| 摘要 |
A gear train between an input shaft and an output shaft includes an output gear, through which the output shaft moves axially, and an intermediate gear coaxial with a control shaft carrying an idler gear meshing with a nut threaded on the output shaft. The idler gear is axially movable between a first position in which a first dog clutch connects the idler gear to the intermediate gear so that the nut rotates relative to the output shaft, thereby causing the shaft to be fed to the right, and a second position in which the first dog clutch is disengaged and a second dog clutch connects the idler gear to a fixed member, thereby causing the rotating shaft to be fed to the left. A collar on the shaft acts on a lever which moves the control shaft together with the idler gear from the first position to an intermediate position. In the intermediate position, balls are urged radially inwards by a bevel on a piston to enter a recess in the control shaft, thereby urging the shaft together with the idler gear to the second position, in which the second clutch is engaged. |
