Plastic guard net clamp and tension testing machine for detecting the same and operating method thereof

Abstract

The present application belongs to the technical field of testing equipment, especially a clamp for plastic protective net and a tension testing machine for testing and an operating method thereof, aiming at the problems that the plastic protective net is easy to slip, locally crushed, the tension of both sides is uneven after clamping, and the existing anti-tear test cannot simulate the rapid crack propagation when being punctured under the state of being stretched tightly, the tension testing machine comprises two groups of the above-mentioned clamps, is further provided with a counterweight rod and a lifting strip for forcibly straightening the protective net, and a ejector pin assembly driven by a rack, a gear, a one-way bearing and a torsional spring, the ejector pin assembly automatically pierces the ejector pin into the protective net when the protective net is stretched to the state of being stretched tightly, and the testing machine further increases the separation stroke of the upper and lower clamps through a pulling rope and a groove wheel, the present application is used for testing the tensile and anti-tear performance of the plastic protective net, can reduce the clamping error, simulate the tearing process under the actual state of being stretched tightly, and reduce the height cost of the equipment.

Description

Technical Field

[0001] This invention relates to the field of testing equipment technology, and in particular to a clamp for plastic protective netting, a tensile testing machine for testing it, and its operating method. Background Technology

[0002] Plastic protective netting is widely used in earthwork engineering, slope protection, and agricultural planting. In order to test its mechanical properties, it is necessary to use clamps to fix its two ends and apply tensile force. Existing clamps usually use two flat plates to directly press the netting with bolts. In this way, the plastic protective netting is soft and is easy to slip off between the clamps when the tensile force increases. In order to prevent slippage, the operator over-tightens the bolts, which will cause the netting wires to be flattened or cracked at the clamping point, causing the sample to break prematurely at the clamp and the test data to be invalid. Existing tensile testing machines typically use the trapezoidal tear method when testing tear resistance. The operator first makes a cut on the relaxed mesh sample with scissors and then stretches it. This method cannot simulate the real working condition of plastic protective netting being under high tension and encountering a sharp object for puncture, causing the crack to expand instantly. In addition, the plastic protective net is soft and it is difficult to ensure that the tension on both sides is uniform when it is manually clamped. The protective net is prone to tilting or wrinkling, resulting in uneven force during the stretching process. The measured tensile force curve is irregular and sawtooth-shaped, which cannot truly reflect the overall mechanical performance of the product. In traditional tensile testing machines, the tensile stroke is entirely determined by the piston rod stroke of the hydraulic cylinder. For plastic protective nets with a large elongation, in order to obtain a complete tensile curve, it is necessary to customize equipment with a very high body height, which results in large manufacturing costs and space occupation. Summary of the Invention

[0003] The purpose of this invention is to overcome the above-mentioned shortcomings of the prior art and provide a clamp for plastic protective netting, a tensile testing machine for testing it, and its operating method. It can achieve anti-slip, node protection clamping, forced uniform tension before clamping, simulate the instantaneous expansion of cracks caused by sharp objects piercing under actual tensioned service conditions, and complete tensile curve testing of materials with large deformation under limited fuselage height. It effectively solves the problems of slippage, local pressure loss, uneven tension, inability to simulate tensioned piercing and tearing, and high cost of large deformation testing in the tensile testing of plastic protective netting.

[0004] To achieve the above objectives, the present invention adopts the following technical solution: A clamp for plastic protective netting includes a clamp body, which is composed of a mounting base, a first clamping plate, and a second clamping plate. The bottom of the mounting base is provided with a trapezoidal groove, and a trapezoidal plate is provided in the trapezoidal groove. The trapezoidal plate cooperates with the trapezoidal groove. The bottom of the trapezoidal plate extends to the bottom of the trapezoidal groove and is fixed with a first U-shaped plate. The opening of the first U-shaped plate faces downward. A connecting plate is fixed to the top of the first clamping plate by bolts. A connecting lug is welded to the top of the connecting plate. The top of the connecting lug extends into the opening of the first U-shaped plate. A fixing rod passes through the first U-shaped plate, and one end of the fixing rod passes through the connecting lug, for connecting the connecting plate to the first U-shaped plate. A clamping mechanism for clamping the protective netting is provided between the first clamping plate and the second clamping plate. The first clamping plate and the second clamping plate cooperate to clamp the protective netting.

[0005] In one possible design, the clamping mechanism includes a plurality of first fastening bolts, one end of each of the plurality of first fastening bolts passing through the second clamping plate and threadedly connected to the first clamping plate, for clamping and fixing the protective net by bringing the first clamping plate and the second clamping plate close to each other. The first clamping plate and the second clamping plate are provided with a wave groove on the side where they are close to each other, and the two wave grooves on the first clamping plate and the second clamping plate cooperate with each other.

[0006] In one possible design, both of the wave grooves are fixed with elastic pads at the troughs.

[0007] The tensile testing machine includes two sets of clamp bodies from the above-mentioned plastic protective net clamps, and the two sets of clamp bodies are placed symmetrically up and down. It also includes a base plate and a top plate. Four support columns are fixed between the top of the base plate and the bottom of the top plate. The four support columns are in pairs. A simulation mechanism is provided between the two support columns in one pair for simulating the tear resistance of the protective net. The simulation mechanism includes multiple pins and a crossbar that pushes the multiple pins to puncture the protective net. It also includes a testing mechanism for driving two sets of clamp bodies to stretch the protective netting, the testing mechanism including a hydraulic cylinder and multiple outer rods; A leveling mechanism is provided on one side of the clamp body located below, which is used to ensure the tension balance on both sides of the protective net when clamping it. The leveling mechanism includes a counterweight rod and a lifting bar.

[0008] In one possible design, the testing mechanism further includes multiple vertical rods that slide through the top plate, with the same lifting plate fixed to the bottom end of each vertical rod. The cylinder body of the hydraulic cylinder is fixed to the top of the top plate, and the bottom end of the piston rod of the hydraulic cylinder slides through the top plate and is fixedly connected to the top of the lifting plate. The clamping body located above is fixed to the bottom of the lifting plate. Each of the multiple outer rods has an inner rod slidably connected inside it, and the top ends of each of the multiple inner rods are fixedly connected to the clamping body located below. The two sets of clamping bodies cooperate to clamp both ends of the protective net. Each of the multiple outer rods has a spring sleeved on its outer wall, and the bottom ends of each of the multiple springs are fixedly connected to the top of the bottom plate through spring seats. The top ends of each of the multiple springs are fixedly connected to the clamping body located below through spring seats. Each of the multiple outer rods has a third fastening bolt threaded on one side, and the third fastening bolt abuts against the inner rod to fix the outer rod and the inner rod together.

[0009] In one possible design, two symmetrically placed second fastening bolts are provided on one side of the first U-shaped plate in the lower clamp body. One end of each of the two second fastening bolts is threaded through the first U-shaped plate, and one end of each of the two second fastening bolts is threaded through the connecting lug, for fixing the first U-shaped plate and the connecting plate in the lower clamp body, so that the connecting plate and the first clamping plate are kept in a horizontal state.

