Adjustable stiff steel column head protection device

Abstract

The application discloses an adjustable stiff steel column head protection device, which comprises a web protection fixing part, a web protection sliding part and a flange protection sliding part, the web protection fixing part is clamped on the web of the stiff steel column head, the web protection sliding part is slidably clamped on the web protection fixing part, and the flange protection sliding part is slidably clamped on the web protection sliding part. The application has the beneficial effects that: through the three-layer nested sliding structure of the web protection fixing part, the web protection sliding part and the flange protection sliding part, flexible adaptation and comprehensive protection of the stiff steel column head of different specifications are realized. The cross-shaped and character-shaped galvanized structure and the U-shaped sliding groove of the web protection fixing part are matched with the anti-skid lines, so that the sliding stability is ensured and the dislocation is prevented. The first folded edge rib of the web protection sliding part is accurately clamped with the S-shaped second folded edge rib of the flange protection sliding part, and the elastic sealing gasket is used for reinforcing sealing and preventing abrasion. Each component is formed through die rolling, is accurate in size, is corrosion-resistant and durable, and is simple in assembly and adjustment.

Description

Technical Field

[0001] This invention relates to the field of building engineering technology, and in particular to an adjustable stiffened steel column head protection device. Background Technology

[0002] Stiffened steel columns are widely used structural components in building engineering, possessing high strength and excellent seismic performance. They are extensively used in high-rise buildings, bridges, industrial plants, and other projects, with their superior mechanical properties making them a preferred choice for many structural engineering projects. With the development of materials science and engineering technology, the manufacturing processes and design methods for stiffened steel columns have been continuously improved. For example, the use of high-strength steel and advanced welding techniques has further enhanced the load-bearing capacity and durability of stiffened steel columns. Various countries have established corresponding standards and specifications for the design and construction of stiffened steel columns to ensure their safety and reliability. The formulation of these standards has promoted the widespread application and technological advancement of stiffened steel columns.

[0003] Despite the significant advantages of reinforced steel columns, there are also some drawbacks and challenges to overcome during their installation and welding. For example, pouring concrete for one layer can contaminate the column head, affecting the installation accuracy and welding quality of the next layer of steel columns.

[0004] Therefore, it is necessary to propose an adjustable stiffened steel column head protection device. Summary of the Invention

[0005] In view of the shortcomings of the prior art, the purpose of this invention is to provide an adjustable stiffened steel column head protection device to solve the pollution problem of stiffened steel column heads with H-shaped, cross-shaped, T-shaped and other cross-sectional types.

[0006] An adjustable stiffened steel column head protection device includes a web plate protection fixing component, a web plate protection sliding component, and a flange protection sliding component. The web plate protection fixing component is clamped onto the web plate of the stiffened steel column head, the web plate protection sliding component is slidably clamped onto the web plate protection fixing component, and the flange protection sliding component is slidably clamped onto the web plate protection sliding component.

[0007] Preferably, the web plate protection fastener is a cross frame structure composed of four Z-shaped galvanized steel plates, and the two ends of the Z-shaped opening of the web plate protection fastener are bent into a first U-shaped groove.

[0008] Preferably, the web plate protection sliding member is a T-shaped frame structure composed of two Z-shaped galvanized steel plates, and the two ends of the Z-shaped opening of the web plate protection sliding member are provided with first folded edge ribs, and the lower part of both sides of the web plate protection sliding member is provided with second U-shaped sliding grooves.

[0009] Preferably, the flange protection sliding member is a zigzag galvanized steel plate, and the two ends of the zigzag opening of the flange protection sliding member are provided with second folded edge ribs.

[0010] Preferably, the first folded edge rib and the second folded edge rib are both S-shaped, and the web plate protection fixing member, the web plate protection sliding member and the flange protection sliding member are all rolled by a specific die.

[0011] Preferably, the second folded edge rib is engaged in the second U-shaped groove, and the first folded edge rib is engaged in the first U-shaped groove.

[0012] Preferably, the inner sidewalls of both the first U-shaped groove and the second U-shaped groove are provided with anti-slip textures.

[0013] Preferably, the second folded edge rib has an elastic sealing gasket attached to the part where it fits with the second U-shaped groove, and the first folded edge rib has an elastic sealing gasket attached to the part where it fits with the first U-shaped groove.

