A tensile test device for plastic film

Abstract

The present invention belongs to the technical field of thin film tensile testing devices, and particularly relates to a plastic thin film tensile testing device, including: a detection bottom plate, two moving plates are slidably connected to the upper end of the detection bottom plate in the horizontal direction; a stretching mechanism, which is arranged at the upper end of the detection bottom plate and is used to drive the two moving plates to move away from each other; a clamping mechanism, which has two and is symmetrically arranged on the relative sides of the two moving plates and is used to clamp and fix the plastic thin film. The clamping mechanism includes a fixed block fixedly connected to the side wall of the moving plate. By setting a length adjustment mechanism in the present invention, during the clamping process, for plastic thin films of different thicknesses, the downward sliding distance of the pressing block is also different, so that the pressure received by the piezoresistor below the pressing block is different, and the stretching parameters for the plastic thin film can be adaptively adjusted according to the thickness of the thin film, making the detected tensile strength of the plastic thin film more consistent with the actual performance.

Description

Technical Field

[0001] The present invention belongs to the technical field of thin film tensile testing devices, and particularly relates to a plastic film tensile testing device. Background Art

[0002] A plastic film tensile testing device is an experimental equipment used to test the mechanical properties of plastic films under tensile forces. It is mainly used to measure key parameters such as the tensile strength, elongation rate, and elastic modulus of the film. These data are crucial for evaluating the quality and performance of plastic films, so it is widely used in fields such as quality control, research and development, product design, and certification of plastic films.

[0003] However, existing tensile testing devices, such as a plastic film tensile testing device and testing method disclosed in Chinese Patent Publication No. CN118670869B, still have the following technical problems during use:

[0004] During the tensile test, it is impossible to precisely control the tensile length according to the thickness of the plastic film. For thinner plastics, a relatively smaller tensile length is required, otherwise the plastic film is likely to break prematurely and no effective test data can be obtained. For thicker plastic films, a relatively larger tensile length is required, otherwise the degree of stretching is likely to be too small, thus unable to fully test the tensile properties of the film, making the tensile test results of the plastic film unrepresentative and resulting in the measured tensile strength not conforming to the actual performance. Summary of the Invention

[0005] The purpose of the present invention is to address the problems raised in the above background art and provide a plastic film tensile testing device that can adaptively adjust the tensile parameters according to the thickness of the film, making the detected tensile strength of the plastic film more consistent with the actual performance.

[0006] To achieve the above purpose, the present invention adopts the following technical solutions:

[0007] A plastic film tensile testing device includes:

[0008] A detection base plate, on the upper end of which two moving plates are slidably connected in the horizontal direction;

[0009] A tensile mechanism, arranged on the upper end of the detection base plate and used to drive the two moving plates to move away from each other;

[0010] The clamping mechanism has two and is symmetrically arranged on the opposite side of the two moving plates for clamping and fixing the plastic film. The clamping mechanism includes a fixed block fixedly connected to the side wall of the moving plate. A sliding block is slidably connected to the side wall of the moving plate. Opposite sides of the fixed block and the sliding block are symmetrically and fixedly connected with mounting frames. A moving box is slidably connected inside the mounting frames. Clamping boxes are fixedly connected to opposite sides of the moving box. A plurality of adsorption holes distributed in a rectangular array are formed on the side of the clamping box away from the moving box. A pressing block is fixedly connected to the sliding block;

[0011] The driving mechanism is arranged on the side wall of the moving plate and is used to drive the sliding block to slide in the vertical direction.

[0012] Preferably, a length adjusting mechanism is further provided on the side wall of the moving plate for adjusting the stretching length of the plastic film according to the thickness of the plastic film. The length adjusting mechanism includes a piezoresistor fixedly connected to the lower end of the pressing block. An elastic telescopic rod is fixedly connected to the side of the moving plate close to the piezoresistor through a stop block. The telescopic end of the elastic telescopic rod is fixedly connected with a top block. Electromagnets are symmetrically and fixedly connected to the sides of the moving box and the mounting frame close to each other. When the two electromagnets are energized, the same poles repel each other. The two electromagnets are connected in series with a power supply device through the piezoresistor. A compression spring is further arranged between the moving box and the mounting frame.

[0013] Preferably, the stretching mechanism includes two first mounting blocks fixedly connected to the upper end of the detection bottom plate. A bidirectional lead screw is rotatably connected between the two first mounting blocks. The spiral directions of the threads on both sides of the bidirectional lead screw are opposite. The two moving plates are respectively in threaded cooperation with the threads on both sides of the bidirectional lead screw. A first motor for driving the bidirectional lead screw is arranged on the side wall of one of the first mounting blocks.

