U.S. patent number RE30,779 [Application Number 06/143,227] was granted by the patent office on 1981-10-20 for filter assembly with replaceable filter element.
This patent grant is currently assigned to Pall Corporation. Invention is credited to Roydon B. Cooper.
United States Patent |
RE30,779 |
Cooper |
October 20, 1981 |
Filter assembly with replaceable filter element
Abstract
A filter assembly is provided having a filter chamber and a
filter element therein that is replaceable without contamination of
filtered fluid with unfiltered fluid even though the filter chamber
is not emptied of unfiltered fluid comprising, in combination, a
filter housing; a filter chamber in the housing; an inlet for
unfiltered fluid and an outlet for filtered fluid in the housing; a
filter element removably disposed in the filter chamber across the
line of fluid flow from the inlet to the outlet so that fluid flow
from the inlet to the outlet normally proceeds through the filter;
a weir spaced from and downstream of the filter element, compelling
filtered fluid from the filter flowing towards the outlet to
proceed upwardly through the space between the weir and the filter
and then by overflow across the weir; and a weir follower
operatively associated with the base of the filter element and
movable along the weir in fluid-tight relation to the base and the
weir, to carry filtered fluid in the space between the weir and the
filter element on the downstream side of the filter element to the
top of the weir while a used filter element is being removed, and
to displace unfiltered fluid in the filter chamber from contact
with the downstream side of a clean filter element while the clean
filter element is being installed. The filter assembly is
particularly suited for use as a return line filter mounted in a
tank.
Inventors: |
Cooper; Roydon B. (Locust
Valley, NY) |
Assignee: |
Pall Corporation (Glen Cove,
NY)
|
Family
ID: |
26840810 |
Appl.
No.: |
06/143,227 |
Filed: |
April 24, 1980 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
Issue Date |
|
Reissue of: |
856959 |
Dec 5, 1977 |
04133763 |
Jan 9, 1979 |
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Current U.S.
Class: |
210/232; 210/441;
210/457 |
Current CPC
Class: |
B01D
35/0276 (20130101); B01D 29/232 (20130101); B01D
35/147 (20130101); B01D 29/96 (20130101); B01D
29/58 (20130101); B01D 35/143 (20130101); B01D
29/21 (20130101); B01D 29/925 (20130101); B01D
35/027 (20130101); B01D 29/94 (20130101); B01D
29/21 (20130101); B01D 29/232 (20130101); B01D
29/58 (20130101); B01D 29/925 (20130101); B01D
29/94 (20130101); B01D 29/96 (20130101); B01D
35/027 (20130101); B01D 35/143 (20130101); B01D
35/147 (20130101); B01D 2201/0415 (20130101); B01D
2201/4084 (20130101); B01D 2201/301 (20130101) |
Current International
Class: |
B01D
29/21 (20060101); B01D 29/13 (20060101); B01D
35/00 (20060101); B01D 35/027 (20060101); B01D
027/04 () |
Field of
Search: |
;210/232,234,236,435,441,446,450,455,457 |
References Cited
[Referenced By]
U.S. Patent Documents
Foreign Patent Documents
Primary Examiner: Cuchlinski, Jr.; William A.
Claims
Having regard to the foregoing disclosure, the following is claimed
as the inventive and patentable embodiments thereof:
1. A filter assembly having a filter chamber and a filter element
therein that is replaceable without contamination of filtered fluid
with unfiltered fluid in the filter chamber even though the filter
chamber is not emptied of unfiltered fluid when a filter element is
removed and installed, comprising, in combination, a filter
housing; a filter chamber in the housing; an inlet for unfiltered
fluid and an outlet for filtered fluid in the housing; a filter
element removably disposed in the filter chamber across the line of
fluid flow from the inlet to the outlet so that fluid flow from the
inlet to the outlet normally proceeds through the filter; a weir
spaced from and downstream of the filter element, compelling
filtered fluid from the filter flowing towards the outlet to
proceed upwardly through the space between the weir and the filter
and then by overflow across the weir; and a weir follower
operatively associated with the base of the filter element
.[.and.]. .Iadd.removably attached to one end of the filter element
and mounted on the weir in a manner to be retained thereon while a
used filter element is being removed, and while a clean filter
element is being installed, and slidably .Iaddend.movable along the
weir in fluid-tight relation to the base and the weir, to carry
filtered fluid in the space between the weir and the filter element
on the downstream side of the filter element to the top of the weir
while a used filter element is being removed, and to displace
unfiltered fluid in the filter chamber from contact with the
downstream side of a clean filter element while the clean filter
element is being installed. .[.2. A filter assembly according to
claim 1, in which the weir follower is removably attached to one
end of the filter element and is slidably mounted on the weir in a
manner to be retained thereon while a used filter element is being
removed, and while a clean filter element is
being installed..]. 3. A filter assembly according to claim
.[.2,.]. .Iadd.1 .Iaddend.in which the filter element is
cylindrical with end caps, and the weir follower is removably
attached to one end cap. .[.4. A filter assembly according to claim
1, in which the weir follower is removably attached to the weir and
fixed to the filter element in a manner to be retained thereon
while a used filter element is being removed, and while a clean
filter element is being installed..]. .[.5. A filter assembly
according to claim 4, in which the filter element is cylindrical
with end
caps, and a weir follower is fixed to each end cap..]. 6. A filter
assembly according to claim 1, in which the filter element is
tubular with an open center and end caps having central apertures,
and the weir and the weir follower are disposed concentrically
within the open center of the
filter element tube. 7. A filter assembly according to claim 6, in
which the top of the weir extends high enough and the filter
chamber volume below the top of the weir is large enough that the
top of the weir is above the level of unfiltered fluid remaining in
the filter chamber after the filter element has been removed, so
that the unfiltered fluid left behind in the chamber does not flow
over the top of the weir into the
outlet for filtered fluid. 8. A filter assembly according to claim
6, in which the filter housing has a projection extending into the
filter chamber above the weir, extending into and sealing off one
end of the filter element at the end cap, with the weir follower
sealing off the
other end of the filter element at the other end cap. 9. A filter
assembly according to claim 1, in which the weir is an upstanding
wall defining an inner wall of the filter chamber on the downstream
side of the filter element with access to the outlet for filtered
fluid being by overflow
across the top of the weir. 10. A filter assembly according to
claim 9, in which the filter element is tubular with an open center
and end caps having central apertures, and the weir is a baffle
disposed concentrically within the filter element upstream of the
filtered fluid outlet of the housing for filtered flow in the
direction from the outside of the filter
element towards the inside. 11. A filter assembly according to
claim 1, in which the filter element is tubular and the weir is a
central standpipe for flow in the direction from the outside of the
filter element towards the inside. .[.12. A filter assembly
according to claim 1, in which the filter element is tubular with
an open center and end caps having central apertures and the weir
follower is an annulus projecting inwardly from an end cap,
slidable along the outside of the weir, having a recess facing the
weir outside, capturing a sealing element in the recess, and
sealing
against the outside of the weir at the sealing element..]. 13. A
filter assembly according to claim 1, in which the filter element
is tubular with an open center and end caps having central
apertures and the weir follower is an annulus projecting outwardly
from the weir, slidable along the outside of the weir, having a
recess facing the filter element end cap, capturing a sealing
element in the recess, and removably sealing against the filter
element end cap, and sliding with the filter element to the top of
the weir when the filter element is being removed, and to the
.[.button.]. .Iadd.bottom .Iaddend.of the weir when the filter
element is
being installed. 14. A filter assembly according to claim 1, having
a detent at the top of the weir, to engage and retain the weir
follower upon removal of the used filter element, the detent being
releasable after installation of a fresh filter element, to permit
the weir follower to proceed with the filter element down the weir
to the operating position.
