The hydraulic actuator of a grab is actuated by a rope system which drives the hydraulic actuator of the gra jaws. The lifting arrangement of the grab with two ropes is utilised for actuating the hydraulic pump. The rotating driving wheel within the housing is driven by chains connected to the ends of the lifting rope. The movement of the lifting rope rotates the wheel which is coupled to the hydraulic pump (7). The delivery direction of this pump is also changed when the rope travel changes direction. This pump may not be reversible and in this case a multiway valve is actuated by the rotating direction of the driving wheel.
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