| 摘要 |
The manhole cover includes a support frame (1) and a safety cover (2) lifted by springs (16) and hinged by two eyelets (4). The eye-lets are supported on two removable half-axles (6) guided in hollow bosses (8,9) formed in the support frame. The cover is fitted with a safety lock (3) which is locked automatically when the cover is closed. Ribs (19) are formed under the surface of the cover, so that it can support the weight of traffic passing over it. The main structure may be made from cast metal. An additional locking system may be provided, to hold the cover open when required so that it is not closed prematurely.
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