| 摘要 |
<P>PROBLEM TO BE SOLVED: To prevent a locked state from being canceled unexpectedly in the case when a spring which energizes a lock member into the locked state is broken. <P>SOLUTION: In an elongation/contraction strut 62 which is supported by a strut main body 61 so as to be movable freely in a length direction, a plurality of engage teeth 72 are formed. The engage teeth 72 are arranged in one line in the length direction of the elongation/contraction strut 62. A lock member 82 for locking the movement of the elongation/contraction strut 62 with respect to the strut main body 61 is oscillated freely around a horizontal supporting shaft 94 which includes an engage claw 102 to be engaged with the engage teeth 72 and crosses a direction in which the line of the engage teeth 72 is arranged. In a state where only the gravity is operated upon the lock member 82 as an external force, the engagement of the engage claw 102 to the engage teeth 72 can be maintained by a rotation moment of the lock member 82 generated by the gravity around the supporting shaft. <P>COPYRIGHT: (C)2013,JPO&INPIT |
