire 14 had a greater spring constant than other wires 24 and 34, so that when pulled, it showed small elongation or scarce elongation. Therefore, the wire 14 alone was pulled in the absence of elongation, when wires 24 and 34 were only stretched, thereby causing bending of bending part 1b toward pull wire 14. Selective heating of the three pull wires 14, 24 and 34 enabled bending in three directions. In addition, control of the heating of the three pull wires 14, 24 and 34 enabled bending in numerous directions. For example, when only 14 and 24 were heated, the scope bent in the direction in between 14 and 24. Example 4 A modified actuator unit U comprising two actuators, a movable part and a pull wire fixed at one end to the movable part was used in this Example, which is shown in Fig. 4. In Fig. 4, all actuator shape memory coil springs are not shown for simplification. In fact, the first and second actuators 2a and 2b each consisted of 13 TiNi shape memory alloy coil springs close-coiled at strand diameter 0.1 mm, outer diameter 0.3 mm, length 18 mm and made to store this coiling state. Said shape memory alloy coil springs were set in the circumferential direction of the tubular body at about equal intervals, and fixed at one end to the movable stainless ring 3 (inner diameter 1.3 mm, outer diameter 1.4 mm) and to actuator fixing members 6, 6 (inner diameter 1.0 mm, outer diameter 1.2 mm) at the other end. The 13 coils of 2a or 2b were electrically connected serially. Then, one end of pull wire 4 was fixed to the movable ring 3 to give an actuator unit U. When this actuator unit U was set on the bending endoscope of Example 1, the length of shape memory alloy coil springs was adjusted to 25 mm, thereby attaining bending of about 60 degrees. Example 5 The modified actuator units U were set in duplicate as shown in Fig. 5. The two actuator units U were fabricated in the same manner as in Example 3 except the size of each member. Actuators 12a, 12b, 22a and 22b each consisted of 6 TiNi shape memory alloy coil springs close-coiled at strand diameter 0.1 mm, outer diameter 0.3 mm, length 20 mm and made to store this coiling state. The outer movable ring 13 was a stainless ring having an inner diameter of 1.3 mm and an outer diameter of 1.4 mm, and the inner movable ring 23 was a stainless ring having an inner diameter of 1.1 mm and an outer diameter of 1.2 mm. The actuator fixing members 6, 6 were stainless rings having an inner diameter of 1.0 mm and an outer diameter of 1.2 mm. When they were applied to the bending endoscope of Example 1, the length of shape memory alloy coil springs was adjusted to 28 mm, thereby attaining bending of about 60 degrees in two directions. Example 6 This Example relates to an endoscope wherein the movable part was divided in the circumferential direction which is shown in Fig. 6. A stainless ring (inner diameter 1.3 mm, outer diameter 1.4 mm) was divided into four in the circumferential direction of the tubular body to give movable parts 13, 23, 33 and 43. Actuators 12a, 12b, 22a, 22b ... each consisting of 3 TiNi shape memory alloy coil springs close-coiled at strand diameter 0.1 mm, outer diameter 0.3 mm, length 28 mm and made to store this coiling state were fixed at one end thereof to respective movable parts, so that they antagonized via each movable part. The other ends were attached to stainless actuator fixing member rings 6, 6 (inner diameter 1.0 mm, outer diameter 1.2 mm). Pull wires 14, 24, 34 and 44 were attached at one end thereof to the movable parts 13, 23, 33 and 43 to give actuator units U1, U2, U3 and U4. When they were applied to the bending endoscope of Example 1, actuator units U1, U2, U3 and U4 were set to cover the tubular body and the length of shape memory alloy coil springs was adjusted to 39 mm, thereby attaining bending of about 60 degrees in four directions. Example 7 This is an example wherein a tapered shape memory alloy coil was used for heating by light. The actuator unit is shown in Fig. 7. The movable part 3 was a stainless ring having an inner diameter of 0.9 mm and an outer diameter of 1.0 mm, and the actuator fixing members 6, 6 were stainless rings having an inner diameter of 0.5 mm and an outer diameter of 0.6 mm. The shape memory alloy coils 2a and 2b were formed at strand diameter 0.3 mm, length 15 mm and made to store this coiling state. The coils were set in a tapered state of 0.6 mm coil inner diameter at actuator fixing member side and 1.0 mm at the movable part side, so that they antagonized each other via the movable part. The pull wire 4 was attached at one end thereof to the movable part 3. Though not shown, an optical fiber for heating shape memory alloy coils was formed at the proximal end side of shape memory alloy coil 2a. They were applied to the outer periphery of the image scope (outer diameter 0.4 mm) shown in Example 1 and used as a bending endoscope. The length of shape memory alloy coils 2a and 2b was each adjusted to 20 mm, thereby attaining bending of about 50 degrees when the original shape of shape memory alloy coil 2a was recovered by laser irradiation from the optical fiber. The bending endoscopes fabricated in Examples 1-7 were activated by heating the shape memory alloy coil springs. As a result, bending of about 40-60 degrees was achieved from the position before heating without buckling at the bending part during on or off operation. While the bending angle was 40-60 degrees, it can be varied by appropriately selecting the material and size of the actuators, as well as material and size of tubular body and image scope. Example 8 A stereoscope of Fig. 8 was fabricated. Two shape memory alloy coil actuators 2a and 2b were fixed at one end thereof to support plates 16, 16 which also fixed actuators 2a and 2b and support image scopes 5, 5, and at the other end thereof to movable part 3 formed between the support plates 16, 16 and movable in the lengthwise direction of the scope to allow antagonistic action of the actuators. The support plates had holes for passing image scopes at the positions toward