U.S. patent application number 11/299841 was filed with the patent office on 2006-05-04 for filter assemblies and valves for filter assemblies.
This patent application is currently assigned to Pall Corporation. Invention is credited to Roger Alexander Buttery, Richard Guy Gutman, Kenneth Roy Weight.
Application Number | 20060091060 11/299841 |
Document ID | / |
Family ID | 10815938 |
Filed Date | 2006-05-04 |
United States Patent
Application |
20060091060 |
Kind Code |
A1 |
Gutman; Richard Guy ; et
al. |
May 4, 2006 |
Filter assemblies and valves for filter assemblies
Abstract
A filter assembly may include a valve which includes a valve
member and a sleeve. The valve member moves between a first
position and a second position in response to rotation of the
sleeve.
Inventors: |
Gutman; Richard Guy;
(Chichester, GB) ; Buttery; Roger Alexander;
(Petersfield, GB) ; Weight; Kenneth Roy; (Denmead,
GB) |
Correspondence
Address: |
LEYDIG VOIT & MAYER, LTD
700 THIRTEENTH ST. NW
SUITE 300
WASHINGTON
DC
20005-3960
US
|
Assignee: |
Pall Corporation
East Hills
NY
|
Family ID: |
10815938 |
Appl. No.: |
11/299841 |
Filed: |
December 13, 2005 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
10694404 |
Oct 28, 2003 |
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11299841 |
Dec 13, 2005 |
|
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09462765 |
Jun 2, 2000 |
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PCT/GB98/01975 |
Jul 6, 1998 |
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10694404 |
Oct 28, 2003 |
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Current U.S.
Class: |
210/418 ;
210/435 |
Current CPC
Class: |
B01D 36/001 20130101;
B01D 27/005 20130101; B01D 27/08 20130101; B01D 36/003 20130101;
B01D 2201/088 20130101; F16K 31/528 20130101; F16L 37/248 20130101;
B01D 2201/16 20130101; B01D 2201/4015 20130101 |
Class at
Publication: |
210/418 ;
210/435 |
International
Class: |
B01D 35/30 20060101
B01D035/30 |
Foreign Application Data
Date |
Code |
Application Number |
Jul 16, 1997 |
GB |
9714965.2 |
Claims
1. A filter assembly comprising: a plastics housing having an
interior, an exterior, an inlet port, and an outlet port; a filter
element in the interior of the housing and including a filter
medium; a passage extending between the interior and the exterior
of the housing; and a valve including a valve member and a
rotatable sleeve, wherein the valve member is located within the
passage and is movable between a first position in which fluid flow
along the passage is permitted and a second position in which the
valve member seals the passage and fluid flow along the passage is
prevented and wherein the valve member moves axially between the
first and second positions in response to rotation of the
sleeve.
2. The filter assembly of claim 1 wherein the valve includes a pin
and a slot which receives the pin, the engagement of the pin in the
slot causing the valve member to move axially between the first and
second positions in response to rotation of the sleeve.
3. The filter assembly of claim 2 wherein the slot is in the
sleeve.
4. The filter assembly of claim 1 wherein the passage includes
first and second portions, the valve member sealing the second
portion in the second position.
5. The filter assembly of claim 4 wherein the second portion of the
passage has a smaller diameter than the first portion.
6. The filter assembly of claim 4 wherein the passage includes a
third portion which extends through the valve member, the first
portion and the third portion of the passage fluidly communicating
in the first position.
7. The filter assembly of claim 4 wherein the first portion of the
passage includes a plurality of spaced ribs.
8. The filter assembly of claim 1 wherein the valve member is
connected to the sleeve and the sleeve moves axially with the valve
member.
9. A filter assembly comprising: a plastics housing having an
interior, an exterior, an inlet port and an outlet port; a filter
element in the interior of the housing and including a filter
medium; a passage which extends between the interior and the
exterior of the housing, the passage having a first portion and a
second portion; and a valve including a rotatable sleeve, a pin, a
slot, and a valve member, wherein the valve member moves between a
first position in which the valve member is in the first portion of
the passage and the valve is open and a second position in which
the valve member is sealed within the second portion of the passage
and the valve is closed, and wherein the valve member moves axially
in the passage in response to rotation of the sleeve and engagement
of the pin in the slot.
