Breakage strength testing device for corrugated carton

Abstract

The invention discloses a corrugated carton bursting strength testing device, and relates to the technical field of bursting strength detection of technical new material corrugated paperboards, the corrugated carton bursting strength testing device comprises a test board, a tester mounted on the test board, a support rod fixedly connected to the table surface of the test board right below the tester, and a clamp disc fixedly connected to the top end of the support rod, a placement groove is formed in the clamp disc, a correction assembly is arranged on the test table, the correction assembly comprises a sliding groove formed in the test table, a sliding plate is slidably connected into the sliding groove, and a containing table is fixedly connected to the end, away from the sliding groove, of the sliding plate. The corrugated board can uniformly bear the pressure applied by a tester, in addition, when the corrugated board is tested and sampled for multiple times, repeated adjustment is not needed before testing, a detector can quickly place the corrugated board in place and start testing, the testing efficiency is greatly improved, and meanwhile, repeated testing caused by the fact that the corrugated board is tilted is reduced.

Description

Technical Field

[0001] The invention relates to the technical field of bursting strength testing of new material corrugated paperboard, in particular to a bursting strength testing device for corrugated paper boxes. Background Art

[0002] At present, in order to increase the durability and pressure resistance of corrugated boxes, some manufacturers and R&D departments are still constantly manufacturing corrugated boxes through a variety of new materials. In the R&D process and the developed corrugated boxes need to pass the bursting strength test, and bursting strength is an important performance indicator of new material corrugated boxes. It is related to fiber length and fiber bonding strength, and is also affected by factors such as pulp mechanical processing method and beating degree. The bursting strength is tested by mechanical stress on corrugated boxes made of solid materials, and a stable pressure is applied for testing. In the actual test process, the following problem of unstable applied pressure will occur.

[0003] In traditional bursting strength testing, the specimens are grouped and attached to a rubber film for testing. The installation of the disc and the placement of the new material corrugated cardboard are all manually adjusted throughout the process, which can easily lead to disc installation deviations and invisible tilt angles. At the same time, when the new material corrugated cardboard is placed, the new material corrugated cardboard cannot be coaxial and concentric with the disc. When the measuring instrument applies pressure to the new material corrugated cardboard, the side of the new material corrugated cardboard will warp, thereby affecting the accuracy of the new material corrugated cardboard bursting strength test value and the inability to apply stable pressure for testing.

[0004] In order to solve the above problems, a device for testing the bursting strength of corrugated boxes is proposed. Summary of the Invention

[0005] In order to solve the above technical problems, a device for testing the bursting strength of corrugated boxes is provided. This technical solution solves the problems raised in the above background technology.

[0006] To achieve the above objectives, the present invention can be implemented by adopting the following technical solutions:

[0007] The present invention provides a device for testing the bursting strength of a corrugated paper box, comprising a test bench, a measuring instrument mounted on the test bench, a support rod fixedly connected to a tabletop directly below the measuring instrument, a fixture plate fixedly connected to the top of the support rod, a placement slot being provided on the fixture plate, and a correction component being provided on the test bench;

[0008] The correction component includes a slide groove provided on the test bench, a sliding plate is slidably connected in the slide groove, an end of the sliding plate away from the slide groove is fixedly connected to the holding platform, the top of the sliding plate is fixedly connected to two T-shaped rods, the outer surfaces of the two T-shaped rods are slidably connected to two limit plates, and the two limit plates are fixedly connected to a correction half ring at one end of the holding platform;

[0009] Furthermore, the inner wall diameter of the placement groove matches the outer wall diameter of the holding table, the outer wall diameter of the two correction half rings after merging matches the inner wall diameter of the placement groove, and the height of the two correction half rings combined with the holding table matches the depth of the placement groove.

[0010] Furthermore, a driving assembly is provided on the limit plate, and the driving assembly includes a servo motor installed on the top of the test bench, and a driving end of the servo motor is fixedly connected to a threaded rod.

[0011] Furthermore, the threaded rod is rotationally connected to the sliding groove, and the threaded rod is threadedly connected to the sliding plate.

