Design and test of mechanism of push-out separating seedling for maize pot seedling

Abstract: Because of the shortage of land resources in China, the increase of maize yield could only depend on increasing the unit yield. The bowl seedling transplanting of maize can prolong crop growth period and improve yield and quality greatly. The advanced transplanting machinery in the world with complex structure, high cost and low efficiency, can only be used in cash crops. The automatic maize transplanter with simple structure, low cost and high efficiency is urgently needed in China. In order to improve the working efficiency, the lever ejection mechanism for transplanting the seedlings of maize that adopted the longitudinal feeding method of continuous conveying was put forward. The structural design, important parameters and working principle of the mechanism were proposed as follow. The 8 driving levers were arranged horizontally on the driving lever shaft, and the phase angle between the adjacent driving levers was 45?. Each driving levers corresponds to 8 levers, and 8 ejector pins correspond to 8 potted seedlings. When the shaft rotated 1 circle, the seedling tray moved down 40 mm, and the height difference between the 2 ejector pins was 5 mm. The shaft spacing of the ejector pins was determined according to the distance between the seeding. The driving shaft of the lever drove the rod to rotate at a constant speed, and the lever swung by the lever. The lever pushed the top rod out of the bowl seedling, and the ejector pin reset under the action of the spring. The related structural parameters were determined firstly. The involute inversion method was used to design the lever contour curve. The rotation angle of cam and the displacement of follower were divided into equal parts by envelope method. The curve enveloped by the axis perpendicular to the end of the follower was the contour curve required by the cam. The lever contour curve was obtained by analytic method, and the intermediate results of all the curves were taken as the lever contour curve. In order to analyse and verify the theoretical design, the force and vibration of the frame during the operation of the mechanism, the virtual prototype model of the lever ejection seedling splitting mechanism was established and imported into ADAMS to simulate the kinematics and dynamic characteristics. The simulation results showed that the simulation was consistent with the theoretical design, and the force changes of the top rod in the process of ejecting bowl seedling were uniform, which fully verified the correctness of the lever design based on the cam contour curve of the maximum effective force. The movement state of the potted seedling is directly related to the weight of the soil bowl and the size of the seedling, so an experiment was carried out to find out the conditions for the potted seedling to meet the performance requirements. The results showed that the weight of soil bowl was 10 g and the height of seedling was 160 mm. The high-speed photographic test was designed to measure the time interval of the seedlings reaching the same height from the ground after the seedlings were pushed out. The results showed that the bowl seedling of maize was orderly and the time interval basically met the requirements. When the working efficiency was higher than 240 times per minute, the interval error was less than 4.07%. In order to verify the performance indexes of the designed prototype, the machine prototype was processed to carry out the field transplanting experiment. The success rate of transplanting was 90.4%, which met the standard of dryland planting. The establishment of the theory and technology laid the research foundation for the development of pop-up bowl seedlings transplanting of maize machine.