One-way filtering structure and injection system pipeline

Abstract

The utility model discloses a one-way filtering structure and an injection system pipeline, which comprise a filter, a first pipeline and a second pipeline, the one-way valve is provided with a valve body and a valve core, the valve body is connected with the filter, the valve body is provided with a second channel communicated with the first channel, the valve core is arranged at the inlet end of the valve body, the valve core is provided with an opening, and the opening is communicated with the second channel; a stopping part is arranged in a first channel of the filter in a protruding mode, the stopping part blocks an opening of the valve element, and when fluid flows through the valve element through the first channel, the valve element is pressed to move in the direction away from the filter, so that the opening is communicated with the first channel. According to the technical scheme, the problems that filters and one-way valves need to be installed one by one in an existing injection system pipeline, and operation is troublesome are solved.

Description

Technical Field

[0001] The utility model relates to the technical field of medical equipment, in particular to a one-way filtering structure and an injection system pipeline. Background Art

[0002] In the traditional injection system pipeline, a filter is provided to filter the liquid medicine to be injected into the body, and a one-way valve is also provided to allow the liquid medicine to pass in one direction and prevent the blood in the body of the infusion subject from flowing back into the injection pipeline.

[0003] When it is necessary to install a filter and a one-way valve, it is usually necessary to install the filter and the one-way valve one by one in the injection system pipeline, which requires two connections and is troublesome to operate. Utility Model Content

[0004] The main purpose of the utility model is to provide a one-way filtering structure and an injection system pipeline, aiming to solve the problem that the existing installation of filters and one-way valves in the injection system pipeline requires installation one by one, which is relatively troublesome to operate.

[0005] To achieve the above-mentioned purpose, the utility model proposes a one-way filtering structure, comprising: a filter, the filter having a first channel; and a one-way valve, the one-way valve having a valve body and a valve core, the valve body being connected to the filter, the valve body having a second channel connected to the first channel, the valve core being arranged at the inlet end of the valve body, the valve core having an opening, and the opening being connected to the second channel; wherein a stopper is convexly provided in the first channel of the filter, the stopper blocks the opening of the valve core, and when the fluid flows from the first channel through the valve core, the valve core is pressed to move in a direction away from the filter to achieve the connection between the opening and the first channel.

[0006] In one embodiment of the utility model, the filter includes an upper cover, a filter screen and a lower cover, the first channel is formed between the upper cover and the lower cover, the lower cover is connected to the inlet end of the valve body, the stopper is protruded in the first channel of the lower cover, the filter screen is arranged between the upper cover and the lower cover, and covers the first channel in the transverse direction.

[0007] In one embodiment of the utility model, a connecting pipe connected to the first channel is provided at one end of the lower cover away from the upper cover, the connecting pipe is connected to the valve body, the bottom wall of the connecting pipe is protrudingly provided with the stopper, the bottom wall of the connecting pipe is provided with a liquid outlet connected to the first channel, and the liquid outlet is located on the outer periphery of the stopper.

[0008] In one embodiment of the utility model, the upper cover and the lower cover are combined to form a filter cavity connected to the first channel, and the filter net is arranged in the filter cavity; the surface of the upper cover facing the lower cover is protruding with a first protrusion, and the surface of the lower cover facing the upper cover is protruding with a second protrusion, and the first protrusion and the second protrusion cooperate to clamp the two end surfaces of the filter net.

[0009] In one embodiment of the utility model, a fixing strip is convexly provided on the surface of the upper cover facing the lower cover, and a fixing groove is concavely provided on the surface of the lower cover facing the upper cover. Both the fixing strip and the fixing groove are located at the periphery of the filter cavity, and the fixing strip is used to press the filter net into the fixing groove.

[0010] In an embodiment of the utility model, the fixing bars are provided in a plurality, the lower cover is provided with fixing grooves matching the number of the fixing bars, and the fixing bars and the fixing grooves are arranged in a one-to-one correspondence.

[0011] In an embodiment of the present invention, the filter screen is connected to the surfaces of the fixing strip and the fixing groove by glue dispensing.

[0012] In one embodiment of the utility model, the surface edge of the upper cover facing the lower cover is provided with a concave connecting groove, and the surface edge of the lower cover facing the upper cover is provided with a convex connecting protrusion, and the connecting protrusion extends into the connecting groove and is connected to the connecting groove.

