US Patent 10219421 Down and/or up force adjustment system

An agricultural device includes a number of row units that each includes a seed furrow opener that creates a furrow in the soil for seed placement. Each row unit is mounted to a toolbar of the device by a four-bar linkage which allows each row unit to move vertically to adjust to the contour of the soil independently of the other row units on the same toolbar. The four-bar linkages include one or more springs which work to transfer weight from the toolbar to the row unit. An actuator varies the tension in the spring thereby adjusting the down or up force applied to the row unit.