A support and reinforcement device for soft soil foundation pit construction

Abstract

The present invention belongs to the field of support and reinforcement technology, and discloses a support and reinforcement device for soft soil foundation pit construction, including a foundation pit slope and a steel strand anchor placed inside the foundation pit slope, and also including: a positioning member, the positioning member is fixedly connected to the steel strand anchor and is located inside the foundation pit slope; a back plate, the back plate is movably connected inside the positioning member; a telescopic member; the movable component includes a rectangular plate, the number of the rectangular plates is the same as the number of conical steel plates, and the rectangular plates are hinged to the inner cavity of a round steel plate. The present invention realizes the preliminary reinforcement of the support for soft soil foundation pit construction by setting the coordination of the conical steel plate and the back plate, and uses a propulsion device to push the steel bar of the back plate, so that the steel bar pushes the steel bar of the back plate to move inside the round steel plate, and the conical steel plate moves outward synchronously. At this time, the sharper side of the outer end of multiple conical steel plates will gradually and simultaneously insert into the soil inside the foundation pit slope, thereby achieving a preliminary reinforcement effect.

Description

Technical Field

[0001] The invention belongs to the technical field of support and reinforcement, and in particular relates to a support and reinforcement device for soft soil foundation pit construction. Background Art

[0002] Support and reinforcement in soft soil foundation pit construction is an important part of ensuring the stability of the foundation pit and construction safety. Through support equipment such as anchor rods, the stability of the soft soil foundation pit is enhanced to ensure the safety of foundation pit construction, control foundation pit deformation, and protect the surrounding environment.

[0003] However, the existing support devices for soft soil foundation pit construction still have disadvantages in actual use: in use, in the construction work of supporting the slope of soft soil foundation pit, holes are generally drilled in the slope area of ​​the soft soil foundation pit, anchor rods are buried in the holes, and then grouting is performed in the holes to achieve support. However, due to the characteristics of soft soil foundation pits such as high water content and porosity ratio, high compressibility and low shear strength, the existing support method of simply pre-buried anchor rods and grouting will greatly reduce the stability of the support. Therefore, a support and reinforcement device for soft soil foundation pit construction is proposed, which greatly improves the support and reinforcement effect of soft soil foundation pits. Summary of the Invention

[0004] In order to solve the problem raised in the above background technology that due to the characteristics of soft soil foundation pits such as high water content and porosity, high compressibility and low shear strength, the existing support means of grouting through simple pre-buried anchor rods will greatly reduce the stability of the support, the present invention provides a support and reinforcement device for soft soil foundation pit construction, which realizes the initial reinforcement of the soft soil foundation pit construction support by arranging the cooperation of structures such as conical steel plates and abutment plates; realizes secondary reinforcement on the basis of the initial reinforcement by arranging the cooperation of structures such as L-shaped steel plates and movable components; realizes tertiary reinforcement on the basis of the secondary reinforcement by arranging the cooperation of structures such as first steel pipes and conical steel pipes.

[0005] To achieve the above-mentioned object, the present invention provides the following technical solution: a support and reinforcement device for soft soil foundation pit construction, comprising a foundation pit slope and a steel strand anchor rod placed inside the foundation pit slope, and further comprising:

[0006] A positioning member, the positioning member being fixedly connected to the steel strand anchor rod and located inside the foundation pit slope;

[0007] an abutment plate movably connected to the interior of the positioning member;

[0008] a telescopic member, the telescopic member being disposed in the positioning member and abutting against the abutment plate;

[0009] A plurality of movable components are provided and fixedly installed inside the positioning member;

[0010] The positioning part includes a round steel plate, and a number of conical steel plates are arranged in a circular shape at equal angles inside the round steel plate, and an L-shaped steel plate is installed on one side of the conical steel plate; the movable component includes a rectangular plate, the number of the rectangular plates is the same as the number of the conical steel plates, and the positions of the rectangular plates correspond to those of the conical steel plates, the rectangular plates are hinged to the inner cavity of the round steel plate, and a pointed plate is connected to one side of the top surface of the rectangular plate, and the pointed plate is embedded in the round steel plate.

