| 摘要 |
PURPOSE: To reduce power consumption of a driving motor, when a driving wheel is in two operating positions, by making the frictional connection to the other or a second rolling face such that it is connected not with the driving wheel itself but with a knob connected to it, and thereby reducing the wear of a friction part. CONSTITUTION: A driving wheel 21 is provided with the other or a second rolling face 74, for which a cylindrical knob 57 is provided having a diameter smaller than that of the driving wheel 21 and projecting coaxially, and for which the knob 57 rolls only in the starting and completing areas where the driving wheel 21 moves from one operating position to the other. In addition, in these two areas, the driving wheel 21 rises from the rolling face 73 relating to the driving wheel 21 while, in the area in between, the knob 57 rises from the other rolling face 74 with the driving wheel 21 rolling along the relative rolling face 73. As a result, heat generation can be kept low between the knob and the other rolling face, and also wear is reduced in the friction part, thereby decreasing the power consumption of the driving motor. |
