The invention relates to a device which in a mounted state on a piece of furniture (3) exerts a force on a furniture part (2), which is movably guided on the piece of furniture, in the opening direction of said furniture part. The device comprises an energy store (4) for moving the furniture part and a charging mechanism (7) for the energy store. A first embodiment is characterised in that first charging control means (8) are provided, which control the charging mechanism in such a way that it charges the energy store when the furniture part is moved in the opening direction (5). A second embodiment is characterised in that mode-selection means for activating or deactivating opening path-limiting means for the furniture part are provided.