Architecture & Infrastructure
Automatic elevator door mechanism
The problem
Shaft doors were opened and closed by hand; an open shaft on an occupied floor was a fatal hazard.
The innovation
A mechanism that opened and closed the shaft door automatically in step with the cage's position.
How it worked
A flexible belt on the cage engages drums at each floor, working levers that operate the doors as the cage arrives and departs.
Why it mattered
Removed one of the most common causes of death in early elevator buildings.
The legacy
Door interlocks are now mandatory in elevator safety codes internationally.
You use this today
Every elevator you step into closes its own doors.
Sources
US Patent 371,207
Primary record
Follow the invention
The monolithic stelae of Aksum
Granite stelae up to about 24 metres long, carved to represent multi-storey buildings with false doors and windows, and erected over rock-cut tomb chambers.
Great Zimbabwe's dry-stone architecture
Coursed dry-stone granite walls up to 11 metres high and 5 metres thick, laid without mortar, enclosing a capital of a major trading state.
The rock-hewn churches of Lalibela
Eleven churches cut downward out of solid rock — walls, roofs, columns, windows and drainage carved from the living stone rather than constructed on it.