Abstract:
A dual plane single-stage actuator is disclosed. The actuator includes a step portion between the coil and head support portions, which increases its stiffness while permitting the coil support portion and head support portion of the actuator to lie in different planes. This allows the actuator to be installed in low-profile drives.

Description:
CROSS REFERENCE TO RELATED APPLICATION  
       [0001]    This application claims the benefit of U.S. Provisional Application No. 60/312,023, filed Aug. 13, 2001. 
     
    
     
       FIELD OF THE INVENTION  
         [0002]    This invention relates generally to the field of hard disc drive data storage devices, and more particularly, but not by way of limitation, to disc drive actuators.  
         BACKGROUND OF THE INVENTION  
         [0003]    Disc drives of the type known as “Winchester” disc drives, or hard disc drives, are well known in the industry. Such disc drives magnetically record digital data on a plurality of circular, concentric data tracks on the surfaces of one or more rigid discs. The discs are typically mounted for rotation on the hub of a brushless DC spindle motor. In disc drives of the current generation, the spindle motor rotates the discs at speeds of up to 15,000 RPM.  
           [0004]    Data are recorded to and retrieved from the discs by at least one read/write head assembly, also known as a head or slider, which are controllably moved from track to track by an actuator assembly. Where more than one head are used, an array of heads are typically vertically aligned. The read/write head assemblies typically comprise an electromagnetic transducer carried on an air bearing slider. This slider acts in a cooperative pneumatic relationship with a thin layer of air dragged along by the spinning discs to fly the head assembly in a closely spaced relationship to the disc surface. In order to maintain the proper flying relationship between the head assemblies and the discs, the head assemblies are attached to and supported by flexures attached to the actuator.  
           [0005]    The actuator assembly used to move the heads from track to track has assumed many forms historically, with most disc drives of the current generation incorporating an actuator of the type referred to as a rotary voice coil actuator. A typical rotary voice coil actuator consists of a pivot shaft fixedly attached to the disc drive housing base member closely adjacent the outer diameter of the discs. The pivot shaft is mounted such that its central axis is normal to the plane of rotation of the discs. The actuator is mounted to the pivot shaft by a pivot assembly, which may take the form of precision ball bearing assemblies within a bearing housing. The actuator supports a flat coil which is suspended in the magnetic field of an array of permanent magnets, which are fixedly mounted to the disc drive housing base member.  
           [0006]    On the side of the actuator bearing housing opposite to the coil, the actuator assembly typically includes one or more vertically aligned, radially extending actuator head mounting arms, to which the head suspensions mentioned above are mounted. These actuator arms extend between the discs, where they support the head assemblies at their desired positions adjacent the disc surfaces. When controlled DC current is applied to the coil, a magnetic field is formed surrounding the coil which interacts with the magnetic field of the permanent magnets to rotate the actuator bearing housing, with the attached head suspensions and head assemblies, in accordance with the well-known Lorentz relationship. As the actuator rotates, the heads are moved generally radially across the data tracks of the discs along an arcuate path.  
           [0007]    As explained above, the actuator assembly typically includes an actuator body that pivots about a pivot mechanism disposed in a medial portion thereof. The function of the pivot mechanism is crucial in meeting performance requirements associated with the positioning of the actuator assembly. A typical pivot mechanism takes the form of a bearing cartridge having upper and lower bearings with a stationary shaft attached to an inner race and a sleeve attached to an outer race. The sleeve has typically been secured within a bore in the actuator body using a set screw, a C-clip, a tolerance ring or press-fitting, while the stationary shaft typically is attached to both the base deck and the top cover of the disc drive. It has also been contemplated that the bearing cartridge could itself be fixed to the base, while the actuator is attached to the pivot shaft which is free to rotate within the pivot cartridge housing, especially in the case of single stage actuators as will now be explained.  
           [0008]    Recently, advances in storage technology have greatly increased the data storage capacity of magnetic storage discs. As a result, a single storage disc is now capable of storing large amounts of data which would have required a stack of several discs in the past. Some drive manufacturers have begun to produce disc drives having fewer discs, and even a single disc, as often a single disc may have storage capacity sufficient for a given application. In addition to the obvious cost advantages gained by using only one disc, one advantage to providing only one disc is that the actuator must carry only one or at most two heads. Such an actuator may have only one arm and therefore have a rotational inertia much smaller than that of conventional actuators with multiple arms. Moreover, an actuator with only one arm may be produced from a single planar sheet of material, supporting a coil at one end and a head suspension at another. This type of actuator may be more easily manufactured than conventional actuators, such as by stamping, and is further advantageous in that it has relatively low inertia, allowing faster seek acceleration and deceleration. On the other hand, a planar element is susceptible to vibration in the first bending mode, in which the member may bend in a direction perpendicular the plane in which it lies, giving it a relatively low resonant frequency, increasing read-write errors while decreasing drive reliability, often culminating in drive failure.  
           [0009]    Drives having only one disc and one actuator arm also offer the opportunity to produce low-profile disc drives having a reduced height. In the past, disc drives were typically used for storage of data in personal computers and in storage arrays for storing huge amounts of data in enterprise applications. Presently, however, drives are being contemplated for use in a wide variety of consumer products, such as television set-top video recorders, video game consoles, and hand-held computers. These applications present a new set of challenges to the drive industry, requiring that drives be more quiet and smaller than ever before. In particular, there is a need to produce drives having a height which is decreased relative to that of conventional drives to enable use in hand-held and card-type applications.  
           [0010]    As drive housings become smaller, however, space availability in the housing has decreased, especially in the vertical direction. Actuator pivot assemblies occupy vertical space, as do voice coil poles and magnets, and spindle motor and hub designs often limit the height at which a disc can be mounted. Often design requirements dictate the disc, magnets and actuator pivot be arranged such that a planar actuator is not capable of being properly aligned with both the disc and VCM.  
           [0011]    What the prior art has been lacking is a planar actuator with increased bandwidth and the ability to fit into increasingly low-profile disc drives.  
         SUMMARY OF THE INVENTION  
         [0012]    The present invention is directed to a dual plane single-stage actuator. The actuator includes a step portion between the coil and head support portions, which increases its stiffness while permitting the coil support portion and head support portion of the actuator to lie in different planes. This allows the actuator to be installed in low-profile drives.  
           [0013]    These and other features and benefits will become apparent upon review of the following figures and the accompanying detailed description.  
       
