Abstract:
The invention includes an impact rebound crash stop pivoting about a pivot between the top and bottom yoke of an actuator magnet assembly. The impact rebound crash stop includes a latch bias tab magnetically attracted to the voice coil magnet when it is near. The invention further includes a proximity latch allowing the actuator to stay on the ramp when not in use. The invention includes actuator arms embedding part of the magnetic proximity latch, actuators, and disk drives using the crash stop and proximity latch, as well as methods of making actuator arms, actuators and disk drives.

Description:
TECHNICAL FIELD 
   This invention relates to latch mechanisms used in parking read-write heads outside the disk media surface(s). 
   BACKGROUND ART 
   Disk drives are an important data storage technology based on several crucial components including disk media surfaces and read-write heads. When in operation, rotation of disk media surfaces, with respect to the read-write heads, causes each read-write head to float a small distance off the disk media surface it accesses. However, for a variety of reasons, disk media surfaces frequently stop rotating when not in operation for awhile. 
   When the disk media surface is not rotating with respect to the read-write head, mechanical vibrations acting upon the disk drive can cause the read-write head to collide with the disk media surface, unless they are separated. 
   This separation is often referred to as “parking” the read-write heads. Parking the read-write heads minimizes the possibility of damaging the disk media surfaces and/or the read-write heads due to these mechanical collisions. Often such parking mechanisms include a ramp on which the head slider(s) are “parked” and a latch mechanism. The purpose of the latch mechanism is to minimize the chance that the actuator will accidentally leave the parking ramp outside the disk media surface and potentially damage the disk media surface(s). 
     FIG. 1A  illustrates a typical prior art high capacity disk drive  10  including actuator arm  30  with voice coil  32 , actuator axis  40 , suspension or head arms  50 - 58  with slider/head unit  60  placed among the disks. 
     FIG. 1B  illustrates a typical prior art high capacity disk drive  10  with actuator  20 , actuator arm  30  with voice coil  32 , actuator axis  40 , head arms  50 - 56  and slider/head units  60 - 66  with the disks removed. 
   Since the 1980&#39;s, high capacity disk drives  10  have used voice coil actuators  20 - 66  to position their read/write heads over specific tracks. The heads are mounted on head sliders  60 - 66 , which float a small distance off the disk drive surface  12  when in operation. Often there is one head per head slider for a given disk drive surface. There are usually multiple heads in a single disk drive, but for economic reasons, usually only one voice coil actuator. 
   Voice coil actuators are further composed of a fixed magnet actuator  20  interacting with a time varying electromagnetic field induced by voice coil  32  to provide a lever action via actuator axis  40 . The lever action acts to move head arms  50 - 56  positioning head slider units  60 - 66  over specific tracks with remarkable speed and accuracy. Actuator arms  30  are often considered to include voice coil  32 , actuator axis  40 , head arms  50 - 56  and head sliders  60 - 66 . Note that actuator arms  30  may have as few as a single head arm  50 . Note also that a single head arm  52  may connect with two head sliders  62  and  64 . 
   While there are many forms of mechanical impact upon a disk drive, only rotary shock in actuator  30 &#39;s plane of motion can bring the read-write heads into collision with disk media surfaces once the read-write heads are parked. These rotary shocks will be described herein based upon a view defining clockwise and counterclockwise rotations with respect to the disk drive base, with a parking zone located to the right of the disk media surfaces as viewed from above the disk base. As will be apparent to one of skill in the art, it is just as possible for a disk drive to use a parking zone on the left of the disk media surfaces. While this is most certainly possible, the discussion hereafter will focus on a parking zone to the right to clarify the discussion. Such a clarification is not meant to limit the scope of the claims. 
     FIG. 1C  illustrates a magnetic latch affixed to an actuator arm  30  of the prior art. 
   A magnet is affixed to the tail end of the voice coil  32  region, which when near a second magnet located in either the top yoke or bottom yolk of the fixed magnet region  20 , will tend to attract actuator  30  to a parking site often inside the disk media. Magnetic latches are used with Crash Start Stop (CSS) designs. 
   While they have been put into production in several circumstances, they place additional requirements on the voice coil actuators. This kind of latch requires additional actuator torque to exit from the parking zone. Further, these latches require sophisticated actuator speed control. Inside disk parking zones also tend to heat the read-write heads more. The read-write heads tend to suffer more frequent mechanical collisions with the disk surface. 