[0012] Furthermore, a conversion assembly is provided on the limit plate, and the conversion assembly includes an adapter groove provided on the sliding plate, a conversion rod is provided in the adapter groove, a spiral groove is provided on the outer surface of the conversion rod, a driving rod is slidably connected inside the spiral groove, and the end of the driving rod away from the conversion rod is fixedly connected to a driving ring, and the outer surface of the driving ring is fixedly connected to a shift rod, and movable grooves are provided on the positions of the shift rods corresponding to the two limit plates, and the inner walls of the two movable grooves are movably connected to movable rods.

[0013] Furthermore, the conversion rod is fixedly connected to the table surface of the test bench, the driving ring is rotationally connected to the adapter groove, and the two movable rods are fixedly connected to the two limit plates.

[0014] Furthermore, a correction component is provided on the outer surface of the support rod, and the correction component includes a sleeve fixedly connected to the outer surface of the support rod, an equipment cavity is opened inside the sleeve, a rotating drum is rotatably connected in the equipment cavity, the outer surface of the rotating drum is fixedly connected to the winding drum, and two ribbons are fixedly connected to the outer surface of the winding drum, and the ends of the two ribbons away from the winding drum are fixedly connected to a sliding rod, and the top of the sliding rod is fixedly connected to an L-shaped correction rod, and the inner wall of the opposite end of the L-shaped correction rod is provided with a correction groove.

[0015] Furthermore, two notches are provided in the sleeve at positions corresponding to the two ribbons, and the two ribbons match the notches. Two sliding grooves are provided on the table surface of the test bench at positions corresponding to the two sliding rods. The two sliding rods are slidingly connected to the two sliding grooves. A coil spring is installed on the outer surface of the rotating cylinder, and springs are provided between the two sliding rods and the two sliding grooves. The two ends of the two springs are respectively fixedly connected to the opposite ends of the two sliding rods and the two sliding grooves.

[0016] As described above, the characteristics and advantages of the corrugated box bursting strength testing device of the present invention are:

[0017] By ensuring the coaxiality and concentricity between the correction disc, the holding table, the fixture disc, and the two correction half rings, it is possible to prevent the disc from being unevenly installed, which would cause the corrugated cardboard to be subjected to excessive local stress when under pressure, resulting in an inaccurate rupture position and an inability to truly reflect the rupture resistance of the entire cardboard. The flat disc can evenly distribute the pressure of the tester on the test area of ​​the corrugated cardboard, thereby applying a stable mechanical pressure.

[0018] By correcting the deflection of the corrugated cardboard, the cardboard will not warp on one side when the tester applies pressure to the cardboard for testing. In this way, the cardboard can evenly withstand the pressure applied by the tester. In addition, when the corrugated cardboard is tested multiple times, the cardboard will be placed flat in the center of the disc, eliminating the need for repeated adjustments before testing. The tester can quickly place the cardboard in place and start testing, greatly improving test efficiency and reducing repeated testing caused by cardboard warping. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] Figure 1 Schematic diagram of the overall structure of the bursting strength testing device for corrugated paper boxes shown in the present invention;

[0020] Figure 2 This is a schematic structural diagram of a test bench for a corrugated paper box bursting strength test device according to the present invention;

[0021] Figure 3 Schematic diagram of the cross-sectional structure of the test bench of the bursting strength test device for corrugated paper boxes shown in the present invention;

[0022] Figure 4 for Figure 3 A partial enlarged view of part A;

[0023] Figure 5 This is a schematic structural diagram of a correction component and a conversion component of a corrugated paper box bursting strength testing device according to the present invention;

[0024] Figure 6 This is a schematic diagram of the conversion rod structure of the corrugated box bursting strength testing device shown in the present invention;

[0025] Figure 7 This is a schematic diagram of the internal structure of the sleeve of the corrugated box bursting strength testing device shown in the present invention;

[0026] Figure 8 This is a schematic structural diagram of the correction component of the bursting strength testing device for corrugated paper boxes shown in the present invention;

[0027] Figure 9 This is a schematic diagram of the winding structure of the corrugated box bursting strength testing device shown in the present invention, including a winding drum and two ribbons.

