Plastic packaging bag heat sealing device and method

Abstract

The invention relates to the technical field of heat sealing, and discloses a plastic packaging bag heat sealing device and a method thereof.The plastic packaging bag heat sealing device comprises a base and a groove formed in the base, and a heating roller set used for guiding a plastic packaging bag is installed at the front end of the top of the base; a positioning assembly used for driving a plastic packaging bag to move is arranged at the top of the base, a heat sealing mechanism is installed on the base at the front end of the positioning assembly, and a cooling mechanism is installed on the base at the tail end of the positioning assembly. The positioning assembly can drive the plastic packaging bag to be repeatedly transferred between the heat sealing mechanism and the cooling mechanism, so that a certain position of the plastic packaging bag can be subjected to heat sealing for multiple times, cooling is conducted through the cooling mechanism after heat sealing each time, then heat sealing of the next time is conducted, and the sealing firmness of the plastic packaging bag is effectively improved through multiple heat sealing operations; and meanwhile, displacement of the plastic packaging bag at the sealing position in the moving process is prevented.

Description

Technical Field

[0001] The invention relates to the technical field of heat sealing, in particular to a heat sealing device and method for a plastic packaging bag. Background Art

[0002] In the modern packaging industry, plastic packaging bags are widely used in product packaging in many fields such as food, daily chemicals, and medicine. The heat sealing quality of plastic packaging bags plays a vital role in the shelf life of the product, moisture-proof and leak-proof performance, and the integrity of the overall packaging.

[0003] Most traditional heat sealing devices for plastic packaging bags use a one-time heat sealing process. This one-time heat sealing method has obvious limitations when facing a variety of factors. First, different types of plastic films have different physical and chemical properties. For example, polyethylene (PE) film is relatively soft and has a low melting point, while polypropylene (PP) film is relatively stiff and has a high melting point. One-time heat sealing is difficult to accurately meet the heat sealing requirements of films of different materials, resulting in uneven fusion effects at the heat seal.

[0004] Secondly, there are also differences in the thickness of plastic packaging bags. Thinner films are prone to excessive melting due to rapid heat transfer during the primary heat sealing process, making the seal thinner and brittle, reducing the firmness of the seal. Thicker films may not be able to fully melt and fuse the inner layer due to insufficient heat and pressure during the primary heat sealing, resulting in a loose heat seal and gaps, which seriously affects the sealing of the packaging bag.

[0005] Furthermore, in the actual production environment, the working conditions of the heat sealing device are not completely stable. For example, as the number of heat sealing increases, the heating efficiency of the heating element may change, and the fluctuation of the ambient temperature and humidity may also interfere with the heat sealing effect. The one-time heat sealing method lacks an effective dynamic adjustment mechanism, and it is difficult to always ensure the stability of the heat seal quality under these changes.

[0006] In addition, for some products with extremely high requirements for sealing, such as high-end food and medicine, the packaging bags that have been heat-sealed once are prone to tiny cracks or debonding at the heat seals after being bumped and squeezed during transportation and storage, causing product leakage and deterioration, causing economic losses to the company and possibly affecting consumer health.

[0007] In summary, the traditional one-time heat-sealing plastic packaging bag heat-sealing device can hardly meet the strict requirements of the modern packaging industry for high sealing and high-quality heat-sealing effects. To this end, the present invention provides a plastic packaging bag heat-sealing device and method thereof. Summary of the invention

[0008] In view of the above-mentioned deficiencies in the prior art, the present invention provides a heat-sealing device and method for a plastic packaging bag, which performs multiple heat sealing at the heat-sealed opening and cools the opening, thereby improving the firmness of the plastic packaging bag seal.

[0009] The present invention provides the following technical solution: a heat-sealing device for plastic packaging bags, comprising a base and a groove formed on the base, a heating roller group for guiding the plastic packaging bag is installed at the front end of the top of the base, a positioning component for driving the plastic packaging bag to move is provided at the top of the base, a heat-sealing mechanism is installed on the base at the front end of the positioning component, a cooling mechanism is installed on the base at the end of the positioning component, the positioning component drives the plastic packaging bag to repeatedly transfer between the heat-sealing mechanism and the cooling mechanism, so that a certain part of the plastic packaging bag is heat-sealed for multiple times, and cooling is performed after each heat-sealing;

[0010] The base is provided with transmission rollers at both ends of the groove, two side plates are installed in the groove of the base, and linear modules are installed on the inner sides of the two side plates, and rotatable rollers are provided on the slides of the two linear modules. The plastic packaging bag passes through the bottom end of the roller, and the roller is driven by the linear module to move up and down in the groove. When the positioning assembly drives the plastic packaging bag to move, the roller moves with the linear module, so that the plastic packaging bag is in a taut state;

[0011] A pair of rollers for outputting plastic packaging bags is installed at the end of the top of the base, and the pair of rollers is driven by a motor.

