Agricultural implement with down-force control

Apparatus for mounting an agricultural implement with respect to a towing tractor, wherein:

• the implement includes a tool bar, on which are mounted one or more rows of ground-penetrating tools;
• the tool bar has a front end and a rear end;
• the tool-bar includes a point TF located near the front of the tool-bar, the point TF being a height HF above the ground surface and the apparatus includes a first-link means for setting the height HF above the ground surface;
• the apparatus includes a means for maintaining the height HF constant, during operation;
• the apparatus includes a means for permitting pitch-mode pivoting movement of the tool-bar relative to the tractor, about point TF;
• the apparatus includes a hydraulically-operable second-link, which is connected between the tractor and a point CF on the tool-bar;
• the point CF is a point on the tool-bar near the front end of the tool-bar, the point CF being spaced from the point TF;
• the second-link is of such structure that its length, being the distance between the tractor and the point CF, can be changed by hydraulic operation;
• the apparatus includes a means for supplying hydraulic pressure to the aforesaid second-link;
• the second-link is effective, when operated by hydraulic pressure, to apply a force between the tractor and point CF, and thereby to exert on the tool-bar a moment about point TF;
• the means for supplying hydraulic pressure to the second link includes a means for maintaining the hydraulic pressure at a constant magnitude;
• and the means for maintaining the hydraulic pressure at a constant magnitude is arranged to be effective to keep the magnitude of the hydraulic pressure constant even through changes in the length of the second-link.