Abstract:
A multi-joint bending structure includes: a first-band-piece including joint potions on both ends; bending-units enabling the multi-joint-bending-structure to change in position between a straight state and a bent state; a third-band-piece including a joint potion provided on one end, the joint portion connected to the joint potion of the end of one of the bending-units; one pair of two linear bodies, each of the linear bodies having one end fixed to the housings and another end movable along the housings; and an assisting-force-generation-mechanism provided at predetermined opposed positions of the pair of two linear bodies and configured to generate assisting force, wherein the assisting-force-generation-mechanism includes rod-like bodies, a contracting-elastic-body inserted into the gap, and two piece members which both the ends of the overlapping potions energized by the piece members switch over, and the contracting force of the elastic-body acts as the assisting force between both the ends.

Description:
CROSS-REFERENCE TO RELATED APPLICATION 
       [0001]    This application is based upon and claims the benefit of priority of the prior Japanese Patent Application No. 2014-022537 filed on Feb. 7, 2014, the entire contents of which are incorporated herein by reference. 
       FIELD 
       [0002]    The embodiments discussed herein are related to a multi-joint bending structure and a wearable device using the structure. 
       BACKGROUND 
       [0003]    In recent years, wearable devices have been put into practical use with achievement of downsizing of information terminals such as mobile phones. The wearable device is a small information terminal usable by being attached to a human body by a band (such a wearable device is hereinafter referred to as a wearable terminal). Promising wearable terminals are of types such as a watch type and a wrist band type in which a terminal is attached with a bendable band wound about an arm. 
         [0004]    Meanwhile, only few wearable terminals are used by being continuously attached to the human bodies in spite of their names “wearable”. Normal wearable terminals are often used in both states attached to or detached from the human body. 
         [0005]    Then, as a band usable in a wearable terminal to attach or detach the wearable terminal, there are a band having a structure disclosed in Japanese Laid-open Patent Publication No. 2005-034340 and a band disclosed in Japanese Laid-open Patent Publication No. 11-239504. Japanese Laid-open Patent Publication No. 2005-034340 discloses a band with magnet in which hard band pieces are joined to make the band elastic and magnets are arranged not to project from the band. 
         [0006]    On the other hand, Japanese Laid-open Patent Publication No. 11-239504 discloses a decorative bracelet in which multiple links (pieces) are joined by columnar bars one after another like joints and the links and the columnar bars are held together by flexible connecting materials. 
         [0007]    However, when a wearable terminal is attached or detached, similar to a watch belt, a belt has to be hooked or unhooked every time. Thus, there is a problem that an attaching/detaching operation is troublesome. There is also another problem that a belt made of resin or a bending-type wrist band tends to keep a bent form even when detached, and is bothersome since the belt or the wrist band bends even after being detached. Similarly, the band disclosed in Japanese Laid-open Patent Publication No. 2005-034340 has problems that since the band has spring force only in a direction in which the band shrinks, the band may not be easily detached, and is bothersome as the band remains bent even after being removed. 
         [0008]    In one aspect, the present application has an object of providing a multi-joint bending structure that may be attached to or detached from a human body with a single touch, and a wearable device (wearable terminal) using the structure. 
       SUMMARY 
       [0009]    According to an aspect of the invention, a multi-joint bending structure includes: a first-band-piece including joint potions on both ends; bending-units enabling the multi-joint-bending-structure to change in position between a straight state and a bent state; a third-band-piece including a joint potion provided on one end, the joint portion connected to the joint potion of the end of one of the bending-units; one pair of two linear bodies, each of the linear bodies having one end fixed to the housings and another end movable along the housings; and an assisting-force-generation-mechanism provided at predetermined opposed positions of the pair of two linear bodies and configured to generate assisting force, wherein the assisting-force-generation-mechanism includes rod-like bodies, a contracting-elastic-body inserted into the gap, and two piece members which both the ends of the overlapping potions energized by the piece members switch over, and the contracting force of the elastic-body acts as the assisting force between both the ends. 
         [0010]    The object and advantages of the invention will be realized and attained by means of the elements and combinations particularly pointed out in the claims. 
         [0011]    It is to be understood that both the foregoing general description and the following detailed description are exemplary and explanatory and are not restrictive of the invention, as claimed. 
     
    
     
       BRIEF DESCRIPTION OF DRAWINGS 
         [0012]      FIG. 1A  is a perspective view illustrating a state in which a user wears a watch-type wearable terminal,  FIG. 1B  is a perspective view illustrating a mechanism for attachment to an arm of the wearable terminal illustrated in  FIG. 1A , and  FIG. 1C  is a perspective view of a bendable wrist band; 
           [0013]      FIG. 2A  is an assembly perspective view illustrating the structure of the multi-joint bending structure of a first example of a first mode of the present application and  FIG. 2B  is a partial perspective view of the structure after assembly of the multi-joint bending structure illustrated in  FIG. 2A ; 
           [0014]      FIG. 3A  is a perspective view illustrating connection with a belt of an assisting force generation mechanism used in the multi-joint bending structure of the present application,  FIG. 3B  is an assembly perspective view illustrating an example of connection with a piece member of an extension spring used in the assisting force generation mechanism illustrated in  FIG. 3A , and  FIG. 3C  is a plan view illustrating a connection state of the extension spring used in the assisting force generation mechanism illustrated in  FIG. 3A  with the piece member; 
           [0015]      FIG. 4A  to  FIG. 4C  are explanatory diagrams illustrating in a phased manner how a belt arranged on an inner periphery side of a bending unit of a multi-joint bending structure changes when the multi-joint bending structure changes in position from an I-like form to a C-like form; 
           [0016]      FIG. 5A  to  FIG. 5E  are explanatory diagrams illustrating operation of the assisting force generation mechanism illustrated in  FIG. 3A ; 
           [0017]      FIG. 6A  is a perspective view when the multi-joint bending structure of the first example of the first mode of the present application is in the I-like form,  FIG. 6B  is a perspective view illustrating a state while the multi-joint bending structure illustrated in  FIG. 6A  is changing in position to the C-like form,  FIG. 6C  is a perspective view illustrating a state in which the multi-joint bending structure illustrated in  FIG. 6B  changes in position to the C-like form,  FIG. 6D  is a sectional view of a member of the multi-joint bending structure illustrated in  FIG. 6A , indicated by a line VID of cutting plane, and  FIG. 6E  is a sectional view of a member of the multi-joint bending structure illustrated in  FIG. 6A , the member being indicated by a line VIE of cutting plane; 
