Gas furnace end with sufficient combustion

Abstract

The utility model relates to the technical field of gas cookers, and provides a gas furnace end with sufficient combustion, which comprises a furnace end base, a gas mixing component, a deformation swirling flame component and a catalytic combustion component, a gas supply chamber is arranged in the furnace end base, a gas inlet is arranged at one end of the gas supply chamber, and a gas outlet is arranged at the other end of the gas supply chamber. An air reforming auxiliary cavity is formed in the inner wall of one side of the front end of the air inlet; the gas mixing component is arranged in the gas supply chamber and used for mixing gas and air entering the gas supply chamber in a grading mode, the gas mixing component comprises a primary mixing cavity, an intermediate rotational flow cavity and a final-stage pressure stabilizing cavity, and spiral flow deflectors are arranged in the primary mixing cavity, the intermediate rotational flow cavity and the final-stage pressure stabilizing cavity; the deformation swirling flame component is arranged above the gas supply chamber and is used for forming adjustable flames; and the catalytic combustion component is arranged above the deformation swirling flame component and is used for carrying out secondary catalytic combustion on the residual gas. The utility model provides a novel gas furnace end structure with sufficient combustion, which has the advantages of high practicability and good combustion effect.

Description

Technical Field

[0001] This utility model relates to the field of gas stove technology, and in particular to a gas burner head that ensures complete combustion. Background Technology

[0002] Most existing gas stoves use single-stage or two-stage gas supply combustion structures, which have problems such as uneven flame distribution, localized overheating, incomplete gas combustion, low energy efficiency, and excessive CO production. The incomplete combustion is particularly severe during high-heat cooking or in drafty environments, affecting safety and energy utilization.

[0003] For example, the prior art CN222527640U discloses a gas burner head that ensures complete combustion. Although the gas burner head can ensure the oxygen content in the combustion zone by isolating the wind disturbance through the windproof furnace frame, it ignores the problem of local areas that are too rich or too lean, resulting in incomplete combustion and reduced thermal efficiency.

[0004] In addition, the existing technology also has the following drawbacks:

[0005] 1. In environments with strong winds, low temperatures, and high humidity, common stove heads are easily blown out by the wind or backfire, affecting cooking stability and safety.

[0006] 2. Due to the single combustion mode, traditional burners are difficult to match with different cookware and heat requirements. The flame coverage is poor and the heat transfer is insufficient, especially at medium and high heat stages, resulting in energy waste.

[0007] 3. Conventional burner designs do not include exhaust gas treatment modules, resulting in large emissions of pollutants such as CO, unburned hydrocarbons, and NOx after combustion, which affects indoor air quality and may even pose a risk of poisoning.

[0008] 4. Most traditional burners still use a "straight-through air intake structure" without any air conditioning, and therefore cannot maintain a stable and efficient combustion state under complex climatic conditions.

[0009] This utility model was developed to address common problems in the field, such as insufficient mixing of gas and air, unstable flame that is prone to extinguishing or backfire, low energy efficiency, uneven heat distribution, serious exhaust pollution, and the inability to adjust the diameter of the gas outlet holes in the burner head during the combustion process. Utility Model Content

[0010] The purpose of this invention is to address the shortcomings of current methods by proposing a gas burner head that ensures complete combustion.

[0011] In order to overcome the shortcomings of the existing technology, the present invention adopts the following technical solution:

[0012] A fully combusting gas burner head includes a burner head base, and further includes a gas mixing component, a deformable swirling flame component, and a catalytic combustion component. The burner head base has a gas supply chamber inside, and one end of the gas supply chamber has an air inlet. An air reforming auxiliary chamber is provided on the inner wall of one side of the front end of the air inlet.

[0013] The gas mixing component is installed in the gas supply chamber and is used to perform staged mixing of the gas and air entering the gas supply chamber. The gas mixing component includes a primary mixing chamber, a secondary swirling chamber and a final pressure stabilizing chamber. Spiral guide vanes are provided in the primary mixing chamber, the secondary swirling chamber and the final pressure stabilizing chamber.

[0014] The deformable swirling flame component is disposed above the gas supply chamber to form an adjustable flame;

[0015] The catalytic combustion component is disposed above the deformable vortex component and is used for secondary catalytic combustion of residual gas.

