Gear 1 rotates about fixed axis A. Rack 2 slides along fixed guides a-a. Gear 1 is composed of two gear segments, b and d, having central angles of 180° each. Rack 2 consists of two toothed portions, e and f, which mesh with gear segments b and d. When gear 1 rotates at uniform velocity, rack 2 travels with stepwise velocity which changes from v₂‘=ω₁r_b to v₂‘'=ω₁r_d, where ω₁ is the angular velocity of gear 1, and r_b and r_d are the pitch radii of gear segments b and d.
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