[0010] In one possible design, the leveling mechanism further includes a protruding strip fixed to one side of the first U-shaped plate in the lower clamp body. Multiple sliding rods slide through the protruding strip, with the tops of each sliding rod fixedly connected to the bottom of the lifting strip. A threaded rod passes through the protruding strip, and a threaded hole is provided within the protruding strip, which is threadedly connected to the threaded rod through the threaded hole. A guide wheel is rotatably connected to one side of the connecting plate in the lower clamp body via a base for guiding the protective net. A counterweight rod is provided above the lifting strip, and the counterweight rod is fixed to the bottom of the protective net by a strap. The top of the lifting strip has an arc-shaped groove that mates with the counterweight rod, and the counterweight rod is located within the arc-shaped groove. A magnet is fixed within the arc-shaped groove, and the outer wall of the counterweight rod has a sheet metal layer, through which the counterweight rod is magnetically connected to the magnet.

[0011] In one possible design, the simulation mechanism further includes two horizontal plates, each fixed to the outer wall of a set of two support columns. A rectangular frame is fixed to one end of each horizontal plate that is close to the other. One end of the crossbar slides through the rectangular frame. A mounting plate is fixed to the end of the rectangular frame facing the protective net. Multiple pins are fixed to one side of the mounting plate for pushing the pins to pierce the protective net. A rotating shaft is located above the rectangular frame, with both ends rotatably connected to two corresponding support columns. A second U-shaped plate is fixedly fitted onto the outer wall of the rotating shaft. The opening of the second U-shaped plate faces downwards, and its bottom end extends into the rectangular frame. Two strip-shaped grooves are provided inside the second U-shaped plate, with a single pin fitted between them. The pin slides smoothly within the grooves and is fixedly inserted through the crossbar. Two protective boxes are rotatably fitted on the outer wall of the rotating shaft. The ends of the two protective boxes that are far apart from each other are fixedly connected to corresponding support columns. Two fixing rings are fixedly fitted on the outer wall of the rotating shaft. The two fixing rings are respectively set in the corresponding protective boxes. The ends of the two fixing rings that are far apart from each other are fixed with torsion springs through spring seats. The ends of the two torsion springs that are far apart from each other are fixedly connected to the inner wall of one side of the corresponding protective box through spring seats. This is used to drive the rotating shaft to reset after it rotates. Two one-way bearings are fitted on the outer wall of the rotating shaft. The two one-way bearings are respectively set in the two protective boxes. The inner ring of the one-way bearing is fixed to the outer wall of the rotating shaft. The outer ring of the one-way bearing is fixed with a gear. Two racks are fixed to the bottom of one side of the lifting plate. The bottom ends of the two racks penetrate the corresponding protective boxes. The two racks mesh with the corresponding gears.

[0012] In one possible design, a mounting rod is fixed to one side of the lifting plate, and the mounting rod is located on the side of the lifting plate away from the rack. A pull rope is fixed to the bottom of the mounting rod. The top of the base plate is rotatably connected to a first grooved wheel and a second grooved wheel via a base. One end of the pull rope is fixedly connected to the bottom of the clamp body located below, guided by the first grooved wheel and the second grooved wheel.

[0013] As the lifting plate moves upward, it simultaneously tensions the mesh and triggers the rack, one-way bearing, and torsion spring to puncture the mesh. Both actions are indispensable, achieving a realistic simulation of dynamic puncture under tension.

[0014] The operation method of the tensile testing machine includes the following steps: S1. Place the upper end of the protective net between the first and second clamping plates of the upper clamping body, tighten the first fastening bolt, so that the second clamping plate moves closer to the first clamping plate, the protective net is clamped, and the protective net bends and deforms along the contour of the wave groove under the action of clamping force. S2. The elastic pad at the trough of the wave groove is compressed by the nodes of the protective net, causing the nodes to sink into the elastic pad. S3. Pass the lower end of the protective net through the guide wheel and pull it downward. Use the strap to fix the counterweight rod to the lower end of the protective net. The counterweight rod falls into the arc groove of the lifting bar and is attracted by the magnet. Rotate the threaded rod to drive the lifting bar to move, and drive the counterweight rod to adjust the pretension of the lower end of the protective net. After the protective net is flattened, use the clamp body below to clamp the lower end of the protective net. Before clamping, tighten the second fastening bolt to lock the connecting ear to the first U-shaped plate. S4. Tighten the third fastening bolt to fix the outer rod and inner rod, start the hydraulic cylinder, and the output shaft of the hydraulic cylinder will drive the lifting plate and the upper clamp body to move upward, applying a tensile load to the protective net; S5. When conducting the tear resistance simulation test, the hydraulic cylinder is activated to move the lifting plate upward. When the displacement of the lifting plate reaches the threshold, the rack and gear mesh, the rack drives the gear to rotate, the gear drives the rotating shaft to rotate through the one-way bearing, the rotating shaft drives the second U-shaped plate to rotate, the second U-shaped plate drives the crossbar to move horizontally through the pin and the strip groove, the crossbar pushes the mounting plate, the pin on the mounting plate pierces the center of the protective net, then the rack and gear disengage, the torsion spring drives the rotating shaft to reset, the pin withdraws, the initial tear is formed in the center of the protective net, the third fastening bolt is tightened to fix the outer rod and the inner rod, the hydraulic cylinder continues to move upward to stretch the protective net until it tears. S6. When the stroke needs to be increased, keep the third fastening bolt loose so that the inner rod can slide freely in the outer rod. Start the hydraulic cylinder. The hydraulic cylinder drives the lifting plate and the upper clamp body to move upward. The lifting plate drives the mounting rod to move upward. The mounting rod pulls the pull rope. The pull rope passes around the first groove wheel and the second groove wheel in sequence and then pulls the lower clamp body to move downward. The spring is stretched and the upper and lower clamp bodies move away from each other. The protective net is stretched quickly.