[0013] In an embodiment of the utility model, a connecting joint is provided at one end of the valve body away from the valve core, and the connecting joint is an inner cone locking joint or an outer cone locking joint.

[0014] The utility model also provides an injection system pipeline, comprising the one-way filtering structure as mentioned above.

[0015] Compared with the prior art, the one-way filtering structure and injection system pipeline provided by the utility model have the following beneficial effects:

[0016] The utility model connects the filter and the one-way valve as a whole. When in use, only the two ends of the one-way filtering structure need to be connected to the injection system pipeline, and there is no need to install them one by one, which reduces the installation steps, improves the installation efficiency and is easy to operate. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] In order to more clearly illustrate the embodiments of the utility model or the technical solutions in the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the utility model. For ordinary technicians in this field, other drawings can be obtained based on the structures shown in these drawings without paying creative work.

[0018] Figure 1 This is a schematic diagram of the overall structure of an embodiment of the one-way filtering structure of the utility model;

[0019] Figure 2 This is one of the exploded schematic diagrams of an embodiment of the one-way filtering structure of the utility model;

[0020] Figure 3 This is the second exploded schematic diagram of an embodiment of the one-way filtering structure of the utility model;

[0021] Figure 4 It is a cross-sectional view of an embodiment of the one-way filtering structure of the utility model;

[0022] Figure 5 It is a cross-sectional view of another embodiment of the one-way filtering structure of the utility model;

[0023] Figure 6 It is a structural schematic diagram of another embodiment of the one-way filtering structure of the utility model.

[0024] Description of Figure Numbers:

[0025] Label name Label name 100 One-way filter structure 1511 Liquid port 1 Filters 152 Second bump 11 First Channel 153 Fixed slot 12 Stopper 154 Connection bump 13 Upper cover 16 Filter chamber 131 First bump 2 Check valve 132 Fixed bar 21 Valve body 133 Connection groove 211 Second channel 14 Filter 212 Connection joints 15 Lower cover 22 Valve core 151 Connecting pipe 221 Opening

[0026] The realization of the purpose, functional features and advantages of the utility model will be further explained in conjunction with embodiments and with reference to the accompanying drawings. DETAILED DESCRIPTION

[0027] The following will be combined with the drawings in the embodiments of the utility model to clearly and completely describe the technical solutions in the embodiments of the utility model. Obviously, the described embodiments are only part of the embodiments of the utility model, not all of the embodiments. Based on the embodiments of the utility model, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the utility model.

[0028] It should be noted that all directional indications in the embodiments of the present invention (such as up, down, left, right, front, back...) are only used to explain the relative position relationship, movement status, etc. between the components under a certain specific posture (as shown in the accompanying drawings). If the specific posture changes, the directional indication will also change accordingly.

[0029] In addition, the descriptions of "first", "second", etc. in the present utility model are only used for descriptive purposes and cannot be understood as indicating or implying their relative importance or implicitly indicating the number of the indicated technical features. Therefore, the features defined as "first" and "second" may explicitly or implicitly include at least one of the features. In addition, the technical solutions between the various embodiments can be combined with each other, but they must be based on the ability of ordinary technicians in this field to implement them. When the combination of technical solutions is contradictory or cannot be implemented, it should be deemed that such a combination of technical solutions does not exist and is not within the scope of protection required by the present utility model.

[0030] Please refer to Figures 1 to 6 The utility model proposes a one-way filtering structure 100, comprising: a filter 1, wherein the filter 1 has a first channel 11; and a one-way valve 2, wherein the one-way valve 2 has a valve body 21 and a valve core 22, wherein the valve body 21 is connected to the filter 1, wherein the valve body 21 has a second channel 211 communicated with the first channel 11, wherein the valve core 22 is arranged at an inlet end of the valve body 21, wherein the valve core 22 has an opening 221, wherein the opening 221 is communicated with the second channel 211; wherein a stopper 12 is convexly arranged in the first channel 11 of the filter 1, wherein the stopper 12 blocks the opening 221 of the valve core 22, and when the fluid flows from the first channel 11 through the valve core 22, the valve core 22 is pressed and moves in a direction away from the filter 1, so as to realize the communication between the opening 221 and the first channel 11.

[0031] Specifically, the one-way filtering structure 100 includes a filter 1 and a one-way valve 2. The filter 1 is used to filter the medicinal solution, and the one-way valve 2 is used to allow the medicinal solution to pass through in one direction and prevent blood from flowing back. The filter 1 and the one-way valve 2 are connected into an integrated structure. When in use, the one-way filtering structure 100 can be directly connected to the injection system pipeline for use.

[0032] A first channel 11 is formed in the filter 1, a second channel 211 is formed in the one-way valve 2, and the first channel 11 is communicated with the second channel 211. The one-way valve 2 includes a valve body 21 and a valve core 22, the valve core 22 is arranged at the inlet end of the valve body 21, an opening 221 is arranged on the valve core 22, and the opening 221 of the valve core 22 is communicated with the second channel 211. When the one-way valve 2 is in a static state, the opening 221 of the valve core 22 always abuts against the stopper 12 of the filter 1, and the stopper 12 blocks the opening 221 of the valve core 22. When the liquid flows from the filter 1 to the one-way valve 2, the valve core 22 will be moved in a direction away from the filter 1 by the pressure of the liquid, the stopper 12 is disconnected from the opening 221 of the valve core 22, and the opening 221 of the valve core 22 is communicated with the first channel 11, so that the liquid can pass through the one-way valve 2 smoothly.

[0033] When the liquid flows in the reverse direction, the valve core 22 will overlap the stopper 12 of the filter 1 through pressure, and the opening 221 of the valve core 22 will be continuously blocked, thereby cutting off the flow to achieve the effect of preventing backflow.

[0034] like Figure 4 The valve core 22 can be connected by a spring, or the valve core 22 can be directly set as an elastic member. In this embodiment, the valve core 22 is an elastic member, and the wall surface of the valve core 22 located at the opening 221 can directly move in a direction away from the filter 1 when subjected to pressure, so that the opening 221 is separated from the stopper 12; after the liquid pressure is released, the wall surface of the valve core 22 will return to a normal state and overlap with the stopper 12.

[0035] When in use, the end of the filter 1 away from the one-way valve 2 is connected to the input direction of the injection system pipeline, and the outlet end of the valve body 21 of the one-way valve 2 is connected to the output direction of the injection system pipeline, thereby realizing the infusion direction from the filter 1 to the one-way valve 2, first filtering the liquid medicine, and then making the liquid medicine flow out in one direction, and preventing the liquid medicine or blood from flowing back. The one-way filter structure 100 is connected to the injection system pipeline, and during the injection or inhalation process, it can not only filter the latex particles in the liquid medicine, but also prevent the liquid from flowing back.

[0036] The utility model connects the filter 1 and the one-way valve 2 as a whole. When in use, it is only necessary to connect the two ends of the one-way filtering structure 100 to the injection system pipeline without installing them one by one, thus reducing the installation steps, improving the installation efficiency and facilitating the operation.

[0037] In an embodiment of the utility model, the filter 1 includes an upper cover 13, a filter screen 14 and a lower cover 15, the first channel 11 is formed between the upper cover 13 and the lower cover 15, the lower cover 15 is connected to the inlet end of the valve body 21, the stopper 12 is protrudingly provided in the first channel 11 of the lower cover 15, the filter screen 14 is arranged between the upper cover 13 and the lower cover 15, and covers the first channel 11 in the transverse direction.

[0038] In detail, the filter 1 includes an upper cover 13, a filter screen 14 and a lower cover 15. The upper cover 13 and the lower cover 15 cooperate to form a first channel 11. The filter screen 14 is arranged between the upper cover 13 and the lower cover 15, and laterally covers the middle of the first channel 11. The medicinal liquid flowing through the first channel 11 needs to be filtered through the filter screen 14. The filter screen 14 can filter the latex particles in the medicinal liquid, thereby ensuring the reliability of the infusion and the health and safety of the users to be infused.

[0039] The lower cover 15 is connected to the valve body 21, and there are various connection methods and connection structures, which can be glue point bonding, undercut connection, or bolt connection. The specific method can be selected according to actual needs.

[0040] The lower cover 15 is provided with a stopper 12 at a position located in the first channel 11. The structure of the stopper 12 can be set according to actual needs. A protrusion or a connecting column or other structure can be protruded on the inner wall of the lower cover 15 to block the opening 221 of the valve core 22. The specific structure can be set according to actual needs.

