Abstract:
An apparatus for use in attaching a head gimbal assembly (HGA) onto an actuator arm of an actuator assembly during an HGA installation process. The apparatus includes, a central body portion with a base support surface; and a pair of support arms extending from the central body portion forming a channel sized to accommodate expansion of an attachment aperture of an actuator arm during the installation process. Each support arm includes, a first and second support surface offset from and parallel to the base support surface. A first support arm thickness is formed between the first support surface and the base support surface, while a second support arm thickness is formed between the second support surface and the base support having a thickness less than the first support arm thickness. Each support arm thickness supports a corresponding HGA adjacent actuator arm during the installation process.

Description:
RELATED APPLICATIONS 
     This application claims the benefit of U.S. Provisional Application No. 60/357,758 entitled HGA COMPRESSION-INSTALL SPACER KEY filed Feb. 19, 2002. 
    
    
     FIELD OF THE INVENTION 
     The claimed invention relates generally to disc drive data storage devices and more particularly, but without limitation, to the attachment of a disc drive head gimbal assembly (HGA) to a rigid actuator arm. 
     BACKGROUND 
     Disc drives are digital data storage devices which store and retrieve large amounts of user data in a fast and efficient manner. The data are magnetically recorded on the surfaces of one or more rigid data storage discs affixed to a spindle motor for rotation at a constant high speed. The discs and spindle motor are commonly referred to as a disc stack. 
     The disc stack is accessed by an array of aligned data transducing heads which are controllably positioned by an actuator assembly. Each head typically includes electromagnetic transducer read and write elements which are carried on an air bearing slider. The slider acts in a cooperative hydrodynamic relationship with a thin layer of air dragged along by the spinning discs to fly each head in a closely spaced relationship to the disc surface. 
     A typical actuator assembly includes a central body which pivots about an actuator axis adjacent the outermost diameter of the disc stack. Rigid actuator arms project from the central body into the disc stack, and flexible suspension assemblies (flexures) project from the ends of the actuator arms to support the heads. 
     The flexures bias the heads toward the disc surfaces and include gimbal features that allow the heads to rotate about three axes (pitch, yaw and roll). Each set of heads, gimbals and flexures is referred to as a head gimbal assembly (HGA). The HGAs are affixed to the ends of the actuator arms using any number of suitable processes including swaging, adhesive, compression (with split actuator arms), etc. 
     An actuator coil of a voice coil motor (VCM) projects from the central body substantially opposite the actuator arms and is immersed in a magnetic field of the VCM. Application of current to the coil causes the actuator to pivot about the actuator axis and move the heads across the disc surfaces. A servo control circuit uses embedded servo data written to the discs to detect head position and generate the requisite coil current to adjust the positions of the heads as desired during operation. 
     One common prior art approach to writing servo data has involved installing the discs into a disc drive and using a servo track writer (STW) to write the servo data to the discs. Current generations of disc drives are increasingly using multiple disc writer (MDW) stations to write the servo data to the discs at a production facility prior to installation of the discs into the drives. 
     An MDW station operates similarly to a disc drive but makes use of several actuator assemblies and several discs to achieve increased production efficiencies. An MDW station can also write the servo data in a gaseous environment having a lower density than ambient air (such as helium) in order to achieve higher yields and/or faster throughput. A typical MDW of the current generation has a capacity on the order of around 10-15 discs. As with disc drives, MDW stations use actuator assemblies with actuator arms and HGAs to write the servo data to the discs. 
     Specially configured tooling is typically used to install an HGA onto an actuator arm (whether for a disc drive actuator or an MDW actuator). To support the HGA during installation, a support element (spacer key) fits against a base plate of the HGA while the HGA is being attached to the actuator arm. 
     A presently utilized spacer key configuration has a “compression-slit” design. For this design, the spacer key is essentially a beam with a longitudinal slit along a length of the beam, dividing the beam into an upper section and a lower section. The size of the slit in the spacer key is selected so that the upper and lower sections can be slightly deflected one toward another. 
