Well point dewatering system for hydraulic engineering construction

Abstract

The invention discloses a well-point dewatering system for hydraulic engineering construction in the technical field of hydraulic engineering construction. The well-point dewatering system comprises a frame body; the at least two positioning pieces are used for fixing the frame body in a well; the triggering frame is elastically and slidably mounted on the frame body through an elastic piece and moves relative to the frame body to drive the positioning piece to move relative to the frame body; the water pumping structure is installed on the frame body in a sliding mode, the water pumping structure comprises an upper shell and a lower shell which are arranged in a sliding mode, and when the water pumping structure pumps water, the upper shell and the lower shell are close to each other; the fastening structures are mounted at two ends of the water pumping structure; the equal-proportion driving part is installed between the frame body and the water pumping structure and used for driving the water pumping structure to move in an equal-proportion mode according to the water level; the counterweight piece is mounted at the top of the frame body and is used for applying downward pressure to the frame body; the working height of the water pumping structure is dynamically adjusted in equal proportion in real time according to the water level, and inlet pressure is always higher than vaporization pressure of liquid at the corresponding temperature.

Description

TECHNICAL FIELD

[0001] The application relates to the technical field of hydraulic engineering construction, in particular to a well point dewatering system for hydraulic engineering construction. BACKGROUND

[0002] In the well point dewatering operation of water conservancy and building engineering, a water pump is usually directly arranged in a well cavity to lower the underground water level by pumping underground water, so as to create dry operation conditions for earthwork excavation and foundation construction.

[0003] At present, the water pump in the well is generally installed in a fixed height mode, and the spatial position thereof cannot be adjusted after installation. This design has significant defects in the actual dewatering process. In the initial operation stage, the vertical distance between the water inlet and the liquid level is large, and the water inlet can rely on sufficient liquid level differential pressure to stably suck in water flow. However, as the underground water level gradually decreases, the liquid level pressure at the water inlet is greatly attenuated. When the pressure is lower than the vaporization pressure corresponding to the current temperature of the underground water, the water body is easy to vaporize at the water inlet. The gas bubbles formed enter the pump body along with the water flow, and are rapidly broken in the high-pressure environment generated by the high-speed rotation of the impeller, causing the "cavitation" phenomenon. On the one hand, the instantaneous impact force of the bubble breaking will cause continuous impact wear to the impeller, pump shell and other components, accelerating the aging and even scrapping of the equipment. On the other hand, the gas bubbles will occupy the water flow channel, causing a significant decrease in the pumping flow and lift, which is difficult to meet the efficiency requirements of the dewatering operation. At the same time, after the distance between the water level and the pump body is reduced, the stability of the water inlet flow is destroyed, and the operating load of the pump body is easy to fluctuate greatly, which not only increases the risk of frequent start-stop of the equipment, but also further aggravates the component wear, seriously affecting the continuous advancement of the dewatering operation.

[0004] The existing technology for improving the well water pump is mainly focused on the optimization of anti-clogging structure and the improvement of corrosion resistance of the material, and has not yet proposed a technical scheme for dynamically adjusting the height of the pump body in view of the core contradiction of "water level decrease-pump body distance from water level surface reduction-inlet water pressure deficiency". SUMMARY

[0005] The technical scheme of the application is to provide a well point dewatering system for hydraulic engineering construction, which dynamically adjusts the working height of the water pumping structure in real time to ensure that the inlet pressure is always higher than the vaporization pressure of the liquid at the corresponding temperature.

[0006] To achieve the above-mentioned purpose, the application provides the following technical scheme: a well point dewatering system for hydraulic engineering construction, comprising a frame body; At least two positioning members are symmetrically installed on the frame body through connecting rods at both ends of each positioning member, and are used for fixing the frame body in the well; A trigger frame is elastically and slidably installed on the frame body through an elastic member, and is used for driving the positioning member to move relative to the frame body by displacement relative to the frame body; A pumping structure is slidably installed on a frame. The pumping structure includes an upper shell and a lower shell that are slidably disposed. When the pumping structure pumps water, the upper shell and the lower shell move closer to each other. A fastening structure is installed at both ends of the pumping structure. When the upper and lower shells are far apart, the drive trigger frame moves relative to the frame. A proportional drive component is installed between the frame and the pumping structure to drive the pumping structure to move proportionally according to the water level. Counterweights, installed at the top of the frame, are used to apply downward pressure to the frame.

