Sludge extrusion dewatering device

Abstract

The present application relates to gravity dewatering device technical field, specifically propose a kind of sludge extrusion dewatering device, including the closed filter cloth of strip type for filtering sludge in gravity dewatering area and the mounting bracket of filter cloth assembly, the inner side of mounting bracket is equipped with the circular roller for driving filter cloth transmission, the upper portion of mounting bracket is equipped with the material spreading plate for reducing the thickness of sludge spreading, the upper surface area of filter cloth for conveying sludge includes horizontal area and inclined area, material spreading plate is located directly above horizontal area, filter cloth is respectively provided with two groups of material distribution components along its conveying direction;The present application is equipped with anti-blocking component one and anti-blocking component two, anti-blocking component one carries out real-time anti-blocking cleaning in sludge conveying section on the surface of filter cloth, anti-blocking component two carries out secondary anti-blocking cleaning after filter cloth conveying sludge, to ensure that the filter cloth entering sludge discharge port position is non-blocking state, so as to ensure the dehydration efficiency in horizontal area and inclined area simultaneously, further improve the overall dehydration efficiency.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of gravity dewatering device, and specifically provides a sludge extrusion dewatering device. BACKGROUND

[0002] Sludge extrusion dewatering treatment is a key link in the sludge treatment process, and its main purpose is to reduce the water content in the sludge by mechanical means, so as to create conditions for subsequent disposal or resource utilization. After sludge extrusion dewatering, the volume of sludge can be reduced, the transportation and disposal costs can be reduced, and the subsequent treatment efficiency can be improved. At the same time, the migration risk of pollutants can also be reduced. Common sludge extrusion dewatering technologies include plate and frame filter press, belt filter press and screw filter press.

[0003] The belt filter press is the most commonly used equipment in actual production, and its dewatering process mainly includes gravity dewatering zone, wedge-shaped pre-pressing zone and high-pressure extrusion zone. The belt filter press can be continuously operated at low energy consumption, but when relying on gravity dewatering, the dewatering zone is in a horizontal state and the sludge is too thick, which will cause the mud and water to be unable to fully seep out. At the same time, in the process of seeping mud and water, small particle sludge is easy to block the filter belt pores, hinder drainage and affect the dewatering efficiency.

[0004] Therefore, there is an urgent need for a sludge extrusion dewatering device that can accelerate the discharge of mud and water and improve the dewatering efficiency. SUMMARY

[0005] In order to solve the above problems, the present application provides a sludge extrusion dewatering device for solving the problems mentioned in the background art.

[0006] In order to achieve the above purpose, the present application adopts the following technical scheme: a sludge extrusion dewatering device, comprising a closed belt filter cloth for filtering sludge in a gravity dewatering zone and a mounting rack for assembling the filter cloth, a circular roller is assembled on the inner side of the mounting rack for driving the filter cloth to transmit, and a paving plate is assembled above the mounting rack for reducing the thickness of the paved sludge. The upper surface area of the filter cloth for conveying sludge includes a horizontal zone and an inclined zone, the paving plate is located directly above the horizontal zone, and two groups of material distribution assemblies are respectively arranged along the conveying direction of the filter cloth. The material distribution assembly is used to separate the sludge to form a plurality of water outlet paths, and the material distribution assembly comprises a plurality of isolation frames abutting against the water outlet path surface of the filter cloth. An anti-blocking assembly one is assembled in the inner part of the isolation frame for cleaning the filter cloth to prevent blockage. A support plate with a plurality of water flow holes on the surface is assembled on the inner side of the mounting rack below the material distribution assembly and supports the filter cloth. The isolation frames of the two material distribution assemblies are staggered.

[0007] Preferably, the anti-blocking assembly one comprises a high-pressure nozzle one assembled in the isolation frame, the surface of the high-pressure nozzle one is provided with a connecting pipe one, the top of the mounting frame is provided with a water supply pipe one for water supply, the inside of the water supply pipe one is communicated with the inside of the connecting pipe one, and the two water supply pipes one are assembled on the surface of the mounting frame through a double U support.

[0008] Preferably, the connecting pipe one is slidingly installed with the isolation frame, the surface of the connecting pipe one is movably sleeved with a connecting spring, and the two ends of the connecting spring are fixed on the surface of the water supply pipe one and the isolation frame respectively.

