Abstract:
An actuator latch system of a hard disk drive selectively locks in place and releases a rotatable swing arm having a front end portion supporting a magnetic head and a rear end portion on which a voice coil motor (VCM) coil is disposed. The actuator latch system includes a notch in the rear end portion of the swing arm, and a rotatable latch lever having a front end portion including a hook and a magnet. The hook is received in the notch in the rear end potion of the swing arm to arrest rotation of the swing arm in a predetermined direction. The magnet of the latch lever faces a section of the VCM coil such that when the hard disk drive is started, the latch lever is rotated by a force generated due to current flowing through the section of the VCM coil faced by the magnet and the magnetic field generated by the magnet. The rotation of the latch lever prevents the hook form interfering with the rotation of the swing arm in the predetermined direction.

Description:
BACKGROUND OF THE INVENTION 
       [0001]    1. Field of the Invention 
         [0002]    The present invention relates to a hard disk drive. More particularly, the present invention relates to an actuator latch system of a hard disk drive, which locks an actuator of the hard disk drive in place when the disk of the hard disk drive is not rotating. 
         [0003]    2. Description of the Art 
         [0004]    Hard disk drives (HDD) are used in electronic devices such as computers to reproduce data from a disk or record data onto the disk. More specifically, in addition to such a disk, an HDD includes a magnetic (read/write) head, an actuator for moving the magnetic head over a desired location (track) of the disk, and a spindle motor for rotating the disk. The magnetic head is floated a predetermined height from the recording surface of the disk while the disk is rotated, and detects/modifies the magnetization of the recording surface of the disk to reproduce/record data from/onto the disk. 
         [0005]    In addition, when the HDD is not in use, that is, when the disk is not rotating, the magnetic head is parked off of the recording surface of the disk. Systems for parking the magnetic head of the HDD include a contact start stop (CSS) type of parking system and a ramp type of parking system. In the CSS type of parking system, an inner circumferential portion of the disk devoid of recorded data is reserved as a parking zone, and the magnetic head is held against the parking zone of the disk when the magnetic head is parked. In the ramp type of parking system, a ramp is disposed radially outwardly of the disk, and the magnetic head is held against the ramp when the magnetic head is parked. 
         [0006]    However, an HDD can be subjected to external shock or vibrations when the HDD is not in use. Such external shock or vibrations have the potential to move the magnetic head out of the parking zone or off of the ramp and onto the recording surface of the disk. If this were allowed to happen, the magnetic head or the recording surface of the disk could be damaged. Therefore, the actuator needs to be locked in place when the magnetic head is parked. To this end, HDDs include various kinds of actuator latch systems. 
         [0007]      FIGS. 1A ,  1 B, and  1 C illustrate a conventional latch system of an HDD for locking the actuator of the HDD in place when the magnetic head is parked. 
         [0008]    Referring to  FIG. 1A , the actuator  10  of the HDD includes a swing arm  12  that is rotatably supported by a pivot  11 , a suspension  13  disposed on an end portion of the swing arm  12 , and a slider  14  supported by the suspension  13 . The head slider  14  contains the magnetic head. The suspension biases the head slider  14  and hence, the magnetic head, toward a (recording) surface of the disk during a read/write operation in which the magnetic head is recording data onto the disk or reading data from the disk. 
         [0009]    In addition, the HDD includes a single lever inertial latch system  20  for locking the actuator  10  in place when the magnetic head is parked on ramp  15 . The inertial latch system  20  includes a latch lever  21  supported so as to be freely rotatable, a latch hook  22  integral with the latch lever  21 , a notch  23  in the swing arm  12  of the actuator  10 , a crash stop  24  that limits the rotation of the swing arm  12  in a clockwise direction, and a latch stop  25  that limits the rotation of latch lever  21  in the clockwise direction. 
         [0010]    As shown in  FIG. 1B , when shock applied to the HDD causes the swing arm  12  of the actuator  10  and the latch lever  21  to rotate counter-clockwise due to inertia, the latch hook  22  is received in the notch  23  such that the rotation of the swing arm  12  of the actuator  10  is arrested. On the other hand, as shown in  FIG. 1C , when shock applied to the HDD causes the swing arm  12  of the actuator  10  and the latch lever  21  to rotate clockwise due to inertia, the swing arm  12  collides with the crash stop  24 , and then rebounds from the crash stop  24  and thus rotates counter-clockwise. At the same time, the latch lever  21  rebounds from the latch stop  25  and thus rotates counter-clockwise. In this case, the latch hook  22  can be received in the notch  23  to arrest the further rotation of the actuator  10  in the counter-clockwise direction. However, the conventional single lever inertial latch system  20  is unreliable. 