[0028] The reference numerals in the drawings of the present invention are: 1. test bench; 2. measuring instrument; 3. support rod; 4. fixture plate; 5. placement slot;

[0029] Correction components: 61, slide; 62, sliding plate; 63, holding table; 64, T-shaped rod; 65, limit plate; 66, correction half ring;

[0030] Driving assembly: 71, servo motor; 72, threaded rod;

[0031] Conversion assembly: 81, adapter groove; 82, conversion rod; 83, spiral groove; 84, drive rod; 85, drive ring; 86, shift rod; 87, movable groove; 88, movable rod;

[0032] Correction components: 91. Sleeve; 92. Equipment cavity; 93. Rotating cylinder; 94. Winding cylinder; 95. Ribbon; 96. Slide rod; 97. L-shaped correction rod; 98. Correction groove; 99. Coil spring; 910. Notch; 911. Sliding groove; 912. Spring. DETAILED DESCRIPTION

[0033] The following will clearly and completely describe the technical solutions in the embodiments of the present invention in conjunction with the drawings in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, rather than all the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative work are within the scope of protection of the present invention.

[0034] See 1~ Figure 9 The figure shows an embodiment of the present invention, and provides a corrugated box bursting strength test device, which will be described in detail below: comprising a test table 1, a measuring instrument 2 mounted on the test table 1, a support rod 3 fixedly connected to the table surface of the test table 1 located directly below the measuring instrument 2, a fixture plate 4 fixedly connected to the top of the support rod 3, a placement slot 5 being provided on the fixture plate 4, and a correction component being provided on the test table 1;

[0035] The correction component includes a slide groove 61 opened on the test bench 1, and a sliding plate 62 is slidably connected in the slide groove 61. The end of the sliding plate 62 away from the slide groove 61 is fixedly connected to the placing platform 63, and the top of the sliding plate 62 is fixedly connected to two T-shaped rods 64. The outer surfaces of the two T-shaped rods 64 are slidably connected to two limit plates 65. The two limit plates 65 are located at one end of the placing platform 63 and are fixedly connected to a correction half ring 66. The two limit plates 65 and the correction half ring 66 are supported and limited by the two T-shaped rods 64. The two correction half rings 66 can be merged into a circular ring. The inner wall diameter of the merged circular ring matches the outer wall diameter of the disc. The disc is a special instrument for testing the ring compression strength of test paper and cardboard.

[0036] Furthermore, the inner wall diameter of the placement groove 5 matches the outer wall diameter of the holding table 63, the outer wall diameter of the two correction half rings 66 after merging matches the inner wall diameter of the placement groove 5, and the height of the two correction half rings 66 combined with the holding table 63 matches the depth of the placement groove 5. The clamp plate 4 is set in an open shape, and the opening is facing the direction of the sliding plate 62, so that the two limit plates 65 and the sliding plate 62 can be embedded in the placement groove 5 with the holding table 63 and the correction half ring 66, so that the disc will not have an invisible tilt during installation, and the flat disc helps to reduce the error of the instrument.

[0037] Furthermore, a driving assembly is provided on the limiting plate 65 , and the driving assembly includes a servo motor 71 installed on the top of the test bench 1 , and a threaded rod 72 is fixedly connected to the driving end of the servo motor 71 .

[0038] Furthermore, the threaded rod 72 is rotationally connected to the sliding groove 61 , and the threaded rod 72 is threadedly connected to the sliding plate 62 .

[0039] Furthermore, a conversion assembly is provided on the limit plate 65, which includes an adapter groove 81 provided on the sliding plate 62, a conversion rod 82 is provided in the adapter groove 81, a spiral groove 83 is provided on the outer surface of the conversion rod 82, a driving rod 84 is slidably connected to the inner side of the spiral groove 83, and a driving ring 85 is fixedly connected to the end of the driving rod 84 away from the conversion rod 82, and a shift rod 86 is fixedly connected to the outer surface of the driving ring 85. The shift rod 86 has movable grooves 87 at the positions corresponding to the two limit plates 65, and the inner walls of the two movable grooves 87 are There is a movable rod 88 in a movable connection, and the force of the sliding plate 62 moving downward can be converted into a rotational force through the conversion rod 82, and transmitted to the movable rod 88 and the limit plate 65 through the dial rod 86, so that the two limit plates 65 and the correction half ring 66 can move relative to each other to correct and clamp the disc. A vertical groove A1 is also provided at the bottom end of the spiral groove 83, so that the two correction half rings 66 have a distance to leave when entering and leaving the placement groove 5, so that the two correction half rings 66 and the placement groove 5 will not affect each other.

