Automatic sieve and chaffer adjustment in a combine harvester

Abstract

In a combine harvester, a microprocessor controls the adjustment of the cleaning sieve or sieves and/or chaffer sieve or sieves in response to information keyed into a keyboard by the combine operator. If the actual setting of a device (sieve or chaffer) is greater than the desired setting the device is first fully opened and maintained in that position for a predetermined period of time to allow foreign objects and crop material to clear itself from the device by normal combine operation. This avoids damage to the control linkage, sieve slats, and so forth. After the device is fully opened and maintained open for the predetermined interval of time it then closes beyond the desired setting by some predetermined amount after which the device is opened to the desired setting. This arrangement insures that the approach to the final adjustment is always made as the device is being opened, thereby allowing for compensation of play or backlash in the mechanical linkages which adjust the device.