Design and experiment of the vertical brush-roller picking device for dry-safflower harvesters

Safflower is one of the dominant characteristic economic crops in Xinjiang, which is used in medicinal materials, oil, dye and feed. At present, the harvesting of safflower filaments still relies on manual labor. With the increase of safflower planting area and the shortage of labor force, many fresh safflower filaments have no time to harvest into dry-safflower filaments. Both the natural dried safflower filaments in the field and the dried safflower filaments collected during opening and then dried by air meet the national pharmacopoeia standards in terms of medicinal ingredients. But the safflower filaments gradually become hard and brittle after drying, which makes it difficult to pinch the filaments when picking by hand, and the filaments are fragile and easy to fall. It makes farmers reluctant to collect dry-safflower filaments, resulting in serious waste. Therefore, it is urgent to develop a dry-safflower harvester. At present, there have been some related research reports on the mechanical harvesting of dry-safflower, all of which are concept machines or ideas for brush-roller picking dry-safflower. However, there are no relevant reports on the theoretical and practical research on how to separate the safflower filaments from the fruit ball and improve the picking rate without damaging the fruit ball. The vertical brush-roller harvester is designed for dry-safflower filaments in dry land, which are generally planted in arid and barren land. Safflower is a top crop, which has the characteristics of one safflower in one branch, different opening time of filaments, and different spatial distribution of fruit balls. The safflower plants are relatively short, and one plant grows 3-7 fruit balls. When safflower filaments bloom from the neck of the fruit ball, safflower seeds are not yet mature. Therefore, when harvesting safflower filaments, it is necessary not to destroy the fruit balls that wrap the immature seeds and the branches that provide nutrients, but only to harvest the filaments threads located at the top of the fruit balls. Aiming at the problems such as low efficiency, high drop rate and no mechanization, a vertical brush-roller harvester was designed based on the physical characteristics and planting patterns of safflower. Firstly, the brush wires arrangement scheme was analyzed theoretically in combination with the structure of the machine, and it was determined that the brush wires arrangement scheme was helix, the helix angle was 30°, the rotation direction was right rotation. Secondly, the mechanical analysis of picking dry-safflower filaments by brush-roller was carried out, in order to find that the key force of the safflower filaments from the fruit balls was the normal force F_N. Furthermore, Hertz elastic contact theory was used to analyze the contact mechanics of normal force F_N, and the contact mechanics model of brush wires and fruit balls was established, which clarified the picking principle and the main factors affecting the picking quality, such as the material, diameter, length of the brush wires and the rotational speed of the brush-roller. Finally, the structural parameter design and kinematic analysis of the vertical brush-roller were carried out, and the main parameters of the picking device were obtained as follows: the length of the brush-roller was 300 mm, the diameter of the brush-roller was 100 mm, the material of the brush wires was polyamide 610 (PA-610), the length of the brush wires was 30 mm, the rotational speed of the brush-roller was 360 r/min, and the diameter of the brush wires was 0.3 mm. The clearance between the vertical brush-roller and the grid rack was determined to be 12 mm through the plant passing rate test. The field picking test showed that the picking rate and fruit damage rate of the vertical brush-roller harvester were 87.04% and 4.19%, respectively. The picking efficiency of harvester was 7.71-10.92 times that of manual picking. The research results can provide reference for the design and optimization of brush-roller harvester and dry-safflower harvester.