A city gas pressure regulating and conveying device

Abstract

The present application discloses a city gas pressure regulating and delivery device, comprising: a pressure regulating chamber, a pressure regulator and an acoustic wave sensor disposed within the pressure regulating chamber, the installation height of the acoustic wave sensor within the pressure regulating chamber being adjustable; a delivery pipeline, comprising an input pipeline and an output pipeline, the input pipeline being connected to the inlet of the pressure regulating chamber, and the output pipeline being connected to the outlet of the pressure regulating chamber; the acoustic wave sensor being located near the inlet end of the pressure regulating chamber, and the pressure regulator being located near the outlet end of the pressure regulating chamber; and the device for adapting to the detection requirements of gas of different densities by adjusting the height position of the acoustic wave sensor within the pressure regulating chamber, detecting the acoustic wave signal of the gas inputted into the input pipeline, and outputting the delivery pressure of the gas through the output pipeline regulated by the pressure regulator. The present invention improves the accuracy of pressure regulation by adjusting the height position of the acoustic wave sensor within the pressure regulating chamber, adapting to the detection requirements of gas of different densities, detecting the acoustic wave signal of the gas inputted into the input pipeline, and outputting the delivery pressure of the gas through the output pipeline regulated by the pressure regulator.

Description

Technical Field

[0001] The present application relates to a city gas pressure regulating and conveying device, belonging to the technical field of gas conveying. Background Art

[0002] The city gas pressure regulating and transmission device is an important part of the urban gas supply system. It is mainly used to adjust natural gas and other gases in the high-pressure transmission pipeline to an appropriate low pressure. The main function of the gas pressure regulating and transmission device is to transport high-pressure gas from the supply source to the low-pressure use point to meet specific needs. In this process, the pressure of the gas needs to be adjusted to keep it within a safe and appropriate range to meet the gas supply needs of various users such as urban residents, commercial, and industrial users. The low-pressure gas after pressure regulation will be further measured through a metering device. Usually, an acoustic wave sensor will be installed in the gas pressure regulating and transmission device to monitor the pressure changes in the gas pipeline in real time. The signal provided by the sensor can be used to adjust the pressure regulating device accordingly to ensure that the output pressure of the gas meets the requirements for billing and monitoring. Finally, the low-pressure gas will be distributed to various user points through the transmission pipeline for user use.

[0003] When using existing devices, different cities and pipeline companies often transport different pipeline gases, such as natural gas (density 0.7-0.9 kg / m3), liquefied petroleum gas (density 2.10 kg / m3), and coal gas (density 0.75 kg / m3). However, since the speed of sound waves propagating in gas is closely related to its density, different types of gas have different frequency responses and attenuation characteristics to sound waves. Sound waves of a specific frequency may be absorbed more in some gases, while propagating farther in other gases. Therefore, when installing the sensor, it is necessary to adjust the height of the sound wave sensor according to the changes in gas type and density to ensure that sufficient echo signals can be captured to improve detection accuracy. However, the sound wave sensor in the pressure regulating and delivery device of existing devices is usually fixed in a fixed position, which easily leads to time delays in the sound wave signal obtained by the sound wave sensor, thereby reducing the accuracy of pressure regulation, which needs to be improved. At the same time, due to factors such as uneven pipe walls, the sound wave signal in the pipeline may be disturbed or unstable. Therefore, the height position of the sound wave sensor needs to be adjusted to improve measurement accuracy. Summary of the Invention

[0004] According to one aspect of the present application, a city gas pressure regulating and delivery device is provided. The device adapts to the detection requirements of gas of different density types by adjusting the height position of the acoustic wave sensor in the pressure regulating chamber, detects the acoustic wave signal of the gas input by the input pipeline, and uses the delivery pressure of the gas output by the output pipeline regulated by the pressure regulator, thereby improving the accuracy of pressure regulation.

