Composite container for storing food

Holder: Same as θ

O Representative: Cabinet Beau ds Loménie, 55, me d'Amsterdam, 75C08 Paris.

D Sales of booklets at ΠMPRÏMERIE NATIONALE, 27, rue de la Convention - 75732 PARIS CEDEX 15

The present invention relates to a container intended to contain food products, as well as a method and an apparatus for producing this container.

Containers intended to contain food products are already well known. It is also known that these containers can be made of many different materials and combinations of materials, for example cardboard, glass, aluminum and certain plastic materials. Of course, advantages and disadvantages are inherent in the use of each of these different materials. For example, cardboard is a relatively solid container material, but has the disadvantage of being relatively permeable to gases, and consequently food products stored in containers made solely of cardboard lose their freshness fairly quickly. On the contrary, glass, aluminum and some plastic materials are relatively impermeable to gases, but it is expensive to make strong containers with the materials because of their relatively high price.

It is therefore desirable for the art of packaging food products to have a container which is strong, relatively impermeable to gases and relatively inexpensive. French Patent Application No. 77-359^9 filed November 29, 1977 in the name of the applicant describes containers that meet these three criteria.

The containers described in this patent application are characterized by having horizontal flanges directed outwards up to at least approximately 3 mm from an inner plastic container, and vertical flanges which extend at least approximately 3 mm the horizontal edges. The inner plastic container is stretched and inflated inside an outer cardboard container. When a food product has been placed in this container, it is closed with a heat sealable lid and preferably then, a second lid. is fitted around the container, at its upper part The containers described in this patent application are used with satisfaction for food products in many cases, but there are other cases in which it would be desirable to store food products in containers with screw-on lids. i.e. the solidity, the relative impermeability to gases and the relatively low price.

bes containers according to the invention meet these criteria

The invention also relates to a method; and an apparatus for carrying them out.

The container according to the invention comprises an outer container made of cardboard and an inner container made of plastic material which is stretched and formed by inflation in the outer container. The container further has nets of plastic material around its upper part, outside the cardboard container, and which are made of plastic material from the inner container, around and outside the upper part of the container. cardboard-based.

Preferably, the outer cardboard container according to the invention has a circular cross-section throughout its length, and it comprises a bottom. In these containers, the stretched and inflated inner plastic container, with one exception, preferably conforms to the shape of the outer container and presses against it. The exception mentioned above is the lower and inner edge of the outer container defined by its vertical wall and its melting there, the inner plastic container is spaced from the outer container in the same way and for the same reasons as described in the aforementioned patent application However, if a light product, for example fried potatoes, or a non-perishable product is to be kept in the container, it may not be necessary to space the inner container from the outer container in the manner described above.

When a product, for example a food product, has been placed in the container according to the invention, it is preferable that a weldable lid is applied to its upper edge, and a lid is screwed on top. According to one embodiment, the sealable lid is initially provided in the form of a gasket pressed against the interior surface of the lid, and it is heat sealed to the upper edge of the container by applying only heat through the lid. after it has been screwed onto the container, it can also be glued to the top edge of the container.

The containers according to the invention are made by first positioning an outer cardboard container in a female mould. The outer cardboard container is positioned so that it protrudes above the top of the female mold. Next, a hot sheet of plastic material is stretched into the mold by means of a mandrel. The mandrel and the mold are made and arranged so that the plastic material is stretched around the upper parts outside of the outer cardboard container.₃ at the same time that it is stretched in sound. interior. When the mandrel has completely penetrated the mold and preferably simultaneously with this penetration, the operation of forming by inflation of the inner container and forming by depression of the threads begins.

The inner containers en.matière plastic according to the invention are formed by inflation₃ in the manner described in the aforementioned French patent application, that is to say that a pressurized gas is introduced inside the mold through holes in the mandrel and communicating with the gas source case. Cornai © according to the aforementioned patent application, if the outer cardboard container has a bottom, a mandrel is used which has holes arranged so that 1 © gas is directed towards the edge or edges of the outer container; defined by 1© splits d© this container and its vertical wall.

According to the invention, the threads are formed by depression without providing the mandrel with a device for forming threads communicating with a source of depression. The net forming device is arranged and made of. so that when © the mandrel is fully engaged in the mold, this device surrounds the plastic material stretched around the upper part outside the cardboard container. Thanks to this arrangement of the net-forming device, plastic nets are made by applying a depression to the plastic satiety stretched around the upper part of the outer cardboard container, this plastic material matching the shape of the net formation.