[0014] Compared with existing technologies, the present invention offers the following advantages: This device achieves flexible adaptation and comprehensive protection for column heads of different specifications of rigid steel columns through a three-layer nested sliding structure consisting of a web plate protection fixing component, a web plate protection sliding component, and a flange protection sliding component. The cross-shaped galvanized structure and U-shaped groove of the web plate protection fixing component, combined with anti-slip texture, ensure stable sliding and prevent displacement. The first folded rib of the web plate protection sliding component and the S-shaped second folded rib of the flange protection sliding component are precisely engaged, and the elastic sealing gasket enhances sealing and wear resistance. All components are molded, ensuring precise dimensions, corrosion resistance, durability, easy assembly and adjustment, reusability to reduce costs, effective resistance to construction damage, and protection of the column head structure. Attached Figure Description

[0015] Figure 1 This is a structural diagram of the present invention; Figure 2 and Figure 3 This is a structural diagram of the web plate protection fastener of the present invention; Figure 4 and Figure 5 This is a structural diagram of the web plate protection sliding member of the present invention; Figure 6 and Figure 7 This is a structural diagram of the flange protection sliding member of the present invention; Figure 8 This is a structural diagram of the stiffened steel column head of the present invention; Figure 9 This is an assembly diagram of the present invention; Figure 10 yes Figure 9 Schematic diagram of AA section; Figure 11 yes Figure 9 A schematic diagram of the BB cross section.

[0016] The attached figures are labeled as follows: 1. Web plate protection fastener; 11. First U-shaped groove; 12. Anti-slip texture; 2. Web plate protection sliding member; 21. First folded edge rib; 22. Second U-shaped groove; 3. Flange protection sliding member; 31. Second folded edge rib; 4. Stiff steel column head; 41. Web plate. Detailed Implementation

[0017] It should be noted that, unless otherwise specified, the embodiments and features described in the present invention can be combined with each other.

[0018] In the description of this invention, it should be understood that the terms "center," "longitudinal," "lateral," "upper," "lower," "front," "rear," "left," "right," "vertical," "horizontal," "top," "bottom," "inner," and "outer," etc., indicating orientation or positional relationships based on the orientation or positional relationships shown in the accompanying drawings, are only for the convenience of describing the invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation, and therefore should not be construed as a limitation of the invention. Furthermore, the terms "first," "second," etc., are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of indicated technical features. Thus, features defined with "first," "second," etc., may explicitly or implicitly include one or more of that feature. In the description of this invention, unless otherwise stated, "a plurality of" means two or more.

[0019] In the description of this invention, it should be noted that, unless otherwise explicitly specified and limited, the terms "installation," "connection," and "linking" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral connection; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium; and they can refer to the internal communication between two components. Those skilled in the art will understand the specific meaning of the above terms in this invention based on the specific circumstances.

[0020] The embodiments of the present invention will be described in detail below with reference to the accompanying drawings, but the present invention can be implemented in many different ways as defined and covered by the claims.

[0021] like Figure 1 and combined Figures 2 to 11As shown, an adjustable stiffened steel column head protection device includes a web plate protection fixing component 1, a web plate protection sliding component 2, and a flange protection sliding component 3. The web plate protection fixing component 1 is engaged on the web plate 41 of the stiffened steel column head 4, the web plate protection sliding component 2 is slidably engaged on the web plate protection fixing component 1, and the flange protection sliding component 3 is slidably engaged on the web plate protection sliding component 2.

[0022] Furthermore, the web plate protection fastener 1 is a cross frame structure composed of four Z-shaped galvanized steel plates, and the two ends of the Z-shaped opening of the web plate protection fastener 1 are bent into U-shaped grooves 11.

[0023] The further technical solution offers the following benefits: The web plate protection fastener 1 employs a cross-frame structure composed of four Z-shaped galvanized steel plates. The Z-shaped structure combines excellent structural strength with lightweight characteristics, and the galvanizing treatment significantly enhances its rust and corrosion resistance, adapting to the complex and humid environment of construction sites and extending the device's service life. The cross-frame structure precisely fits the intersection of the web plates 41 of the stiffened steel column head 4, providing stronger stability and preventing displacement of the device during construction. The U-shaped grooves 11 formed by bending at both ends of the Z-shaped opening provide a stable sliding guide structure for the web plate protection sliding component 2, ensuring smooth sliding. Simultaneously, the U-shaped structure provides a wrapping restraint for the sliding components, preventing them from falling off and improving the overall structural reliability of the device.

