Rigid filter for capsules suitable for extracting beverages, particularly espresso coffee

0001The present invention relates to a rigid filter for capsules which are suitable for extracting beverages, particularly espresso coffee.

0002In the last few years, use of disposable capsules or cartridges containing an edible powdered substance from which a beverage can be extracted by using hot pressurized water has considerably increased.

0003In particular, capsules containing a dose of roasted ground coffee for brewing the so-called Italian "espresso" coffee have become quite popular, because the beverage obtained by such capsules is very close in terms of taste and appearance to the espresso obtained by using conventional espresso-type coffee machines normally used in bars and restaurants.

0004Among those capsules, <patcit id="pcit0001" dnum="WO2005092160A"><text>WO 2005/092160</text></patcit> and <patcit id="pcit0002" dnum="WO2005092162A"><text>WO 2005/092162</text></patcit> disclose a particular capsule which contains a substance in powder form, preferably roasted and ground coffee, the capsule being provided with an elastic septum which generates lasting crema and by means of which it is possible to extract a beverage with improved physical and organoleptic characteristics.

0005The known elastic septum is fixed downstream of the dose of ground coffee and a filter sheet made of paper or tissue is interposed between the dose and the septum. The septum is basically an elastic membrane which has at least one through orifice or slit provided in a central region and which elastically opens when the pressure inside the capsules exceeds a certain threshold.

0006A drawback observed in known capsules is linked to the complexity in manufacturing the capsule. In particular, some operations which complicate the manufacturing process are linked to the proper installation of the paper or tissue filter within the capsule, which mainly causes gripping and handling problems because of the filter's flexibility.

0007Another drawback is due to the fact that capsules which contain ground coffee typically use paper filters in order to retain the solid fractions within the capsule and prevent them from being poured into the external cup. The choice of paper filters entails limitations in the design of the capsule, for example forcing the design of the bottom of the capsule to have no regions in which the filter paper might break under the pressure acting inside the capsule or due to surface unevenness or openings.

0008A filter in polypropylene was proposed in <patcit id="pcit0003" dnum="EP0309708A"><text>EP-A 0 309 708</text></patcit>. However this filter is characterized by frusto-conical openings and by corresponding nipples protruding towards the substance to be extracted. Therefore, this known rigid filter still suffers from manufacturing problems, because the correct orientation with respect to the powdered substance must be observed when the filter is installed within the capsule.

0009Aim of the present invention is to overcome the drawbacks of known capsules by providing a filter that allows a considerable reduction in the manufacturing times and costs of said capsule.

0010Within this aim, an object of the invention is to allow particularly quick and simple installation and fixing of such filter within the capsule.

0011Another object of the invention is to allow good filtering even in presence of surface ridges in the bottom of the capsule where the filter is laid.

0012This aim and these and other objects, which will become better apparent hereinafter, are achieved by a rigid filter for capsules suitable for extracting beverages, comprising a substantially flat body having a plurality of through filtering holes, which are sized so as to block the passage of solid particles and allow passage of brewed water or beverage, characterized in that the holes have a substantially symmetrical shape with respect to the middle plane of the flat body, so that the filter can be inserted into a capsule without taking care of the orientation of such holes with respect to the powdered substance within the capsule.

0013Further characteristics and advantages of the invention will become better apparent from the description of preferred but not exclusive embodiments thereof, illustrated by way of non-limiting examples in the accompanying drawings, wherein: <ul id="ul0001" list-style="none" compact="compact"><li><figref idref="f0001">Figure 1</figref> is an exploded perspective view of a capsule containing the filter according to the invention;</li><li><figref idref="f0002">Figure 2</figref> is a cross-sectional view of the capsule of <figref idref="f0001">figure 1</figref> in an unexploded condition;</li><li><figref idref="f0003">Figure 3</figref> is a plan view of the filter according to a first embodiment of the invention and used in the capsule of <figref idref="f0001">figures 1</figref> and <figref idref="f0002">2</figref>;</li><li><figref idref="f0003">Figure 4</figref> is a plan view of the filter according to a second embodiment of the invention;</li><li><figref idref="f0002">Figure 5</figref> is a cross-sectional view of the filter of <figref idref="f0003">figure 4</figref>, taken along line V-V;</li><li><figref idref="f0003">Figure 6</figref> is a plan view of the filter according to a third embodiment of the invention.</li></ul>

0014In the following description, identical reference numerals designate elements which are identical or have an equivalent technical function.