[0040] Furthermore, the conversion rod 82 is fixedly connected to the table surface of the test bench 1 , the driving ring 85 is rotationally connected to the adapting groove 81 , and the two movable rods 88 are fixedly connected to the two limit plates 65 .

[0041] Furthermore, a correction component is provided on the outer surface of the support rod 3, and the correction component includes a sleeve 91 fixedly connected to the outer surface of the support rod 3, an equipment cavity 92 is opened inside the sleeve 91, a rotating cylinder 93 is rotatably connected in the equipment cavity 92, the outer surface of the rotating cylinder 93 is fixedly connected to the winding cylinder 94, and the outer surface of the winding cylinder 94 is fixedly connected to two ribbons 95, and the ends of the two ribbons 95 away from the winding cylinder 94 are fixedly connected to a slide rod 96, and the top of the slide rod 96 is fixedly connected to an L-shaped correction rod 97, and the inner wall of the opposite end of the L-shaped correction rod 97 is opened.

[0042] Furthermore, two notches 910 are provided in the sleeve 91 corresponding to the positions of the two ribbons 95, and the two ribbons 95 match the notches 910. Two sliding grooves 911 are provided on the table of the test bench 1 corresponding to the positions of the two slide bars 96. The two slide bars 96 are slidably connected to the two sliding grooves 911. A coil spring 99 is installed on the outer surface of the rotating cylinder 93, and a spring 912 is provided between the two slide bars 96 and the two sliding grooves 911. The two ends of the two springs 912 are fixedly connected to the opposite ends of the two slide bars 96 and the two sliding grooves 911 respectively. The telescopic force of a single spring 912 is less than the torque force of the coil spring 99, and the telescopic force of the two springs 912 is greater than the torque force of the coil spring 99. In this way, the two slide bars 96 and the L-shaped correcting rod 97 will always be in a position. In this way, each time the corrugated cardboard is placed, the position of the corrugated cardboard can be accurately located in the center of the disc. In addition, the position of the corrugated board can be guaranteed to be consistent in multiple tests, which will improve the accuracy of the test results.

[0043] In combination with the above embodiments, the entire working process and working principle of the above embodiments are as follows:

[0044] The working state is as follows: when testing is required, the new material corrugated cardboard is first cut to an appropriate size, and then the disc supporting the new material corrugated cardboard is first placed on the holding table 63, and then the servo motor 71 is started to drive the threaded rod 72 to rotate, so that the sliding plate 62 outside the threaded rod 72 will slide down along the track of the slide groove 61, and in the process of the sliding plate 62 moving down, it will also drive the driving ring 85 to move down outside the conversion rod 82, and in the process of the driving ring 85 moving down, the driving rod 84 on the inner wall of the driving ring 85 will be in the spiral groove 83. As the conversion rod 82 is fixed to the table surface of the test bench 1, the driving rod 84 will drive the driving ring 85 to rotate along the trajectory of the spiral groove 83. At this time, the shifting rod 86 will rotate along the driving ring 85. When the shifting rod 86 rotates around the driving ring 85, the inner walls of the two movable grooves 87 on the shifting rod 86 will contact the outer surfaces of the two movable rods 88. Since the two limit plates 65 are slidably connected to the two ends of the two T-shaped rods 64, the two limit plates 65 will rotate along the trajectory of the spiral groove 83. The outer surfaces of the two T-shaped rods 64 are close to each other in similar directions. At this time, the disc placed on the holding platform 63 will be pushed toward the center of the holding platform 63 by the correction half-rings 66 provided at the ends of the two limit plates 65. When the driving rod 84 moves to the bottom end of the spiral groove 83 and enters the vertical groove A1, the two correction half-rings 66 will clamp the disc on the holding platform 63. At this time, the threaded rod 72 is continued to be driven to rotate, so that the sliding plate 62 continues to slide downward. When the two correction half-rings 66 and the holding platform 63 are embedded in the placement slot opened on the clamp plate 4, the disc is placed on the holding platform 63. When the disc is in the groove 5, the servo motor 71 is stopped. At this time, the disc on the holding platform 63 is coaxial with the holding platform 63, the fixture plate 4 and the two correction half rings 66. This can prevent the disc from being uneven or not installed properly during manual installation, which may cause the new material corrugated cardboard to be locally over-stressed or under-stressed when under pressure, resulting in inaccurate rupture positions and failure to truly reflect the rupture resistance of the entire cardboard. The flat disc can evenly distribute the pressure of the measuring instrument 2 over the test area of ​​the new material corrugated cardboard.