[0024] Furthermore, the web plate protection sliding member 2 is a T-shaped frame structure composed of two Z-shaped galvanized steel plates. The two ends of the Z-shaped opening of the web plate protection sliding member 2 are provided with first folded edge ribs 21, and the lower part of both sides of the web plate protection sliding member 2 is provided with second U-shaped sliding grooves 22.

[0025] The further technical solution offers the following benefits: The web plate protection sliding member 2 is composed of two Z-shaped galvanized steel plates forming a T-shaped frame structure. The material properties of the Z-shaped galvanized steel plates give it sufficient load-bearing capacity and resistance to deformation, effectively resisting external impacts and providing reliable protection for the sides of the web plate 41. The T-shaped frame structure can precisely match the cross frame of the web plate protection fixing member 1, ensuring both the flexibility of sliding along the U-shaped groove 11 and further optimizing the coverage and protection range of the web plate 41 and the flange connection area. The first folded edge ribs 21 set at both ends of the Z-shaped opening enhance the structural rigidity of the web plate protection sliding member 2 itself, preventing warping deformation during sliding and under stress. At the same time, it provides a stable mounting support foundation for the flange protection sliding member 3, achieving smoothness and stability of the sliding connection.

[0026] Furthermore, the flange protection sliding member 3 is a zigzag galvanized steel plate, and the two ends of the zigzag opening of the flange protection sliding member 3 are provided with second folded edge ribs 31.

[0027] The further technical solution offers the following benefits: The flange protection sliding member 3 adopts a Z-shaped galvanized steel plate structure. The Z-shaped opening can precisely fit the flange contour of the stiffened steel column head, forming a comprehensive protective covering for the flange surface and edges, preventing the flange from being bumped or scratched during construction, and ensuring the structural accuracy of the steel column flange. The second folded edge ribs 31 set at both ends of the Z-shaped opening can, on the one hand, strengthen the edge structural strength of the flange protection sliding member 3 and avoid edge deformation under stress; on the other hand, they can achieve precise engagement with the web plate protection sliding member 2, providing guidance and limiting for the sliding of the flange protection sliding member 3, ensuring that it can move smoothly along the web plate protection sliding member 2 and accurately adapt to flange dimensions of different widths.

[0028] Furthermore, both the first folded edge rib 21 and the second folded edge rib 31 are S-shaped, and the web plate protection fixing member 1, the web plate protection sliding member 2, and the flange protection sliding member 3 are all rolled by a specific mold.

[0029] The further technical solutions offer the following benefits: Both the first folded edge rib 21 and the second folded edge rib 31 are designed in an S-shape. Compared to a straight folded edge, the S-shaped structure increases the contact area between the two, improving the structural stability after snap-fitting. It also provides a certain degree of elastic buffering capacity, mitigating the impact force during sliding adjustment, reducing component wear, and extending service life. The web plate protection fastener 1, web plate protection sliding component 2, and flange protection sliding component 3 are all rolled using specific molds, ensuring dimensional accuracy and structural consistency of each component, avoiding errors caused by manual processing, resulting in better compatibility between components and smoother sliding adjustment. The mold rolling process enables mass production, improving production efficiency and reducing manufacturing costs. Furthermore, the rolled structure has stronger overall integrity and superior impact and deformation resistance compared to spliced ​​structures.

[0030] Furthermore, the second folded edge rib 31 is engaged in the second U-shaped groove 22, and the first folded edge rib 21 is engaged in the first U-shaped groove 11.

[0031] The further technical solution offers several advantages: By using a nested locking structure where the second folded rib 31 is engaged within the second U-shaped groove 22 and the first folded rib 21 is engaged within the first U-shaped groove 11, a precise linkage of three components is formed. This ensures that each sliding component moves along a preset trajectory during adjustment, preventing offset or jamming and improving the accuracy and smoothness of adjustment. This nested structure allows the components to fit tightly together, enhancing the overall structural rigidity of the device, effectively resisting external lateral and longitudinal impacts, preventing deformation or detachment of the protective device, and further strengthening the protection of the stiffened steel column head. Simultaneously, the nested locking eliminates the need for additional fixing connectors, simplifying the assembly process, facilitating rapid installation and adjustment on-site, and improving construction efficiency.

