Motion transformation mechanisms with local contact

Motion transformation mechanisms can be divided into two main families:

• those with continuous links, in which the links between component parts remain in permanent contact but are mobile; these are essentially the so-called bar mechanisms, examined in the article Springs. Torsion bars and stabilizers of this treaty;

• those with local contact, in which connections between components are point contacts subject to relative displacements.

These local-contact mechanisms are varied, but the main ones are cam-controlled (with a very important special case, gears, also covered in the articles Gears. Definitions, design and calculation [B 636] and Gears. Reducers. Documentation [B 5 645]) , slides and indexing.

Cam mechanisms have been around for a very long time, and form the basis of all mechanical automation systems. Early automata made extensive use of them, the best-known being by Vaucanson. The extremely important modern developments in automation in all fields, and the continual increase in their performance, particularly in terms of speed, call for a very precise study if good reliability is to be ensured; modern computing resources make it possible to meet these requirements.

They include a huge variety of models adapted to each application, which requires a specific determination for each one, hence the importance of the paragraph devoted to them in this article.

Slide mechanisms are much less common today than in the past, and are limited to a few common types for fairly specific applications.

Indexing mechanisms, or indexers, are in fact just special cases of the previous two. Widely used in sequential manufacturing, assembly and other systems, they have been standardized and mass-produced. As a result, they are readily available on the market and can be easily selected by the user to suit his or her own needs.