| 摘要 |
The locking mechanism consists of a hook-shaped catch (10) on the inside of the manhole cover surrounding frame (2), designed to receive a peg (17) on one end of an inverted L-shaped arm pivoted to a bracket (14) on the underside of the cover (4). The arm is rotated to release the catch by a lever (13) with a cam-shaped end which is let into a recess in the cover or, from below, by a chain or cable (18) connected to the tip of the arm's upper horizontal section. When the manhole cover is closed, the control lever is fixed in place by a shutter (15) and a bolt (30) which screws into a nut (32) under a plate (28) in the cover recess. The cover can be equipped with a gas cylinder to facilitate lifting. |
