The term excludes such devices as conveyors, tiering or piling machines, material hoists, skip or furnace hoists, wharf ramps, lift bridges, car lifts, and dumpers.(2) Escalator means a power-driven continuous moving stairway principally intended for the use of persons.(3) No elevator or escalator with a defect which affects safety shall be used.(4) Elevator safety devices shall not be overridde