Plastic film tensile test device and test method

Abstract

The invention relates to the technical field of film testing, in particular to a plastic film tensile testing device and method.The plastic film tensile testing device comprises an outer shell, a protective shell is fixed to the bottom of the inner wall of the outer shell, and a driving mechanism is arranged in the protective shell and comprises a torque motor fixed to one side of the inner wall of the protective shell; according to the two-way synchronous stretching device, a linkage structure of the driving mechanism and the stretching mechanism is arranged, the torque motor is used for driving the worm, the worm gear, the gear and the rack to conduct transmission, two-way synchronous stretching is achieved, and the two-way synchronous stretching device is high in practicability and high in practicability. And the problem of non-uniform stress of the thin film caused by traditional single-point force application is effectively avoided. And in combination with the spring buffer design, the strength in the stretching process is uniformly and progressively increased, accidental damage to the film caused by instantaneous overload is prevented, and the accuracy and reliability of test data are remarkably improved.

Description

Technical Field

[0001] This invention relates to the field of thin film testing technology, specifically to a device and method for testing the tensile strength of plastic films. Background Technology

[0002] Plastic film, as an important flexible packaging and covering material, is widely used in agricultural production, food packaging, industrial protection, and medical and health fields. Its mechanical properties, especially tensile strength and elongation at break, are key indicators for evaluating film quality and ensuring its ability to withstand external forces without damage during use. Therefore, accurate and efficient tensile performance testing of plastic films is of paramount importance for quality control, production process optimization, and new product development.

[0003] Currently, most equipment used for tensile testing of materials on the market is the general-purpose electronic universal testing machine. These machines typically employ a gantry or single-column structure. Their working principle usually involves the control system issuing commands to drive a servo motor to rotate. Torque is transmitted through a synchronous belt or reducer, which in turn drives the ball screw pair to rotate, thus converting the motor's rotational motion into the precise linear motion of the moving beam.

[0004] Existing electronic universal testing machines have some limitations when testing plastic films. They typically use a method of active stretching on one side and fixing on the other, which can easily lead to asymmetrical lateral forces on the film due to misalignment of the clamps or sample installation deviations, resulting in stress concentration and affecting the authenticity of the test results. In addition, these devices generally lack a step to determine the initial "straightness" of the film, often relying on the operator's experience and judgment, which introduces a large human error and makes it difficult to guarantee the comparability of test results between different batches or different operators. Summary of the Invention

[0005] To address the shortcomings of existing technologies, this invention provides a plastic film tensile strength testing device and method, which significantly improves the accuracy and reliability of test data.

[0006] To achieve the above objectives, the present invention provides the following technical solution: a plastic film tensile strength testing device and testing method, comprising an outer shell, a protective shell fixed to the bottom of the inner wall of the outer shell, a driving mechanism disposed inside the protective shell, the driving mechanism comprising a torque motor fixed to one side of the inner wall of the protective shell, a worm gear fixed to the power output end of the torque motor, a worm wheel rotatably connected to the bottom of the middle part of the inner wall of the protective shell, a driving gear fixed to the top of the worm wheel, driven racks meshing on both sides of the driving gear, first connecting rods fixed to opposite ends of the two driven racks, a tensioning mechanism fixed to the top of the two first connecting rods, the tensioning mechanism comprising a movable seat, a support wheel fixed to one side of the movable seat, a limiting mechanism disposed at one end of the support wheel, the limiting mechanism comprising a U-shaped plate movably connected to the movable seat, an electromagnet strip disposed inside the U-shaped plate, a first mounting plate and a second mounting plate respectively fixed to the middle of the two sides of the outer shell, a light sensor and a laser bead respectively fixed to opposite sides of the first mounting plate and the second mounting plate.

[0007] Preferably, a first sliding groove is provided through the middle of both sides of the outer casing, the first mounting plate and the second mounting plate are respectively located in the middle of the two first sliding grooves, and four light sensors and four laser lamp beads are provided, with the four light sensors and four laser lamp beads respectively located at the four corners of the first mounting plate and the four corners of the second mounting plate.

[0008] Preferably, the inner wall of the U-shaped plate is fixed with limit posts at both ends, the electromagnet strip has through holes at both ends, the through holes are movably connected with the limit posts, and the bottom of the inner wall of the U-shaped plate is made of magnets.

[0009] Preferably, a third sliding groove is provided in the middle of the movable seat, the U-shaped plate is slidably connected to the third sliding groove, and the bottom of the inner wall of the U-shaped plate is arranged at the same horizontal plane as the two light sensors located in the same vertical plane.

