LEAKAGE MAGENTISM FLAW DETECTOR FOR FLAW OF INTERNAL HOLE SURFACE

摘要

PURPOSE:To detect a defect part of the internal surface of a tube easily by setting a magnetic tape in a frame which moves in the tube, and moving the frame in a tube- axis direction while bringing the magnetic tape into contact with the tube internal surface and thus recording leakage magnetic flux on the magnetic tape. CONSTITUTION:Once a holding cylinder 1 equipped with a motor 9 is inserted into a body W to be inspected and the motor 9 is driven, currents flow through conductors 2 and 3a to the body W to be inspected to produce a magnetic field around the circumferential surface of an internal hole surface W1. A gear 9a is driven by the motor 9 and once rotary heads 10 and 11 rotate around the holding cylinder 1 through the rotation of a transmission gear 21 engaging said gear 9a, the rotation of the transmission gear 21 is transmitted to a driven gear 22, worm gear device 23, rack gear, etc., to move the rotary head 10 and 11 straight forward. A press-contacting roller 12 provided rotatably to the rotary heads 10 and 11 comes into contact with the internal hole surface W1 through a magnetic tape 16 paid off from a supply reel 17 and also rotates around the holding cylinder 1 while rotating on its own axis, thus recording leakage magnetic flux produced at a defect part on the magnetic tape 16.