Plastic film tensile test device

Abstract

The invention belongs to the technical field of film tensile testing devices, and particularly relates to a plastic film tensile testing device, which comprises a detection bottom plate, the upper end of the detection bottom plate is slidably connected with two moving plates along the horizontal direction; the stretching mechanism is arranged at the upper end of the detection bottom plate and is used for driving the two moving plates to move oppositely; and the two clamping mechanisms are symmetrically arranged on the opposite sides of the two moving plates and used for clamping and fixing the plastic film, and each clamping mechanism comprises a fixing block fixedly connected to the side wall of the corresponding moving plate. By arranging the length adjusting mechanism, in the clamping process, for plastic films with different thicknesses, the downward sliding distances of the pressing block are different, so that the pressure borne by the piezoresistor below the pressing block is different, the stretching parameters of the piezoresistor can be adaptively adjusted according to the thicknesses of the films, and the clamping efficiency is improved. And the detected tensile strength of the plastic film is more consistent with the actual performance.

Description

Technical Field

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

[0002] The plastic film tensile test device is an experimental device used to test the mechanical properties of plastic film under tension. It is mainly used to determine the key parameters of the film such as tensile strength, elongation, elastic modulus, etc. These data are crucial for evaluating the quality and performance of plastic films. Therefore, it is widely used in plastic film quality control, research and development, product design and certification.

[0003] However, the existing tensile test device, such as a plastic film tensile test device and test method disclosed in China Publication No. CN118670869B, still has the following technical problems during use:

[0004] During the tensile test, the stretching length cannot be accurately controlled according to the thickness of the plastic film. For thinner plastics, the stretching length needs to be relatively small, otherwise the plastic film may break prematurely and effective test data cannot be obtained. For thicker plastic films, the stretching length needs to be relatively large, otherwise the stretching degree may be too small, making it impossible 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 being inconsistent with the actual performance. Summary of the invention

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

[0006] In order to achieve the above object, the present invention adopts the following technical solutions:

[0007] A plastic film tensile testing device, comprising:

[0008] A detection bottom plate, the upper end of which is slidably connected with two movable plates in a horizontal direction;

[0009] The stretching mechanism is arranged at the upper end of the detection bottom plate and is used to drive the two moving plates to move in opposite directions;

[0010] A clamping mechanism, having two and symmetrically arranged on opposite sides of two moving plates, for clamping and fixing the plastic film, the clamping mechanism comprising a fixed block fixedly connected to the side wall of the moving plate, a sliding block slidably connected on the side wall of the moving plate, a mounting frame symmetrically fixedly connected to the opposite side of the fixed block and the sliding block, a moving box slidably connected inside the mounting frame, a clamping box fixedly connected to the opposite side of the moving box, a plurality of adsorption holes distributed in a rectangular array are opened on the side of the clamping box away from the moving box, and 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 for driving the sliding block to slide in the vertical direction.

[0012] Preferably, a length adjustment mechanism is also provided on the side wall of the movable plate, which is used to adjust the stretching length of the plastic film according to the thickness of the plastic film, and the length adjustment mechanism includes a varistor fixedly connected to the lower end of the pressing block, and the side of the movable plate close to the varistor is fixedly connected to an elastic telescopic rod through a block, and the telescopic end of the elastic telescopic rod is fixedly connected to a top block, and the side of the movable box and the installation frame close to each other are symmetrically fixedly connected with electromagnets, and the two electromagnets repel each other with the same poles when energized, and the two electromagnets are connected in series with the power supply device through the varistor, and a compression spring is also provided between the movable box and the installation frame.

