Cabin cover ventilation opening protection mechanism

Abstract

The invention discloses a cabin cover ventilation opening protection mechanism, and relates to the technical field of wind driven generators. Comprising an internal protection assembly and a positioning assembly fixedly connected to the outer side of a cabin cover ventilation opening, the positioning assembly comprises a fixing ring, a wind scooper is fixedly connected to the outer wall of the fixing ring, a gear ring is rotationally connected to the inner wall of the wind scooper, and a driving assembly used for driving the gear ring is arranged in the wind scooper; a pre-tightening assembly is arranged on the inner side wall of the gear ring, and the internal protection assembly is connected with the positioning assembly through the pre-tightening assembly. A servo motor in the driving assembly is used for driving a gear ring to rotate, the position of a ventilation opening in the outer protective cover is changed continuously, the ventilation efficiency is improved, a backflow bin formed by a flow guide plate and a backflow plate is used, when external airflow enters the backflow bin, high pressure is formed in the backflow bin, and particulate pollutants such as dust are thrown out from through holes in the backflow plate; and external pollutants entering the cabin are greatly reduced, and the protection performance of the protection mechanism is enhanced.

Description

Technical Field

[0001] This invention belongs to the field of wind turbine technology, and in particular relates to a nacelle hood ventilation opening protection mechanism. Background Technology

[0002] In modern industrial equipment and transportation vehicles, the engine compartment cover is a key component protecting the core internal equipment. The protective performance of its ventilation openings directly affects the operational stability and service life of the equipment. During operation, the equipment inside the engine compartment generates a large amount of heat, which needs to be dissipated in a timely manner through the ventilation openings. At the same time, it is also necessary to prevent external debris, flying insects, birds, animals, and dust particles from entering the engine compartment to avoid damaging the equipment or affecting its normal operation. Currently, the ventilation angles of commonly available engine hood vent protection mechanisms are relatively fixed, making it difficult to meet the ventilation needs under different operating conditions. This affects the heat dissipation of the engine hood, thereby reducing equipment performance and reliability. Furthermore, existing protection mechanisms often rely on a single protective method, such as a simple filter, which has limited ability to block flying insects and animals, failing to effectively prevent them from entering the engine hood and damaging cables, resulting in poor safety. They also do not filter particulate pollutants such as dust thoroughly enough, leading to a large accumulation of dust inside the engine hood over time, affecting the normal operation of the equipment. In addition, the connection methods of traditional protection mechanisms are not robust enough. Under the vibration generated during equipment operation, the connections are prone to loosening, which not only reduces the service life of the protection mechanism but may also cause safety hazards, requiring frequent maintenance and replacement, increasing operating costs. Therefore, a new engine hood vent protection mechanism is proposed. Summary of the Invention

[0003] The purpose of this invention is to address the existing problems by providing a cabin hood ventilation port protection mechanism, thus solving the technical issues.

[0004] The present invention is achieved through the following technical solution: a cabin hood ventilation port protection mechanism, comprising an internal protection component and a positioning component fixedly connected to the outside of the cabin hood ventilation port, the positioning component comprising a positioning ring, a fixing ring fixedly connected to the outer wall of the positioning ring, an air guide shroud fixedly connected to the outer wall of the fixing ring, a toothed ring rotatably connected to the inner wall of the air guide shroud, a driving component for driving the toothed ring being provided inside the air guide shroud, a pre-tightening component being provided on the inner side wall of the toothed ring, and the internal protection component and the positioning component being connected through the pre-tightening component; The internal protective assembly includes an inner protective cover, with circular openings at both the left and right ends. A guide plate is fixedly connected to the inner wall of the inner protective cover, and a return plate is rotatably connected to the inner wall of the inner protective cover. A return chamber is formed between the guide plate and the return plate, and several through holes are provided on the return plate.

[0005] Preferably, the pre-tightening assembly includes a first fixing block and a second fixing block. The first fixing block is fixedly connected to the inner wall of the toothed ring, and the second fixing block is fixedly connected to the outer wall of the return plate. The inner wall of the second fixing block has a threaded hole, and the inner wall of the first fixing block has a fastening bolt inserted into it. The outer wall of the fastening bolt is threadedly connected to the inner wall of the threaded hole.

