Wedge flowmeter for measuring high viscosity media

Abstract

This invention relates to the field of flowmeter technology and proposes a wedge flowmeter for measuring high-viscosity media. The flowmeter includes two end tubes, a middle tube, a welding ring, and a wedge-shaped throttling tube. One end of each end tube has an integrally formed inner tube and an outer tube. The inner tube is spaced apart within the outer tube, and its axial length is greater than that of the outer tube. The middle tube is positioned between the two end tubes, and both ends of the middle tube have chamfered surfaces on their outer sides, with a portion of the chamfered surface extending between the inner and outer tubes. The welding ring is fixedly positioned within the molten pool. The wedge-shaped throttling tube is slidably positioned within the middle tube. This invention, by incorporating the inner and outer tubes on the end tubes, forms a nested, cutable maintenance structure with the middle tube and the wedge-shaped throttling tube. This facilitates the disassembly, replacement, and repair of the wedge-shaped throttling tube, thereby shortening maintenance time, reducing maintenance costs, and ensuring measurement accuracy after repeated assembly of the wedge-shaped throttling tube.

Description

Technical Field

[0001] This invention relates to the field of flow meter technology, and more particularly to a wedge flow meter for measuring high-viscosity media. Background Technology

[0002] A wedge flow meter is a differential pressure flow measurement instrument. It reduces the fluid flow area by installing a wedge-shaped throttling element in the pipeline, creating a pressure difference before and after the element, and thus calculating the flow rate. Wedge flow meters have advantages such as strong self-cleaning ability and suitability for high-viscosity media and media containing solid particles. They are widely used in industries such as petroleum, chemical, metallurgy, and wastewater treatment.

[0003] Under harsh operating conditions of high wear, high corrosion, or easy scaling, the wedge block of the wedge flowmeter, as the core throttling element, is subjected to high-speed fluid scouring, particle impact, chemical corrosion, and thermal stress for a long time. It is prone to erosion wear, pitting, scaling, or geometric deformation, which leads to a decrease in measurement accuracy or even failure.

[0004] Existing wedge flow meters typically have the wedge block welded and fixed to the measuring tube or nested as a whole. For example, a wedge flow meter disclosed in utility model publication CN205593575U has high-pressure and low-pressure tapping pipes at both ends of the measuring tube, and an anti-wear tube is installed inside the measuring tube, with the wedge-shaped throttling block placed inside the anti-wear tube. When the throttling block is damaged due to impact or other reasons, it cannot be replaced individually; the entire flow meter must be replaced. This results in complex, time-consuming, and costly maintenance procedures for the media conveying pipeline. Summary of the Invention

[0005] In view of this, the present invention proposes a wedge flow meter for measuring high viscosity media, which facilitates the disassembly, replacement and maintenance of the wedge-shaped throttling tube, thereby shortening maintenance time, reducing maintenance costs, and ensuring measurement accuracy after repeated assembly of the wedge-shaped throttling tube.

[0006] The technical solution of this invention is implemented as follows: This invention provides a wedge flow meter for measuring high viscosity media, comprising two end tubes, a middle tube, a welding ring, and a wedge-shaped throttling tube. Each end tube has a pressure measuring hole on its top side. One end of each end tube is integrally formed with an inner tube and an outer tube. The inner tube is spaced apart within the outer tube, and the axial length of the inner tube is greater than the axial length of the outer tube. The middle tube is disposed between the two end tubes. Both ends of the middle tube have chamfered surfaces on their outer sides. A portion of the chamfered surface extends between the inner and outer tubes. The chamfered surface, together with the end tubes, the inner tube, and the outer tube, forms a closed maintenance cavity, and together with the outer tube, forms a molten pool. The molten pool and the maintenance cavity are not interconnected. The welding ring is fixedly disposed within the molten pool, and the sidewall of the welding ring is not flush with the sidewall of the end tube. The wedge-shaped throttling tube is slidably disposed within the middle tube and abuts against the two inner tubes.

[0007] Based on the above technical solutions, preferably, the wedge-shaped throttling tube includes a sleeve and a V-shaped wedge. The sleeve is slidably disposed inside the intermediate tube and abuts against the end tube. The V-shaped wedge is integrally formed on the top side of the sleeve, and the V-shaped wedge is continuously disposed with the sleeve.