. A tank for storage of filtered fluid having a feed outlet line
and a return inlet line for circulation of fluid to and from the
tank, and, disposed in the return line upstream of the tank, a
filter assembly
according to claim 1. 16. A tank according to claim 15, in which
the filter assembly has a port for entry of fluid for replenishing
fluid in the tank, and filtering such fluid before entry into the
tank. .Iadd. 17. A filter assembly having a filter chamber and a
filter element therein that is replaceable without contamination of
filtered fluid with unfiltered fluid in the filter chamber even
though the filter chamber is not emptied of unfiltered fluid when a
filter element is removed and installed, comprising, in
combination, a filter housing; a filter chamber in the housing; an
inlet for unfiltered fluid and an outlet for filtered fluid in the
housing; a filter element removably disposed in the filter chamber
across the line of fluid flow from the inlet to the outlet so that
fluid flow from the inlet to the outlet normally proceeds through
the filter; the filter element having a top end and a base end and
being removably attached in fluid-tight relation at the top end to
the filter housing; a weir spaced from and downstream of the filter
element, compelling filtered fluid from the filter flowing towards
the outlet to proceed upwardly through the space between the weir
and the filter and then by overflow across the weir; and a weir
follower operatively associated with the base of the filter element
and movable along the weir in fluid-tight relation to the base and
the weir, to carry filtered fluid in the space between the weir and
the filter element on the downstream side of the filter element to
the top of the weir while a used filter element is being removed,
and to displace unfiltered fluid in the filter chamber from contact
with the downstream side of a clean filter element while the clean
filter element is being installed. .Iaddend. .Iadd. 18. A filter
assembly according to claim 17, in which the weir follower is
removably attached to one end of the filter element and is slidably
mounted on the weir in a manner to be retained thereon while a used
filter element is being removed, and while a clean filter element
is being installed. .Iaddend..Iadd. 19. A filter assembly according
to claim 18, in which the filter element is cylindrical with end
caps, and the weir follower is removably attached to one end cap.
.Iaddend..Iadd. 20. A filter assembly according to claim 17, in
which the weir follower is removably attached to the weir and fixed
to the filter element in a manner to be retained thereon while a
used filter element is being removed, and while a clean filter
element is being installed. .Iaddend..Iadd. 21. A filter assembly
according to claim 20, in which the filter element is cylindrical
with end caps, and a weir follower is fixed to each end cap.
.Iaddend..Iadd. 22. A filter assembly according to claim 17, in
which the filter element is tubular with an open center and end
caps having central apertures, and the weir and the weir follower
are disposed concentrically within the open center of the filter
element tube. .Iaddend..Iadd. 23. A filter assembly according to
claim 22, in which the top of the weir extends high enough and the
filter chamber volume below the top of the weir is large enough
that the top of the weir is above the level of unfiltered fluid
remaining in the filter chamber after the filter element has been
removed, so that the unfiltered fluid left behind in the chamber
does not flow over the top of the weir into the outlet for filtered
fluid. .Iaddend. .Iadd. 24. A filter assembly according to claim
22, in which the filter housing has a projection extending into the
filter chamber above the weir, extending into and sealing off one
end of the filter element at the end cap, with the weir follower
sealing off the other end of the filter element at the other end
cap. .Iaddend..Iadd. 25. A filter assembly according to claim 17,
in which the weir is an upstanding wall defining an inner wall of
the filter chamber on the downstream side of the filter element
with access to the outlet for filtered fluid being by overflow
across the top of the weir. .Iaddend..Iadd. 26. A filter assembly
according to claim 25, in which the filter element is tubular with
an open center and end caps having central apertures, and the weir
is a baffle disposed concentrically within the filter element
upstream of the filtered fluid outlet of the housing for filtered
flow in the direction from the outside of the filter element
towards the inside. .Iaddend..Iadd. 27. A filter assembly according
to claim 17, in which the filter element is tubular and the weir is
a central standpipe for flow in the direction from the outside of
the filter element towards the inside. .Iaddend..Iadd. 28. A filter
assembly according to claim 17, in which the filter element is
tubular with an open center and end caps having central apertures
and the weir follower is an annulus projecting inwardly from an end
cap, slidable along the outside of the weir, having a recess facing
the weir outside, capturing a sealing element in the recess, and
sealing against the outside of the weir at the sealing element.
.Iaddend. .Iadd. 29. A filter assembly according to claim 17, in
which the filter element is tubular with an open center and end
caps having central apertures and the weir follower is an annulus
projecting outwardly from the weir, slidable along the outside of
the weir, having a recess facing the filter element end cap,
capturing a sealing element in the recess, and removably sealing
against the filter element end cap, and sliding with the filter
element to the top of the weir when the filter element is being
removed, and to the bottom of the weir when the filter element is
being installed. .Iaddend..Iadd. 30. A filter assembly according to
claim 29, having a detent at the top of the weir, to engage and
retain the weir follower upon removal of the used filter element,
the detent being releasable after installation of a fresh filter
element, to permit the weir follower to proceed with the filter
element down the weir to the operating position. .Iaddend..Iadd.
31. A tank for storage of filtered fluid having a feed outlet line
and a return inlet line for circulation of fluid to and from the
tank, and, disposed in the return line upstream of the tank, a
filter assembly according to claim 17. .Iaddend..Iadd. 32. A tank
according to claim 31, in which the filter assembly has a port for
entry of fluid for replenishing fluid in the tank, and filtering
such fluid before entry into the tank. .Iaddend.
