The pulley consists of the pulley itself and the driven disk. The pulley and the disk are tightly connected to each other by 1 rubber element. The rubber element with 4 protrusions connects the pulley and the driven disk.
In threatening situations (the compressor is jammed) the forces acting on the protrusions of the rubber element between the driven disk and the pulley increase sharply.
The rotating pulley presses the rubber element against the locked driven disk. The rubber element is deformed at the 4 protrusions. The pressure on the driven disk increases until the disk is deformed and comes off the pulley. This eliminates damage to the belt drive that drives several attachments.