[0008] Based on the above technical solutions, preferably, the end of the sleeve is sealed and abuts against the inner tube, and the axial length of the inner tube gradually decreases from bottom to top.

[0009] Based on the above technical solutions, preferably, the sleeve is coaxially arranged with the end tube, and the inner diameter of the sleeve is smaller than the inner diameter of the end tube.

[0010] Based on the above technical solutions, preferably, the distance between the sleeve end face and the end tube gradually increases in the direction away from the sleeve axis.

[0011] Based on the above technical solutions, preferably, a smooth groove is provided at the bottom of the sleeve, the inner wall of the smooth groove is flush with the inner wall of the end tube, and the smooth groove is located below the V-shaped wedge.

[0012] Based on the above technical solutions, preferably, it also includes an extension tube and a spiral mechanism. The extension tube is connected to one end of one of the end tubes away from the intermediate tube, and the spiral mechanism is disposed inside the extension tube to make the medium inside the extension tube flow spirally.

[0013] Based on the above technical solutions, preferably, the spiral mechanism is a spiral blade, and the spiral blade is fixedly disposed at one end of the extended tube away from the intermediate tube.

[0014] Based on the above technical solutions, preferably, a ceramic ring is also included, which is disposed within the maintenance cavity.

[0015] Based on the above technical solutions, preferably, the wedge-shaped throttling tube further includes a stiffener plate, which is fixedly disposed on the V-shaped wedge block and abuts against the intermediate tube; the stiffener plate is spaced apart from both ends of the V-shaped wedge block.

[0016] The wedge flowmeter for measuring high-viscosity media of the present invention has the following advantages over the prior art:

[0017] (1) By setting an inner tube and an outer tube on the end tube, a nested, cuttable maintenance structure is formed with the middle tube and the wedge-shaped throttling tube, which facilitates the disassembly, replacement and repair of the wedge-shaped throttling tube, thereby shortening the maintenance time, reducing the maintenance cost, and ensuring the measurement accuracy after repeated assembly of the wedge-shaped throttling tube.

[0018] (2) By setting the end of the end tube and the end of the sleeve to be inclined, the wedge-shaped throttling tube can be self-positioned, improving the assembly accuracy of the wedge-shaped throttling tube and ensuring the measurement accuracy of this flow meter.

[0019] (3) By setting an extended tube and a spiral mechanism, and limiting the inner diameter and shape of the sleeve, impurities in the medium can be guided away from the V-shaped wedge, significantly reducing the erosion and wear of the wedge-shaped throttling tube and extending the service life of this flow meter.

[0020] (4) By setting the wedge-shaped throttling tube to include a sleeve, a V-shaped wedge and a stiffener, the processing efficiency of the wedge-shaped throttling tube is improved and the processing cost is reduced. The structural strength and erosion resistance of the wedge-shaped throttling tube are also enhanced. Attached Figure Description

[0021] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0022] Figure 1 This is a perspective view of the wedge flowmeter for measuring high viscosity media according to the present invention.

[0023] Figure 2 This is a cross-sectional view of the wedge flowmeter for measuring high viscosity media according to the present invention.

[0024] Figure 3 This is a left view of the wedge flowmeter for measuring high viscosity media according to the present invention.

[0025] Figure 4 for Figure 2 Enlarged view of point A in the middle.

[0026] Figure 5 for Figure 4 A schematic diagram of the structure under maintenance.

[0027] Figure 6 This is a perspective view of the middle tube of the wedge flowmeter for measuring high viscosity media according to the present invention.

[0028] Figure 7 This is a perspective view of the inner tube of the wedge flowmeter for measuring high viscosity media according to the present invention.

[0029] Figure 8 This is a perspective view of the middle tube in the wedge flowmeter for measuring high viscosity media of the present invention.

[0030] Figure 9This is a cross-sectional view of the extended tube in the wedge flowmeter for measuring high viscosity media of the present invention.

[0031] Figure 10 This is a perspective view of the wedge-shaped throttling tube in the wedge flowmeter for measuring high viscosity media of the present invention.

[0032] The components are: 1. End tube; 11. Inner tube; 12. Outer tube; 101. Pressure measuring hole; 102. Molten pool; 103. Maintenance cavity; 2. Intermediate tube; 21. Chamfered surface; 3. Welding ring; 4. Wedge-shaped throttling tube; 41. Sleeve; 42. V-shaped wedge; 43. Rib plate; 401. Smooth groove; 5. Extension tube; 6. Spiral blade; 7. Ceramic ring. Detailed Implementation

[0033] The technical solutions of this invention will be clearly and completely described below with reference to specific embodiments. Obviously, the described embodiments are only a part of the embodiments of this invention, and not all of them. Based on the embodiments of this invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this invention.

[0034] The wedge flow meter for measuring high viscosity media of the present invention includes two end tubes 1, an intermediate tube 2, a welded ring 3, a wedge-shaped throttling tube 4, an extension tube 5, a spiral mechanism and a ceramic ring 7, and is used to be installed on a media conveying pipeline to measure the flow rate of the medium in the pipeline.

[0035] Two end pipes 1 are spaced apart and connected to a medium conveying pipeline. Each end pipe 1 has a pressure measuring hole 101 on its top side, used to install a pressure sensor. A wedge-shaped throttling tube 4 is connected between the two end pipes 1. Figure 1 and Figure 2 As shown, the wedge-shaped throttling tube 4 has a protruding structure inside, that is, the top side of the inside of the wedge-shaped throttling tube 4 extends towards the center of the wedge-shaped throttling tube 4; when the medium in the pipeline flows through the end pipe 1 through the wedge-shaped throttling tube 4, the flow area decreases and the flow velocity increases. According to Bernoulli's principle, the static pressure decreases, and a measurable differential pressure is generated between the two ends of the wedge-shaped throttling tube 4. The flow rate of the medium is then calculated through this pressure difference, thus realizing the measurement of the medium flow rate.

[0036] As the core throttling element of the wedge flowmeter, the wedge-shaped throttling tube 4 directly withstands the scouring of high-speed fluids, the impact of particulate media, the thermal stress under high temperature and high pressure conditions, and the chemical erosion of corrosive media. Therefore, it is a critical and vulnerable component. During long-term operation, especially when the measured medium contains hard suspended particles (such as coal powder, slurry, catalyst particles), high-velocity sand-containing liquids (such as oilfield produced fluids), or highly corrosive fluids (such as acid and alkali solutions, sulfur-containing oil and gas), the upstream surface, sharp edges, and downstream slope of the wedge-shaped throttling tube 4 are prone to defects such as surface erosion and wear, local pitting or intergranular corrosion, coking / scaling, and thermal fatigue deformation.

[0037] Because the geometric accuracy (wedge angle tolerance is typically required to be within ±0.2°), surface roughness (Ra≤ 1.6 μm), and installation coaxiality of the wedge-shaped throttle tube 4 directly affect the measurement accuracy and range ratio, once any of the above-mentioned damage occurs, its metrological performance cannot be restored by on-site cleaning or simple repairs alone. Therefore, the wedge-shaped throttle tube 4 must be inspected according to the periodic verification procedures or the manufacturer's recommended cycle.

[0038] To improve the maintenance efficiency of the wedge-shaped throttling tube 4, the present invention improves the installation structure of the wedge-shaped throttling tube 4, as follows:

[0039] like Figure 4 and Figure 7 As shown, one end of the end pipe 1 is provided with a flange for connecting to the medium pipeline. The other end of the end pipe 1 is integrally formed with an inner pipe 11 and an outer pipe 12. The inner wall of the inner pipe 11 is flush with the inner wall of the end pipe 1, and the outer wall of the outer pipe 12 is flush with the outer wall of the end pipe 1. The outer wall of the inner pipe 11 and the inner wall of the outer pipe 12 are spaced apart. The axial length of the inner pipe 11 is greater than the axial length of the outer pipe 12.

[0040] like Figure 4 and Figure 8 As shown, the intermediate tube 2 is disposed between the two end tubes 1. Both ends of the intermediate tube 2 are provided with chamfered surfaces 21. Part of the chamfered surfaces 21 extend into the space between the inner tube 11 and the outer tube 12. The chamfered surfaces 21, the end tubes 1, the inner tubes 11 and the outer tubes 12 enclose a closed maintenance cavity 103, and together with the outer tubes 12, they enclose a molten pool 102. The molten pool 102 and the maintenance cavity 103 are not connected to each other. The welding ring 3 is fixedly disposed in the molten pool 102 to achieve a fixed connection between the outer tubes 12 and the intermediate tube 2. The wedge-shaped throttling tube 4 is slidably disposed in the intermediate tube 2 and abuts against the space between the two inner tubes 11.