[0015] Beneficial effects: In this invention, by setting mutually cooperating wave grooves on the clamping surfaces of the first and second clamping plates, the protective net is forced to undergo continuous bending deformation when clamped. The physical bending path effectively increases the frictional resistance and mechanical interlocking force between the protective net and the clamping plates, preventing the protective net from slipping out of the clamp when subjected to large tensile force, thereby improving the success rate of the test and the validity of the data. In this invention, an elastic pad is provided at the trough of the wave groove. When the node of the protective net is pressed into the elastic pad, the elastic pad will partially yield, avoiding direct squeezing and damage to the plastic node by the rigid clamp, preventing the protective net from breaking prematurely at the clamping part, and ensuring that the fracture point of the tensile test is located within the gauge length of the protective net, thereby obtaining accurate tensile strength data. In this invention, the protective net is forcibly straightened and flattened before clamping by the gravity of the counterweight rod and the guidance of the guide wheel. Through the cooperation of the lifting bar and the threaded rod, the operator can precisely adjust the pre-tension of the lower end of the protective net to ensure that the tension on the left and right sides of the protective net is completely balanced. This eliminates the problems of sample skewing and uneven force caused by manual clamping errors, making the measured tensile force curve smooth and continuous, and truly reflecting the overall mechanical properties of the protective net product. In this invention, when the protective net is stretched to a preset tension state, the pin can be automatically inserted into the center of the protective net, simulating the scenario in actual working conditions where the plastic protective net is punctured by a sharp object under high tension. The dynamic puncture process can more realistically reflect the tear resistance of the plastic protective net under service conditions than the traditional method of pre-making incisions on relaxed samples, especially the instantaneous crack propagation characteristics, providing a more reliable basis for product quality assessment. In this invention, a stroke amplification mechanism consisting of a pull rope, a first grooved wheel, a second grooved wheel, and sliding outer and inner rods enables the relative movement distance between the upper and lower clamping bodies to reach twice the stroke of the hydraulic cylinder piston rod. This allows the tensile testing machine to test plastic protective nets with high elongation even with limited machine height, meeting the testing requirements for materials with large deformation and reducing equipment manufacturing costs and space occupation.

[0016] In this invention, the wave groove structure design of the clamping surface, combined with elastic pads, effectively solves the problems of slippage and clamp breakage of plastic protective nets during tensile testing. The leveling mechanism integrated into the tensile testing machine eliminates uneven tension caused by manual clamping, improving the authenticity of test data. The simulation mechanism realizes dynamic puncture under tension, which is closer to actual working conditions. The stroke amplification mechanism uses the cooperation of pull rope and grooved wheel to achieve large stroke tensile testing with a low equipment height. The various mechanisms are linked through a purely mechanical structure, without the need for complex electronic control, ensuring reliable operation and controllable cost. Attached Figure Description

[0017] Figure 1 This is a three-dimensional structural schematic diagram of the clamp for plastic protective netting provided by the present invention; Figure 2 This is a three-dimensional exploded view of the clamp for plastic protective netting provided by the present invention; Figure 3 This is a three-dimensional structural schematic diagram of the tensile testing machine provided by the present invention; Figure 4 This is a three-dimensional structural diagram of the mounting base, lifting plate, and outer rod of the tensile testing machine provided by the present invention; Figure 5 This is a three-dimensional exploded structural diagram of the outer rod and spring of the tensile testing machine provided by the present invention; Figure 6This is a three-dimensional structural diagram of the protrusion and counterweight rod of the tensile testing machine provided by the present invention; Figure 7 This is a three-dimensional exploded view of the lifting bar, guide wheel, and counterweight rod of the tensile testing machine provided by the present invention; Figure 8 This is a three-dimensional structural diagram of the rotating shaft, rectangular frame, and mounting plate of the tensile testing machine provided by the present invention; Figure 9 This is a three-dimensional exploded view of the second U-shaped plate and rectangular frame of the tensile testing machine provided by the present invention; Figure 10 This is a three-dimensional exploded structural diagram of the gears, one-way bearings, and torsion springs of the tensile testing machine provided by the present invention; Figure 11 This is a cross-sectional structural schematic diagram of the tensile testing machine provided by the present invention; Figure 12 This is a three-dimensional structural diagram of the mounting rod, the pull rope, and the second grooved wheel of the tensile testing machine provided by the present invention.

[0018] In the diagram: 1. Mounting base; 2. Trapezoidal groove; 3. Trapezoidal plate; 4. First U-shaped plate; 5. Connecting ear; 6. Connecting plate; 7. Fixing rod; 8. First clamping plate; 9. Second clamping plate; 10. First fastening bolt; 11. Protective net; 12. Corrugated groove; 13. Elastic pad; 14. Base plate; 15. Support column; 16. Top plate; 17. Hydraulic cylinder; 18. Vertical rod; 19. Lifting plate; 20. Outer rod; 21. Inner rod; 22. Spring; 23. Second fastening bolt; 24. Guide wheel 25. Raised bar; 26. Sliding rod; 27. Lifting bar; 28. Threaded rod; 29. ​​Counterweight rod; 30. Horizontal plate; 31. Rectangular frame; 32. Crossbar; 33. Mounting plate; 34. Ejector pin; 35. Rotating shaft; 36. Second U-shaped plate; 37. Strip groove; 38. Pin; 39. Protective box; 40. One-way bearing; 41. Gear; 42. Rack; 43. Torsion spring; 44. Fixing ring; 45. Mounting rod; 46. Pull rope; 47. First grooved wheel; 48. Second grooved wheel. Detailed Implementation

[0019] The technical solutions of the present invention will be clearly and completely described below with reference to the accompanying drawings in the embodiments of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments.

[0020] In one embodiment: Refer to Figure 1 and Figure 2A clamp for plastic protective netting, relating to the field of testing equipment technology, includes a clamp body, which consists of a mounting base 1, a first clamping plate 8, and a second clamping plate 9. The bottom of the mounting base 1 is provided with a trapezoidal groove 2, and a trapezoidal plate 3 is installed inside the trapezoidal groove 2. The shape of the trapezoidal plate 3 matches the trapezoidal groove 2, so that the trapezoidal plate 3 can slide in the trapezoidal groove 2 but cannot fall off the groove opening. The bottom of the trapezoidal plate 3 extends downward to the bottom of the trapezoidal groove 2, and a first U-shaped plate 4 is fixedly connected to the bottom of the trapezoidal plate 3. The opening direction of the first U-shaped plate 4 is downward.

[0021] Reference Figure 1 and Figure 2 A connecting plate 6 is fixedly installed on the top of the first clamping plate 8 by bolts. A connecting lug 5 is welded to the top of the connecting plate 6. The top of the connecting lug 5 extends upward and into the opening of the first U-shaped plate 4. A through hole is provided on the first U-shaped plate 4. The fixing rod 7 passes through the through hole, and one end of the fixing rod 7 also passes through the connecting lug 5. In this way, the fixing rod 7 connects the connecting plate 6 and the first U-shaped plate 4 together, so that the connecting plate 6 can rotate relative to the first U-shaped plate 4 about the axis of the fixing rod 7.