10. The filter assembly of claim 9 wherein the pin and the slot are
arranged with the sleeve and the housing to move the valve member
axially in response to rotation of the sleeve and engagement of the
pin in the slot.
11. The filter assembly of claim 9 wherein the slot is in the
sleeve.
12. The filter assembly of claim 9 wherein the valve member is
connected to the sleeve.
13. The filter assembly of claim 9 wherein the slot is in the
sleeve, the pin is on the housing, and the valve member is
connected to the sleeve and wherein the sleeve and the valve member
move axially in response to rotation of the sleeve and engagement
of the pin in the slot.
14. The filter assembly of claim 9 wherein the passage includes a
third portion which extends through the valve member and wherein
the third portion and the first portion of the passage fluidly
communicate in the first position.
15. The filter assembly of claim 9 wherein the valve member
includes a blind end and wherein the blind end of the valve member
is sealed within the second portion of the passage in the second
position.
16. The filter assembly of claim 9 wherein the first portion of the
passage includes a plurality of ribs.
17. The filter assembly of claim 9 wherein the pin and the slot are
arranged with the sleeve and the housing, the valve member is
connected to the sleeve, the valve member includes a blind end
which is sealed within the second portion of the passage in the
second position, and the passage includes a third portion which
extends through the valve member, the third portion and the first
portion of the passage fluidly communicating in the first
position.
18. The filter assembly of claim 9 wherein the second portion of
the passage has a smaller diameter than the first portion.
19. A valve for a filter assembly comprising a passage member, a
sleeve member surrounding the passage member, and a valve member
having a passage and extending in to the passage member from an end
thereof, one member including a pin and another member including a
co-operating slot such that rotation of the sleeve member results
in axial movement of the valve member between a first position in
which the valve member opens the passage member for fluid
connection with the passage in the valve member and a second
position in which the valve member closes the passage member.
20. A valve according to claim 19 wherein the pin is carried on an
exterior surface of the passage member and the slot extends
helically partially around the sleeve member.
21. A valve according to claim 19 wherein, in the second position,
the valve member sits in and seals against a circumference of the
passage member, closing the passage member, and, in the first
position, the valve member does not seal against the circumference
of the passage member, opening the passage member.
22. A valve according to claim 19 wherein the passage member
includes a larger diameter portion and a smaller diameter portion,
the valve member closing the smaller diameter portion in the second
position thereof.
23. A valve according to claim 22 wherein the valve member includes
a blind end, the blind end entering the smaller diameter portion in
the second position to close the passage member.
24. A valve according to claim 22 wherein the valve member carries
a seal which seals against the smaller diameter portion in the
second position.
25. A valve according to claim 22 wherein the valve member lies
within the larger diameter portion in the first position.
26. A valve according to claim 22 wherein the larger diameter
portion includes a plurality of ribs within said passage member,
the ribs guiding the seal into the smaller diameter portion as the
valve member moves to the second position.
27. A valve according to claim 26 wherein the valve member carries
a seal and the seal includes an O-ring carried in a groove on the
valve member and wherein the ribs keep the O-ring in the groove
when the valve member is in the first position.
28. A valve according to claim 19 wherein the valve member includes
a blind end and wherein the valve member passage includes an
axially extending portion leading to a connector and a radially
extending portion connecting the axial portion to an exterior
surface of the valve member spaced from the blind end.
29. A valve according to claim 19 wherein the sleeve member
surrounds an exterior surface of the passage member and a seal is
provided between the sleeve member and the exterior surface of the
passage member.
30. A valve according to claim 29 wherein the seal includes an
O-ring carried in a groove on the exterior surface of the sleeve
member.
31. A valve according to claim 19 wherein the sleeve member is
connected to the valve member.
Description
[0001] This application is a divisional of U.S. application Ser.
No. 10/694,404, which was filed on Oct. 28, 2003, and is a
continuation of U.S. application Ser. No. 09/462,765, which is now
abandoned and was the United States national phase of International
Application No. PCT/GB98/01975, which was filed on Jul. 6, 1998,
all of which are incorporated by reference.
[0002] The invention relates to filter assemblies and valves.