The mold and the mandrel according to the invention must be arranged and made in such a way that the forming by depression and the forming by inflation take place in the manner described above. last is completely engaged in the mould» rests tightly against the plastic material which is around the upper edge of the outer container» pressing it against the upper edge and thus isolating the chamber vacuum forming chamber by inflation. It has been found that as a result of this pressure the plastics material sticks to the cardboard along the upper edge of the outer container.

The container can be removed from the mold and from the mandrel by any suitable means. One method is to disengage the mold from the mandrel and the outer cardboard container and then unscrew the container from the mandrel. Unscrewing is facilitated by the bonding between the plastics material and the upper edge of the cardboard container mentioned above. Another method is to use a separable mold and a separable mandrel which can be opened to allow removal of the container.

According to the invention, the thread forming device of the mandrel preferably presses tightly against the stretched plastic material outside the cardboard container when the mandrel is fully inserted into the mould. Because of this support, it is preferable that the thread-forming device be arranged and made in such a way that a line defined by the interior part of the thread-forming device and a plane passing through its axis is inclined with respect to the vertical” for example by an angle of the order of 0”5 to 3°” preferably of the order of 1°. This arrangement of the thread forming device facilitates engagement of the mandrel in the mould, with an outer cardboard container positioned therein. Furthermore, the above-mentioned inclination of the thread forming device facilitates the tightening of the lid on the container, since the thread of the lid does not comprise threads inclined with respect to the vertical.

Other characteristics and advantages of the invention will be better understood on reading the following description of an exemplary embodiment and with reference to the appended drawings in which:

Figure 1 is an exploded view of a container according to the invention, Figure 2 is a section of the outer cardboard container according to the invention, Figure J is a plan view of the blank used to form the vertical wall of the outer container of Figure 2, Figure 4 is a plan view of the blank used to form the bottom of the outer container of Figure 2, Figure 5 shows the mandrel, mold, a sheet 10 of plastic material and an outer cardboard container before the plastic material is stretched into this container, Figure 6 is a cross-section of the mandrel, the mould, the plastic sheet and the cardboard container when the plastic sheet is plastic material is completely stretched in the outer cardboard container, but before it is inflated inside the container and before the net is formed there by vacuum, Figure 7 is a section of the mandrel, of the mould, a sheet of plastic material and the cardboard container when the sheet has been inflated to form an inner plastic container and when threads have been formed by vacuum, figure b is a section showing the lower surface of the mandrel element 44, along a plane defined by the lower surface of the element 44 of Figures b and 7) Figure 9 is a large-scale sectional view of one half of the mandrel thread forming device, along a plane passing through the axis of this device, the angle of 1° being exaggerated by way of illustration”

Figure 1 is therefore an exploded perspective view of a

OJ container according to the invention. It comprises an outer container 10 made of cardboard, preferably made of folded cardboard with a circular cross section over its entire height. L, e carton can also be coated with a plastic material, for example polyethylene. In addition” and as shown in Figure 1, the outer cardboard container has a vertical seam 11 over its entire height.

Figures 2 to 4 better show the construction of the outer cardboard container of the present embodiment of the invention. As shown in Figure 2, the outer cardboard container lü has an inner -vertical wall 12, an outer vertical wall 13 and a false bottom H- This outer cardboard container is made from the blanks of Figures 3 and 4 · b¹blank of FIG. 3 bears an adhesive, represented by dots, preferably applied just before the production of the container, on a part of the external vertical wall 13, and on the panel 19 which extends the external vertical wall 13 along the fold line lb- To make the outer cardboard container, the blank in Figure 3 is folded along the fold line ±3, thus forming the edge which constitutes the upper edge read of the finished container* When the blank is thus folded, its edge 1/ shown in Figure 3 is spaced from the fold line lb d¹ about the width of the panel I9. The container can then be finished by: (a) bending the blank so that the glue-coated part of the outer vertical wall 13 comes to the opposite side of this same wall, (b) inserting the blank 14 into the lower part of the blank folded as in -(a) so that the tabs 20 are directed downwards from the panel 14, parallel to the outer vertical wall 13 and, (c) folding the panel 19 so that the tabs 20 are interposed between this panel 19 and the outer vertical wall 13, as shown in Figure 2. During the construction of the container, pressure is applied at the desired places to effect the gluing and keeping the container upright.

