Automatic depth control device for tillage units

Claim 1

In an earth working implement, the combination of a wheeled frame, a vertically movable support arm pivoted to said frame and extending rearwardly therefrom, an earth engaging tool carried by said support arm for raising and lowering movement relative to the frame, a fluid operator mounted on the frame and operatively connected to said support arm for raising and lowering said tool, and a depth control mechanism comprising a control arm movable with and extending forwardly from said support arm, a lever pivotally mounted on said frame at a point intermediate the ends of the lever, said lever having front and rear ends, a link pivotally connecting said control arm to the rear end of said lever, a pair of vertically spaced micro-switches disposed respectively above and below the front end of said lever and selectively actuated thereby as a function of lowering and raising of said tool relative to said frame, a shaft vertically slidable in said frame forwardly of said lever, a ground engaging sensor element provided at the lower end of said shaft, and a detent provided on the upper end portion of the shaft, said detent being disposed between said vertically spaced microswitches for selectively actuating the same as a function of raising and lowering of said frame relative to the ground, and means operatively connecting said micro-switches to said fluid operator for actuating the latter selectively in opposite directions.