| 摘要 |
PROBLEM TO BE SOLVED: To reduce an operator's burden and to prevent noises through an increase in the energizing force of an energizing means by employing an arrangement which eliminates the need to constantly apply an operating force to an operating grip. SOLUTION: A stopper 14 is disposed between a positioning piece 6 and a rear locking pawl 13. When a forward operating force is applied to an operating grip from the outside, the stopper 14 projects radially outward of a main body pipe 2 and enables the rear locking pawl 13 to be locked. When the rear locking piece 13 is in a locked condition and the stopper 14 is pressed by the other leg pipe 50B, the stopper 14 is retracted radially inward of the main body pipe 2 and permits the rear locking pawl 13 to recede.
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