FR2630408A3 - LID BELLOW LID FOR CONTAINER SUCH AS JAR OR CONTAINER FOR HEAT TREATMENT AFTER CLOSING - Google Patents

Abstract

The cover according to the invention comprises an expansion bellows 4 capable of compensating for the variation in pressure inside the container 1 when heat processing is carried out after closure. The expansion bellows may be obtained by producing at least one annular deformation in the section of the cover which is surrounded by the fixing area 3, this deformation preferably being parallel with and adjacent to the fixing area 3. According to a particular embodiment, the deformation is constituted by at least one channel 5, 6 and by at least one rib 7, 8 which are parallel and adjacent.

Description

Bellows with expansion bellows for container such as pot or tray intended to undergo heat treatment after closure
The present invention relates to a leaf-shaped cover intended to be fixed along an annular range adjacent to its periphery, on a container such as a pot or a tray intended to undergo a heat treatment after closure.

 When a product contained inside a container closed by a leaf-shaped cover is subjected to a heat treatment such as precooking, cooking, sterilization or pasteurization, the pressure prevailing inside the container forces the cover to bulge outwards and therefore to stretch. However, as the stretching is generally exerted beyond the elastic limit of the material constituting the cover, the latter can no longer resume its initial dimensions during cooling and then gives an unsightly appearance to the container.

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Furthermore, when the container is made of plastic, it frequently happens that it softens at the temperature of the heat treatment and that the cover deforms it by exerting on it a pull tending to narrow its entry.

 The present invention more particularly proposes to remedy these drawbacks and, to do this, it relates to a leaf-shaped cover which is characterized in that it comprises an expansion bellows capable of compensating for the variation in pressure in the container during heat treatment.

 Thanks to its expansion bellows which is designed to expand when the pressure increases inside the container and to retract when the pressure decreases, the cover according to the invention can no longer be irreversibly stretched during the heat treatment. . The closed container therefore now retains a satisfactory aesthetic appearance after having undergone the heat treatment.

 Furthermore, when the cover according to the invention is fixed to a plastic container, it does not tend to deform the latter during the heat treatment.

 The expansion bellows is preferably obtained by carrying out at least one annular deformation in the part of the cover which is surrounded by the fixing pad.

 It will be noted here that the deformation of the cover is very easily achievable using a matrix.

 To standardize the action of the expansion bellows, it is desirable for the annular deformation to be parallel and adjacent to the attachment range.

 According to a particular embodiment of the invention, the deformation consists of at least one groove and at least one parallel and adjacent rib.

 When the space above the product contained in the container must be as small as possible, the cover may advantageously include an annular part inclined downward from the fixing zone, the expansion bellows then being provided in this annular part.

Two embodiments of the present invention will be described below by way of non-limiting examples with reference to the attached drawing in which:
- Figure l is a top view of a cover according to the invention, this cover being fixed on a container having a circular inlet
- Figure 2 is a partial sectional view on an enlarged scale taken along line II-II of Figure 1; and
- Figure 3 is a schematic sectional view of a cover according to an alternative embodiment.

 The cover that can be seen in FIGS. 1 and 2 is in the form of a disc comprising at least two layers of different materials fixed against each other, these layers possibly being, for example, of aluminum, made of paper or thermoplastic material.

 In the example shown, the cover closes a sterilizable container 1 comprising an annular rim 2 around its inlet; More specifically, it is sealed on the rim 2 of the container 1 along an annular area 3 adjacent to its periphery.

 According to the invention, the cover comprises an expansion bellows 4 capable of compensating for the increase in pressure in the container during sterilization. This bellows, which was produced using a die, is here constituted by an annular deformation parallel and adjacent to the sealing area 3.

 Referring more particularly to FIG. 2, it will be noted that the annular deformation comprises two grooves 5, 6 and two ribs 7, 8 having a substantially semi-circular section.

 The rib 7 is located between the groove 5 which is adjacent to the sealing zone 3 and the groove 6 which is in turn adjacent to the rib 8. Furthermore, the groove 5 and the ribs 7, 8 have substantially the same section while the groove 6 has a section of the order of three to four times greater than theirs.

 Of course, it would not be departing from the scope of the present invention if the number of grooves and ribs was changed or if their section was changed.

 Referring now to the embodiment shown in FIG. 3, it will be noted that the cover comprises an annular part 9 inclined downwards from the sealing zone and that the expansion bellows 4 is housed in this annular part.

 Such a seal has been developed to minimize the space left free in the container.

 Thanks to the present invention, the foil-shaped lids used to make sterilizable containers no longer risk being irreversibly stretched during sterilization. Furthermore, plastic containers which tend to soften when hot no longer risk being deformed by the lids.

 The containers can therefore now retain a suitable aesthetic appearance after sterilization, which can only be appreciated by consumers.

 To be complete, it will finally be specified that the ribs and the grooves constituting the bellows have the advantage of increasing the rigidity and consequently the resistance of the cover.

 The present description has been given in the case where the cover according to the invention is intended to close a sterilizable container. It goes without saying, however, that this cover could be used to close a container intended to be subjected, after closure, to a precooking, a cooking or a pasteurization.

Claims (5)

 1. Leaf-shaped cover intended to be fixed along an annular area (3) adjacent to its periphery, on a container (1) such as a pot or a tray intended to undergo a heat treatment after closure, characterized in that it comprises an expansion bellows (4) capable of compensating for the variation in pressure in the container (1) during the heat treatment.  2. leaf-shaped cover according to claim 1, characterized in that the expansion bellows (4) is obtained by producing at least one annular deformation in the part of the cover which is surrounded by the fixing pad (3) .  3. Leaf-shaped cover according to claim 2, characterized in that the annular deformation is parallel and adjacent to the fixing area (3).  4. leaf-shaped cover according to claim 2 or 3, characterized in that the deformation consists of at least one groove (5, 6) and at least one rib (7, 8) parallel and adjacent.  5. leaf-shaped cover according to any one of claims 2 to 4, characterized in that it comprises an annular part (9) inclined downwards from the fixing zone (3), the expansion bellows (4) being formed in this annular part (9).