Dynamic magnetic information storage or retrieval – Record medium – Disk
Reexamination Certificate
2000-01-28
2001-02-20
Cao, Allen T. (Department: 2754)
Dynamic magnetic information storage or retrieval
Record medium
Disk
C369S282000
Reexamination Certificate
active
06191921
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
This invention relates to disk head assemblies for supporting read/write heads adjacent rotating disks in disk drives and more particularly, to a base plate for attaching a load beam assembly to a head actuator arm.
2. Description of the Prior Art
Disk drives typically include a stack of spaced apart, concentric magnetic storage disks mounted on a common shaft, and an actuator arm assembly encased within a housing. The actuator arm assembly, also called a head stack assembly (HSA), comprises a plurality of arms extending into spacing between the disks. Mounted on the distal end of each arm is a resilient suspension assembly to which is attached an air bearing slider. Included in the suspension assembly is a load beam, which is mounted at one end to the actuator arm by means of a base plate, and a flexure which is attached to the other end of the load beam and pivotally supports the slider on a gimbal that keeps the slider suspended in a horizontal plane regardless of any motion of the load beam.
The load beam provides the resilient spring action that biases the slider toward the surface of a magnetic recording disk, while the flexure provides flexibility for the slider. A thin film magnetic transducer is deposited at an end of the slider to read or write on the magnetic disk.
The actuator arm and load beam elements of the head stack assembly are connected end to end by a base plate which includes a flat flange portion and a cylindrical hub portion or boss. In assembling the head stack, the hub is inserted into a load beam boss hole and the flange portion is welded to the load beam. The hub is then inserted into an actuator arm boss hole. Using a swage ball tool, pressure is applied to cause the hub to expand into the boss hole in the actuator arm, rigidly connecting the hub and attached load beam to the actuator arm boss hole. In the swaging process, a steel ball is pressed through the hub in the base plate. As the hub plastically deforms, it hardens, which is desirable for maintaining a press fit in the actuator arm boss hole.
A typical base plate is stamped in a progressive die in a sequence of forging and coining operations. The base plate is subsequently fully annealed to soften the metal which allows the material in the hub region to yield at a low stress level during a swaging operation. This permits more readily plastic deformation thus creating a greater press fit against the inner wall of the actuator arm boss hole. Since the flange as well as the hub is soft from annealing, the flange deforms easily. Deformations in the flange are transmitted to the load beam that is welded to the flange, causing undesirable fluctuations in the gram load. A prior art solution is to start with a harder base-plate material. But with a harder base-plate material, higher swaging forces are needed to cold work the hub, which in turn deforms the base plate even more severely. As the disk drive industry moves to nano and pico form factors, the effect of swaging on the load force is of even greater concern.
It is therefore an object of this invention is to provide a base plate which will yield in the hub without excessive deformation of the flange.
SUMMARY OF THE INVENTION
The invention is a base plate comprising a flange portion that is hardened; and a hub portion that is softer than the flange portion. The method of manufacturing the base plate comprises steps of: A. stamping a hub from a sheet of metal in a first die operation resulting in a flange portion and a hub portion; B. annealing the flange portion and the hub portion to thereby soften the hub portion; and, C. stamping the flange to a specified flange thickness in a second die operation to thereby harden the flange portion only.
An advantage of this invention is that a hard flange of the base plate results in less gram load change for a given swage force, since the yield strength of the material is much higher and thus less likely to undergo plastic deformation.
A further advantage of this invention is that it provides the means by which to decrease the susceptibility of a flange region of a base plate to plastic deformation while not decreasing the hub region's susceptibility to work hardening during a swaging operation.
REFERENCES:
patent: 4885653 (1989-12-01), Kato
patent: 5729414 (1998-03-01), Goede et al.
Hanrahan Kevin
Schmidt Ryan
Cao Allen T.
Intri-plex Technologies, Inc.
Lamb Owen L.
LandOfFree
All metal base plate having a hardened flange and soft hub... does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with All metal base plate having a hardened flange and soft hub..., we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and All metal base plate having a hardened flange and soft hub... will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-2604085