Combined seal for a rake dryer and method of sealing the same

Abstract

The application discloses a combined seal of a rake dryer and a sealing method thereof, and belongs to the technical field of dryers. The combined seal solves the defects of the mechanical seal of the traditional dryer in the prior art, i.e., the mechanical seal is easy to fail, filler debris enters the dryer, and material pollution is caused. The main structure comprises a rack, a shell and a motor arranged on the rack, a main shaft arranged in the shell, a transmission assembly connecting the motor and the main shaft in a rotating mode, and both ends of the main shaft rotatably installed on a support. End cover plates are arranged at both ends of the shell, a sealing assembly is arranged between the end cover plates and the main shaft and installed on the main shaft, and a mechanical sealing assembly is arranged on the outer side and / or the inner side of the sealing assembly and installed on the main shaft. The application is mainly used on the rake dryer.

Description

Technical Field

[0001] This invention belongs to the field of dryer technology, and more specifically, relates to a combined seal for a rake dryer and its sealing method. Background Technology

[0002] Rake dryers are widely used in pharmaceuticals, chemicals, dyes, pesticides, food, and other fields. They are suitable for slurries, pastes, and powders, as well as heat-sensitive materials requiring low-temperature drying, and easily oxidized, explosive, highly irritating, and highly toxic materials. The material to be dried is added from the top of the shell. Under the continuous forward and reverse rotation of the rake teeth, the material moves axially back and forth, constantly renewing the surface in contact with the inner wall of the shell. Indirect heating by steam and uniform stirring by the rake teeth facilitate the removal of surface moisture / solvent. The vaporized moisture / solvent is condensed and released from the vacuum pump outlet. The dried material is directly discharged from the bottom and bagged. During the drying process, the rake dryer needs to maintain a certain pressure (negative pressure: -0.1~0MPa) and temperature. The material (slurry, paste, powder) must not leak, especially toxic or harmful media. Therefore, the dryer requires a good sealing structure to ensure that the material is neither exposed nor leaks air internally. When the shell is under negative pressure, internal gas leakage can cause a decline in material quality or a violent reaction of the medium. When a slight positive pressure is created inside the casing due to heating, powder leaks into the mechanical seal, causing failure or wear of the seal pair and shortening its lifespan. Since dryers are large pieces of equipment, replacing the mechanical seal is not easy. The dryer's sealing components include a packing gland; when the main shaft rotates, friction between the shaft and the packing generates debris, which enters the dryer and contaminates the material. Based on these usage conditions, a combined seal is needed that can ensure airtightness while preventing packing wear debris from entering the dryer and preventing material powder leakage. Summary of the Invention

[0003] The technical problem to be solved by the present invention is to overcome the shortcomings of the prior art and provide a combined seal and sealing method for a rake dryer. It can effectively prevent the packing gland debris from entering the dryer. The labyrinth PTFE ring and the packing gland also effectively prevent the leakage of materials inside the dryer into the mechanical seal assembly, which would cause the mechanical seal assembly to fail. This combined seal extends the service life of the mechanical seal assembly and improves the quality of the dried material.

[0004] To achieve the above objectives, the present invention employs the following technical solution:

[0005] A combined seal for a rake dryer includes a frame, a housing and a motor mounted on the frame, a main shaft housed inside the housing, the motor being rotatably connected to the main shaft via a transmission assembly, the two ends of the main shaft being rotatably mounted on supports, end caps being provided at both ends of the housing, a sealing assembly mounted on the main shaft being provided between the end caps and the main shaft, and a mechanical seal assembly mounted on the main shaft being provided on the outer and / or inner sides of the sealing assembly.

[0006] Preferably, the sealing assembly includes a bushing, which is installed on the outer ring of the main shaft. A PTFE sleeve, a labyrinth PTFE ring, and a packing gland are disposed in the cavity between the bushing and the main shaft. The labyrinth PTFE ring is disposed between the packing gland and the PTFE sleeve. The upper end of the bushing is provided with a bushing inlet hole communicating with the labyrinth PTFE ring, and the lower end of the bushing is provided with a bushing outlet hole communicating with the labyrinth PTFE ring.

