| 摘要 |
PCT No. PCT/FI92/00194 Sec. 371 Date Dec. 23, 1993 Sec. 102(e) Date Dec. 23, 1993 PCT Filed Jun. 22, 1992 PCT Pub. No. WO93/00286 PCT Pub. Date Jan. 7, 1993.A hoisting boom assembly comprises an upright column being piviotable by a rotary actuator and a first and second boom, the first boom pivotally mounted by its first end on upright column and by its second end on second boom; the second boom having its first section and its second section journalled to be pivotable in a vertical plane; a horizontal shift mechanism as well as a horizontal shift actuator for carrying the free end of the second boom in a horizontal direction; and an actuator fitted between upright column and the first boom for pivoting the first boom. In order to improve its performance, the hoisting boom assembly further includes compensating means for equalizing the forces caused by the operation of a hoisting boom assembly, particularly in situations following and preceding a first and/or a second extreme position assumed by a second boom.
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