A switching valve for a regenerative oxidizer

Abstract

The present application relates to the technical field of sealing, in particular to a switching valve for a regenerative oxidizing furnace, which comprises an adjusting assembly, the adjusting assembly comprises two spring assemblies, when the upper valve plate and the lower valve plate are closed on the corresponding valve port, the two spring assemblies can drive the upper valve plate and the lower valve plate to adhere to the valve port respectively. In the application, the force of the spring assembly in the adjusting assembly can drive the upper valve plate and the lower valve plate to adhere to the valve port respectively, the sealing compensation between the upper valve plate, the lower valve plate and the valve port is automatically adjusted, and the sealing performance of the switching valve of the regenerative oxidizing furnace is ensured.

Description

Technical Field

[0001] This invention relates to the field of sealing technology, and more specifically to a switching valve for a regenerative oxidation furnace. Background Technology

[0002] The regenerative thermal oxidizer works by heating low-concentration methane gas to 800℃-950℃, causing the CH4 in the gas to oxidize and decompose into carbon dioxide and water. Part of the high-temperature gas produced during oxidation flows through a high-temperature flue at the top of the oxidation chamber to waste heat recovery equipment, while the other part flows to a ceramic regenerator, heating and storing heat. The regenerator, in its stored-heat state, is then used for subsequent intake of low-concentration methane gas. The regenerator can be divided into two or more chambers, each undergoing a sequential process of heat storage and release, repeating this cycle continuously to achieve self-sustaining and continuous operation.

[0003] In low-concentration gas utilization systems, a non-standard switching valve is required to ensure smooth switching between each regenerator chamber. Therefore, the switching valve is a key component for the cyclic heat exchange within the regenerator chamber, and it must switch accurately at specified times; its stability and reliability are paramount. However, most existing switching valves in low-concentration gas regenerable oxidizers employ hard seals that cannot be automatically balanced, leading to air leakage issues during prolonged operation. Summary of the Invention

[0004] (I) One of the technical problems to be solved by the present invention is that the switching valve of the existing regenerative oxidation furnace has the problem of air leakage due to air tightness.

[0005] (II) Technical Solution

[0006] To solve the above-mentioned technical problems, the present invention provides a switching valve for a regenerative oxidation furnace, comprising: a plurality of valve bodies, each valve body having a plurality of cavities for communicating with a connecting channel; and valve ports provided on each valve body communicating with the cavities, wherein adjacent valve ports are interconnected.

[0007] An upper movable plate assembly, the upper movable plate assembly including an upper valve plate, the upper valve plate being configured corresponding to the valve port;

[0008] The lower movable plate assembly includes a lower valve plate, which is connected to the upper valve plate, and the lower valve plate is configured to correspond to another valve port.

[0009] The valve stem is lifted, and the upper valve plate and the lower valve plate are respectively connected to the valve stem. The valve body can drive the upper valve plate and the lower valve plate to move, thereby covering or connecting the adjacent valve ports.

[0010] A fixing plate assembly, the fixing plate assembly including a fixing plate fixedly connected to the lifting valve stem, the fixing plate being located between the upper valve plate and the lower valve plate;

[0011] The adjustment assembly includes two spring assemblies. When the upper valve plate and the lower valve plate are closed to the corresponding valve ports, the two spring assemblies can respectively drive the upper valve plate and the lower valve plate to fit against the valve ports.

[0012] According to one embodiment of the present invention, the adjusting assembly further includes a limiting screw and a second nut. The limiting screw passes sequentially through the upper valve plate, the fixing plate, and the lower valve plate. The fixing plate is fixed to the limiting screw by a first fixing nut. The second nut includes an adjusting nut. Two spring assemblies are respectively sleeved on the limiting screw along the vertical direction of the limiting screw. One spring assembly is compressed between the upper valve plate and the adjusting nut, and the other spring assembly is compressed between the lower valve plate and the adjusting nut.

[0013] According to one embodiment of the present invention, the switching valve of the regenerative oxidizer further includes a valve stem guide assembly and a cylinder disposed on the valve body. Part of the valve stem guide assembly is located in the cavity. The valve stem guide assembly is provided with a guide space for the piston of the cylinder to pass through. The valve stem guide assembly and the piston are sealed together.

