Dynamic magnetic information storage or retrieval – Head mounting – Disk record
Reexamination Certificate
1999-04-12
2001-04-17
Cao, Allen T. (Department: 2754)
Dynamic magnetic information storage or retrieval
Head mounting
Disk record
C360S245400
Reexamination Certificate
active
06219203
ABSTRACT:
BACKGROUND OF THE INVENTION
This invention relates in general to a hard disk drive suspension and in particular to an etched microactuator suspension for a high density computer hard disk drive.
Background Art
As the information storage density of computer hard disk drives has increased, so has the need for microactuator suspensions with very low profiles or thicknesses. Lightweight suspensions allow for higher tracking-per-inch (typically, 40K TPI) and greater drive speeds. Although suspensions having thicknesses in the range of 1.0 to 2.5 mils (approximately 0.03 to 0.063 mm) are well known in the art, they are prone to experience a variety of problems. For example, suspensions having a thickness on the lower end of this range are not as stiff and subject to air flow induced vibration, have marginal dynamics (typically around 2 KHz for the first major torsional dynamic frequency), and increased manufacturing cost. Suspensions on the upper end of the range have greater stiffness, but they have increased inertia which can limit the speed of the drive.
Prior art suspension shapes are typically created by two-sided chemical etching processes and supplemental press forming procedures to increase their stiffness. A low percentage of suspensions are partially etched, with etching typically limited to the hinge and gimbal. These suspensions do not use etching for stiffening purposes. They are typically etched to 50% of their original thickness to reduce normal stiffness in the hinge region and to form a low stiffness gimbel at the front end of the load beam. Current designs utilize a full hard thin (1.5 to 2.5 mils) stainless steel load beam having a cross-section which is stiffened by forming rails, bubbles, etc., to raise their dynamic frequencies. Unfortunately, only very simple forms can be made due to manufacturability problems that limit dynamic enhancement. One type of prior art, short length suspension alleviates this shortcoming with a relatively thick 4 mil load beam. However, at a length of only 18 mm, it performs rather poorly in other areas due to the increased mass of the load beam.
SUMMARY OF THE INVENTION
A hard disk drive suspension having a load beam with an original thickness of 4 mils (approximately 0.1 mm) is simultaneously etched on both sides in selected areas to approximately half of its original thickness. The selective partial etching makes intricate features which are otherwise unattainable by conventional forming operations. These features reduce the weight of the load beam and provide a very stiff structure when the etched features or pockets are enclosed in an extended, box-like fashion by a flexure and mount plate. The only press forming operations remaining are to generate a load/unload tab semicircular cross-section and dimple. This configuration more than triples the first torsion frequency from about 2 to 6 KHz or higher, thereby increasing the servo band width by a multiple of 3. Moreover, when the box-like portion of the suspension is replaced by milliactuator motors, the etched suspension meets the mass, inertia, sag, and servo bandwidth requirements with micro-actuation capability.
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patent: 5126904 (1992-06-01), Sakurai
patent: 5313353 (1994-05-01), Kohso et al.
patent: 5353181 (1994-10-01), Frater et al.
patent: 5461525 (1995-10-01), Christianson et al.
patent: 5734526 (1998-03-01), Symons
patent: 5759418 (1998-06-01), Frater et al.
patent: 6028801 (1994-02-01), None
Arya Satya P.
Pan Tzong-Shii
Cao Allen T.
Felsman Bradley Vaden Gunter & Dillon, LLP
International Business Machines - Corporation
Millett Douglas R.
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