Abstract:
A camera includes a base, a focusing lens, a retaining wheel, a pushing member, and a retaining hook. The base has a cylindrical and vertical opening in it. The focusing lens is rotationally fixed within the opening. The retaining wheel is rotationally fixed in the base. The horizontal sides of the retaining wheel include a ratchet side, a smooth side, a first end, and a second end positioned over the connecting portions of the ratchet side and the smooth side. The pushing member is horizontally and movably fixed in the base for moving the focusing lens and the retaining wheel. The retaining hook includes a horizontal arm and a vertical arm. The horizontal arm can move across the upper side of the retaining wheel, and the vertical arm can thus contact each of the horizontal sides of the retaining wheel.

Description:
BACKGROUND OF INVENTION 
     1. Field of the invention 
     The present invention relates to a focus retaining mechanism, and more particularly, to a focus retaining mechanism of a camera. 
     2. Description of the Prior Art 
     Please refer to FIG.  1 . FIG. 1 is a top view of a lens driving device  10  of a camera according to the prior art. The lens driving device  10  is disclosed in U.S. Pat. No. 5,680,649 “LENS DRIVING DEVICE FOR AUTO-FOCUS CAMERA”. The lens driving device  10  comprises a base  12  having a cylindrical and vertical opening  16 , a focusing lens  14  rotatably fixed within the opening  16 , a driving ring  40  rotatably fixed on the periphery of the opening  16  of the base  12 , a shutter-driving ring  44  fixed on the base  12  by hooking the driving ring  40 , a retaining member  42 , a lens barrel  18  mounted on the base  12  by hooking the driving ring  40  and the retaining member  42 , a first bi-directional driving motor  20  and a second bi-directional driving motor  30  fixed on the base  12 , an elastic element  34  mounted on the base  12 , and an electromagnetic valve  22  disposed on the base  12 . 
     In addition, a cylindrical projection  46  disposed on the driving ring  40  engages with an engaging portion  19  of the lens barrel  18 . Thus, when the driving ring  40  is rotated, the lens barrel  18  and the focusing lens  14  are also rotated. The second bi-directional driving motor  30  is used to rotate the shutter-driving ring  44  for controlling a shutter. The first bi-directional driving motor  20  is used to drive the electromagnetic valve  22  for mounting the retaining member  42  in a predetermined position so as to rotate the focusing lens  14  to a corresponding position. Moreover, an idler gear  70  and a first ratchet  50  are used for the transmission between the retaining member  42  and the electromagnetic valve  22 . 
     As shown in FIG. 1, when the second bi-directional driving motor  30  rotates the a shutter-driving ring  44  toward a positive direction via a second ratchet  32  to control an opening position of the shutter, the shutter-driving ring  44  pushes the driving ring  40  to rotate the lens barrel  18  and focusing lens  14 . At the same time, the driving ring  40  also moves the retaining member  42  so that a plurality of gear portions  43  engages with a hold lever  60  one by one. The retaining member  42  rotates the first ratchet  50  by engaging the idler gear  70 . 
     When the second bi-directional driving motor  30  moves the shutter-driving ring  44  toward a positive direction to a predetermined position, which is an appropriate position for focusing, the first bi-directional driving motor  20  controls the electromagnetic valve  22  to stop rotating the first ratchet  50 . At this time, a pull-back action to the retaining member  42 , which is generated by the elastic element  34 , is stopped due to the stop action of the electromagnetic valve  22 . Thus, the lens barrel  18  and the shutter-driving ring  44  do not circumrotate so that the lens driving device  10  can focus and retain position. At this time, the shutter-driving ring  44  moves to a predetermined shutter position and opens the shutter, and the lens barrel  18  also drives the focusing lens  14  to rotate to a corresponding position. 
