| 摘要 |
PROBLEM TO BE SOLVED: To considerably change the lever ratio of a bell crank 31 by switching the connection condition of the other end of a connection link 73. SOLUTION: An intermediate link 45 is provided in the vicinity of the bell crank 31 in a fixed frame 5 in an oscillating manner, a lower end part of the intermediate link 45 is connected to a part in the vicinity of a base end of an upper arm 35 via a connection link 49, a working slider 57 is provided on the fixed frame movably in the horizontal direction, one end part of the connection link 73 is rotatably connected to the working slider 57, and the other end part of the connection link 73 is selectively and rotatably connected to either a tip part of the upper arm 35 or an upper end part of the intermediate link 45.
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