The present invention relates to a method and an apparatus for making capsules or similar containers by means of thermoforming, that are provided with an inner filter suitable for containing a product for preparing a beverage, for example coffee, tea, or other beverages. They are known single-use capsules, sealed with a filtering element or an inner filter, comprising an external container or casing, made of plastic material, having a glass or cup shape, provided with a bottom wall and a side wall defining an open cavity. The opening of the latter is hermetically closed by a covering element in such a way as to seal inside the cavity of the casing the filtering element containing the product from which the beverage is obtained. The covering element and the bottom wall of the container are generally pierceable to allow the introduction of a liquid under pressure, typically water, (typically through the covering element) and the extraction of the beverage obtained by means of percolation of the aforesaid liquid through the product (typically through the bottom wall).

The filter, which is shaped in such a way as to make one respective upward open cavity for containing the product, is sealed to the side wall of the container at its upper peripheral edge. The filter thus divides the interior of the container into one first upper chamber containing the product and accessible through the upper opening of the container (to allow the filling) and one second lower chamber, comprised between the filter and the bottom wall and/or the side , wall of the container, allowing to withdraw the beverage obtained from the product.

The casing of plastic material and the filtering element are generally made separately and associated in one packaging machine which also provides for the filling with the beverage preparation product and closing the capsule with the covering element.

The capsule casing may be made in thermoforming apparatuses comprising a plurality of operating stations through which a sheet of thermoformable plastic material unwound from a coil is advanced by means of suitable advancement means.

Operating stations generally comprise in sequence a heating station, a forming station and a shearing station.

In the heating station the sheet material is prepared for the subsequent forming operation i.e. it is heated until it reaches a predetermined softening temperature, in order to increase plasticity and deformability thereof. The forming station comprises one forming mould wherein one or more punches push the sheet inside respective cavities of a die in such a way as to make the casings. In the shearing station one shearing element separates the casings formed on the plastic material sheet, shearing the latter according to preset cutting outlines.

The capsule casing can alternatively be made in injection forming apparatuses comprising one closed mould wherein the plastic material at the melting temperature is injected at high pressure to make one single capsule or a plurality of capsules, for instance arranged in rows or along a two-dimensional array.

The filtering element, composed of permeable material such as filter paper or non-woven fabric, is made by duly folding a portion of material cut from a film of the aforesaid material unwound from a coil to form a cavity (typically having the conical or truncated cone shape).

The filtering elements are introduced in their respective casings of the capsule and fixed thereto by welding in the packaging machine.

The above described production method is complex and laborious and requires the packaging machine to be provided with a station able to assemble the capsules, in other words to fix the filtering elements to the respective casings.

The steps of withdrawing, moving and inserting the filtering elements are particularly crucial due to the frailty and instability of the filtering elements, once folded and shaped. The assembling station means must be very precise and accurate to ensure that the filtering element is not damaged or deformed or wrongfully positioned in the capsule, thereby causing the capsule to be discarded and consequently decreasing the productivity of the packaging machine.

Such machine is thus more complex and expensive than packaging machines commonly used to fill capsules with products such as coffee, tea and the like.

From WO2013064988 a method and an apparatus for making a beverage capsule are known, such capsule comprising a cup-shaped outer rigid body, comprising a closed bottom and an upper opening coupled with a concave-section filter, extending along the rigid body to form a containment chamber of a dose of product, and a foil lid to close the upper opening of the rigid body along the outer edge of the rigid body thereof.

The method is characterized in that it comprises the following steps:

- positioning a flat piece of filter on the rigid body;

- joining the flat piece of filter at least at the edge of the rigid body;

- forming the piece of filter inward to the rigid body by means of a plastic deformation of the flat piece to define the containment chamber;

- filling in the containment chamber with a dose of product;

- closing the chamber and the rigid outer body with the foil lid.

The method also provides cutting the filter piece from a continuous strip through a cutting unit, moving the filter piece over an opening of the rigid body and subsequently welding the flat filter piece to the outer edge of the rigid body thereof by means of joining means. The method also provides that the forming step includes one first pre-forming step wherein an annular filter portion close to the edge is elastically deformed by stretching by a first annular punch and a second complete forming step wherein a central portion of the filter is elastically deformed by means of a second punch.

The first pre-forming stretching step and the second complete forming stretching step are made by means of hot punches .

The adhesion of the flat filter piece to the outer edge of the rigid body thereof occurs by thermo welding joining means or using a gluing unit.

In the method disclosed in WO2013064988 the step of positioning the filter piece on the body of the capsule is particularly crucial, as a wrongful positioning may compromise the bonding of the filter to the edge of the capsule and cause therefore the discard of the capsule and a productivity decrease.

The apparatus for producing capsules according to WO2013064988 is rather complex as it provides a cutting station for cutting a filter piece from a continuous filtering material strip, a station for positioning and fixing the filter to the capsule and at least one station for forming the filter. Furthermore, the apparatus must be associated to a machine for forming the body of the capsule.

From WO2013171663, in the name of the applicant of the present application, a method and an apparatus are known for making a capsule provided with a casing containing a filtering element suitable for receiving a product for preparing a beverage.

The method provides the following steps:

- applying a film of filtering material to a casing with a cavity so as to cover an opening of said cavity;

- blocking said film to said casing;

- heating and stretching a portion of said film facing said cavity and blocked to said casing such that a filtering element is formed and obtained.

The apparatus comprises superimposing means for applying a film of filtering material to at least one casing with a cavity, in such a way as to cover an opening of said cavity, blocking means for blocking the film of filtering material on the casing, first stretching means comprised in a first stretching station for heating and stretching a portion of the film of filtering material facing said cavity and blocked on said casing so as to obtain a filtering element, and second stretching means comprised in a second stretching station for further stretching and stabilizing the filtering element.

The apparatus disclosed in WO2013171663 is also rather complex, as it provides a station for applying a film of filtering material on the capsule body and two separate stations for the filter formation. Furthermore, the apparatus disclosed in WO2013171663 must also be associated to a machine for forming the body of the capsule.

An object of the present invention is to simplify the methods and apparatuses for forming beverage capsules provided with a filter, a concave section, extending inside a cavity of the capsule body for forming a chamber for containing a dose of a product for producing a beverage.

A further object of the present invention is to provide a method and an apparatus which allow to reduce production costs of capsules and minimize production rejects.

One non limiting embodiment of the method and apparatus according to the invention will be described hereinafter referring to the enclosed drawings, wherein:

Figure 1 is a schematic view of an apparatus according to the invention;

Figure 2 is a view as that of Figure 1 which illustrates a first step of the method according to the invention;

Figure 3 is a view as that of Figure 2 which illustrates a second step of the method according to the invention;

Figure 4 is a view as that of Figure 3 which illustrates a third step of the method according to the invention;

Figure 5 is a schematic view which illustrates a fourth step of the method according to the invention;

Figure 6 is a schematic view which illustrates a variant of the method according to the invention;

Figure 7 is a view as that of Figure 1 , relative to a further variant of the invention;

Figure 8 is a view as that of Figure 1, relative to a still further variant of the invention.

In Figure 1 it is illustrated one forming mould 1 for making beverage capsules provided with a concave-section filtering element 13 (Figure 4) extending inside a cavity of the body 12 of the capsule for forming a containment chamber of a dose of product for producing a beverage.

The mould 1 comprises a lower half mould 2, wherein a plurality of cavities 3 is obtained intended to form the capsule body, and an upper half mould 4 provided with a plurality of stretching elements 5, for instance punches, one for each cavity 3, movable in one direction indicated by the double arrow Fl and intended to form the body 12 of the capsules and the respective filtering elements 13 by stretching a thermoplastic material and a filtering material respectively, as will be explained in detail hereinafter. In the illustrated example it is shown a mould 1 with two cavities 3. It is understood that there can be any number of cavities 3 in the mould 1.

The mould 1 is supplied with a first film 6 of thermoformable plastic material, which can also be, for example, a compostable plastic material, and with a second film 8 of filtering material, in particular a non-woven tissue, and arranged so as to be superimposed to the strip of thermoformable plastic material.

The first film 6 of thermoformable plastic material can be wound on a first coil 7 and the second film 8 of filtering material may be wound on a second coil 9. Alternatively the first film 6 of thermoformable plastic material and the second film 8 of filtering material may be wound on a same coil.

The first film 6 of thermoformable plastic material and the second film 8 of filtering material are advanced together between the upper half mould 4 and the lower half mould 2 in a direction and in an advancement direction indicated by arrow F2, which is perpendicular to direction Fl along which punches 5 are movable. The transversal dimensions of the first film 6 and of the second film 8, in a direction perpendicular to the advancement direction F2 and to the direction Fl, are preferably substantially the same. Upstream of the mould 1, with respect to the advancement direction F2, a preheating device is arranged comprising a pair of heating elements, including, for example, heating plates, or heating lamps, by means of which the first film 6 is heated up to a softening temperature to allow the subsequent deformation for forming the capsule body.

In the illustrated embodiment, only the first film 6 of thermoformable plastic material is passed through the pair of heating elements 10. Alternatively it is possible to place the second coil 9 upstream of the heating elements 10 so that the second film 8 of filtering material also can pass through the heating elements 10 and can be preheated in order to facilitate the deformation during the forming of the filtering elements 13 (Figure 7). If both films are wound on the same coil 16 (Figure 8), this is arranged upstream of the heating elements 10 so that both films can pass through the heating elements to preheat them.

Downstream of the mould 1, with respect to the advancement direction F2, a gripper element 11 is positioned, or a catenary, movable in both ways in the advancement direction F2, which is used to advance the first film 6 and the second film 8 in the advancement direction F2, and to keep them taut. The gripper element 11 , or the catenary, acts as supplying means of the first film 6 and of the second film 8 to the forming mould 1, as while moving in the advancement direction F2 it unwinds the first film 6 and the second film 8 from their respective coils.

If the second film 8 of filtering material has not been preheated, the first film 6 of preheated thermoplastic material heats the second film 8 of filtering material, while the two films are supplied to the mould 1 , so as to facilitate the deformation of the second film 8 of filtering material during the forming of the filtering material 13.

In Figure 1, mould 1 is illustrated in open position, before the starting of the forming of the capsule body and their respective filters.

In Figure 2 it is illustrated a first step of the forming of the capsule body 12 and of the filtering elements 13, wherein the lower half mould 2 and the upper half mould 4 are brought towards one another and punches 5 are moved towards the lower half mould 2 until they contact the first film 6 of thermoplastic material and the second film 8 of filtering material and partially deform them to realize a first stretching of the first film 6 and of the second film 8, by performing a so called "enrichment" process of the thermoplastic material and of the filtering material, avoiding that during the following stretching or deep drawing operations, required for forming the body 12 of the capsule (Figure 6) and the filtering element 13 according to desired sizes and volume, the thermoplastic material and the filtering material may tear or wear thin excessively.

In Figure 3 it is illustrated a second step of the method according to the invention, wherein the mould 1 is closed, clamping the first film 6 and the second film 8 between the lower half mould 2 and the upper half mould 4, and punches 5 are advanced inside the cavities 3 to simultaneously obtain a pre- formation of the bodies 12 of the capsules and of the filtering elements 13.

