Definition
A four-bar chain mechanism has four links and four rotating pairs. The four-bar linkage is a planar mechanism of four rigid members: a frame, an input link, an output link, and a coupler link. Four revolute pairs connect these members, forming a closed-loop kinematic chain with one degree of freedom.
Grashof condition
The Grashof condition for a four-bar linkage states: If the sum of the shortest and longest links of a planar quadrilateral linkage is less than or equal to the sum of the remaining two links, then the shortest link can rotate fully with respect to a neighboring link. In other words, the condition is satisfied if A + C ≤ B + D, where A is the shortest link, C is the longest, and B and D are the other links.
Inversion and its types
Different mechanisms are obtained by fixing different links of a chain.
- Crank-Crank Mechanism: A link is fixed
- Crank-Rocker Mechanism: One link adjacent to shortest link (say B) is fixed
- Crank-Rocker Mechanism: Another one link adjacent to shortest link (say D) is fixed
- Rocker-Rocker Mechanism: C link is fixed
Four-Bar Mechanism Using SOLIDWORKS Desktop
