| 摘要 |
A locking device and method for securing a cover as for a catch basin or manhole in position including two elongate members pivotally connected together end to end so as to be able to articulate. The members are held aligned while being inserted through a cover opening suspended in said opening on a flange on the upper member, the lower member then released to be angled by a spring force to wedge against sidewall and an edge of the cover opening. A bolt extending through the top threaded into a trunnion extending across an intermediate space of the lower member draws the lower member up to create a powerful wedging action to prevent cover removal. The bolt head is recessed into the flange and configured with a special shape engageable only with a special tool to be tamper resistant. A protective plastic cap covers the bolt head and has protrusions sheared off when the cap is removed to provide a tamper indication. A miniature radio transmitter can be installed beneath the cap to transmit an alarm signal when the cap is removed. The locking device is used with a modified manhole cover by installing an adaptor sleeve defining a rectangular opening through which the locking device is inserted, and by connecting an extension arm to the lower member bottom end by use of a shear pin and pivot bolt allowing release of the locking device and cover in the event of an explosion.
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