Thermally sterilizable fluid filter and use of the thermally sterilizable fluid filter

Abstract

A thermally sterilizable fluid filter (10) for concentrating substances contained in a fluid by way of micro-, nano- or ultrafiltration of the fluid, particularly for concentrating a pharmaceutical precursor and/or intermediate, in particular a vaccine, in a fluid. The fluid filter has a filter housing with a fluid inlet, a retentate outlet and a permeate outlet. A filter cartridge is arranged in the filter housing (12) and has a filter medium of a ceramic material and/or a ceramic composite material. The filter cartridge is held with axial play on the filter housing.

Claims

1. A thermally sterilizable fluid filter (10), for the purification of substances contained in a fluid (F) by means of a micro-, nano- or ultrafiltration of the fluid, the fluid filter comprising: a filter housing (12) having: a fluid inlet (18); a permeate collection chamber having a permeate outlet (22); a retentate outlet (20); and a filter cartridge (24) arranged within the filter housing (12) and extending in an axial direction to a longitudinal axis (A) of the filter housing (12), the filter cartridge comprising: a filter medium (26) of a ceramic material or a ceramic composite material; and at least one rubber-elastically deformable sealing ring (40, 42, 52) which abuts the filter cartridge (24) circumferentially sealingly in the radial direction and over which the filter cartridge (24) is held with axial play on the filter housing (12); wherein an overpressure range of the fluid filter (10) when pressurized with the fluid (F) is sealed against the permeate collection chamber (34) by the at least one sealing ring (40, 42, 52); wherein the permeate collection chamber engages around the filter cartridge (24) in the radial direction on an outside and/or engages through the filter cartridge (24); wherein a sealing ring of the at least one sealing ring (40, 42, 52) associated with the fluid inlet (18), comprises a sealing lip (50) which is pressed by the fluid (F) against the filter cartridge (24) pressure-proportional to an operating pressure of the fluid (F) prevailing in the overpressure range of the fluid filter (10); wherein adjacent to the sealing ring (40, 42, 52) with sealing lip (50), a retaining ring (60) is arranged radially between the filter housing (12) and the filter cartridge (24); wherein the retaining ring (60) comprises a plurality of retaining bulges (61) distributed over a circumference, the plurality of retaining bulges extending from a first radius to a second radius; wherein the retaining ring is supported radially inward in a retaining region on an outer circumferential surface of the filter cartridge (24) and radially outwardly to abut the filter housing (12); wherein the retaining bulges (61) extend radially inward to an inner circumference, the diameter of which in a non-compressed non-assembled state is equal to or greater than a diameter of the filter cartridge (24) in the retaining region; or the retaining bulges (61) extend radially inward to an inner circumference, the diameter of which in an non-compressed non-assembled state is equal to or smaller than a diameter of the filter cartridge (24) in the retaining region; wherein the retaining ring (60) is a metallic spring ring and the retaining bulges (61) are designed as spring tongues (65) and which has a slot (64) having an open cross-section.

2. The fluid filter according to claim 1, wherein an annular gap is present radially between the filter cartridge (24) and the filter housing (12) in a region in which the sealing ring (40, 42, 52) sealingly abuts the filter cartridge (24); wherein the annular gap has a width between 0.4 mm to 1.5 mm.

3. The fluid filter according to claim 1, wherein the at least one sealing ring (40, 42, 52) comprises an elastomer.

4. The fluid filter according to claim 1, wherein the fluid filter comprises at least one second sealing ring, which sealingly abuts the filter cartridge (24) in the radial direction and over which the filter cartridge (24) is arranged held on the filter housing (12).

5. The fluid filter according to claim 1, wherein the filter housing (12) includes: a sleeve-shaped or pot-shaped housing part with a first end-side housing opening; and a cover (14, 16) is arranged at the housing opening.

6. The fluid filter according to claim 4, wherein the housing part is sleeve-shaped and has an end-side housing opening at both ends of the housing part; wherein a cover (14, 16) is arranged on each of the two housing openings.