   The outside disk surface approach to parking read-write heads parks the read-write head or heads on a ramp outside the disk surface, removing and/or minimizing the possibility for contact when the disk is not in operation. Latch mechanisms provide at least some assurance that the actuator will remain parked with head sliders on the ramp even after mechanical shocks to the disk drive. 
     FIGS. 2A  to  2 C illustrate the operation of a single lever inertial latch as found in the prior art. 
     FIG. 2A  illustrates the prior art single level inertial latch mechanism including latch arm  100  pivoting about  102  and including latch hook  104 , mechanically fitting with actuator catch mechanism  106 , as well as latch stop  110 , and crash stop  90 , with the latch mechanism at rest. 
   Note that actuator  30  abuts crash stop  90  and that inertial latch arm  100  abuts latch stop  110  when the single-lever inertial latch is at rest. Slider  60  is in position on parking ramp  120 . 
     FIG. 2B  illustrates the prior art single level inertial latch during a clockwise acceleration of actuator  30 . 
   In a clockwise acceleration, actuator  30  moves away from crash stop  90  and actuator catch mechanism  106  engages with inertial latch catch mechanism  104 . 
     FIG. 2C  illustrates the prior art single level inertial latch during a counterclockwise acceleration of the actuator. 
   In a counterclockwise acceleration, the latch may fail if the actuator  30  rebounds from its crash stop  90 . 
     FIG. 3A  illustrates a prior art example of a dual-lever inertial latch at rest. 
   When at rest, a magnet or spring, (which are not shown), biases the small latch arm  142  clockwise, holding the latch  144 - 152  open. 
     FIG. 3B  illustrates a prior art example of a dual-lever inertial latch during a clockwise rotational acceleration of actuator  30 . 
     FIG. 3C  illustrates a prior art example of a dual-lever inertial latch during a counterclockwise rotational acceleration of actuator  30 . 
   The large latch arm  140  rotates in opposite directions during the clockwise and counterclockwise motions of actuator arm  30  of  FIG. 3B and 3C , respectively. Motion of large latch arm  140  in either direction causes the small arm  142  to rotate counterclockwise to the close position. This dual lever action prevents a rebound of actuator arm  30  off the crash stop  90  from escaping the latched condition. 
   SUMMARY OF THE INVENTION 
   The invention includes an impact rebound crash stop pivoting about a pivot  218  between the top and bottom yoke of an actuator magnet assembly  20 . The impact rebound crash stop includes a latch bias tab  210  magnetically attracted to the voice coil  32  magnet when near. The magnet attraction rigidly moves a crash stop  216  about pivot  218 . This motion engages the crash stop  216  with crash stop site  226 , as well as pusher  212  with pusher site  224 . Pusher site  224  and crash stop site  226  are both on the actuator  30  fantail. 
   The impact rebound crash stop uses an impact rebound bi-directional inertial latch and is preferably made of at least one plastic with low elastic coefficient and a magnetically attractive latch bias tab  210 . The plastic is preferably essentially rigid. 
   The invention further includes a proximity latch for an outside disk, ramp loading disk drive allowing the actuator to stay on the ramp when not in use. The proximity latch includes two small magnets  220  bonded to the top and bottom yoke of the voice coil magnet assembly  20  and the impact rebound crash stop. The proximity latch mechanism attracts a magnetically attractive component molded into the actuator fantail. The attraction is toward the crash stop. The two magnets and magnetically attractive component attract each other, but do not make contact. 
   The proximity latch, together with the impact rebound crash stop, provide an outside disk ramp loading disk drive with a very reliable, non-contact break free latch while maintaining a high resistance to accidental latch release during rotary shock conditions. The proximity latch mechanism achieves this without using any inertial latch mechanism, eliminating the extra travel allowance required by an impact rebound inertial latch mechanism. 
   The invention includes the actuator arm  30  embedding the magnetically attractive component  222  in the actuator fantail. The invention further includes an actuator  20 - 66  containing the proximity latch mechanism with the magnetically attractive component  222  and pusher stop  224  in the actuator fantail and crash stop  210 - 218  mounted through its pivot  218  to the top yoke  224  and bottom yoke  222  of the actuator magnet assembly  20 . 