[0006] Preferably, a compression spring is fixedly connected to the outer wall of the fixing block one near the fixing block two, and a limit ring is fixedly connected to the end of the compression spring away from the fixing block one. A limit groove is formed on the outer wall of the fixing block two, and the outer wall of the limit ring abuts against the inner wall of the limit groove.

[0007] Preferably, an outer protective cover is fixedly connected to the outer wall of the toothed ring, a rotating ring is fixedly connected to the outer wall of the outer protective cover, a ball is rotatably connected to the inner wall of the rotating ring, and an annular groove is formed on the inner wall of the air guide cover, with the ball rollingly connected to the inner wall of the annular groove.

[0008] Preferably, the outer protective cover has several ventilation openings, and the inner wall of the outer protective cover is fixedly connected to an electric grid.

[0009] Preferably, the drive assembly includes a servo motor, which is fixedly connected to the inner wall of the air guide shroud. The output end of the servo motor is fixedly connected to a rotating shaft, and the outer wall of the rotating shaft is fixedly connected to a drive gear, which meshes with a gear ring.

[0010] Preferably, a filter screen is fixedly connected to the inner wall of the inner protective cover, and the filter screen is located inside the guide plate.

[0011] Preferably, the outer wall of the inner protective cover is fixedly connected with a plurality of positioning blocks, and each positioning block is fixedly connected with an anti-slip rubber pad.

[0012] Preferably, the outer wall of the positioning ring is symmetrically connected with ear plates, and the ear plates are provided with a plurality of through holes. Each through hole has a screw inserted into its inner wall, and the positioning ring is fixedly connected to the cabin cover by the screws.

[0013] Preferably, the air guide cover has a streamlined structure.

[0014] The present invention has the following advantages over the prior art: 1. This invention provides a nacelle vent protection mechanism. The air guide cover of this protection mechanism has a streamlined structure, which allows external airflow to enter the nacelle more smoothly. At the same time, the servo motor in the drive assembly drives the gear ring to rotate, so that the vents on the outer protective cover continuously change position, improving ventilation efficiency. The return chamber formed by the guide plate and the return plate creates high pressure when external airflow enters, which throws dust and other particulate pollutants out through the through holes on the return plate, greatly reducing the amount of external pollutants entering the nacelle, improving the cleanliness of the nacelle vent, and enhancing the protective performance of the protection mechanism.

[0015] 2. This invention provides a cabin vent protection mechanism with multiple protective measures. The electric grid fixedly connected to the inner wall of the outer protective cover is energized during normal operation, effectively knocking down flying insects and animals passing through the vents and preventing them from entering the cabin and damaging cables, thus ensuring the safe operation of cabin equipment. The filter screen inside the inner protective cover filters the inhaled airflow, further improving the protective effect of this mechanism.

[0016] 3. This invention provides a nacelle canopy ventilation vent protection mechanism. The pre-tightening component design makes the connection between the internal protective component and the positioning component more stable and reliable. Fixing block one and fixing block two are connected by fastening bolts, while a compression spring provides pre-tightening force. A limiting ring and a limiting groove cooperate to prevent misalignment. During installation and use, the elastic deformation of the compression spring can be used for buffering, effectively coping with vibrations and preventing loosening due to vibration. This greatly improves the durability and stability of the protective mechanism and extends its service life. Furthermore, the positioning blocks and anti-slip pads on the outer wall of the inner protective cover improve the fit and sealing between the inner protective cover and the inner wall of the nacelle canopy, further enhancing installation stability. Attached Figure Description

[0017] Figure 1 This is a schematic diagram of the overall structure of the present invention; Figure 2 This is a schematic diagram of the overall structure of the present invention from another angle; Figure 3 This is a schematic diagram of the cross-sectional structure of the nacelle canopy of the present invention; Figure 4 This is a schematic diagram of the toothed ring structure of the present invention; Figure 5 This is a schematic diagram of the cross-sectional structure of the inner cylinder of the present invention; Figure 6 This is a schematic diagram of the protective cover structure of the present invention; Figure 7 This is a schematic diagram of the structure of the motor in this invention; Figure 8 This is a schematic diagram of the overall structure of the protective mechanism of the present invention; Figure 9 For the present invention Figure 4 Enlarged view of point A in the middle; Figure 10 This is a schematic diagram of the toothed ring structure of the present invention; Figure 11 This is a schematic diagram of the structure of the outer protective cover of the present invention.