         [0011]    In the case in which the shock applied to the HDD causes the swing arm  12  to initially rotate counter-clockwise, the rotation of the swing arm  12  is indeed arrested by the latch lever  21  as described above. However, the impulse generated by the engagement between the swing arm  12  and the latch hook  22  causes the latch lever  21  and the swing arm  12  to spring back. Thus, the swing arm  12  rotates clockwise. The swing arm  12  collides with the crash stop  24 , rebounds, and then again rotates counter-clockwise. In this case, though, the rotation of the swing arm  12  and the rotation of the latch lever  21  are poorly timed. As a result, the swing arm  12  is not hooked by the latch hook  22 . Therefore, the swing arm  12  continues to rotate counter-clockwise such that the magnetic head moves off of the ramp  15  and onto the recording surface of the disk. Accordingly, the magnetic head or the recording surface of the disk can be damaged. 
         [0012]      FIGS. 2A ,  2 B, and  2 C show a dual-lever inertial latch system  40  that is designed to obviate the above-described problem of the single lever inertial latch system. 
         [0013]    Referring to  FIG. 2A , the dual-lever inertial latch system  40  includes first and second latch levers  41  and  42  that are supported so as to be freely rotatable, a latch pin  43  integral with the first latch lever  41 , a latch hook  44  integral with the second latch lever  42 , a notch  45  in a swing arm  32  of the actuator  30 , and a crash stop  46  limiting the rotation of the swing arm  32  in the clockwise direction. 
         [0014]    As shown in  FIG. 2B , when shock applied to the HDD causes the swing arm  32  of the actuator  30  and the first and second latch levers  41  and  42  to rotate counter-clockwise due to inertia, the latch hook  44  is received in the notch  45  in the swing arm  32 . Thus, the swing arm  32  of the actuator  30  cannot rotate further. On the other hand, as shown in  FIG. 2C , when shock applied to the HDD causes the swing arm  32  of the actuator  30  and the first latch lever  41  to rotate clockwise due to inertia, the swing arm  32  initially rotates clockwise, then collides with the crash stop  46 , rebounds from the crash stop  46 , and thus rotates counter-clockwise. In addition, the first latch lever  41  rotates clockwise, and the latch pin  43  engages the second latch lever  42  to make the second latch lever  42  rotate in the counter-clockwise direction. Accordingly, the latch hook  44  of the second latch lever  42  is received in the notch  45  and thus, the rotation of the swing arm  32  in the counter-clockwise direction is arrested. 
         [0015]    The conventional dual-lever inertial latch system  40  operates reliably regardless of the direction in which shock is applied to the HDD. However, two latch levers  41  and  42  are required. That is, the structure of the dual lever latch system  40  is complex and bulky. Accordingly, the dual-lever inertial latch system  40  is expensive. Also, it is difficult to incorporate the dual-lever inertial latch system into a small disk drive such as those used in mobile devices. 
         [0016]    Finally, the distance between the notch and the latch hook of a conventional latch system has been minimized in an attempt to improve the reliability of the latch system. However, minimizing this distance increases the likelihood that the latch lever will hook onto the swing arm of the actuator when a read/write operation of the HDD is initiated and the swing arm is rotated counterclockwise. Thus, the magnetic head will remain parked and the HDD will not operate properly. 
       SUMMARY OF THE INVENTION 
       [0017]    An object of the present invention is to provide an actuator latch system of a hard disk drive, which operates properly and reliably. 
         [0018]    According to an aspect of the present invention, there is provided an actuator latch system of a hard disk drive for selectively locking in place and releasing a swing arm of the hard disk drive, wherein a latch lever of the actuator latch system has a front end portion including both a hook and a magnet. 
         [0019]    The swing arm of the hard disk drive is rotated by a voice coil motor (VCM) having a VCM coil disposed on a rear end portion of the swing arm and at least one permanent magnet fixed relative to and juxtaposed with the VCM coil in the direction of the axis of rotation of the swing arm. The swing arm has a notch in a rear end portion thereof, and the hook is moved into and out of the notch to respectively lock the swing arm in place (when the magnetic head is parked) and to release the swing arm (when the hard disk drive is started). A section of the VCM coil extends alongside the magnet of the latch lever when the swing arm is in a position at which the magnetic head is parked and the latch lever is in a position locking the swing arm in place. When the hard disk drive is started, the magnetic field of the magnet of the latch lever and current flowing through the section of the VCM coil facing the magnet of the latch lever interact to rotate the latch lever and thereby move the hook of the latch lever away from the rear end portion of the swing arm. As a result, the latch lever does not interfere with the rotation of the swing arm. 
