A sealing structure of a positive pressure air lock and a method for maintaining pressure therein

Abstract

The present invention provides a sealing structure of a positive pressure air lock and a method for maintaining and building pressure thereof, which relates to a sealing structure including a first sealing area, a second sealing area and an air pressure sealing area located between the first sealing area and the second sealing area; the first sealing area includes a seal one between the rotor and the shell, a seal two between the side end face of the rotor and the end cover, and a seal three between the end cover and the shell, and the seal two is arranged at one end close to the seal one, and the second sealing area includes a seal four between the shaft ends on both sides of the rotor and the end cover, and a seal five installed in the end cover; an air filling hole is opened on the side of the end cover, and an air inlet joint is installed on the air filling hole. The present invention can ensure that the overall sealing of the structure is stronger, the wear of the seal is small, the service life is longer, and there is no need for frequent replacement. The thin sealing strip in the shell is embedded in a wear-resistant nested position, which is wear-resistant and corrosion-resistant, and is easy and cheap to replace. The seal has a small interference fit and a low friction coefficient, and has a low impact on the main engine load.

Description

Technical Field

[0001] The present invention relates to a sealing structure, in particular to a sealing structure of a positive pressure air lock and a method for maintaining pressure therein. Background Art

[0002] At present, it is common to use positive pressure density control system to produce sinking feed in aquatic feed production, and positive pressure air lock must be used in positive pressure density control system. When working, compressed air is introduced into the system to maintain a certain positive pressure (usually 0.1-0.2Mpa) in the whole system. That is, at this time, the working area of ​​the positive pressure air lock must also be maintained at a working pressure of 0.1-0.2Mpa. It is known that the upper area of ​​the positive pressure air lock rotor is set as the working area, where the pressure is maintained at 0.1-0.2Mpa, and the lower area of ​​the positive pressure air lock rotor is set as the unloading area, where it is normal pressure. The actual function of the positive pressure air lock is to transport the material from the working area to the unloading area while maintaining the pressure of the working area.

[0003] However, in the actual production process of feed, the production environment is relatively harsh, because a large amount of powder impurities will be generated during production. These powder impurities can easily enter the gap between the positive pressure air lock rotor and the shell, thereby accelerating the wear of the seal and destroying the sealing performance of the air lock. Therefore, compared with ordinary air locks, positive pressure air locks used in such environments have higher requirements on rotor sealing, overall structural strength, and seal life.

[0004] In the prior art, the sealing of the air lock mainly involves two positions, namely, the sealing between the rotor and the housing and the sealing between the rotor and the end cover;

[0005] First of all, the seal between the rotor and the housing includes two positions. The first is the seal between the rotor blades and the housing, which is generally sealed by a long sealing strip. The main thing is the choice of sealing strip material, which is not explained in this patent. The second is the seal between the short cylindrical surfaces on both sides of the rotor and the housing. The positive pressure air lock in the industry currently mainly has integral sealing rings on both sides of the rotor, and is sealed by interference fit between it and the housing. The sealing ring is large in size and has a large contact area with the housing. Therefore, in this sealing method, both the housing and the sealing ring are prone to greater wear, and it is also easy to cause excessive load on the reducer. The sealing ring is an integral sealing ring, and the replacement cost is also high. The housing is generally made of integral 304 stainless steel, which is not wear-resistant. Once the housing is worn, it is difficult to repair, and the maintenance cost is also high.

[0006] For details, please refer to the patent of a high airtight wear-resistant air lock (Announcement No. CN103538884A), in which the seals on both sides of the rotor are sealed by an integral sealing ring (i.e. the annular sealing ring 6 of the steel plate material mentioned in the patent), and it is hoped that the wear of the integral sealing ring will be compensated by an elastic sealing ring (i.e. the annular sealing strip 5 mentioned in the patent). Because the integral sealing ring is made of metal and is circular, it is impossible for the elastic sealing ring to expand and compensate for the sealing gap. In addition, according to the patent Figure 3 Schematic diagram, the integral sealing ring is actually difficult to match and install. Even if the integral sealing ring is installed, it is impossible for the integral sealing ring and the housing to be exactly coaxial due to the influence of processing accuracy and cumulative assembly error. Therefore, after the assembly is completed, the gap between the integral sealing ring and the housing is either too small to cause interference, or too large to cause uneven sealing gap, thus affecting the sealing effect. Even if the processing cost is not considered, assuming that the parts are extremely accurate, a uniform and small gap can be maintained between the integral sealing ring and the housing after assembly. Although this can indeed achieve a sealing effect, it does not take into account the problem that after the material enters, it will cause the integral sealing ring and the housing to wear, resulting in an increase in the sealing gap and thus the failure of the entire seal.

