This self releasing mechanism is developed at Argone National Laboratory in Illnois, USA, to remove fuel rods from nuclear reactors. It is useful also where human intervention is hazardous or inefficient, such as lowering and releasing loads from helicopters.
There are 3 blue latches disposed around the grapple’s axle.
The green sliding collar is the design’s key feature.
In original design a gasket spring is used instead of the 3 compressed springs.