         [0020]    Also, the section VCM coil that is faced by the magnet of the latch lever, and the poles of the magnet of the latch lever are oriented relative to each other such a thrust generated on the swing arm due to the interaction between the magnetic field and current flowing through the VCM coil acts on the swing arm in a direction that substantially intersects the axis of rotation of the swing arm. Accordingly, the thrust produces little, if any moment about the axis of rotation of the swing arm and hence, the swing arm is not rotated. 
         [0021]    The section of the VCM coil which cooperates with the magnet of the latch lever may be a laterally offset section of the coil. In particular, the laterally offset section of the coil is disposed radially outwardly of the at least one magnet of the VCM in a direction perpendicular to the axis of rotation of the swing arm. 
         [0022]    The magnet of the latch lever may be a permanent magnet. The latch lever may also have an iron member lying along a surface of the permanent magnet. In this case, the permanent magnet faces a section of the VCM coil, and the iron member is disposed on a surface of the permanent magnet which is opposite to the surface of the permanent magnet facing the VCM coil. 
         [0023]    Furthermore, the front end portion of the latch lever may extend over a section of the VCM coil so as to face the top of that section of the VCM coil when the swing arm is in its position at which the magnetic head is parked and the latch lever is in its position locking the swing arm in place. The hook may protrude downwardly at the front end portion of the latch lever. That is, the hook may extend downwardly into the notch when the swing arm is in its position at which the magnetic head is parked and the latch lever is in its position locking the swing arm in place. 
         [0024]    The latch lever may also have a counterbalance at a rear end portion of the latch lever disposed on an opposite side of the axis of rotation of the latch lever from the hook. A magnetic core may be mounted to the counterbalance. In this case, the magnetic core is positioned on the counterbalance so as to located closer to the at least one magnet of the VCM when the latch lever is in an unlatched position than when the latch lever is in its latched position. Therefore, the at least one permanent magnet of the VCM exerts a relatively strong magnetic force of attraction on the iron core when the latch lever is in its unlatched position to ensure that the latch lever remains in its unlatched position while the hard disk drive is operating (carrying out a read/write operation). 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0025]    The above and other features and advantages of the present invention will become more apparent by describing in detail exemplary embodiments thereof with reference to the attached drawings in which: 
           [0026]      FIGS. 1A ,  1 B, and  1 C are each a plan of a conventional single lever inertial latch system of a hard disk drive (HDD), and together illustrate the operation of the latch system; 
           [0027]      FIGS. 2A ,  2 B, and  2 C are each a plan view of a conventional dual-lever inertial latch system of an HDD, and together illustrate the operation of the latch system; 
           [0028]      FIG. 3  is a plan view of an HDD including an actuator latch system according to the present invention; 
           [0029]      FIG. 4  is a perspective view of the actuator latch system of the HDD shown in  FIG. 3 ; 
           [0030]      FIG. 5A  is a perspective view of the rear end portion of the swing arm of the HDD shown in  FIG. 3   
           [0031]      FIG. 5B  is a perspective view of the latch lever of the actuator latch system of the HDD shown in  FIG. 3 , and includes an enlarged view of a magnetic body of the latch lever; 
           [0032]      FIG. 5C  is a perspective view of the latch lever from another angle; 
           [0033]      FIG. 6  is a plan view of the actuator latch system shown in  FIG. 3 ; and 
           [0034]      FIGS. 7 and 8  are each a plan view of a portion of the HDD shown in  FIG. 3 , and respectively illustrate a locking operation and a release operation of the actuator latch system. 
       
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
       [0035]    A hard disk drive (HDD) according to the present invention will now be described more fully with reference to the accompanying drawings. 
         [0036]    Referring to  FIGS. 3 ,  4 , and  5 A through  5 C, the HDD  100  includes a base  110 , a spindle motor  112  mounted to the base  110 , a disk  120  mounted to the spindle motor  112  so as to be rotated by the spindle motor  112 , a magnetic head, and an actuator  130  that moves the magnetic head over the disk  120  to facilitate the recording/reproducing data onto/from the disk  120 . The actuator  130  includes a pivot  131  disposed on the base  110 , a swing arm  132  supported by the pivot  131  so as to be rotatable, a head slider  134  that contains the magnetic head, a suspension assembly  133  disposed on a front end portion of the swing arm  132  and which supports the head slider  134 , and a voice coil motor (VCM) that rotates the swing arm  132  about the central longitudinal axis of the pivot  131 . The elasticity of the suspension assembly  133  biases the magnetic head towards a surface of the disk  120  during a read/write operation in which data is being recorded onto or read from the surface of the disk. 
