Source: {"pile_set_name": "USPTO Backgrounds"}

1. Field of the Invention
The invention relates to cable bushings for offsetting electrical cables. Electrical cables passing through openings in structural members such as framing panels, or walls must be protected from abrasive contact with the edges of the openings. Offset bushings prevent direct contact between the electrical cable and these edges.
2. Description of the Prior Art
Cable bushings have been used for protecting electrical conduits passing through openings in structural members from abrasion. This has required that the bushings prevent contact of the electrical conduit with exposed edges of the opening and that they be anchored at the opening. Where the knock out opening has been of uniform and regular shape, it has been possible to provide matching-contour insertable bushings, as shown for example in U.S. Pat. Nos. 2,912,712 and 4,520,976.
A major limitation to this approach has arisen in cases where the opening or knock-out in the structural member is of an irregular configuration such as keyhole-shaped and the provision of a geometrically conforming bushing would entail the fabrication of a geometrically and structurally complex part at substantial expense. Another major limitation of the prior art approach has been the inability of the matching-contour insertable bushings to accommodate nonuniformities in the dimensions of the opening. Yet another major limitation has arisen where a variety of geometric-shape openings in structural members must be provided with conforming bushings, necessitating that supplies of a variety of bushings be provided. Thus, the cable bushings of the prior art have not proven fully satisfactory.