BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 is a perspective view of a typical head stack assembly from the prior art.
FIG. 2 shows an illustration of a head stack assembly according to the invention.
FIG. 3
a shows a top view of the 2.5 inch head stack assembly according to the invention.
FIG. 3
b shows a cross-section of the pivot bearing assembly, according to the invention.
FIG. 3
c shows a partial cross-sectional side view of a head stack assembly according to the invention.
FIG. 4 illustrates a primary spacer used for locating and securing all other components of a head stack assembly according to the invention.
FIG. 5 shows a secondary spacer used for securing additional suspension arms according to the invention.
FIGS. 6, 7 and 8 show a top view, a side view, and bottom view, respectively, of a head arm assembly according to the invention
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT
Referring now to FIG. 2 showing an exemplary design of a 2.5 inch, or smaller, head stack assembly 50 manufactured in accordance with this invention. In the embodiment shown, the head stack assembly is designed for a disk drive with two disks. The embodiment further includes head assemblies 51a, 51b, 51c and 51d with suspensions distally carrying heads used to read and write information on both sides of these two disks. The details of the four head arm assemblies are best illustrated in FIGS. 3c and 6-8. Referring now to FIG. 3c, a stacked sequence of the above multiplicity of parts are as follows: Starting from the bottom of the head stack assembly 50, there is head arm assembly 51d, a primary spacer 53, two more head arm assemblies 51c and 51b, a secondary spacer 54 and the forth head arm assembly 51a. The lower primary spacer 53 also incorporates a coil 55, which, along with a magnetic structure mounted to the drive base-plate (not shown), is used to rotate the actuator and move the heads across the disk surfaces. The arms 51a-51d and spacers 54, 55 are slipped over a flanged bearing housing 57 containing the cylindrical ball bearings making up the pivot assembly 56 shown in a cross-sectional view in FIG. 3b. A bowed snap ring 58 is placed within a receiving groove located opposite the flanged end of the flanged bearing housing 57. The above mentioned stacked sequence of parts are fixed firmly in place by the applied clamping force provided by the bowed snap ring 58. No other fasteners are needed for the actuator assembly.
As previously mentioned, the proper application of geometrics, kinematics and semi-kinematics design principles are at the center of the present invention. Applying these principles while integrating parts serve the assembly and improves reliability of the pivoting actuator. The design principles provide the full natural tolerance and constraint balance for the assembly of parts. Parts they produce are easier to make, also, function much better as an assembly with zero-stress location.
Referring now to FIG. 4 showing the primary spacer 53, and FIG. 5 showing the secondary spacer 54 are each designed with self-fixturing features. The most critical alignment in a disk drive actuator is accurate and stable azimuth alignment of the various arms and spacers. If the alignment is not accurate the various heads will not all reach the outer and inner radii of the disk surfaces at the same time. This reduces the size of the available recording area on the disks and thereby reduces the maximum amount of data that can be stored by the disk drive. Further, if this alignment is not stable, it is possible that the drive will not be able to read back previously written data, which makes it an unacceptable condition.
In a self-fixturing design, the azimuth alignment is created and maintained by features intrinsic to the suspension arms 51a, 51b, 51c and 51d and spacers 53, 54. FIGS. 4 thru 8 illustrate the self-fixturing properties. FIGS. 4 and 5 show designs of the spacers 53 and 54 with basic self-fixturing features. Preferably, both primary and secondary spacers 53 and 54 respectively, are molded of a rigid plastic which includes, on the primary spacer 53, an over-mold feature 26 securing a motor coil element 25.
Applying geometric design and statistical process control, directs the design of the primary spacer 53 as a receiving element for which the other parts, namely, arm assemblies 51, spacer 54, and flanged bearing housing 56 cooperate. FIG. 4 shows the design of the primary spacer 53 as the central building block for the entire head stack assembly 50 in accordance with this invention. Locating pins 21, 22, 23 and 24 are essential elements in the actuator assembly. Pins 21 and 24 are positioned coaxially, one over the other, as are pins 22 and 23, as shown in FIG. 4.