When the first film 6 of thermoplastic material and the second film 8 of filtering material are clamped between the lower half mould 2 and the upper half mould 4, the thermoplastic material and the filtering material are welded together in preset zones 15, due to the fact that the thermoplastic material, which has been heated by the heating plates 10, is in a softening state, determining, together with the pressure exerted by the two half moulds, the welding of the thermoplastic material with the filtering material. It should be noted that in order to guarantee the welding of the thermoplastic material and of the filtering material it is not necessary to heat the two half moulds, which allows a significant energy saving. In Figure 4 it is illustrated a third step of the method according to the invention, wherein compressed air is injected into the mould 1 through an inlet channel 14 provided, for example, in the upper half mould 4. The inlet of air is indicated with an arrow A, in Figure 4. Compressed air, passing through the second film 8 of the filtering material separates therefrom the first film 6 of thermoplastic material and deforms both of the thermoplastic material and the filtering material until they assume in each cavity 3 the final shape of the respective capsule body 12 and of the filtering element 13.

During or after the inlet of compressed air into the mould, when the first film 6 of thermoplastic material has separated from the second film 8 of filtering material, an extra stroke downwards of the punches 5 can be provided, to increase the depth of the filtering element 13 inside the body 12 of the capsule.

In Figure 5 it is illustrated the final step of the forming of the capsule bodies 12 with their respective filtering elements 13, wherein the mould 1 is opened and the formed capsule bodies 12, with the respective filtering elements 13, are extracted out of the mould 1 which is ready for a subsequent forming cycle.

In Figure 6 it is illustrated a variant of the method according to the invention, wherein the "enrichment" process of the material is omitted. In this variant of the method according to the invention, in a first step, illustrated in Figure 6, the mould is closed, so as to weld together in preset zones 15 the first film 6 of thermoplastic material and the second film 8 of filtering material. As previously explained, it is not necessary to heat the two half moulds to obtain the welding of the thermoplastic material with the filtering material. Thereafter, in a second step, the punches 5 are advanced inside the cavities 3 to obtain a pre-formation of the bodies 12 of the capsules and of the filtering elements 13, similarly to what illustrated in Figure 3.

In a third step, compressed air is introduced into the upper half mould 4, similarly to what illustrated in Figure 4, in order to detach the first film 6 of thermoplastic material from the second film 8 of the filtering material and deform both the thermoplastic material and the filtering material until they assume, in each cavity 3, the final shape of the respective capsule body 12 and of the filtering element 13.

Finally, the mould 1 is opened to extract therefrom the formed capsule bodies 12, with the respective filtering elements 13, as already shown in Figure 5.

The capsule bodies 12 with the respective filtering elements 13, after having been extracted out from the forming mould 1 are sent towards a shearing station (not shown) wherein the capsule bodies 12 are separated from each other by shearing. Shearing may be carried out in zones where the thermoplastic material 6 and the filtering material 8 are welded together, or in zones where the two materials are not welded together. In this latter case it is possible to easily separate the thermoplastic material from the filtering material in the shearing offcuts, facilitating the disposal of offcuts.

Owing to the invention a significant simplification of the process for forming capsule bodies 12 with the respective filtering elements 13 and the forming apparatus is obtained, as the forming of the capsule bodies 12 and of the filtering elements 13 occurs simultaneously in one single mould reducing remarkably the production time and the plant costs, as it is no longer required to provide separate stations for forming the capsule bodies 12 and the filtering elements 13.

Furthermore, the simultaneously forming of the capsule bodies 12 and of the respective filtering elements 13, reduces to the minimum the production rejects, with respect to the methods and apparatuses known in the state of the art. It should be noted that if the first film 6 of thermoplastic material and the second film 8 of filtering material are heated together, it is possible, using heating plates 10, to weld the two films together before they arrive to the forming mould 1 , exerting a pressure by means of heating plates 10.

Thereby the first film of thermoplastic material 6 and the second film 8 of filtering material, being joint together, undergo the same deformations during the formation of the capsule bodies 12 and filtering elements 13, both due to the action of punches, and to the action of compressed air. It is thus possible to obtain filtering elements 13 which substantially have the same shape and size of capsule bodies 12.