Abstract:
According to one aspect, an optical read/write device for reading and/or writing an optical disk includes a rack disposed between the worm gear and the optical pickup head for transferring motion from the worm gear to the optical pickup head. The rack includes a fastening portion for fixing the rack to the optical pickup head, an engaging portion, a spring placed between the fastening portion and the engaging portion for pressing the engaging portion to engage with the worm gear, and a connecting portion. The connecting portion is configured for connecting the fastening portion and the engaging portion and preventing the engaging portion from disengaging from the worm gear.

Description:
BACKGROUND 
     1. Field of the Invention 
     The present invention generally relates to optical read/write devices and, more particularly, to a mechanism for driving an optical pickup head of an optical read/write device. 
     2. Description of Related Art 
     In general, an optical pickup head records or reproduces information while moving across a recording data storage medium such as a disk. The optical pickup head includes a light source for emitting laser light and an objective lens for focusing the laser light to form an optical spot on the disk. As such, the optical pickup head is able to write or read information to or from the optical disk. The optical pickup head is driven by a driving mechanism to move along a path corresponding to a radial direction of the optical disk. 
     A conventional driving mechanism includes a motor, a worm gear connected to a rotor of the motor, and a gear portion attached to the optical pickup head. The gear portion engages the worm gear. The motor drives the worm gear to rotate and the gear portion is moved linearly by the worm gear. Thus the optical pickup head is moved linearly in the radial direction of the optical disk correspondingly. 
     However, the optical pickup head cannot be moved precisely because stress between the worm gear and the gear portion may cause the gear portion to disengage with the worm gear. 
     Therefore, a need exists for an optical read/write device resolving the above problem in the industry. 
     SUMMARY 
     According to one aspect, an optical read/write device for reading and/or writing an optical disk includes a rack disposed between the worm gear and the optical pickup head for transferring motion from the worm gear to the optical pickup head. The rack includes a fastening portion for fixing the rack to the optical pickup head, an engaging portion, a spring placed between the fastening portion and the engaging portion for pressing the engaging portion to engage with the worm gear, and a connecting portion. The connecting portion is configured for connecting the fastening portion and the engaging portion and preventing the engaging portion from disengaging from the worm gear. 
     Other systems, methods, features, and advantages of the present optical read/write device will be or become apparent to one with skill in the art upon examination of the following drawings and detailed description. It is intended that all such additional systems, methods, features, and advantages included within this description, be within the scope of the present device, and be protected by the accompanying claims. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       Many aspects of the present optical read/write device can be better understood with reference to the following drawings. The components in the drawings are not necessarily drawn to scale, emphasis instead being placed upon clearly illustrating the principles of the present device. Moreover, in the drawings, like reference numerals designate corresponding parts throughout the several views. 
         FIG. 1  is an isometric view of an optical read/write device in accordance with an exemplary embodiment. 
         FIG. 2  is an exploded, isometric view of the optical read/write device of  FIG. 1 . 
         FIG. 3  is an enlarged, inverted isometric view of a rack in  FIG. 1 . 
         FIG. 4  is an enlarged, inverted isometric view of the rack in accordance with a second embodiment. 
         FIG. 5  is an enlarged, inverted isometric view of the rack in accordance with a third embodiment. 
     
    
    
     DETAILED DESCRIPTION OF THE EMBODIMENTS 
     Reference will now be made to the drawings to describe preferred embodiments of a present optical read/write device, in detail. 
     Referring to  FIGS. 1 and 2 , an optical read/write device  10  in accordance with an exemplary embodiment is illustrated. The optical read/write device  10  includes a base  20 , an optical pickup head  30  slidably assembled on the base  20 , a driving mechanism  40 , and a spindle motor  60  mounted on the base  20 . 
     The base  20  includes a chassis  22 , a first guide member  24   a , and a second guide member  24   b . A center of the chassis  22  defines a substantially rectangular opening  26 . The spindle motor  60  is mounted adjacent to a shorter side of the chassis  22  and configured for rotating an optical disk (not shown). The guide members  24   a ,  24   b  are correspondingly disposed on opposite longer sides of the chassis  22 . 
