DE2219924A1 - Lid for closing containers and device and method for its manufacture - Google Patents

Description

DR.-ING. OIPL.-ING. M. SC. DIPL.-PHVS. DR. DIPL.-PHV «. HÖGER - LEGAL RIGHTS - GRIESSBACH - HAECKER PATENT LAWYERS IN STUTTGART

Houilleres du Bassin du Nord et du Pas-de-Calais
20, rue des Minimes
Douai (North) France

Lid for closing containers and device and method for its manufacture

The invention relates to a lid for closing containers due to a .Wärmschrepfeiligkeits, with a flat, surrounded by a downwardly extending edge Part and ■ a method for producing such a cover and a device for carrying out the method. The invention relates in particular to a new type of lid intended for the airtight closure of a container is, so that airtight closures and packaging can be made in this way.

There are already various methods and devices for airtight closing of containers known, with removable Capsules or lids made of a plastic material are used, which are made of a metallic or plastic material Locking element held and hermetically sealed

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the, whereby the inviolability and inadequacy of the content is ensured up to the moment at which one intends to use the contents of the container. It has already been suggested in this context that To use heat shrinkage properties of certain polymer films to provide a seal and a tight seal of containers to reach.

Attempts have been made to find out why it has not yet been possible to create lids or closure capsules through the direct application of such heat shrinkable layers or films to manufacture containers to close without being able to do without intermediate caps. It was found, and that by simply repeating experiments that the result of the shrinkability of the films and the influence of heat resulting tensions had the effect of contraction towards the center. «This pulling effect stretched the edges of the film or of the layered plastic material used very strongly and made them thinner and more fragile and possibly even caused irregular and uncontrollable sliding upwards of the edge area. These 'phenomena compromised an airtight seal, even if one took the trouble to to select materials for the container and the sealing layer which are subject to the effects of those used for thermoforming Heat sealable to each other. When, after joining or merging, the film Cooled down, so to speak, i.e. warmed up accordingly and thereby suppressed the tension, you got a misshapen and ugly surface. Apart from that, there is also the risk of getting stuck or breaking out during

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of the manipulations. If one tries to remedy these disadvantages, that one films or layers with larger Thickness is used at times for thermoforming, where you run the risk of changing the shape of the container and its contents.

It has also already been proposed to cover containers directly with lids which have a heat shrinkage capacity by one starts from a flat sheet or a flat film of a non-oriented thermoplastic material whose a part is heated to a suitable temperature and. brought into the shape of a lid with a flat bottom part and cooled and is then cut so that a circumferential edge remains, which is the flat bottom part of the cover thus obtained (see Fig. 1).

In the course of the molding process, the circumference of the flat bottom part increases of the lid and the downwardly extending edge to a substantially radial orientation that the Lid according to the arrows f in Fig. 1 a considerable radial shrinkage capacity and a weak tangential Shrinkage capacity according to the arrows f * in Fig, I. to lend.

Do you want one. Close containers with such a lid, then you have a firm application of the edge to the outer wall of the opening of the container by the heat shrinkage capacity of the Cause cover.

In the course of closing operations of a container with a Lid of the type just described by heat shrinkage jnan can, however, state that under the sole influence

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Due to heat, the lid has the tendency to assume the initial flat shape of the thermoplastic film material from which it originated, which of course contradicts a tight fit of the edge to the opening of the container and the creation of an airtight seal. It is, therefore, necessary to use at Versc.hließen ^of containers when using lids of the type described additional arrangements, which allow to keep the central region of the cover base cold, whereby, however, the method and the machines that such a procedure for closing carry out of containers, become very complicated and expensive.

The invention is therefore based on the object of a cover as well specify a method for producing such a cover and a device for performing the method, at which the lid causes an airtight closure of the container without delay, even if the container is disadvantageous in terms of transport and is exposed to handling impacts. These are in particular containers that hold individual food rations or take drinks,

To solve this problem, the invention is based on a cover of the type mentioned and consists in that the flat Part has a central area with weaker shrinkage capacity than the peripheral area of the flat part and that the edge part has a shrinkage capacity with a large tangential component disposes.

