Abstract:
A rotation assist assembly is an assembly for assisting the rotation of a rotary adjustment member included in a lens barrel, and includes a base portion and a grip portion. The base portion is configured to be wound around the rotary adjustment member along a rotation direction of the rotary adjustment member. The grip portion is coupled to the base portion in the rotation direction, and a user&#39;s finger is placed on this grip portion when rotating the rotary adjustment member. A first maximum dimension from a rotational center of the rotary adjustment member to an outer face of the grip portion in a radial direction of the rotary adjustment member is greater than a second maximum dimension from the rotational center to a radial outer face of the base portion.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
       [0001]    This application claims priority under 35 U.S.C. §119 to Japanese Patent Application No. 2010-209448, filed on Sep. 17, 2010. The entire disclosures of Japanese Patent Applications No. 2010-209448 is hereby incorporated herein by reference. 
       BACKGROUND 
       [0002]    1. Technical Field 
         [0003]    The technology disclosed herein relates to a rotation assist assembly. More specifically, the technology disclosed herein relates to a rotation assist assembly that assists rotation of a rotary adjustment member included in a lens barrel. 
         [0004]    2. Background Information 
         [0005]    The lens barrel of an imaging device has a zoom ring, focus ring, and other such rotary adjustment members. The user can turn the zoom ring to adjust the focal length (image angle) of the optical system and can turn the focus ring to adjust the imaging distance (the distance from the main subject to the imaging device). 
         [0006]    However, these rotary adjustment members come in many different sizes and require varying amounts of force to operate, and users&#39; hands of course also come in all different sizes. Therefore, there may be many users who feel that the rotary adjustment member is difficult to operate when they turn the rotary adjustment member. 
         [0007]    In view of this, there has been proposed an assist device for assisting the rotary operation of a rotary adjustment member (see, for example, Utility Model JP-3,160,546). 
         [0008]    With the assist device discussed in Utility Model JP-3,160,546, however, since the outside diameter of the ring member is constant, it is conceivable that a user may find rotary operation difficult. 
       SUMMARY 
       [0009]    A rotation assist assembly disclosed herein is an assembly for assisting the rotation of a rotary adjustment member included in a lens barrel, and comprises a base portion and a grip portion. The base portion is configured to be wound around the rotary adjustment member along a rotation direction of the rotary adjustment member. The grip portion is coupled to the base portion in the rotation direction, and a user&#39;s finger is placed on this grip portion when rotating the rotary adjustment member. A first maximum dimension from a rotational center of the rotary adjustment member to an outer face of the grip portion in a radial direction of the rotary adjustment member is greater than a second maximum dimension from the rotational center to a radial outer face of the base portion. 
         [0010]    These and other features, aspects and advantages of the technology disclosed herein will become apparent to those skilled in the art from the following detailed description, which, taken in conjunction with the annexed drawings, discloses a embodiments of the invention. 
     
    
     
       BRIEF DESCRIPTION OF DRAWINGS 
         [0011]    Referring now to the attached drawings which form a part of this original disclosure: 
           [0012]      FIG. 1A  is an oblique view of a digital camera to which a rotation assist assembly is mounted, and  FIG. 1B  is an oblique view of a digital camera; 
           [0013]      FIG. 2A  is a plan view of a rotation assist assembly (mounted state), and  FIG. 2B  is a plan view of a grip belt; 
           [0014]      FIG. 3A  is a plan view of a rotation assist assembly (unmounted state), and  FIG. 3B  is a plan view of a rotation assist assembly (unmounted state); 
           [0015]      FIG. 4A  is an oblique view of a grip belt, and  FIG. 4B  is an oblique view of a grip belt; 
           [0016]      FIG. 5  is an oblique view of a grip belt; 
           [0017]      FIG. 6  is an enlarged plan view of a first grip portion; 
           [0018]      FIG. 7  is a cross section along the VII-VII line in  FIG. 6 ; 
           [0019]      FIG. 8A  is an enlarged plan view of a second grip portion, and  FIG. 8B  is an enlarged plan view of a third grip portion; 
           [0020]      FIG. 9A  is a cross section along the IXA-IXA line in  FIG. 9B , and  FIG. 9B  is a plan view of a fixing belt; and 
           [0021]      FIG. 10  is an enlarged plan view of a grip portion (other embodiment). 
       
    
    
     DETAILED DESCRIPTION OF EMBODIMENTS 
       [0022]    Selected embodiments will now be explained with reference to the drawings. It will be apparent to those skilled in the art from this disclosure that the following descriptions of the embodiments are provided for illustration only and not for the purpose of limiting the invention as defined by the appended claims and their equivalents. 
       First Embodiment 
       [0023]    Configuration of Digital Camera 
         [0024]    A digital camera  1  is an imaging device capable of acquiring image data about a subject and is an interchangeable type of digital camera. As shown in  FIGS. 1A and 1B , the digital camera  1  has a camera body  2  and an interchangeable lens unit  3 . 
         [0025]    The interchangeable lens unit  3  (one example of a lens barrel) has a barrel  32  and a zoom ring  31  (an example of a rotary adjustment member). The zoom ring  31  is rotatably supported by the barrel  32 . The focal length (image angle) of an optical system O can be adjusted by turning the zoom ring  31 . 