it is understood that the cardboard outer container described above is only an example and that other shapes may be suitable within the scope of the invention. For example, outer cardboard containers without a bottom can be used according to the invention. Also, containers with a single vertical wall instead of a double wall can be used according to the invention when the strength of a double wall is n is not desired. Furthermore, rather than forming the tabs 20 by V-shaped notches in a blank, as shown in Figure 4, these tabs can be formed by short radial cuts in the blank · be container according to the invention also comprises a inner container 21 of plastics material which, as will be described in more detail later, is stretched and formed by inflating the outer cardboard container. The container according to the invention also comprises threads 22 made of plastic material around the upper part of the outer cardboard container. As shown in Figure 1, the plastic threads 22 are formed in plastic from the inner container around the upper edge 1b of the outer cardboard container. which passes around the upper edge 10 of the outer container is preferably glued to the cardboard during the production of the container.

The inner plastic container 21 is preferably spaced from the corner of the outer cardboard container defined by the intersection of the vertical inner wall 12 and the bottom 14. As per the aforementioned French patent application, the reason for this is that the strength of the container according to the invention is significantly improved by spacing the inner plastic container from the angle of the outer cardboard container defined by the vertical inner wall 12 and the bottom 14.

More particularly, the inner plastic container is preferably spaced approximately three to nine millimeters, preferably of the order of b mm, from the angle formed by the intersection of the inner vertical wall 12 and the bottom. i4.

The plastic material which is used to form the inner expient and the nets according to the invention can be chosen from several different materials, for example the same materials which can be used to make the inner plastic container described in the patent application. French cited above.

Figure 1 shows that the container according to the invention also comprises a weldable lid 23 The weldable lid 23 can be made of several different materials, for example polyethylene, or waxed paper, or several layers of paper, plastic and aluminium, for example including paper, plastic, aluminum foil and plastic. The weldable lid can be applied to the plastic material of the upper edge 1b of the outer cardboard container, by any known means, for example by ultrasound, heat, glue or electronic pulses. The need for a sealable lid depends on the product enclosed in the container. If this product is non-perishable or only slowly perishable, this cover may not be useful.

FIG. 1 also shows that the container according to the invention also comprises a screw-on lid 24. Lids of this type are well known in the packaging technique and may contain a filling of foams, for example polypropylene or polyurethane, which practically fills the same sealing function as weldable cover. Preferably, the screw-on lid contains the weldable lid applied against the inner surface of its upper part.

The lid can be heat sealed to the container by applying heat through the screw-on lid when fitted to the container.

• The figures. 5 at 7 s represent the different phases of formation by stretching and inflation of the inner container 21 in the outer container 10 in cardboard and of formation by depression of the nets 22 around the upper part of the outer container 10 · More particularly, FIG. 5 shows the arrangement of the mandrel 30s of the mold 31s of the plastic sheet 32 ​​and of the outer container 10 before the stretching of the sheet 32 ​​in the container 10. The upper part of the outer container 1O protrudes at the upper part of the mold 31 · As will be explained in more detail later, the plastic threads are formed by depression around the upper part of the outer container 10.

As shown in Figure 5 a the outer container is initially placed in the mold 31 and the plastic sheet 32 ​​is positioned between the mandrel jû I^e mold 31”

As shown in Figures b and ?, in the present embodiment, the grinding wheel 31 is made so that its lower part receives a container with a false bottom 14 set back. Further, the bottom of the mold preferably includes a pad 33, such as silicone rubber, to resiliently support the outer container 10 when positioned in the mold 31.

As also shown in Figures 5 to?₃ the mandrel 30 comprises a piece 34 for drilling by stretching and blowing

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arranged and produced relative to the mold so that the sheet of plastic material can be stretched in the mold 31 by this part. Preferably, piece 34 is tapered as shown in Figure 5. Stretch blow forming piece 34 has holes which communicate through a gas channel 3b with a source of compressed gas, not shown. In addition, part 34 also preferably includes a heater 37 for maintaining the temperature of the plastic material during the stretch and blow forming operations. The heater communicates with a power source, not shown, through a 3Θ channel with heating wires.

