Note: Descriptions are shown in the official language in which they were submitted.
CA 02695299 2010-03-03
KEYED SYSTEM FOR CONNECTION OF FILTER TO FILTER HOLDER
Field of the Invention
This invention relates generally to fluid filters and filters and connections
for the
filters/cartridges to piping, valving, brackets, and other holders that
cooperate with the
filters/cartridges to make them operative in a flowing fluid system. More
specifically, this
invention relates to a system for "keying" a particular filter or filter
cartridge to a particular
cooperating filter head member or filter valve head.
Summary of the Invention
The invention is an apparatus and method wherein a portion of a fluid filter-
holder
connection is structurally adapted so that only matched filters and holders
can cooperate to
allow installation of the filter in the holder and/or to form a fluid seal. In
other words,
each filter and holder combination or "set" is "keyed" so that only that
particular filter
design mates with that holder. According to the invention, there are created
various filter-
holder sets that each have the adaptation, but the adaptation is slightly
shifted in location
and/or different in number, shape, style, or size of adaptation elements, or
otherwise offset
for each set compared to the other sets. This way, a filter from one set may
not be mixed
with a filter from another set, and, therefore, a filter may not be installed
on any but its
own matching holder.
The adaptation preferably involves varying location, number, shape, style,
and/or
size of "key" and "lock" (protrusion(s) and recess(es), respectively) for
different sets of
cooperating filters and holders. For example, mating protrusion(s) and
recess(es) may be
at a certain location on a circumference for one filter-holder set, while a
mating
protrusion(s) and recess(s) of a similar or identical shape may be at a
different location on
the circumference for another filter-holder set, and so on, for each similarly-
shaped-but-
differently-located-adaptation filter and holder set. Thus, in other words,
the protrusion
structure and the recess structure may be selectably locateable around
cooperating
perimeters of a filter and its holder. In addition or instead, the number,
shape, style, and/or
size of protrusions and recesses may be different for various filter-holder
sets, so that only
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purposely-mating, "matched sets" of filters and holders may be connected
together and
successfully used. The protrusion and recess structures are preferably rigidly
molded or
otherwise permanently placed on/in the filter and holder, and so they are not
considered
moveable or adjustable during use. They are, however, easily changed in the
molding or
other manufacturing process, that is, they are easily selectable by choosing
the location,
number, shape, style, and/or size prior to/during manufacture.
This system may include a plurality of sets of filters and holders, each set
having a
differently-located, differently-numbered, differently-shaped, differently-
styled, and/or
differently-sized key and lock, wherein the key and lock of each set cooperate
with each
other to allow that filter to be installed in that holder, but that filter may
not be installed in
any other holder because the key or lock of that filter does not cooperate
with the key or
lock of the other holder. The term "key or lock" is used because the
protrusions may be
placed on either the filter or the holder, and the recess may therefore be
placed on the other
item.
Such a system allows, for example, a water or beverage filtration facility,
experimental pilot plant, or other filter user may control filter placement
accurately. A
facility with multiple, different filtering applications may have filters on
hand for each of
the applications, but the filters will not be confused. For example, in a
facility in which
there are two different applications, many of the two different types of
filters may be kept
in stock and even may be mixed during storage or handling, but the filters
will not be
mixed when installed into the filter holders. This is because the filter
holder and the filters
for the first application are "keyed" differently than the filter holder and
the filters for the
second application. The terms "keying" or "keyed" refer generally to how and
where the
entire key system is located and accomplished, that is, to the positioning,
style, shape, size
and/or number of either one or both of the cooperating key and lock
structures, rather than
specifically to only the location of the "key protrusion." All the filters for
the first
application are keyed the same, that is, to match the first application
holder, and all the
filters for the second application are keyed the same, to match the second
application
holder. The keying for the first application and the keying for the second
application does
not need to be very different, but may be merely, for example, a slightly
different angular
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position for the two protrusions and recesses and/or slightly different
circumferential
lengths for multiple key protrusions within a single protrusion structure
(that is, different
lengths for the portions of the subdivided protrusion structure).
Also, a filter manufacturer may control his product lines more carefully by
using
the invented key system. A manufacturer may key his holders and filters
differently for
different countries, different clients, different distributors, or for
different time periods.
This technique may be used to prevent unauthorized or low-quality copies of
the
manufacturer's filters from easily being made. With so many differently-keyed
filters in
the marketplace provided by the original manufacturer, the incentive to
provide cheap, low
quality copies will be minimized, due to the expense of retooling for each
"key and lock"
set.
The key system may include many different protrusion and recess structures,
for
example, tabs and slots (typically thin or elongated bar and channel
structures or elongated
dove-tail structures), bumps and holes (typically rounded or mounded
structures with
cooperating valleys or holes), wedges and wedge-shaped wells (typically
circular section
structures); protruding plates, flanges, or wings with notches or cutouts to
form multiple
key protrusions in a single protrusion structure; and many other shapes. If a
filter must be
rotated on its longitudinal axis to be installed in a holder, leeway in the
recess structure is
supplied so that the protrusion may enter the recess structure while the
filter still has a
circumferential distance to turn. For example, in the case of an elongated
filter that is
pushed up into a filter head and then rotated on its axis to install its top
end into a filter
head, the recess comprises an axial portion for allowing axial insertion and a
radial/circumferential portion for rotation of the filter on its longitudinal
axis relative to
the filter head.
The key system structures are located on surfaces of filters (or filters
cartridges)
and holders that contact each other during connection of the filter to the
holder. This may
be either surfaces that are involved in mainly providing a physical connection
between the
filter and holder or that also are involved in providing a fluid connection
between the filter
and the holder.
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In preferred embodiments, protrusion structure extends out radially from a
portion
of the upper end of the filter housing, wherein said portion is received
inside the cavity of
the holder. The preferred embodiments of protrusion structure extend radially
outward
from the top end of the filter housing on a shoulder, shelf, plate or flange
provided on or
near the radial upper wall of the filter housing. The outer extremity of the
protrusions on
said shoulder, shelf, plate or flange preferably reach near to, but preferably
not past, the
largest diameter of the filter housing. For example, the protrusions may be
provided on a
circular/cylindrical intermediate shoulder that is coaxial with the central
longitudinal axis
of the filter and intermediate in diameter between the largest-diameter
shoulder and the
central neck of the filter housing. Or, the protrusions may be provided on
plate/flange
structure that is similarly positioned on or parallel to the radial upper wall
of the filter top
end, the plate/flange structure not necessarily being circular or cylindrical
but preferably
having a curved outer edge that may be called the curved perimeter of a filter
surface, the
filter surface being a flange surface. Thus, most preferably, the protrusion
structure is
provided at a location on the top end of the filter that has a diameter
between the largest
diameter of the housing and the diameter of the neck, for example, on an
intermediate
shoulder (see shoulder 32 in the filter of Figures 2 and 4) or on protruding
flanges that
protrude substantially beyond the diameter of the neck but not so far as to
protrude beyond
the largest diameter of the filter (see plates/flanges 120, 130 in Figures 12 -
32). While
other configurations may be effective, for example, protrusions on the largest-
diameter
shoulder (LD in Figure 2, 104 in Figure 12), intermediate-diameter
configurations typically
allow a compact-sized holder to effectively mate with the top end of the
filter without the
holder being required to extend out and down to surround the largest diameter
of the filter.
