Abstract:
An apparatus for increasing the operative force on an air vane latch apparatus in a disc drive involves providing an additional air vane on the pivoting air filter/latch to provide more torque on the latch during low pressure operating conditions and/or when less than an optimum number of discs are installed in the disc drive. The additional air vane is positioned beneath a top disc in the disc stack to at least catch wind generated adjacent the underside surface of the disc by the rotation of the top disc. The wind so generated pushes against this additional air vane supplementing that generated by the upper air vane thus increasing the torque applied to the pivoting air filter by the wind to ensure that there is sufficient wind pressure accumulation against the air vane and air filter latch to unlatch the actuator during all conditions of normal disc drive operation.

Description:
RELATED APPLICATIONS 
     This application claims the benefit of priority of U.S. Provisional Patent Application Serial No. 60/130,300 entitled “DUAL AIR VANE”, filed Apr. 21, 1999. 
    
    
     FIELD OF THE INVENTION 
     This application relates to magnetic disc drives and more particularly to an apparatus for latching a disc drive actuator mechanism in a parked position when the drive is de-energized. 
     BACKGROUND OF THE INVENTION 
     Disc drives are data storage devices that store digital data in magnetic form on a rotating storage medium on a disc. Modern disc drives comprise one or more rigid discs that are coated with a magnetizable medium and mounted on the hub of a spindle motor for rotation at a constant high speed. Information is stored on the discs in a plurality of concentric circular tracks typically by an array of transducers (“heads”) mounted to a radial actuator for movement of the heads relative to the discs. Each of the concentric tracks is generally divided into a plurality of separately addressable data sectors. The read/write transducer, e.g. a magnetoresistive read/write head, is used to transfer data between a desired track and an external environment. During a write operation, data is written onto the disc track and during a read operation the head senses the data previously written on the disc track and transfers the information to the external environment. Critical to both of these operations is the accurate locating of the head over the center of the desired track. 
     The heads are mounted via flexures at the ends of a plurality of actuator arms that project radially outward from the actuator body. The actuator body pivots about a shaft mounted to the disc drive housing at a position closely adjacent the outer extreme of the discs. The pivot shaft is parallel with the axis of rotation of the spindle motor and the discs, so that the heads move in a plane parallel with the surfaces of the discs. 
     Typically, such radial actuators employ a voice coil motor to position the heads with respect to the disc surfaces. The actuator voice coil motor includes a coil mounted on the side of the actuator body opposite the head arms so as to be immersed in the magnetic field of a magnetic circuit comprising one or more permanent magnets and magnetically permeable pole pieces. When controlled direct current (DC) is passed through the coil, an electromagnetic field is set up which interacts with the magnetic field of the magnetic circuit to cause the coil to move in accordance with the well-known Lorentz relationship. As the coil moves, the actuator body pivots about the pivot shaft and the heads move across the disc surfaces. The actuator thus allows the head to move back and forth in an arcuate fashion between an inner radius and an outer radius of the discs. 
     When the drive is de-energized or shut down, the drive motor stops spinning and the actuator is rotated, for example, counterclockwise to position the heads at an inner diameter landing zone location and latch the actuator in this position. Often a magnetic latch is used to maintain the actuator in this position with the heads in the landing zone. When a magnetic latch is used, an inadvertent external shock load, such as the drive being dropped, may cause sufficient rotational force to be applied to the actuator arms to overcome the magnetic attraction and thus the actuator arm may rotate from the landing zone to the data region of the discs without the discs spinning at all. This could destroy the stored data and could destroy the heads themselves. Consequently there is a need for a latch mechanism that ensures that the actuator stays in the parked position any time that the disc drive motor is deenergized and, more importantly, the discs are not spinning. 
