Abstract:
Abstract: The usage of film mulch cultivation technology is ever increasing in China, particularly ranging from fruits and vegetables to a variety of food crops in a large area. Ultra-thin plastic film is commonly used as a soil surface mulch. The long-term laying of plastic film has brought serious mulch residues, due to its polyethylene film is difficult to be degraded in the natural environment. The accumulation of plastic film residues has caused serious negative effects on the crop growth, such as microorganisms in the soil difficult to survive, damage of soil agglomeration structure, obstruction of moisture circulation, soil salinization and compaction. As such, various machines were developed for residual film recovery, with strong adaptability, high recovery rate, and high work efficiency, particularly on the residual film pickup device in tooth-chain type for gathering and tying the film. However, the complicated structure of mechanism limited the application of residual film pickup device. At present, a bent conveyor chain is often used, in order to improve the efficiency of removed film. If the length beyond the critical after the conveyor chain bending, the film pickup teeth are easy to be deformed after impact, resulting in leakage pickup phenomenon, and the incompletely removed film, easy to wind, and low loading. This study aims at the problems of missing inspection, incomplete stripping, and winding of rake type residual plastic film collector during the working process, thereby to design a guiding chain harrow type residual plastic film collector on the surface soil. The main content included the design of guide chain harrow type picking-up film mechanism, and the connection structure between the rake assembly and the transport chain, with emphasis on the transport chain for the removal of film. Specifically, the structure of rake teeth and the arrangement of rake teeth were determined, the rotary film removal device with guide rake to improve the effect of removing film, and a pushing film mechanism was designed at the rear of film collecting box for increasing the loading capacity. A combined method of mechanical and hydraulic pressure was applied to realize the transmission requirements of picking up, removing, and pushing film. A motion analysis and pretests were conducted to optimize the structural parameters of main moving parts. A quasi-horizontal orthogonal test was carried out to verify the reliability of key parts in the machine and the operation performance. The test factors were selected, including the machine advancing velocity, the depth of rake into soil, and the chain rake input speed, and the indexes were the film pickup rate and film winding rate. The results show that the primary and secondary factors that affected the film pickup rate were the chain harrow input speed, the machine advancing velocity, and the depth of rake into soil, whereas, the primary and secondary factors that affected the film winding rate were the chain rake input speed, the depth of rake into soil, and the machine advancing velocity. Taking the film pickup rate as the main index, the integrated balance method was used to determine the optimal operating parameters, where the machine advancing velocity was 8 km/h, depth of rake into soil was 30 mm, and the chain rake input speed was 143 r/min. A field validation test was performed on the better parameter combination, where the film pickup rate was 88.73%, and the film wrapping rate was 1.91%. The findings can provide a sound reference to optimize the design of residual plastic film collector, and further to improve the operation performance.