| 摘要 |
<p>The crane has a jib suspended from a vertical column and derricking in a vertical plane, a hoist rope being reeved round its head and a counter-weight fixed to its foot. The jib (2) is secured by holding devices (3, 4) allowing its head to be derricked, these devices hinging on it and on the column (1). They can be in the form of barrs, ropes or chains. The head of the column and the counter-weight end of the jib can be connected by a bar, while the heads of the column and jib are joined by a rope which can be wound in and paid out.</p> |
