Socket improves rear light sealing integrity

Lisle, IL--Time was when engineers didn't concern themselves with the sealing integrity of exterior rear lights. Exterior rear lights were, after all, typically located in the trunk, so sealing wasn't an issue. But as automakers struggle to find more trunk space and bulbs get pushed to exposed locations, rear lights must be sealed against moisture.

Now, there's a simple way to do it. Using a new sealed-socket design, automotive engineers can dramatically cut the number of potential leak paths to bulbs located in the fenderwells and other exterior locations. Designed by engineers at Tricon Industries, Inc., the new socket connects bulbs to wiring harnesses via an insert-molded circuit. The unit consists of a plastic backplate containing the circuitry and a snap-in bulb-and-socket assembly. When the unit is fully assembled, the bulb-and-socket attach to a joining ring on the rear of the backplate. An O-ring seals the interface between the two. In use, the rear side of the backplate faces out toward the elements, while the bulb-side faces the light's lens.

The new design is significant because it offers O-ring sealing between the circuitry and the removable bulb-and-socket. That's a departure from today's conventional rear light designs, many of which now run wires from the wiring harness to the socket in an exposed area. Such designs typically use foam compression disks.

In addition to the O-ring seal, the new system provides leak integrity by dramatically reducing the number of potential leak paths. That characteristic becomes particularly important for vehicles with multiple rear bulbs for braking, back-up, turn signals, and running lights.

Integrating circuitry into the plastic backplate makes many of the wires and splices leading to the sockets unnecessary. "All of the circuitry is embodied in our backplate, so you don't need all the wires going from socket to socket," explains Donald Paul, engineering director of product development at Tricon. "Instead of three wires leaving the cable harness and going to each bulb socket, we plug the harness directly into a sealed connector on the backplate."

In a worst-case scenario--with park-, brake-, back-up, and turn-signal lights--a vehicle could potentially require as many as a dozen splices, Paul says. In contrast, Tricon's Universal Sealed Socket backplate calls for one harness with only four signal wires and one ground wire--without regard to the number of lamp sockets used.

Tricon engineers custom-design the backplate to accommodate the necessary number of bulbs and locations. In most applications, the Universal Sealed Socket's joining ring is attached to the back of the vehicle's reflector housing, typically by adhesives, hot plate bonding, or ultrasonic welding.

Because the new socket employs a snap-in assembly, it offers another advantage over conventional sockets: It dramatically reduces the possibility of Carpal Tunnel Syndrome in assembly line personnel. The reason: Workers assemble the Universal Sealed Socket with a straight push-in motion, rather than a twist of the wrist.

Tricon engineers say the new design is pending in several 1998 vehicle programs. They expect the need for the sealed socket to grow, as designers move more lamps to the exterior in an effort to maximize trunk space. "Every time you increase the number of exterior connections, you make the system more vulnerable to water intrusion," Paul says. "With this socket, you have an O-ring seal and less wiring, so you reduce potential sealing problems."

Additional details...Contact Patricia Grandle, Tricon Industries, Inc., 1600 Eisenhower Lane, Lisle, IL 60532-2167, (708) 964-2330.