     This deenergized latching has been traditionally accomplished by a wind operated latching mechanism which utilizes wind generated by the spinning discs while the drive motor is energized to push against a pivoting air filter member positioned adjacent the outer margin of the discs. This air filter member has a pivot portion, an air filter portion, and an elongated air vane which extends outward over the top disc in the disc stack. Air drawn along the surface of the disc toward the outer disc rim constitutes a wind that generates a force which pushes against the air vane producing a moment arm in a clockwise direction on the pivoting air filter member. At the other end of the pivot portion of the air filter member is an elongated latch arm and a tab portion that carries a steel ball therein. The steel ball in the tab portion is positioned in the magnetic field generated by the VCM magnets and thus biases the latch counterclockwise such that the latch arm interferes with movement of the actuator arm off of the magnetic latch when the drive is deenergized. 
     The operation of this conventional latch mechanism is completely automatic, driven only by the VCM magnet magnetic field bias and the force exerted by wind against the air filter and air vane when the discs are spinning at normal speed. The size and placement of the steel ball on the tab portion are dictated by the requirement that the latch be disengaged when the discs are operating at full speed and engaged when the discs are turning at less than full operating speed with the actuator arm moved into the parked position. 
     The conventional air vane design has worked well for drives with three or four or more operating discs in the head disc assembly (HDA). However, in the case of drives designed for four discs and having only one or two discs installed in the HDA, there have been cases where the air vane latches failed to rotate and move to the disengaged position when the drive is energized, thus preventing actuator movement and appearing to the user by the software as a disc crash or disc drive failure. In these cases, the failures appear to have occurred at high altitudes and/or elevated temperatures, i.e. under conditions of reduced atmospheric pressure. Accordingly, there is a need for a wind operated latching apparatus for use in disc drives having only one or two discs which automatically disengages the actuator arm when the disc drive motor spins the discs at operating speed and engages the actuator arm when the disc or discs spin at less than operating speed and the actuator arm is in the parked position in a head disc assembly (HDA) designed to accommodate up to four or more discs. 
     SUMMARY OF THE INVENTION 
     Against this backdrop the present invention has been developed. The present invention is an air filter having a dual air vane arrangement with one air vane adapted to extend over the upper surface of a top disc on the disc drive motor and another, supplemental air vane beneath the top disc adapted to extend under the underside surface of the top disc. This arrangement provides an additional moment arm on the pivoting air filter when only one or two discs are located on the drive motor in the HDA. This supplemental air vane is positioned adjacent the outer perimeter of the disc or discs and extends from the air filter portion of the latch member thus capturing additional air flow and thus providing an additional moment arm on the air filter latch when the drive is utilized at high elevations where the air is thinner or at elevated temperatures at which the air is less dense. This additional air vane permits a larger steel ball to be utilized in the latch apparatus thereby ensuring more positive latch and unlatch operations of the apparatus. 
     These and various other features as well as advantages which characterize the present invention will be apparent from a reading of the following detailed description and a review of the associated drawings. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 is a plan view of a disc drive incorporating a dual air vane actuator latch apparatus in accordance with a preferred embodiment of the invention with the head disc assembly cover partially broken away and with portions of the discs broken away. 
     FIG. 2 is a plan view of the disc drive shown in FIG. 1 with the voice coil motor upper magnets and magnet return plate removed and the data disc(s) removed, showing the latch apparatus in accordance with a preferred embodiment of the present invention in a disengaged position, that occurs when the discs are spinning at normal speed, permitting the actuator to rotate to position the read/write heads over the data portion of the disc. 
     FIG. 3 is a plan view of the disc drive as in FIG. 2 showing the actuator parked with the latch apparatus in an engaged position as when the drive motor is de-energized. 
     FIG. 4 is a separate, enlarged, perspective upper view of the air vane latch apparatus of the present invention. 
     FIG. 5 is a separate, enlarged, perspective bottom view of the latch apparatus in accordance with the present invention shown in FIG.  4 . 
