Bridge prestressed carbon fiber material reinforcing construction device and construction method

Abstract

The application relates to the technical field of bridge prestress construction, and discloses a bridge prestress carbon fiber material reinforcing construction device and a construction method. The device comprises a plurality of carbon fiber strip plates arranged at the bottom of a bridge body, a plurality of limiting strip plates arranged at the two ends of the carbon fiber strip plates respectively, and the limiting strip plates are fixed to the bottom of the bridge body through expansion bolts. The limiting strip plates are provided with limiting grooves along the length direction of the limiting strip plates, and the ends of the plurality of carbon fiber strip plates pass through the limiting strip plates through the limiting grooves. The application has the effect of improving the maintenance cost and period of bridge prestress reinforcing construction when a single carbon fiber plate is broken.

Description

Technical Field

[0001] This invention relates to the technical field of prestressed bridge construction, and in particular to a prestressed carbon fiber reinforcement construction device and method for bridges. Background Technology

[0002] Many bridges built in my country in the early stages have reached their design lifespan, and cracks have appeared in the main structure, leading to a decrease in the bridge's load-bearing capacity. To extend the bridge's service life, reinforcement of the main structure is necessary. Existing reinforcement methods include external steel reinforcement, increasing the cross-section of structural members, adding support points, shotcrete reinforcement, bonding high-strength composite materials, and prestressed reinforcement. Prestressed reinforcement primarily uses carbon fiber reinforcement materials, such as carbon fiber plates, carbon fiber cloth, and carbon fiber reinforcing bars.

[0003] Chinese invention patent CN112376447A discloses a prestressed tensioning and anchoring device, which includes a fixed end and a tensioning end fixed to both ends of a carbon fiber plate, and a tensioning device near the tensioning end. The carbon fiber plate and the tensioning and anchoring device are both located at the bottom end of the beam. The fixed end, the tensioning end, and the tensioning device are all fixedly connected to the beam. The tensioning end includes a fixed seat and a tensioning clamp. The fixed seat is fixedly connected to the beam, and the tensioning clamp is fixedly connected to the carbon fiber plate. A connecting member for fixing is provided between the tensioning clamp and the fixed seat. The end of the tensioning clamp away from the fixed seat is connected to the tensioning device.

[0004] Regarding the aforementioned technologies, the prestressed tensioning and anchoring equipment uses a single carbon fiber plate to address the prestress of the bridge. If a single carbon fiber plate breaks, it will increase the maintenance cost and time required for the bridge prestressed reinforcement construction. Summary of the Invention

[0005] To address the issue that the fracture of a single carbon fiber plate increases the maintenance cost and time required for prestressed bridge reinforcement, this application provides a bridge prestressed carbon fiber reinforcement construction device and method.

[0006] Firstly, the present invention provides a bridge prestressed carbon fiber reinforcement construction device, which adopts the following technical solution: A bridge prestressed carbon fiber reinforcement construction device includes several carbon fiber strips disposed at the bottom of the bridge body and several limiting strips disposed at both ends of the carbon fiber strips; the limiting strips are fixed to the bottom of the bridge body by expansion bolts, and the limiting strips are provided with limiting grooves along their own length direction, and the ends of the several carbon fiber strips pass through the limiting grooves through the limiting strips.

[0007] By adopting the above technical solution, the ends of several carbon fiber strips pass through the limiting strips through the limiting grooves, thereby achieving the effect of solving the prestressing of the bridge body by using multiple carbon fiber strips at the bottom.

[0008] Optionally, a locking component is provided at the bottom of the bridge body. The locking component includes a carbon fiber rack fixed to the surface of the carbon fiber strip, a cylindrical gear rotatably installed in the limiting strip, and two cylindrical shafts coaxially fixed to both ends of the cylindrical gear. Several carbon fiber racks are meshed with the cylindrical gear.

[0009] By adopting the above technical solution, the cylindrical gears are meshed with several carbon fiber racks, and the cylindrical gears at both ends of the carbon fiber racks are simultaneously screwed on. The two ends of the carbon fiber racks are tightened by the cylindrical gears, which minimizes the swaying of several carbon fiber strips at the bottom of the bridge body.

