Designer's corner

An unshakable fastener

Vibration-loosening has inspired many solutions over the years—everything from thread lockers to proprietary bolting systems. To these, add a patented threaded fastener developed for NASA.

Honeybee's patented thread forms use a wedge-like contact to resist vibration loosening.

Designed to withstand the rigors of a space launch and in-orbit use, Honeybee's vibration-resistant fastener pairs a standard bolt with a modified nut whose threads feature a flat end and an included angle that differs from the bolt's thread angle. This difference in included angles creates a clearance between the two thread forms until pre-loading, at which point the crest of the nut bites into the root area of the bolt thread in an elastic deformation process.

This wedge-like contact eliminates the effects of loose tolerance fit between mating threads—a major source of vibration loosening—and provides a secure hold under even large vibrational forces. Moreover, it also distributes load stress more evenly than standard threads. The patented thread form can be "reversed" so that the bolt threads change while the nut remains standard. Both variants are available for license.

Roopnarine, Honeybee Robotics, 204 Elizabeth Street, NY, NY 10012; Tel: (212) 966-0661; Fax: (212) 925-0835; E-mail: roop@hbrobotics.com .

Compression latch

Turn the knob or handle of this compression pawl 90 degrees to secure the door or cover; another quarter turn pulls the door against the frame. Compression is 4.5 or 6.5 mm, depending on model, while the clamping dimension is variable.

Good for electrical distribution panels, computer enclosures, and HVAC equipment, the quarter-turn compression pawl offers easy adjustability, vibration resistance, simple installation, and NEMA 4 capability. Position of the knob visually indicates latching status.

DIRAK Konstruktionselemente GmbH & Co.KG, Tel: +49 23 33 837 0; Fax: +49 23 33 837 100; E-mail: info@dirak.com .

Latch installs in a snap

Designed to simplify the assembly of faceplates to rack-mounting rails, this patent-pending latch replaces combinations of cage nuts and panel fasteners with an integrated assembly of metal—usually aluminum—and plastic.

THis new latch uses self-clinching and snap-fit strategy to replace cage nuts and panel fasteners.

The latch attaches to the faceplate through a "self-clinching process," in which the latch's metal base cold flows into undercut holes in the plate for an attachment good to roughly 300 lbs. of pullout force. Once joined to the faceplate, the latch extends two opposing arms through square holes in the plate and in the adjoining rack-mounting rail. These arms, which flex as they push through the mounting rail hole, have a feature that grasps the backside of the mounting rail. To complete the locking, a thermoplastic locking clip then slides between the opposing locking arms, keeping them in place. The resulting latch can withstand pullout forces to about 100 lb. Tooling-wise, the snap-in latch does require a new three-hole punch for the faceplate, but the square hole in the rail remains the same.

Snapping a latch into place as opposed to using cage nuts and related fasteners brings some important assembly advantages. From a DFMA standpoint, the snap-latch does away with two or more pieces of loose hardware. Its manual locking clip also fosters hand assembly and disassembly. Cage nuts, by contrast, need a special tool for removal.

Though it was developed for a particular computer OEM, the snap-in latch will be widely available by the end of the year. PEM has not yet determined the full range of compatible host materials for its new latch, but it has worked successfully in 0.060-inch cold rolled steel.

Brian Bentrim, Penn Engineering & Manufacturing Corp. Box 1000, Danboro, PA; Tel: (215) 766-8853; Fax: (215) 766-3631; E-mail: bbentrim@pemnet.com .