    
    
     DETAILED DESCRIPTION 
     A disc drive  100  constructed in accordance with a preferred embodiment of the present invention is shown in a plan view with portions broken away in FIG.  1 . The disc drive  100  includes a base  102  to which various components of the disc drive  100  are mounted. A top cover  104 , shown partially cut away, cooperates with the base  102  to form an internal, sealed environment for the disc drive in a conventional manner. This assembly is called a head disc assembly (HDA)  101 . The components include a spindle motor  106  that rotates one or more discs  108  at a constant high speed. Information is written to and read from tracks on the discs  108  through the use of an actuator assembly  110 , which rotates about a bearing shaft assembly  112  positioned adjacent the discs  108 . The actuator assembly  110  includes a plurality of actuator arms  114  which extend towards the discs  108 , with one or more flexures  116  extending from each of the actuator arms  114 . Mounted at the distal end of each of the flexures  116  is a head  118  that includes an air bearing slider enabling the head  118  to fly in close proximity adjacent the corresponding surface of the associated disc  108 . 
     The spindle motor  106  is typically de-energized when the disc drive  100  is turned off or not in use for extended periods of time. The heads  118  are moved to park zones near the inner diameter of the discs  108  when the drive motor is de-energized as shown in FIG.  3 . The heads  118  are secured in the park position through the use of an actuator latch arrangement  122 , which prevents inadvertent rotation of the actuator arms  114  when the heads are parked. 
     The radial position of the heads  118  is controlled through the use of a voice coil motor (VCM)  124 , which typically includes a coil  126  attached to the actuator assembly  110 , as well as one or more permanent magnets  120  on return plates  128  which are spaced apart. The magnets and return plates establish a vertical magnetic field between the magnets in which the coil  126  is immersed and suspended for rotation in a horizontal plane between the magnets. The controlled application of current to the coil  126  causes magnetic interaction between the permanent magnets  128  and the coil  126  so that the coil  126  moves in accordance with the well known Lorentz relationship. As the coil  126  moves, the actuator assembly  110  pivots about the bearing shaft assembly  112  and the heads  118  are caused to move across the surfaces of the discs  108 . 
     A flex assembly  130  provides the requisite electrical connection paths for the actuator assembly  110  while allowing pivotal movement of the actuator assembly  110  during operation. The flex assembly includes a preamplifier printed circuit board  132  to which head wires (not shown) are connected; the head wires being routed along the actuator arms  114  and the flexures  116  to the heads  118 . The preamplifier printed circuit board  132  typically includes circuitry for controlling the write currents applied to the heads  118  during a write operation and for amplifying read signals generated by the heads  118  during a read operation. The flex assembly  130  terminates at a flex bracket  134  for communication through the base plate  102  to a disc drive printed circuit board (not shown) mounted to the bottom side of the disc drive  100 . 
     A pivoting dual air vane air filter and latch apparatus  140  in accordance with the present invention is pivotally supported on a pin  142  projecting from one of the magnet return plates  128 . The latch apparatus  140  is shown in FIGS. 1 and 2 rotated clockwise to a disengaged position as would be the case when the drive  100  is at normal operation with the discs  108  rotating at normal speed. 
     The dual air vane air filter and latch apparatus  140  in accordance with a preferred embodiment of the present invention is shown in the drive  100  clearly in FIGS. 2 and 3 and in the separate views of FIGS. 4 and 5. Note that in FIGS. 2 and 3 the upper magnets and return plate  128  and the disc(s)  108  have been removed for clarity. 
     Referring now to FIGS. 4 and 5, the dual air vane air filter and latch apparatus  140  is shown in separate upper and lower perspective views. Apparatus  140  is an injection molded body having an elongated, generally cylindrical tubular pivot portion  144 , an elongated latch arm  146  extending generally radially from one side of the pivot portion  144  and an air filter bracket  148  supported from and extending from an opposite side of the pivot portion  144 . The filter bracket  148  forms an open rectangular frame support for a sheet of air filter media (not shown). 
     The cylindrical pivot portion  144  has an axial through bore  150  sized to receive the pivot pin  142  therein permitting rotation of the apparatus  140  about the axis of the bore  150 . A flat, counterbalance tab portion  152  extends laterally and radially outward from the pivot portion  144  adjacent the latch arm  146 . A clocking tab  171  projecting upward from the upper surface of the latch arm  146  engages a stop located on the top magnet return plate  128  to limit counterclockwise rotation of the apparatus  140  about the pivot pin  142 . In addition, a generally flat, tapered biasing arm member  156  extends from the tab portion  152  so that its tip extends into the magnetic field generated by the VCM magnets  126  when the apparatus is installed on the pivot pin  142 . A steel ball  160  is mounted adjacent the tip  158  in the biasing arm  156 . This ball  160  is in the magnetic field and is located on the biasing arm  156  a predetermined distance from the axis of the pivot portion  144 . 
