Tread mounting system for spiral staircase

摘要

A spiral staircase comprises a mounting column extending along a longitudinal axis. A plurality of tread assemblies each having a tread portion attached to a mounting plate is also provided. The tread assemblies are axially and angularly offset from an adjacent tread assemblies along the mounting column. In this aspect, each mounting plate has a first face that engages a corresponding portion of an outer surface of the mounting column and a second face from which the tread portion extends. Each of the tread assemblies further have attachment hardware that secures the mounting plate to the mounting column. Prior to attachment to the mounting column and in an unstressed state, the mounting plate has a first radius of curvature and the corresponding portion of the outer surface of the mounting column has a second radius of curvature. The first radius of curvature is less than the second radius of curvature so that when the mounting plate is secured to the column with the attachment hardware and the second face of the mounting plate substantially engages the mounting column, the mounting plate is in an elastically deformed state applying tension to the attachment hardware to inhibit loosening thereof.