Research On Key Technologies Of Banana Crown-cutting Mechanization

China is the world’s second top producer of bananas which accounted for planting area of 7.51%and total yields of 10.59%in 2014.Bananas have become one of the most important economic industries in tropical and subtropical regions of China.The treatments of mechanized harvesting help to ensure the quality of banana and enhance extra value.It mainly includes crown-cutting,cleaning,grading and packing.The crown-cutting treatment is operated manually at home and abroad currently which lead to the harvesting line incomplete and cannot achieve completely mechanized.The study of banana crown-cutting key technologies and devices can achieve the goal of banana crown-cutting mechanization and automatically which helps to connect bunch conveying equipment and banana washing equipment.The study will also help to promote the research and application of harvesting line,and promote the industry of banana to the direction of modernization.Aimed at bananas crown-cutting mechanization,basic physical characters and geometry size of major varieties of banana bunch in Guangdong Province has been test,and principles of rachis clamping,crown cutting and banana conveying has been researched and experimented.Bananas crown-cutting device which consist of rachis clamping mechanism,bunch lifting mechanism,crown cutting mechanism and banana conveying mechanism has been designed and the parameters have been optimized.The research is composed as follows:(1)The basic physical characters and geometry size of banana bunch,banana rachis,banana crown and banana hand of Baxijiao(Musa AAA),the major varieties in Guangdong Province,has been test by electronic universal material testing machine and self-made test devices.The study also analyzed the results of the measurements by the method of numerical fitting,image processing and so on.Data shows that the wrap angle of banana crown,maximum thickness of banana crown,axial thickness of banana crown,distance of excenter between neighbouring banana crown,distance of banana crown,weight of banana hand,quantities of banana fingers in banana hand and length of banana finger in banana hand decrease with diameter reduction from beginning side to end side of banana rachis.Data also shows that the moisture content of banana crown increase with diameter reduction from beginning side to end side of banana rachis and the rotation angle of banana crown is linear with neighbouring banana crown.(2)The cutter’s track,resistance and interaction of forces of blade resistance,normal load and friction had been studied based on hanging banana bunch and crown cut by inserting type manually.A theoretical model of bananas crown-cutting is developed based on mechanics of materials and elastic foundation beam theory to research the principles of bananas crown-cutting.The model can figure out the cutting force and cutting track in cutting process under given cutter parameters.The average friction coefficient is 0.71between banana crown and the cutter measured by self-made device.Verification experiments are conducted to analyze the accuracy of theoretical model,which show that the trend of experimental curve is consistent with the theoretical model.The relative error of the peak shearing force between calculated value and experimental average value is 3.01%which indicated that the error is low and the model is reasonable.(3)Four types of hold part of banana rachis clamping device are compared and analyzed from the aspect of application.Curved hold part was identified as the main components of banana rachis clamping device.A theoretical model of bananas rachis-clamping is developed to research the principles of bananas rachis-clamping.Results of verification experiments show that if the clamp part has not damaged the surface structure of banana rachis,the average value of maximum friction force is 122.47±4.43 N as theoretical value is 125.7 N,and the significant analysis showed that there was no significant difference between theoretical value and experimental value.If the clamp part has damaged the surface structure of banana rachis,the r average value of maximum friction force is 355.23±14.26 N as theoretical value is 334.77 N,and the significant analysis showed that there was no significant difference between theoretical value and experimental value.(4)Banana hand conveying device is some equipment to convey crown cut banana hand to the next treatment,and it is the major execution module of banana crown-cutting device.Velocity and mechanical parameters of banana hand conveying mechanism were theoretical analyzed to establish the principles of banana hand conveying.Results show that the maximum speed of safety conveying is 0.80 m/s when relationship between banana hand and the belt is pure-rolling.Results also show that the friction is related to material of conveyor belt,speed of conveyor belt and friction type.Experiments show that the optimal conveying parameters are corrugated belt with speed of 0.35 m/s and wet friction indexed by sliding friction coefficient.(5)Bananas rachis-clamping mechanism,bunch-lifting mechanism,crown-cutting mechanism and banana hand conveying mechanism have been designed and the parameters have been optimized based on basic physical characters and geometry size of major varieties of banana bunch,crown-cutting model,rachis-clamping model and banana hand conveying mechanism.Experiments’results show that the friction between banana rachis and holding part increased significantly to a peak value when using rubber holding part with inner arc surface area of 1 885 mm~2,banana rachis diameter of 69 mm and cylinder gas pressure of 0.5 MPa.Results also show that the optimum parameters of cutters are as follows:diameter of banana rachis is about 45-50 mm,cutting speed is about50-60 mm/s,number of cut sets are about 4-6,angle between thick cutter and axis of banana rachis is about 5°,width of thick cutter is about 8-14 mm,thickness of thick cutter is about 2-3 mm,edge angle of thick cutter is between 20°and 30°,width of thin cutter is about 10-14 mm and thickness of thin cutter is about 0.2-0.4mm.The analysis of key parameters show that the optimal value of conveying speed is 126.58~352.94 mm/s when the lifting speed is 50mm/s and cutting speed is 50 mm/s.