| 摘要 |
Ladder constructions and methods of forming the same wherein box-type or tubular rails are employed. The rung-to-rail connection or joint is formed by providing an opening in one of the rail side walls and an aligned clearance hole in the opposite rail side wall to afford an opening through which a swaging tool is projected and forms an annulus in tight engagement into the inner surfaces surrounding the opening in the first named rail side wall, cooperating swaging means forming an annulus on the outer surfaces surrounding the said opening. A ladder having tubular side rails is hence provided with a rail-to-rung joint on one of the walls by projecting a swaging tool through a clearance hole in an opposite wall. The clearance hole is adapted to be closed by placing a plug in the same and in the event the clearance hole is in the innermost side rail the rung is adapted to be used to close the space provided by the opening in the rail between the rung and one of the side rails. |
