Abstract: Upwardly open vessels are supplied horizontally to an intake location and are taken horizontally from an output location. Between these locations they are inverted and passed past a treatment device by an inverting conveyor having a pair of like endless chains supported on guides to define a transport path lying generally in a vertical plane and having an upstream end opening horizontally at the intake location, a downstream end opening horizontally at the output location, and an intermediate portion vertically offset from the intake and output locations. The chains have substantially parallel and laterally spaced conveying stretches extending and movable downstream along the path from the intake to the output location and past the treatment location and return stretches extending and movable upstream back along and outside the respective conveying stretches between the intake and output locations which can be laterally moved.