[0007] As a further aspect of the present invention, the proportional driving element includes: The rack is fixedly installed on the side wall of the frame. The drive gear is rotatably mounted on the pumping structure and meshes with the fixed rack; The movable rack is slidably mounted on the frame and meshes with the drive gear.

[0008] As a further aspect of the present invention, the pumping structure includes: The upper housing is slidably mounted on the frame, and the upper housing has several cavities, each of which is equipped with an impeller; The lower housing is slidably mounted on the frame. A drive motor is installed inside the lower housing. The output shaft of the drive motor extends into the upper housing and is axially slidably mounted via a flat key and an impeller. The upper sliding sleeve and the lower sliding sleeve are axially elastically slidable by a flat key. The upper sliding sleeve is installed on the upper housing, and the bottom of the lower sliding sleeve is provided with a water inlet. The screen is fixedly installed between the lower sliding sleeve and the lower housing.

[0009] As a further aspect of the present invention, the fastening structure includes: There are at least two slides, which are fixedly installed on the upper and lower housings respectively; The upper limit and lower limit components are slidably installed at both ends of different slides, and can drive the frame and trigger frame respectively; The sleeve and the rod are slidably arranged and fixedly connected to different slide chambers, and the sleeve and the rod are respectively connected to the ends of different slide chambers.

[0010] As a further embodiment of the present invention, the frame includes a hollow vertical tube, and both ends of the vertical tube are fixedly mounted with panels by bolts.

[0011] As a further embodiment of the present invention, the trigger frame includes a base plate, the base plate is fixedly connected to a vertical rod that is slidably disposed with the vertical tube, and a connecting piece is fixedly installed on the top of the vertical rod by means of a bolt.

[0012] As a further aspect of the present invention, each of the positioning elements includes

[0013] There are at least two connecting rods, which are rotatably mounted at both ends of the frame. The positioning rod is rotatably connected to the connecting rod at both ends; The drive rod is rotatably mounted on the positioning rod and the trigger frame; the drive rod is an elastic component.

[0014] Compared with the prior art, the beneficial effects of the present invention are: In this invention, through the linkage design of the proportional drive component and the water level detection device, the changes in the water level in the well can be tracked in real time, and the pumping structure can be dynamically adjusted to ensure that the pressure at the inlet of the pumping structure is always higher than the vaporization pressure of the liquid at the corresponding temperature. This solves the core contradiction in the prior art of "insufficient inlet pressure due to water level drop and water vaporization producing bubbles", reduces the cavitation phenomenon caused by bubble bursting, reduces the impact wear of key components such as impeller and pump casing, slows down the aging of equipment, and avoids the problem of reduced flow rate and head caused by bubbles crowding the water flow channel, thus ensuring the efficient and stable progress of dewatering operations. Attached Figure Description

[0015] To more clearly illustrate the technical solutions of the embodiments of the present invention, the accompanying drawings used in the description of the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0016] Figure 1 This is a schematic diagram of the overall structure of the present invention; Figure 2 For the present invention Figure 1 Enlarged structural diagram at point A in the middle; Figure 3 For the present invention Figure 1 Enlarged structural diagram at point B; Figure 4 This is a schematic diagram of the overall cross-sectional structure of the present invention; Figure 5 For the present invention Figure 4 Enlarged structural diagram at point C; Figure 6 For the present invention Figure 4 Enlarged structural diagram at point D; Figure 7 This is a schematic diagram of the frame and its connection structure of the present invention; Figure 8 This is a schematic diagram of the fastening structure and its connection relationship of the present invention; Figure 9 This is a schematic cross-sectional view of the fastening structure of the present invention; Figure 10 This is a cross-sectional schematic diagram of the pumping structure of the present invention; The attached diagram lists the components represented by each number as follows: 1. Frame; 11. Vertical pipe; 12. Panel; 2. Positioning component; 21. Connecting rod; 22. Positioning rod; 23. Drive rod; 3. Trigger frame; 31. Base plate; 32. Vertical rod; 33. Connecting component; 4. Pumping structure; 41. Upper shell; 42. Cavity; 43. Impeller; 44. Lower shell; 45. Drive motor; 46. Upper sliding sleeve; 47. Lower sliding sleeve; 48. Screen; 49. Inlet; 5. Fastening structure; 51. Slide chamber; 52. Upper limit component; 53. Lower limit component; 54. Sleeve; 55. Sleeve rod; 6. Proportional drive component; 61. Fixed rack; 62. Drive gear; 63. Movable rack; 7. Counterweight. Detailed Implementation

[0017] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. 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.