[0032] Furthermore, the inner sidewalls of the first U-shaped groove 11 and the second U-shaped groove 22 are provided with anti-slip textures 12.

[0033] The benefits of adopting a further technical solution: the anti-slip texture 12 provided on the inner wall of the U-shaped groove 11 can increase the friction between the U-shaped groove 11 and the first folded edge rib 21. When the device is adjusted to the appropriate size, it can effectively prevent the web plate protection sliding component 2 from sliding on its own due to vibration, collision and other factors during construction, ensuring the stability of the device position and guaranteeing the protection effect.

[0034] Furthermore, the second folded edge rib 31 has an elastic sealing gasket attached at the point where it fits with the second U-shaped groove 22, and the first folded edge rib 21 has an elastic sealing gasket attached at the point where it fits with the first U-shaped groove 11.

[0035] The following further technical solutions offer beneficial effects: Elastic sealing gaskets are adhered at the contact points between the second folded rib 31 and the second U-shaped slide groove 22, and between the first folded rib 21 and the first U-shaped slide groove 11. These elastic sealing gaskets 32 fill the gaps between components, further enhancing the tightness of the connection and improving the overall structural stability. They also effectively buffer the impact forces during sliding adjustment, reducing wear and extending component lifespan. Furthermore, the elastic sealing gaskets 32 provide a certain degree of anti-slip function, helping to prevent the sliding parts from shifting after fixing, ensuring the stability of the protection device. They also prevent dust and debris from entering the contact gaps, avoiding blockages that could affect subsequent sliding adjustments and ensuring the device can be reused multiple times.

[0036] Compared with existing technologies, the present invention offers the following advantages: This device achieves flexible adaptation and comprehensive protection for column heads 4 of different specifications of rigid steel columns through a three-layer nested sliding structure consisting of a web plate protection fixing component 1, a web plate protection sliding component 2, and a flange protection sliding component 3. The cross-shaped galvanized structure and U-shaped groove 11 of the web plate protection fixing component 1, combined with anti-slip texture 12, ensure stable sliding and prevent displacement. The first folded edge rib 21 of the web plate protection sliding component 2 and the S-shaped second folded edge rib 31 of the flange protection sliding component 3 are precisely engaged, and the elastic sealing gasket 32 ​​enhances sealing and wear resistance. All components are molded, ensuring precise dimensions, corrosion resistance, durability, easy assembly and adjustment, reusability to reduce costs, effective resistance to construction damage, and protection of the column head structure.

[0037] Working principle: The web plate protection fastener 1, composed of four Z-shaped galvanized steel plates forming a cross-frame structure, is precisely fastened onto the web plate 41 of the stiffened steel column head 4 to complete the foundation fixation. Next, the web plate protection sliding member 2, composed of two Z-shaped galvanized steel plates forming a T-shaped frame structure, is positioned so that its first folded edge rib 21 is inserted into the first U-shaped groove 11 of the web plate protection fastener 1, and the anti-slip texture 12 on the inner side of the first U-shaped groove 11 is used for positioning. Then, the S-shaped second folded edge rib 31 of the flange protection sliding member 3 is inserted into the second U-shaped groove 22 of the web plate protection sliding member 2, and slid and adjusted to fit the flange of the stiffened steel column head 4, with the elastic sealing gasket 32 ​​filling the fitting gap. Finally, after confirming that all components are tightly fitted and fixed in position, the stiffened steel column head 4 is protected. Disassembly can be completed by sliding each component in reverse.

[0038] Example 1: Application of H-shaped stiffened steel column capitals This embodiment focuses on the H-shaped stiffened steel column head commonly used in high-rise building frame structures. The specific steel column parameters are: web height 800mm, thickness 16mm, flange width 400mm, thickness 20mm. During construction, special attention should be paid to protecting the connection between the web and the flange of the column head and the surface to avoid cement slurry contamination during concrete pouring.

