Abstract: Device for coupling an inner shaft and an outer shaft that slide in the direction of a common axis with balls disposed between the two shafts. The balls are disposed in axial grooves of the inner shaft and in axial grooves of the outer shaft. Each row of balls is held by a double spring member that bears on the groove and which pushes on two rolling tracks for the balls, which come into contact with the groove. The two rolling tracks are articulated at the junction of the groove and the inner shaft.