[0003] A known form of filter assembly comprises a housing
providing an inlet port and an outlet port with a filter element
being held in the housing and comprising a filter medium having a
central passage extending between first and second ends of the
filter medium. The first end of the filter medium is connected to
an end cap to close the passage and the second end of the filter
medium is in fluid communication with a port of the housing.
[0004] In this way, fluid passing to the housing flows through the
filter medium in a path including the inlet port, the outlet port
and the passage. Such filters are used extensively for medical,
biomedical and pharmaceutical purposes.
[0005] It is a requirement of such filter assemblies that the
filter element must be capable of being integrity tested. For
water-wettable filter media integrity can be tested by the Water
Bubble Point Test or the Diffusive Forward Flow Test. In the Water
Bubble Point Test, the filter element is placed in a water bath
with both the first and second ends of the passage closed and air
is pumped into the passage at a pressure which is increased until
the first bubble is observed on the exterior of the filter medium.
If the structure of the filter medium has integrity over its whole
volume, this first bubble will appear at a predetermined pressure.
If a bubble or bubbles appear at a lower pressure, it is an
indication that the structure of the filter medium is not uniform
over the whole volume of the filter medium. This can indicate the
incidence of passages through the filter medium which might allow
the passage through the medium in use of unfiltered or only partly
filtered fluid.
[0006] In the Diffusive Forward Flow Test, the filter medium is
wetted with water and surplus water is removed. Air is applied to
one side of the medium at a specified pressure and the diffusive
air flow rate is measured. This diffusive air flow rate has been
found to be related to the removal rating of the medium. A greater
than expected flow rate can indicate lack of integrity of the
medium.
[0007] However, the connection to a water-wettable filter medium of
an end cap can change the characteristics of the medium so that
integrity testing is no longer possible. For example, the
connection can produce hydrophobic zones in the medium which do not
wet out in the integrity test and thus plainly affect the
performance of the medium in the integrity test.
[0008] For this reason, the materials of the filter medium and the
end cap are usually chosen so that connection of the medium and the
end cap does not affect the characteristics of the medium in a
manner that would affect the medium's performance in an integrity
test.
[0009] The material of the end cap is also important for
hydrophobic filter media. Some hydrophobic filter media are easily
damaged by heat. These media are attached to the end cap by heating
the end cap to soften the end cap and inserting the first end of
the medium into the end cap while the end cap is softened. It is
therefore important to choose a material for the end cap that
softens at a relatively low temperature such that the connection
can be carried out without damaging the media.
[0010] However, it is also a requirement for such filter assemblies
that have medical, biomedical and pharmaceutical uses that they can
be sterilized to allow for repeated use. There are two principal
forms of sterilization; in situ steam sterilization and steam
autoclaving. In situ steam sterilization, instead of fluid to be
filtered passing to the filter assembly, high pressure and high
temperature steam are passed through the filter assembly. For
example, the steam pressure may be several bars and the temperature
140.degree. C. In steam autoclaving, the filter assembly is removed
from associated equipment and transferred to an autoclave where it
is steam sterilized. The filter assembly is then removed from the
autoclave, transferred aseptically and replaced in the equipment. A
typical filter assembly might need sterilizing 100 times in its
lifetime.
[0011] Where the housing of such a filter assembly is made of a
plastics material, the second end of the filter medium is usually
connected to the housing by heating the housing material and
inserting the second end of the filter medium into the housing
material. For water-wettable media, in order to produce a water
wettable joint for integrity testing purposes, it is thus necessary
to have the housing of an appropriate material that produces the
required join. For hydrophobic media that are relatively easily
damaged by heat it is necessary for the plastics material of the
housing to have a relatively low softening temperature. Such
plastics materials are not able to withstand the pressures and
temperatures of in situ steam sterilization. Accordingly, such
filter assemblies must be sterilized by autoclaving. This requires
the filter assembly to be removed from service, autoclaved and then
transferred aseptically back into service.
[0012] The known alternative is to house the filter element in a
metal housing. The metal will withstand the temperatures and
pressures of in situ steam sterilization but metal housings are
typically much bulkier than plastics housings and are more
expensive to produce and require cleaning before re-use.
