A synthesis method of four-bar approximate straight-line mechanism was presented based on inflection circle pole theorem, which might produce an infinite number of mechanisms. An analytic method was introduced to prove that the synthesized mechanism might make the fixed pivot of side link and its corresponding moving pivot inter-convertible. The two synthesized linkages with two inter-convertible pivots contained the same Ball point and straight-line direction. The other side link remained unchanged. The synthesizing formulas of crank-rock mechanism were derived and the solution domains were p...
