Dynamic magnetic information storage or retrieval – Head mounting – For shifting head between tracks
Reexamination Certificate
2000-11-20
2003-04-15
Heinz, A. J. (Department: 2652)
Dynamic magnetic information storage or retrieval
Head mounting
For shifting head between tracks
Reexamination Certificate
active
06549379
ABSTRACT:
FIELD OF THE INVENTION
This invention generally relates to computer disc drives and more particularly to a disc drive having a top cover that also performs the function of a voice coil motor pole.
BACKGROUND OF THE INVENTION
The effort to make personal computers more compact has created demand to reduce the size of the disc drive used in personal computers. A major innovation in this direction has been the development of smaller, Winchester-type disc drives (hard disc drives) as replacements for floppy disc drives. Hard disc drives generally provide higher capacities and faster speeds of operation than floppy disc drives, factors which are of great importance for effective use of personal computers running advanced software packages. Many of these disc drives use voice coil motors for positioning a read/write transducer head over a selected track on the rotating hard disc.
The popularity of notebook computers and the advent of hand held computers has led to still another push to reduce the size of hard disk drives. Recently, efforts have been made to reduce the height of hard disc drives, so that the size of the housing for the computer could be minimized. However, further reduction of the physical size of a hard disc drive is constrained by the hard disc drive's functional requirements. For example, the conventional voice coil motor requires at least two stationary magnets, a voice coil, a top pole, a bottom pole, and clearance space between each of these components. The size of these components may be minimized, but the components themselves may not be eliminated, unless the functionality of the components is provided by some other means.
A voice motor coil includes a magnetic circuit that creates a magnetic field operative to move an actuator assembly on which the read/write heads reside. Generally, a voice coil motor includes a top pole, a bottom pole, and a voice coil that moves between the poles. The top and bottom poles hold magnets, thereby creating a magnetic field therebetween. The poles function to provide magnetic paths, such that the magnets are in the magnetic paths with a cross flux to the coil. The voice coil motor moves when the voice coil is energized within the magnetic field. The actuator assembly moves when the voice coil is energized, thereby moving the read/write heads attached thereto.
A conventional disc drive
100
is depicted in FIG.
1
. The disc drive
100
includes a base
120
to which various components of the disc drive
100
are mounted. A top cover
106
, shown partially cut away, cooperates with the base
120
to form an internal, sealed environment for the disc drive in a conventional manner. A printed circuit board
102
is fastened to the underside of the baseplate
120
. The internal components include a spindle motor
112
that rotates one or more discs
108
at a constant high speed. Information is written to and read from tracks on the discs
108
through the use of an actuator assembly
111
, which rotates during a seek operation about a bearing shaft assembly
113
positioned adjacent the discs
108
. The actuator assembly
111
includes a plurality of actuator arms
115
which extend towards the discs
108
, with one or more flexures
116
extending from each of the actuator arms
115
. Mounted at the distal end of each of the flexures
116
is a read/write head
118
(transducer) that includes an air bearing slider enabling the head
118
to fly in close proximity above the corresponding surface of the associated disc
108
. During a seek operation, the track position of the head
118
is controlled through the use of a voice coil motor (VCM)
114
.
A cross-sectional view of a conventional VCM is depicted in FIG.
2
. Referring to
FIGS. 1 and 2
, the conventional VCM
114
includes a coil
126
attached to the actuator assembly
111
. The conventional VCM also includes one or more bi-polar, stationary magnets
128
that establish a magnetic field in which the coil
126
is immersed. The controlled application of current to the coil
126
causes magnetic interaction between the stationary magnets
128
and the coil
126
so that the coil
126
moves in accordance with the well-known Lorentz relationship. The paths of the magnetic field are directed through a top pole
202
and a bottom pole
204
located above and below the voice coil
126
. The top pole
202
and the bottom pole
204
are made of a magnetic permeable material, such as iron or steel. As the coil
126
moves in the magnetic field between the poles, the actuator assembly
111
pivots about the bearing shaft assembly
112
, and the heads
118
are caused to move across the surfaces of the discs
108
.
As discussed, the voice coil motor
110
includes an energizable coil
126
coupled to the actuator assembly
111
and a magnet assembly
200
coupled to the base
120
of the disc drive. In the disc drive depicted, the magnet assembly
200
includes a top pole plate and a bottom pole plate
202
,
204
. The poles
202
,
204
are supported in spaced relation by at least two spacers
206
to form a gap
208
therebetween. The stationary magnets
128
are supported by the poles
202
,
204
to form a permanent magnetic field in the gap
208
. The poles
202
,
204
support the bi-polar stationary magnets
128
to form two bi-directional flux paths
210
,
212
for operation of the voice coil motor. The coil
126
extends into the gap
208
in alignment with the flux paths
210
,
212
for generating a rotating force for operating the actuator assembly
111
proportional to current flowing through the coil
126
.
There is a continual need for a smaller, simpler and more compact disc drive. One approach is to reduce the height of the disk drive. This may involve eliminating one or more of the parts of the voice coil motor (VCM) circuit. However, this approach still requires a complete magnetic circuit. Accordingly, there is a need for a low-height disc drive that reduces the overall height of the disc drive and yet is fully functional.
SUMMARY OF THE INVENTION
Against this backdrop the present invention has been developed. A low-height disc drive has a digital data storage disc rotatably mounted on a drive motor fastened to a base plate rotating the storage disc. The disc drive further includes an actuator assembly mounted to the base plate adjacent the storage disc, the actuator assembly including an actuator arm carrying a transducer for transferring data to and from the disc. The disc drive has a voice coil motor for rotating the actuator assembly to position the transducer with respect to the storage disc. The voice coil motor includes a voice coil fastened to the actuator arm, a stationary magnet attached to a bottom pole on the base plate in spaced, confrontational arrangement with a top pole defining a horizontal gap between the stationary magnet and the top pole through which the voice coil moves.
The hard disc drive of the present invention was specifically designed to be compact yet fully functional. The hard disc drive of the present invention has a magnetically-permeable top cover that functions as the top pole for the magnetic circuit of the voice coil motor (VCM). This functionality eliminates the need for a separate top pole for the VCM's magnetic circuit. Because the need for the separate VCM pole has been eliminated, the hard disc drive can be manufactured such that it is more compact and less expensive than hard disc drives requiring a separate pole.
Alternatively, the top cover can be made of thin magnetically permeable material and folded in an accordion-like manner to provide the magnetic characteristics required to function as a top pole.
REFERENCES:
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patent: 5262912 (1993-11-01), Hudson et al.
patent: 5315466 (1994-05-01), Nishimoto et al.
patent: 5483400 (1996-01-01), Tsujino
patent: 5636091 (1997-06-01), Asano
patent: 5654848 (1997-08-01), Maiers et al.
patent: 5808838 (1998-09-01), Battu
patent: 6047459 (2000-04-01), Fahley et al.
patent: 6125016 (2000-09-01), Lin
patent: 6347023 (2002-02-01
Jenness Sharon M.
Kazmierczak Frederick F.
Heinz A. J.
Merchant & Gould P.C.
Seagate Technology LLC
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