[0014] Preferably, the driving mechanism includes two second mounting blocks fixedly connected to the side wall of the moving plate. A threaded rod is rotatably connected between the two second mounting blocks. The pressing block is in threaded cooperation with the threaded rod. A second motor for driving the threaded rod is fixedly connected to one of the second mounting blocks.

[0015] Preferably, a vertical limiting groove is formed on the moving plate. The pressing block extends to one side of the threaded rod through the vertical limiting groove, and the pressing block is slidably connected to the inner wall of the vertical limiting groove.

[0016] Preferably, a force adjustment mechanism is provided inside the installation frame for adjusting the adsorption force on the plastic film according to the thickness of the plastic film. The force adjustment mechanism includes a push rod fixedly connected to the inner wall of the installation frame. A partition plate is fixedly connected inside the moving box. The internal space of the moving box is divided into a liquid storage chamber and a gas storage chamber by the partition plate. One end of the push rod penetrates the installation frame, extends into the liquid storage chamber and is fixedly connected with a piston plate. The piston plate is airtightly connected to the inner wall of the liquid storage chamber. The partition plate is fixedly communicated with an infusion tube. A control chamber is opened inside the moving box. The liquid storage chamber is communicated with the control chamber through the infusion tube. A lifting block is airtightly and slidably connected to the inner wall of the control chamber. A lifting plate is airtightly and slidably connected inside the clamping box. A connecting rod is fixedly connected between the lifting block and the lifting plate.

[0017] Preferably, a telescopic airbag is fixedly communicated with the part of the infusion tube located in the gas storage chamber, and a switching valve is arranged inside the infusion tube close to the control chamber.

[0018] Preferably, an extension block is fixedly connected to the moving box. A horizontal limit groove is opened on the outer wall of the installation frame. The upper end of the extension block passes through the horizontal limit groove and is fixed with a moving rack. A locking gear is rotatably connected to the side wall of the moving plate through a mounting plate. An electric telescopic rod is also fixedly connected to the side wall of the moving plate. The output end of the electric telescopic rod is fixedly connected with a locking rack. The locking rack and the moving rack are respectively engaged with both sides of the locking gear.

[0019] Preferably, an impact resistance test mechanism is provided on the outer wall of the installation frame fixed to the moving box for performing an impact resistance test on the plastic film and automatically adjusting the impact force according to the thickness of the plastic film. The impact resistance test mechanism includes a guide rail fixedly connected to the outer wall of the installation frame. A counterweight plate is slidably connected in the guide rail along the vertical direction. An air spring is fixedly connected to the lower end of the counterweight plate. An impact block is fixedly connected to the lower end of the air spring. An exhaust plate is airtightly and slidably connected inside the gas storage chamber. An air delivery hose is communicated between the air spring and the space above the exhaust plate in the gas storage chamber.

[0020] Preferably, a wedge-shaped clamping block is arranged at the position of the outer wall of the installation frame inside the guide rail.

[0021] Compared with the existing technology, the advantages of this plastic film tensile test device are as follows:

[0022] 1. By providing a length adjustment mechanism, during the clamping process, for plastic films of different thicknesses, the distance that the pressing block slides downward is different, so that the pressure on the piezoresistor below the pressing block is different. For thinner plastic films, the stretching length is relatively small, thus avoiding premature breakage of the plastic film. For thicker plastic films, the stretching length is relatively large, thus avoiding insufficient stretching degree that may lead to inability to fully test the tensile properties of the film. It can adaptively adjust the stretching parameters according to the thickness of the film, making the detected tensile strength of the plastic film more consistent with its actual performance.

[0023] 2. By providing a force adjustment mechanism, while adjusting the stretching length according to the film thickness, due to the relative displacement between the moving box and the mounting frame, the adsorption force of the clamping box on the plastic film can be adjusted. For thinner plastic films, the air pressure difference between the clamping box and the outside is relatively large, enabling the plastic film to quickly adhere to the mold surface and avoiding wrinkles on the thinner plastic film. For thicker plastic films, the air pressure difference between the clamping box and the outside is relatively small, preventing excessive deformation or stretching of the plastic film caused by applying too large an air pressure difference, or even causing rupture or permanent deformation.