[0005] A city gas pressure regulating and conveying device, characterized by comprising:

[0006] A pressure regulating chamber, wherein a pressure regulator and an acoustic wave sensor are provided in the pressure regulating chamber, and the installation height of the acoustic wave sensor in the pressure regulating chamber is adjustable according to the corresponding gas density;

[0007] a delivery pipeline, comprising an input pipeline and an output pipeline, wherein the input pipeline is connected to the inlet of the pressure regulating chamber, and the output pipeline is connected to the outlet of the pressure regulating chamber;

[0008] The acoustic wave sensor is close to the inlet end of the pressure regulating chamber, and the voltage regulator is close to the outlet end of the pressure regulating chamber;

[0009] By adjusting the height position of the acoustic wave sensor in the pressure regulating chamber, it is adapted to the detection requirements of gas of different density types, detects the acoustic wave signal of the gas input from the input pipeline, and uses the pressure regulator to adjust the delivery pressure of the gas output from the output pipeline based on the detected acoustic wave signal.

[0010] Furthermore, a filter frame is installed in the pressure regulating chamber, the peripheral side of the filter frame is sealed with the inner wall of the pressure regulating chamber, a filter screen is installed in the filter frame, and the filter frame is located at the entrance of the pressure regulating chamber.

[0011] Furthermore, the acoustic wave sensor is installed in the pressure regulating chamber through an adjustable mechanism;

[0012] The adjustable mechanism includes a rotating member and a transmission member, the rotating member includes a first screw rod, the transmission member includes a transmission block and a connecting rod, the transmission block has a threaded hole extending from top to bottom, the first screw rod is installed in the threaded hole, the transmission block is installed on the connecting rod, both ends of the connecting rod are installed with a second screw rod and are rotatably connected to the connecting rod, the bottom of the second screw rod is also connected to an L-shaped block, both ends of the connecting rod close to the side of the filter frame are provided with vertical limiting grooves, parallel square plates are correspondingly installed in the two limiting grooves, and filter plates are also connected between the square plates;

[0013] Two ends of one side of the filter frame are provided with vertical straight grooves, one end of the square plate is installed in the limiting groove, and the other end of the square plate is installed in the straight groove;

[0014] The acoustic wave sensor is mounted on the transmission block and faces the inlet direction of the pressure regulating chamber.

[0015] Furthermore, side grooves are symmetrically provided on the side walls of the pressure regulating chamber, and vertical slide grooves are provided on the side walls of the side grooves, and the filter frame is installed in the slide grooves.

[0016] Furthermore, one end of the top of the pressure regulating chamber is open, and a cover plate is installed at the opening. A first guide hole and two second guide holes are formed through the cover plate, and the two second guide holes are located on both sides of the first guide hole. A first locking cap and a second locking cap are respectively threadedly installed in the second guide hole and the first guide hole;

[0017] The first guide hole is located above the first screw rod, and the second guide hole is located above the second screw rod.

[0018] Furthermore, the adjustable mechanism further comprises a sponge wood wiping board, and the sponge wood wiping board is located between the two square boards;

[0019] The sponge wood rubbing board is parallel to the probe of the acoustic wave sensor.

[0020] Furthermore, the second screw rod passes through the L-shaped block and is threadedly connected to the L-shaped block.

[0021] Furthermore, a slot is provided above the first screw rod and the second screw rod;

[0022] The slots correspond to the positions of the first guide holes and the second guide holes.

[0023] The beneficial effects of this application include:

[0024] 1) The city gas pressure regulating and delivery device provided in this application adapts to the detection requirements of gas of different densities by adjusting the height position of the acoustic wave sensor within the pressure regulating chamber according to the corresponding gas density and pipeline conditions. The device detects the acoustic wave signal of the gas input through the input pipeline and, based on the detected acoustic wave signal, uses the pressure regulator to adjust the delivery pressure of the gas output through the output pipeline, thereby improving the accuracy of pressure regulation.

[0025] Furthermore, by rotating the first screw rod, the first screw rod and the transmission block are threadedly transmitted, so that the transmission block drives the acoustic wave sensor and the connecting rod to move synchronously. At the same time, through the limitation of the straight groove on the opposite plate on the filter frame, the acoustic wave sensor can be adjusted while always being oriented to the side of the input pipeline. As a result, the acoustic wave sensor can adapt to different gases. While increasing adaptability, it is also convenient to adjust the acoustic wave sensor, thereby improving the accuracy of the data detected by the acoustic wave sensor, and enabling the pressure regulator to more accurately analyze and adjust the pressure of the current threshold of the gas, thereby ensuring that the pressure of the gas in the pipeline is stable and appropriate, and improving the efficiency and safety of gas transportation.

