| 摘要 |
<p>A device which facilitates mounting and dismounting a counterweight and is inexpensive. The device comprises hydraulic cylinders (41, 42) mounted on an upper swivel (23), a first cable (55) connecting tip ends of rods (45, 46) of the hydraulic cylinders (41, 42) to a boom (31), and a second cable (58) connecting the tip ends of the rods (45, 46) of the hydraulic cylinders (41, 42) to a counterweight (28), wherein the counterweight (28) can be hung up and down by expansion and contraction of the hydraulic cylinders (41, 42) and rising and falling of the boom (31).</p> |