[0024] 3. By providing an impact resistance test mechanism, when the plastic film is thinner, the expansion degree of the telescopic airbag is larger, making the impact block located at a relatively lower height below the counterweight plate. Thus, when the plastic film is thinner, a smaller impact force is applied to the plastic film. When the plastic film is thicker, the expansion degree of the telescopic airbag is smaller, resulting in a smaller air pressure in the air spring and making the impact block located at a relatively higher height below the counterweight plate. Thus, when the plastic film is thicker, a larger impact force is applied to the plastic film. It can not only perform the impact resistance test on the plastic film, but also automatically change the impact force on the plastic film according to the thickness of the plastic film, improving the detection accuracy of the impact resistance test. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] Figure 1 is a three - dimensional structural schematic diagram of the present invention;

[0026] Figure 2 is Figure 1 the enlarged view of part A in

[0027] Figure 3 is Figure 1 the enlarged view of part B in

[0028] Figure 4 is Figure 1 the enlarged view of part C in

[0029] Figure 5 is the sectional structural schematic diagram of the mounting frame in the present invention;

[0030] Figure 6 Yes Figure 5 It is an enlarged view of part D in the figure.

[0031] In the figure: 1. Detection base plate; 11. Moving plate; 2. Tensile mechanism; 21. First mounting block; 22. Bidirectional lead screw; 23. First motor; 3. Clamping mechanism; 31. Fixed block; 32. Sliding block; 33. Mounting frame; 34. Moving box; 341. Extension block; 342. Horizontal limiting groove; 343. Moving rack; 344. Locking gear; 345. Electric telescopic rod; 346. Locking rack; 35. Clamping box; 36. Adsorption hole; 37. Pressing block; 4. Length adjustment mechanism; 41. Pressure-sensitive resistor; 42. Elastic telescopic rod; 43. Top block; 44. Electromagnet; 45. Compression spring; 5. Driving mechanism; 51. Second mounting block; 52. Threaded rod; 53. Second motor; 6. Vertical limiting groove; 7. Force adjustment mechanism; 71. Push rod; 72. Partition plate; 73. Liquid storage chamber; 74. Gas storage chamber; 75. Piston plate; 76. Liquid infusion pipe; 761. Telescopic airbag; 762. Opening and closing valve; 77. Control chamber; 78. Lifting block; 79. Lifting plate; 710. Connecting rod; 8. Impact resistance test mechanism; 81. Guide rail; 82. Counterweight plate; 83. Air spring; 84. Impact block; 85. Exhaust plate; 86. Gas transmission hose; 9. Wedge-shaped block. Specific implementation mode

[0032] The following embodiments are for illustrative purposes only and are not intended to limit the scope of the present invention.

[0033] Embodiment: Refer to Figures 1 to 6 A tensile test device for plastic film, comprising:

[0034] A detection base plate 1, and two moving plates 11 are slidably connected to the upper end of the detection base plate 1 in the horizontal direction;

[0035] A tensile mechanism 2, which is arranged at the upper end of the detection base plate 1 and is used to drive the two moving plates 11 to move away from each other. The tensile mechanism 2 includes two first mounting blocks 21 fixedly connected to the upper end of the detection base plate 1. A bidirectional lead screw 22 is rotatably connected between the two first mounting blocks 21. The spiral directions of the threads on both sides of the bidirectional lead screw 22 are opposite. The two moving plates 11 are respectively in threaded cooperation with the threads on both sides of the bidirectional lead screw 22. A first motor 23 for driving the bidirectional lead screw 22 is provided on the side wall of one of the first mounting blocks 21. During the tensile test, by driving the bidirectional lead screw 22 to rotate through the first motor 23, the two moving plates 11 can be driven to move away from each other, so as to perform a tensile test on the plastic film after clamping.

[0036] The clamping mechanism 3, having two and symmetrically arranged on the opposite sides of the two moving plates 11, is used to clamp and fix the plastic film. The clamping mechanism 3 includes a fixed block 31 fixedly connected to the side wall of the moving plate 11. A sliding block 32 is slidably connected to the side wall of the moving plate 11 above the fixed block 31. Opposite sides of the fixed block 31 and the sliding block 32 are symmetrically and fixedly connected with mounting frames 33. A moving box 34 is slidably connected inside the mounting frame 33. Clamping boxes 35 are fixedly connected to opposite sides of the moving box 34. A plurality of adsorption holes 36 distributed in a rectangular array are formed on the side of the clamping box 35 away from the moving box 34. A pressing block 37 is fixedly connected to the sliding block 32;

[0037] The driving mechanism 5 is arranged on the side wall of the moving plate 11 and is used to drive the sliding block 32 to slide in the vertical direction. The driving mechanism 5 includes two second mounting blocks 51 fixedly connected to the side wall of the moving plate 11. A threaded rod 52 is rotatably connected between the two second mounting blocks 51. The pressing block 37 is in threaded cooperation with the threaded rod 52. A second motor 53 for driving the threaded rod 52 is fixedly connected to one of the second mounting blocks 51.

