IE pulled 2 tubs of longwall chain onto the pan line using a shield hauler. IE was in the process of pulling the 3rd tub on. A 1/2"" chain got caught in the tail sprocket binding the longwall chain. IE stepped out to see what was stuck. In the process, winch rope came undone, slinging foundry hook. Foundry hook ricocheted off chain tub than hit IE, breaking 2 bones in lower leg.