Drive mechanism for seed metering device

摘要

Seeding apparatus has an opener mounted on the main frame in such a manner that the driven sprocket of a seed metering device on the opener moves slightly toward and away from the axis of the drive sprocket on the main frame as the opener moves up and down relative to the frame during changes in ground contour. To prevent the driving tight stretch of the drive chain between the drive sprocket and driven sprocket from undergoing significant length change during such movement of the opener relative to the frame, the tight stretch is trained around intermediate guide structure in such a manner that the different portions of the tight stretch thus defined all stay substantially constant in length at all times. An arrangement for use with a parallel linkage mounting of the opener has guides on the main frame and the opener that keep the chain portion spanning the frame and opener substantially parallel to the links of the linkage and of substantially the same length as such links. An alternative embodiment for use with a single pivot point-mounted opener positions the guide in the immediate vicinity of the pivot to maintain the spanning portion of the tight stretch between the guide and the driven sprocket substantially constant length at all times.