A down-the-hole drilling rig

Abstract

The present invention discloses a down-the-hole drill, specifically relating to the technical field of drilling equipment, including a drill body and a drill frame, a rotary device is installed at the movable output end of the drill frame, a cross rod is fixed at the output end of the rotary device, a connecting block is fixed on one side of the drill frame, a limiting component is fixed on one side of the connecting block, and an expansion component is provided on the lower side of the limiting component. The down-the-hole drill described in the present invention can push the soil accumulated around the hole outward during the drilling process through the mutual cooperation between the cross rod, the driving gear and the expansion component, so as to prevent the fallen soil from accumulating at the bottom of the borehole or getting stuck between the drill rod and the hole wall, causing the drill rod to be unable to be smoothly lifted or rotated, thereby reducing the impact on the drilling progress; through the mutual cooperation between the expansion component and the pushing component, not only can the soil on the surface of the cross rod be cleaned, but also the soil can be prevented from falling into the borehole during the process of the pushing component pushing the soil.

Description

Technical Field

[0001] The present invention relates to the technical field of drilling equipment, in particular to a down-the-hole drilling rig. Background Art

[0002] A drilling rig is a mechanical device that drives the drill bit to drill in any direction and obtain physical geological data during geological exploration. The main function of the drilling rig is to crush the bottom rock and insert or extract the drilling tool. As a new equipment for construction, after several years of promotion, its advantages such as light weight, high efficiency, energy saving, low noise, low pollution, and wide adaptability to formations have been recognized by more and more people. It has been widely used in construction projects. It has the functions of rotation and impact, which can destroy hard rocks through impact, thereby speeding up the construction progress.

[0003] During the use of down-the-hole drills, the drilled soil accumulates around the borehole. If the soil is not cleaned in time, the soil may fall into the borehole. The fallen soil may accumulate at the bottom of the borehole or get stuck between the drill rod and the hole wall, causing the drill rod to be unable to rise or fall smoothly or rotate, thereby causing a drill stuck accident. The drill stuck will not only affect the drilling progress, but may also damage the drill tool and increase maintenance costs. Manual cleaning can also be used, but in the process of cleaning the soil, stones in the soil may splash and cause harm to the operator. Summary of the Invention

[0004] The purpose of the present invention is to propose a down-the-hole drill to solve the problem that during the use of a down-the-hole drill, fallen soil may accumulate at the bottom of the drill hole or get stuck between the drill rod and the hole wall, causing the drill rod to be unable to be smoothly raised or lowered or rotated, thereby causing a drill sticking accident, affecting the drilling progress, possibly damaging the drilling tool, and increasing maintenance costs.

[0005] In order to achieve the above purpose, the present invention adopts the following technology:

[0006] It includes a drilling rig body and a drill frame, a rotary device is installed at the movable output end of the drill frame, a cross rod is fixed to the output end of the rotary device, a connecting block is fixed to one side of the drill frame, a limiting component is fixed to one side of the connecting block, and an outward expansion component is provided on the lower side of the limiting component;

[0007] The limiting component comprises a flat-top conical tube, and a plurality of limiting grooves in an annular array are formed on the inner side wall of the flat-top conical tube;

[0008] The outward expansion component includes an annular frame, a limiting plate is fixed on the inner surface of the annular frame, and a plurality of annular array slide grooves are formed on the limiting plate. A group of pushing components 1 and a group of pushing components 2 are movably installed in the inner cavities of the plurality of slide grooves, and the pushing components 1 and 2 are adapted to the limiting grooves;

[0009] During the movement of the limiting plate, the pushing component 1 and the pushing component 2 slide along the inner cavity of the limiting groove, and the plurality of pushing components 1 and 2 expand obliquely outward.

[0010] As a further description of a down-the-hole drill rig of the above technology:

[0011] A driving gear is rotatably mounted on one side of the connecting block, and a cross slot adapted to the cross rod is provided on the driving gear.

[0012] As a further description of a down-the-hole drill rig of the above technology:

[0013] The outward expansion component includes two synchronous wheels rotatably mounted on the connecting block, a reciprocating screw is fixed on one side of the two synchronous wheels, and the two synchronous wheels are connected to the driving gear through a synchronous belt.

[0014] As a further description of a down-the-hole drill rig of the above technology:

[0015] The adjacent pushing component 1 and the pushing component 2 are located on the same straight line after being rotated by a certain angle, and the pushing component 1 and the pushing component 2 have the same structure.

