Welding promoting element for a closure of an opening device

A welding promoting element for an opening device is insertable into a lid (25) of said opening device to connect said lid (25) to a closing element (10) closing a pouring opening (14) of said opening device; the welding promoting element comprises a sheet element (31) provided with a layer (32) of electrically conductive material, with a first layer (33) of heat-sealable plastic material and with a second layer (34) of heat-sealable plastic material arranged on opposite sides of said layer (32), said layer (32) having a thickness comprised in the range 5-15 μm and each of said first layer (33) and second layer (34) having a thickness comprised in the range 10-50 μm.

CROSS-REFERENCE TO RELATED PATENT APPLICATIONS

This is a National Phase of International Application No. PCT/EP2017/054068, filed Feb. 22, 2017, which claims the benefit of European Application No. 16158756.3 filed Mar. 4, 2016. The entire contents of the above-referenced applications are expressly incorporated herein by reference.

TECHNICAL FIELD

The present invention relates to a welding promoting element for a closure of an opening device for a container, in particular for a sealed container for packaging pourable food products.

More specifically, the present invention relates to a welding promoting element for a closure of an opening device designed to be directly applied onto a sheet packaging material, in turn adapted to be folded, filled with a pourable food product and sealed to form a finished container.

BACKGROUND OF INVENTION

As known, many pourable food products, such as fruit juice, UHT (ultra-high-temperature treated) milk, wine, tomato sauce, etc., are sold in containers made of sterilized sheet packaging material.

A typical example of this type of containers is the parallelepiped-shaped container for liquid or pourable food products known as Tetra Brik Aseptic (registered trademark), which is made by folding and sealing laminated strip packaging material.

The packaging material has a multilayer structure substantially comprising a base layer for stiffness and strength, which may include a layer of fibrous material, e.g. paper, or mineral-filled polypropylene material, and a number of lamination layers of heat-sealable plastic material, e.g. polyethylene films, covering both sides of the base layer.

In the case of aseptic containers for long-storage products, such as UHT milk, the packaging material also comprises a layer of gas-barrier material, e.g. aluminium foil or ethyl vinyl alcohol (EVOH) film, which is superimposed on a layer of heat-sealable plastic material, and is in turn covered with another layer of heat-sealable plastic material forming the inner face of the container eventually contacting the food product.

Containers of this sort are normally produced on fully automatic packaging machines, which are fed with a web of packaging material that is sterilized on the packaging machine, e.g. by applying a chemical sterilizing agent, such as a hydrogen peroxide solution, which, once sterilization is completed, is removed from the surfaces of the packaging material, e.g. evaporated by heating. The web of packaging material so sterilized is then maintained in a closed, sterile environment, and is folded and sealed longitudinally to form a vertical tube.

The tube is filled with a sterilized or sterile-processed food product, and is sealed and subsequently cut along equally spaced cross sections to form pillow packs, which are then folded mechanically to form respective finished, e.g. substantially parallelepiped-shaped, containers.

Alternatively, the packaging material may be cut into blanks, which are formed into containers on forming spindles, and the containers are filled with the food product and sealed. One example of this type of container is the so-called “gable-top” container known by the trade name Tetra Rex (registered trademark).

To open the containers described above, various solutions have been proposed, including reclosable opening devices made of plastic material and substantially comprising a pouring spout, defining a through pouring opening and fitted to a hole in a wall of the container.

When producing the opening device, the opening of the pouring spout is sealed by a closing element connected integrally to the pouring spout and detachable from it along a tear line. The closing element extends at the same level as the packaging material, so as to seal the hole in the wall of the container. On the side facing the lid, the closing element has an integral projecting pull ring, the free end of which is pulled by the user to detach the closing element from the pouring spout along the tear line and so open the pouring opening. More specifically, the pull ring extends inside, and at a predetermined distance from, the pouring spout.

It is also possible to fix the closing element of the opening device directly over a prelaminated hole in the packaging material, i.e. a hole formed in the base layer only and covered by the other lamination layers, including the layer of gas-barrier material.

In both cases, a removable, e.g. a screw lid, is subsequently fitted to the pouring spout in order to outwardly close the latter.

