| 摘要 |
<p>A boom is disclosed comprising a pivotable structure including an upright support having wheels rotably supported on a rail and a truss supported above the rail by the upright support. A grapple is suspended from the truss and a winch mounted to the pivotable structure for raising and lowering the grapple. Hydraulic circuit means are mounted to the pivotable structure for driving the wheels, winch and grapple. Electric circuit means are also provided for controlling the hydraulic circuit means and which includes a set of solenoid valves mounted on the pivotable structure and a set of solenoid valve actuators mounted off the pivotable structure.</p> |