In especially-preferred embodiments, keyed plate/flanges, or "wings", protrude
out from
the top end of the filter near the shoulder of the filter upper end but
preferably above the
largest-diameter portion of the housing and below the neck, and having an
outer diameter
at the keyed outer edges of the flanges that is intermediate between said
largest-diameter
and the neck diameter. In the direction transfer to the direction in which the
protrusions
extend, the flanges are relative narrow, for example, forming a rectangular
shape in top
view. These embodiments of keyed structure may be applied to filters having
various
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styles of fluid connection, for example, various styles of neck structure
containing fluid
inlet and outlet ports.
By "holder" is meant any of a variety of devices that receive and seal to a
replaceable filter or filter cartridge. This can include a valve head
(including valving to
shut off piping when the filter is removed), a filter bracket that supports
the filter and
provides fluid flow conduits into and out of the filter, and other devices
that contact and
are in fluid communication with the filter.
By "filter" or "filter cartridge" is meant any container of filtration or
treatment
media that is connected to a holder for fluid communication with the holder to
filter and/or
treat the fluid brought into it via the holder. The keyed system invention may
be applied to
whatever structure of a filtering unit is inserted into the head or other
holder, which might
be a unitary filter or a filter cartridge encased partially in an outer
housing below the level
where the filter engages in the head.
Brief Description of the Drawings
Figure 1 is a bottom perspective view of one embodiment of a filter head
according
to the invention, illustrating one embodiment of recesses for the invented key
system.
Figure 2 is a top perspective view of one embodiment of a filter according to
the
invention, illustrating an embodiment of protrusions for the invented key
system
cooperating with the recesses of the filter head of Figure 1.
Figure 3 is a bottom view of the filter head of Figure 1, showing particularly
the
interior surfaces of the filter head.
Figure 4 is a top view of the filter of Figure 2.
Figure 5 is a top perspective view of the filter and filter head of Figures 1-
4
connected together.
Figure 6 is a top view of the filter and head combination of Figure 5, with
protrusions of the filter visible through apertures in the filter head.
Figure 7 is a side cross-sectional view of the filter and head combination of
Figure
and 6, viewed along the lines 7-7 in Figure 6.
Figure 8 is an enlarged detail view of a portion of the cross-sectional Figure
7.
Figure 9 is a top view of the filter head of Figures 1, 3, 5-8, with the
filter removed.
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Figure 10 is a side cross-sectional view of the filter of Figures 1, 3 5-9,
with the
filter removed, viewed along the lines 10-10 in Figure 9.
Figure 11 is a side cross-sectional view of the filter of Figures 1, 3 5-10,
with the
filter removed, viewed along the lines 11-11 in Figure 9.
Figures 12 - 18 illustrate a perspective, first side, front, second side,
rear, top, and
bottom view, respectively, of an especially-preferred embodiment of a keyed
filter, having
a flange system that protrudes radially from the upper end of the filter
housing, above the
shoulder and below the neck. The flange system comprises first and second
(right and left)
flanges, wherein each flange preferably comprises multiple key protrusions,
separated by
notches/indents in the outermost edge of each flange. The embodiment of
Figures 12 - 18
comprises one flange having three key protrusions (two notches/indents) and
one flange
having two key protrusions (one notch/indent).
Figures 19 - 25 illustrate a perspective, first side, front, second side,
rear, top, and
bottom view, respectively, of an alternative embodiment of a keyed filter of
Figures 12 -
18. This embodiment comprises a three-and-three key protrusion system, with
two
notches/indents on one outermost edge of one flange and also two
notches/indents on the
outermost edge of the other, opposing flange.
Figures 26 - 32 illustrates a perspective, first side, front, second side,
rear, top, and
bottom view, respectively, of yet another alternative embodiment of the keyed
filter of
Figures 12 - 18. One of the flanges comprises two key protrusions (one
notches/indents)
of different circumferential lengths, and the other, opposing flange comprises
only a single
protrusion structure as it has no notches/indents. Thus, this embodiment
illustrates that the
invention comprises at least one protrusion structure comprising multiple key
protrusions,
but there are many versions of the keyed system wherein not all of the
protrusion
structures have multiple key protrusions. The central neck of this embodiment
is shown in
dashed lines to denote that alternative neck structure comprising fluid inlet
and outlet ports
may be used, or alternative fluid inlet and outlets ports may be used that do
not necessarily
take the form of an upending neck.
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Figures 33-44 illustrate the filter of Figures 12 - 18 being installed in one
embodiment of a filter head that is keyed to cooperate with said filter, as
further described
below.
Figure 33 portrays axial insertion of the filter into the holder, and Figure
34 portrays
circumferential rotation. While the arrow in Figure 34 may suggest that the
holder is
rotated onto the filter, it will be understood that the filter will typically
be rotated relative
to a stationary holder to install the filter into a holder that has previously
been connected to
fluid inlet and outlet conduits.
Figures 35 - 37 further illustrate the assembled holder plus filter
combination. The
holder plus filter assembly is shown in a front view in Figures 35, with the
holder in cross-
section. The assembly is shown in the top view of Figure 36, with the filter
having been
inserted up into the cavity of the holder before any relative rotation of the
filter and holder.
The assembly is shown in the top view of Figure 37, after the relative
rotation of the filter
and holder (the holder rotated in the direction of the arrow in Figure 36)
that locks the
filter in the holder due to the protrusions being received and retained in the
circumferential
slots/recesses in the head. In each of Figures 36 and 37, the position of the
plate/flange
structure inside the head is shown in dashed lines.
Figures 38 and 39 show side and bottom views of the holder, respectively,
wherein
view line 39 - 39 is included in Figure 38 to assist the reader in
understanding Figure 39.
