| The yield of fresh fruits and vegetables is huge in China,but the loss ratio caused by in the process of circulation and sales is as high as 25-30%.As an effective way to reduce the loss of fruits and vegetables after harvest,the development of wrapping mechanized industry is relatively slow in China.At present,stretch film packaging in domestic basically used manual or semi-automatic methods,the packaging efficiency is low,and the packaging effect is poor,which is difficult to meet the demand for the mechanized packaging industry.Basis on the existing fresh food packaging technology in foreign countries and the characteristics of tensile film ultra-thin and high viscosity,different molding devices and conveying devices were designed,and the optimal solution was selected through the solid prototype test,and finally designed as a new type of clamping horizontal belt packaging machine supply molding device.The device is mainly composed of main driven support roller,horizontal conveyor,clamping horizontal belt mechanism and longitudinal sealing roller mechanism,which mainly completes the supply of stretch film and packaging materials,and coats the upper part of the packaging material and the lower longitudinal sealing operation.The structural parameters were obtained by establishing the mechanical physical model of the upper lamination of the load tray and the mechanical model of the packaging process of the stretch film in the vertical conveyor belt,respectively.The relationship equation between the different adjustment distances of the ball screw and the corresponding clamping pressure of the upper and lower reclining belts was measured by testing.Design the control system of the horizontal belt stretch film feeding and forming device for the packaging machine,carry out key control design for vertical clamping distance adjustment and front and rear tray distance control,and establish a humanmachine interface to manually or automatically control the feeding and forming device.The working parameters of the feeding speed of the clamping horizontal belt,the depression depth of the fluent strip parts,and the inclination angle of the clamping horizontal belt were set as the test factors.And the left offset and right offset were used as the test indicators to the performance of the device.The PVC stretch film with a width of 350 mm and the PP tray containing fresh carrots were selected as the test materials.The test results show that,in the test indicators,the three determinants were ranked in the conveying speed,depression depth,and inclination angle.The quadratic multiple regression equation of test factors and indicators was obtained by fitting the test results.In order to obtain the best combination of working parameters,the software Design-Expert 8.05 b was used for the response surface interaction analysis of the test results,and the optimal parameters were achieved: the conveying speed was 292 mm/s,the depression depth of the fluent strip parts was 10 mm,and the inclination angle of the clamping horizontal belt was 16.3°.Verification of the optimal parameters through experiments showed that the left offset was 10.5 mm and the right offset was 11.4 mm,which was basically consistent with the prediction of the above model.The working efficiency of the feeding and forming device was 23 bags/min.The packaging effect could achieve that the stretch film on the upper part of the tray was smooth,transparent,and without tearing,and the stretch film at the bottom of the tray was sealed longitudinally and neatly,which met the requirements of fresh fruits and vegetables packaging machines.This article can provide a certain theoretical basis and reference for the subsequent mechanized packaging of fresh fruits and vegetables. |
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