EP2886479 discloses an opening device having a closing element that is formed in one piece with a protruding portion extending inside the pouring spout and welded to the lid. The latter is provided with a disk-shaped welding promoting element that is welded to the protruding portion so that, when removing the lid from the pouring spout, the protruding portion and the closing element remain attached to the lid.

The welding promoting element has to be fixedly connected to the lid and to the protruding portion in order to allow a one-step-opening of the opening device, i.e. to assure that the closing element remains attached to the lid, through the protruding portion, when the lid is removed from the spout for the first time.

Therefore, the need is felt for a strong connection between the welding promoting element, the lid and the closing element.

DISCLOSURE OF INVENTION

It is an object of the invention to improve the welding promoting elements to be used in closures of opening devices for containers.

It is another object of the invention to provide a welding promoting element that assures a strong connection between a closing portion of an opening device and a lid of a closure of the opening device.

It is another object of the invention to provide a welding promoting element that significantly limits, or even avoids, detachment of a lid of a closure of an opening device from a closing element of the opening device, when the opening device is opened for the first time.

According to the present invention, there is provided a welding promoting element as claimed in claim1.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS

Number1inFIGS. 1, 3, 4 and 8indicates as a whole a reclosable opening device1for a container100, in particular a sealed container for packaging pourable food products.

In the example shown inFIGS. 1 and 8, the opening device1is applied to a receiving portion2(FIG. 2) of a multilayer sheet packaging material3, in turn folded, filled with a pourable food product and sealed in a known manner to form the container100.

With particular reference toFIG. 2, the packaging material3comprises a base layer4for stiffness and strength, which may be made of fibrous material, e.g. paper, or mineral-filled polypropylene material, and a first layer5aof heat-sealable plastic material, e.g. polyethylene film, and a second layer5bof heat-sealable plastic material, e.g. polyethylene film, covering both sides of the base layer4.

In the case of an aseptic container for long-storage products, such as UHT milk, the packaging material3also comprises a barrier layer6of gas-barrier material, e.g. aluminium foil or ethyl vinyl alcohol (EVOH) film, which is superimposed on the second layer5bof heat-sealable plastic material, and is in turn covered with a third layer5cof heat-sealable plastic material forming the inner face of the container eventually contacting the food product.

In other words, the first layer5a, the second layer5b, the third layer5cand the barrier layer6define respective lamination layers applied to the base layer4when producing packaging material3in the form of a continuous strip.

In the example shown, the receiving portion2is defined by a so-called pre-laminated hole, i.e. a hole9formed through the base layer4and covered by the lamination layers, i.e. the first layer5a, the second layer5b, the third layer5cand the barrier layer6, so that the hole9is sealed by a sheet cover portion10.

In a possible alternative embodiment not shown, the cover portion10may even be defined by only one or some of the lamination layers. For example, the cover portion10may be made solely of gas-barrier material.

In another possible alternative embodiment not shown, the cover portion10may be defined by a patch fixed to the rest of the packaging material3to seal a hole formed, in this case, through the full thickness of such packaging material3.

In a further alternative embodiment not shown, the receiving portion2may be simply defined by a hole formed through the full thickness of the packaging material3and which is destined to be sealed by the opening device1.

With reference toFIGS. 1, 3, 4 and 8, the opening device1has an axis A, which in use is substantially perpendicular to the receiving portion2of the packaging material3.

The opening device1basically comprises:a pouring spout12fixed to the packaging material3at the hole9and having a cylindrical tubular neck13of axis A, defining a pouring opening14, by which to pour in use the content of the container100;a closing element15closing or sealing the pouring opening14and integrally connected to the pouring spout12by a smaller-section, annular membrane16adapted to be easily torn in use; anda closure18fitted to the neck13of the pouring spout12in a removable manner to close or seal the pouring opening14at a region thereof different from that closed by closing element15.

The annular membrane16defines a tear line along which to detach in use the closing element15from the pouring spout12.

In one embodiment of the present invention, the pouring spout12and the closing element15are formed in one piece on the receiving portion2of the packaging material3, whilst the closure18is formed separately from the pouring spout12and the closing element15and then fitted thereto.

In the embodiment disclosed inFIGS. 1 to 4 and 8, the pouring spout12and the closing element15are obtained by molding molten plastic material—in particular by an injection molding operation—on the packaging material3before it is transformed in the container100.

