US Patent 9242422 Quick-connect coupling

A quick-connect coupling for connecting an exchangeable head to a pressing device has balls K1 with a diameter D1, which are radially movably disposed in a ball-holding part on the pressing device. Balls K1 being held radially fixed in a groove on the head with a depth N1 by a locking ring in the connected state. The head has a further peripheral groove with a depth N2. The further groove is designed to hold part of further balls K2 with a diameter D2, wherein the balls K2 are likewise disposed in a radially movable manner in the ball-holding part and wherein the diameter D2 is greater than the diameter D1. The diameter D1 is the same or smaller than the difference between the diameter D2 and the groove depth N2.