Apparatus for magnetic inspection using magnetic shield
US5357198A · kind A · utility
Assignee
Inventors
Key dates
| Filing date | Sep 29, 1992 |
| Grant date | Oct 18, 1994 |
| Priority date | — |
| Expiry date | Sep 29, 2012 |
Classification
- Technology area (CPC G)Physics
- CPC primaryG01N27/82
- WIPO fieldMeasurement
- WIPO sectorInstruments
Abstract
In a magnetic inspection method and apparatus, a magnetizer (4) is provided such that a pair of magnetic poles (4a, 4b) face an object (10) to be inspected. A magnetic field is generated by the magnetizer (4) in the object (10). A magnetic sensor (7a) is situated at a substantially middle point of a line connecting the magnetic poles (4a, 4b) or a line parallel to this connecting line. Shield bodies (22a, 22b, 23a, 23b) with a low coercive force are arranged on those sides of the magnetic sensor (10) which face the magnetic poles. The magnetic sensor (7a) detects a leakage magnetic flux due to an internal or surface defect of the object (10). In addition, the distance (2A) between the shield bodies (22a, 22b) is 2.2 times or more, and 2.8 times or less, the distance (L) between the magnetic sensor (7a) and the object (10). Furthermore, each shield body (23a, 23b) has an L-cross section composed of a vertical portion (24a) and a horizontal portion (24b), and the width (2A) of the horizontal portion (24b) in the direction of arrangement of the magnetic poles (4a, 4b) is 0.4 time or more, and 0.6 time or less, the distance (B) between the magnetic poles.
Source: USPTO / EPO open patent data. Objective bibliographic and citation counts.