[0014] According to one embodiment of the present invention, each spring assembly includes a plurality of springs, and two spring assemblies include the same number of springs; the plurality of springs in each spring assembly are evenly distributed along the circumference of the fixing plate.

[0015] According to one embodiment of the present invention, the upper movable plate assembly further includes a first base, a first bushing, a first graphite disc, and a first pressure cap sleeved outside the lifting valve rod. The upper valve plate is fixedly connected to the first base, the first bushing is installed inside the base, the first pressure cap is connected to the first base by a first bolt, and the first graphite disc is installed between the bushing and the pressure cap. The first pressure cap is pressed by the first bolt to compress the first graphite disc and the lifting valve rod into a tight fit.

[0016] According to one embodiment of the present invention, the switching valve for the regenerative oxidation furnace further includes a shaft elastic retaining ring disposed on the first base.

[0017] According to one embodiment of the present invention, the lower movable plate assembly further includes a second base, a second bushing, a second graphite disc, and a second pressure cap sleeved outside the lifting valve rod. The lower valve plate is fixedly connected to the second base, the second bushing is installed inside the base, the second pressure cap is connected to the second base by a second bolt, and the second graphite disc is installed between the bushing and the pressure cap. The second pressure cap is pressed by the second bolt to compress the second graphite disc and tightly combine it with the lifting valve rod.

[0018] According to one embodiment of the present invention, the switching valve for the regenerative oxidation furnace further includes a shaft elastic retaining ring disposed on the second base.

[0019] According to one embodiment of the present invention, the fixed valve plate assembly further includes a threaded pressure seat and a fixed pressure seat sleeved on the outside of the lifting valve rod, the fixed plate being fixed between the threaded pressure seat and the fixed pressure seat, and the threaded pressure seat and the fixed pressure seat being fixed on the lifting valve rod by means of a tightening anti-slip nut.

[0020] According to one embodiment of the present invention, the threaded pressure seat is located on the side away from the upper valve plate, and the threaded pressure seat is threadedly connected to the lifting valve rod.

[0021] The beneficial effects of the present invention are as follows: In the switching valve for a regenerative oxidizer provided in this application, by adjusting the force of the spring assembly in the adjustment component, the upper valve plate and the lower valve plate can be respectively driven to fit against the valve port, and the sealing compensation between the upper valve plate and the lower valve plate and the valve port can be automatically adjusted to ensure the sealing performance of the switching valve for the regenerative oxidizer. Attached Figure Description

[0022] The advantages of the above and / or additional aspects of the present invention will become apparent and readily understood from the description of the embodiments taken in conjunction with the following drawings, wherein:

[0023] Figure 1 This is a front view of a switching valve for a regenerative oxidation furnace according to an embodiment of the present invention;

[0024] Figure 2 This is a side view of a switching valve for a regenerative oxidation furnace according to an embodiment of the present invention;

[0025] Figure 3 yes Figure 1 A partially enlarged schematic diagram of Part I of the structure;

[0026] Figure 4 yes Figure 3 A magnified schematic diagram of a local structure;

[0027] Figure 5 yes Figure 4 A partially enlarged schematic diagram of part I;

[0028] Figure 6 yes Figure 4 A partially enlarged schematic diagram of part II;

[0029] Figure 7 yes Figure 4 A partially enlarged schematic diagram of part III;

[0030] Figure 8 yes Figure 4 The top view in the image.

[0031] The attached diagram is labeled as follows:

[0032] 1. Cylinder; 2. Cylinder bracket; 3. Upper cavity connecting channel; 4. Lower cavity connecting channel; 5. Valve body; 6. Valve stem guide assembly; 7. Valve port; 8. Lifting valve stem; 9. Shaft elastic retaining ring;

[0033] 10. Upper movable plate assembly; 101. Upper valve plate; 102. First base; 103. First bushing; 104. First graphite packing; 105. First pressure cap;

[0034] 11. Fixing plate assembly; 111. Fixing plate; 112. Threaded pressure seat; 113. Fixing pressure seat; 114. Tighten anti-slip nuts;

[0035] 12. Lower movable plate assembly; 121. Lower valve plate; 122. Second base; 123. Second bushing; 124. Second graphite packing; 125. Second pressure cap;

[0036] 13. Limiting screw; 14. First fixing nut; 15. Second nut; 16. Spring assembly. Detailed Implementation

[0037] To better understand the above-mentioned objectives, features, and advantages of the present invention, the present invention will be further described in detail below with reference to the accompanying drawings and specific embodiments. It should be noted that, unless otherwise specified, the embodiments and features described in these embodiments can be combined with each other.