[0016] Optionally, the deformable vortex component includes an annular nozzle platform, nozzles disposed on the annular nozzle platform, and an arc-shaped spring covering the nozzles, wherein the annular nozzle platform is fastened to the gas supply chamber.

[0017] The arc-shaped spring is made of a temperature-sensitive deformation alloy material and its shape changes dynamically according to the working temperature.

[0018] Optionally, the spiral guide vane is in the shape of a spiral fan blade and is fixed on the side wall of the primary mixing chamber, the intermediate swirling chamber and the final voltage stabilizing chamber, and the angle of the spiral guide vane increases progressively.

[0019] Optionally, the air reforming auxiliary chamber includes a gas separator and a set of high-temperature metal heat exchange plates. The set of high-temperature metal heat exchange plates is connected to the central chamber of the furnace head and conducts heat, and the gas separator discharges moisture.

[0020] Optionally, the temperature-sensitive deformation alloy of the arc-shaped spring is made of shape memory alloy NiTi.

[0021] Optionally, the catalytic combustion component includes a ceramic catalytic combustion layer and a heat insulation cover. The ceramic catalytic combustion layer is installed on the outer surface of the heat insulation cover, and the heat insulation cover is fixedly installed on the burner base and is provided with multiple honeycomb-shaped contact holes to enhance the contact area with the flame airflow.

[0022] Optionally, the coating of the ceramic catalytic combustion layer is a composite precious metal coating containing platinum or rhodium.

[0023] Optionally, the burner base is provided with a first connecting rib and a second connecting rib symmetrically at the front end away from the air inlet. The first connecting rib and the second rib are provided with a first contact end face and a second contact end face, and the first contact end face of the first connecting rib and the second contact end face of the second connecting rib are flush with each other.

[0024] Optionally, two adjacent curved springs may be made of different types of temperature-sensitive deformation alloys.

[0025] Optionally, the arc-shaped spring is made of two layers of metal sheets, with the upper layer being a shape memory alloy and the lower layer being elastic steel, and the shape memory alloy end of the upper layer and the elastic steel end of the lower layer are connected by rivets.

[0026] The beneficial effects achieved by this utility model are:

[0027] 1. Through the cooperation of the gas mixing component and the deformable vortex flame component, the gas and air are fully, graded and high-speed mixed before entering the combustion zone, and the nozzle opening is intelligently adjusted according to the flame temperature to form a stable and dynamically responsive flame output;

[0028] 2. By combining the deformable swirling flame component with the catalytic combustion component, the exhaust gas after flame combustion continuously enters the catalytic reaction zone for secondary flameless oxidation, further improving the integrity of combustion and the efficiency of thermal energy utilization. This ensures that the entire gas burner head has excellent performance in terms of complete combustion, stable flame, improved energy efficiency, and clean emissions, making it particularly suitable for application scenarios with high requirements for energy conservation, environmental protection, and intelligent firepower control.

[0029] 3. Through the cooperation of the gas mixing component, the deformable swirling flame component and the catalytic combustion component, the entire gas burner head is guaranteed to have comprehensive performance advantages such as complete combustion, high thermal efficiency, flame adaptive adjustment, low carbon and environmental protection, and safety and stability during operation;

[0030] 4. The flame is self-adjusted by the deformable swirling flame component, which can achieve self-adjustment and stable output of flame intensity without electronic control, and has significant advantages in energy saving and safety. Attached Figure Description

[0031] The present invention can be further understood from the following description taken in conjunction with the accompanying drawings. The components in the drawings are not necessarily drawn to scale, but rather the emphasis is on illustrating the principles of the embodiments. In different views, the same reference numerals designate the same parts.

[0032] Figure 1 This is a front view schematic diagram of the present utility model.

[0033] Figure 2 for Figure 1 Schematic diagram of cross-section at point AA.

[0034] Figure 3 This is a partial cross-sectional schematic diagram of the air reforming auxiliary cavity of this utility model.

[0035] Figure 4 This is a partial cross-sectional view of the interior of the gas supply chamber of this utility model.

[0036] Figure 5 This is a partial cross-sectional view of the annular nozzle platform of this utility model.

[0037] Figure 6 for Figure 5 Enlarged diagram of point B in the middle.

[0038] Figure 7 This is a top view of the present invention.

[0039] Figure 8 This is a schematic diagram of the side structure of this utility model.

