Spring-tooth type unbaling anti-blocking device for orchard straw mulching machine

Straw mulching has been one of the most essential practices for soil and water conservation, soil fertility, and structure improvement in sustainable agriculture. The current research focused mainly on the mechanism, effect, economic, and ecological benefits of straw mulching. Only a few studies have been reported on mechanization technology and equipment for straw mulching. Previously, an orchard straw mulching machine was developed to realize mechanization. Specifically, the crop straw bales were unbaled and then broken to spread between the rows of the orchard. However, the unbaling-spreading device was easily blocked by the straw, leading to the low quality and efficiency of straw mulching. In this study, a spring-tooth anti-blocking device was developed for the orchard straw mulching machine, according to the mechanical analysis of the straw bale unbaling and breaking process. Firstly, the discrete element model was established for the "anti-blocking device and straw bale" using EDEM software. A comparison was made on the straw disturbance area and straw density variation at the discharge port by the DEM simulation with and without the anti-blocking device. The formation mechanism of straw blockage was explained during the unbaling-spreading operation. The average straw density was reduced by 46% at the inner side of the discharge port. The unbaling resistance torque per unit mass flow rate was reduced by 28.1% in the discharge zone. Specifically, the knife tooth line speed and the feed speed of straw bale were 2.3, and 0.05 m/s, respectively. The simulation results showed that the anti-blocking device effectively reduced the straw density in the knife tooth disturbance area and the discharge port. The straw staying was avoided in the discharge port for the formation of a high-pressure area. Thus, the anti-blocking device reduced the unbaling resistance torque. The optimal working parameters were obtained as 225 r/min for the roller rotate speed of the unbaling-spreading device, 5.0 r/min for the roller rotate speed of the scraper feeding mechanism, and 100 mm for the spring teeth spacing. The verification test showed that the standard deviation reduction rates of resistance torque were 29.5%, 34.0%, and 30.7% under the active roller speeds of 185, 225, and 265 r/min, respectively, in the unbaling-spreading device after the installation of the anti-blocking device. Meantime, the average and peak resistance torque decreased by 16.1% and 28.5%, respectively, indicating the effective anti-blocking device. The finding can also provide a theoretical basis to develop an anti-blocking device for the orchard straw mulching machine.