Description
Filter assemblies are normally so constructed that it is possible
to remove and replace a filter element when the element either
fails or becomes so loaded with contaminants that the system is
starved for filtered fluid downstream of the filter. Removability
is ensured by placing the filter element in a filter chamber or
bowl, to which access is provided either by removing the bowl or by
removing the top of the bowl or chamber. When the filter is
removed, the unfiltered fluid in the chamber before the filter
becomes mixed with the filtered fluid in the chamber downstream of
the filter, and before it is possible to place a fresh filter
element in the assembly, it is necessary to clean out the filter
chamber or bowl of unfiltered fluid, in order to prevent
contamination of the downstream filtered fluid surface or side of
the filter. This is a considerable nuisance, since it wastes fluid,
and is time-consuming.
It is also a particular problem when the filter chamber or bowl is
in an inaccessible location, such as, for example, when mounted in
a tank or reservoir, as, for example in the case of a tank-mounted
return line filter. Such a filter filters the fluid entering the
tank, which filtered fluid is then held in storage in the tank, for
supply of filtered fluid to the system. If any portion of the
unfiltered fluid in the return line is allowed to enter the tank,
the entire tank becomes contaminated, and must be filtered again
before it can be used. In such a situation, it is essential that
the replacement of the filter element be possible without
contamination of the downstream filtered fluid with upstream
unfiltered fluid. In tank-mounted return line filters, this
normally has meant the removal of the entire filter assembly, bowl
and all, and other precautions, which increases the cost and time
for filter element replacement.
Most in-tank filter assemblies are arranged for filtering fluid
flow from the inside-out of a cylindrical filter element. In this
way the contaminants removed by the filter are inside the filter
element, and when the filter element is removed from the filter
bowl or chamber, the likelihood of contamination of the downstream
filtered fluid with contaminants is reduced.
This however considerably complicates the relief valve system for
the filter assembly. It is essential in all return line filters to
provide a bypass path for relief of differential fluid pressure
across the filter element, when the filter element becomes so
loaded with contaminants that the differential pressure across the
filter increases to the point where backpressure affects system
function or filter element collapse is imminent. The provision of a
relief valve for a filter element with inside-out flow usually
takes the form of a reciprocably-mounted filter element which is
itself the relief valve poppet, and which is spring-mounted to
close off the bypass path, but which is moved outwardly from the
valve seat when the differential fluid pressure increases above a
predetermined minimum.
Filter elements are heavy, particularly when loaded with
contaminants, and if a reciprocable filter element is subjected to
vibration and/or external shock, the filter element can oscillate,
and open and close the bypass path, even though the minimum
differential pressure at which the bypass path should be opened has
not yet been reached.
It is also difficult to build a filter for inside-out flow that
withstands flow fatigue. System return lines have very high flow
differences (unlike system pressure lines), and the resistance of a
filter element to differential fluid pressure is greatly diminished
after it has experienced a number of high flow surges. If the
filter element is corrugated, the corrugations are expanded
outwardly into the supporting sheath, stretching and reshaping the
corrugated form, and this flexing of the element eventually
destroys the element.
It would be desirable, therefore, for return line filters mounted
in tanks, to utilize conventional outside-in flow, with
conventional relief or check valves, but this is very difficult to
do, because of the contamination problem of downstream filtered
fluid with unfiltered fluid when the filtered element is being
changed.
What is needed is a mechanical structure which makes it possible to
remove a filter element from a filter bowl or chamber without
emptying the filter bowl or chamber of unfiltered fluid, which
nonetheless prevents such unfiltered fluid from passing downstream
of the filter into the downstream filtered fluid line, and which
also makes it possible to install a clean filter element in a
filter bowl or chamber containing unfiltered fluid without
permitting the escape of unfiltered fluid to the downstream side of
the new filter cartridge or element being installed.
In accordance with the invention, a filter assembly is provided
having a filter chamber and a filter element that is replaceable
without employing the filter chamber of unfiltered fluid. This is
made possible by providing for attachment at the base of the filter
element a weir follower that is movable along a weir in fluid-tight
relation both to the base of the filter element and to the weir.
The weir is spaced from and downstream of the filter element, and
the weir follower moves across this space, sealing it off from the
remainder of the filter chamber. When the contaminated filter
element is being removed, the weir follower carries filtered fluid
in the space downstream of the filter element to the top of the
weir, overflowing into the tank, while the disappearance of the
volumetric displacement of the removed filter element causes the
level of contaminated or unfiltered fluid upstream of the filter to
fall well below the top of the weir. When the clean filter element
is being installed, the weir follower prevents unfiltered fluid in
the filter chamber from contacting the downstream side on the
interior of the filter element. The weir follower compels filtered
fluid in the filter chamber to move downwardly and outwardly to the
upstream side of the element. This makes it possible to protect
both the filtered fluid line and the space downstream of the filter
between the filter and the weir from intrusion by unfiltered fluid
during both removal and installation of a filter element. After
installation of the filter element the weir compels filtered fluid
in the space between the filter element and the weir proceeding
towards the outlet to proceed through the space by upflow, and then
overflow across the weir.
Accordingly, the filter assembly of the invention comprises, in
combination, a filter housing; a filter chamber in the housing; an
inlet for unfiltered fluid and an outlet for filtered fluid in the
housing; a filter element removably disposed in the filter chamber
across the line of fluid flow from the inlet to the outlet, so that
fluid flow normally proceeds through the filter; .Iadd.the filter
element having a top end and a base end and being removably
attached in fluid tight relation at the top end to the filter
housing; .Iaddend.a weir spaced from and downstream of the filter
element defining a space therebetween and compelling filtered fluid
from the filter proceeding towards the outlet to proceed through
the space and then by overflow across the weir; and a weir follower
operatively associated with the base of the filter element and
movable along the weir in fluid-tight relation to the base and the
weir, sealing off the space from the remainder of the filter
chamber, to carry filtered fluid in the space to the top of the
weir while a used filter element is being removed, and to displace
unfiltered fluid in the filter chamber outside the space from
contact with the downstream side of a clean filter element while a
clean filter element is being installed. .Iadd.
