| 摘要 |
Disclosed is a precision printhead transport apparatus. The apparatus includes a differential wheel rotatably mounted upon belt or a printhead carriage which is constrained to move along a printing path. A first portion of an endless belt or band is looped around a first portion of the differential wheel having a first radius and a second portion of the band is looped around a second portion of the differential wheel having a second radius. The band further passes around two pulleys positioned on opposite sides of the differential wheel, one of the pulleys being an idler pulley and the other a driven pulley. A course stepping motor drives the driven pulley and the action of the differential wheel assures that gross rotation of the driven pulley produces only small linear displacement of the printhead carriage. Embodiments disclosed include both smooth and toothed bands and the use of a pair of rigid racks in place of the endless band. Also disclosed are modifications providing for a rapid printhead carriage return stroke accomplished by disengagement of the rack or band from one portion of the differential wheel.
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