A combined fuel filter and method of assembling the same

Abstract

This invention discloses a filter technology, aiming to provide a combined fuel filter and its assembly method. The key technical points include an outer cover, an inner cover connected to the outer cover via a snap-fit ​​structure, and flame-retardant honeycomb filter cotton disposed between the outer and inner covers. The snap-fit ​​structure includes several grooves evenly distributed on the inner sidewall of the outer cover and several sliders evenly distributed on the top outer sidewall of the inner cover and adapted to the grooves. A buckle is provided in the groove near the opening of the outer cover, and a slot matching the buckle is provided on the slider. The top of the slider has a chamfer, with the chamfer's bevel facing the installation direction of the outer cover. The outer and inner covers are snapped together and fixed by the sliding cooperation between the slider and the groove, and the snap-fit ​​between the buckle and the slot. A bracket is provided in the middle of the inner hole of the inner cover, and several uprights are provided on the inner bottom surface of the outer cover. External threads are provided on the bottom outer sidewall of the inner cover. This invention is applicable to the field of filter technology.

Description

Technical Field

[0001] This invention relates to a filter technology, and more specifically, to a combined fuel filter and its assembly method. Background Technology

[0002] During fuel refueling, a filter device is typically installed at the filler neck to prevent impurities and moisture from entering the fuel tank and to avoid hazards caused by static sparks. Existing fuel filters have the following shortcomings: First, the filter material is mostly ordinary non-woven fabric with poor flame retardant properties, easily igniting fuel vapors when exposed to static electricity or high temperatures, posing a significant safety hazard; second, the overall structure of the filter is fixed, making it impossible to flexibly adjust or combine it according to different usage requirements such as fuel tank interface specifications and filtration precision, resulting in poor versatility. Therefore, there is an urgent need for a modularly combinable fuel filter that also possesses high-efficiency flame retardancy to adapt to different usage needs. Summary of the Invention

[0003] To address the shortcomings of existing technologies, the present invention aims to provide a modularly combinable and flame-retardant combined refueling filter and its assembly method.

[0004] To achieve the above objectives, the present invention provides the following technical solution: a combined fuel filter, comprising an outer cover, an inner cover connected to the outer cover via a snap-fit ​​structure, and flame-retardant honeycomb filter cotton disposed between the outer cover and the inner cover; the snap-fit ​​structure includes several grooves evenly distributed on the inner sidewall of the outer cover and several sliders evenly distributed on the top outer sidewall of the inner cover and adapted to the grooves, a buckle is provided in the groove near the opening of the outer cover, and a slot is provided on the slider to match the buckle, and a chamfer is provided on the top of the slider, with the chamfer's bevel facing the installation direction of the outer cover; the outer cover and the inner cover are snapped and fixed by the sliding cooperation of the slider and the groove and the snap-fit ​​of the buckle and the slot; a bracket for placing the flame-retardant honeycomb filter cotton is provided in the middle of the inner hole of the inner cover, and several uprights for fixing and positioning the flame-retardant honeycomb filter cotton are provided on the inner bottom surface of the outer cover; the bottom outer sidewall of the inner cover is provided with external threads.

[0005] The invention is further configured to include a first base that is fixedly connected to the external thread of the inner cover. The first base is integrally formed and has an overall T-shaped cross-section. The first base includes a tube body and a first flange disposed on the outer periphery of the tube body and coaxial with the tube body. A plurality of mounting holes are uniformly opened along the circumferential direction on the end face of the first flange. The inner side of the tube body includes an internal thread that is connected to the external thread of the inner cover and a tapered hole that communicates with the internal thread. The minimum diameter of the tapered hole is transitionally connected to the internal thread. A sealing gasket is fitted on the outer periphery of the tube body and located below the first flange. A plurality of through holes corresponding to the mounting holes are opened on the sealing gasket.

[0006] The invention is further configured to include a mounting assembly fixed to the bottom of the first flange by locking screws, the mounting assembly including a second base and a filter screen; the second base is integrally formed, the second base including a cylindrical body and a second flange disposed on the outer periphery of the cylindrical body and coaxial with the cylindrical body, the top surface of the cylindrical body having a plurality of threaded holes corresponding to the through holes of the first sealing gasket for connection of the locking screws, the first flange and the second base being fixedly connected by locking screws passing through the mounting holes, the through holes of the first sealing gasket, and the threaded holes of the cylindrical body in sequence; a plurality of connecting holes are evenly provided along the circumferential direction on the end face of the second flange, the inner side of the cylindrical body The filter screen is configured as a stepped hole and communicates with the conical hole of the tube body. The filter screen includes an installation part and a filtering part. The installation part has several through holes corresponding to the connection holes. The second flange and the filter screen are fixedly connected by pan head screws passing through the connection holes and the through holes of the installation part in sequence. A flat washer is provided between each pan head screw and the second flange. A second sealing gasket is fitted on the outer periphery of the cylinder body and located below the second flange. A third sealing gasket is fitted on the outer periphery of the filter screen and located below the installation part. Both the second and third sealing gaskets have several through holes corresponding to the connection holes. The hole in the stepped hole near the filtering part of the filter screen is adapted to the diameter of the filtering part.

[0007] The invention is further configured to include a fixing seat fixed to the bottom of the mounting part by pan head screws. The fixing seat is integrally formed and sleeved on the outside of the filter part. The fixing seat includes a hollow column and a third flange disposed on the outer periphery of the hollow column and coaxial with the hollow column. The top surface of the hollow column has a plurality of threaded holes corresponding to the through holes of the sealing gasket three for connection by pan head screws. The second flange and the fixing seat are fixedly connected by pan head screws passing through a flat washer, a connecting hole, the through hole of the sealing gasket two, the through hole of the mounting part, the through hole of the sealing gasket three, and the threaded hole of the hollow column in sequence. A plurality of fixing holes are uniformly opened along the circumferential direction on the end face of the third flange. The inner side of the hollow column is configured as a connecting hole with a trapezoidal cross section. The minimum inner diameter of the connecting hole is larger than the outer diameter of the filter part, and the minimum inner diameter of the connecting hole is close to the mounting part. A sealing gasket four is sleeved on the outer periphery of the hollow column and located below the third flange.

[0008] A method for assembling a combined fuel filter, characterized by comprising the following steps: S1. Place the flame-retardant honeycomb filter cotton on the bracket in the middle of the inner hole of the inner cover, so that the bottom surface of the flame-retardant honeycomb filter cotton is completely in contact with the top surface of the bracket. Then, pre-align the outer cover and the inner cover: then fasten the outer cover on top of the inner cover, so that the sliding groove on the inner side wall of the outer cover is aligned with the slider on the top outer side wall of the inner cover; push the outer cover along the installation direction of the outer cover, so that the slider slides along the sliding groove until the buckle in the sliding groove is engaged in the slot on the slider. At this time, the upright on the inner bottom surface of the outer cover abuts against the flame-retardant honeycomb filter cotton, realizing the axial and circumferential positioning of the flame-retardant honeycomb filter cotton, that is, the snap-fit ​​fixing of the outer cover and the inner cover is completed. S2. Take the first base, align the internal thread of its tube body with the external thread of the outer side wall of the bottom of the inner cover, rotate the first base to tighten and fix the internal thread of the tube body with the external thread of the inner cover, so that the conical hole of the tube body and the inner hole of the inner cover are coaxially connected; then put a sealing gasket on the outer periphery of the tube body of the first base, so that the sealing gasket is attached to the bottom surface of the first flange, and the through hole on the sealing gasket corresponds one-to-one with the mounting hole on the first flange. S3. Pre-align the second base: Align the threaded hole on the top surface of the second base's cylinder with the mounting hole of the first flange and the through hole of the first gasket. Then, take the locking screw, pass it through the mounting hole of the first flange and the through hole of the first gasket, and screw it into the threaded hole of the cylinder. Tighten the locking screw to fix the first flange and the second base in place. Next, place the second gasket on the outer periphery of the second base's cylinder, so that the second gasket fits against the bottom surface of the second flange, and the through hole on the second gasket aligns with the connection hole on the second flange. Correspondingly; place the sealing gasket three on the outer periphery of the filter screen, so that the sealing gasket three fits against the bottom surface of the filter screen mounting part, and the through holes on the sealing gasket three correspond one-to-one with the through holes of the filter screen mounting part. Then align the filter part of the filter screen with the stepped hole of the second base cylinder, so that the through holes on the mounting part of the filter screen are aligned with the connection holes of the second flange and the through holes of the sealing gasket two. Then take the pan head screw, first put the flat washer on the pan head screw, and then pass it through the connection hole of the second flange, the through hole of the sealing gasket two, the through hole of the mounting part, and the through hole of the sealing gasket three in sequence. S4. Place the mounting base over the filter screen, aligning the threaded hole on the top surface of the hollow column of the mounting base with the through hole of sealing gasket three, the through hole of the mounting part, the through hole of sealing gasket two, and the connection hole of the second flange; then screw the pan head screws into the threaded hole of the hollow column and tighten the pan head screws to fix the second flange, filter screen, and mounting base; next, place the sealing gasket four around the outer periphery of the hollow column of the mounting base, so that the sealing gasket four fits against the bottom surface of the third flange, completing the assembly of the combined oil filter; S5. Check the tightness of the connection between the outer cover and the inner cover, and confirm that the buckle is fully engaged in the slot and there is no looseness. At the same time, check whether the flame-retardant honeycomb filter cotton moves synchronously with the inner cover by shaking the outer cover. S6. Inspect the connection between the locking screw and the pan head screw, and observe the pressure deformation of gasket 1, gasket 2, and gasket 3 to ensure that there are no warping or leakage gaps in each gasket. S7. The entire structure is left to stand still and subjected to an axial pressure test to confirm that the overall structure formed by the first base, mounting components and fixing seat is leak-free and that each sealing gasket is in a uniformly compressed state.

[0009] The present invention is further configured such that, in step S4, when the fixing seat, mounting part and second flange are threaded together, the sealing and positioning accuracy is ensured by the following judgment method: after the pan head screw passes through the second flange, sealing gasket two, mounting part and sealing gasket three, the hollow cylinder is first manually screwed in until it fits against sealing gasket three, and then tightened in stages. The first stage reaches 60% of the set torque, the second stage reaches 100%, and after the final tightening, the compression of sealing gasket three and sealing gasket four is detected. When the compression reaches a gradient range of 25%-35% of the original thickness, the installation is deemed qualified, and the concentricity deviation between the connecting hole and the filter screen is <0.1mm.

[0010] The present invention is further configured as follows: In step S7, after the entire assembly is left to stand and an axial pressure test is applied, an axial pressure is applied to the conical hole of the first base, and the deformation of the end face of the third flange of the fixed seat is detected at the same time. When the deformation is <0.05mm and there is no reverse warping of each sealing gasket, the overall assembly is deemed qualified. Furthermore, the joint of sealing gasket one, sealing gasket two, and sealing gasket three is detected by light transmission method or bubble method. If no light is transmitted or no bubbles are generated, the sealing is deemed qualified. Finally, it is confirmed that the combined oil filter meets the preset sealing standard.

[0011] The beneficial effects of this invention are: 1. Compared with existing technologies, the combined refueling filter of this invention uses a groove-slider combination for the outer cover and inner cover. The top of the slider is chamfered to guide smooth sliding and reduce assembly resistance. The groove is equipped with a buckle that precisely engages with the slider slot, achieving quick locking and preventing loosening, which facilitates efficient on-site installation and maintenance. A bracket is set in the middle of the inner cover to firmly support the flame-retardant honeycomb filter cotton and prevent it from shifting or collapsing. The upright on the inner bottom of the outer cover further presses the filter cotton from above, forming axial and circumferential dual positioning, effectively suppressing the movement caused by vibration. The bottom of the inner cover has an external thread design, which facilitates reliable connection with downstream components. The overall structure is compact, easy to disassemble and assemble, and has good flame-retardant performance and filtration stability.

[0012] 2. The combined fuel filter of this invention achieves a standardized and high-strength connection between the filter and the main body of the equipment by adding a first base. The first base is integrally formed and has a T-shaped cross-section, which has good structural rigidity and uniform stress distribution. The inner side of its tube is provided with internal threads and a tapered hole, which forms a stable spiral connection with the outer threads of the inner cover. The tapered hole and the internal thread have a smooth transition, which effectively reduces fluid turning resistance, reduces turbulence and pressure drop, and improves fuel flow efficiency. Multiple mounting holes are arranged on the end face of the first flange, which can be used with locking screws to achieve multi-point fastening and enhance the overall vibration resistance. The sealing gasket is set below the first flange and aligned with the through hole. It can be uniformly compressed under the pre-tightening force of the screw to form a reliable static seal and prevent leakage. This structure takes into account both connection strength and sealing reliability, and is suitable for long-term stable operation in high-pressure and high-frequency vibration environments.

[0013] 3. In this invention, multi-stage filtration and modular assembly are achieved by introducing a second base and a filter screen. The first flange and second base are fixed by locking screws, allowing the stepped hole of the second base to connect with the upstream conical hole, forming a smooth internal flow channel and reducing local resistance and eddy current losses. The filter screen is securely connected to the second flange by pan head screws and flat washers, facilitating easy disassembly and regular cleaning or replacement. Sealing gaskets two and three are respectively arranged below the second flange and below the filter screen mounting section, forming a double sealing barrier under screw pre-tightening, effectively preventing fuel leakage radially or at the end face. The stepped hole section, matching the diameter of the filter section, allows for radial positioning of the filter screen, improving overall coaxiality and preventing localized wear or sealing failure due to sway. This structure significantly improves maintainability and sealing reliability while ensuring filtration accuracy. Attached Figure Description

[0014] Figure 1 This is a perspective view of embodiment 1 of the fuel filter.

[0015] Figure 2 This is a cross-sectional view of embodiment 1 of the fuel filter.

[0016] Figure 3 An exploded view of embodiment 1 of the fuel filter.

[0017] Figure 4 This is a perspective view of embodiment 2 of the fuel filter.

[0018] Figure 5 This is a cross-sectional view of embodiment 2 of the fuel filter.

[0019] Figure 6 This is a perspective view of embodiment 3 of the fuel filter.

[0020] Figure 7 This is a cross-sectional view of embodiment 3 of the fuel filter.

[0021] Figure 8This is a perspective view of embodiment 4 of the fuel filter.

[0022] Figure 9 This is a cross-sectional view of embodiment 4 of the fuel filter.

[0023] Figure 1-9 Reference numerals: 1. Outer cover; 2. Inner cover; 3. Flame-retardant honeycomb filter cotton; 4. Slide groove; 5. Slider; 6. Buckle; 7. Slot; 8. Chamfer; 9. Bracket; 10. Upright pole; 11. First base; 12. Tube body; 13. First flange; 14. Mounting hole; 15. Tapered hole; 16. Sealing gasket one; 17. Locking screw; 18. Second base; 19. Filter screen; 20. Cylinder body; 21. Second flange; 22. Connecting hole; 23. Stepped hole; 24. Mounting part; 25. Filtering part; 26. Flat washer; 27. Sealing gasket two; 28. Sealing gasket three; 29. ​​Pan head screw; 30. Fixing seat; 31. Hollow column; 32. Third flange; 33. Fixing hole; 34. Connecting hole; 35. Sealing gasket four. Detailed Implementation

[0024] Reference Figure 1-9 The embodiments of the combined fuel filter and its assembly method of the present invention are further described below.

[0025] For ease of explanation, spatial relative terms such as “up,” “down,” “left,” and “right” are used in the embodiments to describe the relationship of one element or feature shown in the figures relative to another element or feature. It should be understood that, in addition to the orientations shown in the figures, spatial terms are intended to include different orientations of the device in use or operation. For example, if the device in the figures is inverted, an element described as being “down” of other elements or features would be positioned “up” of those other elements or features. Therefore, the exemplary term “down” can encompass both up and down orientations. The device may be positioned in other ways (rotated 90 degrees or in other orientations), and the spatial relative descriptions used herein will be interpreted accordingly.

[0026] Moreover, relational terms such as “first” and “second” are used merely to distinguish one component from another that has the same name, without necessarily requiring or implying any such actual relationship or order between the components.

[0027] Example 1 Figure 1-3The illustrated modular fuel filter includes an outer cover 1, an inner cover 2 connected to the outer cover 1 via a snap-fit ​​structure, and flame-retardant honeycomb filter cotton 3 disposed between the outer cover 1 and the inner cover 2. The snap-fit ​​structure includes several grooves 4 evenly distributed on the inner sidewall of the outer cover 1 and several sliders 5 evenly distributed on the top outer sidewall of the inner cover 2 and adapted to the grooves 4. A buckle 6 is provided in the groove 4 near the opening of the outer cover 1. A slot 7 matching the buckle 6 is provided on the slider 5. A chamfer 8 is provided on the top of the slider 5, with the bevel of the chamfer 8 facing the installation direction of the outer cover 1. The outer cover 1 and the inner cover 2 are snapped and fixed by the sliding engagement of the slider 5 and the groove 4 and the snap engagement of the buckle 6 and the slot 7. A bracket 9 for placing the flame-retardant honeycomb filter cotton 3 is provided in the middle of the inner hole of the inner cover 2. Several uprights 10 for fixing and positioning the flame-retardant honeycomb filter cotton 3 are provided on the inner bottom surface of the outer cover 1. An external thread is provided on the bottom outer sidewall of the inner cover 2 for easy installation. The outer cover 1 and inner cover 2 are fitted with a sliding groove 4 and a slider 5. The top of the slider 5 is chamfered 8 to guide smooth sliding and reduce assembly resistance. The sliding groove 4 has a buckle 6 that precisely engages with the slider 5's slot 7, achieving quick locking and preventing loosening, facilitating efficient on-site installation and maintenance. A bracket 9 is set in the middle of the inner cover 2 to firmly support the flame-retardant honeycomb filter cotton 3, preventing its displacement or collapse. The upright 10 on the inner bottom surface of the outer cover 1 further presses the filter cotton from above, forming axial and circumferential dual positioning, effectively suppressing movement caused by vibration. The bottom of the inner cover 2 has an external thread design, facilitating reliable connection with downstream components. The overall structure is compact, easy to assemble and disassemble, and has good flame-retardant performance and filtration stability. It is suitable for venting oil tanks at both the power and hydraulic ends, maintaining the pressure balance between the oil tank and atmospheric pressure, and preventing dirt particles from entering the tank from the outside, keeping the oil inside the tank clean.

[0028] Example 2 The difference between this embodiment and embodiment 1 is that a first base 11 is added on top of embodiment 1, such as... Figure 4-5 As shown, it also includes a first base 11 that is fixedly connected to the external thread of the inner cover 2. The first base 11 is integrally formed and has a T-shaped cross section. The first base 11 includes a tube body 12 and a first flange 13 that is disposed on the outer periphery of the tube body 12 and coaxial with the tube body 12. A plurality of mounting holes 14 are evenly opened along the circumferential direction on the end face of the first flange 13. The inner side of the tube body 12 includes an internal thread that is connected to the external thread of the inner cover 2 and a tapered hole 15 that communicates with the internal thread. The minimum diameter of the tapered hole 15 is transitionally connected to the internal thread. A sealing gasket 16 located below the first flange 13 is sleeved on the outer periphery of the tube body 12. A plurality of through holes corresponding to the mounting holes 14 are opened on the sealing gasket 16. By adding a first base 11, a standardized and high-strength connection between the filter and the main body of the equipment is achieved. The first base 11 is integrally formed and has a T-shaped cross-section, with good structural rigidity and uniform stress distribution. The inner side of its tube body 12 is provided with internal threads and a tapered hole 15, which forms a stable spiral connection with the external threads of the inner cover 2. The tapered hole 15 and the internal thread have a smooth transition, which effectively reduces fluid turning resistance, reduces turbulence and pressure drop, and improves fuel flow efficiency. Multiple mounting holes 14 are arranged on the end face of the first flange 13, which can be used with locking screws 17 to achieve multi-point fastening installation and enhance the overall vibration resistance. The sealing gasket 16 is set below the first flange 13 and aligned with the through hole. It can be uniformly compressed under the action of screw preload to form a reliable static seal and prevent leakage. This structure takes into account both connection strength and sealing reliability. This embodiment has more stable characteristics than embodiment 1, which can increase connection strength and is suitable for long-term stable operation in high-pressure and high-frequency vibration environments.

[0029] Example 3 The difference between this embodiment and embodiment 2 is that it further combines and installs components based on embodiment 2, such as... Figure 6-7 As shown, it also includes a mounting assembly fixed to the bottom of the first flange 13 by locking screws 17. The mounting assembly includes a second base 18 and a filter screen 19. The second base 18 is integrally formed and includes a cylindrical body 20 and a second flange 21 disposed on the outer periphery of the cylindrical body 20 and coaxial with the cylindrical body 20. The top surface of the cylindrical body 20 has a plurality of threaded holes corresponding to the through holes of the sealing gasket 16 for connection of the locking screws 17. The first flange 13 and the second base 18 are fixedly connected by locking screws 17 passing through the mounting hole 14, the through hole of the sealing gasket 16, and the threaded hole of the cylindrical body 20 in sequence. The end face of the second flange 21 has a plurality of connecting holes 22 evenly distributed along the circumferential direction. The inner side of the cylindrical body 20 is provided with stepped holes 23, and is connected to the second flange 21. The conical hole 15 of the tube body 12 is connected. The filter screen 19 includes a mounting part 24 and a filtering part 25. The mounting part 24 has several through holes corresponding to the connecting hole 22. The second flange 21 and the filter screen 19 are fixedly connected by pan head screws 29 passing through the connecting hole 22 and the through holes of the mounting part 24 in sequence. A flat washer 26 is provided between each pan head screw 29 and the second flange 21. A second sealing gasket 27 located below the second flange 21 is fitted on the outer periphery of the cylinder body 20. A third sealing gasket 28 located below the mounting part 24 is fitted on the outer periphery of the filter screen 19. Both the second sealing gasket 27 and the third sealing gasket 28 have several through holes corresponding to the connecting hole 22. The hole in the stepped hole 23 near the filtering part 25 of the filter screen 19 is adapted to the diameter of the filtering part 25. By introducing the second base 18 and filter screen 19, multi-stage filtration and modular assembly are achieved. The first flange 13 and the second base 18 are fixed by locking screws 17, allowing the stepped hole 23 of the second base 18 to connect with the upstream conical hole 15, forming a smooth internal flow channel and reducing local resistance and eddy current losses. The filter screen 19 is securely connected to the second flange 21 by pan head screws 29 and flat washers 26, facilitating easy disassembly and regular cleaning or replacement. Sealing gaskets 27 and 28 are respectively located below the second flange 21 and below the filter screen 19 mounting portion 24, forming a double sealing barrier under screw pre-tightening, effectively preventing fuel leakage radially or from the end face. The stepped hole 23, with a diameter matching that of the filter portion 25, allows for radial positioning of the filter screen 19, improving overall coaxiality and preventing localized wear or sealing failure due to sway. This structure significantly improves maintainability and sealing reliability while ensuring filtration accuracy. Compared to Embodiment 2, this embodiment features enhanced connection strength and dual filtration.

[0030] Example 4 The difference between this embodiment and embodiment 3 is that a fixing base 30 is added on the basis of embodiment 3, such as... Figure 8-9 As shown, it also includes a fixing seat 30 fixed to the bottom of the mounting part 24 by pan head screws 29. The fixing seat 30 is integrally formed and sleeved on the outside of the filter part 25. The fixing seat 30 includes a hollow column 31 and a third flange 32 disposed on the outer periphery of the hollow column 31 and coaxial with the hollow column 31. The top surface of the hollow column 31 has several threaded holes corresponding to the through holes of the sealing gasket 28 for connection by pan head screws 29. The second flange 21 and the fixing seat 30 are connected by pan head screws 29 passing through the flat washer 26, the connecting hole 22, and the through hole of the sealing gasket 27 in sequence. The through hole of the mounting part 24, the through hole of the sealing gasket 28, and the threaded hole of the hollow column 31 are fixedly connected; a plurality of fixing holes 33 are evenly opened along the circumferential direction on the end face of the third flange 32; the inner side of the hollow column 31 is set as a connecting hole 34 with a trapezoidal cross section; the minimum inner diameter of the connecting hole 34 is larger than the outer diameter of the filter part 25, and the minimum inner diameter of the connecting hole is close to the mounting part 24; a sealing gasket 35 located below the third flange 32 is fitted on the outer periphery of the hollow column 31; the maximum radius of the sealing gasket 35 is smaller than the minimum distance from the fixing hole 33 to the center of the fourth flange; The addition of a fixing seat 30 further improves the support and sealing system at the end of the filter. The fixing seat 30 is sleeved on the outside of the filter screen 19, and the hollow column 31 and the second flange 21 are firmly constrained by the pan head screws 29, which can effectively suppress the axial movement and radial sway of the filter screen 19. The connecting hole 34 adopts a trapezoidal cross-section design, and the minimum inner diameter is close to the mounting part 24 and larger than the outer diameter of the filter part 25, which not only ensures the smooth passage of fuel, but also avoids interference or scratching of the filter part 25, thus extending the service life of the filter screen 19. The third flange 32 is provided with fixing holes 33, which facilitates docking with external pipelines or equipment by screws or nuts to form a standardized interface. The sealing gasket 35 is arranged below the third flange 32 and can be evenly compressed during connection to form a good end face seal. The overall structure is well-organized and the connection is reliable, making it particularly suitable for refueling systems with high requirements for end sealing and fluid guidance. Compared with embodiment 3, this embodiment has the characteristics of enhanced end constraint and positioning of the filter screen 19.

[0031] A method for assembling a combined fuel filter, characterized by comprising the following steps: S1. Place the flame-retardant honeycomb filter cotton 3 on the bracket 9 in the middle of the inner hole of the inner cover 2, so that the bottom surface of the flame-retardant honeycomb filter cotton 3 is completely attached to the top surface of the bracket 9. Then, pre-align the outer cover 1 with the inner cover 2. Then, fasten the outer cover 1 on top of the inner cover 2, so that the sliding groove 4 on the inner side wall of the outer cover 1 is aligned with the slider 5 on the top outer side wall of the inner cover 2. Push the outer cover 1 along the installation direction of the outer cover 1, so that the slider 5 slides along the sliding groove 4 until the buckle 6 in the sliding groove 4 is engaged in the slot 7 on the slider 5. At this time, the upright 10 on the inner bottom surface of the outer cover 1 abuts against the flame-retardant honeycomb filter cotton 3, realizing the axial and circumferential positioning of the flame-retardant honeycomb filter cotton 3, that is, completing the snap-fit ​​fixing of the outer cover 1 and the inner cover 2. S2. Take the first base 11, align the internal thread of its tube body 12 with the external thread of the bottom outer wall of the inner cover 2, rotate the first base 11 to tighten and fix the internal thread of the tube body 12 with the external thread of the inner cover 2, so that the tapered hole 15 of the tube body 12 is coaxially connected with the inner hole of the inner cover 2; then put the sealing gasket 16 on the outer periphery of the tube body 12 of the first base 11, so that the sealing gasket 16 fits against the bottom surface of the first flange 13, and the through hole on the sealing gasket 16 corresponds one-to-one with the mounting hole 14 on the first flange 13. S3. Pre-align the second base 18. Align the threaded hole on the top surface of the cylinder 20 of the second base 18 with the mounting hole 14 of the first flange 13 and the through hole of the first gasket 16. Then, take the locking screw 17, pass it through the mounting hole 14 of the first flange 13 and the through hole of the first gasket 16, and screw it into the threaded hole of the cylinder 20. Tighten the locking screw 17 to fix the first flange 13 and the second base 18. Next, put the second gasket 27 on the outer periphery of the cylinder 20 of the second base 18, so that the second gasket 27 fits against the bottom surface of the second flange 21, and the through hole on the second gasket 27 corresponds one-to-one with the connection hole 22 on the second flange 21. Sealing gasket 28 is fitted onto the outer periphery of filter screen 19, so that sealing gasket 28 fits against the bottom surface of mounting part 24 of filter screen 19, and the through holes on sealing gasket 28 correspond one-to-one with the through holes of mounting part 24 of filter screen 19. Then, the filter part 25 of filter screen 19 is aligned with the stepped hole 23 of cylinder 20 of second base 18, so that the through holes on mounting part 24 of filter screen 19 are aligned with the connection hole 22 of second flange 21 and the through hole of sealing gasket 27. Then, pan head screw 29 is taken, and flat washer 26 is first put on pan head screw 29, and then passed through the connection hole 22 of second flange 21, the through hole of sealing gasket 27, the through hole of mounting part 24, and the through hole of sealing gasket 28 in sequence. S4. Place the mounting base 30 over the filter screen 19, aligning the threaded hole on the top surface of the hollow column 31 of the mounting base 30 with the through hole of the sealing gasket 28, the through hole of the mounting part 24, the through hole of the sealing gasket 27, and the connection hole 22 of the second flange 21. Then screw the pan head screw 29 into the threaded hole of the hollow column 31 and tighten the pan head screw 29 to fix the second flange 21, the filter screen 19, and the mounting base 30. Next, place the sealing gasket 35 around the outer periphery of the hollow column 31 of the mounting base 30, so that the sealing gasket 35 fits against the bottom surface of the third flange 32, completing the assembly of the combined oil filter. S5. Check the tightness of the connection between the outer cover 1 and the inner cover 2, and confirm that the buckle 6 is fully engaged in the slot 7 and there is no looseness. At the same time, check whether the flame-retardant honeycomb filter cotton 3 moves synchronously with the inner cover 2 by shaking the outer cover 1. S6. Inspect the connection between the locking screw 17 and the pan head screw 29, and observe the pressure deformation of the sealing gasket 16, sealing gasket 27, and sealing gasket 328 to ensure that there are no warping or leakage gaps in each sealing gasket. S7. The entire structure is left to stand still and subjected to an axial pressure test to confirm that the overall structure formed by the first base 11, the mounting components and the fixing seat 30 is leak-free and that each sealing gasket is in a uniformly compressed state. This assembly method achieves efficient and precise assembly of the modular fuel filter through standardized steps and sequential control; it allows operators to select the appropriate filter according to different usage scenarios; in step S1, pre-alignment and sliding groove 4... The slider 5, in conjunction with the outer cover 1, enables rapid positioning and engagement of the inner cover 2. The upright 10 and bracket 9 provide axial and circumferential bidirectional positioning of the flame-retardant honeycomb filter cotton 3, avoiding manual placement errors and improving assembly consistency. Steps S2-S4 sequentially connect the first base 11, the mounting components, and the fixing seat 30. Each component is tightened in a predetermined sequence using threads, through holes, and screws, ensuring accurate gasket positioning and uniform force distribution, significantly improving sealing reliability. S5 Step S7 introduces checks on snap-fit ​​tightness, confirmation of screw connection status, and axial pressure testing, forming a complete closed-loop control of assembly quality. This effectively reduces the risk of leakage and loosening caused by improper assembly, and improves the overall product qualification rate and safety of use.

[0032] In S4, when the fixed seat 30, the mounting part 24 and the second flange 21 are threaded together, the sealing and positioning accuracy is ensured by the following judgment method: After the pan head screw 29 passes through the second flange 21, the second sealing gasket 27, the mounting part 24 and the third sealing gasket 28, the hollow column 31 is first screwed in manually until it fits against the third sealing gasket 28, and then tightened in stages. The first stage reaches 60% of the set torque, the second stage reaches 100%, and after the final tightening, the compression of the third sealing gasket 28 and the fourth sealing gasket 35 is checked. When the compression reaches the gradient range of 25%-35% of the original thickness, the installation is judged to be qualified, and the concentricity deviation between the connecting hole 34 and the filter part 25 of the filter screen 19 is <0.1mm; By introducing tightening processes and quantitative judgment standards, sealing reliability and assembly accuracy were significantly improved. A staged tightening strategy was adopted: first, manually screwing it in until it fits snugly against gasket 3.28, then tightening with 60% and 100% torque increments, effectively releasing assembly stress and preventing gasket damage or thread seizing due to instantaneous overload. Furthermore, the compression of gaskets 3.28 and 4.35 was limited to 25% of their original thickness. The 35% requirement ensures that the sealing gasket is in the optimal rebound and sealing range, avoiding permanent deformation due to overpressure or leakage due to underpressure; the requirement of concentricity deviation <0.1 mm ensures the precise alignment of the connecting hole 34 and the filter screen 19 and filter section 25, reducing fluid disturbance and local wear; the combination of these process parameters and control methods makes the product quality stable and controllable.

[0033] In step S7, after the entire assembly is left to stand and an axial pressure test is applied, axial pressure is applied to the cone hole 15 of the first base 11, and the deformation of the end face of the third flange 32 of the fixed seat 30 is detected. When the deformation is less than 0.05 mm and there is no reverse warping of the gaskets, the overall assembly is deemed qualified. Furthermore, the joints of the first gasket 16, the second gasket 27, and the third gasket 28 are tested by light transmission or bubble test. If no light is transmitted or no bubbles are generated, the sealing is deemed qualified. Finally, it is confirmed that the combined oil filter meets the preset sealing standard. By applying axial pressure and monitoring the deformation of the third flange 32 end face to be <0.05 mm, the rigidity and connection stability of the overall structure can be effectively verified, preventing long-term failure due to material creep or assembly gaps. The requirement that the gasket not warp backwards reflects the sealing quality under stress, avoiding localized warping as a source of leakage. Using light transmission or bubble methods, microscopic defects at the joints of gaskets 16, 2, and 3 can be detected, achieving non-destructive, visual seal verification and significantly improving the defect detection rate. While ensuring assembly accuracy, this greatly reduces the potential risk of leakage, ensuring the filter maintains excellent sealing performance and operational reliability under complex operating conditions for a long time. The above description is only a preferred embodiment of the present invention and is not intended to limit the invention. Ordinary changes and substitutions made by those skilled in the art within the scope of the present invention should be included within the protection scope of the present invention.

Claims

1. A combined fuel filter, characterized in that: Includes an outer cover (1), an inner cover (2) connected to the outer cover (1) via a snap-fit ​​structure, and flame-retardant honeycomb filter cotton (3) disposed between the outer cover (1) and the inner cover (2); the snap-fit ​​structure includes several grooves (4) evenly distributed on the inner sidewall of the outer cover (1) and several sliders (5) evenly distributed on the top outer sidewall of the inner cover (2) and adapted to the grooves (4); a buckle (6) is provided in the groove (4) near the opening of the outer cover (1); the slider (5) is provided with a slot (7) matching the buckle (6); the slider (5) 5) has a chamfer (8) on the top, with the chamfer (8) facing the installation direction of the outer cover (1); the outer cover (1) and the inner cover (2) are fixed by sliding the slider (5) and the groove (4) and snapping the buckle (6) and the groove (7); the inner cover (2) has a bracket (9) in the middle of the inner hole for placing the flame-retardant honeycomb filter cotton (3), and the outer cover (1) has several uprights (10) for fixing and positioning the flame-retardant honeycomb filter cotton (3); the bottom outer wall of the inner cover (2) has an external thread.

2. The combined fuel filter according to claim 1, characterized in that, It also includes a first base (11) that is fixedly connected to the external thread of the inner cover (2). The first base (11) is integrally formed and has a T-shaped cross section. The first base (11) includes a tube body (12) and a first flange (13) that is disposed on the outer periphery of the tube body (12) and coaxial with the tube body (12). A plurality of mounting holes (14) are evenly opened along the circumferential direction on the end face of the first flange (13). The inner side of the tube body (12) includes an internal thread that is connected to the external thread of the inner cover (2) and a tapered hole (15) that communicates with the internal thread. The minimum diameter of the tapered hole (15) is transitionally connected to the internal thread. A sealing gasket (16) located below the first flange (13) is sleeved on the outer periphery of the tube body (12). A plurality of through holes corresponding to the mounting holes (14) are opened on the sealing gasket (16).

3. A combined fuel filter according to claim 2, characterized in that, It also includes a mounting assembly fixed to the bottom of the first flange (13) by locking screws (17). The mounting assembly includes a second base (18) and a filter screen (19). The second base (18) is integrally formed and includes a cylinder (20) and a second flange (21) disposed on the outer periphery of the cylinder (20) and coaxial with the cylinder (20). The top surface of the cylinder (20) has several threaded holes corresponding to the through holes of the first sealing gasket (16) for connecting the locking screws (17). The first flange (13) and the second base (18) are fixedly connected by locking screws (17) passing through the mounting hole (14), the through hole of the first sealing gasket (16), and the threaded hole of the cylinder (20) in sequence. Several connecting holes (22) are evenly provided on the end face of the second flange (21) along the circumferential direction. The inner side of the cylinder (20) is provided with stepped holes (23) and connected to the pipe (12). The tapered hole (15) is connected to the filter screen (19), which includes a mounting part (24) and a filtering part (25). The mounting part (24) has several through holes corresponding to the connecting hole (22). The second flange (21) and the filter screen (19) are fixedly connected by pan head screws (29) passing through the connecting hole (22) and the through holes of the mounting part (24) in sequence. A flat washer (26) is provided between each pan head screw (29) and the second flange (21). The outer periphery of the cylinder (20) is fitted with a second sealing gasket (27) located below the second flange (21), and the outer periphery of the filter screen (19) is fitted with a third sealing gasket (28) located below the mounting part (24). Both the second sealing gasket (27) and the third sealing gasket (28) have several through holes corresponding to the connecting hole (22). The hole in the stepped hole (23) near the filter part (25) of the filter screen (19) is adapted to the diameter of the filter part (25).

4. A combined fuel filter according to claim 3, characterized in that, It also includes a fixing seat (30) fixed to the bottom of the mounting part (24) by pan head screws (29). The fixing seat (30) is integrally formed and sleeved on the outside of the filter part (25). The fixing seat (30) includes a hollow column (31) and a third flange (32) disposed on the outer periphery of the hollow column (31) and coaxial with the hollow column (31). The top surface of the hollow column (31) has a plurality of threaded holes corresponding to the through holes of the sealing gasket (28) for connecting the pan head screws (29). The second flange (21) and the fixing seat (30) are connected by pan head screws (29) passing through flat washers (26) in sequence. The connecting hole (22), the through hole of the second sealing gasket (27), the through hole of the mounting part (24), the through hole of the third sealing gasket (28), and the threaded hole of the hollow column (31) are fixedly connected; a number of fixing holes (33) are evenly opened along the circumferential direction on the end face of the third flange (32); the inner side of the hollow column (31) is set as a connecting hole (34) with a trapezoidal cross section; the minimum inner diameter of the connecting hole (34) is larger than the outer diameter of the filter part (25), and the minimum inner diameter of the connecting hole is close to the mounting part (24); the outer periphery of the hollow column (31) is fitted with a fourth sealing gasket (35) located below the third flange (32).

5. An assembly method for the combined fuel filter according to any one of claims 1-4, characterized in that, Includes the following steps: S1. Place the flame-retardant honeycomb filter cotton (3) on the bracket (9) in the middle of the inner hole of the inner cover (2), so that the bottom surface of the flame-retardant honeycomb filter cotton (3) is completely attached to the top surface of the bracket (9). Then, pre-align the outer cover (1) and the inner cover (2): then fasten the outer cover (1) on top of the inner cover (2), so that the sliding groove (4) on the inner side wall of the outer cover (1) is aligned with the slider (5) on the top outer side wall of the inner cover (2); push the outer cover (1) along the installation direction of the outer cover (1), so that the slider (5) slides along the sliding groove (4) until the buckle (6) in the sliding groove (4) is engaged in the slot (7) on the slider (5). At this time, the upright (10) on the inner bottom surface of the outer cover (1) abuts against the flame-retardant honeycomb filter cotton (3), realizing the axial and circumferential positioning of the flame-retardant honeycomb filter cotton (3), that is, completing the snap-fit ​​fixing of the outer cover (1) and the inner cover (2). S2. Take the first base (11), align the internal thread of its tube body (12) with the external thread of the bottom outer wall of the inner cover (2), rotate the first base (11) to tighten and fix the internal thread of the tube body (12) with the external thread of the inner cover (2), and make the tapered hole (15) of the tube body (12) coaxially connected with the inner hole of the inner cover (2); then put the sealing gasket (16) on the outer periphery of the tube body (12) of the first base (11), so that the sealing gasket (16) fits against the bottom surface of the first flange (13), and the through hole on the sealing gasket (16) corresponds one-to-one with the mounting hole (14) on the first flange (13); S3. Pre-align the second base (18). Align the threaded hole on the top surface of the cylinder (20) of the second base (18) with the mounting hole (14) of the first flange (13) and the through hole of the first gasket (16). Then take the locking screw (17), pass it through the mounting hole (14) of the first flange (13) and the through hole of the first gasket (16) in sequence, and screw it into the threaded hole of the cylinder (20). Tighten the locking screw (17) to fix the first flange (13) and the second base (18) in place. Next, put the second gasket (27) on the outer periphery of the cylinder (20) of the second base (18) so that the second gasket (27) fits against the bottom surface of the second flange (21), and the through hole on the second gasket (27) corresponds one-to-one with the connection hole (22) on the second flange (21). Put the third gasket on the second base (18) into place. (28) is fitted onto the outer periphery of the filter screen (19), so that the sealing gasket three (28) fits against the bottom surface of the filter screen (19) mounting part (24), and the through hole on the sealing gasket three (28) corresponds one-to-one with the through hole of the filter screen (19) mounting part (24). Then, the filter part (25) of the filter screen (19) is aligned with the stepped hole (23) of the second base (18) cylinder (20), so that the through hole on the mounting part (24) of the filter screen (19) is aligned with the connection hole (22) of the second flange (21) and the through hole of the sealing gasket two (27). Then, take the pan head screw (29), first put the flat washer (26) on the pan head screw (29), and then pass it through the connection hole (22) of the second flange (21), the through hole of the sealing gasket two (27), the through hole of the mounting part (24), and the through hole of the sealing gasket three (28) in sequence. S4. Place the fixing seat (30) on the outside of the filter screen (19), aligning the threaded hole on the top surface of the hollow column (31) of the fixing seat (30) with the through hole of the sealing gasket three (28), the through hole of the mounting part (24), the through hole of the sealing gasket two (27), and the connection hole (22) of the second flange (21); then screw the pan head screw (29) into the threaded hole of the hollow column (31) and tighten the pan head screw (29) to fix the second flange (21), the filter screen (19) and the fixing seat (30); then place the sealing gasket four (35) on the outer periphery of the hollow column (31) of the fixing seat (30) so that the sealing gasket four (35) fits against the bottom surface of the third flange (32) to complete the assembly of the combined oil filter; S5. Check the tightness of the connection between the outer cover (1) and the inner cover (2), confirm that the buckle (6) is fully inserted into the slot (7) and there is no looseness. At the same time, check whether the flame-retardant honeycomb filter cotton (3) moves synchronously with the inner cover (2) by shaking the outer cover (1). S6. Check the connection between the locking screw (17) and the pan head screw (29), observe the pressure deformation of the sealing gasket 1 (16), sealing gasket 2 (27), and sealing gasket 3 (28), and ensure that each sealing gasket is free from warping or leakage gaps. S7. The entire structure is left to stand still and subjected to an axial pressure test to confirm that the overall structure formed by the first base (11), the mounting components and the fixing seat (30) is leak-free and that each sealing gasket is in a uniformly compressed state.

6. The assembly method of the combined fuel filter according to claim 5, characterized in that, In S4, when the fixed seat (30), the mounting part (24) and the second flange (21) are threaded together, the sealing and positioning accuracy is ensured by the following judgment method: After the pan head screw (29) passes through the second flange (21), the second sealing gasket (27), the mounting part (24) and the third sealing gasket (28), the hollow column (31) is first screwed in manually until it fits with the third sealing gasket (28), and then tightened in stages. The first stage reaches 60% of the set torque, the second stage reaches 100%, and the compression of the third sealing gasket (28) and the fourth sealing gasket (35) is detected after the final tightening. When the compression reaches the gradient range of 25%-35% of the original thickness, the installation is deemed qualified, and the concentricity deviation between the connecting hole (34) and the filter screen (19) and the filter part (25) is <0.1mm.

7. The assembly method of the combined fuel filter according to claim 5, characterized in that, In S7, after the entire assembly is left to stand and an axial pressure test is applied, an axial pressure is applied to the cone hole (15) of the first base (11), and the deformation of the end face of the third flange (32) of the fixed seat (30) is detected. When the deformation is <0.05mm and no gaskets are tilted in the opposite direction, the overall assembly is deemed qualified. The joints of gasket 1 (16), gasket 2 (27) and gasket 3 (28) are tested by light transmission method or bubble method. If no light is transmitted or no bubbles are generated, the sealing is qualified. Finally, it is confirmed that the combined oil filter meets the preset sealing standard.

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