CN210846422U

CN210846422U - Filter device, filter system and cover

Info

Publication number: CN210846422U
Application number: CN201690001712.8U
Authority: CN
Inventors: B·M·尼尔森; R·维斯塔森
Original assignee: Foss Analytical AS
Current assignee: Foss Analytical AS
Priority date: 2016-09-20
Filing date: 2016-09-20
Publication date: 2020-06-26
Anticipated expiration: 2026-09-20
Also published as: ES1231416Y; RU195122U1; DE212016000289U1; ES1231416U; WO2018055432A1

Abstract

The utility model provides a filter equipment, filtration system and lid. The filter device (2) comprises a sample chamber (10) accommodated in a body (4), the body (4) having an open top (6) communicating with the sample chamber (10); a hole (24) for liquid filtrate; and a lid (12) for closing the open top (6). The lid (12) has a fluid passage (22) covered at one end by a filter medium (20) and providing fluid communication for liquid filtrate from the sample chamber (10). The lid (12) is configured to carry the aperture (24) at a position closer to the outer periphery (11) of the lid (12) than the liquid passage (22) in a plane parallel to the open top (6) when the open top is closed by the lid (12).

Description

Filter device, filter system and cover

Technical Field

The present invention relates to filtration devices, filtration systems and caps, and more particularly to devices, systems and caps for collecting liquid filtrate by centrifugation.

Background

It is often desirable to analyze the liquid after the suspended particles are removed, otherwise the suspended particles may clog the flow system of the analyzer or interfere with the analysis of the liquid. For example, in solvent extraction analysis, an extraction fluid is reacted with a solid sample, particularly a powdered or granular solid sample, and the substance of interest is extracted into a liquid for analysis. A filtration device is generally used, by means of which particles are separated from a liquid in which the particles are suspended using a filtration medium. The liquid filtrate was collected for introduction into the flow system of the analyzer. Centrifuges are also often used to assist in the filtration process. Typically, the filter device is releasably retained in a holder of the centrifuge and is rapidly rotated. The centrifugal force due to this rapid rotation causes the liquid and particles to move along the path in the direction of the force. A filter media is positioned along the path to act as a barrier to the particles.

One such filtration device is disclosed in US3478889, which is used in conjunction with a centrifuge and comprises a disposable filtration unit having a body in which a sample chamber for receiving the liquid to be filtered is arranged. The sample chamber has an open end at the bottom, which open end is closed in use by a lid. The lid is provided with a channel that is fluidly connected to the sample chamber at one end and has an aperture for liquid filtrate at the other end. A filter medium covers at least one end of the channel and forms a common boundary of the sample chamber and the aperture. The filter device is intended to be mounted in a holder of a centrifuge. The holder holds the filter device with the sample chamber above the aperture and during centrifugation the holder and the device are pivoted towards a direction parallel to the direction of action of the centrifugal force, that is to say perpendicular to the axis of rotation of the holder. The liquid to be filtered is moved under centrifugal force from the sample chamber in a direction parallel to its direction of action, through the filter medium, and into the pores, where it is retained as liquid filtrate. Once the centrifugation is completed, the holder and the filter device are pivoted backwards, and the liquid filtrate is again retained in the hole below the sample chamber, again at the lower end of the filter device.

A problem with this known filtration device is that the liquid filtrate remains at the bottom of the device, which makes it difficult to access the liquid filtrate for analysis. Furthermore, having a filter at the bottom before enough filtrate is collected can cause particles to fall under gravity and clog the filter. In addition, in known centrifuges, each sample-containing filter device needs to be balanced with a diametrically opposed weight, usually another sample-containing filter device, to maintain stability of the spin centrifuge and reduce wear.

