The present invention refers to a container with at least three dimensions (sides) constituting a tray of flexible material, and to a relative manufacturing method and apparatus for production of said tray.
In particular, the invention proposes a container as an alternative to the plastic containers currently existing on the market, injection moulded or thermoformed from a flat, high-thickness sheet of plastic or aluminium and drawn.
These are used above all for containing food products, also in the liquid or pasty state.
Such containers are made with different processes and are normally provided with a hingedly openable lid, beneath which may be disposed a sheet which tightly closes the container, or they are provided with a lid welded onto their upper part.
These containers are by nature rather costly.
In addition they have a substantially permanently rigid consistency, so that they occupy large volumes during disposal, thus further worsening the already serious problems of disposal of urban refuse.
Besides this, in the case of high barrier containers, the thickness of the barrier must be suitably high in order to ensure a low permeability to gas or to steam even at the points of greatest deformation and thinning of the wall.
This is particularly valid in the case of co-extrusions containing EVOH or consisting of a drawn aluminium foil.
The barriered plastic trays thus produced—that is by means of thermoforming—cannot be used for packaging moist foods (whose preservation often requires thermal sterilizing treatments) as the stretching process they have undergone tends to make the container collapse under the action of heat.
This does not happen, on the other hand, for containers made of metal, aluminium or drawn steel, but these containers are very expensive.
In any case, the drawing systems, both for plastic sheets and for aluminium sheets, require very costly machines and moulds, especially if high production rates are to be achieved.
The object of the invention is to provide a container that offers a valid alternative to the above containers, maintaining the advantages thereof and eliminating the drawbacks.
In particular, an object of the invention is to provide such a container that can be made in a simple, economical manner and at high speed.
Another object of the invention is to provide such a container that maintains a rigid consistency during use but that can be crumpled and considerably reduced in volume when being discarded, thus facilitating waste disposal.
Yet another object of the present invention is to provide a system for production of such a container that is economical and allows a high production speed.
These objects are achieved by the container according to the invention, which has the characteristics of appended independent claim 1, by a relative production method which has the characteristics of independent claim 8, and by an apparatus that has the characteristics of independent claim 13.
The container according to the invention is made of a flexible material, particularly single- or multi-layer plastic, possibly coupled with a layer of aluminium, which is very thin because it has only to provide a barrier effect without any supporting function.
The container is obtained from a blank—advantageously square, rectangular or polygonal in shape—whose areas near the corners are pleated, that is suitably folded inward and outward, so as to give the container, which takes on the shape of a three-dimensional tray, a certain capacity and consistency in the vertical direction.
Stiffening, if any, in the transverse direction can be obtained, on the other hand, by means of a small frame applied by heat-sealing, by gluing or by other means beneath the upper peripheral edge of the container or by folding of the edge.
The container is then advantageously closed by a sheet, peelable or not, preferably provided with a pull-tab.
Another characteristic that distinguishes the container thus formed if compared with the above-mentioned drawn types is the easy dressing and illustration on all sides.
The flexible material that forms the container can easily be printed with high-speed processes, reel to reel, since it is in any case of limited thickness (maximum 350 microns). Furthermore, construction of the container does not deform the printing, as happens with drawing processes.
Another property of the laminate forming the container is the possibility of having a susceptor function, that is of transforming microwave radiation into thermal energy by printing with inks having said property or by lamination of metallised films with a susceptor effect, all thanks to the homogeneous, planar structure thereof.
The susceptor activity of the laminate can be controlled by the amount of susceptor printing applied, so as to generate areas of the container with different heating, obtaining different cooking when placed in the microwave oven.
An exemplary embodiment of the invention is described hereunder with reference to the appended drawings, in which:
The container according to the invention is described with reference to
The container 1 is realised, in the way that will be described hereunder, starting from a blank 2, shown in
Said frame can be made in several ways. For example, it can be made by means of a continuously extruded wire strip developed from a reel which, when cut into segments, forms the frame without requiring the use of costly moulds. The material can have electrical conductivity characteristics so that welding can take place very swiftly by means of induction or ultrasound heating.
The container 1 is normally closed by a covering sheet 4, peelable or not, not shown in the figures. Before such closing, as shown in
The manner in which the container 1 is made is now described, starting from the blank 2, which is a single- or multi-layer sheet of a material with one or more layers, in particular layers of plastic material—such as polyethylene, polyester, polypropylene, polyamide EVOH—and/or metals, such as aluminium.
In the appended Figures the square-shaped blank 2, which does not have breaks in continuity, gives rise to an octagonal tray, but clearly it could also be rectangular or generally polygonal in shape, in which case a tray of substantially the same polygonal shape would be formed, but with the addition of connecting sides at the corners.
In
A peripheral edge 10 of the blank 2, defined by the square outer edge 11 of the blank and by an inner octagonal peripheral line 12, dashed in
With reference to
In practice, to form the container 1, the eight triangular portions d of the blank 2 are pleated. That is, each triangular portion d is folded inward with respect to the side wall b along the fold line d1 which is brought outward. Furthermore, each triangular portion d is folded outward with respect to the connecting wall c along the fold line d2, which is brought inward.
