Pinion 1 is designed as a segment gear and rotates about fixed axis A. Gear 2 has external teeth b and internal teeth c that mesh alternately with pinion 1, and rotates about fixed axis B. When pinion 1 rotates constantly in one direction, driven gear 2 rotates alternately in each direction. Angle ϕ₂ of clockwise rotation of gear 2 is ϕ₂=(r₁/r₂)ϕ₁ and angle ϕ₂‘ of counterclockwise rotation of gear 2 is ϕ₂‘=(r₁/r₂')ϕ₁ where r₁,r₂ and r₂' are the pitch radii of gears 1 and 2, and angle ϕ₁ is the angle of rotation of gear 1. Angle ϕ₂‘ is larger than angle ϕ₂ by the ratio r₂/r₂' i.e. ϕ₂‘=(r₂/r₂')ϕ₂. To ensure continuous rotation of gear 2 with short stops only at the extreme positions (at reversal) of the toothed segment, gear 1 is to be designed so that the segment begins to mesh with internal teeth c at the instaut it runs out of engagement with external teeth b. Impacts at the instant of engagement are avoided by the provision of supplementary conjugate cam surfaces having profiles with special curves.
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