Why We Use…

Plastic Gears

Over the last one hundred years, automakers have sought ways appeal to consumers with ways to make their car more comfortable. The variation in human physique led to seats and steering wheels that adjust for distance, height, and tilt. Today’s high-end cars can adjust the seat’s fit along the back and sides, along with the latest wrinkle — adjustable pedals, which compensate for leg length at the far end of the extremities.

Teleflex Incorporated is a diversified Fortune 1000 company that designs, manufactures and distributes products and services for automotive, marine, industrial, aerospace and medical markets. Subdivision Telefex Automotive, Troy, MI, is a Tier One global supplier of custom engineered cable controls, electronic throttle controls, transmission shifter control systems and footwell mechanisms to the automotive industry. As often occurs in first-generation designs, the company’s original adjustable pedal system was made to surpass design goals. In response to higher-than-anticipated market demand, the decision came to produce a second-generation unit that would more closely address weight, cost and performance parameters. According to senior engineering manager Avtar Kalsi, “My boss, Charles Meier, has the value engineering, value analysis (VEVA) role in the company. He suggested we could go to plastic gears in the mechanism.”

The Teleflex pedal system uses a worm gear on the end of a motor shaft turning in a gearbox. The output gear transfers the energy 90 degrees to a screw-thread shaft, on which rides a plastic drive-nut that, in turn, moves the pedal assembly forward or back. The unit’s design places the load on the pedals, not on the assembly’s gearbox, so there was the freedom to use plastic gearing without fear of parts failure the first time a driver made a panic stop.

“Plastic gears and worms proved to be a superior alternative to metal or machined steel gears because they are quieter in operation, have more design flexibility and are easier to interface with,” stated Kalsi. He noted that the use of plastic permitted intricate features to be added to the components. Plastic gears are injection molded, and that simplifies alterations for precision angles and the creation of non-standard, more forgiving gear profiles. The gears are also lighter in weight and corrosion resistant, important characteristics in automotive engineering. The lower cost of the gearbox will result in adjustable pedal mechanisms being offered in a wider range of vehicles.

For assistance in design of the new gearbox, Teleflex worked with United Plastics Group, Westmont IL. UPG engineers have frequently partnered with companies in automotive and other industries to develop state-of-the-art technologies for new plastic applications and new manufacturing solutions, as well as “mass customization” — techniques to yield more distinct looking products (e.g. pigmented plastics that give the appearance of metal). “We’re pleased that we could once again work with Teleflex on its innovative pedal system and we look forward to working on future assemblies so that we may continue to meet automotive manufacturers growing demands,” stated UPG’s John Szkutnik, vice president, strategic business automotive.

—RM

UPG
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