Filter element and method for the production thereof

Abstract

This invention relates to a filter element constructed in a bag-like or tubular shape with an internal space extending in the longitudinal direction and having a multi-layer structure. This multi-layer structure includes a permeable outer layer, a permeable inner layer, and at least one intermediate layer disposed between the outer and inner layers. The intermediate layer is constructed as a pore-filled filter element, wherein the filter element has a predetermined axial length, and wherein the outer and inner layers also have predetermined axial lengths. According to the invention, the intermediate layer is constructed to be axially shorter than the outer and inner layers when constructing an overflow region located at the upper axial end region of the filter element. The upper edge of the intermediate layer is axially spaced downward from the upper edges of the outer and inner layers. The outer, inner, and intermediate layers are fixedly connected to each other along at least one longitudinal edge when constructing a longitudinal connecting seam, and the outer and inner layers are fixedly connected to each other along their upper edges when constructing an upper transverse connecting seam. The upper edge of the intermediate layer is freely and unconnected between the outer and inner layers.

Description

Technical Field

[0001] This invention relates to a filter element, particularly a blood filter element, as described in the preamble of claim 1, which is constructed in a bag-like or tubular shape with an internal space extending in the longitudinal direction and has a multi-layered structure that is permeable (or permeable, i.e., The filter comprises an outer layer, a permeable inner layer, and at least one intermediate layer disposed between the outer and inner layers, the intermediate layer being configured as a pore-filled filter element having a predetermined axial length, and wherein the outer and inner layers have predetermined axial lengths.

[0002] The present invention also relates to a method for manufacturing such a filter element, particularly a blood filter element, according to claim 13. Background Technology

[0003] This type of filter element, used as a blood filter, is especially used in so-called cardiopulmonary bypass machines to purify circulating blood and trap excessively large air bubbles in the blood.

[0004] A blood filtration element with three layers is known from WO98 / 15302A1, wherein each layer is mounted on a rigid substrate or frame. The frame is used to pre-determine the columnar shape.

[0005] DE 2530413 C3 discloses a bag-shaped blood filter formed by welding different layers. Summary of the Invention

[0006] The objective of this invention is to describe a simple and robustly constructed filter element, particularly a blood filter element, and a method for manufacturing it, which enables particularly efficient filtration, especially blood filtration.

[0007] This task is accomplished on the one hand by a filter element having the features of claim 1, and on the other hand by a method having the features of claim 13. Preferred embodiments of the invention are described in the dependent claims.

[0008] The filter element according to the invention is characterized in that the intermediate layer is constructed to be axially shorter than the outer and inner layers when constructing an overflow region, the overflow region being arranged at the upper axial end region of the filter element, wherein the upper edge of the intermediate layer is axially spaced downward from the upper edges of the outer and inner layers, the outer, inner, and intermediate layers are fixedly connected to each other along at least one longitudinal edge when constructing a longitudinal connecting seam, and the outer and inner layers are fixedly connected to each other along their upper edges when constructing an upper transverse connecting seam, wherein the upper edge of the intermediate layer is arranged freely and unconnected between the outer and inner layers.

[0009] The basic concept of this invention is that, in a multi-layered structure of a sock-shaped or tubular filter element, the filter element is constructed as an intermediate layer between the outer and inner layers, but with a different length. The intermediate layer is implemented in a defined manner with a shorter axial length, such that its upper edge is spaced apart from the upper edges of the outer and inner layers while allowing for free space. Therefore, in the upper section of the filter element, a structure of only two layers is created, thereby forming an overflow region. The overflow region without an intermediate layer has lower flow resistance. Thus, under certain conditions, excess fluid can be quickly and efficiently diverted through the overflow region, where minimal filtration efficiency is ensured by the outer and inner layers.

