Design and experiment of the baffle-type conveyor belt seedling picking-throwing device and chain breaking device for chain pots automatic transplanter

Seedling transplanting with paper chain pots has been one of the most efficient and sustainable crop cultivation, in order to reduce environmental impact for the simple transplantation, and seedling survival rate. Simultaneously, the seedling root systems can promote multiple crop cultivations, the land replanting index, and crop yield in high-yield and efficient agriculture. However, existing continuous automatic transplantation has been limited to the seedling transplanting with the paper chain pots, only suitable for transplanting dense-planted crops with the same plant spacing. In this study, a seedling picking-throwing device was designed with a baffle/conveyor belt and chain chain-breaking mechanism for the chain-pot transplanter, particularly for a series of transplanting operations, such as the seedling picking, transporting, chain breaking, seedling throwing, and planting. Various mechanisms were composed of the baffle-type conveyor belt, chain breaking, driving system, posture correcting, and planting device. The procedure of the chain pot transplanting was as follows. Firstly, the chain pots were placed on the seedling storage tray in the optimal planting period before transplanting. The initial end of the chain-pot seedling tray was pulled and then placed on the seedling picking and throwing timing belt. The chain pots remained engaged with the seedling transplanting baffles. Secondly, the chain-pot transplanting device was started along a predetermined trajectory using the seedling picking-throwing timing belt. The chain pots were broken by the chain-breaking device, in order to form the independent seedling pot. The planting device and the seedling picking-throwing timing belt were also combined to throw the seedling pots into the seedling cups. Finally, the seedling pots were transported to the seedbed and then planted vertically into the soil. A single-factor bench test was conducted to clarify the influence of different parameters on the success rates of the chain breaking and seedling throwing. The chain-pot seedlings were taken as the experiment object in the suitable planting period. Specifically, the optimal ranges were achieved in the seedling age and the inclination angles of the timing belt. The transplanting frequencies were determined as 28-36 d, 0°-6°, and 50-60 plants/min, respectively. A three-factor, three-level orthogonal experiment was conducted to determine the effects of different factors on the success rate of chain breaking and seedling throwing. An optimal configuration was achieved in the seedling age of 29 d, the timing belt inclination angles of 4°, and the transplanting frequencies of 55 plants/min. Furthermore, the success rate of chain breaking and seedling throwing was 92.44% and 94.60%, respectively, under the optimal configuration. A field experiment was carried out under an optimal combination of working parameters, in order to verify the operation performance of the whole machine. It was found that the success rates of chain breaking and seedling throwing were 90.62% and 93.10%, respectively, which fully met the performance requirements of the seedling transplanter. The finding can provide some insights into the operating parameters of fully automatic transplanters for unmanned transplanting.