[0022] Reference Figure 1 and Figure 2 A clamping mechanism is provided between the first clamping plate 8 and the second clamping plate 9 to clamp the protective net 11. The first clamping plate 8 and the second clamping plate 9 cooperate to complete the clamping action of the protective net 11. The clamping mechanism includes multiple first fastening bolts 10, one end of which passes through the second clamping plate 9 and is threadedly connected to a pre-set threaded hole on the first clamping plate 8. When the operator tightens the first fastening bolts 10, the head of the first fastening bolt 10 pushes the second clamping plate 9 towards the first clamping plate 8, thereby bringing the first clamping plate 8 and the second clamping plate 9 closer together and applying pressure to the protective net 11 located between them, thus achieving clamping and fixing. Preferably, during the tightening process, the end of the first fastening bolt 10 can extend into the protective net 11. Within the mesh, to further enhance positioning and anti-slip effects, the first clamping plate 8 and the second clamping plate 9 are provided with wave grooves 12 on their adjacent sides, i.e., the clamping surfaces. The wave grooves 12 on the first clamping plate 8 and the second clamping plate 9 are corresponding to each other in position and cooperate with each other in the clamping state. When the protective net 11 is clamped, the protective net 11 will produce continuous bending deformation along the contour of the wave groove 12. This deformation is a physical bending on a macroscopic path, rather than relying solely on the local normal pressure on the clamping surface to generate friction. The shape of the wave groove 12 can be a sine curve shape, a trapezoidal wave shape, or an arc wave shape. During processing, the wave groove 12 can be machined on the first clamping plate 8 and the second clamping plate 9 using only conventional CNC milling equipment, resulting in low processing costs.

[0023] Reference Figure 2 To further protect the node structure of the protective net 11, elastic pads 13 are fixedly installed at the troughs of the two corrugated grooves 12. The elastic pads 13 can be made of rubber or polyurethane. When the protective net 11 is clamped, the protruding nodes on the surface of the protective net 11 will be pressed into the elastic pads 13. The elastic pads 13 will undergo local yielding deformation when subjected to pressure, thereby avoiding rigid compression between the rigid clamp and the plastic nodes and preventing the nodes from being crushed.

[0024] In another embodiment: Refer to Figure 3 , Figure 4 and Figure 8 The tensile testing machine includes two sets of clamp bodies in the above-mentioned plastic protective net 11 clamps. These two sets of clamp bodies are placed symmetrically in space. The tensile testing machine also includes a base plate 14 and a top plate 16. Four support columns 15 are fixedly connected between the top of the base plate 14 and the bottom of the top plate 16.

[0025] Reference Figure 3 and Figure 4 The tensile testing machine also includes a testing mechanism, which is used to drive the upper and lower clamp bodies respectively, so that they clamp the two ends of the protective net 11 and apply tensile load to the protective net 11. The testing mechanism includes a hydraulic cylinder 17 and multiple outer rods 20.

[0026] Reference Figures 3-5The testing mechanism also includes multiple vertical rods 18, which slide through through holes in the top plate 16. The bottom ends of all vertical rods 18 are fixedly connected to the same lifting plate 19. The cylinder body of the hydraulic cylinder 17 is bolted to the top of the top plate 16. The bottom end of the piston rod of the hydraulic cylinder 17 slides through the through holes in the top plate 16 and is fixedly connected to the top of the lifting plate 19. The upper clamp body is fixedly installed at the bottom of the lifting plate 19. Multiple outer rods 20 are hollow tubular structures, and each outer rod 20 has an inner rod 21 slidably connected inside. The top ends of all inner rods 21 are fixedly connected to the lower clamp body. The upper and lower clamps are... The main body works in conjunction to clamp the top and bottom of the protective net 11. Each outer rod 20 has a spring 22 fitted on its outer wall. The bottom of the spring 22 is fixedly connected to the top of the base plate 14 via a spring seat, and the top of the spring 22 is fixedly connected to the clamping body located below via another spring seat. The spring 22 is fitted onto the outside of the outer rod 20. Each outer rod 20 has a threaded hole on one side wall, through which a third fastening bolt is threaded. The end of the third fastening bolt extends into the outer rod 20 and abuts against the outer wall of the inner rod 21. By tightening the third fastening bolt, the relative position of the outer rod 20 and the inner rod 21 can be fixed. A dustproof telescopic sleeve (not shown in the figure) is installed at the joint between the top of the outer rod 20 and the inner rod 21. A foldable corrugated protective cover is fitted around the spring 22. The upper and lower ends of the corrugated protective cover are fixedly connected to the clamping body located below and the spring seat on the base plate 14, respectively, to isolate external dust.

[0027] Specifically, before the test begins, the two ends of the protective net 11 are placed between the first clamping plate 8 and the second clamping plate 9 of the upper and lower clamping bodies, respectively. Then, the operator tightens the first fastening bolts 10 on the upper and lower clamping bodies to complete the initial clamping of the two ends of the protective net 11. Next, all the third fastening bolts are tightened to fix the length of the outer rod 20 and the inner rod 21. At this time, the position of the clamping body located below relative to the base plate 14 is fixed. The hydraulic cylinder 17 is activated, and the output axis of the hydraulic cylinder 17 retracts upward, driving the lifting plate 19 and the upper clamping body fixed at its bottom to move upward. The upper clamping body moves upward, applying an upward pulling force to the protective net 11, thus starting the tensile test.

[0028] Reference Figure 6In the clamp body located below, two symmetrically placed second fastening bolts 23 are provided on one side of the first U-shaped plate 4. One end of each of the two second fastening bolts 23 is threaded through the side wall of the first U-shaped plate 4. When needed, the two second fastening bolts 23 can be tightened so that their ends pass through the pre-set holes on the connecting ear 5. In this way, the first U-shaped plate 4 and the connecting plate 6 in the clamp body located below can be locked to prevent the connecting plate 6 from rotating relative to the first U-shaped plate 4. This allows the connecting plate 6 and the first clamping plate 8 to maintain a precise horizontal state, which is convenient for the operator to perform clamping operations on the bottom of the protective net 11.

[0029] Reference Figure 4 and Figure 6 A leveling mechanism is also provided on one side of the clamp body located below. The leveling mechanism is used to ensure that the tension on the left and right sides of the protective net 11 is balanced before the clamp body below clamps the protective net 11, and to eliminate the initial wrinkles and skewing of the protective net 11. The leveling mechanism includes a counterweight rod 29 and a lifting bar 27.

[0030] Reference Figure 4 , Figure 6 and Figure 7 The leveling mechanism also includes a protruding strip 25, which is fixed to one side of the first U-shaped plate 4 located in the lower clamping body. The protruding strip 25 has multiple vertically penetrating sliding holes, each through which a sliding rod 26 slides. The top ends of all sliding rods 26 are fixedly connected to the bottom of the lifting bar 27. A threaded hole is also provided at the center of the protruding strip 25, through which a threaded rod 28 passes and is threadedly connected to the protruding strip 25. The top end of the threaded rod 28 is rotatably connected to the bottom of the lifting bar 27 via a bearing. By rotating the threaded rod 28, the height of the lifting bar 27 can be adjusted. The connecting plate 6 located in the lower clamping body... On one side, a guide wheel 24 is rotatably connected to the base. The guide wheel 24 is used to guide the protective net 11. The counterweight rod 29 is placed above the lifting bar 27. When in use, the operator first fixes the counterweight rod 29 to the lower end of the protective net 11 with straps. The top of the lifting bar 27 is provided with an arc-shaped groove that matches the shape of the counterweight rod 29. The counterweight rod 29 is placed in the arc-shaped groove. A magnet is fixed inside the arc-shaped groove. The outer wall of the counterweight rod 29 is covered with a layer of iron sheet. When the counterweight rod 29 falls into the arc-shaped groove, the counterweight rod 29 generates a magnetic attraction between the iron sheet and the magnet, and is thus attracted to the lifting bar 27.

