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Improvements in and relating to road manhole frames and covers
Improvements in and relating to road manhole frames and covers
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机译：道路井盖和井盖的改进
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391,917. Manhole frames and covers. BROAD & CO., Ltd. and NAYLOR. F.,4 South Wharf, Paddington, London. Jan. 27, 1932, No. 2501. [Class 107.] A manhole cover and frame of the type having tongues 12 on one member adapted to engage grooves 19 on the other member by a rotating or helical movement of the cover, is provided with one or more radial recesses 25 in the peripheral surface of the cover and corresponding slots 26 in the frame, as shown in Figs. 3 and 4, whereby a crowbar or the like may be entered and used leverwise to rotate and lift the cover. The tongues 12, which may be arranged on .the cover, are each provided with one edge 13 inclined at an angle of approximately 45 degrees to the lower edge 14 of the rim 15 of the cover and the other edge 16 inclined at an angle of approximately 120 degrees to the edge 14. The gaps 19 extend completely through a ledge 18 in the frame and have one edge 20 inclined to correspond with the edge 13 of the tongues 12 and the other edge 21 inclined at an angle slightly less than 120 degrees. Ribs 24 are provided either on the surface of the ledge 18 or on the annular edge of the rim 15. When the cover is inserted in the frame, the edges 16 of the tongues rest upon the shoulders 21 A. of the gaps 19 and the weight of the cover then causes the tongues to slide down into the gaps so as to rotate the cover until the edges 13 of the tongues engage the edges 20 of the gaps and the ribs 24 seat firmly upon the abutting surface of the rim 15 or ledge 18. The ends of the recesses 25 in the cover are inclined in the opposite direction to the tongues 12, and the undersides of the slots 26 in the frame are downwardly inclined. The Provisional Specification describes the provision of one or more obliquely-formed entry slots in the frame for the crowbar which is adapted to engage beneath a lip on the cover.
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