Device for detecting seam between abutting workpieces by electron beam

Abstract

A device, for tracking a seam between abutting workpieces by a scanning electron beam, includes a scanning electron beam generating source, a power supply source of the scanning electron beam generating source, at least one secondary emission detector accommodated within a shield and positioned during welding between the scanning electron beam generating source and a workpiece being welded. The detector has an aperture for the scanning electron beam to pass through, and a tap to which is connected a generator of information signals indicative a variation in the surface of the workpiece being welded. This information signal generator is constructed as a differential unit having one input connected to the detector tap, and the other input connected to the power supply source of the scanning electron beam generating source. The information signal indicative of variation in the workpiece surface is formed at the output of the differential unit, and corresponds to the difference between a signal representative of the scanning electron beam pulsation and a signal representative of a secondary electron flow, produced in a zone of electron beam impingement on the workpiece surface being scanned and received by the secondary emission detector.