| 摘要 |
PROBLEM TO BE SOLVED: To securely prevent a snow removing plate from being caught by the action of a force pressing down a steel cover to the inside of a receiving frame on the steel cover when the snow removing plate hits semi-spherical projections even if the steel cover is projected from the receiving frame. SOLUTION: This steel cover for a manhole comprises a groove 1A formed at least partly in an upper corner part and the semi-spherical projections 1B formed in the groove 1A at intervals along the longitudinal direction thereof. COPYRIGHT: (C)2006,JPO&NCIPI
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