           [0018]      FIG. 7A  is a side elevation when the multi-joint bending structure of the first example of the first mode of the present application is in the I-like form,  FIG. 7B  is an arrow view, when viewed from a direction of an arrow VIIB, of a state of the assisting force generation mechanism which is in the multi-joint bending structure illustrated in  FIG. 7A ,  FIG. 7C  is a side elevation illustrating a state in which the multi-joint bending structure illustrated in  FIG. 7A  is changing in position from the I-like form to the C-like form,  FIG. 7D  is an arrow view, when viewed from a direction of an arrow VIID, of a state of the assisting force generation mechanism which is in the multi-joint bending structure illustrated in  FIG. 7C ,  FIG. 7E  is a side elevation when the multi-joint bending structure of the first example of the first embodiment of the present application is in the C-like form, and  FIG. 7F  is an arrow view, when viewed from a direction of an arrow VIIF, of a state of the assisting force generation mechanism which is in the multi-joint bending structure illustrated in  FIG. 7E ; 
           [0019]      FIG. 8A  is an exploded perspective view illustrating a state of a bending rod-like body when the multi-joint bending structure illustrated in  FIG. 7A  and FIG.  7 B is in the I-like form and  FIG. 8B  is an exploded perspective view illustrating a state of the bending rod-like body when the multi-joint bending structure illustrated in  FIG. 7E  and  FIG. 7F  is in the C-like form; 
           [0020]      FIG. 9A  is a plan view illustrating a state of the assisting force generation mechanism when the mufti-joint bending structure of the first example of the first mode of the present application is in the I-like form,  FIG. 9B  is a plan view illustrating a state of the assisting force generation mechanism when a multi-joint bending structure of a second example of the first mode of the present application is in the I-like form, and  FIG. 9C  is a plan view illustrating the assisting force generation mechanism when the multi-joint bending structure of a first example of a second mode of the present application is in the I-like form; 
           [0021]      FIG. 10A  is a side elevation when the multi-joint bending structure of the first example of the second mode illustrated in  FIG. 9C  is in the I-like form,  FIG. 10B  is a side elevation illustrating a side elevation illustrating a state while the multi-joint bending structure illustrated in  FIG. 10A  changes in position from the I-like form to the C-like form,  FIG. 10C  is a side elevation illustrating a state when the multi-joint bending structure illustrated in  FIG. 10B  changes in position to the C-like form,  FIG. 10D  is an arrow view, when viewed from a direction of an arrow XD, of a state of the assisting force generation mechanism which is in the multi-joint bending structure illustrated in  FIG. 10A ,  FIG. 10E  is an arrow view, when viewed from a direction of an arrow VIIB, of a state of the assisting force generation mechanism which is in the multi-joint bending structure illustrated in  FIG. 10B , and FIG.  1 OF is an arrow view when viewed from a direction of an arrow XF, of a state of the assisting force generation mechanism which is in the multi-joint bending structure illustrated in  FIG. 10C ; 
           [0022]      FIG. 11A  is a plan view illustrating a state of the assisting force generation mechanism when a multi-joint bending structure of a second example of the second mode of the present application is in the I-like form,  FIG. 11B  is an assembly perspective view of a specific structure example of the assisting force generation mechanism illustrated in  FIG. 11A , and  FIG. 11C  is a plan view of a state in which an upper-side cover of the assisting force generation mechanism illustrated in  FIG. 11B  is removed; 
           [0023]      FIG. 12A  is a plan view when the assisting force generation mechanism of the specific structure example illustrated in  FIG. 11B ,  FIG. 11C  is in the Hike form,  FIG. 12B  is a side elevation of the multi-joint bending structure illustrated in  FIG. 12A , and  FIG. 12C  is a side elevation when the multi-joint bending structure illustrated in  FIG. 12B  is in the C-like form; 
           [0024]      FIG. 13A  is a plan view illustrating a state of the assisting force generation mechanism when a multi-joint bending structure of a third example of the second mode of the present application is in the I-like form,  FIG. 13B  is a plan view when the multi-joint bending structure of the third example of the second embodiment of the present application is in the I-like form,  FIG. 13C  is a side elevation illustrating a state of the assisting force generation mechanism embedded in the multi-joint bending structure illustrated in  FIG. 13B , and  FIG. 13D  is a side elevation illustrating a state of the assisting force generation mechanism embedded in the multi-joint bending structure when the multi-joint bending structure illustrated in  FIG. 13C  is in the C-like form; 
           [0025]      FIG. 14A  is a plan view of a multi-joint bending structure of the present application which is shaped like an elongate wrist band,  FIG. 14B  is a plan view of a multi-joint bending structure of the present application which is shaped like a wide, straight terminal,  FIG. 14C  is a plan view of a multi-joint bending structure of the present application which is shaped like a watch,  FIG. 14D  is a side elevation when the multi-joint bending structures illustrated in  FIG. 14A  to  FIG. 14C  are in the C-like form,  FIG. 14E  is a perspective view illustrating a usage state in the C-like form of the multi-joint bending structure illustrated in  FIG. 14B , and  FIG. 14F  is a perspective view illustrating a usage state in the I-like form of the multi-joint bending structure illustrated in  FIG. 14B ; and 
           [0026]      FIG. 15A  is an explanatory diagram illustrating an example in which the multi-joint bending structure illustrated in  FIG. 14A  is used as a head band,  FIG. 15B  is an explanatory diagram illustrating an example in which the multi-joint bending structure illustrated in  FIG. 14A  is attached to the waist and used,  FIG. 15C  is an explanatory diagram illustrating an example in which the multi-joint bending structure illustrated in  FIG. 14A  is attached to an animal and used,  FIG. 15D  is an explanatory diagram illustrating an example in which the multi-joint bending structure illustrated in  FIG. 14A  having an embedded shining illumination device is used as a collar for a dog, and  FIG. 15E  is an explanatory diagram illustrating an example in which the multi-joint bending structure illustrated in  FIG. 14A  having an embedded shining illumination device is attached to a human arm and used as a crime-prevention tool. 
       
    
    
     DESCRIPTION OF EMBODIMENTS 
       [0027]    Hereinafter, embodiments of the present application are described in detail based on specific examples. In the examples described below, an example in which an assisting force generation mechanism is embedded in a bending unit of a multi-joint bending structure is described as an example of a first mode, and an example in which an assisting force generation mechanism is embedded in a first band piece part of a multi-joint bending structure is described as an example of a second mode. 
         [0028]    Before examples of the present application are described, first, a wearable device to be attached to the human body and used is described.  FIG. 1A  illustrates a state in which a user wears a watch-type wearable device  90  on an arm W. In the wearable device  90  illustrated in  FIG. 1A , a belt unit  92  is provided on a main body  91  including a display unit  97 , as illustrated in  FIG. 1B . The wearable device  90  is designed to be wound around the arm W and fixed by a buckle  94 . The buckle  94  has a frame  95  and a pin  96 . When the wearable device  90  is attached to the arm W, the belt unit  92  is inserted through the frame  95  and then the pin  96  is inserted into a hole  93  provided at an end of the belt unit  92 . 
         [0029]    Thus, the watch-type wearable device  90  has to be fastened or removed every time the belt unit  92  is attached to or removed from the arm W, and an attaching/detaching operation is troublesome. In addition,  FIG. 1C  illustrates a bendable wrist band  98  which is generally made of resin. Since the wrist band tends to bend when removed, the wrist band in a removed state is bulky and bothersome. Hence, the present application provides a wearable device that may be attached to or detached from the human body with a single touch and that is not bulky even when the wearable device is in a removed state. 