More specifically, the plastic material destined to form the pouring spout12and the closing element15is injected in a molten state onto a first side10a—i.e. the side eventually facing inwards of the final container—of the cover portion10placed in a known manner within a molding apparatus (known per se and not shown). In particular, the molten plastic material covers the first side10aof the cover portion10up to an annular peripheral region thereof so as to form, in this way, the closing element15directly attached to the cover portion10. The molten plastic material is then forced to pierce the cover portion10at such annular peripheral region to form the pouring spout12projecting from a second side10bof the cover portion10. The second side10bis opposite to the first side10a. The second side10bis the side eventually facing outwards of the final container100.

The pouring spout12is attached to the closing element15through the smaller-section annular membrane16, which is in turn adapted to be torn by the user to open the container100.

In this way, the material forming the pre-laminated hole is first pierced through and then resealed by the plastic material forming the pouring spout12.

In practice, the neck13of pouring spout12extends through the cover portion10as a follow-on from the piercing thereof so as to be arranged on both the first side10aand the second side10bof the cover portion10.

The closing element15and the cover portion10of the hole9together define a sealing portion sealing the pouring opening14of the pouring spout12. The closing element15substantially has a confetti shape.

According to a possible alternative not shown, the plastic material destined to form the pouring spout12and the closing element15may be also directly injected in a molten state through a hole of the packaging material3so that such hole is then completely sealed by the closing element15only.

As shown particularly inFIGS. 1, 3, 4 and 8, the pouring spout12further comprises an annular flange20fixed to the packaging material3at the edge of the hole9. The neck13projects axially and integrally from an annular region of the flange20radially interposed between an outer edge21of the flange20and the annular membrane16.

In practice, the closing element15defines a prolongation of the flange20inside the pouring spout and closes or seals a first axial end22of the pouring spout12; in a different manner, the closure18seals a second axial end23, opposite to the first axial end22, of the pouring spout12even after removal in use of the closing element15and the cover portion10.

The closing element15is advantageously formed in one piece with a protruding portion24extending through the pouring opening14and welded to the closure18far away from the closing element15. In other words, the protruding portion24is welded to the closure18at a given, not null, axial distance from the closing element15.

With reference toFIGS. 1 and 3 to 8, the closure basically comprises a lid25and a disk-shaped welding promoting element26to connect the lid25to the protruding portion24.

In particular, the lid25comprises a disk-shaped end wall27, closing the pouring opening14of the pouring spout12at the second end23thereof, and a cylindrical lateral wall28cooperating with the outer surface of the neck13of the pouring spout12.

In the example shown, the lid25is of a screw type and the lateral wall28has an inner thread29, which engages a corresponding outer thread30on the neck13of the pouring spout12.

The lid25further comprises integrally an annular rib27aaxially protruding from the end wall27towards the inside of the lid25and defining a seat27bfor receiving the welding promoting element26.

As shown inFIGS. 1 and 3, the welding promoting element26is defined by a multilayer sheet element31distinct from the lid18and permanently connected to the lid25.

The sheet element31comprises a layer32of electrically conductive material, e.g. an aluminum foil, and a first layer33of heat-sealable plastic material and a second layer34of heat-sealable plastic material that cover both sides of the layer32. The first layer33defines a first face35of the sheet element31and the second layer34defines a second face36—opposite to the first face35—of the sheet element31.

In the embodiment shown, the first face35of the sheet element31is configured to be welded to the end wall27by the heat generated by inducing an electric current in the layer32. Similarly, the face36of the sheet element31is configured to be welded to the protruding portion24by the heat generated by inducing an electric current in the layer32.

As shown inFIGS. 1, 3 and 4, the protruding portion24comprises an annular body37, welded to the second face36of the sheet element31, and two legs38integrally connecting the annular body37to the closing element15. In particular, the legs38have first ends39, integrally connected to respective diametrically opposite portions of the annular body37with respect to axis A, and second ends40integrally connected to the closing element15.

As a possible alternative not shown, the legs38may be also not diametrically opposite one another.

As a further possible alternative not shown, the protruding portion24may comprise more than two legs38angularly spaced from each other.

InFIG. 9there is shown in greater detail that the welding promoting element26comprises the sheet element31and the sheet element31comprises the layer32of electrically conductive material, the first layer of heat-sealable plastic material and the second layer34of heat-sealable plastic material, which are arranged on opposite sides of the layer32.

The layer32has a thickness belonging to the range 5-15 μm.

Each one of the first layer33and the second layer34has a thickness belonging to the range 10-50 μm.

In one embodiment, each one of the first layer33and the second layer34has a thickness belonging to the range 15-30 μm.

In one embodiment, the first layer33and the second layer34are made of a heat-sealable plastic material selected in a group comprising: polyethylene-based material, polypropylene-based material.

In one embodiment, the first layer33and the second layer are made of the same material, i.e. they are both made of polyethylene-based material, or both made of polypropylene-based material.

In one embodiment, an adhesive50is interposed between the layer32and the first layer33and between the layer32and the second layer34so as to increase adhesion between the layer32and the first layer33and between the layer32and the second layer34, respectively.

In one embodiment, the adhesive is a polyurethane-based adhesive.

In one embodiment the first layer33comprises a first layer element51and a further first layer element52.

The further first layer element52is interposed between the first layer element51and the layer32. The first layer element51defines the first face35.

The first layer element51has a thickness comprised in a range of 5-40 μm.

The further first layer element52has a thickness comprised in a range of 5-10 μm.

In one embodiment, the first layer element51has a thickness comprised in a range of 10-20 μm.

In one embodiment, the first layer element51is made of Low Density Polyethylene (LDPE).

In one embodiment, the further first layer element52is made of Linear Low Density Polyethylene (LLDPE).

In one embodiment the second layer34comprises a second layer element53and a further second layer element54.

The further second layer element54is interposed between the second layer element53and the layer32.

The second layer element53defines the second face36.

The second layer element53has a thickness comprised in a range of 5-40 μm.

The further second layer element54has a thickness comprised in a range of 5-10 μm.

In one embodiment, the second layer element53has a thickness comprised in a range of 10-20 μm.

In one embodiment, the second layer element53is made of Low Density Polyethylene (LDPE).

In one embodiment, the further second layer element54is made of Linear Low Density Polyethylene (LLDPE).

In one embodiment, the layer32has a thickness of 12 μm, the first layer element51has a thickness of 18 μm, the further first layer element52has a thickness of 7 μm, the second layer element53has a thickness of 18 μm and the further second element has a thickness of 7 μm.

In one embodiment, the sheet element31of the welding promoting element26has a structure that is symmetrical with respect to the layer32, in other words the first layer33has the same thickness as the second layer34.

In one embodiment, the first layer element51and the second layer element53have the same thickness. Moreover the further first layer element52and the further second layer element54have the same thickness.

The sheet element31of the welding promoting element26has a structure that is symmetrical with respect to the layer32also because the first layer33is made of the same heat-sealable plastic material as the second layer34.

In one embodiment, the first layer element51is made of the same heat-sealable plastic material as the second layer element52. Moreover, the further first layer element53is made of the same heat-sealable plastic material as the further second layer element54.

In one embodiment, the layer32is embossed, in other words the layer32—and therefore the welding promoting element26—comprises a plurality of cavities on one side of the sheet element31and a corresponding plurality of bulges on the opposite side of the sheet element31.

The opening device1is produced as follows.

First of all, the pouring spout12and the closing element15are injection molded in one piece onto the receiving portion2of the packaging material3.

In particular, the packaging material3is placed with the receiving portion2inside a molding apparatus; at this point, the molten plastic material is injected onto the first side10aof the cover portion10and flows along the first side10aup to the annular peripheral region thereof so as to form, in this way, the closing element15directly attached to the cover portion10. The molten plastic material is then forced to pierce the cover portion10at such annular peripheral region to form the pouring spout12projecting from the second side10bof the cover portion10and attached to the closing element15through the annular membrane16. In practice, the material forming the cover portion10is first pierced through and then resealed by the plastic material forming the pouring spout12.

At this point, the packaging material3is sterilized and then folded, filled with a pourable food product and sealed in a known manner to obtain the container100.

The closure18is produced separately from the pouring spout12and the closing element15and then fitted thereto.

In particular, after forming the lid25and the sheet element31, the latter is inserted into the seat27bof the lid25with the face35in contact with the end wall27. The assembly so formed is then inserted between a pressure element41and an electric induction generating element42of an induction heating welding apparatus43. More specifically, in the example shown inFIG. 6, the pressure element41also engages the seat27bof the lid25and cooperates with the face36of the sheet element31.