[0010] Preferably, the top and bottom of both ends of the movable seat are rotatably connected to support wheels, and the two ends of the movable seat are respectively connected through the two first sliding grooves. The support wheels are in contact with the outer wall of the outer shell. Multiple springs are provided, and the multiple springs are arranged horizontally and equidistantly on one side of the movable seat.

[0011] Preferably, the top of the protective shell has a second sliding groove through which the two first connecting rods are slidably connected, and an accordion cover is fixed on the opposite side of the two first connecting rods.

[0012] Preferably, one of the first connecting rods has a scale pointer fixed on one side at the top of the protective shell, and a scale groove is provided on the top of the protective shell near the scale pointer. Multiple scale grooves are provided, and the multiple scale grooves are arranged horizontally and equidistantly.

[0013] Preferably, a control panel is fixed to one side of the outer wall of the outer casing, and a double-control switch and a push-button switch are fixed to one side of the control panel. The double-control switch is electrically connected to the torque motor, and the push-button switch is electrically connected to the electromagnet bar.

[0014] The test method for a plastic film tensile strength testing device, based on the aforementioned plastic film tensile strength testing device, includes the following steps: S1. Place the two ends of the cut film to be tested at the bottom of the inner walls of the two U-shaped plates respectively, and then press the press switch to control the two electromagnet bars to move downwards to limit the film. S2. Press the double control switch again to control the torque motor to rotate clockwise. The two tensioning mechanisms move to both ends. After moving to the point where all four light sensors can detect the light from the four laser beads, press the double control switch to stop the torque motor and record the position of the scale pointer in the scale groove. S3. When it is necessary to test the film limit, continue to press the double control switch until the film breaks. When the film breaks, stop pressing the double control switch, record the distance the scale pointer moves, and calculate the film tensile force according to the number of springs and the spring coefficient. S4. When it is necessary to test whether the film can withstand the tensile test, press the double control switch to control the torque motor to rotate clockwise until the scale pointer moves to the specified scale groove.

[0015] Compared with the prior art, the beneficial effects of the present invention are: 1. This invention achieves bidirectional synchronous stretching by setting up a linkage structure between the driving mechanism and the stretching mechanism, utilizing a torque motor to drive a worm gear and rack and pinion transmission, effectively avoiding the problem of uneven film stress caused by traditional single-point force application. Combined with a spring buffer design, the stretching force increases uniformly during the stretching process, preventing accidental damage to the film from instantaneous overload, and significantly improving the accuracy and reliability of test data. Simultaneously, the limiting mechanism using an electromagnet and a U-shaped plate is easy to operate and provides secure clamping, suitable for film samples of different thicknesses, enhancing the applicability and testing efficiency of the device. 2. This invention utilizes a photodetector and laser bead-based detection mechanism to accurately determine the initial tension state of the film, providing an objective and consistent standard for determining the testing starting point. The combination of the scale pointer and scale groove allows for intuitive recording of the film's tensile displacement. Furthermore, by considering the spring constant and quantity, the actual tensile force can be quickly calculated. 3. This invention integrates the control of a dual-control switch and a push-button switch, making the operation process simple and intuitive. It can be used for extreme tensile testing as well as durability verification under fixed tensile conditions, meeting diverse testing needs. Attached Figure Description

[0016] Figure 1 This is a schematic diagram of the overall device of the present invention.

[0017] Figure 2 This is a cross-sectional schematic diagram of the overall structure of the device of the present invention.

[0018] Figure 3 This is a schematic diagram of the tensioning mechanism of the device of the present invention.

[0019] Figure 4 The device of the present invention Figure 3 An enlarged schematic diagram of the structure of part A.

[0020] Figure 5 This is a schematic diagram of the protective shell structure of the device of the present invention.

[0021] Figure 6 This is a schematic diagram of the structure of the drive mechanism of the device of the present invention.

[0022] In the diagram: 1. Outer shell; 10. First slide groove; 2. Protective shell; 21. Second slide groove; 22. Bellows cover; 23. Scale groove; 24. Scale pointer; 30. Drive mechanism; 31. Torque motor; 32. Worm gear; 33. Worm wheel; 34. Driving gear; 35. Driven rack; 36. First connecting rod; 40. Tensioning mechanism; 41. Moving seat; 42. Spring; 43. Third slide groove; 44. Support wheel; 50. Limiting mechanism; 51. U-shaped plate; 52. Electromagnetic strip; 53. Limiting post; 54. Through hole; 6. Double control switch; 7. Press switch; 8. First mounting plate; 81. Light sensor; 9. Second mounting plate; 91. Laser lamp bead. Detailed Implementation

[0023] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention. Example 1:

[0024] Please see Figures 1 to 6This invention provides a first embodiment of a technical solution: a plastic film tensile strength testing device, comprising an outer shell 1, a protective shell 2 fixed to the bottom of the inner wall of the outer shell 1, a drive mechanism 30 disposed inside the protective shell 2, the drive mechanism 30 including a torque motor 31 fixed to one side of the inner wall of the protective shell 2, a worm gear 32 fixed to the power output end of the torque motor 31, a worm wheel 33 rotatably connected to the bottom of the middle part of the inner wall of the protective shell 2, a driving gear 34 fixed to the top of the worm wheel 33, and driven racks 35 meshing on both sides of the driving gear 34, the two driven racks 35 being opposite to each other. Each end is fixed with a first connecting rod 36, and the top of each of the two first connecting rods 36 is fixed with a tensioning mechanism 40. The tensioning mechanism 40 includes a movable seat 41, a support wheel 42 is fixed on one side of the movable seat 41, and a limit mechanism 50 is provided at one end of the support wheel 42. The limit mechanism 50 includes a U-shaped plate 51 that is movably connected to the movable seat 41. An electromagnet strip 52 is provided inside the U-shaped plate 51. A first mounting plate 8 and a second mounting plate 9 are fixed in the middle of both sides of the outer shell 1, respectively. A light sensor 81 and a laser lamp bead 91 are fixed on opposite sides of the first mounting plate 8 and the second mounting plate 9, respectively.

[0025] Reference Appendix Figure 1 The outer casing 1 has a first groove 10 through the middle of both sides. The first mounting plate 8 and the second mounting plate 9 are respectively located in the middle of the two first grooves 10. There are four light sensors 81 and four laser beads 91. The four light sensors 81 and the four laser beads 91 are respectively located at the four corners of the first mounting plate 8 and the four corners of the second mounting plate 9. The four laser beads 91 emit lasers to the light sensors 81 to determine the position of the film.

[0026] Reference Appendix Figure 4 The U-shaped plate 51 has limit posts 53 fixed at both ends of its inner wall, and the electromagnet strip 52 has through holes 54 at both ends. The through holes 54 are movably connected to the limit posts 53. The bottom of the inner wall of the U-shaped plate 51 is made of magnet. When the film needs to be limited, the electromagnet strip 52 is energized in the reverse direction to keep the electromagnet strip 52 and the bottom U-shaped plate 51 magnetically identical. The electromagnet strip 52 moves upward, and then the two ends of the film are placed under the two electromagnets 52 respectively. When the electromagnet strip 52 is energized normally, the electromagnet strip 52 and the bottom of the U-shaped plate 51 are attracted to each other and squeeze the film to limit it. The limit posts 53 limit the electromagnet strip 52 so that the electromagnet strip 52 can only move vertically up and down.

[0027] Reference Appendix Figure 1 and 3 The movable seat 41 has a third sliding groove 43 in the middle, and the U-shaped plate 51 is slidably connected to the third sliding groove 43. The bottom of the inner wall of the U-shaped plate 51 is set at the same horizontal plane as the two light sensors 81 located on the same vertical plane. The light sensors 81 determine whether the film has just entered the taut state.

[0028] Reference Appendix Figure 3 The top and bottom of the movable seat 41 are rotatably connected to support wheels 44. The two ends of the movable seat 41 are respectively connected to two first sliding grooves 10. The support wheels 44 are in contact with the outer wall of the outer shell 1. The support wheels 44 are in contact with the outer shell 1 to support the movable seat 41 and reduce the friction of the movable seat 4. Multiple springs 42 are provided. The multiple springs 42 are located on one side of the movable seat 41 and are arranged horizontally at equal intervals. The U-shaped plate 51 is connected by the springs 42, so that when the U-shaped plate 51 stretches the film, the force increases evenly and slowly, preventing the film from being directly torn apart.

[0029] Reference Appendix Figure 5 The top of the protective shell 2 is provided with a second sliding groove 21, and the two first connecting rods 36 are slidably connected to the second sliding groove 21. The two first connecting rods 36 are fixed with a bellows cover 22 on opposite sides, so that the two first connecting rods 36 can move inside the protective shell 2. The bellows cover 22 is used to block external dust and impurities and prevent them from entering the protective shell 2 and affecting the operation of the internal drive mechanism 30.

[0030] Reference Appendix Figure 5 One of the first connecting rods 36 has a scale pointer 24 fixed on one side at the top of the protective shell 2. A scale groove 23 is provided on the top of the protective shell 2 near the scale pointer 24. Multiple scale grooves 23 are provided and are arranged horizontally and equidistantly. By cooperating with the pointer 24 and the scale groove 23, the initial detection position of the film and the position of the film after the test are recorded, thereby determining the tensile strength of the film.