[0007] Secondly, the seal between the rotor and the end cover is also divided into two positions. The first is the seal between the end faces on both sides of the rotor and the end cover. At present, the industry generally does not pay attention to the seal here, and only relies on the seal between the short cylindrical surfaces on both sides of the rotor and the shell. The second is the seal between the shaft ends and the end covers on both sides of the rotor. At present, the industry generally uses packing seals. The seal is generally unreliable and the packing is easy to wear. Therefore, it is necessary to tighten the packing gland regularly, and replacing the packing is also troublesome. For the seal between the shaft ends and the end covers on both sides, please refer to the patent for a sealing air lock (Announcement No. CN106986190B), but it only realizes the rotor The seals at the shaft ends on both sides cannot guarantee the sealing of the entire air lock, that is, if the upper part of the air lock rotor is a positive pressure working area and the lower part of the rotor is a unloading area, the powder impurities will pass through the gap between the short cylinders on both sides of the rotor and the shell in the working area (equivalent to a seal in the working area of ​​the present invention) to the area between the rotor and the end cover, and then leak through the gap between the short cylinders on both sides of the rotor and the shell (equivalent to a seal in the unloading area of ​​the present invention) to the unloading area below. Moreover, the labyrinth sleeve disclosed in the above patent is not a true labyrinth seal, and the packing seal itself is unreliable and is more troublesome to disassemble and assemble. Summary of the Invention

[0008] In order to solve the above technical problems, the purpose of the present invention is to provide a sealing structure of a positive pressure air lock and a method for maintaining pressure therefor, which can ensure that the overall sealing of the structure is stronger, and the seals have less wear and tear, a longer life, and a longer maintenance cycle, without the need for frequent replacement. The thin sealing strips in the shell are embedded in a wear-resistant nested position, which is wear-resistant and corrosion-resistant, easy and cheap to replace, the seals have a small interference fit, a low friction coefficient, and a low impact on the main engine load.

[0009] The present invention provides the following technical solutions:

[0010] A sealing structure of a positive pressure air lock comprises a first sealing area, a second sealing area and an air pressure sealing area located between the first sealing area and the second sealing area;

[0011] The first sealing area includes seal 1 between the rotor and the housing, seal 2 between the side end face of the rotor and the end cover, and seal 3 between the end cover and the housing, and seal 2 is arranged at an end close to seal 1, so as to ensure the overall sealing of the positive pressure air lock. Because the positions of seal 1, seal 3 and the subsequent second sealing area are all determined, if seal 2 is arranged close to the center of the rotor, then even if the sealing performance of seal 2 is good, the gas in the working area of ​​the rotor blades of the positive pressure air lock will leak from the space between seal 1 and seal 2 to the discharge area at the bottom;

[0012] The above leakage can refer to the leakage direction of the air lock described in the background and technology, that is: the upper part of the known air lock rotor is the positive pressure working area, and the lower part of the rotor is the unloading area. The powder impurities will pass through the gap between the short cylinders on both sides of the rotor and the shell in the working area (equivalent to a seal in the working area of ​​the present invention) to the area between the rotor and the end cover, and then leak through the gap between the short cylinders on both sides of the rotor and the shell (equivalent to a seal in the unloading area of ​​the present invention) to the unloading area below.

[0013] The second sealing area includes a seal member 4 between the shaft ends and the end cover on both sides of the rotor and a seal member 5 installed in the end cover;

[0014] An air supply hole is provided on the side of the end cover, and an air inlet joint is installed on the air supply hole. Compressed air is introduced between the end cover and the end face of the rotor, and the air pressure sealing area is formed in conjunction with the sealing performance of the first sealing area and the second sealing area. The air pressure in the air pressure sealing area is greater than the working pressure of the working area of ​​the positive pressure air lock rotor blade, making it more difficult for water vapor and powder impurities to enter the first sealing area, thereby improving the overall sealing performance of the air lock;

[0015] At this time, the first sealing area and the second sealing area have better sealing properties, so that the air pressure sealing area can be formed, that is, pressure can be built up here and the gas consumption can be reduced. Ideally, if the sealing property of seal 2 is good enough, the air pressure sealing area and the second sealing area do not need to exist. The positive pressure air lock is sealed enough, and there will be no gas leakage from the shaft end to affect the bearing. However, in actual applications, it is definitely not enough to rely solely on seal 2, because without the air pressure sealing area to form backflush, material impurities will continue to enter the seal 2 area, which will cause the wear of seal 2 to continue to increase, and the sealing gap will increase, which will increase the leakage. When an air pressure sealing area is provided, the gas leaked in the seal 1 area can be backflushed to reduce the leakage of material impurities. The small gap between seal 1 and seal 2 can also be maintained, thereby ensuring the sealing property while reducing the mutual friction between seal 1 and seal 2 to increase its service life. Therefore, the first sealing area, the second sealing area and the air pressure sealing area are indispensable and their positions cannot be replaced. They are also complementary parts.

[0016] Preferably, the seal member 1 comprises a plurality of sealing grooves spaced side by side on the short cylindrical surfaces on both sides of the rotor and thin sealing strips installed in the sealing grooves, the thin sealing strips are made of modified polytetrafluoroethylene material, and wear-resistant nests are installed on both sides of the housing, and the thin sealing strips and the wear-resistant nests are sealed by interference fit;

[0017] It can be seen from this that the above-mentioned seal achieves: sealing between the short cylindrical surfaces on both sides of the rotor and the shell, which can be specifically sealed by three circles of fine sealing strips. The three circles of fine sealing strips are arranged at intervals and have an interference fit with the shell. The overall interference fit is small, and the impact on the reducer load is small. The fine sealing strip is made of modified polytetrafluoroethylene, which is wear-resistant and has a low friction coefficient. The fine sealing strip is a long sealing strip cut and wound, which is easy to replace and low in cost. In addition, a wear-resistant nest is embedded in the matching position of the fine sealing strip in the shell. The wear-resistant nest is made of stainless steel and hardened, which is wear-resistant and corrosion-resistant, and can be replaced. Compared with the overall shell that cannot be repaired after wear or the repair cost is too high, replacing the wear-resistant nest is more convenient and cheap.