[0011] Preferably, a plurality of bolt rings are installed at equal angles in the side wall of the round steel plate, a steel strand anchor rod is placed inside the bolt ring, bolts are arranged on the circumference of the bolt ring, the bolt ring is connected to the steel strand anchor rod by bolts, one end of the steel strand anchor rod is inserted into the inside of the bolt ring, and the bolt is twisted so that one end of the bolt gradually enters the inside of the bolt ring and contacts the outer wall of the steel strand anchor rod, and at the same time, according to Figure 8 It can be seen that there are four bolts on the circumferential side of the bolt. After the steel strand anchor is placed, the four bolts are twisted, and the inner ends of the four bolts will jointly abut against the outer wall of the steel strand anchor, thereby enhancing the firmness between the steel strand anchor and the positioning piece.

[0012] Preferably, two limit blocks for keeping the conical steel plate from moving up and down are symmetrically installed at the connection area between the round steel disc and the conical steel plate;

[0013] The inside of the conical steel plate is provided with a plurality of through grooves, and the top end of the L-shaped steel plate is in contact with the rectangular plate. The design of the limit block inside the round steel plate ensures that the conical steel plate will not deflect when it moves up and down. When the L-shaped steel plate is synchronously driven upward by the conical steel plate, the top end of the L-shaped steel plate will squeeze the rectangular plate, causing the rectangular plate to rotate.

[0014] Preferably, the abutment plate is composed of a steel bar and a steel plate. The steel plate is placed inside the round steel plate. An angle is provided on the side of the steel plate close to the conical steel plate. The end of the steel plate away from the conical steel plate is fixedly connected to the steel bar. The steel bar passes through the round steel plate and extends to the outside of the round steel plate.

[0015] Preferably, the side of the steel plate in the abutment plate close to the conical steel plate is in contact with the telescopic member, and one end of the telescopic member passes through the steel plate in the abutment plate.

[0016] Preferably, the telescopic member includes a first steel tube, which is fixed in the round steel plate, one end of the first steel tube is sleeved inside the abutment plate, and the end of the first steel tube away from the abutment plate is sleeved with a tapered steel tube, and the end of the tapered steel tube away from the first steel tube passes through the round steel plate and extends to the outside of the round steel plate.

[0017] Preferably, the conical steel pipe is sleeved on the outer wall of the first steel pipe, and a limiting ring is installed on one end of the conical steel pipe that is in contact with the abutment plate. When the abutment plate continuously moves inside the round steel disk, it will push the conical steel pipe to move synchronously, so that the end of the conical steel pipe away from the first steel pipe gradually moves outward from the inside of the round steel disk and gradually gets stuck in the soil of the foundation pit slope.

[0018] Preferably, a plurality of slots are provided on the outer wall of the conical steel pipe away from one end of the first steel pipe. When one end of the conical steel pipe extends into the soil at the foundation pit slope, the slots on the outer wall of the conical steel pipe will be synchronously driven to contact the soil.

[0019] Preferably, a first spring is installed on one side of the top surface of the rectangular plate, and the rectangular plate is elastically connected to the round steel disk through the first spring;

[0020] A limiting groove for moving the tip plate is provided inside the round steel disk. The tip plate is located in the limiting groove, and a second spring is installed at one end of the tip plate. The tip plate is elastically connected to the round steel disk through the second spring.

[0021] Preferably, when the L-shaped steel plate is moved upward by external force, the top end of the L-shaped steel plate will press the rectangular plate, so that the rectangular plate will move against the pointed plate while rotating, so that the end of the pointed plate away from the rectangular plate gradually moves outward from the inside of the round steel plate and is inserted into the soil.

[0022] Compared with the prior art, the present invention has the following beneficial effects:

[0023] The present invention realizes the preliminary reinforcement of the soft soil foundation pit construction support by arranging the coordination of the conical steel plate and the abutment plate and other structures. The propulsion equipment is used to push the steel bar of the abutment plate, so that the steel bar pushes the steel plate of the abutment plate to move inside the round steel plate, so that the steel plate contacts the bottom end of each conical steel plate and the conical steel plates move outward synchronously. At this time, the sharper side of the outer end of multiple conical steel plates will gradually be inserted into the soil inside the foundation pit slope at the same time, thereby achieving the preliminary reinforcement effect.