[0009] Preferably, the isolation frame is hexagonal, and the pointed end of the isolation frame faces the conveying direction of the filter cloth.

[0010] Preferably, the anti-blocking assembly two comprises a cleaning pipe provided with a plurality of water outlets, a high-pressure nozzle two is arranged in the inside of the cleaning pipe corresponding to each water outlet, a water supply pipe two is arranged in the inside of the cleaning pipe, and a connecting pipe two is arranged between the high-pressure nozzle two and the water supply pipe two.

[0011] Preferably, the lower surface of the filter cloth is provided with a concave, the cleaning pipe is located in the concave of the lower surface of the filter cloth, and the surface of the mounting frame is provided with two adjusting rollers, which are located on the two sides of the cleaning pipe and abut against the outer surface of the filter cloth.

[0012] Preferably, the plurality of water outlets are circularly and equidistantly distributed around the axis of the cleaning pipe, and are linearly and equidistantly arranged along the axis direction of the cleaning pipe, the inner side of the mounting frame is provided with a flow guide plate, and the flow guide plate is located on the inner side of the filter cloth.

[0013] Preferably, the surface of the water supply pipe two is provided with a plurality of supporting rings, and the plurality of supporting rings are equidistantly arranged in the inside of the cleaning pipe.

[0014] Preferably, the surface of the adjacent high-pressure nozzle two in the circumferential direction is provided with a partition plate, and the partition plate is fixedly installed on the surface of the water supply pipe two.

[0015] Preferably, the thickness of the surface of the water supply pipe two gradually decreases from the middle to the two ends, and the inside diameter is unchanged.

[0016] 1. The technical scheme has the following advantages or beneficial effects: the sludge extrusion dewatering device provided by the application realizes real-time and large-area anti-blocking and cleaning of the filter cloth through the two anti-blocking assembly ones arranged staggeredly, the surface of the filter cloth is cleaned through the high-pressure nozzle one, and the high-pressure nozzle one is protected through the isolation frame, so that the falling speed of the sludge and water is ensured, and the efficiency of gravity dewatering is greatly improved.

[0017] 2. The technical solution has the following advantages or beneficial effects: the sludge extrusion dewatering device provided by the application can ensure the dewatering efficiency in the horizontal area and the inclined area without stopping for anti-blocking cleaning, and further greatly improves the overall dewatering efficiency. BRIEF DESCRIPTION OF DRAWINGS

[0018] The application and its features, shapes and advantages will become more apparent by reading the following detailed description of the non-limiting embodiments with reference to the accompanying drawings. The same reference signs indicate the same parts throughout the drawings, and the drawings are not necessarily drawn to scale, and the emphasis is on showing the main idea of the application.

[0019] Figure 1 is a perspective structural schematic view of the sludge extrusion dewatering device provided by the application.

[0020] Figure 2 is a sectional view of the position of the flow guide plate.

[0021] Figure 3 is a structural schematic view of the installation state of the anti-blocking assembly two and the filter cloth.

[0022] Figure 4 is a perspective structural schematic view of the anti-blocking assembly two.

[0023] Figure 5 is a front view of Figure 4 .

[0024] Figure 6 is a perspective structural schematic view of the anti-blocking assembly one.

[0025] Figure 7 is a partial front sectional view of the position of the anti-blocking assembly one.

[0026] Figure 8 is an enlarged view of A of Figure 7 .

[0027] In the drawings: 1, filter cloth; 2, mounting frame; 3, round roller; 4, laying plate; 5, material distribution assembly; 51, isolation frame; 52, anti-blocking assembly one; 521, high-pressure nozzle one; 522, connecting pipe one; 523, water supply pipe one; 524, double-U support; 53, water flow hole; 54, support plate; 6, anti-blocking assembly two; 61, water outlet hole; 62, cleaning pipe; 63, high-pressure nozzle two; 64, water supply pipe two; 65, connecting pipe two; 7, connecting spring; 8, rubber gasket; 9, adjusting roller; 10, flow guide plate; 11, support ring; 12, partition plate. DETAILED DESCRIPTION

[0028] The technical solutions in the embodiments of the present application will be apparently and completely described below with reference to the drawings in the embodiments of the present application. Obviously, the described embodiments are only part of the embodiments of the present application, rather than all the embodiments. Based on the embodiments in the present application, all the other embodiments obtained by a person of ordinary skill in the art without creative work fall within the protection scope of the present application.

