Dynamic magnetic information storage or retrieval – Head mounting – Disk record
Reexamination Certificate
1996-08-30
2001-10-23
Davis, David (Department: 2652)
Dynamic magnetic information storage or retrieval
Head mounting
Disk record
Reexamination Certificate
active
06307715
ABSTRACT:
TECHNICAL FIELD
The present invention relates to suspensions for transducers that are held in close proximity to relatively moving media, particularly for load beams holding disk drive heads.
BACKGROUND OF THE INVENTION
Information storage drive systems often operate by holding an electromagnetic transducer or head next to a relatively moving magnetic media, such as a disk or tape. The media typically moves in a single direction, so that a stationary transducer can read or write bits of data on a single track that passes next to the transducer, while the employment of a transducer that can move in a direction transverse to the media motion allows access to multiple tracks. Such moveable transducers are commonly attached near distal ends of suspensions in order to facilitate access to various tracks. It is important that a suspension accurately position the transducer along as well as across a recording track in order to eliminate errors and reduce noise.
In order to provide such accurate positioning, a suspension load beam is typically stiff in both lengthwise (“longitudinal”) and sideways (“lateral”) directions, which are both oriented substantially parallel to the plane of the media. Lateral and longitudinal stiffness affords rapid access of a head to various tracks of the media, reduces settling time and increases the ability of the head to follow a single track, all essential to increased drive performance. Stiffness in a given direction of a beam generally correlates with high resonant vibration frequencies of the beam in vibration modes corresponding to those directions, so a greater stiffness or flexibility can be translated into, respectively, a higher or lower resonant vibration frequency. In other words, high resonant vibration frequencies generally reduce positioning error, as perturbations such as may be induced by transducer movement between tracks do not result in large position errors and are quickly diminished, allowing the transducer to accurately read or write.
On the other hand, flexibility of a beam in a direction toward and away from the media, which is termed the “vertical” or “perpendicular” direction in the present invention, is generally desirable to allow the transducer to conform to variations in media height or positioning and to provide a spring force for holding the transducer next to the media, which may include controlling fly height. This bending is typically achieved by creating a spring or hinge portion near a base or mounting end of the beam. Flexibility in the vertical direction, however, may allow undesirable low-frequency resonant vibrations to occur in a torsional mode, since torsional vibration can occur when laterally spaced portions of the beam bend in opposite vertical directions. A torque on the beam is generally induced with any lateral acceleration, which occurs for instance when the head shifts between tracks, since the center of mass of the head is not aligned with the torsional axis of the beam or gimbal. There is a fundamental conflict between the need to allow vertical bending of the beam and the need to reduce the amplitude of torsional vibrations, since the torsional vibrations are simply vertical bending in which one side of the beam is out of phase with the other. These torsional vibrations can cause significant off-track motion leading to noise and errors in reading and/or writing data, and impeding any reduction in transducer access time between tracks.
An object of the present invention is to provide means for preferentially increasing torsional stiffness of a transducer suspension without reducing the vertical bending flexibility.
SUMMARY OF THE INVENTION
The above object is achieved by providing, in at least one place along the length of a drive system arm or beam, a laterally extensive region of vertical flexibility, commonly termed a “hinge” region, with a laterally extending brace joined to a longitudinally limited portion of the hinge. Although the purpose of the brace is to mitigate twisting of the beam about a longitudinal beam axis, the brace itself is stiff against twisting about a lateral axis. This lateral torsional stiffness of the brace prevents the vertically flexible region attached to the brace from simultaneously bending upward on one side of the beam and downward on the other, thereby increasing longitudinal torsional stiffness. At the same time, overall bending of the beam is decreased only along the small portion of the length joined to the laterally extending brace, allowing the beam to provide a relatively soft spring force holding the transducer adjacent the media.
The reason for the success of this invention can be understood by comparing the bending and twisting motions that are possible with a generally planar, flexible yet resilient structure, such as a sheet of metal. Bending of such a structure along a given line in the plane does not cause bending along a perpendicular line in the plane but instead tends to prevent such perpendicular bending. In contrast to bending motion, however, torsional motion about a given line in the plane causes torsional motion about a second perpendicular line in the plane. Reducing torsional motion about an axis can thus be accomplished by reducing torsional motion about a perpendicular axis. A brace that is torsionally stiff about a first direction but limited in length in a second, perpendicular direction can therefore limit torsional flexibility about the second direction without substantially limiting bending along the second direction.
Several types of torsionally stiff braces may be employed to raise the torsional frequency of a suspension beam. Torsional stiffness is caused by resistance to motion about a torsional axis, and thus benefits from a structure having shear strength that is distanced to the axis, the distance providing a moment arm that leverages the strength. In general, a tube-like structure offers high torsional stiffness per unit weight, since a tube has a high shear strength at a distance from its axis but no mass at the axis. Such a tube, extending laterally across a beam, may be joined to a hinge for reducing torsional vibrations in a perpendicular, longitudinal direction. The tube may be cylindrical, offering a high torsional stiffness and a minimal reduction in bendable length along a joined area. Alternatively, a tube may have rectangular or triangular cross-sections which afford greater attachment area, providing more assuredly reduced torsional vibration at a cost of greater non-bendable length. On the other hand, for a multilayer beam having a hinged area formed by a cutout in a layer or layers, a laterally-extending, longitudinally-limited brace may be formed across the hinge by folding the cutout layers and/or leaving the multilayers. The brace should be formed of a material having a matching thermal expansion coefficient as the hinge in order to avoid temperature induced changes in the spring-like hinge, such matching being inherent when a layer is folded back on itself to form the brace.
The brace, the hinge and the entire beam may alternatively be formed of materials micromachined with semiconductor processing techniques, such as etched silicon with embedded or deposited conductive leads for connecting the transducer with drive electronics. Materials such as silicon (Si), silicon carbide (SiC), silicon dioxide (SiO
2
), alumina (Al
2
O
3
) or other strong, workable substances may be used in this case. A stainless steel or other metal suspension beam may also be etched to form hinge strips or deposited with additional layers for a laminated brace, for example. Alternatively, a laminated brace including a plurality of rolled or pressed metal layers may be formed by metal working such as cutting, stamping, bonding and/or welding, such as laser spot welding.
A plurality of such laterally extending braces adjoined by vertically flexible regions can be formed along a suspension beam to increase the vertical flexibility, with the provision that such segmentation should not be periodic in order to avoid creating resonant structures.
Berding Keith R.
Young Kenneth F.
Davis David
Lauer Mark
Read-Rite Corporation
LandOfFree
Head suspension having reduced torsional vibration does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Head suspension having reduced torsional vibration, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Head suspension having reduced torsional vibration will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-2569277