[0038] Specifically, a vertical limiting groove 6 is formed on the moving plate 11. The pressing block 37 extends to one side of the threaded rod 52 through the vertical limiting groove 6, and the pressing block 37 is slidably connected to the inner wall of the vertical limiting groove 6. Through the vertical limiting groove 6, when the threaded rod 52 rotates, the pressing block 37 can only perform vertical displacement along the threaded rod 52, playing a limiting role for the pressing block 37.

[0039] Before the tensile test of the plastic film, the second motor 53 is used to drive the pressing block 37 and the sliding block 32 to slide downward, so that the upper clamping box 35 moves down to be close to the lower clamping box 35, realizing the clamping and fixing of the plastic film. Moreover, through the reduction of the internal air pressure of the clamping box 35, the plastic film can be adsorbed and fixed through a plurality of adsorption holes 36 under the action of the air pressure difference. Compared with the traditional clamping method using clamping plates, when fixing the plastic film in this way, it is not necessary to apply a large force to the plastic film to avoid damage to the plastic film. Just make the clamping box 35 close to the plastic film, and then fix the plastic film by the negative pressure adsorption method, which can ensure the fixing effect of the plastic film and prevent it from falling off during the tensile test.

[0040] A length adjusting mechanism 4 is also provided on the side wall of the moving plate 11 for adjusting the stretching length of the plastic film according to the thickness of the plastic film. The length adjusting mechanism 4 includes a piezoresistor 41 fixedly connected to the lower end of the pressing block 37. One side of the moving plate 11 close to the piezoresistor 41 is fixedly connected with an elastic telescopic rod 42 through a stop block. The telescopic end of the elastic telescopic rod 42 is fixedly connected with a top block 43. The symmetrically fixed connection of electromagnets 44 is provided on the sides of the moving box 34 and the mounting frame 33 close to each other. When the two electromagnets 44 are energized, the same poles repel each other. The two electromagnets 44 are connected in series with the power supply device through the piezoresistor 41. A compression spring 45 is also provided between the moving box 34 and the mounting frame 33.

[0041] Among them, a pressure sensor is provided on the clamping box 35, which can close the second motor 53 after the clamping box 35 is close to the plastic film, so that the upper clamping box 35 no longer approaches the lower clamping box 35, thereby ensuring that the two clamping boxes 35 are close to the plastic film while avoiding applying too much pressure to the plastic film.

[0042] Among them, considering that the thickness difference of the plastic film is small, the piezoresistor 41 can be made of carbon-based materials, which has a strong piezoresistive effect. When the pressure changes slightly, the resistance change of the piezoresistor 41 is more significant, so as to ensure that when the thickness of the plastic film changes, the adjustment of the stretching length of the plastic film, the adsorption force during clamping, and the impact force during impact testing can be realized.

[0043] Aiming at the situation in the prior art that the stretching length cannot be accurately controlled according to the thickness of the plastic film, resulting in the measured tensile strength not conforming to the actual performance, the present invention sets a length adjusting mechanism 4. Before the tensile test of the plastic film, the plastic film needs to be clamped and fixed first. At this time, the pressing block 37 drives the sliding block 32 to slide downward and approach the fixed block 31, so that the two clamping boxes 35 approach each other to clamp the plastic film. During this process, for plastic films of different thicknesses, the distance that the pressing block 37 slides downward is different, so that the pressure received by the piezoresistor 41 below the pressing block 37 is different, further resulting in the following effects:

[0044] For a relatively thin plastic film, the pressing block 37 displaces downward by a relatively large distance. As a result, after the varistor 41 contacts the top block 43, the degree of compression of the elastic telescopic rod 42 is relatively large. Consequently, the elastic element inside the elastic telescopic rod 42 is compressed to a relatively large extent, and the elastic pressure exerted by the elastic element on the varistor 41 is relatively large. This causes the resistance value of the circuit where the varistor 41 is located to be relatively small, the current in the circuit where the electromagnet 44 is located to be relatively large, and the magnetic repulsive force between the two electromagnets 44 to be relatively large. As a result, the moving box 34 moves a relatively large distance towards the central position of the detection base plate 1. After the two moving plates 11 move to the designated position, the distance between the two clamping boxes 35 is relatively small, and the stretching length of the plastic film is relatively small, thus preventing the plastic film from breaking prematurely;

