Electricity: measuring and testing – Magnetic – Calibration
Reexamination Certificate
2000-03-23
2002-09-17
Patidar, Jay (Department: 2862)
Electricity: measuring and testing
Magnetic
Calibration
Reexamination Certificate
active
06452380
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates to a calibration rod and testing apparatus for magnetic rolls. More particularly, the present invention relates to a calibration rod and testing apparatus for magnetic rolls that produces an accurate homing location and probe-to-probe reference for repeated test verification at many testing locations. The grooved track calibration rod can be transported to different equipment to verify that equipment is performing similarly. The apparatus for testing magnetic rolls used in the printing, facsimile and copier industry, has improved accuracy, has temperature compensation, uses a circumferential drive movement from one end of a roll magnet and verifies angular position from the other end, eliminates the possibility of angular inaccuracy from twisting of the part being measured during clamping and provides for improved accuracy of several degrees. The calibration rod and testing apparatus for magnetic rolls utilizes a high order polynomial curve fit of the data to determine the true value of the Gauss level being measured during 360° revolution. The apparatus takes measurements to accurately measure magnetic differences rather than differences in probe variation. The value of other probes will be matched (multiplied by a percentage) to a first master reference probe. The apparatus eliminates twist, which can affect pole location accuracy by several degrees.
DESCRIPTION OF THE PRIOR ART
It is difficult to obtain accurate measurement of magnetic rolls between locations. The most common method of such measurement involves using a tangential probe circumferentially around a roll magnet, positioned at a distance substantially equal to the application distance and down the length (axially) at the same distance. Typical application distances are 8 mm, 10 mm, 12 mm, 16 mm, 20 mm, or 30 mm, where less than 0.0254 mm can cause variation in magnetic response data of 7 Gauss or so at a pole peak reading of 1000 Gauss.
Furthermore, if 100% homogeneous ferrite with nylon binder magnetic rolls are clamped in test fixtures with tension applied to both ends, the magnetic roll being tested can develop twist, which can affect pole location accuracy by several degrees.
In addition, variation in temperature of ferromagnetic materials typically causes a 1.8 Gauss change per degree Celsius (1 Gauss per degree Fahrenheit). As a result, temperature measurement is critical. The usual technique for making such measurements places a tangential probe on an aluminum sleeve disposed around the magnetic roll, and rotating the magnetic roll 360 degrees. The tangential probe is then moved axially, or down-the-length of the magnetic roll. Production samples are then taken throughout the day where ambient temperatures vary. Plant temperatures can vary from 7 degrees C. to 38 degrees C. (45 degree F. to 101 degrees F.).
Tangential probes have an internal element of unknown dimensional maximum sensitivity relative to a center point location and of unknown sensitivity in distance from the outer edge. For example, sensing elements are manufactured within a protective jacket, and the exact distance of the actual sensor to the edge is unknown. Therefore, accurate placement of the probe is unclear, and generally the probe is simply placed directly on the surface of a sleeve, resulting in under-reported field levels. In addition, accuracy when using a sleeve with end plugs independently, and coaxially mounted around a magnet, builds in inaccuracies due to circular run out of the sleeve. Furthermore, although motors used to drive a rotational or axial probe movement can have excellent accuracies of {fraction (1/100)} of a degree, the homing accuracy (return to zero) and mechanical movement accuracy (lead screw) could easily involve ½ degree variation and vibration variation of 0.05 mm. Therefore, results from one test apparatus can have compounded variation, and results from test apparatuses at different locations can have even more sizable variation of up to 15% of a scale reading or approximately 150 Gauss.
SUMMARY OF THE INVENTION
The foregoing and other deficiencies of the prior art are addressed by the present invention which is directed to a calibration rod and testing apparatus for magnetic rolls.
This invention provides an apparatus for testing magnetic rolls used in the printing, facsimile and copier industry, having improved accuracy by employing a calibration rod and master probe data which are employed at separated testing apparatus to assure consistent testing results.
This invention also provides a calibration rod and testing apparatus for magnetic rolls having temperature compensation.
This invention further provides a calibration rod and testing apparatus for magnetic rolls which uses a circumferential drive movement from one end of a roll magnet and has a floating angular position at the other end.
This invention further provides a calibration rod and testing apparatus for magnetic rolls in which the existence of parting line flats on end shafts does not influence magnetic measurement.
This invention further provides a calibration rod and testing apparatus for magnetic rolls which eliminates the possibility of angular inaccuracy from twisting of is the part being measured during clamping and provides for improved accuracy of several degrees.
This invention further provides a calibration rod and testing apparatus for magnetic rolls utilizing a high order polynomial curve fit of the data to determine the true value of the Gauss level being measured during revolution.
This invention further provides a calibration rod and testing apparatus for magnetic rolls in which measurements taken of a production magnetic roll will accurately measure magnetic differences rather than differences in probe characteristics.
This invention further provides a calibration rod and testing apparatus for magnetic rolls in which the value of other probes will be matched (multiplied by a percentage) to a first master reference probe.
This invention further provides a calibration rod and testing apparatus for magnetic rolls which eliminates twist, which can affect pole location accuracy by several degrees.
REFERENCES:
patent: 3097598 (1963-07-01), Hotop et al.
patent: 3714692 (1973-02-01), Bray
patent: 3745626 (1973-07-01), Bray
patent: 4638281 (1987-01-01), Baermann
patent: 5384957 (1995-01-01), Mohri et al.
patent: 5539368 (1996-07-01), Yamashita
patent: 5668519 (1997-09-01), Yamashita
Fieseler Wayne Gerard
Foster Mark Duane
Hackett Robert Edward
Murphy Calvin Dale
Nichols James Edward
Brady John A.
Lexmark International Inc.
Patidar Jay
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