Abstract: This invention relates to an automatic release mechanism for a cultivator which provides good resistance to release of the shank holder and which upon release causes the shank holder to rise to a good height to clear obstacles encountered during operation of the cultivator. The shank holder is mounted so as to pivot about an axis and is retained in the working position by a pair of springs under tension, the forward end of the springs being mounted in front of and beneath the position of the pivot axis of the shank holder, and the moment arm of the springs is such that, as the shank holder pivots, the moment arm decreases resulting in the tangential force applied by the springs to the ground engaging tool about the pivot axis remaining substantially constant during pivoting of the shank holder to clear an obstacle.

Abstract: A cultivator shank is adapted for mounting at one end on a cultivator frame and has an open C-shaped central section with its other end receiving a ground engaging tool. In between its ends, the shank tapers through a profile of changing sectional dimension so that its central section is deeper or thicker, in line with the direction of travel, than the dimension of the central section transverse to the direction of travel.