         [0030]      FIG. 2A  illustrates a structure of a multi-joint bending structure  51  of the first example of the first mode of the present application in or to which a wearable device may be incorporated or attached. In addition,  FIG. 2B  is a partial perspective illustration of appearance after assembly of the multi-joint bending structure  51  illustrated in  FIG. 1A . The multi-joint bending structure  51  includes a first band piece  1 , multiple second band pieces  2  arranged to each of the right and left of the first band piece  1  and forming bending units  4 , and third band pieces  3  connected to tips of the bending units  4  located to the right and left of the first band piece  1 . The first band piece  1  includes joint potions  55  on the right and left sides. Then, six second band pieces  2  each including the joint potions  55  on both (right and left) ends are connected to each of the right and left joint potions  55  to form the bending unit  4 . Then, the third band pieces  3  are connected to the outermost second band pieces  2  by the joint potions  55 . 
         [0031]    When viewed from the lateral side, the first band piece  1  and the second band piece  2  have a trapezoid shape and include parallel long side and short side, as well as two oblique sides. Then, the joint potion  55  connects the long sides of the first band piece  1  and the second band piece  2 . As a result, the first band piece  1  and the second band piece  2  may bend in a direction which makes the adjacent oblique sides move closer, that is to say, toward the short side. Note that a shape when the third band piece  3  is viewed from the lateral face may be the same as the second band piece  2 , the side on the free end side is orthogonal to the long side and the short side since the third band pieces  3  are positioned at both ends of the multi-joint bending structure  51 . 
         [0032]    In housings of the connected first to third band pieces  1  to  3 , a space area SP 1  where to house belts  6 ,  7  and space areas SP 2  where to house assisting force generation mechanisms  5  fixed onto the belts  6 ,  7  are provided on an inner side which becomes an inner peripheral side when the structure is bent. Then, in order to house the belts  6 ,  7  and the assisting force generation mechanism  5  in the space areas SP 1 , SP 2 , the connected first to third band pieces  1  to  3  are dividable into two, i.e., to the right and left.  FIG. 2A  illustrates the connected first to third band pieces  1 L,  2 L,  3 L on the left side and the first to third band pieces  1 R,  2 R,  3 R on the right side. Engagement projections  1 P,  2 P,  3 P on one opposed face of each band piece being fitted into engagement concaves  1 Q,  2 Q,  3 Q ( 1 Q is not illustrated) on the other opposed face, the first band pieces  1 L,  2 L,  3 L on the left side and the first to third band pieces  1 R,  2 R,  3 R on the right side are connected. 
         [0033]    In the multi-joint bending structure  51 , a pair of two parallel belts  6 L,  6 R are provided on one side of the first band piece  1 , while a pair of two parallel belts  7 L,  7 R are provided on the other side. At one end of the belt  6 L and one end of the belt  7 R are provided a hole  8  into which a screw  9  is inserted, thus the one end of the belt  6 L and the one end of the belt  7 R being screwed to the housing of the third band piece  3 . The other ends of the belt  6 L and the belt  7 R are positioned in the first band piece  1  when the bending unit  4  is in a straight state. A hole  8  is also provided at one end of the belt  6 R and at one end of the belt  7 L. The screw  9  is also inserted into the hole  8 , thus the one end of the belt  6 R and the one end of the belt  7 L being screwed to the housing of the first band piece  1 . Other ends of the belt  6 R and the belt  7 L are positioned in the third band piece  3  when the bending unit  4  is in a straight state. When the bending unit  4  bends, the other ends of the belt  6 L and the belt  7 R enter the interior of the first band piece  1 , while the other ends of the belt  6 R and the belt  7 L enter the interior of the third band piece  3 . 
         [0034]    An assisting force generation mechanism  5  provided on each of the pair of belts  6 L,  6 R and the pair of belts  7 L,  7 R includes two bending rod-like bodies  10  and piece members  20  respectively connected to an extension spring  19  and both ends of extension spring  19 . The extension spring  19  is inserted into a gap between opposed faces of the bending rod-like body  10 . The two bending rod-like bodies  10  are fixed onto the belts  6 L,  6 R and the belts  7 L,  7 R, respectively, and to any part where the bending rod-like bodies  10  are not fixed, slits  11  reaching the belts  6 L,  6 R and the belts  7 L,  7 R are provided at predetermined intervals. The two bending rod-like bodies  10  have overlapping portions between which the extension spring  19  is inserted and non-overlapping portions located outside of the overlapping portions. A diameter of the piece member  20  is larger than width of the gap lying between the opposed faces of the bending rod-like bodies  10 . Pulled by the extension spring  19 , the piece member  20  is held on end faces of the bending rod-like bodies  10  located on both sides of the overlapping portions. 
         [0035]    When the bending unit  4  is in a straight state, the multi-joint bending structure  51  is also in a straight state. In a state in which no external force is applied to the multi-joint bending structure  51 , energizing force of the extension spring  19  keeps the multi-joint bending structure  51  in the straight state. Note that since a bent state of the multi-joint bending structure  51  may be hereinafter referred to as a C-like state, the straight state of the multi-joint bending structure  51  may be referred to as an I-like state. Furthermore, a state in which only one bending unit  4  of the multi-joint bending structure  51  is bent may be referred to as a J-like state. 
         [0036]    Here, structure and operation of the assisting force generation mechanism  5  used in the multi-joint bending structure  51  of the present application are described with reference to  FIG. 3A  to  FIG. 5E .  FIG. 3A  illustrates the assisting force generation mechanism  5  which is taken from  FIG. 2A  together with the belts  6 L,  6 R. The assisting force generation mechanism  5  includes bending rod-like bodies  10  which are respectively fixed to the adjacent parallel belts  6 L,  6 R, the extension spring  19 , and the piece members  20 . As illustrated in  FIG. 3B , in the piece member  20 , a part of a disk-like main body  23  is cut out like an arc to form a notch area  21 , and a post  22  is installed in a protruding manner in the notch area  21  close to the outer periphery of the main body  23 . Hook units  19 H of the extension springs  19  are fixed to the post  22 .  FIG. 3C  illustrates a state in which both ends of the extension spring  19  are bridged to the posts  22  of the piece members  20  by means of the hook units  19 H. Since the hook units  19 H of the extension springs  19  are rotatable to the posts  22  of the piece members  20 , the piece members  20  may oscillate with respect to the extension springs  19 . A shape of the piece members  20  is not limited to the shape in this example. 
         [0037]    The two bending rod-like bodies  10  have overlapping portions between which the extension spring  19  is inserted and non-overlapping portions located outside of the overlapping portions. The piece members  20  are latched to end faces of the bending rod-like bodies  10  located at both ends of the overlapping portions. In the state illustrated in  FIG. 3A , the extension spring  19  causes energizing force to act on a direction which makes the two piece members  20  move closer. In addition, since the belts  6 L,  6 R bend making convex the side where the assisting force generation mechanism  5  is provided, slits  11  are provided on the bending rod-like bodies  10  respectively fixed onto the belts  6 L,  6 R so that the bending rod-like bodies  10  may follow bending of the belts  6 L,  6 R. The slits  11  are provided at predetermined intervals from a face opposite to the belts  6 L,  6 R of the bending rod-like bodies  10  so as to reach the belts  6 L,  6 R. 
