PURPOSE: An electron beam is correctly projected on a grooved position by using a plurality of coils for periodic deflection scanning of parallel directed electron beam, and a detector that traps reflected and secondary electron from a surface to be welded.
CONSTITUTION: A welding line 6 is detected and scanned by a detective electron gun 1 provided with deflecting coil 3 and 3' and a collector plate 7 for reflected electrons. The location of the detective electron gun 1 is associated with a welding electron gun 12 such that a connecting line of both centers of each gun 1 and 12 agree with the direction of material transfer. A transfer of material 5 is detected by a touch roll 15 and a pulse generator 16. A time counter 18 transmits a welding line position signal corresponding to the distance between the center of the detective gun 1 and the welding line 16. The signal is stored in a minicomputer 23, then successively read out and analogue-converted to be put in a deflecting coil power source 22 of the welding electron gun 12. Deflecting coils 13 and 13' are magnetized in accordance with the instruction so that a welding beam 14 is directed to the correct position as detected by a detecting electron beam 2.
MORITA KIYOSHI
KINOSHITA MASASHI
SASAGAWA TETSUZOU
