| 摘要 |
PURPOSE: A multipurpose stepped control manhole is provided to heighten safety by preventing the separation by an impact by attaching three PADs and fixing with bolts. CONSTITUTION: The multipurpose stepped control manhole is composed of internal pipes(20,30) and external pipes(18,31), wherein the internal pipes(30) are composed of an upper pipe and a lower pipe. The upper pipe is fixed with a flange(17) and provided with a disk cover having three grooves to attach a knob by avoiding an outer locking protective cover to open a cover and to lock up using a wrench bolt not to be opened easily.
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