         [0038]    Then, when the bending unit  4  bends, the belts  6 L,  6 R also bend and the two bending rod-like bodies  10  move to a direction in which the extension spring  19  is stretched. Here, with reference to  FIG. 4A  to  FIG. 4C , the way how a tip of the belt  6 L moves and length for which the tip protrudes from the first band piece  1  changes when the bending unit  4  formed by the six second band pieces  2  bends is described. As described above, in the state in which the long sides of the first to third band pieces  1  to  3  are connected by the joint potions  55 , as illustrated in FIG,  4 A, gaps Si to S 7  exist between adjacent short sides of the first to third band pieces  1  to  3 . Then, it is supposed that one end of the belt  6 L is fixed by the screw  9  in the third band piece  3  and a free end  6 E protrudes from a joint potion  55 R of the first band piece  1  for length L. 
         [0039]    It is supposed that the bending unit  4  bends to the direction in which adjacent oblique sides of the first to third band pieces  1  to  3  move close and the multi-joint bending structure  51  illustrated in  FIG. 4A  shifts from the I-like form to a state illustrated in  FIG. 4B . In this state, width of the gaps Si to S 7  of the adjacent short sides of the first to third band pieces  1  to  3  is narrow. Then, since one end of the belt  6 L is fixed by the screw  9  in the third band piece  3 , the free end  6 E of the belt  6 L moves for the length for which the width of the gaps S 1  to  57  is narrowed. If the length for which the width of the gaps S 1  to S 7  is narrowed is X, the free end  6 E of the belt  6 L protrudes from the joint potion  55 R of the first band piece  1  only for length (L+X). 
         [0040]    When the multi-joint bending structure  51  illustrated in  FIG. 4B  changes from the I-like form to the C-like form illustrated in  FIG. 4C , the gaps S 1  to S 7  of the adjacent short sides of the first to third band pieces  1  to  3  disappear. Here, if the total length of the gaps S 1  to S 7  of the adjacent short sides of the first to third band pieces  1  to  3  is Y, the free end  6 E of the belt  6 L protrudes from the joint potion  55  of the first band piece  1  only for the length of (L+Y). Then, the free end  6 E of the belt  6 L moves only for the length of Y, which means that the bending rod-like bodies  10  fixed onto the belt  6 L also move only for the length of Y. 
         [0041]    In  FIG. 4A  to  FIG. 4C , movement of the tip  6 E of the belt  6 L when the bending unit  4  bends from the I-like form to the C-like form is described. Then, the tip of the belt  6 R which is paired with the belt  6 L similarly moves to a direction opposite to the traveling direction of the tip  6 E of the belt  6 L. Specifically, since one end of the belt  6 R is fixed by the screw  9  in the first band piece  1 , the tip of the belt  6 R located in the third band piece  3  moves only for the length of Y in the third band piece  3  when the bending unit  4  bends from the I-like form to the C-like form. Then, as the belt  6 R moves, the bending rod-like bodies  10  fixed onto the belt  6 R also move only for the length of Y. 
         [0042]    Then, operation of the assisting force generation section  5  when the bending rod-like bodies  10  fixed on the two belts  6 L,  6 R move in the opposite directions is described with reference to  FIG. 5A  to  FIG. 5E . However, for clarity of description, operation of the assisting force generation mechanism  5  in a state in which the two belts  6 L,  6 R and the bending rod-like bodies  10  move without bending is described. 
         [0043]      FIG. 5A  illustrates a state of belts  6 L,  6 R, two bending rod-like bodies  10  including overlapping portions and non-overlapping portions, an extension spring  19 , and piece members  20  when a bending unit  4  does not bend. Here, it is supposed that the bending rod-like body  10  fixed to the belt  6 L is the bending rod-like body  10 L, the bending rod-like body  10  fixed to the belt  6 R is the bending rod-like body  10 R, a tip of the belt  6 L is  6 E, and a tip of the belt  6 R is  6 F. One of the piece members  20  attached to both ends of the extension spring  19  is latched to an end of the bending rod-like body  10 L on the overlapping portion side, while the other is latched to an end of the bending rod-like body  1 OR on the overlapping portion side. In this state, pulled by the extension spring  19 , the piece members  20  provide the ends where the piece members  20  are latched with energizing force depicted by the arrow. Therefore, the bending rod-like body  10 L and the bending rod-like body  1 OR maintain the state illustrated in  FIG. 5A  unless external force acts. 
         [0044]      FIG. 5B  illustrates a state in which the bending unit  4  is bent from the state illustrated in  FIG. 5A , the tip  6 E of the belt  6 L and a tip  6 F of the belt  6 R move to a direction indicated by an arrow FW, and the overlapping portions of the bending rod-like body  10 L and the bending rod-like body  1 OR increase. In this state, the extension spring  19  is extended and length between the piece members  20  fixed to both ends of the extension spring  19  is large. Then, the piece members  20  provide the latched ends with large energizing force indicated by an arrow. 
         [0045]      FIG. 5C  illustrates a state in which the bending unit  4  is further bent from the state illustrated in  FIG. 5B , the tip  6 E of the belt  6 L and the tip  6 F of the belt  6 R further move to the direction indicated by the arrow FW, and the bending rod-like body  10 L and the bending rod-like body  1 OR perfectly overlap. In this state, the extension spring  19  is also extended to the maximum and the length between the piece members  20  fixed to both ends of the extension spring  19  is largest. Then, since the bending rod-like body  10 L and the bending rod-like body  10 R are in a perfectly overlapped state, the piece members  20  are latched to the ends of both bending rod-like body  1 OL and bending rod-like body  10 R and provide both ends with the energizing force indicated by the arrow. 
         [0046]    When the bending unit  4  is further bent from the state illustrated in  FIG. 5C , and the tip  6 E of the belt  6 L and the tip  6 F of the belt  6 R further move to the direction indicated by an arrow FW, latching ends which latch the piece members  20  switch over Specifically, the piece member  20  latched to one end of the bending rod-like body  1 OL becomes latched to the end of the bending rod-like body  10 R, and the piece member  20  latched to one end of the bending rod-like body  10 R becomes latched to the end of the bending rod-like body  10 L. Then, as illustrated in  FIG. 5D , the direction of the large energizing force provided by the piece member  20  to the latching end of the bending rod-like body  10 L matches the traveling direction of the belt  6 L indicated by the arrow FW. Similarly, the direction of the large energizing force provided by the piece member  20  to the latching end of the bending rod-like body  10 R also matches the traveling direction of the belt  6 R indicated by the arrow FW. 