         [0037]    The VCM includes a VCM coil  137  disposed on a rear end portion of the swing arm  132 , and a magnet or magnets  138  disposed above and/or below the VCM coil  137  so as to face the VCM coil  137 . However, a section  153  of the VCM coil  137  is laterally offset from the general form of the loop of the coil. Hence, this section  153  of the VCM coil will be referred to hereinafter as the “laterally offset section” of the VCM coil. This section  153  of the VCM coil also extends laterally of the magnet(s)  138  of the VCM. That is, the laterally offset section  153  of the VCM coil  137  is disposed radially outwardly of the magnet(s)  138  in a direction perpendicular to the axis of rotation of the swing arm  132 . In this respect, in the embodiment shown in  FIG. 4 , the laterally offset section  153  of the VCM coil  137  is not disposed under the magnet  138 . 
         [0038]    The magnet(s)  138  is/are attached to yokes  139   a,    139   b  which are, in turn, fixed to the base  110 . The VCM is controlled by a servo control system that controls the supply of current to the VCM coil  137 , and rotates the swing arm  132  in a direction according to Fleming&#39;s left-hand rule due to an interaction between the electric current flowing through the VCM coil  137  and the magnetic field formed by the magnets  138 . In particular, when the HDD  100  is turned on and the disk  120  starts rotating, the VCM rotates the swing arm  132  counter-clockwise to move the magnetic head onto a recording surface of the disk  120 . On the other hand, when the HDD  100  is turned off and the disk  120  stops rotating, the VCM rotates the swing arm  132  clockwise so that the magnetic head is moved off of the recording surface of the disk  120  and is parked. More specifically, when the disk  120  stops rotating, the swing arm  132  is rotated clockwise by the VCM, and an end-tab  135  of the suspension assembly  133  is slid up and onto the ramp  140  where it remains to thereby park the magnetic head. 
         [0039]    The HDD  100  also includes an actuator latch system. The actuator latch system retains the actuator  130  when the magnetic head  140  is parked. That is, the actuator latch system prevents external shock or vibrations from rotating the swing arm  132  when the HDD  100  is not in use, i.e., when the magnetic head is parked. In particular, the actuator latch system prevents the magnetic head from being moved into contact with the recording surface of the disk  120  which situation could otherwise result in the recording surface and/or the magnetic head being damaged. 
         [0040]    The actuator latch system includes a member defining a notch  152  at a rear end portion of the swing arm  132 , and a latch lever  160  rotatably supported on the base  110  by a pivot  161 . The rear end portion of the swing arm  132  is generally formed of an injection-molded plastic such that the member defining the notch  152  is easily formed unitarily with the swing arm  132  during the injection molding process. 
         [0041]    The latch lever  160  has a hook  162  at a front end portion thereof and a counterbalance  164  at a rear end portion. In particular, the hook  162  may protrude downward at the front end portion of the latch lever  160  to face the notch  152 . The hook  162  is received within the notch  152  when the swing arm  132  of the actuator  130  is locked in place. Also, at this time, the front end portion of the latch lever  160  extends over the laterally offset section  153  of the VCM coil  137 . In the case in which a magnet  138  is disposed below the VCM coil  137 , the front end portion of the latch lever  160  may instead extend below the laterally offset section  153  of the VCM coil  137 . 
         [0042]    In addition, the latch lever  160  includes a magnetic member  163  at the front end portion thereof. As illustrated in  FIG. 5B , the magnetic member  163  includes a permanent magnet  163   a,  and an iron member  163   b  attached to the top of the permanent magnet  163   a  so as to increase the magnetic flux density. Thus, the permanent magnet  163   a  is juxtaposed with the laterally offset section  153  of the VCM coil  137  in the direction of the axis of rotation of the swing arm, and faces the upper surface of the laterally offset section  153  of the VCM coil  137  when the hook  162  is received within the notch  152  and the swing arm  132  of the actuator  130  is thereby locked in place while the magnetic head is parked. Alternatively, in the case described above in which a magnet  138  is disposed below the VCM coil  137 , the magnetic member  163  may face towards the lower surface of the laterally offset section  153  of the VCM coil  137 , and the hook  162  may protrude upwards at the front end portion of the latch lever  160 . 