[0018] Preferably, the second seal comprises a labyrinth seal ring A fixedly mounted on the end cover by a countersunk screw 1, and a labyrinth seal ring B fixedly mounted on the side end face of the rotor by a cylindrical head screw, the labyrinth seal ring A and the labyrinth seal ring B being arranged in a pair to form a first labyrinth seal between the side end face of the rotor and the end cover, and the labyrinth seal ring A is made of modified polytetrafluoroethylene material, and the labyrinth seal ring B is made of hardened stainless steel material;

[0019] To sum up, a seal can be formed between the end faces on both sides of the rotor and the end covers. Compared with the industry's neglect of the seal at this position, the present invention increases the overall sealing by adding a labyrinth sealing scheme there, and also makes up for the insufficient sealing between the short cylindrical surfaces on both sides of the rotor and the shell. In actual feed production, more powder impurities will be produced. After the powder impurities enter the labyrinth seal, they will fill the sealing gap to form a material seal with better sealing. One of the two paired labyrinth seals is made of stainless steel and hardened, which is wear-resistant and corrosion-resistant. The other is made of modified polytetrafluoroethylene, which is wear-resistant and has a low friction coefficient, thereby reducing the driving load.

[0020] Preferably, the seal three includes an O-ring arranged between the end cover and the housing, so that the end cover and the housing can be statically sealed by the O-ring, and the end cover and the housing are positioned by a stopper, which is convenient for installation. Combined with the dimensional tolerance of high-precision machined parts, the radial runout of the rotor shaft can be effectively reduced, thereby greatly ensuring the sealing and service life of the skeleton oil seal in the second sealing area.

[0021] Preferably, the seal member 4 includes a labyrinth seal ring C made of modified polytetrafluoroethylene material and a labyrinth seal ring D made of hardened stainless steel material. The labyrinth seal ring C is fixed to the rotor shaft by a set screw, and the labyrinth seal ring D is fixed to the end cover by a countersunk screw 2. The labyrinth seal ring C and the labyrinth seal ring D are paired to form a second labyrinth seal.

[0022] Preferably, the sealing element 5 comprises two skeleton oil seals installed in the end cover. The skeleton oil seals serve as the final seal. The two skeleton oil seals cooperate with the low-speed rotating rotor to ensure that there will be no leakage of water vapor, powder impurities at the shaft end of the entire air lock, and no frequent maintenance is required.

[0023] And because the sealing scheme of labyrinth seal plus skeleton oil seal is adopted in the second sealing area, the labyrinth seal once again blocks the possible powder impurities and forms a material seal, which increases the overall sealing performance of the air lock while also reducing the harshness of the sealing working conditions of the subsequent skeleton oil seal, thereby increasing the sealing life of the subsequent skeleton oil seal. One of the two paired labyrinth seals is made of stainless steel and hardened, which is wear-resistant and corrosion-resistant, and the other is made of modified polytetrafluoroethylene, which is wear-resistant and has a low friction coefficient, thereby reducing the driving load. The two skeleton oil seals serve as the last seal to ensure that no water vapor or powder impurities leak out of the air lock, avoiding the reduction of the overall sealing performance of the air lock and the impact on the bearings.

[0024] The end cover and the housing are positioned by the stopper, and the dimensional tolerance of the parts processed with high precision can effectively reduce the radial runout of the rotor shaft, thereby greatly ensuring the sealing and service life of the skeleton oil seal. Compared with the packing seal that requires frequent tightening of the packing gland and replacement of the packing, the present invention can basically achieve maintenance-free at the shaft end seals on both sides of the rotor.

[0025] Preferably, the mating sealing gap of the second labyrinth seal in the diameter direction shows a trend of gradually decreasing from the outside to the inside, thereby achieving a better sealing effect.

[0026] Preferably, an oil channel is also opened on the end cover and a grease nipple is installed at the oil channel port. The grease added by the grease nipple is used to fill the gap between the skeleton oil seal and the second labyrinth seal, and the sealing performance of the second labyrinth seal and the skeleton oil seal form a closed area at the gap. External water vapor and powder impurities cannot easily enter the closed area. Keeping the closed area lubricated and free of impurities is conducive to reducing the wear of the seal and extending the service life. It also reduces the friction resistance and helps to reduce the driving load.

[0027] A method for maintaining pressure buildup in a sealing structure of a positive pressure air lock, based on the above-mentioned sealing structure of a positive pressure air lock, includes the following steps:

[0028] When the positive pressure density control system is initially working, the positive pressure air lock is first opened and compressed air is added through the air inlet joint to form an air pressure sealing area. Initially, there is no water vapor and powder impurities in the first sealing area, the second sealing area and the air pressure sealing area, and there is no compressed air loss in the air pressure sealing area.

