| 摘要 |
PROBLEM TO BE SOLVED: To provide rotatably two driven side sprockets independently in a leader, and to arrange collectively therewith a rotary encoder for detecting a rotational speed of the one driven side sprocket. SOLUTION: A working device elevation means 6 is provided with a pair of hydraulic motors 9 arranged in one end of the leader 4, a pair of driving side sprockets 10 coupled to respective output shafts of the respective hydraulic motors, a sprocket shaft 16 provided rotatably in the other end of the leader, the pair of driven side sprockets 11a, 11b provided in the sprocket shaft, a pair of chains 12 laid respectively over the respective driving side sprockets and the respective driven side sprockets, and connected to a screw drive unit, and the rotary encoder 21 for detecting the rotational speed of the sprocket or the sprocket shaft. The one side driven side sprocket 11a is rotated integrally with the sprocket shaft, and the other side driven side sprocket 11b is rotated with respect to the sprocket shaft. COPYRIGHT: (C)2009,JPO&INPIT
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