7. The fluid filter according to claim 6, wherein at least one of the two sealing rings (40, 42, 52) is arranged in sections between the housing part and one of the covers (14, 16) and sealingly abuts the cover (14, 16) and sealing abuts on the housing part in the axial and/or radial direction, and/or the retaining ring is arranged between the housing part and one of the two covers (14, 16) and sealingly abuts the cover (14, 16) and the housing part in the axial and/or radial direction.

8. The fluid filter according to claim 7, wherein a third sealing ring (40, 42, 52) is arranged axially sealingly between the housing part and the cover (14, 16) associated with the fluid inlet (14, 16).

9. The fluid filter according to claim 1, wherein the sealing rings (40, 42, 52) and/or a base of the retaining ring (60) is designed as an O-ring.

10. The fluid filter according to claim 1, wherein the filter cartridge (24) comprises a ceramic hollow fiber bundle.

11. The fluid filter according to claim 10, wherein the hollow-fiber bundle (28) is fixed to or arranged in at least one holding head (30, 32), at least at one end of the hollow-fiber bundle (28); wherein the sealing ring (40, 42, 52) circumferentially sealingly abuts the at least one holding head (30, 32) in the radial direction and allows an axial clearance of the at least one holding head (30, 32) relative to the filter housing (12); and wherein the retaining region in which the retaining ring (60) with its bulges (61) abuts the filter cartridge (24), is present on the at least one holding head (30, 32).

12. The fluid filter according to claim 11, wherein the at least one holding head (30, 32) is formed of a plastic material of epoxy resin or polyurethane.

13. The fluid filter according to claim 11, wherein at least one holding head (30, 32) seals the permeate collection chamber (24) against the fluid inlet (18) and/or against the retentate outlet (20).

14. The fluid filter according to claim 1, wherein the filter housing (12) consists wholly or partly of stainless steel.

15. The fluid filter according to claim 1, wherein the fluid filter is configured and adapted for concentrating a pharmaceutical precursor and/or intermediate product, or a vaccine, in a fluid for processing foods and/or for producing life science products.

16. A thermally sterilizable fluid filter (10), for the purification of substances contained in a fluid (F) by means of a micro-, nano- or ultrafiltration of the fluid, the fluid filter comprising: a filter housing (12) having: a fluid inlet (18); a permeate collection chamber having a permeate outlet (22); a retentate outlet (20); and a filter cartridge (24) arranged within the filter housing (12) and extending in an axial direction to a longitudinal axis (A) of the filter housing (12), the filter cartridge comprising: a filter medium (26) formed as a ceramic hollow fiber bundle of a ceramic material or a ceramic composite material; and a holding head attached to at least one end of the ceramic hollow fiber bundle; at least one rubber-elastically deformable sealing ring (40, 42, 52) which sealingly abuts the holding head circumferentially, circumferentially sealingly in the radial direction against the filter housing while supporting the holding head in the filter housing in the radial direction, the at least one rubber-elastically deformable sealing ring enabling axial movement of the holding head relative to the filter housing; wherein an overpressure range of the fluid filter (10) when pressurized with the fluid (F) is sealed against the permeate collection chamber (34) by the at least one sealing ring (40, 42, 52); wherein the permeate collection chamber engages around the filter cartridge (24) in the radial direction on an outside and/or engages through the filter cartridge (24); wherein a sealing ring of the at least one sealing ring (40, 42, 52) associated with the fluid inlet (18), comprises a sealing lip (50) which is pressed by the fluid (F) against the filter cartridge (24) pressure-proportional to an operating pressure of the fluid (F) prevailing in the overpressure range of the fluid filter (10); wherein adjacent to the sealing ring (40, 42, 52) with sealing lip (50), a retaining ring (60) is arranged radially between the filter housing (12) and the filter cartridge (24); wherein the retaining ring (60) comprises a plurality of retaining bulges (61) distributed over a circumference of the retaining ring (60), the plurality of retaining bulges extending from a first radius to a second radius; wherein the retaining ring is supported radially inward on a retaining region of an outer circumferential surface of the filter cartridge (24) and radially outwardly to abut the filter housing (12); wherein the retaining bulges (61) are spring tongues; wherein the retaining bulges (61) extend radially inward to an inner circumference, the diameter of which in a non-compressed non-assembled state is equal to or greater than a diameter of the filter cartridge (24) in the retaining region; or the retaining bulges (61) extend radially inward to an inner circumference, the diameter of which in a non-compressed non-assembled state is equal to or smaller than a diameter of the filter cartridge (24) in the retaining region.