[0031] Reference Appendix Figure 1 The outer wall of the outer casing 1 is fixed with a control panel on one side, and a double-control switch 6 and a push switch 7 are fixed on one side of the control panel. The double-control switch 6 is electrically connected to the torque motor 31, and the push switch 7 is electrically connected to the electromagnet bar 52.

[0032] The test method for a plastic film tensile strength testing device, based on the aforementioned plastic film tensile strength testing device, includes the following steps: S1. Place the two ends of the cut film to be tested at the bottom of the inner wall of the two U-shaped plates 51 respectively, and then press the press switch 7 to control the two electromagnet bars 52 to move downward and limit the film. S2. Press the double control switch 6 again to control the torque motor 31 to rotate clockwise. The two tensioning mechanisms 40 move to both ends. After moving to the point where all four light sensors 81 can detect the light from the four laser beads 91, press the double control switch 6 to stop the torque motor 31 and record the position of the scale pointer 24 in the scale groove 23. S3. When it is necessary to test the film limit, continue to press the double control switch 6 until the film breaks. When the film breaks, stop pressing the double control switch 6, record the distance the scale pointer 24 moves, and calculate the film tensile force according to the number of springs 42 and the spring coefficient. S4. When it is necessary to test whether the film can withstand the tensile test, press the double control switch 6 to control the torque motor 31 to rotate clockwise until the scale pointer 24 moves to the designated scale groove 23.

[0033] The workflow of this invention is as follows: First, place the two ends of the cut film to be tested at the bottom of the inner walls of the two U-shaped plates 51. Then, press the press switch 7 to reverse the current to the electromagnet strip 52, keeping the electromagnet strip 52 and the bottom U-shaped plate 51 magnetically identical. The electromagnet strip 52 moves upward. Then, place the two ends of the film under the two electromagnets 52. Then, energize the electromagnet strip 52 normally. The electromagnet strip 52 and the bottom of the U-shaped plate 51 attract each other, squeezing and limiting the film. The limiting post 53 limits the electromagnet strip 52, so that the electromagnet strip 52 can only move vertically up and down. Then, press the double control switch 6 to control the torque motor 31 to rotate clockwise. The torque motor 31 drives the worm gear 32 to rotate, which in turn drives the worm wheel 33 and the driving gear 34 to rotate synchronously, driving the two driven racks 35 and the first connecting gear... The connecting rod 36 moves to both ends, and the two tensioning mechanisms 40 corresponding to the two first connecting rods 36 move to both ends. After moving until all four light sensors 81 can detect the light from the four laser beads 91, press the double control switch 6 to stop the torque motor 31, and record the position of the scale pointer 24 in the scale groove 23. Operate according to the detected data. When it is necessary to test the film limit, continue to press the double control switch 6 until the film breaks. When the film breaks, stop pressing the double control switch 6, record the distance the scale pointer 24 moves, and calculate the film tensile force according to the number of springs 42 and the spring coefficient. When it is necessary to test whether the film can withstand the fixed tension, directly press the double control switch 6 to control the torque motor 31 to rotate clockwise until the scale pointer 24 moves to the designated scale groove 23. Example 2:

[0034] Please see Figures 1 to 6 This is the second embodiment of the present invention, which differs from the first embodiment in that: The light sensor 81 is directly connected to the torque motor 31 and controlled by a suitable controller. When the light sensor 81 detects light initially (when the film sags significantly), the torque motor 31 starts working directly. During the operation of the torque motor 31, the light sensor 81 continuously sends a signal. When the light sensor 81 no longer detects light (the film moves up and blocks the bottom light sensor), and then detects light again (the film is taut after passing the light sensor), the torque motor 31 is immediately stopped. After an interval of ten to twenty seconds (the interval is used by the operator to take readings), the operation resumes.

[0035] Although embodiments of the invention have been shown and described, it will be understood by those skilled in the art that various changes, modifications, substitutions and alterations can be made to these embodiments without departing from the principles and spirit of the invention, the scope of which is defined by the appended claims and their equivalents.