[0010] Optionally, the bottom of the bridge body is provided with a one-way rotating component, which includes an internal gear ring fixedly installed in the limiting strip, ratchet teeth disposed on the inner circumferential surface of the internal gear ring, several telescopic sleeves fixed to the circumference of the cylindrical shaft, a telescopic inclined block passing through the telescopic sleeve, and a compression spring disposed between the telescopic inclined block and the bottom of the inner cylinder of the telescopic sleeve; the internal gear ring is provided with one at each end near the cylindrical gear, and the right-angle surfaces of the telescopic inclined block and the ratchet teeth are fitted together.

[0011] By adopting the above technical solution, the right-angled surface of the ratchet of the internal gear ring is fitted with the right-angled surface of the telescopic inclined block, so that the cylindrical gear can only rotate in one direction, and the two ends of the carbon fiber rack are continuously tightened through the cylindrical gear.

[0012] Optionally, a tension sensing component is provided at the bottom of the bridge body. The tension sensing component includes two tension sensors fixed to the bottom of the bridge body near both ends of the bridge body, a winding reel coaxially fixed to the end of the cylindrical shaft away from the cylindrical gear, and several turns of steel wire strand wound around the outer circumference of the winding reel. The ends of the steel wire strand away from the winding reel are all fixedly connected to the corresponding tension sensors.

[0013] By adopting the above technical solution, the winding wheels at both ends of the cylindrical gear are connected to the tension sensor through steel wire strands. The winding wheels and the cylindrical gear are fixedly connected through a cylindrical shaft. If the tension data of the tension sensor is abnormal, the data center will immediately feed back the abnormal data to the staff for easy inspection.

[0014] Optionally, a reinforcing component is provided at the bottom of the bridge body, the reinforcing component including a plurality of support strips disposed at the bottom of the bridge body; carbon fiber strips are abutted against the bottom of the bridge body by the plurality of support strips, and the support strips are fixed to the bottom of the bridge body by expansion bolts.

[0015] By adopting the above technical solution, the angled bosses at both ends of the support strip are fixed to the bottom of the bridge body by several expansion bolts, thereby further reinforcing the carbon fiber racks and carbon fiber strips.

[0016] Optionally, a protective component is provided at the bottom of the bridge body, the protective component including a corrugated protective cover installed between two adjacent support strips.

[0017] By adopting the above technical solution, the corrugated protective cover covers the entire carbon fiber rack and carbon fiber strip, minimizing the exposure of the carbon fiber rack and carbon fiber strip to the outside world. This reduces the wind and sun exposure of the carbon fiber rack and carbon fiber strip, thereby increasing their service life.

[0018] Optionally, a support component is provided at the bottom of the bridge body. The support component includes a hinged straight rod 1 and a hinged straight rod 2, which are staggered between two adjacent support strips. The centers of the hinged straight rod 1 and the hinged straight rod 2 are hinged to each other, and the hinged straight rod 1 and the hinged straight rod 2 are located in the inner circumference of the corrugated protective cover. The ends of the hinged straight rod 1 and the hinged straight rod 2 that are close to the same support strip slide on the inner side of the same support strip.

[0019] By adopting the above technical solution, several support strips are stretched apart along the length of the carbon fiber strips. Hinged rod one and hinged rod two slide inside the support strips, so that hinged rod one and hinged rod two can be used for internal support of the corrugated protective cover, thus minimizing the deformation of the corrugated protective cover.

[0020] Optionally, the bottom of the bridge body is provided with a telescopic component, which includes two support sleeves respectively disposed between two adjacent support strips and a support rod passing through the near ends of the two support sleeves; the outer peripheral surfaces of the support sleeves are respectively fitted to the bottom surface of the bridge body, and one telescopic component is located on the left and right side walls of the corrugated protective cover, and the two support sleeves of the telescopic component are fixedly connected to the corrugated protective cover.

[0021] By adopting the above technical solution, the side of the corrugated protective cover is attached to the bottom of the bridge body through two support sleeves and support rods.

