Spiral stairs of sectional bolted construction - uses cantilever treads on standard shaft segments which connect in stepped relationship

摘要

The spiral staircase of a sectional bolted construction, comprises standard segmental treads (10) cantilevering from standard string board or shaft segments (12). The two vertical opposed faces (14) of the shaft segments are symmetrically angled to the major face so as to converge on the vertical axis (16) of the staircase. Viewed in major elevation, the shaft segments may have a vertically elongated rectangular outline, comprising a plate with contiguous edge flanges (13, 14). Closed slots (18) and holes (17) in the vertical edge flanges (14) allow the segments to be bolted together in a stepped relationship, the step interval corresp. to the rise between each tread. In plan the shaft segments follow a circular path of which the axis (16) is that of the staircase, the treads comprising planks which are bolted to gusseted (20) cantilever sole plates (11).