[0029] As the positive pressure density control system continues to operate, the thin sealing strip in the first sealing area gradually wears out, and the sealing effect between the short cylindrical surface on the rotor side and the shell is weakened. At this time, since the gas pressure in the pneumatic sealing area is greater than the pressure in the rotor working area, the compressed air in the pneumatic sealing area will pass through the flow channel gap of the first sealing area and flow back to the rotor area of ​​the positive pressure air lock. Most of the compressed air enters the working area of ​​the rotor to help the positive pressure density control system maintain pressure building. Another small amount of compressed air enters the bottom of the rotor and then leaks to the unloading area. At this time, the gas consumption of the pneumatic sealing area increases, but it still meets the requirement that the gas pressure in the pneumatic sealing area is greater than the pressure in the rotor working area. The gas leakage is acceptable, and the air pressure in the pneumatic sealing area can continue to maintain pressure building. At this time, the overall seal of the positive pressure air lock is established;

[0030] As the positive pressure air lock continues to operate, the powder impurities accumulated in the first sealing area fill the labyrinth sealing gap of the first sealing area, so that a material seal can be formed. At this time, the sealing effect of the first sealing area will be enhanced again. At the same time, because the size of the flow channel gap is reduced, the amount of compressed air flowing from the air pressure sealing area through the first sealing area to the rotor in the opposite direction will also decrease, thereby reducing the air consumption of the air pressure sealing area. At this time, the sealing structure of the positive pressure air lock completes the maintenance of pressure buildup, and the overall seal can be maintained continuously.

[0031] After the sealing structure of the positive pressure air lock completes the pressure building, the air consumption in the air pressure sealing area can be maintained within a stable range.

[0032] The above pressure building process can be summarized into three stages:

[0033] In the first stage, the thin sealing strip is not completely worn out, the positive pressure air shutoff is sealed very well, there is no leakage of materials or water vapor, and the air consumption is not large. This process can generally only last for about a week;

[0034] In the second stage, the thin sealing strip is worn out and there is a gap between it and the shell. At this time, the air pressure sealing area starts to work, relying on the back-blowing of air pressure higher than the working area to reduce the entry of materials and water vapor into the first sealing area. At this time, the seal of the air lock has been established, but the air consumption will be a little higher (because the labyrinth seal gap will be relatively larger). This process can generally last for more than one month.

[0035] In the third stage, although there is backflushing, the material will still slowly enter the first sealing area, and the labyrinth seal gap will gradually fill up. At this time, the air lock has better sealing performance, and more importantly, the air consumption is greatly reduced (because the flow channel gap is filled smaller). This process can last for more than one year, which means that the customer does not need to replace the seal for at least one year, and the positive pressure system can still work normally.

[0036] In the third stage, although the gas consumption is greatly reduced, it still does not disappear, but is maintained in a lower stable range. This gas leakage state is more suitable for sealing during actual work, because this tiny leakage can maintain the backblowing of the air pressure sealing area to the seal (just don’t let the gas consumption be as large as in the second stage). This can effectively reduce the entry of materials. Otherwise, even if the labyrinth sealing performance of the first sealing area is good, excessive entry of materials will still cause increased wear at the thin sealing strip (seal 1). If the gap there is large, it will still affect the sealing of the entire air lock.

[0037] The beneficial effects of the present invention are:

[0038] 1. The seal in the first sealing area is used to achieve the seal between the short cylindrical surfaces on both sides of the rotor and the housing. It adopts three circles of thin sealing strips to achieve interference fit and seal, which is easy to replace and low in cost. The overall interference is small and the friction coefficient is low, which has little impact on the load of the reducer. The housing is embedded with wear-resistant nesting, which is wear-resistant and corrosion-resistant, and is easy to replace and low in cost.

[0039] 2. The first sealing area also has a first labyrinth seal between the two sides of the rotor and the end cover. By forming a material seal, the sealing is enhanced and, together with the air pressure sealing area, forms the main sealing area of ​​the positive pressure air lock. The two labyrinth seal rings of the first labyrinth seal are made of hardened stainless steel, which is wear-resistant and corrosion-resistant, and modified polytetrafluoroethylene, which is wear-resistant and has a low friction coefficient.

[0040] 3. The seal between the rotor shaft end and the end cover in the second sealing area adopts a sealing solution of a second labyrinth seal plus a skeleton oil seal. The second labyrinth seal again blocks powder impurities and forms a material seal. The skeleton oil seal serves as the final seal and completely eliminates the possibility of water vapor and powder impurities leaking. At the same time, grease is added to the second sealing area to form a closed area inside the second labyrinth seal and the skeleton oil seal. This can not only improve the sealing performance of the second sealing area, but also reduce the wear of the seal and increase the service life of the seal. The two labyrinth seal rings of the labyrinth seal in the second sealing area are made of hardened stainless steel, which is wear-resistant and corrosion-resistant, and the other is made of modified polytetrafluoroethylene, which is wear-resistant and has a low friction coefficient.

[0041] 4. Compressed air is introduced between the end cover and the rotor end face through the air holes on the side of the end cover, and an air pressure sealing area is formed there in cooperation with the first sealing area and the second sealing area. The pressure in the sealing area is greater than the working pressure in the rotor blades of the positive pressure air lock, which can make it more difficult for water vapor and powder impurities to leak out. BRIEF DESCRIPTION OF THE DRAWINGS

[0042] The accompanying drawings are used to provide a further understanding of the present invention and constitute a part of the specification. Together with the embodiments of the present invention, they are used to explain the present invention and do not constitute a limitation of the present invention. In the accompanying drawings:

[0043] Figure 1 This is a schematic diagram of the three-dimensional structure of the air lock of the present invention (excluding the driving part);

[0044] Figure 2 yes Figure 1 Front view of the structure section of the middle blower;