In a preferred embodiment, the filter assembly of the invention
comprises, in combination, a filter housing; a filter chamber in
the housing; an inlet for unfiltered fluid and an outlet for
filtered fluid in the housing; a filter element removably disposed
in the filter chamber across the line of fluid flow from the inlet
to the outlet, so that fluid flow normally proceeds through the
filter; a weir spaced from and downstream of the filter element
defining a space therebetween and compelling filtered fluid from
the filter proceeding towards the outlet to proceed through the
space and then by overflow across the weir; and a weir follower
operatively associated with the base of the filter element and
movable along the weir in fluid-tight relation to the base and the
weir, sealing off the space from the remainder of the filter
chamber, to carry filtered fluid in the space to the top of the
weir while a used filter element is being removed, and to displace
unfiltered fluid in the filter chamber outside the space from
contact with the downstream side of a clean filter element while a
clean filter element is being installed. .Iaddend.
The weir and the weir follower operatively associated with the
filter element and movable along the weir are preferably arranged
concentrically of the filter element, and within the filter
element, with the top of the weir at approximately two inches above
the maximum level of the fluid in the tank, and at least above the
level of unfiltered fluid remaining in the chamber or bowl after
the displacing filter element has been removed, so that the
unfiltered fluid left behind does not flow over the top of the
weir, to and through the outlet for filtered fluid.
The relative volumes of the displacement of the filter element and
of the filter chamber upstream of the weir are so chosen that when
the filter element is removed, the level of unfiltered fluid in the
filter chamber is below the top of the weir.
The weir is of conventional construction, and can take the form of
an upstanding wall defining an inner wall of the filter chamber or
bowl, with access to the outlet for filtered fluid being by
overflow across the weir. A baffle upstream of the outlet will
serve. If the filter element is tubular, a central standpipe will
serve, for flow in the direction from the outside of the filter
element towards the inside. An external standpipe will serve for
flow in the direction from the inside to the outside of the filter
element.
The weir follower movable along the weir can take any of several
forms. It can, for example, be an annulus attached to or a part of
or projecting inwardly from a tubular filter element end cap,
slidable reciprocably with the filter element, along the weir, and
sealing against the outside wall of the weir; since it is a part of
the base wall of the filter element end cap, such an annulus serves
as a floor seal for the annular space between the filter element
and the weir, and moves up and down on the weir with the filter
element.
The weir follower movable along the weir also can be slidably
attached to the weir, and removably attached to the base of the
filter element, so as to move with the filter element to the top of
the weir when the filter element is being removed, and to the
bottom of the weir when the filter element is being installed.
If desired, a detent or other catch can be placed at the top of the
weir, to engage and retain the weir follower upon removal of the
used filter element, and until installation of a fresh filter
element. The detent or other catch can then be released, to permit
the weir follower to proceed with the filter element back down the
weir, to the normal position for operation.
Preferred embodiments of the filter assembly of the invention are
shown in the drawings, in which:
FIG. 1 is a longitudinal section taken along the line 1--1 of FIG.
3 through a filter assembly of the invention, showing the weir,
weir follower and filter element attached thereto in operating
position, the weir follower in this case being attached to the weir
and in the form of an annulus slidable along the surface of the
weir, and the weir being in the form of a standpipe;
FIG. 2 is a side elevation partially in section of the filter
assembly of FIG. 1, showing the weir follower in position for
removal of the filter element, and before installation of a fresh
filter element, retained in that position by a detent;
FIG. 3 is a cross-sectional view, taken along the line 3--3 of FIG.
2;
FIG. 4 is a longitudinal section taken along the line 4--4 of FIG.
6 through another embodiment of filter assembly in accordance with
the invention, in which the weir is a standpipe, and the weir
follower is an annulus attached to each filter element end cap,
with the filter element installed in operating position in the
assembly;
FIG. 5 is a side elevation partially in section of the filter
assembly of FIG. 4, showing the filter element in position at the
top of the weir, as in replacement of the filter element, and
installation of a fresh filter element;
FIG. 6 is a cross-sectional view taken along the line 6--6 of FIG.
4;
FIG. 7 is a longitudinal section taken along the line 7--7 of FIG.
9 through another embodiment of filter assembly in accordance with
the invention in which the weir is a standpipe, and the weir
follower is an annulus slidably attached to the weir, and removably
attached to one filter element end cap, with the filter element
installed in operating position in the assembly;
FIG. 8 is a side elevation partially in section of the filter
assembly of FIG. 7, showing the filter element in position at the
top of the weir, as in replacement of the filter element, and
installation of a fresh filter element;
FIG. 9 is a cross-sectional view taken along the line 9--9 of FIG.
7; and
FIG. 10 is a cross-sectional view at the top of the filter assembly
taken along line 10--10 of FIG. 7.
The filter assembly shown in FIGS. 1, 2 and 3 has a housing 1 in
two principal parts: a filter head 2, and a filter cannister 3. The
filter cannister 3 is cylindrical, and is open at one end, which is
provided with an annular flange or lip 4, and closed off at the
other end by an apertured cap 5. The cap and flange are attached
thereto by brazing, soldering, welding, spinning or forming.
The filter head 2 has an annular configuration, with a central
chamber 6 closed off at the top end by the cap 7, and at the bottom
end by the filter cannister 3.
The inner face 8 of the filter head 2 has six lateral lugs or
projections 10, each of which is apertured at 11 for reception of
the cap screws 12, which thread into the sockets 13 of the bowl
attachment plate 15. Proper alignment in securing the plate 15 to
the cap screws 12 is ensured by the flanged sockets 13, which nest
in the recesses 14 in the head, and a leak-tight seal between the
lip 4 of the cannister 3 and the plate 15 is provided for by the
gasket ring 17.
The filter assembly has provision for two inlet ports 18,18' in the
filter head 2, but only inlet port 18 is cut through and open. The
outlet port 19 from the assembly is the central aperture of the cap
5 across the base of filter cannister 3.
The cap 7 carries a magnetic pressure indicator 20 of conventional
type, such as described in U.S. Pat. No. 2,942,572 to David B.
Pall, patented June 28, 1960, and a coaxial bidirectional flow
control valve 21 of the type described in U.S. Pat. No. 3,908,693
to Roydon B. Cooper, patented Sept. 30, 1975. The pressure
indicator is installed in a central bore 22 of the cap 7 with
sealing provided by the O-ring 23. Upstream or unfiltered fluid
pressure is sensed at the inner face of the magnetic piston 24 via
the passage 25, in chamber 33 upstream of the filter element and
downstream fluid pressure is sensed at the outer face of the piston
24, at the open interior 26 of the coaxial flow control valve 21,
which is downstream or filtered fluid pressure of the filter
element, since it is in communication with filtered fluid pressure
in the open interior 41 of the filter element.
