Bearings – Rotary bearing – Fluid bearing
Reexamination Certificate
1999-03-18
2001-10-16
Footland, Lenard A. (Department: 3682)
Bearings
Rotary bearing
Fluid bearing
Reexamination Certificate
active
06302586
ABSTRACT:
BACKGROUND OF THE INVENTION
A) Field of Invention
The present invention relates to a fluid sealing device for use with a motor, and more particularly to a fluid sealing device for use with a motor for rotating a disc drive.
B) Description of Related Art
Numerous fluid sealing devices for use with motors for rotating disc drives have been proposed. For example, various embodiments of known fluid sealing devices are shown in abandoned U.S. patent application Ser. No. 08/438,953, which was filed on May 11, 1995, and U.S. patent application Ser. No. 08/442,32 which was filed on May 16, 1995, U.S. Pat. No. 5,675,199.
FIG. 1
of the current application shows a DC motor which uses a known fluid sealing device as described in the '953 application. The motor includes a frame
21
with a center shaft
21
a.
In this motor, a hub
54
is mounted on the center shaft
21
a
of the frame
21
by use of bearings
2
and a magnetic bearing fluid
14
.
A stator core
6
is fixed to an outer surface of the frame
21
and a coil
5
is wound onto the stator core
6
. A drive magnet
7
is attached to an inner periphery of the hub
54
and is positioned to face the stator core
6
. One or more discs, which are not shown, are loaded onto the outer periphery of the hub
54
. Thus, when a voltage is applied to the coil
5
from an external power source, the hub
54
and associated discs are rotated.
The frame
21
and center shaft
21
a
are made of a ferromagnetic material. A magnet
30
having an inclined surface
30
A is positioned near an open end of the frame
21
to form a magnetic circuit. The magnetic circuit includes the magnet
30
, ferromagnetic frame
21
and center shaft
21
a,
as well as the magnetic bearing fluid
14
. This magnetic circuit prevents the magnetic bearing fluid
14
from leaking out of the motor and contaminating the discs.
The DC motor shown in
FIG. 1
also includes bearing fluid absorption members
43
which are attached to an upper surface of the magnet
30
and an outer surface of the shaft
21
a.
Thus, even if the magnetic bearing fluid
14
is not completely contained by a magnetic flux produced from the magnetic circuit, the bearing fluid absorption members
43
will absorb the magnetic fluid and prevent further leakage.
FIG. 2
, which is also included in the '953 application, shows a similar fluid sealing device. Under this arrangement, a magnet
31
and ferromagnetic body
35
, which is fixed to a center shaft
3
, form part of a magnetic circuit to prevent the magnetic bearing fluid
14
from leaking out of the motor and contaminating the discs.
The DC motor shown in
FIG. 2
also uses bearing fluid absorption members
43
. The bearing fluid absorption members
43
of the device shown in
FIG. 2
are also attached to an upper end of a magnet
31
and an outer peripheral surface of a shaft
3
. Similar to the device shown in
FIG. 1
, the bearing fluid absorption members
43
are provided to absorb magnetic bearing fluid which escapes a magnetic flux produced by the magnetic circuit.
FIG. 3
, which is described in the '321 application, shows another known configuration of a fluid sealing device for a DC motor. Referring to
FIG. 3
, a magnet
30
, center shaft
3
, and bearing
2
form part of a magnetic circuit to prevent the magnetic bearing fluid
14
from leaking from a motor.
A plate
41
is mounted to one end of the magnet
30
adjacent to an open end of the shaft
3
to further prevent the magnetic bearing fluid
14
from leaking. Attached to the plate
41
and the shaft
3
are layers
42
which are made of a slippery material such as TEFLON. The layers
42
cause the magnetic bearing fluid
14
coming into contact with them to form into beads or droplets and thus be returned to the reservoir of magnetic bearing fluid
14
.
Bearing fluid absorption members
43
are also provided and positioned on an upper surface of the plate
41
and on the center shaft
3
. The bearing fluid absorption members
43
absorb any magnetic bearing fluid
14
which leaks past the magnetic circuit and the layers
42
.
During conditions of shock and vibration, the bearing fluid escapes from its reservoir. The devices shown in
FIGS. 1 through 3
capture much of the escaped bearing fluid. However, any bearing fluid that is not captured by these devices tends to contaminate the discs affixed to the motor. Thus, there remains a need for an improved bearing fluid sealing device which can more effectively capture and absorb larger amounts of bearing fluid and therefore more effectively prevent bearing fluid from leaking and from contaminating the discs.
OBJECTS OF THE INVENTION
An object of the invention is to provide a bearing fluid sealing device which can more effectively capture and absorb bearing fluid to better prevent bearing fluid from leaking from a motor and contaminating disks.
A further object of the invention is to provide a fluid sealing device with a design that can accommodate known and proven motor structures.
Another object of the invention to provide a fluid sealing device that is low in cost, reliable in use, and which does not compromise or degrade the performance characteristics of the motor.
BRIEF DESCRIPTION
In one embodiment of the invention, a sealing device for bearing fluid in a motor involves an arrangement of a sealing plate and bearing fluid absorption pad mounted axially outward from a reservoir for the bearing fluid. A radially expanded capture space between the reservoir and the combination of plate and pad assures that droplets of bearing fluid impinge on a surface of the bearing fluid absorption pad.
An end surface of the bearing fluid absorption pad is exposed to the capture space above the bearing fluid reservoir. Thus, when bearing fluid leaks, a large surface area of the bearing fluid absorption pad is available to capture and absorb the bearing fluid.
REFERENCES:
patent: 4915510 (1990-04-01), Arvidsson
patent: 5284391 (1994-02-01), Diel
patent: 5323972 (1994-06-01), Kjellqvist
patent: 5328271 (1994-07-01), Titcomb
patent: 5577842 (1996-11-01), Parsoneault
patent: 7310830 (1995-11-01), None
patent: 814403 (1996-01-01), None
patent: 872189 (1996-03-01), None
patent: 861517 (1996-03-01), None
patent: 874864 (1996-03-01), None
Footland Lenard A.
Reed Smith LLP
Sankyo Seiki Mfg. Co. Ltd.
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