[0016] As a further description of a down-the-hole drill rig of the above technology:

[0017] The pushing component 1 includes a connecting rod slidably installed in the inner cavity of the limiting groove, a sliding block is fixed to one end of the connecting rod away from the limiting groove, and a push plate is fixed to one side of the sliding block.

[0018] As a further description of a down-the-hole drill rig of the above technology:

[0019] An expansion component is fixed on one side of the limit plate, and the expansion component includes a fixed ring fixed to the limit plate. A plurality of scrapers in an annular array are rotatably installed on one side of the fixed ring. The plurality of scrapers are adapted to the cross rod, and the outer surfaces of the plurality of scrapers are rotatably connected to a rotating plate 1 rotatably installed between the slider.

[0020] As a further description of a down-the-hole drill rig of the above technology:

[0021] Two sets of mutually perpendicular protective devices are rotatably installed on the lower side of the connecting block. The protective device includes a protective plate rotatably installed with the connecting block, an arc-shaped plate is fixed on one side of the protective plate, and a rotating plate 2 rotatably connected to the slider is rotatably installed on one side of the protective plate, and a groove for the rotation of the arc-shaped plate is opened on the arc-shaped plate.

[0022] In summary, due to the adoption of the above-mentioned technology, the beneficial effects of the present invention are:

[0023] 1. Through the cooperation between the cross rod, driving gear and the outward expansion component, the device can push the soil accumulated around the hole outward during the drilling process to prevent the fallen soil from accumulating at the bottom of the drill hole or getting stuck between the drill rod and the hole wall, causing the drill rod to be unable to rise or rotate smoothly, thereby reducing the impact on the drilling progress; the driving gear rotates, and the two synchronous wheels are rotated through the synchronous belt, and the reciprocating screw connected to the two synchronous wheels rotates, thereby moving the annular frame. During the movement of the annular frame, the slider moves with the limit plate. Due to the sliding connection between the connecting rod and the flat-top cone tube, the pushing component one and the pushing component two move along the inner cavity of the slide groove. The movement trajectory of the multiple pushing components one and the pushing component two is to expand outward and move downward at the same time, presenting a conical movement trajectory, which can push the soil accumulated around the drill hole outward, and prevent the soil from accumulating too much and falling into the drill hole.

[0024] 2. This device can not only clean the dirt on the surface of the cross rod, but also prevent the dirt from falling into the drill hole when the pushing component 1 pushes the dirt through the cooperation between the expansion component and the pushing component 1; under normal conditions, the scraper is in close contact with the cross rod, and the wet dirt on the surface of the cross rod can be scraped off during the movement of the cross rod to clean the cross rod; during the movement of the pushing component 1, due to the rotational connection between the rotating plate 1 and the slider, the scraper can be tilted during the movement of the slider, thereby forming a protection around the drill hole and preventing dirt from falling into the drill hole.

[0025] 3. The mutual cooperation between the two sets of protective devices and the pushing component one in this device can push the soil on the outside, make room for the soil pushed by the pushing component one and the pushing component two, and further prevent the accumulation of soil; during the movement of the pushing component one, since the protective plate and the slider are connected by the rotating plate two, the protective plate can be rotated during the movement of the slider, thereby pushing the soil on the outside and leaving room for the soil pushed by the pushing component one and the pushing component two. During the rotation process, the coverage of the arc plate is larger than that of the protective plate, so that more soil can be pushed to the outside, clearing space for the soil pushed out from the inside.

[0026] 4. This device can prevent stones from flying around by setting up two sets of mutually perpendicular protective devices. The two sets of mutually perpendicular protective devices have different lengths. One set of protective devices is located between the two protective devices of the other set, so that a rectangle is formed between the two sets of protective devices. During the drilling process, broken stones can be prevented from flying around, thereby reducing the risk of injury to the operator. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] Figure 1 It shows a schematic diagram of the overall structure provided by an embodiment of the present invention;

[0028] Figure 2 Shows a schematic diagram of a portion of the structure provided according to an embodiment of the present invention Figure 1 ;

[0029] Figure 3 A schematic diagram of the installation position of a driving gear according to an embodiment of the present invention is shown;

[0030] Figure 4 Shows a schematic diagram of a portion of the structure provided according to an embodiment of the present invention Figure 2 ;