     The second bidirectional driving motor  30  continues to rotate in a positive direction and moves the shutter-driving ring  44  to an utmost position  45 . At the same time, the first bi-directional driving motor  20  drives the electromagnetic valve  22  to rotate the first ratchet  50  so that the first ratchet  50  and the retaining member  42  rotate to corresponding utmost positions. At this time, the second bi-directional driving motor  30  provides no power to the lens driving device  10 . That means after the second bi-directional driving motor  30  moves the shutter-driving ring  44  to utmost position  45 , only the first bidirectional driving motor  20  provides a small amount of power to move focus retaining mechanisms such as the first ratchet  50 , the retaining member  42 , the lens barrel  18 , the shutter-driving ring  44 , and the elastic element  34  back to an initial state. After the first bi-directional driving motor  20  drives the electromagnetic valve  22  and the first ratchet  50  to their utmost positions, the first ratchet  50  does not contact with the electromagnetic valve  22 , and a spring  62  disposed on the base  12  pulls the hold lever  60  back to the initial state. This is an action of closing the shutter. In addition, the elastic element  34  also pulls the retaining member  42  back to the initial state so that the shutter-driving ring  44 , lens barrel  18 , and the first ratchet  50  are also moved back to the initial states. 
     As described above, the prior lens driving device  10  has a complicated focus retaining mechanism, and an electromagnetic valve and a gear assembly are needed. Thus, the complexity and costs of components are increased. In addition, although the electromagnetic valve  22  acts effectively, the available space of the lens driving device  10  is decreased with the use of the electromagnetic valve  22 . 
     SUMMARY OF THE INVENTION 
     It is therefore a primary objective of the claimed invention to provide a focus retaining mechanism of a camera with a simple design to solve the above-mentioned problem. 
     The claimed invention provides a focus retaining mechanism of a camera. The camera comprises a base, a focusing lens, a retaining wheel, a pushing member, and a retaining hook. The base has a cylindrical and vertical opening in it. The focusing lens is rotationally fixed within the opening. The retaining wheel is rotationally fixed in the base. The horizontal sides of the retaining wheel include a ratchet side, a smooth side, a first end, and a second end positioned over the connecting portions of the ratchet side and the smooth side. The pushing member is horizontally and movably fixed in the base for moving the focusing lens and the retaining wheel. The retaining hook includes a horizontal arm and a vertical arm. The horizontal arm can move across the upper side of the retaining wheel, and the vertical arm can thus contact each of the horizontal sides of the retaining wheel. 
     It is an advantage of the claimed invention that a focus retaining mechanism of a camera with a simple design is used for simplifying the focus retaining mechanism. These and other objectives of the present invention will no doubt become obvious to those of ordinary skill in the art after reading the following detailed description of the preferred embodiment, which is illustrated in the various figures and drawings. 
    
    
     BRIEF DESCRIPTION OF DRAWINGS 
     FIG. 1 is a top view of a lens driving device according to the prior art. 
     FIG. 2 is a simplified top view of a lens driving device according to the present invention. 
     FIG. 3 is an exploded diagram of the lens driving device shown in FIG.  2 . 
     FIG. 4 is a cross-sectional view of a bottom portion of a retaining wheel of the lens driving device shown in FIG.  3 . 
     FIG. 5 is a partial cross-sectional view of the retaining wheel of the lens driving device shown in FIG.  3 . 
     FIG. 6 is a cross-sectional view of a top portion of the retaining wheel of the lens driving device shown in FIG.  3 . 
    
    
     DETAILED DESCRIPTION 
     In the present invention, mechanisms for moving a shutter and method thereof are the same as the prior art shown in FIG.  1 . Please refer to FIG.  2  and FIG.  3 . FIG. 2 is a simplified top view of a lens driving device  100  according to the present invention. 
     FIG. 3 is an exploded diagram of the lens driving device  100  shown in FIG.  2 . 
     As shown in FIG.  2  and FIG. 3, the lens driving device  100  comprises a base  102  comprising a cylindrical and vertical opening  106 , a focusing lens  104  rotatably fixed within the opening  106 , a driving ring  110  rotatably mounted on the periphery of the base  102 , a retaining wheel  120  rotationally fixed on the base  102 , a pushing member  112  horizontally and movably fixed on the base  102 , a connecting ring  114  tightly engaged with the driving ring  110  and the pushing member  112  and rotatably fixed on the base  102 , a retaining hook  130  mounted on the base  102 , an elastic element  136  mounted on the base  102 , a step motor  140  mounted on the base  102 , and a first gear  142  and a second gear  144  mounted on the base  102  by engaging with the driving ring  110  and the pushing member  112  respectively. 