[0038] like Figures 1 to 8As shown, the present invention provides a switching valve for a regenerative oxidation furnace, comprising: multiple valve bodies 5, an upper movable plate assembly 10, a lower movable plate assembly 12, a lifting valve rod 8, a fixed plate assembly 11, and an adjusting component; each valve body 5 has multiple cavities for communicating with a connecting channel; each valve body 5 is provided with a valve port 7 communicating with the cavity, and adjacent valve ports 7 are interconnected; the upper movable plate assembly 10 includes an upper valve plate 101, which is disposed corresponding to the valve port 7; the lower movable plate assembly 12 includes a lower valve plate 121, which is connected to the upper valve plate 101, and the lower valve plate 121 is disposed corresponding to another valve port 7; The upper valve plate 101 and the lower valve plate 121 are respectively connected to the lifting valve rod 8. The valve body 5 can drive the upper valve plate 101 and the lower valve plate 121 to move, thereby covering or connecting the adjacent valve ports 7. The fixing plate assembly 11 includes a fixing plate 111 fixedly connected to the lifting valve rod 8. The fixing plate 111 is located between the upper valve plate 101 and the lower valve plate 121. The adjusting assembly includes two spring assemblies 16. When the upper valve plate 101 and the lower valve plate 121 cover the corresponding valve ports 7, the two spring assemblies 16 can respectively drive the upper valve plate 101 and the lower valve plate 121 to fit against the valve ports 7.

[0039] Specifically, taking the case where there are two cavities in this embodiment as an example, the two cavities are arranged along the vertical direction of the valve body 5. The connecting channel includes an upper cavity connecting channel 3 and a lower cavity connecting channel 4 that are respectively connected to the two cavities. The upper cavity connecting channel 3 connects the upper cavity of the two valve bodies 5, and the lower cavity connecting channel 4 connects the lower cavity of the two valve bodies 5.

[0040] It should be noted that the lifting valve stem 8, the upper movable plate assembly 10, the lower movable plate assembly 12, and the fixed plate assembly 11 are located inside the valve body 5 and coincide with the vertical central axis of the annular valve port 7. The upper movable plate assembly 10, the lower movable plate assembly 12, and the fixed plate assembly 11 are mounted on the lifting valve stem 8. The outer diameter of the upper valve plate 101 and the lower valve plate 121 is larger than the outer diameter of the annular valve port 7.

[0041] According to one embodiment of the present invention, the adjusting assembly further includes a limiting screw 13 and a second nut 15. The limiting screw 13 is sequentially disposed through the upper valve plate 101, the fixing plate 111, and the lower valve plate 121. The fixing plate 111 is fixed to the limiting screw 13 by a first fixing nut 14. The second nut 15 includes an adjusting nut, and the two spring assemblies 16 are arranged along the vertical direction of the limiting screw 13. Figure 1The upper and lower parts of the spring assembly 16 are respectively sleeved on the upper valve plate 101 and the adjusting nut, and one spring assembly 16 is compressed between the upper valve plate 101 and the adjusting nut.

[0042] Specifically, the second nut 15 also includes two second fixing nuts, one of which is mounted on the upper surface of the upper valve plate 101, and the other is mounted on the lower surface of the lower valve plate 121. The adjusting nut is mounted on the spring assembly 16 in the opposite direction to the contact between the upper valve plate 101 and the lower valve plate 121.

[0043] During adjustment, the second fixing nut should be tightened first, and then the adjusting nut should be adjusted to ensure that the elastic reaction force of the spring assembly 16 is transmitted to the upper valve plate 101 and the lower valve plate 121, and to ensure that the upper valve plate 101 and the lower valve plate 121 are tightly fitted with the valve port 7 without leakage.