[0029] In order for those skilled in the art to better understand the present application, the present application will be further described in detail below with reference to the drawings and specific embodiments.

[0030] Figure 1 Disclosed is a dewatering structure for a gravity dewatering area in a sludge extrusion dewatering device, which comprises filter cloth 1 for separating sludge and water, the filter cloth 1 is a closed steel wire mesh reinforced filter cloth in the form of a strip, when the sludge and water are on the surface of the filter cloth 1, gravity will cause the sludge and water to flow and separate, the filter cloth 1 is assembled on the surface of a mounting frame 2, the mounting frame 2 is placed on the ground and can be fixed by mounting expansion bolts, a plurality of circular rollers 3 for driving the filter cloth 1 are rotatably assembled on the surface of the mounting frame 2, at this time, the filter cloth 1 is stretched and the side is in the shape of a right-angled trapezoid, the upper surface of the filter cloth 1 is divided into a horizontal area and an inclined area, the inclination angle of the inclined area is set to be between 10°-15°, which not only ensures the rapid falling and discharge of the sludge and water, but also prevents the sludge from flowing with the sludge and water, a paving plate 4 is fixedly installed on the surface of the mounting frame 2 by bolts, the distance between the paving plate 4 and the upper surface of the filter cloth 1 is between 15-25 cm, the paving plate 4 flattens the sludge on the filter cloth 1 to reduce the thickness of the sludge, so that the sludge and water can flow uniformly and quickly to the bottom layer and fall, it should be noted that the paving plate 4 is close to the sludge feeding port, so that the sludge can be quickly flattened and reach the appropriate thickness when it falls on the surface of the filter cloth 1.

[0031] As shown in Figures 1-2 and Figures 6-8 , the surface of the mounting frame 2 is assembled with two groups of material distribution assemblies 5, which are respectively located at the end of the horizontal area and the front end of the inclined area, the material distribution assembly 5 divides the entire surface of the sludge into a plurality of sewage paths, due to the height difference, the sludge and water will fall at the position of the sewage path and flow out, the material distribution assembly 5 comprises a plurality of isolation frames 51, in this embodiment, the number of isolation frames 51 of the two material distribution assemblies 5 is different, one group of isolation frames 51 has six, and the other group of isolation frames 51 has seven, the lower surface of the isolation frame 51 is in the shape of a hexagon, and the tip of the isolation frame 51 faces the conveying direction of the filter cloth 1, when the sludge moves to the position of the isolation frame 51, the isolation frame 51 will guide the sludge, so as to form a sewage path at the position of the isolation frame 51, the two groups of isolation frames 51 need to be alternately distributed.

[0032] The anti-blocking assembly one 52 is installed in the inside of the isolation frame 51, the sewage path formed by the isolation frame 51 at the position is cleaned, the filter cloth 1 is prevented from being blocked, the dehydration efficiency of the sewage path is improved, the anti-blocking assembly one 52 comprises a high-pressure nozzle one 521 which is slidably installed in the inside of the isolation frame 51, the nozzle surface of the high-pressure nozzle one 521 needs to be attached to the surface of the filter cloth 1, so that the water mist of the flushing is prevented from flowing to the surface of the filter cloth 1 and mixing with the mud again, the surface of the high-pressure nozzle one 521 is fixedly welded with a connecting pipe one 522, and meanwhile a water supply pipe one 523 is fixedly installed on the top of the mounting frame 2, the water supply pipe one 523 is communicated with the inside of each connecting pipe one 522, that is, the inside of the water supply pipe one 523 is water-supplied, the sludge water enters the inside of the high-pressure nozzle one 521 through the connecting pipe one 522, so that the surface of the filter cloth 1 passing through the isolation frame 51 is cleaned, and after the cleaning is completed, the sludge water falls again at the position of the sewage path, and can flow out more quickly, and the two water supply pipes one 523 are fixed on the surface of the mounting frame 2 through the cooperation of the double-U supports 524 and bolts.

