an articulated mechanism in which two moving components—a link and a slide block—are coupled to form a sliding kinematic pair or sometimes a rotating or arc pair.
The most common plane four-link gears are divided into groups according to the type of the third moving link: crank-link, rocker-link, slide-link, or double-link. A crank-link mechanism may have rotary, rocking, or translatory link motion. Rocker mechanisms, which are derived from these types of mechanisms by limiting the angular rotation of the crank, are built with rocking links (Figure 1, a) or translatory links (Figure 1, b), are used for the transformation of motion and also as sine mechanisms (Figure 1, c) in computers.
Slide-link mechanisms are designed to transform rocking motion into translatory motion or vice versa; they are also used as tangent mechanisms in computers. Double-link mechanisms are used in machines to provide equal angular velocities of the links with a constant angle between them. This property is used in couplings that permit displacement of the axes of the shafts. Complex multilink gears are used for various purposes—for ex-ample, in control systems for charging the cylinders of internal-combustion engines and in reversing systems of steam engines.
N. IA. NIBERG