Machine Design

Let there be light -- Big shades lift easily with low-friction gears

Large shades go up with half the effort, thanks to a new UltraGlide gearbox sporting low-friction gears made from Delrin acetal.

Delrin acetal with PTFE gives gears inside the window shade's gearbox the low wear and friction needed for a long, quiet service life. It also reduces the effort needed to raise and lower the shade. Self-lubricated gears also won't stain window shade fabric.
Molded-in snap-locking features on various parts of the shade provide fast, simple assembly of the gearbox and its lifting system and eliminate fasteners.

The low-friction gearbox provides mechanical advantage so large Duette Honeycomb window shades from Hunter Douglas Inc., Upper Saddle River, N.J. (, smoothly rise with a lift weight up to 7 lb. Without the gearbox, similarly sized shades would take double the force, says Jim Jones Hunter's engineering manager.

The gearbox is designed by Performance Gear Systems Inc., Downers Grove, Ill. (, using a parallel-axis configuration that operates in two directions. This is key to lifting and lowering the shade. A retractable pull-cord assembly activates the gears which link to a drive shaft located in the shade head rail. Two shaft-mounted pulleys produce up and down movement of the shade's lift cords. The gearbox safely retracts the cord to a preset length after the shade is adjusted, so the cord is out of reach of small children.

The gearbox contains three gears, an input gear, parallel-mounted cluster gear, and output gear. All three gears are molded by Performance Gear from a specially formulated ultralow-friction grade of Delrin acetal from DuPont Engineering Polymers, Wilmington, Del. ( It contains 10% by weight DuPont Teflon PTFE fluoropolymer in micropowder form.

Other gearbox components include the housing, housing cap, and retainer. The retainer holds the gears in the housing and has a bearing shaft for input and output gears. Performance Gear molds these parts from DuPont Zytel 132F nylon resin, an unreinforced, fast-cycling PA66 grade.

-- Jean M. Hoffman
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