[0040] Explanation of reference numerals in the attached drawings: 1. Furnace head base; 2. Air inlet; 3. Air supply chamber; 4. Outer annular air chamber; 5. First connecting rib; 6. Second connecting rib; 7. Second contact end face; 8. First contact end face; 9. Air inlet channel; 10. High-temperature metal heat exchange plate; 11. Connecting channel; 12. One-way drain hole; 13. Water collection tank; 14. Water overflow outlet; 15. Primary mixing chamber; 16. Final stage pressure stabilizing chamber; 17. Annular nozzle platform; 18. Nozzle; 19. Elastic steel; 20. Shape memory alloy; 21. Heat insulation cover; 22. Arc-shaped spring sheet; 23. Condensation guide wall; 24. Spiral guide vane; 24a. First-stage spiral guide vane; 24b. Second-stage spiral guide vane; 24c. Third-stage spiral guide vane. Detailed Implementation

[0041] The following specific embodiments illustrate the implementation of this utility model. Those skilled in the art can understand the advantages and effects of this utility model from the content disclosed in this specification. This utility model can be implemented or applied through other different specific embodiments, and various details in this specification can also be modified and changed based on different viewpoints and applications without departing from the spirit of this utility model. Furthermore, the accompanying drawings of this utility model are for simple illustrative purposes only and are not depictions of actual dimensions, as stated in advance. The following embodiments will further describe the relevant technical content of this utility model in detail, but the disclosed content is not intended to limit the scope of protection of this utility model.

[0042] according to Figure 1 , Figure 2 , Figure 3 , Figure 4 , Figure 5 , Figure 6 , Figure 7 , Figure 8As shown, this embodiment provides a gas burner head with complete combustion. The gas burner head with complete combustion includes a burner head base 1. The gas burner head with complete combustion also includes a gas mixing component, a deformable swirling flame component, and a catalytic combustion component. The burner head base 1 is provided with a gas supply chamber 3 inside. One end of the gas supply chamber 3 is provided with an air inlet 2. An air reforming auxiliary chamber is provided on the inner wall of one side of the front end of the air inlet 2.

[0043] The gas mixing component is disposed in the gas supply chamber 3 and is used to perform staged mixing of the gas and air entering the gas supply chamber 3. The gas mixing component includes a primary mixing chamber 15, a secondary swirling chamber and a final pressure stabilizing chamber 16. Spiral guide vanes 24 are provided in the primary mixing chamber 15, the secondary swirling chamber and the final pressure stabilizing chamber 16.

[0044] The deformable swirling flame component is disposed above the air supply chamber 3 to form an adjustable flame;

[0045] The catalytic combustion component is disposed above the deformable vortex component and is used for secondary catalytic combustion of residual gas.

[0046] Specifically, such as Figure 2 or Figure 4 As shown, in the primary mixing chamber 15 (with first-stage spiral guide vanes 24a), the inlet is slightly enlarged, introducing the combustion gas into initial contact with the air; in the intermediate swirling chamber (with second-stage spiral guide vanes 24b), the spiral guide vanes 24 change direction laterally or at a right angle, increasing the angle of the guide vanes 24 and forming a strong swirling flow; furthermore, in the final pressure stabilizing chamber 16 (with third-stage spiral guide vanes 24c), the density of the guide vanes 24 in the air supply chamber 3 decreases, and the airflow tends to be more balanced. Simultaneously, the outlet of the final pressure stabilizing chamber 16 is connected to 18 nozzles of the deformable swirling flame component.

[0047] In addition, the burner base 1 is also provided with an outer ring gas chamber 4, which is located on the outer periphery of the final stage pressure stabilizing chamber 16.

[0048] In this embodiment, the primary mixing chamber 15, the intermediate swirling chamber, and the final voltage-stabilizing chamber 16 are designed as coaxial cylindrical or L-shaped cavities. In this embodiment, an L-shaped cavity is preferred (e.g., Figure 2 and Figure 4 As shown in the shape of the intake chamber, the guide vanes 24 are sequentially installed on the inner wall of the chamber, and their inclination angle gradually increases along the airflow direction to achieve sequential disturbance and stable output.

