IMPROVEMENTS RELATING TO BEAMED ENERGY CONTROL SYSTEMS

1,271,146. Cutting and welding by fusion. FERRANTI Ltd. 4 Nov., 1970 [24 Oct., 1969], No. 52189/69. Addition to 1,111,865. Headings B3R and B3V. [Also in Divisions G1 and G2] The photo-electric machine control system of Specification 1,111,865 is further provided with means operable when the workpiece is within an enclosure 11 for projecting on to the working surface 12 by way of the projection system 55, 56, 315 a visible image defining the position of the reference point 316 of the photocell with respect to the position of the workpiece, thereby allowing the position of the workpiece to be adjusted so that the desired initial working point corresponds to the image position. Light showing through a condenser 303 and diffuser 304 projects an image of a graticule 305, via a mirror having a half-silvered central portion 313, on to the working surface. The graticule comprises a transparent disc having radial lines ruled thereon (Fig. 2, not shown). The graticule and photo-cell centre 316, on the one hand, and workpiece surface, on the other, are at conjugate foci of the projection system. A filter 151 may be provided in the light path.