Drum B of the electric hoist is driven by shaft A to which sun gear 1 is keyed. Sun gear 1' is rigidly attached to carrier 4 and sun gear 1" to carrier 4'. Sun gears 1, 1' and 1" mesh with planet gears 2, 2' and 2" which are connected by turning pairs to carriers 4, 4' and 4". Gears 2, 2' and 2" mesh with internal gears 3, 3' and 3" which are rigidly attached to drum B. Carrier 4" is fixed. The speeds n₁ and n₃ of gear 1 (and shaft A) and drum B (in rpm) are related by the equation n₃=-n₁(z₁z₁'z₁'')/(z₃'(z₁''+z₃'')(z₁+z₃)+z₁'z₃''(z₁+z₃)+z₁'z₁''z₃) where z₁, z₁', z₁'', z₃, z₃', and z₃''„ are the numbers of teeth of gears 1, 1', 1", 3, 3' and 3". Thus, rotation is transmitted from shaft A to drum B by means of three consecutive planetary mechanisms with a speed reduction. Shaft A and drum B rotate in opposite directions.
$2895$CxG,PR$