         [0047]    As a result, assisted by the energizing force provided to the ends of the bending rod-like bodies  10 L,  10 R to which the piece members  20  are latched, the belts  6 L and  6 R quickly change from the state illustrated in  FIG. 5D  to a state illustrated in  FIG. 5E . The energizing force then may be referred to as assisting force. The state illustrated in  FIG. 5E  is the same as the state illustrated in  FIG. 4C  in which the bending unit  4  is bent completely, and the bending unit  4  does not bend any more. In addition, in the state illustrated in  FIG. 5E , pulled by the extension spring  19 , the piece member  20  provides the latching ends with the energizing force indicated by the arrow. Therefore, unless the external force acts, the bending rod-like body  10 L and the bending rod-like body  10 R maintain the state illustrated in  FIG. 5E . 
         [0048]    When the completely bent bending unit  4  is returned to the straight state, the tip  6 E of the belt  6 L and the tip  6 F of the belt  6 R move to a direction indicated by a dashed arrow BW in  FIG. 5E , and the overlapping portions of the bending rod-like body  10 L and the bending rod-like body  1 OR increase. In this state, the extension spring  19  is extended and the length between the piece members  20  fixed to both ends of the extension spring  19  is large. Then, the piece members  20  provide the latching ends with large energizing force indicated by the arrow. 
         [0049]      FIG. 5C  illustrates a state in which the bending unit  4  is further returned to the straight side from the state illustrated in  FIG. 5D , the tip  6 E of the belt  6 L and the tip  6 F of the belt  6 R further move to the direction indicated by the dashed arrow BW, and the bending rod-like body  10 L and the bending rod-like body  10 R perfectly overlap. In this state, the extension spring  19  is also extended to the maximum and the length between the piece members  20  fixed to both ends of the extension spring  19  is largest. Then, since the bending rod-like body  10 L and the bending rod-like body  10 R are in a perfectly overlapped state, the piece members  20  are latched to the ends of both bending rod-like body  10 L and bending rod-like body  10 R to provide both ends with the energizing force indicated by the arrow. 
         [0050]    When the bending unit  4  is further returned to the straight side from the state illustrated in  FIG. 5C , and the tip  6 E of the belt  6 L and the tip  6 F of the belt  6 R further move to the direction indicated by the arrow BW, the latching ends which latch the piece members  20  switch over Specifically, the piece member  20  latched to one end of the bending rod-like body  10 R becomes latched to the end of the bending rod-like body  10 L, and the piece member  20  latched to one end of the bending rod-like body  10 L becomes latched to the end of the bending rod-like body  10 R. Then, as illustrated in  FIG. 5B , the direction of the large energizing force provided by the piece member  20  to the latching end of the bending rod-like body  10 L matches the traveling direction of the belt  6 L indicated by the dashed arrow BW. Similarly, the direction of the large energizing force provided by the piece member  20  to the latching end of the bending rod-like body  10 R also matches the traveling direction of the belt  6 R indicated by the dashed arrow BW. 
         [0051]    As a result, assisted by the energizing force provided to the ends of the bending rod-like bodies  10 L,  10 R to which the piece members  20  are latched, the belts  6 L and  6 R quickly change from the state illustrated in  FIG. 5B  to the state illustrated in  FIG. 5A . The state illustrated in  FIG. 5A  is the same as the state illustrated in  FIG. 4A  in which the bending unit  4  is completely straight, and the bending unit  4  is straight and no longer changes. As described above, the state illustrated in FIG. SA is a state in which the piece members  20  provide the ends pulled by the extension spring  19  and latched with the energizing force indicated by the arrow, and the bending rod-like body  10 L and the bending rod-like body  10 R maintain the state illustrated in  FIG. 5A  unless the external force acts. 
         [0052]    As described above, according to the assisting force generation mechanisms  5  provided on the belt  6 L and the belt  6 R, when the bending unit  4  changes in position from the straight state to the bent state, a bending operation may be performed smoothly since the assisting force generation mechanisms  5  cause the assisting force to act in the course in which the bending unit  4  is bending. In contrast, when the bending unit  4  changes in position from the bent state to the straight state, an operation to straighten the bending unit  4  may be performed smoothly since the assisting force by the assisting force generation mechanisms  5  acts in the course of the operation to straighten the bending unit  4 . 
         [0053]      FIG. 6A  illustrates a state in which a multi-joint bending structure  51  of the first example of the first mode of the present application is in an I-like form.  FIG. 6B  illustrates a state while the multi-joint bending structure  51  illustrated in  FIG. 6A  changes in position to a C-like form. In addition,  FIG. 6D  is a sectional view of a member indicted by a line VID of cutting plane of the multi-joint bending structure  51  illustrated in FIG,  6 A.  FIG. 6E  is a sectional view of a member indicated by a line VIE of cutting plane of the multi-joint bending structure  51  illustrated in  FIG. 6A , illustrating an internal assisting force generation mechanism  5 . When the multi-joint bending structure  51  changes in position from the state illustrated in  FIG. 6A  to the state illustrated in  FIG. 6B , the external force is applied to the bending unit  4  of the multi-joint bending structure  51  to bend the bending unit  4 . On the one hand, after the multi-joint bending structure  51  changes in position to the state illustrated in  FIG. 6B , and if slight external force is applied to the bending unit  4  in this state, the multi-joint bending structure  51  quickly changes in position from the state illustrated in  FIG. 6B  to the state illustrated in  FIG. 6C  due to operation of the embedded assisting force generation mechanism  5 . 
         [0054]      FIG. 7A  is a view from the lateral face of a state in which the multi-joint bending structure  51  of the first example of the first mode of the present application is in an I-like form. In addition,  FIG. 7B  is a view from a direction of an arrow VIIB of a state of the assisting force generation mechanism  5  fixed to belts  6 L,  6 R which are located within the multi-joint bending structure  51  illustrated in  FIG. 7A . When the multi-joint bending structure  51  is in the I-like form, bending rod-like body  10  of the assisting force generation mechanism  5  is also straight, as illustrated in  FIG. 8A . Note that since the assisting force generation mechanism  5  illustrated in  FIG. 8A  illustrates a state of the bending rod-like body  10 , depiction of an extension spring  19  and piece members  20  is omitted in this figure. In addition, since the assisting force generation mechanisms  5  fixed to belts  7 L,  7 R which are located within the multi-joint bending structure  51  operate similarly to the assisting force generation mechanisms  5  fixed to the belts  6 L,  6 R, depiction and description thereof are omitted. The multi-joint bending structure  51  in the I-like form maintains the I-like form due to the action of the assisting force generation mechanism  5  as described above. 
         [0055]      FIG. 7B  is a view from the lateral face of a state of the multi-joint bending structure  51  changing in position from the I-like form to the C-like form as the external force is applied to the bending unit  4  of the multi-joint bending structure  51  illustrated in  FIG. 7A . In addition,  FIG. 7D  is a view from a direction of an arrow VIID of a state of the assisting force generation mechanism  5  which is located within the multi-joint bending structure  51  illustrated in  FIG. 7C , illustrating a state in which two bending rod-like bodies  10  of the assisting force generation mechanism  5  perfectly overlap. When the multi-joint bending structure  51  changes in position from the I-like form to the C-like form, the external force is applied from the side of an joint potion  55  to the bending unit  4  of the multi-joint bending structure  51  up to this point in time. 
