Electricity: measuring and testing – Magnetic – With compensation for test variable
Patent
1993-02-01
1996-04-30
O'Shea, Sandra L.
Electricity: measuring and testing
Magnetic
With compensation for test variable
324240, 324244, 361146, G01R 3902, G01N 2772
Patent
active
055128211
DESCRIPTION:
BRIEF SUMMARY
BACKGROUND OF THE INVENTION
The present invention relates to a magnetic detecting method and a magnetic detector, in which magnetizers applys magnetic fields crossing over an object made of magnetic material, such as a steel plate, and magnetic sensors are used to detect leakage fluxes generated at magnetically defective portions of the object.
A magnetic detector utilizes magnetism to detect magnetically defective portions of an object, e.g., a thin steel strip, such as flaws or inclusions existing in the surface of the thin steel strip. It is reported that a magnetic detector having a group of magnetic sensors arranged linearly for detecting magnetic fluxes can continuously detect defects existing in a moving thin steel strip, over the entire width thereof. (See Published Unexamined Japanese Utility Model Application 63-107849.)
FIGS. 46A and 46B are sectional views schematically showing the magnetic detector for continuously detecting defects in a moving thin steel strip. FIG. 46C is a side view showing the magnetic detector and also a support device supporting the detector.
As is illustrated in FIG. 46C, a horizontal arm 12 is supported in a frame 11 secured on the floor of a building, by means of a pair of spring members 13a and 13b. The horizontal arm 12 can thereby move up and down. The magnetic detector has a hollow roll 1 and a rigid shaft 2. The rigid shaft 2 is fastened to the center part of the horizontal arm. Two guide rolls 14a and 14b are located at the sides the frame 11, respectively, for guiding a thin steel strip to the outer circumferential surface of the hollow roll 1 of the magnetic detector.
As FIGS. 46A and 46B show, one end of the rigid shaft 2 extends through the hollow roll 1 made of non-magnetic material, located coaxial with the hollow roll 1. The other end of the rigid shaft 2 is fastened to the horizontal arm 12. The rigid shaft 2 is supported and located coaxial with the hollow roll 1, by means of a pair of rolling bearings 3a and 3b. Hence, the hollow roll 1 can freely rotate around the rigid shaft 2.
In the hollow roll 1, a magnetizing core 4c, substantially U-shaped, is fastened to the rigid shaft 2 by a support member 5, having its magnetic poles 4a and 4b positioned near the inner circumferential surface of the hollow roll 1. A magnetizing coil 6 is wound around the magnetizing core 4c. The core 4c and the coil 6 constitute a magnetizer 4. A plurality of magnetic sensors 7a, forming a group 7, are fixed on the rigid shaft 2, located between the magnetic poles 4a and 4b and arranged parallel to the axis of the shaft 2.
A power-supply cable 8 for supplying an exciting current to the magnetizing coil 6, and a signal cable 9 for supplying signals output by the magnetic sensors 7a pass through the rigid shaft 2 and extend outwardly from the shaft 2. Hence, the magnetizer 4 and the group 7 of magnetic sensors are fixed in place, whereas the hollow roll 1 can rotate around the magnetizer 4 and the sensor group 7, slightly spaced apart therefrom.
When the hollow roll 1 of the magnetic detector described above is so moved as to have its outer circumferential surface pushed, with a predetermined pressure, onto one side of a thin steel strip 10 moving in the direction of arrow a, the hollow roll 1 is rotated in the direction of arrow b. This is because the shaft 2 is fastened to the horizontal arm 12.
In the magnetic detector, when an exciting current is supplied to the magnetizing coil 6, the magnetic poles 4a and 4b of the magnetizing core 4c and the thin steel strip 10 form a closed magnetic path. If defects exist in the steel strip 10 or in the surface thereof, the magnetic resistance in the strip 10 changes, generating leakage fluxes. The leakage fluxes are detected by those of the magnetic sensors 7a forming the group 7, which oppose the defective portion of the strip. These magnetic sensors 7a output signals representing the defects.
The levels of the signals detected correspond to the sizes of the defects existing in the thin steel strip 10 or in the surface thereof. The
REFERENCES:
patent: 4510447 (1985-04-01), Moyer
patent: 4564809 (1986-01-01), Huschelrath et al.
patent: 4823081 (1989-04-01), Geisler
patent: 4944028 (1990-07-01), Iijima et al.
Ando Seigo
Inaba Mamoru
Iwanaga Kenichi
Maki Hiroshi
Matsufuji Yasuhiro
NKK Corporation
O'Shea Sandra L.
Patidar J. M.
LandOfFree
Method and apparatus for magnetically detecting defects in an ob does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Method and apparatus for magnetically detecting defects in an ob, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Method and apparatus for magnetically detecting defects in an ob will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-631171