[0045] After the disc is installed, the cut new material corrugated cardboard is placed on the disc, and then a slide bar 96 is pushed to slide along the trajectory of the sliding groove 911 in the direction of the sleeve 91. Because the expansion and contraction force of the two springs 912 is greater than the torque force of the coil spring 99, and the expansion and contraction force of a single spring 912 is less than the torque force of the coil spring 99, when the slide bar 96 is pushed to move along the trajectory of the sliding groove 911, the torque force of the coil spring 99 and the expansion and contraction force of the spring 912 will be unbalanced, and the coil spring 99 will drive the rotating drum 93 and the winding drum 94 to rotate. The winding drum 94 will wind the two ribbons 95 during the rotation process, and the other slide bar 96 will slide toward the direction of the sleeve 91 during the process of the winding drum 94 winding the ribbon 95. At this time, the L-shaped correcting rods 97 at the ends of the two slide bars 96 will correct the new material corrugated cardboard placed on the disc. At the same time, the two L-shaped correcting rods 97 The correcting groove 98 provided on the inner wall on the opposite side can clamp the cut new material corrugated cardboard inside, so that after the inner walls of the correcting groove 98 on the two L-shaped correcting rods 97 come into contact with the diagonal corners of the cut new material corrugated cardboard, the cut new material corrugated cardboard will be pushed to the center of the disc by the two L-shaped correcting rods 97. In this way, when the measuring instrument 2 applies pressure to the new material corrugated cardboard for testing, the new material corrugated cardboard will not be warped on one side, and the edge will not be close to the middle during testing, resulting in insufficient pressure during testing. In this way, the new material corrugated cardboard can evenly withstand the pressure applied by the measuring instrument 2. In addition, when the new material corrugated cardboard is tested and sampled multiple times, the new material corrugated cardboard will be placed flat in the center of the disc, without the need for repeated adjustments before testing. The tester can quickly place the cardboard in place and start testing, which greatly improves the test efficiency and reduces repeated tests caused by the cardboard warping.

[0046] During the relative movement of the two slide bars 96, the spring 912 is also squeezed. When the new material corrugated cardboard is corrected to the center of the disc, the slide bar 96 is stopped. At this time, the two squeezed springs 912 will push the two slide bars 96 to move in opposite directions along the track of the sliding groove 911 because the elastic force is greater than the force of the coil spring 99. After use, the servo motor 71 is started to drive the threaded rod 72 to rotate in the opposite direction, so that the sliding plate 62 will slide upward along the sliding groove 61, and at the same time, the half ring 66 and the holding ring 66 are corrected. The table 63 and the disc will leave the placement groove 5. When the driving rod 84 moves to the end of the vertical groove A1 and enters the spiral groove 83, the driving ring 85 and the shift rod 86 will reverse along the trajectory of the spiral groove 83. At the same time, the inner wall of the movable groove 87 will contact the movable rod 88, causing the two limit plates 65 to slide in opposite directions along the outer surfaces of the two T-shaped rods 64. At this time, the two correcting half rings 66 end their clamping of the disc, and when they move to the end of the slide groove 61 on the sliding plate 62, the servo motor 71 can be turned off.

[0047] It should be noted that, in this document, relational terms such as first and second, etc., are used only to distinguish one entity or operation from another entity or operation, and do not necessarily require or imply any actual relationship or order between these entities or operations. Moreover, the terms "comprises," "comprising," or any other variations thereof are intended to cover non-exclusive inclusion, such that a process, method, article, or device comprising a series of elements includes not only those elements, but also other elements not explicitly listed, or elements inherent to such process, method, article, or device. In the absence of further limitations, an element defined by the phrase "comprising a ..." does not exclude the presence of additional identical elements in the process, method, article, or device comprising the element.

[0048] While embodiments of the present invention have been shown and described, it will be appreciated by those skilled in the art that various changes, modifications, substitutions, and variations may be made to these embodiments without departing from the principles and spirit of the invention, and that the scope of the invention is defined by the appended claims and their equivalents.

