Disclosed is an accumulation device, for accumulating products conveyed within an industrial treatment line, including a set of horizontal trays, arranged in a tray zone as a vertical stack, further including a manipulator, such as a robot, for transferring products between a substantially horizontal closed belt type conveyor and the uppermost tray of the bottom portion of the stack. The trays are movable in the vertical direction, at least in order to bring at a predetermined height the tray to be loaded or unloaded. Also disclosed is a corresponding conveying installation and method.