Epicyclic gearing has long been known in which there is provided a sun gear, a plurality of planet gears, and a ring gear having internal teeth. Such drives have found use in industry, but present various problems. To overcome certain of the problems inherent in epicyclic gearing, wedging-type roller drives have been developed. Such drives are to be found, for example, in Barske U.S. Pat. No. 3,380,312 and in Nelson et al U.S. Pat. No. 3,945,270. In such drives or transmissions there is an input shaft and an output shaft which are somewhat offset radially of one another. The input shaft has a cylindrical external driving portion functionally taking the place of the sun gear in epicyclic gearing. The output shaft is normally joined rigidly to a cylindrical internal ring. (Either the centrally located external cylindrical member or the internal ring member may comprise the input, and the other the output. The cylindrical external roller is used for purposes of illustration. There are three idler rollers which act between the input roller and the driven cylindrical portion. The drive roller and two of the idler rollers turn about substantially fixed axes. The third or wedging roller is movable radially and arcuately. The radial offset of the input and output shaft causes the wedging roller to move into wedging engagement between the driving portion or sun roller and the output cylinder. This causes a certain amount of radial shifting of the drive roller due to a limited amount of deflection under load, whereby the three idler rollers apply substantially equal radial load and tangential drive force.
USPTO Backgrounds
USPTO Backgrounds