[0031] Figure 5 A schematic structural diagram of a position limiting component provided in an embodiment of the present invention is shown;

[0032] Figure 6 The structure of the external expansion component provided by the embodiment of the present invention is shown Figure 1 ;

[0033] Figure 7 It shows a schematic structural diagram of a pushing component according to an embodiment of the present invention;

[0034] Figure 8 The structure of the external expansion component provided by the embodiment of the present invention is shown Figure 2 ;

[0035] Figure 9 It shows a schematic diagram of the connection structure between the expansion component and the pushing component provided in an embodiment of the present invention;

[0036] Figure 10 A schematic diagram showing a state of use of an expansion component according to an embodiment of the present invention is shown;

[0037] Figure 11 It shows a schematic diagram of the use state of the pushing component 1 and the pushing component 2 provided in an embodiment of the present invention;

[0038] Figure 12 A schematic diagram showing the motion trajectories of the first and second pushing components provided according to an embodiment of the present invention is shown;

[0039] Figure 13 A schematic structural diagram of a protective device provided in an embodiment of the present invention is shown;

[0040] Figure 14 A schematic diagram of the rotation trajectory of the protective plate and the curved plate provided according to an embodiment of the present invention is shown.

[0041] Legend:

[0042] 10. Drilling rig body;

[0043] 20. Drilling rack; 21. Rotating device; 22. Cross rod; 23. Connecting block; 24. Driving gear; 25. Cross slot;

[0044] 30. Protective device; 31. Protective plate; 32. Curved plate; 33. Rotating plate 2;

[0045] 40. Limiting component; 41. Flat-top cone tube; 42. Limiting groove;

[0046] 50. External expansion component; 51. Synchronous wheel; 52. Reciprocating screw; 53. Ring frame; 54. Limit plate; 55. Slide;

[0047] 56. Pushing component 1; 561. Connecting rod; 562. Slider; 563. Push plate; 57. Pushing component 2;

[0048] 58. Expansion component; 581. Fixing ring; 582. Scraper; 583. Rotating plate 1. DETAILED DESCRIPTION

[0049] The following will provide a clear and complete description of the down-the-hole drill according to the embodiments of the present invention, in conjunction with the accompanying drawings. Obviously, the described embodiments are only a portion of the embodiments of the present invention, not all of them. All other embodiments derived by persons of ordinary skill in the art based on the embodiments of the present invention without inventive effort are also within the scope of protection of the present invention.

[0050] Example 1

[0051] like Figure 1 and Figure 2 As shown, a down-the-hole drilling rig includes a drilling rig body 10 and a drill rig 20. The drill rig 20 includes an operating table, a hydraulic station, and crawler walking components, and is the main component of the device. The drill rig 20 is rotatably mounted on the drilling rig body 10 and can be adjusted in angle. A rotary device 21 is installed at the movable output end of the drill rig 20. The drill rig 20 controls the up and down movement of the rotary device 21. The rotary device 21 controls the rotation of the drilling tool. A cross rod 22 is fixed to the output end of the rotary device 21. The end of the cross rod 22 away from the rotary device 21 is used to connect the drilling tool. The connected drilling tool includes a drill rod, a ball tooth drill bit, and an impactor.

[0052] Then, if Figure 2 — Figure 4As shown, a connecting block 23 is fixed to one side of the drill frame 20, and a driving gear 24 is rotatably installed on one side of the connecting block 23. The center of the driving gear 24 is in a straight line with the center of the output end of the rotary device 21. A cross slot tube is fixed on the upper side of the driving gear 24, so that the driving gear 24 can still be controlled to rotate when the cross rod 22 moves. A cross slot 25 is provided on the driving gear 24 to match the cross rod 22. The cross slot 25 allows the cross rod 22 to not only move up and down, but also to rotate with the driving gear 24. The cross rod 22 is only a round rod at the lower side of the driving gear 24 without a protrusion. A limiting component 40 is fixed on one side of the connecting block 23. The limiting component 40 corresponds to the cross rod 22. The center line of the limiting component 40 is in a straight line with the center line of the cross rod 22. An outward expansion component 50 is provided on the lower side of the limiting component 40, and the outward expansion component 50 cooperates with the limiting component 40 for use.

