1. IN A WATCH COMPRISING A BARREL DRUM, A BARREL SPINDLE COAXIAL WITH THE DRUM, A MAIN SPRING INTERCONNECTING THE SPINDLE WITH THE DRUM AND A ROCKING WINDING WEIGHT, A DEVICE FOR COUPLING AND UNCOUPLING SAID WEIGHT AND SAID SPRING COMPRISING AN OUTER WHEEL ACTUATED BY THE ROCKING WEIGHT, REVOLVABLY CARRIED BY THE BARREL SPINDLE AND PROVIDED WITH A COAXIAL CIRCULAR RECESS, A RATCHET WHEEL COAXIALLY RIGID WITH THE BARREL SPINDLE AND THE ROTATION OF WHICH WINDS THE MAIN SPRING, A SPINDLE ECCENTRICALLY CARRIED BY THE RATCHET WHEEL AND FACING THE RECESS IN THE OUTER WHEEL, AN INNER WHEEL REVOLVABLY CARRIED BY SAID ECCENTRIC SPINDLE, HOUSED INSIDE THE RECESS IN THE OUTER WHEEL AND PROVIDED WITH A SERIES OF TEETH ON AT LEAST A PORTION OF ITS OUTER PERIPHERY, A RADIAL PROJECTION RIGID WITH THE SAID BARREL SPINDLE AND ADAPTED TO MESH WITH LAST-MENTIONED TEETH TO BE DRIVEN THEREBY TO WIND THE SPRING IN A DIRECTION STARTING FROM AN UNWOUND TOWARDS A FULLY WOUND POSITION, AN ELASTIC U-SHAPED MEMBER FITTED INSIDE THE RECESS IN THE OUTER WHEEL AND INCLUDING TWO ARMS THE OUTER PERIPHERY OF AT LEAST ONE OF WHICH IS ADAPTED TO ENGAGE FRICTIONALLY WHEN EXPANDED THE OUTER SURFACE OF THE RECESS IN THE OUTER WHEEL AND THE INNER PERIPHERIES OF SAID ARMS ENGAGING THE INNER WHEEL TO BE URGED APART THEREBY AND TO URGE SAID ARMS INTO ENGAGEMENT WITH SAID OUTER SURFACE OF THE RECESS, AND COOPERATING MEANS ON THE INNER WHEEL AND INNER PERIPHERIES OF THE ARMS OF THE U-SHAPED MEMBER ADAPTED TO ENSURE A RECEDING MOVEMENT OF SAID ARMS WHEN THE INNER WHEEL HAS REACHED AN ANGULAR POSITION CORRESPONDING TO THE END OF THE ALLOWED SPRING WINDING OPERATION, THE INNER WHEEL BEING THEREAFTER RETURNED TO ITS FORMER POSITION BY THE UNWINDING OF THE SPRING.