Dynamic magnetic information storage or retrieval – Head mounting – Disk record
Reexamination Certificate
1999-06-14
2001-04-10
Cao, Allen T. (Department: 2754)
Dynamic magnetic information storage or retrieval
Head mounting
Disk record
Reexamination Certificate
active
06215623
ABSTRACT:
BACKGROUND OF THE INVENTION
(1). Technical Field
This invention relates to the field of disk drives, in particular, to a method for absorbing unwanted vibrations and resonances in dynamic mechanisms, such as disk drives, is fabricated with an integral dynamic absorber that can be formed where the vibration is to be suppressed. The absorbing system is disposed at a predetermined location on a load beam suspension.
(2). Description of the Prior Art
The following two documents relate to methods dealing with vibration suppression of head suspension assemblies.
U.S. Pat. No. 4,932,019 issued Jun. 5, 1990 to A. Bessho describes a vibration absorbing member for reducing resonance energy in an optical disk drive, but it also is used in conjunction with a drive base and not a head suspension assembly as in the invention.
U.S. Pat. No. 4,703,470 issued Oct. 27, 1987 to Castagna, et al, discloses a dynamic absorber used in a disk drive, but the absorber described has a viscoelastic link element between the absorber base and absorber mass, and is only described as being used on the drive carriage or base casting.
It is well known that high speed mechanisms having moving parts are susceptible to damaging vibratory effects which reduce the expected life of the mechanism. As an example, disk drives which use actuators and associated suspensions for bidirectional accessing of data tracks of a rotating disk suffer from undesirable vibrations and resonances. In the past the designer would add visco-elastic dampers to the suspension. However, outgassing would often occur with visco-elastic dampers creating friction polymers on the slider/disk interface thereby causing premature failure of the disk drive system.
Furthermore, a major objective for improved performance of disk drives is to achieve reduction in the access time of the rotating disk. The access time is dependent upon the mass of the suspension assembly. Thus, it is desirable to reduce the mass of the suspension assembly. The reduction of mass, if not correctly accomplished, may in effect increase the access time due to the increased severity of the structural resonances of the suspension.
Several methods dealing with vibration absorbing devices have been employed in the past to damp unwanted resonance frequencies of dynamic operating mechanisms. The absorbing devices are designed to undergo a resonance at a predetemined frequency which is related to the undesired resonance frequency. Such prior art devices are overly sensitive when undergoing assembly and handling and are not considered reliable since they may fail mechanically during operation.
In a hard disk drive, typically a head slider is positioned by a head suspension assembly (HSA) over a magnetic disk to facilitate reading and writing of information to the disk. The constituent elements of standard HSAs include a swage plate, a resilient zone, a load beam, a flexure and a head slider. The swage plate is positioned at a proximal end of the load beam, adjacent to the resilient zone and is mounted to the suspension by means of a boss and by laser welding. The swage plate provides stiffness to the rear mount section and is configured for mounting the load beam to an actuator arm of a disk drive. The flexure is positioned at a distal end of the load beam. Mounted to the flexure is a head slider with a read/write orientation with respect to an associated disk.
SUMMARY OF THE INVENTION
It is and object of the invention to provide a novel and improved dynamic absorber for reducing unwanted vibrations, resonances, and noise in high speed mechanisms, such as disk drives.
It is another object of the invention is to provide a dynamic absorber that does not add mass to the disk drive system thereby achieving reduction in the access time of the magnetic heads to selected data tracks of the rotating disk.
It is another object of the invention to provide a dynamic absorber that does not require additional process, material, or assembly. It is essentially free after the initial development and setup.
It is still another object of the invention not to introduce foreign material into the disk drive. It will not outgass, corrode, wear, or fall off the suspension.
The foregoing objects of the invention are accomplished and the disadvantages of the prior art overcome by the provision of a disk drive comprising a dynamic absorber that is constitutively included into a load beam of a head suspension assembly. A load beam is typically made of a sheet of stainless steel. Cavities are often etched out of the suspension for control of stiffness, mode shape, and for mass-reduction. The dynamic absorber can be etched within the load beam configuration and within the shape of the cavity, which as mentioned previously can be reconfigured to include the shape of a dynamic absorber.
When a suspension is designed, the mode-shape and natural frequencies are usually known. They are often predicted by simulation and verified by experiments. If a particular mode is of special concern, a dynamic aborber can be placed at a location where the vibration is to be suppressed. To suppress vertical deflection, the absorber can be a simple cantilever beam, or a cantilever with an enlarged tip. This type of absorber is suitable at the antinodes of the vibration, where the vertical displacement is greatest. To suppress rotation, the absorber can be a T-bar. This type of absorber is suitable at the nodes of the vibration, where the rotation is greatest. The natural frequencies of the absorber should match the mode to be suppressed.
Occasionally the natural frequencies of the absorber need to be adjusted, either due to variation of the suspension thickness, or due to a change in the vibration to be suppressed. The adjustment can be accomplished by creating a cavity at the absorber, for example using a laser beam. The amount of adjustment can be controlled by the location of the cavity. The natural frequency is increased if the cavity is near the free end of the absorber. This novel adjustment scheme overcomes the disadvantage of several prior arts, which failed to achieve desired accuracy in natural frequencies.
REFERENCES:
patent: 4703470 (1987-10-01), Castagna et al.
patent: 4760478 (1988-07-01), Pal et al.
patent: 4932019 (1990-06-01), Bessho
patent: 5594607 (1997-01-01), Erpelding et al.
patent: 5606477 (1997-02-01), Erpelding et al.
patent: 5734526 (1998-03-01), Symons
patent: 5825590 (1998-10-01), Ohwe
patent: 5850319 (1998-12-01), Tangren
patent: 5894655 (1999-04-01), Symons
Ackerman Stephen B.
Cao Allen T.
Headway Technologies Inc.
Saile George O.
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