         [0026]    The rotational direction of the zoom ring  31  shall be termed the “rotation direction” (an example of the rotation direction of the rotary adjustment member). The rotation direction substantially coincides with the direction in which a rotation assist assembly  4  is turned and with the circumferential direction of the rotation assist assembly  4 . The radial direction of the zoom ring  31  (a direction perpendicular to the optical axis A) shall be termed the “radial direction” (an example of the radial direction of the rotary adjustment member). The radial direction substantially coincides with the radial direction of the rotation assist assembly  4 . Further, a direction parallel to the optical axis A of the optical system O shall be termed the “optical axis direction” and “width direction” (an example of a width direction perpendicular to the radial direction and the rotation direction). In the following description, the directions explained above will be used to describe the configuration of the various components of the rotation assist assembly  4 . 
         [0027]    Since the rotational center of the zoom ring  31  is disposed along the optical axis A, in the following description the rotational center of the zoom ring  31  shall also be called the rotational center A. 
         [0028]    Rotation Assist Assembly 
         [0029]    The rotation assist assembly  4  is a member that assists the user to rotate the zoom ring  31  and can be mounted on the outer peripheral side of the zoom ring  31 . As shown in  FIGS. 2A to 5 , the rotation assist assembly  4  comprises a grip belt  41 , a fixing belt  42 , and felt  48 . 
         [0030]    Grip Belt 
         [0031]    The grip belt  41  is a substantially belt-shaped member and is entirely and integrally formed from resin, for example. The grip belt  41  substantially has a C shape so as to make it easier to mount to the zoom ring  31 . Since the length of the grip belt  41  is set considerably shorter than the outer periphery of an ordinary rotary adjustment member, the ends of the grip belt  41  do not touch each other when the grip belt  41  is mounted to the rotary adjustment member. In mounting the rotation assist assembly  4  to the zoom ring  31 , the ends of the grip belt  41  are linked by the fixing belt  42  (discussed below). The grip belt  41  has a first base portion  46 , a second base portion  47 , a third base portion  50 , a fourth base portion  49 , a first grip portion  43 , a second grip portion  44 , a third grip portion  45 , and a rotation restricting protrusion  45   a.    
         [0032]    (1) First Base Portion  46   
         [0033]    The first base portion  46  (one example of a base portion, and an example of part of a base portion) is a belt-shaped portion that is wound around the zoom ring  31  in the rotation direction of the zoom ring  31  (the rotation direction of the rotary adjustment member). The first base portion  46  is relatively long compared to the other base portions (the second base portion  47 , the third base portion  50 , and the fourth base portion  49 ), and is disposed between the first grip portion  43  and the third grip portion  45 . 
         [0034]    (2) Second Base Portion  47   
         [0035]    The second base portion  47  (one example of a base portion) is a belt-shaped portion that is wound around the zoom ring  31  in the rotation direction of the zoom ring  31  (the rotation direction of the rotary adjustment member) and is linked to the second grip portion  44  in the rotation direction. The second base portion  47  protrudes in the rotation direction from the second grip portion  44  and forms a first end of the grip belt  41 . 
         [0036]    The second base portion  47  has stoppers  47   a  and  47   b  disposed spaced apart in the rotation direction. The stoppers  47   a  and  47   b  (an example of stoppers) are provided to catch the fixing belt  42  and protrude outward in the radial direction from the second base portion  47 . To catch the fixing belt  42 , the stoppers  47   a  and  47   b  are formed substantially in an L shape when viewed in the width direction (the optical axis direction). 
         [0037]    (3) Third Base Portion  50   
         [0038]    The third base portion  50  (one example of a base portion) is a belt-shaped portion and links the second grip portion  44  and the third grip portion  45  in the rotation direction. The third base portion  50  is disposed between the second grip portion  44  and the third grip portion  45 . The third base portion  50  is shorter than the first base portion  46  and the second base portion  47 . 
         [0039]    (4) Fourth Base Portion  49   
         [0040]    The fourth base portion  49  (one example of a base portion) is a belt-shaped portion, and is linked to the first grip portion  43  in the rotation direction. The fourth base portion  49  protrudes in the rotation direction from the first grip portion  43 , and forms a second end of the grip belt  41 . The fourth base portion  49  is shorter than the first base portion  46  and the second base portion  47 . 
         [0041]    (5) First Grip Portion  43   
         [0042]    The first grip portion  43  (one example of a grip portion, and an example of a first grip portion) is provided for the user to place his fingers on when turning the zoom ring  31 , and forms a substantially belt-shaped portion along with the base portions (the first base portion  46 , the second base portion  47 , the third base portion  50 , and the fourth base portion  49 ). The first grip portion  43  is linked in the rotation direction to the first base portion  46  and the fourth base portion  49 . The first grip portion  43  is disposed between the first base portion  46  and the fourth base portion  49  in the rotation direction, and is formed integrally with the first base portion  46  and the fourth base portion  49 . The first grip portion  43  has four first slits  43   a,  a first anti-slip portion  43   b,  and a pair of mounting grooves  43   e.    
