Effect of double seed-filling chamber structure of combined type-hole metering device on filling properties
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Abstract
Abstract: As a simple and efficient rice planting technology, the precision hill-drop drilling could reach higher yield and better economic benefit in suitable areas. In China, the mechanical direct seeding area has a steady growth in recent years. Great progress has been made in studying on the pneumatic metering device, but the type-hole metering device is still the most widely used on the precision hill-drop drilling machine. The metering device is the core part of the direct seeding machine, and the stability of the seed filling process is an important link to ensure the performance of the seeding. The filling chamber is the most important area for seed-filling process. In this research, we studied the combined hole-type metering device developed by South China Agricultural University. The hole-type roll includes hole-type shell, hole-type roller and adjusting mechanism. A complete hole-type is comprised by the label through holes which are uniformly distributed on the hole-type shell and the small/big type-hole which are uniformly distributed on hole-type roller. The combined hole-type metering device can meet the sowing rate requirement of both conventional rice and hybrid rice simultaneously and it can be most wildly used on the precision rice hill-drop drilling machine. The key parameters of seed-filling initial angle and structure of double seed-filling chamber would affect the seed fluidity and seed-filling stability. In order to study the effect of filling chamber structure on seed-filling performance of combined type-hole metering device, theoretical calculation and experimental verification of seed-filling initial angle, parameters of seed flow adjusting device were carried out. The results of theoretical calculation and the single factor test with the seed-filling initial angle showed that the seed-filling initial angle of combined type-hole metering device was ?40°. Using the type of type-hole, the seed-filling initial angle and the working speed of the metering device as variables, the results of the multi-factor test showed that the optimum seed-filling initial angle was ?20°. Compared with ?10° and 0, seed-filling initial angle at ?20° made smaller differences in the average seeds number per hill and the coefficient of variation with different working speed, while there was no significant (P> 0.05) difference in the average seeds number per hill and the coefficient of variation among ?20°, ?30° and ?40°. Without affecting the seed-filling performance of metering device, the smaller seed-filling initial angle, the larger contact area between seeds and combined type-hole roll, and in theory, the abrasion of type-hole roll would be accelerated and the breakage of the seeds would be increased. Therefore, it was most reasonable to take the seed-filling initial angle for ?20°. The function of seed flow adjusting device was used to regulate the seeds flow from the first filling chamber to the second seed filling chamber, and it changed the position of seed-filling terminate angle to achieve the purpose of regulating the seeding rate. The best distance between the restriction mechanism and the seed metering wheel was 40 mm, which solved the problem that seeds were flung out by the cleaning brush. Using the type of type-hole, the variable of seeds, the position of adjusting plate and the working speed of the seed metering device as variables, the results of the multi-factor test showed that the distance between the regulating seed plate and the type-hole roll can be adjusted within the range of 0?22 mm, and further regulation of seeding rate could be achieved for different types of type-hole and varieties of rice seeds. The design of each parameter was reasonable. In general, seed-filling performance of metering device was improved in this study and the results could enrich our knowledge of the working principle of type-hole metering device.
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