The mandrel also comprises a device 39 for forming threads arranged and produced on this mandrel in such a way that when it is completely engaged in the mold 31, as shown in FIG. 6, the internal edges of the device 39 are very close to the plastic sheet 32 ​​which has been stretched, against the upper part of the outer container 10. The thread forming device 39 shown in FIGS. ό to 7 is in the form of a sleeve which has been made separately from the mandrel. But it is understood that this device for forming threads formed separately from the rest of the mandrel is only preferred and that this arrangement is not essential. of threads comprises channels 4ü which communicate with a vacuum chamber 41, communicating in turn with a source of suction, not shown, through a channel 43” and a connector 42.

Figures b and 7 show that the vacuum chamber

41 is positioned between a first head 44 of the mandrel and a second head 45. The first head 44 and the second head 45 of the mandrel are assembled by screws 46 and the stretch and inflation forming part 34 is fixed to the second head 45 by screws 47

The mandrel 30 also includes a device for maintaining the vacuum created in the chamber 41, the channels 40 and the space between the thread forming device 39 and the plastic sheet 32. As shown in Figures 6 to δ, this device comprises an O-ring 50, an O-ring 51 and a silicone rubber seal 52 The toxic seal 51 and the seal 52 perform the function of maintaining the pressure inside the mold during the inflation forming operation which will be described later.

Before being positioned as shown in Figure 5 and in the manner described above, the sheet of plastic material is preheated to a heat forming temperature, i.e. a temperature which allows formation by stretching and inflation as well than vacuum forming as described below. Preferably, the plastic material is preheated by a radiant heater, not shown. Furthermore, depending on many well-known factors e.g. the plastic material used, the ambient temperature, the temperature to which the material is preheated and the waiting times, etc. it may be necessary or desirable to heat the chuck by means of the heater 37·

As described in the aforementioned French patent application, the thickness of the sheet 52 of unstretched plastic material can vary widely, depending on the dimensions of the container and the material used.

Figure 6 is a section of the mandrel 3θs of the mold 31, the sheet 32 ​​of plastic material and the outer container 10 of cardboard, with the sheet 32 ​​completely stretched in the outer container but before being inflated in this container and before the formation of nets by depression.

As shown in Figure 0, the mandrel 30, the mold 31, the plastic sheet 32 ​​and the outer container 10 are arranged and arranged so that when the drawing operation is completed: (a) the second head 45 of the mandrel is pressed tight against a part of the sheet 32, itself pressed and tight against the upper horizontal wall of the mold 311 (b) a part of the sheet 32 ​​of plastic material is arranged vertically; seated around the upper portion of the outer container 10 projecting above the mold 311 and (c) the silicone rubber liner 52 is pressed and compressed against the upper portion of the sheet 32 ​​to form a seal therebetween. and the plastic sheet.

With the mandrel, mold, plastic sheet and cardboard container positioned as shown in Figure 6, and preferably simultaneously with the end of the stretching operation, the formation by inflation of the inner plastic container and the formation by depression of the nets begins. 11 It is preferred that the inflation-forming and vacuum-forming operations begin approximately simultaneously with the end of the stretching operation for the following reasons: (a) the tendency of the plastic sheet 32 ​​to cling to container 10 in. cardboard thus inhibiting the formation by depression of the nets 22, is. minimized; and (b) cooling of the plastic before completion of inflation forming and vacuum forming is minimized; this cooling: leads to a hardening, beyond the plastic material, inhibiting or prohibiting the formation by inflation and the formation by depression.

Inflation forming is accomplished by directing gas, preferably air, under pressure into holes 35 of mandrel 30, as described in the aforementioned French patent application. Slits, notches or small holes, not shown, are provided in the bottom of the outer cardboard container to prevent a pressure increase in this container during inflation forming and suitable means, not shown, are also provided in the mold 31 to prevent the pressure increase in the mold during inflation.

A wide range of gas pressures may be suitable for inflation forming according to the invention. For example, the pressure at the inlet of the mandrel can be between 0.352 and 3.5 kg/ctn. It is however preferable for reasons of safety and economy to use relatively low pressures, for example less than 2 kg/ctn*^.