[0018] Please see Figures 1-10 The present invention provides a technical solution: a wellpoint dewatering system for water conservancy engineering construction, including a frame 1; There are at least two positioning components 2, and each positioning component 2 is symmetrically installed on the frame 1 at both ends by connecting rods 21, which is used to fix the frame 1 in the well. When the symmetrically arranged positioning components 2 move in the direction away from the frame 1, the positioning components 2 can abut against the well wall and generate positive pressure. This positive pressure can effectively increase the frictional resistance between the positioning components 2 and the well wall, thereby limiting the displacement of the frame 1 relative to the well wall, and finally achieving reliable installation of the frame 1 in the well. The trigger frame 3 is elastically slidably mounted on the frame 1 via an elastic element. By displacing relative to the frame 1, it drives the positioning element 2 to move relative to the frame 1. The relative position of the trigger frame 3 and the frame 1 is adjusted by a traction mechanism (rod or traction rope), and the trigger frame 3 drives the positioning element 2 to displace relative to the frame 1, thereby realizing the installation and disassembly of the frame 1 in the well. Taking the rod-type traction mechanism as an example, two sets of traction mechanisms are connected to the frame 1 and the trigger frame 3 respectively. During operation, the frame 1 is lowered synchronously by the two sets of rods, and the frame 1 and the trigger frame 3 are transported to the preset position in the well. Then, the position of the rod connected to the frame 1 is kept fixed, and the trigger frame 3 is raised by driving the other set of rods, causing the positioning element 2 to move away from the frame 1 and fit tightly against the well wall, thereby limiting the displacement of the frame 1 relative to the well wall.

[0019] The pumping structure 4 is slidably installed on the frame 1. The pumping structure 4 includes an upper shell 41 and a lower shell 44 that are slidably disposed. When the pumping structure 4 pumps water, the upper shell 41 and the lower shell 44 move closer to each other under the action of pressure difference. After the pumping is completed, the upper shell 41 and the lower shell 44 return to their original positions. Fastening structure 5 is installed at both ends of pumping structure 4. When the upper shell 41 and lower shell 44 move away from each other, the drive trigger frame 3 moves relative to frame 1. The proportional drive component 6 is installed between the frame 1 and the pumping structure 4. When the water level fluctuates, it is used to drive the pumping structure 4 to move proportionally according to the water level. The water level detection equipment monitors the dynamic changes of the water level in the well in real time. Taking the float-type detection structure as an example, the float is placed at the monitoring position in the well. The float can rise and fall synchronously with the changes of the water level in the well. The proportional drive component 6 drives the pumping structure 4 to adjust its height proportionally according to the change in the height of the float. This changes the pressure environment at the inlet of the pumping structure 4, so that the pressure at the inlet is always higher than the vaporization pressure of the liquid at the corresponding temperature, thereby avoiding the generation of bubbles due to vaporization of the liquid. Counterweight 7 is installed on the top of frame 1 to apply downward pressure to frame 1; Specifically, the installation process is as follows: Two sets of traction mechanisms are connected to the frame 1 and the trigger frame 3 respectively. During operation, the rods of the two sets of traction mechanisms are lowered synchronously to transport the frame 1 and the trigger frame 3 to the preset installation position inside the well. Subsequently, keeping the position of the rod connected to the frame 1 fixed, the rod connected to the trigger frame 3 is driven to move the trigger frame 3 upward, causing the positioning part 2 to move away from the frame 1 and closely abut against the well wall, thereby limiting the displacement of the frame 1 relative to the well wall. After completing the above positioning, the two sets of traction mechanisms are removed, thus completing the installation of the frame 1. During this process, the counterweight 7 continuously applies pressure to the frame 1 to ensure that the positioning part 2 always remains in contact with the well wall.

