Patent ID: 8555798

Claim:
An apparatus to apply down pressure to a disc opener unit coupled to a tool bar of an agricultural implement by a parallel linkage having an upper link and a lower link, wherein the disc opener unit includes a disc opener mounted to an axle carried by a disc opener frame that is coupled to the tool bar by the parallel linkage, the apparatus comprising: a rockshaft having a first arm pivotably coupled to the upper link or the lower link and a second arm adapted to be pivotably coupled to a down pressure biasing device, the rockshaft further having an actuator mount arm; a rockshaft configured to be pivotably coupled to a tool bar, the rockshaft having first and second opposite sides; a spring trunnion arm projecting from the first side of the rockshaft; a rockshaft pivot arm projecting from the second side of the rockshaft; the actuator mount arm projecting from the second side of the rockshaft; the down pressure device coupled to the spring trunion arm; and an actuator having a first end pivotably connected to a support arm of the agricultural implement and a second end pivotally connected to the actuator mount arm; wherein the actuation of the actuator is configured to rotate the rockshaft to vary the amount of down pressure applied by the down pressure biasing device.