The lengths of the links comply with the conditions: A͞B=A͞D and B͞C=D͞C. Link 3 makes one revolution to two revolutions of link 1. At the extreme positions (dead points), pins a' and b' of link 2 abut against stops a and b of base 4. As a result, uncertainty of motion of the mechanism is eliminated. The dimensions A͞a and A͞b equal: A͞a=B͞a̕ -A͞B and A͞b=B͞b̕-A͞B.
$546$LW,4L$