Method and device for secondary shaping of plastic bottle shrink film

Abstract

The application discloses an out-of-furnace secondary shaping heat shrinkage method and device for preventing plastic bottle shrinkage film from loosening, and the method comprises the following steps: S1, placing a plastic bottle with a shrinkage film on the surface of the plastic bottle into a heating mechanism to heat, so that the shrinkage film is heated and shrunk and adheres to the surface of the plastic bottle; S2, moving the heated plastic bottle out of the heating mechanism to cool the inside of the plastic bottle, so that the plastic bottle is cooled and shrunk to the original size, and the shrinkage film adhered to the surface of the plastic bottle is loosened due to the shrinkage of the plastic bottle; and S3, secondarily heating the shrinkage film, so that the shrinkage film is shrunk again and adheres to the surface of the shrunk plastic bottle. The advantage is that the loosened film body is shrunk again and adheres to the surface of the shrunk bottle through secondary heating, so that the shrinkage film shaping is more accurate.

Description

Technical Field

[0001] This invention relates to the field of packaging, specifically to a method and apparatus for oven-heat shrinkage to prevent shrink film from loosening in plastic bottles. Background Technology

[0002] Currently, the conventional process for heat shrink sleeve labeling is as follows: a pre-made sleeve-shaped heat shrink film is placed over the outside of the bottle, and then the labeled bottle is sent into a heat shrink oven for high-temperature heating, so that the shrink film shrinks and adheres tightly to the surface of the bottle. Finally, the bottle is removed from the oven and allowed to cool naturally or by forced air cooling.

[0003] However, this traditional process has insurmountable quality defects when processing certain plastic bottles (especially HDPE bottles). Some plastic materials have a large coefficient of thermal expansion. In the high-temperature environment of the shrink oven, heat is transferred from the film to the bottle, causing the bottle to passively heat up and expand significantly in outer diameter. The shrink film shrinks under heat in this expanded state and adheres to the bottle surface. However, when the bottle leaves the shrink oven and enters the cooling station, and the bottle temperature gradually drops to room temperature, the plastic material undergoes thermal shrinkage and recovers, and the outer diameter of the bottle shrinks back to its original size. The shrink-shaped label film cannot shrink back synchronously with the bottle, resulting in appearance defects such as loosening, bulging, wrinkling, and poor adhesion of the shrink film.

[0004] Therefore, it is necessary to provide a method and apparatus for oven-heat shrinkage to prevent the shrink film of plastic bottles from loosening during secondary shaping. Summary of the Invention

[0005] This invention provides a method and apparatus for preventing shrink film from loosening in an oven during secondary heat shrinking, which effectively solves the problems of loosening, bulging, wrinkling, and poor adhesion of existing shrink film after labeling.

[0006] The technical solution adopted in this invention is: A method for preventing shrink film from loosening in plastic bottles through secondary heat shrinking outside the oven includes the following steps: S1, placing the plastic bottle covered with shrink film in a heating mechanism for heating, causing the shrink film to shrink and adhere to the surface of the plastic bottle; S2, removing the heated plastic bottle from the heating mechanism, cooling the inside of the plastic bottle, causing the plastic bottle to cool down and shrink back to its original size, causing the shrink film already adhered to the surface of the plastic bottle to loosen due to the shrinkage of the plastic bottle; S3, reheating the shrink film, causing the shrink film to shrink again and adhere to the surface of the shrunken plastic bottle.

[0007] Furthermore, the cooling of the interior of the plastic bottle described in S2 is achieved by introducing a cooling medium into the bottle through a cooling pipe inserted into the bottle opening.

[0008] Furthermore, the cooling medium is introduced into the bottle through the cooling pipe in a one-way constant temperature cold air purging mode. The one-way constant temperature cold air purging mode is as follows: the cooling pipe continuously inputs constant temperature cold air into the bottle, and the hot air inside the bottle is naturally discharged from the gap between the bottle mouth and the cooling pipe.

[0009] Furthermore, the cooling gas supply pipe introduces the cooling medium into the bottle in a circulating sealed cold-in-hot-out heat exchange mode. The circulating sealed cold-in-hot-out heat exchange mode is as follows: after the bottle opening is sealed, the cooling gas supply pipe and the inside of the plastic bottle form a closed-loop airflow channel, and an external suction pipe is connected at the bottle opening. Constant temperature cold air is continuously input into the bottle along one end of the closed-loop airflow channel, and the high temperature hot air inside the bottle is simultaneously discharged along the suction pipe.