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0014]    [0014]FIG. 1 shows a plan view of a disc drive incorporating one embodiment of the actuator of the present invention.  
         [0015]    [0015]FIG. 2 shows a plan view of a one embodiment of an actuator of the present invention.  
         [0016]    [0016]FIG. 3 shows a cross-sectional partial view of a disc drive incorporating one embodiment of the actuator of the present invention.  
         [0017]    [0017]FIG. 4 shows a cross-sectional partial view of a disc drive incorporating another embodiment of an actuator of the present invention. 
     
    
     DETAILED DESCRIPTION OF THE INVENTION  
       [0018]    Turning now to the drawings and specifically to FIG. 1, shown is an exploded view of one example of a disc drive  100  in which the present invention is particularly useful. The disc drive  100  includes a deck  110  to which all other components are directly or indirectly mounted and a top cover  120  which, together with the deck  110 , forms a disc drive housing which encloses delicate internal components and isolates these components from external contaminants.  
         [0019]    The disc drive  100  includes at least one disc  200  which is mounted for rotation on a spindle motor (not shown). The disc or discs  200  include on their surfaces a plurality of circular, concentric data tracks on which data are recorded one or more vertically aligned head assemblies  310 . The head assemblies  310  are supported by flexures  320 , which are attached to arms  325  of actuator  300 . The actuator  300  is mounted to a bearing assembly  400  about which the actuator  300  rotates.  
         [0020]    Power to drive the actuator  300  about the pivot assembly  400  is provided by a voice coil motor (VCM). The VCM includes a coil  330  which is supported by the actuator  300  within the magnetic field of a permanent magnet assembly having spaced upper and lower magnets, the lower of which is illustrated at  340 . Electronic circuitry is provided on a printed circuit board (PCB, not shown) mounted to the underside of the deck  110 . Control signals to drive the VCM are carried between the PCB and the moving actuator  300  via a flexible printed circuit cable (PCC)  370 , which also transmits data signals to and from the heads  330 .  
         [0021]    [0021]FIG. 2 shows a perspective view from beneath one embodiment of an actuator  300  of the present invention. The actuator  300  includes an aperture  380  for mounting to an actuator pivot assembly  400 , as will be explained later. The actuator  300  also has a single arm  325  which is configured to support a read/write head  310  by way of a load beam or flexure  320  at its distal end. Also shown is a coil support portion  335  in which the coil  330  is mounted as part of the VCM which effects rotational movement of the actuator  300 . The arm  325  and coil support portion  335  are separated by a “step” portion  305  which serves a number of different functions.  
         [0022]    One advantage provided by step portion  305  relates to use of space within the drive housing. As drives have become smaller, space requirements within the housing have become more constrained. For example, a conventional spindle motor has a minimum height, such that the surface of a disc mounted upon the spindle motor also has a minimum height at which it may be mounted within the housing. similarly, voice coil magnets  340  and pole pieces  350  have thicknesses and must be spaced within the drive  100 . Where overall drive height is to be minimized, it is often difficult to vertically align the areas to be occupied by the coil support portion  335  of the actuator  300  and the actuator arm  325 . This is especially true when spindle motors and VCM assemblies are imported into a new drive design in an effort to reduce redesign costs.  
         [0023]    [0023]FIG. 3 shows a cross-sectional view of the actuator  300  of FIG. 2 mounted within a drive in which the spaces allocated for the coil support  335  and actuator arm  325  are not horizontally aligned. It can be clearly seen that in this instance, the voice coil magnets  340  and pole pieces  350  chosen restrict the vertical position of the coil  330 . Moreover, it would be impossible to lower the disc  200  enough to allow the arm  320  of an actuator  300  lying in a single plane to be positioned above the disc  200 . In this embodiment of the present invention, however, actuator  300  in fact lies in two planes. The coil support portion  335  lies at a first elevation, allowing the coil to be positioned between voice coil magnets  340 , while actuator arm  325  is positioned at a higher level, allowing it to pass above the upper surface of disc  200 .  
