Multi-cavity hollow subway top plate with ventilation and smoke exhaust functions

Abstract

The invention discloses a multi-cavity hollow subway roof with ventilation and smoke exhaust functions, and relates to the technical field of subway construction.The multi-cavity hollow subway roof comprises a hollow roof body, partition plates are fixedly mounted on the two sides of the interior of the hollow roof body, and the two partition plates divide the interior space of the hollow roof body into a smoke exhaust cavity and two ventilation cavities; the smoke discharging cavity is arranged between the two ventilation cavities, multiple sets of smoke discharging mechanisms are arranged in the smoke discharging cavity, and ventilation mechanisms are arranged in the ventilation cavities. The top plate is arranged to be hollow, the ventilation mechanism and the smoke discharging mechanism are arranged in the top plate, the ventilation mechanism can be used for daily ventilation, and when a large amount of smoke occurs in an emergency, the smoke discharging mechanism can be driven to be matched with the ventilation mechanism to rapidly discharge smoke, so that the ventilation and smoke discharging requirements of the hollow top plate can be met, and the smoke discharging effect is improved. And the internal space of the hollow top plate can be fully utilized, resources are saved, and matching of the subway top plate and the smoke exhaust system is more energy-saving and environment-friendly.

Description

Technical Field

[0001] The invention relates to the technical field of subway construction, and in particular to a multi-cavity hollow subway roof with both ventilation and smoke exhaust functions. Background Art

[0002] Subways are fast, high-capacity rail transit vehicles built in cities. Their construction and operation are also developing in a more efficient and environmentally friendly direction. Against this backdrop, the traditional subway roof design and smoke exhaust methods will expose significant limitations. Since traditional subway roofs are often solid structures, their smoke exhaust design usually arranges the smoke exhaust pipes independently under the roof or sets them in an independent pipe system. This separate design method easily leads to low utilization of the roof space. As an important structural component, the roof contains space resources that can be mined and utilized. The solid structure design will waste its internal space. At the same time, the independently set smoke exhaust pipes not only occupy additional building space, but also increase the overall design complexity, resulting in the need for separate construction of the smoke exhaust pipe system, which prolongs the construction period. This traditional roof design is not only inefficient in resource utilization, but also consumes a lot of manpower, material resources and time costs during the construction process. Summary of the invention

[0003] In view of the deficiencies of the prior art, the present invention provides a multi-cavity hollow subway roof with both ventilation and smoke exhaust functions, which solves the technical problems raised in the above-mentioned background technology.

[0004] In order to solve the above technical problems, the present invention provides the following technical solutions: a multi-cavity hollow subway roof with both ventilation and smoke exhaust functions, comprising a hollow roof, partition plates are fixedly installed on both sides of the interior of the hollow roof, and the two partition plates divide the interior space of the hollow roof into a smoke exhaust cavity and two ventilation cavities, the smoke exhaust cavity is arranged between the two ventilation cavities, and multiple groups of smoke exhaust mechanisms are arranged inside the smoke exhaust cavity, and a ventilation mechanism is arranged inside the ventilation cavity;

[0005] The smoke exhaust mechanism includes a smoke guide pipe inserted between two partition plates, both ends of the smoke guide pipe extend into two ventilation cavities respectively, and both ends of the smoke guide pipe are fixedly sleeved with guide seats, the partition plate is provided with a slide groove for the guide seat to slide, a pair of branch pipes are connected and installed at the bottom of the smoke guide pipe, a draft fan is installed at the lower end of the branch pipe, and a bracket is fixedly installed on the outside of the smoke guide pipe, and a driving member is provided on the bracket to drive the smoke guide pipe to slide along the slide groove.

[0006] Furthermore, the driving member includes a pair of rollers rotatably mounted on both ends of the bracket, and guide rails for the rollers to slide are fixedly mounted on the sides of the two partition plates.

[0007] Furthermore, a servo motor is fixedly installed at the bottom of the bracket, and the output end of the servo motor and the axis of one of the rollers are both fixedly connected to a synchronous wheel one through the bracket, and a synchronous wheel two is rotatably installed on one side of the top of the bracket, and a synchronous belt is commonly installed on the outside of the synchronous wheel two and the two synchronous wheels one, and the axis of the synchronous wheel two is fixedly connected to a gear one, and the axis of the other roller is fixedly connected to a gear two meshing with the gear one.