     The optical pickup head  30  includes a main body  32  for housing optical lenses (not shown) etc. The optical pickup head  30  further includes a first projection portion  34  and a second projection portion  36  correspondingly formed at two lateral sides of the main body  32 . The first projection portion  34  defines a guide hole  342  for slidably receiving the first guide member  24   a . The second projection portion  36  defines a guide notch  362  for slidably receiving the second guide member  24   b . The guide hole  342 , the first guide member  24   a , the guide notch  362 , and the second guide member  24   b  are configured for allowing the optical pickup head  30  to be slidably assembled on the base  20 . 
     The driving mechanism  40  includes a feed motor  44 , a worm gear  46 , a gear seat  48 , and a rack  50 . 
     The feed motor  44  is mounted on the chassis  22  at a same side of the first guide member  24   a . The worm gear  46  is parallel to the first guide member  24   a . An end of the worm gear  46  is connected to a rotor (not shown) of the feed motor  44 , and another end of the worm gear  46  is supported by the gear seat  48 . The surface of the worm gear  46  defines a thread  460 . 
     The rack  50  is connected to the optical pickup head  30  and engaged with the worm gear  46  for driving the optical pickup head  30  to move when the feed motor  44  rotates accordingly. Referring also to  FIG. 3 , the rack  50  includes a fastening portion  52  on one side of the rack  50 , an engaging portion  54  on another side of the rack  50  opposite to the fastening portion  52 , a connecting portion  57 , a restricting portion  55 , and a spring  58 . 
     The fastening portion  52  includes a mounting plate  520 , a base plate  522 , and a block member  524 . The mounting plate  520  is configured for fastening the rack  50  to the optical pickup head  30 . The base plate  522  and the block member  524  perpendicularly extend from the mounting plate  520 . A first cylindrical protrusion  526  is formed on the base plate  522  and protrudes toward the engaging portion  54 . The block member  524  protrudes from the mounting plate  520  along a cylindrical axis of the worm gear  46 . When the optical pickup head  30  is reading/writing information near a center portion of the optical disk, the block member  524  abuts an inner edge  220  adjacent to the spindle motor  60  of the chassis  22 . Thus, the block member  524  prevents the main body  32  of the optical pickup head  30  from colliding with the spindle motor  60 . 
     The engaging portion  54  includes an assembling plate  540 , a pair of engaging teeth  542 , and a second cylindrical protrusion (not shown). The engaging teeth  542  and the second cylindrical protrusion correspondingly protrude from two opposite sides of the assembling plate  540 . The engaging teeth  542  are configured for meshing with the thread  460  of the worm gear  46 , thus rotational motion of the worm gear  46  is converted to linear motion so as to drive the optical pickup head  30 . The second cylindrical protrusion extends toward the first cylindrical protrusion  526 . The second cylindrical protrusion and the first cylindrical protrusion  526  collectively define a gap therebetween. Ends of the spring  58  are sleeved on the first cylindrical protrusion  526  and the second cylindrical protrusion correspondingly. In order words, the spring is compressibly aligned between the assembling plate  540  and the base plate  522  via the first cylindrical protrusion  526  and the second cylindrical protrusion correspondingly. 
     The restricting portion  55  extends from the assembling plate  540  and is configured for preventing the engaging portion  54  from detaching out of the worm gear  46 . The restricting portion  55  includes a junction member  552  and a grasping member  554 . The junction member  552  perpendicularly connects the assembling plate  540  and the grasping member  554 . Thus the assembling plate  540  is parallel to the grasping member  554 . The assembling plate  540  and the grasping member  554  defines a gap therebetween for housing the worm gear  46 . In this embodiment, the grasping member  554  includes two posts. In other embodiments, the grasping member  554  can be a flat plate parallel to the assembling plate  540 . 
     The connecting portion  57  connects the fastening portion  52  and the engaging portion  54  and includes a shock absorber part  571  and a connecting arm  573  for connecting the fastening portion  52  and the junction member  552 . 