Figures 40 and 41 show vertical cross-sectional views of said head, wherein
Figure
40 is viewed along line 40 - 40 in Figure 39 and Figure 41 is viewed along
line 41-41 in
Figure 39.
Figure 42 shows a top cross-sectional view of a lower portion of the head,
viewed
along the line 42 - 42 in Figure 38.
Figure 43 is a top view of the top end of the filter and the lower cross-
section of the
holder as in Figure 42. The filter flanges being inserted up into the lower
cross-sectional
portion of the holder, wherein one may see the three key protrusions (toward
the left of the
figure) sliding axially through mating axial recesses of a first recess
structure in the holder,
and two key protrusions (toward the right of the figure) sliding axially
through mating
axial recesses of a diametrically-opposing recess structure in the holder.
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Figure 44 is a top view of the holder having been rotated (in the direction
shown by
the arrow in Figure 42) relative to the filter, until the key protrusions of
the flanges are
captured in the two diametrically-opposed circumferential recess portions
(also called
"circumferential lock portion") of the two recess structures of the holder. In
this relative
position of the filter and the holder, the filter is captured in the holder
and restrained from
dropping out of the holder in the axial direction unless the filter is
rotation in the opposite
direction relative to the holder so that the key protrusions may drop down
through the axial
recesses for removal of the filter.
Figure 45 is a top view of the entire holder and filter, with the filter
flanges in
dashed lines captured in the two diametrically-opposed circumferential recess
portions as
in Figure 44.
Therefore, Figures 33 - 44 portray an embodiment wherein three key protrusions
(on one side of the filter) slide axially through axial recess portions of a
first recess
structure in the holder and then, upon rotation, preferably all three key
protrusions will
slide into a single circumferential recess portion of said first recess
structure. Also, the
two key protrusions (on the opposing side of the filter) will slide axially
through axial
recess portions of a second recess structure also in the holder (that, in this
embodiment, is
diametrically opposed the first recess structure) and, upon rotation,
preferably both of the
two key protrusions will slide into a single circumferential recess portion of
said second
recess structure. Thus, three key protrusions preferably slide
circumferentially into a
single (one) "circumferential recess portion" of one recess structure, and two
key
protrusions preferably slide circumferentially into a single (one)
"circumferential recess
portion" of another recess structure.
Detailed Description of Preferred Embodiments of the Invention
Referring to the Figures, there are shown several, but not the only
embodiments of
the invented key system. Figures 1-11 illustrate a keyed filter embodiment of
the invented
keyed system, wherein the embodiment may be called a "keyed shoulder"
embodiment
because the protrusion structure is on a shoulder at a location slightly above
the largest-
diameter portion of the housing, wherein the shoulder has a diameter between
said largest-
diameter portion and the neck of the filter. Figures 12 - 44 illustrates
alternative
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embodiments of filters and cooperating filter heads, wherein the keyed
structure is also
located between the largest-diameter portion of the filter top end and the
neck of the filter,
and comprises keyed plates/flange(s) connected to the upper radial surface of
the filter
housing and extending out generally parallel to said upper radial surface away
from two
sides of the base of the central neck.
The key system structures are located on surfaces of filters and holders that
contact
each other during connection of the filter to the holder. The preferred keyed
structures are
on surfaces that are involved in mainly or solely providing a physical
(mechanical)
connection between the filter and holder rather than providing a fluid
connection between
the filter and the holder. In filters comprising fluid inlet and outlet ports
at or near the
longitudinal, central axis of the elongated filter (for example, in an
upending neck), the
shoulder and upper radial surfaces of the filter typically do not liquid-seal
to the filter
holder/valve-head. However, whatever portion of these surfaces must fit up
inside the
interior cavity of the valve-head are candidates for keyed system mating with
the
cooperating surfaces of the interior cavity. In other words, one or more
shoulders and/or
the upper radial surface of the filter top end typically have areas that come
in very close
contact to surfaces of the interior cavity of the holder/valve-head, but they
are not directly
involved in forming a liquid seal between the filter and the holder/valve-
head. These non-
liquid-sealing areas may be keyed so that only a filter with a certain keyed
surface shape
may extend far enough up into the holder/valve-head to be installed and locked
into place.
The protrusions of the key system may extend from or be connected to the upper
radial surface of the filter top end, including, but not necessarily limited
to, protrusions on
a circular/cylindrical intermediate shoulder on the upper radial surface of
the filter (see the
embodiment of Figures 1 - 11), or protrusions on plate-like structures
connected to the
upper radial surface and/or to the neck and extending preferably in two
directions away
from the filter neck (see embodiments of Figures 12 - 44). The protrusions in
each of
these embodiments mate or "nest" in identically-located recesses on the inside
surface of
the holder/valve-head that receives the filter, wherein the mating/nesting
serves both the
purpose of allowing the filter to be axially inserted into the holder/valve-
head and also
(upon rotation) to lock the filter into the holder/valve-head. Therefore, the
key system of
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the preferred embodiments is not a system for keying axial insertion but
accomplishing
locking/securement by other means (such as threaded connection or clamps) but
is rather a
system for both keying the axial insertion and locking-securing the filter
into the
holder/valve-head.
The keyed structure may be said to be located around the outer circumference
and/or on an outer-edge of a portion of the top end of the filter and the
cooperating or
corresponding inner circumference of the valve-head cavity. Preferably at
least one of the
protrusion structures provided on the filter top end comprises multiple key
protrusions
located within an arc of about 90 degrees or less around the
circumference/outer-edge on
which it lies, or more preferably within about 70 degrees or less. The
cooperating recess
structure is preferably located in the cavity surface, facing the filter top
end, and, likewise,
the same number of axial recesses are located within the same amount of
circumference/outer-edge, preferably about 90 or less, and, more preferably,
about 70
degrees or less. While this preferred key system locates the protrusions on
the filter and
the recesses on the head, the opposite is envisioned, wherein the protrusions
may be inside
the filter head and the recesses may be on the filter.
The key system structure of the various sets of filter and cooperating
holders/valve-
heads is typically invisible once the filter is installed. This may result in
differently-keyed
filters having substantially-similarly-shaped outer housing surfaces, and,
hence,
substantially the same exterior appearances. Also, this may result in
differently-keyed
holders/valve-heads having outer surfaces of the same shape, and, hence, the
same exterior
appearances. A manufacturer may include indicia on the outer surface of the
filter and the
outer surface of the holder/valve-head to indicate the different media or
other filter
differences and to indicate what filter will mate with the particular
holder/valve-head.