SUMMERY OF THE UTILITY MODEL

According to a first aspect of the present invention, there is provided a filter device comprising: a sample chamber; a body housing a sample chamber and having an open top communicating with the sample chamber; an aperture; a lid for closing the open top, the lid being provided with an aperture and having a liquid passage for communication with the sample chamber; and a filter medium configured to filter the sample from the sample chamber prior to entry of the sample into the aperture; wherein the aperture is located in the lid, typically at an upper surface of the lid, at a position closer to an outer periphery thereof than the liquid channel, for receiving liquid filtrate (48) therefrom. This has the advantage that subsequent analysis is easier to perform, since the liquid filtrate can collect in the holes in the lid above the filter medium. Furthermore, since the filter medium is located above the sample chamber and above the liquid to be filtered, any particles in the liquid cannot move under the influence of gravity to clog the filter medium.

In some embodiments, the lid is configured with an elliptical cross-section in a plane parallel to the open top when the open top is closed by the lid, and the aperture is located closer to the perimeter of the lid than the liquid passage in a direction along the major axis (M) of the ellipse. This has the following advantages: during centrifugation, the hydrostatic pressure on the liquid is greater in the region of the sample chamber along the major axis, such that the liquid is preferentially directed through the flow conduit and toward the aperture.

In some embodiments, the filter media is attached to the base of the lid to cover the liquid channel. This facilitates assembly of the filter device and, in some embodiments, allows reuse of the filter device by merely replacing the cap.

According to a second aspect of the present invention, there is provided a filtration system comprising a plurality of filtration devices according to the first aspect of the present invention and a centrifuge comprising a plurality of holders, said holders being mounted for rotation about an axis of rotation substantially parallel to the vertical direction, each holder of the plurality of holders being configured to releasably retain an associated filtration device of the plurality of filtration devices with its sample chamber oriented below its filtration media during rotation of the plurality of holders. Hydrostatic pressure created by centrifugal force created by rotation of the holder causes the filtered liquid to move up the inner wall of the sample chamber and through the filter media to be retained in the pores thereof. Since the filter medium remains above the liquid in the sample chamber, clogging of the filter medium due to the influence of gravity is avoided.

According to a third aspect of the present invention, there is provided a method of producing a liquid filtrate using a system according to the second aspect of the present invention to provide the advantages associated with the first and second aspects of the present invention.

Thus, according to a third aspect of the present invention, there is provided a method of producing a liquid filtrate, comprising the steps of: placing the filtration device according to the first aspect of the invention into a rotatable holder of a centrifuge such that the filtration medium and the pores are oriented to be located above a liquid sample to be filtered when the filtration unit is placed in the holder; centrifuging the liquid sample to be filtered while maintaining the filter device in substantially the same orientation as when placed in the holder, such that the sample to be filtered moves upwardly through the filter medium and forms a liquid filtrate which is moved into the well by the centrifugal force on the liquid filtrate.

According to a fourth aspect of the present invention there is provided a lid for closing the open top of a tubular filter body, the lid comprising: a liquid passage extending through the cover from one opposing surface to the other; a filter medium fixed to the cover to cover at least one end of the liquid passage; and an aperture for liquid filtrate located closer to the outer periphery of the cap than the liquid passage.

Drawings

These and other advantages will be understood in view of the following description of non-limiting embodiments of the invention with reference to the figures of the accompanying drawings, in which:

figure 1 shows a first embodiment of a filter device according to the invention;

FIG. 2 shows a lid of the filter device shown in FIG. 1;

fig. 3 shows a centrifuge of a filtration system according to the invention.

FIG. 4 illustrates the filter assembly shown in FIG. 1 used with the centrifuge shown in FIG. 3.

Fig. 5 shows a second embodiment of a filter device according to the invention.

Fig. 6 shows a third embodiment of a filter device according to the invention.

Detailed Description

The first exemplary embodiment of the first filter device 2 according to the first aspect of the present invention shown in fig. 1 and 2 comprises a tubular first body 4, which tubular first body 4 is configured with a first open top 6 and a closed bottom 8 so as to define a first sample chamber 10 inside the tubular first body 4. A first lid 12 is provided as closure for the first open top 6. In this embodiment, the first lid 12 is attached to the tubular first body 4 by a hinge 14, the hinge 14 allowing the first lid 12 to move to close the first open top 6 by a push-fit engagement with the tubular first body 4, and there is provided a portion 16, the portion 16 extending beyond the tubular first body 4 in a plane parallel to the first open top 6 when the first lid 12 is closed. In other embodiments, the hinge 14 may be omitted; in other embodiments, the first lid 12 may be fixed to permanently close the top 6, for example by forming the tubular first body 4 and the first lid 12 as a single piece; or the first cap 12 and the tubular first body 4 may be configured for threaded engagement.