[0031] Specifically, after the upper clamping body has clamped the top of the protective net 11, the operator connects the bottom of the protective net 11 to the counterweight rod 29 via straps. Under the action of its own weight, the counterweight rod 29 will fall downwards, applying a downward pulling force to the protective net 11. This pulling force will forcibly straighten and flatten the protective net 11, effectively eliminating the wrinkles and slack of the protective net 11 in its initial state. At the same time, the guide wheel 24 guides the movement direction of the protective net 11, ensuring that the protective net 11 moves vertically downwards. As the counterweight rod 29 continues to fall... The process continues until the counterweight rod 29 is magnetically attracted into the arc-shaped groove of the lifting bar 27. At this point, the operator adjusts the height of the lifting bar 27 by rotating the threaded rod 28. The lifting bar 27 drives the counterweight rod 29 to move up and down, thereby adjusting the tension of the lower end of the protective net 11 until the entire width of the protective net 11 is evenly stretched and the tension on the left and right sides is balanced. In this state, the operator then operates the clamp body located below to clamp the bottom of the protective net 11. Through the above steps, it can be ensured that the protective net 11 will not tilt or have uneven tension on the left and right sides after clamping.

[0032] Reference Figure 3 and Figure 8 The four support columns 15 are arranged in pairs and located on the left and right sides of the bottom plate 14 and the top plate 16, respectively. A simulation mechanism is set between the two support columns 15 in one group. The simulation mechanism is used to simulate the tear resistance of the protective net 11. The simulation mechanism includes multiple pins 34 and a crossbar 32. The crossbar 32 is used to push the multiple pins 34 to puncture the protective net 11.

[0033] Reference Figure 3 , Figure 4 and Figure 8 The simulation mechanism also includes two horizontal plates 30, which are fixedly connected to the outer walls of the same set of two support columns 15. The two horizontal plates 30 are fixedly connected to the same rectangular frame 31 at their close ends. One end of the horizontal bar 32 slides through the side wall of the rectangular frame 31 and can slide freely in the horizontal direction within the rectangular frame 31. The end of the rectangular frame 31 facing the protective net 11 is fixedly connected to the mounting plate 33. Multiple ejector pins 34 are fixed on one side surface of the mounting plate 33 in a predetermined arrangement, with the tips of the ejector pins 34 facing the protective net 11. The movement of the horizontal bar 32 can drive the mounting plate 33 to move, thereby causing the mounting plate 33 to push the ejector pins 34 to pierce the protective net 11.

[0034] Reference Figure 3 , Figure 4 , Figure 8 and Figure 9A rotating shaft 35 is provided above the rectangular frame 31. The two ends of the rotating shaft 35 are rotatably connected to two corresponding support columns 15 through bearings. A second U-shaped plate 36 is fixedly sleeved on the outer wall of the rotating shaft 35. The opening of the second U-shaped plate 36 faces downward and the bottom end of the second U-shaped plate 36 extends downward and into the interior of the rectangular frame 31. A strip groove 37 is provided on each of the two side walls of the second U-shaped plate 36. The positions of the two strip grooves 37 correspond to each other. The same pin 38 is fitted in the two strip grooves 37 with clearance. The diameter of the pin 38 is smaller than the width of the strip groove 37, so that the pin 38 can slide smoothly in the strip groove 37. The pin 38 is fixedly passed through the crossbar 32 and the pin 38 intersects the axis of the crossbar 32 perpendicularly.

[0035] Reference Figure 3 , Figure 4 and Figures 8-10 Two protective boxes 39 are rotatably fitted on the outer wall of the rotating shaft 35. The ends of the two protective boxes 39 that are far apart from each other are respectively fixedly connected to the corresponding support columns 15. Two fixing rings 44 are also fixedly fitted on the outer wall of the rotating shaft 35. Each fixing ring 44 is respectively set inside a corresponding protective box 39. A torsion spring 43 is fixedly connected to the side of each fixing ring 44 that is far apart from each other through a spring seat. The end of each torsion spring 43 that is far apart from each other is fixedly connected to the inner wall of the corresponding protective box 39 through another spring seat. When the rotating shaft 35 rotates, the torsion spring 43 will be twisted and store elastic potential energy. When the external force disappears, the torsion spring 43 drives the rotating shaft 35 to rotate in the opposite direction and reset. Two one-way bearings 40 are also fitted onto the outer wall of the rotating shaft 35. Each one-way bearing 40 is located inside one of the two protective boxes 39. The inner ring of the one-way bearing 40 is fixedly installed on the outer wall of the rotating shaft 35, and a gear 41 is fixedly installed on the outer ring of the one-way bearing 40. Two racks 42 are fixedly connected to the bottom of one side of the lifting plate 19. The bottom ends of these two racks 42 extend downwards and pass through through holes opened in the corresponding protective boxes 39. Each rack 42 meshes with a gear 41 located in the same protective box 39. The protective box 39 has a sealing groove (not shown in the figure) for the racks 42 to pass through. A felt sealing ring or an elastic dust curtain is installed in the sealing groove to scrape off debris from the surface of the racks 42 during reciprocating motion. The protective box 39 forms a relatively enclosed space, in which the gear 41, one-way bearing 40 and torsion spring 43 are housed to prevent external debris from entering.

[0036] Specifically, during the process of hydraulic cylinder 17 driving lifting plate 19 upward to pull protective net 11 upward, lifting plate 19 simultaneously drives two racks 42 to move upward. When the upward displacement of lifting plate 19 reaches a preset value, such as reaching the tension threshold of protective net 11 in actual working state, rack 42 begins to mesh with gear 41. As rack 42 moves upward, it drives gear 41 to rotate. At this time, one-way bearing 40 is in a locked state, that is, the outer ring of one-way bearing 40 drives the inner ring and the rotating shaft 35 fixed on the inner ring to rotate together. When rotating shaft 35 rotates, it drives the second U-shaped plate 36 to rotate counterclockwise. When the second U-shaped plate 36 rotates, the strip groove 37 on it pushes the pin 38. As the second U-shaped plate 36 rotates, the pin 38 will... Forced to move along the strip groove 37, the crossbar 32 moves horizontally towards the protective net 11. The crossbar 32 pushes the mounting plate 33, and the pin 34 on the mounting plate 33 then pierces the central area of ​​the protective net 11, which is in a highly tensioned state. Afterward, as the lifting plate 19 continues to move upward, the rack 42 disengages from the gear 41. At this time, the driving force applied to the rotating shaft 35 disappears. Under the action of the reset torque of the torsion spring 43, the rotating shaft 35 rotates clockwise in the opposite direction. The rotating shaft 35 drives the second U-shaped plate 36 to reset. The crossbar 32, the mounting plate 33, and the pin 34 also retract away from the protective net 11. During the whole process, the protective net 11 is pierced by the pin 34 in a dynamically tensioned state. Then, it continues to be stretched and the expansion and tearing process of the crack is observed. All actions are completed in one continuous motion.