Also, a user may look at the key system structure as long as the filter is
uninstalled. In any
event, when the user attempts to install a filter, only properly-keyed filters
can be installed
into the holder/valve-head.
The following discussion describes the preferred embodiments shown in the
Figures, plus comments on some variations. One of average skill may envision
alternative
embodiments besides those mentioned that are within the scope of the
invention.
CA 02695299 2010-03-03
Keyed Filter, Figures 1-11
Referring to Figures 1-11, there is shown one, but not the only, embodiment of
the
invented key system for a filter and a filter holder (herein also called a
filter "head"). The
preferred filter head 10 and cooperating filter 20 are illustrated separately
in Figures 1 and
2, wherein one may see the "lock" recess structure included in the head 10 and
the "key"
protrusion structure included on the filter 20. One may understand from this
Description
that embodiments of the invention also include a mirror-image arrangement,
wherein
"key" protrusions are on the head 10 and cooperating "lock" recesses are on
the filter 20.
Or, a combination of the two arrangements may be used, wherein one or more
sets of
"lock" recesses are on the head and cooperating "key" protrusions are on the
filter, plus
one or more sets of protrusions on the head and cooperating recesses on the
filter.
The preferred embodiment of filter head may be of the general type illustrated
by
the systems in U.S. Patents No. 4,857,189 and Design 356,625, and, once the
disclosure of
the present invention is viewed, one of skill in the art will be able to
construct a filter head
that will be operative and operatively connect with a cooperating filter.
Filters
conventionally built for such filter head systems are shown in U.S. Patents
No. 4,857,189
and Design 356,625, for example.
In the preferred embodiment, the recess structure 22 in the head comprises an
axial
portion and a circumferential portion. The axial portion preferably comprises
a plurality of
axial recesses 24 in the inner, lower surface of the head 10, which might be
called the
"inside rim" of the filter head near the outer edge 23 of the head. The axial
recesses 24 are
separated by partition ridges 28, which are spaced apart on, and protrude
radially inward
from, the surfaces of the lock recesses 24. In combination with adjacent
ridges 26',
partition ridges 28 define the circumferential length of each axial recess 24.
The
circumferential portion 40 of the recess structure 22 comprises a
circumferentially-
extending slot or other recess, generally but not necessarily exactly,
transverse to the axis
of the head 10 and the filter 10 and located "above" ridges 26.
In the preferred molded structure of the interior of the head 10, ridges 26
and
partition ridges 28 serve as obstacles for any improperly keyed filter to be
inserted into the
filter head 10, and also, once the filter has been rotated on its axis, as
obstacles for filter
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removal. Once the filter is inserted axially past the partition ridges 28, by
the key
protrusions 34 sliding into the head through the axial recesses 24, the filter
may then be
rotated so that the key protrusions 34 (preferably multiple key protrusions
34) slide
circumferentially into the circumferential recess portion 40. The filter is
preferably
operable only once the filter has been inserted axially to the full extent
desired and the
filter has been rotated to lock the filter into head, and preferably only a
properly-keyed
filter can be installed.
The ridges 26 illustrated in Figure 1 are one example of many embodiments that
help to define the lower boundary of the circumferential recess portion 40,
and that lock
the filter from axial movement by retaining the key protrusions 34 in the
circumferential
recess portion 40. The plurality of closely-spaced ridges 26 are preferred
because they
provide a barrier to axial filter movement while minimizing the amount of
plastic needed
in molding of the head 10. Alternatively, each set of ridges 26 may have the
space
between the ridges 26 filled in, that is, replaced with a solid, continuous
structure that
protrudes, relative to the circumferential recess portion 40, inward toward
the central axis
of the head. Or, ridges 26 may be reduced in number or only occupy part of the
space
below the lock portion 40. In other words, the structure located "below" the
circumferential recess portion 40 near outer edge 23, and serving as an
obstacle to axial
movement, may be of various shapes, size, and locations as long as one or more
key
protrusions 34 on the filter is blocked by said structure. At a minimum,
therefore, there
should be inwardly-protruding structure below at least one or more key
protrusions 34
when one or more of the key protrusions 34 in positioned in the
circumferential recess
portion 40. Not all key protrusions need to be received/engaged in the
circumferential
recess portion, when the filter is "fully rotationally engaged," which means
the point at
which the filter is rotated to the fullest extent allowed by a rotation stop
in the
circumferential recess portion. To limit rotation of the filter, specifically,
to limit
circumferential movement of the key protrusions 34 in the circumferential
recess portion
40, a rotation stop surface 41 is provided by extensions of ridges 26 or other
structure.
Thus, circumferential recess portions of various lengths will have a rotation
stop surface,
even in the case of closely adjacent sets of lock recesses to prevent rotation
of the key
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protrusions past the circumferential recess portion and into the space above
the adjacent
set of axial recesses. The rotation stop surface preferably comprises the
circumferential
recess portion having a closed end or other abutment surface against which
abuts one of
the key protrusions when the filter is fully-rotated.
In the head 10 of Figures 1- 11, each of the recess structures has three axial
recesses
24 that are of different circumferential lengths, specifically, three recesses
of long, medium
and short length relative to each other. Other numbers and lengths/sizes may
be used, for
example, two or four recesses, or more, and one long and two short recesses,
or two long
and two short recesses, or a plurality of recesses all of differing lengths.
As in a lock and
key system for a door latch, many different combinations may be devised, and
are included
in the invention.
While there may be only one recess structure and one cooperating protrusion
structure, there are preferably more. Preferably, there is a plurality of
recess structures in
the filter head, and most preferably, there are two recesses structures (each
with axial
recess portions and a circumferential recess portion) that are diametrically
opposing each
other, as in Figures 1- 11. Preferably, therefore, the cooperating protrusion
structures
number the same as the recess structures, for example, two protrusions
structures
diametrically opposing each other on the filter.
Referring to Figures 3 and 4, one may see that the circumferential distances
of
greatest interest may be described as:
D, which is the circumferential length of the preferred axial recesses 24 and
the
circumferential length of the preferred cooperating protrusions structure 33
(made
up of multiple key protrusions 34);
B, which is the distance between the axial recesses 24 or between the
cooperating
key protrusions 34, wherein B includes the circumferential recess portion 40
of the
recess structure, wherein circumferential recess portion 40 may exist in the
range of
only a small part of distance B to substantially all of distance B except for
a small
rotation stop surface; and
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CA 02695299 2010-03-03
T, which is the total distance between the "start" of one set of axial
recesses 24 or
cooperating key protrusions 34 and the "start" of the adjacent set.
The absolute lengths of D, T, and B, and the lengths of D, T, and B relative
to each
other, may be varied. In the example of two recess structures (and therefore
the two
cooperating protrusion structures) each of the two sets may have different D
lengths.
In Figure 1, the first set of axial recesses 24 is clearly shown, and the
second set of
axial recesses, located about 180 degrees (distance T) from the first set, is
located at
position 25 on Figure 1. Thus, these two sets of axial recesses shown in the
Figures are
generally diametrically opposed, with the axial recesses 24 taking up 70
degrees (distance
D) and the circumferential recess portion 40 taking up about 70 degrees of the
110 degrees
(distance B) which extends between the two sets axial recesses 24. This
results in each
part of a recess structure 22 being 180 degrees away from the corresponding
part of the
other recess structure, and the two recess structures 22 being spaced evenly
around the
entire 360 degrees.
Preferably, the circumferential recess portion is as long as the entire length
of the
key protrusions, however, this is not always necessarily the case. The recess
structures 22
may be closer together (distance T) than 180 degrees, for example, with two
identically-
constructed or differently-constructed recess structures spaced 90 degrees
(distance T), for
example, in which case the lock recesses 24 might take up about 70 degrees of
that 90
degrees, leaving up to slightly less than 20 degrees (20 degrees minus enough
distance for
a small rotation stop surface) for the circumferential recess portion 40. This
would be an
example of an embodiment in which the circumferential recess portion is not as
circumferentially long as the circumferential length of the axial recess
portion. In such an
embodiment, only some of the key protrusions 34 (or part of a key protrusion),
would slide
circumferentially into ("be engaged in") the circumferential recess portion,
while some of
the key protrusions 34 (or part of a key protrusion) would not be received
("not engaged")
in the circumferential recess portion; this would be sufficient, although not
preferred, for
locking the filter in the head. In the case of the circumferential recess
portion being
shorter in length than the total length of the key protrusions and a key
protrusion(s) being
unengaged in the circumferential recess portion, one or more key protrusions
or a part of a
14
CA 02695299 2010-03-03
key protrusion, in effect, would hang over the axial recesses. In such a case,
the
unengaged key protrusion(s) might still be supported by one or more ridges 28.
As long as
some of the key protrusion(s) is/are engaged in the circumferential recess
portion, the filter
is engaged in the head, until the filter is rotated in reverse to an unlock
point, that is, to a
point where all necessary key protrusions slide can slide down through the
axial recesses.
Another example would be to have the two recess structures within only a
portion
of the circumference of the head 10, for example, within 180 degrees (for two
recess
structures where T = 90 degree) or 270 degrees (for two recess structures
where T = 135
degrees).
Preferably, the axial recesses of each recess structure are all contained
within 90
degrees or less (distance D) or, more preferably, within 70 degrees or less
(distance D).
Especially preferred embodiments have axial recesses (and likewise cooperating
key
protrusions) from a maximum of 70 degrees down to a minimum of 30 degrees on
the
circumference of the inner rim of the filter head. Less than 30 is also
possible, but is less
preferred. In Figure 1, the first set of axial recesses is within about 70
degrees ( "D" in
Figures 3 and 4).
Distance B may be within a wide range of lengths. For example, preferably, but
not
necessarily, B may be up to about 150 degrees (B equals 150 degrees when, for
example,
D is 30 degrees and T is 180 degrees) and down to about 30 degrees (B equals
30 degrees
when, for example, D is 70 degrees and T is 100 degrees; or B equals 30
degrees when, for
example, D is 30 degrees and T is 60 degrees). Other B distances may be
outside the range
of 30 - 150 degrees, particularly when B is very large (greater than 150
degrees) because D
is very small (less than 30 degrees) or when B is very small (less than 30
degrees) because
the two sets of recesses are very close together. In the case where B is very
small, one
would expect many of such embodiments to have circumferential recess portion
only a
fraction of the length of D, that is, only part of the key protrusions would
fit into the
circumferential recess portion before hitting a rotation stop surface in the
circumferential
recess portion.
Also shown in Figure 4 are circumferential lengths 134, 134', 134" of the key
protrusions (which preferably equate to very slightly less than the
circumferential lengths
CA 02695299 2010-03-03
of the matching axial recesses 24), and the circumferential lengths of spaces
(notches/indents) 128, 128' between the protrusions (which preferably equate
to very
slightly more than the circumferential lengths of the matching ridges 28).
Preferably, but
not necessarily, lengths 134, 134', 134" (which are not necessarily equal to
each other) are
much greater than the lengths of the spaces 128, 128' (which are not
necessarily equal to
each other). For example, preferably the lengths of said protrusion are at
least twice that
of said spaces, and, more preferably three times or more.
Figure 2 illustrates a filter 20 that is keyed to cooperate with the head 10
of Figure
1. The central neck 29 of the filter contains the connections/seals for fluid
communication
between the filter and the head. Radially-spaced from the neck 29 is shoulder
32. On
shoulder 32 are two protrusion structures 33 each comprising a set of key
protrusions 34
(that is, comprising multiple key protrusions 34), generally diametrically
opposed to match
the locations of the two recess structures (each comprising multiple axial
recesses and one
circumferential recess portion) in the filter head. Each set of key
protrusions preferably
includes the same number, size, and arrangement of key protrusions 34 as the
filter head
has axial recesses, so that the "key" of the filter fits into the "lock" of
the filter head, in
effect. The preferred key protrusions curve on the radius of the shoulder of
the filter and
have a curved outer surface from top to bottom. To match the axial recesses,
each set of
key protrusions in the embodiment of Figure 2 include three "end-to-end"
protrusions,
sized large, medium, and small, in circumferential lengths generally equal to
the axial
recesses in Figure 1. In the embodiment portrayed in Figures 1 and 2, the key
protrusions
34 protrude radially outward from a portion of the shoulder structure that is
larger in
diameter than the central neck 29 but that is smaller than the largest
diameter of the filter
(thus, an intermediate diameter). However, it may be noted that filters of
many shapes,
diameters, and structures, may be provided with embodiments of the invented
key system,
and the key protrusions may protrude out from other locations and other
diameters on the
filter. For example, the key protrusions may less-preferably protrude out from
the largest
diameter of the filter, from a shoulder that represents an intermediate
diameter, or from
other portions of the top end of the filter, such as the cap or top end
structure that
substantially forms/closes the top end of the filter and forms the transition
between the
16
CA 02695299 2010-03-03
axial sidewall of the housing and the central neck. An important consideration
in the
selection of key protrusion location is the size and spacing of the key
protrusions, and how
the filter head will receive and cooperate said key protrusions, especially in
view of the
preferred feature wherein more than one key protrusion slides
circumferentially into a
single circumferential recess portion (also called "circumferential lock
portion") in the
head. It is preferred that the key protrusions are located on a shoulder
distanced from the
central neck, or that they extend radially outward a significant distance from
the central
neck to be nearer to the largest-diameter portion of the filter housing than
to the neck.
