Package making – Methods – Gas filling and/or evacuating and closing
Patent
1989-08-07
1991-01-08
Spruill, Robert L.
Package making
Methods
Gas filling and/or evacuating and closing
53 97, 53101, 53329, 53432, 53478, 53510, 156 68, B65B 728, B65B 3102, C14B 102
Patent
active
049825550
DESCRIPTION:
BRIEF SUMMARY
FIELD OF THE INVENTION
The present invention relates to a method and to a device for the sealing of a container.
BACKGROUND
A need frequently arises for the sealing of a container, e.g. a container of plastic material, by a laminate whose shape has been adapted to the shape of the opening, prior to the placing of the laminate on, or into, the opening. It has been known to seal containers with the aid of a foil of multilayer material, where the foil, after the container has been sealed, is trimmed in order to remove the parts of the foil projecting outside the edge of the container opening.
One problem which is encountered on the sealing of containers by means of foils, and especially by means of multilayer foils, is that on heating the foil it tends to become deformed because of curling. Since the foil as a rule is relatively thin, it assumes ambient temperature after a short time or is heated rapidly on being subjected to thermal radiaton. Such an environment exists for the foil when containers are to be sealed which are filled with warm or hot contents, and generally occurs on packaging foodstuffs. In certain applications, and especially when the foil is composed of layers of materials having different coefficients of linear expansion, the problem associated with the deformation of the foil is accentuated. When the foil gets warm it will curl so that if on the foil, e.g., the layer with the greatest coefficient of linear expansion faces the container opening, the circumferential outer edge of the foil will be raised, whereas on opposite placing of the layer the outer edge is displaced downwards.
The aforementioned deformations, as a rule, can be overcome if a foil in the form of a band is stretched over one or more containers and is fixed to the opening part of the respective container, so that the foil during sealing is kept stretched by mechanical means which counteract the tendency of the foil to curl. When the foil has thus been fixed, any projecting parts are cut off the respective container. However, in cases where the foil consisting of several layers is cut into wafers, each of a shape corresponding to the shape of the opening part of the container, prior to being fixed to the opening part of the container, it is not possible to stretch the foil by mechanical means, e.g. between its edges, so as to prevent the undesirable deformation (curling up) which on sealing of e.g. hot-filled containers entails only too often the occurrence of leaky closures.
SUMMARY OF THE INVENTION
In accordance with the present invention the aforementioned problem of sealing a container by means of a foil cut in advance, which forms a wafer of a shape adapted to the shape of the opening part of the container which is to be sealed, is eliminated.
This is achieved by means of a method and a device which are specified in the characterizing parts of claim 1 and claim 10, respectively.
In a preferred embodiment of the invention the sealing of the container takes place while an outer sealing means, in leakproof manner, delimits a space which accomodates the edge zone and the storage space of the container, the space being evacuated and, whilst maintaining a vacuum, the edge zone of the wafer being fixed in leakproof manner to the joining means.
The invention also comprises embodiments where for the formation of the joint between the wafer and the actual joining means, a fixing agent (bonding layer) is applied to the underside of the wafer, exclusively to the bonding surface of the opening part or to the underside of the wafer as well as to the bonding surface of the opening part. It is obvious that in certain applications such an agent is applied exclusively to the bonding surface of the opening part. It is obvious that in certain applications the agent is coated exclusively onto the underside of the outer edge zone of the wafer.
BRIEF DESCRIPTION OF THE FIGURES OF THE DRAWING
The invention is described in more detail in connection with a number of figures, wherein
FIG. 1 shows a section through a wafer,
FIGS. 2-4 ar
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Bianca Beth
PLM AB
Spruill Robert L.
LandOfFree
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