[0033] In order to prevent the sludge from affecting the normal cleaning of the high-pressure nozzle one 521, the high-pressure nozzle one 521 needs to be completely covered by the isolation frame 51 for protection, therefore the surface of the connecting pipe one 522 movably sleeves the connecting spring 7, the two ends of the connecting spring 7 are fixedly connected to the surface of the water supply pipe one 523 and the isolation frame 51 respectively, when the high-pressure nozzle one 521 is attached to the surface of the filter cloth 1, the connecting spring 7 is in a compressed state, and the isolation frame 51 can be tightly attached to the surface of the filter cloth 1, at this time, the surface of the mounting frame 2 is fixedly installed with a supporting plate 54, the supporting plate 54 is in the same vertical position as the isolation frame 51, and provides a supporting force for the filter cloth 1, and meanwhile, in order to ensure that the sludge water can normally flow out, a plurality of water flow holes 53 are formed in the surface of the supporting plate 54, so that the discharged sludge water can normally flow out, it should be noted that, since the filter cloth 1 is in transmission, in order to prevent the isolation frame 51 from causing great friction damage to the surface of the filter cloth 1, a rubber gasket 8 which is shaped and adapted is bonded to the lower surface of the isolation frame 51, the rubber gasket 8 is attached to the surface of the filter cloth 1, and can also strengthen the sealing performance of the isolation frame 51.

[0034] Since the isolation frames 51 of the two groups of material distribution assemblies 5 are alternately distributed, therefore in the moving process of the filter cloth 1, the surface of the filter cloth 1 can be cleaned by the high-pressure nozzle one 521 in the inside of the isolation frame 51, and in the process of conveying the sludge, the dehydration efficiency can be greatly improved, but since the transmission of the filter cloth 1 is a circulating process, when the sludge in the gravity dehydration area is separated from the surface of the filter cloth 1, the filter cloth 1 is transmitted to the sludge discharging port position, and the sludge still needs to be dehydrated in the horizontal area, therefore in order to ensure the dehydration efficiency at the position, the anti-blocking assembly two 6 is assembled to the lower surface of the filter cloth 1, so as to cooperate with the anti-blocking assembly one 52 to realize the anti-blocking of the entire filter cloth 1 conveying section.

[0035] As Figures 1-2 andFigures 3-5 As shown, the anti-blocking assembly 6 includes a cleaning pipe 62, the lower moving path of the filter cloth 1 is provided with a lower recess, the cleaning pipe 62 is located inside the lower recess and is attached to the surface of the filter cloth 1, the cleaning pipe 62 is rotatably arranged on the inner side of the mounting frame 2, and two adjusting rollers 9 are also rotatably arranged on the inner side of the mounting frame 2, the two adjusting rollers 9 are respectively located on the two sides of the cleaning pipe 62 and are attached to the outer surface of the filter cloth 1 to guide the filter cloth 1. It should be noted that the cleaning pipe 62 also rotates during use to reduce the friction between the cleaning pipe 62 and the surface of the filter cloth 1 and prevent the surface of the filter cloth 1 from being greatly worn.

[0036] A plurality of water outlets 61 are formed on the surface of the cleaning pipe 62. In this embodiment, the water outlets 61 are circularly and equidistantly distributed around the axis of the cleaning pipe 62, and are linearly and equidistantly distributed along the axis direction of the cleaning pipe 62. A water supply pipe 64 is arranged through the inside of the cleaning pipe 62. Each water outlet 61 is provided with a high-pressure nozzle 63. A connecting pipe 65 is fixedly arranged between each high-pressure nozzle 63 and the water supply pipe 64. The washing water enters the inside of the water supply pipe 64 and enters the inside of the high-pressure nozzle 63 through the connecting pipe 65. Since the filter cloth 1 is attached to the surface of the cleaning pipe 62, and the gap on the outer side of the filter cloth 1 is opened when the filter cloth 1 is bent, the high-pressure washing water impacts on the surface of the filter cloth 1, which can ensure that the silt cleaning is more thorough, thereby improving the efficiency of the sludge gravity dewatering. In order to prevent the mud water above the filter cloth 1 from flowing to the lower position of the filter cloth 1, a V-shaped flow guide plate 10 is fixedly arranged on the surface of the mounting frame 2 to prevent the water flow from causing secondary blocking of the filter cloth 1 and avoid affecting the dewatering efficiency.