This allows more room for larger multiple key protrusions to be located within
preferably
70 - 90 degrees on the filter, and so that there is sufficient space inside
the filter head so
that said multiple key protrusions may be slide circumferentially into their
single
circumferential recess/slot after sliding axially into the filter head.
In use, when the filter 20 is inserted into the head 10, the key protrusions
34 must be
matched up with the axial recesses 24 so that the filter can be moved axially
into the filter
head. The key protrusions 34 slide into their corresponding axial recesses 24
(which are
the first portion of the recess system) and the inner rim of the head extends
down over the
top of the filter. Then, the filter is rotated on its axis relative to the
head to lock the filter
into the head. This is made possible by the second portion of the recess
structure of the
filter head, the circumferential recess portion 40, which extends continuously
above the
ridges 26 for preferably, but not necessarily, a distance equal to or slightly
greater than the
total length of one set of key protrusions. When the filter is inserted and
rotated, the key
protrusions 34 slide circumferentially into the circumferential recess portion
40 of the
recess structure until being fully rotationally engaged (rotationally limited
by the stop
surface at the end of the circumferential recess portion) and are "locked"
above the ridges
26 by virtue that they cannot be pulled axially downward past the ridges 26.
When the
filter is fully inserted and locked into the head, as shown in Figure 5 and 6,
one may see
the key protrusions 34 through the apertures 42 in the filter head wall. To
remove the
filter, the filter is rotated on its axis in the opposite direction to move
the key protrusions
34 from above the ridges 26 to again align with axial recesses 24, so that the
key
protrusions may slide axially down and out of the head through the axial
recesses.
17
CA 02695299 2010-03-03
Friction, or a biasing means if desired, or other locking means, may be used
to bias the
filter from sliding in reverse out of the head until the user purposely
removes the filter.
With the invented key system for filter and head, it is economical and
convenient to
mold sets of filters and heads with matching key system structure, and to mold
many
different sets with different key system structure. For example, for one
application, a key
system structure may include four lock recesses and four key protrusions in
each of two
sets on the filter and on the head, and the recesses and protrusions may be,
for example,
two short alternating with two long. For another application, a key system
structure may
include three recesses and three protrusions, all of which are long. Filters
with the three-
recess and protrusion key system would not fit into heads with the four-recess
and
protrusion key system, so there would be no chance of mixing-up the filters.
Keyed Filter Flanges, Figures 12 - 44
Figures 12 - 44 illustrate alternative embodiments of key protrusions
extending
from the top end of the filter at a location intermediate between the outer-
most diameter
(largest-diameter portion) of the top end and the central neck. The key
protrusions may be
part of a generally radial plate(s)/flange(s) that is/are connected or
integral with the upper
radial surface of the cap of the filter, wherein the generally radial
plate(s)/flange(s) may be
said to extend up and outward from the upper radial surface of the cap. In the
embodiments portrayed, the plate(s)/flange(s) also are connected to the outer
surface of the
central neck, but extend a significant distance away from the central neck so
that their
outer edges are located nearer to the outer-most diameter of the filter top
end than to the
neck. The preferred generally radial plates/flanges protrude out from
preferably two sides
of the base of the neck, wherein these "right and left" (or first and second)
plates/flanges
may be connected by narrow plate/flange structure that extends "in front of'
and "behind"
the neck. Thus, the two plates/flanges may be two separate plates/flanges or
may be
considered portions of a single plate/flange that surrounds the neck but that
protrudes
farther to the right and left than to the front and rear.
Referring specifically to Figures 12 - 18, elongated filter 100 comprises a
housing
containing filter media (not shown), wherein the housing comprises a
cylindrical axial
18
CA 02695299 2010-03-03
sidewall 102, a largest-diameter shoulder 104, an upper radial wall 106, and a
central neck
108 that includes fluid inlet and outlet ports/passages 109.
Between the upper radial wall 106 and the neck 108 is a flange structure 110
that is
keyed to mate with a cooperating holder 400. The preferred flange structure
110 sweeps
upward from the radial wall 106 and outward in two directions (called herein,
for
convenience, the right and left) away from the central neck to form two flange
portions or
"wings" 120, 130 that reach nearly out to the largest-diameter shoulder 104 of
the filter.
Preferably, the wings 120, 130 reach more than 50 percent of the way toward
the largest
diameter shoulder 104 from the outer surface of the central neck, and, more
preferably, 75
- 95 percent of the way, as portrayed to best advantage in the top views of
Figures 17, 24,
and 31. The junction of the wings with the upper radial wall 106 at the right
and left is a
curved junction 122, 132 about midway between the outer diameter of the
central neck and
the largest-diameter of the filter top end. The flange structure 110 extends
less far in the
forward and rearward directions, so that the junctions 124, 134 of the front
and rear
surfaces of the wings 120, 130 to the upper radial wall 106 are near the
central neck.
Thus, the flange structure 110 is a generally rectangular plate structure that
extends farther
to the right and left than to the front and rear of the filter. The two wings
120, 130 are
connected to each other by narrow bars 140 of flange structure along the front
and rear of
the central neck, but, alternatively, the flange structure may not include
these connecting
structures and the flange structure may extend out away from the central neck
without
having a portion that passes around the front and rear of the central neck.
The keying of the filter 100 comprises at least one of the wings 120, 130
having
multiple key protrusions, separated or defined by notches in the outer edge
121, 131 of the
wings. In the embodiment of Figures 12 - 18, both wings 120, 130 have key
protrusions,
that is, key protrusions 126 (separated by notches 128) on wing 120, and key
protrusions
136 (separated by notch 138) on wing 130.
As will be understood after reading the detailed description of the invented
keying
system in the Summary of the Invention and portions of the Detailed
Description above,
these key protrusions (three key protrusions 126 in one protrusion structure,
wing 120, and
two key protrusions 136 in the other protrusion structure, wing 130) are
examples of many
19
CA 02695299 2010-03-03
different key protrusions numbers, circumferential lengths, styles, and sizes
that may be
provided in the outer edges 121, 131 of the wings 120, 130. The key
protrusions of filter
100 may be called a "three plus two" key protrusion structure, or a "two plus
one" notch
structure, for example.