[0022] Secondly, the present invention provides a bridge prestressed carbon fiber reinforcement construction method, used to operate the aforementioned bridge prestressed carbon fiber reinforcement construction device, comprising the following steps: S1. Several carbon fiber strips are placed at the bottom of the bridge body, and carbon fiber racks are fixed to the surface of the carbon fiber strips away from the bridge body. S2. Two locking components are placed at both ends of the carbon fiber strip. At this time, the cylindrical gear meshes with several carbon fiber racks, and the two ends of the carbon fiber racks are tightened by the locking components. S3. The cylindrical gear achieves unidirectional rotation through a unidirectional rotating component, so that the two ends of the carbon fiber rack are continuously tightened through the cylindrical gear. If the tension data of the tension sensing component is abnormal, the data center will immediately feed back the abnormal data to the staff for easy inspection. S4. Place the reinforcing component at the bottom of the carbon fiber strip, and cover the entire carbon fiber rack and carbon fiber strip with a corrugated protective cover. The reinforcing component further reinforces several carbon fiber racks and carbon fiber strips. S5. The sides of the corrugated protective cover are attached to the bottom of the bridge body through two support sleeves. S6. The leftmost support strip and the rightmost support strip are fixedly connected to the two limiting strips respectively.

[0023] By adopting the above technical solution, the carbon fiber rack is tightened by the cylindrical gear, which minimizes the swaying of several carbon fiber strips at the bottom of the bridge body. The winding wheels at both ends of the cylindrical gear are connected to the tension sensor through steel wire strands. The winding wheels and the cylindrical gear are fixedly connected through a cylindrical shaft. If the tension data of the tension sensor is abnormal, the data center will immediately feed back the abnormal data to the staff for easy inspection.

[0024] In summary, this application includes at least one of the following beneficial technical effects: 1. The ends of several carbon fiber strips pass through the limiting strips via limiting grooves, thereby achieving the effect of prestressing the bridge by using multiple carbon fiber strips at the bottom of the bridge body; 2. The cylindrical gears are meshed with several carbon fiber racks. The cylindrical gears at both ends of the carbon fiber racks are screwed on simultaneously, and the two ends of the carbon fiber racks are tightened through the cylindrical gears to minimize the shaking of several carbon fiber strips at the bottom of the bridge body. 3. The right-angled surface of the ratchet of the internal gear ring is fitted with the right-angled surface of the telescopic wedge, so that the cylindrical gear can only rotate in one direction, and the two ends of the carbon fiber rack are continuously tightened through the cylindrical gear. Attached Figure Description

[0025] Figure 1This is a schematic diagram of the construction device for reinforcing bridges with prestressed carbon fiber materials.

[0026] Figure 2 This is an exploded view of the bottom structure of the bridge body in an embodiment of this application.

[0027] Figure 3 This is a schematic diagram of a partial structure at the bottom of the bridge body.

[0028] Figure 4 This is a cross-sectional schematic diagram of the internal structure of the internal gear ring in an embodiment of this application.

[0029] Reference numerals: 11. Bridge body; 12. Carbon fiber strip; 13. Carbon fiber rack; 14. Limiting strip; 15. Limiting boss; 16. Limiting groove; 17. Strip through groove; 18. Cylindrical gear; 19. Cylindrical shaft; 20. Internal gear ring; 21. Rattle tooth; 22. Telescopic sleeve; 23. Telescopic wedge; 24. Compression spring; 25. Winding reel; 26. Steel wire strand; 27. Tension sensor; 28. Support strip; 29. ​​Hinge straight rod one; 30. Hinge straight rod two; 31. Clearance through groove; 32. Cylindrical slider; 33. Telescopic component; 34. Support sleeve; 35. Support straight rod; 36. Angular boss; 37. Corrugated protective cover. Detailed Implementation

[0030] The following is in conjunction with the appendix Figure 1-4 This application will be described in further detail.

[0031] Reference Figure 1-3 As shown, a bridge prestressed carbon fiber reinforcement construction device includes carbon fiber strips 12 arranged along the length of the bridge body 11 at the bottom of the bridge body 11, and several carbon fiber strips 12 arranged along the width of the bridge body 11. Carbon fiber toothed racks 13 are bonded to the surface of the carbon fiber strips 12 away from the bridge body 11 by adhesive. The carbon fiber toothed racks 13 are arranged along the length of the carbon fiber strips 12, and the two ends of the carbon fiber strips 12 are respectively aligned with the two ends of the carbon fiber toothed racks 13. Limiting strips 14 are provided at the bottom of the bridge body 11 along the width of the bridge body 11, with one limiting strip 14 located at each end of the carbon fiber strips 12. Limiting bosses 15 are fixed to both ends of the limiting strips 14, and the limiting bosses 15 are fixed to the bottom of the bridge body 11 by several expansion bolts, thus achieving the goal of fixing both ends of the limiting strips 14 to the bottom of the bridge body 11 by expansion bolts.

