Overview
This lecture covers the history, mechanics, and safety systems of escalators, with a focus on a major accident in Rome, escalator innovations, and the importance of proper maintenance.
The Rome Escalator Accident
- In October 2018, an overloaded escalator in Rome failed, injuring 24 people.
- The main motor overloaded, safety systems failed in succession, and the brakes could not stop the escalator.
- Investigations revealed sabotage, disabled error logs, and falsified maintenance records.
- Authorities found gross negligence and deliberate safety device manipulation by maintenance contractors and transit officials.
History and Invention of Escalators
- The first escalator, invented by Jesse Reno in 1896, was originally a ride at Coney Island.
- Early escalators used steep conveyor belts, which were unsafe and uncomfortable.
- George Wheeler invented the modern step design, allowing steps to stay level during movement.
- Charles Seeberger commercialized Wheeler’s design with Otis, debuting at the 1900 Paris Exposition.
How Escalators Work
- Escalators use an electric motor with a reduction gearbox to turn a chain of steps.
- Each step is attached to the chain and guided by tracks that keep steps level on the incline.
- At the end, steps flip upside down before returning underneath.
- Modern escalators use AC induction motors for stable speed, and regenerative braking to generate electricity when loaded.
Escalator Safety Features and Improvements
- Early designs caused entrapment of shoes and clothing; shunts and grooved steps with comb plates reduced this risk.
- Skirt brushes were added to prevent items from being trapped at the sides.
- Handrails are driven slightly faster than steps to compensate for wear.
- Multiple redundant brakes and sensors are installed for emergency stops.
Lessons Learned and Importance of Maintenance
- Escalators are structurally over-engineered for safety but rely on proper and honest maintenance.
- Catastrophic failures are generally caused by human neglect, not design flaws.
- Regular, transparent maintenance is critical to public safety.
Key Terms & Definitions
- Regenerative Braking — A system where a motor generates electricity when resisting motion, converting mechanical energy back into electrical.
- Comb Plate — A grooved plate at the top and bottom of escalators that interlocks with steps to reduce entrapment.
- Skirt Brush — Safety brushes on the escalator sides to prevent items from being caught between the step and skirt.
- Reduction Gearbox — Gear mechanism reducing motor speed while increasing torque for escalator movement.
- Step Chain — Reinforced chain system that pulls escalator steps around the loop.
Action Items / Next Steps
- Review the sequence of events in the Rome accident for potential exam questions.
- Understand and be able to explain the main parts and safety features of modern escalators.
- Study the key inventors and improvements in escalator history for short-answer responses.