How the Revolving Door Was Invented
The 1888 patent for the revolving door, designed to keep buildings warm while allowing people to enter and exit easily.
Original patent title: “Storm-door structure”
The 1888 patent for the revolving door, designed to keep buildings warm while allowing people to enter and exit easily. Granted to Theophilus Van Kannel in 1888 with 3 forward citations.
Key facts
Coverage
What does this patent actually cover?
The patent describes a central vertical shaft with radiating wings that rotate within a circular enclosure. This mechanism creates a continuous seal between the outside and inside of a building. By maintaining this seal, the door prevents cold drafts from entering and warm air from escaping, which was a significant improvement over traditional swinging doors that let in large gusts of wind every time they opened.
The gap
What does this patent NOT cover?
- Does not cover automatic or motorized revolving doors
- Does not cover sliding or traditional hinged door mechanisms
- Does not cover security-focused revolving doors with anti-tailgating sensors
These exclusions are unique to PatentBrief — derived from the actual claim language, not patent-office boilerplate.
What made this novel
The genius lies in the 'always-closed' design; the door is never fully open to the outside, effectively acting as an airlock for pedestrians.
The Patent Drawing
Schematic visualization of the patent's claim structure. Hand-drawn diagrams in progress for each landmark patent.
Where you've seen this
Real-world examples
Standard revolving doors in hotel lobbies
Office building entrances
Department store revolving entryways
Why it matters
The bigger picture
Before this invention, opening a door in a busy building during winter caused massive heat loss and uncomfortable drafts. The revolving door became a staple of urban architecture, allowing large public buildings and hotels to maintain climate control while handling high foot traffic.
Granted
August 7, 1888
Market context
Who's building on this
Companies in this space
Modern architectural firms and manufacturers like Boon Edam and Dormakaba continue to refine this design by adding glass aesthetics, speed control, and electronic sensors.
Market impact
This invention fundamentally changed urban architecture and HVAC requirements for large buildings. It allowed skyscrapers and high-traffic commercial spaces to exist in cold climates without constant, massive heat loss at the ground level.
Claim 1 — Plain English
What this patent covers
The patent describes a central vertical shaft with radiating wings that rotate within a circular enclosure. This mechanism creates a continuous seal between the outside and inside of a building. By maintaining this seal, the door prevents cold drafts from entering and warm air from escaping, which was a significant improvement over traditional swinging doors that let in large gusts of wind every time they opened.
The clever bit
The genius lies in the 'always-closed' design; the door is never fully open to the outside, effectively acting as an airlock for pedestrians.
What it does not cover
- Does not cover automatic or motorized revolving doors
- Does not cover sliding or traditional hinged door mechanisms
- Does not cover security-focused revolving doors with anti-tailgating sensors
PatentBrief Score
Impact Score
Limited data
Citation count
12/40
Early citations
Claim breadth
0/20
Narrow claimsclaimsThe numbered statements at the end of a patent that legally define what the inventor owns.Read more →
Recency
0/20
Older than 20 years
Assignee scale
0/20
Independent or smaller assigneeassigneeThe entity that owns the patent — usually the inventor's employer or a company.Read more →
PatentBrief Impact Score — based on citation count, claim breadth, recency, and assignee scale. Not a legal assessment.
Heuristic Value Estimate
What this patent might be worth
$2K – $7K
Midpoint $4K · expired or expiring · industry ×0.7
Heuristic only — blends forward/backward citation counts, claim scope, time remaining, litigation history, and CPC-derived industry baseline. Real valuations need a professional appraisal.
Concepts involved
Citations
Patent lineage
Cite this patent
(1888). How the Revolving Door Was Invented (U.S. Patent No. 387,571). U.S. Patent and Trademark Office. https://patentbrief.org/patent/us/387571/revolving-door-van-kannel
Auto-generated from the patent record. Double-check author order and the issue date against the official USPTO document before submitting.
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Common Questions
Frequently Asked Questions
What does How the Revolving Door Was Invented cover?
The 1888 patent for the revolving door, designed to keep buildings warm while allowing people to enter and exit easily.
Who owns patent US 387571?
Theophilus Van Kannel owns this patent, granted in 1888.
When does this patent expire?
This patent has expired and is now in the public domain — anyone can use the invention freely.
What is patent US 387571 cited by?
This patent has been cited by 3 later patents that build on its ideas.
What problem does this patent solve?
Before this invention, opening a door in a busy building during winter caused massive heat loss and uncomfortable drafts. The revolving door became a staple of urban architecture, allowing large public buildings and hotels to maintain climate control while handling high foot traffic.
What does this patent NOT cover?
Does not cover automatic or motorized revolving doors
Patent monitoring