[0012] Preferably, the positioning assembly includes two linear modules installed on a base, and a rectangular frame is installed on the slide of the two linear modules, the rectangular frame is provided with two positioning plates that can slide up and down, and the positioning plates slide up and down with the bottom end of the rectangular frame through positioning columns at both ends, the rectangular frame is provided with two electromagnets, and iron sheets are embedded in the positioning plates, and the positioning plates are adsorbed by the electromagnets to move up and clamp the plastic packaging bag with the rectangular frame, so that the rectangular frame clamps a certain section on the plastic packaging bag and moves under the drive of the two linear modules, so that the heat-sealed part of the plastic packaging bag undergoes multiple heat-sealing and cooling treatments by the heat-sealing mechanism and the cooling mechanism.

[0013] Preferably, the heat sealing mechanism includes a U-shaped bracket installed on the base and a support frame installed inside the base, the U-shaped bracket and the support frame are both provided with slidable guide columns, and heat sealing blocks are installed on the guide columns, the U-shaped bracket and the support frame are both provided with A electric cylinders for pushing the heat sealing blocks to move, and the base is provided with a rectangular opening for the heat sealing blocks to pass through, and the two A electric cylinders are driven simultaneously to enable the two heat sealing blocks to heat seal the plastic packaging bag from upper and lower positions.

[0014] Preferably, the heat sealing block includes an insulating shell and an electric heating rod installed inside the insulating shell, and the interior of the insulating shell is filled with heat-conducting oil for heat conduction. A heat-conducting plate is installed on the top of the insulating shell, and a layer of hot-melt cloth is covered on the heat-conducting plate. The heat-conducting oil is heated by the electric heating rod so that the heat-conducting oil transfers the heat evenly to the heat-conducting plate. The temperature on the heat-conducting plate is evenly distributed and the plastic packaging bag is heat-sealed.

[0015] Preferably, the cooling mechanism includes an air guide frame installed on a base, the bottom end of the air guide frame is provided with a nozzle for cooling the plastic packaging bag, an electric cylinder B is installed inside the base, and the movable end of the electric cylinder B is connected to the cooling block, the base is provided with a movable port for exporting the cooling block, a radiator and a water pump are provided inside the base, the water inlet on the cooling block is connected to the water pump through a pipe, and the water pump and the radiator are connected through a pipe, the water outlet on the cooling block is connected to the radiator through a pipe, and a fan is provided inside the base, and the fan transmits wind to the air guide frame and the radiator through the pipe respectively.

[0016] Preferably, the radiator includes a rectangular shell and several groups of cooling fins installed inside the rectangular shell, and the cooling fins are provided with circuitously distributed heat pipes. An air guide cover is installed at one end of the rectangular shell, and the fan is connected to the air guide cover through a pipe, so that the wind cools the cooling fins.

[0017] A heat sealing method for a plastic packaging bag, the specific operations are as follows:

[0018] S1, the plastic packaging bag is heated by a heating roller group, passes through a heat sealing mechanism and passes through a positioning assembly, then passes through a cooling mechanism, passes through the bottom of the roller shaft, and finally leads out of a pair of rollers;

[0019] S2, first, the positioning component clamps the plastic packaging bag on the heat-sealing mechanism, and the heat-sealing mechanism heat-seals the plastic packaging bag at the clamping position of the positioning component, then the positioning component drives the plastic packaging bag to move to the cooling mechanism, and at the same time, the linear module drives the roller to move downward in the groove to tighten the plastic packaging bag, and when the plastic packaging bag moves to the cooling mechanism, the cooling mechanism cools the heat-sealed portion of the plastic packaging bag;

[0020] S3, after cooling, the positioning assembly drives the plastic packaging bag back to the heat sealing mechanism for secondary heat sealing, and at the same time, the linear module drives the roller to move upward in the groove, and then the operation in step 2 is performed to perform secondary heat sealing on the plastic packaging bag;

[0021] S4. After the secondary heat sealing, the positioning component releases the plastic packaging bag and drives the plastic packaging bag to output the set length through the roller group. Then the positioning component clamps the plastic packaging bag again and drives the clamped part of the plastic packaging bag to move to the heat sealing mechanism. At the same time, the linear module drives the roller to move up in the groove to restore the principle. The plastic packaging bag is repeatedly heat-sealed at a fixed distance.