[0026] 2) The city gas pressure regulating and transmission device provided in the present application can always perform primary filtration on the gas transported through the input pipeline by setting a filter, and by setting a connecting rod, when the height of the acoustic wave sensor is adjusted, the thread of the second screw rod will limit the L-shaped block, synchronously driving the square plate and the filter plate between the square plates to move synchronously, which can perform secondary filtration while also protecting the probe of the acoustic wave sensor, effectively reducing the adhesion of particles and impurities that have not been filtered initially to the probe of the acoustic wave sensor, and reducing maintenance.

[0027] 3) The urban gas pressure regulating and conveying device provided in the present application can cause the second screw rod and the L-shaped block to be threadedly transmitted by rotating the second screw rod. At the same time, due to the limitation of the straight groove on the square plate, the square plate and the filter plate are driven to move, which can avoid the acoustic wave sensor being blocked by the square plate and the filter plate when the adjustment height is too high and cannot be adjusted. The filter plate can also be fine-tuned more accurately according to the position of the gas conveying in the input pipeline and the pressure regulating chamber, thereby completing more effective secondary filtration, increasing the filtering effect of the device, and thus ensuring the safety and stability of gas transportation.

[0028] 4) The city gas pressure regulating and conveying device provided in the present application is configured to provide a first guide hole and a second guide hole, and optimize the positions of the first screw rod and the second screw rod below the first guide hole and the second guide hole. At the same time, slots are opened on the first screw rod and the second screw rod, so that the operator can unscrew the first locking cap and the second locking cap and use a flat-blade screwdriver to insert the screwdriver into the slot and rotate it to complete the adjustment of the acoustic wave sensor and the filter plate without removing the cover plate, thereby facilitating subsequent maintenance.

[0029] 5) The city gas pressure regulating and transmission device provided in the present application optimizes the structure and layout of the device so that the device is an integrated structure as a whole. The overall structure is compact, and the side groove design allows the square plate to be effectively embedded inside the side groove, effectively increasing the space utilization inside the pressure regulating chamber. BRIEF DESCRIPTION OF THE DRAWINGS

[0030] Figure 1 It is a schematic diagram of the three-dimensional structure of the present invention;

[0031] Figure 2 It is a schematic diagram of the three-dimensional explosion structure of the present invention;

[0032] Figure 3 This is a schematic diagram of the cover plate connection explosion structure of the present invention;

[0033] Figure 4 This is a three-dimensional schematic diagram of the overall structure of the pressure regulating chamber of the present invention;

[0034] Figure 5 This is a schematic diagram of the three-dimensional structure of the pressure regulating chamber of the present invention;

[0035] Figure 6 is a cross-sectional view of the pressure regulating chamber of the present invention;

[0036] Figure 7 This is a schematic diagram of the explosion structure of the first screw rod connection of the present invention;

[0037] Figure 8 This is a schematic diagram of the explosion structure of the filter plate connection of the present invention;

[0038] List of parts and reference numerals: 1-pressure regulating chamber; 2-pressure regulator; 3-acoustic sensor; 4-input pipe; 5-output pipe; 6-filter frame; 7-filter screen; 8-first screw rod; 9-transmission block; 10-connecting rod; 11-threaded hole; 12-second screw rod; 13-L-shaped block; 14-limiting groove; 15-square plate; 16-filter plate; 17-straight groove; 18-side groove; 19-slide groove; 20-cover plate; 21-first guide hole; 22-second guide hole; 23-first locking cap; 24-second locking cap; 25-sponge wood wiping board; 26-slot. DETAILED DESCRIPTION

[0039] The present application is described in detail below with reference to embodiments, but the present application is not limited to these embodiments.

[0040] See also Figure 1-8 A city gas pressure regulating and conveying device, characterized by comprising:

[0041] A pressure regulating chamber, wherein a pressure regulator 2 and an acoustic wave sensor 3 are provided in the pressure regulating chamber 1. The installation height of the acoustic wave sensor 3 in the pressure regulating chamber 1 is adjustable according to the corresponding gas density;

[0042] The pressure regulating chamber can be provided with an acrylic plate, so that the staff can observe the situation inside the pressure regulating chamber.

