Abstract: A segmented pulley transmission [20] is provided. A pulley assembly [36] is rotationally mounted on an axle [32]. The pulley assembly [36] includes a core pulley [45] having a first set of mating features on a peripheral surface thereof. A pulley segment set comprises a number of pulley segments [48] slidably mounted in the pulley assembly and arranged in a ring concentric with the core pulley [45]. The pulley segments [48] are individually actuatable out of the pulley assembly into an engaging position and into the pulley assembly into a non-engaging position. The pulley segments [48] have a second set of mating features [52] on an peripheral surface matching the first set of mating features. An endless drive member [47] has corresponding mating features on an inside surface for engaging the first and second sets of mating features of the core pulley [45] and the pulley segments [48] in an engaging position. Contact between the endless drive member [47] and a core pulley defines a contact zone [CZ].

Abstract: A key pulley segment in a synchronized, segmentally interchanging pulley transmission system is either first or last in a pulley segment set to engage an endless member. The first or last key segment teeth to engage or disengage, respectively, are shortened or completely trimmed, and the adjacent pulley segment to the key segment is elongated such that the inward portion of the tooth profile extends toward the key segment. Shortened tooth or teeth and an elongated adjacent segment together allow for many pulley segments to be designed as key segments. Completely trimmed teeth may be engineered to create a supporting surface for the endless member on the key segment. The elongated adjacent segment may have an extending portion which slidably mates with the supporting surface of the key segment, thereby receiving radial support therefrom.