Rima hydraulic anti-sway system works on a reaction principle, the hardware of the system consists into four winches, properly located on the trolley frame and connected to the head block through suitable steel ropes.
The winches, controlled by the hydraulic unit, act in such a way to damp the oscillation: during the oscillation the two ropes pulled by the head block, are held back with a considerable force, proportional to the load; the two ropes that go slack are wound with a soft force. The difference of forces, always opposite to the oscillation, allows the damping.
The calibration of the forces is achieved by electronic control of proportional valves.
Side shift function: as an option, it is possible to provide a function of shifting of the spreader in the two directions, transversal or longitudinal, creating on purpose a difference of forces on the proper couple of anti sway ropes; this allows small final shifting of the spreader, without moving crane bridge or trolley.
Easy to see advantages, for example, in the case of application on RTG’s where gantry movement generate tyre compression.
Smooth and effective damping allowing a quick positioning of the container on trailer or stock pile.
The system works also on skew oscillations
No negative impact on the operator:
the electronic anti-sway systems are very often excluded by the operators, because, acting on the control of trolley travel, up to a certain extent, they catch the control of trolley speed/position out of the hands of the operator, creating a sensation of unsafety. The hydraulic anti-sway just helps the operator, reducing drastically the oscillations but leaves always the complete control of position and speed of the trolley in the hands of the operator.
Possibility of retrofitting:
the system can be quite easily utilised to retrofit existing cranes not provided with efficient anti sway, in order to improve considerably, their productivity.