Lecture 8 Four bar planar mechanism
The Simplest Mechanism consists of four binary links, each connected by a kinematic pair of revolute (hinge) type, and is known as a four-bar mechanism.Its motion is defined by four key dimensions- the lengths of its four links (l₁,l₂,l₃,l₄).
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| The Kinematics Diagram of 4R (Four Revolute) Mechanism |
Link O₂O₄ is grounded as Frame. Links O₂A and O₄B execute a pure rotary motion, being hinged to the frame, and link AB executes a generalized plane motion, being composed of both translation and rotation. Such a link is termed as 'floating link'. When a link hinged to the frame can make a complete rotation, it is called a 'crank', and it is called a 'rocker' when such a link can execute only an oscillatory motion. Usually, one of the links hinged to the frame is chosen as the "input link" and the other as the "output link" or the 'follower'. 'Floating link' is also called as 'coupler'.
The revolute pairs (hinges) O₂ and O₄ that connects input link and output link to the fixed frame are called fixed pivots. The revolute pairs (hinges) A and B that connects moving links to the floating link are called moving pivots.
Source :
Theory of Mechanisms and Machines - A Ghosh and Mallik A K - Affiliated East West Press