Brakes – Internal-resistance motion retarder – Magnetic fluid or material
Reexamination Certificate
2002-03-19
2004-11-30
Butler, Douglas C. (Department: 3683)
Brakes
Internal-resistance motion retarder
Magnetic fluid or material
C188S267000
Reexamination Certificate
active
06823971
ABSTRACT:
FIELD OF THE INVENTION AND RELATED ART STATEMENT
The present invention relates to a simplified loading device capable of applying a fixed load to a moving element such as a motor shaft without the occurrence of friction.
As is well known, a motor braking method has been used in which a sliding brake is incorporated in a motor casing for a motor, and this brake is always applied to provide braking torque at the time of stoppage.
FIG. 6
shows a simplified braking mechanism for a reversible motor, which has been used conventionally.
A motor casing
100
for a motor contains a stator
101
and a rotor
102
, and a brake disc
104
is mounted on a rotating shaft
103
of the rotor
102
. On the inside face of the motor casing
100
opposed to the brake disc
104
are disposed a plurality of brake shoes
105
which are in slidable contact with the brake disc
104
. The brake shoe
105
is inserted in a hole
108
formed axially in a bearing housing portion
107
on which a bearing
106
for supporting the rotating shaft
103
is mounted, and is urged toward the brake disc
104
via a coil spring
109
. Reference numeral
110
denotes a spring support plate.
This braking mechanism is configured so that the brake shoes
105
are always pressed on the brake disc
104
by the urging force of the coil spring
109
to bring the brake shoes
105
into contact with the brake disc
104
, and thereby a load is developed due to friction, by which braking action and holding torque at the time of stoppage are obtained.
FIG. 7
shows a braking mechanism that obtains a load using a permanent magnet.
A rotating disc
112
mounted with a hysteresis material
111
along the circumferential direction on one side face in the axial direction. On the other hand, a yoke
114
provided with a permanent magnet
113
on a face opposed to the hysteresis material
111
is mounted on a bearing
106
supporting the rotating shaft
103
. The relative rotation of the permanent magnet
113
and the hysteresis material
111
around the same axis develops a load due to magnetism.
However, according to the above-described braking mechanism using friction, the loading force is changed by the time change of surface condition of a shoe material used for the brake shoe
105
, and the service life is limited by the wear of shoe material.
Also, in the above-described hysteresis brake, the loading force depends on magnetic lines passing through a gap between the permanent magnet
113
and the hysteresis material
111
, so that the gap must be adjusted delicately, and also the expensive hysteresis material
111
must be used.
OBJECT AND SUMMARY OF THE INVENTION
The present invention has been made to solve the above problems, and accordingly an object thereof is to provide a simplified loading device capable of generating a high and steady loading force and being made smaller in size as compared with the related art.
To achieve the above object, the present invention provides a simplified loading device in which a permanent magnet is arranged between a moving element and a fixed element for holding the moving element, a magnetic fluid is disposed in a gap developed at some midpoint in a magnetic circuit in which the magnetic flux of the permanent magnet passes through the moving element, and a shearing force of the magnetic fluid produced by the magnetic flux of the permanent magnet is exerted on the moving element as a loading force.
Also, the present invention provides a simplified loading device in which a permanent magnet is arranged between a rotating shaft and a fixed element for holding the rotating shaft, a magnetic fluid is disposed in a gap developed at some midpoint in a magnetic circuit in which the magnetic flux of the permanent magnet passes through the rotating shaft, and a shearing force of the magnetic fluid produced by the magnetic flux of the permanent magnet is exerted on the rotating shaft as a loading force.
In the present invention, the magnetic fluid is disposed on the peripheral surface of the rotating shaft or the inside surface of the fixed element.
Further, in the present invention, magnetic powder is dispersed in a solution as the magnetic fluid, a drag against shearing due to a fixed chain is created under a condition in which a fixed magnetic force is exerted, and a fixed drag is created even after shearing has been performed.
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patent: 2650684 (1953-09-01), English, Jr. et al.
patent: 3366903 (1968-01-01), Searle et al.
patent: 4200003 (1980-04-01), Miller
patent: 4239092 (1980-12-01), Janson
patent: 4856631 (1989-08-01), Okamoto et al.
patent: 4974706 (1990-12-01), Maji et al.
patent: 5598908 (1997-02-01), York et al.
patent: 5947238 (1999-09-01), Jolly et al.
patent: 6412618 (2002-07-01), Stretch et al.
patent: 6464050 (2002-10-01), Smith et al.
patent: 6466119 (2002-10-01), Drew
patent: WO 99/06731 (1999-02-01), None
Nakano Masami
Saito Makoto
Takeda Hiroshi
Butler Douglas C.
King Bradley
Oriental Motor Co., Inc.
Trop Pruner & Hu P.C.
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