[0043] A delivery pipeline, comprising an input pipeline 4 and an output pipeline 5, wherein the input pipeline 4 is connected to the inlet of the pressure regulating chamber 1, and the output pipeline 5 is connected to the outlet of the pressure regulating chamber 1;

[0044] The acoustic wave sensor 3 is close to the inlet end of the pressure regulating chamber 1, and the pressure regulator 2 is close to the outlet end of the pressure regulating chamber 1, and is used to adjust the pressure at the outlet end of the pressure regulating chamber 1;

[0045] By adjusting the height position of the acoustic wave sensor 3 in the pressure regulating chamber 1, it is adapted to the detection requirements of gas of different density types, and the acoustic wave signal of the gas input by the input pipe 4 is detected. According to the detected acoustic wave signal, the delivery pressure of the gas output by the output pipe 5 is adjusted by the pressure regulator 2.

[0046] Specifically, because different types of gas have different frequency responses and attenuation characteristics to sound waves, sound waves of a specific frequency may be absorbed more in some gases and propagate farther in other gases. Therefore, when installing the sensor, it is necessary to adjust the height of the acoustic wave sensor according to changes in gas type and density to ensure that sufficient echo signals can be captured to improve detection accuracy; and then adjust the pressure through the pressure regulator to improve the accuracy of pressure regulation.

[0047] When gas is being transported, some impurities (such as iron filings and particulate matter) are likely to remain in the pipeline or on the pipe wall during pipeline maintenance and construction. This can cause disturbances or instability in the acoustic wave signal in the pipeline. This can cause impurities such as iron filings on the inner wall of the pipeline to adhere to the ultrasonic probe during gas transportation, affecting the accuracy of the ultrasonic probe's pressure detection.

[0048] A filter frame 6 is further installed in the pressure regulating chamber 1 , a filter screen 7 is installed in the filter frame 6 , and the filter frame 6 is located at the entrance of the pressure regulating chamber 1 .

[0049] The acoustic wave sensor 3 is installed in the pressure regulating chamber 1 through an adjustable mechanism;

[0050] The adjustable mechanism includes a rotating member and a transmission member, the rotating member includes a first screw rod 8, the transmission member includes a transmission block 9 and a connecting rod 10, the transmission block 9 has a threaded hole 11 that runs from top to bottom, the first screw rod 8 is installed in the threaded hole 11, the transmission block 9 is installed on the connecting rod 10, and second screw rods 12 are installed at both ends of the connecting rod 10 and are rotatably connected to the connecting rod 10. The bottom of the second screw rod 12 is also connected to an L-shaped block 13, and both ends of the connecting rod 12 close to the side of the filter frame 6 are provided with vertical limiting grooves 14, and parallel square plates 15 are correspondingly installed in the two limiting grooves 14, and filter plates 16 are also connected between the square plates 15;

[0051] Wherein, the limiting groove is a cross-shaped limiting groove, and one end of the square plate connected to the limiting groove is a cross limiting block, and the cross limiting block slides in the cross limiting groove;

[0052] The filter frame 6 is provided with vertical straight grooves 17 at both ends of one side. One end of the square plate 15 is installed in the limiting groove 14, and the other end of the square plate 15 is installed in the straight groove 17.

[0053] By setting the cross limit groove and the straight groove, the cross limit block and the square plate can be effectively limited and supported when moving, thereby avoiding shaking and increasing the stability of the device when adjusting the acoustic wave sensor and the filter plate.

[0054] The acoustic wave sensor 3 is mounted on the transmission block 9 and faces the inlet direction of the pressure regulating chamber 1 .

[0055] Side grooves 18 are symmetrically provided on the side walls of the pressure regulating chamber 1 . Vertical chute grooves 19 are provided on the side walls of the side grooves 18 . The filter frame 6 is installed in the chute grooves 19 .

[0056] Specifically, during use, the position of the acoustic wave sensor can be adjusted according to the type of gas transported by the input pipeline and the output pipeline: first, the cover plate can be removed from the top groove by removing the screws, and then the first screw can be rotated. At this time, the rotation of the first screw will be threaded with the transmission block, so that the transmission block drives the acoustic wave sensor and the connecting rod to move synchronously. Due to the movement of the connecting rod and the limitation of the thread of the second screw on the L-shaped block, the connecting rod will drive the L-shaped block and the square plate on the L-shaped block to move up and down in the side groove and the straight groove in the rectangular frame. By rotating the first screw, the first screw and the transmission block are threaded, so that the transmission block drives the acoustic wave sensor and the connecting rod to move synchronously. At the same time, through the limitation of the square plate by the straight groove on the filter frame, the adjustment can be completed while the direction of the acoustic wave sensor is always on the side of the air intake pipe, so that the acoustic wave sensor can adapt to different gases. Increasing adaptability also facilitates the adjustment of the acoustic wave sensor, thereby improving the accuracy of the data detected by the acoustic wave sensor, and thus enabling the pressure regulator to more accurately analyze and adjust the pressure based on the current threshold of the gas.

