Container for preserved food with a flexible bottom, and corresponding production method

Abstract

The invention relates to a container for preserved food comprising a metal body having at least one end closed hermetically by a bottom formed by a flexible film.

Claims

1. A can (1) comprising a metal body (2) having a top part (22) closed hermetically by a first bottom (3) and a bottom part (23) closed hermetically by a second bottom (3), characterized in that the first bottom is formed by a foil (31) forming a flexible bottom, directly welded onto the metal body (2) so as to withstand the pressure stresses during a heat treatment (sterilization) of the can (1), wherein the flexible bottom is not peelable.

2. The can (1) as claimed in claim 1, characterized in that said first bottom (3) has a precut part (313), consisting of partial incision of the foil while maintaining the impermeability to air, to allow later easy opening of the can.

3. The can (1) as claimed in claim 2, characterized in that the precut part (313) is associated with a visual marking.

4. The can as claimed in claim 1, characterized in that the second bottom (3) is also formed by a foil (31).

5. The can (1) as claimed in claim 1, characterized in that said foil (31) comprises at least one metal layer (310b).

6. The can (1) as claimed in claim 1, characterized in that, for a standard 850 ml can, the weight of the metal body (2) is less than 50 g.

7. The can (1) as claimed in claim 4, characterized in that said first and second bottoms (3) are welded onto the top part (22) and the bottom part (23) respectively of said metal body (2).

8. The can (1) as claimed in claim 7, characterized in that the top (22) and bottom (23) parts of the metal body (2) of the can (1) are respectively folded/rolled so as to form a peripheral rim (24, 25) at each end of the can (1).

9. The can (1) as claimed in claim 8, characterized in that said rims (24, 25) are of different forms.

10. The can (1) as claimed in claim 1, characterized in that said metal body (2) has a truncated cone form.

11. A method for manufacturing a can (1) as claimed in claim 1, characterized in that it comprises a step of welding a flexible bottom to an end of the metal body, in conditions allowing said flexible bottom to withstand the pressure stresses which occur during a heat treatment of the can (1).

12. The method as claimed in claim 11, characterized in that the welding of the flexible bottom onto the end of the metal body is performed by heat sealing.

13. The method as claimed in claim 12, characterized in that said flexible bottom has a bottom membrane of polypropylene, that is heat sealed onto the end of the metal body covered with a polypropylene-filled lacquer.

14. The method as claimed in claim 11, characterized in that it also comprises one or more of the following steps, performed before or after the step indicated in claim 11: a step of filling the metal body with one or more food products; a step of crimping a rigid bottom onto the other end of the metal body so as to hermetically close the can.

15. The method as claimed in claim 11, characterized in that the can is of stamped type, and that the filling of the metal body with one or more food products is performed before the welding step of claim 11.

16. The method for manufacturing a can as claimed in claim 11, characterized in that it further comprises a step of folding/rolling the welded part of said body of the can so as to form a peripheral rim at the end of the can.

17. The method for manufacturing a can as claimed in claim 11, characterized in that it comprises a step of heat treatment (sterilization) of the can hermetically closed at its two ends.

18. The method for manufacturing a can as claimed in claim 11, characterized in that it further comprises a step of precutting the flexible bottom in order to allow easy opening of the can, preferentially after heat treatment.

Description

4. LIST OF THE FIGURES

(1) Other features and advantages of the invention will become more clearly apparent on reading the following description of an exemplary embodiment, given as a simple illustrative and nonlimiting example, and the attached drawings, in which:

(2) FIG. 1 is a perspective view of a can according to the invention, comprising two flexible bottoms;

(3) FIG. 2 is a schematic view in cross section of the metal body of the can of FIG. 1 during the manufacturing thereof;

(4) FIG. 3 illustrates an example of a foil that can be used on a can according to the invention showing the precut part intended to facilitate the opening of the can;

(5) FIG. 4 is an exploded view of the various layers that make up a foil according to the invention;

(6) FIG. 5 is a partial schematic representation, in cross section, of the top and bottom joins between the metal body and the foil of the can of FIG. 1;

(7) FIG. 6 illustrates an example of storage of two cans according to the invention, in particular when they have two flexible bottoms;

(8) FIG. 7 illustrates the main steps of the method for manufacturing a can according to the invention, comprising two flexible bottoms, and as described in the examples; and

(9) FIG. 8 is a perspective view of another form of can according to the invention.

