Patent ID: 6860805

Claim:
An agricultural machine having a plurality of crop transport units wherein the crop transport units convey crop streams in opposite directions and are spaced apart to define a crop through-gap where the opposing crop streams are received, and having a cleaning device having a forced-draught fan before the cleaning device, further comprising: an exhaust fan located after the cleaning device such that the exhaust fan and the forced-draught fan produce an air stream which is directed from the forced-draught fan to the exhaust fan, thereby creating an air flow in the through-gap of the straw walker step; wherein the forced-draught fan and exhaust fan generate an air stream having a speed; at least one air speed measuring device for measuring said air stream speed, located between the crop transport units; a control and regulating device for receiving the air stream speed from the at least one air stream speed measuring device and regulating said air stream; wherein the control and regulating device is programmed with a preset target speed value, compares the measured air stream speed to the preset target speed value and sends an output speed change value to said exhaust fan to adjust said fan's rotational speed, thereby adjusting the speed of the air stream to substantially equal the preset target speed value.