[0045] For a relatively thick plastic film, the pressing block 37 displaces downward by a relatively small distance, resulting in a relatively small degree of compression of the elastic element inside the elastic telescopic rod 42. The elastic pressure exerted by the elastic element on the varistor 41 is relatively small, causing the resistance value of the circuit where the varistor 41 is located to be relatively large, and the magnetic repulsive force between the two electromagnets 44 to be relatively small. As a result, the moving box 34 moves a relatively small distance towards the central position of the detection base plate 1. After the two moving plates 11 move to the designated position, the distance between the two clamping boxes 35 is relatively large, and the stretching length of the plastic film is relatively large, thus preventing the stretching degree from being too small to fully test the tensile properties of the film;

[0046] Therefore, it is possible to adaptively adjust the stretching parameters for the plastic film according to its thickness, making the detected tensile strength of the plastic film more consistent with its actual performance. For plastic films of different thicknesses, they can be stretched to different lengths. By observing the intact state of plastic films with different thicknesses at different stretching lengths, it can be determined whether plastic films of corresponding thicknesses meet the qualified standards under corresponding test conditions, improving the applicable range of the tensile detection for plastic films. The same principle applies to the impact resistance test.

[0047] Inside the installation frame 33, there is a force adjustment mechanism 7 for adjusting the adsorption force on the plastic film according to the thickness of the plastic film. The force adjustment mechanism 7 includes a push rod 71 fixedly connected to the inner wall of the installation frame 33. Inside the moving box 34, there is a partition plate 72 fixedly connected. The internal space of the moving box 34 is divided into a liquid storage chamber 73 and a gas storage chamber 74 by the partition plate 72. One end of the push rod 71 penetrates through the installation frame 33, extends into the liquid storage chamber 73, and is fixedly connected with a piston plate 75. The piston plate 75 is airtight with the inner wall of the liquid storage chamber 73. A liquid infusion pipe 76 is fixedly connected to the partition plate 72. A control chamber 77 is opened inside the moving box 34. The liquid storage chamber 73 is communicated with the control chamber 77 through the liquid infusion pipe 76. An elevating block 78 is airtight and slidably connected to the inner wall of the control chamber 77. An elevating plate 79 is airtight and slidably connected to the inside of the clamping box 35. A connecting rod 710 is fixedly connected between the elevating block 78 and the elevating plate 79.

[0048] It is worth mentioning that by setting the force adjustment mechanism 7, while adjusting the stretching length according to the film thickness, since relative displacement will occur between the moving box 34 and the mounting frame 33, the adsorption force of the clamping box 35 on the plastic film can be adjusted. The specific adjustment process is as follows:

[0049] For thinner plastic films, the moving box 34 moves a larger distance towards the center position of the detection bottom plate 1. Therefore, the piston plate 75 moves a larger distance in the liquid storage chamber 73, causing more hydraulic oil in the liquid storage chamber 73 to enter the control chamber 77 through the liquid delivery pipe 76. This makes the lifting block 78 and the lifting plate 79 displace upward by a larger distance, resulting in a larger space below the lifting plate 79 inside the clamping box 35. Consequently, the internal air pressure of the clamping box 35 is smaller, and the air pressure difference between it and the outside is relatively larger. This enables the plastic film to quickly adhere to the mold surface, ensuring a good adsorption effect while avoiding wrinkles in the thinner plastic film and reducing the generation of air gaps and wrinkles;

[0050] For thicker plastic films, the moving box 34 moves a smaller distance towards the center position of the detection bottom plate 1. Therefore, the piston plate 75 moves a smaller distance in the liquid storage chamber 73, causing the lifting block 78 and the lifting plate 79 to displace upward by a smaller distance, resulting in a smaller space below the lifting plate 79 inside the clamping box 35. Consequently, the internal air pressure of the clamping box 35 is larger, and the air pressure difference between it and the outside is relatively smaller, avoiding excessive deformation or stretching of the plastic film due to an excessive air pressure difference, or even causing rupture or permanent deformation.

[0051] Specifically, a telescopic airbag 761 is fixedly connected to the part of the liquid delivery pipe 76 located in the air storage chamber 74, and an opening and closing valve 762 is provided inside the liquid delivery pipe 76 near the control chamber 77. During the process of clamping the plastic film, the movement of the piston plate 75 first delivers the hydraulic oil in the liquid storage chamber 73 to the liquid delivery pipe 76 and the telescopic airbag 761. At this time, the opening and closing valve 762 is closed. After the clamping box 35 is in close contact with the plastic film and the second motor 53 is turned off, the opening and closing valve 762 is opened to ensure that the lifting plate 79 can only displace after the clamping box 35 contacts the plastic film, thereby ensuring the adsorption and fixation of the plastic film.

