Quick assembly type LED display screen infrared touch frame structure

Abstract

The utility model discloses a quick assembly type LED display screen infrared touch frame structure, and relates to the technical field of display screen infrared touch frames, the quick assembly type LED display screen infrared touch frame structure comprises a fixed frame and a plurality of integrated display screens, and a left touch frame and a right touch frame are respectively arranged in the left side position and the right side position of the fixed frame. During use, through the upper touch frame and the lower touch frame which are connected to the integrated display screen, when the touch frames and the integrated display screen are connected and installed together, the infrared touch frames do not need to be spliced in advance, and then the whole infrared touch frame is lifted up and bonded to the side faces of the periphery of the integrated display screen; the connection and installation operation of the touch frames and the integrated display screens can be completed only by sequentially connecting the multiple integrated display screens to the fixing frame in a sliding mode from left to right through the limiting strips and then connecting main board wires in the multiple upper touch frames, the multiple lower touch frames, the left touch frame and the right touch frame together, and the time of the connection and installation operation is shortened.

Description

Technical Field

[0001] This utility model relates to the field of infrared touch frame technology for display screens, and in particular to a quick-assembly type infrared touch frame structure for LED display screens. Background Technology

[0002] Infrared touch frames are an advanced touch interaction technology that uses infrared sensing technology to detect and track user touch behavior. Compared with traditional touch screens, infrared touch frames have higher precision and sensitivity, enabling a more natural and intuitive interaction.

[0003] The infrared touch frame works by using infrared sensing technology to achieve touch positioning. It mainly consists of four parts: infrared emitters, infrared receivers, a control circuit, and a touch detection algorithm. The infrared emitters and receivers are distributed around the touch frame, forming a crisscrossing infrared matrix. When no object is touching the screen, the infrared light is normally received by the receivers; when an object touches the screen, some of the infrared light is blocked, causing the receivers to fail to receive a signal. The control circuit controls the timing of the infrared light emission and collects signals from the receivers. The touch detection algorithm uses these signals to determine the touch position and converts the position information into coordinate data, which is then output to the host computer.

[0004] The existing infrared touch frame installation requires the splicing screen to be installed and debugged first, and then the infrared touch frame is spliced ​​and connected on the ground. After that, multiple people lift it up and stick it to the frame around the splicing screen with double-sided tape. When removing it, the touch frame must be separated from the adhesive tape first, and then it can be disassembled. Both installation and removal take a lot of time. In order to solve the above problems, we propose a quick-assembly LED display infrared touch frame structure. Utility Model Content

[0005] The purpose of this utility model is to provide a quick-assembly LED display infrared touch frame structure to solve the problem mentioned in the background art that the existing infrared touch frames require a lot of time to install or remove, which reduces the practicality of the infrared touch frames.

[0006] To achieve the above objectives, this utility model provides the following technical solution: a quick-assembly LED display infrared touch frame structure, comprising a fixed frame and multiple integrated displays. A left touch frame and a right touch frame are respectively installed in the left and right positions of the fixed frame. An upper touch frame and a lower touch frame are fixedly connected to each of the multiple integrated displays. Two limiting strips are symmetrically fixedly connected to the back of the fixed frame. The multiple integrated displays are slidably connected between the two limiting strips from left to right through a sliding groove. The sides of any two adjacent integrated displays are tightly abutted together. The mainboards in the multiple upper touch frames, multiple lower touch frames, left touch frames, and right touch frames are connected together by wires. Two fixing components are symmetrically connected to the left and right sides of the fixed frame.

[0007] The two fixing components are used to fix the multiple integrated displays to the fixing frame.

[0008] Preferably, the left side of the integrated display screen is connected to a first slot and a second plug, and the right side of the integrated display screen is connected to a first plug and a second slot. The first plug can be inserted into the first slot on the adjacent integrated display screen on the right, and the second plug can be inserted into the second slot on the adjacent integrated display screen on the left. The first slot and the first plug are electrically connected to the internal motherboard of the upper touch frame on the integrated display screen, and the second plug and the second slot are electrically connected to the internal motherboard of the lower touch frame on the integrated display screen. The advantage of this arrangement is that it eliminates the need to manually connect the wires extending from the motherboards of adjacent upper or lower touch frames, saving the splicing time of the touch frames and thus improving the installation and connection speed between the infrared touch frame and the display screen, thereby improving the practicality and convenience of the infrared touch frame structure.

[0009] Preferably, the fixing component includes a fixing plate fixedly connected to the left or right side of the fixing frame. The back of the fixing plate has two symmetrical cavities. Two rotating arms are symmetrically connected to the two cavities through a first rotating rod and a first torsion spring. A clamping plate is fixedly connected between the ends of the two rotating arms away from the fixing plate. The advantage of this arrangement is that multiple integrated displays can be stably fixed on the fixing frame, ensuring the stability and reliability of the infrared touch frame structure.

[0010] Preferably, the fixing component further includes a limiting mechanism connected to the fixing plate. The limiting mechanism is used to limit and fix the rotating arm. The advantage of this setting is that it can prevent the clamping plate from swinging during the clamping process of the integrated display screen, and effectively improve the limiting and fixing effect of the integrated display screen.

[0011] Preferably, the limiting mechanism includes two mounting cavities and a rectangular cavity symmetrically opened on the back of the fixing plate. The two mounting cavities are symmetrically located on the upper and lower sides of the rectangular cavity. Two pairs of pull rods are symmetrically and movably inserted into the inner top and bottom walls of the rectangular cavity. The ends of the two pairs of pull rods that are far apart pass through the inner top and bottom walls of the rectangular cavity and extend into the two mounting cavities. Two rectangular blocks are symmetrically and fixedly connected between the ends of the two pull rods that are far apart. Two first elastic elements are symmetrically and fixedly connected between the sides of the two rectangular blocks that are close to each other and the inner walls of the two mounting cavities. Two first limiting rods are symmetrically and fixedly connected on the sides of the two rectangular blocks that are far apart. Two limiting grooves are symmetrically opened on the sides of the two rotating arms that are close to each other. The ends of the two first limiting rods that are far apart pass through the inner walls of the two mounting cavities and are movably inserted into the limiting grooves on the two rotating arms. Two pull plates are symmetrically and fixedly connected between the ends of the two pairs of pull rods that are close to each other. The advantage of this arrangement is that the limiting and fixing operation of the rotating arms can be easily completed, improving the convenience and practicality of the infrared touch frame structure.

[0012] Preferably, the fixing component further includes a connecting mechanism disposed on the fixing plate, the connecting mechanism being used to connect two close-to-each pull plates together. The advantage of this arrangement is that it facilitates the removal of the integrated display screen from the fixing frame or the sliding connection of the integrated display screen to the integrated display screen.

[0013] Preferably, the connecting mechanism includes two pairs of slots symmetrically opened on the front and back of the lower pull plate. The connecting mechanism also includes two pairs of strip-shaped elastic sheets symmetrically fixedly connected on the front and back of the upper pull plate. Two pairs of locking blocks are symmetrically fixedly connected to one end of the two pairs of elastic sheets near the lower pull plate. The two pairs of locking blocks can be respectively locked into the two pairs of slots under the elastic action of the elastic sheets. The advantage of this setting is that it makes the connection operation between the two pull plates simple and convenient, and further improves the convenience of the infrared touch frame structure.

[0014] In summary, the technical effects and advantages of this utility model are as follows:

[0015] 1. In this utility model, by setting an upper touch frame and a lower touch frame connected to the integrated display screen, when connecting and installing the touch frame and the integrated display screen together, it is not necessary to first splice the infrared touch frame and then lift and stick the entire infrared touch frame to the four sides of the integrated display screen. Instead, multiple integrated display screens are simply slid and connected to the fixed frame from left to right through the limiting strips. Then, the motherboard wires in the multiple upper touch frames, multiple lower touch frames, left touch frame and right touch frame are connected together to complete the connection and installation operation of the touch frame and the integrated display screen. This shortens the connection and installation operation time and improves the practicality and convenience of the infrared touch frame structure.

[0016] 2. In this utility model, the fixed components enable the two pairs of rotating arms to rotate towards each other under the elastic force of the first rotating rod and the first torsion spring. The two pairs of rotating arms can respectively drive the two clamps to press tightly against the left side of the leftmost integrated display screen and the right side of the rightmost integrated display screen. In this way, multiple integrated display screens can be stably fixed on the fixed frame, ensuring the stability and reliability of the infrared touch frame structure. Attached Figure Description

[0017] To more clearly illustrate the technical solutions in the embodiments of this utility model or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of this utility model. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0018] Figure 1 This is a first structural schematic diagram of the present invention;

[0019] Figure 2 This is a schematic diagram of the second structure of the present invention;

[0020] Figure 3 This is a schematic diagram of the first partial structure of the present invention;

[0021] Figure 4 This is a partial front view of the present invention;

[0022] Figure 5 This is a partial left view of the present invention;

[0023] Figure 6 This is a cross-sectional view of the fixing component in this utility model;

[0024] Figure 7 In this utility model Figure 3 Enlarged view of point A in the middle;

[0025] Figure 8 For the present utility model Figure 5 Enlarged view of point B in the middle;

[0026] Figure 9 For the present utility model Figure 5 Enlarged view of point C in the middle;

[0027] Figure 10 For the present utility model Figure 6 Enlarged view of point D in the middle;

[0028] Figure 11 For the present utility model Figure 6 Enlarged diagram of point E in the middle.

[0029] In the diagram: 1. Fixed frame; 11. Left touch frame; 12. Right touch frame; 2. Integrated display screen; 21. Upper touch frame; 22. Lower touch frame; 23. Screen; 31. Slide groove; 32. Limiting strip; 41. First slot; 42. Second plug; 5. Fixed assembly; 51. Fixed plate; 52. Cavity; 53. Rotating arm; 54. Clamping plate; 55. Limiting mechanism; 551. Mounting cavity; 552. Rectangular cavity; 553. Pull rod; 554. Rectangular block; 555. First elastic element; 556. First limiting rod; 557. Pull plate; 56. Connecting mechanism; 561. Slot; 562. Elastic sheet; 563. Block; 57. Second limiting rod. Detailed Implementation

[0030] The technical solutions of the present utility model will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present utility model, and not all embodiments. Based on the embodiments of the present utility model, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the protection scope of the present utility model.

[0031] Please refer to Figures 1-11 The diagram shows a quick-assembly LED display infrared touch frame structure, including a fixed frame 1 and multiple integrated display screens 2. The integrated display screens 2 have a screen 23 mounted on the front. The left touch frame 11 and the right touch frame 12 are mounted on the left and right sides of the fixed frame 1, respectively. The multiple integrated display screens 2 are each fixedly connected to an upper touch frame 21 and a lower touch frame 22. Two limiting strips 32 are symmetrically fixedly connected to the back of the fixed frame 1. The multiple integrated display screens 2 are slidably connected between the two limiting strips 32 from left to right through a sliding groove 31. The sides of any two adjacent integrated display screens 2 are pressed together. The mainboards in the multiple upper touch frames 21, multiple lower touch frames 22, left touch frames 11 and right touch frames 12 are connected together by wires. Two fixing components 5 are symmetrically connected to the left and right sides of the fixed frame 1.

[0032] Two fixing components 5 are used to fix multiple integrated displays 2 to the fixing frame 1.

[0033] refer to Figures 7-9The left side of the integrated display screen 2 is connected to a first slot 41 and a second plug 42, and the right side of the integrated display screen 2 is connected to a first plug and a second slot. The first plug can be inserted into the first slot 41 on the right adjacent integrated display screen 2, and the second plug 42 can be inserted into the second slot on the left adjacent integrated display screen 2. The first slot 41 and the first plug are both electrically connected to the internal motherboard of the upper touch frame 21 on the integrated display screen 2. The second plug 42 and the second slot are both electrically connected to the internal motherboard of the lower touch frame 22 on the integrated display screen 2.

[0034] Specifically, by inserting the first plug into the adjacent first slot 41 on the right and the second plug 42 into the adjacent second slot on the left, the electrical connection between the mainboards of two adjacent upper touch frames 21 and two adjacent lower touch frames 22 can be completed when multiple integrated displays 2 are slidably connected to the back of the fixed frame 1 in sequence, and the adjacent sides of the integrated displays 2 are pressed together. This eliminates the need to manually connect the wires extending from the mainboards of adjacent upper touch frames 21 or adjacent lower touch frames 22, saving the splicing time of the touch frame and thus improving the installation and connection speed between the infrared touch frame and the display screen, and improving the practicality and convenience of the infrared touch frame structure.

