Second Inversion:

In this case link 2 is fixed and link 3 acts as crank. Link 1 is a slotted link that facilitates movement of link 4 that is a slider. This arrangement gives rapid return motion mechanism. The motion of link 1 may be taped with a link and provided to ram of shaper machine. Given figure shows this mechanism and it is known as Whitworth Quick Return Motion Mechanism. The forward stroke begins when link 3 takes position O₄Q. At that time, point A is at A₁. The forward stroke ends while link 3 takes position O₄P and point A takes position A₂. The return stroke occur when link 3 moves from position O₄P to O₄Q. The stroke length is distance among A₁ & A₂ along line of stroke. If acute angle < PO₄ Q = θ & crank rotates at constant speed ω.