17. The fluid filter according to claim 16, wherein the filter housing (12) includes: a sleeve-shaped or pot-shaped housing part with a first end-side housing opening; and a cover (14, 16) is arranged at the housing opening.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) Further features and advantages of the invention will become apparent from the following detailed description of exemplary embodiments of the invention, with reference to the figures of the drawing, which show details essential to the invention, and from the claims.

(2) The individual features may be implemented individually for themselves or in several combinations in variants of the invention.

(3) In the schematic drawing, embodiments of the invention are shown, which are explained in more detail in the following description.

(4) In the drawings:

(5) FIG. 1 shows a fluid filter in perspective view from the outside;

(6) FIG. 2 is a longitudinal sectional view of the fluid filter of FIG. 1;

(7) FIG. 3 shows a filter cartridge with a hollow fiber bundle in a perspective view;

(8) FIGS. 4 and 5 are detailed views of the end regions of the fluid filter of FIG. 1 in longitudinal section;

(9) FIG. 6 is a schematic representation of a use of a fluid filter;

(10) FIG. 7 is a longitudinal sectional view of a further embodiment of the fluid filter with retaining rings;

(11) FIG. 8 is an isometric view of a filter cartridge according to another embodiment of the fluid filter;

(12) FIG. 9 is a side view of the fluid filter according to another embodiment;

(13) FIG. 10 is an isometric view of a filter cartridge according to still another embodiment of the fluid filter;

(14) FIG. 11 is a detail of a longitudinal sectional view of a fluid filter according to still another embodiment;

(15) FIG. 12 is a cross-sectional view B-B according to FIG. 11; and

(16) FIGS. 13 to 17 show exemplary embodiments for retaining rings formed as spring rings according to still another embodiment of the fluid filter.

EMBODIMENT(S) OF THE INVENTION

(17) FIG. 1 shows a fluid filter 10 in a perspective view. The fluid filter 10 has a multi-part filter housing 12 with a sleeve-shaped housing tube 13. At the end-side housing openings, an inlet cover 14 and a retentate cover 16 are arranged in each case. The inlet cover 14 has a nozzle-shaped fluid inlet 18. The retentate 16 has a retentate outlet 20, which is also formed nozzle-shaped. On the housing tube 13 are two permeate outlets 22, which are welded on in the embodiment shown. The permeate outlets 22 are formed nozzle-shaped.

(18) At least one clamp 23 is provided, preferably a plurality of clamps 23, for attachment of the fluid filter 10. The clamp(s) 23 surrounds or surround the filter housing 12. Their diameter is dimensioned such that the fluid filter 10 can be fixed substantially tension-free in the clamp or clamps 23. In addition, the clamps 23 fulfill the task of pressing the cover 14, 16 in the axial direction on the housing tube 13; this is achieved by an internal, axially mutually conical or chamfered circumferential groove on the inner lateral surface of the clamps 23, whereby an axial compression can be generated when tightening the clamps 23.

(19) In this embodiment, the housing tube 13 and the cover 14, 16 are made of stainless steel. Furthermore, the fluid inlet 18, the fluid outlet 20, the permeate outlets 22 and/or the clamps 23 may also be made of stainless steel.

(20) FIG. 2 shows the fluid filter 10 of FIG. 1 in longitudinal section. It can be seen first that the filter housing 12 forms an interior with the housing tube 13 and the covers 14, 16.

(21) The fluid filter 10 is elongated and has a longitudinal axis A defining an axial direction.

