The patent badge is an abbreviated version of the USPTO patent document. The patent badge does contain a link to the full patent document.
The patent badge is an abbreviated version of the USPTO patent document. The patent badge covers the following: Patent number, Date patent was issued, Date patent was filed, Title of the patent, Applicant, Inventor, Assignee, Attorney firm, Primary examiner, Assistant examiner, CPCs, and Abstract. The patent badge does contain a link to the full patent document (in Adobe Acrobat format, aka pdf). To download or print any patent click here.
Patent No.:
Date of Patent:
May. 10, 1994
Filed:
Mar. 21, 1991
Bernard Bisiaux, Valenciennes, FR;
Vallourec Industries, Boulogne Billancourt, FR;
Abstract
The method and the apparatus relate to the detection of faults in the wall of a passing metal tube. A solenoid or solenoids generate two alternating magnetic fields of different frequenceis, the frequencies being chosen from the range of medium and high frequencies, in order to produce in the wall of a tube eddy currents which interact with the faults. The signals resulting from these interactions are detected by at least one detection solenoid and each difference in amplitude D between the signals obtained at the two frequencies for one and the same fault is compared with a specific difference which constitutes a threshold for rejection of the corresponding tube. Application of the method and of the apparatus to the inspection of ferrous or non-ferrous magnetic and non-magnetic metal tubes.