[0032] Reference Figure 2-4As shown, the limiting strip 14 has a limiting groove 16 along its length near the bridge body 11, and a strip through groove 17 along its length away from the bridge body 11. The limiting groove 16 is located through the left and right side walls of the limiting strip 14. The end of the carbon fiber strip 12 passes through the limiting strip 14 via the limiting groove 16. A cylindrical gear 18 is provided on the limiting strip 14 through the strip through groove 17. Both ends of the cylindrical gear 18 are coaxially fixed with cylindrical rotating shafts 19. The ends of the cylindrical rotating shafts 19 away from the cylindrical gear 18 are rotatably mounted on the inner wall of the strip through groove 17, so that the cylindrical gear 18 is rotatably mounted inside the limiting strip 14. The cylindrical gear 18 meshes with several carbon fiber racks 13, and an internal gear ring 20 is fixedly installed on the inner side wall of the strip through groove 17.

[0033] Reference Figure 2-4 As shown, the internal gear ring 20 is coaxially arranged with the cylindrical shaft 19. A ring of ratchet teeth 21 is provided on the inner circumferential surface of the internal gear ring 20. One ratchet tooth 21 is provided at each end of the internal gear ring 20 near the cylindrical gear 18. A telescopic sleeve 22 is fixedly installed on the circumference of the cylindrical shaft 19. Two telescopic sleeves 22 are arranged circumferentially around the axis of the cylindrical shaft 19. A telescopic inclined block 23 passes through the telescopic sleeve 22 away from the cylindrical shaft 19. The right-angled surfaces of the telescopic inclined block 23 and the ratchet teeth 21 are fitted together. A compression spring 24 is provided between the end of the telescopic inclined block 23 and the bottom of the inner cylinder of the telescopic sleeve 22. A limiting strip 14 extends through the end of the cylindrical shaft 19 away from the cylindrical gear 18. A winding wheel 25 is coaxially fixed to the end of the cylindrical shaft 19 away from the cylindrical gear 18. Tension sensors 27 are fixed at the bottom of the bridge body 11 near its two ends.

[0034] Reference Figure 2-4 As shown, several turns of steel wire strand 26 are wound around the circumference of the winding reel 25. The ends of the two steel wire strands 26 on the same side of the bridge body 11, away from the winding reel 25, are fixedly connected to the tension sensor 27. Several support strips 28 are provided along the length of the bridge body 11 at its bottom. The support strips 28 are located between two limiting strips 14 and are arranged along the width of the bridge body 11. A hinged straight rod 1 29 and a hinged straight rod 20 are staggered between two adjacent support strips 28. The center positions of the hinged straight rod 1 29 and the hinged straight rod 20 are hinged to each other. A clearance groove 31 is provided through the support strip 28 along the length of the bridge body 11. The ends of the hinged straight rod 1 29 and the hinged straight rod 20 near the same support strip 28 pass through the clearance groove 31 into the same support strip 28.

[0035] Reference Figure 2-4As shown, both the ends of the first hinged rod 29 and the second hinged rod 30 are vertically fixed with cylindrical sliders 32. The cylindrical sliders 32 at the ends of the first hinged rod 29 and the second hinged rod 30 are engaged with the inner side of the corresponding support plate 28, so that the ends of the first hinged rod 29 and the second hinged rod 30 can slide along the length of the support plate 28 to the inner side of the corresponding support plate 28. A telescopic component 33 is provided between two adjacent support plates 28, with one telescopic component 33 at each end of the support plate 28. The telescopic component 33 includes two support sleeves 34 that are vertically fixed to the adjacent surfaces of the two adjacent support plates 28. The ends of the two support sleeves 34 that are close to each other are connected by a support rod 35. The outer circumferential surfaces of the two support sleeves 34 of the telescopic component 33 are respectively fitted to the bottom surface of the bridge body 11.

