| 摘要 |
The rear extremity of the auxiliary arm 7, integral with each side of a throat pulley 10', 10'' is joined to the front extremity of the main arm 3 around the spindle 6. The arms 13', 13'' of the counterweight 14 are each integral with a throat pulley 28', 28'' and are joined around the spindle 12 at the rear extremity of the main arm 3. A flexible cable 27', 27'' is placed on each pair of pulleys 10', 28' and 10'', 28'' whilst being fixed at a point of each of the two pulleys. Control by a twin effect hydraulic thrustor 16 for the simultaneous movement of the cables 27', 27'' towards the front ensures a tilting of the auxiliary arm 7 and simultaneous lifting of the counterweight 14 obtaining the automatic balancing of the jib.The invention ensures the automatic balancing of the jib of the crane whilst eliminating the presence of variable lever arms.
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