[0049] Furthermore, the gas mixing component is composed of a primary mixing chamber 15, an intermediate swirling chamber, and a final pressure-stabilizing chamber 16 connected in series. Each of the three chambers is equipped with a spiral guide vane 24, forming a staged mixing channel. As air and fuel gas pass through each chamber, they rotate and mix layer by layer and are output under stable pressure, thereby improving mixing uniformity and enhancing flame stability and thermal efficiency.

[0050] The spiral guide vane 24 is in the shape of a spiral fan blade and is fixed on the side wall of the primary mixing chamber 15, the intermediate swirling chamber and the final voltage stabilizing chamber 16, and the angle of the spiral guide vane 24 increases progressively.

[0051] Optionally, the deformable vortex component includes an annular nozzle platform 17, a nozzle 18 disposed on the annular nozzle platform 17, and an arc-shaped spring sheet 22 covering the nozzle 18, wherein the annular nozzle platform 17 is fastened to the air supply chamber 3.

[0052] The arc-shaped spring 22 is made of a temperature-sensitive deformable alloy material and its shape changes dynamically according to the working temperature.

[0053] like Figure 4 As shown, the annular nozzle platform 17 is located at the end of the gas supply chamber outlet direction, so that the combustion position can be adjusted by the deformable swirling flame component to achieve self-adjustment and stable output of flame intensity.

[0054] Optionally, the two adjacent arc-shaped springs 22 may be made of different types of temperature-sensitive deformation alloys.

[0055] Optionally, the arc-shaped spring 22 is made of two layers of metal sheets, with the upper layer being a shape memory alloy 20 and the lower layer being an elastic steel 19, and one end of the upper shape memory alloy 20 and one end of the lower elastic steel 19 are connected by rivets.

[0056] In this embodiment, when the combustion temperature is low, the arc-shaped spring 22 is in a contracted or bent state, partially blocking the nozzle 18, forming a small, stable flame, improving combustion efficiency and suppressing backfire; when the temperature rises to a set threshold (e.g., above 300°C), the temperature-sensitive shape memory alloy 20 undergoes a phase change, the bent spring gradually flattens, the opening of the nozzle 18 increases, and the airflow and flame intensity are enhanced accordingly, meeting the requirements of high-heat cooking. By setting springs with different phase change temperatures, the nozzles in different areas can be opened sequentially, constructing an intelligent flame control capability with zoned response and progressively variable diameter.

[0057] If a composite structure of upper and lower layers (shape memory alloy 20 and elastic steel 19) is used and fixedly connected by rivets, it can automatically return to its original position after the temperature drops, avoiding the spring from remaining in the open state and ensuring dynamic responsiveness and structural life.

[0058] Overall, the deformable vortex flame component can achieve self-adjustment and stable output of flame intensity without electronic control, and has significant advantages in energy saving and safety.

[0059] The deformable vortex flame component forms an adaptive nozzle 18 structure that can dynamically adjust the flame intensity and shape according to temperature by setting an annular nozzle platform 17, nozzles 18 and a temperature-sensitive arc-shaped spring sheet 22 covering it.

[0060] Optionally, the temperature-sensitive deformation alloy of the arc-shaped spring 22 is made of shape memory alloy NiTi.

[0061] Optionally, the air reforming auxiliary chamber includes a gas separator and a set of high-temperature metal heat exchange plates 10. The set of high-temperature metal heat exchange plates 10 is connected to the central chamber of the furnace head and conducts heat, and discharges moisture through the gas separator.

[0062] In this embodiment, the gas burner head includes a gas supply chamber 3 disposed inside the burner head base 1, and one end of the gas supply chamber 3 is provided with an air inlet 2.

[0063] The air reforming auxiliary chamber is equipped with a high-temperature metal heat exchange plate 10 and a gas separator, which are used to preheat the incoming air and remove moisture.

[0064] Specifically, one end or part of the high-temperature metal heat exchanger 10 is attached to the metal shell corresponding to the central flame combustion zone of the furnace head, and the other end or part of the high-temperature metal heat exchanger 10 extends horizontally in the air reforming auxiliary chamber (e.g., Figure 3 (as shown), and performs moisture removal operation on the incoming air;

[0065] The metal casing has excellent thermal conductivity, allowing heat generated during combustion to be transferred from the flame zone to the surface of the heat exchange fins. Air comes into full contact with the heat exchange fins as it passes through the air reforming auxiliary chamber, achieving heating. The heated air is more prone to condensation or vaporization desorption, and the moisture in the air is subsequently effectively removed by gas separators (such as condenser walls and water collection tank 13).