   The invention includes the making of these actuators with their crash stop and proximity latch mechanisms, as well as the making of disk drives using these actuators, and the disk drives themselves. 
   The invention includes the method of parking an actuator through the operation of an internal crash stop and the operation of the internal proximity latch. The invention also includes the method of parking a disk drive using the method of parking the actuator. 
   These and other advantages of the present invention will become apparent upon reading the following detailed descriptions and studying the various figures of the drawings. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
       FIG. 1A  illustrates a typical prior art high capacity disk drive  10  including actuator arm  30  with voice coil  32 , actuator axis  40 , suspension or head arms  50 - 58  with slider/head unit  60  placed among the disks; 
       FIG. 1B  illustrates a typical prior art high capacity disk drive  10  with actuator  20 , actuator arm  30  with voice coil  32 , actuator axis  40 , head arms  50 - 56  and slider/head units  60 - 66  with the disks removed; 
       FIG. 1C  illustrates a magnetic latch affixed to an actuator arm  30  of the prior art; 
       FIG. 2A  illustrates the prior art single level inertial latch mechanism including latch arm  100  pivoting about  102  and including latch hook  104 , mechanically fitting with actuator catch mechanism  106 , as well as latch stop  110 , and crash stop  90 , with the latch mechanism at rest; 
       FIG. 2B  illustrates the prior art single level inertial latch during a clockwise acceleration of actuator  30 ; 
       FIG. 2C  illustrates the prior art single level inertial latch during a counterclockwise acceleration of the actuator; 
       FIG. 3A  illustrates a prior art example of a dual-lever inertial latch at rest; 
       FIG. 3B  illustrates a prior art example of a dual-lever inertial latch during a clockwise rotational acceleration of actuator  30 ; 
       FIG. 3C  illustrates a prior art example of a dual-lever inertial latch during a counterclockwise rotational acceleration of actuator  30 ; 
       FIG. 4  illustrates an impact rebound type bi-directional inertial latch; 
       FIG. 5A  illustrates the proximity latch mechanism in the open position; 
       FIG. 5B  illustrates the proximity latch mechanism in the closed position; 
       FIG. 6A  illustrates a side view of the proximity latch mechanism as housed in the voice coil magnet assembly; and 
       FIG. 6B  illustrates a perspective view of the proximity latch mechanism. 
   

   DETAILED DESCRIPTION OF THE INVENTION 
   A proximity latch for an outside disk ramp loading disk drives allows the actuator to stay on the ramp when not in use (see  FIGS. 5A  to  6 B). 
     FIG. 4  illustrates an impact rebound type bi-directional inertial latch. 
   The inertial latch rests in an open position due to a light bias torque applied by the magnetic attraction between the voice coil  32  magnet and the balance steel  200  when there is no externally induced rotational acceleration acting upon actuator arm  30 . 
   Actuator arm  30  and the latch assembly  102 - 104 - 202  are rotationally balanced. During clockwise rotational acceleration of the disk drive, the latch  102 - 104  rotates in the counterclockwise direction with respect to the base. This latch motion causes the latch hook  104  to engage the barb  106  on the actuator  30  tail. 
   During counterclockwise rotational acceleration of the disk drive, actuator arm  30  rebounds from its crash stop  90  and the latch  202 - 102 - 104  also rebounds in the clockwise direction with respect to the base, due to the actuator tail touching the rebound part  202  of the latch. This latch motion causes the latch hook  104  to engage the barb  104  on the actuator  30  tail. 
     FIG. 5A  illustrates the proximity latch mechanism in the open position. 
     FIG. 5B  illustrates the proximity latch mechanism in the closed position. 
     FIG. 6A  illustrates a side view of the proximity latch mechanism as housed in the voice coil magnet assembly. 
     FIG. 6B  illustrates a perspective view of the proximity latch mechanism. 
   The proximity latch includes two small magnets  220  bonded to the top yoke  22  and bottom yoke  24  of the actuator assembly  20  and an impact rebound crash stop  216 . The impact rebound crash stop  216  uses an impact rebound bi-directional inertial latch  210 - 218 . The impact rebound bi-directional latch includes pusher  212 , latch pivot  218  and latch bias tab  210 . 
