Metal working – Method of mechanical manufacture – Electrical device making
Reexamination Certificate
2001-02-22
2002-09-24
Huson, Gregory (Department: 3751)
Metal working
Method of mechanical manufacture
Electrical device making
C029S759000
Reexamination Certificate
active
06453541
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Technical Field
The present invention relates to the field of disc drive assembly and more particularly to methods and apparatuses for centering discs and other components of disc drives.
2. Description of the Related Art
Imbalance in the components of a disc drive is a significant limitation on the disc drive performance. To reduce the effect of imbalances, a number of techniques have been described, attempting to address this problem. One technique involves determining the imbalance in a disc mass and coupling and then attempting to cancel out this imbalance by adding or removing mass in an opposite direction. Another technique involves forcing the mass imbalances to be offset 180 degrees apart (with pre-calculated value) attempting to balance the mass. While opposing imbalances are supposed to cancel each other out in reality this seldom works.
As in most drive industries, the conventional approach to attempting to overcome imbalances in the assembly of a disc pack is to introduce a balancing station. In the balancing station, the imbalanced plane and coupling are measured, and then masses are added or removed to balance the disc pack. However, disadvantageously this involves more capital investment, additional steps in the process of assembling a disc drive, as well as more space and resource requirements. Still further, disadvantageously the technique of measuring balance and the approach of adding/removing mass has it own limitations and as a result increases the complexity of the assembly process.
U.S. Pat. No. 5,043,973 issued to Ocheltree at al. on Aug. 27, 1991 describes a method of centering a disc with a single contact element using a damping force and a spring force. In this method, external force is applied to a disc producing in an elliptical spin. The contact element is then backed off until the disc is centered. This works with a single disc, but in the case of multiple discs only one disc has a near perfect center while the others do not. Tolerance of the roundness of a disc is a key factor limiting this technique. Thus, not all the discs contact the contact element.
Thus, a need clearly exists for an improved system for eliminating or at least ameliorating mass imbalance in the assembly of a disc pack.
SUMMARY OF THE INVENTION
In accordance with a first aspect of the invention, there is disclosed a method of centering a disc and motor assembly. The assembly includes a rotational hub of a motor, at least one annular spacer element, and at least one annular disc. The at least one annular spacer element and the at least one annular disc are in substantially concentric alignment about the rotational hub. In the method, the rotational hub is centered using three points of contact. Each of the at least one disc is centered using three points of contact applied to the periphery of the at least one disc. Each of the at least one annular spacer element is centered using three points of contact. The alignment and positioning of the points of contact for the three centering steps are precisely controlled. The method may also include the step of fastening a fastening device to the disc and motor assembly to firmly clamp the rotational hub, the at least one annular spacer element, and the at least one annular disc together before withdrawing the three points of contact in each of the three centering steps. Optionally, the fastening device is a retaining nut, and the rotational hub has a threaded portion complementarily formed to the retaining nut for interengagement therebetween.
Preferably, the disc and motor assembly includes at least two discs, a spacer element being located between each adjacent pair of discs. More preferably, the number of discs is five or ten, with corresponding spacers placed between pairs of discs, depending upon the particular disc drive configuration.
Preferably, the three points of contact for the hub-centering step are three motor centering springs. Each of the motor centering springs may include: an annular body; a leaf body being substantially hemispherical and disposed within the annular body, the leaf body having two over rotation stops formed at opposite locations of the leaf body and an overload stop, each of the stops in proximity to an internal edge of the annular body; and a leaf spring connecting the leaf body with the annular body.
Preferably, the three points of contact for the disc centering step for each disc are three disc centering springs. Each of the disc centering springs may include: an annular body; a leaf body being substantially hemispherical and disposed within the annular body, the leaf body having two over-rotation stops formed at opposite locations of the leaf body and an overload stop, each of the stops in proximity to an internal edge of the annular body; and a leaf spring connecting the leaf body with the annular body.
Preferably, the three points of contact for the spacer-element centering step for each spacer element are three spacer-element centering springs. Each of the spacer-element centering springs may include a plate-like member having a substantially circular lobe. The plate-like member further includes a substantially circular inner lobe formed by a groove in the plate-like member, the substantially circular inner lobe having an overload stop formed therein.
In accordance with a second aspect of the invention, there is disclosed an apparatus for centering a disc and motor assembly. The assembly includes a rotational hub of a motor, at least one annular spacer element, and at least one annular disc. The at least one annular spacer element and the at least one annular disc are in substantially concentric alignment about the rotational hub. The apparatus includes: a device for centering the rotational hub using three points of contact; a device for centering each of the at least one disc using three points of contact applied to the periphery of the at least one disc; and a device for centering each of the at least one annular spacer element using three points of contact. The alignment and positioning of the points of contact for the three centering means are precisely controlled.
REFERENCES:
patent: 6094804 (2000-08-01), Chuang et al.
patent: 6158112 (2000-12-01), Kim et al.
patent: 6295717 (2001-10-01), Chuang et al.
Guthrie Duncan
Lee Soon How
Tan Ricky Chong Ho
Bracewell & Patterson L.L.P.
deVore Peter
Huson Gregory
Martin Robert B.
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