In FIG. 5, the secondary spacer 54 also receives head arm assemblies. As described earlier, and illustrated in FIGS. 2 and 3c, the head stack assembly is designed for a disk drive with two disks. Four head arm assemblies 51a-51d with attached suspensions 52a-52d with attached thin-film magnetic head elements used to read and write magnetic information on both sides of these two disks. The perspective view of the head stack assembly in FIG. 2 best shows the overall design package. The assembly configuration of the four head arm assemblies and associated spacers and cartridge bearing is best illustrated in FIGS. 3c, 4 and 5. An exemplary sequence starts from the bottom of the head stack assembly 50. Firstly, head arm assembly 51d is inverted and urged onto shorter molded pins 23, 24 disposed under the primary spacer 53, shown in FIG. 4. The shorter pins are coaxially in line with the upper pins 21, 22. Secondly, arm 51c is urged, right-side up, onto the longer molded pins 21, 22 disposed on the top side of primary spacer 53. Thirdly, arm 51b is inverted and urged onto the longer molded pins 21, 22 on top of arm 51c previously assembled onto primary spacer 53. Right side-side up implies an orientation such that the slider containing the magnetic head element is on the lower face of the head arm assembly. Secondary spacer 54, refer to FIG. 5, is urged onto the upper pins 21, 22 of primary spacer 53 over the previously assembled arms 51c and 51b, therein sandwiching the two arms between spacers 53, 54 The slotted hole and squared hole (not shown in FIG. 5) disposed at the underside of secondary spacer 54 are coaxially in line with molded pins 21, 22 of primary spacer 53 and the upper and shorter molded pins 31 and 32 of secondary spacer 54. Arm 51a is placed right-side up urged onto pins 31 and 32.
In a self-fixturing design, the azimuth alignment is created and maintained by features provided on the suspension arms 51 and spacers 53, 54. Referring now to FIGS. 3a, 3c and 6-8 showing the design of the suspension arm 51. FIG. 3a illustrates a top view of the suspension arm having two square stamped alignment holes 63, and 64, and one stamped alignment slot 62 in each of the suspension arms. Only one of the square holes 63 is used in combination with the alignment slot 62. This allows a single production tool to be used for suspension arms designed for both right-side-up and inverted use. Each suspension arm 51a-51d is located in the X and Y directions by a molded pin on a spacer passing through the alignment hole in the suspension arms. The azimuth alignment of each arm relative to the spacers is controlled by a molded pin on a spacer going through the alignment slot in the suspension arm. In both of these two interfaces there is a small amount of interference between the pins and the corresponding features on the suspensions arms so that the positions of the arms are explicitly set and controlled.
During the assembly of the suspension arms, an interference between the holes in suspensions 51 and the locating pins in the primary spacer 53 and secondary spacer 54 requires a force to urge the suspension arm over the pins. In the case of a slot sliding over a pin, the force is greatly reduced because there is only contact between the pins and slot at two linear areas on opposite sides of the pins. To reduce the force required to urge the holes over the pins, square holes are used in the suspension arms instead of round holes, thereby reducing the contact to only four linear areas of contact. In FIGS. 6,7 and 8 showing a top view of a typical suspension according to the invention, a side view, and a bottom view respectively.
With this combination of geometrics and kinematics and semi-kinematics design principles, all of the suspension arms and both spacers are accurately and securely aligned to each other and the alignment is not dependant on external tooling. Moreover, because of the interference at the interfaces, the azimuth alignment of the various parts is well controlled and will not shift over time.
In summary therefore, is a rotary actuator assembly for a 2.5 inch disk drive or smaller. The disk drive having a support base and a pivot bearing assembly. The rotary actuator assembly includes a primary spacer standard having a top surface separated from a bottom surface. The primary spacer standard receives at least one suspension arm assembly standard and one secondary spacer standard. The primary spacer is designed having a semi-kinematic arrangement for controlling azimuth alignment. The primary spacer standard includes a datum hole having a pivot axis, the datum hole receives the pivot bearing assembly. A plurality of locator pins are disposed on the top surface and are coaxially aligned with locator pins on the bottom surface. The locator pins receive suspension arm assemblies and a secondary spacer. Accommodation is made for an included coil assembly.
While the invention has been particularly shown and described with reference to the preferred embodiment, it will be understood by those skilled in the art that various changes in form and details may be made without departing from the spirit and scope of the inventions.
Patent Application
20080024926
