To solve the problem of the impossibility of the so-called post-fitting, wherein after the bolt head or nut is tightened, a slip-off preventive device cannot be fitted.
This slip-off preventive device for bolts and nuts is composed of: an intervening member 3 interposed between the bolt head Ba or a nut N and a member A to be fixed; a closed-end cylindrical outer wrapping cylinder 1 storing the bolt head Ba or the nut N, and provided with an insertion hole 2 allowing the intervening member 3 to loosely pass therethrough and allowing the bolt head Ba or the nut N to forcibly pass therethrough; and a closing lid 4 blocking up the opening part of the outer wrapping cylinder 1 as the outer wrapping cylinder 1 is still rotatable. The already tightened bolt head Ba or nut T is forcibly passed through the insertion hole 2 of the outer wrapping cylinder 1 to be stored in the outer wrapping cylinder 1, and further the bolt head Ba or nut N is completely surrounded with the outer wrapping cylinder 1 and the closing lid 4, so that the bolt head Ba or nut N cannot be loosened. Further, when the bottom of the outer wrapping cylinder 1 is brought into contact with the member A to be fixed by the closing lid 4, a gap between the outer wrapping cylinder 1 and the member A to be fixed is not enlarged so that a tool such as a bar cannot be inserted to prevent forced removal of the outer wrapping cylinder 1 and completely inhibit the bolt B or the nut N from being slipped off. Thus, the invention solves the problem that the protective means for the bolt and the nut in use cannot be post-fitted.
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