[0045] Figure 3 yes Figure 1 A top-down structural cross-section of the central air blower;

[0046] Figure 4 It is a structural schematic diagram of the air shutoff rotor in the present invention;

[0047] Figure 5 yes Figure 2 A partial enlarged view of part A;

[0048] Figure 6 yes Figure 2 A partial enlarged view of part B;

[0049] Figure 7 yes Figure 3 A partial enlarged view of part C in the middle;

[0050] Markings in the figure:

[0051] 1. Rotor; 101. Rotor shaft; 102. Rotor side end face; 103. Rotor side short cylindrical surface; 2. Housing; 3. End cover; 4. First sealing area; 401. Thin sealing strip; 402. Wear-resistant nesting; 403. Labyrinth seal A; 404. Labyrinth seal B; 405. O-ring; 406. Cylindrical head screw; 407. Countersunk screw 1; 5. Second sealing area; 501. Labyrinth seal C; 502. Labyrinth seal D; 503. Skeleton oil seal; 504. Set screw; 505. Countersunk screw 2; 506. Oil nozzle; 507. Oil channel; 6. Air pressure sealing area; 7. Air intake joint. DETAILED DESCRIPTION

[0052] Example 1

[0053] like Figure 1-7 As shown, a sealing structure of a positive pressure air lock, in this embodiment, includes a first sealing area 4, a second sealing area 5 and an air pressure sealing area 6 located between the first sealing area 4 and the second sealing area 5;

[0054] The first sealing area 4 includes a seal 1 between the rotor 1 and the housing 2, a seal 2 between the side end surface of the rotor 1 and the end cover 3, and a seal 3 between the end cover 3 and the housing 2, and the seal 2 is arranged at an end close to the seal 1 to ensure the overall sealing of the positive pressure air lock. Because the positions of the seal 1, the seal 3 and the subsequent second sealing area 5 are all determined, if the seal 2 is arranged close to the center of the rotor 1, then even if the sealing performance of the seal 2 is good, the gas in the working area of ​​the blades of the positive pressure air lock rotor 1 will leak from the space between the seal 1 and the seal 2 to the discharge area at the bottom;

[0055] The above leakage can refer to the leakage direction of the air lock described in the background and technology, that is: it is known that the upper part of the air lock rotor 1 is the positive pressure working area, and the lower part of the rotor 1 is the unloading area. The powder impurities will pass through the gap between the short cylinders on both sides of the rotor 1 and the shell 2 in the working area (equivalent to a seal in the working area of ​​the present invention) to the area between the rotor 1 and the end cover 3, and then leak through the gap between the short cylinders on both sides of the rotor 1 and the shell 2 (equivalent to a seal in the unloading area of ​​the present invention) to the unloading area below.

[0056] The second sealing area 5 includes a seal 4 between the shaft ends on both sides of the rotor 1 and the end cover 3, and a seal 5 installed in the end cover 3;

[0057] An air supply hole is provided on the side of the end cover 3, and an air inlet connector 7 is installed on the air supply hole. Compressed air is introduced between the end cover 3 and the rotor side end face 102, and the sealing performance of the first sealing area 4 and the second sealing area 5 are combined to form an air pressure sealing area 6. The air pressure in the air pressure sealing area 6 is greater than the working pressure of the blade working area of ​​the positive pressure air lock rotor 1, making it more difficult for water vapor and powder impurities to enter the first sealing area 4, thereby improving the overall sealing performance of the air lock.

[0058] At this time, the first sealing area 4 and the second sealing area 5 have good sealing properties, and the air pressure sealing area 6 can be formed, that is, the pressure can be built up here and the gas consumption can be reduced. Ideally, if the sealing property of the second seal is good enough, the air pressure sealing area 6 and the second sealing area 5 are unnecessary. The positive pressure air lock is sealed enough, and there will be no gas leakage from the shaft end to affect the bearing. However, in actual applications, it is definitely not enough to rely on the second seal alone, because without the backflush formed by the air pressure sealing area 6, material impurities will continue to enter the second seal area, and then This causes the wear of seal 2 to increase continuously, and the sealing gap to increase, which in turn increases the amount of air leakage. When an air pressure sealing area 6 is provided, the gas leaked in the seal area 1 can be back-blown to reduce the leakage of material impurities. The small gap between seal 1 and seal 2 can also be maintained, thereby ensuring the sealing performance while also reducing the mutual friction between seal 1 and seal 2 to increase their service life. Therefore, the first sealing area 4, the second sealing area 5 and the air pressure sealing area 6 are indispensable and their positions cannot be replaced. They are also complementary parts.

[0059] The first seal comprises multiple sealing grooves spaced side by side on the short cylindrical surfaces of the rotor 1 and thin sealing strips 401 installed in the sealing grooves. The thin sealing strips 401 are made of modified polytetrafluoroethylene. Wear-resistant inserts 402 are installed on both sides of the housing 2. The thin sealing strips 401 and the wear-resistant inserts 402 are sealed by an interference fit.

