| 摘要 |
A rack-type drive for displacing a movable part longitudinally and horisontally relative to a stationary part has a longitudinally extending rack fixed on one of the parts which is formed above the rack with a longitudinal slot through which the rack is exposed upward and the other part is above the one part. A drive shaft rotatable about a horizontal and transverse upper axis on the other part is provided with a drive gear operatively engaged down through the slot with the rack. A pair of outer idler rollers generally below and longitudinally flanking the drive gear are rotatable about respective horizontal and transverse lower axes and a pair of inner idler rollers rotatable about the transverse axis on the drive shaft coaxially flank the drive gear and have outer peripheries lying relative to the axis radially outside the gear. A belt extending along and covering the slot to both longitudinal sides of the other part passes under the outer idler rollers and over the inner idler rollers in engagement with the peripheries thereof but out of contact with the drive gear . |