[0036] Reference Figure 2-4 As shown, angled bosses 36 are fixed to both ends of the support strip 28. The angled bosses 36 are fixed to the bottom of the bridge body 11 by several expansion bolts, thus fixing both ends of the support strip 28 to the bottom of the bridge body 11 by expansion bolts. Carbon fiber strips 12 and carbon fiber racks 13 are fixed to the bottom of the bridge body 11 by the support strip 28. Corrugated protective covers 37 are provided on the surfaces of two adjacent support strips 28 that are close to each other. The left and right side walls of the corrugated protective cover 37 are respectively provided with two telescopic components 33. The support sleeve 34 and support rod 35 of the same telescopic component 33 pass through the corrugated protective cover 37. Hinged rod 1 29 and hinged rod 2 30 are provided in the inner circumference of the corrugated protective cover 37.

[0037] A method for reinforcing bridges with prestressed carbon fiber materials, used to operate the aforementioned bridge prestressed carbon fiber material reinforcement construction device, includes the following steps: S1. Several carbon fiber strips 12 are placed at the bottom of the bridge body 11, and carbon fiber toothed strips 13 are bonded to the surface of the carbon fiber strips 12 away from the bridge body 11 by adhesive. S2. First, place the two limiting strips 14 at both ends of the carbon fiber strip 12. Then, pass the ends of the carbon fiber strip 12 through the limiting grooves 16 to the limiting strips 14. The limiting protrusions 15 at both ends of the limiting strips 14 are fixed to the bottom of the bridge body 11 by several expansion bolts. S3. At this time, the cylindrical gear 18 is meshed with several carbon fiber racks 13. The cylindrical gears 18 at both ends of the carbon fiber racks 13 are simultaneously screwed. The two ends of the carbon fiber racks 13 are tightened through the cylindrical gears 18 to avoid the several carbon fiber strips 12 from shaking at the bottom of the bridge body 11 as much as possible. S4. The ratchet 21 of the internal gear ring 20 is fitted with the right-angle side of the telescopic inclined block 23, so that the cylindrical gear 18 can only rotate in one direction, and the two ends of the carbon fiber rack 13 are continuously tightened through the cylindrical gear 18. S5. The winding wheels 25 at both ends of the cylindrical gear 18 are connected to the tension sensor 27 via steel wire strands 26. The winding wheels 25 and the cylindrical gear 18 are fixedly connected via a cylindrical shaft 19. If the tension data of the tension sensor 27 is abnormal, the data center will immediately feed back the abnormal data to the staff for easy inspection. S6. First, place several support strips 28 at the bottom of carbon fiber strip 12, then pull several support strips 28 apart along the length of carbon fiber strip 12. Hinged straight rod 1 29 and hinged straight rod 2 30 slide on the inside of the support strip 28 to realize the corrugated protective cover 37 covering the carbon fiber rack 13 and carbon fiber strip 12. S7. The side of the corrugated protective cover 37 is attached to the bottom of the bridge body 11 through two support sleeves 34 and support rods 35. The angled bosses 36 at both ends of the support strip 28 are fixed to the bottom of the bridge body 11 by several expansion bolts, so as to further reinforce several carbon fiber racks 13 and carbon fiber strips 12. S8, the leftmost support strip 28 and the rightmost support strip 28 are fixedly connected to the two limiting strips 14 by welding.

[0038] The above are all preferred embodiments of this application and are not intended to limit the scope of protection of this application. Therefore, all equivalent changes made in accordance with the structure, shape and principle of this application should be covered within the scope of protection of this application.

Claims

1. A bridge prestressed carbon fiber plate reinforcement construction device, characterized in that: It includes several carbon fiber strips (12) disposed at the bottom of the bridge body (11) and several limiting strips (14) respectively disposed at both ends of the carbon fiber strips (12); the limiting strips (14) are fixed to the bottom of the bridge body (11) by expansion bolts, and the limiting strips (14) are provided with limiting grooves (16) along their own length direction, and the ends of several carbon fiber strips (12) pass through the limiting strips (14) through the limiting grooves (16); The bottom of the bridge body (11) is provided with a locking component, which includes a carbon fiber rack (13) fixed to the surface of the carbon fiber strip (12), a cylindrical gear (18) rotatably installed in the limiting strip (14), and two cylindrical shafts (19) respectively coaxially fixed to both ends of the cylindrical gear (18); several carbon fiber racks (13) are meshed with the cylindrical gear (18); The bottom of the bridge body (11) is provided with a one-way rotating component. The one-way rotating component includes an internal gear ring (20) fixedly installed in the limiting strip (14), a ratchet (21) provided on the inner circumferential surface of the internal gear ring (20), a number of telescopic sleeves (22) fixed on the periphery of the cylindrical shaft (19), a telescopic inclined block (23) passing through the telescopic sleeve (22), and a compression spring (24) provided between the telescopic inclined block (23) and the bottom of the inner cylinder of the telescopic sleeve (22). The internal gear ring (20) is provided with one at each end near the cylindrical gear (18), and the right-angle surfaces of the telescopic inclined block (23) and the ratchet (21) are fitted together. The bottom of the bridge body (11) is provided with a tension sensing component, which includes two tension sensors (27) fixed to the bottom of the bridge body (11) near both ends of the bridge body (11), a winding wheel (25) coaxially fixed to the end of the cylindrical shaft (19) away from the cylindrical gear (18), and several turns of steel wire strand (26) wound around the outer circumference of the winding wheel (25); the ends of the steel wire strand (26) away from the winding wheel (25) are all fixedly connected to the corresponding tension sensors (27).

