Design and test of seed cleaning device of pneumatic metering device for rice

Objective  In order to reduce the reabsorption of rice seeds in pneumatic metering device, a seed cleaning device vertical to the surface of the seed metering plate was designed.

Method  The force acting on rice seed and the working principle of the seed cleaning device were analyzed when the pneumatic metering device was working, and the force model during the seed suction process was established. The super hybrid rice ‘Wufengyou 615’ was used as the experimental object. The precision test of seed metering device was carried out with or without seed cleaning device. Under a negative pressure of 4.0 kPa in the suction chamber, the effects of two factors, including the thickness of seed cleaning block and the rotational speed of seed metering plate, on seed cleaning were tested and analyzed.

Result  After using the seed cleaning device, the ratio of 1−3 seeds per hill increased from 62.02% to 90.00%, and the ratio of ≥4 seeds per hill decreased from 37.98% to 5.00%. When the thickness of seed cleaning block was 3.5 mm and the rotational speeds of seed metering plate were 15, 20 and 25 r/min respectively, the ratios of 1, 2 and 3 seeds per hill were 95.18%, 95.16% and 95.23% respectively, and the missing hill rates were 2.07%, 2.76% and 4.56% respectively, which met the requirements of field sowing for super hybrid rice.

Conclusion  When the negative pressure in suction chamber is constant, reducing the rotational speed of seed plate can improve the cleaning effect of the seed cleaning device and the sowing precision of the seed metering device. Based on the structure of rice pneumatic metering device, we designed a seed cleaning device which can effectively clear rice seeds adsorbed by the seed metering device, and this research provides a basis for improving the precision of rice pneumatic metering device.