The flow control valve 21 is supported on the valve cage 28
attached to portion 29 of the cap 7. The cage 28 is attached to the
cap by the snap ring 30, fitting in the recess 31 of the cap. A
plurality of ports 32 together with chamber 33 define a bypass
passage leading from the inlet port 18 to the outlet port 19 via
the relief valve element 34 of the flow control valve 21. This
element engages the inner face of cap 7 and serves a relief
function, in that, in response to a pressure differential across
the valve between the inlet and outlet ports that exceeds a
predetermined minimum, it opens and thus permits bypass flow via
ports 32 and chamber 33. This predetermined minimum is however
greater than the diferential pressure at which the pressure
indicator 20 gives a signal, also sensed by the differential
pressure indicator at chamber 33 via passage 25.
Thus, the differential pressure indicator indicates when the filter
element becomes loaded sufficiently that opening of the relief
valve 34 is imminent, and before it is actually opened, thus making
it possible to change the filter element before unfiltered bypass
flow begins. Then, in the event that the filter element be not
changed and differential pressure continues to increase, valve 34
opens, and the bypass passage is opened to prevent collapse of the
filter element or system instability from excess back pressure or
pressure relief arising from high viscosity oil on cold
start-up.
The valve cage 28 attached to the head cap 7 supporting the flow
control valve 21 also seals and supports one end of the filter
element 40, and actually projects into the open interior 41 of the
filter element. The end cap 43 of the filter element 40 defines an
internal recess 44, in which is captured an O-ring seal 45, which
ensures a fluid-tight connection between the filter end cap and the
cage, and thus prevents bypass of unfiltered fluid from space 6
into the space 41 in the interior of the filter element 40.
The filter element 40 carries between the end caps 43 and 46 a
perforated core 47, and a corrugated microporous multilayer filter
sheet 48 having a microporous layer of bonded nonwoven inorganic
fibers attached to a substrate, with an average pore diameter
within the range from 3 to 25.mu.. While this filter assembly does
not include it, an external sheath can also be provided, to protect
the outer surface of the filter element.
The valve cage 28 also centers the filter element in the filter
cannister, with a space 50 therebetween, and also spaces the core
of the filter element from the weir 51, with the space 52
therebetween. In this case, the weir 51 is in the form of a
standpipe, disposed in and securely attached to the base cap 5 at
the periphery of the outlet 19. The space 52 collects filtered
fluid that has passed through the filter, and the fluid flows
through the space upwardly towards the top 51a of the weir 51.
Securely attached to the inside wall of the weir, opposite each
other at 53, at the top of the weir, are two spring detents 55, in
the form of resilient wire with an outward projection 58.
Movable reciprocably along the outside of the weir is an annular
weir follower 60, which engages the exterior of the weir 51 in a
fluid-tight seal by way of the O-ring 61 captured in the recess 62,
and also engages the filter element end cap 46 in a fluid-tight
seal by way of the O-ring 63, captured in the recess 64 of the end
cap, thus sealing off space 52 from the rest of the space in the
cannister 3. The element installation guide 65 of the weir follower
60 guides the end cap 46 of the filter element into engagement with
the weir follower 60.
The weir follower 60 includes a recess 68, shaped to receive the
projections 58 of the detents 55, and thus the weir follower 60 can
be retained at the top of the weir. This makes it possible to
remove the filter element from the weir follower 60 against the
retaining action of the O-ring 63, when the follower has reached
the end of its travel at the top of the weir.
Since the filter element is sealed to the housing both at its upper
and lower end caps 43, 46, it will be apparent that normal fluid
flow from the inlet 18 to the outlet 19 of the filter housing 1
will proceed from the inlet port 18 into the space 6, then into
space 50, and then through the filter and core into the space 52
between the weir 51 and the inside of the filter core. The filtered
fluid proceeds upwardly through space 52 and then by overflow over
the top 51a of the weir into the open interior 59 of the weir, and
then proceeds downwardly directly to the outlet 19 and then leaves
the cannister 3.
Attached to the lower face of the base cap 5 of the filter
cannister is a spider 66, which has a central aperture 67 in its
base 74 in which is securely fastened a bolt 69. The end portion of
the bolt is threaded, and receives a cap nut 70.
The cap nut and bolt secure across the outlet 19 from the filter
cannister a fluid diffuser distributor 71 of stainless steel wire
mesh sheet. The sheet is held between retaining plates 72, 73, and
ensures that flow from the outlet is distributed relatively
uniformly at a velocity of approximately 2 ft/sec. This inhibits
aeration and eliminates turbulent flow in the tank downstream of
the filter assembly (not shown).
In order to replace the filter element, it is necessary to remove
the cap 7 from the filter head 2. The cap, which is externally
threaded at 27, is retained in the threaded socket 37 of the filter
head, and a fluid-tight seal at the interior portion of the socket
is ensured by the O-ring seal 39. Accordingly, the cap 7 is simply
unscrewed from its socket, carrying with it the cage 28. The cage
28 has a peripheral circumferential groove 28a, which is shaped to
intercept the O-ring 45 on end cap 43, and thus as it is being
withdrawn with cap 7 retains and carries with it the filter element
40. The filter element 40 and weir follower 60 accordingly move
together to the top of the weir 51 with withdrawal of the cage
28.
Since the weir follower 60 is secured to the filter element end cap
46 and to the weir 51 in a fluid-tight seal on each side, filtered
fluid above the weir follower in the space 52 is carried up with
the filter element, and continues to flow by overflow into the weir
51, as the filter element 40 and weir follower 60 proceed up
through the cannister, while the unfiltered fluid in the cannister
flows into the space beneath, just vacated by the filter element.
The volume below the top 51a of the weir and formerly occupied by
the filter element 40 and space 52 is adequate to receive all of
the unfiltered fluid in the chamber 50, as well as the unfiltered
fluid in the space 6 above the cannister 3 in the filter head 2,
and this unfiltered fluid thus cannot reach the top and flow over
into the weir, into the filtered fluid line downstream of the
filter.
When the weir follower reaches the top of the weir, recess 68
engages projections 58, and is retained by the detents 55, and the
filter element can now be withdrawn from the weir follower, and
replaced. Removal from the weir follower is simple, since the
filter element is held there only by the squeezed O-ring 63.
A clean filter element is installed by placing the upper end cap 43
thereof over the cage 28, with O-ring 45 locked in groove 44, and
then lowering the assembly into the cannister, bringing the lower
end cap 46 into engagement with the weir follower 60, where it is
sealed in place by the O-ring 63. The cap and attached assembly is
then pushed down along the weir 51, until the threaded portion of
the cap 7 reaches the threaded portion of the socket. The cap can
then be screwed into the socket, and the closure made complete.
