Combine harvesters

Claim 1

Apparatus for controlling the forward speed of a combine harvester in dependence upon the grain loss at a selected location in the harvester, comprising an electronic clock circuit which operates to provide an output of electrical pulses of constant duration at a constant frequency, a first control element in the clock circuit being adapted to be energized and deenergized upon initiation and termination respectively of each clock pulse, a delay circuit including a second control element adapted to be energized a predetermined time after initiation of each clock pulse and to be deenergized at the termination of each clock pulse, and an electronic counting circuit having transducer means for providing electrical output pulses representative of grain discharged in a sample of the grain loss at the selected location in the harvester, counting means supplied with pulses derived from the transducer output pulses and a third control element energized when the counting level in the counting means reaches a required value and deenergized upon termination of each clock pulse, the operation of the counting circuit being initiated at the commencement of each clock pulse and being adapted so that if before operation of the delay circuit to energize the second control element the counting level achieved by the counting circuit reaches the required value, the third control element is energized and effects operation of drive means to slow down the forward motion of the harvester until such time as the delay circuit causes energization of the second control means whereupon slowing down of the harvester forward speed is halted, whilst, if the required counting level is not reached before energization of the delay circuit the second control element is energized and causes speeding up of the harvester to occur until either the third control element is energized or the first control element is deenergized.