The bucket has a straight side (31) in front and a rounded side (32) opposite to the straight side. An edge (34) is supported on a rectangular support frame (4) or on a closed U shape support frame (5). The edge (34) has two rectilinear lateral sides (33) joined by the rounded side and perpendicular to a rectilinear side. The shape of the frame (5) is same as that of the edge (34).