[0060] It can be seen from this that the above-mentioned seal achieves: sealing between the short cylindrical surfaces on both sides of the rotor 1 and the shell 2, which can be specifically sealed by three circles of fine sealing strips 401. The three circles of fine sealing strips 401 are arranged at intervals and have an interference fit with the shell 2. The overall interference fit is small, and the impact on the reducer load is small. The fine sealing strip 401 is made of modified polytetrafluoroethylene, which is wear-resistant and has a low friction coefficient. The fine sealing strip 401 is a long sealing strip that is cut and wound, which is easy to replace and low in cost. In addition, a wear-resistant nest 402 is embedded in the matching position of the fine sealing strip 401 in the shell 2. The wear-resistant nest 402 is made of stainless steel and hardened, which is wear-resistant and corrosion-resistant, and can be replaced. Compared with the overall shell 2 that cannot be repaired after being worn or the repair cost is too high, replacing the wear-resistant nest 402 is more convenient and cheap.

[0061] Seal 2 includes a labyrinth seal A403 fixedly mounted on the end cover 3 via countersunk screws 407, and a labyrinth seal B404 fixedly mounted on the side end face of the rotor 1 via cylindrical head screws 406. Labyrinth seals A403 and B404 are paired to form a first labyrinth seal between the side end face of the rotor 1 and the end cover 3. Labyrinth seal A403 is made of modified polytetrafluoroethylene, and labyrinth seal B404 is made of hardened stainless steel.

[0062] In summary, a seal can be formed between the end faces on both sides of the rotor 1 and the end cover 3. Compared with the industry's neglect of the seal at this position, the present invention increases the overall sealing by adding a labyrinth sealing scheme there, and also makes up for the insufficient sealing between the short cylindrical surfaces on both sides of the rotor 1 and the shell 2. In actual feed production, more powder impurities will be produced. After the powder impurities enter the labyrinth seal, the sealing gap will be filled to form a material seal with better sealing. One of the two paired labyrinth seals is made of stainless steel and hardened, which is wear-resistant and corrosion-resistant. The other is made of modified polytetrafluoroethylene, which is wear-resistant and has a low friction coefficient, thereby reducing the driving load.

[0063] The third seal comprises an O-ring 405 disposed between the end cover 3 and the housing 2, thereby enabling a static seal between the end cover 3 and the housing 2 via the O-ring 405, and positioning between the end cover 3 and the housing 2 via a stopper, which facilitates installation and, in combination with the dimensional tolerances of high-precision machined parts, effectively reduces radial runout of the rotor shaft 101, thereby greatly ensuring the sealing performance and service life of the skeleton oil seal 503 in the second sealing area 5.

[0064] Seal 4 includes a labyrinth seal C501 made of modified polytetrafluoroethylene and a labyrinth seal D502 made of hardened stainless steel. Labyrinth seal C501 is fixed to the rotor shaft 101 by a set screw 504, and labyrinth seal D502 is fixed to the end cover 3 by a second countersunk screw 505. Labyrinth seal C501 and labyrinth seal D502 are paired to form a second labyrinth seal.

[0065] The seal 5 includes two skeleton oil seals 503 installed in the end cover 3. The skeleton oil seals 503 serve as the final seal. The two skeleton oil seals 503 cooperate with the low-speed rotating rotor 1 to ensure that there will be no leakage of water vapor, powder impurities at the shaft end of the entire air lock, and no frequent maintenance is required.

[0066] And because the sealing scheme of labyrinth seal plus skeleton oil seal 503 is adopted in the second sealing area 5, the labyrinth seal once again blocks the possible powder impurities and forms a material seal, which increases the overall sealing performance of the air lock while also reducing the severity of the sealing working conditions of the subsequent skeleton oil seal 503, thereby increasing the sealing life of the subsequent skeleton oil seal 503. One of the two paired labyrinth seals is made of stainless steel and hardened, which is wear-resistant and corrosion-resistant, and the other is made of modified polytetrafluoroethylene, which is wear-resistant and has a low friction coefficient, thereby reducing the driving load. The two skeleton oil seals 503 serve as the last seal to ensure that no water vapor or powder impurities leak out of the air lock, thereby avoiding a reduction in the overall sealing performance of the air lock and an impact on the bearings.

[0067] The end cover 3 and the housing 2 are positioned by means of a stop, and combined with the dimensional tolerances of components machined with high precision, the radial runout of the rotor shaft 101 can be effectively reduced, thereby greatly ensuring the sealing performance and service life of the skeleton oil seal 503. Compared with packing seals that require frequent tightening of the packing gland and replacement of the packing, the present invention can basically achieve maintenance-free operation at the shaft end seals on both sides of the rotor 1.

[0068] The matching sealing gap of the second labyrinth seal in the diameter direction shows a trend of gradually decreasing from the outside to the inside, thereby achieving a better sealing effect.

[0069] An oil passage 507 is also provided on the end cover 3, and a grease nipple 506 is installed at the end of the oil passage 507. The grease added by the grease nipple 506 is used to fill the gap between the skeleton oil seal 503 and the second labyrinth seal, and the sealing performance of the second labyrinth seal and the skeleton oil seal 503 form a closed area at the gap. External water vapor and powder impurities cannot easily enter the closed area. Keeping the closed area lubricated and free of impurities is conducive to reducing the wear of the seal and extending the service life. At the same time, it also reduces the friction resistance and helps to reduce the driving load.