[0008] Furthermore, a limiting member for fixing the smoke guide pipe is provided inside the partition plate, and the limiting member includes a lifting plate sliding inside the partition plate, and a lifting groove for sliding the lifting plate is provided inside the partition plate, and at least four equidistantly distributed connecting springs are fixedly installed between the inner bottom wall of the lifting groove and the lifting plate, a plurality of equidistantly distributed clamping columns are fixedly installed on the top of the lifting plate, and a clamping groove matched with the clamping column is provided at the bottom of the guide seat.

[0009] Furthermore, electromagnets are fixedly installed on both sides of the lifting slot, and iron blocks are fixedly connected to both ends of the lifting plate.

[0010] Furthermore, a plurality of louver plates distributed at equal distances are fixedly mounted on the inner bottom wall of the smoke exhaust cavity.

[0011] Furthermore, the ventilation mechanism includes a plurality of exhaust fans fixedly mounted on the top wall of the ventilation cavity, the plurality of exhaust fans are arranged at equal intervals, and a plurality of air inlet fans are fixedly mounted on the inner bottom wall of the ventilation cavity and are distributed at equal intervals, and the air inlet fans and exhaust fans are arranged alternately.

[0012] Furthermore, support heads are provided at both upper and lower ends of the partition plate, reinforcement strips are fixedly installed at the four corners of the hollow top plate, a plurality of reinforcing ribs are fixedly installed between two of the reinforcement strips on the same side, and a pair of through-hoops are installed between the plurality of reinforcing ribs.

[0013] Furthermore, dustproof plates are movably mounted on both ends of the hollow top plate, and circular holes matching the exhaust fan are formed on the dustproof plates.

[0014] Furthermore, a cavity is provided in the hollow top plate, and the volume of the cavity accounts for 70%-85% of the total volume of the hollow top plate.

[0015] By means of the above technical solution, the present invention provides a multi-cavity hollow subway roof with both ventilation and smoke exhaust functions, which has at least the following beneficial effects:

[0016] 1. The present invention arranges the roof to be hollow and divides its internal space into a smoke exhaust chamber and two ventilation chambers. A ventilation mechanism and a smoke exhaust mechanism are respectively arranged in the ventilation chamber and the smoke exhaust chamber. The ventilation mechanism can be used for daily ventilation. When a large amount of smoke occurs in an emergency, the smoke exhaust mechanism can be driven to cooperate with the ventilation mechanism to quickly exhaust the smoke. This can not only meet the ventilation and smoke exhaust requirements of the hollow roof, but also make full use of the internal space of the hollow roof, save resources, and make the cooperation between the subway roof and the smoke exhaust system more energy-saving and environmentally friendly.

[0017] 2. The present invention provides a movable smoke guide pipe. When encountering a smoke event, the driving member can drive the smoke guide pipe to slide to the smoke generation location for targeted smoke exhaust. The induced draft fan inhales the smoke and discharges it to the ventilation cavity through the smoke guide pipe, and cooperates with the exhaust fan and the air intake fan in the ventilation cavity to quickly exhaust the smoke, thereby improving the smoke exhaust efficiency of the equipment.

[0018] 3. The present invention can ensure the stability of the top plate in a hollow state and optimize the overall support of the hollow top plate by arranging reinforcement strips, reinforcing ribs and through-hoops. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] The drawings described herein are used to provide a further understanding of the present application and constitute a part of the present application. The illustrative embodiments of the present application and their descriptions are used to explain the present application and do not constitute an improper limitation on the present application. In the drawings:

[0020] Figure 1 It is a schematic diagram of the overall structure of the present invention;

[0021] Figure 2 This is one of the schematic diagrams of the internal structure of the hollow top plate of the present invention;

[0022] Figure 3 This is the second schematic diagram of the internal structure of the hollow top plate of the present invention;

[0023] Figure 4 It is a schematic diagram of the smoke exhaust mechanism structure of the present invention;

[0024] Figure 5 It is a schematic diagram of the structure of the driving member of the present invention;

[0025] Figure 6 It is a schematic diagram of the smoke guide pipe structure of the present invention;

[0026] Figure 7 It is a schematic diagram of the structure of the position-limiting member of the present invention;

[0027] Figure 8 It is a schematic diagram of the reinforcing rib structure of the present invention.

