Orbital drive mechanism

Abstract

In a compact high-torque mechanical speed changer of the type in which different relative speeds may be realized through substitution of different cooperating planet and sun gear components one of which has teeth in the form of lobes of continuous substantially epitrochoid curvature and the other of which has circularly-curved teeth differing in number by one, orbiting motions associated with angular movements are resolved and angular motions are developed about a non-orbiting axis by way of a unique 'zero-velocity' transmission plate having peripheral circular-sided openings cooperating with an array of circular pins, rollers or the like. The lobed gear and the transmission plate are advantageously fixed together for orbital motion in response to rotation of a shaft eccentric, and are of about the same diameter, and their cooperating toothed companions are preferably of the type involving discrete roller-pin teeth, and are of the same diameter. These cooperating sets are substantially identical in important dimensional respects, and portions can therefore be changed to effect different speed ratios, with the same counterweighting serving to offset eccentricities. The changer housing and interior mountings for gear combinations accommodate different sets, as desired, to yield various relative speeds of the relatively-rotatable parts, and the transmission plate orbiting component may advantageously be replaced by a lobed component to extend the range of speed ratios which are available from one basic size of speed changer.