Development of potato harvester with buffer type potato-impurity separation sieve

Abstract: Harvesting is the most crucial step of the whole potato production mechanization process, and the most challenging issue is to separate potato, soil and impurity thoroughly and meanwhile control the damage rate and bruising rate of potato. It is widely recognized that there exists some unsatisfactory separation effect problems like higher bruising rate and damage rate and lower exposed rate during the process of mechanical potato harvest. To solve these problems, based on the technology of potato-impurity separation with 2 segment of high frequency and low amplitude vibration separation, potato seedling separation and side conveying and low position laying, a new potato harvester was improved through setting low position laying segment and potato-impurity separation device with buffer sieve. The potato harvester was consisted of digging parts, soil loosening and depth control wheel, cutting device of soil and seedling, separation sieve, vibration adjustment device, device of potato and seedling separation, device of side conveying of seedling, low position laying device and compaction leveling device. In that way, it can reduce the drop height effectively and benefit for potato-impurity separating and potato-seeding separating during the process of mechanical potato harvest. As such, the field harvesting experiments were carried out, when the harvesting speed was 0.88 m/s, the effects of the inclination angle of buffer sieve on the kinematic characteristics of potato and seedling were analyzed when the inclination angle of buffer sieve was 27°, 36° and 45°, and the better inclination angle of buffer sieve 36° was selected. At the meantime, the results showed that peak impact acceleration produced by potatoes on the buffer sieve was relatively small, and the peak impact acceleration mainly came from the impact contact between potatoes and the separation sieve. Therefore, it is demonstrated that the low position laying device had a good performance to reduce drop impact, and to reduce the damage rate and bruising rate. The field harvesting experiments results showed that, the productivity was 0.41 and 0.54 hm2/h, the damage rate was 1.47% and 1.12%, and the bruising rate was 1.89% and 1.07%, respectively when the harvest speed was 0.88 and 1.16 m/s, the field harvesting experiment results and evaluation indeices met the requirements of relevant standards. The results also indicated the peak impact acceleration and impact number of potatoes were decreased with the increase of harvesting speed, which could effectively reduce the damage rate and bruising rate. However, the exposed rate decreased with the increase of harvesting speed, the main reason was the mixture of potato-impurity influxing into the separation sieve in unit time increased correspondingly, and soil worked as buffer in the process of potato-impurity separation with the increase of harvesting speed. On the contrary, the peak impact acceleration and impact time of potatoes were increased significantlyCompared with the potatoes located in the middle of the ridge on the separation sieve, it was easy to produce the larger peak impact acceleration when potatoes located on the separation sieve corresponding to the edge position of potato ridge, it was mainly due to the relatively weak soil buffering and protection for potatoes at this location, so the probability of direct contact between potatoes and rods was greater. This research may provide a technical reference for further study on the loss reduction control method of potato-impurity separation and the optimization and improvement of potato-impurity separation process.