Fall prevention device of bracing of drilling axis

摘要

PROBLEM TO BE SOLVED: To provide a fall prevention device for a steady brace of an excavation shaft having no excessive force on an operating bar and a horizontal shaft during a lifting operation after exchanging wires and capable of detaching the operating bar from a support piece without high resistance.;SOLUTION: A fall prevention device 8 comprises: a support piece 9; an operating bar 11; a spring member 12; a wire attachment part 13 provided at an upper end of the operating bar 11; and a rotation inhibition part 14 capable of inhibiting further rotation with the operating bar 11 tilting when the operating bar 11 is rotated by a spring force. As the steady brace 5 becomes standing posture against the spring force when the steady brace 5 is suspended by a wire 4, the steady brace 5 can move vertically while the operating bar 11 is prevented from being brought into contact with the support piece 9. When the wire 4 is cut or loosened, the operating bar 11 is rotated by the spring force until further rotation is inhibited by the rotation inhibition part 14 and the tilted posture of the operating bar 11 is held, and, in this state, a lower end of the operating bar 11 held in the tilted posture comes in contact with the upper part of the support piece 9, which prevents the steady brace 5 from falling.;COPYRIGHT: (C)2012,JPO&INPIT