Adjustment mechanism

An adjustment mechanism comprising:

• a fixed support;
• an inlet member mounted to pivot relative to the support about a pivot axis, said inlet member being urged resiliently towards a rest position and being movable in a first angular direction from the rest position over a first angular sector, and in a second angular direction opposite to the first direction, from the rest position and over a second angular sector;
• a transmission member mounted to turn about the pivot axis;
• and
• a drive stage comprising:
• a bearing surface secured to the transmission member, which bearing surface is in the form of a surface of revolution centered on the pivot axis and co-operates with the inlet member to define a hollow intermediate annular space, the inlet member having a plurality, n, of projections, where n is not less than 2, said projections projecting into said intermediate annular space and each defining first and second wedge-shaped zones in said intermediate annular space, said first and second wedge-shaped zones diverging respectively in the first and second angular directions;
• n compression springs disposed in the intermediate annular space between the projections of the inlet member;
• n pairs of wedging bodies corresponding respectively to the various projections of the inlet member and each comprising first and second rigid wedging bodies which are disposed in the intermediate annular space and which are urged towards the corresponding projections by two of said compression springs each bearing against the first wedging body of a pair of wedging bodies and against the second wedging body of an adjacent pair of wedging bodies, the first and second wedging bodies of the first pair thus being urged towards the first and second wedge-shaped zones defined by the first projection to tend to become wedged between said first projection and the bearing surface of the transmission member;
• and
• n fixed fingers comprising at least first and second fingers, which are secured to the support and which are disposed in said intermediate annular space, the projections of the inlet member being disposed respectively in register with the fixed fingers when said inlet member is in its rest position, the fixed fingers comprising a first finger presenting width in a circumferential direction about the pivot axis sufficient for the two wedging bodies of the corresponding pair of wedging bodies to come into abutment against said first finger when the inlet member is in its rest position, such that the inlet member is urged towards its rest position by the first and second springs of the wedging bodies;
• wherein the first finger and the corresponding projection are so shaped that the corresponding wedging bodies come into abutment against said first finger, thereby preventing them from wedging between the corresponding projection and the bearing surface of the transmission member while the inlet member is in its rest position;
• and
• wherein the second finger and the corresponding projection are so shaped that said second finger does not interfere with the corresponding wedging bodies while the inlet member is in the rest position, these wedging bodies then wedging between the corresponding projection and the bearing surface of the transmission member.