[0070] Example 2

[0071] A method for maintaining pressure buildup in a sealing structure of a positive pressure air lock, based on the above-mentioned sealing structure of a positive pressure air lock, includes the following steps:

[0072] When the positive pressure density control system is working, the air lock is first opened and compressed air is added through the air inlet connector 7 to form the air pressure sealing area 6. At this time, there is no water vapor, powder impurities, etc. in the first sealing area 4, the second sealing area 5 and the air pressure sealing area 6, the sealing effect is good, and there is no compressed air loss in the air pressure sealing area 6. After a period of operation, the thin sealing strip 401 in the first sealing zone 4 gradually wears away, weakening the sealing effect between the short cylindrical surface 103 on the rotor side and the housing 2. However, thanks to the dimensional tolerances of the components manufactured with high precision, the gap there is very small. At this point, because the gas pressure in the pneumatic sealing zone 6 is greater than the pressure in the working area of ​​the rotor 1, the compressed air in the pneumatic sealing zone 6 passes through the labyrinth seal in the first sealing zone 4 and then flows back into the airlock rotor 1 through the tiny gap between the short cylindrical surface 103 on the rotor side and the wear-resistant insert 402 in the first sealing zone 4. Most of the compressed air enters the working area of ​​the rotor 1, helping the positive pressure density control system maintain pressure build. A small amount of compressed air enters the bottom of the rotor 1 and leaks into the discharge area. At this time, the air consumption in the pneumatic sealing zone 6 increases, but the leakage rate is acceptable, and the pneumatic sealing zone 6 continues to maintain pressure. At the same time, because the compressed air is blown into the rotor in the reverse direction, moisture and powder impurities are less likely to enter the first sealing zone 4. At this point, the overall airlock seal is established, but the overall air consumption is slightly higher. However, a small amount of powder impurities will still enter the first sealing area 4, slowly accumulating more and more, and the powder impurities gradually fill the labyrinth seal gap of the first sealing area 4 to form a material seal. However, since the rotor 1 and the end cover 3 are rotating relative to each other, the labyrinth seal gap cannot be completely filled, and a tiny gap will gradually form. Compared with the larger sealing gap of the previous labyrinth seal itself, the sealing effect of the first sealing area 4 is greatly enhanced at this time. At the same time, since the flow channel gap is greatly reduced, the amount of compressed air flowing back to the rotor 1 through the first sealing area 4 by the pneumatic sealing area 6 is also greatly reduced, and the air consumption of the pneumatic sealing area 6 is greatly reduced. The overall seal of the air lock continues to be maintained, and the overall air consumption is low. The main function of the second sealing area 5 is to help establish and maintain the pneumatic sealing area 6 and to serve as the last barrier to seal the rotor shaft end of the air lock to ensure that there is no possibility of leakage of any water vapor or powder impurities.

[0073] The pressure building process in the present invention specifically includes three stages:

[0074] In the first stage, the thin sealing strip 401 is not completely worn out, the positive pressure air shutoff is sealed very well, there is no leakage of material or water vapor, and the air consumption is not large. This process can generally only last for about a week;

[0075] In the second stage, the thin sealing strip is worn out and there is a gap between it and the shell 2. At this time, the air pressure sealing area 6 starts to work, relying on the back-blowing of air pressure higher than the working area to reduce the entry of materials and water vapor into the first sealing area 4. At this time, the seal of the air lock has been established, but the air consumption will be a little higher (because the labyrinth seal gap will be relatively larger). This process can generally last for more than one month.

[0076] In the third stage, although there is backflushing, the material will still slowly enter the first sealing area 4, and the labyrinth seal gap will gradually fill up. At this time, the air lock has better sealing performance, and more importantly, the air consumption is greatly reduced (because the flow channel gap is filled smaller). This process can last for more than one year, which means that the customer does not need to replace the seal for at least one year, and the positive pressure system can still work normally.

[0077] In the third stage, although the gas consumption is greatly reduced, it still does not disappear, but is maintained within a lower stable range. This gas leakage state is more suitable for sealing during actual work, because this tiny leakage can maintain the backflushing of the air pressure sealing area 6 to the seal (just don't use as much gas consumption as in the second stage). This can effectively reduce the entry of materials. Otherwise, even if the labyrinth sealing performance of the first sealing area is good, excessive entry of materials will still cause increased wear at the thin sealing strip 401 (seal 1). If the gap there is large, it will still affect the sealing of the entire air lock.

[0078] The above description is merely a preferred embodiment of the present invention and is not intended to limit the present invention. Although the present invention has been described in detail with reference to the aforementioned embodiments, those skilled in the art will be able to modify the technical solutions described in the aforementioned embodiments or replace some of the technical features therein with equivalents. Any modifications, equivalent replacements, improvements, etc. made within the spirit and principles of the present invention shall be included within the scope of protection of the present invention.