[0041] The chamfered surface 21 and the nesting relationship between the intermediate tube 2 and the inner tube 11 can position the intermediate tube 2, thereby helping to improve the assembly efficiency of the intermediate tube 2. The chamfered surface 21 also makes it easier for the intermediate tube 2 to be inserted between the inner tube 11 and the outer tube 12. At the same time, the molten pool 102 formed by the chamfered surface 21 and the outer tube 12 is V-shaped, which can improve the welding quality and welding efficiency of the welding ring 3.

[0042] like Figure 4 and Figure 5 As shown, along the position of the maintenance cavity 103 (e.g.) Figure 4 When cutting the outer tube 12 (as shown by the dashed line), the outer tube 12 can be separated along the cutting position, thereby separating the middle tube 2 from the end tube 1, and separating the wedge-shaped throttling tube 4 from the inner tube 11, so as to replace the wedge-shaped throttling tube 4; after the wedge-shaped throttling tube 4 is replaced, the outer tube 12 is then welded together along the cutting position, or a part of the outer tube 12 on the middle tube 2 is ground off, and the middle tube 2 and the outer tube 12 are re-welded, thus completing the maintenance of the flow meter.

[0043] The sidewall of the welding ring 3 is not flush with the sidewall of the end pipe 1, that is, the welding ring 3 does not completely fill the molten pool 102 or protrudes from the molten pool 102. The position of the welding ring 3 can be clearly observed from the appearance, thereby determining the position of the maintenance cavity 103. When the wedge-shaped throttling tube 4 needs to be cut to maintain it, the cutting position can be avoided from deviating from the maintenance cavity 103, thus improving the maintenance quality of the flow meter.

[0044] The ceramic ring 7 is filled and disposed in the maintenance cavity 103. On the one hand, the ceramic ring 7 can improve the overall structural strength of the flow meter and prevent the outer tube 12 from collapsing during use, cutting and welding; on the other hand, the ceramic ring 7 can prevent the welding ring 3 from seeping into the maintenance cavity 103, preventing the intermediate tube 2 from sticking to the end tube 1 or the inner tube 11, and ensuring the flow meter's quick maintenance function.

[0045] The wedge-shaped throttling tube 4 includes a sleeve 41, a V-shaped wedge 42, and a stiffener 43. The sleeve 41 is slidably disposed inside the intermediate tube 2 and abuts against the inner tube 11. A slot is provided in the middle of the top side of the sleeve 41. The V-shaped wedge 42 is integrally formed in the slot, and the edge of the V-shaped wedge 42 is continuously disposed with the sleeve 41. The wedge-shaped throttling tube 4 with this structure can be stamped from a circular steel tube, which can not only reduce the processing cost of the wedge-shaped throttling tube 4, but also improve the processing efficiency of the wedge-shaped throttling tube 4.

[0046] The stiffener 43 is used to enhance the structural strength of the V-shaped wedge 42, especially the structural strength of the frontal surface of the V-shaped wedge 42. The stiffener 43 is fixedly installed on the V-shaped wedge 42 and abuts against the intermediate pipe 2.

[0047] like Figure 10As shown, the stiffener 43 is M-shaped when viewed from above, with one end of its two pointed tips (the left end in the figure) facing the inflow end of the medium, thus better dispersing the stress on the upstream surface of the V-shaped wedge 42; the stiffener 43 and the two ends of the V-shaped wedge 42 are spaced apart, as shown... Figure 2 As shown, the left and right ends of the stiffener 43 are respectively enclosed by the V-shaped wedge 42 and the middle tube 2 to form a triangular cavity structure, which further enhances the structural strength of the wedge-shaped throttling tube 4.

[0048] To prevent media leakage and improve the fixing firmness of sleeve 41, it is preferable to make the end of sleeve 41 seal against the inner tube 11; to improve the flow stability of the media, it is preferable to make sleeve 41 and end tube 1 coaxial.

