Inventors:
Arnold Wilson - Mapleton UT
International Classification:
E04G 1136
Abstract:
A collapsible and reusable umbrella concrete form for casting a concrete shell roof in the form of a dome, the collapsible umbrella form comprising a central stem or column equipped with a base, a jack abutment plate for vertically adjusting the stem in respect to the base, the jack abutment plate being immediately above the base, a rib support connector at the top of the column, and a plurality of strut connectors slidably carried by the central portion of the column, each being axially displacable along the column but keyed so as to be non-rotatable in respect to the column. The top connector of the column releasably receives the upper end of each rib support, each rib support being radially disposed outwardly and arcuately downwardly from said top column connector, the array of rib connectors in plan view giving the appearance of radial spokes, each equally angularly spaced from the next, and being connected one to the other by a plurality of ring members, one ring member defining the outer periphery of the form. Each rib support is held in the described arcuately depending disposition against collapse by three diagonal strut members bridging between an intermediate location along the rib support and one of the strut connectors. The degree of arc and the effective radius spanned by the rib supports may be varied within limits depending upon the relative position of the strut connectors along the length of the column.