[0053] To protect operators, such as Figure 3 As shown, two sets of mutually perpendicular protective devices 30 are rotatably installed on the lower side of the connecting block 23. One set of protective devices 30 has two, and the two sets of mutually perpendicular protective devices 30 have different lengths. One set of protective devices 30 is located between the two protective devices 30 of the other set, so that a rectangle is formed between the two sets of protective devices 30. During the drilling process, broken stones can be prevented from splashing around, thereby reducing the risk of injury to the operator.

[0054] Further, if Figure 5 As shown, the limiting component 40 includes a flat-top conical tube 41 fixedly mounted on the connecting block 23. The flat-top conical tube 41 corresponds to the cross rod 22, so that the cross rod 22 can pass through the center of the inner cavity of the rotating device 21. The inner cavity side wall of the flat-top conical tube 41 is provided with a plurality of limiting grooves 42 in an annular array.

[0055] Further, if Figure 6 and Figure 8 As shown, the expansion component 50 includes two synchronous wheels 51 rotatably mounted on the connecting block 23. The two synchronous wheels 51 are symmetrical to each other. A reciprocating screw 52 is fixed to one side of each synchronous wheel 51. The reciprocating screw 52 passes through the connecting block 23 and there is no connection between the connecting block 23. The two synchronous wheels 51 are connected to the driving gear 24 via a synchronous belt. The rotation of the driving gear 24 can drive the two synchronous wheels 51 to rotate, thereby rotating the two reciprocating screws 52. The synchronous belt connection can ensure that the two synchronous wheels 51 rotate at the same angle and speed.

[0056] Next, the expansion component 50 further includes an annular frame 53. Two mounting blocks on the annular frame 53 are threadedly connected to two reciprocating screws 52. The rotation of the two reciprocating screws 52 can move the annular frame 53 up and down. A limit plate 54 is fixed to the inner surface of the annular frame 53. The limit plate 54 is integrally formed by a circular plate and a plurality of straight plates and is fixed to the inner surface of the annular frame 53. The center of the circular plate is aligned with the center of the cross rod 22 on the same straight line. The limit plate 54 is provided with a plurality of annular arrays of slide grooves 55. The plurality of slide grooves 55 correspond to the plurality of limit grooves 42. The upper side of each slide groove 55 corresponds to a limit groove 42 aligned on the same straight line.

[0057] Among them, a group of pushing parts 56 and a group of pushing parts 57 are movably installed in the inner cavity of the multiple slide grooves 55. The pushing parts 56 and the pushing parts 57 in the group of pushing parts 56 and the pushing parts 57 are both annular arrays. There is a certain angle difference between the group of pushing parts 56 and the group of pushing parts 57.

[0058] The adjacent pushing components 1 56 and 2 57 are positioned on the same straight line after being rotated at a certain angle. In this embodiment, the adjacent pushing components 1 56 and 2 57 are positioned on the same straight line after being rotated forty-five degrees. There are four pushing components 1 56 and four pushing components 2 57 in a set of pushing components 1 56 and 2 57.

[0059] The pushing component 1 56 and the pushing component 2 57 have the same structure. The pushing component 1 56 and the pushing component 2 57 have the same structure but different lengths, so that the pushing component 2 57 and the pushing component 1 56 can cooperate with each other to operate.

[0060] Among them, such as Figure 11 and Figure 12 As shown, the pushing component 1 56 and the pushing component 2 57 are adapted to the limiting groove 42, and the pushing component 1 56 and the pushing component 2 57 slide in the inner cavity of the limiting groove 42. During the movement of the limiting plate 54, due to the action of the limiting groove 42, the pushing component 1 56 and the pushing component 2 57 slide along the inner cavity of the limiting groove 42. Multiple pushing components 1 56 and pushing components 2 57 expand obliquely outward, which can push the soil near the drill hole outward.

[0061] Further, if Figure 7 As shown, the pushing component 1 56 includes a connecting rod 561 slidably installed in the inner cavity of the limiting groove 42. The connecting rod 561 is located in the inner cavity of the slide groove 55. The slide groove 55 limits the moving direction of the connecting rod 561. A slider 562 is fixed to the end of the connecting rod 561 away from the limiting groove 42. The slider 562 is slidably connected to the limiting plate 54. A push plate 563 is fixed to one side of the slider 562. One side of the push plate 563 is an inclined surface to facilitate pushing the soil.

