Gear rack 1 slides in fixed guides A-A and meshes with pinion 4 which, in turn, meshes with rack 2. Rack 2 slides in fixed guides C-C. Rack 3 is connected by turning pair B to pinion 4 and meshes with pinion 5 which rotates about fixed axis D. The two addends are proportional to the linear displacements s₁ and s₂ of racks 1 and 2. The linear displacement s₃ of rack 3 is proportional to the half-sum of addends s₁ and s₂, entered by shifting racks 1 and 2. Thus s₃=(s₁+s₂)/2. The required sum is read off as the angle ϕ₅ of rotation of pinion 5 which is ϕ₅=s₃/R=1/(2R)(s₁+s₂) where R is the pitch radius of pinion 5.
$2947$CxG,MO$