The gear assembly has a driver gear and a driven gear for transmitting motor torque from the motor to the idler.

The driving motor supplied rotation force to the gear assembly so as to pivot the arm connected to the gear assembly.

When the second gear rotates while revolving, the third gear rotates.

The second gear engages the first gear.

The second gear meshes with both the first gear and the third gear.

The first gear may be a floating gear.

The third gear transfers motion to a fourth gear.

The first gear and the second gear have a difference in the number of teeth, and/or the second gear and the third gear have a difference in the number of teeth.

When the second gear revolves while some of the teeth of the second gear mesh with some of the teeth of the first gear, the second gear rotates.

The second gear (5) is engaged with the fourth gear (8).

The first gear is rotated to drive the second gear.

If the third gear is externally toothed, the second gear is internally toothed, and if the third gear is internally toothed, the second gear is externally toothed.

The first gear (3) is engaged with the third gear (6).

If the third gear is externally toothed, the second gear is internally toothed, and if the third gear internally toothed, the second gear is externally toothed.

In the eccentric gear pair (27), the first outer gear (28) meshes with the first inner gear (31) and the second outer gear (29) meshes with the second inner gear (32).