     The purpose of the compression-slit design is to account for a difference in a size of a gap between two opposed actuator arms. A first gap size exists when installing a first HGA to the first actuator arm. A second gap size exists when attaching a second HGA to the opposed second actuator arm because the second gap size will differ from the first gap size by a thickness of the HGA. 
     Problems have arisen with the use of the spacer key of the compression-slit design. As a compromise between two gap sizes, the spacer key typically does not quite fit either gap size properly and thus fails to completely bias the HGAs flush with either actuator arm. Also, after many uses, the spacer key can lose elasticity and thus does not return to the original spacing size. 
     Thus, the spacer key does not provide full contact with a baseplate of the HGA, which causes the HGAs to be skewed with respect to the actuator arms. This in turn causes relatively large differences to occur in the actuator arm spacing. As a result, the HGAs are not seated flush against the actuator arms and can loosen or become detached during subsequent use. 
     Although spacer keys of the existing art have been found operable, there remains a continued need in the art for improved configurations that overcome these and other limitations of the existing art. 
     SUMMARY OF THE INVENTION 
     The present invention (as embodied herein and as claimed below) is generally directed to an apparatus and method for installing a head gimbal assembly (HGA) onto an actuator arm of an actuator assembly. 
     In accordance with preferred embodiments, a spacer key is provided comprising a support arm having a base support surface and adjacent first and second support surfaces opposite the base support surface. 
     The support arm has a first thickness from the first support surface to the base support surface and a second thickness from the second support surface to the base support surface. The second thickness is greater than the first thickness by a distance nominally equal to a thickness of an HGA base plate. 
     In this way, a selected one of the first and second support surfaces contactingly biases the HGA against an actuator arm while the base support surface contactingly biases a second member adjacent the actuator arm. Preferably, the second member comprises a second actuator arm. 
     The support arm further preferably comprises a radiused shoulder portion between the first and second support surfaces. The spacer key further preferably comprises a central body portion from which the support arm extends, and a handle which projects from the central body portion to facilitate positioning of the spacer key with respect to the actuator arm. 
     A number of HGAs are preferably installed onto corresponding actuator arms by placing a first HGA onto a first actuator arm; inserting the spacer key between the first HGA and a second member adjacent the first actuator arm so that the second support surface contactingly biases the first HGA against the first actuator arm and so that the base surface contactingly biases the second member; and attaching the first HGA to the first actuator arm. 
     As before, the second member preferably comprises a second actuator arm and the method further preferably comprises retracting the spacer key and placing a second HGA onto the second actuator arm in a facing relationship to the first HGA; inserting the spacer key between the first and second HGAs so that the first support surface contactingly biases the first HGA against the first actuator arm and so that the base surface contactingly biases the second HGA against the second actuator arm; and attaching the second HGA to the second actuator arm. 
     Preferably, each HGA comprises a base plate from which an attachment boss extends and each actuator arm comprises an attachment aperture. Each HGA is thus attached to an actuator arm by applying a force to expand the attachment aperture; inserting the attachment boss into the expanded attachment aperture; and releasing the applied force to cause an inner wall of the HGA attachment aperture to grip the HGA boss and thereby secure the base plate to the actuator arm. 
     These and various other features and advantages which characterize the claimed invention will become apparent upon reading the following detailed description and upon reviewing the associated drawings. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a top plan view of a disc drive constructed in accordance with preferred embodiments of the present invention, the disc drive including a number of rotatable discs and an actuator assembly which supports a number of head gimbal assemblies (HGAs). 
         FIG. 2  is an isometric view of an actuator assembly of a multiple disc writer (MDW) station used to write servo data to the discs of the disc drive of FIG.  1 . 
         FIG. 3  is an isometric view of a head gimbal assembly (HGA) of the MDW actuator assembly of FIG.  2 . 
         FIG. 4  is an isometric view of a support element (spacer key) operably configured to support the HGA of  FIG. 2  during installation onto the MDW station actuator assembly of FIG.  3 . The spacer key can also be used to support the HGAs of  FIG. 1  during installation onto the disc drive actuator assembly of  FIG. 1 , as desired. 