[0049] like Figure 2 As shown, the axial length of the inner tube 11 gradually decreases from bottom to top, meaning that the end of the inner tube 11 away from the end tube 1 is inclined. Correspondingly, the end of the sleeve 41 is also inclined. When assembling the flow meter, firstly, one end of the intermediate tube 2 is welded to one of the end tubes 1. Then, the wedge-shaped throttling tube 4 is inserted into the other end of the intermediate tube 2. Finally, by vertically placing the intermediate tube 2 or squeezing the wedge-shaped throttling tube 4, the end of the wedge-shaped throttling tube 4 is sealed and fitted to the inner tube 11, thus achieving the positioning of the wedge-shaped throttling tube 4, ensuring the accuracy of the assembly position of the V-shaped wedge 42, and improving the assembly efficiency of the V-shaped wedge 42.

[0050] The measured medium may contain some impurities, especially for high-viscosity media. Impurities are not easy to settle. During the flow of the medium, impurities will collide with the V-shaped wedge 42, making the flow-facing surface of the V-shaped wedge 42 more prone to erosion and wear. In order to improve the service life of the flow meter, it is necessary to guide the impurities in the medium to reduce the probability of impurities contacting the V-shaped wedge 42.

[0051] The extended tube 5 and the spiral mechanism are used to guide impurities in the medium. For example... Figure 9 As shown, the left end of the extension pipe 5 is connected to the medium conveying pipeline, and the right end of the extension pipe 5 is connected to the left end of the left-side pipe 1. The spiral mechanism is located inside the extension pipe 5, as shown. Figure 3 As shown, the inner diameter of sleeve 41 is smaller than the inner diameter of end pipe 1; when the medium in the conveying pipeline flows into the extension pipe 5, the spiral mechanism causes the medium in the extension pipe 5 to flow in a spiral motion, using centrifugal force to throw larger impurities to the side wall of the extension pipe 5, such as... Figure 2 As shown, when the medium continues to flow into the left end pipe 1, the impurities located on the side wall of the extension pipe 5 are guided by the inclined end face of the sleeve 41 to move to the lower position of the flow meter channel, thereby avoiding the V-shaped wedge 42 and protecting the V-shaped wedge 42.

[0052] like Figure 4As shown, the end face of the sleeve 41 is conical, and the distance between the end face of the sleeve 41 and the end tube 1 gradually increases in the direction away from the axis of the sleeve 41. When impurities flow to the end of the sleeve 41 with the medium, the conical end face of the sleeve 41 can limit the impurities and prevent them from directly flipping over into the sleeve 41 without being guided by the end face of the sleeve 41.

[0053] like Figure 3 , Figure 6 and Figure 8 As shown, a smooth groove 401 is provided at the bottom inside the sleeve 41. The smooth groove 401 is located below the V-shaped wedge 42, and the inner wall of the smooth groove 401 is flush with the inner wall of the end pipe 1, thereby preventing impurities from accumulating below the end of the sleeve 41 and ensuring smooth flow of the medium.

[0054] Helical mechanisms can take many forms, such as helical pipes or guide vanes like helical blades. For example... Figure 9 As shown, it is preferable to fix the spiral blade 6 inside the extension tube 5 at one end away from the middle tube 2. When the spiral-flowing medium passes through the right end and the left end tube 1 of the extension tube 5, it can return to a stable state, thereby improving the detection accuracy of the flow meter.

[0055] The working principle of the wedge flowmeter for measuring high viscosity media of the present invention is as follows:

[0056] The medium in the conveying pipeline flows into the extension pipe 5. The spiral mechanism causes the medium to flow in a spiral shape into the first end pipe 1. When the medium passes through the wedge-shaped throttling pipe 4, a pressure difference is generated at both ends of the wedge-shaped throttling pipe 4, so the flow rate of the medium in the flow meter can be calculated, and the flow rate of the medium can be measured. In this process, the spirally flowing medium throws the internal impurities to the outer position. When the medium flows through the end of the sleeve 41, it is guided by the end of the sleeve 41, causing the impurities to move down and away from the V-shaped wedge block 42, thus extending the service life of the flow meter.