[0037] In this embodiment, the row of water outlets at the top of the cleaning pipe 62 cannot clean the filter cloth 1 when the cleaning pipe 62 rotates. However, since the cleaning pipe 62 only prevents blocking of the surface of the filter cloth 1 at intervals, and the high-pressure nozzle 63 does not spray a large amount of water during cleaning, the air-borne washing water and the washed-down mud water can be recycled into the collection water tank and reused after filtration and other treatments, which can avoid waste of water resources.

[0038] In order to ensure that the installation of the high-pressure nozzle 63 is more stable, a plurality of support rings 11 are fixedly arranged on the surface of the water supply pipe 64. The support rings 11 are fixedly arranged in the inside of the cleaning pipe 62. The surface of each high-pressure nozzle 63 is fixedly arranged with a partition plate 12 in the circumferential direction to isolate the part of the sprayed washing water that falls back into the inside of the cleaning pipe 62. The inside diameter of the water supply pipe 64 is constant, and the thickness gradually decreases from the middle to the two ends of the surface, so as to guide the backflow washing water out and avoid causing secondary blocking of the surface of the filter cloth 1.

[0039] In the present application, the two anti-blocking components one 52 arranged at the end of the horizontal area and the front end of the inclined area of the upper surface of the filter cloth 1 are used to carry out two-stage alternating anti-blocking cleaning of the upper surface of the filter cloth 1, and the anti-blocking component two 6 arranged at the lower surface of the filter cloth 1 is used to carry out third-stage anti-blocking cleaning of the lower surface of the filter cloth 1, so that the whole conveying section of the filter cloth 1 is cleaned without stopping to carry out anti-blocking cleaning, and the dewatering efficiency of the sludge is greatly improved; although the present application increases two anti-blocking components one 52, anti-blocking component two 6 and corresponding high-pressure water pump and other structures compared with the prior art, the equipment cost is increased, but the present application does not need to stop to carry out anti-blocking cleaning, and the anti-blocking cleaning operation of the filter cloth 1 can be carried out during the sludge dewatering process, so that the speed and efficiency of the sludge dewatering are greatly improved, thereby great economic benefits are provided for the sludge dewatering treatment plant, and the equipment cost of the increased structure compared with the prior art can be completely ignored from the long-term economic benefits.

[0040] It should be particularly pointed out that the water supply pipe one 523 and the water supply pipe two 64 are connected through the water outlet of the high-pressure water pump (not shown in the figure), the water inlet of the high-pressure water pump is connected with the water collecting tank through the water conveying pipe (not shown in the figure), the water collecting tank is used to collect the sludge water left after the sludge is filtered by the filter cloth 1 (not shown in the figure), the washing water extracted by the high-pressure water pump is the sludge water, and the sludge water left after the sludge is filtered is extracted by the high-pressure water pump to carry out the anti-blocking washing of the filter cloth 1 at regular intervals, without the need of connecting external water, wherein since the filter cloth 1 is a steel wire mesh reinforced filter cloth with high strength, after many tests by the person skilled in the art, the water spraying pressure of the high-pressure water pump is adjusted to a suitable value, and the interval time of the regular anti-blocking washing is adjusted to a reasonable time, so that the water spraying pressure of the high-pressure water pump through the high-pressure nozzle one 521 and the high-pressure nozzle two 63 will not damage the filter cloth 1.

[0041] In the description of the present application, it should be understood that the terms "center", "longitudinal", "transverse", "length", "width", "thickness", "upper", "lower", "vertical", "horizontal", "top", "bottom", "inner", "outer", "clockwise", "counterclockwise", "axial", "radial", "circumferential" and the like indicate the orientation or positional relationship based on the orientation or positional relationship shown in the drawings, and are only for the convenience of describing the present application and simplifying the description, and therefore cannot be understood as indicating or implying that the devices or elements referred to must have a particular orientation, be constructed and operated in a particular orientation, and therefore cannot be understood as limiting the present application.

[0042] In the description of the application, it also needs to be explained that, unless otherwise explicitly specified and limited, the terms "set", "connected", "mounted", "connected" should be understood broadly, for example, can be fixedly connected, can also be detachably connected, or integrally connected; can be mechanically connected, can also be electrically connected; can be directly connected, can also be indirectly connected through an intermediate medium, can be the communication inside two elements. For those skilled in the art, the specific meaning of the above terms in the application can be understood according to the specific circumstances.