outer periphery from actuators 2a and 2b, so as to support image scopes 5, 5 as mentioned above. The support plates had a ring shape to secure a space inside the stereoscope. The image scopes 5, 5 passed through the holes formed in the support plates 16, 16 and projected from the distal end side support plate 16 toward the distal end. They were placed in a parallel relationship to interpose actuators 2a, 2b and movable part 3 therebetween. The support plates were fixed to the image scopes. In this way, a part of the image scope located at the distal end side from the support plate 16 became a bending part which could bend. The pull wires 4, 4 were fixed at one end thereof to the movable part 3 and to the distal end side of image scopes 5, 5 at the other end. The shape memory alloy coils were treated to store close coiling state beforehand and attached upon stretching. The prepared stereoscope functioned according to the following principle. The shape memory coil 2a at the proximal side was heated to recover its original close coiling state. As a result, the movable part moved to the proximal side (downward in the Figure) and pulled wires 4 and 4. Consequently, the bending parts of image scopes 5, 5 bent to change their angles. A treatment such as superimposing of the images obtained from the two image scopes by an image processing device not shown here gives a stereoscopic image. Example 9 A stereoscope of Figs. 9 and 10 was fabricated. Fig. 9 is a lengthwise cross section of the stereoscope of this Example. Fig. 10 is a cross section of Fig. 9 along A-A. Specifically, two image guides 15a and 15b were placed in a protection tube 19 at a certain distance, and they were fixed by support plates 16, 16 and a co-activation wire ring 20 which was hung on the two image guides at a distal side from the support plates. Note that the support plates had holes alone for passing image guides 15, 15, four light guides 25 and pull wire 4. When a multi-functional scope was desired by forming various sensors, additional holes may be formed as appropriate. The protection tube 19 was provided with a stroke control window 18 in advance. The two shape memory alloy coils 2a and 2b were fixed to movable ring 3 at one end and disposed on the outer periphery of the protection tube 19. The two shape memory alloy coils 2a and 2b were stretched and fixed at the other end to the protection tube 19. A displacement limiting rod 17 was attached to movable ring 3 orthogonally to the line connecting two image guides 15, 15, and pull wire 4 was attached at one end to displacement limiting rod 17 and to the center of the co-activation wire 20 at the other end. Four light guides 25 were formed in parallel with image guides 15, 15, and transparent cap 21 was set at the distal end thereof. The prepared stereoscope functioned according to the following principle. The shape memory coil 2a was heated by a current from a power source not shown to recover original close coiling state. As a result, movable part 3 moved downward in the Figure, and pulled wire 4. Consequently, a downward force was applied to the center portion of co-activation wire 20, which in turn pulled the two image guides 15, 15 connected by the co-activation wire 20, toward the center of the scope to vary angle of convergence. A treatment such as superimposing of the images obtained from two image guides gives a stereoscopic image. Example 10 A stereoscope of Fig. 11 was fabricated. The shape memory alloy coil was disposed between support plates 16, 16 which also fixed integrated shape memory alloy coil consisting of two actuators 2a and 2b and movable part 3, and support image scopes 5, 5, wherein the both ends of shape memory alloy coil were fixed to the support plates 16, 16. Holes for passing image scopes were formed in the part toward the outer periphery from the coil attaching parts of support plates 16, 16. Two image scopes 5, 5 passed through the holes and partially projected toward the distal end side of the scope beyond the support plate 16. The scopes were placed in parallel, interposing the shape memory alloy coils. A co-activation wire ring 20 was set on the two image scopes at a distal side from the support plates. The pull wire 4 was fixed at one end to the center portion in the lengthwise direction of the shape memory alloy coil and to the center portion of the co-activation wire 20 between the image scopes, at the other end. To make possible heating of the entire proximal actuator 2a by light, the shape memory alloy coil was tapered to have the minimum diameter at the center portion in the lengthwise direction, and maximum diameter at the both ends. An optical fiber 22 for laser irradiation was disposed at the proximal end side of the shape memory alloy coil. This taper structure permitted irradiation of the light in the entirety of the actuator 2a, and materials with poor thermal conduction, such as TiNi alloy, could be heated in the entirety of the actuator. Inasmuch as the movable part and actuators were integrally formed, the connection between the both members was not necessary, and connection of lead wires was also obviated by heating by light. As a result, fabrication was facilitated and narrower scope could be obtained with less numbers of constituent elements. As explained in the foregoing, the bending mechanism of the present invention is free of displacement of movable part when bending action is not needed, since two actuators are used which antagonize each other via movable part. Moreover, bending part is not subject to force, since pull wire is not activated in this state, whereby buckling of the bending part can be eliminated. A simple structure of activator unit, which is the most significant part of the bending mechanism, facilitates reduction of the size of the structure. The stereoscope of the present invention is free of buckling of image guide and the like, and can be co-activated with image guide and the like. In consequence, angle of convergence can be adjusted easily and a desired three-dimensional view can be obtained easily.

