Patent Publication Number: US-2004052199-A1

Title: Disk device

Description:
TECHNICAL FIELD  
       [0001] The present invention relates to disk recording or playback devices having a tilt adjusting mechanism for tilting a pickup relative to the signal bearing surface of a disk.  
       BACKGROUND ART  
       [0002]FIG. 12 is a perspective view of a conventional disk recording or playback device. A chassis  1  is provided thereon with a turntable  13  for placing a disk  7  thereon as is well known, and a pickup  2  movable toward or away from the turntable  13 . The pickup  2  has an objective  22  on its upper surface and is movable as guided by two guide rods  4 ,  4  on the chassis  1 . Each guide rod  4  has opposite ends fitting in respective brackets  9 ,  9  on the chassis  1 .  
       [0003] A motor M mounted on the chassis  1  at a side portion thereof is coupled by a gear mechanism  21  to a rack  20  provided on a side portion of the pickup  2 . When energized, the motor M rotates gears of the gear mechanism  21  to move the pickup  2 .  
       [0004]FIG. 13 is a rear view of the disk  7 . Pits  73 ,  73  are formed in the signal bearing surface of the disk  7  circumferentially thereof. The intensity of light reflected from the disk differs when the laser beam is projected on the pit  73  and when the laser beam is projected on a portion other than the pit  73 . This reproduces a digital signal comprising 0 and 1.  
       [0005] Available in recent years are disks  7  adapted to record signals thereon at a high density. These disks are smaller in the spacing D between pits  73 ,  73  in the radial direction of the disk shown in FIG. 13.  
       [0006] Accordingly, if the optical axis of the laser beam slightly inclines relative to the signal bearing surface of the disk  7 , it is likely that the signal can not be reproduced correctly since a pit  73  in a wrong position is irradiated with the beam.  
       [0007] It is therefore proposed to provide a mechanism on the chassis  1  for adjusting the tilt of the pickup  2  and to finely adjust the tilt of the pickup  2  during the process for fabricating the disk recording or playback device for smooth reproduction of signals which are recorded on disks at a high density.  
       [0008]FIG. 14 is aside elevation in section of an adjusting mechanism  5 . The chassis  1  has provided thereon a bracket  9  having a recess  90  for one end of a guide rod  4  to fit in. The bracket  9  is fastened to the chassis  1  with a screw  30  driven into the chassis  1 .  
       [0009] A compression spring  50  for biasing the guide rod  4  upward is provided in the recess  90 . An adjusting screw  6  is driven into the bracket  9  for depressing the guide rod  4  against the compression spring  50 . When the adjusting screw  6  is turned, the end of the guide rod  4  is moved upward or downward, so that the guide rod  4  tilts within a plane containing the direction of movement of the pickup  2  and orthogonal to the chassis  1 . The tilt of the pickup  2  can be finely adjusted in this way.  
       [0010] The prior art involves the likelihood that the bracket will deviate to move in a plane parallel to the chassis  1 , i.e., in a horizontal plane, when the bracket  9  is fastened to the chassis  1  with the screw  30 . Even if the tilt of the pickup  2  is accurately adjustable, the likelihood of the guide rod  4  deviating to move within a horizontal plane then makes it impossible for the pickup  2  to accurately move toward the center of the disk.  
       [0011] Furthermore, there is a slight clearance between a side wall defining the recess  90  and the guide rod  4  fitted in the recess  90 . The guide rod  4  is therefore likely to deviate or move within the clearance unless the adjusting screw  6  depresses the guide rod  4  accurately.  
       [0012] An object of the present invention is to accurately position a mechanism for adjusting the tilt of a pickup on a chassis, to prevent a guide rod from inadvertently deviating to move within a plane substantially parallel to the chassis and to give the device of the type described increased resistance to impact due, for example, to falling.  
       DISCLOSURE OF THE INVENTION  
       [0013] The invention provides a disk recording or playback device comprising a pickup  2  provided on a chassis  1  and movable toward or away from a center of a disk  7 , a guide rod  4  extending in the direction of movement of the pickup  2  and having the pickup  2  fitted therearound, and an adjusting mechanism  5  for altering the tilt angle of the guide rod  4  within a plane containing the direction of movement of the pickup  2  and orthogonal to an upper surface of the chassis  1 , the adjusting mechanism  5  comprising a bracket  9  for holding an end of the guide rod  4 , a compression spring  50  for biasing the guide rod  4 , and an adjusting screw  6  for depressing the guide rod  4  against the compression spring  50 . The adjusting mechanism  5  further comprises first positioning means  3  for positioning the bracket  9  in place on the chassis  1 , and second positioning means  8  for positioning the adjusting screw  6  in a plane substantially parallel to the surface of the chassis  1  and accurately pointing the direction of advance of the adjusting screw  6  toward a center C of the guide rod  4 . A boss  95  is provided inside the compression spring  50 , and has a height not permitting the pickup  2  to contact the chassis  1  when the guide rod  4  comes into contact with the boss  95 .  
       [0014] Alternatively, the adjusting mechanism  5  comprises first positioning means  3  for positioning the bracket  9  in place on the chassis  1 , and second positioning means  8  for positioning the adjusting screw  6  in a plane substantially parallel to the surface of the chassis  1  and accurately pointing the direction of advance of the adjusting screw  6  toward a center C of the guide rod  4 . The bracket  9  has a guide portion  93  provided with a wall  96  having a height not permitting the pickup  2  to contact the chassis  1  when the guide rod  4  comes into contact with the wall  96 . 
     
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
     [0015]FIG. 1 is a plan view of a disk recording or playback device.  
     [0016]FIG. 2 is a sectional side elevation of FIG. 1 showing a bracket of first embodiment.  
     [0017]FIG. 3 is a sectional side elevation of FIG. 1 showing a bracket of second embodiment.  
     [0018]FIG. 4 is an exploded perspective view of the bracket, guide rod and bearing plate according to the first embodiment.  
     [0019]FIG. 5 is a sectional view showing the bracket of the first embodiment as adjusted.  
     [0020]FIG. 6 is a sectional view showing the bracket of the first embodiment as subjected to an impact.  
     [0021]FIG. 7 is an exploded perspective view of the bracket, guide rod and bearing plate according to the second embodiment.  
     [0022]FIG. 8 is a sectional view showing the bracket of the second embodiment as adjusted.  
     [0023]FIG. 9 is a sectional view showing the bracket of the second embodiment as subjected to an impact.  
     [0024]FIG. 10 is a rear view of a chassis.  
     [0025]FIG. 11 is a plan view of the bearing plate.  
     [0026]FIG. 12 is a perspective view of a conventional disk recording or playback device.  
     [0027]FIG. 13 is a rear view of a disk.  
     [0028]FIG. 14 is a side elevation in section of an adjusting mechanism. 
    
    
     BEST MODE OF CARRYING OUT THE INVENTION  
     [0029] With reference to the drawings, embodiments of the invention will be described below in detail.  
     [0030]FIG. 1 is a plan view of a disk recording or playback device.  
     [0031] As in the prior art, a turntable  13  for rotating a disk  7  is provided at a side portion of an opening  14  formed in a chassis  1 , and a pickup  2  comprising an objective  22  for projecting a beam on the disk  7  is so disposed as to be movable toward or away from the turntable  13 .  
     [0032] The pickup  2  is fittingly mounted on guide rods  4 ,  4  each supported at opposite ends thereof by respective brackets  9 ,  9 , and is designed to move on a phantom line L connecting the respective centers of the lens  22  and the turntable  13 .  
     [0033] A motor  17  is mounted on the chassis  1  laterally of the opening  14  and coupled to the pickup  2  by an intermediate gear  15 . When energized, the motor  17  moves the pickup  2 .  
     [0034] The chassis  1  has outer peripheral edges, which are bent upward to provide upright walls  12 ,  12  fastened to a cabinet (not shown) disposed externally of the chassis  1 .  