The first lid 12 has a first lower surface 18 and an opposite first upper surface 19 bounded by the same first outer perimeter 11. At least a portion 18a of the first lower surface 18 serves as a carrier for the first filter medium 20, here a planar filter medium, which may be provided, for example, by a filter paper or membrane filter of known type, so that when the first lid 12 is closed over the first open top 6 of the tubular first body 4, the carrier (portion 18a) positions the first filter medium 20 over the liquid to be filtered held in the first sample chamber 10. It should be understood that in other embodiments, at least a portion of the first upper surface 19 may alternatively or additionally serve as a support for the first filter media 20.

Referring also to fig. 2, wherein the first lid 12 is shown in a closed position, the first lid 12 is further provided with a first aperture 24 at its first upper surface 19 for receiving liquid filtrate. In this embodiment, the first hole 24 is located in the portion 16 of the cover outside the tubular first body 4 so as to extend from the first upper surface 19 along the first body 4 in this closed position.

Liquid passages, here comprising at least one through hole (first liquid passage 22) (here two) between the

opposing surfaces

18,19, are provided in the lid (12) for liquid communication with the first sample compartment 10 to provide liquid filtrate for retention in the first hole 24. At least one open end of each of the at least one through-hole (first liquid passage 22) is covered with the first filter medium 20. In this embodiment, the portion 18a of the first lower surface 18 acts as a carrier, recessed to receive the open end 6 of the first body 4.

More generally, the first hole 24 is closer to the first outer periphery 11 of the first lid 12 than the first liquid passage 22 (through hole) itself in the flow direction of the liquid filtrate of the first liquid passage 22. This relative positioning of the first bore 24 and the first liquid channel 22 facilitates the flow of liquid filtrate from the first liquid channel 22 into the first bore 24 during centrifugation, as will be described further below.

In this embodiment, the first lid 12 is further provided with a conduit 26, the conduit 26 providing access to the first sample compartment 10 from outside the first filter device 2 and not being covered by the first filter medium 20. In some embodiments, such as where it is desired to introduce liquid into the first sample chamber 10 prior to closing the first lid 12, the conduit 26 may be omitted. In some embodiments, a seal (omitted from fig. 1 and 2 for clarity) may be provided as an element of the first cap 12 to prevent accidental ingress or egress of liquid. The seal is configured with at least a first aperture 24 and optionally a region directly above the conduit 26 (when present), which are pierceable or removable, for example by a hollow needle or pipette, to provide external access to these features. For this purpose, thin foils, films, walls or films may be employed in these areas, or may be provided over the entire first upper surface 19.

A centrifuge 30, which is a component of a filtration system according to the second aspect of the invention, is shown in fig. 3 and comprises a housing 32, a motor 34 being accommodated in the housing 32. The motor 34 is operable to rotate the holder 36 about a substantially vertical axis a. In the present embodiment, the holder 36 is coupled to the motor 34 by a bearing 38 and shaft 40 arrangement.

In this embodiment, the holder 36 is open at the top and has an internal dimension suitable for receiving a filter device (e.g., 2) according to the first aspect of the invention, so as to hold the first filter device 2 with the first filter medium 20 upright and the first lid 12 above the liquid in the first sample chamber 10 prior to centrifugation. The holder 36 is configured to hold the received first filter device 2 in this upright position during centrifugation, thereby holding the first cover 12 in a plane substantially perpendicular to the axis of rotation a. In this embodiment, the substantially vertical axis of rotation a extends along the center of the first filter device 2 from the bottom 8 all the way to the first lid 12. This has the advantage that the first filter device 2 need not be balanced during rotation, allowing centrifugation of a single sample without causing excessive wear of the centrifuge 30.