2. The bridge prestressed carbon fiber plate reinforcement construction device according to claim 1, characterized in that: The bottom of the bridge body (11) is provided with a reinforcing component, which includes a number of support strips (28) provided at the bottom of the bridge body (11); carbon fiber strips (12) are attached to the bottom of the bridge body (11) through the support strips (28), and the support strips (28) are fixed to the bottom of the bridge body (11) by expansion bolts.

3. The bridge prestressed carbon fiber plate reinforcement construction device according to claim 2, characterized in that: The bottom of the bridge body (11) is provided with a protective component, which includes a corrugated protective cover (37) installed between two adjacent support strips (28).

4. The bridge prestressed carbon fiber plate reinforcement construction device according to claim 3, characterized in that: The bottom of the bridge body (11) is provided with a support component, which includes a hinged straight rod one (29) and a hinged straight rod two (30) staggered between two adjacent support strips (28); the center of the hinged straight rod one (29) and the hinged straight rod two (30) are hinged to each other, and the hinged straight rod one (29) and the hinged straight rod two (30) are located in the inner circumference of the corrugated protective cover (37); the ends of the hinged straight rod one (29) and the hinged straight rod two (30) near the same support strip (28) slide on the inner side of the same support strip (28).

5. The bridge prestressed carbon fiber plate reinforcement construction device according to claim 3, characterized in that: The bottom of the bridge body (11) is provided with a telescopic component (33). The telescopic component (33) includes two support sleeves (34) respectively disposed between two adjacent support strips (28) and a support rod (35) passing through the near ends of the two support sleeves (34). The outer peripheral surfaces of the support sleeves (34) are respectively fitted to the bottom surface of the bridge body (11). The telescopic component (33) is located on the left and right side walls of the corrugated protective cover (37). The two support sleeves (34) of the telescopic component (33) are fixedly connected to the corrugated protective cover (37).

6. A method for constructing bridge prestressed carbon fiber plate reinforcement, used to operate the bridge prestressed carbon fiber plate reinforcement construction device according to any one of claims 3-5, characterized in that, Includes the following steps: S1. Several carbon fiber strips (12) are placed at the bottom of the bridge body (11), and carbon fiber racks (13) are fixed to the surface of the carbon fiber strips (12) away from the bridge body (11). S2. Two locking components are placed at both ends of the carbon fiber strip (12). At this time, the cylindrical gear (18) meshes with several carbon fiber racks (13), and the two ends of the carbon fiber racks (13) are tightened by the locking components. S3, the cylindrical gear (18) achieves unidirectional rotation through the unidirectional rotating component, so that the two ends of the carbon fiber rack (13) are continuously tightened through the cylindrical gear (18). If the tension data of the tension sensing component is abnormal, the data center will immediately feed back the abnormal data to the staff so that the staff can repair it. S4. Place the reinforcing component at the bottom of the carbon fiber strip (12), and the corrugated protective cover (37) covers the entire carbon fiber rack (13) and carbon fiber strip (12). The reinforcing component further reinforces several carbon fiber racks (13) and carbon fiber strips (12). S5. The side of the corrugated protective cover (37) is attached to the bottom of the bridge body (11) through two support sleeves (34); S6. The leftmost support strip (28) and the rightmost support strip (28) are fixedly connected to the two limiting strips (14) respectively.

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