Claims

1. A device for testing the bursting strength of a corrugated box, comprising a test bench (1) and a measuring instrument (2) mounted on the test bench (1), characterized in that: The test bench (1) is located on a table directly below the measuring instrument (2), and is fixedly connected to a support rod (3). The top end of the support rod (3) is fixedly connected to a fixture disk (4), and a placement slot (5) is provided on the fixture disk (4). A correction component is provided on the test bench (1); The correction component includes a slide groove (61) provided on the test bench (1), a sliding plate (62) is slidably connected in the slide groove (61), an end of the sliding plate (62) away from the slide groove (61) is fixedly connected to a holding platform (63), the top of the sliding plate (62) is fixedly connected to two T-shaped rods (64), the outer surfaces of the two T-shaped rods (64) are slidably connected to two limit plates (65), and one end of the two limit plates (65) located on the holding platform (63) is fixedly connected to a correction half ring (66).

2. The device for testing the bursting strength of a corrugated box according to claim 1, characterized in that: The inner wall diameter of the placement groove (5) matches the outer wall diameter of the holding platform (63), the outer wall diameter of the two correction half rings (66) after merging matches the inner wall diameter of the placement groove (5), and the height of the two correction half rings (66) after merging and the holding platform (63) matches the depth of the placement groove (5).

3. The device for testing the bursting strength of a corrugated box according to claim 2, characterized in that: A driving assembly is provided on the limiting plate (65), and the driving assembly includes a servo motor (71) installed on the top of the test bench (1), and a threaded rod (72) is fixedly connected to the driving end of the servo motor (71).

4. The device for testing the bursting strength of a corrugated box according to claim 3, wherein: The threaded rod (72) is rotationally connected to the slide groove (61), and the threaded rod (72) is threadedly connected to the sliding plate (62).

5. The device for testing the bursting strength of a corrugated box according to claim 4, characterized in that: A conversion assembly is provided on the limit plate (65), and the conversion assembly includes an adapting groove (81) provided on the sliding plate (62), a conversion rod (82) is provided in the adapting groove (81), a spiral groove (83) is provided on the outer surface of the conversion rod (82), a driving rod (84) is slidably connected inside the spiral groove (83), an end of the driving rod (84) away from the conversion rod (82) is fixedly connected to a driving ring (85), an outer surface of the driving ring (85) is fixedly connected to a shifting rod (86), and the shifting rod (86) is provided with movable grooves (87) at positions corresponding to the two limit plates (65), and the inner walls of the two movable grooves (87) are movably connected to movable rods (88).

6. The device for testing the bursting strength of a corrugated box according to claim 5, characterized in that: The conversion rod (82) is fixedly connected to the table surface of the test table (1), the driving ring (85) is rotationally connected to the adapting groove (81), and the two movable rods (88) are fixedly connected to the two limiting plates (65).

7. The device for testing the bursting strength of a corrugated box according to claim 6, characterized in that: The outer surface of the support rod (3) is provided with a correction component, which includes a sleeve (91) fixedly connected to the outer surface of the support rod (3), an equipment cavity (92) opened inside the sleeve (91), a rotating cylinder (93) rotatably connected inside the equipment cavity (92), the outer surface of the rotating cylinder (93) is fixedly connected to a winding cylinder (94), the outer surface of the winding cylinder (94) is fixedly connected to two ribbons (95), the ends of the two ribbons (95) away from the winding cylinder (94) are fixedly connected to a sliding rod (96), the top end of the sliding rod (96) is fixedly connected to an L-shaped correction rod (97), and the inner wall of the opposite end of the L-shaped correction rod (97) is provided with a correction groove (98).

8. The device for testing the bursting strength of a corrugated box according to claim 7, characterized in that: The sleeve (91) is provided with two notches (910) at positions corresponding to the two ribbons (95), and the two ribbons (95) match the notches (910). Two sliding grooves (911) are provided on the table surface of the test bench (1) at positions corresponding to the two slide bars (96). The two slide bars (96) are slidably connected to the two sliding grooves (911). A coil spring (99) is installed on the outer surface of the rotating cylinder (93). A spring (912) is provided between the two slide bars (96) and the two sliding grooves (911). The two ends of the two springs (912) are fixedly connected to the ends of the two slide bars (96) opposite to the two sliding grooves (911).

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