How Intermittent Windshield Wipers Work

Robert Kearns' 1967 patent for the first electronic intermittent windshield wiper system that mimics the human eye's blinking motion.

What it covers

This patent describes an electronic control circuit for windshield wipers that introduces a pause between each wipe. It uses a transistor to act as a switch that cuts power to the wiper motor at the end of a cycle. A capacitive timing circuit then holds the motor off for a set duration before triggering the next cycle. A mechanical switch linked to the motor's position ensures the wipers always return to the bottom of the windshield before the pause begins.

What it doesn't cover

• —Does not cover purely mechanical or vacuum-based intermittent wiper systems.
• —Does not cover systems that adjust wipe speed based on rain sensors or optical detection.
• —Does not cover continuous-speed wiper systems that lack a dwell period.

The clever bit

The innovation lies in using a capacitor to create a variable time delay that controls a transistor, allowing the motor to 'rest' at the bottom of its arc rather than running continuously.

Why it matters

This invention solved the problem of driving in light rain, where constant wiping creates annoying noise and smears the windshield. It became the subject of one of the most famous patent infringement cases in history, pitting the inventor, Robert Kearns, against major automotive manufacturers who adopted his technology without licensing it.

Real-world examples

• 1.Standard intermittent wiper settings on almost every car manufactured since the 1970s.
• 2.The 'delay' setting on automotive wiper stalks.