     [0035]FIGS. 2 and 3 are side elevations in section showing brackets  9  as seen from the direction A in FIG. 1. FIG. 2 shows the bracket of a first embodiment of the invention to be described later, and FIG. 3 shows the bracket of a second embodiment. The bracket  9  is fastened to the chassis  1  with a screw  30  driven into the bracket from below the chassis  1 . The bracket  9  has a recess  90  for the end of the guide rod  4  to fit in, and a compression spring  50  for biasing the guide rod  4  upward is disposed in the recess  90 .  
     [0036] The top of the bracket  9  is covered with a bearing plate  80 , which is fastened to the bracket  9  with a screw  85 . An adjusting screw  6  is in screw-thread engagement with the bearing plate  80  and has a lower end in contact with the top of the guide rod  4 . The arrangement is so designed that the direction of advance of the adjusting screw  6  is pointed toward the center C of the guide rod  4 .  
     [0037]FIG. 4 is an exploded perspective view of the bracket  9 , guide rod  4  and bearing plate  80  according to the first embodiment of the invention, with the chassis  1  shown as partly broken away.  
     [0038] The chassis  1  has an aperture  10  for the bracket  9  to partly fit in. Extending from the bracket  9  is a tongue  91  fitting in the aperture  10 . The tongue  91  has an upper surface flush with the upper surface of the chassis  1 . Thus, the tongue  91  is positioned below the guide rod  4 . The tongue  91  has a circular-arc form and is in contact with an edge  11  of the chassis defining the aperture  10 , whereby the bracket  9  is positioned in place in the plane of the chassis  1  with respect to horizontal directions.  
     [0039] The recess  90  has a guide portion  93  with a width permitting the guide rod  4  to slightly loosely fit into the portion  93 , and an accommodating portion  94  extending from the guide portion  93  in the form of a protuberant space and having the compression spring  50  fitted therein.  
     [0040] Formed on the bottom surface of the recess  90  is a boss  95  having a diameter slightly smaller than the inside diameter of the compression spring  50 .  
     [0041] The boss  95  has a height not permitting the pickup  2  to contact the chassis  1  when the guide rod  4  is brought into contact with the boss  95 .  
     [0042] This limits the movable range of the guide rod  4  as shown in FIGS. 5 and 6, making it possible to prevent the collision of the pickup  2  with the chassis  1  even when the device is subjected to an impact in the event of falling.  
     [0043]FIG. 7 is an exploded perspective view of the bracket  9 , guide rod  4  and bearing plate  80  according to the second embodiment of the invention, with a chassis  1  shown as partly broken away.  
     [0044] As is the case with the first embodiment, the chassis  1  has an aperture  10  for the bracket  9  to partly fit in. Extending from the bracket  9  is a tongue  91  fitting in the aperture  10 . The tongue  91  has an upper surface flush with the upper surface of the chassis  1 . Thus, the tongue  91  is positioned below the guide rod  4 . The tongue  91  has a circular-arc form and is in contact with an edge  11  of the chassis defining the aperture  10 , whereby the bracket  9  is positioned in place with respect to horizontal directions in the plane of the chassis  1 .  
     [0045] A recess  90  has a guide portion  93  with a width permitting the guide rod  4  to slightly loosely fit into the portion  93 , and an accommodating portion  94  extending from the guide portion  93  in the form of a protuberant space and having a compression spring  50  fitted therein.  
     [0046] The guide portion  93  of the bracket  9  is provided with a wall  96  having a cutout for the guide rod  4  to fit in.  
     [0047] The wall  96  has a height not permitting the contact of the pickup  2  with the chassis  1  when the guide rod  4  is brought into contact with the wall.  
     [0048] This limits the movable range of the guide rod  4  as shown in FIGS. 8 and 9, making it possible to prevent the collision of the pickup  2  with the chassis  1  even when the device is subjected to an impact in the event of falling.  
     [0049] The top wall of the bracket  9  has positioning projections  92 ,  92   a  fittable into the bearing plate  80 , and a screw bore  82  positioned at one side of the arrangement of projections  92 ,  92   a  for driving a plate fastening screw  85  thereinto.  
