| Rape is an oil crops that has a high economic efficiency, rape dross and straw can be reused through some programs. Yangtze River basin is the main producing areas of winter rapeseed, since the planting contradiction against rice, seedling transplanting remains an important way of cultivation. 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 two main processing operations for transplantation. Nowadays, transplanting developed better than seedlings separation, the development of seedling separation is relatively slow due to easy damage of the tender seedlings, difficult control of freedom for the seedling. So the job of seedling separation is sub largely completed by hand during mechanized transplanting. However, some detaching devices have complicated structure, easily make damage to seedlings and have poor adaptability. And therefore, in this paper, a conveyor belt type detaching device of rapeseed transplanter for rapeseed pot seedlings was introduced to solve this problem on the basis of systematic analysis on detaching device of seedling transplanting machine. It can work well with double five-bar transplanting mechanism. This research provides a reference for the research of seedling separation and improved machine structure, it has certain significance for the development of seedling transplanting machine. The main research contents and results of this paper were as follows:1) The way of separation and transplanting for bare rape seedling was conducted, and the corresponding device was researched, too. Rape pot seedling was selected as the object for the research of seedling separation and relative device. Hinge-damper-type seedling separation was put forward based on the dimensions of pots, and the conveyor type seedling detaching device was designed, too. The structural features and working process was introduced in this paper. The corresponding rape transplanter was developed and the key structural parameters and operating parameters of seedling detaching device was determined as well. Wherein, the cylinder radius was 25 mm, and had the same rotational speed with the planting drive shaft, the value is equal to planting frequency. The capacity of conveyor was 10 pot seedlings, the width of conveyor was 50 mm. The spacing between two hinge axis was 85 mm.2) The seedling separation process was divided into transmission and detaching stage, stability conditions of transporting pot seedlings was analyzed. The 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.3) According to the force condition of the pot seedling in the seedling separation process, the force tests of seedling pot and pot seedling were carried out to evaluate the mechanical properties. The TMS-CONSOLE type texture analyzer produced by American FTC company was used for the integrity tests, and the test including single flat compression, repeated flat compression and repeated line type compression. The test would lay the foundation of research of pot seedling integrity. The results showed that the process of single flat compression for pot seedling can be divided into pre-compression, linear elastic, yielding and strain hardening four stages, the minimum yield strength was 6.8~7.1 N. Repeat compression test showed that all the test values of seedling pots were greater than the corresponding pot seedling, and pot seedling had good ability to maintain the integrity. Repeated line tpye compression showed that the hardness of seedling pot overall trend was first increases and then decreases, and the range of hardness is small, the anti-compression force of pot seedling would increasing by the height increases, and it also had a good recovery ability.4) A clip-inclined transportation and level clamping-type seedling detaching device was put forward in this article, which can be improved seedling separation reliability. The inclination angle of the conveyor belt, guide slim relative spacing, structural parameter of level clamping mechanism and cam profile parameters of the improved cam synchronization control system were analyzed and determined. The key parameters were as follows: the inclination angle of the conveyor belt was 15 °. In order to achieve good effect of supporting seedlings, the spacing of guide slim should be as small as possible without affecting seedling delivery. The width of Hinge horizontal section was 20 mm of the level clamping mechanism, and hinge spacing was 15 mm, the installation intervals of rotation axis should be 105 mm, and hinge rotation angle was 34 °. Rod length was 47 mm, the effective length of waist-round hole on pull plate was 2.1 mm. The base circle radius of improved cam was 30 mm, pushing travel was 20 mm, which can reduced the maximum pressure angle for 13.11 °.5) Bench test of seedling detaching device and field test of rape pot seedling transplanter were carried out. Bench test showed that the detaching ratio of the device was greatly influenced by the transmission ratio and the detaching frequency. The detaching ratio could be reach 90% and the flipping ratio was 6% when the detaching frequency was 40 pots per minute and the transmission ratio was 3 times. Field experimental observations showed that the seedling and pots were not fractured, the qualified ratio of rapeseed pot seedlings was 88.67%, which met the transplanting requirements. |
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