Abstract: A first (5) of the sheets has, near the zone (6) of overlap, stiffening parts (74) designed to resist the bending of the sheet along the zone of overlap. At least one region of the first sheet (5) is made to project, cantilever fashion, into the zone (6) of overlap. The stiffening parts are located near this cantilevered region. A pressing mechanism of a laser welding installation (2) is made to press against another sheet (4) to hold the sheets in contact with one another at the zone (6) of overlap. The laser welding installation is used to weld the sheets together along the zone of overlap. Application to the welding together, by transparency-welding, of sheets of the external skin of railway vehicle bodies.

Abstract: This installation (2) for laser welding at least two overlapping parts (4, 5) comprises a laser source (16), a head (18) for focusing, in the zone of overlap (6), a laser beam emitted by the source, a mechanism (24) for pressing on a first (4) of the parts and intended to co-operate with means (26) for retaining another part (5) so as to hold the parts that are to be welded pressed together in the region of their zone of overlap, and means (10, 14) for the relative displacement of the head with respect to the zone of overlap of the parts that are to be welded. The pressing mechanism (24) is subject to the displacement of the head parallel to the zone of overlap. The pressing mechanism comprises an element (44) for pressing on rolling means that are intended to roll along the first part (4). This element is free to rotate about an axis. The rolling means automatically orientate themselves in the direction of displacement of the head (18) parallel to the zone (6) of overlap by the rotation of the said element.