(22) A filter cartridge 24 is arranged in the interior. The filter cartridge 24 comprises two holding heads 30, 32, between which a filter medium 26 is fixed. The filter medium 26 comprises a hollow fiber bundle 28. The hollow fiber bundle 28 comprises a ceramic material and is in particular formed as a ceramic hollow fiber bundle.

(23) A permeate collection chamber 34 is formed between the two holding heads 30, 32 and the housing tube 13. The permeate collection chamber 34 is fluidly connected to the permeate outlets 22. In this exemplary embodiment, the permeate collection chamber 34 engages around and passes through the filter cartridge 24 or the filter medium 26 in the region of the hollow fiber bundle 28. In an alternative embodiment, in particular if the filter medium 26 is formed as a volume body, the permeate collection chamber 34 surrounds the filter medium 26 in the radial direction on the outside and, for example, in an annularly circumferential manner.

(24) It can also be seen that the fluid filter 10 comprises a fluid inlet region 36 in the region of the fluid inlet 18. In the region of the retentate outlet 20, the fluid filter 10 comprises a retentate outlet region 38. The fluid or retentate entering through the fluid inlet 18 collects in the regions 36, 38.

(25) It can be seen that the two holding heads 30, 32 separate the permeate collection chamber 34 from the fluid inlet region 36 and the fluid inlet 18 as well as from the retentate outlet region 38 and the retentate outlet 20. For this purpose, the holding heads 30, 32 are arranged in a cross-section filling manner in the filter housing 12.

(26) Thus, during filter operation, a fluid to be filtered may enter the fluid filter 10 via the fluid inlet 18. Via the fluid inlet region 36 and the holding head 30, the fluid enters the hollow fiber bundle 28. There, the fluid is split due to the filter properties of the hollow fiber bundle 28 into a permeate and a retentate. The permeate exits the hollow fibers of the hollow fiber bundle 28 on the wall side and thus enters the permeate collection chamber 34. The permeate can then be removed via the permeate outlets 22.

(27) By contrast, the retentate flows through the filter cartridge 24 over the length of the hollow fiber bundle 28 until it enters the retentate outlet region 38 on the holding head 32 and exits there via the retentate outlet 20.

(28) Since the permeate is separated from the fluid in this way, the retentate is concentrated, for example, with respect to the initial fluid. In filter operation, the fluid filter 10 or the fluid inlet 18 can be acted upon by an overpressure, for example in the range from 4 to 8 bar.

(29) For sterilization, the fluid inlet 18 is supplied with superheated steam. In this case, the pressure of the superheated steam can be kept lower than the operating pressure in the filter mode. Despite lower pressure, the steam can pass completely through the entire fluid filter 10 and, in particular, the filter cartridge 24 or can flow completely through it for sterilization. The superheated steam may alternatively or additionally be supplied or removed by one or both of the permeate outlets 22 and/or the fluid outlet 20.

(30) In this embodiment of the invention, the filter cartridge 24 is wholly or—preferably—partially arranged with axial play along the longitudinal axis A in the filter housing 12.

(31) For this purpose—as will be described in more detail in FIGS. 4 and 5—the filter cartridge 12 is fixedly supported on its holding head 32 substantially by a sealing ring 42 arranged on the retentate outlet side. This fixed support is achieved by an arrangement of the sealing ring 42 in a substantially conical or chamfered sealing groove on the side of the cover 16, which results in an axial-radial compression of the sealing ring 42 when assembling the housing parts 13, 16 and thus leads to an axial fixing of the filter cartridge 24 with respect to the housing 12. On the other hand, the filter cartridge 24 is supported in a floating manner on a sealing ring 40 arranged on the fluid inlet side, i.e. it is supported with significant axial play. If, therefore, there is a longitudinal expansion due to, for example, a temperature change of the filter cartridge 24, the holding head 30 can shift along the longitudinal axis A. In this case, the axial play available to the filter cartridge 24 is dimensioned such that, even at the highest permitted operating temperature, the holding head 30 remains free to move.