[0039] Step 1: Component preparation and inspection. Select a cross-shaped frame structure web protection fastener composed of 4 Z-shaped galvanized steel plates (each Z-shaped steel plate is 850mm high, 50mm wide, and 3mm thick), a T-shaped frame structure web protection sliding component composed of 2 Z-shaped galvanized steel plates (each Z-shaped steel plate is 450mm long, 50mm wide, and 3mm thick), and 4 Z-shaped galvanized steel plate flange protection sliding components (each component is 420mm long, 60mm wide, and 3mm thick). Check that all components are free from deformation, the galvanized layer is intact, the first and second folded ribs (both S-shaped) are undamaged, the elastic sealing gasket is firmly attached, and the anti-slip texture on the inner side of the first and second U-shaped sliding grooves is clear.

[0040] Step 2: Install the web plate protection fastener. Precisely fasten the cross-frame structure web plate protection fastener onto the web plate of the H-shaped stiff steel column head, so that the four extended ends of the cross frame correspond to the four directions of the web plate (up, down, left, and right) and fit against the web plate surface. Use the wrapping property of the zigzag structure to achieve foundation fixation, ensuring that the fastener is not loose or displaced. The U-shaped groove opening faces the flange direction.

[0041] Step 3: Adjustment and installation of the web protection sliding component. Insert the first folded rib of the web protection sliding component of the T-shaped frame structure into the first U-shaped groove of the web protection fixing component. Adjust it up and down along the groove until the side of the web protection sliding component is completely in contact with both sides of the web of the H-shaped steel column. The elastic sealing gasket at the contact point tightly fills the gap. The anti-slip texture on the inside of the groove is used to achieve positioning and prevent the sliding component from shifting on its own, thus completing the comprehensive protection of the web.

[0042] Step 4: Adjustment and installation of the flange protection sliding component. Insert the second folded edge rib of the flange protection sliding component into the second U-shaped groove of the web plate protection sliding component, and slide it along the groove towards the flange. Adjust until the flange protection sliding component completely covers the upper and lower flanges of the H-shaped steel column, and the flange surface is tightly fitted with the inner wall of the protection sliding component. The elastic sealing gasket further enhances the sealing effect, preventing cement slurry and dust from entering, thus completing the assembly of the entire device.

[0043] Step 5: Verification and disassembly of the protective effect. During the pouring of this layer of concrete, the device effectively prevented cement slurry from contaminating the column head of the steel column. After the pouring was completed, the reverse sliding flange protected the sliding component and the web plate protected the sliding component. After disassembling each component in sequence and cleaning the residual debris on the surface, it can be used for the protection of the column head of the next H-shaped stiff steel column of the same type or different specifications. The components were unworn and the sealing performance was intact.

[0044] Example 2: Application of Adapted Cross-Shaped Reinforced Steel Column Capitals This embodiment is for the cross-shaped stiffened steel column head used in industrial plants. The specific steel column parameters are: web height 900mm, thickness 18mm, four flange widths 350mm, thickness 18mm. The column head of this type of steel column has a complex cross section, which needs to achieve full protection of the web intersection and the four flanges, while adapting to its symmetrical structure.

[0045] Step 1: Component preparation and adaptation adjustment. Select web plate protection fasteners, web plate protection sliding parts, and flange protection sliding parts that are consistent with the specifications of Example 1. For the symmetrical structure of the cross-shaped steel column, adjust the cross frame of the web plate protection fastener to be completely aligned with the intersection of the web plate of the steel column, ensuring that the four extension ends are evenly distributed and adapted to the size of the cross web plate.

[0046] Step 2: Fix the web plate protection fastener. The web plate protection fastener of the cross frame structure is clamped at the intersection of the web plates of the cross-shaped stiff steel column head, so that the zigzag opening of the fastener fits tightly against the web plate surface. The symmetry of the cross frame is used to achieve balanced fixation, avoid the device displacement caused by uneven force, and ensure that the first U-shaped slide groove faces the four flange directions with accurate positioning.

[0047] Step 3: Install and adjust the web plate protection sliding parts. Insert the two T-shaped frame structure web plate protection sliding parts into the first U-shaped groove of the web plate protection fixing part, and slide them along the groove towards the four flanges to adjust them so that the web plate protection sliding parts cover the four sides of the cross web plate. During the adjustment process, ensure that the first folded edge rib fits tightly with the first U-shaped groove, the elastic sealing gasket plays a sealing role, and the anti-slip texture achieves positioning, ensuring that the sliding parts are firmly fixed and without loosening.

