A transmission device for two or more shafts is provided having two first cylindrical sleeves which are connected to the first shaft and can be mechanically coupled or uncoupled with two second cylindrical sleeves connected to the second shaft or to a third shaft aligned with the second shaft, by tightening or loosening, respectively, two helical springs arranged in a substantially coaxial manner astride these cylindrical sleeves. Two control collars are mechanically coupled with two tubular members, so that the mutual translation of the control collars with respect to the tubular members also causes their mutual rotation, the ends of the helical springs being arranged into seats made in the control collars and in the tubular members so that their mutual rotation tightens or loosens the coils of the helical springs, thereby causing the coupling or the uncoupling, respectively, between the first cylindrical sleeves and the second cylindrical sleeves.