For this linkage r3 = r4 and r1 : r2 : r3 : rp = 2.3 : 1.1 : 2.8 : 5.65. The coupler point for this linkage has nearly constant velocity along the center portion of the straight motion.
This linkage is a Grashof crank-rocker.
In this example:
r1 = 2.3 , r2 = 1.1 , r3 = 2.8 , r4 = 2.8 , rp = 5.65
theta1 = 0 , beta = 0
To see an animations of this linkage select the link below: