HERMETIC SEALING DEVICE FOR PACKAGES CONTAINING FOOD PRODUCTS

Abstract

The sealing device, forming the object of this invention, for packages containing food products, includes a unit for gripping and/or feeding a piece of thin flexible material forming a film used to cover and at least partly seal the food product; a sealing element which includes a rheostat having an annular body and two terminals extending from the annular body and connectable to a voltage generator capable of generating and maintaining an electrical potential difference at the ends of the two terminals in such a way as to cause to flow along the rheostat an electric current capable of heating the annular body to a predetermined sealing temperature. Each terminal has at the point of its connection to the annular body of the rheostat a cross section whose surface area is the smallest compared to the cross sections at all other points of the terminal.

Claims

1. A hermetic sealing device for packages containing food products, comprising a unit for gripping and/or feeding a piece of thin flexible material forming a film used to cover and at least partly seal a food product on the package; a sealing element comprising a rheostat having an annular body and two terminals extending from the annular body and connectable to a voltage generator capable of generating and maintaining an electrical potential difference at the ends of the two terminals in such a way as to cause to flow along the rheostat an electric current capable of heating the annular body to a predetermined sealing temperature; each terminal has at the point of its connection to the annular body of the rheostat a cross section whose surface area is the smallest compared to the cross sections at all other points of the terminal; the annular body of the rheostat is intended to come into contact with the piece of film positioned in contact with a predetermined portion of the package for a predetermined length of time long enough to seal the piece of film along the package in such a way as to hermetically seal the product between the package and the piece of film.

2. The hermetic sealing device according to claim 1, wherein the packages are capsules containing aromatic substances for infusions, comprising a unit for gripping and/or feeding a piece of thin flexible material forming a film used to make the lid of a cup-shaped capsule having a free edge defining the filler mouth; a sealing element comprising a rheostat having an annular body and two terminals extending from the annular body and connectable to a voltage generator capable of generating and maintaining an electrical potential difference at the ends of the two terminals in such a way as to cause to flow along the rheostat an electric current capable of heating the annular body to a predetermined sealing temperature; each terminal has at the point of its connection to the annular body of the rheostat a cross section whose surface area is the smallest compared to the cross sections at all other points of the terminal; the annular body of the rheostat is intended to come into contact with the piece of film positioned with its outer edge in contact with the free edge of the mouth of the capsule for a predetermined length of time long enough to seal the piece of film along the edge of the capsule, thereby closing the capsule.

3. The hermetic sealing device according to claim 1, wherein the packages are individual wrappers, each wrapped around a food product such as a chocolate, a sweet or the like, comprising a sheet of wrapping material designed to receive one such product on one face of it, and comprising a unit for gripping and/or feeding a piece of a thin film of flexible material used to make an element for covering and sealing the food product on the sheet of wrapping material; a sealing element comprising a rheostat having an annular body and two terminals extending from the annular body and connectable to a voltage generator capable of generating and maintaining an electrical potential difference at the ends of the two terminals in such a way as to cause to flow along the rheostat an electric current capable of heating the annular body to a predetermined sealing temperature; each terminal has at the point of its connection to the annular body of the rheostat a cross section whose surface area is the smallest compared to the cross sections at all other points of the terminal; the annular body of the rheostat is shaped in such a way that the product covered with the covering and sealing element can pass through the rheostat, which is designed to surround the base of the product and come into contact with the piece of film placed in contact with the sheet of wrapping material for a predetermined length of time long enough to seal the piece of film onto the sheet of wrapping material for its full length around the base of the product itself.

4. The device according to claim 1, wherein it comprises a blade mounted coaxially with the gripping unit and with the annular body of the rheostat, the blade being designed to cut from a web of the flexible material the piece of film which is to be picked up by the gripping unit.

5. The device according to claim 1, wherein at the point of contact of each terminal with the annular body of the rheostat an electrical node is defined where the current is divided into two secondary currents which flow along the annular body and meet at the other terminal; at each node the portion of the terminal residing around the cross section whose surface area is the smallest compared to the cross sections at all other points of the terminal defines a predetermined electrical resistance which is the largest of those measured at any other cross section of the respective terminal.

6. The device according to claim 1, wherein at the portion of the terminal residing around the cross section whose surface area is the smallest compared to the cross sections at all other points of the terminal, the Joule effect produces a temperature which is higher than that which can be produced at any other point of the terminal.

Description

BRIEF DESCRIPTION OF DRAWINGS

[0024] Further features of the invention and its advantages are more apparent in the non-limiting description below, with reference to a preferred but non-exclusive embodiment of a sealing device as illustrated in the accompanying drawings, in which:

[0025] FIG. 1 is an exploded perspective view of a device according to this invention for hermetically sealing packages which contain food products;

[0026] FIG. 2 shows the sealing device of FIG. 1, when assembled, in a schematic front view and partly in cross section;

[0027] FIG. 3 shows the cross section through line III-III of FIG. 2;

[0028] FIGS. 4-7 illustrate a rheostat of the sealing device of FIG. 1 in schematic side, front, top and perspective views, respectively;

[0029] FIG. 8 illustrates the detail A from FIG. 7 in an enlarged, schematic view;

[0030] FIGS. 9-12 illustrate the sealing device of FIG. 3 in a sequence of configurations for hermetically sealing a coffee capsule;

[0031] FIG. 13 illustrates a detail from FIG. 12 in an enlarged, schematic view;

[0032] FIGS. 14-18 illustrate a device according to this invention for hermetically sealing packages which contain food products, in particular sweets, chocolates and similar products.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS OF THE INVENTION

[0033] With reference to FIGS. 1-3, the numeral 1 denotes a device according to this invention for sealing capsules 100 containing aromatic substances for infusions.

[0034] By way of an example, FIG. 13 shows a capsule 100 basically comprising a container 101, for example cup-shaped. The container 101 has a filler mouth 102 and a bottom 103 through which is dispensed the beverage produced during use of the capsule 100 by effect of the infusion of the water with an aromatic substance present in the container and not illustrated.

[0035] The reference capsules 100 are single-use capsules and further comprise a perforatable lid 104 through which water can be fed and which is applied by sealing. The capsules 100 may also comprise a bottom lining 105, for example a filter element, positioned, in the example illustrated, on the bottom 103 of the container 101.

[0036] The container 101 has a free edge 106 defining the mouth 102 on which the lid 104 is applied and sealed.

[0037] The lid 104 is made from a web W of flexible material from which a piece Sp of thin flexible material is cut. The shape of the lid may vary in particular as a function of the shape of the container 101 and of the mouth 102. Generally speaking, the lid has the shape of a disc but alternative embodiments are imaginable.

[0038] The sealing device 1 comprises a gripping unit 2, for example operating by suction. More specifically, the gripping unit 2 is a suction cup provided with a suction duct 3.

[0039] The gripping unit 2 extends and is movable along a longitudinal axis 4 for picking up and holding the piece Sp of film of flexible material used to make the lid 104 of the capsule 100.

[0040] The sealing device 1 also comprises a sealing element 5 comprising a rheostat 6 having an annular body 7 and two terminals 8 extending from the annular body 7. The annular body 7 preferably has a planar form, that is to say, it has an upper annular surface 7a and a lower annular surface 7b, both annular in shape and lying in parallel planes.

[0041] The gripping unit 2 is disposed coaxially with the annular body 7 of the rheostat 6 and traverses it along the longitudinal axis 4.

[0042] FIGS. 4-7 illustrate a possible embodiment of the rheostat 6. The shape of the annular body 7, which, in the example illustrated, is circular, depends on the shape of the lid 104 and of the capsule 100.

[0043] The terminals 8 are connectable to a voltage generator capable of generating and maintaining an electrical potential difference V at the ends of the two terminals in such a way as to cause to flow along the rheostat 6 an electric current capable of heating the annular body 7 to a predetermined sealing temperature. The numeral 9 schematically indicates the electrical connections to the voltage generator 10 forming part of the sealing element.

[0044] As shown in more detail in FIG. 8, each terminal 8 has at the point of its connection to the annular body 7 of the rheostat 6 a cross section S1 whose surface area is the smallest compared to the cross sections at all other points of the terminal.

[0045] It should be noted that the annular body 7 of the rheostat 6 is intended to come into contact with the piece Sp of film positioned with its outer edge in contact with the free outer edge 106 of the mouth 102 of the capsule 100 for a predetermined length of time long enough to seal the piece Sp of film along the edge of the capsule, thereby closing the capsule.

[0046] With reference to FIG. 8, the point of contact of each terminal 8 with the annular body 7 of the rheostat 6 defines an electrical node 11 where the current i is divided into two secondary currents i1 and i2 which flow along the annular body 7 and meet at the other terminal. More specifically, FIG. 8 shows a perspective view of a node 11 of the rheostat, highlighting the surfaces S, S1 and S2 which the current flows through.

[0047] The surface S is the surface of a transverse cross section of one of the two terminals of the rheostat. The other terminal and the corresponding node are similar in shape. As is evident from this figure, S1<S.

