Device for locking a shell and stretcher comprising such a locking device

A device for locking a shell, the device comprising at least one jaw intended to clamp the shell and pivoting between an open position and a closed position around a pivot axis parallel to a longitudinal axis of the shell, the pivot axis of the jaw being located between an upper end and a lower end of the jaw, the lower end of the jaw being intended to receive the shell to allow it to close, the locking device comprising a cam and a pivoting lever, the lower end of the jaw comprising a notch intended to interfere with a catch of the cam for retaining the jaw in the closed position, the cam being secured to the pivoting lever, the pivoting of the lever thus allowing the catch to be moved clear from the rotating path of the notch of the jaw, which allows the jaw to open, wherein the lever is intended to be pivotally activated by the pushing of an external member, the locking device comprising a first spring and a 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 being to bias the lever toward an upper position so as to bring the catch of the cam into contact with the jaw, the second spring being intended to be activated by the pushing of the member and countering the action of the first spring, thus making it possible to delay the lifting of the lever and the locking catch when removing the member.