[0044] According to an embodiment of the present invention, the switching valve of the regenerative oxidation furnace further includes a valve stem guide assembly 6 and a cylinder 1 disposed on the valve body 5. Part of the valve stem guide assembly 6 is located in the cavity. The valve stem guide assembly 6 is provided with a guide space for the piston of the cylinder 1 to pass through. The valve stem guide assembly 6 and the piston are sealed together.

[0045] Specifically, the valve stem guide assembly 6 is rod-shaped, and the piston rod of the cylinder 1 is sleeved in the guide space of the valve stem guide assembly 6.

[0046] According to one embodiment of the present invention, each spring assembly 16 includes a plurality of springs, and two spring assemblies 16 include the same number of springs; the plurality of springs in each spring assembly 16 are evenly distributed along the circumference of the fixing plate.

[0047] Specifically, in this embodiment, each spring assembly 16 includes eight springs, which are evenly distributed around the circumference of the fixed plate 111, i.e., eight limiting screws 13 are provided. Two springs are sleeved along the vertical direction of each limiting screw 13, and adjusting nuts are provided above and below each spring. Through multiple adjusting nuts and multiple spring assemblies 16, the sealing between the entire upper valve plate 101 and lower valve plate 121 and the valve port 7 can be adjusted.

[0048] According to one embodiment of the present invention, the upper movable plate assembly 10 further includes a first base 102, a first bushing 103, a first graphite disc, and a first pressure cap 105 sleeved outside the lifting valve rod 8. The upper valve plate 101 is fixedly connected to the first base 102, the first bushing 103 is installed inside the base, the first pressure cap 105 is connected to the first base 102 by a first bolt, and the root 104 of the first graphite disc is installed between the bushing and the pressure cap. The first pressure cap 105 is pressed by the first bolt to squeeze the first graphite disc and the lifting valve rod 8 into a tight fit.

[0049] Specifically, the first bushing 103 is installed inside the first base 102, and the first pressure cover 105 is pressed by the first bolt to squeeze the first graphite disc and the lifting valve rod 8 tightly together to form an axial seal.

[0050] According to one embodiment of the present invention, the switching valve for the regenerative oxidation furnace further includes a shaft elastic retaining ring 9 disposed on the first base 102.

[0051] The upper end face of the upper movable valve plate assembly is provided with a shaft elastic retaining ring 9, which can limit the movement of the upper movable valve plate assembly.

[0052] According to one embodiment of the present invention, the lower movable plate assembly 12 further includes a second base 122, a second bushing 123, a second graphite disc, and a second pressure cap 125 sleeved outside the lifting valve rod 8. The lower valve plate 121 is fixedly connected to the second base 122, the second bushing 123 is installed inside the base, the second pressure cap 125 is connected to the second base 122 by a second bolt, and the second graphite disc root 124 is installed between the bushing and the pressure cap. The second pressure cap 125 is pressed by the second bolt to compress the second graphite disc and the lifting valve rod 8 into a tight fit.

[0053] Specifically, the second bushing 123 is installed inside the second base 122, and the second pressure cover 125 is pressed by the second bolt to squeeze the second graphite disc and the lifting valve stem 8 tightly together to form an axial seal.

[0054] According to one embodiment of the present invention, the switching valve for the regenerative oxidation furnace further includes a shaft elastic retaining ring 9 disposed on the second base 122.

[0055] The lower end face of the lower movable valve plate assembly is provided with a shaft elastic retaining ring 9, which can limit the movement of the lower movable valve plate assembly.

[0056] According to one embodiment of the present invention, the fixed valve plate assembly further includes a threaded pressure seat 112 and a fixed pressure seat 113 sleeved on the lifting valve rod 8. The fixed plate 111 is fixed between the threaded pressure seat 112 and the fixed pressure seat 113. The threaded pressure seat 112 and the fixed pressure seat 113 are fixed on the lifting valve rod 8 by a tightening anti-slip nut 114.

[0057] Specifically, the threaded pressure seat 112 and the fixed pressure seat 113 are fixed to the lifting valve rod 8 by a tightening anti-slip nut 114, which can limit the position of the fixed plate 111.