[0010] Furthermore, the secondary heating is performed by using a hot air sweeping mechanism to heat the surface of the shrink film.

[0011] Furthermore, the heating mechanism is a heat shrink oven, and both the cooling and the secondary heating are completed outside the outlet of the heat shrink oven.

[0012] An external secondary heat shrink device for preventing shrink film from loosening on plastic bottles is used to implement the external secondary heat shrink method for preventing shrink film from loosening on plastic bottles. A heating mechanism is used to heat the plastic bottle covered with shrink film, causing the shrink film to shrink and adhere to the surface of the plastic bottle. An external cooling mechanism is located outside the outlet of the heating mechanism and is used to cool the interior of the plastic bottle after it has been heated, causing the plastic bottle to cool down and shrink back to its original size. An external secondary heating mechanism, located downstream of the external cooling mechanism, is used to reheat the shrink film that has loosened due to the shrinkage of the plastic bottle, so that the shrink film shrinks again and adheres to the surface of the shrunken plastic bottle; a conveyor line is used to carry the plastic bottle and transport it sequentially through the heating mechanism, the external cooling mechanism and the external secondary heating mechanism.

[0013] Furthermore, the conveyor line includes a conveyor line and a positioning component disposed on the conveyor line, the positioning component being used to fix the plastic bottle.

[0014] Furthermore, the external cooling mechanism includes a gas storage tank for storing cooling medium, a cooling gas delivery pipe connected to the gas storage tank, and a sliding clamping assembly for driving the cooling gas delivery pipe to move synchronously along the conveyor line.

[0015] Furthermore, the external cooling mechanism includes a gas storage tank for storing cooling medium, a cooling gas delivery pipe connected to the gas storage tank, a sliding clamping assembly for driving the cooling gas delivery pipe to move synchronously along the conveyor line, a lifting assembly that is horizontally moved by the sliding clamping assembly, a sealing head and a suction pipe disposed on the lifting assembly. The ends of the cooling gas delivery pipe and the suction pipe are fixedly disposed on the sealing head. The lifting assembly drives the sealing head to connect and seal with the mouth of the plastic bottle, so that the air inlet of the suction pipe and the air outlet of the cooling gas delivery pipe extend into the inside of the plastic bottle, and the straight-line distance between the air inlet of the suction pipe and the mouth of the bottle is less than the straight-line distance between the air outlet of the cooling gas delivery pipe and the mouth of the bottle.

[0016] Beneficial effects of the invention: 1. In this application, the shrink film is first initially bonded under conventional heating conditions. Then, active cooling inside the bottle causes the expanded bottle to shrink back to its room temperature size. At this point, the shrink film bonded to the bottle surface experiences uniform pre-relaxation due to the bottle shrinkage. Finally, a second heating process tightens the relaxed film again and bonds it to the shrunken bottle surface. These three steps proceed sequentially, transforming the uncontrollable dimensional differences in traditional processes into controllable pre-relaxation and ultimately eliminating them, resulting in more precise shrink film forming.

[0017] 2. This application concentrates all the modifications on the outside of the original heat shrink furnace's outlet. The cooling mechanism and secondary heating mechanism are both installed as independent modules on the outside of the furnace body, requiring no changes to the original furnace structure, hot air system, or conveyor channels. For existing production lines already in operation, the equipment investment for this modification method is far lower than replacing the entire line or customizing the furnace body. Furthermore, the installation and commissioning cycle is short, it is ready to use immediately, and it has almost no impact on normal production rhythm.

[0018] 3. This invention provides two in-bottle cooling methods for users to choose from based on their actual needs. The unidirectional constant-temperature cold air purging mode utilizes the natural gap at the bottle opening for exhaust, eliminating the need for sealing and extraction components. It boasts the simplest structure and lowest maintenance costs, making it suitable for large-scale mass production scenarios where equipment investment is critical. The circulating sealed cold-in, hot-out heat exchange mode forms a closed-loop circulation through a sealing head that connects to the bottle opening. This results in more uniform heat exchange and higher temperature control accuracy, making it suitable for bottles with thicker walls or stricter appearance requirements. Both modes share the same main equipment unit, allowing for flexible switching and adaptability to production needs at different precision levels.

[0019] 4. In the secondary heating stage, the present invention adopts a sweeping heating method. The hot air only sweeps the surface of the shrink film for a short time. The heat penetration is shallow and the action time is short. While the film is heated and tightened, the bottle itself will not experience a significant temperature rise. Attached Figure Description

[0020] Figure 1A flowchart of an out-of-oven secondary heat shrinkage method for preventing shrink film from loosening in plastic bottles, provided as an embodiment of this application.