     [0050] The bearing plate  80  is provided with cutouts  81 ,  81  for the respective positioning projections  92 ,  92   a  to fit in. Formed in the bearing plate  80  at opposite sides of the cutouts  81 ,  81  are a screw hole  82  for the adjusting screw  6  to be driven in, and a hole  83  for the plate fastening screw  85  to be inserted through.  
     [0051] [Attaching Brackets] 
     [0052] (First Positioning Means] 
     [0053] The bracket  9  is attached to the chassis  1  by the following procedure.  
     [0054]FIG. 10 is a rear view of the chassis  1 . First, the chassis  1  is turned upside down, and the bracket  9  is inserted into the aperture  10  from below the chassis  1 . With the tongue  91  fitted in the aperture  10 , the bracket  9  is fixed to a jig  98  to restrain the bracket  9  from turning in a horizontal plane.  
     [0055] The fastening screw  30  is driven into the bracket  9  through the chassis  1 . The screw  30  turns clockwise by tightening up, so that when the head of the screw  30  comes into contact with the chassis  1 , the chassis  1  turns clockwise due to the friction between the chassis and the head of the screw  30 . The aperture-defining edge  11  comes into contact with the tongue  91 , whereby the bracket  9  is positioned in place on the chassis  1 . Since the tongue  91  has a circular-arc form, the tongue  91  invariably comes into contact with one point on the edge  11  for positioning. Thus, the tongue  91  of the bracket  9  and the edge  11  provide the first positioning means  3 . The bracket  9  is positioned in place on the chassis  1  simultaneously when the bracket  9  is fastened with the screw  30 . This saves time and labor in positioning.  
     [0056] (Second Positioning Means)  
     [0057] Next, the chassis  1  is turned downside up, the bearing plate  80  is placed over the bracket  9  having the compression spring  50  and guide rod  4  inserted therein, and the plate fastening screw  85  is driven through the hole  83  into the screw bore  82  in the bracket  9 . The screw  85  is turned clockwise by tightening up, and when the head of the screw  85  comes into contact with the bearing plate  80 , the plate  80  turns clockwise due to the friction between the plate and the head of the screw  85 .  
     [0058] With reference to FIG. 11 which is a plan view of the bearing plate  80 , the cutout portion  81  on the clockwise side comes into contact with the positioning projection  92 , whereby the plate  80  is positioned in place in a plane parallel to the plane of the chassis  1 . Thus, the positioning projection  92  and the cutout  81  in the bearing plate  80  provide the second positioning means  8 . The bearing plate  80  is positioned in place within a plane substantially parallel to the chassis  1  simultaneously when the plate  80  is fastened with the screw  85 . This saves time and labor in positioning the plate.  
     [0059] When the adjusting screw  6  is turned after the bracket  9  has been attached, the guide rod  4  has its tilt adjusted in a plane containing the direction of movement of the pickup  2  and orthogonal to the chassis  1 .  
     [0060]FIG. 5 is a view in section taken along a plane containing the line C-C in FIG. 4. The direction of advance of the adjusting screw  6  is pointed toward the center C of the guide rod  4  by positioning the bearing plate  80  in place within a plane parallel to the plane of the chassis  1 .  
     [0061] Unless the bearing plate  80  is accurately positioned within a plane parallel to the plane of the chassis  1 , the direction of advance of the adjusting screw  6  swerves from the center C of the guide rod  4 . As previously stated, there is a small clearance in the guide portion  93  of the recess  90  around the guide rod  4 , whereas if the direction of advance of the adjusting screw  6  deviates from the center C of the guide rod  4 , the adjusting screw  6  pushes the rod  4  at an eccentric portion, permitting the guide rod  4  to laterally deviate in a direction orthogonal to the rod  4  within the range of the clearance.  
     [0062] Since the pickup  2  moves along the guide rod  4 , the path of movement of the pickup  2  then deflects from a phantom line L extending toward the center of the disk as shown in FIG. 1. Accordingly, accurately pointing the direction of advance of the adjusting screw  6  toward the center C of the guide rod  4  restrains the rod  4  from laterally deviating toward a direction orthogonal to the rod  4  within the guide portion  93 .  
