Experimental Studies on the Improvement of the Performance of the Upper Feed Thresher

Abstract

Most of the Japanese combine harvesters apply the lower feed type thresher, but recently the adoption of upper feed type thresher increases.
This report summarizes the results of the experiments which were carried on to clarify as well as to improve the performance of the upper feed type thresher.
There were no separating and tailing return unit on the test machine in order to simplify the test and clear up the aim. The machine with cylinder, concave, feeder chain and the cover was used.
Firstly, the performance of the U-1 type (upper feed) and L-1 type (lower feed) were compared. Then, basing upon the first experiment results, the perforrmance of U-2 type (upper type) and L-2 (lower type) which were manufactured with dimetions as close as possible were compared.
Well-dried rice crop “Nihonbare” was used for the test.
The following facts were made clear by the performance comparison from the test results. The upper feed type makes less chaff from straw in the cylinder chamber and requires less power as compared with the lower feed type, but the percentage of grain that dropped down from the concave was less and grain losses entered into the straw were high. There was no difference in the percentage of tailings, unthreshed grain and damaged grain produced from both types.
Then, experiments were carried over to see how the grain losses inter into the straw could be reduced. By attaching teeth to concave, attaching plates to the cylinder, increasing the number of partion plates and changing the shape and number of teeth, it was possible to reduce these grain losses from 10% to 5%. Since the general standard less than 0.5% losses for the lower feed type, was not attained further studies will be requred.