Vibration device for a conveying apparatus (21) to convey a metal charge in a longitudinal direction (X) comprising at least two vibration mechanisms (25, 26) each disposed on opposite sides of the conveying apparatus (21) so as to feed the metal charge. The vibration mechanisms (25, 26) comprise at least a first plurality of eccentric masses (31, 32, 33) having their mass barycenters (B) oriented in parallel directions to each other, and a second plurality of eccentric masses (34, 35) having their mass barycenters (B) disposed angularly offset with respect to the disposition of the barycenters of the first plurality of eccentric masses (31, 32, 33).