The floating stage at Lake Idroscalo in Milan, Italy, is equipped with a considerable amount of sophisticated technology, including a stage roof that can be raised or lowered as needed. It is due to a cleverly devised actuator technology from Pfaff-silberblau Hebezeugfabrik GmbH & Co. KG of Derching/Friedberg, Germany.
The equipment, which was developed by the engineers from the Southern German drive technology specialist, not only meets the stringent safety standards (BGV C1) that are in place to protect the performers, it can also handle the extreme environmental conditions that arise there: The roof-lifting construction, which the operators can lift or lower using actuator technology from Pfaff-silberblau, resists precipitation and moisture from the lake, withstands tremendous heat and temperatures below the freezing point, and ensures absolute safety and smooth operation, even when heavy winds blow.
The actuator system consists of four optimised size-100 worm-gear screw jacks (SHEs) with reinforced buttress-thread spindles and long, electrically monitored safety nuts. These special SHEs are mechanically coupled in pairs, and installed at the double-scissors to the left and right of the stage. Since the space available in the scissor units is confined, the worm-gear screw jacks were reinforced to enable them to handle loads of up to 150 tonnes. As a result, the two power trains have an overall lifting capacity of 6,000 kN, which is distributed across the four lifting elements. This ensures that the worm-gear screw jacks, which offer an overall driving power of about two times 18.5 kW, can move a 500-t load at a lifting speed of approximately 90 mm/min.
The long, electrically monitored safety nuts ensure that the high possible safety levels are maintained: If one of the nuts fractures, a mechanical limit switch with positive opening operation turns the system off. Electric synchronisation of the actuators is accomplished with the aid of a pulse cam in the safety nut. This cam transmits a precisely defined number of impulses to the control unit across the entire stroke length via an inductive limit switch. These impulses are then evaluated in the SPC control unit, which was also supplied by Pfaff-silberblau. Infrared temperature sensors in the lifting elements automatically shut the system off, when it is overloaded or overheated. For added safety, an equalising cross beam ensures that the load is distributed evenly among the individual pairs of worm-gear screw jacks.
At Motek 2006, at Booth 4327 in Hall 4, Pfaff-silberblau will be presenting technology that complements its outstanding actuator solutions (such as the equipment being used for the lake stage in Milan). The exhibits will include, for instance, Pfaff-silberblau electromechanical linear actuators with extended standard options, KTA 1401-certified worm-gear screw jacks, worm-gear screw jacks and linear actuators that are protected against potentially explosive hazards, as well as the PHOENIX multi-stage telescopic lifting column from ALLTEC, a Pfaff-silberblau subsidiary.