[0037] It also includes a control system, which includes a programmable logic controller (PLC) or a microcontroller (MCU). The hydraulic valve group of the hydraulic cylinder 17 and the displacement sensor (not shown in the figure) used to detect the displacement of the lifting plate 19 are all electrically connected to the control system. The control system controls the start, stop and reverse of the hydraulic cylinder 17 according to a preset displacement threshold or tension value.

[0038] In another embodiment: Refer to Figure 4 , Figure 11 and 12 A mounting rod 45 is fixedly connected to one side of the lifting plate 19. The mounting rod 45 is located on the side of the lifting plate 19 away from the rack 42. A pull rope 46 is fixedly connected to the bottom of the mounting rod 45. The top of the base plate 14 is rotatably connected to the first grooved wheel 47 and the second grooved wheel 48 through the base. One end of the pull rope 46 passes through the grooves of the first grooved wheel 47 and the second grooved wheel 48 in sequence, and is finally fixedly connected to the bottom of the clamp body located below.

[0039] Before the test begins, all third fastening bolts need to be loosened so that the outer rod 20 and the inner rod 21 can slide freely. When the hydraulic cylinder 17 is activated and the lifting plate 19 is moved upward, the lifting plate 19 moves the mounting rod 45 upward. The mounting rod 45 pulls the pull rope 46. The pull rope 46, through the reversing action of the first groove wheel 47 and the second groove wheel 48, converts the upward pulling force into a downward pulling force, which acts on the bottom of the clamp body located below. Therefore, when the lifting plate 19 moves upward, the clamp body below will move downward at the same time. The speed at which the two clamp bodies move away from each other is twice the moving speed of the lifting plate 19, and their relative displacement distance is also twice the stroke of the piston rod of the hydraulic cylinder 17.

[0040] The operation method of the tensile testing machine includes the following steps: S1. The operator first places the upper end of the plastic protective net 11 sample to be tested between the first clamping plate 8 and the second clamping plate 9 in the clamp body located above. Then, the operator tightens the multiple first fastening bolts 10 on the clamp body. The screw of the first fastening bolt 10 passes through the second clamping plate 9 and connects with the threaded hole on the first clamping plate 8. As the first fastening bolts 10 are tightened, the second clamping plate 9 moves closer to the first clamping plate 8, and the protective net 11 is clamped between the first clamping plate 8 and the second clamping plate 9. Since the first clamping plate 8 and the second clamping plate 9 are provided with wave grooves 12 on their opposite surfaces, the protective net 11 is forced to produce continuous bending deformation along the contour of the wave grooves 12 under the action of clamping force. This wave-shaped bending path greatly increases the contact area and frictional resistance between the protective net 11 and the clamping plate. At the same time, the mesh of the protective net 11 bends multiple times at the crests and troughs, so that the protective net 11 cannot slip out of the clamping plate when subjected to tensile force. S2. When the elastic pad 13 located at the trough of the wave groove 12 is squeezed by the node of the protective net 11, it will undergo elastic compression, causing the node to sink into the pad, which increases the fitting resistance at the node and avoids the node from being damaged by rigid compression. S3. After completing the upper clamping, the operator passes the lower end of the protective net 11 through the guide wheel 24 and pulls it downwards. The operator uses straps to fix the counterweight rod 29 to the lower end of the protective net 11. Under the gravity of the counterweight rod 29, the protective net 11 is pulled downwards and straightened. The guide wheel 24 guides the protective net 11 to move vertically downwards, ensuring that it is not tilted. The counterweight rod 29 at the lower end of the protective net 11 finally falls into the arc-shaped groove at the top of the lifting bar 27 and is attracted by the magnet block in the arc-shaped groove. At this time, the operator rotates the threaded rod 28. The threaded rod 28 engages with the threaded hole in the protrusion 25, driving the... The lifting bar 27 moves up and down, and the lifting bar 27 drives the counterweight bar 29 to move, thereby precisely adjusting the pretension of the lower end of the protective net 11 until the entire width of the protective net 11 is completely flattened and the tension on the left and right sides reaches a balanced state. After the flattening is completed, the operator operates the clamp body located below and clamps the lower end of the protective net 11 in the same way. Before clamping the lower clamp body, the operator can tighten the two second fastening bolts 23 to lock the connecting ear 5 in the lower clamp body with the first U-shaped plate 4, ensuring that the first clamping plate 8 and the second clamping plate 9 are in a horizontal state for easy operation. S4. The operator tightens all the third fastening bolts to fix the length of the outer rod 20 and the inner rod 21. Then, the hydraulic cylinder 17 is started. The output shaft of the hydraulic cylinder 17 retracts upward, driving the lifting plate 19 and the upper clamp body to move upward. The upper clamp body applies a tensile load to the protective net 11, and the sensor records the tensile force and displacement data. S5. If a tear resistance simulation test is required, start the hydraulic cylinder 17. The hydraulic cylinder 17 drives the lifting plate 19 to move upward. In the initial stage of the upward movement of the lifting plate 19, when the displacement of the lifting plate 19 reaches the preset threshold, the rack 42 fixed on its side begins to mesh with the gear 41 in the simulation mechanism. The rack 42 moves upward and drives the gear 41 to rotate. Due to the presence of the one-way bearing 40, the rotation of the gear 41 will drive the rotating shaft 35 to rotate. The second U-shaped plate 36 on the rotating shaft 35 will rotate accordingly. Through the cooperation of the pin 38 and the strip groove 37, the rotational motion is converted into the horizontal linear motion of the crossbar 32. The crossbar 32 pushes the mounting plate 33, and the ejector pin 3 on the mounting plate 33... 4. Quickly insert the needle into the center of the protective net 11, which is in a highly tensioned state. Then, the rack 42 disengages from the gear 41, the torsion spring 43 drives the rotating shaft 35 to reset, and the ejector pin 34 exits the protective net 11. At this time, an initial tear has been pierced in the center of the protective net 11. The operator then tightens all the third fastening bolts to fix the length of the outer rod 20 and the inner rod 21. The hydraulic cylinder 17 continues to move upward to stretch the protective net 11 with the initial tear until the protective net 11 is completely torn. Throughout the process, from tensioning and insertion to continued stretching, all actions are triggered by a single continuous action of the hydraulic cylinder 17, without the need for additional control logic or external pneumatic components. S6. After the protective net 11 is clamped and leveled, the operator keeps all the third fastening bolts in the loosened state. At this time, the inner rod 21 can slide freely inside the outer rod 20. The operator starts the hydraulic cylinder 17, and the output axis of the hydraulic cylinder 17 retracts upward, driving the lifting plate 19 and the upper clamp body to move upward. At the same time as the lifting plate 19 moves upward, it drives the mounting rod 45 fixed on one side to move upward synchronously. The mounting rod 45 pulls the pull rope 46. The pull rope 46 passes through the groove of the first grooved wheel 47 and the groove of the second grooved wheel 48 in sequence. The first grooved wheel 47 and the second grooved wheel 48 are both rotatably connected to the base plate 14 through the base, as... The reversing element, the end of the pull rope 46, is fixedly connected to the bottom of the clamp body located below. Therefore, when the mounting rod 45 pulls the pull rope 46 upward, the pull rope 46 applies a downward pulling force to the bottom of the clamp body below through the reversing action of the two grooved wheels. Under the action of this pulling force, the clamp body below moves vertically downward along the guide direction of the outer rod 20. The spring 22 is further stretched in this process. The upward speed of the upper clamp body is equal to the downward speed of the lower clamp body. The relative speed at which the two move away from each other is twice the moving speed of the upper clamp body. The protective net 11 is stretched rapidly, and its internal tensile stress rises rapidly.