[0028] In the figure:

[0029] 1. Hollow top plate; 101. Partition plate; 102. Smoke exhaust cavity; 103. Ventilation cavity; 104. Slide groove; 105. Reinforcement rib; 106. Through-hoop; 107. Reinforcement strip; 1011. Support head;

[0030] 2. Smoke exhaust mechanism; 201. Smoke guide pipe; 202. Guide seat; 203. Branch pipe; 204. Bracket; 205. Driving member; 2051. Roller; 2052. Guide rail; 2053. Servo motor; 2054. Synchronous wheel 1; 2055. Synchronous wheel 2; 2056. Synchronous belt; 2057. Gear 1; 2058. Gear 2; 206. induced draft fan; 207. Limiting member; 2071. Lifting plate; 2072. Lifting slot; 2073. Connecting spring; 2074. Clamping column; 2075. Clamping slot; 2076. Electromagnet; 2077. Iron block; 208. Shutter plate;

[0031] 3. Ventilation mechanism; 301. Exhaust fan; 302. Intake fan;

[0032] 4. Dustproof plate. DETAILED DESCRIPTION

[0033] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0034] Since traditional subway roofs are often solid structures, their smoke exhaust designs usually arrange the smoke exhaust ducts independently under the roof or set them in an independent duct system. This separate design method easily leads to low utilization of the roof space, which is not only inefficient in resource utilization, but also consumes a lot of manpower, material resources and time costs during the construction process.

[0035] To solve the above-mentioned defects in the construction of the subway roof, please refer to Figure 1-Figure 8The present invention provides a multi-cavity hollow subway roof with both ventilation and smoke exhaust functions, which can make use of the internal space of the roof and set the smoke exhaust system inside the roof, which not only saves space but also reduces construction costs. The subway roof is based on a hollow roof 1. A cavity is opened in the hollow roof 1. The volume of the cavity accounts for 70%-85% of the total volume of the hollow roof 1. Compared with the traditional solid roof, the hollow roof can greatly reduce the amount of material used and save resources. Partition plates 101 are fixedly installed on both sides of the interior of the hollow roof 1. The partition plates 101 are made of fireproof boards to improve the overall fire resistance of the hollow roof 1. The two partition plates 101 divide the internal space of the hollow roof 1 into a smoke exhaust chamber 102 and two ventilation chambers 103. The smoke exhaust chamber 102 is set between the two ventilation chambers 103. The smoke exhaust cavity 102 is provided with a plurality of smoke exhaust mechanisms 2, and the ventilation cavity 103 is provided with a ventilation mechanism 3; the traditional solid roof is set as a hollow roof 1, and the smoke exhaust mechanism 2 and the ventilation mechanism 3 are set in the hollow roof 1, and the ventilation mechanism 3 is used for daily ventilation. When a large amount of smoke occurs in an emergency, the smoke exhaust mechanism 2 can be driven to cooperate with the ventilation mechanism 3 to quickly exhaust the smoke, which can meet the ventilation and smoke exhaust requirements of the hollow roof 1, and make full use of the internal space of the hollow roof 1, save resources, and make the cooperation between the subway roof and the smoke exhaust system more energy-saving and environmentally friendly.

[0036] In order to achieve the smoke exhaust effect of the above-mentioned smoke exhaust mechanism 2, the smoke exhaust mechanism 2 is set as a smoke guide pipe 201 inserted between the two partition plates 101, the two ends of the smoke guide pipe 201 extend into the two ventilation chambers 103 respectively, and the two ends of the smoke guide pipe 201 are fixedly sleeved with guide seats 202, and the partition plate 101 is provided with a slide groove 104 for the guide seat 202 to slide. A pair of branch pipes 203 are connected and installed at the bottom of the smoke guide pipe 201, and a draft fan 206 is installed at the lower end of the branch pipe 203. A bracket 204 is also fixedly installed on the outside of the smoke guide pipe 201, and a driving member 205 is provided on the bracket 204 for driving the smoke guide pipe 201 to slide along the slide groove 104. When there is a large amount of smoke unexpectedly, the position of the smoke is received through an external smoke sensor, and then the driving component 205 is driven by the control center. The driving component 205 can drive multiple smoke guide pipes 201 to slide to the place where the smoke is generated, and then the induced draft fan 206 can be driven to draw the smoke into the branch pipe 203. The smoke enters the smoke guide pipe 201 along the branch pipe 203, and then is discharged from the smoke guide pipe 201 to the ventilation chambers 103 on both sides. At the same time, the ventilation mechanism 3 is driven for ventilation, which can quickly exhaust the smoke. Compared with the traditional fixed smoke exhaust system, this movable smoke exhaust mechanism 2 can absorb the smoke in a targeted manner at the place where the smoke is generated, with higher smoke exhaust efficiency, realizing green construction.