         [0024]    Another advantage provided by step feature  305  is higher stiffness. A simple planar actuator is relatively stiff in a horizontal direction, meaning it has high resonant frequencies in the system mode. However, a planar actuator is susceptible to out of plane vibrations, leading to a relative low resonant frequency in the bending modes. This is especially true where pivot mounting opening  380  is large enough to accommodate an entire pivot cartridge as in embodiment of FIG. 2. It can be seen in FIG. 2 that step portion  305  may be configured as a curved vertical surface, and may even partially surround the aperture  380  serving to stiffen the actuator  300  in the vertical direction.  
         [0025]    The dual-plane actuator  300  may be formed by any of a number of methods and materials. It has been found that stamping the actuator  300  out of a metallic sheet material is a particularly effective method. However, it is also contemplated that the actuator  300  could be injection molded of a plastic material, or formed of a number of parts without departing from the spirit of the invention.  
         [0026]    It should also be understood that FIGS. 2 and 3 represent only one embodiment of a multi-plane actuator. For example, the coil support portion  335  could be higher than the actuator arm  325 . As another example, the step portion  305  could be located closer on the other side of aperture  380 , nearer the actuator arm  325  than the coil support  335 .  
         [0027]    It is even contemplated that the actuator  300  could lie in more than two planes. FIG. 4 illustrates one embodiment of a disc drive in which the actuator  300  is mounted atop a pivot cartridge  410  via a threaded element and a small aperture  385  in the actuator  300 . In this embodiment, the actuator  300  is provided with two step portions  306 , 307  which allow the coil support portion  335 , the actuator arm  325  and the actuator pivot portion  385  to be located at three different elevations. In addition, the addition of a second step portion would further stiffen the actuator  300  in the area about the pivot portion  385  near the actuator arm  325 .  
         [0028]    Alternatively stated, a first contemplated embodiment of the invention takes the form of an actuator (such as  300 ) for use in a disc drive (such as  100 ), including a coil support portion (such as  335 ) configured to support a coil (such as  330 ) and generally defining a first plane, and a single arm portion (such as  325 ) configured to support a head suspension assembly (such as  320 ) and generally defining a second plane, the first plane being distinct from the first plane. The first plane may be parallel to the second plane. The coil support portion (such as  335 ) and the arm portion (such as  325 ) may be integrally formed. The actuator (such as  300 ) may also include a step portion (such as  305 ) lying between the coil support portion (such as  335 ) and the arm portion (such as  325 ). The step portion (such as  305 ) may be curved. Optionally, the step portion (such as  305 ) may be connected to the coil support portion (such as  335 ). The coil support portion (such as  335 ), the arm portion (such as  325 ) and the step portion (such as  305 ) may be integrally formed. Optionally, the actuator (such as  300 ) may be formed by stamping. The first plane may be horizontal and the step portion may extend vertically.  
         [0029]    Alternately stated, a second contemplated embodiment of the invention takes the form of a disc drive (such as  100 ) including a base (such as  110 ) and an actuator (such as  300 ) rotatably mounted to the base (such as  110 ). The actuator (such as  300 ) includes a coil support portion (such as  335 ) positioned at a first height above the base (such as  110 ) and a single arm support portion (such as  325 ) positioned at a second height above the base (such as  110 ). The second height is different than the first height. The coil support portion (such as  335 ) may be configured to support a coil (such as  330 ). The arm portion (such as  325 ) may be configured to support a head suspension assembly (such as  320 ). The coil support portion (such as  335 ) may be generally planar. The arm portion (such as  325 ) my be generally planar. Optionally, the actuator (such as  300 ) may be formed by stamping.  
         [0030]    In short, it is apparent that the present invention is particularly suited to provide the benefits described above. While particular embodiments of the invention have been described herein, modifications to the embodiments which fall within the envisioned scope of the invention may suggest themselves to one of skill in the art who reads this disclosure.