[0058] According to one embodiment of the present invention, the threaded pressure seat 112 is located on the side away from the upper valve plate 101, and the threaded pressure seat 112 is threadedly connected to the lifting valve rod 8.

[0059] Specifically, in order to prevent the threaded pressure seat 112 from being affected by gravity and to bear the weight of the fixed pressure seat 113, an internal thread is provided on the threaded pressure seat 112 to be threadedly connected to the lifting valve stem 8.

[0060] The switching valve for a regenerative oxidizer provided in this application includes a cylinder 1 and a cylinder bracket 2 connecting the cylinder 1 to a valve body 5. The upper movable valve plate assembly 10 includes an upper valve plate 101, a first base 102, a first bushing 103, a first graphite disc 104, and a first pressure cap 105. The fixed plate assembly 11 includes a fixed plate 111, a threaded pressure seat 112, a fixed pressure seat 113, and a tightening anti-slip nut 114. The lower movable valve plate assembly 12 includes a lower valve plate 121, a second base 122, a second bushing 123, a second graphite packing 124, and a second pressure cap 125. Two adjacent valve bodies 5 are connected by multiple sets of arranged bolt assemblies. Multiple sets of bolt assemblies are arranged on the valve stem guide assembly 6 and the valve port 7, respectively. The connection is fixed to the valve body 5; the fixing plate 111 is installed between the threaded pressure seat and the fixed pressure seat 113, and the fixing plate 111 is fixed by tightening the threaded pressure seat and the fixed pressure seat 113 with bolts. The anti-slip nut 114 is installed on the lower surface of the threaded pressure seat and the upper surface of the fixed pressure seat 113 and connected to the lifting valve rod 8 to prevent the fixing plate from sliding when the lifting valve rod 8 moves up and down; multiple sets of limit screws 13 pass through the upper movable valve plate group 10, the fixing plate group 11, the lower movable valve plate group 12, the spring assembly 16, the first fixing nut 14 and the second nut 15; the second fixing nut is installed on the upper surface of the upper valve plate 101 and the lower surface of the lower valve plate 121, respectively fixing the displacement of the upper movable valve plate group 10 and the lower movable valve plate group 12. One spring assembly 16 is installed between the upper movable valve plate group 10 and the fixing plate group 11, and another spring assembly 16 is installed between the lower movable valve plate group 12 and the fixing plate group 11. The adjusting nut is mounted in the opposite direction to the upper and lower valve plates of the spring assembly 16.

[0061] During initial installation, the second fixing nut should be tightened first, and then the adjusting nut should be adjusted to ensure that the elastic reaction force of the spring assembly is transmitted to the upper valve plate 101 and the lower valve plate 121.

[0062] During operation, when the upper movable valve plate assembly 10 is in the upward closed state, the upper movable valve plate assembly 10 automatically adjusts and balances the tightness of the upper valve plate 101 and the valve port 7 through the elastic reaction force of the spring assembly 16 connecting the fixed plate assembly 11 and the limiting screw 13. This achieves automatic adjustment and compensation of the sealing between the upper valve plate 101 and the valve port 7, ensuring sealing performance. The automatic adjustment and compensation of the sealing between the lower valve plate and the valve port is the same as described above.

[0063] In summary, the switching valve for a regenerative oxidizer provided in this application can, by adjusting the force of the spring assembly in the adjustment component, drive the upper valve plate and the lower valve plate to fit against the valve port, automatically adjusting the sealing compensation between the upper and lower valve plates and the valve port, thus ensuring the sealing performance of the switching valve for the regenerative oxidizer.

[0064] In the description of this invention, it should be noted that the terms "upper" and "lower," etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings, and are only for the convenience of describing the invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation, and therefore should not be construed as a limitation of the invention. Furthermore, the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance.

[0065] In the description of this invention, it should be noted that, unless otherwise explicitly specified and limited, the terms "installation," "connection," and "linkage" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral connection; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium; and they can refer to a connection within two components. Those skilled in the art can understand the specific meaning of the above terms in this invention based on the specific circumstances. Furthermore, in the description of this invention, unless otherwise stated, "a plurality of" means two or more.

