Dynamic magnetic information storage or retrieval – Head mounting – Disk record
Reexamination Certificate
1999-05-12
2001-03-06
Klimowicz, William (Department: 2652)
Dynamic magnetic information storage or retrieval
Head mounting
Disk record
Reexamination Certificate
active
06198602
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
This invention relates to disk drive suspensions and, more particularly, to components for disk drive suspensions. In disk drive suspensions, the load beam that carries the slider adjacent the disk is supported in cantilevered relation from an actuator arm that is shifted to correspondingly move the slider by way of the load beam. The load beam is attached to a mount plate that comprises a base and a boss and the mount plate is then attached to the actuator arm, frequently by staking the mounting plate boss to an opening in the actuator arm.
The invention replaces the usual staking method of attachment with split ring techniques that offers numerous advantages.
2. Related Art
Patents on mounting load beams to actuators include U.S. Pat. Nos. 4,829,395, 5,172,286, and 5,187,626. In these and similar devices the mounting plate annular boss is deliberately made undersized relative to the mating circular opening in the actuator arm but of a malleable metal so that the boss can be expanded to a friction fit with the surrounding arm opening. The arm may be one or a series of arms formed from a machined casting (i.e. an actuator arm or an E-block) to which one or more head gimbal assemblies (HGAs) are to be attached by staking or swaging. The resulting assembly is a head stack assembly (HSA). As shown in U.S. Pat. No. 4,829,395, a ball, or two, each progressively oversized relative to the inside diameter of the boss is passed through each boss within a surrounding arm opening aligned in a stack and by staking or swaging the boss outward make an interference fit between the HGA boss ODs and the ID of the hole in the actuator. With reference to
FIG. 6A
PRIOR ART the actuator arm
1
has a circular opening
2
of a predetermined diameter. Mount plate
3
has an annular boss
4
that is smaller in diameter than opening
2
and easily fits into the opening. Boss
4
has a bore
5
of a predetermined ID selected, as is the metal used, to permit deformation of the boss wall
6
into the surrounding opening
2
. Ball
7
has diameter smaller than the opening
2
but larger than the ID of the boss bore
5
. When forced through the bore
5
the ball
7
forces the boss wall radially into the inner wall
8
of the opening
2
to stake the mount plate
3
to the arm
1
. See
FIG. 6B
, PRIOR ART.
The known method of staking the HGAs inevitably results in deformation of the mount plate. The deformation results in variations in the gram load (preload) applied by the suspension to the slider both as a function of staking direction or orientation (up facing as opposed to down facing) and also randomly due to part dimensional variation. Attempts to improve this usually trade off cost, by making the parts more precise or other performance parameters. For example, the gram load change can be reduced (improved) by making a less rugged attachment, trading torque resistance for gram change.
The industry trend is, however, toward allowing ever smaller tolerances on gram load variation while simultaneously seeking ever lower cost of each piece part and assembly. Variation in gram load is to be minimized as a cost-increasing factor to the disk drive. A common practice to overcome the variation in gram load is to make an adjustment to the stack by “tweaking” the suspension after the staking step takes place. This involves extra labor and thus cost and impacts yields of the assemblies as well again increasing costs.
When an HGA has the gram load changed from the original value, the target optimization of the suspension is lost. Such optimization is a key step in the suspension fabrication process whereby the mandrel that forms the preload on the suspension is adjusted for radius and location in such a way that the harmful resonances of the suspension are minimized. Typically, this part of the fabrication set-up may take several days to accomplish, and once done is kept until the set up is broken done to make something else on that assembly line. When the suspension is adjusted from the original value in gram load without the requisite precision, including the evaluation of the resonance effects, the optimization is lost and the suspension may induce resonances in the HAS or the disk drive. In the worst case, this could result in an inoperable drive assembly that would fail before it left the disk drive manufacturer.
SUMMARY OF THE INVENTION
The industry trend is to thinner baseplate flanges, that offer the prospect of a decrease in the mass that must be accelerated when the disk drive undergoes a “seek”, that is in is moving from one track location radius to another. The ability of the HSA to accelerate from one track to another is proportional to its moment of inertia, which in turn depends on the mass being accelerated and the distance of that mass from the rotation center (the actuator bearing centerline). A thinner baseplate will, however, not be as rigid as a thicker one (by the cube of the ratio of thicknesses) and will be more easily deformed in staking operations, thus again raising the variance in gram load problems noted above.
It is an object, therefore, of the present invention to provide an alternative method of HGA attachment to the actuator in the stack build. It is a further object to provide a mounting plate-actuator arm assembly, incorporating the load beam, using a mounting plate boss larger, not smaller, than the arm circular opening, and assembling the mounting plate and arm together not by swaging or staking, but by the use of a split ring structure. The split ring structure, incorporated into the annular boss or the boss-receiving arm opening allows the interfittment of putatively noninterfitting parts by expanding or contracting depending on whether the split ring is inside or outside the assembly, and preserves their angular orientation by resiliently urging the parts into engagement as a function of the split ring slot tending to return to its preassembly larger or smaller width. It is a further object to provide a lead chamfer of the boss to facilitate insertion, and to provide a camming shoulder on the boss to increase radial forces in the assembled device.
These and other objects of the invention to become apparent, hereinafter, are realized in an assembly comprising a mounting plate having an annular boss of a predetermined outside diameter, an actuator having a circular opening of a predetermined inside diameter smaller than the boss outside diameter, at least one of the annular boss and the circular opening having a through slot allowing respectively contraction of the boss to less than actuator the circular opening or expansion of the actuator circular opening to greater than the boss outside diameter to permit their interfittment, the mounting plate boss and the actuator opening being interfitted, and a load beam attached to the mounting plate between the mounting plate and the actuator in their interfitted condition.
In this and like embodiments, typically, the boss comprises an annular wall, the through slot being formed in the boss annular wall to have its long axis parallel with the axis of revolution of the boss annular wall to facilitate compression of the boss annular wall to a diameter that interfits with the actuator circular opening, or the actuator comprises an arm defining a wall surrounding the circular opening, the through slot being formed in the wall and arm to have its long axis perpendicular to the axis of revolution of the opening surrounding wall to facilitate expansion of the circular opening to a diameter that fits over the annular boss.
In either of the foregoing embodiments, typically, the mounting plate is formed of full hard stainless steel having an Rc of 40-45, the through slot is about 0.005 inch in width and sufficiently deep to extend through the annular boss wall boss or the actuator circular opening wall, and the annular boss is champfered about its outer upper edge to facilitate entry of the boss into the circular opening.
In a specific form useful for the many presently contemplated HSA
Coon Warren
Vera Daniel
Bachand Louis J.
Klimowicz William
Magnecomp Corp.
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