In all kinds of crane with two group of motor durm(motor hoist),each group motor durm lead two wire ropes, they make one group wire ropes rooted in the balance frame for supporting, another group of wire rope pass the up beam pulley and the down beam pulley, composite a pulley block as open and closed grab bucket.
Working beginning, support wire rope will lift the grab bucket in well place, and then shut down the support rope, reply on the dead weight of the down beam forced the down beam big shaft as center open the garb body. When the two ear plates’ touch piece smash together, the grab body part open maximum. When opening the grab bucket, the up beam pulley and down beam pulley‘s center distance increase. And then the support rope put down, the opened grab bucket fall on the captured materials above, and packed around the open and close rope, the up beam pulley and the down beam pulleys’ center distance return to its original position. Thus completing the capture the grab materials process. In the last, lifting open and close rope and support rope at the same time, the whole grab bucket is lifted, according to the crane, move the grab bucket to the discharge yard, unloading the materials.