         [0043]    The first slits  43   a  (one example of first slits) are disposed at the radial inner face of the first grip portion  43 , and extend in the radial direction. The four first slits  43   a  are disposed at different positions in the rotation direction, and are disposed substantially equidistantly in the rotation direction. Since the first slits  43   a  are formed relatively deep in the radial direction, the stiffness of the first grip portion  43  in the rotation direction (and particularly the stiffness of the inner peripheral part of the first grip portion  43 ) is lowered by the first slits  43   a,  and the first grip portion  43  becomes stretchable in the rotation direction. In this embodiment, the dimension of the first slits  43   a  in the radial direction is greater than one-half the dimension M 11  of the first grip portion  43  in the radial direction. 
         [0044]    In this embodiment, the ends of the fixing belt  42  are hooked onto the four first slits  43   a.  More specifically, as shown in  FIG. 6 , the first slits  43   a  each have a concave part  43   d.  The concave parts  43   d  are provided to prevent insertion parts  42   c,    42   d,  and  42   e  (discussed below) of the fixing belt  42  from falling out, and have a substantially semicircular shape when viewed in the width direction. The concave parts  43   d  are disposed at the side walls of the first slits  43   a  on the fourth base portion  49  side. The positions of the concave parts  43   d  may be disposed at the side walls of the first slits  43   a  on the first base portion  46  side, but when the direction in which the fixing belt  42  is hooked is taken into account, it is preferable to dispose the concave parts  43   d  at the side walls of the first slits  43   a  on the fourth base portion  49  side (the side walls on the side closer to the stoppers  47   a  and  47   b  in the rotation direction). 
         [0045]    As shown in  FIGS. 6 and 7 , the mounting grooves  43   e  are formed so that a pair of coupling portions  42   a  (discussed below) of the fixing belt  42  can be fitted in, and extend in the rotation direction. The positions of the mounting grooves  43   e  in the radial direction are substantially the same as the positions of the concave parts  43   d  in the radial direction. As shown in  FIG. 7 , the mounting grooves  43   e  have a substantially semicircular shape when viewed in the rotation direction. 
         [0046]    As shown in  FIGS. 2A to 6 , the first anti-slip portion  43   b  has a textured shape in which concave and convex parts are repeatedly formed in the rotation direction. More specifically, the first anti-slip portion  43   b  has a plurality of first grooves  43   c  disposed equidistantly in the rotation direction. The textured shape is formed by the plurality of first grooves  43   c.    
         [0047]    (6) Second Grip Portion  44   
         [0048]    As shown in  FIGS. 2A to 5  and  FIG. 8A , the second grip portion  44  (one example of a grip portion, and an example of a second grip portion) is provided for the user to place his fingers on when turning the zoom ring  31 , and forms a substantially belt-shaped portion along with the base portions (the first base portion  46 , the second base portion  47 , the third base portion  50 , and the fourth base portion  49 ). The second grip portion  44  is linked in the rotation direction to the second base portion  47  and the third base portion  50 . The first grip portion  43  and the second grip portion  44  are disposed spaced apart in the rotation direction. In this embodiment, the first grip portion  43  and the second grip portion  44  are disposed on opposite sides of the optical axis A. The second grip portion  44  is disposed between the second base portion  47  and the third grip portion  45  in the rotation direction, and is formed integrally with the second base portion  47  and the third base portion  50 . The second grip portion  44  has three second slits  44   a  and a second anti-slip portion  44   b.    
         [0049]    The second slits  44   a  (an example of second slits) are disposed at the radial inner face of the second grip portion  44 , and extend in the radial direction. The three second slits  44   a  are disposed at different positions in the rotation direction, and are disposed substantially equidistantly in the rotation direction. Since the second slits  44   a  are formed relatively deep in the radial direction, the stiffness of the second grip portion  44  in the rotation direction (and particularly the stiffness of the inner peripheral part of the second grip portion  44 ) is lowered by the second slits  44   a,  and the second grip portion  44  becomes in the rotation direction. In this embodiment, the dimension of the second slits  44   a  in the radial direction is greater than one-half the dimension M 21  of the second grip portion  44  in the radial direction. 
         [0050]    The second anti-slip portion  44   b  has a textured shape in which concave and convex parts are repeatedly formed in the rotation direction. More specifically, the second anti-slip portion  44   b  has a plurality of second grooves  44   c  disposed equidistantly in the rotation direction. The textured shape is formed by the plurality of second grooves  44   c.    
         [0051]    (7) Third Grip Portion  45   
         [0052]    As shown in  FIGS. 2A to 5  and  FIG. 8B , the third grip portion  45  (one example of a grip portion) is provided for the user to place his fingers on or to grasp with his fingers when turning the zoom ring  31 , and is linked to the first base portion  46  and the third base portion  50  in the rotation direction. The third grip portion  45  is disposed between the first base portion  46  and the third base portion  50  in the rotation direction, and is formed integrally with the first base portion  46  and the third base portion  50 . 