[0035] refer to Figure 1 , Figure 2 and Figure 6 The fixing component 5 includes a fixing plate 51 fixedly connected to the left or right side of the fixing frame 1. Two cavities 52 are symmetrically opened on the back of the fixing plate 51. Two rotating arms 53 are symmetrically rotatably connected in the two cavities 52 through a first rotating rod and a first torsion spring. A clamping plate 54 is fixedly connected between the ends of the two rotating arms 53 away from the fixing plate 51.

[0036] Specifically, under the elastic force of the first rotating rod and the first torsion spring, the two pairs of rotating arms 53 can be driven to rotate in the same direction. The two pairs of rotating arms 53 can drive the two clamps 54 to press against the left side of the leftmost integrated display screen 2 and the right side of the rightmost integrated display screen 2 respectively. In this way, multiple integrated display screens 2 can be stably fixed on the fixed frame 1, ensuring the stability and reliability of the infrared touch frame structure.

[0037] refer to Figure 6 The fixing component 5 also includes a limiting mechanism 55 connected to the fixing plate 51, which is used to limit and fix the rotating arm 53.

[0038] Specifically, it can prevent the clamping plate 54 from swinging during the clamping process of the integrated display screen 2, effectively improving the limiting and fixing effect of the integrated display screen 2.

[0039] refer to Figure 6, Figure 10 and Figure 11 The limiting mechanism 55 includes two mounting cavities 551 and a rectangular cavity 552 symmetrically formed on the back of the fixing plate 51. The two mounting cavities 551 are symmetrically located on the upper and lower sides of the rectangular cavity 552, respectively. Two pairs of pull rods 553 are symmetrically and movably inserted into the inner top and bottom walls of the rectangular cavity 552. The ends of the two pairs of pull rods 553 that are far apart pass through the inner top and bottom walls of the rectangular cavity 552 and extend into the two mounting cavities 551, respectively. Two rectangular blocks 554 are symmetrically and fixedly connected between the ends of the two pull rods 553. Two first elastic elements 555 are symmetrically fixedly connected between the adjacent sides of the two rectangular blocks 554 and the inner walls of the two mounting cavities 551. Two first limiting rods 556 are symmetrically fixedly connected on the distant sides of the two rectangular blocks 554. Two limiting grooves are symmetrically opened on the adjacent sides of the two rotating arms 53. The distant ends of the two first limiting rods 556 pass through the inner walls of the two mounting cavities 551 and are respectively movably inserted into the limiting grooves on the two rotating arms 53. Two pull plates 557 are symmetrically fixedly connected between the adjacent ends of the two pairs of pull rods 553.

[0040] Specifically, this allows the operator to simply pull the two pull plates 557 in a direction closer together. The two pull plates 557 can overcome the elastic force of the first elastic element 555 and pull the two first limiting rods 556 out of the two limiting slots through the pull rod 553 and the rectangular block 554. This conveniently releases the limiting fixation of the rotating arm 53. Conversely, when the two clamping plates 54 clamp the integrated display screen 2, releasing the two pull plates 557 allows the two first limiting rods 556 to be inserted into the two limiting slots under the elastic force of the first elastic element 555. This conveniently completes the limiting fixation operation of the rotating arm 53, improving the convenience and practicality of the infrared touch frame structure.

[0041] refer to Figure 6 and Figure 11 The fixing component 5 also includes a connecting mechanism 56 provided on the fixing plate 51, which is used to connect two close-to-close pull plates 557 together.

[0042] Specifically, after pulling the two pull plates 557 to pull the first limiting rod 556 out of the limiting groove, the two pull plates 557 can be connected together. This eliminates the need for the operator to constantly apply pulling force to the two pull plates 557 to ensure that the first limiting rod 556 does not reset. This makes it easier for the operator to rotate the clamp 54 to a position away from the integrated display screen 2, which facilitates the removal of the integrated display screen 2 from the fixed frame 1 or the sliding connection of the integrated display screen 2 to the integrated display screen 2.