[0013] Preferably, the stretching mechanism includes two first mounting blocks fixedly connected to the upper end of the detection base plate, a bidirectional screw is rotatably connected between the two first mounting blocks, the spiral directions of the threads on both sides of the bidirectional screw are opposite, the two movable plates are respectively threadedly engaged with the threads on both sides of the bidirectional screw, and a first motor for driving the bidirectional screw is provided 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 walls of the movable plate, a threaded rod is rotatably connected between the two second mounting blocks, the pressing block is threadably matched with the threaded rod, and 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 movable 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 of 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 to the interior of the movable box, the internal space of the movable box is divided into a liquid storage chamber and an air storage chamber by the partition plate, one end of the push rod passes through the installation frame, extends into the liquid storage chamber and is fixedly connected to a piston plate, the piston plate is air-tightly connected to the inner wall of the liquid storage chamber, an infusion tube is fixedly connected to the partition plate, a control chamber is provided inside the movable box, the liquid storage chamber is connected to the control chamber through the infusion tube, the inner wall of the control chamber is air-tightly slidably connected to a lifting block, the interior of the clamping box is air-tightly slidably connected to a lifting plate, and a connecting rod is fixedly connected between the lifting block and the lifting plate.

[0017] Preferably, the portion of the infusion tube located in the air storage chamber is fixedly connected to a telescopic airbag, and an opening and closing valve is provided inside a side of the infusion tube close to the control chamber.

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

[0019] Preferably, an impact resistance testing mechanism is provided on the outer wall of the mounting frame fixed to the moving box, 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 includes a guide rail fixedly connected to the outer wall of the mounting frame, a counterweight plate is slidably connected to 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 slidably connected to the inside of the air storage chamber, and an air supply hose is connected between the air spring and the space above the exhaust plate in the air storage chamber.

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

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

[0022] 1. The present invention sets a length adjustment mechanism. During the clamping process, for plastic films of different thicknesses, the distances that the pressing block slides downward are different, so that the pressures on the varistor below the pressing block are different. For thinner plastic films, the stretching length is relatively small, thereby avoiding premature breakage of the plastic film. For thicker plastic films, the stretching length is relatively large, thereby avoiding the inability to fully test the tensile properties of the film due to too small a stretching degree. The stretching parameters can be adaptively adjusted according to the thickness of the film, so that the detected tensile strength of the plastic film is more consistent with the actual performance.

[0023] 2. The present invention provides a force adjustment mechanism. While adjusting the stretching length according to the thickness of the film, due to the relative displacement between the movable 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 world is relatively large, which can enable the plastic film to quickly fit to the mold surface and avoid wrinkles on the thinner plastic film. For thicker plastic films, the air pressure difference between the clamping box and the outside world is relatively small, which avoids excessive deformation or stretching of the plastic film due to excessive pressure difference, or even rupture or permanent deformation.

[0024] 3. The present invention sets an impact resistance testing mechanism. When the plastic film is thin, the expansion degree of the telescopic airbag is greater, so that the impact block is located at a relatively low height below the counterweight plate, thereby applying a smaller impact force to the plastic film when the plastic film is thin; and when the plastic film is thick, the expansion degree of the telescopic airbag is less, so that the air pressure in the air spring is smaller, so that the impact block is located at a relatively high height below the counterweight plate, thereby applying a larger impact force to the plastic film when the plastic film is thick. Not only can the impact resistance test of the plastic film be realized, but the impact force on the plastic film automatically changes with the thickness of the plastic film, thereby improving the detection accuracy of the impact resistance test. BRIEF DESCRIPTION OF THE DRAWINGS

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

[0026] Figure 2 yes Figure 1 The enlarged view of point A in the middle;

[0027] Figure 3 yes Figure 1 The enlarged view of point B in the middle;

[0028] Figure 4 yes Figure 1 Enlarged view of point C in the middle;

[0029] Figure 5 It is a schematic diagram of the cross-sectional structure of the installation frame in the present invention;

[0030] Figure 6 yes Figure 5 Enlarged view of point D in the middle.