[0024] The present invention realizes secondary reinforcement on the basis of primary reinforcement by arranging the cooperation of structures such as L-shaped steel plates and movable components. The conical steel plates drive the L-shaped steel plates to move synchronously, so that the L-shaped steel plates resist the rectangular plates to flip over, and one end of the top surface of the rectangular plates resists one end of the pointed plates to move outward from the inside of the round steel plate and gradually insert into the soil. The holes for grouting of existing pre-buried anchor rods are generally opened in an inclined shape, resulting in multiple pointed plates forming a barb-like shape when they are moved outward and inserted into the soil at the same time, thereby increasing the activity resistance between the device and the holes, thereby achieving the effect of secondary reinforcement.

[0025] The present invention realizes tertiary reinforcement on the basis of secondary reinforcement by arranging the coordination of the first steel pipe and the tapered steel pipe and other structures. The middle length of the first steel pipe and the tapered steel pipe is increased by the push of the anti-plate. When the slurry is poured in, part of the slurry can enter the interior of the tapered steel pipe through the first steel pipe, and contact the soil inside the foundation pit slope through the groove hole on the outer side of the tapered steel pipe, thereby expanding the contact range between the slurry and the foundation pit slope, thereby improving the reinforcement effect. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] Figure 1 It is a schematic diagram of the structure of the present invention;

[0027] Figure 2 Schematic diagram of the structural coordination relationship between the steel strand anchor rod and the positioning member of the present invention;

[0028] Figure 3 Schematic diagram of the structural matching relationship between the tapered steel plate and the bolt ring of the present invention;

[0029] Figure 4 Schematic diagram of the subdivision structure of the telescopic member of the present invention;

[0030] Figure 5 for Figure 4 A schematic diagram of the partially enlarged structure at center A;

[0031] Figure 6 Schematic diagram of the structural coordination relationship between the tapered steel plate and the L-shaped steel plate of the present invention;

[0032] Figure 7 for Figure 6 A schematic diagram of the partially enlarged structure at point B in the middle;

[0033] Figure 8 This is a schematic diagram of the structural coordination relationship between the first steel pipe and the bolt ring of the present invention;

[0034] Figure 9 Schematic diagram of the structural coordination relationship between the round steel disc and the conical steel plate of the present invention;

[0035] Figure 10 for Figure 9 Schematic diagram of the partially enlarged structure at point C in the middle.

[0036] In the figure: 1. Foundation pit slope; 2. Steel strand anchor rod; 3. Positioning piece; 31. Round steel plate; 32. Conical steel plate; 33. Bolt ring; 34. L-shaped steel plate; 4. Abutment plate; 5. Telescopic piece; 51. First steel pipe; 52. Conical steel pipe; 6. Movable assembly; 61. Rectangular plate; 62. First spring; 63. Pointed plate; 64. Second spring. DETAILED DESCRIPTION

[0037] The following will clearly and completely describe the technical solutions in the embodiments of the present invention in conjunction with the accompanying drawings. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative efforts are within the scope of protection of the present invention.

[0038] like Figures 1 to 10 As shown, the present invention provides a support and reinforcement device for soft soil foundation pit construction, comprising a foundation pit slope 1 and a steel strand anchor rod 2 placed inside the foundation pit slope 1, and further comprising:

[0039] The positioning member 3 is fixedly connected to the steel strand anchor rod 2 and is located inside the foundation pit slope 1;

[0040] Abutment plate 4, which is movably connected to the interior of the positioning member 3;

[0041] The telescopic member 5 is arranged in the positioning member 3 and abuts against the abutment plate 4;

[0042] The movable assembly 6 is provided in multiple groups and is fixedly installed inside the positioning member 3;

[0043] The positioning part 3 includes a round steel plate 31, and several conical steel plates 32 are arranged in a ring at equal angles inside the round steel plate 31. An L-shaped steel plate 34 is installed on one side of the conical steel plate 32; the movable component 6 includes a rectangular plate 61, the number of rectangular plates 61 is the same as the number of conical steel plates 32, and the position corresponds to the conical steel plates 32. The rectangular plate 61 is hinged to the inner cavity of the round steel plate 31, and a pointed plate 63 is connected to one side of the top surface of the rectangular plate 61, and the pointed plate 63 is embedded in the round steel plate 31.

[0044] like Figure 4 and Figure 8 As shown, a plurality of bolt rings 33 are installed at equal angles in a circular shape on the side wall of the round steel plate 31. The steel strand anchor rod 2 is placed inside the bolt ring 33. Bolts are arranged on the circumference of the bolt ring 33. The bolt ring 33 is connected to the steel strand anchor rod 2 through bolts.