[0062] Then, if Figure 9 and Figure 10 As shown, an expansion component 58 is fixed to one side of the limit plate 54. The expansion component 58 is located at the center of the limit plate 54. The expansion component 58 includes a fixed ring 581 fixed to the limit plate 54. A plurality of scrapers 582 in an annular array are rotatably mounted on one side of the fixed ring 581. The side of the scrapers 582 away from the fixed ring 581 is in close contact with the cross rod 22. The plurality of scrapers 582 are adapted to the cross rod 22. One side of the plurality of scrapers 582 is in close contact with the surface of the cross rod 22 but does not affect the movement of the scrapers 582.

[0063] The outer surfaces of the multiple scrapers 582 are rotatably connected to a rotating plate 583 rotatably mounted between the slider 562. The movement of the slider 562 can rotate the scrapers 582. The multiple scrapers 582 simultaneously expand outward to push the soil around the drill hole outward to prevent the soil from falling into the drill hole. At the same time, the retracted scrapers 582 can scrape the soil on the surface of the cross rod 22.

[0064] Next, the center of the fixed ring 581 and the limiting plate 54 are both provided with a circular groove adapted to the cross rod 22, so that the cross rod 22 can move up and down normally without causing the fixed ring 581 and the limiting plate 54 to rotate;

[0065] In addition, the scraper 582 is adapted to the cross rod 22 . In a normal state, the scraper 582 is in close contact with the cross rod 22 . When the cross rod 22 moves, the scraper 582 can scrape off the dirt on the surface of the cross rod 22 and clean the surface of the cross rod 22 .

[0066] Further, if Figure 13 As shown, the protective device 30 includes a protective plate 31 rotatably mounted on the connecting block 23, and a curved plate 32 is fixed to one side of the protective plate 31. The curved plate 32 is on the same horizontal plane as the protective plate 31. However, during the rotation process, the coverage of the curved plate 32 is larger than that of the protective plate 31. Figure 14 As shown, more soil can be pushed outward to clear space for the soil pushed outward;

[0067] Among them, a rotating plate 2 33 is rotatably installed on one side of the protective plate 31 and is rotatably connected to the slider 562. A groove for the rotation of the curved plate 32 is opened on the curved plate 32. During the movement of the slider 562, the protective plate 31 can be pushed to rotate through the connected rotating plate 2 33.

[0068] It should be noted that the drilling rig body 10, drill frame 20, rotary device 21, synchronous wheel 51 and reciprocating screw 52 in the present invention are all existing technologies, and their installation and control methods are also conventional designs, which will not be elaborated in detail in the present invention.

[0069] Working principle of the invention: This device is a down-the-hole drill, which is mainly used to push the soil accumulated around the drill hole during the drilling process to prevent the soil from falling into the borehole cavity and accumulating at the bottom of the borehole or getting stuck between the drill rod and the hole wall, causing the drill rod to be unable to rise or rotate smoothly;

[0070] Specifically, during use, the cross rod 22 is connected to the drill tool to drill a hole in the ground. The drilled soil accumulates around the drill hole to form a flat-top cone. Then, during the rotation of the cross rod 22, the cross-slot tube and the cross slot 25 act to cause the driving gear 24 to rotate along with the cross rod 22.

[0071] Next, the driving gear 24 rotates, and the two synchronous wheels 51 rotate through the synchronous belt. The reciprocating screw 52 connected to the two synchronous wheels 51 rotates, thereby moving the annular frame 53. During the movement of the annular frame 53, the slider 562 moves along with the limit plate 54. Due to the sliding connection between the connecting rod 561 and the flat-top cone tube 41, the pushing component 1 56 and the pushing component 2 57 move along the inner cavity of the slide groove 55, as shown in FIG. Figure 11 and Figure 12 As shown, the movement trajectory of the plurality of pushing components 1 56 and 2 57 is to expand outward while moving downward, presenting a conical movement trajectory, which can push the soil accumulated around the drill hole outward to prevent the soil from accumulating too much and falling into the drill hole;

[0072] Furthermore, the plurality of pushing components 1 56 and the pushing components 2 57 are not in the same circular plane. The length of the pushing component 1 56 is greater than that of the pushing component 2 57 , so that more soil in the bottom layer can be pushed further.