[0018] In the diagram: 1. Positioning assembly; 101. Positioning ring; 102. Fixing ring; 103. Ear plate; 104. Screw; 2. Internal protection assembly; 201. Inner protective cover; 202. Flow guide plate; 203. Return plate; 204. Return chamber; 205. Through hole; 3. Pre-tightening assembly; 301. Fixing block one; 302. Compression spring; 303. Limiting ring; 304. Fixing block two; 305. Threaded hole; 306. Limiting groove; 307. Fastening bolt; 4. Filter screen; 5. Positioning block; 6. Anti-slip pad; 7. Gear ring; 8. Drive assembly; 801. Servo motor; 802. Rotating shaft; 803. Drive gear; 9. Outer protective cover; 10. Ventilation port; 11. Electric grid; 12. Air guide cover; 13. Rotating ring; 14. Ball bearing. Detailed Implementation

[0019] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0020] Example 1: Please see Figure 1-11 As shown, the present invention provides a technical solution: a cabin vent protection mechanism, including an internal protection component 2 and a positioning component 1 fixedly connected to the outside of the cabin vent. The positioning component 1 includes a positioning ring 101, and ear plates 103 are symmetrically connected to the outer wall of the positioning ring 101. Several through holes are opened on the ear plates 103, and screws 104 are inserted into the inner wall of each through hole. The positioning ring 101 is fixedly connected to the cabin vent by screws 104. A fixing ring 102 is fixedly connected to the outer wall of the positioning ring 101. An air guide shroud 12 is fixedly connected to the outer wall of the fixing ring 102. A toothed ring 7 is rotatably connected to the inner wall of the air guide shroud 12. A driving component 8 for driving the toothed ring 7 is provided inside the air guide shroud 12. A pre-tightening component 3 is provided on the inner side wall of the toothed ring 7. The internal protection component 2 and the positioning component 1 are connected through the pre-tightening component 3. The internal protective assembly 2 includes an inner protective cover 201. Circular openings are provided at both ends of the inner protective cover 201. A guide plate 202 is fixedly connected to the inner wall of the inner protective cover 201, and a return plate 203 is rotatably connected to the inner wall of the inner protective cover 201. A return chamber 204 is formed between the guide plate 202 and the return plate 203. Several through holes 205 are provided on the return plate 203. In use, the positioning ring 101 in the positioning assembly 1 is first fixed to the outside of the cabin hood ventilation opening with screws 104. After fixing, the fixing ring 102, the air guide cover 12 and other components are also fixed. Then, the return plate 203 in the internal protective assembly 2 is connected to the toothed ring 7 with the fastening bolt 307 in the pre-tightening assembly 3, so that the inner protective cover 201 is installed inside the ventilation opening 10. During installation, first align the second fixing block 304 on the return plate 203 with the first fixing block 301 on the inner side of the gear ring 7, and then tighten the fastening bolt 307 so that the return plate 203 is connected to the gear ring 7 through the fastening bolt 307. When the cabin cover is running, start the servo motor 801 to drive the rotating shaft 802 to rotate. When the rotating shaft 802 rotates, it drives the drive gear 803 to rotate, thereby driving the gear ring 7 to rotate under the action of the drive gear 803. When the gear ring 7 rotates, it drives the return plate 203 to rotate at high speed inside the inner protective cover 201, which accelerates the airflow speed inside the inner protective cover 201. Both the deflector plate 202 and the return plate 203 adopt a streamlined structure design. When the external airflow enters the vent 10 through the air guide shroud 12, the deflector plate 202 guides part of the airflow into the return chamber 204 between it and the return plate 203. As the airflow continues to converge, high pressure is gradually formed in the return chamber 204. Dust and other particulate pollutants drawn into the return chamber 204 from the vent 10 are thrown out through the through hole 205 on the return plate 203, reducing the entry of external dust and other particulate pollutants into the cabin, improving the cleanliness of the cabin shroud and enhancing the protective effect of this protective component.

