Method for closing a package

Abstract: A package comprising a tray and a removable lid, which tray is made of plastics material and is especially intended for keeping and heating of ready-cooked food, and which lid is made of cardboard and/or plastics material. The package include a plastic film (3) the area of which is at least as large as that of the lid (2) and which is heat-sealed to the lid and to the edge (1a) surrounding the opening of the tray (1) and the characteristics of which are such that the lid and the plastic film are removable from the edge without the lid or the tray being destroyed. The invention also comprises a method for sealing the package.

Description: Technical field The present invention relates to a method for sealing a package. The package comprises a tray and a lid, which tray is made of plastics material and is especially intended for keeping ready-cooked food and heating of same in a microwave oven, and which is made of cardboard and/or plastics material. Prior art It is known to keep and to heat ready-cooked food in packages consisting of a tray provided with a lid. It is essential that the food should not be affected by the packaging material and that the lid should be easily removable from the tray. A package fulfilling these requirements comprises an aluminium tray with a card-board and/or aluminium lid which is attached to the tray by folding the edges surrounding the opening of the tray inwardly over the lid, and which can be removed therefrom after said edges have been folded away from the lid. Disadvantages of this package are that sealing is carried out manually, that the food cannot be heated inside the package in a microwave oven and that the sealing will not be liquidproof. A package in which the food can be heated in a microwave oven and which can be sealed mechanically comprises a tray of plastics material such as CPET and a lid made of plastic-coated cardboard, which lid can be welded (heat-sealed) to the edges of the tray opening. A disadvantage of this kind of package is that the lid is difficult to remove from the tray and often breaks when being removed. Further, it is known to weld a plastic film to a CPET tray. With this kind of package it is difficult to tear and to remove the film without touching the food. Moreover, it is not possible to provide the film with information in the form of, for example, advertising or a text stating the contents of the package, and packages of this kind are therefore often supplied in cardboard cases provided with such information. FR-A-1 379 891 discloses a tray and two superimposed thermoplastic lids which are connected to the tray in two separate operations with the connection lines between the tray and the lids at a distance from each other. CH-A-475 883 discloses a polypropylene tray and a lid comprising a polypropylene sheet covered by an ethylene layer. The layer is welded to the tray so that the lid can be easily removed from the tray. Description of the invention It is an object of the present invention to improve sealing of packages of the above-mentioned kind and to seal these in a simple, nonexpensive and efficient way. This object is accomplished by providing the package of the invention with the features stated in the characterizing portions of the claims. Description of the figures The one figure of the drawing is a schematic, exploded perspective view showing sealing of a package according to the invention. Preferred embodiment The package according to the invention comprises a tray 1 of thermoformed CPET with an opening surrounded by a folded, approximately 5 mm wide edge which extends round the whole of the tray 1, a lid 2 of cardboard and plastics material, suitably a material marketed under the name of Invercote (registered trademark) G + AP (ethylene acrylic acid), and a film or sheeting 3 of polyester, suitably a film marketed under the name of Mylar (registered trademark) OL. The materials of the tray 1, lid 2 and film 3 are heat-sealable to each other, however, if the lid were to be heat-sealed (welded) straight onto the tray, it would not be possible to remove it from the tray without it being destroyed (torn). The figure shows the package being sealed. After the tray 1 has been filled with ready-cooked food, it is placed on a support 4 provided with a rubber plate 5 with upwardly oriented edges 5a surrounding the base of the tray. This can be done manually or by means of a suitable feeding device. A roll 6, on which the film 3 is wound in the form of a band, is located over and adjacent the support 4. The width of the roll 6 and therefore of the film 3 corresponds to or is slightly wider than the length of the tray 1, i.e. the greatest distance between opposite parts of the edges 1a. For each tray 1 placed on the plate 5, the film 3 is intended to be advanced immediately over or in contact with the tray in the direction of the arrow a distance which corresponds to or is slightly longer than the width of the tray, by a suitable device not shown in the figure. The lid 2 is placed, manually or by a device not shown, on top of the film 2 exactly over the tray 1. The area of the lid 2 is selected such that the lid will cover the tray opening and the entire edge 1a. At a distance over the plate 5 slightly exceeding the height of the tray 1 there is arranged a welding head 7. The head 7 is provided with a lower plane surface, the area of which corresponds to the area of the lid 2. The head 7 is movable towards and away from the tray 1 with the film 3 and lid 2 thereon, and its temperature is such that heat-sealing or welding of the film to the tray and of the lid to the film will take place when the head is briefly pressed against these. After or in connection with the above described heat-sealing a sleeve 8 with a heated, lipshaped lower edge 8a, which sleeve surrounds the welding head 7 and is guided by same, is carried downwardly towards the tray 1, whereby the film 3 will melt immediately outside the lid 2 so that the parts of the film surrounding the lid will be separated from the now finished package, which will then be removed from the support 4 either manually or by some suitable feeding-out device. Owing to the film 3 being inserted between the lid 2 and the tray 1 and owing to the properties of the material of which they are made, there is provided a package the contents of which can be heated in a microwave oven (also with the lid attached), and the top side of which can be preprinted or provided with print or the like in connection with sealing and the lid of which can be removed by the so called peel-off effect, i.e. the film is easily removable from the tray without the lid getting torn or destroyed in some other way. Although only one embodiment of the invention has been described above and shown on the drawing, it will be understood that the invention is not limited to said embodiment but only by the scope of the claims.

Claims: A method for sealing a package comprising a tray (1) and a lid (2), which tray is made of plastics material and is especially intended for keeping of ready-cooked food and heating of same in a microwave oven, and which lid is made of cardboard and/or plastics material, the method including that the tray with contents is placed on a support (4,5), that a plastic film (3), the area of which is larger than that of the tray opening, is placed over the tray opening, and that the lid, the area of which is larger than that of the tray opening, is placed on top of the plastic film, characterized in that the plastic film (3) is welded to the tray (1) and the lid (2) is welded to the plastic film in one and the same operation. A method according to claim 1, characterized in that the area of the plastic film (3) is essentially larger than that of the lid (2) when the plastic film is placed over the tray and is given substantially the same length-width dimension as the lid in connection with its being welded to the tray (1). A method according to claim 2, characterized in that the plastic film (3) in the form of a band is advanced to a position over the tray (1) in which the plastic film is given substantially the same length-width dimension as the lid (2) through separation by means of heat.

Inventors: AXELSSON KATARINA, INGEMARSSON HAEKAN, AXELSSON, KATARINA, INGEMARSSON, HAEKAN, Ingemarsson, Häkan
Applicants: CERBO AB, AB CERBO
Application year: 1990
Main classification: B65B7
IPC codes: B65B7, B65D77