         [0053]    The third grip portion  45  has a third anti-slip portion  45   b.  The third anti-slip portion  45   b  has a textured shape in which concave and convex parts are repeatedly formed. More specifically, the third anti-slip portion  45   b  has a plurality of third grooves  45   c  disposed equidistantly in the radial direction. The textured shape is formed by the plurality of third grooves  45   c.    
         [0054]    (8) Rotation Restricting Protrusion 
         [0055]    The rotation restricting protrusion  45   a  is provided to reduce deviation of the grip belt  41  in the rotation direction with respect to the zoom ring  31 , and is disposed at the radial inner face of the third grip portion  45 . More specifically, as shown in  FIG. 8B , the rotation restricting protrusion  45   a  protrudes inwardly in the radial direction from the radial inner face of the third grip portion  45 . As shown in  FIG. 5 , in this embodiment the rotation restricting protrusion  45   a  extends in a slender form in the width direction, and has a length that is the same as the width of the third grip portion  45 . For example, as shown in  FIG. 8B , a plurality of grooves  31   a  are formed for anti-slip purposes around the outer peripheral face of the zoom ring  31 . When the rotation assist assembly  4  is mounted to the zoom ring  31  so that the rotation restricting protrusion  45   a  fits into one of the grooves  31   a,  then even if the rotation assist assembly  4  tries to slip in the rotation direction with respect to the zoom ring  31 , the rotation restricting protrusion  45   a  will hit the grooves  31   a,  which suppresses sliding of the rotation assist assembly  4 . 
         [0056]    In this embodiment, the rotation restricting protrusion  45   a  is provided at only one location when viewed in the width direction. 
         [0057]    Fixing Belt 
         [0058]    As shown in  FIGS. 2A ,  3 A, and  3 B, the fixing belt  42  (one example of a fixing portion) is a member for fastening the grip belt  41  wound around the zoom ring  31 , and the whole belt is formed integrally from rubber, for example. In this embodiment, the stiffness of the fixing belt  42  is lower than the stiffness of the material of the grip belt  41 . More precisely, the stretchability of the fixing belt  42  allows it to be pulled and extended during mounting. As shown in  FIGS. 9A and 9B , the fixing belt  42  has a pair of coupling portions  42   a,  three insertion parts  42   c,    42   d,  and  42   e,  and a belt end  42   f.    
         [0059]    The pair of coupling portions  42   a  extend in slender form in the rotation direction, and link the three insertion parts  42   c,    42   d,  and  42   e  and the belt end  42   f.  The insertion parts  42   c,    42   d,  and  42   e  (one example of insertion parts) link the pair of coupling portions  42   a  in the width direction, and are disposed spaced apart in the rotation direction. One of the insertion parts  42   c,    42   d,  and  42   e  is removably inserted into one of the four first slits  43   a.    
         [0060]    The belt end  42   f  (one example of a mounting part) is removably hooked onto the stopper  47   a  or  47   b.  The belt end  42   f  is the portion that the user grasps when hooking the fixing belt  42  onto the stopper  47   a  or  47   b.  Because the fixing belt  42  is made of rubber, the belt end  42   f  can be pulled and the entire fixing belt  42  extended when the belt end  42   f  is hooked to the stopper  47   a  or  47   b.  In a state in which the rotation assist assembly  4  is mounted to the zoom ring  31 , the pair of coupling portions  42   a  is fitted into the pair of mounting grooves  43   e.    
         [0061]    Felt 
         [0062]    As shown in  FIG. 2A , the felt  48  is provided to reducing slippage of the rotation assist assembly  4  in the rotation direction with respect to the zoom ring  31 , and is fixed on the inside of the grip belt  41  (more precisely, the inside of the second base portion  47 ). The felt  48  is provided as an assist to the rotation restricting protrusion  45   a.  The felt  48  is formed of nonwoven fabric, for example. In this embodiment, the dimension of the felt  48  in the rotation direction is substantially the same as the dimension of the second base portion  47  in the rotation direction. 
         [0063]    The grip belt  41  has positioning protrusions  48   a  and  48   b  so that the felt  48  does not move in the rotation direction with respect to the grip belt  41 . The positioning protrusions  48   a  and  48   b  are disposed spaced apart in the rotation direction, and the felt  48  is disposed between the positioning protrusions  48   a  and  48   b  in the rotation direction. The dimension of the positioning protrusions  48   a  and  48   b  in the radial direction is set to be less than the thickness of the felt  48  (the dimension in the radial direction). This prevents the positioning protrusions  48   a  and  48   b  from coming into contact with the zoom ring  31 . That is, unlike the rotation restricting protrusion  45   a,  the positioning protrusions  48   a  and  48   b  do not themselves have the function of reducing slippage of the grip belt  41  with respect to the zoom ring  31 . 
         [0064]    Dimensional Relation of Various Components 
         [0065]    The dimensional relation between the various components of the grip belt  41  will now be described. 
