Dynamic magnetic information storage or retrieval – Head mounting – Disk record
Reexamination Certificate
1998-08-06
2002-07-23
Klimowicz, William (Department: 2652)
Dynamic magnetic information storage or retrieval
Head mounting
Disk record
Reexamination Certificate
active
06424497
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
This invention has to do with disk drive suspensions, and more particularly with improvements in the mounting of load beams to actuator arms in the production of disk drive suspensions and head stack assemblies of such suspensions.
2. Related Art
Workers in the art have designed novel mounting plates for specific purposes. See U.S. Pat. No. 4,829,395 to Coon et al, and U.S. Pat. No. 5,187,626 to Hopkins et al. In U.S. Pat. No. 5,689,389 to Braunhelm a low profile mounting plate is disclosed having as a critical feature a ratio of the mounting plate bore diameter being at least 85% of the mounting plate flange opening diameter. The Braunhelm device is illustrated in
FIG. 4
of the attached drawings. It will be noted that Braunheim teaches a mounting plate P having a planar flange F and an annular boss B with a center bore CB having a opening R surrounded by a wall C. Bore CB has a very substantial shoulder S marking the transition from flange opening Q to the bore CB. The bore wall C is deflected into the surrounding actuator arm AA staking hole H by driving the staking ball L through the bore. Braunhelm's teaching of an 85% ratio of boss bore CB to flange opening Q leaves the shoulder S to be engaged by the staking ball L in a manner that imparts large axial forces on the mounting plate P. In fact only radial forces are desired, not axial forces since axial forces tend to bend the flange F from its intended planarity causing changes in gram force loads exerted by the load beam LB held between the flange F and the actuator arm AA. Moreover, the effect tends to vary with the direction of the axial force. The compression force direction (shown in
FIG. 5
) produces a small significant loss in gram load but typically considerably less than the loss effected from a tension force resultant from driving the ball L in the opposite the direction of the illustration in FIG.
5
. Since the typical actuator arm has an upper and lower suspension, there is no choice but to drive the staking ball in both compression and tension in swaging two mounting plates on a common actuator arm. The ratio of boss bore to flange opening taught by Braunhelm at 85% is far too low. While Braunhelm places no upper limit on this ratio it is evident that he contemplates maintaining a substantial shoulder S, and this dictates a ratio of about 85% and certainly not as much as 90%.
SUMMARY OF THE INVENTION
The present invention seeks to substantially eliminate the shoulder between the flange opening and the boss bore, and to make other improvements in the design of a mounting plate. To do so, the invention increases the boss bore diameter to a value ensuring radial engagement forces upon staking, but minimizing axial engagement forces. In addition the flange opening is minimized to just a slip fit clearance for the staking ball or tool. This ensures the correct path for the staking ball into the boss bore. The arrangement further permits the staking fixture to support the flange closer to the boss bore, assisting in maintaining the flange uncrowned up or down by axial forces on the boss.
As mentioned, a source of unpredictable performance deviation in disk drive suspensions is the sometime discrepancy introduced by changes in the gram load exerted by the load beam as a result of distortion of the mounting plate occurring as the mounting plate carrying the load beam is staked to the actuator. The mounting plate has a substantially planar, flat flange portion and normal thereto a boss portion comprising an annular wall centered on a small diameter bore. The suspension load beam is affixed to the plate flange portion; the suspension actuator is engaged with the plate bore portion within the actuator staking hole by the staking operation. In the staking operation, a staking tool, such as a staking ball, is forced through the bore of the mounting plate boss portion to force the boss portion to engage the surrounding wall of the actuator staking hole. Uniformity of result is not always realized even with standardized operation. Among the most vexing deviations from the norm are the dissimilar changes in gram loading from an intended standard to some other value, different for the load beam on one side of the actuator arm from those for the load beam on the other side of the load beam. These variations divergent changes vary with the direction of the staking ball through the mounting plate bore. Since it is not predictable in which direction it will be necessary to drive the staking tool, unpredictable effects visit suspension assembly construction, lowering yield, increasing costs, and preventing the obtaining of maximum performance consistently.
The invention utilizes an improved mounting plate structure to minimize variations in the load beam gram load values in the produced suspensions. The invention makes more uniform and more predictable the effects on gram load of staking the mounting plate and its load beam to the actuator arm. Suspensions having upper and lower load beams on a common actuator arm are typically staked with a common staking tool traveling in a single up or down direction. Staked suspensions have been prone to variations in gram load changes in the upper and lower suspensions dependent on the direction of the staking tool; these variations are minimized by the invention mounting system. The new mounting plate structure features a novel boss bore design of relatively increased diameter to have a smaller radial displacement and thus less resistance to axial travel of the staking tool. Additionally the invention greatly reduces the flange opening leading to the boss bore e.g. to a slip fit size relative to the staking tool, to lessen the size difference between the flange opening and the boss bore. The combination of increased bore size and reduced flange opening size substantially eliminates the annular shoulder between the flange opening and the boss bore. The substantial absence of this annular shoulder reduces the axial impact when the staking tool is driven through the mounting plate, as there is less physical obstruction projecting radially in the path of the staking tool, while the boss bore remains slightly undersized for tool passage so that the bore wall is deflected radially outward into actuator arm engagement. The minimally differentiated (from the flange opening) boss bore diameter is maintained substantially uniform throughout the length of the mounting plate bore, the bore length being increased as necessary to provide useful level of static force between the actuator arm staking hole and the mounting plate boss portion to control the load beam during movement of the actuator arm. The reduced flange opening enables closer support of the mounting plate flange by the staking fixture during staking and this too blocks unwanted distortion of the plate flange and limits further unwanted gram load changes in the suspension from the staking operation, particularly gram load variations between upper and lower suspensions on a common actuator arm.
Study of the results of many staking operations, in either direction, reveals that the mounting plate flange is distorted by an axial shift of the mounting plate boss toward or away from the mounting plate flange depending on the direction of the staking tool. This axial shift is an unwanted addition to the radial displacement of the bore wall being sought, but appears necessary if adequate force of engagement between the actuator hole wall and the mounting plate boss, e.g., an engagement force at a minimum, expressed as static locking torque, of 4-5 inch ounces of torque, is to be obtained.
It is accordingly an object of the invention to provide a novel disk drive suspension, and more particularly a disk drive suspension mounting plate which offers the requisite static locking torque for successfully engaging the actuator while carrying the load beam of the disk drive suspension, but avoids unwanted axial shifting causing distortion of the plate flange from its planarity. A further object
Bachand Louis J.
Klimowicz William
Magnecomp-Corp
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