[0021] An outer protective cover 9 is fixedly connected to the outer wall of the toothed ring 7. Several ventilation openings 10 are provided on the outer protective cover 9. A rotating ring 13 is fixedly connected to the outer wall of the outer protective cover 9. A ball bearing 14 is rotatably connected to the inner wall of the rotating ring 13. An annular groove is provided on the inner wall of the air guide cover 12. The ball bearing 14 is rotatably connected to the inner wall of the annular groove. The air guide cover 12 has a streamlined structure. The width of the upper part of the air guide cover 12 is greater than the width of its lower part, which effectively ensures that the airflow can be evenly distributed at the ventilation openings 10. The rotating ring 13 on the outer wall of the outer protective cover 9 rolls in the annular groove on the inner wall of the air guide cover 12 through the ball bearing 14, ensuring that the outer protective cover 9 rotates smoothly. The drive assembly 8 includes a servo motor 801, which is fixedly connected to the inner wall of the air guide shroud 12. The output end of the servo motor 801 is fixedly connected to a rotating shaft 802, and the outer wall of the rotating shaft 802 is fixedly connected to a drive gear 803, which meshes with the gear ring 7. When the wind turbine is running, the outside airflow enters the vent of the nacelle through the air guide shroud 12. The air guide shroud 12 has a streamlined structure and the upper width is wider than the lower width, which allows the airflow to be evenly distributed at the vent 10, reducing the pressure drop and ensuring that the airflow enters the nacelle smoothly. Then, the servo motor 801 is started, and its output shaft 802 drives the drive gear 803 to rotate. Since the drive gear 803 is meshed with the gear ring 7, it drives the gear ring 7 to rotate on the inner wall of the air guide shroud 12. When the gear ring 7 rotates, it drives the outer protective cover 9, which is fixedly connected to its outer wall, to rotate. The vent 10 on the outer protective cover 9 continuously changes position to achieve multi-angle ventilation and improve ventilation efficiency.

[0022] An electric grid 11 is fixedly connected to the inner wall of the outer protective cover 9. When the protective mechanism is in normal operation, the electric grid 11 on the inner wall of the outer protective cover 9 is energized. When flying insects, birds and animals fly over the ventilation opening 10, they can be knocked down by the electric grid 11, preventing them from flying into the cabin and gnawing on the cables, thus improving the protective effect of the protective mechanism and the safety of the cabin cover.

[0023] A filter screen 4 is fixedly connected to the inner wall of the inner protective cover 201. The filter screen 4 is located inside the guide plate 202. The airflow drawn into the inner protective cover 201 can be further filtered through the filter screen, which can fully improve the dust reduction effect.

[0024] Example 2: Please see Figure 1-10 As shown, based on Embodiment 1, the present invention provides a technical solution: the pre-tightening component 3 includes a first fixing block 301 and a second fixing block 304. The first fixing block 301 is fixedly connected to the inner wall of the toothed ring 7, and the second fixing block 304 is fixedly connected to the outer wall of the return plate 203. The inner wall of the second fixing block 304 is provided with a threaded hole 305. A fastening bolt 307 is inserted into the inner wall of the first fixing block 301, and the outer wall of the fastening bolt 307 is threadedly connected to the inner wall of the threaded hole 305.

[0025] A compression spring 302 is fixedly connected to the outer wall of the fixing block 301 near the fixing block 304. A limit ring 303 is fixedly connected to the end of the compression spring 302 away from the fixing block 301. A limit groove 306 is formed on the outer wall of the fixing block 304, and the outer wall of the limit ring 303 abuts against the inner wall of the limit groove 306. When installing the pre-tightening assembly 3, first align the fixing block 301 and the fixing block 304, then pass the fastening bolt 307 through the inner wall of the fixing block 301 and thread it into the threaded hole 305 on the inner wall of the fixing block 304. During connection, the bolt is used to tighten the bolt. The compression spring 302 and the limiting ring 303 on the first fixing block 301 provide preload force between the first fixing block 301 and the second fixing block 304. That is, during installation, the compression spring 302 is in a compressed state, and the limiting ring 303 is pressed against the limiting groove 306, making the connection more secure and preventing misalignment of the first fixing block 301 and the second fixing block 304 during installation and use. The elastic deformation of the compression spring 302 itself is used for buffering, ensuring the stable connection between the internal protective component 2 and the positioning component 1, avoiding loosening of the connection due to vibration, and improving the durability of the protective mechanism.

