Abstract: A multi-point laser welding installation for vehicle bodies includes apparatus for positioning the pieces to be welded, apparatus for gripping the pieces and apparatus for welding the positioned and gripped pieces at specific points. The apparatus for positioning and gripping are provided with bearing surfaces. The shape of these surfaces conforms to the shape of the pieces. The apparatus for positioning and gripping include cavity which open the pieces at right angles. The welding apparatus is fixed on the positioning and/or gripping apparatus in order to ensure spot welding of the pieces at right angles to the cavities.

Abstract: Method of and installation for spot-welding by laser beam, the method characterized in that the focusing means (3) undergoes displacement so that the point of focus (4) of the beam on the workpieces (4, 5) describes at least a path which is closed upon itself and of which the surface area of fusion obtained corresponds to the desired spot weld.The invention is applied to the welding of superposed workpieces.

Abstract: A method of spot-welding by laser beam, comprising a laser beam generator (10) and at least one means receiving the laser beam and focusing it on the pieces to be welded.

Abstract: An apparatus for the working of materials in a vacuum by means of an electron beam. A vacuum machining facility incorporating a first chamber which includes a longitudinal gap which determines a vacuum tight area around the machining line of the parts to be machined, a flexible sealing strip to plug the gap and a second leakproof chamber which houses an electron gun. The second chamber abutting the first chamber, includes an orifice located close to the gap through which the electron beam passes. The second chamber is movable on the first chamber along the gap. An apparatus is included which moves the plugging strip out of and to the side of the gap in the proximity of the orifice, the plugging strip being fully housed inside the gap except in the region close to the orifice.