Claims: A bending mechanism comprising: a tubular or linear body (1), having a main body (1a) and a bending part (1b) formed at the distal end of the main body (1a), a movable part (3) which can move in the lengthwise direction of said tubular or linear body (1), a first actuator (2a) moving said movable part (3), and a pull wire (4) which extends in the lengthwise direction along the bending part (1b), one end of the wire (4) being fixed to one end side of the bending part (1b) and the other end of the wire (4) being fixed to the movable part (3) set at the other end side of the bending part (1b), wherein the actuator (2a) is a shape memory element, characterized by a second actuator (2b) moving said movable part (3), the two actuators (2a,2b) being arranged to antagonize via said movable part (3), and the movable part (3) and the two actuators (2a,2b) being arranged outside of said tubular or linear body (1). The bending mechanism of claim 1, wherein the two actuators (2a,2b) are both shape memory elements. The bending mechanism of claim 2, comprising a first pull wire (4a) and a second pull wire (4b), wherein the first actuator (2a) pulls the first wire (4a) to bend the bending part to one direction, and the second actuator (2b) pulls the second wire (4b) to bend the bending part to a different direction. The bending mechanism of one of claims 1-3, comprising two or more pull wires (14,24,34) of shape memory alloy coils, wherein the pull wires (14,24,34) can be heated separately. The bending mechanism of one of claims 1-4, comprising plural actuator units (U1,U2), wherein the pull wire (14,24) is set at a predetermined circumferential position and extends along the direction of the bending parts, wherein one movable part (13,23) and one pull wire (14,24) is one actuator unit, when two actuators are provided. The bending mechanism of claim 5, wherein the actuator unit (U1,U2) is set in duplicate in the radial direction of the tubular or linear body (1). The bending mechanism of claim 5, wherein the movable part (13,23,33,43) is divided in the circumferential direction of the tubular or linear body, each divided part (13,23,33,43) having two actuators and a pull wire (14,24,34) to form an actuator unit (U1,U2,U3,U4). The bending mechanism of one of claims 1-7, wherein the shape memory element (2a,2b) comprises a shape memory alloy coil. The bending mechanism of claim 1, wherein the actuator comprises plural shape memory elements. A stereoscope comprising: two image guides (5) disposed at a certain distance, each guide (5) having a bending part, a single movable part (3) which can move in the lengthwise direction, wherein operation of the movable part (3) concurrently activates the bending parts of the two image guides (5), a first actuator (2a) moving said movable part (3) and a second actuator (2b) moving said movable part (3), wherein at least one of the actuators (2a) is a shape memory element and the two actuators (2a,2b) are arranged to antagonize via said movable part (3), and at least one pull wire (4) which extends in the lengthwise direction along the bending part, one end of the wire (4) being fixed to the movable part (3) and the other end of the wire (4) being fixed to the end sides of one or both of the bending parts. The stereoscope of claim 10, wherein two actuators (2a,2b) comprise shape memory elements. The stereoscope of claim 10 or 11, wherein the shape memory element (2a,2b) is a shape memory alloy coil. The stereoscope of one of claims 10-12, wherein a coupling wire (20) is set to link the two image guides (5) at the distal end portion thereof, and one end of the pull wire (4) is connected to the coupling wire (20) and the other end of the wire (4) is connected to the movable part (3). The stereoscope of one of claims 10-12, wherein two pull wires (4) are provided, and one end of the two pull wires (4) is connected to each distal end portion of the two image guides (5) and the other end thereof is connected to the movable part (3), respectively.

Inventors: HOSOTANI KATSUNORI, MAEDA SHIGEO, TOHYAMA OSAMU, HOSOTANI, KATSUNORI, MAEDA, SHIGEO, TOHYAMA, OSAMU, Hosotani, Katsunori, c/o Itami Fact., Maeda, Shigeo, c/o Itami Fact., Tohyama, Osamu, c/o Itami Fact.
Applicants: MITSUBISHI CABLE IND LTD, MITSUBISHI CABLE INDUSTRIES, LTD.
Application year: 1996
Main classification: A61B1
IPC codes: A61B1