Electricity: measuring and testing – Magnetic – Displacement
Reexamination Certificate
1999-10-19
2001-10-16
Snow, Walter E. (Department: 2862)
Electricity: measuring and testing
Magnetic
Displacement
C324S207220, C324S262000
Reexamination Certificate
active
06304080
ABSTRACT:
FIELD OF THE INVENTION
The invention relates generally to the field of magnetic field measuring systems. More particularly, the invention concerns a system capable of verifying the location of physical features on a complex magnetic element such as miniature multi-pole, high energy, magnetic rotors that drives electromagnetic camera shutter actuators.
BACKGROUND OF THE INVENTION
Miniature bipolar cylindrical magnets are used as the drive element (rotor) in electromagnetic components such as electromagnetic camera shutter actuators. To ensure proper and reliable shutter performance, the polarization (operating point) and orientation of the magnets need to be controlled to a high degree of accuracy. However, during the mass production of these magnets significant variations occur in both of these characteristics. These variations are due to non-uniformity's of the bulk materials from which the magnets are cut and from variations in the magnetizing field strength over the group of magnets that are bulk magnetized. Moreover, experience indicates that it is difficult, if not impossible, to eliminate both of these causes.
There have been several attempts to provide an apparatus and method for rapidly determining de magnetization and orientation for purposes of selecting only those magnets that have acceptable values.
Referring to
FIG. 1
, one such existing apparatus
1
, disclosed in Research Disclosure No. 37841, dated October 1995, comprises a rectangular ferromagnetic core
11
with two gap regions
2
and
3
. A field sensor
4
is positioned in gap region
3
that is connected to a Gaussmeter
5
, and a first angular meter device
6
. First angular meter device
6
further comprises a first needle pointer
7
connected to a first support member
8
that is mounted for rotation about a pivot axis
9
, and a marked scale
10
for determining the angular deflection of the first needle pointer
7
from the vertical straight up position (illustrated in FIG.
1
). The ferromagnetic core
11
and the first angular meter device
6
are mounted on a frame
12
that is constructed from a non-magnetic material such as aluminum. The core
11
is fixed to the frame
12
whereas the first angular meter device
6
is mounted for translation along the frame
12
as indicated by the solid arrow in FIG.
1
.
Referring to
FIG. 2
, a second prior art apparatus
14
(also disclosed in the above referenced Research Disclosure) for rapidly determining the orientation of miniature bipolar magnets for purposes of selection for assembly is illustrated. According to
FIG. 2
, the apparatus
14
comprises a second angular meter device
16
that is mounted for linear translation relative to a stationary member
18
. The second angular meter device
16
, made from non-magnetic material, comprises a second needle pointer
20
connected to a second support member
22
that is mounted for rotation about a pivot axis
24
. As shown in
FIG. 2
, second angular metering device
16
further includes a marked scale
26
for determining the angular deflection of the second needle pointer
20
from its detent position. The second support member
22
which is mounted for rotation has a top portion (not shown) that is designed to hold a miniature bipolar magnet that is to be tested. The stationary member
18
is made from non-magnetic steel and comprises a base
28
, and support structure
30
which supports two ferromagnetic pole pieces
32
a
and
32
b
that are in a spaced-apart relation. The second angular meter device
16
is mounted for translation as indicated by the dotted arrow in FIG.
2
.
Referring again to
FIG. 1
, an existing method for evaluating the polarization and orientation of miniature bipolar magnets
40
include the step of initially providing first angular meter device
6
in position A, separated from core
11
. A miniature bipolar cylindrical magnet
40
is mounted on first support member
8
of first angular meter device
6
with its “anticipated” north pole
40
a
vertically up. In this initial position, first needle pointer
7
is straight up indicating 0 degrees of deflection on the marked scale
10
. The first angular meter device
6
is then moved to position B as illustrated until the magnet
40
is symmetrically positioned in gap region
2
of core
11
. The magnet
40
will then align itself in the gap
2
so that its “true” north pole
40
a
is symmetrically positioned with respect to tapered pole tip
2
a.
If the “true” north pole
40
a
is offset in an angular sense from the “anticipated” north pole, the magnet
40
will rotate and first needle pointer
7
will deflect indicating the angular offset on the marked scale
10
. In this way, the orientation of the magnet
40
is determined. Once the magnet
40
has oriented itself, it comes to rest. In its rest position, the flux from the magnet
40
passes through the core
11
and is directed through gap region
3
where the field sensor
4
is located. The field through the sensor
4
is registered on Gaussmeter
5
. This registered field value is compared to a calibration field value from a known magnet. In this way, the magnetization of the magnet
40
is determined. Depending on the results of the test, the magnet
40
is either accepted or rejected.
A shortcoming of the aforementioned existing apparatus and method for screening bipolar magnets
40
is that they do not have the ability to verify manufacturing variability and magnetization in complex magnetic rotors. More importantly, existing apparatus and methods, as described above, do not have the ability to compare magnetic flux density of a magnet with angular position or angular position of certain post features with reference to magnetic poles. Moreover, existing models do not have the ability to display acquired data and then compare such data with predetermined calibrated complex magnetic elements, such as magnetic rotors.
Therefore, a need persists in the art for a measurement apparatus and method that can generate specific magnetic flux and angular position data of bipolar miniature magnets for determining their acceptability for use in electromagnetic components, such as high speed shutter applications.
SUMMARY OF THE INVENTION
It is, therefore, an object of the invention to provide a system capable of verifying manufacturing variability and magnetization in complex magnetic elements, such as magnetic rotors for driving electromagnetic components.
It is another object of the invention to provide a system that correlates physical features to angular positions of magnetic poles arranged on a complex magnetic element, such as a magnetic rotor.
Still another object of the invention is to provide a system that produces and displays multiple data arrays including relative angular positions of each point, magnetic pole flux density and post magnetic flux density.
Yet another object of the invention is to provide a system that simultaneously measures the radial components of a magnetic field even when spatial separation between magnetic poles is less than 1 mm, and the magnetic element has a complicated 3-dimensional shape.
Yet another object of the invention is to provide a system that can produce measurement results in a relatively short time.
The present invention is directed to overcoming one or more of the problems set forth above. Briefly summarized, according to one aspect of the present invention, a system measures magnetic properties of each one of a plurality of magnetic poles and each one of a plurality of physical features arranged on a complex magnetic element having a fixed reference feature thereon. The system includes means for rotating the magnetic element so as to continuously expose each one of the plurality of magnetic poles and each one of the plurality of physical features to a measurement of magnetic flux. An encoder means, operably connected to the means for rotating, generates a first signal corresponding to an angular position of each one of the plurality of magnetic poles relative to a predetermined one of the plurality of physical features.
Kenny Gary R.
Reznik Svetlana
Bailey, Sr. Clyde E.
Eastman Kodak Company
Snow Walter E.
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