A jaw pivoting about an axis for clamping the shell, a lower end of the jaw receives the shell to allow closure. The notch intended to interfere with a catch of a cam to retain the jaw in the closed position. The cam is rigidly connected to a pivoting lever which allows the catch to be moved from the path of the notch to allow the jaw to open. The lever is to be pivotally activated through the force of an external component. The device includes a first and second spring each acting on the lever in an opposing manner, the second spring being stiffer than the first spring. The effect of the first spring is to lift the lever. The second spring counters the action of the first spring in order to delay the lifting of the lever and the catch when removing the component.