Claims

1. A device and method for testing the tensile strength of plastic film, characterized in that: The device includes an outer shell (1), a protective shell (2) fixed to the bottom of the inner wall of the outer shell (1), a drive mechanism (30) inside the protective shell (2), the drive mechanism (30) including a torque motor (31) fixed to one side of the inner wall of the protective shell (2), a worm gear (32) fixed to the power output end of the torque motor (31), a worm wheel (33) rotatably connected to the bottom of the middle part of the inner wall of the protective shell (2), a drive gear (34) fixed to the top of the worm wheel (33), driven racks (35) meshing on both sides of the drive gear (34), and first connecting rods (36) fixed to opposite ends of the two driven racks (35). The top of each connecting rod (36) is fixed with a tensioning mechanism (40). The tensioning mechanism (40) includes a movable seat (41). A support wheel (42) is fixed on one side of the movable seat (41). A limiting mechanism (50) is provided at one end of the support wheel (42). The limiting mechanism (50) includes a U-shaped plate (51) that is movably connected to the movable seat (41). An electromagnet strip (52) is provided inside the U-shaped plate (51). A first mounting plate (8) and a second mounting plate (9) are fixed in the middle of both sides of the outer shell (1). A light sensor (81) and a laser lamp bead (91) are fixed on opposite sides of the first mounting plate (8) and the second mounting plate (9).

2. The plastic film tensile strength testing device according to claim 1, characterized in that: The outer casing (1) has a first groove (10) through the middle of both sides. The first mounting plate (8) and the second mounting plate (9) are respectively located in the middle of the two first grooves (10). There are four light sensors (81) and four laser beads (91). The four light sensors (81) and the four laser beads (91) are respectively located at the four corners of the first mounting plate (8) and the four corners of the second mounting plate (9).

3. The plastic film tensile strength testing device according to claim 2, characterized in that: Both ends of the inner wall of the U-shaped plate (51) are fixed with limit posts (53), and both ends of the electromagnet strip (52) are provided with through holes (54). The through holes (54) are movably connected with the limit posts (53). The bottom of the inner wall of the U-shaped plate (51) is made of magnets.

4. The plastic film tensile strength testing device according to claim 3, characterized in that: The movable seat (41) has a third sliding groove (43) in the middle. The U-shaped plate (51) is slidably connected to the third sliding groove (43). The bottom of the inner wall of the U-shaped plate (51) is set at the same horizontal plane as the two light sensors (81) located in the same vertical plane.

5. The tensile strength testing device for plastic film according to claim 4, characterized in that: The top and bottom of both ends of the movable seat (41) are rotatably connected with support wheels (44). The two ends of the movable seat (41) are respectively connected through the two first sliding grooves (10). The support wheels (44) are in contact with the outer wall of the outer shell (1). Multiple springs (42) are provided. The multiple springs (42) are located on one side of the movable seat (41) and are arranged horizontally at equal intervals.

6. The tensile strength testing device for plastic film according to claim 1, characterized in that: The top of the protective shell (2) is provided with a second sliding groove (21), and the two first connecting rods (36) are slidably connected to the second sliding groove (21). The two first connecting rods (36) are fixed with a bellows cover (22) on opposite sides.

7. The tensile strength testing device for plastic film according to claim 6, characterized in that: One of the first connecting rods (36) has a scale pointer (24) fixed on one side at the top of the protective shell (2). The top of the protective shell (2) is provided with a scale groove (23) near the scale pointer (24). There are multiple scale grooves (23), and the multiple scale grooves (23) are arranged horizontally at equal intervals.

8. The tensile strength testing device for plastic film according to claim 1, characterized in that: A control panel is fixed on one side of the outer wall of the outer shell (1). A double-control switch (6) and a push switch (7) are fixed on one side of the control panel. The double-control switch (6) is electrically connected to the torque motor (31), and the push switch (7) is electrically connected to the electromagnet bar (52).

9. A test method for a plastic film tensile strength testing device according to any one of claims 1-8, based on the aforementioned plastic film tensile strength testing device, characterized in that: Includes the following steps: S1. Place the two ends of the cut film to be tested at the bottom of the inner wall of the two U-shaped plates (51), and then press the press switch (7) to control the two electromagnet bars (52) to move downward to limit the film. S2. Press the double control switch (6) again to control the torque motor (31) to rotate clockwise. The two tensioning mechanisms (40) move to both ends. After moving to the point where all four light sensors (81) can detect the light from the four laser beads (91), press the double control switch (6) to stop the torque motor (31) and record the position of the scale pointer (24) in the scale groove (23). S3. When it is necessary to test the film limit, continue to press the double control switch (6) until the film breaks. When the film breaks, stop pressing the double control switch (6), record the distance the scale pointer (24) moves, and calculate the film tensile force according to the number of springs (42) and the spring coefficient. S4. When it is necessary to test whether the film can withstand the tension, press the double control switch (6) directly to control the torque motor (31) to rotate clockwise until the scale pointer (24) moves to the designated scale groove (23).

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