A heat exchanger

Abstract

The present application relates to heat exchange equipment technical field, disclose a kind of heat exchanger, comprising: shell, its inside is provided with heat exchange cavity, the heat exchange cavity is provided with multiple heat exchange pipes extending along left and right direction;Baffle assembly, it includes flow blocking part, baffle and adjusting part, the flow blocking part is set to the top or bottom of the heat exchange cavity, multiple heat exchange pipes pass through the flow blocking part respectively, the surface of the flow blocking part is provided with multiple baffles, the adjusting part is set between the shell and the flow blocking part, the adjusting part is drivingly connected multiple baffles, the adjusting part can drive multiple baffles to rotate to be set along up and down direction or obliquely, the baffle assembly is spaced apart and is provided with multiple along left and right direction, the flow blocking part can be adjusted by setting oblique state, can improve the turbulence formed when liquid flows, reduce flow dead zone, improve heat exchange efficiency.

Description

Technical Field

[0001] This invention relates to the field of heat exchange equipment technology, and more particularly to a heat exchanger. Background Technology

[0002] Heat exchangers are used to transfer some of the heat from a hot fluid to a cold fluid, achieving heat exchange. For example, a shell-and-tube heat exchanger has multiple heat exchange tubes inside for the flow of the heat exchange medium. During operation, a hot fluid is introduced into the heat exchanger and flows from one end of the heat exchange tubes to the other, while a cold fluid is introduced into the heat exchange tubes to exchange heat with the hot fluid outside the tubes. To improve the flow path of the hot fluid within the heat exchanger, multiple baffles are usually installed. However, baffles can easily create flow dead zones, causing uneven heat exchange and reducing heat exchange efficiency. Therefore, there is a pressing need for a heat exchanger with better flowability to improve heat exchange efficiency. Summary of the Invention

[0003] The purpose of this invention is to provide a heat exchanger to solve one or more technical problems existing in the prior art, and at least provide a beneficial option or create conditions.

[0004] The solution to the technical problem of this invention is:

[0005] A heat exchanger includes: a shell having a heat exchange cavity inside, wherein multiple heat exchange tubes extending in a left-right direction are disposed within the heat exchange cavity; and a baffle assembly including a flow-blocking part, baffle plates, and an adjusting part, wherein the flow-blocking part is disposed at the top or bottom of the heat exchange cavity, the multiple heat exchange tubes respectively pass through the flow-blocking part, the surface of the flow-blocking part is provided with multiple baffle plates, the adjusting part is disposed between the shell and the flow-blocking part, the adjusting part is throttle connected to the multiple baffle plates, and the adjusting part can drive the multiple baffle plates to rotate to be arranged in a vertical direction or at an angle, and the baffle assembly has multiple baffles spaced apart in a left-right direction.

[0006] This technical solution has at least the following beneficial effects: A heat exchange chamber for heat exchange is provided inside the outer casing. During operation, a heat exchange medium is supplied to multiple heat exchange tubes, while the liquid requiring heat exchange is supplied into the heat exchange chamber. The liquid flows from one end of the heat exchange tube to the other. When the liquid passes through the baffle assembly, the baffle can block the flow of the liquid, causing the liquid to flow along the surface of the baffle to bypass it. When the liquid passes the surface of the baffle, it will pass through a baffle plate disposed on the surface of the baffle. The adjusting unit can adjust the orientation of the baffle plate, thereby changing the state of the liquid flowing along the surface of the baffle. When the adjusting unit drives multiple baffle plates to rotate in the vertical direction, the baffle plates have little effect on the liquid flow along the surface of the baffle. However, when the adjusting unit drives multiple baffle plates to rotate at an angle, the baffle plates will change the state of the liquid flow along the surface of the baffle. The surface flow creates turbulence at this location, which helps to disrupt the boundary layer and disturb the corners between the baffle and the heat exchange chamber, reducing dead zones and improving heat exchange efficiency. Since multiple baffles are spaced apart along the left and right directions, in practical applications, the baffles near the liquid inflow can be adjusted to a larger tilt angle to create stronger lateral disturbances, allowing the fluid to mix quickly and preventing fouling buildup. Conversely, the baffles near the liquid outflow can be adjusted to a smaller tilt angle to reduce flow resistance and allow the fluid to drain smoothly. By setting baffles with adjustable tilt, turbulence generated during liquid flow can be enhanced, dead zones reduced, heat exchange efficiency improved, and sufficient vibration provided in areas prone to fouling reduced boundary layer thickening and extended internal cleaning cycles.