     The shock absorber part  571  includes a first restricting arm  5711 , a second restricting arm  5712 , and an resilient member  5713 . The first restricting arm  5711  perpendicularly extends from the base plate  522  toward the assembling plate  540 . The second restricting arm  5712  perpendicularly extends from the assembling plate  540  opposite to the first restricting arm  5711 . In this embodiment, the resilient member  5713  is a U-shaped arm with two ends of the U-shaped arm connecting free ends of the first restricting arm  5711  and the second restricting arm  5712  respectively. In other alternative embodiments, the resilient member  5713  can be a spring, an M-shaped, V-shaped, or W-shaped arm. 
     Referring to  FIGS. 1 and 2 , a detailed assembly procedure of the optical read/write device  10  will now be described. First, the spindle motor  60  is secured to the chassis  22 . The guide members  24   a ,  24   b  respectively pass through the guide hole  342  and the guide notch  362  of the optical pickup head  30 . Then the guide members  24   a ,  24   b  are respectively mounted on the two longer sides of the chassis  22 . Thus, the optical pickup head  30  is slidably assembled on the base  20 . The feed motor  44  and the gear seat  48  are mounted on the chassis  22  with the worm gear  46  being parallel and adjacent to the first guide member  24   a.    
     The rack  50  is then connected to the optical pickup head  30 . That is, the mounting plate  520  is fixed to the main body  32  of the optical pickup head  30 . Thus, the rack  50  engages with the worm gear  46  in a manner that the worm gear  46  is received in the gap between the grasping member  554  and the assembling plate  540 . Thus the engaging teeth  542  are meshed with the thread  460  of the worm gear  46  because the spring  58  pushes the assembling plate  540 . 
     When the optical read/write device  10  reads data from or writes data onto the optical disk, the feed motor  44  drives the worm gear  46  to rotate. The rack  50  moves linearly because the engaging teeth  542  of the rack  50  mesh with the thread  460  of the worm gear  46 . Accordingly, the optical pickup head  30  moves linearly because the rack  50  is fixed to the optical pickup head  30 . 
     Referring to  FIG. 3 , when the pressure between the worm gear  46  and the engaging teeth  542  becomes too high that the engaging teeth  542  is about to detach from the thread  460 , the engaging portion  54  is pushed toward the base plate  522 . The resilient member  5713  is compressed accordingly. A maximum compressed length of the resilient member  5713  is determined by the depth of the thread  460 . That is, the maximum length is configured to be less than or equal to the depth of the thread  460 . Thus, a distance the engaging portion  54  is pushed toward the base is limited by the resilient member  5713 , thus preventing the engaging teeth  542  from detaching out of the thread  460  when the pressure is too high. 
     Referring to  FIG. 4 , a second embodiment of a rack  50   a  is illustrated. Comparing to the rack  50  in  FIG. 3 , the first restricting arm  5711   a  and the second restricting arm  5712   a  of the shock absorber part  571   a  are spaced apart by a deviation gap  572 . When the engaging portion  54  is pushed toward the base plate  522  and deviates to a predetermined distance, the second restricting arm  5712   a  will collide with the first restricting arm  5711   a . Thus, the shock absorber part  571   a  will prevent the engaging teeth  542  from separating from the thread  460 . 
     Referring to  FIG. 5 , a third embodiment of a rack  50   b  is illustrated. Comparing to the rack  50   a  in  FIG. 4 , the first restricting arm  5711   b  and the second restricting arm  5712   b  of the shock absorber part  571   b  partially offset each other. The height of the first restricting arm  5711   b  with respect to the junction member  552  is less than that of the second restricting arm  5712   b . When the engaging portion  54  is pushed toward the base plate  522  and deviates to a predetermined distance, the second restricting arm  5712   b  will collide with the first restricting arm  5711   b . Thus, the shock absorber part  571   b  will prevent the engaging teeth  542  from separating from the thread  460 . 
     The foregoing description of the exemplary embodiments of the invention has been presented only for the purposes of illustration and description and is not intended to be exhaustive or to limit the invention to the precise forms disclosed. Many modifications and variations are possible in light of the above teaching. The embodiments were chosen and described in order to explain the principles of the invention and their practical application so as to enable others skilled in the art to utilize the invention and various embodiments and with various modifications as are suited to the particular use contemplated. Alternative embodiments will become apparent to those skilled in the art to which the present invention pertains without departing from its spirit and scope. Accordingly, the scope of the present invention is defined by the appended claims rather than the foregoing description and the exemplary embodiments described therein.