As shown in fig. 1 and 2, the tubular first body 4 may be configured with an elliptical cross-section in a plane parallel to the open end 6. Then, two through holes (first liquid passages 22) are positioned along the major axis M (also referred to as the major axis) of the ellipse, substantially equidistant from the center C of the ellipse, and equidistant on both sides of the center C of the ellipse, so that when the first lid 12 is closed, the through holes (first liquid passages 22) are positioned adjacent to the portion of the inner wall 46 of the first sample cell 10 that intersects the major axis M. The first hole 24 is similarly positioned along the major axis M of the ellipse, substantially equidistant from and on either side of the center C of the ellipse, at a position further from the center C and closer to the first outer periphery 11 of the first lid 12 than the two through holes (first liquid passage 22). Although it is not necessary to provide the tubular first body 4 with an oval cross-section, the advantages this provides can be understood in view of the operation of the centrifuge to spin such a filter, as described below with reference to fig. 4. However, regardless of the cross-sectional shape of the tubular first body 4, the first aperture 24 must be located near the first outer periphery 11 of the first lid 12, as will be apparent from the following description.

Fig. 4(a) shows in partial cross-section the first filter device 2 mounted in a corresponding holder 36 of the centrifuge 30 of fig. 3 prior to centrifugation. As can be seen in fig. 4(a), the first lid 12 of the first filter device 2 closes the first open top 6 of the first sample chamber 10 and holds the first filter medium 20 above the liquid 42 to be filtered. The first filter medium 20 is positioned to cover the through-holes (first liquid passage 22) forming the liquid passages but avoid the conduit 26. The first aperture 24 is shown as being located outside the tubular first body 4 in a direction along the major axis M of the elliptical first lid 12. The first lid 12 is sealed over its entire first upper surface 19 with a first foil seal 44.

Fig. 4(b) and (c) show, in partial cross-section, the first filter device 2 mounted in the respective holder 36 by rotation of the holder 36 about a substantially vertical axis a during centrifugation, as indicated by the arrows in fig. 4 (b). As can be seen from fig. 4(b), the centrifugation of the liquid 42 to be filtered in the first sample compartment 10 is to push it towards the first inner surface 46 defining the first sample compartment 10 and then move it upwards along the first inner surface 46 towards the first lid 12. Due to the elliptical cross-sectional shape of the tubular first body 4, the hydrostatic pressure on the liquid 42 during centrifugation is higher along the portion of the first inner surface 46 of the first sample chamber 10 that intersects the major axis M than elsewhere (i.e., toward the focal point of the ellipse). As shown by the arrows in fig. 4(c), the effect is that the liquid 42 preferably travels up the portion of the first inner surface 46, through the first filter medium 20 covering the through-holes (first liquid channels 22) to form a liquid filtrate, which is then moved, due to the centrifugal effect, towards the first holes 24 further away along the major axis M of the oblong first cover 12. After centrifugation (fig. 4(d)), the liquid filtrate 48 remains in the first bore 24, while the remainder of the liquid 42 is returned to the first sample chamber 10.

The liquid filtrate 48 may then be accessed from outside the first filtration device 2 by piercing the region 50 of the first foil seal 44 directly above the first aperture 24, for example using a hollow needle (not shown) in fluid communication with the liquid inlet of the analysis device.

One illustrative use of the filter element 2 and centrifuge 30 depicted in fig. 4(a) is their use in solvent extraction assays. A granular or powdered sample, for example a wheat sample, is first introduced into the first sample chamber 10 through the first open top 6 and the first lid 12 is closed. After perforation of the first foil seal 44 in the region 27 above the liquid channel 26, an extraction liquid, for example a 30% by volume aqueous ethanol solution, is introduced from the outside of the first filter device 2 through the needle of, for example, a syringe via the conduit 26 into the first sample chamber 10. It will be appreciated that in this alternative the extraction fluid may be introduced through the first open top 6 before being closed by the first lid 12. However, the former has the advantage that the solid sample can be transported more easily in the closed, sealed first filter device 2 to the location where the measurement is to be performed or stored there without any risk of loss of sample.

