918,573. Moulding precast prestressed concrete articles. STANTON & STAVELEY Ltd. Aug. 18, 1961, No. 29855/61. Class 87(2). Prestressed articles such as lamp standards are made in a tubular mould d furnished with a single slit e, Fig. 2 (not shown) from end to end, by a method in which reinforcing wires r passing through the mould are pretensioned, concrete is cast in the mould and, after setting, the pretensioning forces are transferred to the ends of the article to compress it longitudinally and tend to release the article from the mould. An assembly of wires r, held by anchor plates j, k and passing through distributer plates m, n attached to a mandrel a, is placed in the mould d and the plates m, k are fixed to a flange f and a plate o respectively. The mandrel a is removed, the nuts s on studs p are adjusted to tension the wires r, and the concrete poured in and allowed to set. The nuts s are then slackened to transfer the forces to the article, This causes, both a longitudinal contraction of the article which tends to free it from the mould, and a slight lateral expansion which is accommodated by opening of the longitudinal slit. The article is then removed from the mould by jacks.
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