[0007] Preferably, the lower end of the air outlet of the bushing is connected to a visible hopper via a connecting pipe and flange one, and the lower end of the visible hopper is provided with a discharge port plug via flange two.

[0008] Preferably, a purge exhaust port is provided on one side of the visible hopper.

[0009] Preferably, the side of the packing gland is sealed by a packing gland, which is installed on the circumference of the main shaft, and the side of the PTFE sleeve is sealed by a gland, which is installed on the circumference of the main shaft.

[0010] Preferably, a temporary storage bin is provided between the air inlet of the bushing and the labyrinth PTFE ring.

[0011] Preferably, the inner ring of the labyrinth PTFE ring is provided with an annular inner guide groove, and the outer ring is provided with an annular outer guide groove, and the inner guide groove and the outer guide groove are connected through a discharge hole.

[0012] A sealing method, employing a combined seal of a rake dryer as described above, includes the following steps:

[0013] S1: The main shaft rotates, but the packing gland does not rotate. The packing gland can prevent powder from entering the mechanical seal assembly, but after long-term friction, the packing gland will produce fragments and powder.

[0014] S2: When the inside of the housing is slightly positively pressured, as the main shaft rotates, the material first enters the labyrinth PTFE ring and then enters the temporary storage bin through the discharge port of the inner guide groove. Under its own weight, the material falls into the visible bin through the vent hole of the bushing, the connecting pipe, and the flange. When the inside of the housing is negatively pressured, the dust and powder generated by the long-term friction of the packing gland enter the labyrinth PTFE ring and, as the main shaft rotates, enter the temporary storage bin through the discharge port of the inner guide groove. Then, under its own weight, the dust and powder fall into the visible bin through the discharge port of the labyrinth PTFE ring, the vent hole of the bushing, the connecting pipe, and the flange.

[0015] Preferably, the method further includes the following steps:

[0016] S3: When the visible hopper is full, the crushed material and powder are discharged by twisting the plug at the outlet below the second flange.

[0017] S4: When the labyrinth PTFE ring becomes blocked, nitrogen is introduced through the air inlet of the bushing. During the nitrogen purging, the nitrogen flows through the air inlet of the bushing, the temporary storage bin, the labyrinth PTFE ring, the air outlet of the bushing, the connecting pipe, flange 1, and the visible bin. Finally, the nitrogen is blown out from the purging exhaust port. The blockage is left in the visible bin, ensuring that the entire system is unblocked and unobstructed.

[0018] Compared with the prior art, the beneficial effects of the present invention are:

[0019] 1. When the main shaft rotates, the packing gland does not rotate, which creates friction and acts as a rough seal, preventing powder from entering the mechanical seal assembly. This is equivalent to a double seal. However, the existing technology uses ordinary sealing rings, which have the disadvantages of being inconvenient to install and remove, getting stuck on the main shaft and affecting rotation, and having poor sealing effect.

[0020] 2. It guides the flow of materials. When the material (fragments and powders generated by the long-term friction of the packing gland) is full, it comes out from the air outlet of the bushing and enters the visible hopper through the hole in the middle of the flange. If blockage occurs, nitrogen is introduced into the air inlet of the bushing to prevent blockage. If the visible hopper is full, it can be discharged by unscrewing the plug at the bottom outlet. By allowing the fragments and powders generated by the long-term friction of the packing gland to flow into the visible hopper, the fragments and powders are prevented from entering the dryer.

[0021] 3. The combined seal designed in this invention can effectively prevent packing gland debris from entering the dryer. The labyrinth PTFE rings working in conjunction with the packing gland also effectively prevent material leakage from the dryer into the mechanical seal assembly, thus preventing the mechanical seal assembly from failing. This combined seal extends the service life of the mechanical seal assembly and improves the quality of the dried material. Attached Figure Description

[0022] Figure 1 This is a schematic diagram of the structure of the present invention;

[0023] Figure 2 This is a schematic diagram of the sealing assembly in this invention;

[0024] Figure 3 This is a front view of the labyrinth tetrafluoroethylene ring in this invention;

[0025] Figure 4 This is a left view of the labyrinth tetrafluoroethylene ring in this invention;

[0026] Figure 5 for Figure 4 Sectional view of AA.

