Note : Les descriptions sont présentées dans la langue officielle dans laquelle elles ont été soumises.
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FILTERING ELEMENT FOR USE IN A FILTERING DEVICE
The present invention relates to a filter element
for use in a filter device.
More particularly, the invention relates to a filter
element provided with a central opening and designed to
be assembled with an element of the same type so as to
form a filter. The filter is suitable for being
associated with other filters, thereby constituting a
filter block for placing inside a case to make a filter
cartridge.
In general, each filter element has two faces, one
inside and the other outside the filter, and an inner rim
defining the outline of the central opening and a
peripheral outer rim with a screen mounted between the
rims parallel to said inside and outside faces. Each
face of the filter element also has radial ribs extending
in register between the inner and outer rims to form
angular sectors on the inside and outside faces.
Furthermore, each rib on the inside face of one of
the elements comes into contact with a facing rib on the
inside face of the other element so as to define cells
which are fed firstly via admission passages formed
through the inner rim in each sector of the outside face
of each element and opening out to the outside, and
secondly via delivery passages formed through the outer
rim of each sector of the inside face of each element,
each delivery passage of one of the elements being placed
in register with a passage of the other element so as to
form a delivery orifice.
These filter elements generally have a central
opening to form a feed duct which is thus disposed on the
axis of the filter, the fluid for filtering penetrating
into the filter via the admission passages formed through
the inner rim and leaving it via the delivery passages
formed through the outer rim, or vice versa.
The filter cartridges generally in use comprise at
least one filter plus a distributor for distributing the
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fluid to be filtered, the distributor being mounted
rotatably on the axis inside the duct. The distributor
is provided with a sectioning chamber for periodically
isolating at least two angular sectors disposed on the
outside face of each filter element, and communicating at
this particular moment solely with the two sectors by
means of passages made through the inner rims of said
sectors.
In a variant embodiment, the filter device further
comprises a sealing and guiding sheath mounted coaxially
between the distributor and the filter. The sheath has a
plurality of orifices in its cylindrical wall so that
said orifices are situated facing admission passages of
at least one filter forming the filter block.
Thus, a portion of the fluid that has already been
filtered is introduced as a back flow via the delivery
orifices and then into the angular sectors that have been
isolated so as to enable their portions of the screen to
be cleaned by back-washing.
As a result, it must be observed that an isolated
sector is a sector which does not contribute to active
filtering of the fluid to be purified.
Since known filter elements generally possess eight
angular sectors per inside and outside face, it follows
that during successive closure at determined moments of
two sectors at a time, the filter capacity of the filter
is about 75%.
Furthermore, each angular sector of the filter
elements includes a radial frame extending between the
inner and outer rims, and concentric annular
reinforcement extending transversely as two consecutive
radial ribs. Thus, the filter capacity of the filter is
further decreased because of the screen being masked by
said reinforcement, which is contrary to the desired
objective.
Furthermore, known filter elements are made of metal
and more generally of aluminum, thus giving rise to the
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presence of swarf between the screen and the radial ribs,
the inner and outer rims, and also the radial and annular
reinforcement. A major drawback of having such swarf
present is that the mesh in a portion of the screen can
become blocked, thereby likewise reducing filter
capacity.
Furthermore, said swarf is liable to become detached
and thus to be conveyed in the supposedly purified fluid,
and that can have particularly harmful effects on the
mechanical members situated downstream from the filters.
Furthermore, the screens used with known filter
elements are themselves made of metal and usually of
stainless steel, which limits the mesh size, and
consequently limits the fineness of filtering.
Known filter elements are relatively heavy, and
manufacture thereof by being overmolded on the screen
requires high temperatures of the order of 800°C, which
gives rise to large amounts of energy expenditure and
thus to a relatively high cost price. Finally, the
structure of such elements does not lend itself to making
elements that are not plane, for example elements that
are conical.