[0037] In order to achieve the effect that the above-mentioned driving member 205 drives the smoke guide tube 201 to slide, a pair of rollers 2051 are rotatably installed at the two ends of the bracket 204, and the sides of the two partition plates 101 are fixedly installed with guide rails 2052 for the rollers 2051 to slide. The rollers 2051 can rotate and roll along the guide rails 2052, thereby driving the smoke guide tube 201 to slide. A servo motor 2053 is fixedly installed at the bottom of the bracket 204. The output end of the servo motor 2053 and the axis of one of the rollers 2051 pass through the bracket 204 and are fixedly connected with a synchronous wheel 1 2054. A synchronous wheel 2055 is rotatably installed on one side of the top of the bracket 204. The synchronous wheel 2055 and the outer parts of the two synchronous wheels 1 2054 are jointly installed with a synchronous wheel 2053. The synchronous belt 2056 is provided, and the axis of the synchronous wheel 2055 is fixedly connected with the gear 1 2057, and the axis of the other roller 2051 is fixedly connected with the gear 2 2058 meshing with the gear 1 2057. The driving servo motor 2053 can drive one of the synchronous wheels 1 2054 to rotate. The synchronous wheel 1 2054 rotates through the synchronous belt 2056 to drive the other synchronous wheel 1 2054 and the synchronous wheel 2 2055 to rotate. The synchronous wheel 2 2055 drives the gear 2 2058 to rotate in the opposite direction through the gear 1 2057, thereby driving the two rollers 2051 to rotate in the opposite direction. The two rollers 2051 roll along the guide rail 2052 to realize the sliding of the smoke guide pipe 201, and the smoke guide pipe 201 can be slid to the smoke location for smoke exhaust.

[0038] During smoke exhaust, in order to prevent the smoke guide pipe 201 from automatically deviating, a limiting member 207 for fixing the smoke guide pipe 201 is provided inside the partition plate 101. The limiting member 207 includes a lifting plate 2071 that slides inside the partition plate 101. A lifting groove 2072 is provided inside the partition plate 101 for the lifting plate 2071 to slide. At least four equidistantly distributed connecting springs 2073 are fixedly installed between the inner bottom wall of the lifting groove 2072 and the lifting plate 2071. A plurality of equidistantly distributed clamping columns 2074 are fixedly installed on the top of the lifting plate 2071. A clamping groove 2075 adapted to the clamping column 2074 is provided at the bottom of the guide seat 202. Electromagnets 2076 are fixedly installed on both sides of the lifting groove 2072. Iron blocks 2077 are fixedly connected to both ends of the lifting plate 2071. In the initial state, the lifting plate 2071 is connected to the lifting plate 2071 by the connecting spring 2073. The elastic force pushes the card column 2074 upward, and the card column 2074 can enter the card slot 2075 to limit the sliding of the guide seat 202. When the position of the smoke guide pipe 201 needs to be adjusted, the electromagnet 2076 is energized. After the electromagnet 2076 is energized, a magnetic force is generated between it and the iron block 2077, which can attract the iron block 2077 to slide downward. At this time, the connecting spring 2073 is deformed, and the iron block 2077 drives the card column 2074 to slide out of the card slot 2075 through the lifting plate 2071. After the position of the smoke guide pipe 201 is adjusted, the power supply of the electromagnet 2076 is disconnected, the magnetic force disappears, and the lifting plate 2071 can be reset by the elastic force of the connecting spring 2073, driving the card column 2074 to re-enter the card slot 2075, limiting the guide seat 202, preventing the guide seat 202 from sliding automatically, and ensuring the stability of the smoke exhaust mechanism 2 as a whole in the smoke exhaust chamber 102.

