Hydraulic control system for the swivel arm of an elevating work platform

摘要

A hydraulic control system for the swivel arm of an elevating work platform has a double-acting lifting cylinder with a piston rod on one side, the base side of which cylinder is allocated to the lifting movement and the annular-area side of which is allocated to the lowering operation and which is controlled via a directional control valve. Furthermore, the control system contains overload protection which blocks load-moment-increasing movements of the swivel arm upon response and has a pressure transducer connected to the base side of the lifting cylinder. In order to make such a control system simpler and more reliable, the pressure transducer is a pressure switch set to the limit pressure of the incipient overload state. Here, the piston area at the base side of the lifting cylinder is many times greater than that at the annular-area side, and the annular-area side of the lifting cylinder is activated via a pressure-reducing valve which is connected downstream of the directional control valve and the output pressure of which is many times smaller than the limit pressure.