[0052] Specifically, an extension block 341 is fixedly connected to the moving box 34. A horizontal limiting groove 342 is formed in the outer wall of the mounting frame 33. The upper end of the extension block 341 passes through the horizontal limiting groove 342 and is fixed with a moving rack 343. A locking gear 344 is rotatably connected to the side wall of the moving plate 11 through a mounting plate. A telescopic electric cylinder 345 is also fixedly connected to the side wall of the moving plate 11. A locking rack 346 is fixedly connected to the output end of the telescopic electric cylinder 345. The locking rack 346 and the moving rack 343 are respectively engaged with both sides of the locking gear 344. During the process of clamping the plastic film, the telescopic electric cylinder 345 is used to move the locking rack 346 away from the locking gear 344, so that when the moving box 34 is displaced relative to the mounting frame 33, the process of the moving rack 343 moving and driving the locking gear 344 to rotate will not be hindered. During the process of stretching and detecting the plastic film after clamping is completed, the telescopic electric cylinder 345 is used to move the locking rack 346 close to the locking gear 344 and engage with the locking gear 344, so that the moving box 34 cannot be displaced relative to the mounting frame 33 during the stretching process, ensuring that the stretching length of the plastic film is consistent with the preset value, and thus ensuring the accuracy of the tensile strength test.

[0053] An impact resistance testing mechanism 8 is provided on the outer wall of the mounting frame 33 fixed to the moving box 34, which is used to perform an impact resistance test on the plastic film and automatically adjust the impact force according to the thickness of the plastic film. The impact resistance testing mechanism 8 includes a guide rail 81 fixedly connected to the outer wall of the mounting frame 33. A counterweight plate 82 is slidably connected in the guide rail 81 along the vertical direction. An air spring 83 is fixedly connected to the lower end of the counterweight plate 82. An impact block 84 is fixedly connected to the lower end of the air spring 83. An exhaust plate 85 is hermetically slidably connected inside the air storage chamber 74. An air delivery hose 86 is connected between the air spring 83 and the space above the exhaust plate 85 inside the air storage chamber 74.

[0054] Specifically, when the exhaust plate 85 is not pushed by the expansion airbag 761, it will reset under the action of gravity, thus facilitating the next impact resistance test.

[0055] In addition, the present invention is also provided with an impact resistance test mechanism 8. During the clamping process, when the plastic film is relatively thin, the moving range of the piston plate 75 is relatively large, and the expansion degree of the telescopic airbag 761 is relatively large. Therefore, the upward movement range of the exhaust plate 85 in the air storage chamber 74 is relatively large, so that more air in the air storage chamber 74 is discharged into the air spring 83, making the air pressure in the air spring 83 relatively large and the elastic resistance of the air spring 83 relatively large, causing the impact block 84 to be at a relatively low height below the counterweight plate 82. Thus, when the plastic film is relatively thin, the counterweight plate 82 and the impact block 84 apply a relatively small impact force to the plastic film when falling. While when the plastic film is relatively thick, the moving range of the piston plate 75 is relatively small, and the expansion degree of the telescopic airbag 761 is relatively small, making the air pressure in the air spring 83 relatively small and the elastic force of the air spring 83 relatively small, causing the impact block 84 to be at a relatively high height below the counterweight plate 82. Thus, when the plastic film is relatively thick, the counterweight plate 82 and the impact block 84 apply a relatively large impact force to the plastic film when falling. This not only can achieve the impact resistance test for the plastic film, but also the impact force on the plastic film automatically changes with the thickness of the plastic film, improving the detection accuracy of the impact resistance test.

[0056] Specifically, a wedge-shaped clamping block 9 is provided at the position of the outer wall of the mounting frame 33 inside the guide rail 81, and a tension spring is provided between the wedge-shaped clamping block 9 and the inside of the mounting frame 33. The wedge-shaped clamping block 9 can limit the counterweight plate 82 and the impact block 84 when the impact resistance test is not carried out, so that the counterweight plate 82 and the impact block 84 cannot fall. And after the counterweight plate 82 and the impact block 84 fall, only need to slide them upward to above the wedge-shaped clamping block 9, then the wedge-shaped clamping block 9 will automatically pop out under the elastic force of the tension spring and continue to limit the counterweight plate 82 to ensure the next impact resistance test for the plastic film.