[0010] Another aspect of the invention is that if the fixed connection between the intermediate layer and the outer and inner layers exists at least along the longitudinal edge with longitudinal connecting seams, it is sufficient for fixing the position of the intermediate layer in the filter element. In particular, the invention is based on the understanding that the upper edge of the intermediate layer can remain free and unconnected. Thus, in manufacturing the filter element, it is particularly convenient to omit the use of additional welding foil to connect the inner layers. A sufficiently robust structure is achieved by connecting the intermediate layer to the other two layers along the longitudinal edge and connecting the outer and inner layers at the upper edge. A higher and more effective filtration area is achieved with a smaller number of connecting seams.

[0011] Therefore, a particularly advantageous and functional structure for filter elements can be obtained with efficient manufacturing.

[0012] The filter element according to the invention is installed in principle such that the inflow of the fluid to be purified, especially blood, into the internal space is from above or front. For purification, the fluid flows radially outward through the peripheral wall of the filter element, which is approximately hollow and cylindrical. The filter element may be tubular with upper and lower openings, or alternatively, may be bag-shaped or sock-shaped, with the lower opening closed. The filter element generally operates such that, during normal filtration operation, the fluid to be purified, especially blood, passes through the wall of the filter element through the lower and middle regions of the three-layer structure. Additional filtration effects, especially cascade filtration with the middle layer, can be obtained through the corresponding construction of the inner layers. If accidental blockage or foaming occurs in this area, the fluid can also overflow radially outward through the two overflow regions. Thus, especially when the filter element is used as a blood filtration element, for example through a cardiopulmonary bypass machine, and therefore for patients.

[0013] In principle, in an alternative design, the fluid to be purified (such as blood) can also flow radially from the outside to the inside.

[0014] In a preferred embodiment of the invention, the outer layer, inner layer, and / or intermediate layer are fixedly connected to each other at their lower edges when the lower transverse connecting seam is constructed. Here, only two layers or all layers can be connected to each other in a ring shape. This improves the stability of the structure. For bag filter elements, the lower transverse connecting seam is constructed such that the opening of the internal space is completely closed downwards.

[0015] Generally, the filter element according to the invention can be constructed such that an initial material having three overlapping layers cut (or fabricated, i.e., konfektioniert) according to a desired length and double width is folded once and overlapped with each other. To form a filter element, particularly a tubular one, a fixed connection can then be made along the longitudinal edges, thus forming a filter element with only one longitudinal connecting seam. The tubular shape can be columnar or conical.

[0016] A particularly stable design of the present invention is that it comprises a structure consisting of two halves, which are fixedly connected to each other along two longitudinal edges by constructing two longitudinal connecting seams. The respective halves can be cut identically and each has three layers. Here, according to the invention, the middle layer is defined as being axially shorter than the outer and inner layers.

[0017] Another preferred embodiment of the invention is that the axial length of the overflow region is between 5% and 30% of the axial length of the filter element. In the actual filtration region, the sidewalls of the filter element are constructed in three layers, while in the overflow region, a two-layer structure consisting of an outer layer and an inner layer is formed without an intermediate layer.

[0018] In principle, the layers can be joined using any suitable joining method. Particularly advantageous in manufacturing is that at least one joint edge is formed by ultrasonic welding. This allows polymer materials with smaller joint widths to be efficiently and reliably joined together even with narrow and clean joint edges.

[0019] To form a bag-shaped filter element, particularly a blood filter element, according to one embodiment of the invention, the lower transverse connecting seam is configured to form a closed bottom. This prevents fluid (such as blood) from freely flowing downwards through the filter element. Thus, purification of all fluid entering the filter element is ensured.

[0020] Generally, the porous intermediate layer used for filtration can be constructed in any suitable manner. A particularly suitable improvement according to the invention is that the filter element has a filter woven fabric, a filter membrane, a filter knitted fabric, and / or a filter nonwoven fabric (or filter nonwoven material, i.e., Filtervlies). Depending on the filtration task, the pore size or opening size, the opening ratio of the filter area, and the filtration performance or flow resistance can be selected.