         [0066]    As shown in  FIGS. 2A and 6 , the first grip portion  43  extends in slender form in the rotation direction, so the dimension M 13  of the first grip portion  43  in the rotation direction is greater than the dimension M 11  in the radial direction. Also, the dimension M 12  of the first anti-slip portion  43   b  in the rotation direction is greater than the dimension M 11 . The dimension M 13  here is the dimension in the rotation direction from the boundary between the first grip portion  43  and the first base portion  46  to the boundary between the first grip portion  43  and the fourth base portion  49 . The first grip portion  43  has a curved part R at its base. 
         [0067]    As shown in  FIGS. 2A and 8A , just as with the first grip portion  43 , the second grip portion  44  extends in slender form in the rotation direction, so the dimension M 23  of the second grip portion  44  in the rotation direction is greater than the dimension M 21  in the radial direction. Also, the dimension M 22  of the second anti-slip portion  44   b  in the rotation direction is greater than the dimension M 21 . The dimension M 23  here is the dimension in the rotation direction from the boundary between the second grip portion  44  and the third base portion  50  to the boundary between the second grip portion  44  and the second base portion  47 . The second grip portion  44  has a curved part R at its base. 
         [0068]    Meanwhile, as shown in  FIGS. 2A and 8B , unlike with the first grip portion  43  and the second grip portion  44 , the third grip portion  45  extends in slender form in the radial direction, so the dimension M 33  of the third grip portion  45  in the rotation direction is less than the dimension M 31  in the radial direction. 
         [0069]    Also, as shown in  FIG. 2A , first maximum dimensions (dimensions L 1 , L 2 , and L 3 ) from the rotational center of the zoom ring  31  (the optical axis A) to the radial outer faces of the grip portions (the first grip portion  43 , the second grip portion  44 , and the third grip portion  45 ) are greater than a second maximum dimension (dimension L 0 ) from the rotational center (optical axis A) to the radial outer faces of the base portions (the first base portion  46 , the second base portion  47 , the third base portion  50 , and the fourth base portion  49 ). More specifically, the dimension L 1  from the optical axis A to the radial outer face of the first grip portion  43  is greater than the dimension L 0  from the optical axis A to the radial outer faces of the base portions (the first base portion  46 , the second base portion  47 , the third base portion  50 , and the fourth base portion  49 ). The dimension L 2  from the optical axis A to the radial outer face of the second grip portion  44  is greater than the dimension L 0  from the optical axis A to the radial outer faces of the base portions (the first base portion  46 , the second base portion  47 , the third base portion  50 , and the fourth base portion  49 ). Further, the dimension L 3  from the optical axis A to the radial outer face of the third grip portion  45  is greater than the dimension L 0  from the optical axis A to the radial outer faces of the base portions (the first base portion  46 , the second base portion  47 , the third base portion  50 , and the fourth base portion  49 ). Therefore, a relatively large rotational moment can be obtained when the user turns the ring by using the first grip portion  43 , the second grip portion  44 , and the third grip portion  45 . 
         [0070]    As shown in  FIG. 2A , the dimensions of the grip portions (the first grip portion  43 , the second grip portion  44 , and the third grip portion  45 ) in the radial direction (the dimensions M 11 , M 21 , and M 31 ) are greater than the dimensions of the base portions (the first base portion  46 , the second base portion  47 , the third base portion  50 , and the fourth base portion  49 ) in the radial direction (the dimension M 0 ). More specifically, the dimension M 11  of the first grip portion  43  in the radial direction is greater than the dimension M 0  of the base portions (the first base portion  46 , the second base portion  47 , the third base portion  50 , and the fourth base portion  49 ) in the radial direction. The dimension M 21  of the second grip portion  44  in the radial direction is greater than the dimension M 0  of the base portions (the first base portion  46 , the second base portion  47 , the third base portion  50 , and the fourth base portion  49 ) in the radial direction. The dimension M 31  of the third grip portion  45  in the radial direction is greater than the dimension M 0  of the base portions (the first base portion  46 , the second base portion  47 , the third base portion  50 , and the fourth base portion  49 ) in the radial direction. Thus, the first grip portion  43 , the second grip portion  44 , and the third grip portion  45  protrude outward in the radial direction from the base portions (the first base portion  46 , the second base portion  47 , the third base portion  50 , and the fourth base portion  49 ), so it is easy for the user to hook his fingers onto these, and since the base portions (the first base portion  46 , the second base portion  47 , the third base portion  50 , and the fourth base portion  49 ) can be thinner, it is easier to mount the grip belt  41  to the zoom ring  31 . 
         [0071]    In this embodiment, the dimension M 13  of the first grip portion  43  in the rotation direction is greater than the dimension M 23  of the second grip portion  44  in the rotation direction. Accordingly, even if the length of the rotary adjustment member around its outer periphery varies, the first grip portion  43  and the second grip portion  44  will be disposed on substantially opposite sides of the rotational center. 
         [0072]    Mounting and Removal 
         [0073]    The mounting and removal of the rotation assist assembly  4  will now be described. 
         [0074]    As shown in  FIGS. 3A and 3B , for example, the grip belt  41  is wound around the zoom ring  31  in a state in which the belt end  42   f  of the fixing belt  42  has been removed from the stoppers  47   a  and  47   b.  At this point, since the first grip portion  43  has the first slits  43   a,  and the second grip portion  44  has the second slits  44   a,  it is easy to open the grip belt  41  wide. 
