of the carriage 3 and protecting most of the functional members mounted on this carriage furthermore a handling hand grip 133 is also fastened onto the frame of the carriage 3 and more precisely on one face thereof opposite to the torch 40 this grip 133 permits the handling and the installation of the machine 1 as well as the manual displacement of the carriage 3 with respect to the stationary support 2 it also appears from fig1 and 5 that the stationary support is constituted essentially by a rail the longitudinal direction of which coincides with the feed path of travel t of the carriage here the rail 22 is thus rectilinear and substantially parallel to the axis x this rail 22 is constituted by a section with a length corresponding to that of the profile p to be welded and of the order of three meters a toothed rack 221 visible on fig4 and 5 is fastened to the rail 22 in parallel relation to x this toothed rack 221 extends throughout the length of the rail 22 and co operates with a toothed pinion 521 made fast to for rotation with the first drive member 51 previously described the toothed pinion 521 the axis of rotation of which is substantially parallel to y is in engagement with the teeth of the toothed rack 221 so that if the motor 51 is actuated the carriage 3.