[0021] A particular advantage of an improvement according to the invention is that the opening size or pore size of the filter element is between 10 μm and 400 μm, especially between 25 μm and 60 μm. This can be achieved, in particular, by constructing the filter element as a filter fabric, wherein preferably, an opening share between 30% and 60% of the total filtration area can be achieved. This is achieved, in particular, by using very fine threads, preferably between 10 μm and 30 μm, especially between 18 μm and 28 μm.

[0022] In principle, the outer and inner layers have a permeable structure, particularly with larger openings or pores than the intermediate layers. According to one construction variant of the invention, it is advantageous that the outer and / or inner layers are constructed of woven fabric, knitted fabric, mesh, grid, and / or nonwoven fabric. The use of woven or knitted fabrics (preferably formed with monofilaments or polyfilaments) is particularly suitable. This largely prevents components from detaching from the layers.

[0023] The exceptionally good purification effect is achieved by using polymer materials, particularly polyester or polyamide, for the middle, outer, and inner layers. These materials are medically approved and of exceptionally pure purity.

[0024] Furthermore, according to an improvement of the invention, it is particularly advantageous that the intermediate layer, outer layer, and inner layer are made of the same material. The use of the same material improves applicability in the medical field and facilitates licensing as a medical product. Especially when combined with welding, particularly ultrasonic welding, a filter element of pure type can be formed without additional adhesives or other materials. This ensures a particularly high level of product safety.

[0025] Another advantageous embodiment of the invention is that the opening size of the outer and / or inner layers is between 100 μm and 400 μm, particularly between 150 μm and 300 μm. Thus, the flow resistance in the filter element is hardly affected, especially in the intermediate layer where filtration is primarily performed. Furthermore, when the opening proportion in this size range, particularly in the outer and inner layers, exceeds 50%, good overflow function is achieved for the overflow area.

[0026] Regarding the method for manufacturing filter elements, particularly blood filter elements, the present invention is characterized in that the outer and inner layers are fixedly connected to each other at their upper edges with a transversely connected seam in the upper part of the structure, wherein an intermediate layer is arranged in the intermediate space between the outer and inner layers, and the upper edge of the intermediate layer remains free and unconnected. Thus, a filter element with overflow function can be realized in the upper region using only a double-layer structure, wherein the upper edge of the intermediate layer performing filtration remains free and unconnected between the outer and inner layers.

[0027] This method can be used to efficiently manufacture the previously described filter elements, such as blood filter elements, thereby achieving the advantages described above.

[0028] According to an improvement of the invention, particularly good bonding between the various flexible layers can be provided, i.e., the outer, inner and / or intermediate layers are joined at their outer edges via ultrasonic welding, thermal welding, bonding and / or thermal bonding. Especially in the case of ultrasonic welding and thermal welding, the use of adhesives or additional components can be eliminated.

[0029] Another suitable variation of the invention involves forming an intermediate shape, either bag-shaped or tubular, with an external connecting seam by connecting a flexible layer, and then flipping (or de-rolling, i.e., gestülpt) the intermediate shape to form a filter element, wherein the connecting seam is rotated inward. This provides a protected arrangement of the connecting seam at the intermediate product. Furthermore, during the inflow of the filter element from the inside, it is ensured that even if the smallest components detach from the connecting seam, these components cannot reach actual blood circulation when used as a blood filter element, as they are then captured by the intermediate layer that subsequently performs filtration in the flow direction.