[0027] In the diagram: 1. Housing; 2. End cover plate; 3. Sealing assembly; 4. Support; 5. Frame; 6. Motor; 7. Transmission assembly; 8. Main shaft; 31. Bushing; 32. PTFE sleeve; 33. Gland; 34. Bushing vent; 35. Connecting pipe; 36. Flange 1; 37. Visible hopper; 38. Outlet plug; 39. Flange 2; 40. Purge vent; 41. Packing gland; 42. Packing gland; 43. Mechanical seal assembly; 44. Labyrinth PTFE ring; 45. Temporary storage hopper; 46. Bushing inlet; 48. Outer guide groove; 49. Outlet; 50. Inner guide groove; 51. Labyrinth groove. Detailed Implementation

[0028] The present invention will be further described below through specific embodiments and in conjunction with the accompanying drawings.

[0029] Example 1:

[0030] like Figure 1 As shown, a combined seal for a rake dryer includes a frame 5, a housing 1 and a motor 6 mounted on the frame 5, a main shaft 8 disposed inside the housing 1, the motor 6 being rotatably connected to the main shaft 8 via a transmission assembly 7, the two ends of the main shaft 8 being rotatably mounted on supports 4, end caps 2 being provided at both ends of the housing 1, a sealing assembly 3 mounted on the main shaft 8 being disposed between the end caps 2 and the main shaft 8, and a mechanical seal assembly 43 mounted on the main shaft 8 being disposed on the outer and / or inner sides of the sealing assembly 3.

[0031] like Figure 2 As shown, the sealing assembly 3 includes a bushing 31, which is installed on the outer ring of the main shaft 8. A PTFE sleeve 32, a labyrinth PTFE ring 44, and a packing gland 42 are disposed in the cavity between the bushing 31 and the main shaft 8. The labyrinth PTFE ring 44 is disposed between the packing gland 42 and the PTFE sleeve 32. The upper end of the bushing 31 has a bushing inlet 46 communicating with the labyrinth PTFE ring 44, and the lower end of the bushing 31 has a bushing outlet 34 communicating with the labyrinth PTFE ring 44. The bushing 31 primarily serves to support and install the sealing assembly 3.

[0032] The lower end of the bushing vent 34 is connected to a visible hopper 37 via a connecting pipe 35 and flange 36. A discharge plug 38 is installed at the lower end of the visible hopper 37 via flange 39. A purge vent 40 is provided on one side of the visible hopper 37. The visible hopper 37 is used to receive materials and debris. It is made of high-temperature resistant tempered glass, allowing for constant observation of the stored material to prevent blockage and ensure the performance of the sealing assembly 3.

[0033] The side of the packing gland 42 is sealed by a packing gland 41, which is mounted on the circumference of the main shaft 8. The side of the PTFE sleeve 32 is sealed by a gland 33, which is also mounted on the circumference of the main shaft 8. The material of the packing gland 42 is selected according to the characteristics of the material. The cooperation between the gland 33 and the PTFE sleeve 32 inside the dryer mainly serves to support the labyrinth PTFE ring 44 and the packing gland 42. The packing gland 41, by pressing the packing gland 42, serves to connect the mechanical seal assembly 43.

[0034] A temporary storage bin 45 is provided between the air inlet 46 of the bushing and the labyrinth PTFE ring 44.

[0035] like Figure 3-5 As shown, the inner ring of the labyrinth PTFE ring 44 is provided with an annular inner guide groove 50, and the outer ring is provided with an annular outer guide groove 48. The inner guide groove 50 and the outer guide groove 48 are connected through a discharge hole 49. The labyrinth PTFE ring 44 is used to guide materials and debris, and can be purged with nitrogen. The inner ring of the labyrinth PTFE ring 44 is also provided with one or more annular labyrinth grooves 51. The labyrinth grooves 51 are multiple annular small grooves made according to the working conditions and material conditions. Materials / debris enter the labyrinth grooves 51 and temporarily accumulate. The top of the labyrinth grooves 51 cooperates with the main shaft 8 to prevent material leakage. The labyrinth grooves 51 can effectively prevent axial leakage along the main shaft 8 and play a labyrinth sealing role. After prolonged friction, the packing gland 42 will generate dust, powder and other materials which are stored in the inner ring of the labyrinth PTFE ring 44 and the temporary storage bin 45 on the outside. Under its own gravity, the dust, powder and other materials enter the bottom through the outer guide channel 48, and finally enter the visible hopper 37 through the bushing vent 34, the pipe 35 and the flange 36.