0015With reference to <figref idref="f0001">Figures 1</figref> and <figref idref="f0002">2</figref>, a capsule suitable to contain the filter according to the invention, generally designated by the reference numeral 1, is substantially cylindrical (but it can also be frustum-shaped or prism-like) and comprises a box-like body which is formed preferably by two portions, i.e. a cup-shaped portion 2 and an element 3 for closing the cup-shaped portion 2 in an upward region. The closure element 3 is provided with an input port 3a, which preferably but not necessarily protrudes and is closed and can be opened in a known manner by the beverage extraction machine by piercing in order to allow the inflow of hot water under pressure into the capsule. The cup 2 and the closure element 3 are welded together preferably by means of ultrasound or known similar techniques, as disclosed for instance in prior art documents <patcit id="pcit0004" dnum="WO2005092160A"><text>WO 2005/092160</text></patcit> and <patcit id="pcit0005" dnum="WO2005092162A"><text>WO 2005/092162</text></patcit>, which are herein incorporated by reference.

0016The box-like body 2, 3 contains a substance in powder form 4, preferably ground coffee, which is suitable to allow the extraction of a beverage, for example espresso coffee, by means of hot water under pressure. The substance in powder form 4 can be comprised between two filtering elements 5a and 5b, which are adapted to retain the solid fractions, for example the granular coffee residues, within the capsule 1.

0017At least one of such filtering elements, preferably the lower filtering element 5b, is provided according to the invention and is preferably made of molded plastics, such as polypropylene. The filter may also be made of metal or any other material which makes the filter substantially rigid. With the term "rigid" it is meant a substantially planar body which does not significantly buckle under typical pressures inside capsules for extracting beverages, e.g. under pressures of up to 10 bars.

0018The box-like body of the capsule has a base 6 provided with an output port 7 for the outflow of the extracted beverage. The base comprises preferably a plurality of ridges 61, which are adapted to define narrow channels 62 between the base and the lower filter 5b in order to convey the extracted beverage toward the output port 7. The channel are quite thin, preferably about 1mm wide or less.

0019The ridges 61 may be arc-shaped and concentrically displaced around the output port 7, so that the channels 62 are directed concentrically to one another and mutually radially connected, as in <patcit id="pcit0006" dnum="WO2005092160A"><text>WO 2005/092160</text></patcit> and <patcit id="pcit0007" dnum="WO2005092162A"><text>WO 2005/092162</text></patcit>.

0020The filter 5b can be simply laid onto the base 6 or can be attached at its peripheral region. Preferably, the ridges 61 support the filter 5b, so as to prevent the filter from buckling during the beverage extraction phase.

0021The output port 7, arranged preferably in a central region of the base 6 and surrounded by a rim 8, is substantially closed by an elastic crema forming septum 9 which can open under pressure.

0022The septum 9 comprises an elastic membrane made of elastomeric or rubber-like material, preferably a thermoplastic elastomer (TPE) such as SEBS (a styrene-ethylene-butylene-styrene block copolymer) or Laprene® (based on SEBS and polyolefins).

0023The elastic membrane can comprise a through orifice 10, which is adapted to keep closed the septum 9 and therefore the beverage output port 7 when the capsule 1 is not used and is adapted to allow the beverage to pass when the pressure inside the capsule exceeds a certain value, for example 6 bars, causing a deformation and therefore a widening of the orifice 10.

0024As an alternative to the through orifice 10, the elastic membrane can comprise a blind orifice (not shown in the figures), which can be opened by breaking when the pressure in the capsule reaches a certain threshold.

0025The elastic septum 9 can be co-molded together with the box-like body 2, 3 of the capsule 1, which is preferably made of polypropylene, so as to eliminate intermediate mechanical operations for fixing the septum 9 to the rim 8 of the output port 7.

0026As an alternative, the elastic membrane can be co-molded together with a rigid supporting ring (not shown in the figures), which is adapted to be interlocked in a protruding cylindrical rim of the output port 7.

0027The capsule 1 further comprises a safety lid 11, which is mounted on the box-like body at the base 6 so as to increase the axial dimension of the box-like body. More specifically, the lid 11 is fixed to the box-like body of the capsule so as to protrude from the base 6 substantially in the direction of the axis of symmetry of the capsule along the direction of the stream of water.

0028The lid 11 is preferably fixed mechanically to a peripheral rim 15 of the base 6, for example by snap action, so as to allow its quick fitting to the box-like body of the capsule 1.

0029The safety lid 11 is provided with a cylindrical shoulder 12 which is engaged on the septum 9 and is adapted to retain the septum 9 against the output port 7 provided in the base 6, so as to prevent the septum from being accidentally expelled from the capsule due to the high pressures reached during beverage extraction.

0030The shoulder 12 can have at least one passage 14 in order to allow the beverage to exit from the capsule 1 by passing through the safety lid 11. For this purpose, the lid 11 comprises at least one output opening 13.

0031The lid 11 may be provided with a second closed cylindrical wall 16, which surrounds the shoulder 12 and can be interlocked within a circular seat 17 which is defined on the base 6 around the output port 7. The walls 12 and 16 thus define a cylindrical ring in which the beverage that exits from the orifice 10 of the septum 9 flows before reaching the output opening 13 provided in the safety lid 11.