[0030] As already mentioned, the filter element of the present invention is preferably used as a blood filter element, for example, in a cardiopulmonary bypass machine. However, it is also suitable for filtering other fluids, which, according to the present invention, can be understood in particular as fluids with or without a solid and with or without a gaseous component. Attached Figure Description

[0031] The present invention will now be further described with reference to preferred embodiments, which are schematically illustrated in the accompanying drawings. Wherein:

[0032] Figure 1 A side view of the first filter element according to the present invention is shown;

[0033] Figure 2 It shows Figure 1 A cross-sectional view of the filter element;

[0034] Figure 3It shows the view from above based on Figure 1 and Figure 2 A top view of the filter element;

[0035] Figure 4 It shows Figure 2 A magnified view of detail A;

[0036] Figure 5 It shows Figure 2 A magnified view of detail B;

[0037] Figure 6 A side view of the second filter element according to the present invention is shown;

[0038] Figure 7 It shows Figure 6 A cross-sectional view of the filter element;

[0039] Figure 8 It shows the view from above based on Figure 6 and Figure 7 A top view of the filter element;

[0040] Figure 9 It shows Figure 7 A magnified view of detail A; and

[0041] Figure 10 It shows Figure 7 A magnified view of detail B;

[0042] Figure 11 A side view of the third filter element according to the present invention is shown;

[0043] Figure 12 It shows Figure 11 A cross-sectional view of the filter element;

[0044] Figure 13 It shows the view from above based on Figure 11 and Figure 12 A top view of the filter element;

[0045] Figure 14 It shows Figure 12 A magnified view of detail A; and

[0046] Figure 15 It shows Figure 12 Enlarged view of detail B

[0047] Figure 16 A side view of the fourth filter element according to the present invention is shown;

[0048] Figure 17 It shows Figure 16 A cross-sectional view of the filter element;

[0049] Figure 18 It shows the view from above based on Figure 16 and Figure 17 A top view of the filter element;

[0050] Figure 19 It shows Figure 17 A magnified view of detail A; and

[0051] Figure 20 It shows Figure 17 A magnified view of detail B. Detailed Implementation

[0052] according to Figures 1 to 5 The image shows a first embodiment of a filter element 10 according to the invention, which is tubularly constructed with a continuous internal space 16 having an upper opening 15 and a lower opening 17. The tubular filter element 10 is slightly tapered along the longitudinal axis 12 toward the lower opening 17. The openings 15 and 17 are constructed to be approximately circular.

[0053] The filter element 10 consists of two halves 14 connected to each other along two longitudinal edges of the longitudinal axis 12 by a longitudinal connecting seam 20. This connection can be made, in particular, by means of ultrasonic welding. Each half 14 has three layers: an outer layer 30, an inner layer 32, and an intermediate layer 34 disposed therein in an intermediate space 33. The intermediate layer 34 is a filter element with fine pores, while the outer layer 30 and the inner layer 32 can have larger pore openings. The outer layer 30 and the inner layer 32 have the same axial length, while the intermediate layer 34 is constructed to be axially shorter in a defined manner.

[0054] In the filter element 10 shown, three layers are connected to each other, for example by ultrasonic welding, along two longitudinal connecting seams 20 and along a lower transverse connecting seam 24. The lower transverse connecting seam 24 is constructed in a ring shape and thus surrounds the lower opening 17. The region having a total of three layers forms a filter region 44, which extends from bottom to top for approximately 80% of the axial length of the filter element 10.

[0055] As in Figure 4 As clearly shown, in the upper region, the wall of the filter element 10 is constructed with only two layers: an outer layer 30 and an inner layer 32. The outer layer 30 and the inner layer 32 are welded together via an annular upper transverse connecting seam 22, which encloses the intermediate space 33. These two layers form an overflow region 40 in the filter element 10, which allows for better fluid flow through the wall due to significantly lower flow resistance in the event of upward backflow.

[0056] The intermediate layer 34 terminates at the lower end of the overflow region 40, wherein the upper edge 36 of the intermediate layer 34 is freely located in the intermediate space 33 between the outer layer 30 and the inner layer 32, and there is no direct fixed connection between the upper edge 36 and the adjacent outer layer 30 or the adjacent inner layer 32.

[0057] according to Figure 5 In order to seal the lower filter area 44, the outer layer 30, the inner layer 32 and the middle layer 34 are welded and fixedly connected to each other via the annular lower transverse connecting seam 24.

[0058] In the illustrated embodiment, the inflow of the fluid to be purified occurs along the longitudinal axis 12 through the upper opening 15. Due to the existing pressure difference, the fluid can flow radially outward from the internal space 16 of the filter element 10. At the normal fill ratio (or fill factor), In the case of flow filtration, this is achieved through the three-layer filtration zone 44, while radial flow can also occur in the upper overflow zone 40 in the event of potential blockage (or backflow). When used as a blood filtration element, the pore structure of the outer layer 30 and the inner layer 32 can be configured such that larger particle sizes and air bubbles that are critical to the patient are trapped, even without achieving the same filtration and purification effect as in the case of flow filtration in the filtration zone 44 with the additional intermediate layer 34.

[0059] exist Figures 6 to 10 Another design possibility for the filter element 10 according to the invention is shown. This filter element 10 has the same characteristics as previously described. Figures 1 to 5 The filter element 10 has a basically the same structure, however, it forms a bag-like structure with a closed bottom 18. The filter element 10 is also made of two halves 14 by overlapping each other and welding along the longitudinal edges using longitudinal connecting seams 20. Additionally, the outer layer 30, the inner layer 32 and the intermediate layer 34 arranged therebetween are also fixedly connected at their lower ends via linear lower transverse connecting seams 24, wherein a closed bottom 18 is formed.

[0060] The intermediate layer 34 (which includes the actual porous filter element) extends from the lower end to approximately 80% of the total length of the filter element 10, forming three filter regions 44. In the remaining two upper regions with an outer layer 30 and an inner layer 32, an overflow region 40 is formed, which allows for easier flow through the walls of the filter element 10.

[0061] In this embodiment of the filter element 10, the inflow of the fluid to be purified also occurs from above through a generally circular opening 15 into the internal space 16 of the filter element 10. Due to the pressure difference present, the fluid can pass from the inside out through the walls of the three-layer filtration zone 44, or radially outward through the two-layer overflow zone 40 at the corresponding fill height.

[0062] At the upper end, the outer layer 30 and the inner layer 32 are directly welded together via the upper transverse connecting seam 22, which is constructed in a ring shape to form an upper opening. Overall, this achieves a sock-like or tent-shaped structure for the filter element 10.

[0063] exist Figures 11 to 15 A third embodiment of the filter element 10 according to the present invention is shown. This filter element 10 is used in... Figures 1 to 5 The filter element 10 shown according to the first embodiment is substantially the same. Its difference from the first embodiment lies only in that: [the filter element is modified as shown in the first embodiment]. Figure 1 and Figure 2 and Figure 11 and Figure 12 As can be seen from the comparison, the filter element 10 does not taper downwards. Therefore, it has a generally columnar shape.

[0064] exist Figures 16 to 20 The image shows a fourth embodiment of the filter element 10 according to the invention. This filter element 10 generally corresponds to the second embodiment, wherein it also has a bag-like structure with a closed bottom 18. However, compared to the second embodiment, this embodiment extends taperedly towards the lower opening 17 in only one dimension. This is particularly evident through comparison. Figure 6 and Figure 16 visible.

Claims

1. A blood filtration element having a bag-shaped or tubular internal space (16) extending in the longitudinal direction, and having a multi-layer structure, said multi-layer structure having a permeable outer layer (30), a permeable inner layer (32), and at least one intermediate layer (34) disposed between said outer layer (30) and said inner layer (32), said intermediate layer being configured as a porous blood filtration element, wherein, The blood filtration element (10) has a preset axial length, and the outer layer (30) and the inner layer (32) have preset axial lengths. Its features are, The intermediate layer (34) is constructed to be axially shorter than the outer layer (30) and the inner layer (32) in the case of constructing the overflow region (40), the overflow region being arranged at the axially upper end region of the blood filtration element (10), wherein the upper edge (36) of the intermediate layer (34) is axially spaced downward from the upper edges of the outer layer (30) and the inner layer (32). The outer layer (30), the inner layer (32), and the intermediate layer (34) are fixedly connected to each other along at least one longitudinal edge when constructing a longitudinal connecting seam (20), and The outer layer (30) and the inner layer (32) are fixedly connected to each other along their upper edges when the upper transverse connecting seam (22) is constructed, wherein the upper edge of the middle layer (34) is arranged freely and unconnected between the outer layer (30) and the inner layer (32).

2. The blood filtration element according to claim 1, Its features are, The outer layer (30), the inner layer (32), and / or the intermediate layer (34) are fixedly connected to each other at their lower edges when the lower transverse connecting seam (24) is constructed.

3. The blood filtration element according to claim 1 or 2, Its features are, It has a structure consisting of two halves (14), and The two halves (14) are fixedly connected to each other along the two longitudinal edges in the case of constructing two longitudinal connecting seams (20).

4. The blood filtration element according to claim 1 or 2, Its features are, The axial length of the overflow region (40) is between 5% and 30% of the axial length of the blood filtration element (10).

5. The blood filtration element according to claim 1 or 2, Its features are, At least one connecting seam edge (20, 22, 24) is formed by ultrasonic welding.

6. The blood filtration element according to claim 2, Its features are, The lower transverse connecting seam (24) is constructed to form a closed bottom (18).

7. The blood filtration element according to claim 1 or 2, Its features are, The blood filtration element comprises a filter fabric, a filter membrane, a filter knitted fabric, and / or a filter nonwoven fabric.

8. The blood filtration element according to claim 1 or 2, Its features are, The opening size or pore size of the blood filtration element is between 10 μm and 400 μm.

9. The blood filtration element according to claim 1 or 2, Its features are, The outer layer (30) and / or the inner layer (32) are constructed of woven fabric, knitted fabric, mesh, grid and / or nonwoven fabric.

10. The blood filtration element according to claim 1 or 2, Its features are, The intermediate layer (34), the outer layer (30), and the inner layer (32) are made of polymer materials.

11. The blood filtration element according to claim 1 or 2, Its features are, The intermediate layer (34), the outer layer (30), and the inner layer (34) are made of the same material.

12. The blood filtration element according to claim 1 or 2, Its features are, The opening size of the outer layer (30) and / or the inner layer (32) is between 100 μm and 400 μm.

13. The blood filtration element according to claim 8, Its features are, The opening size or pore size of the blood filtration element is between 25 μm and 60 μm.

14. The blood filtration element according to claim 10, Its features are, The polymer material is polyester or polyamide.

15. The blood filtration element according to claim 12, Its features are, The opening size of the outer layer (30) and / or the inner layer (32) is between 150 μm and 300 μm.

16. A method for manufacturing a blood filter element according to any one of claims 1 to 15, Its features are, The outer layer and the inner layer (32) are fixedly connected to each other at their upper edges with a transverse connecting seam (22) at the upper part of the structure, wherein the intermediate layer (34) is arranged in the intermediate space (33) between the outer layer (30) and the inner layer (32), and the upper edge of the intermediate layer (34) remains free and unconnected.

17. The method according to claim 16, Its features are, The outer layer (30), the inner layer (32) and / or the intermediate layer (34) are joined at their outer edges by ultrasonic welding, thermal welding, bonding and / or thermal bonding.

18. The method according to claim 16 or 17, Its features are, By connecting the layers (30, 32, 34), a bag-shaped or tubular intermediate shape with connecting seams (20, 22, 24) located on the outside is formed, and The intermediate shape is flipped to form the blood filter element (10), wherein the connecting seam edges (20, 22, 24) are rotated inward.

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