         [0056]    On the one hand, in the state illustrated in  FIG. 7C  and  FIG. 7D , when slight external force is further applied, as described above, the piece member  20  of the assisting force generation mechanism  5  moves and is latched to an end of the bending rod-like body  10  adjacent to the bending rod-like body  10  to which the piece member  20  has been latched till now. Then, a direction in which two piece members  20  of the assisting force generation mechanism  5  energize the bending rod-like bodies  10  matches a travelling direction of the belts  6 L,  6 R to which the bending rod-like bodies  10  are fixed, and the belts  6 L,  6 R move due to the energizing force provided by the piece members  20  to the bending rod-like bodies  10 , even if no external force is applied. 
         [0057]    As a result, the multi-joint bending structure  51  quickly changes from a bent state illustrated in  FIG. 7C  to the C-like form illustrated in  FIG. 7E .  FIG. 7F  is a view from a direction of an arrow VHF of a state of the assisting force generation mechanism S which is within the multi-joint bending structure  51  illustrated in  FIG. 7E .  FIG. 8B  illustrates a state of the assisting force generation mechanism  5  when the multi-joint bending structure  51  illustrated in  FIG. 7F  is in the C-like form. The bending rod-like bodies  10  accommodate bending of the belts  6 L,  6 R as parts of slits  11  are spaced and open like a fan. Note that since the assisting force generation mechanism  5  in  FIG. 8B  illustrates a state of the bending rod-like bodies  10 , depiction of the extension spring  19  and the piece members  20  is omitted in this figure. The multi-joint bending structure  51  in the C-like form maintains the C-like form due to the action of the assisting force generation mechanism  5  as described above. 
         [0058]    When the multi-joint bending structure  51  in the C-like form is returned to the multi-joint bending structure  51  in the I-like form, the external force is applied from inside to the bending unit  4  of the multi-joint bending structure  51  illustrated in  FIG. 7E  to return the multi-joint bending structure  51  to the state illustrated in  FIG. 7C . If slight external force is further applied after the multi-joint bending structure  51  is returned to the state illustrated in  FIG. 7C , the piece member  20  of the assisting force generation mechanism  5  moves and is latched to end of the bending rod-like body  10  adjacent to the bending rod-like body  10  to which the piece member  20  has been latched till now. Then, the direction in which the two piece members  20  of the assisting force generation mechanism  5  energize the bending rod-like bodies  10  matches the travelling direction of the belts  6 L,  6 R to which the bending rod-like bodies  10  are fixed, and the belts  6 L,  6 R move due to the energizing force of the piece members  20  even if no external force is applied. 
         [0059]    As a result, the multi-joint bending structure  51  quickly changes from the bent state illustrated in  FIG. 7C  to the I-like form and afterward the I-like form is maintained. As such, when the multi-joint bending structure  51  is changed from the I-like form to the C-like form, or when the multi-joint bending structure  51  is returned from the C-like form to the I-like form, the external force may be applied partly, and then, due to the action of the assisting force generation mechanism  5 , a desired form may be automatically obtained. 
         [0060]      FIG. 9A  illustrates a state of an assisting force generation mechanism  5  when a multi-joint bending structure  51  of the first example of the first mode of the present application as described above is in an I-like form. For the multi-joint bending structure  51  of the first example of the first mode, a pair of belts  6 L,  6 R and a pair of belts  7 L,  7 R are respectively placed in housings of the second and third band pieces  2 ,  3  located to the right and left of the first band piece  1 , and are provided with the assisting force generation mechanisms  5 . In contrast to this, a multi-joint bending structure  52  of a second example of the first mode of the present application illustrated in  FIG. 9B  is possible in which the number of belts is reduced by integration of the belt  6 L with the belt  7 L and of the belt  6 R with the belt  7 R. 
         [0061]    In the multi-joint bending structure  52 , only a pair of belts  6 L,  6 R is provided in housings of the first to third band pieces  1  to  3 . The belts  6 L,  6 R pass through the first band piece  1  and are arranged within the second and third band pieces  2 ,  3  which are located at both sides of the first band piece  1 . Then, one end of the belt  6 L is fixed by the screw  9  in the third band piece  3  located on one side of the first band piece  1 . Similarly, one end of the belt  6 R is fixed by a screw  9  in the third band piece  3  on the other side of the first band piece  1 . Free ends  6 E,  6 F of the belts  6 L,  6 R are respectively in the third band pieces  3 . 
         [0062]    The assisting force generation mechanisms  5  in the multi-joint bending structure  52  are the same as the assisting force generation mechanisms  5  in the multi-joint bending structure  51  and are provided respectively in bending units  4  located to the right and left of the first band piece  1 . In the multi-joint bending structure  52 , a position of the bending unit  4  in the assisting force generation mechanism  5  is the same as a position of the bending unit  4  of the assisting force generation mechanism  5  in the multi-joint bending structure  51 . Therefore, operation of the assisting force generation mechanism  5  when the multi-joint bending structure  52  is changed between the Hike form and the C-like form is exactly the same as the operation of the assisting force generation mechanism  5  when the multi-joint bending structure  51  described above is changed between the I-like form and the C-like form. Thus, a description of the operation of the assisting force generation mechanism  5  when the multi-joint bending structure  52  is changed between the I-like form and the C-like form is omitted. 
         [0063]      FIG. 9C  illustrates a position and a state of the assisting force generation mechanism  5  when a multi-joint bending structure  61  of a first example of a second mode of the present application is in an I-like form. In the multi-joint bending structures  51 ,  52  of the first and second examples of the first mode, the assisting force generation mechanism  5  is provided within the bending unit  4 . Thus, in the assisting force generation mechanism  5  are provided bending rod-like bodies  10  that are equipped with slits  11  and may change shape in response to bending of the belts  6 L,  6 R and the belts  7 L,  7 R. 
         [0064]    On the one hand, in the second mode, as in the multi-joint bending structure  61  of the first example illustrated in  FIG. 9C , the assisting force generation mechanism  5  is provided within the first band piece  1 , which differs from the first mode. A connection structure by joint potions  55  of the first to third band pieces  1  to  3  in the second mode is the same as a connection structure of the first mode. Also, the second mode does not have to have a space where the assisting force generation mechanism  5  is housed in the bending unit  4 . Furthermore, in the second mode, since the first band piece  1  does not bend, a non-bending rod-like body  12  is provided in place of the bending rod-like body  10  of the first mode. Note that the bending rod-like body  10  of the first mode may be used in the second mode. 
         [0065]    A pair of belts  6 L,  6 R is provided in the multi-joint bending structure  61 . The belt  6 L is fixed by a screw  9  in the third band piece  3  whose one end is on one side of the first band piece  1 . Similarly, the belt  6 R is fixed by a screw  9  in the third band piece  3  whose one end is on the other side of the first band piece  1 . Free ends  6 E,  6 F of the belts  6 L,  6 R are respectively located in the first band piece  1 . In the neighborhood of the free ends  6 E,  6 F of the belts  6 L,  6 R, the rod-like bodies  12  are fixed in an opposed state, being spaced apart by predetermined gaps. 
