Description

Field of the art

The present invention operates in the scope of packaging machines. More specifically, in the field of packaging dedicated to products which require a preservation in a vacuum or modified atmosphere or, more generally, for all those packages in which the presence of air within the sealed compartment is to be avoided.

Prior art

The packaging field is presently one of the most technologically advanced fields. Given the increasing request for packaged products of any type, in particular food, for the large-scale retail trade in supermarkets, the machines that seal the containers must work at very high speeds and with incredibly high efficiency.

A great number of products, not only of food nature, are sealed today with a protective plastic film which is sealed on the edge of the tray by suitable heat-sealing machines. Due to the sealing, the vacuum or modified atmosphere conditions are preserved up to the first opening of the container. Normally, when the final user brakes the seal in order to start consuming the product, he/she removes the previously heat-sealed protective wrap. If the product is not finished, the consumer will have a secondary plastic covering available, reversibly engageable with the edge of the tray. This second closure, even if not hermetic, slightly slows the now- inevitable oxidation and protects the product from contact with external agents.

Some food manufacturing companies sell their own product in packaged containers with only the lid but without film. The object of the present invention relates to this particular type of package without film, both for products submersed in water or cream (olives, mozzarella, feta cheese, Russian salad, etc.) and for dry products (scamorza cheeses, aged cheese, sandwiches, desserts, fruit, etc.). The request to postpone the expiry date of the product provides for the packaging with vacuum or with the preservation in modified atmosphere.

Since presently there are no systems that can create vacuum conditions in the tray before applying the lid and it is not possible to create the vacuum after the lid has already been applied, up to now producers have proceeded with the conventional application, preferring imperfect and approximative techniques such as filling the tray with water or sealing by hand with only the upper lid made of plastic, settling for a brief expiry time of the products thereof. These techniques have a number of critical issues, it being in fact very complicated to seal containers without the use of the protective film. The results of a manual application jeopardize the quality and freshness of the product due to human error, with numerous risks for the producer in terms of image and for the consumers who could buy a product that is not perfectly sealed and hence not fresh or even damaging for the health.

The invention sets out to overcome these limits with a special application for a completely automatic packaging line.

For the aforesaid reasons, the manufacturers of lid-placer machines, which intend to package trays under vacuum without the use of the heat-sealed film, have provided machines which provide for the following conditions: the cap used must be semi-rigid and plastic, and have an edge which encloses the perimeter of the container and, at the internal side, be characterized by a height lowering so as to slightly“embed” within the tray.

Starting from this type of cap, a first technique for vacuum packaging without the use of the plastic film provides for the previous filling of the container with water or with a mixture of water or another liquid up to the brim. At this point, by pressing the cap and compressing with force, a packaging lacking air should be obtained. The results of this technique have been decidedly disappointing, determining the swelling of the container tray (or its breakage due to the non-compressibility of water) which arranges the container with spontaneous opening of the lid due to the residual positive pressure within the container. This is disappointing also from the aesthetic standpoint since the container appears deformed after the lid application. There was therefore the attempt to precisely calculate the volume occupied by the recessed edge of the lid, by stoichiometrically measuring the water introduced into the container so as to prevent the swelling of the tray due to an overpressure. Such measurement was in fact impossible since, above all in food field, the products to be preserved are never entirely identical with each other and even when these are weighed and metered with as much precision as possible, these could have an unpredictable number of air bubbles therein that would render the product compressible, frustrating attempts to attain the pursued objectives.

The vacuum sealing of a product without heat-sealed film therefore still remains an activity executed manually by operators, who first constrain the container to only one side of the lid, after which they progressively press the lid from the center towards the edges, ensuring the elimination of all the air contained therein without swelling the tray.

Machines which are able to execute this movement, ensuring the correct sealing of the tray even without the heat-sealed film, are not known.

Description of the invention

According to the present invention, a packaging machine is attained for sealing containers in a vacuum with or without modified atmosphere and in the absence of heat-sealed film, which effectively solves the abovementioned problems.

Advantageously, the present invention allows the hermetic closure of trays without the heat- sealed plastic film, hence without the use of sealing materials and/or of sealing towers in which the plastic film is applied with heat. An advantage for the environment and a cost reduction for the food producer since the cost of the packaging machine is lower (there is no sealing tower) and additionally the cost of the film is eliminated since it is not used. Finally, the environmental advantage should not be underestimated, due to elimination of the plastic film of the package.

The advantages of the machine, object of the present invention, are multiple and are of considerable importance, and resolve a problem of the industrial field in question that has never been solved.