[0013] It is also a problem with filter assemblies in providing
valves for the inlet port and the outlet port. Such valves need to
be capable of steam sterilization, and many are not.
[0014] According to a first aspect of the invention, filter
assemblies may comprise a plastics housing, a filter element, a
passage, and a valve. The housing has an interior, an exterior, an
inlet port, and an outlet port. The filter element is in the
interior of the housing and includes a filter medium. The passage
extends between the interior and the exterior of the housing. The
valve includes a valve member and a rotatable sleeve. The valve
member is located within the passage and is movable between a first
position and a second position. In the first position, fluid flow
along the passage is permitted. In the second position, the valve
member seals the passage and fluid flow along the passage is
prevented. The valve member moves axially between the first and
second positions in response to rotation of the sleeve.
[0015] According to a second aspect of the invention, filter
assemblies may comprise a plastics housing, a filter element, a
passage, and a valve. The housing has an interior, an exterior, an
inlet port, and an outlet port. The filter element is in the
interior of the housing and includes a filter medium. The passage
extends between the interior and the exterior of the housing and
has a first portion and a second portion. The valve includes a
rotatable sleeve, a pin, a slot, and a valve member. The valve
member moves between a first position and a second position. In the
first position, the valve member is in the first portion of the
passage and the valve is open. In the second position, the valve
member is sealed within the second portion of the passage and the
valve is closed. The valve member moves axially in the passage in
response to rotation of the sleeve and engagement of the pin in the
slot.
[0016] According to a third aspect of the invention, valves for
filter assemblies may comprise a passage member, a sleeve member,
and a valve member. The sleeve member surrounds the passage member.
The valve member has a passage and extends into the passage member
from an end of the passage member. One member includes a pin and
another member includes a co-operating slot. Rotation of the sleeve
member results in axial movement of the valve member between a
first position and a second position. In the first position the
valve member opens the passage member for fluid connection with the
passage in the valve member, and in the second position the valve
member closes the passage member.
[0017] The following is a more detailed description of an
embodiment of the invention, by way of example, reference being
made to the accompanying drawings in which:
[0018] FIG. 1 is an exploded view of a filter assembly showing
first and second parts of a filter housing, a filter element within
the housing and valves connected to inlet and drainage ports of the
housing,
[0019] FIG. 2 is a cross-section on the axis of the housing of FIG.
1, showing one valve in an open position and a second valve in a
closed position,
[0020] FIG. 3 is detail B of FIG. 2 showing the open valve to a
larger scale, and
[0021] FIG. 4 is detail C of FIG. 2 showing the closed valve to a
larger scale.
[0022] Referring to the drawings, and particularly FIG. 1, the
filter assembly comprises a housing indicated generally at 10, a
filter element 11 encapsulated in the housing 10 and two valves 12
carried by the housing 10.
[0023] The housing 10 comprises a first housing part 13 and a
second housing part 14. Both parts are made, for example moulded,
from a polysulphone material. The first housing part 13 includes an
end wall 15 provided with an inlet port 16 for the medium to be
filtered, and a circular cross-section side wall 17 extending
downwardly from the end wall 15 and terminating at a circular edge
18. An outwardly facing annular rebate 19 is formed in the side
wall 17 adjacent the edge.
[0024] An air vent port 20 is formed at the junction between the
end wall 15 and the side wall 17 and extends in a direction
generally radially relative to the axis 21 (see FIG. 2) of the
housing 10. The inner surface 60 of the air vent port 20 defines a
passage having a smaller diameter portion 22 closer to the side
wall 17 and a larger diameter portion 23 further from the side wall
17 and terminating at the end of the air vent port 20. Five ribs 61
extend into the larger diameter portion 23 from the inner surface
60. The ribs 61 are spaced equi-angularly around the surface 60.
Each rib 61 has an edge 62 that is continuous and in line with the
inner surface 60 at the small diameter portion of the passage.
[0025] The air vent port 20 has an exterior surface 24 provided
with an annular groove 25 adjacent the end of the port 20 which
carries an O-ring seal 26. In addition, this surface 24 has two
pins 27 projecting radially from the surface at respective
positions on the surface spaced from the end of the port 20. The
function of the seal 26 and the pins 27 is described below.