[0020] The proportional drive component 6 is linked with the water level detection equipment. The water level detection equipment monitors the water level changes in the well in real time. The proportional drive component 6 adjusts the working height of the pumping structure 4 synchronously according to the water level detection results to regulate the pressure at the inlet of the pumping structure 4, so that the pressure at the inlet is always higher than the vaporization pressure of the liquid at the corresponding temperature, thereby avoiding the generation of bubbles by liquid vaporization.

[0021] In summary, through the linkage design of the proportional drive component 6 and the water level detection equipment, the changes in the water level in the well can be tracked in real time, and the pumping structure 4 can be driven to dynamically adjust the working height simultaneously, ensuring that the pressure at the inlet of the pumping structure 4 is always higher than the vaporization pressure of the liquid at the corresponding temperature. This solves the core contradiction in the existing technology of "insufficient inlet pressure due to water level drop and water vaporization producing bubbles", reduces the cavitation phenomenon caused by bubble bursting, reduces the impact wear of key components such as impeller and pump casing, slows down the aging of equipment, and avoids the problem of reduced flow rate and head caused by bubbles crowding the water flow channel, thus ensuring the efficient and stable progress of dewatering operations.

[0022] As a further aspect of the present invention, the proportional drive element 6 includes: The rack 61 is fixedly installed on the side wall of the frame 1; The drive gear 62 is rotatably mounted on the pumping structure 4 and meshes with the fixed rack 61; The movable rack 63 is slidably mounted on the frame 1 and meshes with the drive gear 62 for synchronous movement according to the water level. Specifically, the monitoring results of the water level detection equipment synchronously drive the movable rack 63 to generate displacement; taking a float-type water level detection equipment as an example, when the water level in the well rises, the float rises synchronously with the water level and drives the movable rack 63 to move in the same direction, and the movable rack 63 drives the drive gear 62 meshing with it to rotate; since the drive gear 62 also meshes with the fixed rack 61, under the guidance of the fixed rack 61, the drive gear 62 moves in the same direction and proportionally with the movable rack 63, thereby driving the pumping structure 4 connected to it to rise in the same direction and proportionally with the water level; conversely, when the water level... During descent, the float descends, reducing the tension applied to the pumping structure 4. This tension change is proportional to the distance the water level drops. The pumping structure 4 descends under gravity, moving in the same direction as the water level and proportionally. Through the proportional adjustment of the proportional drive component 6, the height of the pumping structure 4 can be adjusted within a preset range according to the rise and fall of the water level. This not only precisely controls the pressure at the inlet of the pumping structure 4, preventing liquid vaporization and bubble generation, but also prevents the pumping structure 4 from rising and falling significantly, thereby reducing wear on the frame 1 and the pumping structure 4, while also avoiding the risk of pipes above the pumping structure 4 becoming entangled.

[0023] As a further embodiment of the present invention, the pumping structure 4 includes: The upper housing 41 is slidably mounted on the frame 1. The upper housing 41 has several cavities 42, and each cavity 42 is equipped with an impeller 43. The lower housing 44 is slidably mounted on the frame 1. A drive motor 45 is installed inside the lower housing 44. The output shaft of the drive motor 45 extends into the upper housing 41 and is axially slidably mounted via a flat key and an impeller 43. The upper sliding sleeve 46 and the lower sliding sleeve 47 are axially elastically slidable by a flat key. The upper sliding sleeve 46 is installed on the upper housing 41, and the lower sliding sleeve 47 is provided with a water inlet 49 at the bottom. Screen 48 is fixedly installed between the sliding sleeve 47 and the lower housing 44; Specifically, the drive motor 45 drives the impeller 43 to rotate through the output shaft. With the high-speed rotation of the impeller 43, a vacuum area is quickly formed inside the cavity 42 and in the space between the upper sliding sleeve 46 and the lower sliding sleeve 47. Under the action of the internal and external pressure difference, the upper sliding sleeve 46 and the lower sliding sleeve 47 approach each other and compress the elastic element between them (in this embodiment, the elastic element is a spring plate, and the function of the elastic element is to drive the upper sliding sleeve 46 and the lower sliding sleeve 47 to reset), thereby driving the upper housing 41 and the lower housing 44 to approach each other synchronously. When the upper housing 41 and the lower housing 44 move to the limit position, the external water flows through the screen 48 under the action of the pressure difference, enters the interior of the upper housing 41 through the water inlet 49, and finally exits from the top, thereby realizing continuous drainage operation. When drainage stops, the upper sliding sleeve 46 and the lower sliding sleeve 47 move away from each other in opposite directions under the push of the elastic restoring force of the elastic element until the distance between them returns to the initial state.

