Using the linear spring concept and including a link between rotation and traslation here I present how to achieve spiral - like movement of a shape.
Combining the rotation and the amount of "traslation" of the spring in the constrained bone you can make different spirals. It has the limitation of lengh due to the limited length of the mechanism, but it works!.
It only needs one keyframe to do all the spiral movement. and another of its benefit is that you can turn in oposite direction only with one keyframe.