EE HAD CLEANED OUT ELEVATOR ROCK CHUTE AND TURNED THE ELEVATOR BACK ON THE ENSURE THE PIPE WAS CLEAR. ONCE THE CHUTE WAS CONFIRMED TO BE CLEAN, THE COVER WAS LOWERED BACK INTO PLACE AND APPREN TLY THE CORNER OF THE LID CAME IN CONTACT WITH AN ELEVATOR BUCKET CAUSING THE COVER TO KICK BACK OPEN. THE KICKBACK OF THE LID STRUCK THE EE ON THE JAW AREA.