[0022] Compared with the prior art, the present invention has the following beneficial effects:

[0023] (1) The positioning component can drive the plastic packaging bag to repeatedly transfer between the heat sealing mechanism and the cooling mechanism, so that a certain part of the plastic packaging bag can be heat-sealed multiple times. After each heat sealing, the bag is cooled by the cooling mechanism before the next heat sealing. The multiple heat sealing operations effectively improve the firmness of the plastic packaging bag seal, and prevent the plastic packaging bag from being displaced at the seal during the movement. The heat-sealed part of the plastic packaging bag is clamped to facilitate positioning during the movement, so that the plastic packaging bag is in the same position during multiple heat sealing operations.

[0024] (2) The heating roller group heats the entire roll of plastic packaging bags, avoiding the thermal stress caused by local heating at the seal, which may cause micro cracks at the seal or weaken the connection between the seal and the bag body. By properly heating the entire bag body, the temperature difference is reduced, thereby extending the service life of the packaging bag and ensuring the sealing of the seal;

[0025] (3) The design of the heat sealing mechanism adopts double-sided heat sealing to better fuse the two layers of plastic film, further improving the firmness of the heat seal, while avoiding the heat seal strength deviation caused by uneven temperature during heat sealing, and preventing local overheating that causes excessive melting of the material or local insufficient temperature that causes a loose heat seal;

[0026] (4) The linear module is used to drive the roller to move, so that the plastic packaging bag is always kept in a taut state. In this way, when the roller group outputs the plastic packaging bag at a fixed distance, the error can be reduced, which is conducive to accurately controlling the fixed-distance conveying and packaging process of the packaging bag;

[0027] (5) The cooling mechanism adopts a combination of two cooling methods. On the one hand, the plastic packaging bag is cooled by wind; on the other hand, the cooling block is brought into contact with the sealed bottom surface of the plastic packaging bag to cool it. Under the action of wind, the plastic packaging bag is close to the cooling block to transfer and dissipate heat. This dual cooling method can quickly and effectively reduce the temperature after heat sealing, improve production efficiency, and avoid the problem of extrusion caused by heat dissipation during contact. BRIEF DESCRIPTION OF THE DRAWINGS

[0028] Figure 1 It is a schematic diagram of the overall structure of the present invention;

[0029] Figure 2For the present invention Figure 1 Schematic diagram of the local structure;

[0030] Figure 3 It is a schematic diagram of the positioning component of the present invention;

[0031] Figure 4 It is a schematic diagram of the heat sealing mechanism of the present invention;

[0032] Figure 5 It is a schematic diagram of the heat sealing block of the present invention;

[0033] Figure 6 It is a schematic diagram of the cooling mechanism of the present invention;

[0034] Figure 7 It is a schematic diagram of the structure of the radiator of the present invention.

[0035] In the figure: 1. base; 2. groove; 3. heating roller group; 4. positioning assembly; 5. heat sealing mechanism; 6. cooling mechanism; 7. transmission roller; 8. side plate; 9. linear module; 10. roller; 11. roller group; 41. linear module; 42. rectangular frame; 43. positioning plate; 44. positioning column; 45. electromagnet; 51. U-shaped bracket; 52. support frame; 53. guide column; 54. heat sealing block; 55. electric cylinder A; 541. heat insulation shell; 542. electric heating rod; 543. heat conduction plate; 544. hot melt cloth; 61. air guide frame; 62. nozzle; 63. electric cylinder B; 64. cooling block; 65. radiator; 66. water pump; 67. fan; 651. rectangular shell; 652. cooling fins; 653. heat pipe; 654. air guide cover. DETAILED DESCRIPTION

[0036] In order to make the objectives, technical solutions and advantages of the embodiments of the present disclosure clearer, the technical solutions of the embodiments of the present disclosure will be clearly and completely described below in conjunction with the drawings of the embodiments of the present disclosure. In order to keep the following description of the embodiments of the present disclosure clear and concise, the present disclosure omits detailed descriptions of known functions and known components to avoid unnecessary confusion of the concepts of the present invention.

