Hollow screw simplifies assembly of.anything

March 2, 1998 Design News

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Hollow screw simplifies assembly of?anything

The Superscrew? eliminates the problem of stripped heads, offers greater safety and   integrity

Charles J. Murray, Senior Regional Editor

Houston, TX--Since the time of Archimedes, screws have been regarded as a fast, easy means of locking things together: Just grab a screwdriver, slide it into a slotted head, push, and turn. Simple, right?

Well, maybe not. Every day, thousands of people curse the ineffectiveness of stripped screws. Worse, countless more injure themselves when they strike their hands on the sharp edge of a sheet metal housing after a screwdriver slips from its slot.

If metallurgist Ian Royle has his way, however, the world will one day forget the frustration of dealing with stripped head slots, nor will it recall the difficulties of driving wobbly screws into place. In fact, with Royle's new screw design, users will no longer need to do the age-old "push and turn." Instead, they will merely turn.

Royle's new design, known as the Superscrew, eliminates the need to push a screw into place because it has no traditional slotted head. The Superscrew consists of a hollow cylindrical body with lobes on the inside of the hollow cylinder. The lobes, which run the length of the fastener, engage the splines of a screwdriver. When the user turns the screwdriver, the splines contact the lobes, turning the hollow screw along with it.

In essence, Royle's design moves the point of contact from the head to the inner diameter of the screw. In doing so, it eliminates the need for users to push the screwdriver. "Using the old conventional method, the screw always wobbles when you try to insert it," Royle says. "By putting the driver inside, instead of on top, we get perfect alignment between the screw and the driver. Wherever the driver goes, the screw always goes with it."

By operating in this way, the Superscrew offers several key advantages over conventional screws. Among them:

Safety: One of the most common industrial accidents occurs when assemblers apply considerable compression to maintain driver force. When the screw wobbles, the assembler's force is pushed in a different direction, usually toward the work area, sometimes toward moving machinery. The Superscrew eliminates that problem because it eliminates the use of compressive force altogether. To seat the screw, the user merely turns the screwdriver.

Royle says that his design also offers other advantages. Because the tube has a more efficient structural form, the Superscrew has a higher strength-to-weight ratio. The open space of the tube also offers functional potential as a wiring conduit or coolant duct.

Although tooling costs for the Superscrew are 5%-20% higher than conventional screws, Royle contends that its overall cost would be less than conventional screws in volume manufacturing. The reason: The hollow screw would have material costs ranging from 35% to 60% less than conventional, depending on the material.

Royle already is working with aerospace manufacturers to adopt the concept for metal structures, skins, and composites. The product is also being developed to replace fasteners in a wide variety of other assemblies, he says. Tube screws incorporating self-tapping and cam swaged threading and self-locking capability will replace screw, rivets, and locating pins used in sheet metal assemblies, as well as in plastics, foams, composites, and wooden structures. Says Royle: "Ultimately, we believe it has the potential to replace the screw in any application."

Additional details?Contact Ian Royle, Technology Transfer International, P.O. Box 1943, Houston, TX 77272-1943, (281) 879-5532.