[0057] One end of the top of the pressure regulating chamber 1 is open, and a cover plate 20 is installed at the opening.

[0058] It is worth noting that, in order to ensure sealing, a sealing layer is further provided under the cover plate to seal the pressure regulating cavity, and the sealing layer is specifically a rubber layer;

[0059] The cover plate is detachably connected to the top of the pressure regulating chamber. A first guide hole 21 and two second guide holes 22 are formed through the cover plate 20. The two second guide holes 22 are located on both sides of the first guide hole 21. A first locking cap 23 and a second locking cap 24 are respectively threadedly installed in the second guide hole 22 and the first guide hole 21.

[0060] The first guide hole 21 is located above the first screw rod 8 , and the second guide hole 22 is located above the second screw rod 12 .

[0061] The adjustable mechanism further includes a sponge wood wiping board 25, and the sponge wood wiping board 25 is located between the two square boards 15;

[0062] The sponge wood rubbing board 25 is parallel to the probe of the acoustic wave sensor 3 .

[0063] The second screw rod 12 passes through the L-shaped block 13 and is threadedly connected to the L-shaped block 13 .

[0064] A slot 26 is provided above each of the first screw rod 8 and the second screw rod 12;

[0065] The slot 26 corresponds to the position of the first guide hole 8 and the second guide hole 12 .

[0066] Specifically, when the probe of the acoustic wave sensor moves to a suitable position, the filter plate can be fine-tuned according to the density of the gas: first, the two second screw rods can be rotated synchronously, so that the two second screw rods and the L-shaped block are threadedly transmitted. At the same time, due to the limitation of the straight groove on the other plate, the L-shaped block will drive the square plate to move vertically synchronously, and at this time the cross limit block will slide in the cross limit groove. By rotating the second screw rod, the second screw rod and the L-shaped block can be threadedly transmitted. At the same time, due to the limitation of the straight groove on the other plate, the square plate and the filter plate can be driven to move. This can avoid the acoustic wave sensor being blocked by the square plate and the filter plate when the adjustment height is too high and cannot be adjusted. It can also be adjusted according to the gas in the input pipeline and the adjustment height. The position of the gas conveyed in the pressure chamber can be used to more accurately fine-tune the filter plate, thereby completing a more effective secondary filtration, increasing the filtering effect of the device, and ensuring the safety and stability of gas transmission. By rotating the second screw rod, the second screw rod and the L-shaped block can be threadedly driven. At the same time, the straight groove limits the square plate, thereby driving the square plate and the filter plate to move, which can avoid the acoustic wave sensor being blocked by the square plate and the filter plate when the adjustment height is too high and unable to be adjusted. In addition, the filter plate can be more accurately fine-tuned according to the position of the gas conveyed in the input pipeline and the pressure regulating chamber, thereby completing a more effective secondary filtration, increasing the filtering effect of the device, and ensuring the safety and stability of gas transmission.

[0067] When it slides to the appropriate position, the second screw rod can be stopped from rotating. When the probe of the acoustic wave sensor needs to be cleaned and the acoustic wave sensor and the filter plate need to be adjusted in the later use, the first locking cap and the second locking cap on the cover can be loosened, and then a flat-head screwdriver can be inserted into the slots in the first screw rod and the second screw rod through the first guide hole or the second guide hole to make adjustments without removing the cover. The acoustic wave sensor and the filter plate can be adjusted separately. If the acoustic wave sensor needs to be cleaned, the slot in the second screw rod can be directly rotated with a flat-head screwdriver, and then the staff can observe the sub-pressure of the pressure regulating chamber. At the acrylic board, the two square plates drive the sponge wood eraser to descend to complete the cleaning of the acoustic wave sensor probe, and then the second screw rod can be reversed to reset the square plate to complete the cleaning of the acoustic wave sensor, and by setting the first guide hole and the second guide hole, and optimizing the positions of the first screw rod and the second screw rod below the first guide hole and the second guide hole, and at the same time, by opening slots on the first screw rod and the second screw rod, the operator can unscrew the first locking cap and the second locking cap and use a flat-blade screwdriver to insert the slot and rotate it to complete the adjustment of the acoustic wave sensor and the filter plate without removing the cover, which is convenient for later maintenance.