[0037] See also Figure 1 and Figure 2 A heat sealing device for plastic packaging bags is mainly composed of a base 1, a groove 2, a heating roller group 3, a positioning component 4, a heat sealing mechanism 5, a cooling mechanism 6, a transmission roller 7, a side plate 8, a linear module 9, a roller shaft 10 and a pair of rollers 11.

[0038] A heating roller group 3 is provided at the front end of the base 1 for guiding the plastic packaging bag, and the heating roller group 3 heats the rolled plastic packaging bag. During the heat sealing process, if only the seal is quickly and locally heated, a large temperature difference will occur between the seal and the surrounding unheated parts. This temperature difference will cause thermal stress, just like a piece of hot metal suddenly put into cold water will produce stress. For plastic packaging bags, thermal stress may cause tiny cracks at the seal or weaken the connection between the seal and other parts of the bag body. Proper heating of the entire bag body can reduce this temperature difference, thereby reducing thermal stress, extending the service life of the packaging bag and ensuring the sealing of the seal.

[0039] A positioning component 4 is provided on the top of the base 1 to drive the plastic packaging bag to move, a heat sealing mechanism 5 is installed at the front end of the positioning component 4, and a cooling mechanism 6 is installed at the end. The positioning component 4 can drive the plastic packaging bag to repeatedly transfer between the heat sealing mechanism 5 and the cooling mechanism 6, so that a certain part of the plastic packaging bag can be heat-sealed multiple times and cooled after each heat sealing.

[0040] The positioning component 4 is used to clamp a specific part of the roll-shaped plastic packaging bag, so that it is repeatedly heat-sealed and cooled between the heat-sealing mechanism 5 and the cooling mechanism 6. The firmness of the seal of the plastic packaging bag is improved by multiple heat sealings, and the heat-sealing mechanism 5 and the cooling mechanism 6 need to be restored to their original positions after each heat sealing and cooling, so that the positioning component 4 can move back and forth between the heat-sealing mechanism 5 and the cooling mechanism 6 without obstruction.

[0041] Transmission rollers 7 are arranged at both ends of the groove 2 of the base 1, two side plates 8 are installed in the groove 2, and a rotatable roller shaft 10 is arranged on the linear module 9 on the inner side of the side plate 8. The plastic packaging bag passes through the bottom end of the roller shaft 10, and the linear module 9 drives the roller shaft 10 to move up and down in the groove 2. When the positioning component 4 drives the plastic packaging bag to move, the roller shaft 10 moves with the linear module 9 to keep the plastic packaging bag in a taut state. A pair of rollers 11 driven by a motor is installed at the top end of the base 1 for outputting the plastic packaging bag.

[0042] The linear module 9 is used to drive the roller 10 to move, so that the plastic packaging bag is kept in a uniformly taut state, so that the roller group 11 can reduce the error when outputting the plastic packaging bag at a fixed distance, and the two transmission rollers 7 are equipped to reduce the friction between the plastic packaging bag and the groove 2.

[0043] See also Figure 3 The positioning assembly 4 includes two linear modules 41 mounted on the base 1. A rectangular frame 42 is mounted on the slide of the linear module 41. A positioning plate 43 that can slide up and down is provided on the rectangular frame 42. The positioning plate 43 is slidably connected to the bottom of the rectangular frame 42 through positioning columns 44 at both ends. There are two electromagnets 45 on the rectangular frame 42. An iron sheet is embedded on the positioning plate 43.

[0044] The electromagnet 45 is energized and adsorbed to move the positioning plate 43 upward to clamp the plastic packaging bag with the rectangular frame 42, so that the two positioning plates 43 and the rectangular frame 42 clamp a section of the plastic packaging bag to prevent the plastic packaging bag from being displaced during the movement. The rectangular frame 42 moves under the drive of the two linear modules 41, so that the heat-sealed part is subjected to multiple heat-sealing and cooling treatments by the heat-sealing mechanism 5 and the cooling mechanism 6. In this way, the clamped part of the plastic packaging bag moves under the drive of the linear module 41, which is convenient for controlling its position and accurately positioning it on the heat-sealing mechanism 5 and the cooling mechanism 6 during repeated movement. In this way, when the heat-sealing mechanism 5 is heat-sealed, it can be heat-sealed at the same position for multiple times, avoiding the displacement of the heat-sealed position and causing damage during multiple heat-sealing processes.