[0026] Several positioning blocks 5 are fixedly connected to the outer wall of the inner protective cover 201. Each positioning block 5 is fixedly connected to an anti-slip pad 6, which is made of rubber. Under the action of the fastening bolts 307, the inner protective cover 201 and the toothed ring 7 always maintain a certain tension, so that the positioning blocks 5 are close to the inner wall of the cabin cover. Under the action of the anti-slip pads 6, not only is the fit between the inner protective cover 201 and the inner wall of the cabin cover improved, and the sealing performance of the protective mechanism to the cabin cover ventilation opening is improved, but the installation stability of the inner protective cover 201 is also enhanced.

[0027] Working principle: In use, first, fix the positioning ring 101 in the positioning assembly 1 to the outside of the hood ventilation opening with screws 104. After fixing, the fixing ring 102, air guide shroud 12 and other components are also fixed. Next, connect the return plate 203 in the internal protection assembly 2 to the toothed ring 7 with the fastening bolts 307 in the pre-tightening assembly 3, so that the inner protective cover 201 is installed inside the ventilation opening. Then, align the second fixing block 304 on the return plate 203 with the first fixing block 301 on the inside of the toothed ring 7, and then tighten the fastening bolts 307 to allow the return plate 203 to pass through. The gear ring 7 is connected to the fastening bolt 307. When the nacelle cover is running, the servo motor 801 is started to drive the rotating shaft 802 to rotate. When the rotating shaft 802 rotates, it drives the drive gear 803 to rotate, thereby driving the gear ring 7 to rotate under the action of the drive gear 803. When the gear ring 7 rotates, it drives the return plate 203 to rotate at high speed inside the inner protective cover 201, which accelerates the airflow speed inside the inner protective cover 201. Both the guide plate 202 and the return plate 203 adopt a streamlined structure design. When the external airflow enters the ventilation opening 10 through the air guide cover 12, the guide plate... 202 directs a portion of the airflow into the return chamber 204 between itself and the return plate 203. As the airflow continues to converge, high pressure gradually forms inside the return chamber 204, causing dust and other particulate pollutants drawn into the return chamber 204 from the vent 10 to be ejected through the through holes 205 on the return plate 203. This reduces the entry of external dust and other particulate pollutants into the nacelle, improving the cleanliness of the nacelle enclosure and enhancing the protective effect of the protective components. When the wind turbine is running, external airflow enters the vent of the nacelle enclosure through the air guide shroud 12, which has a streamlined structure. Furthermore, the upper width is greater than the lower width, which allows the airflow to be evenly distributed at the vent 10, reducing the pressure drop and ensuring that the airflow enters the cabin smoothly. Then, the servo motor 801 is started, which causes the rotating shaft 802 at its output end to drive the drive gear 803 to rotate. Since the drive gear 803 is meshed with the gear ring 7, it drives the gear ring 7 to rotate on the inner wall of the air guide shroud 12. When the gear ring 7 rotates, it drives the outer protective cover 9, which is fixedly connected to its outer wall, to rotate. The vent 10 on the outer protective cover 9 continuously changes position to achieve multi-angle ventilation and improve ventilation efficiency. When the protective mechanism is in normal operation, the electric grid 11 on the inner wall of the outer protective cover 9 is energized. When flying insects, birds and animals fly over the ventilation opening 10, they can be knocked down by the electric grid 11, preventing them from flying into the cabin and gnawing on the cables, thus improving the protective effect of the protective mechanism and the safety of the cabin cover.

[0028] It should be noted that, in this document, relational terms such as "first" and "second" are used merely to distinguish one entity or operation from another, and do not necessarily require or imply any such actual relationship or order between these entities or operations. Furthermore, the terms "comprising," "including," or any other variations thereof are intended to cover non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such a process, method, article, or apparatus. Without further limitations, the phrase "comprising an element defined as..." does not exclude the presence of other identical elements in the process, method, article, or apparatus that includes said element.

[0029] Although embodiments of the invention have been shown and described, it will be understood by those skilled in the art that various changes, modifications, substitutions and alterations can be made to these embodiments without departing from the principles and spirit of the invention, the scope of which is defined by the appended claims and their equivalents.