[0073] The expansion member 58 can push the soil near the drill hole outward during the movement of the pushing member 56 to prevent the soil from falling into the drill hole during the pushing process of the pushing member 56. In addition, the scraper 582 is in close contact with the cross rod 22, so that the wet soil on the surface of the cross rod 22 can be scraped off during the movement of the cross rod 22 to clean the cross rod 22.

[0074] During the movement of the pushing member 56, the rotary plate 583 and the slider 562 are rotatably connected, so that the scraper 582 can be tilted during the movement of the slider 562, thereby forming a protection around the drill hole and preventing soil from falling into the drill hole.

[0075] In addition, during the movement of the pushing component 1 56, since the protective plate 31 and the slider 562 are connected by the rotating plate 2 33, the protective plate 31 can be rotated during the movement of the slider 562, thereby pushing the soil on the outside and leaving space for the soil pushed by the pushing component 1 56 and the pushing component 2 57. During the rotation process, the coverage of the arc plate 32 is larger than that of the protective plate 31. Figure 14 As shown, more soil can be pushed outward to clear space for the soil pushed outward.

[0076] The above description is only a preferred specific embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any technician familiar with the technical field, within the technical scope disclosed by the present invention, who makes equivalent replacements or changes to a down-the-hole drill and its inventive concept according to the technology of the present invention, should be covered by the scope of protection of the present invention.

Claims

1. A down-the-hole drill, comprising a drill body (10) and a drill frame (20), characterized in that: The movable output end of the drill frame (20) is provided with a rotary device (21), the output end of the rotary device (21) is fixed with a cross rod (22), a connecting block (23) is fixed on one side of the drill frame (20), a driving gear (24) is rotatably mounted on one side of the connecting block (23), a cross slot (25) adapted to the cross rod (22) is provided on the driving gear (24), a limiting component (40) is fixed on one side of the connecting block (23), and an outward expansion component (50) is provided on the lower side of the limiting component (40); The limiting component (40) comprises a flat-top conical tube (41), and a plurality of limiting grooves (42) in an annular array are formed on the inner side wall of the flat-top conical tube (41); The outward expansion component (50) includes an annular frame (53), a limiting plate (54) is fixed on the inner surface of the annular frame (53), a plurality of annular array slide grooves (55) are provided on the limiting plate (54), a group of pushing components (56) and a group of pushing components (57) are movably installed in the inner cavity of the plurality of slide grooves (55), and the pushing components (56) and the pushing components (57) are adapted to the limiting grooves (42); The outward expansion component (50) further includes two synchronous wheels (51) rotatably mounted on the connecting block (23), a reciprocating screw (52) being fixed on one side of the two synchronous wheels (51), and the two synchronous wheels (51) are connected to the driving gear (24) via a synchronous belt; The pushing component (56) includes a connecting rod (561) slidably mounted in the inner cavity of the limiting groove (42), a slider (562) is fixed to one end of the connecting rod (561) away from the limiting groove (42), and a push plate (563) is fixed to one side of the slider (562); During the movement of the limiting plate (54), the pushing component 1 (56) and the pushing component 2 (57) slide along the inner cavity of the limiting groove (42), and the plurality of pushing components 1 (56) and the pushing components 2 (57) expand obliquely outward.

2. A down-the-hole drill according to claim 1, characterized in that: The adjacent pushing component 1 (56) and the pushing component 2 (57) are located on the same straight line after being rotated at a certain angle, and the pushing component 1 (56) and the pushing component 2 (57) have the same structure.

3. A down-the-hole drill according to claim 1, characterized in that: An expansion component (58) is fixed to one side of the limit plate (54), and the expansion component (58) includes a fixed ring (581) fixed to the limit plate (54). A plurality of scrapers (582) in an annular array are rotatably mounted on one side of the fixed ring (581). The plurality of scrapers (582) are adapted to the cross rod (22), and the outer surfaces of the plurality of scrapers (582) are rotatably connected to a rotating plate (583) rotatably mounted between the slider (562).

4. A down-the-hole drill according to claim 1, characterized in that: Two sets of mutually perpendicular protective devices (30) are rotatably mounted on the lower side of the connecting block (23). The protective device (30) includes a protective plate (31) rotatably mounted on the connecting block (23). An arc-shaped plate (32) is fixed on one side of the protective plate (31). A second rotating plate (33) rotatably connected to the slider (562) is rotatably mounted on one side of the protective plate (31). A groove for rotating the arc-shaped plate (32) is provided on the arc-shaped plate (32).

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