[0031] In the figure: 1, detection base plate; 11, moving plate; 2, stretching mechanism; 21, first mounting block; 22, bidirectional screw rod; 23, first motor; 3, clamping mechanism; 31, fixed block; 32, sliding block; 33, mounting frame; 34, moving box; 341, extension block; 342, horizontal limit 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, varistor; 42, elastic telescopic rod; 43, top block; 44, electromagnet; 4 5. Compression spring; 5. Driving mechanism; 51. Second mounting block; 52. Threaded rod; 53. Second motor; 6. Vertical limit groove; 7. Force adjustment mechanism; 71. Push rod; 72. Partition plate; 73. Liquid storage chamber; 74. Air storage chamber; 75. Piston plate; 76. Infusion tube; 761. Telescopic airbag; 762. Opening and closing valve; 77. Control chamber; 78. Lifting block; 79. Lifting plate; 710. Connecting rod; 8. Impact resistance testing mechanism; 81. Guide rail; 82. Counterweight plate; 83. Air spring; 84. Impact block; 85. Exhaust plate; 86. Air hose; 9. Wedge-shaped block. DETAILED DESCRIPTION

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

[0033] Example: Refer to Figures 1 to 6 , a plastic film tensile testing device, comprising:

[0034] A detection base plate 1, the upper end of which is slidably connected with two movable plates 11 in a horizontal direction;

[0035] The 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 away from each other. The stretching mechanism 2 includes 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 spiral directions of the threads on both sides of the bidirectional screw rod 22 are opposite. The two movable plates 11 are respectively threadedly matched with the threads on both sides of the bidirectional screw rod 22. 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. During the tensile test, the bidirectional screw rod 22 is driven to rotate by the first motor 23, which can drive the two movable plates 11 away from each other, thereby performing a tensile test on the plastic film after clamping.

[0036] The clamping mechanism 3 has two and is symmetrically arranged on opposite sides of the two moving plates 11, and 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 on the side wall of the moving plate 11 and on the fixed block 31, and a mounting frame 33 is symmetrically fixedly connected to the opposite side of the fixed block 31 and the sliding block 32, and a moving box 34 is slidably connected inside the mounting frame 33, and a clamping box 35 is fixedly connected to the opposite side of the moving box 34, and a plurality of adsorption holes 36 distributed in a rectangular array are opened on the side of the clamping box 35 away from the moving box 34, and 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 movable 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 movable plate 11, and a threaded rod 52 is rotatably connected between the two second mounting blocks 51. The pressing block 37 is threadedly matched with the threaded rod 52, and 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 limit groove 6 is opened on the movable plate 11, and the pressing block 37 extends to one side of the threaded rod 52 through the vertical limit groove 6, and the pressing block 37 is slidably connected to the inner wall of the vertical limit groove 6. Through the vertical limit groove 6, when the threaded rod 52 rotates, the pressing block 37 can only be vertically displaced along the threaded rod 52, which plays a limiting role on the pressing block 37.

[0039] Before the tensile test of the plastic film is performed, the second motor 53 drives the pressing block 37 and the sliding block 32 to slide downward, so that the upper clamping box 35 moves down to be in close contact with the lower clamping box 35, so as to clamp and fix the plastic film. Moreover, the air pressure inside the clamping box 35 can be reduced, and the plastic film can be adsorbed and fixed through multiple adsorption holes 36 under the action of the air pressure difference. Compared with the traditional method of clamping by a clamping plate, this method does not require applying a large force to the plastic film when fixing the plastic film, so as to avoid damage to the plastic film. It is only necessary to make the clamping box 35 close to the plastic film, and then fix the plastic film by negative pressure adsorption, so as to ensure the fixing effect of the plastic film and avoid it from falling off during the tensile test.

[0040] A length adjustment mechanism 4 is also provided on the side wall of the movable plate 11, which is used to adjust the stretching length of the plastic film according to the thickness of the plastic film. The length adjustment mechanism 4 includes a varistor 41 fixedly connected to the lower end of the pressing block 37. An elastic telescopic rod 42 is fixedly connected to the side of the movable plate 11 close to the varistor 41 through a block, and the telescopic end of the elastic telescopic rod 42 is fixedly connected to a top block 43. Electromagnets 44 are symmetrically fixedly connected to the side where the movable box 34 and the installation frame 33 are 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 varistor 41. A compression spring 45 is also provided between the movable box 34 and the installation frame 33.