[0057] The functional principle of the present invention can be elaborated through the following operation modes:

[0058] Before the tensile test of the plastic film, the pressing block 37 and the sliding block 32 are driven by the second motor 53 to slide downward, so that the upper clamping box 35 moves downward to be in close contact with the lower clamping box 35, realizing the clamping and fixing of the plastic film;

[0059] Subsequently, the first motor 23 drives the bidirectional lead screw 22 to rotate, driving the two moving plates 11 to move away from each other, thereby carrying out the tensile test on the plastic film after clamping;

[0060] For a relatively thin plastic film, the pressing block 37 displaces downward by a relatively large distance, the pressure received by the piezoresistor 41 is relatively large, the magnetic repulsive force between the two electromagnets 44 is relatively large. After the two moving plates 11 move to the designated positions, the distance between the two clamping boxes 35 on both sides is relatively small, and the stretching length of the plastic film is relatively small. At the same time, after the opening and closing valve 762 is opened, the air pressure difference between the inside of the clamping box 35 and the outside is relatively large, which can enable the plastic film to quickly adhere to the surface of the mold, avoiding wrinkles on the relatively thin plastic film. In addition, the expansion degree of the telescopic airbag 761 is relatively large, enabling more air in the air storage chamber 74 to be discharged into the air spring 83. The elastic force of the air spring 83 is relatively large, making the impact block 84 located at a relatively low height below the counterweight plate 82. Therefore, when performing the impact resistance test, a relatively small impact force is applied to the plastic film;

[0061] For a relatively thick plastic film, the pressing block 37 displaces downward by a relatively small distance, the pressure received by the piezoresistor 41 is relatively small, the magnetic repulsive force between the two electromagnets 44 is relatively small. After the two moving plates 11 move to the designated positions, the distance between the two clamping boxes 35 on both sides is relatively large, and the stretching length of the plastic film is relatively large. At the same time, after the opening and closing valve 762 is opened, the air pressure difference between the inside of the clamping box 35 and the outside is relatively small, avoiding excessive deformation or stretching of the plastic film caused by an excessive air pressure difference. In addition, the expansion degree of the telescopic airbag 761 is relatively small, making the impact block 84 located at a relatively high height below the counterweight plate 82. Therefore, when the plastic film is relatively thick, a relatively large impact force is applied to the plastic film.

[0062] The above are only the preferred embodiments of the present invention and are not intended to limit the present invention. Any modifications, equivalent replacements, improvements, etc. made within the spirit and principles of the present invention shall be included within the protection scope of the present invention.

Claims

1. A plastic film tensile testing device, characterized in that: include: A detection base plate (1), wherein the upper end of the detection base plate (1) is slidably connected to two movable plates (11) in a horizontal direction; A stretching mechanism (2) is arranged at the upper end of the detection base plate (1) and is used to drive the two movable plates (11) to move in opposite directions; A clamping mechanism (3) having two portions symmetrically arranged on opposite sides of two movable plates (11) for clamping and fixing the plastic film, the clamping mechanism (3) comprising a fixed block (31) fixedly connected to a side wall of the movable plate (11), a sliding block (32) slidably connected on the side wall of the movable plate (11) and on the fixed block (31), a mounting frame (33) symmetrically fixedly connected to opposite sides of the fixed block (31) and the sliding block (32), a movable box (34) slidably connected inside the mounting frame (33), a clamping box (35) fixedly connected to opposite sides of the movable box (34), a plurality of adsorption holes (36) distributed in a rectangular array are provided on a side of the clamping box (35) away from the movable box (34), and a pressing block (37) is fixedly connected to the sliding block (32); A length adjustment mechanism (4) is also provided on the side wall of the movable plate (11) for adjusting the stretching length of the plastic film according to the thickness of the plastic film, the length adjustment mechanism (4) comprising a varistor (41) fixedly connected to the lower end of the pressing block (37), a side of the movable plate (11) close to the varistor (41) is fixedly connected to an elastic telescopic rod (42) via a stopper, the telescopic end of the elastic telescopic rod (42) is fixedly connected to a top block (43), and electromagnets (44) are symmetrically fixedly connected to the side of the movable box (34) and the mounting frame (33) close to each other, the two electromagnets (44) repel each other with the same poles when energized, the two electromagnets (44) are connected in series with the power supply device via the varistor (41), and a compression spring (45) is also provided between the movable box (34) and the mounting frame (33); The driving mechanism (5) is arranged on the side wall of the moving plate (11) and is used to drive the sliding block (32) to slide in a vertical direction.