[0048] Step 4: Install and adjust the flange protection sliding parts. Select 4 flange protection sliding parts and insert their second folded edge ribs into the second U-shaped groove of the corresponding web plate protection sliding part. Slide them along the groove towards the flange end and adjust until the flange protection sliding parts completely cover the ends and surfaces of the four flanges, fit tightly without gaps, and the elastic sealing gasket effectively prevents debris and cement slurry from entering the column head surface during construction, achieving comprehensive protection.

[0049] Step 5: Maintenance and Reuse during Construction. During construction, regularly check the fixation of the device. If slight displacement occurs due to vibration, the components can be reset by sliding adjustment. After the concrete of this layer is poured, disassemble the components and clean them. They can be adapted to other specifications of cross-shaped rigid steel column heads (by adjusting the position of the sliding parts, they can be adapted to cross-shaped steel columns with a flange width of 300-450mm and a web height of 700-1000mm), thus achieving reuse and reducing construction costs.

[0050] Both embodiments verify the adjustability, adaptability, and protective effect of this device. It can be flexibly adjusted according to the different cross-sectional types and sizes of stiff steel column heads. It is easy to assemble and quick to disassemble, effectively solving the problem of column head contamination, ensuring the installation accuracy and welding quality of the next layer of steel columns, and has the advantages of corrosion resistance, durability, and reusability, which meets the actual needs of building construction.

[0051] The above description is merely a preferred embodiment of the present invention and does not limit the patent scope of the present invention. Any equivalent structural or procedural transformations made based on the content of the present invention's specification and drawings, or direct or indirect applications in other related technical fields, are similarly included within the patent protection scope of the present invention.

Claims

1. An adjustable stiffened steel column head protection device, characterized in that: It includes a web protection fixing member (1), a web protection sliding member (2) and a flange protection sliding member (3). The web protection fixing member (1) is clamped on the web (41) of the column head of the stiffened steel column (4). The web protection sliding member (2) is slidably clamped on the web protection fixing member (1), and the flange protection sliding member (3) is slidably clamped on the web protection sliding member (2).

2. The adjustable stiffened steel column head protection device as described in claim 1, characterized in that: The web protection fixing member (1) is a cross-frame structure composed of 4 U-shaped galvanized steel plates. The two ends of the opening of the U-shape of the web protection fixing member (1) are bent into a first U-shaped chute (11).

3. The adjustable stiffened steel column head protection device as described in claim 1, characterized in that: The web protection sliding member (2) is a T-frame structure composed of 2 U-shaped galvanized steel plates. The two ends of the opening of the U-shape of the web protection sliding member (2) are provided with first flanging ribs (21). The lower parts of the two side edges of the web protection sliding member (2) are provided with second U-shaped chutes (22).

4. The adjustable stiffened steel column head protection device as described in claim 1, characterized in that: The flange protection sliding member (3) is a U-shaped galvanized steel plate. The two ends of the opening of the U-shape of the flange protection sliding member (3) are provided with second flanging ribs (31).

5. An adjustable stiffened steel column head protection device as described in claim 4, characterized in that: The first flanging ribs (21) and the second flanging ribs (31) are both S-shaped. The web protection fixing member (1), the web protection sliding member (2) and the flange protection sliding member (3) are all rolled by a specific mold.

6. The adjustable stiffened steel column head protection device as described in claim 5, characterized in that: The second flanging rib (31) is clamped in the second U-shaped chute (22), and the first flanging rib (21) is clamped in the first U-shaped chute (11).

7. The adjustable stiffened steel column head protection device as described in claim 2, characterized in that: The inner side walls of the first U-shaped chute (11) and the second U-shaped chute (22) are provided with anti-slip patterns (12).

8. An adjustable stiffened steel column head protection device as described in claim 6, characterized in that: An elastic sealing pad is pasted at the joint where the second flanging rib (31) fits with the second U-shaped chute (22), and an elastic sealing pad is pasted at the joint where the first flanging rib (21) fits with the first U-shaped chute (11).

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