5. DETAILED DESCRIPTION OF THE INVENTION

(10) 5.1 General Principle

(11) The invention relates therefore to a novel type of can comprising one or two bottoms, or lids, in the form of a foil. Such a can is distinguished from the known cans which implement rigid (relatively thick) metal bottoms at each of their ends.

(12) These flexible bottoms are intended to absorb the pressure stresses to which the can is subjected when the latter undergoes a heat treatment (sterilization) intended to preserve the food products that it contains. The thickness of the body of the can can thus be reduced.

(13) Consequently, the particular structure of the can according to the invention makes it possible to reduce the needs in terms of metal in relation to the current cans and reduces the manufacturing costs.

(14) 5.2 Structure of the can

(15) One embodiment of a can according to the invention, comprising two flexible bottoms, is described hereinbelow in relation to FIGS. 1 to 6. These figures and the teaching hereinbelow are also applicable when the can contains only a single flexible bottom.

(16) As illustrated in FIG. 1, the can 1 comprises a metal body 2 of cylindrical section. The metal body 2 is secured at both its ends to a flexible bottom 3 to produce the hermetic closure of the can 1.

(17) The metal body 2, which is preferably of steel or aluminum, has, in longitudinal cross section, a substantially parallelepipedal profile, as illustrated in FIG. 2.

(18) The profile shows two rectilinear and parallel walls 21 ending at each of their ends with flat annular parts 22, 23 which extend at right angles to the walls 21, over the perimeter of the opening (these flat parts 22, 23 are deliberately overdimensioned in FIG. 2 for clarity).

(19) The flat parts 22, 23 are each intended to receive a flexible bottom.

(20) For this, flexible bottoms 3, in the form of a foil 31, are affixed respectively onto the top 22 and bottom 23 parts before being secured thereto by welding (induction or resistance welding, for example). The welding has to be strong/resistant enough to ensure an optimal strength of the flexible bottoms 3 during the heat treatment (sterilization) of the can 1.

(21) The peripheral part or perimeter 311 of the foil 31 is therefore directly welded onto the flat annular parts 22, 23 of the metal body 2.

(22) Once the foils 31 are secured to the metal body 2, the top 22 and bottom 23 parts are rolled on themselves, as illustrated in FIG. 5.

(23) This rolling, in double folded seam form for example, forms a top rim 24 and a bottom rim 25 respectively encompassing the top part 22 and the bottom part 23 of the metal body 2 and the peripheral part 311 of the corresponding foil 31.

(24) Such a rim makes it possible to protect the foils 31 from the impacts and frictions that could possibly degrade the seal-tightness of the can 1, particularly during the handling and the transportation of the can 1 (in automatic conveyor systems, for example).

(25) Note that the top rim 24 is oriented toward the interior of the can 1 and that the bottom rim 25 is oriented toward the exterior of the can 1. This allows a stable stacking and optimized storage of the cans 1, one on top of the other, as illustrated in FIG. 6. It is however also possible to envisage a top rim 24 oriented toward the exterior of the can 1 and a bottom rim 25 oriented toward the interior of the can 1.

(26) 5.3 Structure of the Flexible Bottom

(27) The flexible bottom 3 of the invention is formed by a foil 31 made up of one or more layers. The layers can consist of different materials, such as polypropylene, aluminum or polyethylene.

(28) In the example illustrated in FIG. 4, the foil 31 of the flexible bottom 3 comprises two plastic layers 310a and 310c between which is inserted a metal foil, an aluminum foil 310b in this example.

(29) Such a combination of materials allows an optimal resistance while guaranteeing a strong flexibility of the flexible bottom 3, that is to say that the foil is capable of being stretched without breaking.

(30) The implementation of an aluminum foil 310b in such a flexible bottom 3 makes it possible to guarantee a reliable oxygen barrier. This aspect contributes to the long-term preservation of the sterilized foodstuffs which then allows for long-term ambient storage.

(31) The plastic layer 310c situated between the aluminum foil 310b and the flat parts 22, 23 ensures an optimal sealing of the flexible bottoms 3 on the metal body 2 of the can.

(32) Such a flexible bottom 3 also has a small thickness and a reduced weight.

(33) In fact, for a so-called 4/4 standard format can, the flexible bottom 3 has a weight of less than 10 g, and more specifically less than 5 g.

(34) Preferably, the weight of the flexible bottom 3 is equal to 3 g.

(35) If these values are compared to those of the bottoms of the cans of the prior art, namely 16 g for a standard rigid bottom, 22 g for a rigid bottom with easy opening by a gripping ring and 10 g for a peelable bottom, it can be seen that the weight saving, and therefore material saving, is relatively significant.