         FIG. 5  provides a top plan view of the spacer key of FIG.  4 . 
         FIG. 6  provides a side elevational, partial cross-sectional view to generally illustrate use of the spacer key of  FIG. 4  to support the installation of a first HGA between adjacent actuator arms. 
         FIG. 7  provides a side elevational, partial cross-sectional view to generally illustrate use of the spacer key of  FIG. 4  to support the installation of a second HGA between the actuator arms of FIG.  6 . 
         FIG. 8  is an HGA INSTALLATION routine generally illustrative of steps carried out in accordance with preferred embodiments to install HGAs using the spacer key of FIG.  4 . 
     
    
    
     DETAILED DESCRIPTION 
       FIG. 1  provides a top plan view of disc drive data storage device  100  constructed in accordance with preferred embodiments. A base deck  102  and a top cover  104  (shown in partial cutaway) cooperate to form a sealed housing for the disc drive  100 . 
     A spindle motor  106  is mounted to the base deck  102  within the housing and supports a number of rigid data storage discs  108  for rotation at a constant speed. An actuator assembly  110  is mounted to the base deck  102  adjacent the discs  108 . The actuator assembly  110  includes a central body  112  configured for rotation about an actuator axis by a cartridge bearing assembly  114 . 
     Rigid actuator arms  116  project from the central body  114  toward the discs  108  and support head gimbal assemblies (HGAs)  118  comprising flexible suspension assemblies (flexures)  120  and data transducing heads  122 . The HGAs  118  enable the heads  122  to be supported over the disc surfaces by air currents established by disc rotation. 
     An actuator coil  124  projects from the central body  112  opposite the actuator arms  116  and is immersed in a magnetic field of a voice coil motor (VCM)  125 . Application of current to the coil  124  causes the coil  124  to move within the magnetic field, inducing rotation of the central body  112  about the actuator axis and movement of the heads  122  across the disc surfaces. 
     For reference, a magnetic toggle latch  126  secures the actuator assembly  110  in a parked position when the disc drive is deactivated, and a flex circuit assembly  128  provides electrical communication paths between the actuator assembly  110  and disc drive electronics mounted to a printed circuit board (PCB) mounted to the underside of the base deck  102 . 
     A servo control circuit (not shown) of the disc drive  100  uses embedded servo data written to the discs  108  in order to control the position of the heads  120  during operation. The servo data are preferably written to the discs using a multiple disc writer (MDW) station which concurrently writes the servo data to a relatively large population (e.g., 10-15) of the discs  108 . Once the servo data are written, the appropriate number of discs  108  for the disc drive  100  (e.g., 2-3) are selected and installed into the disc drive  100 . 
     The MDW station employs one or more MDW actuator assemblies  130 , such as shown in FIG.  2 . The MDW actuator assembly  130  is generally similar to the disc drive actuator assembly  110  of FIG.  1  and includes a central body portion  132 , rigid actuator arms  134  and MDW head gimbal assemblies (HGAs)  136 . A representative MDW HGA  36  is shown in greater detail in FIG.  3 . 
     The MDW HGA  136  includes a rigid base plate  138 , a flexible suspension assembly (flexure)  140 , a gimbal portion  142  and a data transducing head  144 . A ramp load tab  146  allows the HGA  136  to be offloaded onto a ramp structure (not shown) during nonoperation. Flex on suspension (FOS) conductors  148  are routed as shown to provide electrical communication paths with the head  144 . 
     A substantially cylindrically shaped HGA boss  150  extends from the base plate  138 . The boss  150  has an outside diameter slightly larger than a diameter of an HGA attachment aperture  152  of the MDW actuator arm  134  (FIG.  2 ). 
     The split construction of the MDW actuator arm  134  allows expansion of the HGA attachment aperture  152  to receive the boss  150 , after which the aperture  152  is released to compressingly engage the boss  150  and secure the HGA  136  to the actuator arm  134 . While a split construction attachment methodology is preferred, it will be apparent that other attachment methodologies can readily be employed depending upon the requirements of a given application. 
