Stretch Packaging Technology (2)

The product is placed in a platter and pushed by a supply device onto a supply conveyor to a push-up site (the long side of the platter is perpendicular to the advancement direction). At the same time, the film cut in advance by the required length is sent over the push-up section. Clip the four sides of the film with a clip, place the contents on the top of the putter, and push the part up. As the push-up portion rises up against the film, the film is stretched, and then the left, right and back film clips are released while the three-sided film is folded in under the pan. Then start the output conveyor belt with flexible foam, push the platter forward, the front film stretched, at the same time, loosen the front film clip, fold the film under the shallow pan, and then send the package On to the heat seal plate, the final seal is performed.
Continuous linear operation method: This is the earliest form of automatic stretch packaging. Because it is not stable enough to package higher products, it is limited in use. The operation process is shown in Figure 12-10.

The product placed in the platter is delivered by the supply device to the film (the long side of the tray is perpendicular to the advancement direction). When the front part of a package is sealed at the same time, the film of the two reels is sealed at the same time, the packaged object is sent there, and the film is stretched while continuing to advance. When the packaged product is completely covered, the back pad is sealed and cut with a sealing cutter. Then, the left and right ends of the film are stretched and folded into the bottom surface of the shallow pan. Finally, it is sealed on the heat seal plate.
There is another way of operating the continuous linear operation method, see Figure 12-11.

The product placed in the shallow tray is advanced horizontally by the feeding device while the two sides of the film are folded downwards, and the two sides of the film are heat-sealed by a heat sealing roller to form a longitudinal slit, and the film forms a cylinder. In the form, wrap the package in it (the direction of the long side of the platter is the same as the direction of advancement). While closing the seam, go forward. When the knife is reached, the rear part of the package is heat-sealed and the front film transverse sealing seam of the next package is formed. Then, the front and back ends of the film are stretched and then folded toward the bottom surface of the tray, and are sealed on the heat sealing plate.
2. Methods used for transport packaging Stretch packaging is used for transport packaging. Compared to traditional wooden boxes, corrugated boxes and other packaging, it has the characteristics of light weight and low cost, so it is rapidly and widely used. Most of this packaging is used for pallet collection, and sometimes for pallet-free packaging. Stretch packaging for transport packaging, according to the different films can be divided into the whole film packaging method and narrow film wrapping packaging method; according to the different operating methods can be divided into rotary operation and straight-through operation According to the level of productivity, it can be divided into portable, platform, conveyor belt feeding, automatic and other methods.
(1) The whole film packaging method uses the entire film package with the width equal to or greater than the height of the goods. This method is suitable for packing shaped goods, which is economical and effective, such as the packaging of export goods by ordinary ships; 20kg large bags; heavy and unstable goods; and occasions requiring high packaging efficiency per unit time. The disadvantage of this method is that a wide variety of films are stored in the material warehouse. There are two ways to operate a common device:
a. Rotary operation method It is to put the goods on a platform that can be turned, stick the end of the film to the goods, then rotate the platform, rotate the film while stretching the film to wrap the wrapping, cut the film after a few weeks, and cut the end Stick to the goods.
There are two basic methods for stretching a film. One is to use a friction roller to limit the speed at which the film is pulled from the film roll, thereby stretching the film. The general stretch rate is 5% to 55%; the other is Two pairs of rollers with different rotation speeds are used. The input speed of the film input roller is lower than that of the output roller, so that the film is stretched, and the stretching rate is generally 10% to 100%. In order to eliminate the unfavorable factors of the sudden increase of the speed in the four corners of the square cargo packaging process, a pneumatic regulator is often used to keep the film tension even. See Figure 12-12.

The equipment used in this method is semi-automatic, that is, the film is stuck at the beginning, and the film is cut off at the end, either manually or fully automated.
b. The straight-through operation method puts the goods on a conveyor belt and moves them forward. There is a gantry type shelf at the packing position. Two film rolls stand upright on both sides of the conveyor belt and are equipped with a friction stretching roller. At the beginning of the package, the ends of the two films are first heat-sealed to the goods. When the goods move forward, the film is wrapped on it while the film is stretched to a certain position, the film is cut off, and the ends are stuck to the back of the goods. The equipment used in this method is semi-automatic and fully automatic as well as rotary type.
(2) Narrow film wound packaging method uses a narrow web film (width is generally 50 ~ 70cm), spirally wound from top to bottom until the wrapping is completed, about 1/3 part between two laps overlapping. This method is suitable for packing high or inconsistent cargoes and irregularly shaped or light cargoes. Packaging is less efficient, but a wide film can be used to wrap goods of different shapes and stack heights. The equipment used is either manually operated or automatically operated. The basic principle is shown in Figure 12-13. The operation is as follows:
a. The cargo is stacked on a slewing platform, the film is pulled from the drum, and the ends are glued to the upper part of the cargo. The platform is then rotated and the cargo is rotated, and the film is wound while being stretched.
b. At the beginning of operation, the film roll is at the top of the column. As the film is wound, the roll moves downwards and the film forms a spiral package on the surface of the cargo from top to bottom.
c. After all the goods have been tightly packed, they are cut with a cutter, and the ends of the film are bonded together with a heat seal plate. The packaging is completed.