[0007] As a further improvement to the above technical solution, the flow-blocking part includes a flow-blocking shell and a movable frame. The flow-blocking shell is disposed at the top or bottom of the heat exchange chamber. Multiple heat exchange tubes pass through the flow-blocking shell. The surface of the flow-blocking shell is provided with clearance slots corresponding to the positions between two upper and lower heat exchange tubes. Multiple clearance slots are spaced apart in the vertical direction. The adjustment part is disposed between the outer shell and the movable frame. The movable frame is slidably connected to the flow-blocking shell in the front-back direction. The movable frame is provided with transmission plates corresponding to the positions of the multiple clearance slots. Multiple transmission plates are connected to connecting shafts. Multiple connecting shafts pass through the multiple clearance slots and are rotatably connected to the flow-blocking plates. The other side of the multiple flow-blocking plates is movably connected to the surface of the flow-blocking shell. The baffle shell mainly serves to block and change the direction of liquid flow in the heat exchange chamber. The movable frame is set inside the baffle shell, and its transmission plate can block the clearance slots opened on the baffle shell, which helps to prevent liquid from passing directly through the clearance slots. During operation, the movable frame can be slid back and forth inside the baffle shell by the adjustment part, thereby adjusting the state of the baffle plate. For example, when the adjustment part is moved forward inside the movable frame, it can drive the baffle plate to rotate on the transmission plate, and when the adjustment part is moved backward inside the movable frame, it can drive the baffle plate to rotate in the opposite direction on the transmission plate, thereby adjusting the baffle plate between the vertical and inclined states.

[0008] As a further improvement to the above technical solution, the adjusting part includes a drive shaft, one end of which is threadedly connected to the movable frame, and the other end of which extends out of the baffle shell and the outer shell. When it is necessary to adjust the state of the baffle, the drive shaft is rotated forward or backward. Since the movable frame is threadedly connected to the drive shaft and has a sliding connection structure within the baffle shell, the movable frame can be driven to slide forward or backward within the baffle shell.

[0009] As a further improvement to the above technical solution, mechanical seals are respectively provided between the drive shaft and the baffle shell and the outer shell. The mechanical seals formed between the drive shaft and the baffle shell and the outer shell provide double protection, effectively reducing the leakage of liquid from the rotating connection between the drive shaft and the baffle shell and the outer shell.

[0010] As a further improvement to the above technical solution, the adjustment unit also includes a motor, which is disposed on the outside of the housing and is driven by the drive shaft. The motor drives the drive shaft to rotate, thereby allowing for better automatic adjustment of the baffle plate's state according to different flow rates and temperatures of the liquid during operation.

[0011] As a further improvement to the above technical solution, a sliding sleeve is provided on the side of the movable frame away from the drive shaft, and a sliding column is provided on the side of the baffle shell away from the drive shaft. The sliding column and the sliding sleeve are connected in cooperation. On the side of the movable frame away from the drive shaft that provides power, the cooperation between the sliding sleeve and the sliding column can further improve the stability of the movable frame's movement.

[0012] As a further improvement to the above technical solution, each of the multiple baffles is provided with a guide groove extending in the vertical direction, and the baffle shell is provided with a guide post corresponding to the positions of the multiple guide grooves, with the multiple guide posts inserted into the multiple guide grooves respectively. When the baffle is in a vertical state, the guide post is located at one end of the guide groove near the drive shaft and rotatably connected to the drive plate. When the drive plate moves, it can drive the baffle to rotate, at which time the guide post moves within the guide groove, thus realizing the movable connection between the baffle and the baffle shell.

[0013] As a further improvement to the above technical solution, multiple clearance slots are respectively provided on the left and right sides of the flow-blocking shell. Correspondingly, transmission plates are respectively provided on the movable frame at the positions of the multiple clearance slots on the left and right sides of the flow-blocking shell, and adjustable flow-blocking plates are also provided between the left and right sides of the flow-blocking shell and the transmission plates located on the left and right sides, so that the liquid passing through the left and right sides of the flow-blocking shell can be turbulent and guided.

