Abstract: A rail-travelling conveyor device to be advanced supported by two mutually parallel rails, comprising: a carrier frame, a load compartment substantially firmly connected with the carrier frame, said load compartment being arranged at least partly below the rails, said load compartment having a maximum extent in the longitudinal direction of the rails, a plurality of driving wheels engaging the rails, at least one motor which is connected with the conveyor device and which drives at least one driving wheel. The device is characterized by each driving wheel having a separate rotational shaft connected with the carrier frame, said rotational shafts having rotational axes fixed with respect to the carrier frame, said rotational shafts being arranged within the said maximum extent of the load compartment in the longitudinal direction of the rails, and guide means to guide the conveyor device through curves.

Abstract: In a method of dosing fibers, such as steel fibers to be mixed in concrete, a supply of fibers (5) is stored in first vibration feeder (2) and is moved from this by means of a second vibration feeder (3). For each dosing operation, a proportioned quantity of fibers (5) is transferred at a stepless rate or a stepwise declining rate from the first to the second vibration feeder (2, 3) while the second vibration feeder (3) stands still. This vibration feeder (3) then transports the transferred fiber quantity further on to the subsequent process while the first vibration feeder (2) stands still. The fibers can hereby be dosed more accurately and uniformly than known before.