GB1363302A - Manholes - Google Patents

Abstract

1363302 Manholes HEPWORTH IRON CO Ltd 13 Oct 1972 [16 July 1971] 33429/71 Heading E1C A manhole comprises an access chamber A of moulded plastics material with a closed bottom and inlet forming portions, as C 1 to C 8 spaced around the lower end of the sides of the chamber and an invert-forming insert D of moulded plastics material fitting in the bottom of the chamber and having at least one upwardly facing channel as D 4 , D 5 , D 7 forming an invert between two of the inlet forming portions. Preferably the insert is a tight fit in the chamber bottom with its sides K blocking off the unused inlets and is snapped past an inward projection M just above the inlets. The insert may be either a closed body with a bottom L or it may be an open shell reinforced by ribs at locations not bearing invert channels (Fig. 6 not shown). The inlet forming portions may be knock outs in the chamber wall, sealing being effected round a pipe-end inserted in a knocked out hole by means of a grommet (Fig. 11 not shown) or the ends H of the outwardly projecting blind spigots C 1 to C 8 may be pierced or cut off to provide access. The upper end of the chamber A is formed as a socket to receive an extension piece E with an outward flange G for contacting a manhole cover. Additional socketing extension pieces may be provided between the chamber A and extension piece E. Instead of the rectangular form shown, the chamber, extensions and insert may be of octagonal or circular cross-section and the chamber may serve simply as a former surrounded in use by low grade concrete or other settable filler or by a built-up structure.