Pallets are fed one at a time from a feed conveyor into a lifter unit, lifted to a takeoff conveyor, and conveyed out of the lifter subsystem. A stopper on the feed conveyor prevents the motion of the pallet into the lifter when the stopper is raised. The pneumatically actuated lifter contains a bidirectional motor for loading and unloading pallets.

A pallet will be fully loaded into the lifter only when the stopper is down, the feed conveyor motor is on, and the lifter motor is engaged in the loading direction. If  the stopper is down and the feed conveyor is on but the lifter motor is off or engaged in the unloading direction, the pallet will only be loaded halfway into the lifter and may be damaged if the lifter is then actuated in the upward direction.

A pallet will be fully unloaded from the lifter only when the takeoff motor is on and the lifter motor is engaged in the unloading direction. If  the lifter motor is engaged in the unloading direction but the takeoff conveyor motor is on, the pallet will only be unloaded halfway into the takeoff conveyor and may be damaged if the lifter is then actuated in the downward direction.