2. The plastic film tensile testing device according to claim 1, characterized in that: The stretching mechanism (2) comprises two first mounting blocks (21) fixedly connected to the upper end of the detection base plate (1); a bidirectional screw rod (22) is rotatably connected between the two first mounting blocks (21); the screw threads on both sides of the bidirectional screw rod (22) have opposite spiral directions; the two movable plates (11) are respectively threadedly engaged with the screw threads on both sides of the bidirectional screw rod (22); and a first motor (23) for driving the bidirectional screw rod (22) is provided on the side wall of one of the first mounting blocks (21).

3. The plastic film tensile testing device according to claim 1, characterized in that: The driving mechanism (5) comprises two second mounting blocks (51) fixedly connected to the side wall of the movable plate (11), a threaded rod (52) being rotatably connected between the two second mounting blocks (51), the pressing block (37) being threadably engaged with the threaded rod (52), and a second motor (53) for driving the threaded rod (52) being fixedly connected to one of the second mounting blocks (51).

4. The plastic film tensile testing device according to claim 3, characterized in that: The movable plate (11) is provided with a vertical limiting groove (6), the pressing block (37) extends through the vertical limiting groove (6) to one side of the threaded rod (52), and the pressing block (37) is slidably connected to the inner wall of the vertical limiting groove (6).

5. The plastic film tensile testing device according to claim 1, characterized in that: A force adjustment mechanism (7) is provided inside the installation frame (33) for adjusting the adsorption force of the plastic film according to the thickness of the plastic film. The force adjustment mechanism (7) comprises a push rod (71) fixedly connected to the inner wall of the installation frame (33). A partition plate (72) is fixedly connected to the inside of the moving box (34). The internal space of the moving box (34) is divided into a liquid storage chamber (73) and an air storage chamber (74) by the partition plate (72). One end of the push rod (71) passes through the installation frame (33), extends into the liquid storage chamber (73) and is fixedly connected to a piston plate. (75), the piston plate (75) is air-tightly connected to the inner wall of the liquid storage chamber (73), the partition plate (72) is fixedly connected to a liquid infusion tube (76), a control chamber (77) is opened inside the movable box (34), the liquid storage chamber (73) is connected to the control chamber (77) through the liquid infusion tube (76), the inner wall of the control chamber (77) is air-tightly slidably connected to a lifting block (78), the interior of the clamping box (35) is air-tightly slidably connected to a lifting plate (79), and a connecting rod (710) is fixedly connected between the lifting block (78) and the lifting plate (79).

6. The plastic film tensile testing device according to claim 5, characterized in that: The portion of the infusion tube (76) located in the air storage chamber (74) is fixedly connected to a telescopic air bag (761), and an opening and closing valve (762) is provided inside a side of the infusion tube (76) close to the control chamber (77).

7. The plastic film tensile testing device according to claim 5, characterized in that: An extension block (341) is fixedly connected to the moving box (34), a horizontal limit slot (342) is provided on the outer wall of the mounting frame (33), the upper end of the extension block (341) passes through the horizontal limit slot (342) and is fixed with a moving rack (343), a locking gear (344) is rotatably connected to the side wall of the moving plate (11) via a mounting plate, an electric telescopic rod (345) is also fixedly connected to the side wall of the moving plate (11), a locking rack (346) is fixedly connected to the output end of the electric telescopic rod (345), and the locking rack (346) and the moving rack (343) are respectively meshed with two sides of the locking gear (344).

8. The plastic film tensile testing device according to claim 5, characterized in that: An impact resistance testing mechanism (8) is provided on the outer wall of the installation frame (33) fixed to the moving box (34), which is used to perform an impact resistance test on the plastic film and automatically adjust the impact force according to the thickness of the plastic film. The impact resistance testing mechanism (8) comprises a guide rail (81) fixedly connected to the outer wall of the installation frame (33), a counterweight plate (82) slidably connected in the vertical direction in the guide rail (81), an air spring (83) fixedly connected to the lower end of the counterweight plate (82), an impact block (84) fixedly connected to the lower end of the air spring (83), an exhaust plate (85) airtightly slidably connected inside the air storage chamber (74), and an air delivery hose (86) is connected between the air spring (83) and the space above the exhaust plate (85) in the air storage chamber (74).

9. The plastic film tensile testing device according to claim 8, characterized in that: A wedge-shaped clamping block (9) is provided at a position on the outer wall of the installation frame (33) located inside the guide rail (81).

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