[0041] Among them, a pressure sensor is arranged on the clamping box 35, and the second motor 53 can be turned off after the clamping box 35 is in close contact with the plastic film, so that the upper clamping box 35 is no longer close to the lower clamping box 35, thereby ensuring that the two clamping boxes 35 are in close contact with the plastic film while avoiding applying a large pressure to the plastic film;

[0042] Among them, considering that the thickness difference of the plastic film is small, the varistor 41 can be made of carbon-based material, which has a strong piezoresistive effect. When subjected to a small pressure change, the resistance change of the varistor 41 is more significant, thereby ensuring that when the thickness of the plastic film changes, the stretching length of the plastic film, the adsorption force when clamping, and the impact force during impact testing are adjusted.

[0043] In view of the fact that the tensile length cannot be accurately controlled according to the thickness of the plastic film in the prior art, resulting in the measured tensile strength not being consistent with the actual performance, the present invention sets a length adjustment mechanism 4. Before the tensile test of the plastic film is performed, the plastic film needs to be clamped and fixed. 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 can approach each other to clamp the plastic film. In this process, for plastic films of different thicknesses, the downward sliding distance of the pressing block 37 is also different, so that the pressure on the varistor 41 below the pressing block 37 is different, which further produces the following effects:

[0044] For a thinner plastic film, the pressing block 37 moves downward a greater distance, so that after the varistor 41 contacts the top block 43, the elastic telescopic rod 42 is compressed to a greater extent, so that the elastic element inside the elastic telescopic rod 42 is compressed to a greater extent, and the elastic pressure applied by the elastic element on the varistor 41 is greater, so that the resistance value of the circuit where the varistor 41 is located is smaller, so that the current of the circuit where the electromagnet 44 is located is larger, and the magnetic repulsion between the two electromagnets 44 is larger, so that the movable box 34 moves to the center position of the detection bottom plate 1 by a larger amplitude, so that after the two movable plates 11 move to the specified position, the distance between the clamping boxes 35 on both sides is relatively small, and the stretching length of the plastic film is relatively small, so as to avoid premature breakage of the plastic film;

[0045] For thicker plastic films, the downward displacement distance of the pressing block 37 is shorter, so that the elastic element inside the elastic telescopic rod 42 is less compressed, and the elastic pressure applied by the elastic element on the varistor 41 is smaller, so that the resistance value of the circuit where the varistor 41 is located is larger, and the magnetic repulsion between the two electromagnets 44 is smaller, so that the range of movement of the moving box 34 toward the center position of the detection bottom plate 1 is smaller, so that after the two moving plates 11 move to the specified position, the distance between the clamping boxes 35 on both sides is relatively large, and the stretching length of the plastic film is relatively large, thereby avoiding the inability to fully test the tensile properties of the film due to too small a stretching degree;

[0046] Therefore, the stretching parameters can be adaptively adjusted according to the thickness of the film, so that the detected tensile strength of the plastic film is more consistent with the actual performance. For plastic films of different thicknesses, they can be stretched to different lengths. The intact state of films of different thicknesses at different stretching lengths can be used to judge whether films of corresponding thicknesses meet the qualified standards under corresponding test conditions, thereby improving the scope of application of tensile testing of plastic films, and the same applies to impact testing.

[0047] A force adjustment mechanism 7 is provided inside the mounting frame 33 for adjusting the adsorption force of 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 mounting frame 33. A partition plate 72 is fixedly connected inside 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 mounting 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. A liquid infusion tube 76 is fixedly connected to the partition plate 72. A control chamber 77 is provided inside the moving 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. A connecting rod 710 is fixedly connected between the lifting block 78 and the lifting plate 79.

[0048] It is worth mentioning that the present invention is provided with a strength adjustment mechanism 7. While adjusting the stretching length according to the thickness of the film, since relative displacement occurs between the moving box 34 and the mounting frame 33, the adsorption strength of the clamping box 35 on the plastic film can be adjusted. The specific adjustment process is as follows:

[0049] For a thinner plastic film, the movable box 34 moves to a larger extent toward the center of the detection base plate 1, so that the piston plate 75 moves to a larger extent in the liquid storage chamber 73, so that more hydraulic oil in the liquid storage chamber 73 enters the control chamber 77 through the infusion tube 76, so that the lifting block 78 and the lifting plate 79 move upward by a larger distance, so that the space below the lifting plate 79 in the clamping box 35 is larger, so that the internal air pressure of the clamping box 35 is smaller, and the air pressure difference between it and the outside is relatively large, so that the plastic film can be quickly attached to the mold surface, ensuring a good adsorption effect while avoiding wrinkles in the thin plastic film, reducing the generation of air gaps and wrinkles;