       FIG. 4  shows an isometric view of a support element (spacer key)  160  constructed and used in accordance with preferred embodiments of the present invention to support the MDW HGAs  136  during installation onto the MDW actuator arms  134 . It will be recognized, however, that the spacer key  160  can also be used to attach the disc drive HGAs  118  onto the disc drive actuator arms  116 , as desired during assembly of the disc drive actuator assembly  110 . 
     The spacer key  160  includes a central body portion  162 , a handle portion  164  and a blade portion  166 . The handle portion  164  affixes to a positioning shuttle (not shown) for automatic or manual positioning of the spacer key  160 . The body portion  162  preferably includes a small detent  168  that indicates and maintains a position of the spacer key with respect to the positioning shuttle. 
     The blade portion  166  includes parallel cantilevered support arms  170  that form a u-shaped channel  172  to provide clearance and alignment during HGA installation for passage of an HGA attachment tooling, such as a swage tool (not shown), between the support arms  170 . 
     As further shown in a top plan view of FIG.  5  and side elevational views of  FIGS. 6-7 , the support arms  170  each include a first support surface  174 , a second support surface  176  and a base support surface  178 . The first and second support surfaces  174 ,  176  extend along the top of each support arm  170  and the base support surface  178  extends along the bottom of each support arm  170 . The respective first, second and support surfaces  174 ,  176  and  178  are preferably planar and parallel one with respect to another. 
     As best shown in  FIGS. 6-7 , the first support surface  174  and the base support surface  178  are oriented to provide a first thickness T 1  of each support arm  170 . The second support surface  176  and the base support surface  178  provide a second thickness T 2  greater than the first thickness. A radiused shoulder  180  provides a smooth transition between the first and second support surfaces  174 ,  176 . 
     Each support arm  170  further preferably includes a tapered leading surface  182  with a radiused shoulder  184  between the leading surface  182  and the first surface  174 , and a trailing surface  186  with another radiused shoulder  188  between the trailing surface  186  and the second support surface  176 . Although a thickness T 3  of the support arm  170  between the trailing surface  176  is shown in  FIGS. 6-7  to be slightly less than the thickness T 2 , in an alternative preferred embodiment the thickness T 3  can be readily configured to be greater than the thickness T 2 , as desired. 
     The thickness T 1  is preferably selected to be nominally equal to the distance between two adjacent actuator arms  134  with two interposing HGA base plates  138  (see FIG.  7 ). The thickness T 2  is similarly preferably selected to be nominally equal to the distance between two adjacent actuator arms  134  with one interposing HGA base plate  138  (see FIG.  6 ). In this way, the difference between thicknesses T 1  and T 2  is selected to be nominally equal to the thickness of a single HGA base plate  138 . 
       FIG. 8  provides a flow chart for an HGA INSTALLATION routine  200 , generally illustrative of steps carried out in accordance with preferred embodiments to install an HGA (such as the MDW HGA  136 ) onto an actuator arm (such as the MDW actuator arm  134 ) using the spacer key  160 . 
     The desired actuator arms  134  and HGAs  136  are provided at step  202 , and a first HGA  136  is placed onto the first actuator arm  134  at step  204 . 
     The spacer key  160  is inserted at step  206  to bias the base plate  138  of the first HGA  136  against the first actuator arm  134 . This is preferably carried out as shown in  FIG. 6  so that the second surface  176  abuts the base plate  138  and the base surface  178  abuts an adjacent, second actuator arm  134 . The first HGA  134  is then attached to the first actuator arm  134  at step  208  while the spacer key  160  maintains pressing support and alignment of the first HGA  136 . The spacer key  160  is then withdrawn. 
     The flow of  FIG. 8  continues to step  210  wherein a second HGA  136  is placed adjacent the second actuator arm  134 , and the spacer key  160  is again inserted at step  212  to bias the base plate  138  of the second HGA  136  against the second actuator arm  134 . This is preferably carried out as shown by FIG.  7 . The second HGA  136  is affixed to the second actuator arm  134  at step  214 . Although the routine is shown to then end at step  216 , it will be understood that the foregoing steps are repeated as required until all of the HGAs are installed onto associated actuator arms. 
