Adjustment and release unit for a concave of a threshing system of a combine harvester

An adjustment and release unit for supporting a concave beneath a threshing unit of a combine harvester, the adjustment and release unit comprising:

• a rotary control shaft;
• an actuator for controlling an angular position of the rotary control shaft, wherein the actuator comprises a hydraulic piston;
• a set of concave support arms, which extend downwardly from the rotary control shaft to the concave, wherein an angular orientation of the rotary control shaft determines a depth of the concave beneath the adjustment and release unit;
• and
• a linkage between the rotary control shaft and a mounting point, the linkage incorporating the actuator,
• wherein the linkage further comprises a spring arrangement in series with the actuator for releasing the concave in response to foreign objects entering the threshing unit against a spring bias of the spring arrangement, wherein the spring arrangement is between the rotary control shaft and the actuator or is between the actuator and the mounting point and wherein the spring arrangement comprises at least one spring positioned parallel with, and to the side of, the hydraulic piston.