[0041] However, as is well known to those skilled in the art, the working principle and wiring method of the hydraulic cylinder 17 are conventional means or common knowledge, and will not be described in detail here. Those skilled in the art can make any selections according to their needs or convenience.

[0042] The accompanying drawings in this application are for illustrative purposes only. The dimensions and shapes of the components shown are not actual limitations but are merely schematic representations. In actual implementation, the components can be reasonably configured and adjusted according to specific needs and actual conditions.

[0043] The above description is only a preferred embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any equivalent substitutions or modifications made by those skilled in the art within the scope of the technology disclosed in the present invention, based on the technical solution and inventive concept of the present invention, should be covered within the scope of protection of the present invention.

Claims

1. A clamp for plastic protective netting, characterized in that, The fixture includes a main body, which is composed of a mounting base (1), a first clamping plate (8), and a second clamping plate (9). The bottom of the mounting base (1) is provided with a trapezoidal groove (2), and a trapezoidal plate (3) is provided in the trapezoidal groove (2). The trapezoidal plate (3) cooperates with the trapezoidal groove (2). The bottom of the trapezoidal plate (3) extends to the bottom of the trapezoidal groove (2) and is fixed with a first U-shaped plate (4). The opening of the first U-shaped plate (4) faces downward. The top of the first clamping plate (8) is fixed with a connecting plate (6) by bolts. The top of the connecting plate (6) is welded with a connecting ear (5). The top of the connecting ear (5) extends into the opening of the first U-shaped plate (4). A fixing rod (7) passes through the first U-shaped plate (4), and one end of the fixing rod (7) passes through the connecting ear (5) to connect the connecting plate (6) and the first U-shaped plate (4). A clamping mechanism for clamping the protective net (11) is provided between the first clamping plate (8) and the second clamping plate (9). The first clamping plate (8) and the second clamping plate (9) cooperate to clamp the protective net (11).

2. The clamp for plastic protective netting according to claim 1, characterized in that, The clamping mechanism includes multiple first fastening bolts (10), one end of each of the multiple first fastening bolts (10) passes through the second clamping plate (9) and is threadedly connected to the first clamping plate (8), which is used to bring the first clamping plate (8) and the second clamping plate (9) closer to each other to clamp and fix the protective net (11). The first clamping plate (8) and the second clamping plate (9) are provided with wave grooves (12) on the side where they are close to each other, and the two wave grooves (12) on the first clamping plate (8) and the second clamping plate (9) cooperate with each other.

3. The clamp for plastic protective netting according to claim 2, characterized in that, Both of the wave grooves (12) are fixed with elastic pads (13) at the trough positions.

4. A tensile testing machine, comprising two sets of clamp bodies from the clamps for plastic protective netting as described in claim 3, wherein the two sets of clamp bodies are arranged symmetrically in a vertical position, characterized in that, It also includes a base plate (14) and a top plate (16). Four support columns (15) are fixed between the top of the base plate (14) and the bottom of the top plate (16). The four support columns (15) are in pairs. A simulation mechanism is provided between the two support columns (15) in one pair to simulate the tear resistance of the protective net (11). The simulation mechanism includes multiple pins (34) and a crossbar (32) that pushes the multiple pins (34) to puncture the protective net (11). It also includes a testing mechanism for driving two sets of clamp bodies to stretch the protective net (11) respectively. The testing mechanism includes a hydraulic cylinder (17) and multiple outer rods (20). A leveling mechanism is provided on one side of the clamp body located below, which is used to ensure the tension balance on both sides of the protective net (11) when clamping the protective net (11). The leveling mechanism includes a counterweight rod (29) and a lifting bar (27).

5. The tensile testing machine according to claim 4, characterized in that, The testing mechanism also includes multiple vertical rods (18) that slide through the top plate (16). The bottom ends of the multiple vertical rods (18) are fixed to the same lifting plate (19). The cylinder body of the hydraulic cylinder (17) is fixed to the top of the top plate (16). The bottom end of the piston rod of the hydraulic cylinder (17) slides through the top plate (16) and is fixedly connected to the top of the lifting plate (19). The clamp body located above is fixed to the bottom of the lifting plate (19). The multiple outer rods (20) are all slidably connected to inner rods (21). The top ends of the multiple inner rods (21) are all connected to the bottom of the lifting plate (19). The clamping bodies are fixedly connected, and the two clamping bodies cooperate to clamp the two ends of the protective net (11). The outer walls of the multiple outer rods (20) are fitted with springs (22). The bottom ends of the multiple springs (22) are fixedly connected to the top of the base plate (14) through spring seats. The top ends of the multiple springs (22) are fixedly connected to the clamping bodies located below through spring seats. The outer rods (20) are threaded with a third fastening bolt on one side, and the third fastening bolt abuts against the inner rod (21) to fix the outer rods (20) and the inner rods (21) in place.

6. The tensile testing machine according to claim 5, characterized in that, Two second fastening bolts (23) are provided on one side of the first U-shaped plate (4) in the lower clamp body. One end of each of the two second fastening bolts (23) is threaded through the first U-shaped plate (4), and one end of each of the two second fastening bolts (23) is threaded through the connecting ear (5). This is used to fix the first U-shaped plate (4) and the connecting plate (6) in the lower clamp body, so that the connecting plate (6) and the first clamping plate (8) remain in a horizontal state.

