An electric assist device for a bicycle comprising a shaft coupled in rotation with a pair of cranks and being able to be rotated in a positive direction by an electric motor, a connection mechanism being placed between the motor and the shaft, which connection mechanism has at least three distinct states. The states includes State 1, termed assist state, in which the motor transmits a torque to the shaft via a drive part which rotates at the same speed as the shaft, State 2, termed freewheel state, in which the rotation of the shaft in the positive direction is greater than that of the drive part, and State 3, termed disconnection state, in which a rotation in the positive direction or in the negative direction of the shaft cannot cause the motor to rotate.

A power transmission mechanism for a turbomachine is provided, having a reduction gear having a first gear and a second gear having different reduction ratios and each having a first gear wheel mounted so as to be able to rotate freely on a shared first axle and a second gear wheel mounted on a shared second axle; and a coupling member having an annular body with an axis of revolution having first and second rows of helical coupling teeth, which are respectively oriented opposite and substantially parallel to the first and second directions, the coupling member being mounted so as to rotate with and slide axially on said first axle so as to occupy at least two predetermined axial meshing positions in which the coupling teeth mesh with complementary meshing projections of one of the first gear wheels which is then made to rotate with the first axle.

A power transmission mechanism for a turbomachine is provided, having a reduction gear having a first gear and a second gear having different reduction ratios and each having a first gear wheel mounted so as to be able to rotate freely on a shared first axle and a second gear wheel mounted on a shared second axle; and a coupling member having an annular body with an axis of revolution having first and second rows of helical coupling teeth, which are respectively oriented opposite and substantially parallel to the first and second directions, the coupling member being mounted so as to rotate with and slide axially on said first axle so as to occupy at least two predetermined axial meshing positions in which the coupling teeth mesh with complementary meshing projections of one of the first gear wheels which is then made to rotate with the first axle.

A power transmission device has a back torque transmission cam that brings driving clutch plates 6 and driven clutch plates 7 into press contact with each other. A second clutch member 4b is moved when a rotational force is input to a first clutch member 4a via the output shaft 3. The pressure member 5 is located at a non-actuation position. A torque transmission portion transmits a rotational force transmitted to the second clutch member 4b to the first clutch member 4a not via the back torque transmission cam.

A power transmission device has a back torque transmission cam that brings driving clutch plates 6 and driven clutch plates 7 into press contact with each other. This occurs by moving a second clutch member 4b when a rotational force is input to a first clutch member 4a, via the output shaft 3. A pressure member 5 is located at a non-actuation position. A back torque transmission cam can hold abutment between an interlocking member 9 and weight member 8 by moving the second clutch member 4b in a direction of being brought into proximity to the interlocking member 9.

A power transmission device has a back torque transmission cam that brings driving clutch plates 6 and driven clutch plates 7 into press contact with each other. This occurs by moving a second clutch member 4b when a rotational force is input to a first clutch member 4a, via the output shaft 3. A pressure member 5 is located at a non-actuation position. A back torque transmission cam can hold abutment between an interlocking member 9 and weight member 8 by moving the second clutch member 4b in a direction of being brought into proximity to the interlocking member 9.

The present invention relates to a clutch (100) comprising: a rotatable housing (101); a fixed hub (201) internal to the housing (101) and a movable hub (202) axially mounted onto the fixed hub (201); a plurality of discs (204) interposed between the fixed hub (201) and the movable hub (202). The fixed hub (201) and the movable hub (202) axially slide, getting farther or closer so as to transmit a variable axial load onto the discs (204), to selectively transmit a torque. The clutch (100) further comprises a pressure plate assembly (208) for controlling the variable axial load, including a centrifugal assembly (210) comprising: a rotatable mass holder (211) and a plurality of mass elements (212) radially disposed. Each mass element (212) comprises a pivot (301) and is configured for a displacement (1002) by pivoting under centrifugal effects. The mass elements (212) are thus configured for exerting an axial thrust within the pressure plate assembly (208), to bring the movable hub (202) closer to the fixed hub (201), so as to increase the variable axial load and allowing the clutch (100) (automatic) engagement. Each mass element (212) comprises a main body (302) and a column element (303) which connects the pivot (301) with the main body (302).

A clutch device transmits a torque between a rotatable drive-input element and a rotatable drive-output element. Upon demand, the elements are coupled in non-positively locking fashion by a clutch element. Each of the drive-input element and the drive-output element form one clutch surface. A clutch gap decreases in a radial direction relative to at least one axis of rotation of the elements. The clutch element can be placed into a first position and into a second position which differ with regard to the radial position within the clutch gap and thus with regard to the contact pressure between the clutch element and the clutch surfaces. The clutch device permits an axial arrangement of its components, namely, the drive-input element, the clutch elements and the drive-output element, that keeps the size of a clutch device small in a radial direction relative to the axes of rotation.

A clutch device transmits a torque between a rotatable drive-input element and a rotatable drive-output element. Upon demand, the elements are coupled in non-positively locking fashion by a clutch element. Each of the drive-input element and the drive-output element form one clutch surface. A clutch gap decreases in a radial direction relative to at least one axis of rotation of the elements. The clutch element can be placed into a first position and into a second position which differ with regard to the radial position within the clutch gap and thus with regard to the contact pressure between the clutch element and the clutch surfaces. The clutch device permits an axial arrangement of its components, namely, the drive-input element, the clutch elements and the drive-output element, that keeps the size of a clutch device small in a radial direction relative to the axes of rotation.

A power transmission device has a back torque transmission cam that brings driving clutch plates 6 and driven clutch plates 7 into press contact with each other. A second clutch member 4b is moved when a rotational force is input to a first clutch member 4a via the output shaft 3. The pressure member 5 is located at a non-actuation position. A torque transmission portion transmits a rotational force transmitted to the second clutch member 4b to the first clutch member 4a not via the back torque transmission cam.