[0024] As a further aspect of the present invention, the fastening structure 5 includes: There are at least two slides 51, which are fixedly installed on the upper housing 41 and the lower housing 44 respectively; The upper limit component 52 and the lower limit component 53 are respectively slidably disposed at both ends of different slides 51, and can respectively drive the frame 1 and the trigger frame 3; The sleeve 54 and the sleeve rod 55 are slidably arranged and are fixedly connected to different slides 51 respectively, and the sleeve 54 and the sleeve rod 55 are respectively connected to the ends of different slides 51; Specifically, when the upper housing 41 and the lower housing 44 move away from each other, they respectively drive the slide chambers 51 fixedly connected to them to move synchronously. The two slide chambers 51 then drive the sleeve 54 and the sleeve rod 55 to move away from each other, increasing the internal space of the sleeve 54 and the sleeve rod 55, which in turn reduces the air pressure inside the slide chambers 51. Under this pressure difference, the upper limit member 52 and the lower limit member 53 slide outward from the slide chambers 51. When the upper limit member 52 and the lower limit member 53 come into contact with the frame 1 and the trigger frame 3 respectively, they drive the frame 1 and the trigger frame 3 to produce a slight relative displacement. As the frame 1 and the trigger frame 3 move away from each other, the positioning... The positive pressure between component 2 and the well wall decreases synchronously; conversely, when the upper shell 41 and the lower shell 44 approach each other, the sleeve 54 and the sleeve rod 55 approach each other, and the internal space of the two shrinks. The upper limit component 52 and the lower limit component 53 slide into the slide chamber 51 and disengage from the frame 1 and the trigger frame 3. At this time, the frame 1 and the trigger frame 3 return to their initial relative positions under the action of the elastic element (spring in this embodiment) between them, ensuring that the positioning component 2 and the well wall maintain the preset positive pressure, thereby effectively avoiding the positional displacement of the frame 1 caused by external factors such as equipment vibration, and ensuring the installation stability of the frame 1 during the drainage operation.

[0025] As a further embodiment of the present invention, the frame 1 includes a hollow vertical tube 11, and a panel 12 is fixedly installed at both ends of the vertical tube 11 by bolts; the panel 12 is installed at both ends of the vertical tube 11 by bolts, which can be quickly assembled, and the panels 12 at both ends can limit the lifting limit of the pumping structure 4.

[0026] As a further embodiment of the present invention, the trigger frame 3 includes a base plate 31, and a vertical rod 32 that is slidably connected to the base plate 31 and is slidably disposed with the vertical tube 11. A connecting piece 33 is fixedly installed on the top of the vertical rod 32 by bolts; the connecting piece 33 facilitates the connection of an external traction mechanism.

[0027] As a further aspect of the present invention, each positioning element 2 includes

[0028] There are at least two connecting rods 21, which are rotatably mounted at both ends of the frame 1. Positioning rod 22, with both ends rotatably connected to connecting rod 21; The drive rod 23 is rotatably mounted on the positioning rod 22 and the trigger frame 3, and the drive rod 23 is an elastic component. When the trigger frame 3 is relatively close to the frame 1, taking the upward movement of the trigger frame 3 relative to the frame 1 as an example: during the upward movement of the trigger frame 3 relative to the frame 1, the drive rod 23 is pushed to move upward synchronously with the hinged end of the drive rod 23. The drive rod 23 then pushes the positioning rod 22. Under the traction of the connecting rod 21, the positioning rod 22 moves in the direction away from the frame 1 until the positioning rod 22 abuts against the well wall, and the positive pressure between the positioning rod 22 and the well wall is sufficient to completely offset the weight of the equipment itself. The drive rod 23 is an elastic component. Its working mechanism is as follows: when the positioning rod 22 contacts the well wall, if the trigger frame 3 continues to be applied with an upward force relative to the frame 1, the drive rod 23 can store elastic potential energy through elastic bending deformation. After the pumping operation is completed, when the trigger frame 3 moves slightly downward relative to the frame 1, the drive rod 23 can rebound and release some of the elastic potential energy, and its bending amplitude will decrease accordingly, thereby reducing the normal pressure between the positioning rod 22 and the well wall, so as to facilitate the disassembly operation of the frame 1. Conversely, during the pumping operation, the fastening structure 5 releases the trigger frame 3 and the frame 1, so that the two maintain a preset distance, thereby improving the installation stability of the frame 1.