The target substance for the assay, e.g. mycotoxins, is extracted from the granular sample over time into an extraction liquid, which then forms the liquid to be filtered 42. The first filter device 2 containing the mixture of the solid wheat sample and the liquid 42 to be filtered is then placed into the holder 36 of the centrifuge 30 so that it is contained in the first sample compartment 10 beneath the first filter medium 20 carried by the first lid 12. During centrifugation, the liquid containing the target substance extracted from the sample is pushed up the first inner surface 46 of the first sample cell 10 and through the flow conduit (first liquid channel 22) covered by the first filter medium 20 to form a liquid filtrate 48 above the first sample cell 10. The liquid filtrate moves away from the through-hole (first liquid channel 22) in a plane perpendicular to the rotation axis a and falls into the first hole 24, where it remains. Once the centrifuge 30 is stopped, the first filtration device 2 leaves a liquid filtrate 48 in the first aperture 24 that is separated from the extraction liquid and sample retained in the first sample cell 10. The liquid filtrate 48 may then be accessed for measurement by a hollow needle or pipette being pressed through the region 50 above the first well 24 to enter the liquid filtrate 48. A pumping system of the assay instrument may be provided in the liquid filtrate 48, the centrifuge 30 may be integrated with the assay instrument, the pumping system being in fluid communication with a hollow needle or pipette and operable to move the filtrate 48 from the first aperture 24 to a measurement region of the assay instrument.

A second embodiment of a second filter device 52 is shown in fig. 5 and comprises a tubular second body 54, here having a circular cross-section, provided with a second open top 55 and a closed bottom 58 to form a second sample chamber 60 for the liquid to be filtered. The upper annular surface 62 of the second open top 55 is configured to act as a carrier to support a planar second filter media 64, such as filter paper or a membrane filter, in a plane parallel to the closed bottom 58. As in the present embodiment, a second filter medium 64 is optionally secured to second upper surface 62, such as by gluing, and may be configured with a central opening (dashed line structure 66) to provide access to second sample chamber 60 from outside tubular second body 54. As shown in this embodiment, the filter media may alternatively be continuous over the second open top 55. To access the second sample chamber 60 from outside the tubular second body 54, the second filter medium 64 is pierced, for example, with a syringe needle or pipette. In this embodiment, the tubular second body 54 has a circular cross-section, but may be oval, as in the embodiment shown in fig. 1.

In an alternative embodiment (also shown in fig. 5), the carrier 68 is configured as an open rigid frame 70 having an annular base 72 with a planar third filter media 74 extending over the annular base 72 and secured to the base 72 about its periphery. It should be understood that the third filter media 74 may alternatively extend on an annular top portion opposite the base 72 without departing from the claimed invention. The carrier 68 of this alternative embodiment is formed in a push-fit engagement with the inner wall 76 of the tubular second body 54 and may be inserted into the filter second body 54 after introduction of a sample for measurement, such as a powdered or granular sample, and after interaction of a liquid (e.g., a liquid solvent) with the sample for measurement, a liquid (e.g., a liquid solvent) is introduced into the powdered or granular sample to form the liquid to be filtered. In another embodiment, the frame 70 forms a hollow carrier into which a filter media of known depth can be placed.

The second filter device 52 further includes a removable second cap 78 (shown in cross-section in fig. 5) configured to engage, e.g., push-fit or threaded, with the tubular second body 54 to close the second open top 55. In this embodiment, the second cap 78 has a second inner surface 80 for push-fit engagement with an outer surface 82 of the tubular second body 54. Thus, the second inner surface 80 can slide over the outer surface 82 until the second upper surface 62 of the tubular second body 54 abuts a stop, shoulder or other protrusion, here an annular stop 84, of the second cap 78, and then closes the second open top 55 of the tubular second body 54. When the second lid 78 covers the second open top 55, a second hole 86 for liquid filtrate, here for example formed as a single annular hole, is formed inside the second lid 78 in a portion 94 of the second lid 78 located proximal to the second outer periphery 83 of the second lid 78 and outside the outer surface 82 of the tubular second body 54. The second liquid passage 81 is bounded by the second inner surface 80 and is further from the second outer perimeter 83 of the second lid 78 than the second aperture 86. Second open top 55 is closed with second lid 78 such that second aperture 86 is in fluid communication with second sample chamber 60 via second filter medium 64, third filter medium 74, and second fluid passageway 81.