         [0075]    In winding the grip belt  41  around the zoom ring  31 , the position of the grip belt  41  is adjusted so that the rotation restricting protrusion  45   a  fits into the grooves  31   a  of the zoom ring  31  (see  FIG. 8B ). This reduces slippage of the rotation assist assembly  4  in the rotation direction with respect to the zoom ring  31 . 
         [0076]    After the grip belt  41  has been wound around the zoom ring  31 , the belt end  42   f  of the fixing belt  42  is hooked onto the stoppers  47   a  or  47   b.  At this point, one of the stoppers  47   a  and  47   b  is selected so that the fixing belt  42  will be stretched out somewhat. Also, the length of the rotation assist assembly  4  in the rotation direction can be adjusted, and the tightness of the rotation assist assembly  4  can be adjusted, by changing in which of the four firsts slit  43   a  the insertion part  42   c  is hooked, or by changing which of the insertion parts  42   c,    42   d,  and  42   e  is hooked in the first slit  43   a.    
         [0077]    In removing the rotation assist assembly  4  from the zoom ring  31 , the belt end  42   f  is removed from the stopper  47   a  or  47   b  while the belt end  42   f  is pulled. When the fixing belt  42  is removed from the stopper  47   a  or  47   b,  the grip belt  41  can be opened wide and removed from the zoom ring  31 . 
         [0078]    Zooming 
         [0079]    When the user performs a zooming operation, he places his fingers on the first grip portion  43  and the second grip portion  44  of the rotation assist assembly  4 , and turns the zoom ring  31  and the rotation assist assembly  4 . Since the first anti-slip portion  43   b  and the second anti-slip portion  44   b  have a textured shape, the fingers do not readily slip. Also, the dimension L 1  from the rotational center A to the radial outer face of the first grip portion  43  is greater than the dimension L 0  from the rotational center A to the radial outer face of the base portions (the first base portion  46 , the second base portion  47 , the third base portion  50 , and the fourth base portion  49 ). Accordingly, it is easy to obtain a relatively large rotational moment, and this makes the operation easier. 
         [0080]    Also, there may be times when the user grasps the third grip portion  45  with his fingers and turns the zoom ring  31 . In this case, since the third grip portion  45  has the pair of third anti-slip portions  45   b,  the fingers are less likely to slip. Also, since the third grip portion  45  is narrower in the radial direction than the first grip portion  43  and the second grip portion  44 , it is easy to obtain a relatively large rotational moment, and the operation is easier. 
         [0081]    Features of Rotation Assist Assembly 
         [0082]    The features of the rotation assist assembly  4  described above are compiled below. 
         [0083]    (1) The dimensions (L 1 , L 2 , and L 3 ) from the rotational center A of the zoom ring  31  to the radial outer faces of the grip portions (the first grip portion  43 , the second grip portion  44 , and the third grip portion  45 ) are greater than the dimension (L 0 ) from the rotational center A to the radial outer faces of the base portions (the first base portion  46 , the second base portion  47 , the third base portion  50 , and the fourth base portion  49 ). More specifically, the dimension L 1  from the rotational center A to the radial outer face of the first grip portion  43  is greater than the dimension L 0  from the rotational center A to the radial outer faces of the base portions (the first base portion  46 , the second base portion  47 , the third base portion  50 , and the fourth base portion  49 ). The dimension L 2  from the rotational center A to the radial outer face of the second grip portion  44  is greater than the dimension L 0  from the rotational center A to the radial outer faces of the base portions (the first base portion  46 , the second base portion  47 , the third base portion  50 , and the fourth base portion  49 ). The dimension L 3  from the rotational center A to the radial outer face of the third grip portion  45  is greater than the dimension L 0  from the rotational center A to the radial outer faces of the base portions (the first base portion  46 , the second base portion  47 , the third base portion  50 , and the fourth base portion  49 ). Therefore, when the user places his fingers on the grip portions (the first grip portion  43 , the second grip portion  44 , and the third grip portion  45 ) and turns the rotation assist assembly  4 , a relatively large rotational moment can be easily obtained, which makes the operation easier. 
         [0084]    (2) The dimensions (M 11 , M 21 , and M 31 ) of the grip portions (the first grip portion  43 , the second grip portion  44 , and the third grip portion  45 ) in the radial direction is greater than the dimension (M 0 ) of the base portions (the first base portion  46 , the second base portion  47 , the third base portion  50 , and the fourth base portion  49 ) in the radial direction. More specifically, the dimensions M 11 , M 21 , and M 31  of the first grip portion  43 , the second grip portion  44 , and the third grip portion  45  in the radial direction are greater than the dimension (M 0 ) of the base portions (the first base portion  46 , the second base portion  47 , the third base portion  50 , and the fourth base portion  49 ) in the radial direction. Therefore, the above-mentioned dimensions L 1 , L 2 , and L 3  can be made greater than the dimension L 0 , while ensuring the required stiffness in the first grip portion  43 , the second grip portion  44 , and the third grip portion  45 . 
