Irreversible adjustment mechanism

An irreversible adjustment mechanism comprising:

• a fixed support,
• an input part pivoting mounted relative to the support around an axis of rotation, this input part being resiliently assisted to a neutral position and being moveable along a first direction from the neutral position, in a first angular sector, and along a second direction opposite to the first direction from the neutral position, in a second angular sector,
• an intermediate part pivoting mounted around the axis of rotation,
• a driving stage connecting the input part to the intermediate part and adapted to:
• positively drive the intermediate part with the input part by means of at least one driving part when the input part is moved by moving away from its neutral position,
• and to move the driving part with the input part when this input part returns to its neutral position, with friction of the driving part against the intermediate part,
• a locking surface which is integral with the support and which has a shape of revolution centered on the axis of rotation,
• an output part which is pivoting mounted around the axis of rotation and which is shaped to delimit, with the locking surface, at least one pair of wedge shaped spaces including first and second hollow wedge-shaped spaces, these first and second wedge-shaped spaces diverging respectively in the first and second angular directions,
• and a locking stage connecting the intermediate part to the output part, this locking stage comprising:
• at least one pair of clamping bodies including first and second rigid clamping bodies which are arranged respectively in the first and second wedge-shaped spaces and which are resiliently assisted respectively in the first and second angular directions to be wedged between the output part and the locking surface,
• at least first and second rigid stop surfaces integral with the intermediate part, which are directed respectively in the first and second angular directions, the first stop surface being adapted to abut against the first clamping body unwedging it when the intermediate part turns in the first angular direction, and the second stop surface being adapted to abut against the second clamping body unwedging it when the intermediate part turns in the second angular direction, the first and second stop surfaces having a certain angular play relative to the first and second clamping bodies,
• and at least first and second counter stop surfaces which are integral with the output part, the first counter stop surface being adapted to limit the relative movement of the intermediate part relative to the output part in the first angular direction after said first stop surface has sufficiently moved the first clamping body in order to unwedge it, so as to then make said output part be driven by the intermediate part, and the second counter stop surface being adapted to limit the relative movement of the intermediate part relative to the output part in the second angular direction after said second stop surface has sufficiently moved the second clamping body to unwedge it, so as to then make said output part be driven by the intermediate part, wherein the intermediate part is braked relative to the support, with a braking torque sufficient to hold the intermediate part fixed during each return movement of the input part to its neutral position after locking of the locking stage.