[0048] The two surfaces S2 are the transverse cross sections of the annular body 7.

[0049] At each node 11 the portion of the terminal residing around the cross section S1, whose surface area is the smallest compared to the cross sections at all other points of the terminal, defines a predetermined electrical resistance R1 which is the largest of those measured at any other cross section of the respective terminal.

[0050] In effect, as is known, resistance R is the inverse of the electrical conductance G and is defined as follows:

R=1/G=L/S=L/S

where is the electrical conductivity (whose inverse is the electrical resistivity), L is the distance between the points across which the resistance is measured (hence the length of the rheostat), S is the area of the cross section perpendicular to the direction of the current.

[0051] It thus follows that the resistance R offered by the surface S to the flow of current i is lower than the resistance R1 offered by the surface S1 and the resistance R2 offered by the surface S2, because the smaller the surface, the higher the resistance.

[0052] At the portion of the terminal residing around the cross section S1 whose surface area is the smallest compared to the cross sections at all other points of the terminal, the Joule effect produces a temperature which is higher than that which can be produced at any other point of the terminal.

[0053] In effect, increasing the value of the resistance increases the value of the power that can be converted to heat by the Joule effect according to the known relation P=RI.sup.2.

[0054] The effect of reducing the transverse surface area of the terminals at their points of connection with the annular body 7 allows keeping the annular body 7 of the rheostat at the required sealing temperature without increasing the current i.

[0055] Thus, reducing the transverse cross section of the terminals at their points of connection with the annular body 7 increases the heat at the node 11, which contrasts the cooling effect that would occur at the node if the surfaces meeting at the node (that is, the transverse surfaces of the annular body 7 and the transverse surfaces of the terminal 8) were added up. Further, the current i at the node 11 is divided into two currents i1 and i2 which flow to the left and to the right of the surface S1, respectively and which are able to keep the annular body 7 of the rheostat at the required sealing temperature.

[0056] This allows preventing excessive cooling at the node, limiting the value of the current i and preventing increases in leakages which are directly proportional to the square of the current i itself.

[0057] In addition to the above, it should be noted that in the context of the node 11, the lengths are negligible and thus, the related resistance is directly influenced only by the value of the cross section S1. On the contrary, the length of the annular body 7 is not only not negligible but also greater than the other parts of the rheostat, thus further and significantly increasing the sealing temperature obtainable under the same conditions of current used.

[0058] With reference to the figures, the terminals 8 have a straight stretch 8a for mechanical connection to a supporting sleeve 12 and for electrical connection to the voltage generator 10. The straight stretch 8a extends perpendicularly to the planar form of the annular body 7 and is preferably provided with slots 8c for fastening it to the sleeve 12.

[0059] Each terminal 8 also has a connecting stretch 8b disposed at an angle to the straight stretch 8a and to the planar form of the annular body 7. Preferably, the cross section S of the straight stretch 8a is constant, whilst the transverse cross section of the connecting stretch 8b decreases to its minimum value S1 at the point of connection to the annular body 7.

[0060] The sleeve 12 defines a through cavity 13 which extends along the longitudinal axis 4 and inside which the gripping unit 2 is coaxially disposed. More specifically, the gripping unit 2 is movable along the longitudinal axis 4 relative to the sleeve 12 by means of movement devices not illustrated. With reference to FIGS. 9-12, the gripping unit 2 is movable inside the sleeve 12 between a raised position, illustrated in FIG. 11, and a lowered position, illustrated in FIG. 10, where it picks up the piece Sp just after it has been cut.

[0061] The raised position, as will become clearer as this description continues, corresponds to a sealing position. In other words, the gripping unit 2 is movable along the longitudinal axis 4 relative to the rheostat 6 (attached to the sleeve 12), between a raised position and a lowered position.

[0062] The sealing device 1 also comprises a blade 14 disposed coaxially with the gripping unit 2 and with the annular body 7 of the rheostat. More specifically, the blade 14 is tubular and the gripping unit 2 is located inside the blade itself. The blade 14 is designed to cut from the web W of flexible material the piece Sp of film which is to be picked up by the gripping unit 2.

[0063] More specifically, the blade 14 is mounted on a support 15 and is movable along the longitudinal axis 4 which thus represents a cutting direction, preferably vertical and at right angles to the web W. The blade is movable between a raised, rest position, illustrated in FIG. 9, and a lowered, cutting position, illustrated in FIG. 10. More specifically, the blade 14 intercepts the web W along its feed path P in the respective lowered position.

