A conveyor conveys palletized articles to a loading dock. A
bogie movable along rails between different loading docks, supports an independently movable
carriage, which may roll out of the
bogie once the latter reaches a desired loading dock. The
carriage then loads with a forklift provided on the
carriage, the articles from the conveyor into a semi-trailer located at the loading dock. The carriage is provided with a linkage pivotally installed on its main frame, the linkage carrying four lateral guide wheels which protrude laterally beyond all other structural elements of the carriage. The linkage integrally links the guide wheels into a common pivotal displacement, with the guide wheels remaining symmetrically disposed relative to the carriage frame. A hydraulic
piston biases the guide wheels towards an outer limit position at all times, and the guide wheels are forcibly pivotable, against the bias of the
piston, towards an inner limit position. The
bogie carrying the carriage is provided with fixed lateral railings, and with pivotable gates which may be pivoted into an opened condition when the bogie is in facing register with the loading dock, until the gates outer free end portions abut against the inner side walls of the semi-trailer. Thus, continuous side panels are formed on each side of the carriage, by the railings, gates and semi-trailer side walls. The carriage may then move between the bogie and semi-trailer with its guide wheels continuously engaging the side panels, for allowing the carriage to self-align and self-center itself into the semi-trailer due to the bias on the linkage of the
piston while article loading and unloading operations are accomplished.