         [0085]    (3) Since the first grip portion  43  has the four first slits  43   a  disposed on a radial inner face and extending in the radial direction, the portion of the first grip portion  43  that is on the inside in the radial direction can be stretched in the rotation direction. Consequently, the required stiffness can be ensured in the first grip portion  43 , while the grip belt  41  can be opened wide when it is being wound onto the zoom ring  31 , which makes it easier to mount the grip belt  41  to the zoom ring  31 . 
         [0086]    Also, since the second grip portion  44  has the three second slits  44   a  disposed on a radial inner face and extending in the radial direction, the portion of the second grip portion  44  that is on the inside in the radial direction can be stretched in the rotation direction. Consequently, the required stiffness can be ensured in the second grip portion  44 , while the grip belt  41  can be opened wide when it is being wound onto the zoom ring  31 , which makes it easier to mount the grip belt  41  to the zoom ring  31 . 
         [0087]    (4) Since the fixing belt  42  has the insertion parts  42   c,    42   d,  and  42   e  that are removably inserted into the first slits  43   a,  the tightness of the rotation assist assembly  4  can be adjusted by adjusting which of the insertion parts  42   c,    42   d,  and  42   e  is hooked in the first slit  43   a.    
         [0088]    (5) Since the first grip portion  43  has the plurality of first slits  43   a  disposed at different positions in the rotation direction, the first grip  43  readily expand and contract in the rotation direction, and the grip belt  41  can be opened wide, and the rotation assist assembly  4  can be easily removed and mounted, when the grip belt  41  is wound onto the zoom ring  31 , or when the grip belt  41  is removed from the zoom ring  31 . The same applies to the second grip portion  44 , since the plurality of second slits  44   a  are disposed at different positions in the rotation direction. 
         [0089]    Also, since the first slits  43   a  allow the first grip portion  43  to expand and contract easily in the rotation direction, even if the diameter of the zoom ring  31  varies, the grip belt  41  (and particularly the first grip portion  43  and its surrounding part) will readily conform to the outer periphery of the zoom ring  31 , and the mounting state of the rotation assist assembly  4  can be stabilized regardless of the diameter of the rotary adjustment member. The same applies to the second grip portion  44 . 
         [0090]    Furthermore, the tightness of the rotation assist assembly  4  can be fine-tuned by changing the first slit  43   a  in which the fixing belt  42  is hooked. 
         [0091]    That is, the plurality of first slits  43   a  not only have the function of allowing the rotation assist assembly  4  to conform to the shape of the outer periphery of different rotary adjustment members, but also have the function of adjusting the tightness of the rotation assist assembly  4 . 
         [0092]    (6) Since the rotation assist assembly  4  has the first grip portion  43  and the second grip portion  44 , it is easy for the user to grasp the rotation assist assembly  4  with his fingers, which makes operation easier. 
         [0093]    (7) The first grip portion  43  has the first anti-slip portion  43   b,  which has a textured shape in which concave and convex parts are repeatedly formed in the rotation direction, and the second grip portion  44  has the second anti-slip portion  44   b,  in which concave and convex parts are repeatedly formed in the rotation direction. Therefore, the fingers do not readily slip when the user operates the rotation assist assembly  4 . 
         [0094]    (8) Since the second base portion  47  has the stoppers  47   a  and  47   b  disposed at different positions in the rotation direction, the tightness of the rotation assist assembly  4  can be adjusted by hooking the fixing belt  42  in one of the stoppers  47   a  and  47   b.    
         [0095]    (9) The grip belt  41  has the rotation restricting protrusion  45   a,  which protrudes inwardly in the radial direction from the radial inner face of the third grip portion  45  so as to be inserted into one of the grooves  31   a  of the zoom ring  31 . When the grip belt  41  is mounted to the zoom ring  31  such that the rotation restricting protrusion  45   a  is inserted into one of the grooves  31   a,  if the grip belt  41  should try to slip in the rotation direction with respect to the zoom ring  31 , the rotation restricting protrusion  45   a  will hit the groove  31   a,  and this reduces slippage of the grip belt  41  in the rotation direction with respect to the zoom ring  31 . 
         [0096]    Also, since the rotation restricting protrusion  45   a  is provided at just one location when viewed in the width direction, it can be inserted more easily into the grooves  31   a  than when the rotation restricting protrusion  45   a  is provided at a plurality of locations. 
       Other Embodiments 
       [0097]    The present invention is not limited to the above embodiments, and various changes and modifications are possible without departing from the scope of the invention. 
         [0098]    (A) The rotary adjustment member to which the rotation assist assembly  4  is mounted is not limited to the zoom ring  31 , and may be a focus ring instead, for example. Also, the lens barrel having the rotary adjustment member is not limited to being an interchangeable lens unit, and may be a lens barrel installed in an integrated type of imaging device. 
         [0099]    (B) The rotation assist assembly  4  has the grip belt  41 , the fixing belt  42 , and the felt  48 , but the grip belt  41  and the fixing belt  42  may be formed integrally, for example, and the felt  48  omitted. 
         [0100]    Also, the grip portions (the first grip portion  43 , the second grip portion  44 , and the third grip portion  45 ) may be separate from the base portions (the first base portion  46 , the second base portion  47 , the third base portion  50 , and the fourth base portion  49 ). 
