| 摘要 |
<p>A drive tractor of the type usually mounted in pairs at opposite edges of a web of edge-perforated sheet material such as printout paper has an endless drive belt mounted on a chassis. The drive belt has pin members projecting from it to engage edge perforations in the web and is engaged with a drive wheel having sprocket teeth which engage a drive formation on the inner surface of the belt. The sprocket wheel is engaged by a drive shaft to be driven thereby. The sprocket teeth and belt tread are respectively configured to mesh only in a predetermined relative position of the pin members relative to the rotational position of the drive wheel. The drive wheel is configured to seat on the drive shaft in a predetermined rotational orientation. Therefore, when a pair of such tractors in mounted on a common drive shaft their respective drive wheels are in the same rotational orientation which automatically transversely aligns the respective pin members of the paired tractors.</p> |
