First Inversion:

The first inversion is attained by fixing link 1. By doing so a mechanism known Scotch Yoke is achieved. The link 1 is a slider alike to link 3. Link 2 acts as a crank. Link 4 is a slotted link. While link 2 rotates, link 4 contain simple harmonic motion for angle 'θ' of link 2, the displacement of link 4 is provided by

                                                                 x = OA sin θ

    Scotch Yoke Mechanism