[0045] Adopt the above solution: insert one end of the strand anchor rod 2 into the inside of the bolt ring 33, and twist the bolt so that one end of the bolt gradually enters the inside of the bolt ring 33 and contacts the outer wall of the strand anchor rod 2. Figure 8 It can be seen that there are four bolts arranged around the bolt ring 33. When the steel strand anchor rod 2 is placed, the four bolts are twisted, and the inner ends of the four bolts will jointly abut against the outer wall of the steel strand anchor rod 2, thereby enhancing the firmness between the steel strand anchor rod 2 and the positioning member 3.

[0046] like Figure 9 and Figure 10As shown, two limit blocks for keeping the conical steel plate 32 moving up and down are symmetrically installed in the connection area between the round steel plate 31 and the conical steel plate 32;

[0047] A plurality of through slots are formed inside the conical steel plate 32 , and the top end of the L-shaped steel plate 34 is in contact with and connected to the rectangular plate 61 .

[0048] The above solution is adopted: the design of the internal limit block of the round steel plate 31 ensures that when the conical steel plate 32 moves up and down, no deflection occurs. When the L-shaped steel plate 34 is synchronously driven upward by the conical steel plate 32, the top of the L-shaped steel plate 34 will squeeze the rectangular plate 61, causing the rectangular plate 61 to rotate.

[0049] like Figure 3 and Figure 4 As shown, the abutment plate 4 is composed of a steel bar and a steel plate. The steel plate is placed inside the round steel plate 31. An angle is provided on the side of the steel plate close to the conical steel plate 32. The end of the steel plate away from the conical steel plate 32 is fixedly connected to the steel bar. The steel bar passes through the round steel plate 31 and extends to the outside of the round steel plate 31.

[0050] The above solution is adopted: the steel bar on the abutment plate 4 drives the steel bar plate to move in the inner cavity of the round steel plate 31. When the steel bar plate moves, the end at the angle opened will abut the conical steel plate 32, so that the top end of the conical steel plate 32 moves smoothly from the inside of the round steel plate 31 to the outside.

[0051] like Figure 4 and Figure 5 As shown, the side of the steel plate in the abutment plate 4 close to the conical steel plate 32 is in contact with the telescopic member 5 , and one end of the telescopic member 5 passes through the steel plate in the abutment plate 4 .

[0052] like Figure 4 and Figure 5 As shown, the telescopic member 5 includes a first steel tube 51, which is fixed in the round steel plate 31. One end of the first steel tube 51 is sleeved inside the abutment plate 4. The end of the first steel tube 51 away from the abutment plate 4 is sleeved with a tapered steel tube 52. The end of the tapered steel tube 52 away from the first steel tube 51 passes through the round steel plate 31 and extends to the outside of the round steel plate 31.

[0053] like Figure 5 As shown, the conical steel pipe 52 is sleeved on the outer wall of the first steel pipe 51 , and a limiting ring is installed on one end of the conical steel pipe 52 that is in contact with the plate 4 .

[0054] Adopting the above solution: when the abutment plate 4 continuously moves inside the round steel plate 31, it will push the conical steel pipe 52 to move synchronously, so that the end of the conical steel pipe 52 away from the first steel pipe 51 gradually moves outward from the inside of the round steel plate 31 and gradually gets stuck in the soil of the foundation pit slope 1.

[0055] like Figure 5 and Figure 8 As shown, a plurality of slots are provided on the outer wall of the conical steel pipe 52 away from one end of the first steel pipe 51. When one end of the conical steel pipe 52 extends into the soil of the foundation pit slope 1, the slots on the outer wall of the conical steel pipe 52 will be synchronously driven to contact the soil.

[0056] Adopting the above scheme: when grouting operation is performed on the holes opened inside the foundation pit slope 1, that is, grouting is performed on the steel strand anchor rod 2, at this time, part of the slurry will enter the interior of the conical steel pipe 52 through the first steel pipe 51, and contact the soil inside the foundation pit slope 1 through the groove hole on the outer wall of the conical steel pipe 52.

