Note : Les descriptions sont présentées dans la langue officielle dans laquelle elles ont été soumises.
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Title: An apparatus for preparin~ hot beversges
The present invention relates to ~n apparatus
for makin~ or preparing one or more consump~ion units
of a hot beverage, in particul~r coffee, comprising
a combination of a filter pan and a di~po~able filter
cartridge wi~h filters of fibrous web material fitting
therein, with the filter pan and the filter cartridge
being provided with coacting wall6 which ensure a
water seal between the said portions when the filter
cartridge has been introduced into the filter pan
and water i6 bein~ infused.
ln ~ ~imilar apparatus di~closed in U.S. patent
4,550,024 issued oct. 2g, 1985, the filter cartridges
and the filter pan are dimensioned in such a manner
that the ~eal is obtained by means of the c~pillary
forces occurring durin~ the infusion of water in the
space between the 6aid coacting wall~, thus achieving
that practically all of the water in~used particip~tes
in the extraction.
A major drawback of the known apparatus,
however, iB that for obtaining the de~ired capillary
ef~ect, a very clo~e toleranse Df the cartridge ~nd
~he filter p~n is required. On the other hand, it
is also known ~see French patent 1,347,~92 and German
Auslegeschrift 1,207,866) to effect the combin~tion
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in such a manner that the filter cartridge has to
be pushed into the filter pan with some force, however,
with the risk of damaging the top filter, as well
as of soiling one's fingers upon removal of the cartridge
after use.
It is an object of the present invention
to remove these drawbacks.
The apparatus is characterized to that end
in that the filter pan and the filter cartridge are
made of materials having different coefficients of
expansion and the portions coacting for sealing purposes
are dimensioned in such a manner that, on insertion
of the filter cartridge, it rests without clamping
or loosely in the cartridge and the water seal is
obtained by means of capillary forces and/or clamping
occur~ing during the infusion of the hot water owing
to the difference in coefficients of expansion.
It is thus achieved that the filter cartridge
can have a larger tolerance relative to the filter
pan than is the case in the known construction, for
either by the capillary effect or by clamping or both,
a water seal is obtained between the filter pan and
the cartridge. Besides, the cartridge will have a
loose position in the filter pan at ambient temperature,
so that said pan can be removed without manual contact.
Naturally, it is clear that the disposable
filter cartridge should be made of a material having
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a larger coefficient of expansion than that of the
filter pan material. An example of a suitable combination
is a filter pan of aluminum and a disposable filter
cartridge of polypropylene.
Another solution for the above tolerance
problem is that the filter cartridge and the filter
pan are conical and that the angle between said conical
side walls and the axis of the cartridge is 3-10,
preferably 6.
It has been experimentally found that when
the angle is too small, there is produced too large
a clamping force between the coacting conical walls,
so that the removal of the cartridge from the filter
pan gives problems.
It has also been found that when the angle
between the coacting, conical peripheral walls and
the vertical is too large, the cartridge will float
when water is being infused, which is .~ result of
leakage water penetrating between the two conical
walls. This results in a major part of the water not
participating in the extraction.
Some embodiments of the present invention
will now be described, by way of example, with reference
to the accompanying drawings, in which:
Fig. la is a part-sectional la-teral view
of a first embodimen~ at ambient temperature;
Fig. lb shows the apparatus shown in Fig.l
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but during u~e, i.e. after hot water has been infu6ed;
Figs. 2a and 2b are vie~ ~imilar to Fig.
1~ and lb, re~pectively snd ~howing a second embodiment
of the apparatu~ according to the pre~ent inven~ion;
Fig. 3 i6 a view similar to Figs. 1 and
2 of a third embodiment
Fig. 4 is a cro56-sectional view on the
line IV-IV of Fig. 3; and
: Figs. 5 and 6 show an embodiment of a coacting
filter pan and filter cartridge with, ~ucce~sively,
too ~mall an angle between the vertical and the conical
: wall~ (Fig. 5), and too large an angle between the
conical walls and the vertical (Fig. 6).
In Fig~. la, lb, 2a and 2b, the ssme parts
have identical reference numeral~.
A6 6hown in Fig. la, a filter pan 1 partly
shown accommodate6 a dispo~able filter cartridge 2.
Since such a filter pan and cartridge are known per
~e (see e.g. u.s. patent no. 4,550,024, mentioned
in ~he introduction), these will not be further de~cribed
hereinaf~er.
In the combination shown at the ambient
temperature in Fig. 1, there i~ a ~ h~ clearance
between cartridge and pan, a~ ~hown in the figure,
to the effect that the cartridge at smbient emperature
ha~ a loo~e, at lea~t non-cl~mping, po~ition in the
filter pan.
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Fig. lb shows the situation after the infusion
of hot water, so that the pan and cartridge are expanded,
on the understanding that as a result of the larger
coefficient of expansion of the cartridge, this now
rests clampingly in the filter pan.
Fig. 2a shows a combination of cartridge
and pan at ambient temperature with a considerably
larger clearance being present than in the assembly
shown in Fig. la. After infusion of hot water, in
the combination shown in Fig. 2a, the situation shown
in Fig. 2b will occur, wherein the clearance between
; the coacting walls of the filter pan and the cartridge
is substantially reduced. It is true that as a result,
there will be no clamping effect, but the clearance
between the said walls has become of such a nature
that a water seal is obtained through capillary forces.
The embodiment shown in Figs. 3 and 4 shows
a filter cartridge 3 received in a filter pan 4, wherein
the cartridge does not rest with an upper peripheral
edge on the pan, as in the embodiments shown in Figs.
1 and 2, but wherein the cartridge 3 with its inclined
side wall 5 (Fig. 3 left hand part) rests on the corre-
sponding side wall 6 of pan 4.
; The embodiment shown in Figs. 3 and 4 shows
`~ 25 a filter cartridge with a given unroundness: the cartridge
has such a position in the filter pan that this is
clampingly received in the pan in the places indicated
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at 7, while in the places indicated at 8, there is
provided such a space between the said edges that
this produces a capillary seal only after infusion
of hot water due to expansion in the above places.
In this manner, leakage will be prevented even in
the case of unroundness.
It will be clear that the admissable tolerances
of the dimensions of the filter pan and cartridge
depend on ~he materials of which the parts in question
are made. Naturallyl a great many different combinations
are possible: as an example was already mentioned
hereinbefore a filter pan of aluminum and a filter
cartridge of polypropylene. The combination may also
consist of e.g. a filter cartridge of polypropylene
(coefficient of expansion 0.0015 mm/mm/C) and a filter
pan of polystyrene (coefficient of expansion 0.0008 mm/mm/C)
or a filter cartridge of polypropylene or polystyrene
and a filter pan of poiycarbonate (coefficient of
expansion 0.0007 mm/mm/C).
In the embodiment shown in Figs. 5 and 6,
a filter pan 11 shown only partly is provided with
a conically bulged portion 12 wherein fits a filter
cartridge 13 having a conical peripheral wall 14.
The angle between the conical wall and the vertical
is indicated at ~.
~ hen in both cases the filter cartridge
is dropped either from a given height into the cavity
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of the filter pan, or is pressed into it at a given
force, this will arrive therein at a given force K
It will be clear that at a smaller angle, the chance
of further depression is larger than when angle ~ is
larger. This implies that at a smaller angle ~, the
force necessary for removal is likewise larger than
when angle ~ is larger.
Summarizing the above~ it can be stated
that in the first case (Fig. 5), a very large clamping
force is produced, which may result in problems on
removal of the filter cartridge from the filter pan.
In the second case (Fig. 6), the clamping force will
be insufficient to ensure that during the infusion
of water, no floating will occur as a result of the
penetratlon of water between the two conical walls.
It is observed in this respect that mostly
a slight pushing force will be sufficient, although
in the latter case the nominal force is insufficient
to seal existing high spots between pan and cartridge;
these forces will become sufficiently large when heating
takes place during use to ensure a proper sealing;
in cold condition, the nominal force will again be
sufficiently small to allow an easy removal of the
cartridge.
As already stated earlier, the materials
used will be of influence for the filter cartridge
or the filter pan.