[0014] As a further improvement to the above technical solution, multiple heat exchange fins are spaced apart in the left-right direction between two adjacent baffle components, and multiple heat exchange tubes pass through the heat exchange fins respectively. The heat of the heat exchange tubes can be conducted to the heat exchange fins, thereby improving the efficiency of heat conduction from the heat exchange tubes. When the liquid passes through the area between the two baffle shells, the liquid passes through multiple heat exchange fins, which increase the heat exchange area between the liquid and the liquid, thereby improving the heat exchange efficiency between the liquid and the heat exchange tubes.

[0015] As a further improvement to the above technical solution, multiple baffles are provided between two adjacent heat exchange fins. Elastic plates are connected to the left and right sides of each baffle between the two heat exchange fins. A gap is formed between two adjacent heat exchange fins, allowing liquid to flow through. The baffle is located within this gap. When liquid passes through this gap, the baffle can agitate the liquid, creating turbulence. Since the left and right sides of the baffle are connected to the heat exchange fins via elastic plates, the baffle itself vibrates to a certain amplitude, effectively reducing scale formation when liquid flows through the heat exchange fins and the baffle, preventing blockage of the gap. Attached Figure Description

[0016] To more clearly illustrate the technical solutions in the embodiments of the present invention, the accompanying drawings used in the description of the embodiments will be briefly explained below. Obviously, the described drawings are only a part of the embodiments of the present invention, and not all of them. Those skilled in the art can obtain other design schemes and drawings based on these drawings without creative effort.

[0017] Figure 1 This is a schematic diagram of the overall structure of the present invention.

[0018] Figure 2 This is a schematic diagram of the overall structure of the invention along a vertical cross-section passing through the central axis of the outer shell.

[0019] Figure 3 yes Figure 2 A magnified view of part A.

[0020] Figure 4 yes Figure 3 The diagram shows a partial enlargement of part B, where the baffle plate is rotated in the up-down direction.

[0021] Figure 5 This is a rear view of part of the baffle shell, where the dashed lines indicate the positions of the guide grooves and guide pillars, and the baffles are set in the vertical direction.

[0022] Figure 6 This is a rear view of part of the baffle shell, where the dashed lines indicate the positions of the guide grooves and guide pillars, and the baffle is set in an inclined direction.

[0023] Figure 7 yes Figure 3 A magnified view of part C.

[0024] In the attached diagram: 1-outer shell, 11-heat exchange chamber, 12-heat exchange tube, 2-baffle assembly, 21-baffle plate, 22-baffle shell, 221-guide post, 222-avoidance slot, 23-movable frame, 231-transmission plate, 232-guide groove, 233-connecting shaft, 24-motor, 31-heat exchange fins, 321-turbulence plate, 322-elastic plate. Detailed Implementation

[0025] The following will clearly and completely describe the concept, specific structure, and technical effects of the present invention in conjunction with embodiments and accompanying drawings, so as to fully understand the purpose, features, and effects of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, not all of them. Other embodiments obtained by those skilled in the art based on the embodiments of the present invention without creative effort are all within the scope of protection of the present invention. Furthermore, all connection relationships mentioned herein do not simply refer to direct connection of components, but rather to the ability to form a better connection structure by adding or reducing connecting accessories according to specific implementation conditions. The various technical features in this invention can be combined interactively without contradicting each other.

[0026] Reference Figures 1 to 6 A heat exchanger includes: a shell 1, inside which a heat exchange chamber 11 is disposed, wherein multiple heat exchange tubes 12 extending in a left-right direction are disposed within the heat exchange chamber 11; naturally, an inlet chamber and an outlet chamber are disposed on one side of the heat exchange chamber 11 within the shell 1; one end of some heat exchange tubes 12 is connected to the inlet chamber, and one end of some heat exchange tubes 12 is connected to the outlet chamber; a transfer chamber is disposed on the other side of the heat exchange chamber 11 within the shell 1, and the other ends of all heat exchange tubes 12 are respectively connected to the transfer chamber; an inlet is disposed on one side of the heat exchange chamber 11 within the shell 1; and... An outlet is provided on the other side of the heat exchange chamber 11; the flow baffle assembly 2 includes a flow blocking part, a flow baffle 21 and an adjustment part. The flow blocking part is provided at the top or bottom of the heat exchange chamber 11. Multiple heat exchange tubes 12 pass through the flow blocking part respectively. Multiple flow baffles 21 are provided on the surface of the flow blocking part. The adjustment part is provided between the outer shell 1 and the flow blocking part. The adjustment part is connected to multiple flow baffles 21. The adjustment part can drive multiple flow baffles 21 to rotate to be arranged in the vertical direction or at an angle. Multiple flow baffle assemblies 2 are spaced apart in the horizontal direction.

