Design and experiments of the potato combine harvester with elastic rubbing technology

A combine harvester can be one of the most important links for the potatoes gathering and conveying. However, the current potato combine harvester cannot fully meet the large-scale production in recent years, such as the non-ideal performance of impurity removal, the high rate of potato damage, bruising and impure content in the soil cleaning. In this study, a potato combine harvester was designed with the elastic rubbing technology. The harvesting process was also selected by the "double vibration separation, elastic rubbing type, buffering and loss reducing potatoes gathering and conveying". The main components included the excavation, hydraulic control potato soil separation, elastic rubbing impurity removal, as well as the buffering and reducing losses potatoes gathering and conveying device. A systematic analysis was implemented to clarify the movement track and collision characteristics of potatoes, according the optimal structure of the whole machine, the characteristics of harvesting, and the working principle. A combination of structural parameters were then determined for the key components, in order to fully meet the requirements of efficient separation and impurity removal, as well as the loss reduction and prevention. The whole harvesting process was divided into the three sections of the double vibrating potato soil separation, the elastic rubbing type soil cleaning and impurity removal, as well as the buffer potatoes gathering and conveying. The frequency and amplitude of the vibration were adjusted under the harvest conditions in the double vibration adjustable separation device in time. The rates of the potato damage and bruising were then reduced during the process of the potato and soil separation. The longitudinal non-equidistant soil cleaning and impurity removal device was used to reduce the collision frequency of potato, and then slow down the drop impact response, indicating the higher harvest quality, and the lower impurity content. The buffering and reducing losses potatoes gathering and conveying device was optimized to accurately control the drop height and position of potato at the end of the conveyor belt, in order to effectively avoid the drop damage during potato harvesting. The experiment result showed that the loss rates of the prototype were 1.17% and 1.43%, the potato damage rates were 1.30% and 1.27%, the bruising rates were 1.98% and 1.84% and the productivity values were 0.41 and 0.54 hm²/h, respectively, when the operating velocity values were 3.17 and 4.16 km/h, respectively. All performance indicators were met the requirements of national standards. Once the harvester was operated at a high speed, there was the significant increase in the material flow entering the elastic rubbing impurity removal device in a unit time, indicating the increasing burden of soil cleaning and impurity removal. Among them, part of the soil, seedlings, and vines were remained to mix in the potato cluster, resulting in a high impurity content. By contrast, the low operation speed was greatly contributed to the reduced impurities entering the soil cleaning and impurity removal stage. A better performance was achieved in the removal from the surface soil layer of potatoes in the soil cleaning and impurity removal device. But there was the weak protective effect of the soil on the surface of potatoes, leading to an increase in the frequency of direct contact between potatoes and the soil cleaning and impurity removal wheel. As such, the impurity content was much lower, whereas, there was an increase in the damage and bruising rate of potatoes, compared with the high operation speed. This finding can provide a strong reference for the subsequent research, equipment development, and optimization improvement.