[0064] Preferably, the support 15 and the sealing element 5 comprising a rheostat 6 move as one along the longitudinal axis 4 during the movement of the cutting blade 14, as described below.

[0065] The sealing device 1 according to this invention is applicable to a machine for making capsules 100, not illustrated, comprising for example means for moving the containers along a predetermined path. The machine may also comprise means for moving the web W of flexible material along the predetermined feed path P.

[0066] FIGS. 9-12 illustrate the cutting and sealing sequence followed by the sealing device 1 in the machine for making capsules 100.

[0067] During one step in machine operation, the sealing device 1 may be positioned above the web W, as illustrated for example in FIG. 9, where both the gripping unit 2 and the blade 14 are in the raised position.

[0068] After that, the sealing device 1 may operate at the path P of the web W to cut the piece Sp. This operating step is illustrated for example in FIG. 10, where the blade 14 (together with the support 15) has reached the lowered, cutting position During the cutting step, the web W may be stopped or the sealing device 1 may move along the path P synchronously with the web W. FIG. 10 also shows that when the gripping unit 2 reaches the lowered position, it catches hold of the piece Sp.

[0069] The machine may comprise a matrix, not illustrated, acting in conjunction with the blade 14 to give the web W a clean cut.

[0070] Next, as illustrated for example in FIG. 11, the gripping unit 2 is raised relative to the blade 14 and the rheostat 6 so as to bring the top surface of the piece Sp into contact with the underside surface 7a of the annular body 7.

[0071] In a subsequent step, illustrated for example in FIG. 12, a container 101 is placed under the sealing device 1 and the underside surface of the piece Sp is placed in contact with the free edge 106 defining the filler mouth 102. This position corresponds to the sealing position illustrated in more detail in FIG. 13.

[0072] Advantageously, the sealing device according to this invention is efficient and capable of reconciling the opposite needs to optimize both sealing and electrical efficiency. More specifically, terminals with varying cross sections are used to avoid excessive cooling at the node so as to combine the need to operate at high sealing temperatures on the one hand with the need to limit leakages on the other. Furthermore, the combination of rheostat and blade allows improving machine efficiency because there is no need for intermediate transfers of the pieces of film, which remain associated with the same gripping unit from the moment they are cut to the moment they are sealed.

[0073] In FIGS. 14 to 18, the numeral 16 denotes a food product such as, for example, a chocolate, a sweet or a similar product.

[0074] The gripping unit 2 is a suction cup 17 for picking up and feeding a piece Sp of thin flexible material forming a film used to cover and at least partly seal a chocolate 16.

[0075] The package consists of an envelope 18 wrapped around the chocolate 16.

[0076] The envelope comprises a sheet 19 of wrapping material designed to receive, on one of its faces, the chocolate 16.

[0077] A plurality of sheets 19 are fed and made to advance on a conveyor belt 20.

[0078] The gripping unit 2 places the piece Sp of flexible material over the chocolate 16.

[0079] As illustrated in the figure and in exactly the same way as the case of the capsules 100, the annular body 7 of the rheostat 6 is designed to come into contact with the piece Sp of film which, with the edge of it around the product 16, is in contact with the face of the sheet 19 on which the chocolate 16 is positioned.

[0080] The foregoing description of all the features of the sealing element 5 provided with the rheostat 6 whose annular body 7 is connectable to the voltage generator 10 also applies to the embodiment illustrated in FIGS. 14 to 18.

[0081] The annular body 7 is thus provided with the two terminals 8 which, when connected to the same voltage generator 10, enable the latter to generate and maintain an electrical potential difference at the ends of the two terminals 8 in such a way as to cause to flow along the rheostat 6 an electric current capable of heating the annular body 7 to a predetermined sealing temperature.

[0082] The annular body 7 of the rheostat 6 is intended to come into contact with the piece Sp of film positioned in contact with a predetermined portion of the packagein practice along the edge surrounding the chocolate 16for a predetermined length of time long enough to seal the piece Sp of film to the sheet 19 in such a way as to hermetically seal the product between the packagethat is, the sheet 19and the piece Sp of film.

[0083] Once the piece Sp is hermetically sealed around and encloses the chocolate 16 within it, the sheet 19 is folded around the group consisting of the chocolate and the piece Sp in such a way as to obtain an envelope 18 which constitutes the package 100.

[0084] It should be noted that the annular body 7 of the rheostat 6 may have different internal diameters so that it can be placed around the food product 16 without touching or damaging it during the sealing operations described above.

[0085] It is also evident that the annular body 7 may have different shapes such as, for example, triangular, rectangular or square.