Actuator device for a bicycle gearshift and related bicycle gearshift

1. An actuator device for a bicycle gearshift, the actuator device comprising:

an actuation linkage including a first body configured to be associated with a bicycle frame, a second body configured to be associated with a derailleur of the bicycle gearshift and a pair of articulating connection rods that connect the first body and the second body;

a drive member configured to control the deformation of the actuation linkage and comprising a motor fixedly connected to one of the first body and second body and a motion transmission element configured to be set in rotation by the motor about a rotation axis (X);

a fastening/release mechanism operatively arranged between said motion transmission element and a connection rod of said pair of connection rods and comprising:

a first member rotatable about the rotation axis (X) as a unit with said motion transmission element;

a second member rotatable about the rotation axis (X) together with said connection rod;

an elastic element operatively arranged between the first member and the second member and that exerts a predetermined pre-load stress on the first member and on the second member;

wherein the fastening/release mechanism is selectively configurable in a fastening operative condition in which the first member is rotatable about the rotation axis (X) as a unit with the second member, and in a release operative condition in which the first member and the second member can rotate with respect to one another about the rotation axis (X), said fastening operative condition being defined when the fastening/release mechanism is subjected to a stress lower than said predetermined pre-load stress and said release operative condition being defined when the fastening/release mechanism is subjected to a stress greater than said predetermined pre-load stress.

2. The actuator device according to claim 1 , wherein the second member is fixedly connected to a rotation pin rotatably associated with said connection rod and extending along an axis (Y) parallel to said rotation axis (X).

3. The actuator device according to claim 2 , wherein said connection rod comprises:

a first frame having a first hole configured to house a first end portion of the motion transmission element and a second hole configured to house an end portion of the rotation pin;

a second frame fixedly associated with the first frame;

wherein the fastening/release mechanism is operatively arranged between the first frame and the second frame.

4. The actuator device according to claim 2 , wherein the second member comprises two arms and wherein the rotation pin is arranged between the two arms.

5. The actuator device according to claim 4 , wherein the second member is substantially L-shaped.

6. The actuator device according to claim 1 , wherein the elastic element is a torsion spring.

7. The actuator device according to claim 6 , wherein the second member is fixedly connected to a rotation pin rotatably associated with said connection rod and extending along an axis (Y) parallel to said rotation axis (X), and wherein the torsion spring comprises a central portion arranged coaxially to the rotation pin, a first end portion in contact with the first member and a second end portion in contact with the second member.

8. The actuator device according to claim 1 , wherein one of the first member and the second member comprises a torque transfer element and the other of the first member and the second member comprises a housing seat configured to house the torque transfer element when the fastening/release mechanism is in the fastening operative condition.

9. The actuator device according to claim 8 , wherein the second member comprises two arms and the rotation pin is arranged between the two arms, and wherein the torque transfer element is arranged on one of said two arms.

10. The actuator device according to claim 9 , wherein the second member is fixedly connected to a rotation pin rotatably associated with said connection rod and extending along an axis (Y) parallel to said rotation axis (X), and wherein the torsion spring comprises a central portion arranged coaxially to the rotation pin, a first end portion in contact with the first member and a second end portion in contact with the second member, and wherein the other of said two arms comprises a pin in contact with the second end portion of the torsion spring.

11. The actuator device according to claim 1 , wherein the first member is coaxial to the rotation axis (X).

12. The actuator device according to claim 11 , wherein the second member is fixedly connected to a rotation pin rotatably associated with said connection rod and extending along an axis (Y) parallel to said rotation axis (X), and wherein the torsion spring comprises a central portion arranged coaxially to the rotation pin, a first end portion in contact with the first member and a second end portion in contact with the second member, and wherein the first member comprises a substantially cylindrical annular body in contact with the first end portion of the torsion spring and a shaped annular body axially adjacent to the substantially cylindrical annular body.

13. The actuator device according to claim 12 , wherein one of the first member and the second member comprises a torque transfer element and the other of the first member and the second member comprises a housing seat configured to house the torque transfer element when the fastening/release mechanism is in the fastening operative condition, and wherein the housing seat is formed in said shaped annular body.

14. The actuator device according to claim 13 , wherein the housing seat defines a recessed surface portion between two substantially cylindrical surface portions having equal diameters.

15. A bicycle gearshift comprising the actuator device according to claim 1 .