# 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.

- **Patent:** US 387571
- **Original title:** Storm-door structure
- **Owner:** Theophilus Van Kannel
- **Granted:** 1888
- **Status:** Active
- **Times cited:** 3
- **Field:** mechanical, automotive

## What it does

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.

## 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

## 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.

## Real-world examples

1. Standard revolving doors in hotel lobbies
2. Office building entrances
3. Department store revolving entryways

## Why it matters

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.

## 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

**Full plain-English explainer:** https://patentbrief.org/patent/us/387571/revolving-door-van-kannel

**Original patent:** https://patents.google.com/patent/US387571

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_Source: PatentBrief — https://patentbrief.org. Patent facts are from public records; the plain-English explanation is PatentBrief's._


## Related patents

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- [How the Gatling Gun's Rotating Barrel Mechanism Works](https://patentbrief.org/patent/us/36836/gatling-gun) — Richard Gatling's 1862 patent for a multi-barrel firearm that used a hand-cranked rotating mechanism to fire bullets in rapid succession.
- [Leamon Souder's 1903 Design for a Spiral Escalator](https://patentbrief.org/patent/us/723325/escalator-moving-stairway) — A 1903 patent for a mechanical staircase that moves in a circular, spiraling path to transport people between floors.
- [How Mary Anderson Invented the Windshield Wiper](https://patentbrief.org/patent/us/743801/windshield-wiper-anderson) — A 1903 invention by Mary Anderson that allowed drivers to manually clear rain and snow from their windshields using a lever inside the vehicle.
- [Early Car Wheel Traction Device](https://patentbrief.org/patent/us/1141798/zipper-slide-fastener) — A 1915 patent for a metal device clamped to a car wheel to improve traction on slippery surfaces.