Claims

1. A method for maintaining pressure buildup in a sealing structure of a positive pressure air lock, based on a sealing structure of a positive pressure air lock, characterized in that: The sealing structure comprises a first sealing area (4), a second sealing area (5), and an air pressure sealing area (6) located between the first sealing area (4) and the second sealing area (5); The first sealing area (4) includes a seal 1 between the rotor (1) and the housing (2), a seal 2 between the side end face of the rotor (1) and the end cover (3), and a seal 3 between the end cover (3) and the housing (2), and the seal 2 is arranged at one end close to the seal 1; the second sealing area (5) includes a seal 4 between the shaft ends on both sides of the rotor (1) and the end cover (3), and a seal 5 installed in the end cover (3); an air filling hole is opened on the side of the end cover (3), and an air inlet joint (7) is installed on the air filling hole, and compressed air is introduced between the end cover (3) and the side end face (102) of the rotor, and the sealing performance of the first sealing area (4) and the second sealing area (5) is matched to form the air pressure sealing area (6), and the air pressure in the air pressure sealing area (6) is greater than the working pressure of the blade working area of ​​the positive pressure air lock rotor (1); The method for maintaining pressure buildup includes the following steps: When the positive pressure density control system is initially operated, the positive pressure air lock is first opened and compressed air is added through the air inlet connector (7) to form an air pressure sealing area (6); initially, there is no water vapor and powder impurities in the first sealing area (4), the second sealing area (5) and the air pressure sealing area (6), and there is no compressed air loss in the air pressure sealing area (6); As the positive pressure density control system continues to operate, the thin sealing strip (401) in the first sealing area (4) gradually wears out, and the sealing effect between the short cylindrical surface (103) on the rotor side and the shell (2) is weakened. At this time, since the gas pressure in the air pressure sealing area (6) is greater than the pressure in the working area of ​​the rotor (1), the compressed air in the air pressure sealing area (6) will pass through the flow channel gap of the first sealing area (4) and flow back to the positive pressure air lock rotor (1) area, wherein most of the compressed air enters the working area of ​​the rotor (1) to help the positive pressure density control system maintain pressure building, and a small amount of compressed air enters the bottom of the rotor (1) and then leaks to the unloading area. At this time, the gas consumption of the air pressure sealing area (6) increases, but it still satisfies the gas pressure in the air pressure sealing area (6) greater than the pressure in the working area of ​​the rotor (1), and the gas leakage is acceptable. The air pressure in the air pressure sealing area (6) can continue to maintain pressure building. At this time, the overall seal of the positive pressure air lock is established; As the positive pressure air lock continues to operate, the powder impurities accumulated in the first sealing area (4) fill the labyrinth sealing gap of the first sealing area (4), so that a material seal can be formed. At this time, the sealing effect of the first sealing area (4) will be enhanced again. At the same time, because the size of the flow channel gap is reduced, the amount of compressed air flowing from the air pressure sealing area (6) through the first sealing area (4) to the rotor (1) in the reverse direction will also decrease, thereby reducing the air consumption of the air pressure sealing area (6). At this time, the sealing structure of the positive pressure air lock completes the pressure building, and the overall seal can be maintained continuously.

2. A method for maintaining pressure buildup in a sealing structure of a positive pressure air lock according to claim 1, characterized in that: The sealing element 1 comprises a plurality of sealing grooves arranged in parallel and spaced apart on the short cylindrical surfaces on both sides of the rotor (1) and a thin sealing strip (401) installed in the sealing groove, wherein the thin sealing strip (401) is made of modified polytetrafluoroethylene material, and wear-resistant nests (402) are installed on both sides of the housing (2), and the thin sealing strip (401) and the wear-resistant nests (402) are sealed by interference fit.

3. A method for maintaining pressure buildup in a sealing structure of a positive pressure air lock according to claim 1, characterized in that: The second sealing member comprises a labyrinth seal ring A (403) fixedly mounted on the end cover (3) by a countersunk screw (407) and a labyrinth seal ring B (404) fixedly mounted on the side end face of the rotor (1) by a cylindrical head screw (406). The labyrinth seal ring A (403) and the labyrinth seal ring B (404) are arranged in pairs to form a first labyrinth seal between the side end face of the rotor (1) and the end cover (3). The labyrinth seal ring A (403) is made of modified polytetrafluoroethylene material, and the labyrinth seal ring B (404) is made of hardened stainless steel material.

4. A method for maintaining pressure buildup in a sealing structure of a positive pressure air lock according to claim 1, characterized in that: The sealing member 3 comprises an O-ring (405) arranged between the end cover (3) and the housing (2), and the end cover (3) and the housing (2) are positioned by a stop.

5. A method for maintaining pressure buildup in a sealing structure of a positive pressure air lock according to claim 1, characterized in that: The sealing member 4 comprises a labyrinth seal ring C (501) made of modified polytetrafluoroethylene material and a labyrinth seal ring D (502) made of hardened stainless steel material. The labyrinth seal ring C (501) is fixed to the rotor shaft (101) by a set screw (504), and the labyrinth seal ring D (502) is fixed to the end cover (3) by a second countersunk screw (505). The labyrinth seal ring C (501) and the labyrinth seal ring D (502) are paired to form a second labyrinth seal.

6. A method for maintaining pressure buildup in a sealing structure of a positive pressure air lock according to claim 5, characterized in that: The sealing member 5 comprises two skeleton oil seals (503) installed in the end cover (3).

7. A method for maintaining pressure buildup in a sealing structure of a positive pressure air lock according to claim 5, characterized in that: The mating sealing gap of the second labyrinth seal in the diameter direction shows a trend of gradually decreasing from the outside to the inside.

8. A method for maintaining pressure buildup in a sealing structure of a positive pressure air lock according to claim 6, characterized in that: The end cover (3) is also provided with an oil passage (507) and a grease nipple (506) is installed at the end of the oil passage (507). Lubricating grease added by the grease nipple (506) is used to fill the gap between the skeleton oil seal (503) and the second labyrinth seal, and cooperates with the sealing performance of the second labyrinth seal and the skeleton oil seal (503) to form a closed area at the gap.

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