[0021] Figure 2 The schematic diagram shows the out-of-furnace secondary shaping heat shrink device for preventing plastic bottle shrink film from loosening, provided in the embodiments of this application, which uses a unidirectional constant temperature cold air blowing mode for cooling.

[0022] Figure 3 The schematic diagram shows the furnace-side secondary shaping heat shrink device for preventing plastic bottle shrink film from loosening, provided in the embodiments of this application, which uses a circulating sealed cold-in-hot-out heat exchange mode for cooling.

[0023] Figure 4 This is a comparison diagram between this application and a comparative example.

[0024] The following are marked in the diagram: 1. Heating mechanism; 2. Conveyor line; 3. Cooling air supply pipe; 4. Sliding clamping assembly; 5. Lifting assembly; 6. Sealing head; 7. Suction pipe; 100. Plastic bottle. Detailed Implementation

[0025] To make the above-mentioned objects, features and advantages of the present invention more apparent and understandable, the specific embodiments of the present invention will be described in detail below with reference to the accompanying drawings.

[0026] like Figure 1 As shown, the first embodiment provided in this application is a method for preventing the shrink film of a plastic bottle from loosening during secondary heat shrinking outside the oven. The method includes the following steps: S1, placing a plastic bottle 100 covered with shrink film in a heating mechanism 1 for heating, causing the shrink film to shrink and adhere to the surface of the plastic bottle 100; S2, removing the heated plastic bottle 100 from the heating mechanism 1, cooling the interior of the plastic bottle 100, causing the plastic bottle 100 to cool down and shrink back to its original size, causing the shrink film already adhered to the surface of the plastic bottle 100 to loosen due to the shrinkage of the plastic bottle 100; S3, reheating the shrink film, causing it to shrink again and adhere to the surface of the shrunken plastic bottle 100.

[0027] Depend on Figure 4 It can be intuitively concluded that Figure 4 The product selected in the left box is the finished product obtained using this method, in which the shrink film is well formed and the plastic bottle 100 has no loosening. The product on the right is the finished product obtained using the existing method, which has loosening and bulging.

[0028] In the above design, there is no need to modify the original heating mechanism 1. It is only necessary to add a cooling mechanism and a secondary heating mechanism 1 to the original heating mechanism 1. This can ensure that the shrink film is flat and tight after final forming, and there is no loosening or bulging.

[0029] Specifically: the cooling of the interior of the plastic bottle 100 described in S2 is achieved by introducing a cooling medium into the bottle through a cooling air supply pipe 3 inserted into the bottle opening of the plastic bottle 100.

[0030] In the above design, by introducing the cooling medium into the plastic bottle 100, the shrinkage process of the bottle material proceeds uniformly from the inside out, avoiding bottle tilting or local dents caused by uneven cooling. Simultaneously, this method utilizes the bottle opening as a natural channel, making the insertion and removal of the pipe simple and reliable. The start and stop of cooling can be precisely controlled, ensuring that each bottle has stably shrunk to its original size before entering the secondary heating station, providing a consistent bottle size benchmark for subsequent secondary shaping.

[0031] Specifically: the cooling gas supply pipe 3 introduces the cooling medium into the bottle in a one-way constant temperature cold air purging mode. The one-way constant temperature cold air purging mode is as follows: the cooling gas supply pipe 3 continuously inputs constant temperature cold air into the bottle, and the hot air in the bottle is naturally discharged from the gap between the bottle mouth and the cooling gas supply pipe 3.

[0032] In the above design, a cooling air supply pipe 3 extends into the bottle opening to continuously supply air. The hot air inside the bottle is discharged through the natural gap between the bottle opening and the pipe, eliminating the need for additional sealing structures or suction components. This achieves rapid heat exchange inside the bottle, timely cooling response, and a simple and reliable airflow organization method, resulting in an extremely low system failure rate. By eliminating complex sealing and suction components, equipment investment and maintenance costs are effectively controlled.

[0033] Specifically: the cooling gas supply pipe 3 introduces the cooling medium into the bottle in a circulating sealed cold-in-hot-out heat exchange mode; the circulating sealed cold-in-hot-out heat exchange mode is as follows: after the bottle opening is sealed, the cooling gas supply pipe 3 and the inside of the plastic bottle 100 form a closed-loop airflow channel, and an external suction pipe 7 is connected at the bottle opening. Constant temperature cold air is continuously input into the bottle along one end of the closed-loop airflow channel, and high temperature hot air in the bottle is simultaneously discharged along the suction pipe 7.