Claims

1. A cabin canopy ventilation opening protection mechanism, comprising an internal protection component (2) and a positioning component (1) fixedly connected to the outside of the cabin canopy ventilation opening, characterized in that: The positioning component (1) includes a positioning ring (101), a fixing ring (102) is fixedly connected to the outer wall of the positioning ring (101), a wind guide shroud (12) is fixedly connected to the outer wall of the fixing ring (102), a toothed ring (7) is rotatably connected to the inner wall of the wind guide shroud (12), a driving component (8) for driving the toothed ring (7) is provided inside the wind guide shroud (12), a pre-tightening component (3) is provided on the inner side wall of the toothed ring (7), and the internal protection component (2) is connected to the positioning component (1) through the pre-tightening component (3). The internal protective component (2) includes an inner protective cover (201), with circular openings at both the left and right ends of the inner protective cover (201). A guide plate (202) is fixedly connected to the inner wall of the inner protective cover (201), and a return plate (203) is rotatably connected to the inner wall of the inner protective cover (201). A return chamber (204) is formed between the guide plate (202) and the return plate (203), and a plurality of through holes (205) are provided on the return plate (203).

2. The cabin vent protection mechanism according to claim 1, characterized in that: The pre-tightening assembly (3) includes a first fixing block (301) and a second fixing block (304). The first fixing block (301) is fixedly connected to the inner wall of the toothed ring (7), and the second fixing block (304) is fixedly connected to the outer wall of the return plate (203). The inner wall of the second fixing block (304) is provided with a threaded hole (305). The inner wall of the first fixing block (301) is inserted with a fastening bolt (307), and the outer wall of the fastening bolt (307) is threadedly connected to the inner wall of the threaded hole (305).

3. The cabin hood ventilation opening protection mechanism according to claim 2, characterized in that: A compression spring (302) is fixedly connected to the outer wall of the fixed block one (301) near the fixed block two (304). A limiting ring (303) is fixedly connected to the end of the compression spring (302) away from the fixed block one (301). A limiting groove (306) is opened on the outer wall of the fixed block two (304). The outer wall of the limiting ring (303) abuts against the inner wall of the limiting groove (306).

4. The cabin hood ventilation opening protection mechanism according to claim 1, characterized in that: The outer wall of the toothed ring (7) is fixedly connected to an outer protective cover (9), the outer wall of the outer protective cover (9) is fixedly connected to a rotating ring (13), the inner wall of the rotating ring (13) is rotatably connected to a ball (14), the inner wall of the air guide cover (12) is provided with an annular groove, and the ball (14) is rotatably connected to the inner wall of the annular groove.

5. The cabin hood ventilation opening protection mechanism according to claim 4, characterized in that: The outer protective cover (9) has several ventilation openings (10), and the inner wall of the outer protective cover (9) is fixedly connected to an electric grid (11).

6. The cabin hood ventilation opening protection mechanism according to claim 1, characterized in that: The drive assembly (8) includes a servo motor (801), which is fixedly connected to the inner wall of the air guide shroud (12). The output end of the servo motor (801) is fixedly connected to a rotating shaft (802), and the outer wall of the rotating shaft (802) is fixedly connected to a drive gear (803). The drive gear (803) meshes with a gear ring (7).

7. The cabin vent protection mechanism according to claim 1, characterized in that: The inner wall of the inner protective cover (201) is fixedly connected with a filter screen (4), which is located inside the guide plate (202).

8. The cabin hood ventilation opening protection mechanism according to claim 1, characterized in that: The outer wall of the inner protective cover (201) is fixedly connected with a number of positioning blocks (5), and each positioning block (5) is fixedly connected with an anti-slip rubber pad (6).

9. The cabin vent protection mechanism according to claim 1, characterized in that: The outer wall of the positioning ring (101) is symmetrically connected with ear plates (103). The ear plates (103) have several through holes, and each through hole has a screw (104) inserted into its inner wall. The positioning ring (101) is fixedly connected to the cabin cover by the screws (104).

10. A cabin hood ventilation opening protection mechanism according to claim 1, characterized in that: The air guide cover (12) has a streamlined structure.

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