Consequently, an object of the present invention is
to propose a filter element enabling the above technical
problems to be solved.
The invention achieves this object by the fact that
each inside face and each outside face comprises at least
sixteen angular sectors, each sector being formed by a
free portion of screen, and in that the ratio of the free
filter area of the screen over the total area of the
element lies in the range 55% to 68%.
According to another characteristic, each delivery
passage includes a stiffening stud whose top end is in
contact with the stiffening stud of the other element.
According to yet another characteristic, each inside
face and each outside face comprises at least four facing
ribs that are diametrically opposite in pairs, each of
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which ribs has a bulge that is at least partially
cylindrical and that is secured to the outer rim.
According to yet another characteristic, the filter
element is made of a thermoplastic material such as
polyamide.
According to another characteristic, the screen is
made of a material such as polyamide or polyester with a
mean mesh size of less than 20 Vim.
According to yet another characteristic, the screen
is made of stainless steel.
According to another characteristic, the filter
element is in the form of a disk.
In another variant, the filter element is conical in
shape.
while the screen is being back-washed, the filter
element of the invention thus makes it possible to take a
small number of angular sectors out of service at a time.
In other words, by adopting the dispositions of the
invention it is possible in a given amount of space to
provide a filter that has better filtering efficiency
than before, i.e. a filter capable of purifying or
processing a volume of fluid greater than the volume
processed by prior filter elements.
It should also be observed that this increase in
filter efficiency is further improved by the fact that
the surfaces of the screens situated between two
consecutive, radial ribs do not have any radial or annular
reinforcement.
The invention will be better understood and
secondary characteristics and advantages thereof will
appear on reading the following description and the
accompanying drawings, in which:
Figure 1 is a front view of the inside face of the
filter element of the invention;
~ Figure 2 is a front view of the outside face of
the filter element; and
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Figure 3 is a section view on line III-III of
Figure 1 showing two filters assembled one against the
other, each filter being made up of two filter elements.
A filter element 1 of the invention is shown in
5 Figures 1 and 2, which figures show respectively the
inside face 2 and the outside face 3 of said filter
element 1.
Thus, the filter element 1 which is in the form of a
disk in this embodiment is defined axially by its two
transverse faces, respectively its inside face 2 and its
outside face 3.
The filter element 1 is also defined radially by a
peripheral outer rim 4 and by a central opening 16, the
outline of the opening being defined by an inner rim 5
against which a rotary distributor of fluid to be
purified comes into sliding contact after the filter
element has been mounted in the filter block (not shown).
A screen 6 is mounted between the outside face 3 and
the inside face 2, and between the outer rim 4 and the
inner rim 5, in such a manner that the screen 6 is
parallel to the inside and outside faces 2 and 3.
The inside face 2 of the filter element 1 also has
radial ribs 72 that are regularly spaced apart
interconnecting the inner and outer rims 4 and 5 to form
angular sectors 21 in which the screen 6 presents a free
filter surface. This surface is thus not encumbered by
any reinforcement.
The outside face 3 also has radial ribs 73 that are
regularly spaced apart, extending in register with the
radial ribs 72 of the inside face 2 and thus
interconnecting the inner and outer rims 5 and 4 to form
angular sectors 31 in register with the angular sectors
21.
The total thickness of the radial ribs 72 and 73 in
register is equal to the complete thickness of the filter
element 1.
CORRECTED SHEET
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As can be seen in Figure 1, each angular sector 21
of the inside face 2 is provided on its outer rim 4 with
a delivery passage 10 for delivering purified fluid and
opening to the outside. Each delivery passage 10 also
has a stud 11 whose top end lies in the plane common to
the radial ribs 72 and the inner rim 5.
Similarly, in Figure 2, each angular sector 31 of
the outside face 3 is provided on its inner rim 5 with an
admission passage 9 for the fluid to be filtered.