At the same time as pleating, the four side walls b are raised with respect to the bottom a, forming the four substantially vertical connecting walls c so as to increase the stiffness and the resistance to compression of the container 1. The square connecting wall c stiffens the corresponding corner of the container 1, especially in the vertical direction, acting as a strut.
The way in which folding of the triangular portions d of the blank 2 takes place is shown better in
Once the eight triangular portions d of the blank 2 have been folded, and thus the side walls b and the connecting walls c have been raised, the frame 3, which is made of a sufficiently rigid plastic material, is inserted, if necessary, from beneath and the peripheral edge 10 of the blank, is folded thereon and is fixed thereto with suitable means, such as heat-sealing, adhesive and the like.
The frame 3 gives the container 1 a stiffness prevalently in the transverse directions which, together with, the vertical stiffness imparted by the square connecting walls c acting as corner struts, determines a structure which is substantially rigid during use, despite being made in large part of flexible material.
The tray container 1 may then be closed with a suitable lid, for example by applying to the upper edge 10 thereof—by heat sealing, gluing or the like—a single- or multi-layer sheet 4. The protruding corner parts 15 are then trimmed so as to obtain a substantially rectangular and uniform upper peripheral edge The covering sheet can be removed by peeling or otherwise, an operation which is facilitated by providing a pull-tab thereon.
From the above description the advantages of the container according to the invention are evident, in that it is made in an extremely simple and economical manner being made up essentially of a blank 2 of flexible sheet material, of a substantially rigid frame 3 (if any) and of a covering sheet, if any.
The production process of the container 1 can easily be automated, providing for automatic pleating of the eight triangular portions d near the apexes of the blank 2, to form a parallelepiped tray, insertion of the frame, if any, and folding and fixing on the frame of the peripheral edge 10.
By way of example, with reference to
With reference for now to
A support 106 is mounted in the mobile plate 103 and protrudes downward therefrom. A top mould 108 is fixed to the support 106 by means of a vertical shaft 107, provided with a certain vertical play. The top mould 108 is shaped substantially as an octagonal plate which reproduces the outline of the bottom a (
Four folding and heat sealing plates 109 are connected to the mobile plate 103 and protrude downward, in an inclined manner, converging towards the four smaller sides of the top mould 108, that is to say the sides in register with the connecting walls c (
A bottom mould 128 is mounted, with a certain vertical play, on the base frame 101. The bottom mould 128 is mounted on compression spring means (not shown) ad has a vertical stroke selected to be equal to the depth of the container 2 that is to be formed.
A shown in
Four connecting and pleating plates 132 are disposed to coincide with the smaller sides or connecting sides of the bottom mould 128. As shown better in
In this manner, the triangular portion 133 of the connecting and pleating plate is shaped as an isosceles triangle with the hypotenuse opposite the smaller side of the bottom mould 128. Two edges 133a with angles of 45° are subtended on the hypotenuse of the triangular part 133. The hypotenuse of the triangular part 133 is parallel to the smaller side of the bottom mould 128 and the catheti of the triangular part 133 are aligned with the larger sides of the bottom mould 128.
It should be noted that a first space 141 is formed between the larger side of the bottom mould 128 and the respective side heating plate 129, a second space 142 is formed between the smaller side of the bottom mould 128 and the hypotenuse of the triangular portion 133 and a third space 143 is formed between the cathetus of the triangular portion 133 and the respective side heating plate 129.
Returning to
Then, as shown in
In this manner the blank 2, which is situated between the bottom mould 128 and the top mould 108, is drawn. That is to say the bottom wall a of the blank 2 is lowered with respect to the peripheral edge part 10, which remains on the side heating plates 129 and on the connecting and pleating plates 132.
In this manner:
It should be noted that the fold line d2 of the triangle d is brought towards the inside of the container by means of the 45° edges 133a between the hypotenuse and the catheti of the triangular plate 133, whereas the fold line d1 is brought towards the outside by means of overlaying of the flaps inside the space 143 between the cathetus of the triangular pleating plate 133 and the heating plate 129.
In this situation, as shown in
As a result, the ends of the oblique folding and heat sealing plates 109, as they descend, fold the corner parts of the edge 10 of the blank 2 in abutment against the top surface of the connecting plates 133 and the end parts of the heating plates 129. Thus the oblique plates 109 act as heat-sealing counter-bars, pressing the portions of heat-sealing f on the heating plates 129.
During this operation, the heat-sealing part f (
As shown in
Once the heat-sealing is finished, the mobile plate 103 is raised together with the top mould 108, and then the spring means are released, raising the bottom mould 128 on which the formed container is disposed.
The container according to the invention is a valid alternative to thermoformed containers erected vertically, by means of suitable folds, from rigid or drawn materials and can be used—preferably but not exclusively—for food products.
Of course, the invention is not limited to the particular embodiment described above and illustrated in the appended drawings, but numerous modifications of detail within the reach of a person skilled in the art can be made thereto without thereby departing from the scope of the invention as set forth in the appended claims.
Number | Date | Country | Kind |
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04425703.8 | Sep 2004 | EP | regional |