[0036] The labyrinth PTFE ring 44 guides the material flow. When the material (fragments and powders generated by the long-term friction of the packing gland 42) is full, it exits from the bushing vent 34 and flows into the visible hopper 37 through the hole in the middle of the flange 36. If blockage occurs, nitrogen is introduced into the bushing vent 46 to prevent blockage. If the visible hopper 37 is full, it can be drained by unscrewing the lower outlet plug 38. By allowing the fragments and powders generated by the long-term friction of the packing gland 42 to flow into the visible hopper 37, the fragments and powders are prevented from entering the dryer.

[0037] Example 2:

[0038] A sealing method, employing a combined seal of a rake dryer as described in Example 1, includes the following steps:

[0039] S1: The main shaft 8 rotates while the packing gland 42 does not rotate. The packing gland 42 can prevent powder from entering the mechanical seal assembly 43. However, after long-term friction, the packing gland 42 will produce fragments and powder. When the main shaft 8 rotates, the packing gland 42 does not rotate, which has a frictional effect on it, playing a rough sealing role and preventing powder from entering the mechanical seal assembly 43. This is equivalent to a double seal. However, the existing technology uses ordinary sealing rings, which have the disadvantages of inconvenient installation and removal, getting stuck on the main shaft and affecting rotation, and poor sealing effect.

[0040] S2: When the inside of the housing 1 is slightly positively pressured, as the main shaft 8 rotates, the material first enters the labyrinth PTFE ring 44, and then enters the temporary storage bin 45 through the discharge hole 49 of the inner guide groove 50. Under the weight of the material, the material falls into the visible bin 37 through the bushing vent 34, the connecting pipe 35, and the flange 36. When the inside of the housing 1 is negatively pressured, the dust and powder generated by the long-term friction of the packing gland 42 enters the labyrinth PTFE ring 44. As the main shaft 8 rotates, the material enters the temporary storage bin 45 through the discharge hole 49 of the inner guide groove 50. Then, under the weight of the dust and powder, the dust and powder fall into the visible bin 37 through the discharge hole 49 in the labyrinth PTFE ring 44, the bushing vent 34, the connecting pipe 35, and the flange 36.

[0041] S3: When the visible hopper 37 is full, the crushed material and powder are discharged through the discharge port plug 38 below the flange 2 39.

[0042] S4: When the labyrinth PTFE ring 44 becomes blocked, nitrogen is introduced through the bushing air inlet 46. During nitrogen purging, the nitrogen flows through the bushing air inlet 46, temporary storage bin 45, labyrinth PTFE ring 44, bushing air outlet 34, pipe 35, flange 36, and visible bin 37. Finally, the nitrogen is blown out from the purging exhaust port 40. The blockage remains in the visible bin 37. The blockage that enters the visible bin 37 is discharged through step S3, so that the whole system is unblocked and unobstructed.

[0043] The bushing 31 has a bushing inlet 46 and a bushing outlet 34, which are connected to the labyrinth PTFE ring 44. Nitrogen gas at a certain pressure can be passed through these holes to purge the material, preventing material from passing through the packing gland 42 and entering the mechanical seal assembly 43, thus causing contamination and wear and extending the mechanical seal's service life. During normal operation of the dryer, the interior is under negative pressure. Tiny debris from the friction between the packing gland 42 and the main shaft 8 enters the labyrinth PTFE ring 44. As the main shaft 8 rotates and the debris's own weight causes it to fall into the visible hopper 37. Nitrogen gas at a certain pressure is then passed through the bushing inlet 46 and outlet 34 on the bushing 31 to purge the debris, effectively preventing it from entering the dryer and contaminating the material. With increasing demands for product quality, the presence of impurities in the material is unacceptable. Particularly during the drying process, the friction between the rotating main shaft 8 and the packing gland 42 produces tiny debris, a major source of material impurities. Users place high demands on the lifespan of the mechanical seal assembly 43, but disassembling and replacing the mechanical seal is difficult due to the transmission characteristics of the dryer. The combined seal designed in this invention effectively prevents material leakage to the outside and impurities leakage to the inside, thus improving product quality and the lifespan of the mechanical seal assembly 43.