[0050] For thicker plastic films, the movable box 34 moves to a smaller extent toward the center of the detection base plate 1, so that the piston plate 75 moves to a smaller extent in the liquid storage chamber 73, and the lifting block 78 and the lifting plate 79 move upwards to a smaller distance, so that the space below the lifting plate 79 in the clamping box 35 is smaller, so that the internal air pressure of the clamping box 35 is larger, and the air pressure difference between it and the outside is relatively small, thereby avoiding excessive deformation or stretching of the plastic film due to excessive air pressure difference, or even rupture or permanent deformation.

[0051] Specifically, the part of the infusion tube 76 located in the air storage chamber 74 is fixedly connected to the telescopic airbag 761, and an opening and closing valve 762 is provided inside the side of the infusion tube 76 close to the control chamber 77. In the process of clamping the plastic film, the movement of the piston plate 75 first transports the hydraulic oil in the liquid storage chamber 73 to the infusion tube 76 and the telescopic airbag 761. At this time, the opening and closing valve 762 is closed, and the clamping box 35 is close to the plastic film. After the second motor 53 is turned off, the opening and closing valve 762 is opened to ensure that the lifting plate 79 can only be displaced 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 limit slot 342 is opened 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 through the 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, the locking rack 346 and the moving rack 343 are respectively meshed with the two sides of the locking gear 344, and in the process of clamping the plastic film, The electric telescopic rod 345 makes the locking rack 346 move away from the locking gear 344, so that when the movable box 34 is displaced relative to the mounting frame 33, the process of the movable rack 343 moving and driving the locking gear 344 to rotate will not be hindered. When the clamping is completed and the plastic film is stretched and tested, the locking rack 346 is moved close to the locking gear 344 and meshed with the locking gear 344 through the electric telescopic rod 345, so that the movable box 34 cannot be displaced relative to the mounting frame 33 during the stretching process, thereby ensuring that the stretching length of the plastic film is consistent with the preset value, thereby ensuring the accuracy of the tensile 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 impact resistance testing 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, and a counterweight plate 82 is slidably connected to the guide rail 81 along the vertical direction. An air spring 83 is fixedly connected to the lower end of the counterweight plate 82, and an impact block 84 is fixedly connected to the lower end of the air spring 83. An exhaust plate 85 is airtightly slidably connected to the interior of the air storage chamber 74, and an air hose 86 is connected between the air spring 83 and the space above the exhaust plate 85 in the air storage chamber 74.

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

[0055] In addition, the present invention further provides an impact resistance testing mechanism 8. During the clamping process, when the plastic film is relatively thin, the piston plate 75 moves with a larger amplitude, and the expansion degree of the telescopic airbag 761 is relatively large, so that the exhaust plate 85 moves upward in the air storage chamber 74 with a larger amplitude, so that more air in the air storage chamber 74 is discharged into the air spring 83, so that the air pressure in the air spring 83 is relatively large, and the elastic resistance of the air spring 83 is relatively large, so that the impact block 84 is located at a relatively low height below the counterweight plate 82, so that when the plastic film is relatively thin, the counterweight plate 82 and the impact block 84 are more likely to impact the plastic film when falling. The film exerts a smaller impact force, and when the plastic film is thicker, the movement amplitude of the piston plate 75 is smaller, and the expansion degree of the telescopic airbag 761 is smaller, so that the air pressure in the air spring 83 is smaller, and the elastic force of the air spring 83 is smaller, so that the impact block 84 is located at a relatively high height below the counterweight plate 82. Therefore, when the plastic film is thicker, the counterweight plate 82 and the impact block 84 exert a larger impact force on the plastic film when falling, which not only can realize the impact resistance test of the plastic film, but also the impact force on the plastic film automatically changes with the thickness of the plastic film, thereby improving the detection accuracy of the impact resistance test.

