An improved tool has been devised for applying torque to lock and unlock knurled collars on circular electrical connectors. The tool was originally designed for, and used by, astronauts working in outer space on the Hubble Space Telescope (HST). The tool is readily adaptable to terrestrial use in installing and removing the same or similar circular electrical connectors as well as a wide variety of other cylindrical objects, the tightening and loosening of which entail considerable amounts of torque.

Other tools developed previously for mating or demating electrical connector collars were either designed for use on specific connectors or too generic and incapable of applying the requisite amount of torque [40 lb-in. (4.52 N-m)] for the HST application. In contrast, the present improved tool can be used on a variety of connector sizes and is capable of applying the requisite amount of torque. Indeed, only a moderate amount of hand clasping force [25 lb (˜111 N)] is necessary for applying double the requisite amount of torque.

The tool consists of two stainless steel arms that pivot about a common point. Attached to the gripping jaws on the arms are a total of four flat pads, made of commercially available rubberlike epoxy. The pads make tangential contact with the circular connector collar. Under the gripping force, the pads deform into greater conformity with the gripped object and are thereby capable of exerting a greater tangential frictional force. Hence, this jaw-and-pad combination enables the tool to fit circular connectors of different diameters and to exert greater torque than could otherwise be applied. A simple spring-lever resists the user's hand-grasping force with just enough force to return the gripping jaws to the wide-open position.

Although deformation of the pads in repeated use of the tool degrades performance, the amount of degradation may be acceptable in some applications and was acceptable in the original HST application. In that application, the tool performed as required when used to loosen, then later to tighten, 36 connectors in an operation to remove and replace a power control unit. Theoretically, the tool could be used to perform the operation a total of five times.

This work was done by Kathryn Gaulke and Russel Werneth of Goddard Space Flight Center, John Grunsfeld of Johnson Space Center, and Patrick O'Neill and Russ Snyder of Swales Aerospace. For further information, access the Technical Support Package (TSP) free on-line at under the Mechanics category. GSC-14670-1

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NASA Tech Briefs Magazine

This article first appeared in the October, 2006 issue of NASA Tech Briefs Magazine.

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