[0027] In this heat exchanger, a heat exchange chamber 11 for heat exchange is provided inside the outer shell 1. During operation, heat exchange medium is supplied to multiple heat exchange tubes 12, while the liquid to be heat exchanged is supplied into the heat exchange chamber 11. The liquid flows from one end of the heat exchange tube 12 to the other end. When the liquid passes through the baffle assembly 2, the baffle can block the flow of the liquid, causing the liquid to flow along the surface of the baffle to bypass the baffle. When the liquid passes through the surface of the baffle, it will pass through the baffle plate 21 provided on the surface of the baffle. The adjustment unit can adjust the posture of the baffle plate 21, thereby changing the state of the liquid flowing along the surface of the baffle. When the adjustment unit drives the multiple baffle plates 21 to be set in the vertical direction, the baffle plates 21 have little effect on the liquid flowing along the surface of the baffle. However, when the adjustment unit drives the multiple baffle plates 21 to be set at an angle, the baffle plates 21 will change the state of the liquid flowing along the surface of the baffle. The flow state on the surface of the flow section causes turbulence to form at this location, which helps to break the boundary layer formed by the fluid and disturb the corner positions between the baffle and the heat exchange chamber 11, reducing dead zones and improving heat exchange efficiency. Since multiple baffle components 2 are spaced apart in the left and right direction, in practical applications, the baffle 21 located near the liquid inflow position can be adjusted to a larger tilt angle, which helps to create stronger lateral disturbances, allowing the fluid to mix quickly and preventing the accumulation of fouling. The baffle 21 near the liquid outflow position is adjusted to a smaller tilt angle to reduce flow resistance and allow the fluid to flow out smoothly. In this way, by setting the baffle 21 with adjustable tilt, the turbulence formed during liquid flow can be improved, dead zones can be reduced, heat exchange efficiency can be improved, and sufficient vibration can be provided in areas prone to fouling, reducing boundary layer thickening and extending the internal cleaning cycle.

[0028] As a specific embodiment of the flow-blocking part, the flow-blocking part includes a flow-blocking shell 22 and a movable frame 23. The flow-blocking shell 22 is disposed at the top or bottom of the heat exchange chamber 11. A plurality of heat exchange tubes 12 pass through the flow-blocking shell 22 respectively. The surface of the flow-blocking shell 22 is provided with clearance slots 222 at positions corresponding to the positions between two upper and lower heat exchange tubes 12. A plurality of clearance slots 222 are spaced apart in the vertical direction. The adjustment part is disposed between the outer shell 1 and the movable frame 23. The movable frame 23 is slidably connected to the flow-blocking shell 22 in the front-back direction. The movable frame 23 is provided with transmission plates 231 at positions corresponding to the plurality of clearance slots 222 respectively. A connecting shaft 233 is connected to the plurality of transmission plates 231 respectively. The plurality of connecting shafts 233 pass through the plurality of clearance slots 222 and are rotatably connected to the flow-blocking plates 21 respectively. The other side of the plurality of flow-blocking plates 21 is movably connected to the surface of the flow-blocking shell 22. The baffle shell 22 mainly serves to block and change the direction of liquid flow in the heat exchange chamber 11. The movable frame 23 is set inside the baffle shell 22. The transmission plate 231 set inside it can block the clearance slot 222 opened on the baffle shell 22, which helps to prevent liquid from passing directly through the clearance slot 222. During operation, the movable frame 23 can be slid back and forth in the baffle shell 22 by the adjustment part, thereby adjusting the state of the baffle plate 21. For example, when the adjustment part moves forward in the movable frame 23, it can drive the baffle plate 21 to rotate on the transmission plate 231. When the adjustment part moves backward in the movable frame 23, it can drive the baffle plate 21 to rotate in the opposite direction on the transmission plate 231, thereby adjusting the baffle plate 21 between the vertical and inclined states.