[0066] like Figure 3 As shown, the gas separator includes an air inlet channel 9, a condensation guide wall 23 located at the cold end of the air channel, and a water collection tank 13. After the incoming air is preheated by the heat exchange plate, some water vapor condenses and collects along the condensation wall to the water collection tank 13, and is discharged from the one-way drain hole 12 at the bottom of the water collection tank 13.

[0067] The air intake channel 9 is located on the burner base 1 and communicates with the air reforming auxiliary chamber. For example... Figure 1 As shown, external air enters the air reforming auxiliary chamber through the air intake channel 9 (i.e., through...). Figure 1 Enter in the direction indicated by F.

[0068] The gas separator also includes a water overflow port 14, which is located on the bottom wall of the burner base 1 and communicates with the outside to allow condensed water vapor to be discharged. Figure 1 As shown, the condensed water is discharged from the overflow outlet under the action of gravity, and flows along the... Figure 1 The droplets fall in the direction indicated by E in the middle.

[0069] The dried air, after the above treatment, is then drawn into the outer annular gas chamber 4 through the connecting channel 11 under the negative pressure of the gas nozzle, and is fully mixed with the injected gas in the mixing component near the final pressure stabilizing chamber 16.

[0070] Unlike traditional methods that use natural air intake, this invention achieves dynamic preheating of the combustion air through structural heat conduction, increasing its heat content and reducing its moisture content. This not only improves combustion efficiency but also enhances flame stability and low-temperature ignition performance, making it particularly suitable for environments with high humidity, extreme cold, or strong ventilation disturbances.

[0071] By combining the gas mixing component with the deformable vortex flame component, the gas and air are fully, graded and mixed at high speed before entering the combustion zone, and the nozzle opening is intelligently adjusted according to the flame temperature to form a stable and dynamically responsive flame output.

[0072] Optionally, the catalytic combustion component includes a ceramic catalytic combustion layer and a heat insulation cover 21. The ceramic catalytic combustion layer is installed on the outer surface of the heat insulation cover 21. The heat insulation cover 21 is fixedly installed on the burner base 1 and is provided with multiple honeycomb-shaped contact holes to enhance the contact area with the flame airflow.

[0073] Optionally, the coating of the ceramic catalytic combustion layer is a composite precious metal coating containing platinum or rhodium.

[0074] During operation, the exhaust gas (containing CO, carbon monoxide, methane, etc.) emitted after high-temperature combustion flows through a honeycomb ceramic structure coated with precious metal catalysts (such as platinum, palladium, and rhodium), where it undergoes a low-temperature oxidation reaction with the catalyst surface. Within a temperature range of 250℃ to 500℃, the residual gas is converted into CO2 and H2O without open flame, releasing heat.

[0075] The tail flame conducts heat to the catalytic layer, where a stable temperature is maintained by the heat shield 21, enhancing the sustainability of the reaction. This catalytic combustion component effectively purifies emissions, improves thermal efficiency, and reduces the concentration of harmful gases, all without requiring additional energy input. It possesses highly efficient, environmentally friendly, and passively self-driven combustion optimization capabilities.

[0076] By combining the deformable swirling flame component with the catalytic combustion component, the exhaust gas after flame combustion continuously enters the catalytic reaction zone for secondary flameless oxidation, further improving combustion integrity and thermal energy utilization efficiency. This ensures that the entire gas burner head has excellent performance in terms of complete combustion, stable flame, improved energy efficiency, and clean emissions, making it particularly suitable for application scenarios with high requirements for energy conservation, environmental protection, and intelligent firepower control.

[0077] Optionally, the burner base 1 is symmetrically provided with a first connecting rib 5 and a second connecting rib 6 at the front end away from the air inlet 2. The first connecting rib 5 and the second rib are provided with a first contact end face 8 and a second contact end face 7, and the first contact end face 8 of the first connecting rib 5 and the second contact end face 7 of the second connecting rib 6 are flush with each other.

[0078] Among them, the two symmetrically arranged connecting ribs provide a clear mechanical positioning reference. During assembly, other modules (such as furnace panel, sealing shell, outer cover) only need to be aligned with its contact end face to achieve quick and accurate alignment and reduce manual adjustment errors.

