Abstract: Welding apparatus for a motorcar body comprising a pair of welding jig units positioned on opposing sides of a combining station which are movable laterally for positioning and holding thereon side panels of the body and a carrier movable between the combining station and a setting station for positioning and holding thereon the floor panel and the roof panel of the motorcar body. The structures of the carrier and the welding jig units are disclosed. Each welding jig unit can be turnable between an inwardly facing position and an outwardly facing one.

Abstract: An exchanging apparatus for exchanging welding jig units of an automatic welding apparatus on an assembly line. The automatic welding apparatus includes a combining station where a work to be assembled is combined and welded by detachable welding jig units, and a set carrier for moving the work along a conveying railway to and from the combining station. The exchanging apparatus comprises an exchanging railway which crosses the conveying railway through a switch mechanism and at least two exchanging carriers, each having thereon a gripping means for gripping a welding jig unit. Each of the above carriers is mounted on a plurality of wheels, each of which is turnable about a fixed vertical shaft on the respective carrier.