A composite filter cartridge

Abstract

A composite filter element comprises a housing, an interface base arranged at the bottom of the housing, and a first filter unit and a second filter unit vertically arranged inside the housing, the first filter unit being located above the second filter unit; the interface base is provided with a central channel and a first annular flow channel, a second annular flow channel and a third annular flow channel arranged in a ring shape from inside to outside, and the bottom is provided with a first water inlet hole, a second water inlet hole, a first water outlet hole and a second water outlet hole corresponding to each flow channel; the third annular flow channel guides the water flow to the first filter unit and merges into the first central pipe, the second annular flow channel guides the water flow to the second filter unit and flows into the first annular flow channel through the gap, and the second central pipe is connected to the central channel and penetrates the first central pipe. Through the layered and independent design of the multiple annular flow channels and the corresponding arrangement of the special water inlet and outlet holes, the water paths are completely physically isolated and independently guided, the water flow cross talk and cross contamination are effectively avoided, the water flow distribution efficiency and the filtration reliability are improved, and the highly integrated structure greatly reduces the volume of the filter element, which is more suitable for the needs of modern water purification equipment miniaturization, high integration and multiple water path circulation.

Description

Technical Field

[0001] This utility model relates to the field of fluid treatment and distribution equipment technology, specifically to a composite filter element adapted to multi-channel water circulation. Background Technology

[0002] In water purification equipment, filter cartridges are the core components for achieving advanced water treatment. Traditional water purification systems typically use multiple independent filter cartridges to perform pre-filtration, reverse osmosis filtration, and post-filtration functions, connected to the water circuit board via complex external piping. This design results in a bulky system, cumbersome assembly, high risk of leakage, and inconvenient maintenance and replacement.

[0003] To address the aforementioned issues, the industry has gradually developed composite integrated filter elements that integrate the pre-filter and post-filter units into the same housing. For example, Chinese utility model patent application number 201922151602.8 (authorization announcement number CN211752964U) discloses "An Integrated Composite Pre- and Post-Filter Element." This filter element adopts a cylindrical filter element body, with a pre-filter unit at one end and a post-filter unit at the other end. Through the combined design of the pre-filter sleeve, the pre-filter body, the post-filter sleeve, and the post-filter body, the physical integration of the pre- and post-filter elements is achieved, effectively reducing the volume and connection points of the filter element itself and improving the modularity of the filter element.

[0004] However, this composite filter element employs a decentralized inlet and outlet port layout, with the inlet and outlet ports located in different parts such as the front top cover, the front filter sleeve, or the rear filter sleeve. This lack of a centralized flow channel integration structure results in insufficient physical isolation and independent flow channel guidance between the various water paths, making it difficult to achieve complete separation and efficient distribution of multiple water paths within a limited space. This is particularly problematic when adapting to a "pre-filtration → reverse osmosis → post-filtration" system, where insufficient flow channel isolation easily leads to water flow interference and cross-contamination. This not only affects filtration accuracy but also results in a complex external piping layout due to the decentralized inlet and outlet ports, limiting the filter element's practical application in compact multi-channel circulation systems.

[0005] Therefore, how to further optimize the internal flow channel architecture and interface design of existing composite filter elements to achieve complete water path isolation, efficient fluid distribution, and reliable interface sealing, so as to meet the urgent needs of modern water purification equipment for miniaturization, high integration, and multi-water path circulation performance, has become a key technical problem that needs to be solved by those skilled in the art. Utility Model Content

[0006] The technical problem to be solved by this utility model is to provide a composite filter element that adopts a multi-layered annular flow channel with independent layered design to achieve complete water channel isolation and efficient fluid distribution, in view of the above-mentioned technical status.

[0007] The technical solution adopted by this utility model to solve the above-mentioned technical problems is as follows: The filtration system includes a shell, an interface base located at the bottom of the shell, and a first filter unit and a second filter unit vertically arranged inside the shell. The first filter unit is located above the second filter unit. The interface base is provided with a central channel, a first annular flow channel, a second annular flow channel and a third annular flow channel communicating with the inside of the shell. The first annular flow channel, the second annular flow channel and the third annular flow channel surround the outer periphery of the central channel from the inside to the outside. The bottom of the interface base is provided with two water inlets and two water outlets corresponding to the central channel and the three annular flow channels respectively.

[0008] The third annular flow channel is used to guide water flow from the corresponding inlet hole to the outer periphery of the first filter unit. After filtration, the water flows out from the inner periphery outlet and merges into the first central pipe located in the middle.

[0009] The second annular flow channel is used to guide water flow from the corresponding inlet hole upwards into the outer periphery of the second filter unit. After filtration, the water flows out from the inner periphery outlet side and flows into the first annular flow channel through the gap between the inner periphery and the second central tube located in the middle.

[0010] The second central tube is connected to the central channel and is vertically connected to the first central tube.

[0011] To improve the structural integration and sealing reliability of the first filter unit, and to ensure a clear water flow path and stable filtration effect, preferably, the first filter unit further includes a first upper cover, a first lower cover, and a first filter component disposed between the first upper cover and the first lower cover. The first filter component is a hollow annular body, with the outer periphery forming the water inlet side and the inner periphery forming the water outlet side. The first central tube is located in the hollow part of the first filter component, and its upper and lower ends are respectively connected to the first upper cover and the first lower cover. The first lower cover is also provided with a first insertion hole for the first central tube to be inserted, and the first central tube and / or the connection between the first central tube and the first upper cover and the first lower cover is provided with a first water passage hole for water to flow through.

[0012] To optimize the installation structure and internal water flow guidance of the second filter unit, and to achieve precise docking with the interface base and efficient filtration, preferably, the second filter unit further includes a housing, a second top cover, and a second filter component. The housing has an opening at its bottom and a water guide on its bottom wall. The second filter component is built into the housing and its upper and lower ends are respectively connected to the second top cover and the water guide. The edge of the opening has a first water guide wall extending downward into the second annular flow channel, and the water guide has a second water guide wall extending downward into the first annular flow channel. Under the guidance of the first water guide wall, the water flows from the second annular flow channel to the water inlet side of the outer periphery of the second filter component. The filtered water flows into the first annular flow channel under the guidance of the second water guide wall.

[0013] To ensure uniform distribution and smooth flow of water inside the second filtration unit and to avoid short circuits or dead zones, preferably, a second water passage hole is provided at the connection between the water guide and the bottom wall of the housing, and the second water passage hole is circumferentially distributed around the outer periphery of the opening.

[0014] To enhance the sealing performance between each flow channel and the first and second water guide walls, and to prevent water leakage and crosstalk, preferably, a first sealing ring is provided between the inner peripheral wall of the second annular flow channel and the first water guide wall, and a second sealing ring is provided between the inner peripheral wall of the first annular flow channel and the second water guide wall.

[0015] To achieve a quick and reliable connection between the second filter unit and the first filter unit, and to ensure stable conduction and sealing of the second central tube, preferably, the top of the second upper cover is provided with a connector for inserting into the first insertion hole, and a third sealing ring is provided between the first insertion hole and the connector, and the connector is in communication with the second central tube; the bottom of the second upper cover is also provided with a second insertion hole for inserting the top of the second central tube, and the bottom of the second central tube is sealed to the central channel of the interface base through a sealing ring.

[0016] To improve the modularity and ease of production of the interface base, and to facilitate manufacturing and maintenance, preferably, the interface base includes a connecting sleeve, a first interface seat, and a second interface seat that is mated below the first interface seat. Both the first and second interface seats are built into the connecting sleeve, and the central channel, the first annular flow channel, the second annular flow channel, and the third annular flow channel are provided on the first interface seat.

[0017] To achieve precise connection between the internal flow channels and external pipelines of the interface base, and to ensure that each water path is independently connected and does not interfere with each other, preferably, the bottom of the first interface base has four docking holes that respectively connect the central channel, the first annular flow channel, the second annular flow channel, and the third annular flow channel; the top of the second interface base has four water guides that are connected to the four docking holes, and the bottom of the second interface base has four insertion pipes that are respectively connected to the four water guides. The bottom opening of the insertion pipe corresponding to the third annular flow channel constitutes the first water inlet, the bottom opening of the insertion pipe corresponding to the second annular flow channel constitutes the second water inlet, the bottom opening of the insertion pipe corresponding to the central channel constitutes the first water outlet, and the bottom opening of the insertion pipe corresponding to the first annular flow channel constitutes the second water outlet.

[0018] To further improve the sealing reliability of the internal docking of the interface base and prevent leakage at the interface, preferably, four fourth sealing rings are provided on the docking surfaces of the first interface base and the second interface base, which surround the outer periphery of the corresponding docking holes.

[0019] In order to clarify the functional positioning of the first filter unit and the second filter unit and adapt them to the multi-stage water purification needs of pre-filtration and post-filtration, preferably, the first filter unit is a pre-filtration unit and the second filter unit is a post-filtration unit.

[0020] Compared with the prior art, the advantages of this utility model are as follows: A central channel, a first annular flow channel, a second annular flow channel, and a third annular flow channel communicating with the interior of the outer shell are provided on the interface base, with the three annular flow channels sequentially surrounding the outer periphery of the central channel from the inside out. Simultaneously, a first water inlet hole, a second water inlet hole, a first water outlet hole, and a second water outlet hole corresponding to each flow channel are provided at the bottom of the interface base. Water is guided upwards from the first water inlet hole to the outer periphery of the first filter unit via the third annular flow channel. After filtration, the water flows out from the inner periphery of the filter unit and merges into the first central pipe. Water is guided upwards from the second water inlet hole to the second filter unit via the second annular flow channel. On the outer periphery of the filter unit, after filtration, the water flows out from the inner periphery and into the first annular flow channel through the gap between the inner periphery and the second central tube. At the same time, the second central tube is connected to the central channel and the first central tube is connected vertically. Due to the adoption of a multi-layer annular flow channel with independent layered design and corresponding dedicated inlet and outlet holes, complete physical isolation and independent guidance between water paths are achieved, effectively avoiding water flow interference and cross-contamination, significantly improving water flow distribution efficiency and filtration reliability. At the same time, the highly integrated structural design greatly reduces the size of the filter element, making it more suitable for the needs of modern water purification equipment for miniaturization, high integration and multi-water circulation performance. Attached Figure Description

[0021] Figure 1 This is a three-dimensional structural diagram of this embodiment;

[0022] Figure 2 This is a schematic diagram of the bottom-view three-dimensional structure of this embodiment;

[0023] Figure 3 This is a schematic diagram of the decomposed state structure of this embodiment;

[0024] Figure 4 This is a schematic diagram of the decomposed state structure of the first filtering unit in this embodiment;

[0025] Figure 5 This is a schematic diagram of the decomposed state structure of the second filtering unit in this embodiment;

[0026] Figure 6 This is a three-dimensional structural diagram of the interface base in this embodiment;

[0027] Figure 7 This is a schematic diagram of the exploded state structure of the interface base in this embodiment;

[0028] Figure 8This is a schematic diagram of the exploded state structure of the interface base from another angle in this embodiment;

[0029] Figure 9 This is a top-view orthographic projection view of the first interface socket in this embodiment;

[0030] Figure 10 This is a bottom orthographic projection view of the first interface socket in this embodiment;

[0031] Figure 11 This is a cross-sectional structural diagram of this embodiment;

[0032] Figure 12 This is a schematic diagram of the water circuit of the first filtration unit in this embodiment;

[0033] Figure 13 This is a schematic diagram of the water circuit of the second filtration unit in this embodiment. Detailed Implementation

[0034] The present invention will be further described in detail below with reference to the accompanying drawings and embodiments.

[0035] Figures 1-13 The figure shown is the preferred embodiment of this utility model.

[0036] The composite filter element in this embodiment is a composite filter element assembly that integrates pre-filtration and post-filtration functions. Its core function is to achieve dual filtration of pre-treatment and post-taste optimization. It needs to be used in conjunction with an external water circuit board A and a reverse osmosis filter module B. The composite filter element mainly includes a shell 1, an interface base 2, a first filter unit 3, and a second filter unit 4. It aims to solve the problems of existing composite filter elements that use a parallel inlet and outlet layout, lack effective physical isolation and independent flow channel guidance for each water circuit, are prone to water flow interference and cross-contamination, and cannot be adapted to compact multi-water circuit circulation systems. Through multi-layer annular flow channel layered independent design and interface integration optimization, it achieves complete water circuit isolation, efficient distribution and reliable sealing, meeting the miniaturization and high integration requirements of modern water purification equipment.

[0037] The structure and connection relationship of each component in this embodiment are as follows:

[0038] Shell 1: Reference Figure 1 , Figure 12 and Figure 11 As shown, the outer shell 1 has a columnar structure and is sealed and molded from food-grade plastic. The upper part of the internal chamber houses the first filter unit 3, and the lower part houses the second filter unit 4, i.e., the second filter unit 4 is located below the first filter unit 3. The first filter unit 3 is filled with a composite filter media of PP cotton and activated carbon to remove large particulate impurities such as silt and rust from the raw water; the second filter unit 4 is filled with compressed activated carbon filter media to adsorb residual chlorine in the water and improve the taste of drinking water.

[0039] Interface base 2: Reference Figures 6 to 10 As shown, the interface base 2 is a key component for connecting the composite filter element to the external water circuit board. It is connected to the bottom of the outer shell 1 and includes a connecting sleeve 21, a first interface seat 22, and a second interface seat 23 that is connected to the bottom of the first interface seat 22. The first interface seat 22 and the second interface seat 23 are both built into the connecting sleeve 21. The connecting sleeve 21 is connected to the bottom of the outer shell 1, and its outer side wall is provided with a locking block that adapts to the slot of the external water circuit board, which is used to lock and position the filter element with the annular connecting wall of the water circuit board.

[0040] The first interface seat 22 has a central channel 2a and three annular channels. The three annular channels, from the inside out, are a first annular channel 2b, a second annular channel 2c, and a third annular channel 2d, sequentially surrounding the outside of the central channel 2a. The central channel 2a and each annular channel are independently connected to the interior of the outer shell 1. The bottom of the first interface seat 22 has four mating holes 22a that respectively connect to the central channel 2a, the first annular channel 2b, the second annular channel 2c, and the third annular channel 2d. The specific structure of the mating holes 22a is described in [reference needed]. Figure 10 and Figure 11 As shown.

[0041] The top of the second interface seat 23 is provided with four water guide ports 23a that are connected to the four docking holes 22a respectively, and the bottom is formed with four insertion pipes 23b that are connected to the four water guide ports 23a respectively. The four insertion pipes 23b are respectively connected to the central channel 2a, the first annular flow channel 2b, the second annular flow channel 2c and the third annular flow channel 2d. The bottom opening of the insertion pipe 23b corresponding to the third annular flow channel 2d forms the first water inlet 2e, the one corresponding to the second annular flow channel 2c forms the second water inlet 2f, the one corresponding to the central channel 2a forms the first water outlet 2g, and the one corresponding to the first annular flow channel 2b forms the second water outlet 2h.

[0042] The mating surfaces of the first interface seat 22 and the second interface seat 23 are provided with four fourth sealing rings 9 surrounding the outer periphery of the corresponding mating holes 22a, which are used to enhance the sealing performance of the mating surfaces and prevent water leakage and crosstalk between different flow channels.

[0043] The third annular channel 2d is connected to the inlet of the first filter unit 3 through a corresponding water guide, and the central channel 2a is connected to the outlet of the first filter unit 3 through a corresponding water guide; the second annular channel 2c is connected to the inlet of the second filter unit 4 through a corresponding water guide, and the first annular channel 2b is connected to the outlet of the second filter unit 4 through a corresponding water guide.

[0044] First Filtering Unit 3: Reference Figure 3 , Figure 4 and Figure 11As shown, the first filtration unit 3 is a pre-filtration module used to achieve preliminary purification of raw water, and mainly includes a first central tube 3a, a first upper cover 3b, a first lower cover 3c and a first filtration component 3d.

[0045] The first filter element 3d is a hollow annular body, with its upper and lower ends connected to the first upper cover 3b and the first lower cover 3c, respectively. The outer periphery forms the water inlet side, and the inner periphery forms the water outlet side. The interior is filled with a composite filter material of PP cotton and activated carbon, which can effectively intercept large particulate impurities and some organic matter in the raw water. The first central tube 3a is located in the hollow part of the first filter element 3d, with its upper and lower ends connected to the first upper cover 3b and the first lower cover 3c, respectively. The first lower cover 3c is also provided with a first insertion hole 3e for the first central tube 3a to be inserted. The first central tube 3a and / or the connection between the first central tube 3a and the first upper cover 3b and the first lower cover 3c are provided with a first water passage hole 3f for water to flow through. The filtered water can flow into the interior of the first central tube 3a through the first water passage hole 3f.

[0046] Second filter unit 4: Reference Figure 3 , Figure 5 and Figure 11 As shown, the second filtration unit 4 is a post-filtration module used to optimize the taste of pure water. It mainly includes a second central tube 4a, a casing 4b, a second top cover 4c, a second filtration component 4d, and a water guide component 4f.

[0047] The casing 4b has an opening 4e at its bottom and a water guide 4f on its bottom wall. The second filter component 4d is built into the casing 4b and its upper and lower ends are connected to the second top cover 4c and the water guide 4f, respectively. The outer periphery is the water inlet side and the inner periphery is the water outlet side. The interior is filled with compressed activated carbon filter material to adsorb residual chlorine and odor substances in the water. The edge of the opening 4e has a first water guide wall 4g extending downward into the second annular flow channel 2c. The water guide 4f has a second water guide wall 4h extending downward into the first annular flow channel 2b. Under the guidance of the first water guide wall 4g, the water flows from the second annular flow channel 2c to the water inlet side of the outer periphery of the second filter component 4d. The filtered water flows into the first annular flow channel 2b under the guidance of the second water guide wall 4h.

[0048] A second water passage hole 4i is provided at the connection between the water guide component 4f and the bottom wall of the casing 4b, allowing water to flow through. The second water passage holes 4i are circumferentially distributed on the outer periphery of the opening 4e, ensuring that the filtered water can flow smoothly into the inner side of the water guide component 4f. A first sealing ring 5 is provided between the inner peripheral wall of the second annular flow channel 2c and the first water guide wall 4g, and a second sealing ring 6 is provided between the inner peripheral wall of the first annular flow channel 2b and the second water guide wall 4h, to enhance the sealing performance at the connection between the flow channel and the water guide wall and prevent water flow interference.

[0049] The second upper cover 4c has a connector 4j at the top for inserting into the first insertion hole 3e. A third sealing ring 7 is provided between the first insertion hole 3e and the connector 4j. The connector 4j is connected to the second central tube 4a. The bottom of the second upper cover 4c also has a second insertion hole 4k for inserting the top of the second central tube 4a. The bottom of the second central tube 4a is sealed to the central hole 2a of the interface base 2 through a sealing ring 8, so as to realize the structural connection and flow channel connection between the first filter unit 3 and the second filter unit 4.

[0050] The composite filter element in this embodiment achieves deep water treatment through a multi-path water circulation process of "pre-filtration → post-filtration". Its specific working principle is explained as follows:

[0051] 1. Pre-filtration stage: Raw water enters the interface base 2 through the first inlet hole 2e of the second interface seat 23 via the external water circuit board, flows upward into the guide port 23a through the corresponding plug-in pipe 23b, and then enters the third annular flow channel 2d of the first interface seat 22 through the docking hole 22a. After being evenly distributed circumferentially within the third annular flow channel 2d, the raw water flows upward from bottom to top, smoothly entering the outer peripheral inlet side of the first filter component 3d along the gap between the inner wall of the outer shell 1 and the outer periphery of the first filter unit 3. After the pre-filtration removes large particles such as silt and rust, the raw water flows out from the inner peripheral outlet side of the first filter component 3d, flows into the interior of the first central pipe 3a through the first water passage hole 3f on the side wall of the first central pipe 3a, then flows through the plug-in pipe 4j and the second central pipe 4a to the central channel 2a, and finally flows out from the first outlet hole 2g to the reverse osmosis filter module through the docking hole 22a, the guide port 23a, and the corresponding plug-in pipe 23b. Figure 2 The image shown in section B is a reverse osmosis filtration module. Figure 12 This is a schematic diagram of the water circuit for the pre-filtration stage.