[0041] In one embodiment of the utility model, a connecting pipe 151 communicating with the first channel 11 is provided at one end of the lower cover 15 away from the upper cover 13, the connecting pipe 151 is connected to the valve body 21, the bottom wall of the connecting pipe 151 is protrudingly provided with the stopper 12, the bottom wall of the connecting pipe 151 is provided with a liquid port 1511 communicating with the first channel 11, and the liquid port 1511 is located on the outer periphery of the stopper 12.

[0042] It should be understood that a connecting pipe 151 is provided at one end of the lower cover 15 close to the one-way valve 2, and is connected to the valve body 21 through the connecting pipe 151. A stopper 12 is provided in the connecting pipe 151 to block the opening 221 of the valve core 22. The connecting pipe 151 is provided to facilitate connection with the valve body 21, and the connection is more convenient.

[0043] like Figure 3 and Figure 4 The bottom wall of the connecting tube 151 is provided with a stopper 12, and a liquid passage 1511 is provided on the outer periphery of the stopper 12. The liquid medicine flows through the upper cover 13 into the liquid passage 1511, and then enters the cavity between the stopper 12 and the valve core 22, providing pressure to the valve core 22, pushing the valve core 22 open, and allowing the liquid medicine to pass smoothly. The multiple liquid passages 1511 on the bottom wall of the connecting tube 151 can better push the valve core 22 open.

[0044] In addition, a joint pipe is also provided at one end of the upper cover 13 away from the lower cover 15 for connection to the injection pipeline system. The joint pipe can be configured as an inner conical joint or an outer conical joint.

[0045] In one embodiment of the utility model, the upper cover 13 and the lower cover 15 are combined to form a filter cavity 16 connected to the first channel 11, and the filter screen 14 is arranged in the filter cavity 16; the surface of the upper cover 13 facing the lower cover 15 is protrudingly provided with a first protrusion 131, and the surface of the lower cover 15 facing the upper cover 13 is protrudingly provided with a second protrusion 152, and the first protrusion 131 and the second protrusion 152 cooperate to be clamped on the two end surfaces of the filter screen 14.

[0046] It is worth noting that a filter chamber 16 is formed between the upper cover 13 and the lower cover 15. The size of the filter chamber 16 is larger than the size of the first channel 11. The filter screen 14 is arranged in the filter chamber 16 and covers the filter chamber 16 laterally. When the medicinal liquid enters the filter chamber 16 from the first channel 11 of the upper cover 13, it is filtered through the filter screen 14 and then flows into the one-way valve 2.

[0047] A first protrusion 131 is convexly provided on the surface of the upper cover 13 located in the filter cavity 16, and a second protrusion 152 is convexly provided on the surface of the lower cover 15 located in the filter cavity 16. The first protrusion 131 cooperates with the second protrusion 152 to clamp the filter screen 14, so that the middle part of the filter screen 14 is fixed. When the liquid medicine flows through the filter screen 14, the filter screen 14 can be supported vertically to prevent the filter screen 14 from falling off. By fixing the middle part of the filter screen 14, the degree of fixation of the filter screen 14 is strengthened, the stability of the connection of the filter screen 14 is improved, the impact force of the liquid medicine on the filter screen 14 is balanced, and the filter screen 14 is prevented from falling off from the upper cover 13 and the lower cover 15.

[0048] In addition, if Figure 2 and Figure 3 There are multiple first protrusions 131 and second protrusions 152, which are arranged in an arc-shaped block. The filter screen 14 is clamped by the multiple first protrusions 131 and the multiple second protrusions 152, so that the filter screen 14 is fixed more stably and firmly.

[0049] In one embodiment of the utility model, a fixing strip 132 is convexly provided on the surface of the upper cover 13 facing the lower cover 15, and a fixing groove 153 is concavely provided on the surface of the lower cover 15 facing the upper cover 13. Both the fixing strip 132 and the fixing groove 153 are located at the periphery of the filter cavity 16, and the fixing strip 132 is used to press the filter screen 14 against the fixing groove 153.

