Rear derailleur

1. An electronic rear derailleur for a bicycle, comprising:

a base member for attachment to a frame member of the bicycle;

a movable member having a cage assembly attached thereto;

a linkage coupling the movable member to the base member and operative to permit movement of the movable member relative to the base member;

a power source connected to one of the base member and the movable member;

a motor positioned at the other of the base member and the movable member; and

an electrical conductor connecting the power source to the motor.

2. The electronic rear derailleur of claim 1 , wherein the power source is removably connected to the base member and the motor is positioned at the movable member.

3. The electronic rear derailleur of claim 2 , wherein the linkage includes an outer link and an inner link.

4. The electronic rear derailleur of claim 3 , further comprising a first pin that pivotally connects the outer link to the base member, a second pin that pivotally connects the inner link to the base member, a third pin that pivotally connects the outer link to the movable member, and a fourth pin that pivotally connects the inner link to the movable member.

5. The electronic rear derailleur of claim 4 , wherein the movable member includes a gear housing.

6. The electronic rear derailleur of claim 5 , further comprising a transmission positioned in the gear housing, the transmission operated by the motor.

7. The electronic rear derailleur of claim 6 , wherein the motor is positioned in the gear housing.

8. The electronic rear derailleur of claim 7 , wherein the motor includes an output shaft with a worm disposed thereon.

9. The electronic rear derailleur of claim 8 , wherein the worm operates the transmission to operate an output gear of the transmission.

10. The electronic rear derailleur of claim 9 , wherein the output gear is coupled to the inner link to move the movable member.

11. The electronic rear derailleur of claim 9 , wherein the transmission includes at least one gear connecting the worm to the output gear.

12. The electronic rear derailleur of claim 9 , wherein the output gear is arranged on the fourth pin.

13. The electronic rear derailleur of claim 9 , wherein the output gear is arranged about the fourth pin.

14. The electronic rear derailleur of claim 13 , wherein the output gear is rotatably arranged about the fourth pin.

15. The electronic rear derailleur of claim 9 , further comprising a drive arm coupled to the output gear, the drive arm acting on the inner link to move the moveable member.

16. The electronic rear derailleur of claim 15 , wherein the drive arm contacts a projection of the inner link on a first side of the drive arm.

17. The electronic rear derailleur of claim 16 , further comprising a clutch spring disposed on the second pin, the clutch spring biasably contacting the drive arm.

18. The electronic rear derailleur of claim 17 , wherein the clutch spring includes a free end extending toward the movable member and contacting the drive arm on a second side of the drive arm, wherein the second side is opposite the first side of the drive arm.

19. The electronic rear derailleur of claim 9 , further comprising an encoder gear meshed with the output gear.

20. The electronic rear derailleur of claim 19 , further comprising a magnet holder disposed within the gear housing, the magnet holder provided with a magnet responsive to motion of the encoder gear, and a sensor positioned to sense the angular position of the encoder gear by way of the position of the magnet.