   The proximity latch mechanism attracts a magnetically attractive component  222  molded into the actuator fantail toward the two small magnets  220 . The actuator fantail is further formed of a pusher stop  224  and a crash stop site  226 . The attraction is toward the pusher  212 . Note that the small magnets  220  are preferably magnetically aligned so that their North poles point in essentially the same direction. 
   The two small magnets  220  and magnetically attractive component  222  attract each other, but do not make contact. However, as the two small magnets  220  and the magnetically attractive component  222  approach each other, pusher stop  224  engages pusher  210 , rotating the proximity latch mechanism  210 - 218  about latch pivot  218  to engage crash stop  216  and crash stop site  226 . 
   The magnetically attractive component  222  is preferably made of a magnetically attractive form of steel, preferably number 430. 
   Note that the proximity latch mechanism illustrated in  FIGS. 5A and 5B  does not use an impact rebound inertial latching mechanism. This eliminates the extra travel allowance required in all the designs illustrated by  FIGS. 1C  to  4 . 
   The impact rebound crash stop  216  halts the actuator  30  at a contact point illustrated in FIG.  5 B through engagement with crash stop site  226  on actuator arm  30 . 
   The magnetic force between the magnetically attractive actuator component  222  and the two non-contact magnets  220 , provide a torque upon the actuator. This magnetic force is preferably between 4.8 and 6.0 Newton-meter^2. This preferred magnetic force supports high rotary shock performance in the clockwise direction. The impact rebound crash stop  216  is used to keep the actuator  30  from rebounding during counterclockwise rotary shocks. The impact rebound crash stop  216  is built into the voice coil magnet assembly as shown in FIG.  6 B. 
   When the actuator approaches the impact rebound crash stop, the magnetic latching mechanism engages and helps the actuator to move faster into the crash stop. The magnetic latching mechanism includes the magnetic attraction between the two small magnets and magnetically attractive component molded into the actuator. The two small magnets are placed on the top and bottom yokes of the voice coil magnet assembly exactly so that the actuator is maintained at a parking “home” where the impact rebound crash stop is located. As the magnetically attractive component of the actuator slowly approaches the flux generated by these two small magnets, the actuator pushes upon the impact rebound crash stop. The impact rebound crash stop is rotated clockwise until the impact rebound crash stop touches the actuator by its latch arm at the crash stop. 
   The proximity latch mechanism helps a disk drive resist relatively high rotary shock in the clockwise direction with respect to the disk drive base. This resistance depends upon the magnetic attractive force between the two small magnets and the magnetically attractive component molded into the actuator. 
   The impact rebound crash stop helps increase rotary shock performance in the counterclockwise direction with respect to the disk drive base. The impact response crash stop is preferably made from plastic, preferably from an ultem plastic material. The actuator fan tail is preferably includes a plastic overmold made of vectra. 
   The elastic coefficient between the plastic impact response crash stop and the plastic overmold actuator fantail is less than one, preferably about 0.6. The elastic coefficient being less than one contributes to very minimal rebound effect from impact between the actuator fantail and the impact rebound crash stop. The loss of high energy during the impact also significantly reduces the chance of sudden impact rebound motion. This reduction in the chance of sudden impact rebound motion, combined with the reduced energy of any sudden impact rebound motion, both contribute to high rotary shock resistance in the counterclockwise direction with respect to the disk drive base. 
   The latch bias tab  210  is molded into the latch mechanism and supports the latch opening its arm automatically when the actuator is controlled to move out in a desirable speed. The latch opens its arm based upon the attractive force generated on the latch bias tab  210  by the voice coil magnet  32 . The latch bias tab  210  is preferably composed of a magnetically attractive steel compound preferably SUS 430 steel. 
   The invention secures read-write head parking through rotational shocks of 25,000 to 30,000 radians/sec^2 of up to two milliseconds duration. Note that the contemporary industry standard is support for up to 20,000 radians/sec^2. 
   Depending upon the small magnets, the performance can protect read-write head parking under even more severe conditions. The small magnets preferably have magnetic strengths of 48 MGO and are preferably 1.5 millimeters thick and 3 millimeters by 4 millimeters wide. 
   The preceding embodiments have been provided by way of example and are not meant to constrain the scope of the following claims.