[0057] When it is necessary to replace the wedge-shaped throttle tube 4, firstly... Figure 4 The outer tube 12 is cut at the position shown by the dashed line, and then the middle tube 2 is separated from the end tube 1 to replace the wedge-shaped throttling tube 4. After the wedge-shaped throttling tube 4 is replaced, the operation is repeated in reverse order to re-weld the outer tube 12 so that the middle tube 2 and the end tube 1 are fixed together. When replacing the wedge-shaped throttling tube 4, its inclined end face can realize the quick positioning of the wedge-shaped throttling tube 4, thereby ensuring the measurement accuracy of this flowmeter.

[0058] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A wedge flowmeter for high viscosity media, characterized in that: It includes two end pipes (1), an intermediate pipe (2), a welded ring (3), and a wedge-shaped throttling pipe (4), wherein, The top side of the end tube (1) is provided with a pressure measuring hole (101). One end of the end tube (1) is integrally formed with an inner tube (11) and an outer tube (12). The inner tube (11) is spaced apart inside the outer tube (12), and the axial length of the inner tube (11) is greater than the axial length of the outer tube (12). The intermediate tube (2) is disposed between the two end tubes (1). Both ends of the intermediate tube (2) are provided with chamfered surfaces (21). A portion of the chamfered surfaces (21) extends into the space between the inner tube (11) and the outer tube (12). The chamfered surfaces (21), the end tubes (1), the inner tubes (11) and the outer tubes (12) enclose a closed maintenance cavity (103), and together with the outer tubes (12), they enclose a molten pool (102). The molten pool (102) and the maintenance cavity (103) are not connected to each other. The welding ring (3) is fixedly disposed in the molten pool (102), and the side wall of the welding ring (3) is not flush with the side wall of the end tube (1); The wedge-shaped throttling tube (4) is slidably disposed inside the intermediate tube (2) and abuts against the two inner tubes (11); When the wedge-shaped throttling tube (4) needs to be replaced, one of the outer tubes (12) is first cut at the position of the maintenance cavity (103), and then the middle tube (2) is separated from the end tube (1) to replace the wedge-shaped throttling tube (4); after the wedge-shaped throttling tube (4) is replaced, the operation is repeated in reverse order to re-weld the outer tube (12) so that the middle tube (2) and the end tube (1) are fixed together; The wedge-shaped throttling tube (4) includes a sleeve (41) and a V-shaped wedge (42). The sleeve (41) is slidably disposed inside the intermediate tube (2) and abuts against the end tube (1). The V-shaped wedge (42) is integrally formed on the top side of the sleeve (41) and the V-shaped wedge (42) is continuously disposed with the sleeve (41). The end of the sleeve (41) is sealed against the inner tube (11), and the axial length of the inner tube (11) gradually decreases from bottom to top; The sleeve (41) is coaxially arranged with the end tube (1), and the inner diameter of the sleeve (41) is smaller than the inner diameter of the end tube (1); The distance between the end face of the sleeve (41) and the end tube (1) gradually increases in the direction away from the axis of the sleeve (41); A smooth groove (401) is provided at the bottom inside the sleeve (41). The inner wall of the smooth groove (401) is flush with the inner wall of the end tube (1), and the smooth groove (401) is located below the V-shaped wedge (42). It also includes an extension tube (5) and a spiral mechanism. The extension tube (5) is connected to one end of one of the end tubes (1) away from the intermediate tube (2). The spiral mechanism is disposed inside the extension tube (5) to cause the medium inside the extension tube (5) to flow spirally.

2. The wedge flow meter for measuring high viscosity media as described in claim 1, characterized in that: The spiral mechanism is a spiral blade (6), which is fixedly disposed inside the extended tube (5) at one end away from the intermediate tube (2).

3. The wedge flow meter for measuring high-viscosity media as described in claim 1 or 2, characterized in that: It also includes a ceramic ring (7), which is disposed in the maintenance cavity (103).

4. The wedge flow meter for measuring high viscosity media as described in claim 1, characterized in that: The wedge-shaped throttling tube (4) also includes a stiffener (43), which is fixedly disposed on the V-shaped wedge (42) and abuts against the intermediate tube (2); The stiffening plate (43) and the two ends of the V-shaped wedge (42) are spaced apart.

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