     [0063] Because the range in which the guide rod is movable in the direction of height is limited by the boss  95  or the wall  96 , the guide rod  4  is prevented from inadvertently deviating and moving within a plane substantially parallel to the chassis  1  and precluded from shifting or deforming due to an impact, for example, of falling of the device.  
     [0064] The boss  96  and the wall  96  have a height lower than the desired tilt adjusting range and not permitting the pickup  2  to contact the chassis  1  when the guide rod  4  is brought into intimate contact with the boss or the wall. The desired tilt adjusting range is such a range that makes it possible to absorb, for example, the error involved in mounting the pickup  2  and the distortion of the chassis  1 , and to mount the pickup  2  in place with predetermined accuracy relative to the disk surface  
     [0065] Consequently, the guide rod  4  is held between the adjusting screw  6  and the compression spring  50  by being pushed up by the force of the spring at all times during tilt adjustment, and is highly responsive to the tightening or loosening turn of the adjusting screw  6  to ensure accurate tilt adjustment.  
     [0066] After the adjustment of tilt, the adjusting screw  6  is locked with an adhesive and thereby prevented from loosening through spontaneous turning. By virtue of the pushing-up force of the compression spring  50 , the guide rod  4  remains at an unaltered level to accurately maintain the adjusted tilt angle even if subjected to some vibration or like disturbance from outside, obviating the likelihood that the tilt angle of the pickup will vary.  
     [0067] Further if the device is subjected to an impact due, for example, to falling, the following situation will be encountered.  
     [0068] For example if the user allowed the device to fall off the desk down onto the floor in an error, the device is subjected to acceleration of as great as 100 G, possible causing the pickup  2  to collide with the chassis  1  depending on the direction of fall.  
     [0069] The pickup  2  is a precision optical system comprising an assembly of many small parts, is therefore susceptible to impact and becomes no longer operable for normal recording or playback if the optical system is distorted by colliding with the chassis  1  with 100 G.  
     [0070] In the event of the present device falling, the guide rod  4  comes to a halt at the level of the boss  95  or wall  96 .  
     [0071] When the guide rod  4  moves from the adjusted position to this level due to impact, the repulsive force of the compression spring  50  attenuates the acceleration, and the deflection of the guide rod  4  absorbs the impact.  
     [0072] Thus, a great reduction in acceleration mitigates the impact unlike the case wherein the pickup  2  collides directly with the chassis  1 .  
     [0073] In this way, the pickup can be protected from impact.  
     INDUSTRIAL APPLICABILITY  
     [0074] The bracket  9  can be mounted as accurately positioned on the chassis  1  by the first positioning means  3 . This eliminates the likelihood that the guide rod  4  will deviate or move in a plane parallel to the chassis  1 .  
     [0075] Furthermore, the direction of advance of the adjusting screw  6  is pointed toward the center C of the guide rod  4  by the second positioning means  8 . The height of the compression spring  50  as fully compressed is lower than the tilt adjusting range, and when the guide rod  43  is positioned on the spring  50  of compressed height, the pickup  2  is held out of contact with the chassis  1 . Accordingly, the guide rod  4  is held between the adjusting screw  6  and the compression spring  50  by being pushed up by the force of the spring at all times during tilt adjustment, and is highly responsive to the tightening or loosening turn of the adjusting screw  6  to ensure accurate tilt adjustment.  
     [0076] In the event of the device falling, the guide rod  4  comes to a halt at the level of the boss  95  or wall  96 , so that when the guide rod  4  moves from the adjusted position to this level due to impact, the repulsive force of the compression spring  50  attenuates the acceleration, and the deflection of the guide rod  4  absorbs the impact to greatly reduce the acceleration and mitigate the impact unlike the case wherein the pickup  2  collides directly with the chassis  1 .  
     [0077] The boss  95  and the wall  96  are given a height not permitting the pickup  2  to contact the chassis  1  when the guide rod  4  is brought into contact with the boss  95  or the wall  96 , whereby the pickup can be protected from impact.