[0043] refer to Figure 11The connecting mechanism 56 includes two pairs of slots 561 symmetrically opened on the front and back of the lower pull plate 557. The connecting mechanism 56 also includes two pairs of strip-shaped elastic pieces 562 symmetrically fixedly connected on the front and back of the upper pull plate 557. Two pairs of locking blocks 563 are symmetrically fixedly connected to one end of the two pairs of elastic pieces 562 near the lower pull plate 557. The two pairs of locking blocks 563 can be respectively locked into the two pairs of slots 561 under the elastic action of the elastic pieces 562.

[0044] Specifically, when the two pull plates 557 are pulled to their closest positions, the two pairs of elastic pieces 562 are pushed apart in opposite directions, which makes it easy for the two pairs of locking blocks 563 to be inserted into the two pairs of locking slots 561 respectively. This makes the connection operation between the two pull plates 557 simple and convenient, further improving the convenience of the infrared touch frame structure.

[0045] Two pairs of second limiting rods 57 are symmetrically fixedly connected to the two pairs of rectangular blocks 554 on their far sides. The two pairs of second limiting rods 57 can be inserted into the two pairs of limiting grooves when the two pairs of rotating arms 53 are in a position parallel to the front of the fixed frame 1. This allows the two clamping plates 54 to be stably held in a position away from the fixed frame 1, which makes it easier for the staff to slide the integrated display screen 2 onto or remove it from the fixed frame 1, further improving the convenience of the infrared touch frame structure.

[0046] Working principle: During connection and installation, after rotating the two pairs of rotating arms 53 in opposite directions to a position parallel to the front of the fixed frame 1, insert the two pairs of second limiting rods 57 into the limiting grooves on the two pairs of rotating arms 53 respectively. This allows the two clamping plates 54 to be stably held in a position away from the fixed frame 1, making it easier for the staff to slide multiple integrated display screens 2 from left to right between the two limiting strips 32, and to make the adjacent sides of the integrated display screens 2 close together.

[0047] When adjacent integrated display screens 2 are pressed together on their close sides, the first plug on the integrated display screen 2 can be inserted into the first slot 41 on the adjacent right integrated display screen 2, and the second plug 42 on the integrated display screen 2 can be inserted into the second slot on the adjacent left integrated display screen 2. In this way, when multiple integrated display screens 2 are slidably connected to the back of the fixed frame 1 in sequence, the electrical connection between the mainboards of two adjacent upper touch frames 21 and two adjacent lower touch frames 22 can be completed when the adjacent integrated display screens 2 are pressed together on their close sides. This eliminates the need to manually connect the wires extending from the mainboards of adjacent upper touch frames 21 or adjacent lower touch frames 22, saving the splicing time of the touch frame and thus improving the installation and connection speed between the infrared touch frame and the display screen, and improving the practicality and convenience of the infrared touch frame structure.

[0048] Then, the two pairs of pull plates 557 are pulled toward each other, causing the two pairs of second limiting rods 57 to be pulled out from the two pairs of limiting grooves. In this way, under the elastic force of the first rotating rod and the first torsion spring, the two pairs of rotating arms 53 can be driven to rotate toward each other. The two pairs of rotating arms 53 can respectively drive the two clamping plates 54 to press tightly against the left side of the leftmost integrated display screen 2 and the right side of the rightmost integrated display screen 2. In this way, multiple integrated display screens 2 can be stably fixed on the fixed frame 1, ensuring the stability and reliability of the infrared touch frame structure.

[0049] Then, the two pairs of pull plates 557 are released again. The two pairs of first limiting rods 556 can move in opposite directions under the elastic force of the first elastic element 555 and be inserted into the two pairs of limiting grooves respectively. This can prevent the clamping plate 54 from swinging during the clamping process of the integrated display screen 2, and effectively improve the limiting and fixing effect of the integrated display screen 2.

[0050] Finally, it should be noted that the above are merely preferred embodiments of the present utility model and are not intended to limit the present utility model. Although the present utility model has been described in detail with reference to the foregoing embodiments, those skilled in the art can still modify the technical solutions described in the foregoing embodiments or make equivalent substitutions for some of the technical features. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present utility model should be included within the protection scope of the present utility model.