[0050] In detail, the edge of the filter screen 14 is arranged between the surfaces of the upper cover 13 and the lower cover 15 located at the outer periphery of the filter chamber 16, a fixing strip 132 is convexly arranged on the surface of the upper cover 13 located at the outer periphery of the filter chamber 16, and a fixing groove 153 is concavely arranged on the surface of the lower cover 15 located at the outer periphery of the filter chamber 16, the fixing strip 132 and the fixing groove 153 are arranged in coordination with each other, and the fixing strip 132 is used to press the edge of the filter screen 14 into the fixing groove 153, thereby fixing the edge portion of the filter screen 14, and when the medicinal liquid flows through the filter screen 14 and impacts the filter screen 14 to generate tension, the tension exerted on the filter screen 14 by the impact force of the liquid can be reduced, and the filter screen 14 can be fixed at the edge of the filter screen 14 to prevent the filter screen 14 from falling off from the upper cover 13 and the lower cover 15, so that the fixation of the filter screen 14 is more stable and firm. By cooperating with the first protrusion 131 and the second protrusion 152, the middle and edge of the filter screen 14 are fixed, thereby improving the stability of the connection of the filter screen 14 and making the one-way filtering structure 100 more reliable when used.

[0051] In an embodiment of the present invention, a plurality of fixing bars 132 are provided, and the lower cover 15 is provided with fixing grooves 153 matching the number of the fixing bars 132 . The fixing bars 132 and the fixing grooves 153 are arranged in a one-to-one correspondence.

[0052] Specifically, Figure 5 There are multiple fixing strips 132 and fixing grooves 153, and the fixing strips 132 cooperate with the fixing grooves 153 to fix the filter screen 14 at multiple points, so that the fixing area of ​​the filter screen 14 is increased, and the filter screen 14 can be better fixed during use, and the connection of the filter screen 14 is more firm, stable and reliable.

[0053] It is worth noting that Figure 2 and Figure 3 The fixing strip 132 is arranged around the circumference of the upper cover 13, and the fixing groove 153 is also arranged around the circumference of the lower cover 15, forming an annular fixing strip 132 and a fixing groove 153, which can fix the filter net 14 along the circumference of the filter net 14, and can better fix the filter net 14, making the installation of the filter net 14 more stable and not easy to fall off during use.

[0054] In an embodiment of the present invention, the filter screen 14 is connected to the surfaces of the fixing strip 132 and the fixing groove 153 by dispensing glue.

[0055] In detail, when the fixing strip 132 presses the filter 14 into the fixing groove 153, the filter 14 can be connected to the fixing strip 132 and the surface of the fixing groove 153 by dispensing glue, which has high firmness and can withstand sustained pressure, making the filter 14 more reliable when used and not easy to fall off.

[0056] In one embodiment of the utility model, a surface edge of the upper cover 13 facing the lower cover 15 is provided with a concave connecting groove 133, and a surface edge of the lower cover 15 facing the upper cover 13 is provided with a convex connecting protrusion 154, and the connecting protrusion 154 extends into the connecting groove 133 and is connected to the connecting groove 133.

[0057] In detail, a filter chamber 16 is formed in the middle of the upper cover 13 and the lower cover 15. The upper cover 13 and the lower cover 15 are connected by setting a connecting protrusion 154 and a connecting groove 133 on the edge. The connecting protrusion 154 and the connecting groove 133 cooperate to connect, so that the connection is more stable and has good sealing to prevent external leakage.

[0058] The connection between the connection protrusion 154 and the connection groove 133 can be achieved by glue point connection or welding, and the specific connection method can be selected according to actual needs.

[0059] In an embodiment of the present utility model, a connecting joint 212 is provided at one end of the valve body 21 away from the valve core 22 , and the connecting joint 212 is an inner cone locking joint or an outer cone locking joint.

[0060] In detail, the one-way valve 2 can be provided with a corresponding connection joint 212 according to actual needs, which can be provided as an inner cone locking joint or an outer cone locking joint, or the one-way valve 2 can be directly bonded to the injection system pipeline without a joint. The joint forms at both ends of the one-way filtering structure 100 can be set according to actual needs, such as Figure 4 , the one-way valve 2 is a locking joint with an inner cone; Figure 6 , the one-way valve 2 is provided with an external conical locking joint.

