For this linkage r2 = r3 = rp. Lengths for r1 and r4 may be chosen freely, however increasing the length of r4 reduces the deviation of P from a straight line.
This linkage is a non-Grashof outward/outward limited triple-rocker.
In this example:
r1 = 10 , r2 = 5 , r3 = 5 , r4 = 5 , rp = 5
theta1 = -30 deg , beta = 180 deg
To see animations of this linkage select the links below: