Shaft end sealing structure of double-screw bulking machine

Abstract

A shaft end sealing structure of a double-screw bulking machine is characterized in that a pushing double screw is fixed at one end, close to a bulking cavity, of a main shaft, and a middle connected sealing box and a middle support are connected to form a closed cavity; the main shaft I and the main shaft II penetrate through the middle support and the middle connected sealing box; the sealing mechanism is arranged between the middle support and the middle connected sealing box, the sealing mechanism comprises a first sealing assembly and a second sealing assembly which are arranged on the first main shaft and the second main shaft, the first sealing assembly comprises an inner ring framework oil seal and an inner ring spacer ring, the inner ring spacer ring is communicated with an air channel, and the second sealing assembly comprises an outer ring framework oil seal and an inner ring spacer ring; the second sealing assembly comprises an outer ring framework oil seal and an outer ring spacer ring, and the outer ring spacer ring communicates with the oil way channel. One end of the gas path channel is communicated with the inner ring spacer ring, the other end of the gas path channel is communicated with a compressed air source and introduces compressed air, and one end of the oil path channel is communicated with the outer ring spacer ring, and the other end of the oil path channel is communicated with an oil source through an oil injection pipe and introduces lubricating oil.

Description

Technical Field

[0001] This invention relates to the field of extrusion equipment for food, feed, biomass, etc., specifically a sealing structure for the end of the main shaft of a twin-screw extruder suitable for high temperature, high pressure, and high humidity conditions. Background Technology

[0002] Twin-screw extruders, as core equipment in the food, feed, and biomass processing industries, operate by driving twin screws to rotate at high speed through a main shaft. This forces materials within the machine cavity to be compressed and matured under extreme conditions of high temperature (150-200℃), high pressure (1.0-3.0MPa), and high humidity (containing a large amount of water vapor), before being pushed towards the discharge end. However, in actual production, the "backflow phenomenon" of materials and steam remains a key issue restricting the stable operation of the equipment. Although the spiral structure of the twin-screw extruder generates an axial thrust towards the discharge end, 1%-5% of trace materials (such as grain powder and feed pellets) and high-temperature steam still diffuse towards the feed end shaft along the gap between the main shaft and the machine cavity. If the shaft end sealing structure cannot effectively block this, it will trigger a series of chain problems, which is a core pain point that current technology urgently needs to overcome.

[0003] Existing shaft end sealing solutions for twin-screw extruders are mainly designed around a "single mechanical seal" and have not been systematically optimized for the special characteristics of high-temperature, high-pressure, and high-humidity operating conditions. Specific structural defects are as follows: Existing technologies generally employ a single structure: either a "single-stage sealing packing" or a "single-lip skeleton oil seal." The former achieves sealing through the contact between a flexible packing (such as ordinary aramid fiber packing) and the spindle. However, the packing is prone to softening at temperatures above 150°C and easily compressed and deformed under pressures of 3.0 MPa. Furthermore, the high-speed friction (100-500 r / min) with the spindle leads to significant wear within 1-2 months, resulting in increased sealing gaps and material leakage. The latter uses a single-lip rubber oil seal for line contact sealing with the spindle. However, the contact area of ​​a single-lip structure is only 50% of that of a double-lip structure, making it unable to withstand the "penetrating force" of steam under high pressure. Moreover, the rubber material is prone to aging and cracking at temperatures above 200°C, typically requiring replacement every 2-3 months. More importantly, these single-seal structures lack any redundancy protection—once the seal fails partially (such as packing wear or oil seal lip cracking), material and steam will leak directly, necessitating immediate shutdown for repairs and preventing continuous production.

[0004] In existing sealing structures, the sealing packing typically contacts the metal sealing hole wall of the intermediate support directly. When the spindle rotates at high speed, the relative friction between the packing and the metal hole wall causes both to wear synchronously. On one hand, the wear of the packing accelerates the widening of the sealing gap, shortening its service life. On the other hand, the wear of the intermediate support sealing hole leads to an increase in the inner diameter of the sealing hole. Even if a new packing is replaced, a tight fit cannot be achieved through pre-tightening force, ultimately requiring the replacement of the entire intermediate support, significantly increasing maintenance costs (the purchase cost of a single intermediate support is approximately 2000-5000 yuan). Furthermore, although some solutions include a simple retaining ring, the gap between the retaining ring and the spindle is usually greater than 1mm, which cannot effectively block fine particles (such as grain powder with a particle size of 0.1-0.5mm), still causing the material to directly scour the sealing packing, exacerbating wear.

[0005] Current technology lacks a dedicated lubrication and cooling system, leaving the seals in a state of "high temperature + dry friction" for extended periods. At the contact point between the lip and the spindle of a single-lip skeleton oil seal, the friction temperature can rise to 180-220℃ due to the lack of a continuous lubricating oil film, far exceeding the tolerance limit of ordinary nitrile rubber oil seals (120℃). This causes the seal lip to carbonize and crack within 2-3 months. The friction between the sealing packing and the spindle also generates a large amount of heat. If heat cannot be dissipated in time, the aging rate of the packing material will accelerate by 30%-50%, further shortening the seal life. Simultaneously, the high temperature also puts the vapor within the sealing gap in a "superheated state," making it more penetrating and more likely to leak from the tiny gaps in the seal.

[0006] The aforementioned structural limitations directly lead to a triple dilemma for existing sealing technologies in practical applications: frequent material and water leaks, high maintenance costs, and low production efficiency. The specific impacts are as follows: Material leaking from the shaft end accumulates around the equipment, forming dust (such as grain powder leakage during food puffing). This not only pollutes the production environment (requiring 1-2 hours of cleaning daily) but also poses a risk of dust explosion (such as sawdust leakage during biomass puffing). Simultaneously, the leaked high-temperature steam increases humidity around the equipment, potentially causing electrical components (such as the spindle drive motor and control switches) to short-circuit due to moisture, increasing the probability of equipment failure. Based on a 10-ton-per-day puffing machine, the leakage rate of the existing sealing structure is approximately 0.5%-1%, resulting in an annual material waste of 1.8-3.6 tons. At a food raw material price of 2000 yuan / ton and a feed raw material price of 3000 yuan / ton, the annual material waste cost is approximately 3600-10800 yuan.

[0007] The existing sealing structure has a short replacement cycle for seals (packing, oil seals) (1-3 months / time), and the maintenance process is complex: replacing the sealing packing requires disassembling the main shaft, intermediate support, and other components, with a single maintenance time of approximately 2-4 hours; replacing the skeleton oil seal requires first removing the drive unit (such as a geared motor) and then taking out the main shaft, with a single maintenance time of approximately 4-6 hours. Based on 4-6 replacements per year, the annual downtime for a single machine can reach 16-36 hours. Assuming an hourly output value of 500-1000 yuan, the annual downtime loss is approximately 8000-36000 yuan. Adding the cost of purchasing seals (approximately 1000-2000 yuan per year) and replacing intermediate supports (approximately 2000-5000 yuan per year), the annual maintenance cost for a single machine can reach 11,000-43,000 yuan, significantly increasing the burden on enterprises.

[0008] Existing sealing technologies cannot meet the adaptability requirements of multiple industries and operating conditions: In the food extrusion field, ordinary sealing packing (such as aramid packing containing metal impurities) may pose a risk of harmful substance release, failing to meet the GB16798-2021 "Food Machinery Safety and Hygiene" standard; in the biomass extrusion field (such as sawdust and straw extrusion), the material has high hardness, and leaked material will cause stronger erosion and wear on the sealing components, further shortening the lifespan of existing sealing structures to less than one month; in high-pressure extrusion conditions (such as feed pelleting at a pressure of 2.5-3.0 MPa), existing single-stage seals cannot resist the backflow of high-pressure steam, and the leakage rate can rise to 2%-3%, completely failing to meet production requirements.