0032Reference is now made to the lower filter element 5b according to the invention and to be preferably used in the above capsule 1. Obviously, the person skilled in the art will understand that such filter can be used in any capsule containing powdered substances from which a beverage can be extracted by using water under pressure.

0033The filter 5b is adapted to retain the solid particles of the beverage extracted from the powdered substance 4 with the same effectiveness as filter paper. In particular, the filter 5b comprises a flat body 51 surrounded by a thicker rim 52 which protrudes to the same extent from both faces of the flat body 51. A plurality of through holes 53 is also provided in the flat body 51, which are sized so as to block the passage of solid particles and allow the passage of brewed water or beverage.

0034The holes 53 can be displaced according to any pattern throughout the flat body 51. For instance, the holes 53 can be displaced according to a grid-like pattern as in <figref idref="f0003">Figure 3</figref> or along concentric circumferences as in <figref idref="f0003">Figure 4</figref>. Advantageously, if the filter has to be laid onto a plurality of ridges which define channels for conveying the beverage towards the capsule outlet, it is preferred that the holes 53 be superimposed to such channels and not to the ridges, so as to prevent the holes from being clogged by the ridges and, accordingly, to improve both the homogeneity of the beverage fluxes and the filtering efficiency.

0035For instance, the holes 53 of filter 5b of <figref idref="f0003">Figure 4</figref> are mutually concentrically arranged so as to be aligned with the concentric and radial channels 62 of capsule 1.

0036The holes 53 have a symmetrical shape with respect to the middle plane F of the flat body 51, so that the filter can be inserted into a capsule without taking care of the orientation of such holes with respect to the powdered substance within the capsule.

0037In particular, the diameter of each hole 53 in a middle region 54 thereof is narrower than the diameter of the hole 53 in the face regions 55 of the flat body 51, so that the cross-section of each hole 53 symmetrically diverges from the middle region 54 towards the face regions 55. The double-frustum shape of the holes 53 gives the filter a better sturdiness than a cylindrical shape and is also useful during molding of the filter 5b, in particular when the mold has to be opened and the filter removed.

0038The divergence angle from the middle region 54 to any face region 55 is preferably from 1° through 20° or 30°, more preferably about 10°. The diameter of each middle region 54 is preferably from 0.1mm to 1.0mm, more preferably from 0.2mm through 0.4mm and even more preferably from 0.25mm through 0.35mm.

0039In order to further increase the filtering efficiency, the above holes can be arranged in a staggered configuration 53a-53b, as in <figref idref="f0003">Figure 6</figref>, along patterns 58 (e.g. concentric circular patterns) to be placed above the conveying channels on the bottom of the capsule, such as channels 62. In this way, the density of holes along the patterns, and above the conveying channels, is substantially doubled with respect, for instance, to the filter of <figref idref="f0003">Figure 4</figref>.

0040The flat body 51 of the filter 5b can be provided with a substantially circular central region 56 having no holes. Such "full" central region 56 is particularly suitable for capsules containing an elastic septum for generating crema, such as the capsule 1 of <figref idref="f0001">figures 1</figref> and <figref idref="f0002">2</figref>, because it avoids the high pressurized brewed water to directly hit the septum 9.

0041Moreover, the absence of holes in the central region 56 improves the filtering action of filter 5b. In fact, the filter 5b may buckle during the beverage extraction phase because of the presence of an open area below the filter's central region, i.e. the output port 7. If holes were present in the central region 56, such holes would widen, thus worsening the filtering action.

0042For this reason, the diameter of the full central region 56 of the filter 5b is chosen to be substantially equal to the diameter of the outlet port 7. The person skilled in the art can appreciate that the filter 5b with a region devoid of any through holes can be used in any capsules for extracting beverages which comprise a quite large open area where the filter could buckle.

0043The filter 5b may also comprise an undercut 57 around the inner periphery of the rim 52, which is useful during molding.

0044In fact, the filter according to the invention, which is preferably manufactured using two symmetrical molds having respective frustum-shaped pins facing one another so as to define the holes 53, is held at the undercut 56 when it has to be expelled.

0045It has been found that the invention fully achieves the intended aim, since it allows to considerably simplify the assembling operation of capsules for making beverages. Although the invention has been conceived in particular for capsules suitable for preparing espresso coffee, it can in any case be used more generally for capsules which contain edible substances in general adapted to produce a beverage by percolation or to filter holders to be used in beverage or espresso coffee extraction machines.

0046The capsule and the filter thus conceived are susceptible of numerous modifications and variations, all of which are within the scope of the appended claims. All the details may further be replaced with other technically equivalent elements.

0047In practice, the materials used, as well as the dimensions, may be any according to requirements and to the state of the art.

0048Where technical features mentioned in any claim are followed by reference signs, those reference signs have been included for the sole purpose of increasing the intelligibility of the claims and accordingly, such reference signs do not have any limiting effect on the interpretation of each element identified by way of example by such reference signs.