Coupling system for a chronograph

A coupling system for a chronograph mechanism, said system comprising:

• an input wheel intended to be driven by a drive member;
• an output wheel intended to drive at least one display member;
• an intermediate wheel continuously kinematically connected to a first wheel chosen from said input wheel and said output wheel, said intermediate wheel being mounted so that it can change between a coupled state in which said input wheel is kinematically connected to said output wheel and an uncoupled state in which said kinematic connection is broken;
• wherein said system further includes:
• a first friction wheel constrained to rotate with said intermediate wheel and a second friction wheel constrained to rotate with a second wheel chosen from said input wheel and said output wheel, said friction wheels being at least partially coplanar and being adapted to transmit rotation between said intermediate wheel and said second wheel, or vice versa, when said system is in the coupled state;
• a first safety wheel constrained to rotate with said intermediate wheel and comprising a first set of safety teeth and a second safety wheel constrained to rotate with said second wheel and comprising a second set of safety teeth, said sets of safety teeth being conformed in order to interpenetrate mutually when said intermediate wheel is in the coupled state.