Figures 19 - 25 illustrate a filter 200 very similar to filter 100, but the
wings 220,
230 are keyed differently, specifically, in a "three plus three" key
protrusion structure (key
protrusions 226 and 236) or a "two plus two" notch structure. Figures 26 - 32
illustrate
yet another filter 300 of generally the same structure as filters 100 and 200,
except that
only one of the protrusions structures (wing 320) comprises multiple key
protrusions 326.
The other protrusion structure (wing 330) has no notches to subdivide the
protrusion
structure, and so is said not to have multiple key protrusions.
It will be understood from the above description of the invented key systems,
that
the notches need not be evenly spaced along the outer edges of the wings, and,
therefore,
the key protrusions of these embodiments may have different
arc/circumferential lengths
(so-called because the outer edges are curved). For example, for a three-key-
protrusion
set, one may be short and two may be relatively long, or one may be short, one
may be
medium, and one may be long. For a two protrusion set, for example, one may be
short
and one may be relatively long. The entire circumferential length of the outer
edge 121,
131 of the wings corresponds to preferably less than a 90 degree arc, and more
preferably
less than a 70 degree arc.
Figures 26 - 33 show the central neck in dashed lines to remind the reader
that
alternative neck structure may be provided and/or that fluid connection may be
made
without an upending central neck by providing alternative ports or passages in
the filter
upper end. Concentric ports/passages at the central axis of the filter are
preferred, however,
because they may mate with cooperating tubes/passages of the holder/head while
the filter
is installed by a method that includes axial insertion followed by rotation of
the filter on its
axis relative to the head.
A preferred holder 400, with liquid inlet and outlet conduits 409, is
portrayed in
Figures 33 - 44, alone and in combination with filter 100. The holder 400
comprises a
recess structure 420, 430 for each protrusion structures (each wing 120, 130)
on the filter
CA 02695299 2010-03-03
100. Each recess structure 420, 430 comprises at least one axial recess
portion and a
single circumferential recess portion. For wings that comprise multiple key
protrusions,
the respective recess structure comprises multiple axial recesses that
match/mate with the
key protrusions of that wing. One may note that, for wings that do not have
multiple key
protrusions (for example, see the non-notched wing 330 of the embodiment of
Figures 26
- 32) only one axial recess is required. The recess structures comprises axial
recesses 426,
436 that match the length and number of the key protrusions 126, 136, so that
said axial
recesses 426, 436 can receive the key protrusions during axial insertion of
the filter up into
the head, without the partition ridges 428, 429 blocking the key protrusions
126, 136.
Therefore, the filter 100 is inserted up into the holder 400, with the filter
positioned so that
the key protrusions 126, 136 slide up through axial recesses 426, 436 until
the key
protrusions 126, 136 pass the partition ridges 428, 429 to be above the ridges
428, 429. At
this point, the filter may be rotated on its axis, so that each set of key
protrusions (the set
on wing 120, and the set on wing 130) slides circumferentially in the
direction of rotation
into the circumferential recess portion 440, 450 of its respective recess
structure, said
recess portions 440, 450 being in mechanical connection and communication with
said
axial recesses 426, 436, respectively, for example, by means of the ends of
said recess
portions 440, 450 closest to said axial recesses 426, 436 being open to the
top ends of the
axial recesses.
Below and defining the lower edge of the circumferential recess portions 440,
450
are ledges 460, 462 with radially-protruding ridges 464; the substantially
continuous
ledges 460, 462 with spaced ridges 464 below the ledges 460, 462 are preferred
because
they provide a barrier to axial filter movement while minimizing the amount of
plastic
needed in molding of the head 400.
Circumferential recess portions 440, 450 may be open at their outer
perimeters,
rather than having a solid wall(s) at their outer perimeters/outer
extremities; the "outer
perimeter" of circumferential recess portion 440 is called-out as 470 in
Figure 41 and is
understood to be an aperture all the way through the wall of the holder. It is
the ledges
460, 462 below the received wings 120, 130 that block the filter from being
pulled out of
the holder (rather than any outside structure radially distanced out from the
received wings
21
CA 02695299 2010-03-03
120, 130). Therefore, as shown in Figure 38, because the recess portions 440,
450 are
open at part or all of their outer perimeters, the ledge 460, 462 of each
circumferential
recess portion 440, 450 is visible from outside the holder 400. A small
portion of the outer
perimeter of the recess portion 440, 450 may be closed, for example, in the
form of a bar
or reinforcing strut 455 that strengthens the holder in the vicinity of recess
portions 440,
450. A rotation stop surface 466 is provided, for each circumferential recess
portion 440,
450, to limit rotation of the key protrusions. The rotation stop surface may
be provided by
closing the end of each recess portion 440, 450 that is opposite the end near
the axial
recesses, and/or by providing various styles of abutment surface, for example,
an abutment
surface that is generally perpendicular to the surface of each ledge 460, 462.
Therefore, in a similar way as described above for the embodiment for Figures
1-
11, multiple of the key protrusions on a single wing slide circumferentially
into a single
(one) circumferential recess portion, rather than each key protrusion having
its own
circumferential recess, slot, or cammed ramp surface. Thus, in this
embodiment, at least
one of the circumferential recess portions will contain, when the filter is
installed, multiple
key protrusions.
Referring specifically to the top views of the holder and filter assembly in
Figures
36 and 37, Figure 36 shows the location of the flange structure 110 in dashed
lines when it
has been slid up through the axial recesses of the holder, prior to rotation.
Upon rotation,
the wings 120, 130 slide into their respective circumferential recesses
portions 440, 450,
which means that at least a plurality (and preferably all) of the multiple key
protrusions
126 of wing 120 slide into a single circumferential recess portion 440, and
that at least a
plurality (and preferably all) of the multiple key protrusions 136 of wing 130
slide into a
single circumferential recess portion 450. In other words, preferably all of
the keyed
protrusions of each set slide into their respective single circumferential
recess portion or
"respective slot."
Referring to Figures 39 - 43, there is shown to best advantage the recess
structures
420, 430 that comprise axial recesses 426, 436 (see Figure 39) and respective
circumferential recess portions 440 and 450 having ledges 460, 462 (see Figure
40). By
referring to the cross-sectional views in Figure 41- 43, one may understand
how axial
22
CA 02695299 2010-03-03
recesses 426, 436 allow the key protrusions 126, 136 of the wings 120, 130 to
pass beyond
the partition ridges 428, 429 (see Figure 42), and then, upon rotation of the
filter, the key
protrusions will slide over ledges 460, 462 of the circumferential recess
portions 440, 450
to be retained in the holder by said ledges 460, 462 (see Figure 43 where the
holder has
been rotated relative to the filter). Figure 44 is a top view of the entire
holder with the
filter shown in dashed lines inserted and locked into the holder as in Figure
43.