[0045] See also Figure 4 The heat sealing mechanism 5 is composed of a U-shaped bracket 51 installed on the base 1 and a support frame 52 inside the base 1. The U-shaped bracket 51 and the support frame 52 are both provided with a slidable guide column 53, and a heat sealing block 54 is installed on the guide column 53. The U-shaped bracket 51 and the support frame 52 are both provided with an A electric cylinder 55 for pushing the heat sealing block 54 to move. There is a rectangular opening on the base 1 for the heat sealing block 54 to pass through. Two A electric cylinders 55 are driven simultaneously to make the two heat sealing blocks 54 heat-seal the plastic packaging bag from the upper and lower positions. The double-sided heat sealing method is used to provide the plastic packaging bag with firmness.

[0046] See also Figure 5 The heat sealing block 54 includes a heat insulating shell 541 with an electric heating rod 542 installed inside. The heat insulating shell 541 is filled with heat conducting oil. A heat conducting plate 543 is provided at the top of the heat insulating shell 541. A hot melt cloth 544 is covered on the heat conducting plate 543. The electric heating rod 542 heats the heat conducting oil. The heat conducting oil has good thermal conductivity. The heat is evenly transferred to the heat conducting plate 543 for heat sealing. If the temperature of the heat conducting plate 543 is uneven, it will cause a large deviation in the heat sealing strength test result. Local overheating may cause excessive melting of the material and reduce the heat sealing strength. Insufficient local temperature may cause the heat sealing to be loose, which also affects the accuracy of the heat sealing strength.

[0047] See also Figure 6 and Figure 7The cooling mechanism 6 includes an air guide frame 61 installed on the base 1. The bottom of the air guide frame 61 has a nozzle 62 to cool the plastic packaging bag. The base 1 has a B electric cylinder 63 inside, and its movable end is connected to the cooling block 64. The base 1 has a movable port for the cooling block 64 to be led out. The base 1 is provided with a radiator 65 and a water pump 66 inside. The water inlet of the cooling block 64 is connected to the water pump 66. There are pipes connecting the water pump 66 and the radiator 65, and the water outlet of the cooling block 64 and the radiator 65. There is also a fan 67 inside the base 1. The fan 67 transmits wind to the air guide frame 61 and the radiator 65 through the pipe. The radiator 65 includes a rectangular shell 651, and there are several groups of heat dissipation fins 652 inside. The heat dissipation fins 652 have circuitously distributed heat conduction pipes 653. There is a wind guide cover 654 at one end of the rectangular shell 651. The fan 67 is connected to the wind guide cover 654 through a pipe to cool the heat dissipation fins 652.

[0048] The B electric cylinder 63 drives the cooling block 64 to be guided out from the base 1 and contact the bottom surface of the plastic packaging bag seal, and the nozzle 62 on the air guide frame 61 blows air to cool the plastic packaging bag seal below. Under the wind force, the plastic packaging bag is tightly attached to the cooling block 64, and the cooling block 64 is used to cool the plastic packaging bag seal again. In this cooling process, the fan 67 continues to output and provides wind force to the nozzle 62 and the radiator 65. The water pump 66 guides the liquid in the cooling block 64 out of the radiator 65, cools it by wind force, and then re-introduces it into the cooling block 64, thus forming a cooling cycle. Using wind force to cool down and the cooling block 64 to cool down again can avoid the two cooling blocks 64 from contacting the plastic packaging bag seal together. If the contact pressure is too large, it will affect the sealing of the plastic packaging bag seal.

