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

A rigid filter for capsules suitable for extracting beverages, comprising a 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, wherein 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.

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

BACKGROUND OF THE INVENTION

In 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.

In 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.

Among those capsules, WO 2005/092160 and WO 2005/092162 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.

The 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.

A 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.

Another 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.

A filter in polypropylene was proposed in EP-A 0 309 708. 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.

SUMMARY OF THE INVENTION

Aim 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.

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

Another 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.

This 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.

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

DESCRIPTION OF THE PREFERRED EMBODIMENTS

With reference toFIGS. 1 and 2, a capsule suitable to contain the filter according to the invention, generally designated by the reference numeral1, 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 portion2and an element3for closing the cup-shaped portion2in an upward region. The closure element3is provided with an input port3a, 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 cup2and the closure element3are welded together preferably by means of ultrasound or known similar techniques, as disclosed for instance in prior art documents WO 2005/092160 and WO 2005/092162, which are herein incorporated by reference.

The box-like body2,3contains a substance in powder form4, 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 form4can be comprised between two filtering elements5aand5b, which are adapted to retain the solid fractions, for example the granular coffee residues, within the capsule1.

At least one of such filtering elements, preferably the lower filtering element5b, 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.

The box-like body of the capsule has a base6provided with an output port7for the outflow of the extracted beverage. The base comprises preferably a plurality of ridges61, which are adapted to define narrow channels62between the base and the lower filter5bin order to convey the extracted beverage toward the output port7. The channel are quite thin, preferably about 1 mm wide or less.

The filter5bcan be simply laid onto the base6or can be attached at its peripheral region. Preferably, the ridges61support the filter5b, so as to prevent the filter from buckling during the beverage extraction phase.

The ridges61may be arc-shaped and concentrically displaced around the output port7, so that the channels62are directed concentrically to one another and mutually radially connected, as in WO 2005/092160 and WO 2005/092162.

The output port7, arranged preferably in a central region of the base6and surrounded by a rim8, is substantially closed by an elastic crema forming septum9which can open under pressure.

The septum9comprises 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).

The elastic membrane can comprise a through orifice10, which is adapted to keep closed the septum9and therefore the beverage output port7when the capsule1is 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 orifice10.

As an alternative to the through orifice10, 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.

The elastic septum9can be co-molded together with the box-like body2,3of the capsule1, which is preferably made of polypropylene, so as to eliminate intermediate mechanical operations for fixing the septum9to the rim8of the output port7.

As 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 port7.

The capsule1further comprises a safety lid11, which is mounted on the box-like body at the base6so as to increase the axial dimension of the box-like body. More specifically, the lid11is fixed to the box-like body of the capsule so as to protrude from the base6substantially in the direction of the axis of symmetry of the capsule along the direction of the stream of water.

The lid11is preferably fixed mechanically to a peripheral rim15of the base6, for example by snap action, so as to allow its quick fitting to the box-like body of the capsule1.

The safety lid11is provided with a cylindrical shoulder12which is engaged on the septum9and is adapted to retain the septum9against the output port7provided in the base6, so as to prevent the septum from being accidentally expelled from the capsule due to the high pressures reached during beverage extraction.

The shoulder12can have at least one passage14in order to allow the beverage to exit from the capsule1by passing through the safety lid11. For this purpose, the lid11comprises at least one output opening13.

The lid11may be provided with a second closed cylindrical wall16, which surrounds the shoulder12and can be interlocked within a circular seat17which is defined on the base6around the output port7. The walls12and16thus define a cylindrical ring in which the beverage that exits from the orifice10of the septum9flows before reaching the output opening13provided in the safety lid11.

Reference is now made to the lower filter element5baccording to the invention and to be preferably used in the above capsule1. 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.

The filter5bis adapted to retain the solid particles of the beverage extracted from the powdered substance4with the same effectiveness as filter paper. In particular, the filter5bcomprises a flat body51surrounded by a thicker rim52which protrudes to the same extent from both faces of the flat body51. A plurality of through holes53is also provided in the flat body51, which are sized so as to block the passage of solid particles and allow the passage of brewed water or beverage.

The holes53can be displaced according to any pattern throughout the flat body51. For instance, the holes53can be displaced according to a grid-like pattern as inFIG. 3or along concentric circumferences as inFIG. 4. 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 holes53be 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.

For instance, the holes53of filter5bofFIG. 4are mutually concentrically arranged so as to be aligned with the concentric and radial channels62of capsule1.

The holes53have a symmetrical shape with respect to the middle plane F of the flat body51, 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.

In particular, the diameter of each hole53in a middle region54thereof is narrower than the diameter of the hole53in the face regions55of the flat body51, so that the cross-section of each hole53symmetrically diverges from the middle region54towards the face regions55. The double-frustum shape of the holes53gives the filter a better sturdiness than a cylindrical shape and is also useful during molding of the filter5b, in particular when the mold has to be opened and the filter removed.

The divergence angle from the middle region54to any face region55is preferably from 1° through 20° or 30°, more preferably about 10°. The diameter of each middle region54is preferably from 0.1 mm to 1.0 mm, more preferably from 0.2 mm through 0.4 mm and even more preferably from 0.25 mm through 0.35 mm.

In order to further increase the filtering efficiency, the above holes can be arranged in a staggered configuration53a-53b, as inFIG. 6, along patterns58(e.g. concentric circular patterns) to be placed above the conveying channels on the bottom of the capsule, such as channels62. 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 ofFIG. 4.

The flat body51of the filter5bcan be provided with a substantially circular central region56having no holes. Such “full” central region56is particularly suitable for capsules containing an elastic septum for generating crema, such as the capsule1ofFIGS. 1 and 2, because it avoids the high pressurized brewed water to directly hit the septum9.

Moreover, the absence of holes in the central region56improves the filtering action of filter5b. In fact, the filter5bmay buckle during the beverage extraction phase because of the presence of an open area below the filter's central region, i.e. the output port7. If holes were present in the central region56, such holes would widen, thus worsening the filtering action.

For this reason, the diameter of the full central region56of the filter5bis chosen to be substantially equal to the diameter of the outlet port7. The person skilled in the art can appreciate that the filter5bwith 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.

The filter5bmay also comprise an undercut57around the inner periphery of the rim52, which is useful during molding.

In 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 holes53, is held at the undercut56when it has to be expelled.

It 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.

The 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.

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