US 3,944,163 · Granted 1976-03-16

The Seat Belt Reel That Learned to Lock Up

This patent describes a smarter seat belt reel that automatically locks when you jerk forward suddenly, but can still be adjusted slightly by hand once it grabs you. It's the mechanical brains that made modern seat belts actually work instead of just being loose straps.

Curated and verified by the IsItPatented Editorial team

The plain-English version

What it protects

The claim covers a seat belt retractor mechanism with a spool that winds and unwinds the belt, paired locking wheels with teeth that catch a locking plate when the belt is pulled suddenly, and a spring that retracts the belt back to normal. What's protected is the specific arrangement where the lock can be temporarily prevented or overridden through a mechanical connection, allowing the wearer to adjust their position slightly even after the belt has engaged.

Why it matters

This patent represents a critical safety innovation in automotive design. Before this kind of smart retractor, seat belts were either completely loose or completely rigid. This design solved a real problem: keeping passengers safe during sudden stops or crashes while still allowing normal movement during regular driving. It became the foundation for three-point seat belt systems that are now standard in every car on the road.

Real-world use

Every time you lean forward or shift in your car seat and feel the belt tighten, then allow a bit of give as you settle back, you're experiencing the mechanism this patent protects.

Original USPTO abstract

A seat belt retracting apparatus having a spool mounted for rotation on a frame member and adapted to have a seat belt wound thereon, a pair of locking wheels having a plurality of locking teeth and fixedly mounted on the spool, a locking plate engageable with the locking teeth of the locking wheels when the seat belt is protracted and engages the body of a passenger thereby locking the seat belt against further protraction, and a retracting coil spring normally urging the spool in the retracting direction. In the apparatus, lock preventing means are provided for cooperation with the locking wheels through a driving connection between them so that the locking wheels can be temporarily prevented from the locked position and can protract over some pre-selected steps in the state in which the seat belt is engaged on the passenger's body.

Patent details

Publication number: US 3,944,163
Filing date: 1974-03-18
Grant date: 1976-03-16
Assignee: Kabushiki Kaisha Tokai Rika Denki Seisakusho
Inventor(s): HAYASHI; YOSHIHIRO, MATSUI; KENJI
CPC class: B60R22/353

View original record on Google Patents →

Want to file your own patent?

Curious how safety systems get patented? Run your own automotive gadget ideas through our free scanner to see if the space is already locked down.

Free patentability scan