[0049] A heat sealing method for a plastic packaging bag, the specific operations are as follows:

[0050] S1, the plastic packaging bag is heated by the heating roller group 3, passes through the heat sealing mechanism 5 and passes through the positioning assembly 4, then passes through the cooling mechanism 6, passes through the bottom of the roller shaft 10, and finally leads out from the roller group 11;

[0051] S2, first, the positioning component 4 clamps the plastic packaging bag on the heat-sealing mechanism 5, and the heat-sealing mechanism 5 heat-seals the plastic packaging bag at the clamping position of the positioning component 4, then the positioning component 4 drives the plastic packaging bag to move to the cooling mechanism 6, and at the same time, the linear module 9 drives the roller 10 to move downward in the groove 2 to tighten the plastic packaging bag, and when the plastic packaging bag moves to the cooling mechanism 6, the cooling mechanism 6 cools the heat-sealed position of the plastic packaging bag;

[0052] S3, after cooling, the positioning assembly 4 drives the plastic packaging bag back to the heat sealing mechanism 5 for secondary heat sealing, and at the same time, the linear module 9 drives the roller 10 to move upward in the groove 2, and then the operation in step 2 is performed to perform secondary heat sealing on the plastic packaging bag;

[0053] S4. After the secondary heat sealing, the positioning component 4 releases the plastic packaging bag and drives the plastic packaging bag to output a set length through the roller group 11. Then the positioning component 4 clamps the plastic packaging bag again and drives the clamped part of the plastic packaging bag to move to the heat sealing mechanism 5. At the same time, the linear module 9 drives the roller 10 to move upward in the groove 2 to restore the principle. The plastic packaging bag is repeatedly heat-sealed at a fixed distance.

[0054] The above embodiments are only exemplary embodiments of the present invention and are not intended to limit the present invention. The protection scope of the present invention is defined by the claims. Those skilled in the art may make various modifications or equivalent substitutions to the present invention within the essence and protection scope of the present invention, and such modifications or equivalent substitutions shall also be deemed to fall within the protection scope of the present invention.

Claims

1. A heat sealing device for plastic packaging bags, characterized in that: The invention comprises a base (1) and a groove (2) formed on the base (1); a heating roller group (3) for guiding a plastic packaging bag is installed at the front end of the top of the base (1); a positioning component (4) for driving the plastic packaging bag to move is provided at the top of the base (1); a heat sealing mechanism (5) is installed on the base (1) at the front end of the positioning component (4); a cooling mechanism (6) is installed on the base (1) at the end of the positioning component (4); the positioning component (4) drives the plastic packaging bag to repeatedly transfer between the heat sealing mechanism (5) and the cooling mechanism (6), so that a certain part of the plastic packaging bag is heat-sealed for multiple times, and cooling is performed after each heat sealing; The base (1) is provided with transmission rollers (7) at both ends of the groove (2), the groove (2) of the base (1) is provided with two side plates (8), and the inner sides of the two side plates (8) are provided with linear modules (9), and the slides of the two linear modules (9) are provided with rotatable rollers (10), the plastic packaging bag passes through the bottom end of the rollers (10), and the rollers (10) are driven by the linear modules (9) to move up and down in the groove (2), and when the positioning assembly (4) drives the plastic packaging bag to move, the rollers (10) move along with the linear modules (9), so that the plastic packaging bag is in a taut state; A pair of rollers (11) for outputting plastic packaging bags is installed at the end of the top of the base (1), and the pair of rollers (11) is driven by a motor.

2. A heat sealing device for plastic packaging bags according to claim 1, characterized in that: The positioning assembly (4) comprises two linear modules (41) mounted on a base (1), and a rectangular frame (42) is mounted on the slides of the two linear modules (41). The rectangular frame (42) is provided with two positioning plates (43) that can slide up and down, and the positioning plates (43) slide up and down with the bottom of the rectangular frame (42) through positioning columns (44) at both ends. The rectangular frame (42) is provided with two electromagnets (45), and an iron sheet is embedded on the positioning plate (43). The electromagnets (45) adsorb the positioning plates (43) so that the positioning plates (43) move up and clamp the plastic packaging bag with the rectangular frame (42), so that the rectangular frame (42) clamps a certain section on the plastic packaging bag and moves under the drive of the two linear modules (41), so that the heat-sealed portion of the plastic packaging bag undergoes multiple heat-sealing and cooling treatments by the heat-sealing mechanism (5) and the cooling mechanism (6).

