What is advancemet in fourbar linkage mechanism

A four-link mechanism with four revolute joints is commonly called a four-bar mechanism.

Application of four-bar mechanisms to machinery is numerous. Some typical applications will involve:

a) Correlation of the angular rotations of the links connected to the fixed page link (commonly known as correlation of crank angles or function generation). In such applications we would like to have a certain functional relation such as q14 = f(q12) to be realised by the four-bar mechanism. A simple example will be to convert a linear scale to a logarithmic scale within a certain range.b) Link that has no connection to the fixed page link is known as the coupler link. A point on this page link (which is known as the coupler point) will describe a path on the fixed link, which is called the coupler-point-curve. By proper choice of page link dimensions useful curves, such as a straight-line or a circular arc, may be found. c) The positions of the coupler-link may be used as the output of the four-bar mechanism. As shown in figure below, the four-bar mechanism used for the dump truck requires that the center of gravity of the dumper to move on an inclined straight line while it is being tilted (why?).

The above applications can be solved by the methods of synthesis which is beyond the topic. In this chapter we shall discuss some basic characteristics of the four-bar.