[0039] Reference Figure 3 As shown, a plurality of louver plates 208 equidistantly distributed are fixedly mounted on the inner bottom wall of the smoke exhaust chamber 102 , and smoke can be absorbed by the induced draft fan 206 through the louver plates 208 .

[0040] In order to achieve the ventilation effect of the above-mentioned ventilation mechanism 3, the ventilation mechanism 3 is configured to be a plurality of exhaust fans 301 fixedly installed on the inner top wall of the ventilation cavity 103, the plurality of exhaust fans 301 are arranged at equal intervals, and the inner bottom wall of the ventilation cavity 103 is fixedly installed with a plurality of equally distributed air inlet fans 302, the air inlet fans 302 and the exhaust fans 301 are staggered, driving the air inlet fans 302 to suck air into the ventilation cavity 103, and then the air inlet fans 302 discharge the air to form a unidirectional airflow, thereby achieving the ventilation effect.

[0041] Although setting the top plate to be hollow can save the space occupied by the smoke exhaust mechanism 2 and the ventilation mechanism 3, the stability of the smoke exhaust mechanism 2 will be relatively poor compared with the traditional solid top plate. In order to solve this technical problem, support heads 1011 are provided at the upper and lower ends of the partition plate 101, and reinforcement strips 107 are fixedly installed at the four corners of the hollow top plate 1. A plurality of reinforcing ribs 105 are fixedly installed between the two reinforcement strips 107 on the same side, and a pair of through-hoops 106 are commonly installed between the plurality of reinforcement ribs 105. The support head 1011 is arranged in a trapezoidal shape, which can improve the supporting effect of the partition plate 101 on the hollow top plate 1, and the reinforcement strips 107 can reinforce the overall frame of the hollow top plate 1, and together with the reinforcing ribs 105 and the through-hoops 106, the stability of the hollow top plate 1 can be further improved.

[0042] In order to prevent foreign matter or rodents and insects from entering the hollow top plate 1, dustproof plates 4 are movably installed at both ends of the hollow top plate 1. The dustproof plates 4 are provided with circular holes that are compatible with the exhaust fan 301. While ensuring the ventilation and smoke exhaust effects of the hollow top plate 1, the internal space of the hollow top plate 1 is protected to ensure the safety of equipment use.

[0043] The control method of the present invention is automatic control through a controller. The control circuit of the controller can be implemented by simple programming by technicians in this field. The provision of power is also common knowledge in this field. The present invention is mainly used to protect mechanical devices, so the present invention will no longer explain the control method and circuit connection in detail.

[0044] It should be noted that, in this article, the terms "comprises", "includes" or any other variations thereof are intended to cover non-exclusive inclusion, so that a process, method, article or apparatus that includes a series of elements includes not only those elements, but also other elements not explicitly listed, or also includes elements inherent to such process, method, article or apparatus.

[0045] Although embodiments of the present invention have been shown and described, it will be appreciated by those skilled in the art that various changes, modifications, substitutions and variations may be made to the embodiments without departing from the principles and spirit of the present invention, and that the scope of the present invention is defined by the appended claims and their equivalents.

Claims

1. A multi-cavity hollow subway roof with both ventilation and smoke exhaust functions, comprising a hollow roof (1), characterized in that: Partition plates (101) are fixedly installed on both sides of the interior of the hollow top plate (1), and the two partition plates (101) divide the interior space of the hollow top plate (1) into a smoke exhaust chamber (102) and two ventilation chambers (103); the smoke exhaust chamber (102) is arranged between the two ventilation chambers (103), and a plurality of smoke exhaust mechanisms (2) are arranged inside the smoke exhaust chamber (102), and a ventilation mechanism (3) is arranged inside the ventilation chamber (103); The smoke exhaust mechanism (2) comprises a smoke guide pipe (201) inserted between two partition plates (101), the two ends of the smoke guide pipe (201) respectively extending into two ventilation chambers (103), and the two ends of the smoke guide pipe (201) are fixedly sleeved with guide seats (202), the partition plate (101) is provided with a slide groove (104) for the guide seat (202) to slide, a pair of branch pipes (203) are connected and installed at the bottom of the smoke guide pipe (201), and a draft fan (206) is installed at the lower end of the branch pipe (203), and a bracket (204) is also fixedly installed on the outside of the smoke guide pipe (201), and a driving member (205) is provided on the bracket (204) for driving the smoke guide pipe (201) to slide along the slide groove (104).

