US 6,294,989 · Granted 2001-09-25
How Donnelly's Tire Pressure Light Changed Dashboard Design Forever
Before smartphones told you everything, cars had to show you when your tires were losing air. This patent describes putting a little light on your car's side mirror that glows when tire pressure drops, so you'd catch a flat before it ruins your day.
The plain-English version
What it protects
The claim covers an automated system that senses tire pressure through sensors, runs that data through a vehicle control unit, and then illuminates an external indicator light (typically mounted on a rearview mirror or other exterior vehicle surface) to alert the driver. What's protected here is the specific combination of wireless pressure sensing, electronic processing, and exterior display placement — not just any tire pressure warning, but this architectural approach of putting the warning light outside where it's highly visible.
Why it matters
This patent represents an early step toward mandatory tire pressure monitoring, which became a federal safety requirement in the US after 2007. By moving the indicator from the dashboard to an exterior mirror, Donnelly's design made warnings more noticeable and harder to ignore — a small design choice that influenced how safety features were integrated into vehicles for decades. The patent also shows how automotive suppliers innovate by combining existing sensors with novel placement strategies rather than inventing entirely new technology.
Real-world use
Every time you see a small amber light on your car's side mirror when a tire is underinflated, you're looking at the direct descendant of this patent's core idea.
Original USPTO abstract
A vehicular tire inflation monitoring system is provided for a vehicle that includes at least one tire inflation indicator assembly, visible exterior of the vehicle, positioned at an exterior vehicle portion, such as at an exterior rearview mirror assembly. The at least one tire inflation indicator assembly provides an indication of the inflation condition of at least one of the vehicle tires. The tire inflation monitoring system includes a control receiving at least one input from at least one tire pressure sensor sensing pressure of at least one vehicle tire. The control produces an output to illuminate the at least one tire inflation indicator assembly.
Patent details
- Publication number
- US 6,294,989
- Filing date
- 2000-02-28
- Grant date
- 2001-09-25
- Assignee
- Donnelly Corporation
- Inventor(s)
- SCHOFIELD KENNETH, LYNAM NIALL R.
- CPC class
- B60Q1/2665
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