(32) This ensures that the filter cartridge 24 is at any time is not exposed or not substantially exposed to any mechanical, in particular temperature-induced, stresses. Even if the—ceramic—filter medium 26 has a particularly high brittleness, breakage due to the axial play is reliably avoided.

(33) FIG. 3 shows the filter cartridge 24 in a perspective view. The hollow-fiber bundle 28, which is delimited at the ends by the holding heads 30, 32, can be seen once again. In this embodiment, the hollow fiber bundle 28 has nine ceramic hollow fibers. These pass through openings 46 through the holding heads 30 and 32, respectively.

(34) In this embodiment, the radial outer sides of the holding heads 30, 32 are formed as sealing surfaces. In particular, in this embodiment, the outer sides are equipped with an additional sealing material.

(35) The holding heads 30, 32 are made of plastic, in particular epoxy resin. In particular, the holding heads 30, 32 are made by embedding the hollow fiber bundle 28 in the plastic, in particular casting the hollow fiber bundle therein, and after curing, trimming the side surfaces of the holding heads 30, 32. The holding heads 30, 32 may alternatively also comprise a so-called pot shell, i.e. a sleeve-shaped casing of a holding head core, which may consist, for example, of polyetheretherketone (PEEK) or another material compatible with the core material with respect to the thermal expansion coefficient.

(36) FIG. 4 shows a detailed view of the fluid filter 10 according to the detail IV of FIG. 2 in longitudinal section. Note the extent of the fluid inlet region 36 along the longitudinal axis A. This is chosen such that, corresponding to a maximum permissible operating temperature, there is sufficient space for an axial play of the filter cartridge 24 or of the holding head 30.

(37) It can be seen that the sealing ring 40 is seated in a recess 48 of the cover 14. It is located on the filter cartridge 24 and in particular radially circumferentially and sealingly on the holding head 30.

(38) The sealing ring 40 is designed as a pressure-proportional seal. In particular, it has a radially inwardly facing sealing lip 50, with which it abuts the holding head 30. In this exemplary embodiment, the fluid inlet region 36 corresponds to an overpressure region of the fluid filter 10. If the overpressure region is then subjected to pressurized fluid, in particular high-pressure, standing fluid to be filtered, the sealing lip 50 is pressed against the filter cartridge 24 and in this case in particular against the holding head 30, substantially proportionally to the pressure of the fluid. This results in a pressure-proportional seal. The sealing ring may also have more than one sealing lip 50 (in an embodiment not shown in a drawing), for example a radially inwardly extending sealing lip 50 which abuts the filter cartridge and a radially outwardly extending sealing lip which sealingly abuts the housing. In this embodiment, both sealing lips, which form V-shaped legs of the sealing ring in a non-compressed, non-assembled state, can also have the same length. The angle of the V-shaped projecting legs, each forming a sealing lip, can also be the same.

(39) By forming the sealing ring 40 with a sealing lip 50, its contact surface on the holding head 30 is comparatively small. As a result, the sealing ring 40 also forms a radially floating support for the filter cartridge 24 and for the holding head 30; but mainly the lip seal 40 should compensate for relative axial movements. In particular, the filter cartridge 24 is displaceable axially along the longitudinal axis A with its fluid inlet-side end or the holding head 30 within the fluid inlet 36.

(40) A third sealing ring 52 can furthermore be seen in FIG. 4. The third sealing ring 52 is in the form of an O-ring. The third sealing ring 52 is arranged between the housing tube 13 and the inlet cover 14 in an axially sealing manner. It sits in a recess of the housing tube 13.

(41) The sealing ring 40 and the third sealing ring 52 are made of rubber-elastically deformable material, in particular an elastomer.

(42) FIG. 5 shows a detailed view corresponding to FIG. 4 of the retentate outlet region 38 or the marking V of FIG. 2 in longitudinal section. The holding head 32 is arranged on the retentate outlet side, which holding head is radially surrounded by the housing tube 13, and the retentate cover 16 is evident. The retentate outlet region 38 with the retentate outlet 20 is located on the head side of the holding head 32.