[0026] The second housing part 14 includes a second end wall 28
provided with a disc-shaped stand 29. The second end wall 28 has
its end remote from the stand of generally annular shape coaxial
with the axis 21 of the housing 10. This portion of the second end
wall 28 is provided with an inwardly facing rebate 30.
[0027] As best seen in FIG. 2, the second end wall 28 has an outlet
port 31 in the form of a generally circular cross-section passage
co-axial with the axis 21 of the housing 10 and extending through
the second end wall 28 and the stand 29. The end of the outlet port
31 within the housing 10 forms an annular flange 32.
[0028] A drainage port 33 is provided in the second end wall 28 and
extends radially from the second end wall 28 relative to the axis
21 of the housing 10. The drainage port 33 is constructed similarly
to the air vent port 20 (parts common to the two ports 20,33 are
given the same reference numerals and will not be described in
detail).
[0029] The filter element 11 comprises a filter medium 34, a first
end cap 35, a second end cap 36 and a cage 37. The filter medium
may be of any convenient material and any convenient shape that
provides a central passage for the flow of fluid to be filtered.
For example, the filter medium 34 may be annular. The material may
be pleated or unpleated. Examples of suitable filter media are
those sold by Pall Corporation under the trademarks ULTIPOR,
FLUORODYNE, SUPOR and EMFLON.
[0030] The filter medium 34 has a first end and a second end with
the passage extending between the ends. The first end cap 35 is
disc-shaped and is formed from a plastics material. The first end
cap 35 is preferably connected to the first end of the filter
medium 34 by heating the end cap 35 to soften the end cap 35 and
then inserting the filter medium into the softened end cap material
to form a join.
[0031] The material of the first end cap 35 is chosen so that, when
the filter medium 34 is connected to the first end cap 35, the
characteristics of the medium 34 are not materially changed. In
particular, when the filter medium 34 is of a water-wettable
material, the material of the first end cap is chosen to that a
water wettable joint is formed between the filter medium 34 and the
first end cap 35. In this case, the end cap material will depend on
the material of the filter medium 34. For example, when the filter
medium 34 is a FLUORODYNE or SUPOR medium, the end cap 35 maybe
composed of polypropylene. When the filter medium 34 is composed of
a nylon material the first end cap 35 may be composed of a
polyester or nylon material.
[0032] It is important to obtain a water-wettable joint between
water-wettable filter media and the first end cap 35 in order to
allow the filter element to be integrity tested. An integrity test
involves the filter element being placed in a bath of water (with
the ends of the passage closed) and air is then supplied to the
passage at increasing pressure. The bath is then observed to
determine at what pressure the first bubble appears on the exterior
of the filter medium. If the porous structure of the filter medium
is integral over the whole area of the filter medium, then the
first bubble will appear at a relatively high pressure. If,
however, the porous structure is not integral over the whole area
of the filter medium 34, then the first bubble will appear at a
relatively lower pressure. If the junction between the first end
cap 35 and the filter medium 34 is not water-wettable, it creates a
hydrophobic zone through which air passes readily since the porous
structure is not wetted out by water. Although this does not
normally affect filtration during use of the assembly, it is not
possible to test the integrity as described above. The formation of
hydrophobic zones similarly prevents the medium being tested by the
Diffusive Forward Flow Test described above.
[0033] Where the filter medium 34 is hydrophobic, it is important
to ensure that the first end cap 35 is composed of a material that
can be softened at a temperature that is sufficiently low so that
the integrity of the medium 35 is not damaged by the insertion
process. For example, when the filter medium 34 is composed of PVDF
(such as an EMFLON 2 medium) the first end cap 35 may be composed
of polypropylene. Where the filter medium 35 is composed of PTFE,
which is relatively resistant to heat, it is also preferable to use
polypropylene end caps.
[0034] The second end cap 36 comprises a flat annular portion 38
with a central aperture. A projecting tube 39 surrounds the
aperture and extends away from the filter medium 34 in a direction
normal to the plane of the flat annular portion 38. The tube 39 is
provided with two annular seals 40 on its exterior surface 41. Four
flanges 42 project radially outwardly of the flat annular portion
38 and are equi-angularly spaced around this portion 38.