In view of the above disclosure, it may be noted that important, but not all
embodiments, of the invented keyed system may be described as a keyed system
for filters
and their holders, the keyed system comprising a filter and a cooperating
holder; wherein
the filter has a filter surface with a perimeter and at least one protrusion
structure on said
perimeter and the filter holder has a holder surface with a perimeter having
at least one
cooperating recess structure, wherein the locations of said at least one
protrusion structure
and said at least one recess structure are selectively locateable to different
circumferential
locations on said perimeters to prevent said filter from being installed in
any but its
cooperative holder, wherein the improvement in the keyed system is
characterized by: said
at least one cooperating recess structure including a first recess structure
comprising a
plurality of axial recess portions separated by ridges, and a single
circumferentially-
extending recess portion having an open end near, and in mechanical
communication with,
said axial recess portions; and wherein said filter top end comprises an axial
side wall, an
upper radial surface, a shoulder at a junction between said axial side wall
and said upper
radial surface, and central neck upending from said upper radial surface at a
longitudinal
axis of the filter; wherein said at least one protrusion structure includes a
first flange that
comprises a plurality of key protrusions that slide through a plurality of
said axial recess
portions of the first recess structure during axial insertion of the filter
into the holder and,
upon angular rotation of the filter in the holder, said plurality of key
protrusions of the first
flange are all received in said single circumferentially-extending recess
portion of the first
recess structure to lock the filter in said holder; and wherein said first
flange has an inner
end connected to said upper radial surface at or near said central neck, the
first flange
extends radially outward over, and spaced from, said upper radial surface, and
the first
flange has an outer end with an outer edge that comprises said plurality of
key protrusions,
23
CA 02695299 2010-03-03
said outer edge of the first flange being located at a distance from the
central neck. The
outer edge of the first flange may be located at a distance from the central
neck that is in
the range of 75 - 95 percent of the distance between said central neck and
said shoulder.
Said plurality of key protrusions of the first flange may be located within an
arc of 90
degrees or less on said outer edge of the flange. Said plurality of key
protrusions of the
first flange may be located within an arc of 70 degrees or less on said outer
edge of the
flange.
Said at least one protrusion structure of the filter may further comprises a
second
flange comprising a plurality of key protrusions and the at least one recess
structure further
comprises a second recess structure, wherein the locations of said second
flange and the
second recess structure are selectively locateable to different
circumferential locations on
said perimeters to prevent said filter from being installed in any but its
cooperative holder;
wherein the second recess structure comprises a plurality of axial recess
portions separated
by ridges, and the second recess structure further comprises a single
circumferentially-
extending recess portion having an open end near, and in mechanical
communication with,
the axial portions of the second recess structure; wherein said plurality of
key protrusions
of the second flange structure slide through a plurality of said axial recess
portions of the
second recess structure during axial insertion of the filter into the holder,
and, upon
angular rotation of the filter in the holder, said plurality of key
protrusions of said second
flange are received in the single circumferentially-extending recess portion
of the second
recess structure; and wherein said second flange has an inner end connected to
said upper
radial surface at or near said central neck, the second flange extends
radially outward over,
and spaced from, said upper radial surface in a direction generally opposite
from said first
flange, and the second flange has an outer end with an outer edge that
comprises said
plurality of key protrusions, said outer edge of the second flange being
located at a
distance from the central neck that is in the range of 75 - 95 percent of the
distance
between said central neck and said shoulder. Said first flange and said second
flange may
extend radially away from said central neck 180 degrees from each other. Said
plurality of
key protrusions of the first flange may be located within an arc of 90 degrees
or less on
said outer edge of the first flange, and said plurality of key protrusions of
said second
24
CA 02695299 2010-03-03
flange may be within an arc of 90 degrees or less on said outer edge of the
second flange
generally diametrically opposite of said first flange. Said plurality of key
protrusions of
the first flange may be located within an arc of 70 degrees or less on said
outer edge of the
first flange, and said plurality of key protrusions of said second flange may
be within an
arc of 70 degrees or less on said outer edge of the second flange generally
diametrically
opposite of said first flange.
Said plurality of key protrusions of said first flange may have a
circumferential
length, and the single circumferentially-extending recess portion of the first
recess
structure may have a circumferencial length at least as long as the
circumferential length
of the plurality of key protrusions of the first flange. Said plurality of key
protrusions of
said second flange may have s a circumferential length and the single
circumferentially-
extending recess portion of the second recess structure may have a
circumferential length
at least as long as the circumferential length of the plurality of key
protrusions of the
second flange. Said single circumferentially-extending recess portion of the
first recess
structure further may have a rotational stop adapted to limit rotation of the
filter at an end
opposite of said open end. Also, said single circumferentially-extending
recess portion of
the second recess structure may have a second rotational stop adapted to limit
rotation of
the filter.
As described above for the embodiment of Figures 1 - 11, not all of the key
protrusions of a given protrusion structure need to be received in the
circumferentially-
extending recess portion of the respective recess structure in the holder. For
example,
multiple key protrusions of the first flange may slide into said
circumferential recess
portion, but there may be additional key protrusions on the first flange that
do not fit into
the circumferential recess portion. It is preferred that most or all fit into
the
circumferential recess portion, but there may be additional key protrusions
that slide
through their own respective axial recess portions but do not enter the
circumferential
recess portion and therefore, overhang the axial recess portions. In other
words, for any
given cooperating protrusion structure and recess structure, the keyed
protrusion structure
(or keyed filter surface) may further comprise one or more additional key
protrusions, and
said recess structure (or keyed holder surface) may further comprise one or
more additional
CA 02695299 2010-03-03
axial recess portions in mechanical communication with said single
circumferentially-
extending recess portion, wherein said one or more additional key protrusions
slide
through said additional axial recess portions during said axial insertion of
the filter into the
holder, and wherein said circumferential recess portion is of such a
circumferential length
that, upon angular rotation of the filter in the holder, at least some of said
additional key
protrusions are not received in said circumferential recess portion.
Although this invention has been described above with reference to particular
means, materials and embodiments, it is to be understood that the invention is
not limited
to these disclosed particulars, but extends instead to all equivalents within
the broad scope
of the following claims.
26