[0009] To address the aforementioned issues, some existing technologies have attempted optimizations (such as the "a shaft end seal for an extruder" disclosed in patent CN108991765A), but they still haven't overcome the core limitations: this solution only adds a single-stage skeleton oil seal within the sealing seat, without setting up a positive pressure protection chamber or a lubrication system. On the one hand, the single-stage oil seal still cannot withstand the backflow of steam under high temperature and pressure, and the seal failure problem is not fundamentally solved; on the other hand, the lack of lubrication means that the oil seal life is not significantly improved, and there is no redundant protection design, so shutdown and maintenance are still required after seal failure. In addition, this solution does not include a wear-resistant ring and a leak-proof retaining ring, so the problems of rapid wear of the seal and material erosion of the seal still exist. Essentially, it is still a localized improvement of a "single seal," without forming a systematic sealing system, and cannot meet the requirements of long-term stable operation of a twin-screw extruder.

[0010] Therefore, there is an urgent need to provide a shaft end sealing system that is compact in structure, has reliable sealing performance, redundant sealing capability, and is easy to maintain. Summary of the Invention

[0011] Objective of this invention: To overcome the shortcomings of existing technologies, this invention provides a shaft end sealing system that is compact in structure, has reliable sealing performance, redundant sealing capability, and is easy to maintain. Technical solution: A shaft end sealing structure for a twin-screw extruder, comprising: The pusher twin screw, main shaft one, and main shaft two are connected to main shaft one and main shaft two respectively; The twin-screw pusher is fixed at one end of the puffing spindle near the puffing cavity. The intermediate integrated sealed box is connected to the intermediate support to form a sealed cavity; Main shaft one and main shaft two pass through the intermediate support and the intermediate integrated sealed box; It also includes a sealing mechanism, located between the intermediate support and the intermediate integrated sealing box. The sealing mechanism includes a first sealing assembly and a second sealing assembly disposed on main shaft one and main shaft two. The first sealing assembly includes an inner ring skeleton oil seal and an inner ring spacer, with the inner ring spacer connecting to the gas passage. The second sealing assembly includes an outer ring skeleton oil seal and an outer ring spacer, with the outer ring spacer connected to the oil passage. The air passage connects at one end to the inner ring spacer and at the other end to a compressed air source, introducing compressed air. The oil passage is connected at one end to the outer ring spacer and at the other end to the oil source via an oil injection pipe, which introduces lubricating oil.

[0012] The sealing mechanism includes a sealing seat and a sealing seat cover. The air passage and the oil passage are disposed on the sealing seat. The sealing seat is fixed to the intermediate support by bolts. The sealing seat cover is pressed against the sealing seat.

[0013] The sealing seat includes an annular portion and a central portion. Two gas passages are provided at both ends of the annular portion, and the oil passage is provided in the central portion.

[0014] The first and second main shafts pass through the sealing holes of the intermediate support and the intermediate integrated sealing box, respectively. The first and second main shafts are connected to the drive device through a spline coupling. The first and second main shafts are arranged parallel to each other and adapted to the working chamber of the pusher twin screw. The axial distance between the two main shafts matches the screw center distance of the pusher twin screw, ensuring that the pusher twin screw can achieve stable material pushing and meshing extrusion during rotation.

[0015] The intermediate support is provided with a sealing hole, and a wear-resistant ring and a sealing packing are installed in sequence in the sealing hole; the wear-resistant ring is disposed between the sealing packing and the inner wall of the sealing hole of the intermediate support.

[0016] It also includes a leak-proof retaining ring, which is installed on the first main shaft and the second main shaft and is located on the side of the intermediate support near the puffing chamber. It is used to cooperate with the pusher twin screw to prevent the material from contacting the intermediate support.

[0017] The air passage is connected to an external compressed air source via an air pipe tee, and the air pipe tee is fixed to the intermediate integrated sealed box via an air pipe fixing cover.

[0018] The inner ring skeleton oil seal and the inner ring spacer are described. The inner ring spacer is embedded in the annular groove of the air passage, and its axial thickness is consistent with the width of the air passage. The inner ring spacer contacts the main shaft. The inner ring skeleton oil seal is configured with a double lip structure and is located in the oil seal groove of the sealing seat, fitting against the end face of the inner ring spacer. The lip faces the expansion cavity side. The inner ring of the inner ring skeleton oil seal is interference-fitted with the spindle, and the outer ring of the inner ring skeleton oil seal is transition-fitted with the oil seal groove.

[0019] The outer ring includes a skeleton oil seal and an outer ring spacer. The outer ring spacer is embedded in the annular groove of the oil passage, and the inner ring of the outer ring spacer contacts the main shaft. The outer ring skeleton oil seal is configured as a single lip structure and is installed in the outer ring oil seal groove of the sealing seat, with the lip facing away from the expansion cavity.

[0020] It also includes an intermediate integrated sealing cover; the intermediate integrated sealing cover is bolted to the top of the intermediate integrated sealing box.

[0021] Compared with the prior art, the beneficial effects of the present invention are as follows: Leakage rate is significantly reduced: through the source prevention of leakage by "pushing twin screws + leak-proof retaining ring", the first seal of "sealing packing", the enhanced seal of "air path assistance", and the backup seal of "closed cavity air pressure", the leakage rate is reduced by more than 90% and material waste is reduced to less than 0.5%. Extended seal life: Wear-resistant rings isolate the packing from the support, extending the packing replacement cycle from 7-15 days to 30-45 days; continuous lubrication of the oil circuit extends the oil seal life from 1 month to 3 months, reducing maintenance frequency by 60%. Increased production efficiency: The air pressure in the sealed chamber serves as a backup seal, allowing normal production to continue for 1-2 hours even if the main seal fails, thus avoiding sudden shutdowns and increasing production efficiency by more than 15%. High structural reliability: The integrated sealed box in the middle reduces splicing gaps, and the gas-oil synergistic design takes into account both sealing and lubrication. The overall structure is suitable for high temperature, high pressure and high humidity conditions, and has strong stability. Attached Figure Description

[0022] Figure 1 Schematic diagram of the shaft end structure of the extruder Figure 1 (Overall assembly relationship diagram); Figure 2 Schematic diagram of the shaft end structure of the extruder Figure 2 (Component breakdown diagram); Figure 3 Cross-sectional view of the shaft end structure of the extruder; Figure 4 Enlarged view of a portion of the structure at the shaft end of the extruder; The markings in the diagram are: 1-Pushing twin screw; 2-Intermediate integrated sealing cover; 3-Intermediate support; 4-Intermediate integrated sealing box; 5-Leak-proof retaining ring; 6-Main shaft one; 7-Main shaft two; 8-Sealing packing; 9-Wear-resistant ring; 10-Sealed cavity; 11-Splined sleeve coupling; 12-Sealing device; 13-Air pipe tee; 14-Air pipe fixing cover; 15-Branch straight connector; 16-Oil injection pipe; 17-Air pipe; 120-Air passage; 121-Sealing seat; 122-Sealing seat gland; 123-Air pipe right angle connector; 124-Inner ring skeleton oil seal; 125-Inner ring spacer; 126-Oil passage; 127-Oil injection nozzle; 128-Outer ring skeleton oil seal; 129-Outer ring spacer. Detailed Implementation

[0023] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative and not intended to limit the invention. All other embodiments obtained by those skilled in the art based on the embodiments of this invention without inventive effort are within the scope of protection of this invention.

[0024] It should be noted that the descriptions involving "first," "second," etc., in this invention are for descriptive purposes only and should not be construed as indicating or implying their relative importance or implicitly specifying the number of technical features indicated. Therefore, a feature defined with "first" or "second" may explicitly or implicitly include at least one of that feature. Furthermore, the technical solutions of the various embodiments can be combined with each other, but this must be based on the ability of those skilled in the art to implement them. If the combination of technical solutions is contradictory or impossible to implement, it should be considered that such a combination of technical solutions does not exist and is not within the scope of protection claimed by this invention.

[0025] like Figures 1 to 4 As shown, the specific assembly and operation process of the twin-screw extruder shaft end sealing structure in this embodiment is as follows: Structural assembly: Install the feeding twin screw (1) at the front end of the puffing chamber, and heat-fit the anti-leakage retaining ring (5) on the main shaft one (6) and the main shaft two (7), and close to the end face of the feeding twin screw (1); The pusher twin screw (1) adopts an optimized helix angle design, which generates an axial thrust towards the discharge end when rotating, pushing more than 95% of the material to the discharge end; the anti-leakage retaining ring (5) is a ring structure, which is interference fit with the main shaft one (6) and the main shaft two (7), and the gap between its end face and the end face of the pusher twin screw (1) is controlled at 0.5-1mm, which can prevent the small amount of material that has not been pushed from directly contacting the intermediate support (3), reducing the load on the sealing components from the source and avoiding the scouring and wear of the material on the subsequent sealing components.

[0026] The intermediate support (3) is fixed to the end face of the extruder barrel by bolts. Wear-resistant rings (9) and aramid fiber sealing packing (8) are installed in the two sets of sealing holes of the intermediate support (3) in sequence. The sealing hole of the intermediate support (3) is a stepped hole structure. The wear-resistant ring (9) is an annular metal part (tungsten carbide or stainless steel can be selected). It is interference-fitted to the front end of the sealing hole (near the expansion cavity side). Its inner diameter and the gap between the main shaft are ≤0.1mm, which can avoid direct friction between the sealing packing (8) and the metal hole wall of the intermediate support (3). The sealing packing (8) uses flexible sealing material (aramid fiber or polytetrafluoroethylene impregnated graphite can be selected) and fills between the wear-resistant ring (9) and the sealing device (12). It achieves tight fit with the main shaft through the pre-tightening force of the sealing seat cover (122) and directly blocks the material and water vapor that break through the leak-proof ring (5).

[0027] Assembly of sealing device (12): The inner ring spacer (125), inner ring skeleton oil seal (124), outer ring spacer (129), and two outer ring skeleton oil seals (128) are sequentially installed into the cavity of the sealing seat (121), and the sealing seat (121) is fixed on the intermediate support (3) by bolts. Finally, the sealing seat cover (122) is used to press the sealing seat (121) tightly. Inner ring skeleton oil seal (124) + outer ring skeleton oil seal (128). Both the inner ring skeleton oil seal (124) and the outer ring skeleton oil seal (128) are double-lip structures (the lip material is nitrile rubber and fluororubber). The inner ring skeleton oil seal (124) is located outside the air passage (120) and can block the leakage of compressed air in the sealed cavity (10), while further blocking air that may be entrained with water vapor. Two to three outer ring skeleton oil seals (128) are arranged side by side and installed outside the oil passage (126). They can not only prevent lubricating oil leakage, but also block external dust and impurities from entering the sealing system, forming a "two-way auxiliary seal".

[0028] The intermediate integrated sealed box (4) is connected to the intermediate support (3) through the intermediate integrated sealed cover (2) to form a sealed cavity (10); the air pipe tee (13) is fixed on the intermediate integrated sealed box (4) through the air pipe fixing cover (14), one end of the air pipe (17) is connected to an external compressed air source, and the other end is connected to the air pipe tee (13). The air pipe tee (13) is connected to the air passage (120) of the inner ring spacer (125) through the air pipe right angle connector (123); one end of the oil injection pipe (16) is connected to an external lubricating oil source, and the other end is connected to the oil passage (126) of the outer ring spacer (129) through the oil injection nozzle (127); The intermediate integrated sealing box (4) and the intermediate support (3) form a sealed cavity (10) with a volume of about 50-100cm³ (estimated based on equipment size) through the intermediate integrated sealing cover (2); the air passage (120) is a Φ3-5mm (reasonable aperture range) through hole radially opened by the inner ring spacer (125), which is connected to the external compressed air source through the air pipe tee (13) and the air pipe right angle connector (123), and can introduce 0.2-0.6MPa of compressed air into the sealed cavity (10) to form a stable positive pressure. This positive pressure can not only push the sealing packing (8) to further adhere to the main shaft and enhance its sealing effect, but also form an "air curtain" on the surface of the main shaft after the sealing packing (8) wears, preventing the material and steam from continuing to diffuse to the shaft end, which is the "redundant protection core" of the sealing system.

[0029] Main shaft one (6) and main shaft two (7) pass through the sealing hole and the sealed cavity (10) of the intermediate support (3) respectively, and are finally connected to the geared motor (drive device) through the spline coupling (11).

[0030] Work process: When production starts, an external compressed air source introduces 0.4MPa of compressed air into the sealed cavity (10) to form a stable positive pressure in the sealed cavity (10); an external lubricating oil source injects lubricating oil into the oil passage (126) through the oil injection nozzle (127), and the lubricating oil is evenly distributed on the surface of the inner ring skeleton oil seal (124) and the outer ring skeleton oil seal (128); The rotating twin screw (1) pushes most of the material to the discharge end, and the anti-leakage retaining ring (5) blocks a small amount of reverse material, preventing the material from directly contacting the sealing hole of the intermediate support (3). If a small amount of material or steam breaks through the leak-proof ring (5), it will first be blocked by the sealing packing (8); if the sealing packing (8) is worn due to long-term use, the positive pressure air in the sealed cavity (10) will form an air curtain on the surface of the main shaft through the air passage (120), preventing the material and steam from continuing to leak to the shaft end. The inner ring skeleton oil seal (124) further blocks the trace amount of water vapor that may be trapped in the air curtain, and the outer ring skeleton oil seal (128) (two side by side) prevents the lubricating oil from leaking to the outside; while lubricating the oil seal, the lubricating oil also carries away the heat generated by the friction between the oil seal and the spindle, thus preventing the oil seal from failing due to high temperature. During maintenance, only the sealing seat cover (122) needs to be removed to take out the inner ring skeleton oil seal (124) and the outer ring skeleton oil seal (128) for replacement. There is no need to disassemble the spindle or the intermediate integrated sealing box (4), and the maintenance time is shortened to less than 30 minutes.

[0031] Positive pressure redundancy protection: The positive pressure of the sealed cavity (10) is designed for "dynamic adjustment". When the pressure inside the cavity drops due to wear of the sealing packing (8), the external compressed air source can automatically replenish the pressure through the pressure sensor (not mentioned in the document, but a necessary component for achieving dynamic adjustment) to maintain a pressure range of 0.2-0.6MPa. Even if the inner ring skeleton oil seal (124) fails partially, the positive pressure air can still form sufficient blocking pressure through the oil seal gap to ensure that materials and steam do not leak, achieving the redundancy effect of "continuous production can still be carried out even if the seal fails partially".

[0032] Redundant protection with multiple oil seals: 2-3 outer ring skeleton oil seals (128) are arranged side by side, using the "series sealing" logic. If the first oil seal leaks due to wear, the second and third oil seals can continue to block the lubricating oil, avoiding dry friction failure of the seal due to lubricating oil loss. At the same time, compared with the single-lip oil seal, the double-lip skeleton oil seal has a sealing contact area that is more than 50% larger, and can withstand higher pressure and speed (suitable for the working speed of the spindle 100-500r / min), further improving the sealing reliability.

[0033] Example 2 (Adapted for high-voltage conditions) Based on Example 1, the following adjustments were made for high-pressure expansion conditions with a pressure of up to 2.5 MPa: The number of outer ring skeleton oil seals (128) was increased from 2 to 3 to enhance the sealing effect of lubricating oil and auxiliary sealing effect; The pressure of compressed air in the sealed chamber (10) is adjusted to 0.6MPa to ensure that the positive pressure is sufficient to resist the backflow force of materials and steam under high pressure conditions.

[0034] Experimental verification: The adjusted structure operated continuously for 1000 hours under the conditions of 2.5MPa pressure and 200℃ temperature, with a leakage rate of <0.1g / h, no material or water leakage, and stable sealing performance. Example

[0035] Based on Example 1, the following material adjustments were made to meet the hygiene requirements of food puffing equipment: The material of the sealing packing (8) has been changed from aramid fiber to polytetrafluoroethylene impregnated graphite, which has the characteristics of high and low temperature resistance, wear resistance and compliance with food hygiene standards; The material of the wear-resistant ring (9) was changed to tungsten carbide, which improved wear resistance while preventing the precipitation of metal ions; The lubricating oil was replaced with food-grade white oil, which meets the requirements of GB16798-2021 "Food Machinery Safety and Hygiene" standard.

[0036] All components of this structure that come into contact with food meet the hygiene requirements for food machinery, and no harmful substances are released, making it suitable for the production of puffed foods.

[0037] For the high temperature of 150-200℃, high pressure of 1.0-3.0MPa and high humidity environment of the extruder, each sealing component is made of weather-resistant material: the sealing packing (8) is made of polytetrafluoroethylene impregnated graphite that can withstand temperatures above 250℃, the lip of the skeleton oil seal is made of fluororubber that can withstand temperatures above 200℃, and the wear ring (9) is made of wear-resistant and high-temperature resistant tungsten carbide to ensure that the material does not soften or age under extreme working conditions.

[0038] The pressure of the air circuit system can be adjusted according to the expansion conditions. For example, 0.2-0.3MPa compressed air is introduced under low pressure conditions (1.0-1.5MPa) and 0.5-0.6MPa compressed air is introduced under high pressure conditions (2.5-3.0MPa) to ensure that the positive pressure of the sealed cavity (10) is always higher than the reverse pressure in the expansion cavity, thus achieving "dynamic pressure matching".

[0039] The oil passage (126) can be selected with different types of lubricating oil according to the working conditions. For example, anti-wear hydraulic oil is selected for industrial puffing equipment, and food-grade white oil is selected for food puffing equipment. The oil injection nozzle (127) is a one-way valve structure, which can realize quantitative and timed oil injection (it is recommended to inject 10-20mL of oil every 8 hours) to ensure that the skeleton oil seal can still maintain good lubrication at high temperature and avoid dry friction wear.

[0040] The sealing device (12) consists of a sealing seat (121), an inner ring spacer (125), an outer ring spacer (129), and a skeleton oil seal. These components are fixed by bolts on the sealing seat cover (122). When replacing the seal, only the sealing seat cover (122) needs to be removed to take out the failed seals in sequence. There is no need to disassemble large components such as the main shaft and the intermediate integrated sealing box (4). The maintenance time can be shortened to less than 30 minutes (the traditional structure requires 2-4 hours).

[0041] The air pipe tee (13) is fixed by the air pipe fixing cap (14), and the oil injection pipe (16) is quickly connected by the oil injection nozzle (127). When disassembling, only the air pipe joint and the oil injection nozzle need to be loosened, which facilitates the separate maintenance of the air circuit and the oil circuit and avoids the shutdown of the entire sealing system due to local faults.

[0042] The above description is only a preferred embodiment of the present invention. It should be noted that for those skilled in the art, several improvements and modifications can be made without departing from the principle of the present invention, and these improvements and modifications should also be considered within the scope of protection of the present invention.