[0029] In a specific embodiment of the adjustment unit, the adjustment unit includes a drive shaft, one end of which is threadedly connected to the movable frame 23, and the other end of which extends out of the baffle shell 22 and the outer shell 1. When it is necessary to adjust the state of the baffle plate 21, rotating the drive shaft forward or backward causes the movable frame 23 to slide forward or backward within the baffle shell 22, as the movable frame 23 is threadedly connected to the drive shaft and has a sliding connection structure within the baffle shell 22.

[0030] A rotatable connection structure is provided at the position where the drive shaft passes through the baffle shell 22 and the outer shell 1, thereby improving the stability of the drive shaft operation. Specifically, mechanical seals are respectively provided between the drive shaft and the baffle shell 22 and the outer shell 1. The mechanical seals formed between the drive shaft and the baffle shell 22 and the outer shell 1 provide double protection, effectively reducing the leakage of liquid from the rotatable connection between the drive shaft and the baffle shell 22 and the outer shell 1.

[0031] The drive shaft can be adjusted manually, but in this embodiment, it can be adjusted automatically. Specifically, the adjustment unit also includes a motor 24, which is located on the outside of the housing 1 and is connected to the drive shaft. The motor 24 can drive the drive shaft to rotate, thereby allowing for better automatic adjustment of the baffle 21's state according to different flow rates and temperatures of the liquid during operation.

[0032] A sliding connection structure can be formed between the transmission plate 231 and the baffle shell 22, thereby enabling the movable frame 23 to be slidably connected within the baffle shell 22. In this embodiment, a sliding sleeve is provided on the side of the movable frame 23 away from the transmission shaft, and a sliding column is provided on the side of the baffle shell 22 away from the transmission shaft. The sliding column and the sliding sleeve are connected in cooperation. In practical applications, multiple sliding columns and sliding sleeves can be provided respectively. On the side of the movable frame 23 away from the transmission shaft that provides power, the cooperation between the sliding sleeve and the sliding column can further improve the stability of the movable frame 23's movement.

[0033] The baffle plate 21 can be connected to the baffle shell 22 via a connecting rod, thereby achieving a movable connection between the two. In this embodiment, each of the baffle plates 21 is provided with a guide groove 232 extending in the vertical direction. The baffle shell 22 is provided with guide posts 221 corresponding to the positions of the guide grooves 232, and the guide posts 221 are inserted into the guide grooves 232. When the baffle plate 21 is in a vertical state, the guide posts 221 are located in the guide grooves 232 and are rotatably connected to one end of the transmission plate 231 near the transmission shaft. When the transmission plate 231 moves, it can drive the baffle plate 21 to rotate. At this time, the guide posts 221 move within the guide grooves 232, thus achieving a movable connection between the baffle plate 21 and the baffle shell 22.

[0034] In the above embodiment, a baffle plate 21 may be provided only on one side of the baffle shell 22. However, to further increase the turbulence of the liquid in the heat exchange chamber 11, in this embodiment, multiple clearance slots 222 are provided on the left and right sides of the baffle shell 22. Correspondingly, a transmission plate 231 is provided on the movable frame 23 at the positions of the multiple clearance slots 222 on the left and right sides of the baffle shell 22. An adjustable baffle plate 21 is also provided between the left and right sides of the baffle shell 22 and the transmission plate 231 located on the left and right sides, so that the liquid passing through the left and right sides of the baffle shell 22 can be turbulent and guided.

[0035] To improve the heat exchange efficiency between the liquid and the heat exchange tube 12, such as Figure 7As shown, in this embodiment, multiple heat exchange fins 31 are spaced apart in the left-right direction between two adjacent baffle components 2, and multiple heat exchange tubes 12 pass through the heat exchange fins 31 respectively. The heat of the heat exchange tubes 12 can be conducted to the heat exchange fins 31, thereby improving the efficiency of heat conduction from the heat exchange tubes 12. When the liquid passes through the area between the two baffle shells 22, the liquid passes through multiple heat exchange fins 31, which increase the heat exchange area between the liquid and the heat exchange tubes 12, thereby improving the heat exchange efficiency between the liquid and the heat exchange tubes 12.