As this is being done, the unfiltered fluid is displaced around the
bottom and up along the outside of the filter element into the
space 50 between the filter element and the filter cannister. Some
of this fluid may proceed through the filter into the space 52 that
now is created between the filter and the weir, thus reducing the
volume of fluid that needs to be accommodated on the upsteam side
of the filter in space 50. Unfiltered fluid can enter the space 52
between the filter element and the weir only by passage through the
filter, because of the weir follower 60, and its sealing engagement
both with the weir and with the filter end cap 46. Thus, the filter
element can be installed in the cannister without danger of
contamination of the filtered fluid line with unfiltered fluid.
The flow distributor at the outlet end of the filter cannister can
be removed and replaced when required, simply by removal of the cap
nut 70.
The filter assembly shown in FIGS. 4, 5 and 6 is generally similar
to that of FIGS. 1, 2 and 3, except that the weir follower is
attached to the filter element end caps instead of to the weir, and
is removable therewith from the weir. Consequently, the description
of the embodiment of FIGS. 4, 5 and 6 will be confined to the
discussion of the weir follower.
Since a weir follower is attached to each end cap, there is a
slightly differing engagement of the top end cap of the filter to
the cage 87 attached to the cap 93. It will be understood that the
remainder of the description of the filter assembly of FIGS. 1, 2
and 3 is applicable to the filter assembly of FIGS. 4, 5 and 6, and
like reference numerals are therefore applied to like parts.
In this case, the end caps 80, 81 of the filter element 79 are each
provided with identical weir followers 82, 83, projecting inwardly
from the end cap, each with a recess 84 that captures an O-ring 85,
shaped to sealingly engage the portion 86 of the cage 87, and the
groove 89, as well as the weir 88. The portion 86, for
standardization of parts, is identical in external diameter with
the external diameter of the weir 88. Thus, the filter element 79
can in fact be installed either side up in the assembly and the
weir followers 82, 83 will seal against both cage and weir, either
way.
The lower weir follower 83 of end cap 81 via its O-ring seal 85
engages the outside wall of the weir 88 in a fluid-tight seal.
Since the weir follower 83 is securely attached to the end cap in a
fluid-tight seal, the space 90 between the core 91 of the filter
element and the weir 88 is effectively sealed off against entry of
unfiltered fluid except through the filter, and the upper weir
follower 82 of end cap 80 via its O-ring seal 85 likewise ensures
that entry of unfiltered fluid over the top of the filter element
from the space 90 between the filter element and the cage 87 is
also prevented.
In order to remove the filter element, one simply unscrews the cap
93 of the filter head, and withdraws it from the cannister together
with cage 87. The cage groove 89 engages the weir follower 82 via
O-ring 85, so that the filter element is retained to the cage 87,
and is removed with the cap from the head. As this is being done,
the filter element is slid up along the weir 88. As the filter
element is being withdrawn, the unfiltered fluid in the space 95 on
the outside of the filter element can enter the volume formerly
occupied by the filter element 79 and the space 90 between it and
the weir 88, and this volume is sufficient to accommodate below the
top of the weir 88 all of the unfiltered fluid in the space 95
between the filter element and the cannister, and the space 94
above this, in the filter head. Accordingly, the filter element 79
can be withdrawn without contamination of the filtered fluid line
with unfiltered fluid flowing over the top of the weir 88.
When it is desired to install a fresh filter element, one simply
inserts one end cap weir follower over the cage 87, so that the
cage engages the weir follower, and the other end cap weir follower
over the top of the weir 88, and then pushes the head cap 93, cage
87 and the filter element 79 down along the weir into the
cannister. As one does so, the unfiltered fluid beneath the filter
is displaced into the space 95 between the filter and the
cannister. As it is thus being displaced, some of it can filter
through the filter into the space 90, now re-created between the
filter and the weir, thus becoming filtered fluid, but by the time
the filter has been pushed down to the bottom of the cannister, all
of the unfiltered fluid has been displaced outwardly and upwardly.
Thus, the filter element can be installed without contamination of
the downstream side of the element with unfiltered fluid.
The filter head cap can then be threaded into place. After the cap
has been installed in a leak-tight manner, the filter assembly is
ready for operation, and bypass of unfiltered fluid is effectively
prevented until the filter element is loaded with contaminants, to
the point that the flow control valve bypass opens, as indicated
previously.
The filter assembly shown in FIGS. 7, 8, 9 and 10 is especially
designed for use as an in-tank return line filter, and as such is
generally similar to that of FIGS. 1 to 6, with provision of a fill
port on the upstream side of the filter so that addition of fluid
to the tank is via the filter. This filter assembly has a housing
100 in two principal parts: a filter head 102 and a filter
cannister 103. The filter cannister 103 is cylindrical, and is open
at one end, which is provided with an annular flange or lip 104,
and closed off at the other end by an apertured cap 105. The cap
and flange are attached thereto by brazing, soldering, welding,
spinning or forming.
The filter head 102 has an annular configuration, with a central
chamber 106 closed off at the top end by the cap 107, and at the
bottom end by the filter cannister 103.
The housing is provided with an annular ring 109 which can be
welded in place at the outer periphery to the tank, thus
facilitating permanent installation of the assembly in any kind of
tank.
The inner face 108 of the filter head 102 has six lateral lugs or
projections .[.100.]. .Iadd.110.Iaddend., each of which is
apertured at 111 for reception of the cap screws 112, which pass
through the bores 111 of the lugs 110 and are secured in threaded
sockets 113 in the ring 109. A leak-tight seal between the lip 104
of the cannister 103 and the ring 109 is provided for by the gasket
ring 117.
The filter head 102 has an inlet port 118. The outlet port 119 is
the aperture in cap 105 at the other end of the filter cannister
103.
The cap 107 carries at one side, off center, a magnetic pressure
indicator 120 of conventional type, such as described in U.S. Pat.
No. 2,942,572 to David B. Pall, patented June 28, 1960, and from
two to eight relief valves 121 of the conventional poppet type. The
pressure indicator is installed in a side bore 122 of the cap 107,
with sealing provided by the O-ring seal 123. Upstream unfiltered
fluid pressure is sensed at the inner face of the magnetic piston
124 via the passage 125, leading to chamber 106, upstream of the
filter element, and downstream fluid pressure is sensed at the
outer face of the piston 124, via the passage 126 to the filtered
fluid space 141 on the interior, i.e., downstream, of the filter
element.
