| 摘要 |
The invention relates to an arrangement for lifting or lowering a crane jib (2) or the like in an excavator or similar lifting apparatus (1), in which a load is lifted by means of a pressure medium operated lifting cylinder (3), the load consisting of a useful load proper to be lifted, and of a base load, comprised of parts belonging to the apparatus (1) itself which are to be lifted and lowered, to be lifted together with the useful load, in addition to which is provided a weight-relieving cylinder (II), which is arranged to charge a pressure accumulator (9) when the crane jib (2) is being lowered and correspondingly to discharge the pressure accumulator (9) when the crane jib is being lifted. The lifting cylinder (3) comprises a first cylinder space (I) bordered by the main cylinder (4), the main piston (5) and the rod (6) of the main piston, a second cylinder space (II) bordered by the main cylinder (4) and the main piston (5), and a third cylinder space (III) provided inside the hollow rod (6) of the main piston (5), in which cylinder space is a fixed auxiliary piston (7) extending inside the rod (6) of the main piston (5), the first cylinder space (I) of the said lifting cylinder (3) being connected to a pressure medium circuit (8) effecting the lowering of the crane jib (2) of the lifting apparatus (1), the second cylinder space (II) of the lifting cylinder (3) being connected to a pressure accumulator (9), whereby the said second cylinder space (II) forms a weight-relieving cylinder, and the third cylinder space (III) of the lifting cylinder (3) being connected to the pressure medium circuit (10) effecting the lifting of the crane jib (2) of the lifting apparatus (1). |
