A test device suitable for uniform speed mining simulation of long working face in ultra-thin coal seam

Abstract

The present application relates to the field of simulation test equipment, and discloses a test device suitable for uniform speed mining simulation of long working face of ultra-thin coal seam, comprising: a model box composed of multiple box walls and used for placing a test model; a mining mechanism used for being embedded in the test model and comprising upper and lower bearing plates arranged in parallel; the lower surface of the upper bearing plate is fixedly provided with an upper tooth plate, and the upper surface of the lower bearing plate is fixedly provided with a lower tooth plate; the upper tooth plate and the lower tooth plate are continuously toothed structures matched with each other and both have protruding teeth and lower grooves alternately distributed; and a limiting device acting between the upper tooth plate and the lower tooth plate and used for locking the upper tooth plate and the lower tooth plate at an initial supporting position. The present application adopts the staggered tooth plate structure, the initial supporting state is realized by the protruding teeth being abutted against each other, the height is determined by the tooth height only, and the limiting device is used for locking the upper tooth plate and the lower tooth plate at the initial supporting position, so that the initial thickness is not occupied, and the ultra-thin coal seam with extremely small thickness can be simulated.

Description

Technical Field

[0001] This invention relates to the field of simulation test equipment processing, and specifically to a test device suitable for simulating uniform mining in long working faces of ultra-thin coal seams. Background Technology

[0002] In physical simulation experiments of coal mining, accurately simulating the coal seam mining process is crucial for studying the movement patterns of overlying strata and the characteristics of mine pressure manifestation. Existing technologies include devices that simulate coal seam mining through pre-embedded mechanical structures. For example, application number 202110461385.1 proposes a pre-supported, precise pressure-relief sensing coal seam mining simulation test device. This device achieves mechanized simulated coal seam mining by changing the spacing between bearing plates through the relative movement of wedge blocks, offering advantages such as minimal disturbance and monitorability.

[0003] However, further research and practical applications revealed that the aforementioned wedge-shaped structure is limited by processing technology and material strength. Furthermore, this structure is independently positioned between the upper and lower bearing plates and requires a certain initial thickness. When simulating extremely thin coal seams (e.g., a few centimeters or even thinner in geological similarity scenarios), the structure cannot be processed to such a thinness, or even if it is barely processed, its stiffness cannot meet the requirements for stable support of the overlying strata, making it impossible to effectively conduct simulation tests of ultra-thin coal seam mining.

[0004] Therefore, there is an urgent need for a simulation test device suitable for ultra-thin coal seams that ensures a small initial support thickness. Summary of the Invention

[0005] In view of this, the present invention provides a test apparatus suitable for simulating uniform-speed mining in long working faces of ultra-thin coal seams, in order to solve the problems mentioned in the background art, and specifically discloses the following contents: A test apparatus suitable for simulating uniform-rate long-face mining in ultra-thin coal seams, comprising: Model box: Composed of multiple box walls, used to hold experimental models; Loading mechanism: Used to apply vertical loads to the sample model inside the model box, which is set at the top of the model box; Recovery mechanism: used to be embedded inside the sample model, including an upper bearing plate and a lower bearing plate arranged in parallel; an upper toothed plate is fixedly provided on the lower surface of the upper bearing plate, and a lower toothed plate is fixedly provided on the upper surface of the lower bearing plate; the upper toothed plate and the lower toothed plate are mutually matched continuous toothed structures, each having alternately distributed protruding teeth and lower grooves; Limiting device: acting between the upper and lower jaw plates, used to lock the upper and lower jaw plates in the initial support position; in the initial support position, the protruding teeth of the upper jaw plate and the protruding teeth of the lower jaw plate are vertically aligned to form a first support height; When the limiting device is released and a horizontal tension is applied to the upper bearing plate, the upper tooth plate and the lower tooth plate slide horizontally relative to each other, causing the protruding teeth of the upper tooth plate to slide into the lower groove of the lower tooth plate, forming a second support height that is less than the first support height.

[0006] Furthermore, the teeth of the upper and lower tooth plates are trapezoidal.

[0007] Furthermore, it also includes an external traction device for providing a uniform horizontal pulling force to the upper bearing plate.

[0008] Furthermore, the limiting device includes an active locking unit and a passive locking unit; the active locking unit is fixedly disposed at one end of the upper jaw plate and is used to lock the upper jaw plate and one end of the lower jaw plate; the passive locking unit is fixedly disposed at the other end of the lower jaw plate and is used to lock the upper jaw plate and the other end of the lower jaw plate.

[0009] Furthermore, the active locking unit includes an upper locking block and a first driving block; the upper locking block is fixedly disposed at one end of the lower jaw plate, and one end of the upper jaw plate is provided with a lower locking groove adapted to the upper locking block; the upper locking block is provided with a horizontal upper transverse groove adapted to the first driving block, and the upper locking block is also provided with a vertical upper groove communicating with the horizontal upper groove, and a second driving block is slidably disposed in the vertical upper groove; the first driving block and the second driving block are engaged by a wedge-shaped surface and are slidably connected; when the first driving block moves to the right, it drives the second driving block to move downward and extend downward from the vertical upper groove; the lower locking groove is provided with a first insertion port for accommodating the second driving block to extend in; The first drive block is rotatably connected to a rotating shaft on the side away from the second drive block; the rotating shaft extends outward from the upper clamping block on the side away from the first drive block and is fixedly connected to a turntable; the rotating shaft is threadedly connected to the upper clamping block. The driven locking unit includes a lower locking block, which is fixedly disposed at the other end of the lower jaw plate, and the other end of the upper jaw plate is provided with an upper locking groove that is adapted to the lower locking block.

[0010] Furthermore, it also includes a transmission unit, wherein a first transmission groove is horizontally provided inside the lower support plate, and a transmission block is slidably provided in the first transmission groove. One end of the first transmission groove is connected to the first extension inlet, and the end of the transmission block near the first extension inlet engages with the wedge-shaped surface of the protruding end of the second driving block. When the second driving block moves downward from the first extension inlet to the first transmission groove, it drives the transmission block to move to the right. The lower locking block has a vertical groove inside, and a driven block is slidably disposed inside the lower groove; the upper locking slot has a limiting opening for accommodating the driven block to extend into it; the other end of the first transmission groove is connected to the lower groove through a second extension opening; the end of the transmission block near the second extension opening engages with the wedge-shaped surface at the bottom of the driven block and is slidably connected; when the transmission block moves to the right, it drives the top of the driven block to extend into the limiting opening; The lower support plate is also horizontally provided with a second transmission groove that communicates with the first transmission groove. A guide rod is fixedly provided in the second transmission groove. A connecting block is fixedly provided at the bottom of the transmission block. The connecting block is sleeved on the guide rod. A return spring is also sleeved on the guide rod. One end of the return spring is connected to the connecting block, and the other end is connected to the end wall of the second transmission groove.

[0011] The beneficial effects of this invention are as follows: This invention employs an interlaced tooth plate structure, where the initial support state is achieved by the opposing of protruding teeth. Its height is determined solely by the tooth height, resulting in a simple mechanical structure that allows for the fabrication of extremely small initial thicknesses. This perfectly solves the problem that traditional wedge structures cannot be applied to the simulation of ultra-thin coal seams.

[0012] The present invention employs a limiting device acting between the upper and lower jaw plates to lock the upper and lower jaw plates in the initial support position without occupying the initial thickness, thus simulating an ultra-thin coal seam with extremely small thickness. Attached Figure Description

[0013] To more clearly illustrate the technical solutions in the embodiments of the present invention 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 embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on the provided drawings without creative effort.

[0014] Figure 1 This is a front view of an experimental device for simulating uniform mining in long working faces of ultra-thin coal seams according to the present invention.

[0015] Figure 2 This is a side view of the upper support plate in this invention.

[0016] Figure 3 This is a side view of the lower support plate in this invention.

[0017] Figure 4 This is a schematic diagram of the internal structure of the upper and lower support plates in this invention when they are at the first support height and not locked.

[0018] Figure 5 for Figure 4 Enlarged view of point A in the middle.

[0019] Figure 6 for Figure 4 Enlarged view of section B in the middle.

[0020] Figure 7 This is a schematic diagram of the internal structure of the upper and lower support plates in this invention when they are at the first support height and locked.

[0021] Figure 8 for Figure 7 Enlarged view of point C.

[0022] Figure 9 for Figure 7 Enlarged view of point D in the middle.

[0023] Figure 10 This is a schematic diagram of the structure when the upper and lower support plates are at the second support height in this invention.

[0024] In the figure: 1-Base; 2-Box wall; 3-Roof strata; 4-Loading mechanism; 5-Mining mechanism; 51-Upper bearing plate; 511-Upper toothed plate; 512-Upper slot; 513-Limiting port; 52-Lower bearing plate; 521-Lower toothed plate; 522-Lower slot; 523-First transmission groove; 524-Second transmission groove; 525-Transmission block; 526-Connecting block; 527-Guide rod; 528-Reset spring; 6-Upper locking block; 61-Upper horizontal groove; 62-Upper vertical groove; 71-Turntable; 72-Rotating shaft; 73-First driving block; 74-Second driving block; 8-Lower locking block; 81-Lower vertical groove; 9-Driven block. Detailed Implementation

[0025] The technical solutions in the embodiments of the present invention will be clearly and completely described below. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0026] It should be noted that the terms "first," "second," etc., in the specification, claims, and accompanying drawings of this application are used to distinguish similar objects and are not necessarily used to describe a specific order or sequence. It should be understood that such data can be used interchangeably where appropriate for the purposes of describing embodiments of this application herein. Furthermore, the terms "comprising" and "having," and any variations thereof, are intended to cover non-exclusive inclusion; for example, a process, method, system, product, or device that includes a series of steps or components is not necessarily limited to those explicitly listed, but may include other steps or components not explicitly listed or inherent to such processes, methods, products, or devices.

[0027] In this application, the terms "upper," "lower," "left," "right," "front," "rear," "top," "bottom," "inner," "outer," "middle," "vertical," "horizontal," "lateral," and "longitudinal" indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. These terms are primarily for the purpose of better describing this application and its embodiments, and are not intended to limit the indicated device, element, or component to having a specific orientation, or to be constructed and operated in a specific orientation.

[0028] Furthermore, in addition to indicating location or positional relationship, some of the aforementioned terms may also have other meanings. For example, the term "above" may also be used in some cases to indicate a certain dependency or connection relationship. Those skilled in the art can understand the specific meaning of these terms in this application based on the specific circumstances.

[0029] Furthermore, the terms "installation," "setup," "equipped with," "connection," "linking," and "socketing" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral structure; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium, or an internal connection between two devices, components, or parts. Those skilled in the art can understand the specific meaning of these terms in this application based on the specific circumstances.

[0030] See appendix Figure 1-10 This invention discloses a test apparatus suitable for simulating uniform-speed mining in long working faces of ultra-thin coal seams, comprising: Model box: Composed of multiple box walls 2 spliced ​​together, used to hold test models; In this embodiment, the model box adopts a cubic box structure for placing the test model, including a base 1 and four box walls 2 fixed to the base; the box walls 2 are composed of multiple vertically arranged steel beams that are detachably connected, and the two ends of the steel beams can be detachably connected to the ends of the steel beams of adjacent box walls. When one steel beam is removed, it will not affect the fixation of the other steel beams. It is understood that the steel beams can be detachably connected by bolts or screws, or by snap-fit.

[0031] Loading mechanism 4: Used to be installed at the top of the model box to apply vertical load to the sample model inside the model box; The recovery mechanism 5 is used to be embedded inside the sample model and includes an upper bearing plate 51 and a lower bearing plate 52 arranged in parallel. An upper toothed plate 511 is fixedly provided on the lower surface of the upper bearing plate 51, and a lower toothed plate 521 is fixedly provided on the upper surface of the lower bearing plate 52. The upper toothed plate 511 and the lower toothed plate 521 are mutually matched continuous toothed structures, each with alternating protruding teeth and grooves. Limiting device: It acts between the upper tooth plate 511 and the lower tooth plate 521 to lock the upper tooth plate 511 and the lower tooth plate 521 in the initial support position; in the initial support position, the protruding teeth of the upper tooth plate 511 and the protruding teeth of the lower tooth plate 521 are vertically aligned to form the first support height. When the limiting device is released and a horizontal pulling force is applied to the upper bearing plate 51, the upper tooth plate 511 and the lower tooth plate 521 slide horizontally relative to each other, causing the protruding teeth of the upper tooth plate 511 to slide into the lower groove of the lower tooth plate 521, forming a second support height that is less than the first support height.

[0032] In this embodiment, the mining mechanism 5 is embedded in the sample model to simulate the coal seam to be mined. The process of removing the mining mechanism 5 from the sample model can be used to simulate the mining process. That is, the mining mechanism 5 is embedded in the sample model when it is at the first support height, and is removed from the sample model after it is changed to the second support height.

[0033] In this embodiment, a pressure sensor may be installed in the sample model to monitor data.

[0034] The teeth of the upper tooth plate 511 and the lower tooth plate 521 are trapezoidal.

[0035] A test device suitable for simulating uniform-speed mining in long working faces of ultra-thin coal seams also includes an external traction device, which is used to provide a uniform horizontal tension to the upper bearing plate 51.

[0036] The limiting device includes an active locking unit and a passive locking unit; the active locking unit is fixedly disposed at one end of the upper tooth plate 511 and is used to lock the upper tooth plate 511 and one end of the lower tooth plate 521; the passive locking unit is fixedly disposed at the other end of the lower tooth plate 521 and is used to lock the upper tooth plate 511 and the other end of the lower tooth plate 521.

[0037] The active locking unit includes an upper locking block 6 and a first driving block 73. The upper locking block 6 is fixedly disposed at one end of the lower jaw plate 521. One end of the upper jaw plate 511 is provided with a lower locking groove 522 adapted to the upper locking block 6. The upper locking block 6 is provided with a horizontal upper transverse groove 61 adapted to the first driving block 73. The upper locking block 6 is also provided with a vertical upper groove 62 communicating with the upper transverse groove 61. A second driving block 74 is slidably disposed in the upper vertical groove 62. The first driving block 73 and the second driving block 74 are engaged by a wedge-shaped surface and are slidably connected. When the first driving block 73 moves to the right, it drives the second driving block 74 to move downward and extend downward from the upper vertical groove 62. The lower locking groove 522 is provided with a first insertion port for accommodating the second driving block 74 to extend in. The first drive block 73 is rotatably connected to a rotating shaft 72 on the side away from the second drive block 74; the rotating shaft 72 extends outward from the upper locking block 6 on the side away from the first drive block 73 and is fixedly connected to a turntable 71; the rotating shaft 72 is threadedly connected to the upper locking block 6. The driven locking unit includes a lower locking block 8, which is fixedly disposed at the other end of the lower tooth plate 521, and the other end of the upper tooth plate 511 is provided with an upper locking groove 512 that is adapted to the lower locking block 8.

[0038] In this embodiment, the cooperation between the lower locking block 8 and the upper locking groove 512 is used to restrict the upper bearing plate 51 from moving horizontally to the right relative to the lower bearing plate 52; after the second driving block 74 extends into the first insertion port, it is used to restrict the upper bearing plate 51 from moving horizontally to the left relative to the lower bearing plate 52. Specifically, when the limiting device is working, the protruding teeth of the upper tooth plate 511 and the protruding teeth of the lower tooth plate 521 are first aligned vertically. At this time, the second driving block 74 is located in the upper vertical groove 62 and does not extend outward. Then, the turntable 71 is rotated, causing the first driving block 73 to move to the right. With the cooperation of the wedge-shaped surface, the second driving block 74 is driven to move downward and extend downward from the upper vertical groove 62 until it extends into the first insertion port, thus locking the upper bearing plate 51 and the lower bearing plate 52. After the turntable 71 is rotated to the set position, the turntable 71 can also be locked a second time by other existing locking mechanisms.

[0039] A test device suitable for simulating uniform speed mining in long working faces of ultra-thin coal seams also includes a transmission unit. A first transmission groove 523 is horizontally provided inside the lower bearing plate 52. A transmission block 525 is slidably provided in the first transmission groove 523. One end of the first transmission groove 523 is connected to a first extension inlet. The end of the transmission block 525 near the first extension inlet is engaged with the wedge-shaped surface of the protruding end of the second driving block 74. When the second driving block 74 moves downward from the first extension inlet to the first transmission groove 523, it drives the transmission block 525 to move to the right. The lower locking block 8 has a vertical groove 81 inside, and a driven block 9 is slidably disposed inside the lower groove 81; a limiting opening 513 is provided at the upper locking groove 512 to accommodate the driven block 9 extending into it; the other end of the first transmission groove 523 is connected to the lower groove 81 through a second extension opening; the end of the transmission block 525 near the second extension opening is engaged with the wedge-shaped surface at the bottom of the driven block 9 and is slidably connected; when the transmission block 525 moves to the right, it drives the top of the driven block 9 to extend into the limiting opening 513; The lower support plate 52 is also horizontally provided with a second transmission groove 524 that communicates with the first transmission groove 523. A guide rod 527 is fixedly provided in the second transmission groove 524. A connecting block 526 is fixedly provided at the bottom of the transmission block 525. The connecting block 526 is sleeved on the guide rod 527. A return spring 528 is also sleeved on the guide rod 527. One end of the return spring 528 is connected to the connecting block 526, and the other end is connected to the end wall of the second transmission groove 524.

[0040] In this embodiment, in the initial state, the top of the driven block 9 does not extend beyond the lower vertical groove 81. When the second driving block 74 extends into the first insertion port, the transmission block 525 moves to the right under the cooperation of the second driving block 74 and the transmission block 525, thereby pushing the driven block 9 upward, so that the driven block 9 extends into the limiting port 513, further restricting the upper bearing plate 51 from moving horizontally to the right relative to the lower bearing plate 52. During this process, the return spring 528 is compressed.

[0041] A working method for an experimental device suitable for simulating uniform-speed long-face mining in ultra-thin coal seams: The sample model is poured into the model box. While pouring the sample model, the steel beams of the box wall 2 are assembled simultaneously, so that the box wall 2 and the sample model are raised synchronously. After the sample model is poured to the set height, three sets of recovery mechanisms 5 are placed on the sample model. Each set has multiple recovery mechanisms 5 arranged side by side. At this time, the recovery mechanisms 5 are at the first support height and are locked by the limiting device. After the recovery mechanisms 5 are placed, the sample model is poured until the set height is reached, and then the loading mechanism 4 is installed. After the sample model is dried, the loading mechanism 4 is activated to apply a vertical load to the sample model to simulate the pressure of the top rock layer 3. Finally, the steel beam on the front side wall of the mining mechanism 5 is removed, exposing the mining mechanism 5. When the workers release the limiting device and apply a horizontal pulling force to the upper bearing plate 51 through the external traction device, the upper tooth plate 511 and the lower tooth plate 521 slide horizontally relative to each other, causing the protruding teeth of the upper tooth plate 511 to slide into the lower groove of the lower tooth plate 521, forming a second support height that is less than the first support height. Then, the mining mechanism 5 is taken out in sequence to simulate the mining process.

[0042] The above are merely preferred embodiments of this application and are not intended to limit this application. Various modifications and variations can be made to this application by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of this application should be included within the protection scope of this application.

Claims

1. A test device suitable for simulating uniform-speed long-face mining in ultra-thin coal seams, characterized in that, include: Model box: It is composed of multiple box walls (2) spliced ​​together and is used to place the test model; Loading mechanism (4): used to be set on the top of the model box to apply vertical load to the sample model inside the model box; The recovery mechanism (5) is used to be embedded inside the sample model and includes an upper bearing plate (51) and a lower bearing plate (52) arranged in parallel. The lower surface of the upper bearing plate (51) is fixedly provided with an upper toothed plate (511), and the upper surface of the lower bearing plate (52) is fixedly provided with a lower toothed plate (521). The upper toothed plate (511) and the lower toothed plate (521) are mutually matched continuous toothed structures, each having alternating protruding teeth and lower grooves. Limiting device: acts on the upper tooth plate (511) and the lower tooth plate (521) to lock the upper tooth plate (511) and the lower tooth plate (521) in the initial support position; in the initial support position, the protruding teeth of the upper tooth plate (511) and the protruding teeth of the lower tooth plate (521) are vertically aligned to form a first support height; When the limiting device is released and a horizontal pulling force is applied to the upper bearing plate (51), the upper tooth plate (511) and the lower tooth plate (521) slide horizontally relative to each other, causing the protruding teeth of the upper tooth plate (511) to slide into the lower groove of the lower tooth plate (521), forming a second support height that is less than the first support height.

2. The experimental device for simulating uniform-speed mining in long working faces of ultra-thin coal seams according to claim 1, characterized in that, The teeth of the upper tooth plate (511) and the lower tooth plate (521) are trapezoidal.

3. The experimental device for simulating uniform-speed mining in long working faces of ultra-thin coal seams according to claim 1, characterized in that, It also includes an external traction device for providing a uniform horizontal tension to the upper bearing plate (51).

4. The experimental device for simulating uniform-speed mining in long working faces of ultra-thin coal seams according to claim 1, characterized in that, The limiting device includes an active locking unit and a passive locking unit; the active locking unit is fixedly disposed at one end of the upper tooth plate (511) and is used to lock the upper tooth plate (511) and one end of the lower tooth plate (521); the passive locking unit is fixedly disposed at the other end of the lower tooth plate (521) and is used to lock the upper tooth plate (511) and the other end of the lower tooth plate (521).

5. The experimental device for simulating uniform-speed mining in long working faces of ultra-thin coal seams according to claim 4, characterized in that, The active locking unit includes an upper locking block (6) and a first driving block (73); the upper locking block (6) is fixedly disposed at one end of the lower tooth plate (521), and one end of the upper tooth plate (511) is provided with a lower locking groove (522) adapted to the upper locking block (6); the upper locking block (6) is provided with an upper horizontal groove (61) adapted to the first driving block (73) horizontally inside, and the upper locking block (6) is also provided with an upper vertical groove (62) communicating with the upper horizontal groove (61) vertically inside, and a second driving block (74) is slidably disposed in the upper vertical groove (62); the first driving block (73) and the second driving block (74) are engaged by a wedge-shaped surface and slidably connected; when the first driving block (73) moves to the right, it drives the second driving block (74) to move downward and extend downward from the upper vertical groove (62); the lower locking groove (522) is provided with a first insertion port for accommodating the second driving block (74) to extend in; The first drive block (73) is rotatably connected to a rotating shaft (72) on the side away from the second drive block (74); the rotating shaft (72) extends outward from the upper locking block (6) on the side away from the first drive block (73) and is fixedly connected to a turntable (71); the rotating shaft (72) is threadedly connected to the upper locking block (6); The driven locking unit includes a lower locking block (8), which is fixedly disposed at the other end of the lower tooth plate (521), and the other end of the upper tooth plate (511) is provided with an upper locking groove (512) that is adapted to the lower locking block (8).

6. The experimental device for simulating uniform-speed mining in long working faces of ultra-thin coal seams according to claim 5, characterized in that, It also includes a transmission unit. The lower support plate (52) is horizontally provided with a first transmission groove (523). A transmission block (525) is slidably provided in the first transmission groove (523). One end of the first transmission groove (523) is connected to the first inlet. The end of the transmission block (525) near the first inlet is engaged with the wedge-shaped surface of the protruding end of the second drive block (74). When the second drive block (74) moves downward from the first inlet to the first transmission groove (523), it drives the transmission block (525) to move to the right. The lower locking block (8) has a vertical groove (81) inside, and a driven block (9) is slidably arranged inside the lower groove (81); a limiting opening (513) is provided at the upper locking groove (512) to accommodate the driven block (9) extending in; the other end of the first transmission groove (523) is connected to the lower groove (81) through a second extension opening; the end of the transmission block (525) near the second extension opening is engaged with the wedge-shaped surface at the bottom end of the driven block (9) and is slidably connected; when the transmission block (525) moves to the right, it drives the top end of the driven block (9) to extend into the limiting opening (513). The lower support plate (52) is also horizontally provided with a second transmission groove (524) that communicates with the first transmission groove (523). A guide rod (527) is fixedly provided in the second transmission groove (524). A connecting block (526) is fixedly provided at the bottom of the transmission block (525). The connecting block (526) is sleeved on the guide rod (527). A return spring (528) is also sleeved on the guide rod (527). One end of the return spring (528) is connected to the connecting block (526), ​​and the other end is connected to the end wall of the second transmission groove (524).

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