         [0043]    In either case, the hook  162  of the latch lever  160  engages the swing arm  132  within the notch  152  to prevent the swing arm  132  from rotating when an external shock is applied to the hard disk drive  100  while the magnetic head is parked. On the other hand, the magnetic member  163  and the laterally offset section  153  of the VCM coil  137  co-act to rotate the latch lever  160  clockwise during a normal operation of the hard disk drive  100 , to thereby prevent the hook  162  of the latch lever  160  from arresting the counter-clockwise rotation of the swing arm  132 . The various ways in which the actuator latch system functions will be described in more detail below. 
         [0044]    The rotation of the swing arm  132  in the clockwise direction due to inertia, when a shock is applied to the HDD while the magnetic head is parked, is restricted by the counterbalance  164 . More specifically, the counterbalance  164  collides with a side of the rear end of the swing arm  132  as the swing arm rotates clockwise to prevent the swing arm  132  from rotating further in the clockwise direction. The counterbalance  164  may include a buffering arm  171  for buffering the shock generated when the counterbalance  164  and the swing arm  132  collide. To this end, the buffering arm  171  is preferably formed of an elastic material, for example, a plastic material such as polyimide. Also, the buffering arm  171  may have a protrusion  172  that projects toward the side of the rear end of the swing arm  132 . The protrusion  172  reduces the area of contact between the buffering arm  171  and the swing arm  132  in order to minimize the amount of particles that are produced when the buffering arm  171  and the swing arm  132  collide. 
         [0045]    The latch system may also have a stopper  111  positioned on the base  110  to block the counterbalance  164 . More specifically, the stopper  111  collides with the counterbalance  164  of the latch lever  160  when the latch lever  160  rotates counter-clockwise due to inertia. Thus, the stopper  111  limits the rotation of the latch lever  160  in the counter-clockwise direction. In addition, the counterbalance  164  may have a hole  167  extending therein in the direction of the thickness of the latch lever  160 . The hole  167  helps the counterbalance  164  absorb shock when the counterbalance  164  collides with the stopper  111  and thus, prevents the latch lever  160  from being damaged and helps to minimize noise. 
         [0046]    Furthermore, the latch system may also have a first core  155  and a second core  165  disposed, respectively, in the swing arm  132  and the latch lever  160 . The first core  155  is disposed in a corner of the rear end portion of the swing arm  132 . The first core  155  may be a (ferro)magnetic body, for example, an iron or steel body, so that a magnetic force of attraction is generated between the first core  155  and the magnet(s)  138 . Therefore, the first core  155  applies torque to the swing arm  132  in the clockwise direction. The torque prevents the actuator  130  from being moved by weak shocks and vibrations. 
         [0047]    The second core  165  may be also formed of a (ferro)magnetic body, for example, a steel body, so that a magnetic force of attraction is generated between the second core  165  and the magnet(s)  138 . However, the second iron core  165  is disposed further from the magnet(s)  138  than the first core  155  when the magnetic head of the actuator  130  is parked. At this time, an insignificant magnetic force acts between the second core  165  and the magnet(s)  138 . However, when the hard disk drive  100  is turned on and the swing arm  132  of the actuator  130  is rotated counterclockwise, the latch lever  160  is rotated clockwise, and the distance between the second core  165  and the magnet  138  is reduced. Accordingly, the magnetic force of attraction between the second core  165  and the magnet  138  increases to such an extent that the latch lever  160  is rotated clockwise, i.e., the magnetic force of attraction between the second core  165  and the magnet  138  ensures that the swing arm  132  remains unlatched. 
         [0048]    The interaction between the laterally offset section  153  of the VCM coil  137  and the magnetic member  163  of the latch lever  160 , which are characteristic components of the present invention, will now be described in more detail with reference to  FIGS. 4 and 6 . 
