Radially contracting ring shutter - is for bore of concrete chimney of square section and has corner sections with wedge shaped beams

摘要

A radially contractable sectional ring frame is used in shuttering the bore of a polygonal section chimney or similar structure of in situ reinforced concrete. Wedge shape vertical beams are moved between the sections to effect assembly and striking. A shutter of four right angled sections may be used to form a square chimney, the barrel being formed by conventional shutters. The conjunctive ends of the sections are symmetrically inclined to subtend an angle opening out on the interior of the chimney, crank-handle operated screw jacks being used to move the wedges into the angles and vice versa. Double spring piston mechanisms may effect automatic contraction as the wedges are withdrawn.