11 Fieldwork 11.2 Description and function 67087 69373 11.2.2 Threshing mechanism Threshing is performed by drum and concave. The bulk of the grain together with the chaff and broken straw passes through the concave onto the prepara- tion floor of the sieve pan. The impeller delivers the straw and remainder of the grain to the straw walkers. A deflector curtain behind the impeller holds back bouncing grains and deflects them down onto the front of the straw walkers. 69375 11.2.3 Straw walker The straw walkers separate the remainder of the grain from the straw. The straw is either removed out of the combine through the rear panel or undergoes further processing by special attachments (e. g.
straw chop- per). The grains separated by the straw walkers are returned to the sieve pan via the under-walker return floor. Crankshafts with agitator tines intensify the loos- ening of the straw on the straw walkers. 69377 11.2.4 Cleaning unit Grain mixed with chaff and broken straw is fluffed by means of the shaking action of the preparation floor and at the same time moved onto the sieves. The wind blast of the cleaning fan blows the light parti- cles (chaff) to the rear, out of the machine. The grain falls through the upper and lower sieve into the clean grain auger trough and is conveyed into the grain tank by the clean grain elevator.
All parts heavier than chaff and bigger than grain travel over the upper sieve and lower sieve, drop into the returns auger and are moved to the returns elevator. The elevator carries the returns to the drum for further threshing. Swinging the grain tank unloading tube into operating position allows the grain tank to be quickly emptied into a truck or trailer alongside the combine. 69380 11.2.5 Disawning When combining grain which is unusually hard to dis- awn or in which it is hard to separate the seeds from the heads or husks, additional disawning plates can be installed in the concave. 00 0293 210 2 - BA DOMINATOR 150/140/130 - 12/09 195