Claims

1. A combined seal for a rake dryer, comprising a frame (5), a housing (1) and a motor (6) mounted on the frame (5), a main shaft (8) disposed inside the housing (1), the motor (6) being rotatably connected to the main shaft (8) via a transmission assembly (7), and both ends of the main shaft (8) being rotatably mounted on supports (4), characterized in that: The housing (1) is provided with end cover plates (2) at both ends, and a sealing assembly (3) installed on the main shaft (8) is provided between the end cover plates (2) and the main shaft (8). A mechanical seal assembly (43) installed on the main shaft (8) is provided on the outer side and / or inner side of the sealing assembly (3). The sealing assembly (3) includes a bushing (31), which is installed on the outer ring of the main shaft (8). A PTFE sleeve (32), a labyrinth PTFE ring (44), and a packing gland (42) are provided in the cavity between the bushing (31) and the main shaft (8). The labyrinth PTFE ring (44) is located between the packing gland (42) and the PTFE sleeve (32). The upper end of the bushing (31) is provided with a bushing inlet (46) communicating with the labyrinth PTFE ring (44), and the lower end of the bushing (31) is provided with a bushing outlet (34) communicating with the labyrinth PTFE ring (44). The inner ring of the labyrinth PTFE ring (44) is provided with an annular inner guide groove (50), and the outer ring is provided with an annular outer guide groove (48). The inner guide groove (50) and the outer guide groove (48) are connected through the discharge hole (49). The labyrinth PTFE ring (44) is used to guide materials and debris impurities, and can be purged with nitrogen. The lower end of the bushing vent (34) is connected to a visible hopper (37) via a pipe (35) and a flange (36). The lower end of the visible hopper (37) is provided with a discharge plug (38) via a flange (39). A purge exhaust port (40) is provided on one side of the visible hopper (37). The side of the packing gland (42) is sealed by a packing gland (41), which is installed on the periphery of the main shaft (8). The side of the PTFE sleeve (32) is sealed by a gland (33), which is installed on the periphery of the main shaft (8).

2. The combined seal of the rake dryer according to claim 1, characterized in that: A temporary storage bin (45) is provided between the air inlet (46) of the bushing and the labyrinth PTFE ring (44).

3. A sealing method, characterized in that: The combined seal of the rake dryer as described in claim 2 includes the following steps: S1: The main shaft (8) rotates, while the packing gland (42) does not rotate. The packing gland (42) can prevent powder from entering the mechanical seal assembly (43), but after long-term friction, the packing gland (42) will produce fragments and powder. S2: When the inside of the shell (1) is slightly positive, as the main shaft (8) rotates, the material first enters the labyrinth PTFE ring (44), and enters the temporary storage bin (45) through the discharge hole (49) of the inner guide groove (50). Under the weight of the material, the material falls into the visible bin (37) through the bushing vent (34), pipe (35), and flange (36). When the inside of the shell (1) is negative, the dust and powder generated by the long-term friction of the packing gland (42) enter the labyrinth PTFE ring (44). As the main shaft (8) rotates, it enters the temporary storage bin (45) through the discharge hole (49) of the inner guide groove (50). Then, under the weight of the dust and powder, the dust and powder fall into the visible bin (37) through the discharge hole (49) of the labyrinth PTFE ring (44), the bushing vent (34), pipe (35), and flange (36).

4. The sealing method according to claim 3, characterized in that: It also includes the following steps: S3: When the visible hopper (37) is full, the crushed powder is discharged through the outlet plug (38) below the flange two (39).

5. The sealing method according to claim 4, characterized in that: It also includes the following steps: S4: When the labyrinth PTFE ring (44) is blocked, nitrogen is introduced through the bushing air inlet (46). When the nitrogen is purged, it passes through the bushing air inlet (46), temporary storage bin (45), labyrinth PTFE ring (44), bushing air outlet (34), pipe (35), flange (36), and visible bin (37). Finally, the nitrogen is blown out from the purging exhaust port (40). The blockage is stored in the visible bin (37), so that the whole is not blocked and is unobstructed.

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