         [0066]    Then, when the multi-joint bending structure  61  is in the I-like form, two rod-like bodies  12  are fixed on the belts  6 L,  6 R so that overlapping portions and non-overlapping portions exist on the two rod-like bodies  12 . The second mode is similar to the first mode in that an extension spring  19  is inserted between the gap of the two rod-like bodies  12 , and piece members  20  connected to both ends of the extension spring  19  are latched to ends of the rod-like bodies  12  located on both sides of the overlapping portion of the rod-like body  12 , thereby forming the assisting force generation mechanism  5 . 
         [0067]      FIG. 10A  is a view from the lateral face of the state in which the multi-joint bending structure  61  of the first example of the second mode illustrated in  FIG. 9C  is in the I-like form. In addition,  FIG. 10B  is a view from the lateral face of a state in which the multi-joint bending structure  61  illustrated in  FIG. 10A  is changing in position from the I-like form to the C-like form. Furthermore, FIG.  10 C is a view from the lateral face of a state in which the multi-joint bending structure  61  illustrated in  FIG. 10B  changes in position to the C-like form. 
         [0068]    Then,  FIG. 10D  is a view from a direction of an arrow XD of a state of the assisting force generation mechanism  5  which is within the first band piece  1  of the multi-joint bending structure  61  illustrated in  FIG. 10A . In addition,  FIG. 10E  is a view from a direction of an arrow XE of a state of the assisting force generation mechanism  5  which is within the first band  1  of the multi-joint bending structure  61  illustrated in  FIG. 10B . Furthermore, FIG.  1 OF is a view from a direction of an arrow XF of a state of the assisting force generation mechanism  5  which is within the first band  1  of the multi-joint bending structure  61  illustrated in  FIG. 10C . 
         [0069]    When the multi-joint bending structure  61  changes in position from the I-like form illustrated in  FIG. 10A  to the C-like form illustrated in  FIG. 10C  by going through the bent form illustrated  FIG. 10B , the assisting force generation mechanism  5  operates as illustrated in  FIG. 10D  to  FIG. 10F . If the bending rod-like body  10  is replaced by the rod-like body  12 , this operation is the same as the operation of the assisting force generation mechanism  5  in the multi-joint bending structure  51  of the first example of the first mode described above. Thus, same members are assigned same numerals and a description of this operation is omitted. 
         [0070]      FIG. 11A  illustrates a state of an assisting force generation mechanism  5  when a multi-joint bending structure  62  of a second example of the second mode of the present application is in an I-like form. In the multi-joint bending structure  61  of the first example of the second mode described in  FIG. 9C  and  FIG. 10A  to  FIG. 10F , the belts  6 L,  6 R may respectively move independently.  FIG. 10A  to  FIG. 10F  describe that the bending units  4  on both sides of the first band piece  1  similarly bend and how the multi-joint bending structure  61  in the I-like form as illustrated in  FIG. 10A  changes in position to the multi-joint bending structure  61  in the C-like form as illustrated in  FIG. 10C . However, in the multi-joint bending structure  61  of the first example of the second mode, it is possible to bend only the bending unit  4  on the one side of the first band piece  1  and form the multi-joint bending structure  61  in a J-like form. 
         [0071]    On the one hand, in the multi-joint bending structure  62  of the second example of the second mode, provision of a pinion  13  in the assisting force generation mechanism  5  does not allow respective belts to move independently. Specifically, in the multi-joint bending structure  62 , the belts  6 L,  6 R are connected by the pinion  13 . Thus, when the belt  6 L moves, the belt  6 R moves in an opposite direction to the belt  6 L by an equal distance as the belt  6 L. This is a difference between the multi-joint bending structure  61  of the first example of the second mode and the multi-joint bending structure  62  of the second example. 
         [0072]      FIG. 11B  illustrates a specific structure example of the assisting force generation mechanism  5  illustrated in  FIG. 11A  and the assisting force generation mechanism  5  is provided in the first band piece  1 . The first band piece  1  includes an upper case  18 U and a lower case  18 L. Note that in this specific structure example, depiction of a joint potion between the first band piece  1  and the second band piece  2  is omitted.  FIG. 11C  illustrates a state in which the upper-side cover of the assisting force generation mechanism  5  illustrated in  FIG. 11B  is removed with the pinion  13  remaining intact. The upper case  18 U is shaped like a bathtub and the pinion  13  is rotatably fixed to a rotating shaft  13 A which is installed at a central part of a concave  18 A in a protruding manner. In addition, on a wall part  18 W 1  in short direction of the upper case  18 U is formed a belt notch  16  for causing the belts  6 L,  6 R to pass. On a wall part  18 W 2  in a longitudinal direction is formed a lever notch  17  for causing a lever  15  to be described below to move. 
         [0073]    In the lower case  18 L, a step part  18 D to which the wall parts  18 W 1 ,  18 W 2  of the upper case  18 U are mounted is formed in a peripheral area, and there is bottom face  18 B surrounded by the step part  18 D. The belts  6 L,  6 R slide over the bottom face  18 B. Racks  14  are provided on upper surfaces of the rod-like bodies  12  which are fixed onto the belts  6 L,  6 R. Gear wheels provided in the racks  14  are opposed and a distance between the racks  14  is equal to a diameter of the pinion  13  installed on the upper cover  18 U. In addition, the lever  15  is installed in a protruding manner on the lateral face of the rod-like body  12  in the longitudinal direction. The points that the extension spring  19  is inserted in a gap between the two rod-like bodies  12  and the piece members  20  connected to both ends of the extension spring  19  are latched to the end faces of the overlapping portions of the rod-like bodies  12  is the same as hereinbefore. When the upper case  18 U is installed on the lower case  18 L, the pinion  13  engages with the rack  14  and the lever  15  protrudes outward from the lever notch  17 , as illustrated in  FIG. 11C . 
         [0074]      FIG. 12A  is a planar view of a state of the multi-joint bending structure  62  in the I-like form including the first band piece in which the assisting force generation mechanism  5  of the specific example illustrated in  FIG. 11B ,  FIG. 11C  is embedded. The lever  15  protrudes from the lateral faces on both sides of the band piece  1 . Total length Li of the multi-joint bending structure  62  may be approximately 60 mm and width L 2  approximately 10 mm.  FIG. 12B  illustrates a state viewed from the lateral face of the multi-joint bending structure  62  illustrated in  FIG. 12A . Length L 3  of the first band piece  1  may be approximately 35 mm and height L 4  approximately 10 mm.  FIG. 12C  is a view from the lateral face in which the multi-joint bending structure  62  is in the C-like form. When the multi-joint bending structure  62  has dimensions described above, an inner diameter L 5  of the multi-joint bending structure  62 , when in the C-like form, is approximately 55 mm, which enables the multi-joint bending structure  62  to be attached to a wrist and the like. 