[0052] 2. Post-filtration stage: Pure water flowing from the reverse osmosis module enters the second inlet hole 2f of the second interface seat 23 of the interface base 2 through the external water circuit board A, and flows into the second annular flow channel 2c of the first interface seat 22 through the corresponding connecting pipe 23b, water guide 23a and docking hole 22a. Guided by the first water guide wall 4g, the water flows from bottom to top through the opening 4e at the bottom of the casing 4b and enters the interior of the casing 4b. It is distributed along the gap between the inner wall of the casing 4b and the outer periphery of the second filter component 4d and is introduced into the outer periphery inlet side of the second filter component 4d. After the pure water is filtered to adsorb residual chlorine and improve the taste, it flows out from the inner periphery outlet side of the second filter component 4d and flows into the inner side of the water guide component 4f through the second water passage hole 4i at the connection between the water guide component 4f and the bottom wall of the casing 4b. Guided by the second water guide wall 4h, the optimized water flow enters the first annular flow channel 2b of the first interface seat 22, then flows through the docking hole 22a, the water guide port 23a and the corresponding insertion pipe 23b, and flows out from the second water outlet 2h for user use. Figure 2 A in the diagram represents the water channel panel. Figure 13 This is a schematic diagram of the water circuit for the post-filtration stage.

[0053] Throughout the entire operation, the first sealing ring 5 ensures the seal between the second annular flow channel 2c and the first water guide wall 4g; the second sealing ring 6 isolates the first annular flow channel 2b from the second water guide wall 4h; the third sealing ring 7 prevents leakage at the connection between the first filter unit 3 and the second filter unit 4; the fourth sealing ring 9 prevents crosstalk within the interface base 2; and the sealing ring 8 ensures a sealed connection between the second central tube 4a and the central hole 2a. This multi-layered sealing structure, combined with the physical isolation of the layered annular flow channels, completely eliminates crosstalk and contamination between different water paths. Simultaneously, the integrated "two-in, two-out" interface reduces external pipe connections, lowering the risk of leakage. The compact radial flow channel layout significantly reduces the filter element volume, perfectly adapting to the needs of multi-water circulation equipment such as small water purifiers.

[0054] It should be noted that in the description of this embodiment, the terms "front," "rear," "left," "right," "up," "down," etc., indicating the orientation or positional relationship are based on the orientation or positional relationship shown in the accompanying drawings. They are merely for the convenience of describing this utility model and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on this utility model. The terms "installation," "connection," and "linking" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral connection; they can refer to a direct connection or an indirect connection through an intermediate medium; they can refer to the internal connection of two components. For those skilled in the art, the specific meaning of the above terms in this utility model can be understood according to the specific circumstances.

Claims

1. A composite filter element, comprising a housing (1), an interface base (2) disposed at the bottom of the housing (1), and a first filter unit (3) and a second filter unit (4) vertically disposed inside the housing (1), wherein the first filter unit (3) is located above the second filter unit (4), characterized in that: The interface base (2) is provided with a central channel (2a), a first annular flow channel (2b), a second annular flow channel (2c) and a third annular flow channel (2d) that communicate with the interior of the outer shell (1). The first annular flow channel (2b), the second annular flow channel (2c) and the third annular flow channel (2d) surround the outer periphery of the central channel (2a) from the inside to the outside. The bottom of the interface base (2) is provided with a first water inlet (2e) corresponding to the third annular flow channel (2d), a second water inlet (2f) corresponding to the second annular flow channel (2c), a second water outlet (2h) corresponding to the first annular flow channel (2b) and a first water outlet (2g) corresponding to the central channel (2a). The third annular flow channel (2d) is used to guide water flow from the corresponding first inlet hole (2e) upward into the outer periphery of the first filter unit (3). After filtration, the water flows out from the inner periphery of the filter unit and merges into the first central pipe (3a) located in the middle. The second annular flow channel (2c) is used to guide water flow from the corresponding second inlet hole (2f) upward into the outer periphery of the second filter unit (4). After filtration, the water flows out from the inner periphery outlet side and flows into the first annular flow channel (2b) through the gap between the inner periphery and the second central pipe (4a) located in the middle. The second central tube (4a) is connected to the central channel (2a) and is vertically connected to the first central tube (3a).

