On the Synthesis of Delta Four-Bar Straight-line Linkage

We present the cause and result of circle point curve degeneration, when the given Ball's point is located on the fixed bar. The theory to synthesize four bar straight line linkage, whose coupler curve has four infinite points contact with its tangent, is discussed with the help of Euler Savary equation. The figuration of the obtained four bar linkage is like a delta, so the gained four bar linkage is calleda Delta mechanisms. Based on the above synthesis,the conditions for obtaining crank and rocker mechanism is analyzed too.