LADDER WORKING LIMIT BASED LADDER STOPPING DEVICE FOR AERIAL LADDER TRUCK

There is provided a ladder-working-load-limit-bared ladder stopping device for a vehicle such as a fire engine truck equipped with a hydraulically operated vertically and horizontally swingable and extensible ladder, wherein a working load limit for the ladder is determined on the basis of the extension of the ladder and its vertical angle. Conditions corresponding to combinations of the vertical angle and the extension of the ladder such as to reach said predetermined condition are sensed and are used to actuate hydraulic mean whereby the operating levers of the hydraulic valves controlling the ladder are automatically returned to their neutral position, and to actuate a warning device such as a marker lamp, the operating mechanism then being operable only in such a sense as to decrease the working load, whereupon the marker lamp is turned off to indicate that the ladder is within its safe working load limit.