Claims

1. A shaft end seal structure of a twin-screw extruder, characterized by: It comprises: Pushing material double screw, main shaft one, main shaft two, intermediate support and intermediate connected sealing box; The pushing material double screw is connected to the main shaft one and the main shaft two respectively; The pushing material double screw is fixed to one end of the main shaft one and the main shaft two close to the puffing cavity, The leakage prevention check ring is installed on the main shaft one and the main shaft two and is located on one side of the intermediate support close to the puffing cavity, used for cooperating with the pushing material double screw, The intermediate connected sealing box is connected with the intermediate support to form a closed cavity; The main shaft one and the main shaft two penetrate through the intermediate support and the intermediate connected sealing box; It also comprises a sealing mechanism arranged between the intermediate support and the intermediate connected sealing box, the sealing mechanism comprising a first sealing assembly and a second sealing assembly arranged on the main shaft one and the main shaft two, The first sealing assembly comprises an inner ring skeleton oil seal and an inner ring spacer ring, and the inner ring spacer ring is communicated with an air passage, The second sealing assembly comprises an outer ring skeleton oil seal and an outer ring spacer ring, and the outer ring spacer ring is communicated with an oil passage; The air passage is communicated with the inner ring spacer ring at one end and is communicated with a compressed air source at the other end to introduce compressed air, The oil passage is communicated with the outer ring spacer ring at one end and is communicated with an oil source through an oil injection pipe at the other end to introduce lubricating oil.

2. The shaft end sealing structure of the double screw puffing machine according to claim 1, characterized in that: The sealing mechanism comprises a sealing seat and a sealing seat gland, the air passage and the oil passage are arranged in the sealing seat, the sealing seat is fixed to the intermediate support through bolts, and the sealing seat gland is pressed against the sealing seat; The sealing seat comprises a ring part and a middle part, the air passage is provided with two ends distributed in the ring part, and the oil passage is arranged in the middle part.

3. The shaft end seal structure of a twin-screw extruder according to claim 1, characterized by: The main shaft one and the main shaft two penetrate through the sealing hole of the intermediate support and the intermediate connected sealing box, the main shaft one and the main shaft two are connected with a driving device through a spline sleeve coupling, the main shaft one and the main shaft two are arranged in parallel and adapt to the working cavity of the pushing material double screw, the distance between the axes of the two main shafts matches the center distance of the pushing material double screw, and the pushing material double screw can realize stable pushing and meshing extrusion of materials during rotation.

4. The shaft end sealing structure of the double screw puffing machine according to claim 3, characterized in that: The intermediate support is provided with a sealing hole, a wear-resistant ring and a sealing packing are sequentially arranged in the sealing hole, and the wear-resistant ring is arranged between the sealing packing and the inner wall of the sealing hole of the intermediate support.

5. The shaft end sealing structure of the double screw puffing machine according to claim 1, characterized in that: The air passage is connected with an external compressed air source through an air pipe three-way joint, and the air pipe three-way joint is fixed on the intermediate connected sealing box through an air pipe fixed cover.

6. The shaft end seal structure of a twin-screw extruder according to claim 1, characterized by: The inner ring skeleton oil seal and the inner ring spacer ring, the inner ring spacer ring is embedded in the annular groove of the air passage, the axial thickness is consistent with the width of the air passage, and the inner ring spacer ring is in contact with the main shaft The inner ring skeleton oil seal is arranged in a double-lip structure, arranged in the oil seal groove of the sealing seat, in contact with the end face of the inner ring spacer ring, the lip is directed to the puffing cavity side, the inner ring of the inner ring skeleton oil seal is in interference fit with the main shaft, and the outer ring of the inner ring skeleton oil seal is in transition fit with the oil seal groove.

7. The shaft end sealing structure of a twin-screw extruder according to claim 1, characterized in that: an outer ring skeleton oil seal and an outer ring spacer ring, the outer ring spacer ring being embedded in an annular groove of an oil passage, an inner ring of the outer ring spacer ring being in contact with the main shaft, the outer ring skeleton oil seal being provided as a single-lip structure and being installed in an outer ring oil seal groove of a sealing seat, the lip being directed away from the extrusion cavity.

8. The shaft end seal structure of a twin-screw extruder according to claim 1, characterized by: Further comprising an intermediate connecting body sealing cover; the intermediate connecting body sealing cover being bolted on the top of the intermediate connecting body sealing box.

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