ATTEMPTING TO CLEAR CHUTE WITHOUT SHUTTING DOWN OR LOCKING OUT THE CONVEYOR BELT. GUARD WAS NOT A BOLT DOWN TYPE, BUT RESTED IN GROOVES. A BELT WIPER WAS ATTACHED TO THE GUARD. THE WIPER ON TH E UNDERSIDE OF THE TOP BELT WAS PULLED INTO THE HEAD PULLEY & SLAMMED THE GUARD INTO THE WORKER,PINNING HIM BETWEEN THE GUARD & THE HAND RAIL. INTERNAL INJURIES; ESTIMATED 5-6 WEEKS LOST TIME