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Plastic Locking Bolt Resists Corrosion

Plastic Locking Bolt Resists Corrosion

The latest version of Permanent Technologies' TineLok(TM) self-locking, vibration-resistant fastener is made from fiberglass-impregnated plastic to provide corrosion resistance and fastener weight savings up to 70%.

The basic nut-and-bolt locking mechanism was one of the Design News' best products of the year for 2002 (see DN 12.02.02, p.57). The bolt consist of longitudinal channels and thread notches into which tines inside the nut engage when the nut is rotated into place-locking the nut from counter-rotating off, even under vibration. The multiple tines ensure locking engagement. Based on specific applications, the number of tines and bolt channels can be varied.

Locking action is not dependent on the clamping torque, but the nut can be removed easily, according to the company, with a special tool that slips around the bolt circumference on to the nut, lifting the tines from the thread channels. Both the nut and bolt may then be reused.

President and CEO Loren Ball says engineers chose DuPont Zytel(R) for both the injection-molded bolt and nut. "Long glass fibers are used in the bolt material, which line up along its length, for longitudinal strength," he says. Unlike the metal versions of the fastener nut where the threads and tines are separate pieces swaged together, the plastic nut and tines are injection molded in one piece. (To increase their strength, the plastic tines also run the full length of the nut, unlike stronger metal tines that only need to be installed near the end.) A collapsible-core injection mold for the nut was required to facilitate part removal from the die. For the nut, short glass-fiber loaded Zytel is used to provide flexibility of the tines as well as strength.

Ball adds that the company is looking at other plastics to expand the line. One future version may use plastic-coated metal tines to retain corrosion resistance and provide even greater strength.

Applications for the plastic fasteners include automotive and off-road vehicles, aerospace, and marine systems, as well as defense weapons. Permanent Technologies, Enter 628

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