         [0101]    Further, the grip belt  41  has the first grip portion  43 , the second grip portion  44 , and the third grip portion  45 , but need only have one or more grip portions. Also, the grip belt  41  has the first base portion  46 , the second base portion  47 , the third base portion  50 , and the fourth base portion  49 , but need only have one or more grip portions. 
         [0102]    The shape and disposition of the first grip portion  43 , the second grip portion  44 , and the third grip portion  45  are not limited to those in the above embodiment. 
         [0103]    (C) In the above embodiment, the dimensions (M 11 , M 21 , and M 31 ) of the grip portions (the first grip portion  43 , the second grip portion  44 , and the third grip portion  45 ) in the radial direction is greater than the dimension (M 0 ) of the base portions (the first base portion  46 , the second base portion  47 , the third base portion  50 , and the fourth base portion  49 ) in the radial direction, but it is also conceivable that the dimensions of the grip portions in the radial direction be the same as the dimension of the base portion in the radial direction, or be less than the dimension in the radial direction. In this case, the first grip portion  43  has a shape like that of the first grip portion  143  shown in  FIG. 10 , for example. 
         [0104]    (D) In the above embodiment, the first grip portion  43  has the four first slits  43   a,  but the first grip portion  43  need not have the first slits  43   a.  Also, the second grip portion  44  has the three second slits  44   a,  but the second grip portion  44  need not have the second slits  44   a.    
         [0105]    Also, the dimensions of the first slits  43   a  and the second slits  44   a  are not limited to those in the above embodiment. 
         [0106]    (E) With the above embodiment, the insertion part of the fixing belt  42  is inserted into one of the first slits  43   a,  but may be inserted into the second slits  44   a.    
         [0107]    (F) In the above embodiment, the grip portions (the first grip portion  43 , the second grip portion  44 , and the third grip portion  45 ) have a textured shape, but need not have a textured shape. Also, the positions and shapes of the second anti-slip portion  44   b  and the third anti-slip portion  45   b  are not limited to those in the above embodiments. For example, the first anti-slip portion  43   b  has a plurality of first grooves  43   c,  but the textured shape may be formed by something other than grooves. 
         [0108]    (G) In the above embodiment, the two stoppers  47   a  and  47   b  are provided to the second base portion  47 , but there need only been one or more stoppers for hooking the fixing belt  42 . 
         [0109]    (H) In the above embodiment, the grip belt  41  has the rotation restricting protrusion  45   a,  but the grip belt  41  need not have the rotation restricting protrusion  45   a.  Also, the rotation restricting protrusion  45   a  extends in slender form in the width direction, but need not do so, may be instead be a simple protrusion. 
         [0110]    Also, the rotation restricting protrusion  45   a  may be provided at a plurality of locations, but when insertion into the grooves  31  a is taken into account, it is preferable to provide the rotation restricting protrusion  45   a  at just one location when viewed in the width direction. 
       General Interpretation of Terms 
       [0111]    In understanding the scope of the present disclosure, the term “comprising” and its derivatives, as used herein, are intended to be open ended terms that specify the presence of the stated features, elements, components, groups, integers, and/or steps, but do not exclude the presence of other unstated features, elements, components, groups, integers and/or steps. The foregoing also applies to words having similar meanings such as the terms, “including”, “having” and their derivatives. Also, the terms “part,” “section,” “portion,” “member” or “element” when used in the singular can have the dual meaning of a single part or a plurality of parts. Also as used herein to describe the above embodiment(s), the following directional terms “forward”, “rearward”, “above”, “downward”, “vertical”, “horizontal”, “below” and “transverse” as well as any other similar directional terms refer to those directions of a rotation assist assembly used for a lens barrel. Accordingly, these terms, as utilized to describe the present invention should be interpreted relative to a rotation assist assembly used for a lens barrel. 
         [0112]    The term “configured” as used herein to describe a component, section, or part of a device implies the existence of other unclaimed or unmentioned components, sections, members or parts of the device to carry out a desired function. 
         [0113]    The terms of degree such as “substantially”, “about” and “approximately” as used herein mean a reasonable amount of deviation of the modified term such that the end result is not significantly changed. 
         [0114]    While only selected embodiments have been chosen to illustrate the present invention, it will be apparent to those skilled in the art from this disclosure that various changes and modifications can be made herein without departing from the scope of the invention as defined in the appended claims. For example, the size, shape, location or orientation of the various components can be changed as needed and/or desired. Components that are shown directly connected or contacting each other can have intermediate structures disposed between them. The functions of one element can be performed by two, and vice versa. The structures and functions of one embodiment can be adopted in another embodiment. It is not necessary for all advantages to be present in a particular embodiment at the same time. Every feature which is unique from the prior art, alone or in combination with other features, also should be considered a separate description of further inventions by the applicant, including the structural and/or functional concepts embodied by such feature(s). Thus, the foregoing descriptions of the embodiments according to the present invention are provided for illustration only, and not for the purpose of limiting the invention as defined by the appended claims and their equivalents.