Abstract: The device includes first and second elements which are intended to be rigidly connected each to a respective length of an elongated mechanical transmission member, such as a push-pull cable, a rod or a bar, and are slidably arranged relative to each other in the axial direction of the transmission member. A locking member is radially movable between a locking position, in which it drivingly connects the two elements for translation with each other, and a unlocking position, in which it disconnects the two elements from each other, thereby making them free to translate relative to each other. A cam member is free to translate axially relative to the first and second elements and has at least one cam surface which cooperates with the respective locking member so as to keep this latter in the locking position up to the predetermined travel value and to move it into the unlocking position in case of travel values higher than the predetermined travel value.