     The retaining hook  130  comprises a horizontal arm  132  movably mounted on the base  102  and a vertical arm  134  installed beneath the horizontal arm  132 . The horizontal arm  132  and the vertical arm  134  are monolithically formed out of a flexible material such as metallic wire. The middle portion of the metallic wire is ring like and surrounds a shaft  103  on the base  102 . Both ends of the metallic wire extended from the middle portion together form a “V” shape. The horizontal arm  132  and the vertical arm  134  are formed on one end. The other end props up the sidewall of the base  102 . Thus, one end of the horizontal arm  132  is mounted on the shaft  103  so as to rotate flexibly. 
     The elastic element  136  is connected to a transmission lever  116  on the connecting ring  114  for mounting the connecting ring  114  flexibly so as to move and hook the driving ring  110  and the pushing mpmber  112 . The driving ring  110  comprises a gear side  111  extruded to the ring-like edge for engaging with a top gear portion  143  of the first gear  142 . The step motor  140  drives the first gear  142  to rotate via the bottom gear portion  141  pf the first gear  142 . Since the top gear portion  143  of the first gear  142  has a smaller diameter than the bottom gear portion  141 , the first gear  142  shrinks the rotating momentum of the related motion of the driving ring  110  to the step motor  140 . The second gear  144  is an amplifying gear with an upside-down design of the first gear  142 . The second gear  144  comprises a bottom gear portion  145  engaging with the gear side  115  of the connecting ring  114  and a top gear portion  146  engaging with the gear side  123  of the pushing member  112 . The connecting ring  114  further comprises a lens connecting lever  118 . When the step motor  140  drives the first gear  142  to rotate, a front end  113  of the gear side  111  of the driving ring  110  urges the lever  116  on the connecting ring  114  so that the connecting ring  114  urges the second gear  144  to rotate so is to move the pushing member  112 . At the same time, the lexs connecting lever  118  on the connecting ring  114  moves th focusing lens  104  downward rotatably. 
     The retaining wheel  120  is a spiral gear  120  having an arc-shaped component with a ratchet side  122  in the horizontal direction on an outer side of the retaining wheel  120 , a smooth side  124  with a sidewall of a first sliding groove  125  and a second sliding groove  127  on an inner side of the retaining wheel  120 , and a first end  126  and a second end  128  disposed on two ends between the ratchet side  122  and the smooth side  124 . The ratchet side  122  and the smooth side  124  of the retaining wheel  120  are both substantially circular peripheries, and the ratchet side  122  has a smaller radius than the smooth side  124  and is positioned above the smooth side  124 . In addition, the horizontal arm  132  of the retaining hook  130  moves horizontally above the retaining wheel  120  so that the vertical end  134  beneath the horizontal arm  132  touches each horizontal side of the retaining wheel  120 . 
     Please refer to FIG. 4 to FIG.  6 . FIG. 4 is a cross-sectional view of a bottom portion of the retaining wheel  120  of the lens driving device shown in FIG. 3 along a line A-A. FIG. 5 is a partial cross-sectional view of the retaining wheel  120  of the lens driving device shown in FIG. 3 along the line A—A. FIG. 6 is a cross-sectional view of a top portion of the retaining wheel  120  of the lens driving device shown in FIG. 3 along the line A—A. The first sliding groove  125  of the smooth side  124  of the retaining wheel  120  is used to guide a bottom end of the vertical arm  134  of the retaining hook  130 . When vertical arm  134  of the retaining hook  130  passes through the first end  126  of the retaining wheel  120 , the vertical arm  134  is guided upward to an initial end of the ratchet side  122  from a terminal end of the first sliding groove  125  of the smooth side  124 . The initial end of the ratchet side  122  guides the vertical arm  134  upward along the smooth side  124  to the second end  128  of the retaining wheel  120 . Moreover, the second sliding groove  127  on the second end  128  of the retaining wheel  120  is used to guide the bottom end of the vertical arm  134  downward to an initial end of the second sliding groove  127  of the smooth side  124  from a terminal end of the ratchet side  122 . 