[0057] like Figure 7 As shown, a first spring 62 is installed on one side of the top surface of the rectangular plate 61, and the rectangular plate 61 is elastically connected to the round steel plate 31 through the first spring 62;

[0058] A limiting groove for moving the pointed plate 63 is provided inside the round steel disk 31 . The pointed plate 63 is located in the limiting groove, and a second spring 64 is installed at one end of the pointed plate 63 . The pointed plate 63 is elastically connected to the round steel disk 31 via the second spring 64 .

[0059] like Figure 7 As shown, when the L-shaped steel plate 34 is moved upward by an external force, the top end of the L-shaped steel plate 34 presses against the rectangular plate 61, so that the rectangular plate 61 rotates while resisting the movement of the pointed plate 63, so that the end of the pointed plate 63 away from the rectangular plate 61 gradually moves outward from the inside of the round steel plate 31 and is inserted into the soil.

[0060] The working principle and use process of the present invention:

[0061] First, insert one end of the steel strand anchor rod 2 into the bolt ring 33, and tighten the steel strand anchor rod 2 by twisting the bolts outside the bolt ring 33 to fix the steel strand anchor rod 2 to the round steel plate 31. Then, place the steel strand anchor rod 2, the positioning piece 3, and the parts placed inside the positioning piece 3 together in the hole area in the foundation pit slope 1. The round steel plate 31 can ensure that the steel strand anchor rod 2 is always located in the center area of ​​the hole.

[0062] Secondly, after the device is placed, the propulsion device is used to push the steel bar of the plate 4, so that the steel bar pushes the steel plate of the plate 4 to move inside the round steel plate 31. During the movement, the steel plate of the plate 4 will respectively contact the bottom end of each conical steel plate 32, so that the multiple conical steel plates 32 move outward synchronously. At this time, the sharper side of the outer ends of the multiple conical steel plates 32 will gradually and simultaneously be inserted into the soil inside the foundation pit slope 1;

[0063] As the conical steel plate 32 moves, it drives the L-shaped steel plate 34 to move synchronously, and causes the end of the L-shaped steel plate 34 close to the movable component 6 to abut against one end of the rectangular plate 61, causing the rectangular plate 61 to flip over. During the flipping process of the rectangular plate 61, one end of the top surface of the rectangular plate 61 gradually contacts the pointed plate 63, and then abuts against the pointed plate 63, causing the end of the pointed plate 63 away from the rectangular plate 61 to move outward from the inside of the round steel plate 31 and gradually insert into the soil.

[0064] Subsequently, as the abutment plate 4 gradually moves, the end of the conical steel pipe 52 away from the first steel pipe 51 will move outward from the inside of the round steel plate 31 and be inserted into the soil of the foundation pit slope 1. At this time, the slots on the outside of the conical steel pipe 52 will also contact the soil synchronously. At this time, the preliminary installation work is completed, and then grouting work is carried out into the holes opened in the foundation pit slope 1. At this time, the slurry will fill the inside of the steel strand anchor rod 2, and at the same time, part of the slurry will enter the inside of the conical steel pipe 52 through the first steel pipe 51, and contact the soil inside the foundation pit slope 1 through the slots on the outside of the conical steel pipe 52.

[0065] It should be noted that, in this document, relational terms such as first and second, etc., are used only to distinguish one entity or operation from another entity or operation, and do not necessarily require or imply any actual relationship or order between these entities or operations. Moreover, the terms "comprises," "comprising," or any other variations thereof are intended to cover non-exclusive inclusion, such that a process, method, article, or apparatus that includes a list of elements includes not only those elements but also other elements not explicitly listed, or elements inherent to such process, method, article, or apparatus.

[0066] While embodiments of the present invention have been shown and described, it will be appreciated by those skilled in the art that various changes, modifications, substitutions, and variations may be made to these embodiments without departing from the principles and spirit of the invention, and that the scope of the invention is defined by the appended claims and their equivalents.

