Compact clutch

Compact clutch comprising a driven shaft on which the following are mounted:

• a gear wheel;
• a driving bush;
• a driven bush;
• a coil spring with first and second ends;
• a first collar comprising a first recess and cam surfaces on the collar's radially outer surface;
• and
• a second collar comprising a second recess and cam surfaces on the collar's radially inner surface;
• wherein:
• the gear wheel, the driving bush and the driven bush are arranged axially next to each other;
• the gear wheel and the driving bush re constrained together in a circumferential direction;
• the driving bush and the driven bush each have an external diameter that is the same;
• the coil spring has, in a rest condition, an internal diameter slightly greater than the external diameter of each of the driving bush and the driven bush;
• the coil spring surrounds externally the driving bush and the driven bush;
• the first collar surrounds externally the coil spring and the first recess receives the first end of the coil spring;
• and
• the second collar surrounds externally the first collar and the second recess receives the second end of the coil spring;
• and wherein:
• the second collar is displaceable in an axial direction between a rest position and a working position;
• whereby when the second collar is in the rest position the coil spring is in a rest condition;
• and
• when the second collar is displaced into the working position:
• the cam surfaces convert axial displacement of the second collar into a relative rotation between the first collar and the second collar;
• and
• the relative rotation between the first collar and the second collar produces a relative rotation between the first end and the second end of the coil spring;
• whereby the relative rotation between the first end and the second end produces a tightening of the coil spring around the driving bush and the driven bush;
• and
• the tightening of the coil spring constrains together by means of friction the driving bush and the driven bush;
• and wherein:
• the gear wheel, the driving bush and the driven bush are constrained to the driven shaft in the axial direction by means of two stop rings;
• the driven bush is constrained to the driven shaft in the circumferential direction by means of at least one tongue;
• and
• the at least one tongue ensures engagement between the driven bush and the driven shaft in the circumferential direction, while in the axial direction the driven bush is slidable with respect to the driven shaft in at least one direction.