More in detail the present machine is able to reproduce, in an automated manner, the movements that a human operator would carry out for a correct closure of an airtight container, creating a vacuum at its interior.

In a second embodiment variant, moreover, the machine described in detail hereinbelow is able to make a closure in modified atmosphere, this too without the heat-sealed plastic film: this is an opportunity entirely unexplored in the world of mechanics for packaging machines. Advantageously, the present machine makes use of known modules which attain the steps of:

- distributing the trays in the corresponding container sliding seats or alveoli of the conveyor belt;

- filling the product to be packaged inside the tray, possibly following a step of weighing or metering so as to make the content of the trays uniform, within the limits set by the nature of the product.

The operation of the invention can be verified on any packaging machine where a lid-placer group and a vacuum bell can be applied (heat-sealers of any type including thermoforming, rotary, etc.).

In a first embodiment version of the application, the trays are subjected to filling the product (liquid or solid) and/or to a second filling of a liquid substance, such as water or a solution in brine, which fills the trays up to the brim before their closure.

It is important to specify that the trays used are common trays provided with an upper edge adapted to be engaged, in a hermetic manner, with the perimeter edge of a common lid having an upper surface recessed with respect to the height of the edge of the tray. This configuration of the tray-lid assembly is that more suitable for the preservation of the hermetic sealing condition of the seal.

According to such first embodiment of the machine, object of the present invention, following the filling with the liquid, the trays cross a positioning station. Here, the corresponding lid is engaged with the edge of the tray for only one side or for about 10-40% of its perimeter. This operation is executed by a common lid-applying damped plunger, connected to a suction cup suitable to retain the lid. In this invention, however, the axis of the suction cup that retains the lid is not aligned with the edge of the tray, rather it is tilted so as to place only one part of the edge of the container in contact with the corresponding portion of the edge of the tray and more precisely the part that is situated in the advancing direction of the catenary in order to allow that it be autonomously maintained in position, blocked on the container.

Following the engagement, even if partial, between the tray and the lid, a part of the liquid that fills the tray exits from the tray itself and will flow out by means of suitable disposal channels.

At this point, the tray-lid assembly, partially connected, is carried by the catenary into a closing station.

Here, a cylindrical roller, independent for each container, is adapted to compress the lid on the edge of the tray in a progressive manner, starting from the already-engaged flap up to reaching the opposite end of the container. Each roller is advantageously configured with at least three areas: a central area in which the diameter of the roller is greater, suitable to compress the lid at the recessed surface which can have a surface that is smooth, corrugated, convex or of any form suitable to apply a pressing pressure on the center of the lid; a pair of lateral areas, arranged at the ends of the cylinder which constitutes the roller, suitable to impart the compression force at the lid edge so as to obtain the coupling between the tray and the lid over the entire surface of the container.

The pressure imparted by the roller on the lid is suitably calibrated in order to allow the exit of all the air present in the package, together with a part of the liquid, thus obtaining the vacuum effect.

Also in the closing station, discharge channels for the excess liquid will be advantageously present.

As is known, on the market, there are multiple types of containers which are suitable not only for the very different range of products to be packaged but also for different consumers and requirements of various type. There are therefore containers which have recesses in which a small spoon is present, with which the user can grasp and serve the content itself of the tray, or containers with lid with particular shape or other type. For this purpose, the rollers installed in the closing station can be variously configured with recesses or swelling or missing areas, in order to modulate the pressure to be applied to the various areas, preserving the integrity of the container.

In addition, still in the closing station, at the arm which carries all the rollers, springs will be advantageously present that are suitable to damp the pressure of the roller on the lid. By means of screws, the hardness of the springs is advantageously adjustable by an operator in order to be adapted to different lid and container models.

It could happen that at the time of the roller’s pressing at the final flap of the container, the container itself can be lifted from the alveolus of the catenary in which it is transported and be overturned. In order to prevent this, it is preferable to include a stabilizing bar in the closing station which stops the possible overturning of the trays in the final moments of roller passage. The entire group with rollers (one for each track of parallel trays present on the machine) can be lifted from the surface and be deactivated in the operation thereof if the system must close trays without liquids, applying the vacuum in another version of the invention described hereinbelow.

Another possible and preferable component of the machine, in this first embodiment, is situated downstream of the closing station; this is a compression station. In this section of the machine, the perfect closure of the tray is advantageously ensured. It could in fact occur that one edge of the lid is not perfectly aligned with the underlying edge of the tray, generating an imperfect closure. This can occur in different situations. For example, if it is desired to use two different lids on the same container, or two lids for the same container, produced by two different producers which have minimum size differences that prevent the correct coupling thereof with the same diameter of the pressure roller, or it can occur that the plastic containers and the respective lids do not have a size regularity, or it can happen due to other reasons tied to the coupling precision. The compression station wishes to correct this situation, by imparting another pressure to the lid from the top downward, fixing possible areas where the coupling is not perfectly aligned after the passage under the pressure rollers.