Claims

1. A support and reinforcement device for soft soil foundation pit construction, comprising a foundation pit slope (1) and a steel strand anchor rod (2) placed inside the foundation pit slope (1), characterized in that: Also includes: A positioning member (3), the positioning member (3) being fixedly connected to the steel strand anchor rod (2) and being located inside the foundation pit slope (1); Abutment plate (4), the abutment plate (4) being movably connected to the interior of the positioning member (3); A telescopic member (5), the telescopic member (5) being arranged in the positioning member (3) and abutting against the abutment plate (4); A movable assembly (6), wherein the movable assembly (6) is provided in multiple groups and is fixedly mounted inside the positioning member (3); The positioning member (3) includes a round steel plate (31), a plurality of conical steel plates (32) are arranged in a circular shape at equal angles in the inner ring of the round steel plate (31), and an L-shaped steel plate (34) is installed on one side of the conical steel plate (32); the movable component (6) includes a rectangular plate (61), the number of the rectangular plates (61) is the same as the number of the conical steel plates (32), and the positions of the rectangular plates (61) correspond to the conical steel plates (32), the rectangular plates (61) are hinged to the inner cavity of the round steel plate (31), and one side of the top surface of the rectangular plate (61) is abutted and connected with a pointed plate (63), and the pointed plate (63) is embedded in the round steel plate (31); The telescopic member (5) includes a first steel tube (51), the first steel tube (51) is fixedly connected to the round steel plate (31), one end of the first steel tube (51) is sleeved inside the support plate (4), the end of the first steel tube (51) away from the support plate (4) is sleeved with a conical steel tube (52), and the end of the conical steel tube (52) away from the first steel tube (51) passes through the round steel plate (31) and extends to the outside of the round steel plate (31); The conical steel tube (52) is sleeved on the outer wall of the first steel tube (51), and a limiting ring is installed at one end of the conical steel tube (52) that is in contact with the abutment plate (4); During the movement, the abutting plate (4) abuts against the conical steel plate (32), so that the top end of the conical steel plate (32) smoothly moves outward from the inside of the round steel plate (31), and the conical steel plate (32) drives the L-shaped steel plate (34) to move at the same time. The top end of the L-shaped steel plate (34) abuts against the rectangular plate (61), so that the rectangular plate (61) abuts against the movement of the pointed plate (63) while rotating, so that the end of the pointed plate (63) away from the rectangular plate (61) gradually moves outward from the inside of the round steel plate (31) and is inserted into the soil.

2. The support and reinforcement device for soft soil foundation pit construction according to claim 1 is characterized in that: A plurality of bolt rings (33) are annularly mounted at equal angles on the side wall of the round steel plate (31), a steel strand anchor rod (2) is placed inside the bolt ring (33), bolts are arranged on the circumference of the bolt ring (33), and the bolt ring (33) is connected to the steel strand anchor rod (2) via the bolts.

3. The support and reinforcement device for soft soil foundation pit construction according to claim 1 is characterized in that: Two limit blocks for keeping the conical steel plate (32) from moving up and down are symmetrically installed in the connection area between the round steel disc (31) and the conical steel plate (32), and a plurality of through slots are provided inside the conical steel plate (32).

4. The support and reinforcement device for soft soil foundation pit construction according to claim 1 is characterized in that: The abutment plate (4) is composed of a steel bar and a steel plate. The steel plate is placed inside the round steel plate (31). A bevel is provided on the side of the steel plate close to the conical steel plate (32). An end of the steel plate away from the conical steel plate (32) is fixedly connected to the steel bar. The steel bar passes through the round steel plate (31) and extends to the outside of the round steel plate (31).

5. The support and reinforcement device for soft soil foundation pit construction according to claim 4, characterized in that: The side of the steel plate in the abutment plate (4) close to the conical steel plate (32) is in contact with the telescopic member (5), and one end of the telescopic member (5) passes through the steel plate in the abutment plate (4).

6. The support and reinforcement device for soft soil foundation pit construction according to claim 1, characterized in that: The outer wall of the conical steel pipe (52) away from one end of the first steel pipe (51) is provided with a plurality of slots. When one end of the conical steel pipe (52) extends into the soil of the foundation pit slope (1), the slots on the outer wall of the conical steel pipe (52) are simultaneously driven to contact the soil.

7. The support and reinforcement device for soft soil foundation pit construction according to claim 1, characterized in that: A first spring (62) is installed on one side of the top surface of the rectangular plate (61), and the rectangular plate (61) is elastically connected to the round steel plate (31) via the first spring (62); A limiting groove for moving the pointed plate (63) is provided inside the round steel disc (31), the pointed plate (63) is located in the limiting groove, and a second spring (64) is installed at one end of the pointed plate (63), and the pointed plate (63) is elastically connected to the round steel disc (31) via the second spring (64).

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