WHILE LOADING 3 (50') NEW CONVEYORS ONTO A SEMI TRAILER, THE 3RD CONVEYOR SWAYED AND BUMPED THE TWO LOADED CONVEYORS CAUSING THEM TO SLIDE OFF THE TRAILER. 3 EE'S WERE STANDING ON THE CATWALK S OF THE FIRST 2 CONVEYORS THAT WERE LOADED. AS THE CONVEYORS FELL THE EE'S FELL WITH THEM, STRIKING INJURED IN THE CHEST AREA.