2. The multi-cavity hollow subway roof with ventilation and smoke exhaust functions according to claim 1 is characterized in that: The driving member (205) comprises a pair of rollers (2051) rotatably mounted on both ends of the bracket (204), and guide rails (2052) for the rollers (2051) to slide are fixedly mounted on the sides of the two partition plates (101).

3. The multi-cavity hollow subway roof with ventilation and smoke exhaust functions according to claim 2 is characterized in that: A servo motor (2053) is fixedly mounted on the bottom of the bracket (204); the output end of the servo motor (2053) and the axis of one of the rollers (2051) pass through the bracket (204) and are fixedly connected to a synchronous wheel 1 (2054); a synchronous wheel 2 (2055) is rotatably mounted on one side of the top of the bracket (204); a synchronous belt (2056) is commonly mounted on the outside of the synchronous wheel 2 (2055) and the two synchronous wheels 1 (2054); the axis of the synchronous wheel 2 (2055) is fixedly connected to a gear 1 (2057); and the axis of the other roller (2051) is fixedly connected to a gear 2 (2058) meshing with the gear 1 (2057).

4. The multi-cavity hollow subway roof with ventilation and smoke exhaust functions according to claim 1 is characterized in that: A limiting member (207) for fixing the smoke guide tube (201) is arranged inside the partition plate (101), and the limiting member (207) comprises a lifting plate (2071) sliding inside the partition plate (101); a lifting groove (2072) for the lifting plate (2071) to slide is provided inside the partition plate (101); at least four equidistantly distributed connecting springs (2073) are fixedly installed between the inner bottom wall of the lifting groove (2072) and the lifting plate (2071); a plurality of equidistantly distributed clamping columns (2074) are fixedly installed on the top of the lifting plate (2071); and a clamping groove (2075) adapted to the clamping column (2074) is provided at the bottom of the guide seat (202).

5. The multi-cavity hollow subway roof with ventilation and smoke exhaust functions according to claim 4 is characterized in that: Electromagnets (2076) are fixedly installed on both sides of the lifting groove (2072), and iron blocks (2077) are fixedly connected to both ends of the lifting plate (2071).

6. The multi-cavity hollow subway roof with ventilation and smoke exhaust functions according to claim 1 is characterized in that: A plurality of equidistantly distributed louver plates (208) are fixedly mounted on the inner bottom wall of the smoke exhaust chamber (102).

7. The multi-cavity hollow subway roof with ventilation and smoke exhaust functions according to claim 1 is characterized in that: The ventilation mechanism (3) comprises a plurality of exhaust fans (301) fixedly mounted on the inner top wall of the ventilation cavity (103), the plurality of exhaust fans (301) being arranged at equal intervals, and a plurality of air inlet fans (302) being fixedly mounted on the inner bottom wall of the ventilation cavity (103) and being distributed at equal intervals, the air inlet fans (302) and the exhaust fans (301) being arranged in an alternating manner.

8. The multi-cavity hollow subway roof with ventilation and smoke exhaust functions according to claim 1 is characterized in that: Support heads (1011) are provided at both upper and lower ends of the partition plate (101), reinforcement strips (107) are fixedly installed at the four corners of the hollow top plate (1), a plurality of reinforcing ribs (105) are fixedly installed between two of the reinforcement strips (107) on the same side, and a pair of through-hoops (106) are installed between the plurality of reinforcement strips (105).

9. The multi-cavity hollow subway roof with ventilation and smoke exhaust functions according to claim 1 is characterized in that: Dustproof plates (4) are movably mounted on both ends of the hollow top plate (1), and circular holes matching the exhaust fan (301) are provided on the dustproof plates (4).

10. The multi-cavity hollow subway roof with ventilation and smoke exhaust functions according to claim 1 is characterized in that: A cavity is provided in the hollow top plate (1), and the volume of the cavity accounts for 70% to 85% of the total volume of the hollow top plate (1).

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