The figure illustrates a chair-base mechanism with a bushing-mounted drag chain. The bushing-mount design provides for one end of the drag chain to be free to pivot; this provision makes it possible to wrap the drag chain to a radius smaller than that achievable in mechanisms previously designed for the same purpose. The utility of mechanisms like this one lies in applications in which rotation of machinery involves significant turning radii, so that bending of cables that run through drag chains involve relatively tight arcs.
The bushing-mounted drag chain contains cables and wires for actuating controls on a mechanical chair that can be rotated through 280° by use of the chair-base mechanism. In addition to being bushing-mounted, the drag chain is bearing-mounted on the upper bearing block; because of this, the bend radius of the chain varies with rotation of the chair in such a way as to maintain an overall compact system. This design feature reduces the amount of external floor space needed for a given length of drag chain and limits the overall length of the drag chain.
The chair-base mechanism with the bushing-mounted drag chain is in use at the Dexterous Robotics Laboratory at Johnson Space Center. The potential of the economical and efficient design of this mechanism has not yet been fully realized; future applications could occur in Hurco (or equivalent) drill presses, any similar rotating machinery in which drag chains are employed, and mechanisms for rotating gantry assemblies or other machinery.
This work was done by Myron A. Diftler of Lockheed Martin Corp. for Johnson Space Center. No further documentation is available. MSC-22732.