| 摘要 |
PROBLEM TO BE SOLVED: To provide a lock mechanism wherein work efficiencies for an upper unit can be improved and there is no need for an unlocking operation wherein a lever or the like is used. SOLUTION: One end of an upper unit is swingably supported by a lower unit so that when the upper unit is swung, the end of the upper unit moves toward and away from the lower unit. When the end of the upper unit is moved to a location away from the lower unit, a roller 15 provided in a lock mechanism 14 is projected to a lock position on the swinging track of the upper unit by being urged by a spring 17 to restrict the swinging of the upper unit. And if a force of a predetermined value or more is exerted on the upper unit, the roller 15 is retracted from the lock position to release the upper unit. Thus, an operator does not need to perform a lock and unlock operations so that a malfunction of the operator can be avoided.
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