(43) By means of the holding head 32 and the sealing ring 42, the permeate collection chamber 34 is also sealed off from the retentate outlet region 38.

(44) In contrast to the sealing ring 40, however, the retentate outlet-side sealing ring 42 contacts both the housing tube 13 and the retentate cover 16 and the holding head 32 of the filter cartridge 24. Due to its press fit, the sealing ring 42 here seals both the retaining head 32 and the filter cartridge 24 circumferentially against the cover 16, both radially. In addition, the sealing ring 42 axially seals the cover 16 against the housing tube 13.

(45) In this embodiment, the sealing ring 42 is formed as an O-ring. It is also made of rubber-elastic material, in particular an elastomer. It is seated in a recess of the retentate outlet cover 16. For sealing pressure of the holding head 32, the contact pressure of the sealing ring 42 is chosen such that the filter cartridge 24 is fixed substantially stationary even in the case of a low operating pressure in the overpressure range or the fluid inlet region 36 (FIG. 2). Thus, the sealing ring 42 forms a fixed support. Together with the sealing ring 40 (FIG. 2), this results in a support of the filter cartridge 24 on the filter housing 12 (FIG. 1) corresponding to a fixed/floating support.

(46) In an alternative embodiment, it is provided that the sealing ring 40 or the sealing ring 42 is seated in a recess of their respective nearest holding head 30, 32 or a recess of the housing tube 13 instead of in the covers 14, 16.

(47) To assemble the fluid filter 10 (see also FIGS. 1 and 2), it is sufficient to successively fit all individual parts on or into one another, in particular in a reversibly detachable manner. For this purpose, first the filter cartridge 24 is inserted into the housing tube 13.

(48) Subsequently, the third sealing ring 52 is inserted laterally into the housing tube 13. Equipped with the sealing rings 40, 42, the covers 14, 16 are then assembled on the end side of the housing tube 13, for example, flanged using the clamps 23. The fluid inlet 18, the retentate outlet 20 and the permeate outlets 22 and the clamps 23 are finally attached to the rest of the filter housing 12 on the outside.

(49) A schematic illustration of a use of the fluid filter 10 according to the invention, for example for concentrating a pharmaceutical precursor and/or intermediate product in a fluid such as a vaccine in a vaccine fluid, is shown in FIG. 6. Of course, the application is not limited thereto; further applications may be in the production of life science products such as cosmetics or in the processing of foodstuffs.

(50) For this example, it is assumed that the fluid to be filtered is an aqueous vaccine mixture to be concentrated. In other words, in this embodiment, the carrier substance is water.

(51) FIG. 6 is a schematic representation of the fluid filter 10 with its fluid inlet 18, the retentate outlet 20 and the permeate outlets 22 combined in this schematic illustration.

(52) In filter operation, the fluid inlet 18 of the fluid filter 10 is acted upon by a fluid F to be filtered. To achieve an optimal filter result, the fluid F is under overpressure, for example 5 bar.

(53) The fluid F is divided into a permeate P and a retentate R in the filter cartridge 24 (FIG. 1) and in particular in its hollow filter bundle 28 (FIG. 1). The permeate initially passes through walls of the hollow fibers of the hollow fiber bundle 28. The permeate P initially collects in the permeate collection chamber 24 (FIG. 1) before it leaves the fluid filter 10 via the permeate outlet 22. By filtering the fluid F to be filtered, the permeate P is depleted of vaccine and, on the other hand, has an increased content of the carrier substance, in this case water.

(54) The retentate R, on the other hand, is concentrated within the filter cartridge 24 and leaves the fluid filter 10 via the retentate outlet 20.

(55) For thermal sterilization, water vapor is introduced into the fluid inlet 18 instead of the fluid F to be filtered in the sterilization mode. In this exemplary embodiment, the pressure of the steam is chosen to be lower than the pressure or overpressure of the fluid F to be filtered in the filter mode. During sterilization, some of the water vapor passes via the filter cartridge 24 to the permeate outlet 22 and another part of the water to the retentate outlet 20. Thus, the fluid filter 10 is sterilized in all its sub-areas by the steam.

(56) Taking a synopsis of all the figures of the drawing, the invention relates in summary in one exemplary embodiment to a thermally sterilizable, in particular steam-sterilizable, fluid filter 10. The fluid filter 10 is particularly suitable for concentrating substances or mixtures of substances, for example pharmaceutical precursors and/or intermediates, in particular vaccines, in a fluid F. The products thus result in a retentate R with increased concentration of substances or mixtures of substances as well as a permeate P, which is depleted in terms of substances or mixtures. The fluid filter 10 has a particularly long service life, even with frequent sterilization. In particular, therefore, a use of the fluid filter for concentrating pharmaceutical precursors and/or intermediates, in particular of vaccines, is proposed. This is achieved by mechanical stresses, in particular thermally induced tensions, for example, on or in a filter cartridge 12 of the fluid filter 10 already being constructively avoided or at least reduced.

(57) For this purpose, the fluid filter 10 has a filter housing 12 with an inlet cover 14 and a retentate outlet cover 16 and a housing tube 13 arranged between the covers 14, 16. The fluid filter 10 has a fluid inlet 18 with a fluid inlet region 36, a retentate outlet 20 with a retentate outlet region 38 and one or more permeate outlets 22 that are fluidly connected to a permeate collection chamber 34.

(58) The filter housing 12 forms an interior, in which the filter cartridge 24 is arranged, in particular centrally along a longitudinal axis A of the filter housing 12. The filter cartridge 24 comprises a filter medium 26, which is delimited by two holding heads 30, 32 formed of plastic, in and between which a hollow fiber bundle 28, in this embodiment a ceramic hollow fiber bundle, is arranged. The hollow fiber bundle 28 forms passage openings 46 in the holding heads 30, 32.

(59) Sealing rings 40, 42 formed as O-rings are arranged in the covers 14, 16. In particular, the sealing ring 40 is seated in a recess 48 of the inlet cover 14. The sealing ring 40 provided with an inner side sealing lip 50 seals the holding head 30 radially against the filter housing 12, in particular in a pressure-assisted manner. By contrast, the sealing ring 42 seals both radially its associated holding head 32 against the cover 16 and the cover 16 axially against the housing tube 13. A third sealing ring 52 seals the opposing inlet cover 14 against the housing tube 13.

(60) Overall, the sealing rings 40, 42 form a kind of fixed/floating support of the filter cartridge 24 in the filter housing 12, so that the filter cartridge 24 has axial play to compensate for thermally induced changes in length.

(61) As an alternative to the flow-through variant/operating mode shown in FIG. 6, a so-called dead-end filtration can, of course, also be carried out with the fluid filter according to the invention: for this purpose, the filter cartridge, in particular the ceramic hollow fibers, would be closed at an end facing away from the fluid inlet, so that either a valuable or harmful product would be retained within the filter cartridge. However, with respect to the permeate outlet, this additional embodiment is not different; the main difference is that no fluid outlet (retentate outlet) must be provided.

(62) FIG. 7 shows a fluid filter 10 according to a further embodiment. Functionally, this does not differ from the variants described above. Significant differences exist, however, in terms of support/sealing of the filter cartridge 24 relative to the filter housing 12. Here, radial play is present, which has the width s, between the filter housing 12 (more precisely, both between the housing tube 13 and the covers 14, 16) and the holding heads 30, 32 of the filter cartridge 24. Via this comparatively wide gap s, manufacturing tolerances of the filter cartridge 24 can be compensated with respect to axial offset/concentricity, without a tension/restraint being at risk. Furthermore, angle deviations can also be easily compensated; the filter cartridge has a slightly tilted mounting position in this case. This is particularly important when using ceramic hollow fiber bundles 28 as the filter medium 26.

