You can freely build on Leamon Souder's 1903 Design for a Spiral Escalator
This patent expired in 1922. Every claim — 0 independent, 0 dependent — is now unenforceable. Anyone can use, reproduce, manufacture, sell, or offer for sale this technology without a license.
Original assignee
Individual
Patent granted
1903
Expired
1922
Forward citations
17
What this patent covers
The patent describes a mechanical system where steps are mounted on a continuous chain that follows a helical or spiral track. As the chain moves, the steps rise or descend while simultaneously rotating around a central axis. This design intended to save space compared to traditional straight escalators by allowing the stairs to fit into a circular shaft.
What is now free to use
All 0 claims of US 723325 are in the public domain. Specifically:
The 0 dependent claims add narrowing limitations and are also free.
What is NOT covered
Patent expiry frees this specific invention. Separately-patented improvements made after expiry may still be protected.
Does not cover standard linear escalators that move in a straight line.
Does not cover elevators that use a vertical cable-and-pulley system.
Does not cover stationary spiral staircases that lack a motorized moving mechanism.
Who is building on this today
Companies like Mitsubishi Electric are the primary modern manufacturers of spiral escalators, having refined the complex engineering required to make such systems safe and reliable for public use.
Products built on expired version of this technology
Spiral escalators found in high-end shopping malls like the ones in the Westfield San Francisco Centre.
How to cite this patent in your documentation
Individual. US Patent 723325. Moving spiral stairway or elevator.. Granted 1903, expired 1922. Now in the public domain.
Note: This is a convenience citation. Consult a patent attorney for formal freedom-to-operate analysis.
PatentBrief is an educational resource and does not provide legal advice. Patent expiration information is derived from USPTO records and may not reflect continuation patents, divisional filings, or separately-patented improvements. For commercial use or production decisions, obtain a formal freedom-to-operate (FTO) opinion from a registered patent attorney.