Abstract: The present invention relates to an endless chain structure incorporating a series of cages with a mechanism for varying the distance between the cages. The cages are arranged in two rows, one above the other, and are very close together in the straight stretches. Each of the cages is attached to a mechanism for varying the distances which determine an increase or a reduction in the separation between the cages before or after, respectively their passage over end pulleys or wheels of the structure, so that a cage begins its ascent towards the upper level or its descent towards the lower level, following a curved line determined by the rim of the pulley, to avoid the cage in question from being reached or touched by the cage immediately following and travelling in a direction that is still rectilinear.