Crop unloader drive with tensioner

An agricultural combine comprising:

• a chassis configured for movement on a surface;
• a threshing and separating system attached to the chassis;
• a hopper located on the chassis and configured to retain crop material therein;
• and
• A crop unloader system comprising:
• an elevator assembly comprising:
• an elevator frame,
• an elevator drive attached to the elevator frame,
• an elevator drive motor attached to the elevator frame and configured to selectively operate the elevator drive,
• an elevator drive output attached to the elevator frame and configured to be driven about an elevator drive output axis by the elevator drive motor, and
• a grain elevator configured to be driven by the elevator drive;
• a boom assembly comprising:
• a boom frame connected to the elevator frame at a boom pivot axis that is parallel with the elevator drive output axis, the boom frame being rotatable about the boom pivot axis relative to the elevator frame through a range of motion between a first angular position and a second angular position,
• an unloader drive input attached to the boom frame and configured to rotate about an unloader drive input axis,
• an unloader conveyor belt operatively connected to the unloader drive input, and an unloader belt chute surrounding the unloader conveyor belt;
• an endless flexible drive operatively connected between the elevator drive output and the unloader drive input;
• and
• a tensioning assembly comprising:
• a tensioner link pivotally connected to one of the elevator frame and the boom frame at a first tensioner pivot,
• a control link pivotally connected to the other of the elevator frame and the boom frame at a second tensioner pivot, and pivotally connected to the tensioner link at a third tensioner pivot, the third tensioner pivot being spaced from the first tensioner pivot and the second tensioner pivot,
• an idler wheel operatively connected to the tensioner link, and configured to generate a tension load on the endless flexible drive,
• wherein the tensioning assembly is configured to maintain the tension load on the endless flexible drive within a predetermined range, throughout the range of motion of the boom frame relative to the elevator frame.