[0034] In the above design, by sealing the bottle opening, a closed-loop circulation channel is formed between the cooling air supply pipe 3, the interior of the plastic bottle 100, and the suction pipe 7. Cold air is continuously input through the cooling air supply pipe 3, while hot air is simultaneously extracted from the suction pipe 7. Forced convection heat transfer ensures a uniform temperature distribution inside the bottle, preventing localized temperature differences where the bottom of the bottle is completely cooled while the neck remains uncold. This mode offers rapid cooling and high temperature control accuracy, making it particularly suitable for plastic bottles 100 with thick walls or complex shapes. It effectively avoids uneven bottle shrinkage or appearance defects caused by excessive temperature differences.

[0035] Specifically, the secondary heating is performed by using a hot air sweeping mechanism to heat the surface of the shrink film.

[0036] In the above design, hot air only briefly sweeps the surface of the shrink film, resulting in shallow heat penetration. While the film shrinks due to heat, the bottle itself does not significantly heat up. This feature ensures that the bottle, having cooled and shrunk to its original size, maintains dimensional stability during reheating, preventing the recurrence of problems caused by re-expansion in traditional processes. Furthermore, the sweeping air heating method allows for flexible adjustment of heating power and airflow according to production line speed, ensuring high compatibility with the production line cycle and not affecting overall production efficiency.

[0037] Specifically: the heating mechanism 1 is a heat shrink oven, and the cooling and the secondary heating are both completed outside the outlet of the heat shrink oven.

[0038] In the above design, both the cooling and secondary heating processes are located outside the outlet of the heat shrink furnace, meaning that all modifications are completed after the existing shrink furnace. For older production lines already in operation, no changes are required to the furnace structure, heating system, or conveying channels; simply adding a cooling device and secondary heating mechanism 1 after the furnace is sufficient to upgrade the process.

[0039] The second embodiment provided in this application is an out-of-oven secondary shaping heat shrink device for preventing the shrink film of plastic bottles from loosening. It is used to implement the out-of-oven secondary shaping heat shrink method for preventing the shrink film of plastic bottles from loosening. The heating mechanism 1 is used to heat the plastic bottle 100 covered with the shrink film, so that the shrink film is heated and shrinks and adheres to the surface of the plastic bottle 100. An external cooling mechanism is located outside the outlet of the heating mechanism 1 and is used to cool the interior of the plastic bottle 100 after it has been heated by the heating mechanism 1, so that the plastic bottle 100 cools down and shrinks back to its original size. An external secondary heating mechanism 1 is located downstream of the external cooling mechanism and is used to perform secondary heating on the shrink film that has become loose due to the shrinkage of the plastic bottle 100, so that the shrink film shrinks again and adheres to the surface of the shrunken plastic bottle 100. Conveyor line 2 is used to carry the plastic bottle 100 and transport it sequentially through the heating mechanism 1, the external cooling mechanism and the external secondary heating mechanism 1.

[0040] In actual use, after the heating mechanism 1 completes the initial heat shrink of the shrink film, the bottle is sequentially conveyed to the external cooling mechanism and the external secondary heating mechanism 1 located outside the outlet of the heating mechanism 1 via the conveyor line 2. The external cooling mechanism immediately performs active cooling on the inside of the bottle after it is removed from the heating mechanism 1, so that the expanded bottle is quickly cooled down and shrinks back to its original size. The shrink film that has been attached to the surface of the bottle is uniformly pre-relaxed due to the reduction in the size of the bottle. Then, the external secondary heating mechanism 1 heats the relaxed shrink film again, causing it to shrink again and attach to the surface of the shrunken bottle.

[0041] In the above design, the cooling mechanism and the secondary heating mechanism 1 are both independently set outside the outlet of the heating mechanism 1. No structural modifications are required to the original heat shrink furnace body. It can be installed and used immediately, with low modification costs and strong adaptability, providing a practical solution for the transformation and upgrading of old production lines to address the problem of loosening.

[0042] Specifically: the conveyor line 2 includes a conveyor line 2 and a positioning component disposed on the conveyor line 2, the positioning component being used to fix the plastic bottle 100.

[0043] In actual use, the positioning component is used to position the plastic bottle 100 in the conveyor line 2 to ensure that the plastic bottle 100 moves synchronously with the conveyor component.