         [0049]    When the hard disk drive  100  starts operating, current (i) is controlled to flow in a clockwise direction in the VCM coil  137 . The current (i) flows through the VCM coil  137  within the magnetic field generated by the magnet  138 . Accordingly, thrust is applied to the VCM coil  137 . Because the magnet  138  has its poles oriented as illustrated in  FIG. 4 , the thrust is applied in the counterclockwise direction and therefore causes the swing arm  132  to rotate in the counterclockwise direction (denoted by arrow S). At the same time, thrust is applied to the laterally offset section  153  of the VCM coil  137  by the interaction between the current (i) and the magnetic field generated by the permanent magnet  163   a  of the magnetic member  163  disposed on the front end portion of the latch lever  160 . The thrust applied to the laterally offset section  153  of the VCM coil  137  is directed towards the pivot  131  of the actuator, i.e., the thrust acts in a direction that substantially intersects the axis of rotation of the swing arm  132 . Thus, there is no moment produced about the axis of rotation and hence, the swing arm  132  is not rotated due to this interaction. Rather, the front end portion of the latch lever  160 , to which the magnetic member  163  is mounted, is rotated in the clockwise direction (denoted by arrow L). Thus, the swing arm  132  is unlatched, and the hook  162  of the latch lever  160  is prevented from re-engaging the swing arm  132 . Therefore, the hard disk drive  100  will operate properly and reliably. 
         [0050]    A locking operation and a release operation of the actuator latch system will now be described with reference to  FIGS. 7 and 8 . 
         [0051]    First, referring to  FIG. 7 , when the operation of the hard disk drive  100  is terminated and the magnetic head in the slider  134  is parked on the ramp  140 , the swing arm  132  is rotated clockwise around the pivot  131  by the VCM. At this time, the rear end portion of the swing arm  132  contacts the counterbalance  164  of the latch lever  160 . Consequently, the latch lever  160  is pushed by the swing arm  132  so as to rotate counterclockwise about the latch pivot  161 . As a result, the counterbalance  164  of the latch lever  160  contacts the stopper  111 , whereupon the counterclockwise rotation of the latch lever  160  is arrested. 
         [0052]    Thus, the magnetic head is parked on the ramp  140 , and the swing arm  132  is locked in place by the clockwise torque that is applied to the swing arm  132  by the first core  155  and the magnet  138 . As mentioned above, at this time, the second core  165  in the counterbalance  164  of the latch lever  160  is spaced from the magnet  138  by such a large distance that the interaction between the second core  165  and the magnet  138  has little effect on the latch lever  160 . 
         [0053]    Meanwhile, the hard disk drive  100  can experience shocks when the magnetic head is parked. If the shock is larger than the torque exerted on the swing arm  132  by the first iron core  155  and the magnet  138 , the swing arm  132  can begin to rotate counterclockwise due to inertia. However, in this case, the hook  162  of the latch lever  160  enters the notch  152  in the rear end portion of the swing arm  132  and thus, rotation of the swing arm  132  in the counterclockwise direction is arrested before the magnetic head contacts the disk. 
         [0054]    On the other hand, shock applied to the hard disk drive  100  may act in a direction that urges the swing arm  132  to rotate clockwise. However, in this case, the swing arm  132  does not rotate clockwise because the rear end portion of the swing arm  132  and the counterbalance  164  of the latch lever  160  are in contact. Rather, the rear end portion of the swing arm  132  rebounds from the counterbalance  164  and the swing arm  132  thus begins to rotate counterclockwise. As described above, the counterclockwise rotation of the swing arm  132  is arrested by the hook  162  of the latch lever  160 . 
         [0055]    Next, referring to  FIG. 8 , a read/write operation is initiated by controlling the current to flow clockwise through the VCM coil  137 . The resulting thrust on the VCM coil  137  is sufficient to overcome the clockwise torque that is applied to the swing arm  132  by the interaction between first core  155  and the magnet  138 . As a result, the swing arm  132  begins to rotate counterclockwise. At the same time, as described above, the latch lever  160  is rotated clockwise by the interaction between the laterally offset section  153  of the VCM coil  137  and the magnetic member  163  of the latch lever  160 . Accordingly, the hook  162  of the latch lever  160  does not interfere with the counterclockwise rotation of the swing arm  132  and thus, the hard disk drive  100  will operate normally and reliably. Also, as the latch lever  160  rotates clockwise, the distance between the second iron core  165  and the magnet  138  is reduced. Thus, a magnetic force is applied between the second core  165  and the magnet  138 . Thus, the latch lever  160  is kept away from the swing arm  132 , i.e., the unlatched state of the swing arm  132  is maintained by the magnetic force between the second core  165  and the magnet  138 . 
         [0056]    Finally, although the present invention has been described in connection with the preferred embodiments thereof, it is to be understood that the scope of the present invention is not so limited. On the contrary, various modifications of and changes to the preferred embodiments will be apparent to those of ordinary skill in the art. Thus, changes to and modifications of the preferred embodiments may fall within the true spirit and scope of the invention as defined by the appended claims.