means of the worm screw in order to facilitate an understanding of the characteristics of the invention and forming an integral part of this descriptive specification some drawings are attached in which figures on an illustrative rather than limiting basis the following has been represented fig1 u2014 is a partial view in profile of a door fitted with a lock provided with the clutch mechanism object of the invention fig2 u2014 is a view similar to fig1 with the clutch mechanism applied to a different lock fig3 u2014 is a perspective exploded view of the components of the clutch mechanism object of the invention fig4 u2014 is a plant view of the same clutch mechanism as in fig3 with all components assembled with the exception of the cover enclosing the casing and in a door closed position and without actuating the motor fig5 u2014 is a similar view to fig4 when the outside handle has been turned and the door cannot be opened or the bolt cannot be retracted fig6 u2014 is a similar view to fig4 and 5 with the clutch mechanism in the rest position but with the motor actuated producing engagement of the clutch which will permit the door to be opened when the outside handle is turned fig7 u2014 is a similar view to.