Demag Mobile Cranes Gmbh & Co., Kg

Hans Allgeier

J&uuml;rgen Appel

J&uuml;rgen Schlachter

A method for synchronously retracting and extending a jib of a crane having a plurality of telescoping lengths, preferably in a vehicle crane, extending and retracting being with driving means which is one of a hydraulically-driven, multistage telescoping cylinder and a plurality of single-stage telescoping cylinders operated in parallel. A pre-control transmitter transmits an electrical signal to an input of regulating electronics, which reference signal serves as a reference value for the telescoping speed of a telescoping cylinder or stage which takes on the task of guiding, and the actual value for the current position of the telescoping cylinders or stages is reported to the regulating electronics, and the latter compares the actual value of the telescoping cylinder or stage assuming the guidance task to the actual value of the telescoping cylinders or stages to be controlled and, in the event that an impermissible deviation is determined, the telescoping speed of the rest of the telescoping cylinders is increased or reduced until a synchronous telescoping of all telescoping cylinders and stages occurs.

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Zweibrücken, Germany

Hans Allgeier