It will be observed that there are as many angular
sectors 21 on the inside face 2 as there are angular
sectors 31 on the outside face 3, that these angular
sectors 21 and 31 are sixteen in number, and that they
are in register. Furthermore, at least four ribs 72 and
73, respectively on each of the inside face 2 and outside
face 3 are provided with partially cylindrical bulges 13
secured to the outer rim 4. Naturally, the ribs 72 and
73 possessing these bulges 13 are placed in register with
one another, and as can be seen from Figure l, two
adjacent ribs 72 are provided at their bulges 13 with
small tubular projections 19 having respective bores 20
passing therethrough.
When two identical filter elements 1 are assembled
inside face to inside face, each projection 19 is
designed to engage in a complementary bore 14 formed in
each bulge 13 of those two ribs 72 of the other filter
element 1 that do not have projections 19.
According to another advantageous characteristic,
the filter element 1 is made by molding a plastics
material such as polyamide, thereby making it more
flexible and avoiding the formation of any swarf over the
openings in the mesh of the screen 6 and making it
possible to improve the filter efficiency of the filter
element.
Furthermore, this material also makes it possible to
use screens made of polyamide or of polyester. Such
screens have a mean mesh size of less than 20 Vim, thereby
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making it possible to further improve the fineness of
filtering.
The operation of a filter block made up of two
filters each made up of two filter elements 1 is
explained below with reference to Figure 3.
Two filter elements 1 are assembled together with
their inside faces 2 placed facing each other, the
projections 19 of one element being inserted in the bores
14 of the other element with radial interference.
Each rib 72 of the inside face of one of the
elements comes into leakproof contact with a facing rib
72 on the inside face 2 of the other element so that
together with their screens 6 they define cells.
These cells are made leakproof at their inner rims
by the inner rims 5 of the filter elements 1 of a filter
being put into contact with each other, and thus each
delivery passage 10 of one of the elements is placed
facing a delivery passage 10 of the other element so that
together they form a delivery orifice 18.
Since the radial width of the delivery passages 18
is relatively large in the peripheral outer rim 4, the
stiffening studs 11 serve simultaneously to maintain
leakproof contact between the outer rims 4 of the two
outside faces 3 during juxtaposition of a plurality of
filters, and also to keep the section of each delivery
orifice 18 constant.
As shown in Figure 3, two filters are juxtaposed
firstly so as to associate the various angular sectors 21
and 31 and secondly so as to associate the bulges 13 of
these elements.
Thus, a fluid carrying impurities and to be
filtered, is engaged in the feed duct formed by the
central openings 16 of the various filter elements 1, and
is conveyed (arrows F) via the admission passages 9 to
the angular sectors 31 of the outside faces 3 of the
various filter elements 1.
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The fluid situated adjacent to the outside faces 3
can escape only by passing through the screen 6 since the
outer peripheral rims 4 of the outside faces 3 are in
leakproof contact, thereby preventing the fluid from
escaping directly.
The liquid therefore passes through the screen 6
where it has its impurities removed, and passes through
the cells 17 before leaving the filter via the delivery
orifices 18.
It should also be observed that since each filter
element has sixteen angular sectors per outside face 3
and per inside face 2, it follows that when pairs of
sectors 21 are obscured in succession at determined
moments by a sectioning chamber (not shown) of a
distributor of the fluid to be filtered and mounted to
rotate coaxially in the central opening of two filters,
the filter capacity of each filter is about 87.5%.
Naturally, the filter block shown in Figure 3 could
be constituted by a single filter made of two filter
elements 1, these filter elements having their outside
faces 3 disposed in a case (not shown) in such a manner
that the angular sectors 31 form two admission half-
chambers. Similarly, the filter element 1 can be
frustoconical in shape with an inside face 2 parallel to
the outside face 3.
The invention is not limited to the embodiments
described, but on the contrary covers all variants which
could be applied thereto without going beyond its ambit
or its spirit.
