| 摘要 |
A central body (1) has a pair of extensible arms (4) with a locking mechanism (5,6) capable of exerting a strong force against a structure, panel etc. Interchangeable panels (9) are attachable to the central body, of varying shapes corresponding to the cross-section of the conduit or tunnel to be closed. The panels are articulated to the central body about vertical hinges, for movement to define different extents of closure of the conduit, and in their most open position bear against stop surfaces of a stabilising panel attached to the central body. The extensible arms move within one or more vertical apertures of the central body, and may be defined by the shaft of a hydraulic jack.
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