Claims

1. A quick-assembly LED display infrared touch frame structure, comprising a fixed frame (1) and multiple integrated display screens (2), characterized in that: A left touch frame (11) and a right touch frame (12) are respectively installed in the left and right positions of the fixed frame (1). An upper touch frame (21) and a lower touch frame (22) are fixedly connected to each of the multiple integrated displays (2). Two limiting strips (32) are symmetrically fixedly connected to the back of the fixed frame (1). The multiple integrated displays (2) are slidably connected between the two limiting strips (32) from left to right through the slide groove (31). The sides of any two adjacent integrated displays (2) are pressed together. The motherboards in the multiple upper touch frames (21), multiple lower touch frames (22), left touch frames (11) and right touch frames (12) are connected together by wires. Two fixing components (5) are symmetrically connected to the left and right sides of the fixed frame (1). The two fixing components (5) are used to fix the multiple integrated displays (2) to the fixing frame (1).

2. The infrared touch frame structure for a rapid assembly LED display screen according to claim 1, characterized in that: The integrated display screen (2) has a first slot (41) and a second plug (42) connected to its left side, and a first plug and a second slot connected to its right side. The first plug can be inserted into the first slot (41) on the right adjacent integrated display screen (2), and the second plug (42) can be inserted into the second slot on the left adjacent integrated display screen (2). The first slot (41) and the first plug are electrically connected to the internal motherboard of the upper touch frame (21) on the integrated display screen (2), and the second plug (42) and the second slot are electrically connected to the internal motherboard of the lower touch frame (22) on the integrated display screen (2).

3. The infrared touch frame structure for a rapid assembly LED display screen according to claim 2, characterized in that: The fixing component (5) includes a fixing plate (51) fixedly connected to the left or right side of the fixing frame (1). The back of the fixing plate (51) has two symmetrical cavities (52). Two rotating arms (53) are symmetrically connected in the two cavities (52) through a first rotating rod and a first torsion spring. A clamping plate (54) is fixedly connected between the ends of the two rotating arms (53) away from the fixing plate (51).

4. The infrared touch frame structure for a rapid assembly LED display screen according to claim 3, characterized in that: The fixing component (5) also includes a limiting mechanism (55) connected to the fixing plate (51), which is used to limit and fix the rotating arm (53).

5. The infrared touch frame structure for a rapid assembly LED display screen according to claim 4, characterized in that: The limiting mechanism (55) includes two mounting cavities (551) and a rectangular cavity (552) symmetrically opened on the back of the fixing plate (51). The two mounting cavities (551) are symmetrically located on the upper and lower sides of the rectangular cavity (552). Two pairs of pull rods (553) are symmetrically and movably inserted into the inner top and bottom walls of the rectangular cavity (552). The ends of the two pairs of pull rods (553) that are far apart pass through the inner top and bottom walls of the rectangular cavity (552) and extend into the two mounting cavities (551). Two rectangular blocks (554) are symmetrically and fixedly connected between the ends of the two pull rods (553). Two first elastic elements (555) are symmetrically fixedly connected between the adjacent sides of the two rectangular blocks (554) and the inner walls of the two mounting cavities (551). Two first limiting rods (556) are symmetrically fixedly connected on the opposite sides of the two rectangular blocks (554). Two limiting grooves are symmetrically opened on the adjacent sides of the two rotating arms (53). The opposite ends of the two first limiting rods (556) pass through the inner walls of the two mounting cavities (551) and are respectively movably inserted into the limiting grooves on the two rotating arms (53). Two pull plates (557) are symmetrically fixedly connected between the adjacent ends of the two pairs of pull rods (553).

6. The infrared touch frame structure for a rapid assembly LED display screen according to claim 5, characterized in that: The fixing component (5) further includes a connecting mechanism (56) disposed on the fixing plate (51), the connecting mechanism (56) being used to connect two pull plates (557) that are close to each other together.

7. The infrared touch frame structure for a rapid assembly LED display screen according to claim 6, characterized in that: The connecting mechanism (56) includes two pairs of slots (561) symmetrically opened on the front and back of the lower pull plate (557). The connecting mechanism (56) also includes two pairs of strip-shaped elastic pieces (562) symmetrically fixedly connected on the front and back of the upper pull plate (557). Two pairs of locking blocks (563) are symmetrically fixedly connected to one end of the two pairs of elastic pieces (562) near the lower pull plate (557). The two pairs of locking blocks (563) can be respectively locked into the two pairs of slots (561) under the elastic action of the elastic pieces (562).

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