Claims

1. A wellpoint dewatering system for water conservancy engineering construction, comprising a frame (1), characterized in that: There are at least two positioning components (2), and each positioning component (2) is symmetrically installed on the frame (1) at both ends by connecting rods (21) for fixing the frame (1) in the well; The trigger frame (3) is elastically slidably mounted on the frame (1) by means of an elastic element. By displacing relative to the frame (1), it drives the positioning element (2) to move relative to the frame (1). The pumping structure (4) is slidably installed on the frame (1). The pumping structure (4) includes an upper shell (41) and a lower shell (44) that are slidably disposed. When the pumping structure (4) pumps water, the upper shell (41) and the lower shell (44) move closer to each other. The fastening structure (5) is installed at both ends of the pumping structure (4). When the upper shell (41) and the lower shell (44) move away from each other, the drive trigger frame (3) moves relative to the frame (1). A proportional drive component (6) is installed between the frame (1) and the pumping structure (4) to drive the pumping structure (4) to move proportionally according to the water level. Counterweight (7) is installed on top of frame (1) to apply downward pressure to frame (1).

2. The wellpoint dewatering system for water conservancy engineering construction according to claim 1, characterized in that: The proportional drive element (6) includes: A fixed rack (61) is fixedly installed on the side wall of the frame (1); The drive gear (62) is rotatably mounted on the pumping structure (4) and meshes with the fixed rack (61); The movable rack (63) is slidably mounted on the frame (1) and meshes with the drive gear (62).

3. The wellpoint dewatering system for water conservancy engineering construction according to claim 1, characterized in that: The pumping structure (4) includes; The upper housing (41) is slidably mounted on the frame (1). The upper housing (41) has several cavities (42), and each cavity (42) is equipped with an impeller (43). The lower housing (44) is slidably mounted on the frame (1). A drive motor (45) is provided inside the lower housing (44). The output shaft of the drive motor (45) extends into the upper housing (41) and is axially slidably mounted via a flat key and an impeller (43). The upper sliding sleeve (46) and the lower sliding sleeve (47) are axially elastically slidably set by a flat key. The upper sliding sleeve (46) is installed on the upper housing (41), and the lower sliding sleeve (47) is provided with a water inlet (49) at the bottom. The screen (48) is fixedly installed between the sliding sleeve (47) and the lower housing (44).

4. The wellpoint dewatering system for water conservancy engineering construction according to claim 1, characterized in that: The fastening structure (5) includes: There are at least two slides (51), which are fixedly installed on the upper housing (41) and the lower housing (44) respectively; The upper limit component (52) and the lower limit component (53) are respectively slidably set at both ends of different slides (51), and can drive the frame (1) and the trigger frame (3) respectively; The sleeve (54) and the sleeve rod (55) are slidably arranged and are fixedly connected to different slides (51), and the sleeve (54) and the sleeve rod (55) are respectively connected to the ends of different slides (51).

5. A wellpoint dewatering system for water conservancy engineering construction according to claim 1, characterized in that: The frame (1) includes a hollow vertical tube (11), and both ends of the vertical tube (11) are fixed with panels (12) by bolts.

6. A wellpoint dewatering system for water conservancy engineering construction according to claim 5, characterized in that: The trigger frame (3) includes a base plate (31), and a vertical rod (32) that is slidably connected to the base plate (31) and is slidably connected to the vertical tube (11). A connector (33) is fixedly installed on the top of the vertical rod (32) by bolts.

7. A wellpoint dewatering system for water conservancy engineering construction according to claim 1, characterized in that: Each of the positioning elements (2) includes There are at least two connecting rods (21), which are rotatably set at both ends of the frame (1); The positioning rod (22) is rotatably set at both ends with the connecting rod (21); The drive rod (23) is rotatably mounted on the positioning rod (22) and the trigger frame (3); the drive rod (23) is an elastic member.

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