The lengths of the links comply with the conditions: A͞B=B͞C and A͞D=C͞D. Angle ϕ of total swing of rocker arm 3 equals ϕ=4arcsin(A͞B/A͞D). At the extreme positions, axes A and C of the links coincide and, unless a special device is provided, driving crank 1 and connecting rod 2 may begin to rotate about axis A as a single link. In this case, rocker arm 3 will be stationary and its axis DC will coincide with the direction AD.
$544$LW,4L$