     The magnetic field of the VCM interacts with the ball  160  to provide a torque on the apparatus  140  in a counterclockwise direction, as viewed from the top as in FIG.  1 . Thus the apparatus  140  is constantly biased as shown by the arrows  162  in FIG. 3, toward engagement of the latch arm  146  with the actuator coil overmold  164  to prevent movement of the actuator assembly  110  off of the magnetic latch  122  when it is latched. The actuator assembly  110  is rotated as shown by the arrow  166  to a latched position when the drive  100  is de-energized. The actuator arms  114  rotate fully counterclockwise to a park position as shown in FIG. 3 which positions the heads  118  over the landing zone on the disc  108  (not shown in FIG.  3 ). In this position, when the discs are stopped or are spinning at less than operational speed, the coil overmold  164  is then captured between the latch  122  and the latch arm  146 , thus ensuring that the heads  118  stay in the landing zone. 
     Referring back now to FIGS. 4 and 5, the air filter bracket  148  has one side joined with the pivot portion  144 . An air vane  168  extends outward from the other side of the air filter bracket  148 . This air vane  168  is positioned so as to rotate over the upper surface of the disc  108  as shown in FIGS. 1 and 2. The air vane  168  is also positioned just above the upper surface of the disc so that it is in the path of wind generated by the rotating disc  108  during normal drive operation. This wind exerts a force on the air vane  168  tending to rotate the apparatus  140  clockwise in opposition to the magnetic torque on the apparatus  140  generated by the interaction of the ball  160  in the magnetic field of the VCM. When the wind force against the air vane  168  and the air filter in the bracket  148  exceeds the torque from the ball  160 , the apparatus  140  will rotate clockwise, permitting the latch arm  146  to disengage the actuator coil overmold  164 . The VCM can then rotate the actuator arms  114  from the park position to the data region of the disc. 
     However, in environmental conditions having reduced air pressure, such as at elevated temperatures above about 25° Centigrade, or at high altitudes generally above about 14,000 feet, and with a reduced number of discs in the drive, the wind generated by normal operation of the drive motor is insufficient to cause rotation of the apparatus  140 . Therefore, there is another air vane  170  that extends from the air filter bracket  148 . The second or lower air vane  170  is a generally rectangular body that extends horizontally beneath the disc  108  parallel to the plane of the disc  108  but at an acute skew angle to the air vane  168  such that the upper air vane  168  extends initially further into the path of the wind than the lower air vane  170 . The angle is preferably chosen such that the air vane and air filter latch apparatus  140  can preferably be installed in the drive  100  during drive assembly after the disc or discs  108  have been installed on the motor  106  on the baseplate  102 . That is, the lower air vane  170  is preferably positioned outside the diameter of the disc or discs  108  when the apparatus  140  has been rotated to a latched position as shown in FIG.  3 . 
     The lower air vane  170  is preferably oriented normal to the plane of the disc  108  and is preferably also wider than the upper air vane so as to present a larger surface area than the upper air vane against which the wind generated by the rotating disc  108  exerts a force. The second or lower air vane  170  extends from the bracket in a direction normal to the pivot axis and parallel to the plane of the disc  108  such that the upper and lower air vanes  168  and  170  are vertically spaced apart and sandwich the disc  108  therebetween. 
     The two vane design, with air vanes  168  and  170  being at different skew angles with respect to the pivot portion  144 , provides the ability of the air vanes to capture two different air streams. The air vane  168  catches air from the shearing effect of the large top disc surface. The lower vane  170  is positioned to catch air that is pumped out to the outer edge of the disc  108  from the centrifugal effect. This caught air is then constrained and directed by the topography of the cover  104  onto the lower air vane  170 . 
     The presence of the second lower air vane  170  also permits a larger size of ball  160  to potentially be utilized in the drive  100  since the total wind force on the two air vanes is greater and thus the torque generated by the disc rotating at normal operational speed is generally greater than in conventional air vane air filter and latch arrangements. This results in an improvement in the tendency for the apparatus  140  to stay in either the latched or unlatched positions, thus providing more positive latching and unlatching when the disc or discs  108  reach operating speed. 
     In summary the present invention may be viewed as a disc drive (such as  100 ) having a head disc assembly (such as  101 ) sized to accommodate up to four data storage discs (such as  108 ) therein, the head disc assembly (such as  101 ) having a baseplate (such as  102 ) and one or two data storage discs rotatably mounted on a spin motor (such as  106 ) fastened to the baseplate (such as  102 ) and an actuator assembly (such as  110 ) mounted adjacent the data storage disc (such as  108 ) in the head disc assembly (such as  101 ) for rotating an actuator arm (such as  114 ) over a portion of the disc (such as  108 ), and a wind actuated air filter and latch apparatus (such as  140 ) operable at reduced air pressure such as at elevated temperatures and elevations in excess of 14,000 feet. The wind actuated air filter and latch apparatus has a pivot portion (such as  144 ) rotatably mounted in the disc drive adjacent the disc. The latch (such as  146 ) rotates from a latched position, in which the heads (such as  118 ) are in a park position, preventing movement of the actuator arm (such as  114 ) to an unlatched position permitting movement of the actuator arm (such as  114 ) only when the spin motor rotates the data storage disc (such as  108 ) at a speed approaching normal operating speed. 
     The wind actuated air filter and latch apparatus (such as  140 ) has a unitary body having a pivot portion (such as  144 ) rotatably mounted in the disc drive adjacent the disc (such as  108 ) on a stationary pivot pin (such as  142 ) and a latch arm member (such as  146 ) extending from one side of the pivot portion (such as  142 ) toward the actuator assembly (such as  110 ). The apparatus (such as  140 ) also has an air filter bracket (such as  148 ) extending from another side of the pivot portion (such as  142 ) for holding an air filter in a path of wind generated by the disc (such as  108 ) and exert a rotational force on the unitary body, an upper air vane member (such as  168 ) extending outward from the bracket (such as  148 ) over a portion of the disc to catch the wind and exert a rotational force on the pivot portion (such as  144 ), and a lower air vane member (such as  170 ) extending from the bracket (such as  148 ) beneath the upper air vane member parallel to the upper air vane member (such as  168 ) to also catch the wind and exert an additional rotational force on the pivot portion (such as  144 ). The upper and lower air vane members (such as  168  and  170 ) sandwich a portion of the disc (such as  108 ) between them. 
     Viewed another way, the present invention preferably is a dual air vane air filter and latch apparatus (such as  140 ) for use in a disc drive (such as  100 ) wherein the drive has one or two data storage discs (such as  108 ) rotatably mounted on a spin motor (such as  106 ) fastened to a baseplate, an actuator assembly (such as  110 ) mounted adjacent the data storage disc (such as  108 ) for rotating an actuator arm (such as  114 ) over a portion of the disc. The dual air vane air filter and latch apparatus (such as  140 ) includes a unitary body having a pivot portion (such as  144 ) rotatably mounted in the disc drive (such as  100 ) adjacent the disc (such as  108 ). A latch arm member (such as  146 ) extends from one side of the pivot portion (such as  144 ) toward the actuator assembly (such as  110 ) for engaging the actuator assembly (such as  110 ). An air filter bracket (such as  148 ) extends from another side of the pivot portion (such as  144 ). The bracket (such as  148 ) holds an air filter in a path of wind generated by the disc (such as  108 ) when the disc (such as  108 ) rotates at a normal operating speed. An upper air vane member (such as  168 ) extends outward from the bracket (such as  148 ). The upper air vane member (such as  168 ) is adapted to extend over a portion of one disc. A lower air vane member (such as  170 ) extends from the bracket (such as  148 ) beneath the upper air vane member (such as  168 ) parallel to the upper air vane member. The lower air vane member (such as  170 ) is wider than the upper air vane member (such as  168 ). The lower air vane member such as  170 ) also extends from the bracket (such as  148 ) at an acute angle from the upper air vane member. The upper and lower air vane members (such as  168  and  170 ) are vertically spaced apart so that they sandwich a portion of the disc (such as  108 ) between them, and both catch wind generated by the rotating disc to exert a rotational force, or torque, on the pivot portion (such as  144 ). 
     The pivot portion (such as  144 ) has a through bore (such as  150 ) adapted to receive a stationary pivot pin (such as  142 ) mounted in the disc drive (such as  100 ). The pivot pin (such as  142 ) and the through bore (such as  150 ) has a central pivot axis extending parallel to the axis of rotation of the disc (such as  108 ) and the upper and lower vane members (such as  168  and  170 ) extend outward from the bracket (such as  148 ) each in a plane normal to the pivot axis. 
     Stated another way, the present invention preferably is a disc drive (such as  100 ) that has one or more data storage discs (such as  108 ) rotatably mounted on a spin motor (such as  106 ) fastened to a baseplate (such as  102 ) and an actuator assembly (such as  110 ) mounted adjacent the data storage disc for rotating an actuator arm (such as  114 ) over a portion of the disc. The disc drive (such as  100 ) includes a dual air vane air filter and latch apparatus (such as  140 ) having a unitary body having a pivot portion (such as  144 ) rotatably mounted in the disc drive (such as  100 ) adjacent the at least one disc (such as  108 ) on a stationary pivot pin (such as  142 ). A latch arm member (such as  146 ) extends from one side of the pivot portion (such as  144 ) toward the actuator assembly (such as  110 ) and prevents rotation of the actuator arms (such as  114 ) unless the disc is rotating at or near normal operational speed. An air filter bracket (such as  148 ) extends from another side of the pivot portion (such as  144 ) for holding an air filter in a path of wind generated by the at least one disc (such as  108 ) when the disc is rotating at a normal operating speed. An upper air vane member (such as  168 ) extends outward from the bracket (such as  148 ) which is adapted to extend over a portion of the disc (such as  108 ) and a lower air vane member (such as  170 ) extends from the bracket beneath the upper air vane member (such as  168 ) parallel to the upper air vane member (such as  168 ). The lower air vane member (such as  170 ) has a width greater than a width of the upper air vane member (such as  168 ) and the lower air vane member (such as  170 ) extends from the air filter bracket (such as  148 ) at an acute angle from the upper air vane member (such as  168 ). Further, the upper and lower air vane members (such as  168  and  170 ) are vertically spaced apart. The vane members (such as  168  and  170  extend into the path of wind generated by the rotating disc (such as  108 ) so as to exert a torque on the pivot portion (such as  144 ) as the rotating disc approaches normal operating speed, to rotate the latch member  146  out of engagement with the actuator assembly (such as  110 ). 
     The pivot portion (such as  144 ) has a through bore (such as  150 ) adapted to receive the stationary pivot pin (such as  142 ) mounted in the disc drive (such as  100 ). The through bore (such as  150 ) has a central pivot axis and the upper and lower vane members (such as  168  and  170 ) extend outward from the air filter bracket (such as  148 ) each in a plane normal to the pivot axis and the upper and lower vane members (such as  168  and  170 ) sandwich the disc (such as  108 ) between them. 
     It will be clear that the present invention is well adapted to attain the ends and advantages mentioned as well as those inherent therein. While a presently preferred embodiment has been described for purposes of this disclosure, numerous changes may be made which will readily suggest themselves to those skilled in the art. For example, as just stated above, the second air vane permits a larger ball  160  to be used. The material utilized to form the apparatus  140  may be any suitable material. The shape of the second air vane may also differ from that illustrated. These are only representative changes and various other size, shape and configuration changes may be readily apparent. Accordingly, all such modifications, changes and alternatives are encompassed in the spirit of the invention disclosed and as defined in the appended claims.