Gear 1 is keyed to shaft a, rotates about fixed axis B and meshes with gear 4 which is rigidly attached to gear 5. Gear 5 meshes with gear 2 which is keyed to shaft b and rotates about axis B. Gears 4 and 5 are connected by turning pair A to carrier 3 which rotates about shaft b. Worm wheel segment 7 is rigidly attached to carrier 3 and meshes with worm 6 which rotates about fixed axis C. Since the worm gearing is self-locking, carrier 3 is stationary when gear 1 rotates, and the speeds n₁ and n₂ of gears 1 and 2 are related by the equation n₂=n₁(z₁z₅)/(z₂z₄) where z₁, z₂, z₄ and z₅ are the numbers of teeth of gears 1, 2, 4 and 5. Here the mechanism operates as an ordinary double reducing gear. If worm 6 is rotated, the mechanism operates as a differential reducing gear because worm wheel segment 7 turns carrier 3 through a certain angle within the limits allowed by the included angle of the segment. In this case, the speeds n₁, n₂ and n₃ of gears 1 and 2, and carrier 3 are related by the equation n₃=n₁(z₁z₅)/(z₁z₅-z₂z₄)-n₂(z₂z₄)/(z₁z₅-z₂z₄).
$2923$CxG,DR$