The Computer Modeling of the Ball Gear of Concave Cone Teeth

Abstract

The ball gear or globular gear is a ball; on the ball there are a series of holes. The ball gear is the key component of the robot’s wrist. As shown in fig.1, by using the ball crowns of two different ball centers as a joint curve surface, and their ball center as a rotational center, the ball gearing can be formed on two ball surfaces with convex teeth and concave teeth engaging each other. The robot’s wrist differs from the wrist of human kind in that, it can transmit rotational movement from the upper arm to the lower arm continuously, while the angle between the upper arm and the lower arm is changing. In the formal papers, the protruding teeth have the shape of a cone, while the concave teeth are the conjugate surface of them. The protruding teeth with straight surface are of cause easy to be machined. But the concave teeth are very hard to be machined. The special machining method such as the electric spark machining has to be employed to deal with this kind of work.