US 5,498,164 · Granted 1996-03-12
The Liquid-Metal Steering Wheel Connector That Never Wears Out
Your steering wheel spins, but the horn, cruise control, and airbag wires stay still—so how do they talk to each other? This patent uses conductive liquid (like mercury) trapped in sealed chambers between rotating and stationary plates to pass electricity without any moving parts wearing down. It's like a slip ring, but instead of sliding metal-on-metal, electricity flows through a thin layer of conductive liquid.
The plain-English version
What it protects
The claim covers an electrical connector for a steering column that uses electrically conductive liquid (mercury or silicone) sealed in annular chambers between a rotating plate and a stationary plate. What's protected here is the specific design where terminals from both plates are physically separated but electrically connected only through the conductive liquid medium, eliminating mechanical wear. The method of injecting the liquid through hollow capillaries and sealing it is also covered by the claims.
Why it matters
Steering wheel connectors traditionally used sliding metal contacts that wear out over time, potentially causing electrical failures in critical systems like airbags and horns. By replacing mechanical contact with conductive liquid, this patent solves a reliability problem that plagued the automotive industry. A connector that never wears means fewer warranty claims, longer vehicle life, and safer steering wheels that maintain electrical function for the life of the car.
Real-world use
Every time you press your car horn or use the cruise control buttons on your steering wheel, electricity is flowing through one of these liquid-filled connector chambers, with no metal surfaces grinding against each other.
Original USPTO abstract
An electrical connector for a steering wheel which utilizes a non-wear electrical interconnection characterized by terminals of a base terminal bus and terminals of a rotor terminal bus being physically separated yet mutually electrically connected via contact with an electrically conductive liquid situated in one or more annular chambers located between outer faces of a rotor plate and a base plate. The rotor terminal bus is connected with the rotor plate and the base terminal bus is connected with the base plate. The base and rotor plates are connected together in a manner that permits relative rotation therebetween. The electrically conductive liquid is provided in each of the annular chambers by being preferably injected through a hollow capillary of at least one of the rotor and base terminals of each annular chamber, and then sealed, such as by solder. Preferred electrically conductive liquids include mercury or silicone. Electrical wiring is connected with each of the rotor terminal bus and the base terminal bus in an otherwise conventional manner known in the automotive art.
Patent details
- Publication number
- US 5,498,164
- Filing date
- 1994-05-09
- Grant date
- 1996-03-12
- Assignee
- Ward; Mark C. / Hodder; Roger A.
- Inventor(s)
- WARD; MARK C., HODDER; ROGER A.
- CPC class
- B60R16/027
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