Design and experiment of film packaging machine for Citrus reticulata

Citrus need to be packaged in the film bags before the storage, particularly on the type of Citrus reticulata. The water permeability of thin film is normally used to monitor the water evaporation and gas composition inside the package, aiming to extend the long shelf life of Citrus reticulata. In this study, a novel automatic packaging machine was proposed for the storage of Citrus reticulata, using the upper and lower double-layer films, combined with the heat sealing and edge cutting mechanism, in order to replace the traditional bagging packaging mode in the manual operation. A four-side sealing bag making/packaging machine was also designed for easy operation in the daily life. Six kinds of devices mainly included a multi-row feeding device, a Citrus reticulata conveying device, a sealing and cutting lifting device, a combined sealing and cutting device, a film feeding device, and a residual film collecting device. The sealed front film was used to drive the back film in the feeding of film. The relationship between the tensile strength of films and the film width was obtained in the pre-experimental analysis. The optimal value of film width was selected to avoid the film tearing during the working process. The hemispherical loading structure can be used to realize the continuous bag packaging in multiple rows and columns for Citrus reticulata. The multi-row feeding device was integrated with the various sensors and motors, thereby to implement the flip of movable plates. Two rows of citrus were operated in one feeding stage. The chain transmission and support were adopted in the citrus conveying device to transport the citrus among each station. The combined sealing and cutting devices were equipped with two cross-cutting knives and five longitudinal cutting knives, where simultaneously sealing and cutting two rows and four columns of citrus. Its built-in spring knife holder can ensure the tightness of hot cutting knife and the film during the sealing and cutting process. A connection device was set to provide the positive pressure that required for sealing and cutting, while to compensate the error of processing and assembly. A crank slider mechanism was selected for the sealing and cutting lifting device. An ADMAS software was used to carry out the kinematics analysis of lifting device, where the crank slider mechanism served as the main body, whereas the compression and relaxation of the spring in the built-in spring tool holder as the device without stopping. The relationship between the motor speed and the heat sealing time was also established in the two configurations. The motor speed was finally determined to be 20 r/min. Taking the Wenzhou mandarin orange as the test object, the case study demonstrated that the packaging rate of the citrus film packaging machine was 98.6%, the quality rate was 93.3%, and the packaging speed was 97.6 pieces/min, indicating the automatically mechanized bagging of fruits for storage. The findings can provide a sound reference for the development and optimization of the film packaging machine for the storage of Citrus reticulata.