[0066] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A switching valve for a regenerative oxidation furnace, characterized in that, include: Multiple valve bodies, each valve body having multiple cavities for communicating with a connecting channel; each valve body is provided with a valve port communicating with the cavity, and adjacent valve ports can communicate with each other; An upper movable plate assembly, the upper movable plate assembly including an upper valve plate, the upper valve plate being disposed corresponding to the valve port; The lower movable plate assembly includes a lower valve plate, which is connected to the upper valve plate, and the lower valve plate is configured to correspond to another valve port. The valve stem is lifted, and the upper valve plate and the lower valve plate are respectively connected to the valve stem. The valve body can drive the upper valve plate and the lower valve plate to move, thereby covering or connecting the adjacent valve ports. A fixing plate assembly, the fixing plate assembly including a fixing plate fixedly connected to the lifting valve stem, the fixing plate being located between the upper valve plate and the lower valve plate; An adjustment assembly includes two spring assemblies. When the upper valve plate and the lower valve plate are closed to the corresponding valve ports, the two spring assemblies can respectively drive the upper valve plate and the lower valve plate to fit against the valve ports. The adjusting assembly further includes a limiting screw and a second nut. The limiting screw passes sequentially through the upper valve plate, the fixing plate, and the lower valve plate. The fixing plate is fixed to the limiting screw by a first fixing nut. The second nut includes an adjusting nut. Two spring assemblies are respectively sleeved on the limiting screw along the vertical direction of the limiting screw. One spring assembly is compressed between the upper valve plate and the adjusting nut, and the other spring assembly is compressed between the lower valve plate and the adjusting nut.

2. The switching valve for a regenerative oxidizer according to claim 1, characterized in that: The switching valve of the regenerative oxidizer also includes a valve stem guide assembly and a cylinder disposed on the valve body. Part of the valve stem guide assembly is located in the cavity. The valve stem guide assembly is provided with a guide space for the piston of the cylinder to pass through. The valve stem guide assembly and the piston are sealed together.

3. The switching valve for a regenerative oxidizer according to claim 1, characterized in that: Each spring assembly includes a plurality of springs, and two spring assemblies include the same number of springs; the plurality of springs in each spring assembly are evenly distributed along the circumference of the fixed plate.

4. The switching valve for a regenerative oxidizer according to claim 1, characterized in that: The upper movable plate assembly also includes a first base, a first bushing, a first graphite disc, and a first pressure cap sleeved outside the lifting valve rod. The upper valve plate is fixedly connected to the first base, the first bushing is installed inside the base, the first pressure cap is connected to the first base by a first bolt, and the first graphite disc is installed between the bushing and the pressure cap. The first pressure cap is pressed by the first bolt to squeeze the first graphite disc and the lifting valve rod into a tight fit.

5. The switching valve for a regenerative oxidizer according to claim 4, characterized in that: The switching valve for the regenerative oxidation furnace also includes a shaft elastic retaining ring disposed on the first base.

6. The switching valve for a regenerative oxidizer according to claim 1, characterized in that: The lower movable plate assembly also includes a second base, a second bushing, a second graphite disc, and a second pressure cap sleeved outside the lifting valve rod. The lower valve plate is fixedly connected to the second base, the second bushing is installed inside the base, the second pressure cap is connected to the second base by a second bolt, and the second graphite disc is installed between the bushing and the pressure cap. The second pressure cap is pressed by the second bolt to squeeze the second graphite disc and the lifting valve rod tightly together.

7. The switching valve for a regenerative oxidizer according to claim 6, characterized in that: The switching valve for the regenerative oxidation furnace also includes a shaft elastic retaining ring disposed on the second base.

8. The switching valve for a regenerative oxidizer according to claim 1, characterized in that: The fixed valve plate assembly also includes a threaded pressure seat and a fixed pressure seat sleeved on the outside of the lifting valve rod. The fixed plate is fixed between the threaded pressure seat and the fixed pressure seat. The threaded pressure seat and the fixed pressure seat are fixed on the lifting valve rod by tightening anti-slip nuts.

9. The switching valve for a regenerative oxidizer according to claim 8, characterized in that: The threaded pressure seat is located on the side away from the upper valve plate, and the threaded pressure seat is threadedly connected to the lifting valve rod.

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