(36) The implementation of a flexible bottom 3 at each of the ends of the metal body 2 makes it possible to relieve the body of the can of the stresses linked to the pressure variations between the interior and the exterior of the can 1, during sterilization in particular.

(37) Indeed, the flexible bottoms 3 are capable of being deformed reversibly, so as to vary the internal volume of the can thus making it possible to absorb the pressure variations.

(38) In other words, the flexible bottoms 3 allow the can 1 to inflate and shrink upon pressure variations occurring during the heat treatment.

(39) Since the metal body 2 is less stressed during the heat treatment, its thickness, and therefore its weight, are reduced relative to a conventional can.

(40) Still for a can of standard 4/4 format, a conventional metal body has a weight of the order of 51 g.

(41) The implementation of two flexible bottoms according to the invention allows for the implementation of a metal body 2 of reduced thickness and having a weight less than 50 g.

(42) Preferentially, the weight of the metal body 2 is less than 40 g.

(43) Consequently, a can 1 according to the invention, implementing two flexible bottoms of 3 g each and a conventional can body (50 g) has a maximum total weight of 56 g. The cans of the prior art which have a conventional 51 g body, a conventional 16 g rigid bottom and a peelable 10 g bottom have a weight of 77 g, which is much greater.

(44) The weight saving of the can 1 of the invention is therefore at least 15 g.

(45) 5.4 Easy Opening of the can

(46) One of the foils 31 of the can 1 has a precut 313 which is intended to embrittle the flexible bottom 3 and allow an easy opening of the can 1.

(47) The precut 313 of the flexible bottom 3 is implemented in a conventional way, preferably by a laser cutting technique.

(48) This operation is performed after sterilization of the can 1 so as not to embrittle the flexible bottom 3 which has to guarantee an optimal seal-tightness of the can 1. In effect, as stressed previously, during the sterilization, the flexible bottom 3 is subjected to significant stresses due to the pressure variations internal to the can 1.

(49) This precut 313 is indicated to the user through an ink tracing, by dotted line for example.

(50) When the user wants to open the can 1, it is sufficient for him or her to apply a relatively low pressure to the part 312 of the foil 31 situated within the precut 313, in proximity thereto. This pressure, which can be applied using a spoon for example, causes the part 312 of the flexible bottom 3 situated within the precut 313 to break and allows the user to access the content inside the can.

(51) Thus, the opening of the can 1 of the invention requires no particular tool and does not require any significant effort on the part of the user. This approach allows for easy opening (opening requiring only a little effort and no particular tool) and guarantees an optimal seal-tightness of the can 1.

(52) 5.5 Method for Manufacturing the can

(53) The can of the invention is obtained by a different manufacturing method compared to that of the cans of the prior art.

(54) When the can has two flexible bottoms, such a manufacturing method comprises: a step of welding E1 of a first flexible bottom 3 onto a first flat part 23 (bottom part) of the metal body 2; preferentially, a step of folding/rolling E2 of the bottom part 23 on itself to form a rim 25; a step of filling E3 of the metal body 2 with one or more food products; a step of welding E4 of a second flexible bottom 3 onto the second flat part 22 (top part) of the metal body so as to hermetically close the assembly; preferentially, a step of folding/rolling E5 of the top part 22 on itself to form a rim 24; preferentially a step of heat treatment (sterilization) E6 of the can 1; preferentially, a step of precutting E7 of at least one of the two flexible bottoms 3 in order to allow for an easy opening of the can 1.

(55) Note that the method for manufacturing such a can according to the invention does not require the implementation of a crimping operation.

(56) 5.6 Other Aspects and Variants

(57) The structure of the can according to the invention offers an optimal resistance to the pressures undergone during the sterilization of the food content.

(58) The can according to the invention offers easy opening for the user and guarantees a perfect seal-tightness.

(59) Such a can is also lightweight, robust, simple and inexpensive to manufacture.

(60) Moreover, the precut can take forms other than a circular form.

(61) The implementation of a flexible bottom according to the invention makes it possible to dispense with the conventional metal bottom production standards and therefore consider the production of cans of varying forms.

(62) FIG. 8 shows a can 1 having a can body 2 in truncated cone form, the diameter of the bottom flexible bottom (not visible) being less than that of the top flexible bottom 3.

(63) This particular form makes it possible to stack the tapered cans one on top of the other stably, but also one inside the other, compactly, once the cans are empty.

(64) The stacking of the cans one inside the other can be performed before the can is filled and/or after the content of the can has been consumed.