The electric induction generating element42comprises a coil44and cooperates with an external surface of the end wall27of the lid25opposite the surface of the end wall27cooperating with the sheet element31.

By activating the coil44, an electric current is induced in the layer32of electrically conductive material of the sheet element31, with a consequent generation of localized heat producing the welding of the face35of heat-sealable plastic material to the end wall27of lid25.

The closure18is then fitted to pouring spout12of container100with reciprocal engagement of the inner thread29and the outer thread30.

At this point, the container100with the opening device1cooperates with an electric induction generating element46(seeFIG. 8). More specifically, the electric induction generating element46is similar to the electric induction generating element42and comprises a coil48.

The electric induction generating element46cooperates with the external surface of the end wall27of the lid25opposite the surface of the end wall27cooperating with the sheet element31.

By activating the coil48, an electric current is induced in the layer32of electrically conductive material of the sheet element31, with a consequent generation of localized heat producing the welding of the face36of heat-sealable plastic material to the annular body37of the protruding portion24.

This induction heating welding operation is performed at a distance, non null, along the axis A from the closing element15and, therefore, from the adjacent packaging material3, with no risk to damage it.

According to a possible alternative not shown, the closure18may be fitted to the pouring spout12and welded to the protruding portion24of the closing element15by an induction heating welding operation carried out directly on the packaging material3in the form of a web, i.e. before such packaging material3is transformed in the finished container100.

In actual use, the first opening of the container is obtained by rotating the lid25with respect to the pouring spout12about the axis A. At the beginning of the rotation impressed by the user on the lid25, the legs38bend in the direction of rotation, so exerting a pulling action on the closing element15at a given point of the annular membrane16; in other words, due to the presence of the bending legs38, the torque exerted on the lid25is transformed in a pulling action on the closing element15, which starts to detach from the pouring spout12at two given points along the annular membrane16.

By continuing to rotate the lid25, it unscrews completely from the pouring spout12together with the closing element15, which remains attached to the lid25(seeFIG. 4) and therefore fully detaches along the annular membrane16from the pouring spout12.

Owing to the welding promoting element according to the invention it is possible to strongly and reliably connect the lid to the closing element.

In particular, it has been found that with a first layer of heat-sealable plastic material and a second layer of heat-sealable plastic material having the claimed thicknesses it is possible to prevent the detachment of the lid and the closing element during first opening of the opening device.

The adhesion of the lid and the closing element is also enabled by the use of polyethylene-based material, or polypropylene-based material, as the heat-sealable plastic material.

The firm mutual attachment of the lid and the closing element is also improved by the adhesive, particularly by the polyurethane-based adhesive.

In addition, it has been found that a good welding of the lid and the closing element is obtained by using a welding promoting element in which the sheet element has a structure that is symmetrical with respect to the layer of electrically conductive material, in particular a welding promoting element in which the first layer of heat-sealable plastic material is made of the same material of, and has the same thickness as, the second layer of heat-sealable plastic material. In one case, the first layer element of the first layer and the second layer element of the second layer are made of the same material and have the same thickness. Similarly, the further first layer element of the first layer and the further second layer element of the second layer are made of the same material and have the same thickness.

In this way, the welding promoting element exerts the same welding promoting action both on the lid and on the closing element, so strongly bonding the lid and the closing element to each other.

In particular, in case the first layer element and the second layer element are made of Low Density Polyethylene (LDPE) and the further first layer element and the further second layer element are made of Linear Low Density Polyethylene (LLDPE), the welding promoting element combines together good sealing properties, given by the outer layers of Low Density Polyethylene (LDPE), and good elasticity, given by the inner layers of Linear Low Density Polyethylene (LLDPE).

Finally, in case the layer of electrically conductive material is embossed, the welding promoting element has an improved sealability since the bulges projecting from the sheet element acts as areas of localized increased melting of the heat-sealable plastic material. In other words, the heat-sealable plastic material is more easily melted at the bulges of the sheet element so improving the welding promoting capability of the welding promoting element.

Clearly, changes may be made to the welding promoting element without, however, departing from the scope of protection as defined in the accompanying claims.