The relief valves 121 are press-fitted into sockets in the head
137, and are in flow connection on their upstream side via passages
132 with space 106, and on their downstream side with chamber 133
of the cap 107. A filter element adapter 128 is threaded into the
socket 134 of the head 137 in fluid flow connection at its open
interior with the chamber 133 leading to the outlet port 119 via
the open interiors of the adapter 128 and weir 151. In response to
a pressure differential across the valves 121 between the inlet
port 118 and outlet port 119 that exceeds a predetermined minimum,
the valves 121 open, and thus permit bypass flow via passages 132,
133 into and through the adapter 128 and weir 151 to the outlet
119. This predetermined minimum is how ever greater than the
differential pressure sensed by the differential pressure indicator
at passages 125, 126 at which the pressure indicator 120 gives a
signal.
Thus, the differential pressure indicator indicates when the filter
element becomes loaded sufficiently that opening of the relief
valves 121 is imminent, and before they are actually opened, making
it possible to change the filter element before unfiltered bypass
flow begins. In the event that the filter element be not changed,
and differential pressure continues to increase, one to eight of
the relief valves 121 open, and the bypass passages 132, 133 are
opened to prevent collapse of the filter element or system
instability from excess back pressure or pressure relief arising
from high viscosity oil on cold start-up.
The head cap 107 also has a through bore 180 opening at one end to
the exterior of the cap at threaded port 181 which is closed off by
fill cap 182, and opening at the other end to the chamber 106. This
bore serves as a fill passage, to add liquid to the tank in which
the assembly is installed, and all such liquid since it is admitted
upstream of the filter is filtered as it passes into the tank.
The element adapter 128 attached to the head cap 107 at socket 134
thereof supports one end of the filter element 140, and actually
projects into the open interior 141 of the filter element. There is
an external recess 142 of this portion of the element adapter 128.
The end cap 143 of the filter element 140 carries a weir follower
155 projecting inwardly, which defines a recess 144, in which is
captured an O-ring 145, which ensures a fluid-tight connection
between the filter end cap and the element adapter, and thus
prevents bypass of unfiltered fluid into the space 141 in the
interior of the filter element 140.
The filter element 140 carries between end caps 143 and 146 a
perforated core 147, and a corrugated microporous multilayer filter
sheet 148 having a microporous layer of bonded nonwoven inorganic
fibers attached to a substrate, with an average pore diameter
within the range from 3 to 25.mu.. While this filter assembly does
not include it, an external sheath can be provided, to protect the
outer surface of the filter element.
The element adapter 128 centers the filter element in the filter
cannister, with a space 150 therebetween, and spaces the core of
the filter element from the weir 151, with the space 152
therebetween. In this case, the weir 151 is in the form of a
standpipe, disposed in and securely attached to the outlet 119 in
the base cap 105 of the filter cannister.
Securely attached to the inside wall of the weir, opposite each
other at 153, at the top of the weir, are two spring detents 155,
in the form of resilient wire with an outward projection 158.
The end cap 146 carries a weir follower 158 which is movable
reciprocably along the outside of the weir and engages the exterior
of the weir 151 in a fluid-tight seal by way of the O-ring 161
captured in the recess 162.
The adapter 128 includes a groove 142, shaped to intercept O-ring
145 of the weir follower 155, and thus when the cap 107 is being
removed from the cannister 103 the filter element is retained to
the cap, and carried with it. This makes it possible to remove the
filter element at the same time as the cap 107 is being
withdrawn.
Since the filter element is sealed to the adapter 128 at its upper
end cap 143 and to the weir at its lower end cap 146, it will be
apparent that normal fluid flow from the inlet 118 to the outlet
119 of the filter housing 100 will proceed from the inlet port 118
into the space 106, then into space 150, and then through the
filter 140 into the space 152 between the weir and the inside of
the filter core. The filtered fluid proceeds by overflow over the
top of the weir 151 into the open interior 159 of the weir, and
then proceeds directly to the outlet 119 from the cannister
103.
Attached to the lower face of the base cap 105 of the filter
cannister is a spider 166, which has a central aperture 167 in its
base 168 in which is securely fastened a bolt 169. The end portion
of the bolt is threaded, and receives a cap nut 170.
The cap nut and bolt secure across the outlet 119 from the filter
cannister a fluid diffuser distributor 171 of stainless steel wire
mesh sheet. The sheet is held between retaining plates 172, 173,
and ensures that flow from the outlet is distributed relatively
uniformly at a velocity of approximately 2 ft/sec. This inhibits
aeration and eliminates turbulent flow in the tank downstream of
the filter assembly (not shown).
In order to replace the filter element, all that is necessary is to
remove the cap 107 of the filter head 102. The cap, which is
externally threaded at 127, is retained in the threaded socket 137
of the filter head, and a fluid-tight seal at the interior portion
of the socket is ensured by the O-ring seal 139. Accordingly, the
cap 107 is simply unscrewed from its socket, carrying with it the
adapter 128, and with the adapter the filter element 140, the end
cap 143 being held by O-ring 145 in groove 142. The filter element
140 and weir follower 158 move together to the top of the weir 151.
Since the follower 158 seals against the weir 151 in a fluid-tight
seal, filtered fluid above the weir follower in space 152 is
carried up with the filter element 140, and continues to flow by
overflow into the weir 151, as the filter element 140 and weir
follower 158 proceed up through the cannister, while the unfiltered
fluid in the cannister flows into the space beneath, formerly
occupied by the filter element 140 and space 152. The volume thus
released for unfiltered fluid is adequate, by the time the filter
element 140 has reached the top of the weir 151, to receive all of
the unfiltered fluid in the space 150, as well as in the space 106
above the filter element in the filter head 102, and this
unfiltered fluid is below the top of the weir and thus does not
flow into the filtered fluid line downstream of the filter.
When the weir follower 158 reaches the top of the weir 151, the
filter element can be withdrawn and replaced.
A fresh filter element is installed by placing the projecting
portion of the adapter 128 into the weir follower 155 of end cap
143, and then placing weir follower 158 of the lower end cap 146
over the weir 151. The assembly is then pushed down along the weir
until the threaded portion of the cap 107 reaches the threaded
portion of the socket. The cap can then be screwed into the socket,
and the closure completed.