3. A heat sealing device for plastic packaging bags according to claim 1, characterized in that: The heat sealing mechanism (5) comprises a U-shaped bracket (51) mounted on a base (1) and a support frame (52) mounted inside the base (1); the U-shaped bracket (51) and the support frame (52) are both provided with slidable guide pillars (53), and the guide pillars (53) are both provided with heat sealing blocks (54); the U-shaped bracket (51) and the support frame (52) are both provided with A electric cylinders (55) for pushing the heat sealing blocks (54) to move; and the base (1) is provided with a rectangular opening for the heat sealing blocks (54) to pass through, and two A electric cylinders (55) are driven simultaneously, so that the two heat sealing blocks (54) heat seal the plastic packaging bag from upper and lower positions.

4. A heat sealing device for plastic packaging bags according to claim 3, characterized in that: The heat sealing block (54) comprises a heat insulating shell (541) and an electric heating rod (542) installed inside the heat insulating shell (541), and the inside of the heat insulating shell (541) is filled with heat conducting oil for heat conduction, and a heat conducting plate (543) is installed on the top of the heat insulating shell (541), and a layer of hot melt cloth (544) is coated on the heat conducting plate (543). The heat conducting oil is heated by the electric heating rod (542), so that the heat conducting oil transfers heat evenly to the heat conducting plate (543), and the temperature on the heat conducting plate (543) is evenly distributed and the plastic packaging bag is heat-sealed.

5. A heat sealing device for plastic packaging bags according to claim 1, characterized in that: The cooling mechanism (6) comprises an air guide frame (61) mounted on a base (1), the bottom end of the air guide frame (61) being provided with a nozzle (62) for cooling the plastic packaging bag, an electric cylinder (63) located at B being mounted inside the base (1), and the movable end of the electric cylinder (63) being connected to a cooling block (64), a movable port for guiding out the cooling block (64) being provided on the base (1), a radiator (65) and a water pump (66) being provided inside the base (1), a water inlet on the cooling block (64) being connected to the water pump (66) through a pipeline, and the water pump (66) and the radiator (65) being connected through a pipeline, a water outlet on the cooling block (64) being connected to the radiator (65) through a pipeline, and a fan (67) being provided inside the base (1), and the fan (67) conveying wind to the air guide frame (61) and the radiator (65) respectively through the pipeline.

6. A heat sealing device for plastic packaging bags according to claim 5, characterized in that: The radiator (65) comprises a rectangular shell (651) and a plurality of groups of heat dissipation fins (652) installed inside the rectangular shell (651), and the heat dissipation fins (652) are provided with heat conduction pipes (653) distributed in a circuitous manner. An air guide cover (654) is installed at one end of the rectangular shell (651), and the fan (67) is connected to the air guide cover (654) through a pipeline, so that the wind force cools the heat dissipation fins (652).

7. A method for heat sealing a plastic packaging bag, characterized in that: The heat sealing device for plastic packaging bags according to any one of claims 1 to 6 is used, and the specific operations are as follows: S1, the plastic packaging bag is heated by a heating roller group (3), passes through a heat sealing mechanism (5) and passes through a positioning assembly (4), then passes through a cooling mechanism (6), passes through the bottom of a roller shaft (10), and finally is led out from a pair of rollers (11); S2, first, the positioning component (4) clamps the plastic packaging bag located on the heat-sealing mechanism (5), and the heat-sealing mechanism (5) heat-seals the plastic packaging bag at the clamping position of the positioning component (4), then the positioning component (4) drives the plastic packaging bag to move to the cooling mechanism (6), and at the same time the linear module (9) drives the roller (10) to move downward in the groove (2), so that the plastic packaging bag is tightened, and when the plastic packaging bag moves to the cooling mechanism (6), the cooling mechanism (6) cools the heat-sealed portion of the plastic packaging bag; S3, after cooling, the positioning assembly (4) drives the plastic packaging bag back to the heat sealing mechanism (5) for secondary heat sealing, and at the same time, the linear module (9) drives the roller (10) to move upward in the groove (2), and then the operation in step 2 is performed to perform secondary heat sealing on the plastic packaging bag; S4. After the second heat sealing, the positioning component (4) releases the plastic packaging bag and drives the plastic packaging bag to output a set length through the roller group (11). Then the positioning component (4) clamps the plastic packaging bag again and drives the clamped part of the plastic packaging bag to move to the heat sealing mechanism (5). At the same time, the linear module (9) drives the roller (10) to move upward in the groove (2) to restore the principle. The plastic packaging bag is repeatedly heat-sealed at a fixed distance.

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