[0044] In the above design, the positioning component effectively avoids pipe collisions, insertion failures, or cooling interruptions caused by bottle misalignment. At the same time, it ensures that the cooling pipe and the bottle mouth maintain precise alignment during the following movement. From the two dimensions of positional accuracy and motion stability, it guarantees the continuity and reliability of the cooling and secondary heating processes, significantly improving the operational stability of the device and the product yield.

[0045] Specifically: such as Figure 2 As shown, the external cooling mechanism includes a gas storage tank for storing cooling medium, a cooling gas delivery pipe 3 connected to the gas storage tank, and a sliding clamping assembly 4 for driving the cooling gas delivery pipe 3 to move synchronously along the conveyor line 2.

[0046] In actual use, the gas storage tank stores the cooling medium and provides a stable gas source for the system; the cooling gas delivery pipe 3 is connected to the gas storage tank and serves as a channel for delivering the cooling medium, introducing cold air into the bottle body; the sliding clamping assembly 4 drives the cooling gas delivery pipe 3 to move synchronously along the direction of the conveyor line 2, ensuring that the cooling gas delivery pipe 3 follows the plastic bottle 100 on the conveyor line 2 at the same speed after being inserted into the bottle mouth, thus achieving uninterrupted cooling during the conveying process.

[0047] In the above design, the external cooling mechanism can achieve a one-way constant temperature cold air purging mode for the plastic bottle 100.

[0048] Specifically: such as Figure 3As shown, the external cooling mechanism includes a gas storage tank for storing cooling medium, a cooling gas delivery pipe 3 connected to the gas storage tank, a sliding clamping assembly 4 for driving the cooling gas delivery pipe 3 to move synchronously along the conveyor line 2, a lifting assembly 5 that is horizontally moved by the sliding clamping assembly 4, a sealing head 6 and a suction pipe 7 disposed on the lifting assembly 5. The ends of the cooling gas delivery pipe 3 and the suction pipe 7 are fixedly disposed on the sealing head 6. The lifting assembly 5 drives the sealing head 6 to connect and seal with the bottle mouth of the plastic bottle 100, so that the air inlet of the suction pipe 7 and the air outlet of the cooling gas delivery pipe 3 extend into the interior of the plastic bottle 100, and the straight-line distance between the air inlet of the suction pipe 7 and the bottle mouth is less than the straight-line distance between the air outlet of the cooling gas delivery pipe 3 and the bottle mouth.

[0049] In actual use, the sliding clamping assembly 4 drives the lifting assembly 5 to move horizontally along the conveying direction. The lifting assembly 5 drives the sealing head 6 to rise and fall to connect and seal with the bottle mouth. The ends of the cooling gas supply pipe 3 and the suction pipe 7 are both fixed on the sealing head 6. The two are inserted into the bottle synchronously with the sealing head 6 to form a closed loop. The air inlet of the suction pipe 7 is configured to be closer to the bottle mouth than the air outlet of the cooling gas supply pipe 3: After the cold air enters the bottle from the air outlet of the cooling gas supply pipe 3, it flows towards the bottom of the bottle. After completing heat exchange with the high-temperature bottle wall in the bottom area, the temperature rises. The hot air, due to its lower density, naturally rises to the bottleneck area. The air inlet of the suction pipe 7 is located at this position, giving priority to discharging the rising hot air that has completed heat exchange, thereby effectively avoiding the problems of cold air short-circuiting and hot air retention.

[0050] In the above design, the external cooling mechanism can achieve a circulating, sealed, cold-in-hot-out heat exchange mode to cool the plastic bottle 100.

[0051] In further detail, it should be understood that the above description is only a specific embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A method for preventing shrink film from loosening during secondary heat shrinking outside the oven, characterized by: The process includes the following steps: S1, placing the plastic bottle (100) covered with shrink film in the heating mechanism (1) for heating, so that the shrink film shrinks and adheres to the surface of the plastic bottle (100); S2, removing the heated plastic bottle (100) from the heating mechanism (1), cooling the inside of the plastic bottle (100), so that the plastic bottle (100) cools down and shrinks back to its original size, and the shrink film that has adhered to the surface of the plastic bottle (100) loosens due to the shrinkage of the plastic bottle (100); S3, heating the shrink film a second time, so that the shrink film shrinks again and adheres to the surface of the shrunken plastic bottle (100).

2. The method for preventing shrink film from loosening in plastic bottles through secondary heat shrinking outside the oven according to claim 1, characterized in that: The cooling of the interior of the plastic bottle (100) described in S2 is achieved by introducing a cooling medium into the bottle through a cooling pipe inserted into the bottle opening of the plastic bottle (100).