7. The tensile testing machine according to claim 6, characterized in that, The leveling mechanism also includes a protruding strip (25), which is fixed to one side of the first U-shaped plate (4) in the lower clamp body. Multiple sliding rods (26) slide through the protruding strip (25), and the top ends of the multiple sliding rods (26) are fixedly connected to the bottom of the lifting bar (27). A threaded rod (28) passes through the protruding strip (25), and a threaded hole is provided in the protruding strip (25). The protruding strip (25) is threadedly connected to the threaded rod (28) through the threaded hole. The connecting plate (6) in the lower clamp body... A guide wheel (24) is rotatably connected to one side via a base to guide the protective net (11). A counterweight rod (29) is provided above the lifting bar (27). The counterweight rod (29) is fixed to the bottom of the protective net (11) by a strap. The top of the lifting bar (27) is provided with an arc-shaped groove that matches the counterweight rod (29), and the counterweight rod (29) is located in the arc-shaped groove. A magnet is fixed in the arc-shaped groove. The outer wall of the counterweight rod (29) is provided with a sheet metal layer. The counterweight rod (29) is magnetically connected to the magnet through the sheet metal layer.

8. The tensile testing machine according to claim 7, characterized in that, The simulation mechanism also includes two horizontal plates (30), which are respectively fixed to the outer walls of the same set of two support columns (15). The ends of the two horizontal plates (30) that are close to each other are fixed to the same rectangular frame (31). One end of the horizontal bar (32) slides through the rectangular frame (31). An installation plate (33) is fixed to the end of the rectangular frame (31) facing the protective net (11). Multiple ejector pins (34) are fixed to one side of the installation plate (33) to allow the installation plate (33) to push the ejector pins (34) to pierce the protective net (11). The rectangular frame (31)... A rotating shaft (35) is provided at the top, and the two ends of the rotating shaft (35) are respectively rotatably connected to two corresponding support columns (15). A second U-shaped plate (36) is fixedly sleeved on the outer wall of the rotating shaft (35). The opening of the second U-shaped plate (36) faces downward, and the bottom end of the second U-shaped plate (36) extends into the rectangular frame (31). Two strip grooves (37) are provided in the second U-shaped plate (36). The same pin (38) is fitted in the two strip grooves (37) with a gap. The pin (38) slides smoothly in the strip grooves (37). The pin (38) is fixedly inserted through the crossbar (3). 2) Two protective boxes (39) are rotatably fitted on the outer wall of the rotating shaft (35). The ends of the two protective boxes (39) that are far apart from each other are fixedly connected to the corresponding support column (15). Two fixing rings (44) are fixedly fitted on the outer wall of the rotating shaft (35). The two fixing rings (44) are respectively set in the corresponding protective boxes (39). The sides of the two fixing rings (44) that are far apart from each other are fixed with torsion springs (43) through spring seats. The ends of the two torsion springs (43) that are far apart from each other are fixedly connected to the inner wall of one side of the corresponding protective box (39) through spring seats, for use in rotation After the shaft (35) rotates, it drives the rotating shaft (35) to reset and rotate. Two one-way bearings (40) are sleeved on the outer wall of the rotating shaft (35). The two one-way bearings (40) are respectively set in two protective boxes (39). The inner ring of the one-way bearing (40) is fixed to the outer wall of the rotating shaft (35). The outer ring of the one-way bearing (40) is fixed with a gear (41). Two racks (42) are fixed at the bottom of one side of the lifting plate (19). The bottom ends of the two racks (42) penetrate the corresponding protective boxes (39). The two racks (42) mesh with the corresponding gears (41).

9. The tensile testing machine according to claim 8, characterized in that, A mounting rod (45) is fixed on one side of the lifting plate (19), and the mounting rod (45) is located on the side of the lifting plate (19) away from the rack (42). A pull rope (46) is fixed at the bottom of the mounting rod (45). The top of the base plate (14) is rotatably connected to a first grooved wheel (47) and a second grooved wheel (48) through a base. One end of the pull rope (46) is fixedly connected to the bottom of the clamp body located below through the guidance of the first grooved wheel (47) and the second grooved wheel (48).

10. A method for operating a tensile testing machine, applied to the tensile testing machine of claim 9, characterized in that, Includes the following steps: S1. Place the upper end of the protective net (11) between the first clamping plate (8) and the second clamping plate (9) of the upper clamping body, tighten the first fastening bolt (10), so that the second clamping plate (9) moves closer to the first clamping plate (8), the protective net (11) is clamped, and the protective net (11) bends and deforms along the contour of the wave groove (12) under the action of clamping force. S2, The elastic pad (13) at the trough of the wave groove (12) is compressed by the nodes of the protective net (11), causing the nodes to sink into the elastic pad (13); S3. Pass the lower end of the protective net (11) through the guide wheel (24) and pull it downward. Fix the counterweight rod (29) to the lower end of the protective net (11) with the strap. The counterweight rod (29) falls into the arc groove of the lifting bar (27) and is attracted by the magnet. Rotate the threaded rod (28) to drive the lifting bar (27) to move, and drive the counterweight rod (29) to adjust the pretension of the lower end of the protective net (11). After the protective net (11) is flattened, use the clamp body below to clamp the lower end of the protective net (11). Before clamping, tighten the second fastening bolt (23) to lock the connecting ear (5) and the first U-shaped plate (4). S4. Tighten the third fastening bolt to fix the outer rod (20) and inner rod (21), start the hydraulic cylinder (17), the output shaft of the hydraulic cylinder (17) drives the lifting plate (19) and the upper clamp body to move upward, and apply tensile load to the protective net (11); S5. During the tear resistance simulation test, the hydraulic cylinder (17) is activated to move the lifting plate (19) upward. When the displacement of the lifting plate (19) reaches the threshold, the rack (42) meshes with the gear (41), and the rack (42) drives the gear (41) to rotate. The gear (41) drives the rotating shaft (35) to rotate through the one-way bearing (40). The rotating shaft (35) drives the second U-shaped plate (36) to rotate. The second U-shaped plate (36) drives the crossbar through the pin (38) and the strip groove (37). (32) Move horizontally, the crossbar (32) pushes the mounting plate (33), the pin (34) on the mounting plate (33) pierces the center of the protective net (11), then the rack (42) disengages from the gear (41), the torsion spring (43) drives the rotating shaft (35) to reset, the pin (34) withdraws, the initial crack is formed in the center of the protective net (11), tighten the third fastening bolt to fix the outer rod (20) and the inner rod (21), the hydraulic cylinder (17) continues to move upward to stretch the protective net (11) until it tears; S6. When the stroke needs to be increased, keep the third fastening bolt loose so that the inner rod (21) can slide freely in the outer rod (20). Start the hydraulic cylinder (17). The hydraulic cylinder (17) drives the lifting plate (19) and the upper clamp body to move up. The lifting plate (19) drives the mounting rod (45) to move up. The mounting rod (45) pulls the pull rope (46). The pull rope (46) passes around the first groove wheel (47) and the second groove wheel (48) in sequence and then pulls the lower clamp body to move down. The spring (22) is stretched, and the upper and lower clamp bodies move away from each other. The protective net (11) is stretched quickly.

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