2. The composite filter element according to claim 1, characterized in that: The first filter unit (3) further includes a first upper cover (3b), a first lower cover (3c) and a first filter component (3d) disposed between the first upper cover (3b) and the first lower cover (3c). The first filter component (3d) is a hollow annular body. The outer periphery of the first filter component (3d) forms an inlet side and the inner periphery forms an outlet side. The first central tube (3a) is located in the hollow part of the first filter component (3d), and its upper and lower ends are connected to the first upper cover (3b) and the first lower cover (3c) respectively. The first lower cover (3c) is also provided with a first insertion hole (3e) for the first central tube (3a) to be inserted. The first central tube (3a) and / or the connection between the first central tube (3a) and the first upper cover (3b) and the first lower cover (3c) is provided with a first water passage hole (3f) for water to flow through.

3. The composite filter element according to claim 2, characterized in that: The second filter unit (4) further includes a housing (4b), a second upper cover (4c), and a second filter component (4d). The housing (4b) has an opening (4e) at the bottom and a water guide (4f) on the bottom wall of the housing (4b). The second filter component (4d) is built into the housing (4b) and its upper and lower ends are respectively connected to the second upper cover (4c) and the water guide (4f). The opening (4e) has a first water guide wall (4g) extending downward into the second annular flow channel (2c) along its edge, and the water guide (4f) has a second water guide wall (4h) extending downward into the first annular flow channel (2b). Under the guidance of the first water guide wall (4g), the water flows from the second annular flow channel (2c) to the water inlet side of the outer periphery of the second filter component (4d). The filtered water flows into the first annular flow channel (2b) under the guidance of the second water guide wall (4h).

4. The composite filter element according to claim 3, characterized in that: The water guide (4f) and the bottom wall of the casing (4b) are provided with a second water passage hole (4i) for water to flow through. The second water passage hole (4i) is circumferentially distributed on the outer periphery of the edge of the opening (4e).

5. The composite filter element according to claim 3, characterized in that: A first sealing ring (5) is provided between the inner peripheral wall of the second annular flow channel (2c) and the first water guiding wall (4g), and a second sealing ring (6) is provided between the inner peripheral wall of the first annular flow channel (2b) and the second water guiding wall (4h).

6. The composite filter element according to claim 3, characterized in that: The top of the second upper cover (4c) is provided with a plug tube (4j) for inserting into the first socket (3e), and a third sealing ring (7) is provided between the first socket (3e) and the plug tube (4j). The plug tube (4j) is in communication with the second central tube (4a). The bottom of the second upper cover (4c) is also provided with a second insertion hole (4k) for the top of the second central tube (4a) to be inserted. The bottom of the second central tube (4a) is sealed to the central channel (2a) of the interface base (2) by a sealing ring (8).

7. The composite filter element according to any one of claims 1 to 6, characterized in that: The interface base (2) includes a connecting sleeve (21), a first interface seat (22), and a second interface seat (23) mating below the first interface seat (22). The first interface seat (22) and the second interface seat (23) are both built into the connecting sleeve (21). The central channel (2a), the first annular flow channel (2b), the second annular flow channel (2c), and the third annular flow channel (2d) are provided on the first interface seat (22).

8. The composite filter element according to claim 7, characterized in that: The bottom of the first interface seat (22) has four docking holes (22a) that respectively connect the central channel (2a), the first annular channel (2b), the second annular channel (2c) and the third annular channel (2d); The top of the second interface seat (23) is provided with four water inlets (23a) that are connected to the four docking holes (22a) respectively. The bottom of the second interface seat (23) is provided with four plug-in pipes (23b) that are respectively connected to the four water inlets (23a). The bottom opening of the plug-in pipe (23b) corresponding to the third annular flow channel (2d) constitutes the first water inlet (2e). The bottom opening of the plug-in pipe (23b) corresponding to the second annular flow channel (2c) constitutes the second water inlet (2f). The bottom opening of the plug-in pipe (23b) corresponding to the central channel (2a) constitutes the first water outlet (2g). The bottom opening of the plug-in pipe (23b) corresponding to the first annular flow channel (2b) constitutes the second water outlet (2h).

9. The composite filter element according to claim 8, characterized in that: The first interface seat (22) and the second interface seat (23) are provided with four fourth sealing rings (9) surrounding the outer periphery of the corresponding docking hole (22a).

10. The composite filter element according to claim 1, characterized in that: The first filter unit (3) is a pre-filter unit, and the second filter unit (4) is a post-filter unit.

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