     It will be noted that, based on the configurations of the disc drive actuator assembly  110  and the MDW actuator assembly  130 , HGAs (such as  118 ,  136 ) will be typically installed in locations that are between adjacent actuator arms (such as arms  116 ,  134 ). However, the spacer key  160  can likewise be used as desired to install an HGA onto an actuator arm without an adjacent actuator arm (such as, for example, in situations where a single actuator arm is used or where actuator arms are subsequently stacked after HGA installation). 
     In this case the thicknesses T 1  and T 2  can still readily be advantageously used to properly register the HGA, even if the base surface  178  abuts a second member (such as a precisely located control surface, a base deck, etc.) rather than another actuator arm or HGA base plate. 
     It will now be understood that the present invention is generally directed to an apparatus and method for installing a head gimbal assembly (HGA) onto an actuator arm of an actuator assembly. 
     In accordance with preferred embodiments, a spacer key (such as  160 ) is provided comprising a support arm (such as  170 ) having a base support surface (such as  178 ) and adjacent first and second support surfaces (such as  174 ,  176 ) opposite the base support surface. 
     The support arm has a first thickness (such as T 1 ) from the first support surface to the base support surface and a second thickness (such as T 2 ) from the second support surface to the base support surface. The second thickness is greater than the first thickness by a distance nominally equal to a thickness of an HGA (such as  118 ,  136 ). 
     In this way, a selected one of the first and second support surfaces contactingly biases the HGA against an actuator arm (such as  116 ,  134 ) while the base support surface contactingly biases a second member adjacent the actuator arm. Preferably, the second member comprises a second actuator arm. 
     The support arm further preferably comprises a radiused shoulder portion (such as  180 ) between the first and second support surfaces. The spacer key further preferably comprises a central body portion (such as  162 ) from which the support arm extends, and a handle (such as  164 ) which projects from the central body portion to facilitate positioning of the spacer key with respect to the actuator arm. 
     A number of HGAs are preferably installed onto corresponding actuator arms by placing a first HGA onto a first actuator arm (such as by step  204 ); inserting the spacer key between the first HGA and a second member adjacent the first actuator arm so that the second support surface contactingly biases the first HGA against the first actuator arm and so that the base surface contactingly biases the second member (such as by step  206 ); and attaching the first HGA to the first actuator arm (such as by step  208 ). 
     As before, the second member preferably comprises a second actuator arm and the method further preferably comprises retracting the spacer key and placing a second HGA onto the second actuator arm in a facing relationship to the first HGA (such as by step  210 ); inserting the spacer key between the first and second HGAs so that the first support surface contactingly biases the first HGA against the first actuator arm and so that the base surface contactinly biases the second HGA against the second actuator arm (such as by step  212 ); and attaching the second HGA to the second actuator arm (such as by step  214 ). 
     Preferably, the first HGA comprises a base plate (such as  138 ) from which an attachment boss (such as  150 ) extends, wherein the first actuator arm comprises an attachment aperture (such as  152 ), and wherein the step of attaching the first HGA to the first actuator arm comprises applying a force to expand the attachment aperture; inserting the attachment boss into the expanded attachment aperture; and releasing the applied force to cause an inner wall of the first HGA attachment aperture to grip the first HGA boss and thereby secure the base plate to the first actuator arm. 
     It is to be understood that even though numerous characteristics and advantages of various embodiments of the present invention have been set forth in the foregoing description, together with details of the structure and function of various embodiments of the invention, this detailed description is illustrative only, and changes may be made in detail, especially in matters of structure and arrangements of parts within the principles of the present invention to the full extent indicated by the broad general meaning of the terms in which the appended claims are expressed. For example, the particular elements may vary depending on the particular application of the spacer key without departing from the spirit and scope of the present invention. 
     In addition, although the embodiments described herein are directed to a spacer key used to affix an HGA onto an actuator arm for a disc drive or MDW station, it will be appreciated by those skilled in the art that the spacer key can be used in other applications including other types of data storage devices without departing from the spirit and scope of the claimed invention.