[0035] The outer diameter of the tube 39 is generally equal to the
interior diameter of the outlet port 31.
[0036] For any filter medium 34, the material of the second end cap
is chosen based on the same considerations affecting the choice of
the material of the first end cap. The material of the second end
cap 36 will normally, but not necessarily, be the same as the
material of the first end cap 35. The filter medium 34 is connected
to the second end cap 36 by heating the second end cap 36 and then
inserting the filter medium 34 into the softened material. The cage
37, which is of known type, surrounds the exterior surface of the
filter medium 34 between the first and second end caps 35,36.
[0037] The filter element 11 is mounted in the housing in the
following way. First, the tube 39 on the second end cap 36 is
inserted into the outlet port 31 in the second end wall 28. The
seals 40 prevent leakage between these parts. When fully inserted,
the flange 32 of the outlet port 31 bears against the under-surface
of the flat annular portion 38 of the second end cap 36. This holds
the filter element 11 in the second end wall 28 coaxial with the
housing axis 21. In addition, it connects the interior passage of
the filter medium 34 with the outlet port 31 via the tube 39.
[0038] The first housing part 13 is then placed over the filter
element 11 with the edge 18 fitting within the second end wall 28
and the rebate 19 adjacent this edge mating with the rebate 30 in
the second end wall 28. The first and second housing parts 13,14
are then welded together around the rebates 19,30.
[0039] When so positioned, the edge 18 of the side wall 17 bears
against the flanges 42. The effect of this is to clamp the filter
element 11 between this edge 18 and the end of the flange 32
surrounding the outlet port 31 and contacting the second end cap
36. In this way, the filter element 11 is held firmly in position
encapsulated in the housing 10.
[0040] Referring next to FIGS. 3 and 4 in particular, the valves 12
control flow through the air vent port 20 and the drainage port 33.
The valves 12 are identical and so only one of them will be
described.
[0041] The valve 12 comprises an elongated valve member 43 which is
generally circular in cross-section. The valve member 43 has a
blind end 44 within the associated port. The blind end 44 carries
an O-ring 45 in a groove provided on an exterior surface. The
remainder of the valve member 43 has an axial passage 46 leading to
a connector 47 for connection to a hose or pipe. In FIG. 3 the
connector 47 has an annular triangular-section rib 63 and in FIG. 4
the connector 47 has a succession of axially spaced ribs 64. At
least one radial passage 48 connects the end of the axial passage
46 adjacent the blind end 44 with the exterior surface of the valve
member 43.
[0042] A sleeve 49 is arranged coaxially with the axis of the valve
member 43 and is spaced from the valve member 43 by an annular
radially extending flange 50. The sleeve 49 is a sliding fit over
the exterior surface 24 of the associated port 20,31. In addition,
the sleeve is provided with two helical slots 51 (seen best in FIG.
1) extending around a portion of the sleeve 49. Each pin 27 is
received in a respective one of the slots 51.
[0043] The sleeve 49 can thus be rotated relative to the associated
port 20,33 with such rotation being controlled by the engagement of
the pin 27 in the slot 51 to cause the sleeve 49 also to move
axially relative to the associated port 20,33. This rotation can
take place in both senses.
[0044] The effect of this rotation is best seen in FIGS. 3 and 4.
At one limit of rotation in one sense, as seen in FIG. 3, the blind
end 44 of the valve member 43 lies in the larger diameter portion
23 of the associated port 20,33. When so positioned, the valve
member 43, and the associated O-ring 45, do not obstruct the port
and so allow flow into the port, through the radial passage 48 and
along the axial passage 46. Reverse flow is, of course, also
possible. Leakage around the sleeve 49 is prevented by the O-ring
seal 26 on the exterior surface 24 of the port 20,33. The O-ring 45
is kept pressed into the groove on the outer surface of the blind
end by the ribs 61--the edges 62 bearing against the O-ring 45.