[0079] In addition, the flush contact surfaces form a uniform pressure-bearing platform, which helps to create uniform force during subsequent screw fixing or snap-fit ​​connection, thereby improving the overall stability of the burner base 1 installation connection.

[0080] By cooperating with the gas mixing component, the deformable swirling flame component, and the catalytic combustion component, the entire gas burner head is guaranteed to have comprehensive performance advantages during operation, including complete combustion, high thermal efficiency, adaptive flame adjustment, low carbon emissions, environmental protection, safety, and stability.

[0081] The above-disclosed content is only a preferred and feasible embodiment of the present utility model, and is not intended to limit the protection scope of the present utility model. Therefore, all equivalent technical changes made based on the contents of the present utility model specification and drawings are included within the protection scope of the present utility model. Furthermore, the elements therein can be updated as technology develops.

Claims

1. A gas burner head for complete combustion, the gas burner head for complete combustion comprising a burner head base, characterized in that, The fully combusted gas burner head also includes a gas mixing component, a deformable swirling flame component, and a catalytic combustion component. The burner head base is provided with a gas supply chamber, and one end of the gas supply chamber is provided with an air inlet. An air reforming auxiliary chamber is provided on the inner wall of one side of the front end of the air inlet. The gas mixing component is installed in the gas supply chamber and is used to perform staged mixing of the gas and air entering the gas supply chamber. The gas mixing component includes a primary mixing chamber, a secondary swirling chamber and a final pressure stabilizing chamber. Spiral guide vanes are provided in the primary mixing chamber, the secondary swirling chamber and the final pressure stabilizing chamber. The deformable swirling flame component is disposed above the gas supply chamber to form an adjustable flame; The catalytic combustion component is disposed above the deformable vortex component and is used for secondary catalytic combustion of residual gas.

2. The gas burner head with complete combustion according to claim 1, characterized in that, The deformable vortex component includes an annular nozzle platform, nozzles disposed on the annular nozzle platform, and an arc-shaped spring sheet covering the nozzles, with the annular nozzle platform covering the gas supply chamber. The arc-shaped spring is made of a temperature-sensitive deformation alloy material and its shape changes dynamically according to the working temperature.

3. The gas burner head with complete combustion according to claim 1 or 2, characterized in that, The spiral guide vane is in the shape of a spiral fan blade and is fixed on the side wall of the primary mixing chamber, the intermediate swirling chamber and the final voltage stabilizing chamber, and the angle of the spiral guide vane increases progressively.

4. The gas burner head with complete combustion according to claim 3, characterized in that, The air reforming auxiliary chamber includes a gas separator and a set of high-temperature metal heat exchange plates. The set of high-temperature metal heat exchange plates is connected to the central chamber of the furnace head and conducts heat, and the gas separator discharges moisture.

5. The gas burner head with complete combustion according to claim 2, characterized in that, The temperature-sensitive deformation alloy of the arc-shaped spring is made of shape memory alloy NiTi.

6. The gas burner head with complete combustion according to claim 1 or 5, characterized in that, The catalytic combustion component includes a ceramic catalytic combustion layer and a heat insulation cover. The ceramic catalytic combustion layer is installed on the outer surface of the heat insulation cover, and the heat insulation cover is fixedly installed on the burner base and is provided with multiple honeycomb-shaped contact holes to enhance the contact area with the flame airflow.

7. The gas burner head with complete combustion according to claim 6, characterized in that, The coating of the ceramic catalytic combustion layer is a composite precious metal coating containing platinum or rhodium.

8. The gas burner head with complete combustion according to claim 1, characterized in that, The burner base is symmetrically provided with a first connecting rib and a second connecting rib at the front end away from the air inlet. The first connecting rib and the second rib are provided with a first contact end face and a second contact end face, and the first contact end face of the first connecting rib and the second contact end face of the second connecting rib are flush with each other.

9. The gas burner head with complete combustion according to claim 2, characterized in that, The two adjacent arc-shaped springs are made of different types of temperature-sensitive deformation alloys.

10. The gas burner head with complete combustion according to claim 9, characterized in that, The arc-shaped spring is made of two layers of metal sheets. The upper layer is a shape memory alloy and the lower layer is elastic steel. The shape memory alloy end of the upper layer and the elastic steel end of the lower layer are connected by rivets.

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