[0043] The preferred embodiments of the application are described above. It should be understood that the application is not limited to the above specific embodiments, and the devices and structures not described in detail should be understood as being implemented in the ordinary way in the art; any person skilled in the art can make many possible changes and modifications, or modify equivalent embodiments without departing from the technical solution of the application, which does not affect the essential content of the application. Therefore, any simple modification, equivalent change and modification made to the above embodiments according to the technical essence of the application, without departing from the technical solution of the application, still belongs to the protection scope of the technical solution of the application.

Claims

1. A sludge extrusion dewatering device, characterized by: The invention discloses a closed belt filter cloth and an installation frame for filtering sludge in a gravity dewatering area, wherein the inner side of the installation frame is equipped with a circular roller for driving the filter cloth, and the upper side of the installation frame is equipped with a paving plate for reducing the thickness of the sludge. The upper surface area of the filter cloth for conveying sludge comprises a horizontal area and an inclined area, the paving plate is located directly above the horizontal area, two groups of distribution assemblies are respectively arranged along the conveying direction of the filter cloth, the distribution assemblies are used for separating sludge to form multiple sewage paths, the distribution assemblies comprise multiple isolation frames abutting against the surface of the filter cloth, the inner side of the isolation frame is equipped with a blockage prevention assembly I for cleaning the filter cloth to prevent blockage, the inner side of the installation frame is equipped with a support plate located below the distribution assembly and supporting the filter cloth, the isolation frames of the two distribution assemblies are staggered. The surface of the filter cloth is attached with a blockage prevention assembly II for cleaning the filter cloth after conveying sludge, which cooperates with the blockage prevention assembly I to clean the blockage of the entire conveying section of the filter cloth.

2. A sludge extrusion dewatering device according to claim 1, characterised in that: The blockage prevention assembly I comprises a high-pressure nozzle I arranged in the inner side of the isolation frame, the surface of the high-pressure nozzle I is equipped with a connecting pipe I, the top of the installation frame is equipped with a water supply pipe I for water supply, the inner side of the water supply pipe I is in communication with the inner side of the connecting pipe I, and two water supply pipes I are arranged on the surface of the installation frame through a double-U support.

3. A sludge dewatering device according to claim 2, wherein: The connecting pipe I is slidably arranged on the isolation frame, the surface of the connecting pipe I is movably sleeved with a connecting spring, the two ends of the connecting spring are respectively fixed on the surface of the water supply pipe I and the isolation frame, and the lower end of the isolation frame is attached with a rubber gasket for improving the sealing performance.

4. The sludge dewatering device according to claim 1, wherein: The isolation frame is hexagonal, and the pointed end of the isolation frame faces the conveying direction of the filter cloth.

5. The sludge dewatering device according to claim 1, wherein: The blockage prevention assembly II comprises a cleaning pipe with multiple water outlets on the surface, a high-pressure nozzle II is arranged in the inner side of the cleaning pipe corresponding to each water outlet, a water supply pipe II is arranged in the inner side of the cleaning pipe, and a connecting pipe II is arranged between the high-pressure nozzle II and the water supply pipe II.

6. A sludge dewatering device according to claim 5, wherein: The lower surface of the filter cloth is concave, the cleaning pipe is located in the inner side of the concave portion of the lower surface of the filter cloth, and the surface of the installation frame is equipped with two adjusting rollers located on both sides of the cleaning pipe and attached to the outer surface of the filter cloth.

7. The sludge extrusion dewatering device according to claim 5, characterized in that: The multiple water outlets are circularly and equidistantly distributed around the axis of the cleaning pipe, and are linearly and equidistantly arranged along the axis direction of the cleaning pipe, the inner side of the installation frame is equipped with a guide plate located on the inner side of the filter cloth.

8. A sludge extrusion dewatering device according to claim 5, characterised in that: The surface of the water supply pipe II is equipped with multiple support rings equidistantly arranged in the inner side of the cleaning pipe.

9. A sludge dewatering device according to claim 5, wherein: The surface of the high-pressure nozzle II located adjacent to each other in the circumferential direction is equipped with a partition plate fixedly arranged on the surface of the water supply pipe II.

10. The sludge dewatering device according to claim 5, wherein: The thickness of the surface of the water supply pipe II gradually decreases from the middle to the two ends, and the inner diameter remains unchanged.

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