Safflower is a kind of high-value economic crop, but due to its growth characteristics, it is very difficult to realize mechanized harvesting. At present, the mechanized harvesting technology of safflower has some disadvantages, for example, precise position is required, which means the labor intensity is still large. Therefore comb-type safflower harvesting device was been designed, which was expected to achieve mechanized blind mining and reduce labor costs. When it's working, it pushed the moving teeth by the pre-tightening force of the spring in the cam returning section, so that the moving teeth and the fixed teeth were closed, and the filament was clamped. The rotation of the main shaft driven the clamped filament to rotate, and the pulling action of the filament was completed. In the cam lift section, the push rod was topped, the spring was pressed, the moving teeth was separated from the fixed teeth, the filament was dropped, and the harvesting work was completed. In order to further study the comb-type device and improve the work quality for the comb-type machine, the height limiting device for comb-type safflower harvesting machine was designed, which was a limit rod mounted under the comb-type picking head and could be adjusted by the mounting plates on both sides. This device could stabilize the safflower flower ball, making it easier for the filament to enter the comb-type picking teeth gap, thereby increasing the recovery rate. At the same time, by limiting the position of the flower ball, the device could also reduce the damage to the flower ball. In this test, a single comb-type picking device and its corresponding height limiting device were used to analyze the effect of the height limiting device on the picking of individual flower filaments. The experiment chose the safflower of "Yu Min stingless" as the object. In order to determine the operation parameters of height limiting device for comb-type safflower harvesting machine, according to its structural parameters and working parameters, the response surface experiment with 3 factors and 5 levels was completed on the height limiting device for comb-type safflower harvesting machine. 3 parameters, including comb-type picking head speed, limit rod mounting angle and limit gap were selected as the input variables, and removal rate, drop rate and damage rate of the flower ball were selected as the output parameters. Quadratic orthogonal rotary regressive experimental design was employed to develop the second order polynomial regression model, which explained the relationship between the input and output parameters. By the Design Expert 10 software, the corresponding mathematical regression model was established, the influence of significant factor on the quality of operation was analyzed, and the experimental parameters were optimized. The optimal combination of parameters determined was as follows: comb-type picking head speed was 83 r/min, limit rod mounting angle was 2° and limit gap was 3 mm. From the results of predicting model, the average of removal rate was 90.01%, the drop rate was 2.23% and the damage rate of the flower ball was 1.92%. In order to verify the feasibility of the parameter matching, with the optimal parameters, the verification test of the machine was done on the safflower after the flowering between 1-5 d. The results showed that, under the combination of optimization parameters, the average of removal rate was 89.73%, the drop rate was 2.13% and the damage rate of flower ball is 2.05%. The experimental results had little difference with the results predicted by the model. Though the safflower harvesting experiments, the height limiting device for comb-type safflower harvesting machine was basically consistent with the technical requirement. The research results can provide reference for the comb-type picking machine. © 2019, Editorial Department of the Transactions of the Chinese Society of Agricultural Engineering. All right reserved.