This object is obtained with a plunger that governs a damped compression plate. In the preferred embodiment, said compression plate is provided or not provided with a plurality of independent damping springs, arranged depending on the shape of the container to be sealed. In a second embodiment included in the present invention, the trays are likewise sealed in the absence of the heat-sealed plastic film but, in place of the liquid preservation solution, a gas or gaseous mixture is advantageously used, adapted to constitute the so-called“modified atmosphere” adapted to extend the useful lifetime of the product and slow the natural deterioration thereof mainly due to the contact with oxygen.

In this second embodiment, the trays filled with the product are partially engaged with one edge of the lid, which will seal them. This step is executed by a positioning device tilted like that described in the preceding version of the invention.

The tray-lid assembly, in which the lid is still partially lifted, is then introduced into an airtight closing bell. Here, the air is first suctioned by means of a common vacuum pump. Possibly the gas for the packaging in“modified atmosphere” can be introduced, if the client requests it. After having attained the vacuum or the atmosphere with which it is desired to close the package, a compression plate will conclude the closure of the lid on the edge of the tray. Said compression plate simply imparts a pressure in vertical direction on the lid already partially engaged with the edge of the tray.

Possibly, in a still more advantageous embodiment of this variant of the present machine, a compression station can be arranged like that described above, applicable to the first variant of the machine.

The fact that, as stated above, the upper surface of the lid is recessed facilitates the fact that the closure is hermetic up to the first opening by the final user.

The possibility to hermetically seal a container in a vacuum or in modified atmosphere without the use of the protective wrap and without having it previously filled with liquid, was, before the present invention, something that could not be attained. Hence, the particular case is configured according to which this variant of the machine is capable of producing the packages of new design, which are themselves a new product.

Due to this variant of the machine, in fact, it will finally be possible to produce containers in a vacuum or in modified atmosphere only constituted by tray and lid, hence lacking the heat- sealed plastic film which previously was indispensable. The advantages offered by the present invention are evident in light of that described set forth up to now and will be even clearer due to the enclosed figures and to the relative detailed description. DescriDtion of the figures

The invention will be described hereinbelow in at least one preferred embodiment by way of a non-limiting example, with the aid of the enclosed figures, in which:

- FIGURE 1 shows the type of container affected by the present invention, i.e. a tray 10 with a lid 15 with upper surface 17 that is recessed with respect to the edge 11 of the tray 10. - FIGURE 2 schematically illustrates the machine of the present invention according to a first embodiment during its working steps for closing the containers.

- FIGURE 3 shows in detail the steps of moving a roller 510 on the lid 15 of a container in order to be able to seal it under vacuum.

- FIGURE 4 schematically shows the machine of the present invention according to a second embodiment with the addition of a closing bell 600.

- FIGURE 5 shows the preferred embodiment of the machine, object of the present invention, which incorporates all of the items described for the previous two versions.

Detailed description of the invention

The present invention will now be illustrated as a non-limiting or non-binding example, with reference to the figures which illustrate several embodiments relative to the present inventive concept.

With reference to FIG. 5, the preferred embodiment of the present machine is shown.

That illustrated is situated downstream of elements that are common to the already-known packaging machines. This is a module suitable to unstack and distribute a plurality of trays 10 in corresponding alveoli of a conveyor catenary or of a common sliding surface in common packaging machines with pushing rods; a first module for filling each tray 10 with a predetermined amount of the product to be preserved; a possible second module for filling the vacant volume of the trays 10 with a quantity of water or other fluid solution such to fill each tray 10 up to the brim or up to the upper edge 11.

Independent of the filling of the tray 10, according to the present invention this will be subjected to a positioning station 400, visible in numerous figures. This is suitable to stably constrain a portion of a lid 15 with the corresponding portion of an underlying tray 10. This operation is carried out by a positioning device 450 constituted by a plunger 420, damped or not damped by means of suitable springs, and a suction cup 410 suitable to be stably and reversibly engaged with the upper surface of said lid 15. The particular characteristic of the positioning station 400 lies in the fact that the suction cup and the component that sustains it 410 is tilted with respect to the horizontal plane in a manner so as to have the lid 15 with a tilt with respect to the upper edge 11 of the corresponding tray 10 comprised between 1° and 45°. More in detail an engagement will be sought that extends for about 10-40% of the perimeter of the edge 11 of the tray 10.

