The invention comprises a frame (2) configured to be towed and positioned over a hay bale (3) resting on the ground, said frame (2, 17) comprising means for holding and vertically lifting a bale (3a) off the ground to an upper stacking position, characterised in that said means for vertically lifting (5, 14, 15) the bale (3a) include at least one pair of vertical slide carriages (5a, 5b) of means for holding (14) said bale, said carriages (5a, 5b) being disposed in opposition to each other on the sides of a bale (3) holding compartment (6) of said frame (2, 17), said accumulator also comprising means for suspending (16) said bale (3a) in said upper stacking position while said carriages (5a, 5b) move towards a lower loading position in the interior of said compartment (6) in order to receive a new bale (3b), the entrance of said compartment (6) being susceptible of becoming free to receive said new bale (3b) while said slide carriages (5a, 5b) remain on standby. Fig. 2 and fig. 4
