| 摘要 |
A drive apparatus for a grab device comprising two grab arms, which can be moved like pincers, preferably for a two bucket grab, consists of two hydraulic pivot motors whose shaft journals of the pivot shaft projecting over the motor housing carry the grab arms. Each of the pivot motors has a cylindrical tube piece which is provided at its inner wall with a section which is provided with an internal thread and which is in engagement with a section of the pivot shaft provided with an external thread. The tube piece is a ring piston axially displaceable in but held non-rotatably in a cylinder space formed in one of the housings. The pitch of the threads is so large that the ring piston is able to give the pivot shafts the required torque by its axial displacement. The displacement path of the ring piston between the two annular cylinder chambers, which are alternatively high and low pressure chambers which can be loaded with hydraulic oil, corresponds to the desired pivot angle of the two buckets.
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