[0061] When an inner conical locking joint is used, it can be connected to an outer conical locking joint of a syringe; when an inner conical locking joint is used, the one-way filtering structure 100 can be set at the end of the injection pipeline system, such as directly connecting the inner conical locking joint to an indwelling needle.

[0062] The utility model also provides an injection system pipeline (not shown), comprising the one-way filtering structure 100 as described above.

[0063] Specifically, the injection system pipeline includes various types, such as high-pressure syringes, disposable infusion sets, etc. The one-way filtering structure 100 can be directly installed on the injection system pipeline, has the functions of filtering and preventing backflow, and is easy to operate.

[0064] The specific structure of the one-way filtering structure 100 refers to the above embodiments. Since the injection system pipeline adopts all the technical solutions of all the above embodiments, it at least has all the beneficial effects brought by the technical solutions of the above embodiments, which will not be described one by one here.

[0065] The above description is only a preferred embodiment of the present invention, and does not limit the patent scope of the present invention. All equivalent structural changes made by using the contents of the present invention specification and drawings under the inventive concept of the present invention, or directly / indirectly applied in other related technical fields are included in the patent protection scope of the present invention.

Claims

1. A one-way filtering structure, characterized in that: include: a filter having a first channel; and A one-way valve, the one-way valve comprising a valve body and a valve core, the valve body being connected to the filter, the valve body having a second passage communicating with the first passage, the valve core being disposed at an inlet end of the valve body, the valve core having an opening, and the opening communicating with the second passage; Wherein, a stopper is protruding inside the first channel of the filter, and the stopper blocks the opening of the valve core. When the fluid flows through the valve core from the first channel, the valve core is pressed to move away from the filter to achieve communication between the opening and the first channel.

2. The one-way filtering structure according to claim 1, characterized in that: The filter includes an upper cover, a filter screen and a lower cover, the first channel is formed between the upper cover and the lower cover, the lower cover is connected to the inlet end of the valve body, the stopper is protruding in the first channel of the lower cover, the filter screen is arranged between the upper cover and the lower cover, and covers the first channel in the transverse direction.

3. The one-way filtering structure according to claim 2, characterized in that: A connecting pipe communicating with the first channel is provided at one end of the lower cover away from the upper cover, the connecting pipe is connected to the valve body, the bottom wall of the connecting pipe is protrudingly provided with the stopper, the bottom wall of the connecting pipe is provided with a liquid outlet communicating with the first channel, and the liquid outlet is located on the periphery of the stopper.

4. The one-way filtering structure according to claim 2, characterized in that: The upper cover and the lower cover are combined to form a filter cavity communicated with the first channel, and the filter screen is arranged in the filter cavity; A first protrusion is convexly provided on the surface of the upper cover facing the lower cover, and a second protrusion is convexly provided on the surface of the lower cover facing the upper cover. The first protrusion cooperates with the second protrusion to be clamped on both end surfaces of the filter screen.

5. The one-way filtering structure according to claim 4, characterized in that: A fixing strip is convexly provided on the surface of the upper cover facing the lower cover, and a fixing groove is concavely provided on the surface of the lower cover facing the upper cover. Both the fixing strip and the fixing groove are located at the periphery of the filter cavity, and the fixing strip is used to press the filter screen into the fixing groove.

6. The one-way filtering structure according to claim 5, characterized in that: The fixing bars are provided in a plurality, and the lower cover is provided with fixing grooves matching the number of the fixing bars, and the fixing bars and the fixing grooves are arranged in a one-to-one correspondence.

7. The one-way filtering structure according to claim 5, characterized in that: The filter screen is connected to the surfaces of the fixing strip and the fixing groove by glue dispensing.

8. The one-way filtering structure according to any one of claims 2 to 7, characterized in that: A surface edge of the upper cover facing the lower cover is provided with a concave connection groove, and a surface edge of the lower cover facing the upper cover is provided with a convex connection protrusion, and the connection protrusion extends into the connection groove and is connected with the connection groove.

9. The one-way filtering structure according to any one of claims 1 to 7, characterized in that: A connecting joint is provided at one end of the valve body away from the valve core, and the connecting joint is an inner cone locking joint or an outer cone locking joint.

10. An injection system pipeline, characterized in that: It comprises the one-way filtering structure as claimed in any one of claims 1 to 9.

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