Analysis on detaching process of detaching device and seedling pot integrity about rape transplanter

Mechanization transplanting for rapeseed pot seedling can alleviate labor intensity of manpower and shorten reviving time of rapeseed pot seedling. Seedling detaching and transplanting are the 2 main processing operations for transplantation. The stability of detaching has an important influence on the transplanting operation, and the pot seedlings should be stable during transporting and kept integrity for better transplanting quality. However, some detaching devices have complicated structure and easily make damage to seedlings. And therefore, in this paper, a conveyor belt type detaching device of rapeseed transplanter for rapeseed pot seedlings was introduced to solve this problem. The process of detaching was analyzed and the kinematics models in the stage of transmission and detaching were established to explore the stability conditions of transporting pot seedlings. The integrity tests of seedling pot were carried out to evaluate the mechanical properties of rapeseed pot seedlings. The TMS-CONSOLE type texture analyzer produced by American FTC company was used for the integrity tests. Results showed that the stability of transportation was obviously affected by the friction coefficient between seedling pot and materials of key devices in the transmission stage. The dynamic friction coefficient (DFC) between pot and detaching hinge was less than 0.3375, and the DFC between pot and conveyor belt ranged from 0.5 of the DFC between pot and detaching hinge to 0.3375. Accordingly, the rapeseed pot seedlings were transported stationarily. The stability of clamped pots in detaching stage was obviously influenced by the clamping force and clamping height. When the clamping height was lower and the clamping force was larger, the clamped pot seedlings were kept stable more easily. The 3 clamped pots were stable without slippage when the clamping force was more than 0.32 N, and would not flip over when the clamped force was more than 1.2 N. Single flat compression, repeated flat compression and repeated line type compression were included in the integrity tests. The results of single flat compression showed that the fracture resistance force of top edge of seedling pot was more than 6.8 N, and thus the pots maintained certain elasticity and restoring ability. The results of repeated flat compression showed that the number of compression did not influence springiness obviously. The condition of seedling pot damage became worse with the increase of the compression number. The results of repeated line type compression showed that the anti-compression force increased with the increase of clamping height. In order to keep the integrity of seedling pot, the anti-compression force applied was more than 1.99 N, and this requirement was easy to satisfy. To keep the integrity of pot in the detaching process, the clamping force should be proper. Bench test was developed to verify the analyzed results. The results of bench test showed that the detaching ratio of the device was greatly influenced by the transmission ratio and the detaching frequency. The detaching ratio was 90% when the detaching frequency was 40 pots per minute and the transmission ratio was 3 times. The experimental observations showed that the seedling pots were not fractured, and the pot medium were not obviously destructed. The qualified ratio of rapeseed pot seedlings in field test was 88.67%, which basically met transplanting requirements. This research provides a reference for the analysis of seedling separation stability of rapeseed transplanter and also for the research on the synchronization between detaching and planting.