The machine disclosed herein comprises a rotary vat (13) provided with an opening (23) closed by a door (24). Said door comprises locking members and the machine is provided with an automatic locking-unlocking device (26) arranged to automatically lock the door (24) on the vat (13) or to unlock and lift the door to clear the opening (23) of the vat. Said machine further comprises members (27) to load the vat and mechanical drive members to drive the vat (13).