| 摘要 |
PROBLEM TO BE SOLVED: To form a cover body and a blocking plate structure as castings and engage the blocking plate structure with the cover body without any mechanical working at a required part and without any separate parts. SOLUTION: The blocking plate structure is engaged with the iron cover cover body by forming a cutout part for pinching of a U shape in plan view on a peripheral edge part of the iron cover cover body made of cast iron, etc., constituting a projection extending toward a cover center and having a vertical side wall along a U shaped parallel part on a back surface of the cutout part, forming a groove both ends of which are blocked and in parallel with a cover surface at a position symmetrical to an opposed surface of the side wall parallel part, integrally forming a blocking part to cover the U shaped cutout part and fit with a play and a heavy bob to maintain a blocking state at the time of assembling and closing the cover respectively on both ends, forming a projected part roughly at right angles from its midway, constituting the blocking plate structure symmetrically having shafts on head end both surfaces of the projected part, inserting the shafts of the blocking plate structure into an opening part of the vertical side wall in a parallel state and fitting loose the shafts in a groove of the side wall by twisting them at right angles as they are.
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