     As shown in FIG. 4 to FIG. 6, when the step motor  140  drives the driving ring  110  to rotate in a positive direction via the first gear  142 , the driving ring  110  moves the connecting ring  114  so that the lens connecting lever  118  on the connecting ring  114  moves the focusing lens  104  downward rotatably along the opening  106 . At the same time, the connecting ring  114  moves the pushing member  112  to rotate the retaining wheel  120  in the positive direction via the second gear  144 . A pull-back force generated by the elastic element  136  acts on the transmission lever  116  on the connecting ring  114 . The vertical arm  134  of the retaining hook  130  contacts the ratchet side  122  of the retaining wheel  120  at the first end  126  and slides along the ratchet side  122 . When the step motor  140  moves the driving ring  110  in the positive direction to a predetermined position, which is a proper position for focusing, the step motor  140  stops in order to move the focusing lens  104  downward via the connecting ring  114 . At the same time, the vertical arm  134  of the retaining hook  130  engages with the ratchet side  122  of the retaining wheel  120 . Thus, the position of the pushing member  112  is fixed by the elastic force generated by the elastic element  136  in order to retain focus. 
     The ratchet side  122  comprises a plurality of ratchets. Each ratchet provides the focusing lens with a focusing position for satisfying the requirement of having different focusing positions. Since a number of the ratchets corresponds to a number of focusing levels, more focusing positions can be obtained by increasing a number of teeth in the first gear  142  and the second gear  144 . Therefore, the focus control can be improved. 
     After the focusing lens  104  completes the action of focusing and retaining, the step motor  140  reverses. At this time, the pushing member  112  and the connecting ring  114  rmmain in the retained position, but the driving ring  110  is urged to rotate in an opposite direction so as to move a shutter switch using another end  113  of the gear side  111  to complete a photographing action. 
     After finishing the photographing action, the step motor  140  turns to rotate in the positive direction and moves the focusing lens  10  downward rotatably via the connecting ring  114 . Finally, the vertical arm  134  of the retaining hook  130  leaves the ratchet side  122  of the retaining wheel  120 , passes through the second end  128  of the retaining wheel  120  and slides toward the second sliding groove  127  of the smooth side  124  of the retaining wheel  120 . At this time, the focus retaining mechanisms of the lens driving device  100  such as the driving ring  110 , the pushing member  112 , the retaining wheel  120 , and the elastic element  136  already reach corresponding limiting positions. After that, the elastic element  136  pulls the connecting ring  114  so that the lens connecting lever  118  on the connecting ring  114  moves the focusing lens  104  upward rotatably along the opening  106  and the pushing member  112  is rotated in an opposite direction due to the transmission of the second gear  144 . When the elastic element  136  pulls the connecting ring  114  and makes the pushing member  112  rotate reversibly, the step motor  140  also rotates reversibly so as to prevent generating a reverse rotating force on the pushing member  112 . At this time, the vertical arm  134  of the retaining hook  130  slides downward along the sidewall of the second sliding groove  127  on the smooth side  124  of the retaining wheel  120  until passing through the first end  126  of the retaining wheel  120  to the initial state. In the same manner, the focus retaining mechanisms of the lens driving device  100  such as the driving ring  110 , the pushing member  112 , the retaining wheel  120 , and the elastic element  136  also move back to their initial positions. Thus, a focus retaining process of the lens driving device of the camera  100  is completed. 
     In contrast with the prior art, the lens driving device  100  in the present invention is obviously different from the prior lens driving device  10 . The focus retaining mechanisms of the lens driving devices  100  only uses the retaining hook  130  and the retaining wheel  120 , which are designed simply, for retaining without adding any other electric device or gear sets. Thus, more space is available inside the lens driving device of the camera, and the manufacturing cost is also reduced. 
     Those skilled in the art will readily observe that numerous modifications and alterations of the device may be made while retaining the teaching of the invention. Accordingly, the above disclosure should be construed as limited only by the metes and bounds of the appended claims.