[0045] Rotation of the sleeve 49 in the opposite sense moves the
blind end 44 into the smaller diameter portion. The O-ring 45 is
guided into the smaller diameter portion by the edges 62. Maximum
rotation in the opposite sense disposes the valve member as shown
in FIG. 4. In this disposition, the blind end 44 lies within the
smaller diameter portion 22 of the associated port 20,33. The
O-ring 45 seals against the inner surface 60 of the port 20, 33 so
preventing flow through the value. It will be appreciated that
because the seal is made against the circumference of the smaller
portion 22 (and not, for example, against a radially extending
seat) the port 20, 33 and the valve member 43 can undergo
differential expansion during heating without causing damage to the
valve as the blind end 44 simply moves axially with the small
portion 22.
[0046] Thus, by twisting the sleeve 49 is one sense or the other,
the associated port 20, 33 can be opening or closed. It will also
be appreciated that the pin 27 and slot 51 mechanism prevents the
valve 12 being disengaged completely from the associated port 20,
33.
[0047] The valves 12 are preferably made from a polysulphone
material.
[0048] The housing parts 13, 14 and the valves 12 may also be made
from any other suitable plastics material capable of withstanding
in-line sterilization. As stated above, in-line sterilization
involves passing steam under pressure through the housing. The
exterior of the housing is kept at atmospheric pressure and so
there is a pressure differential across the housing. The minimum
temperature and pressure of steam commonly used for sterilization
is generally about 121.degree. C. at about 1 bar above atmospheric
pressure, although in some circumstances, in particular if exposure
to the steam is prolonged, sterilization may be achievable at lower
temperatures and pressures. However, it is often desirable to
sterilize the assembly in-line under harsher conditions, for
example using steam at about 142.degree. C. and about 2.83 bar
above atmospheric pressure. The housing is preferably resistant to
such harsher conditions. Examples of plastics other than
polysulphone that are suitable are PEEK, PEK, polyphenyleneoxide,
polyphenylenesulphide, polyethersulphone polyalkoxysulphone and
polyarylsulphone.
[0049] In use, the filter assembly described above with reference
to the drawings is mounted in a line containing a fluid to be
filtered. This may be, for example, a medical, biomedical or
pharmaceutical fluid. A tube leading from a source of fluid to be
filtered is connected to the inlet 16. The outlet port 31 is
connected to a receiver of filtered fluid. The drainage port 33 is
connected to a tube leading to a receiver for drained fluid. The
valve 12 of the air vent port 20 is opened and the valve 12 of the
drainage port 33 is closed. Fluid to be filtered is then fed
through the inlet 16 to fill the housing 10. The air vent port 20
is then shut. The fluid passes through the filter medium 34 where
it is filtered and the filtered fluid enters the passage before
passing through the tube 39 and the outlet port 31.
[0050] When the filter assembly is to be sterilized, the inlet 16
is disconnected from the supply of fluid to be filtered and the
outlet port 31 is disconnected from the receiver of filtered fluid.
The drainage port valve 12 is open to drain excess fluid from the
housing 10. The inlet 16 is then connected to a supply of steam
under pressure and the outlet port 31 is connected to a drain. The
valves 12 are left slightly open. Steam at the pressure of several
bars and a temperature of about 140.degree. C. is then fed through
the housing to steam sterilize the filter material 34 and the other
components. The housing 10, since it is made of polysulphone (or
another suitable plastics material), is able to withstand the
temperature and pressure of the steam. The same is true of the
valves 12; because they are made of polysulphone (or another
suitable plastics material), they will withstand the in-line steam
sterilization without damage.
[0051] Once steam sterilization is complete, water can be drained
by fully opening the drainage port valve 12 and the filter assembly
reconnected for filtering fluid.
[0052] By separating the caps 35,35 from the housing 10, these
parts can be made in different materials to provide the water
wettability necessary for the filter medium 34 and the resistance
to in-line steam sterilization necessary for the housing 10.
[0053] It will be appreciated that there are a number of
modifications that can be made to the arrangement described
above.
[0054] The valves 12 need not be as described above. Any suitable
valves could be used. The plastics material of the housing 10 need
not be polysulphone, it could be any material that is capable of
withstanding in-line steam sterilization. The filter element 11
need not be clamped in the housing 10 as described, it could be
held in any suitable way. The cage 37 need not be as described, any
suitable cage could be provided. The filter medium 34 may be
provided with upstream and/or downstream drainage layers.
* * * * *