Device for welding structures, such as motor-vehicle bodies or parts thereof, constituted by loosely preassembled, pressed sheet-metal elements

A device for welding structures constituted by loosely preassembled, pressed sheet-metal elements, particularly but not exclusively motor-vehicle bodies and parts thereof, the device including:

• a station for positioning and welding the components of the structure,
• a conveyor line for transporting the loosely preassembled structures to the station,
• at least two pairs of positioning frames disposed in the station on either side of the conveyor line, each pair of positioning frames having locating devices which can engage the structure to be welded and are suitable for the specific geometric shape of a structure of a particular type,
• welding means in said station for welding the elements of the structure after they have been positioned correctly by the respective pair of positioning frames,
• means for transporting the positioning frames in order to bring the pair of positioning frames corresponding to the type of structure to be welded at the time in question into an operative position in the welding station,
• said transporting means including:
• two rotary drums which are disposed in the station on either side of the conveyor line and are rotatable about respective axes parallel to the conveyor line, each drum being associated with the positioning frames on one side of the station,
• means for restraining respective positioning frames in fixed positions on each drum during its rotation, and
• means for completely removing one positioning frame from the respective rotary drum when the drum is stationary and for moving the frame transverse the conveyor line towards an operative position adjacent the structure to be welded and, in the opposite direction, from its operative position to return the positioning frame to the respective rotary drum,
• wherein:
• the means for restraining the respective positioning frames on each rotary drum include a pair of annular tracks disposed in two parallel planes perpendicular to the axis of rotation of the drum,
• the ends of each positioning frame are guided on the annular tracks,
• each rotary drum includes a motor-driven shaft, two rotors connected to the shaft, and means on each rotor for entraining the positioning frames in rotation about the axis of the drum, guided on the two annular tracks,
• each annular track has a fixed, main sector which is connected rigidly to a fixed support structure and an auxiliary sector which completes the ring of the track and is separate from the main sector on the side of the ring which faces the conveyor line, and
• the means for transporting the positioning frames include, for each side of the station, two auxiliary support structures to which the two auxiliary sectors of the annular tracks are connected rigidly and which are movable transverse the conveyor line.