(63) In order to prevent, in particular in case of a horizontal installation position, that support forces which are too strong act on the sealing lip 50 of the sealing ring 40, which support forces can, over time, lead to there being no effective seal, a retaining ring 60 is provided at both ends, which comprises a plurality of radially outwardly extending retaining bulges 61 distributed over its circumference, which retaining bulges in turn are supported on a retaining region on the lateral surface of the holding heads 30, 32.

(64) The retaining ring 60 may optionally be an O-ring made of a plastic material, e.g. an elastomer, wherein the retaining bulges 61 are formed as nubs. This is shown in FIG. 8. Due to the merely punctiform/linear contact or the very small contact surface between retaining bulges 61 and retaining head 30, 32, it is achieved that the holding heads 30, 32 can be displaced axially with relatively little friction in spite of the radial guidance; this is important in order to be able to compensate for relative length expansions between filter cartridge 24 and filter housing 12, in particular during thermal sterilization.

(65) FIG. 9 shows a side view of the fluid filter from FIG. 7. Here the clamp 23 can be seen which connects the cover 14 with the housing tube 13, which is closable in this exemplary embodiment by a wing nut. Furthermore, the passage openings 46 of the hollow fiber bundle 28 can be seen through the holding head 32.

(66) FIG. 10 shows a filter cartridge 24 of a fluid filter according to a further embodiment. The filter cartridge 24 per se corresponds in its construction to the variants described above. A difference with respect to FIG. 7 is with regard to the design of the retaining ring 60, which here is a spring ring made of a preferably metallic material, in particular stainless steel. The retaining bulges 61 are formed in the form of radially inwardly directed concave bulges. The bulges are preferably distributed over the circumference at a regular distance, wherein in each case between two circumferentially adjacent concave bulges non-bulging connecting portions are provided, in each of which a radially outwardly directed support pin 62 is arranged, which in turn allows the smallest possible contact with the inner lateral surface of the filter housing.

(67) The section of a longitudinal section of a fluid filter 24, which is shown in FIG. 11, again differs from the construction of the retaining ring 60 from the variants described above. The retaining ring 60 has in the present case a radially inner, continuous, circumferential, sleeve-shaped support region 63, which is supported in a retaining region of the holding head 30. Furthermore, the retaining ring has spring tongues which form the retaining bulges 61 and which extend from the support region on both sides in the axial direction and radially inwardly and are designed to abut the inner lateral surface of the filter housing 12, in particular of the housing tube 13. The operation of the sealing ring 40 with sealing lip 50 differs in this case just as little from the above-described variants as the effect of the sealing ring 52, which in turn seals the cover 14 axially relative to the housing tube 13. Reference is further made to FIG. 12, which shows the section B-B according to FIG. 11.

(68) Through all variants of the retaining ring described herein, it is advantageously achieved (in particular in cooperation with the gap s) on the one hand that production-related position tolerances with respect to concentricity, parallelism and angularity of the two holding heads 30, 32 of the filter cartridge can be compensated for without loading the lip seal 50 in a horizontal installation position. On the other hand, it is ensured that, due to the small area contact of the retaining ring 60 with the holding heads 30, 32 and/or the filter housing 12, a simple, i.e. low-friction, axial mobility of the filter cartridge relative to the filter housing 12 is possible, in particular to compensate for relative thermal length expansions.

(69) In FIGS. 13-17, some other embodiments of retaining rings 60 are shown, which are configured as spring rings made of metal. These each comprise a complete slot 64, which offers advantages for ease of assembly as well as for simple and cost-effective production; furthermore, a diameter compensation in the largest possible diameter range can be achieved. The spring rings can be made of a strip material, wherein the retaining bulges, which are present here in the form of spring tongues 65, are obtained by punching and bending. Depending on the embodiment, the spring tongues 65 can extend radially inwardly and/or radially outwardly, wherein combinations are also possible. In the embodiment of the retaining ring of FIG. 13b, which corresponds to that shown in the assembly of FIG. 10, radially outwardly directed support pins 62 are also provided, which are respectively present in connecting portions between inwardly bulged portions of the retaining ring 60.