[0068] The above descriptions are merely a few embodiments of the present application and do not constitute any form of limitation to the present application. Although the present application discloses the preferred embodiments as above, they are not intended to limit the present application. Any technical personnel familiar with the present profession, without departing from the scope of the technical solution of the present application, using the technical content disclosed above to make slight changes or modifications are equivalent to equivalent implementation cases and fall within the scope of the technical solution.

Claims

1. A city gas pressure regulating and conveying device, characterized in that: include: A pressure regulating chamber (1) is provided with a pressure regulator (2) and an acoustic wave sensor (3), and the installation height of the acoustic wave sensor (3) in the pressure regulating chamber (1) is adjustable according to the corresponding gas density; a delivery pipeline comprises an input pipeline (4) and an output pipeline (5), the input pipeline (4) is connected to the inlet of the pressure regulating chamber (1), and the output pipeline (5) is connected to the outlet of the pressure regulating chamber (1); the acoustic wave sensor (3) is close to the inlet end of the pressure regulating chamber (1), and the pressure regulator (2) is close to the outlet end of the pressure regulating chamber (1); by adjusting the height position of the acoustic wave sensor (3) in the pressure regulating chamber (1), the detection requirements of gas of different density types are met, the acoustic wave signal of the gas inputted by the input pipeline (4) is detected, and according to the detected acoustic wave signal, the delivery pressure of the gas outputted by the output pipeline (5) is adjusted by the pressure regulator (2); A filter frame (6) is also installed in the pressure regulating chamber (1), the peripheral side of the filter frame (6) is sealedly connected to the inner wall of the pressure regulating chamber (1), a filter screen (7) is installed in the filter frame (6), and the filter frame (6) is located at the entrance of the pressure regulating chamber (1); The acoustic wave sensor (3) is installed in the pressure regulating chamber (1) through an adjustable mechanism; the adjustable mechanism includes a rotating member and a transmission member, the rotating member includes a first screw rod (8), the transmission member includes a transmission block (9) and a connecting rod (10), the transmission block (9) has a threaded hole (11) that passes through from top to bottom, the first screw rod (8) is installed in the threaded hole (11), the transmission block (9) is installed on the connecting rod (10), and the two ends of the connecting rod (10) are both installed with a second screw rod (12) and are rotatably connected to the connecting rod (10), and the bottom of the second screw rod (12) is also connected to An L-shaped block (13), both ends of the connecting rod (12) close to the filter frame (6) are provided with vertical limiting grooves (14), and parallel square plates (15) are correspondingly installed in the two limiting grooves (14), and a filter plate (16) is also connected between the square plates (15); vertical straight grooves (17) are provided at both ends of one side of the filter frame (6), one end of the square plate (15) is installed in the limiting groove (14), and the other end of the square plate (15) is installed in the straight groove (17); the acoustic wave sensor (3) is installed on the transmission block (9) and faces the inlet direction of the pressure regulating chamber (1); Side grooves (18) are symmetrically provided on the side walls of the pressure regulating chamber (1), and vertical chute grooves (19) are provided on the side walls of the side grooves (18), and the filter frame (6) is installed in the chute grooves (19); One end of the top of the pressure regulating chamber (1) is open, and a cover plate (20) is installed at the opening. A first guide hole (21) and two second guide holes (22) are formed through the cover plate (20). The two second guide holes (22) are located on both sides of the first guide hole (21). A first locking cap (23) and a second locking cap (24) are respectively threadedly installed inside the second guide hole (22) and the first guide hole (21); the first guide hole (21) is located above the first screw rod (8), and the second guide hole (22) is located above the second screw rod (12); The adjustable mechanism further comprises a sponge wood wiping board (25), the sponge wood wiping board (25) being located between the two square boards (15); the sponge wood wiping board (25) being parallel to the probe of the acoustic wave sensor (3); The second screw rod (12) passes through the L-shaped block (13) and is threadedly connected to the L-shaped block (13); A slot (26) is provided above the first screw rod (8) and the second screw rod; the slot (26) corresponds to the position of the first guide hole (21) and the second guide hole (22).

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