It is understood that it is within the scope of the invention to use mandrels with stretch and inflation forming pieces which are not tapered. But it is also understood that with certain types of containers, a gas must be directed from the forming part 34 by stretching and inflating in the manner described in the aforementioned patent application, i.e. ( (a) if the outer cardboard receptacle has a bottom, the gas must be directed towards an angle of the receptacle defined by the intersection of the bottom and at least one vertical wall of this receptacle; and (b) if the outer fiberboard receptacle has more than one vertical wall, the gas must be directed to each corner of the receptacle defined by the intersection of two vertical walls. With respect to condition (b) above, it is of course that the upper part of the outer container must have a circular section so that circular nets are formed around.

The reason and the advantages of directing a gas in the manner described above are explained in the aforementioned French patent application and will not be repeated here.

It was indicated above that a wide gas pressure range at the chuck inlet could be suitable. It is however preferable that the air pressure be controlled during inflation so that the inner plastic container is spaced from the lower corners of the outer cardboard container defined by the intersection of the bottom of this container and each vertical wall . More particularly, as explained above, the inflation is preferably controlled such that the inner plastic container is spaced about 3 mm to about 9 mm from the bottom corners of the outer container. Furthermore, the gas used for inflation can be heated, either by the mandrel or by the external device, in order to maintain the plastic material in the state of thermal formation during the inflation operation.

Vacuum forming is accomplished by applying suction through channels 40 into the space between the plastic sheet 32 ​​and the net forming device 39. The suction applied can vary widely but preferably is of the order of 25 to 750 mm of mercury at the suction inlet of the mandrel 30 As shown in Figures 5 to 7> the air channels 4o are preferably arranged and made so that the suction is applied at points exteriors of the grooves of the device 39 for forming threads. The channels 40 are located in several places around the circumference of the device 39 and are preferably sufficiently small so that the plastic material is not sucked in during this operation.

Figure 7 shows plastic sheet 32, mandrel 30, mold J1 and outer container 10 at the end of the inflation forming and vacuum forming operation. At this point the source of gas and suction can be turned off and the container can be removed from the mold.

One method of removing the container is to release the mold from the container and mandrel and then unscrew the container from the mandrel. The unscrewing of the container is facilitated because, as explained above, in the present embodiment, the sheet of plastic material 32 is glued to the upper edge of the outer cardboard container during the production of the container. This sticking results from the pressure applied to the sheet 32 ​​by the gasket 52 in. silicone foam during the production of the container

It · is within the scope of the invention to remove the container from the mold and from the mandrel by other means. For example, a split mold and a split mandrel which are open to allow removal of the container may be suitable.

It should be noted that the portion of the sheet 32 ​​which extends outside the threads 22, as shown in Figure 7, must be cut from the container. One method is to use scissors or other cutting devices after the container has been removed from the mold. Another method is to provide a cutter in the mold and/or mandrel so that the plastic sheet 32 ​​is cut by shearing, either during the stretching operation or shortly thereafter while the container is still in the mould.

Other methods of cutting the sheet 32 ​​can be imagined, still within the scope of the invention. If the containers according to the invention are used to contain food products, precautions can be taken to ensure that no burr of plastic material enters the interior of the container, during and after the cutting operation. For example, if a split mold and a split mandrel are used, and the plastic material is cut into the mould, material deposition inside the container can be avoided by removing the container vertically and upwards after opening. mold and mandrel.

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To facilitate the entry of the outer cardboard container into the mandrel, it is preferred that the net forming device be arranged and constructed so that the line defined by the inner parts of the net forming device and a yaw containing the axis . , of this device is slightly inclined relative to the vertical, for exençle of the order of 0.5 to 3 °, preferably 1 °. Figure 9 shows this angle, exaggerated for illustration. Of course, it results from this embodiment of the thread forming device that the line defined by the inner part of the threads formed by depression in the container and a plane passing through the axis of these threads is also slightly inclined with respect to the vertical . Since the threads of the screw-on lid are not inclined with respect to the vertical, the inclination described above facilitates the tight fitting of the lid on the container, i.e. the lower part of the threads in plastic material is arranged in such a way that a part rests firmly against the threads of the cover.

When the container is removed from the mold and the mandrel, it may be filled with a food or other product. As indicated above, and depending on the product, it may be desirable to heat seal the container containing the product, with a sealable lid. This container can also receive a screwed lid.

It is understood that many modifications can be made to the embodiment described and illustrated without departing from the scope of the invention. For example, the stretch and inflation forming piece need not have a heater. Furthermore, other methods and means of applying and maintaining a vacuum between the plastic sheet and the thread forming device, as shown in Figure ό, remain within the scope of the invention.