Dynamic magnetic information storage or retrieval – Head mounting – For shifting head between tracks
Reexamination Certificate
2000-10-13
2001-09-11
Davis, David (Department: 1652)
Dynamic magnetic information storage or retrieval
Head mounting
For shifting head between tracks
C360S265200, C403S372000, C384S535000
Reexamination Certificate
active
06288878
ABSTRACT:
FIELD OF THE INVENTION
This invention relates generally to the field of disc drive storage devices, and more particularly, but not by way of limitation, to a tolerance ring with increased hoop strength and resistance to deformation.
BACKGROUND OF THE INVENTION
Modern hard disc drives comprise a mechanical housing which encloses one or more rigid discs that are rotated at a constant high speed. Data are stored on the discs in a plurality of concentric circular tracks by an array of transducers (“head”) mounted to a radial actuator for movement of the heads relative to the discs.
The heads are mounted via flexures at the end of a plurality of arms that project radially outward from an actuator body. The actuator body pivots about a pivot shaft, such as a vertical post which extends upwardly from the housing. The post is parallel with the axis of rotation of the discs so that the heads move in a plane parallel with the surface of the discs.
Typically, such radial actuators employ a voice coil motor to position the heads with respect to the disc surfaces. The voice coil motor includes a magnetic circuit mounted to the disc drive housing and a coil mounted on the side of the actuator body opposite the head arms so as to be immersed in the magnetic field of the magnetic circuit. When controlled current is passed through the coil, an electromagnetic field is set up which interacts with the magnetic field of the magnetic circuit to cause the coil to move in accordance with the well-known Lorentz relationship. As the coil moves, the actuator body pivots about the post and the heads move across the disc surfaces.
In the manufacturing of a disc drive, it is important that the actuator assembly be placed in the proper location, centered on all three axes, longitudinal, latitudinal, and translational (x, y, and z) with respect to the discs. Typically, the actuator assembly has a large bored recess which accommodates a cartridge bearing assembly with a pair of ball bearing assemblies to accommodate rotation of the actuator assembly about the z-axis. The cartridge bearing assembly includes an inner bored recess to allow the actuator assembly to fit over the pivot post. The diameters of the large bored recess and the inner recess are maintained within predetermined, close tolerance ranges.
A tolerance ring can be advantageously used to compensate for variances of the part manufacturing tolerances and thus retain the proper positioning of the actuator assembly in all three axes. Typically, prior art tolerance rings consist of a corrugated sheet of metal formed into an open cylindrical shape. The tolerance ring is then provisioned around the post and stationarily held in position by an anchoring groove in the pivot post. In most applications, the tolerance ring serves only as a manufacturing aid and provides no additional function after completed manufacture. Exemplary prior art tolerance ring configurations are disclosed in U.S. Pat. No. 5,315,465 issued to Blanks, U.S. Pat. No. 4,286,894 issued to Rongley, and U.S. Pat. No. 3,838,928 issued to Blaurock et al.
Although widely used, most prior art tolerance rings fail to exhibit adequate hoop strength. Hoop strength is a measure of the grasping force that a tolerance ring is capable of exerting when engaged with the pivot post. Significantly, inadequate hoop strength may cause an impermissible degree of movement between the tolerance ring and the pivot post. Consequent placement of the actuator assembly over an improperly positioned tolerance ring may cause the tolerance ring to foul or be forced out of the anchoring groove.
Additionally, a tolerance ring with insufficient hoop strength is susceptible to deformation during shipping and handling. Frequently as a result of mishandling the tolerance ring experiences a helical deformation in which the tolerance ring “twists” about a central axis, thereby rendering the tolerance ring useless for subsequent manufacturing purposes. The likelihood of deformation during shipping and handling reduces the efficiency of the manufacturing process by necessitating the inspection of the parts before introduction into automated assembly.
With an increasing demand for improved consistency in the installation of actuator assemblies, there remains a continuing need for the development of a tolerance ring which is resistant to deformation and which exhibits increased hoop strength. It is to such improvements that the present invention is directed.
SUMMARY OF THE INVENTION
The present invention is directed to a tolerance ring that provides increased hoop strength and resistance to deformation.
As exemplified by preferred embodiments, a disc drive includes a basedeck which supports an upwardly extending shaft, such as a post, which defines an actuator pivot axis. A tolerance ring constructed in accordance with preferred embodiments of the present invention is placed on the post so as to circumferentially extend about an outer surface of the post. An actuator assembly with an inner bored recess is thereafter placed onto the post so that the tolerance ring is compressed between the surface of the inner bored recess and the outer surface of the post, thereby maintaining a desired nominal centering of the actuator assembly about the actuator pivot axis.
The mechanical configuration of the tolerance ring is selected to provide increased hoop strength and includes a substantially cylindrical base portion from which at least one brace portion and a plurality of contact portions project. The brace portion preferably extends along the circumference of the base portion and preferably comprises either a circumferentially extending ridge or flange.
Various other advantages and features of the present invention will be apparent from the following detailed description when read in conjunction with the drawings and appended claims.
REFERENCES:
patent: 3700271 (1972-10-01), Blaurock et al.
patent: 3776653 (1973-12-01), Buzogany
patent: 5539597 (1996-07-01), Blanks
patent: 5548458 (1996-08-01), Pelstring et al.
patent: 5983485 (1999-11-01), Misso
patent: 6163441 (2000-12-01), Wood et al.
Eddings Dana P.
Jones Inman L.
Misso Nigel F.
Seewald Denis A.
Crowe & Dunlevy
Davis David
Seagate Technology LLC
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