Helical staircase with central upright tube

摘要

The upright tube (2) retains several, mutually helically fitted stairs (7) of wood, metal, or plastics. The stair outer ends are fitted with railing post for a hand rail. The upright tube outer surface is fitted with a number of axially extending, undercut grooves (3), in which are secured adjustably stair carriers (4).Pref. the upright tube has ten to eighteen grooves which may extend over its entire length. The groove undercuts are typically inclined. The grooves may have a hammer head, or a dovetail cross-section. The shape of the stair carriers is specified.