Disc clamp for improved disc stack balance

Details Disc clamp for improved disc stack balance Disc clamp for improved disc stack balance

2000-06-30

2003-04-01

Ometz, David L. (Department: 2653)

Dynamic magnetic information storage or retrieval

Record transport with head stationary during transducing

Disk record

C360S098080, C369S270100

Reexamination Certificate

active

06542330

ABSTRACT:

FIELD OF THE INVENTION
The present invention relates generally to disc drives. More particularly, the present invention relates to a disc clamp for a disc drive and a disc drive that includes such a disc clamp.
BACKGROUND OF THE INVENTION
Disc drives generally include a drive hub or spindle that can be driven to rotate by a suitable motor to drive a magnetic or optical data storage disc or discs about the axis of the hub or spindle. Where the disc drive includes more than a single disc it is said to include a disc stack assembly (DSA), in which the discs are stacked substantially coaxially in spaced-apart relationship relative to the hub. In either arrangement, it is necessary to employ a clamping mechanism to clamp the disc or discs securely in position against axial and radial movement. The propensity for such movement is most likely during acceleration and deceleration of the hub, and when the disc drive is subject to shock loads, such as may occur during movement from one location to another, or if the disc drive is knocked. Thus the clamping mechanism must exert a firm clamping force to resist undesirable movement of the above kind. Examples of clamping mechanisms suitable for use in disc drives, can be found in the specification of U.S. Pat. Nos. 4,864,443, 5,243,481, 5,590,004 and 5,880,905.
Once the particular clamping mechanism employed has been applied, the disc or discs of the disc drive are fixed in position, such that any eccentric misalignment of one or more of the discs is permanent. Any misalignment can affect the performance of the disc drive by generating eccentric loads, which can affect the accuracy of the read signal taken from each disc. Therefore, it is important that the discs be balanced prior to the application of the clamping mechanism.
One arrangement for balancing a DSA is to bias successive discs in opposite directions against the outer surface of the hub. In this arrangement, an eccentric force generated by one disc of the DSA is balanced by a substantially equal and opposite eccentric force generated by the next disc in the DSA. However in this arrangement, significant unbalanced eccentric forces can still arise during rotation of the DSA by eccentric misalignment of the disc clamp. A need exists to provide a disc clamp arrangement which substantially reduces or eliminates eccentric forces generated by the disc clamp in a disc drive arrangement of this kind. The present invention meets this need and offers other advantages not proposed or recognized in the prior art.
SUMMARY OF THE INVENTION
The present invention relates to the use of a disc clamp in a disc drive which meets the above mentioned need and offers other advantages over the prior art.
In accordance with one embodiment of the invention there is provided a disc drive having a drive hub which is rotatable about an axis, a motor for driving the hub about its axis, at least two spaced apart discs which are axially stacked about the hub, and a disc clamp. The disc clamp is of annular plate form defining a central, circular opening and includes at least three radially inwardly extending tabs depending from the circumferential edge of the central opening, which are spaced substantially equidistantly thereabout. The radial inward extent of each of the tabs is substantially equal and is arranged so that with the disc clamp in the clamping position and in coaxial alignment with the hub, the radially innermost edge of the tabs is closely adjacent but spaced from the outer surface of the hub. The disc clamp is resiliently flexible and includes a continuous, annular disc contact region adjacent the outer circumferential edge of thereof. The disc further includes at least three screw openings each for receiving a screw fastener for fastening the disc clamp to the hub in the clamping position. In the clamping position of the disc clamp, the disc resiliently flexes to cause the annular disc contact region to bear against the surface of the outermost stacked disc to clamp the disc stack against radial and axial movement.
Another embodiment of the present invention provides a disc clamp with frustoconical cross-section, such that the annular disc contact region is below the central opening when the disc clamp is viewed in a horizontal plane. The annular disc contact region is formed by a continuous channel formed adjacent the outer circumferential edge of the disc clamp, which presents a curved contact surface for contact with the facing surface of a disc of the disc stack.
In a different embodiment, the corners of each of the three tabs are rounded to minimize particle debris which may be created when the hub it comes into contact with the tabs during operation.
In another embodiment, the disc clamp is formed by a metal stamping process.
In another embodiment, the disc clamp is formed by a machining process.
In yet another embodiment, the radially innermost edge of the tabs is spaced from the outer axial surface of the hub by a distance in the range 0.002″ and 0.0005″, when the disc clamp is fastened to the hub in an operative condition.
Another aspect of the present invention provides a disc clamp which includes assembly openings arranged for receipt of assembly pins for positioning the disc clamp in place during assembly. It is preferable that three assembly openings are provided, with each being disposed between a pair of screw openings.


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