Coupling device (7; 7'; 7"), comprising: - a first wheel (1; 1'; 1"), - a second wheel (2; 2'; 2"), - a lever (6; 6'; 6") pivoted around a first axis (6f; 6f'; 6f") and comprising: o at least one first element (61; 61'; 61") for guiding in rotation of the first wheel (1; 1'; 1"), o at least one friction element (62; 62'; 62") which is designed to co-operate with an at least substantially cylindrical portion (10c; 10c'; 10c") of the first wheel (1; 1'; 1"), o at least one resilient element (63; 63'; 63") which is designed to return resiliently the at least one friction element (62; 62'; 62") to a state of co-operation with the said at least substantially cylindrical portion (10c; 10c'; 10c") of the first wheel (1; 1'; 1"), o a second element (66; 66'; 66") for guiding in rotation of the lever around the first axis (6f; 6f'; 6f"), the first guiding element (61; 61'; 61") comprising support surfaces (60a, 60b, 60c and 60d) which are designed to co-operate by contact with the said at least substantially cylindrical portion (10c; 10c'; 10c"), the support surfaces (60a, 60b, 60c and 60d): - having an infinite radius of curvature, or - being bosses or - being designed to co-operate by means of localized contact with the at least substantially cylindrical portion (10c; 10c'; 10c") of the first wheel (1; 1'; 1"), the lever (6; 6'; 6") being provided with two resilient arms (6a, 6b; 6a', 6b'; 6a", 6b") each comprising at least one of the support surfaces (60a, 60b, 60c and 60d), the first wheel (1; 1'; 1") being able, according to the state of the coupling, and in particular according to the position of the lever (6; 6'; 6"), to go: - into a first position in which it is directly engaged with a third wheel of a first kinematic chain, and - into a second position in which it is not directly engaged with the third wheel, and the first wheel (1; 1'; 1") and the second wheel (2; 2'; 2") being connected kinematically, and notably connected kinematically by meshing, and in particular connected kinematically by direct meshing, and the coupling device (7; 7'; 7") being arranged such that the rotation, around its axis, of the first wheel (1; 1'; 1") involves the rotation of the lever (6; 6'; 6") around the first axis until the lever (6; 6'; 6") or the first wheel (1; 1'; 1") abuts an element. - a first wheel (1; 1'; 1"), - a second wheel (2; 2'; 2"), - a lever (6; 6'; 6") pivoted around a first axis (6f; 6f'; 6f") and comprising: o at least one first element (61; 61'; 61") for guiding in rotation of the first wheel (1; 1'; 1"), o at least one friction element (62; 62'; 62") which is designed to co-operate with an at least substantially cylindrical portion (10c; 10c'; 10c") of the first wheel (1; 1'; 1"), o at least one resilient element (63; 63'; 63") which is designed to return resiliently the at least one friction element (62; 62'; 62") to a state of co-operation with the said at least substantially cylindrical portion (10c; 10c'; 10c") of the first wheel (1; 1'; 1"), o a second element (66; 66'; 66") for guiding in rotation of the lever around the first axis (6f; 6f'; 6f"), o at least one first element (61; 61'; 61") for guiding in rotation of the first wheel (1; 1'; 1"), o at least one friction element (62; 62'; 62") which is designed to co-operate with an at least substantially cylindrical portion (10c; 10c'; 10c") of the first wheel (1; 1'; 1"), o at least one resilient element (63; 63'; 63") which is designed to return resiliently the at least one friction element (62; 62'; 62") to a state of co-operation with the said at least substantially cylindrical portion (10c; 10c'; 10c") of the first wheel (1; 1'; 1"), o a second element (66; 66'; 66") for guiding in rotation of the lever around the first axis (6f; 6f'; 6f"), the first guiding element (61; 61'; 61") comprising support surfaces (60a, 60b, 60c and 60d) which are designed to co-operate by contact with the said at least substantially cylindrical portion (10c; 10c'; 10c"), the support surfaces (60a, 60b, 60c and 60d): - having an infinite radius of curvature, or - being bosses or - being designed to co-operate by means of localized contact with the at least substantially cylindrical portion (10c; 10c'; 10c") of the first wheel (1; 1'; 1"), - having an infinite radius of curvature, or - being bosses or - being designed to co-operate by means of localized contact with the at least substantially cylindrical portion (10c; 10c'; 10c") of the first wheel (1; 1'; 1"), the lever (6; 6'; 6") being provided with two resilient arms (6a, 6b; 6a', 6b'; 6a", 6b") each comprising at least one of the support surfaces (60a, 60b, 60c and 60d), the first wheel (1; 1'; 1") being able, according to the state of the coupling, and in particular according to the position of the lever (6; 6'; 6"), to go: - into a first position in which it is directly engaged with a third wheel of a first kinematic chain, and - into a second position in which it is not directly engaged with the third wheel, and - into a first position in which it is directly engaged with a third wheel of a first kinematic chain, and - into a second position in which it is not directly engaged with the third wheel, and the first wheel (1; 1'; 1") and the second wheel (2; 2'; 2") being connected kinematically, and notably connected kinematically by meshing, and in particular connected kinematically by direct meshing, and the coupling device (7; 7'; 7") being arranged such that the rotation, around its axis, of the first wheel (1; 1'; 1") involves the rotation of the lever (6; 6'; 6") around the first axis until the lever (6; 6'; 6") or the first wheel (1; 1'; 1") abuts an element.