Dynamic magnetic information storage or retrieval – Head mounting – Disk record
Reexamination Certificate
1999-07-27
2001-04-10
Evans, Jefferson (Department: 2652)
Dynamic magnetic information storage or retrieval
Head mounting
Disk record
Reexamination Certificate
active
06215624
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
This invention relates to disk drive suspensions, and more particularly to improvements in the mounting plates used to secure load beams to actuator arms. In the invention, positive coupling is obtained between the mounting plate and the actuator arms by defining cooperating locking structure on the respective components. The mounting plate thus does not rely merely on radial forces between the mounting plate boss and the actuator arm bore opening to engage the mounting plate and arm, as is conventional, but uses added structure to better ensure that there is no slippage between the arm and the load beam.
2. Related Art
Disk drive suspensions typically comprise a load beam carried on an actuator arm by virtue of the load beam base portion being welded to a mounting plate that is swaged into engagement with a bore in the actuator arm, e.g. as shown in U.S. Pat. No. 4,829,395. The mounting plate had a central, annular boss and a planar base surrounding the boss. The boss was swaged into the bore of the actuator arm for securing the load beam, attached to the mounting plate, to the arm. Originally, the mounting plates comprised machine-turned structures that of necessity were axially symmetric. Later, stamped versions were made that were identical in form, or nearly so, to the machine turned originals. Still later, designers took advantage of the stamping process to make extended mounting plate designs that were not axially symmetric.
Through all of this evolutionary change, the mounting plate design in use was an attempt to compromise staking integrity (torque-out), needed for secure connection of the load beam to the actuator arm, with gram load change, i.e. the change in the gram load imposed by the load beam in response to the staking operation. These two parameters were usually traded off against each other, so that improving one had a resulting degradation of the other, because of the nature of the staking operation.
The staking of the mounting plate to the actuator arm bore has been accomplished by swaging. In swaging, a series of steel balls of increasing diameter and all larger than the boss ID are pushed through the mounting plate annular boss to force the boss OD outward and into engagement with the surrounding bore of the actuator arm. This engagement provides a swaged joint. The tolerances of the stamped mounting plate and the actuator arm usually provide marginal retention (torque) values, i.e. resistance to slippage between the mounting plate boss and the arm bore.
The accepted method of determining swaged retention values is to test for rotational torque. A torque meter is attached to the stamped swage mount and rotated until the mount is displaced. Normally this test is done as an in process control operation. By adjusting the ball size, for a given combination of mount plate design and actuator dimensions, torque retention can be improved at the expense of gram load change. To assure torque values that are acceptable (10 in-oz or above) over a wide range of actuators sizes that may vary from the nominal design value due to manufacturing tolerance, a conservative approach would be to use a larger ball size than is absolutely necessary. This assures the worst case torque is sufficiently high. But, in this case the gram load change will be higher that desirable.
And, as drive size is reduced and the actuator becomes thinner and thus has a shorter boss height, the area of engagement is reduced and the retention torque becomes even less because the retention torque is proportional to the engagement length (defined as the amount of overlapping distance between the actuator and the boss of the mounting plate.
SUMMARY OF THE INVENTION
There is a need for higher torque retention values without increasing concomitant gram load change than is available with the current generation of mounting plate designs.
It is an object, therefore, to provide in a disk drive suspension higher torque values without undesirable increases in gram load changes. It is a further object to obtain such balance between torque improvement and gram load change at no increase in manufacturing cost, and in a manner consistent with present manufacturing techniques.
These and other objects of the invention are realized with a novel mounting plate having one or more normally disposed tabs that will interlock with cooperating structure on the actuator arm. These tabs provide an estimated 4 to 5 times increase in the torque values now provided by non-positive engagements typical of the past art. The tabs are to be a very close fit to the cooperating structure such as slots. Known stamping processes can be used as these routinely form features sized to within 0.0005 inches or less. If the tabs and slots happened to slightly interfere, the clamping force that holds the stack in vertical compression during staking would force a press fit. This clamping force is typically 100 to 140 lbs, which is equivalent to 2500 to 3500 PSI when applied to the 0.200 inch by 0.200 inch (0.040 square inch) mounting plate area.
The invention enhanced mounting plate system can be provided with either torque enhancing tabs on the mounting plate base, to interfit with slots on the actuator arm, or the torque enhancing tabs can be developed on the actuator arm to interfit with slots formed in the mounting plate base. No particular number, shape or size of cooperating locking structure tab and slot structures is required provided the objects of the invention are realized, and their pattern can be symmetrical or nonsymmetrical. Preferably, but not necessarily, the parts are formed by stamping techniques where the cost to form additional features in the part will be minimal with no increase in per part charges after a minor increase in tooling costs. Other forming techniques can be used.
A further advantage of the invention is that enhanced mounting plate/actuator arm system can be used within the standard assembly process now used by most Head Stack Assembly (HSA) manufacturers, by interfitting the parts following the juxtaposition of the loose pieces of the HSA onto the staking fixture, and before staking. The process steps to build the headstack assembly are otherwise unchanged. At the earlier Head Gimbal Assembly (HGA) level, minor tooling changes may required to handle the protruding tabs at the fixtures for slider bonding, gram load check, and electrical and flying height testing.
The foregoing objects and advantages of the invention are realized in a disk drive suspension for mounting to an actuator arm having a through opening and an actuator opening edge margin face theresurrounding, the suspension being adapted to cantilever-support from the actuator arm a slider disposed in operating proximity to a disk, the suspension comprising a suspension assembly of a load beam having a base portion and a mounting plate having a central boss and a surrounding base to which said load beam base porion is fixed, said boss defining a mounting plate through opening, said mounting plate base defining an edge margin face surrounding the mounting plate through opening and in opposed relation to the actuator arm edge margin face, the actuator arm and the mounting plate opposed edge margin faces defining distributed pairs of cooperating interfitting members on their respective opening edge margin faces, the interfitting members being arranged to block relative rotation between the actuator arm and the load beam mounting plate.
In this and like embodiments, typically, the mounting plate defines first cooperating interfitting members comprising a distributed series of apertures, and the actuator arm defines second cooperating interfitting members comprising a distributed series of tabs complementary to and arranged in interfitting relation with the aperture series, the mounting plate apertures are circularly distributed about the mounting plate through opening, the tab series being circularly distributed about the actuator arm through opening, the mounting plate apertures comprise longitudin
Coon Warren
Summers Robert
Bachand Louis J.
Evans Jefferson
Magnecomp Corp.
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