| 摘要 |
The longitudinal members comprise a tubular housing (8) and the bars (2) comprise a sleeve (11). The sleeve (11) is engaged in a corresponding lateral opening (9) in the housing (8) and its outer surface has an uneven circular shape. A metal core (15) is centred within the sleeve (11) by means of a spider (28). A setting material (13) fills the free spaces in liaison with one another within the housing (8) and the sleeve (11), and holds captive the sleeve (11) of the bar (2), thereby preventing its rotation. Blocks of filling foam (14), previously set in place, restrict the amount of setting material (13) required, the latter also serving to hold the sheaths (18) protecting the threaded rods (6) captive, said rods anchoring the ladder to a load-bearing structure. For use as a permanent fixture in manholes for gaining access to sewers.
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