         [0075]    In addition, if the lever  15  is fixed to the rod-like body  12  in a protruding manner and the lever  15  protrudes outside of the upper case  18 U with the upper case  18 U attached to the lower case  18 L of the first piece band  1 , it is possible to change shape of the multi-joint bending structure  62  by sliding the lever  15 . Specifically, in the state illustrated in  FIG. 12A , by moving the lever  15  to a direction depicted by an arrow, it is possible to change shape of the multi-joint bending structure  62  from the I-like form to the C-like form illustrated in  FIG. 12C . Operation of the assisting force generation mechanism  5  in the multi-joint bending structure  62  is similar to the operation of the assisting force generation mechanism  5  in the multi-joint bending structure  61 . 
         [0076]      FIG. 13A  is a planar view of a state of an assisting force generation mechanism  5  when a multi-joint bending structure  63  of a third example of the second mode of the present application is in an I-like form. The multi-joint bending structure  63  of the third example of the second mode has a modified structure of the assisting force generation mechanism  5  of the multi-joint bending structure  61  of the first example of the second mode. While one assisting force generation mechanism  5  is provided within the first band piece  1  of the multi-joint bending structure  61 , a first assisting force generation mechanism  5 A and a second assisting force generation mechanism  5 B are provided within the first band piece  1  in the multi-joint bending structure  63 . 
         [0077]    The first assisting force generation mechanism  5 A includes a moving rod-like body  12 M provided on the side of a free end  6 E of a belt  6 L and a fixed rod-like body  12 F provided on a housing of the first band piece  1 . Then, two piece members  20  connected by an extension spring  19  are bridged between ends of overlapping portions of the moving rod-like body  12 M and the fixed rod-like body  12 F. 
         [0078]    Similarly, the second assisting force generation mechanism  5 B includes a moving rod-like body  12 M provided on the side of a free end  6 F of a belt  6 R and a fixed rod-like body  12 F provided on a housing of the first band piece  1 . Then, two piece members  20  connected by the extension spring  19  are bridged between the ends of the moving rod-like body  12 M and the fixed rod-like body  12 F. Width of the moving rod-like body  12 M and of the fixed rod-like body  12 F is equal to width of the rod-like body  12  of the assisting force generation mechanism  5 . Thus, the same belts as the belts  6 L,  6 R used in the multi-joint bending structure  61  may be used for the belts  6 L,  6 R. 
         [0079]      FIG. 13B  is a planar view of a state in which the multi-joint bending structure  63  of the third example of the second mode of the present application is in the I-like form.  FIG. 13C  illustrates a state of the first and second assisting force generation mechanism  5 A,  5 B embedded in the multi-joint bending structure  63  illustrated in  FIG. 13B . The operation of the first and second assisting force generation mechanism  5 A,  5 B when the multi-joint bending structure  63  changes shape between the Hike form and the C-like form is similar to the operation of the rod-like body  12  in the assisting force generation mechanism  5  as described hereinbefore. Therefore, in the state illustrated in  FIG. 13C , if external force is applied to a bending unit  4  from outside of an joint potion  55 , the multi-joint bending structure  63  easily changes shape to the C-like form illustrated in  FIG. 13D  due to the operation of the first and second assisting force generation mechanisms  5 A,  5 B. This also applies when the multi-joint bending structure  63  is returned from the C-like form to the I-like form. 
         [0080]    Here, a usage example of the multi-joint bending structure  50  is described through the use of the multi-joint bending structure  50  which represents the multi-joint bending structures  51 ,  52 ,  61 ,  62 ,  63  of the examples described above.  FIG. 14A  is a view illustrating the multi-joint bending structure  50  having an elongate wrist-band shape. An electronic device such as a pedometer may be embedded in the housing of the multi-joint bending structure  50 .  FIG. 14B  illustrates the multi-joint bending structure  50  having a wide band shape. A terminal may be embedded as an electronic device in the housing of the multi-joint bending structure  50  in this example.  FIG. 14C  illustrates the multi-joint bending structure  50  having a watch shape. Since only a first band piece  1  of the multi-joint bending structure  50  in this example is wide, the terminal may be embedded in or overlappingly attached to the first band piece  1 . 
         [0081]    The multi-joint bending structure  50  illustrated in  FIG. 14A  to  FIG. 14C  may be caused to change the shape to the C-like form illustrated in  FIG. 14D  to be used by being put on the arm W as illustrated in  FIG. 14E . In addition, since the multi-joint bending structure  50  illustrated in  FIG. 14B  is wide, the multi-joint bending structure  50  may be used as a terminal in a straight shape illustrated in  FIG. 14F . As such, the multi-joint bending structure  50  in which the assisting force generation mechanism  5  is embedded in and an electronic device is embedded or attached may be used as an electronic device even in a bent state or in a stretched state. 
         [0082]    Furthermore, by making length when the first to third band pieces  1  to  3  are connected longer, the multi-joint bending structure  50  may be attached to the head HD as a head band as illustrated in  FIG. 15A  or may be used by being attached to the waist BD as illustrated in  FIG. 15B . Furthermore, the multi-joint bending structure  50  may be attached not only to the human body but also to an animal  80  as illustrated in  FIG. 15C . When the multi-joint bending structure  50  is used being attached to the animal  80 , and if a GPS device is embedded in any of the first to third band pieces  1  to  3 , it is convenient to look for the animal  80 . 
         [0083]    In addition, since the multi-joint bending structure  50  of the present application may be easily attached or detached, the multi-joint bending structure  50  is useful in walking a dog on the road at night if an illumination device which shines or blinks is embedded as an electronic device and is attached to the neck of the animal  80  as illustrated in  FIG. 15D . In addition, as illustrated in  FIG. 15E , if an illumination device is embedded in the wrist-band shaped multi-joint bending structure  50  which is then attached to the arm W, the multi-joint bending structure  50 —is useful for an anticrime measure for women or children at night. In addition, the multi-joint bending structure  50  of the present application in which the assisting force generation mechanism  5  is embedded may be easily attached or detached even if the multi-joint bending structure is attached to one arm and only the other arm may be used. 
         [0084]    Note that while in the examples described above, the bending rod-like body or the rod-like body of the assisting force generation mechanism is fixed to the belt, the bending rod-like body or the rod-like body may be fixed to a linear body other than a belt, such as a wire. In addition, there is no special limitation to the number of the second band pieces forming the bending unit of the assisting force generation mechanism or dimensions of the assisting force generation mechanism. 
         [0085]    So far the present application has been described in detail with reference to preferred embodiments, in particular. For easy understanding of the present application, specific modes of the present application are described below. 
         [0086]    All examples and conditional language recited herein are intended for pedagogical purposes to aid the reader in understanding the invention and the concepts contributed by the inventor to furthering the art, and are to be construed as being without limitation to such specifically recited examples and conditions, nor does the organization of such examples in the specification relate to a showing of the superiority and inferiority of the invention. Although the embodiments of the present invention have been described in detail, it should be understood that the various changes, substitutions, and alterations could be made hereto without departing from the spirit and scope of the invention.