As this is being done, the unfiltered fluid is displaced outwardly
and upwardly around the bottom and outside of the filter element
140 into the space 150 between the filter element and the filter
cannister. Some of this fluid may proceed through the filter into
the space 152, now re-created between the filter and the weir, thus
reducing the volume of fluid to be accommodated on the upstream
side of the filter, in space 150. Unfiltered fluid cannot enter the
space 152 between the filter elements and the weir except by
passage through the filter, because of the weir follower 158, and
its sealing engagement with the weir. Thus, the filter element can
be installed in the cannister without danger of contamination of
the filtered fluid line with unfiltered fluid. The level of
unfiltered fluid in the cannister will be below the top of the
filter and the weir, when installation is complete.
After the filter and the cap have been fully installed, and the cap
107 sealed to the head, flow can again begin.
The flow distributor at the outlet end of the filter bowl can be
removed and replaced when required, simply by removal of the cap
nut.
The drawings all show embodiments having internal weirs for
filtered flow from outside-in of the filter element.
If flow through the filter is from inside-out, then the weir can be
concentrically disposed outside the filter element, and the weir
follower will be outside the filter element as well, between the
filter element and the weir. Then, unfiltered liquid is confined
inside the weir, rather than outside. The filtered fluid is of
course collected and distributed from outside the weir, but
otherwise the assembly is exactly the same.
The drawings all show embodiments having cylindrical filter
elements. The invention is also applicable to flat or curved sheet
filter elements, such as a corrugated filter sheet. In this case,
the filter chamber is in two parts, with the weir a compartmenting
divider wall separating the two parts. The filter is disposed on
one side of the weir, with the weir follower and space
therebetween. Again the weir flow proceeds through the filter to
the space between the filter and weir, over the top of the weir.
Filtered fluid is collected on the other side of the weir and the
weir and weir follower protect the downstream side of the filter
from contamination with unfiltered fluid, when the filter is
removed.
The filter assemblies of the invention are useful with any filter
element having a filter sheet in tubular or cylindrical form,
provided with end caps to close off the interior space enclosed by
the filter sheet, and give control of the flow of filtrate. One or
both of the end caps can be provided with flow passages for
filtrate flow. The caps can be of any desired material, appropriate
to the system and the need, and are bonded to the cylinder ends in
a leak-proof seal by appropriate bonding agents. Such filter
elements are conventional, and well known to those skilled in this
art, and form no part of the instant invention. Melt-sealed end
caps, as disclosed in U.S. Pat. No. 3,457,339, patented July 22,
1969, to David B. Pall, et al, may be used.
The filter sheets can be formed of any porous sheet material having
pores extending from surface to surface. One or several sheets of
the same or varying porosity, and one or more of which may act as
prefilters, can be employed, in close juxtaposition, or even bonded
together, or also spaced apart. Sheets such as open-weave wire or
plastic mesh may be added. Paper, which can, if desired, be
resin-impregnated, is a preferred base material, since it yields an
effective, versatile and inexpensive fluid-permeable filter medium.
The invention is, however, applicable to sheet materials formed of
any type of fiber, including not only cellulose fibers but also
synthetic resin fibers and fibers of other cellulose derivatives
including, for example, fibers of polyvinyl chloride, polyethylene,
polypropylene, polyvinylidene chloride, cellulose acetate,
cellulose acetate propionate, viscose rayon, polyacrylonitrile,
polymers of terephthalic acid and ethylene glycol, polyamides, and
protein fibers of various sorts, such as zein and the alginates,
glass, asbestos, potassium titanate, mineral wool, polystyrene,
rubber, casein, hemp, jute, linen, cotton, silk, wool, and mohair.
Also useful, in addition to papers, are textile and wire fabrics,
and woven and nonwoven fibrous layers of all kinds, such as felts,
mats and bats made of fibrous materials of any of the types listed
above, and woven wire mesh.
The sheet material should in most cases be sufficiently rigid to be
self-supporting when folded in cylindrical form, but if it is not,
a core and/or external sheath of rigid metal, plastic or similar
rigid material can be provided, as a support.
Also, the filter sheet material of which the filter elements of the
invention are made can be, if desired, impregnated with a synthetic
resin or cellulose derivative to increase its strength and
resistance to wear by the fluid being filtered. The impregnating
agent can be any material useful in the impregnation of papers and
textile materials. Such materials are well known in the paper and
textile arts, and form no part of the instant invention. The
impregnating agents can be in liquid form, capable of undergoing
solidification as by polymerization, cross-linking, or the like.
They can also be in solid form, and applied to the base from a
solution in an inert solvent, or as melts. Representative
impregnating resins include phenol-formaldehyde resins,
urea-formaldehyde resins, melamine-formaldehyde resins, polyester
resins, and polyepoxide resins.
The end caps capping the filter tube or cylinder can be of any
desired material, such as metal or plastic. The end cap should be
rigid, and attached to the tube or cylinder in a leak-tight seal.
The end cap can be formed by molding or casting in the desired
shape, integral or in one piece with the means movable along the
weir, if this be part of the end cap, as in FIGS. 4 to 6.
The core and/or sheath support sections and end caps can be formed
of any desired material sufficiently rigid to provide adequate
support for the filter sheet with which it is to be used. Metal
core supports are preferred, such as core supports of stainless
steel or aluminum, which are readily stamped in any desired
cross-sectional configuration, and which will retain that
configuration and provide the desired rigidity. Stainless steel,
which provides greater resistance to certain highly reactive
fluids, is preferred. Steel, copper, magnesium, beryllium,
titanium, nickel, iron and various alloys thereof are typical
additional metals which can be used.
The core and/or sheath supports and end caps also can be formed of
rigid synthetic polymeric materials and cellulose derivatives, such
as, for example, glass, ceramics, phenol-formaldehyde resins,
polytetrafluoroethylene, polychlorotrifluoroethylene,
urea-formaldehyde resins, melamine-formaldehyde resins, polyvinyl
chloride, polyvinylidene chloride, polystyrene, epoxy resins,
polyoxymethylene, polypropylene, polyethylene, polyvinyl butyral,
cellulose acetate, ethyl cellulose and cellulose acetate
propionate. Cores made of such materials can be formed into core
sections by molding from powders of the material, or by stamping or
shaping of sheets of the material. This may be easier than molding
the entire core support, in the case of complex cross-sectional
configurations and when complex end connections for the core
support are necessary. The plurality of sections composing such
core supports of the invention can be bonded together by
application of heat and pressure, or a suitable adhesive, or by
application of a solvent for the material which will make possible
fusion of the adjacent edges of the sections at the seams.
A suitable core is described in U.S. Pat. No. 3,246,766, to David
B. Pall.
* * * * *