3. The method for preventing shrink film from loosening in plastic bottles through secondary heat shrinking outside the oven according to claim 1, characterized in that: The cooling medium is introduced into the bottle through the cooling pipe in a one-way constant temperature cold air purging mode. The one-way constant temperature cold air purging mode is as follows: the cooling pipe continuously inputs constant temperature cold air into the bottle, and the hot air inside the bottle is naturally discharged from the gap between the bottle mouth and the cooling pipe.

4. The method for preventing shrink film from loosening in plastic bottles through secondary heat shrinking outside the oven according to claim 1, characterized in that: The cooling gas supply pipe (3) introduces the cooling medium into the bottle in a circulating sealed cold-in-hot-out heat exchange mode. The circulating sealed cold-in-hot-out heat exchange mode is as follows: after the bottle opening is sealed, the cooling gas supply pipe (3) and the inside of the plastic bottle (100) form a closed-loop airflow channel, and an air suction pipe (7) is connected to the outside of the bottle opening. The constant temperature cold air is continuously input into the bottle along one end of the closed-loop airflow channel, and the high temperature hot air in the bottle is discharged synchronously along the air suction pipe (7).

5. The method for preventing shrink film from loosening in plastic bottles through secondary heat shrinking outside the oven according to claim 1, characterized in that: The secondary heating is performed by using a hot air sweeping mechanism to heat the surface of the shrink film.

6. The method for preventing shrink film from loosening in plastic bottles through secondary heat shrinking outside the oven according to claim 1, characterized in that: The heating mechanism (1) is a heat shrink oven, and the cooling and the secondary heating are both completed outside the outlet of the heat shrink oven.

7. An external secondary heat shrink device for preventing shrink film from loosening in plastic bottles, used to implement the external secondary heat shrink method for preventing shrink film from loosening in plastic bottles as described in any one of claims 1 to 6, characterized in that: Heating mechanism (1) is used to heat the plastic bottle (100) covered with shrink film, so that the shrink film shrinks and adheres to the surface of the plastic bottle (100) by heat; An external cooling mechanism is located outside the outlet of the heating mechanism (1) and is used to cool the inside of the plastic bottle (100) after it has been heated by the heating mechanism (1), so that the plastic bottle (100) cools down and shrinks back to its original size; An external secondary heating mechanism (1) is located downstream of the external cooling mechanism and is used to perform secondary heating on the shrink film that has become loose due to the shrinkage of the plastic bottle (100), so that the shrink film shrinks again and adheres to the surface of the shrunken plastic bottle (100). The conveyor line (2) is used to carry the plastic bottle (100) and transport it sequentially through the heating mechanism (1), the external cooling mechanism and the external secondary heating mechanism (1).

8. The oven-mounted secondary heat shrink device for preventing shrink film from loosening on plastic bottles according to claim 1, characterized in that: The conveyor line (2) includes a conveyor line (2) and a positioning component disposed on the conveyor line (2), the positioning component being used to fix the plastic bottle (100).

9. The oven-mounted secondary heat shrink device for preventing shrink film from loosening on plastic bottles according to claim 1, characterized in that: The furnace cooling mechanism includes a gas storage tank for storing cooling medium, a cooling gas delivery pipe (3) connected to the gas storage tank, and a sliding clamping assembly (4) for driving the cooling gas delivery pipe (3) to move synchronously along the conveyor line (2).

10. The oven-mounted secondary heat shrink device for preventing shrink film from loosening on plastic bottles according to claim 1, characterized in that: The external cooling mechanism includes a gas storage tank for storing cooling medium, a cooling gas delivery pipe (3) connected to the gas storage tank, a sliding clamping assembly (4) for driving the cooling gas delivery pipe (3) to move synchronously along the conveyor line (2), a lifting assembly (5) that is moved horizontally by the sliding clamping assembly (4), a sealing head (6) set on the lifting assembly (5), and a suction pipe (7). The ends of the cooling gas delivery pipe (3) and the suction pipe (7) are fixedly set on the sealing head (6). The lifting assembly (5) drives the sealing head (6) to connect and seal with the mouth of the plastic bottle (100), so that the air inlet of the suction pipe (7) and the air outlet of the cooling gas delivery pipe (3) extend into the plastic bottle (100), and the straight distance between the air inlet of the suction pipe (7) and the mouth of the bottle is less than the straight distance between the air outlet of the cooling gas delivery pipe (3) and the mouth of the bottle.

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