In a variation of this embodiment, the planar second and third filter media 64, 74 may be secured to the annular stop 84 of the second cover 78, which then also serves as a carrier for the filter media. Thus, when the second open end 55 is closed by the second cover 78, the planar second and third filter media 64, 74 cover the second open end 55.

In another variant, a lower wall portion 92 of the second lid 78 may be removed, this lower wall portion 92 delimiting the second aperture 86 of the presently described embodiment, to allow the filtrate to exit for collection outside the second filtering device 52. In fact, the embodiment of the first filtering means 2 described with reference to fig. 1 can be similarly modified.

In use, the second embodiment of second filter device 52 is held upright for centrifugation, for example in holder 36 of the centrifuge according to fig. 3, such that second filter medium 64, third filter medium 74 lie in a plane substantially perpendicular to the vertical axis of rotation about which second filter device 52 will rotate during centrifugation and filtration takes place over the particle-containing liquid in second sample chamber 60. During centrifugation, liquid in second sample chamber 60 is urged toward inner wall 76 and thus moves upwardly along wall 76 toward second filter medium 64, third filter medium 74 under the influence of centrifugal forces exerted thereon. Thus, the centrifugal action causes the liquid to be transported through the second filter media 64, the third filter media 74 and travel as liquid filtrate toward the second aperture 86 (see arrows in fig. 5), being retained in the second aperture 86. After centrifugation, the liquid filtrate in the second well 86 may be removed for assay, for example by squeezing through a suitably formed area 88 of the second cap 78 above the second well 86 using a hollow needle or pipette. Alternatively, the second cap 78 may be removed from the tubular body and then inverted such that the liquid filtrate from the second aperture 86 flows to an area 90 of the second cap 78 for entry through the opening formed by the second inner surface 80.

A third embodiment of a third filter device 96 according to the present invention is shown in fig. 6 and includes a tubular third body 98 of circular cross-section, the tubular third body 98 being configured with a third open end 100 and a closed bottom 104 so as to define a sample chamber within the tubular third body 98. Optionally, a lip 102 is provided on the tubular third body 98 that extends into the third sample chamber 108, e.g., and as shown in this embodiment, protrudes into the third open end 100.

The third filter device 96 further includes a third cover 112 for closing the third open end 100. In this embodiment, the third cap 112 is formed as an eccentric ellipsoid having a portion 116 with a third aperture 118 formed in the portion 116 to receive liquid filtrate. When the third cap 112 closes the third open end 100, the portion 116 extends beyond the tubular third body 98 in a plane containing the third open end 100 along the major axis M of the oblong fourth cap 122, and the third hole 118 extends downwardly from the third upper surface 117 in a direction along the third body 98. The third cover 112 is also provided with a plurality of through holes (third liquid channels 120) between the third lower surface 115 and the opposite third upper surface 117. The through holes (third liquid passages 120) are located in the third cover 112 farther from the third outer periphery 111 than the third hole 118, and the through holes (third liquid passages 120) are located to cover the third opening end 100 near the lip 102 when the third opening end 100 is closed by the third cover 112. A fourth filter medium 114 (dashed lines in FIG. 6) is secured to third lower surface 115 to cover the through-hole (third fluid passage 120) for preventing fluid from flowing from third sample chamber 108 into third aperture 118 without first passing through fourth filter medium 114. A fourth cover 122, for example a metal or plastic foil, covers the third upper surface 117 of the third cover 112, the third upper surface 117 being opposite the third lower surface 115 and preventing the sample or liquid filtrate from flowing out during centrifugation.

In another embodiment of the filter device according to the present invention (not shown), both the cover and the tubular body may be formed to have a circular cross-section. The lid is then preferably provided with an inclined floor to direct liquid filtrate preferentially from the liquid passage to the aperture located beyond the tubular body portion towards the outer periphery of the lid at the inclined bottom.

In use, the third embodiment of the third filter device 96 according to fig. 6 is held upright for centrifugation, for example in the holder 36 of the centrifuge according to fig. 3, such that the fourth filter medium 114 lies in a plane substantially perpendicular to a vertical axis of rotation about which the third filter device 96 will rotate during centrifugation and remains above the particle-containing liquid for filtration in the third sample chamber 108. During centrifugation, liquids and particles in third sample chamber 108 move toward third inner surface 106 of tubular third body 98 and move upward along third inner surface 106 toward fourth filter medium 114. Relatively larger pieces of particles tend to be located outside the liquid and closer to the third inner surface 106. The lips 102 of the third body 98 act as a barrier to reduce their contact with the fourth filter media 114 as they move upward. The liquid is moved through the fourth filter media 114 and into the third cap 112 through the plurality of through-holes (third liquid passage 120). Due to the shape of the third cover 112 and the position of the third aperture 118, the liquid filtrate thus formed preferentially flows to the third aperture 118, and the liquid filtrate remains in the third aperture 118 after centrifugation. Access to the liquid filtrate is achieved by penetrating or removing at least part of the fourth cap 122 over the third aperture 118.

It should be understood that after use, particularly where the first and

third covers

12, 112 are configured with the first and

fourth filter media

20, 114 secured to the surface (portion 18a), the third lower surface 115 to cover the first and third

fluid passages

22, 120, the entire first filter assembly 2, second filter assembly 52, and third filter assembly 96 may be discarded or only the first, second, and third covers 12, 78, 112 replaced.

Claims

1. A filtration device comprising a sample chamber; a body housing a sample chamber and having an open top communicating with the sample chamber; an aperture; a lid for closing the open top, the lid being configured with an aperture and a liquid channel for communicating with the sample chamber; and a filter medium configured to filter the sample from the sample chamber before the sample enters the aperture; wherein the aperture is located in the lid closer to its outer periphery than the liquid channel to receive liquid filtrate therefrom; characterized in that the lid is configured with an elliptical cross-section in a plane parallel to the open top when the lid closes the open top, and the hole is located closer to the periphery of the lid than the liquid channel in a direction along the major axis (M) of the ellipse; wherein the body is configured with a circular or elliptical cross-section in a plane parallel to the open top and the lid is an eccentric ellipsoid.

2. The filter device according to claim 1, wherein the hole is located in the cover at a position outside the body in a plane parallel to the open top when the cover closes the open top.

3. The filter device of claim 2, wherein the aperture comprises a plurality of apertures extending in a direction of the body.

4. The filter device according to claim 1, wherein the filter medium is fixed to the cover to cover one end of the liquid passage.

5. The filter device of claim 4, wherein the lid is further configured with at least one channel uncovered by the filter medium, thereby providing communication between the sample chamber and an exterior of the body.

6. The filter device according to claim 1, wherein the filter medium (is a planar filter medium.

7. A filtration system characterized by comprising a plurality of filtration devices according to any one of the preceding claims and a centrifuge comprising a plurality of holders mounted for rotation about a substantially vertical axis of rotation (a), each holder of the plurality of holders configured to releasably retain an associated filtration device of the plurality of filtration devices oriented with the sample chamber below the filtration media during rotation of the plurality of holders.

8. A lid for closing the open top of the tubular filter body, the lid including a liquid passage extending through the lid; a filter medium fixed to the cover to cover at least one end of the liquid passage; and an aperture for liquid filtrate located in the lid closer to its outer periphery than the liquid passage; characterized in that the lid is configured with an elliptical cross-section in a plane parallel to the open top when the lid closes the open top, and the hole is located closer to the periphery of the lid than the liquid channel in a direction along the major axis (M) of the ellipse; wherein the body is configured with a circular cross-section in a plane parallel to the open top and the lid is an eccentric ellipsoid.

9. The lid of claim 8, wherein a seal is provided that covers an upper surface of the lid.