| 摘要 |
A sliding gear keyed or splined to a main shaft has external teeth selectively engageable with either of two driving gears on a pair of continuously rotating countershafts and in its neutral position is releasably coupled by one or more ball checks to a surrounding control ring for joint axial motion. The ring is provided with beveled surfaces enabling its frictional rotary entrainment by similar surfaces of the driving gears upon a limited axial shifting of the sliding gear in one or the other direction. The control ring also has one or more internal ridges extending between teeth of the sliding gear for joint rotation therewith; in several embodiments, these ridges are sufficiently narrower than the spacing between adjacent gear teeth to allow for a limited relative rotation between ring and gear, the ridges then having retaining formations which prevent a relative axial shift into a meshing position of the sliding gear until synchronism has been achieved between the main shaft and the corresponding countershaft. |