[0056] Specifically, a wedge-shaped block 9 is provided on the outer wall of the mounting frame 33 at a position within the guide rail 81, and a tension spring is provided between the wedge-shaped block 9 and the inside of the mounting frame 33. The wedge-shaped block 9 can limit the counterweight plate 82 and the impact block 84 when the impact resistance test is not performed, so that the counterweight plate 82 and the impact block 84 cannot fall. After the counterweight plate 82 and the impact block 84 fall, they only need to be slid upward to above the wedge-shaped block 9, so that the wedge-shaped block 9 can 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 of the plastic film.

[0057] The present invention can be explained by the following operation mode:

[0058] Before the tensile test of the plastic film is performed, the second motor 53 drives the pressing block 37 and the sliding block 32 to slide downward, so that the upper clamping box 35 moves down to be in close contact with the lower clamping box 35, so as to clamp and fix the plastic film;

[0059] Subsequently, the bidirectional screw rod 22 is driven to rotate by the first motor 23, driving the two movable plates 11 to move away from each other, thereby performing a tensile test on the plastic film after clamping;

[0060] For a thinner plastic film, the pressing block 37 moves downward for a longer distance, the pressure on the varistor 41 is greater, and the magnetic repulsion between the two electromagnets 44 is greater, so that after the two movable plates 11 move to the specified position, the distance between the 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 and the outside of the clamping box 35 is relatively large, which can make the plastic film quickly fit to the mold surface and avoid wrinkles on the thinner plastic film. In addition, the expansion degree of the telescopic airbag 761 is greater, so that more air in the air storage chamber 74 is discharged into the air spring 83. The elastic force of the air spring 83 is greater, so that the impact block 84 is located at a relatively low height below the counterweight plate 82, so that when the impact resistance test is performed, a smaller impact force is applied to the plastic film.

[0061] For thicker plastic films, the pressing block 37 moves downward for a shorter distance, the pressure on the varistor 41 is smaller, and the magnetic repulsion between the two electromagnets 44 is smaller. As a result, after the two movable plates 11 are moved to the specified position, the distance between the 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 and the outside of the clamping box 35 is relatively small, avoiding excessive deformation or stretching of the plastic film due to excessive air pressure difference. In addition, the expansion degree of the telescopic airbag 761 is smaller, so that the impact block 84 is located at a relatively high height below the counterweight plate 82, thereby exerting a larger impact force on the plastic film when the plastic film is thicker.

[0062] The above description is only a preferred 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 principle of the present invention should be included in 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 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 the 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 on 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 on 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); 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.

2. The plastic film tensile testing device according to claim 1, characterized in that: 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) comprises 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) through a stopper. The telescopic end of the elastic telescopic rod (42) is fixedly connected to a top block (43). Electromagnets (44) are symmetrically fixedly connected to the side of the movable 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 a power supply device through the varistor (41). A compression spring (45) is also provided between the movable box (34) and the mounting frame (33).

3. 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).

4. 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 matched 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).

5. The plastic film tensile testing device according to claim 4, 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).

6. 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 inside 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 with a liquid infusion tube (76), a control chamber (77) is opened inside the movable box (34), the liquid storage chamber (73) is connected with the control chamber (77) through the liquid infusion tube (76), the inner wall of the control chamber (77) is air-tightly slidably connected with a lifting block (78), the interior of the clamping box (35) is air-tightly slidably connected with a lifting plate (79), and a connecting rod (710) is fixedly connected between the lifting block (78) and the lifting plate (79).

7. The plastic film tensile testing device according to claim 6, 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 the side of the infusion tube (76) close to the control chamber (77).

8. The plastic film tensile testing device according to claim 6, 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) through the 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).

9. The plastic film tensile testing device according to claim 6, 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) is slidably connected in the vertical direction in the guide rail (81), 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 airtightly slidably connected inside the air storage chamber (74), and an air supply hose (86) is connected between the air spring (83) and the space above the exhaust plate (85) in the air storage chamber (74).

10. The plastic film tensile testing device according to claim 9, 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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