In Fig. 2(a), the suction cup 410 is lifted and engaged with a lid 15. In Fig. 2(b), the suction cup 410, lowering by means of said plunger 420, compresses a portion of the edge 16 of said lid 15 on the corresponding edge portion 11 of the tray 10, determining the stable engagement of the two portions.

Upon executing this pre-engagement between tray 10 and lid 15, the machine will act depending on the type of filling of the container 10-15. If this is full of liquid or cream and it is intended to be closed in a vacuum, the machine will actuate a closing station 500.

Alternatively, if the container 10-15 must be sealed in a vacuum but without filling liquid, or if it must be closed in modified atmosphere, the machine will avoid passing below the closing station 500 in order to direct the container 10-15 directly to a closing bell 600.

The closing station 500 is suitable to complete the engagement between said lids 15 and said trays 10 by means of a plurality of cylindrical rollers 510 (one roller for each row of trays present on the machine), adapted to press said lids 15 downward in a progressive and gradual manner.

The exerted pressure is determined and adjustable due to common adjustable damping springs 520.

The movement that determines the closure under vacuum is illustrated in detail in Figure 3 and starts from the end already constrained between lid 15 and tray 10 in the preceding positioning station 400, up to reaching the opposite end.

As is clear from the abovementioned figures, each cylindrical roller 510 compri ses at least one central portion 515 with greater diameter and a pair of smaller lateral portions 518 that are placed in proximity to the bases of the cylinder which constitutes the roller 510 itself. The central portion 515, being more projected, compresses the lid 15 at the recessed upper surface 17. The lateral portions 518, having small diameter, contact the perimeter edge 16 of the lid 15, determining stable and hermetic coupling.

Examining Fig. 3(d), it can be observed that when the roller 510 presses on the last edge 16 remaining to be compressed, a levering force could be generated which tends to overturn the container 10-15. In order to avoid this possibility, the closing station 500, in its preferred version, also comprises a stabilizing bar 530 which, in the aforesaid case, stops the overturning movement of the just-sealed container 10-15. Said stabilizing bar can be fixed, adjustable and of any shape depending on the container model.

Downstream of the closing station 500, compression means 800 are present which are suitable to guarantee the correctness of the coupling between each tray 10 and the corresponding lid 15 and hence the hermetic sealing. These compression means 800 comprise a compression plate 810 connected to a plunger 830 which moves it in the vertical direction in order to push the lid 15 of each tray 10 downward with a predetermined force, correcting possible defects that may have occurred in the closing station 500.

In order to ensure the adaptability of the compression means for each case of imperfect closure, each compression plate 810 is provided with a plurality of mutually independent damping springs 820-821 suitable to impart a modulated compression force as a function of the positioning of the edge 16 of the lid 15 on the edge 11 of the corresponding tray 10.

In this particular embodiment, the compression means 800 are integrated in a closing bell 600, which, however, in the case of containers 10-15 subjected to the closing station 500 does not enter into operation.

The present machine is, in fact, provided with means for activating and deactivating said closing station 500 and said closing bell 600 so as to alternately subject the containers 10-15 to one or the other depending on the desired packaging type.

In the second case under examination, i.e. that in which it is desired to seal the containers 10- 15 under dry conditions, without having them previously filled with liquid or cream and without the use of the heat-sealed plastic wrap, the closing station 500 will be deactivated, activating the closing bell 600 in its place.

In this part of the machine, the containers 10-15 will arrive partially closed by the positioning station 400, which always maintains the same operation.

The closing bell 600 is airtight, connected to a common vacuum pump 610 and/or to a common gas introduction system 620 for the introduction of the modified atmosphere in the containers 10-15. When the closing bell 600 receives the containers (Fig. 4(a)), it is closed (Fig. 4(b)) and the aforesaid pumps 610-620 first create the vacuum and then, if required, fill the internal space of the closing bell 600 with the desired gas. The system can al so close the container with vacuum if the gas introduction function is deactivated. Only at this point can the above- described compression means 800 come into operation, which will close the container 10-15. At the end of the closure, air will be re-introduced within the closing bell 600 which will open and will allow the sealed containers 10-15 to move away in order to receive new ones.

It is important to specify that in this second process form of the machine, the exiting containers

10-15 are entirely new products on the market. Indeed, hermetic packages without heat-sealed plastic wrap did not previously exist on the market, such packages capable of preserving, under dry conditions, a predetermined quantity of any one product in a vacuum or modified atmosphere.

Finally, it is clear that modifications, additions or variants that are obvious for a man skilled in the art can be made to the invention described up to now, without departing from the protective scope provided by the enclosed claims.