[0036] Furthermore, multiple baffles 321 are provided between two adjacent heat exchange fins 31. Elastic plates 322 are connected to the left and right sides of each baffle 321 and the two heat exchange fins 31, respectively. In practical applications, the baffles 321 can be inclined or spirally arranged, primarily to agitate the flowing liquid and improve the convective heat transfer coefficient. A gap is formed between two adjacent heat exchange fins 31, allowing liquid to flow through. The baffles 321 are located within this gap. When the liquid passes through this gap, the baffles 321 agitate the liquid, creating turbulence. Since the left and right sides of the baffles 321 are connected to the heat exchange fins 31 via elastic plates 322, the baffles 321 themselves vibrate to a certain amplitude, effectively reducing scale formation when the liquid flows through the heat exchange fins 31 and the baffles 321, preventing blockage of the gap.

[0037] The preferred embodiments of the present invention have been described in detail above, but the present invention is not limited to the embodiments described. Those skilled in the art can make various equivalent modifications or substitutions without departing from the spirit of the present invention, and these equivalent modifications or substitutions are all included within the scope defined by the claims of this application.

Claims

1. A heat exchanger, characterized in that: include: The outer shell (1) has a heat exchange chamber (11) inside, and multiple heat exchange tubes (12) extending in the left and right directions are arranged inside the heat exchange chamber (11). The flow baffle assembly (2) includes a flow baffle, a flow baffle (21) and an adjustment part. The flow baffle is disposed at the top or bottom of the heat exchange chamber (11). Multiple heat exchange tubes (12) pass through the flow baffle respectively. Multiple flow baffles (21) are disposed on the surface of the flow baffle. The adjustment part is disposed between the outer shell (1) and the flow baffle. The adjustment part is connected to multiple flow baffles (21) in a driving manner. The adjustment part can drive multiple flow baffles (21) to rotate to be disposed in the vertical direction or at an angle. Multiple flow baffle assemblies (2) are spaced apart in the left and right direction. The baffle includes a baffle shell (22) and a movable frame (23). The baffle shell (22) is disposed at the top or bottom of the heat exchange chamber (11). Multiple heat exchange tubes (12) pass through the baffle shell (22). A clearance slot (222) is provided on the surface of the baffle shell (22) at a position corresponding to the position between two upper and lower heat exchange tubes (12). Multiple clearance slots (222) are spaced apart along the vertical direction. The adjustment part is disposed between the outer shell (1) and the movable frame (23). The movable frame (23) is slidably connected to the baffle shell (22) in the front-back direction. The movable frame (23) is provided with transmission plates (231) at the positions corresponding to the multiple clearance slots (222). The multiple transmission plates (231) are respectively connected with connecting shafts (233). The multiple connecting shafts (233) pass through the multiple clearance slots (222) and are rotatably connected to the baffle plates (21). The other side of the multiple baffle plates (21) is movably connected to the surface of the baffle shell (22). The adjustment unit includes a drive shaft, one end of which is threadedly connected to the movable frame (23), and the other end of which extends out of the baffle shell (22) and the outer shell (1). The adjustment unit also includes a motor (24), which is disposed on the outside of the housing (1) and is connected to the drive shaft. Multiple heat exchange fins (31) are spaced apart in the left-right direction between two adjacent baffle components (2), and multiple heat exchange tubes (12) pass through the heat exchange fins (31) respectively. Multiple baffles (321) are provided between two adjacent heat exchange fins (31), and elastic plates (322) are connected to the left and right sides of the baffles (321) respectively between the two heat exchange fins (31).

2. A heat exchanger according to claim 1, characterized in that: Mechanical seals are respectively provided between the drive shaft and the baffle shell (22) and the outer shell (1).

3. A heat exchanger according to claim 1, characterized in that: The movable frame (23) is provided with a sliding sleeve on the side away from the drive shaft, and the baffle shell (22) is provided with a sliding column on the side away from the drive shaft. The sliding column and the sliding sleeve are connected to each other.

4. A heat exchanger according to claim 1, characterized in that: Each of the baffles (21) is provided with a guide groove (232) extending in the vertical direction. The baffle shell (22) is provided with a guide post (221) at the position corresponding to the multiple guide grooves (232). The multiple guide posts (221) are inserted into the multiple guide grooves (232).

5. A heat exchanger according to claim 1, characterized in that: The flow-blocking shell (22) is provided with a plurality of clearance slots (222) on its left and right sides respectively.

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