When rotation axes are located on the same plane and placed at 90 degrees or more to each other, rotation of the driving shaft can be transmitted to the driven shaft by connecting the two axes using a coil spring. (See [Fig.1] for details.)

Since the direction-changing unit connected with this coil spring can be designed with some flexibility as long as the driven shaft axis is 90 degrees or larger, it will be utilized for mechanisms requiring assembly adjustment or sorting by the products' grade and more.
[Fig.2] illustrates examples of a driven shaft connection for a mechanism compatible with various models.

Because a coil spring is used for connecting the component, the following disadvantages must be kept in mind when designing this mechanism.

Disadvantages (limitation of rotary diversion performance)

1. When the angle (θ in Fig.1) of the two axes become small (less than 90 degrees), the rotary transmission becomes unstable.
2. Adopting this mechanism to a system involving high-speed rotation or varying rotation speed will result in less precision.
3. The helical direction of a coil spring must be same as the direction of shaft rotation.
4. The coil spring may fracture owing to fatigue.

Application examples

1. Rotation adjustment mechanism compatible with various models
2. Transmission mechanism having a small rotary torque
3. Simple adjustment mechanism in a rotary system

In the next volume, we will learn about the boost mechanism designed to generate a large force from a small force (human power).