A method according to the invention for producing such a lid has the following method steps that at least a part of a thermoplastic, softened plastic film is preformed in such a way that this part is formed

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gives the preform of a lid, the preform being the same appearance and smaller dimensions than that, which the lid should have after application that the preform in a homogeneous manner by maintaining the assumed Shape is made stress-free and that then a rapid deformation including a radial expansion this preform is made, the deformation being associated with an immediate quenching process.

The invention also relates to airtight containers, which can be produced by using the lid according to the invention and under the influence of thermal radiation, such a container preferably has a bead, a cutout or an extension along its opening or has an oblique surface.

Experience has shown that the lid according to the invention has the preform of the during manufacture the found shape of the lid, so to speak, "in memory" and has the tendency to use this shape alone under the influence to accept a thermal radiation again. Such a cover, which is subjected to thermal radiation, pulls itself in its central one Area less than its urangular area together. When such a lid is placed on a suitable opening of a container, the circumferential area and the downward extending edge much faster than the central area below the Influence of the heat together and attaches itself firmly and tightly to the container. In this way one gains a firm, secure one circumferential closure and a seal and only one low tension in the central area, which is sufficient to keep the lid base flat, but is too weak around the "lid edge" to pull up.

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The fact that the lid according to the invention has a shape memory of a preform / on which it is influenced Tending to withdraw from thermal radiation is an essential inventive feature and distinguishes it of previously known arrangements. Furthermore, the fact that the downwardly extending lid edge has a shrinkage capacity with a strong Tangentia! component, under the influence of heat in an excellent transverse seal. The quality of this fixed facility is so good that it is without the use of adhesives and without adhesive processes has succeeded in achieving airtight seals with containers, their

a funnel-like one
Edges without λ 'expansion were smoothed, although these containers were not described by the manufacturer as suitable for achieving an airtight seal without an adhesive connection.

Further refinements of the invention are the subject of the subclaims and laid down in these. In the following, the structure and mode of operation of the cover according to the invention are illustrated with reference to the figures, a method for its production and a device for carrying out this method in more detail explained. Show:

Fig. 1 shows a lid of known shape, which is used to

explain the arrangement of existing voltages in a known cover,

2 shows a longitudinal section through a container closed by a lid according to the invention as well as the lid itself before it is placed on the container and due to its heat shrinkability has been linked to this, the

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3 and 4 show exemplary embodiments of a device in a schematic sectional view for the production of the lid according to the invention, while the

FIG. 5 shows in perspective the one shown in FIGS. 3 and 4 with the aid of that Devices obtained covers shows.

In Fig. 2, a cup-like, closable container 1 is shown, which has a rotationally symmetrical shape and has a circular opening 2, which on its edge with a bead 3 is provided. "^

In the following description, "Manufacture and how to obtain a lid is described which is intended to hermetically seal this cup 1 due to heat shrinkage, wherein the cover assumes the profile shown with reference numeral 4 in FIG.

FIGS. 3 and 4 serve to explain the manufacturing process, using a device that enables the production of a lid according to the invention by thermoforming, annealing or Tempering and subsequent deformation with quenching allowed.

This device is essentially composed of a male mold 5 and a female mold 6, which are arranged one above the other and both are provided with ventilation passages 7.

The male mold 5 also has means for heating in the form of a heating element 8, for example a heating candle, as well Arrangements, not shown, which allow a negative pressure or an overpressure to be generated inside the male mold.

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Finally, the projection 11 of the male mold is rotationally symmetrical with a flat roof, similar to the shape 4, which accept the lid after heat shrinking on the container should, with the dimensions of the projection, in particular the diameter of the upper planar part 12, much smaller are than the corresponding dimensions of the shape 4 of the lid.

The inner wall of the recess 13 in the die also forms a flat bottom part 14, which corresponds to the projection 11, but in its dimensions, in particular what the The diameter of the bottom part 14 is much larger,

The die 6 has devices for cooling, shown in the form of a water snake, - ¹ ^ d an intermediate ring 15 , which consists of thermally insulating material.

The device is completed by holding and fastening elements 16 for a sheet 17 of a plastic material from which the cover is made. In the end facilities are also provided, which are symbolically represented by the arrows F and F * and the one directed upwards Movement of the male mold 5 and a downward movement of the female mold 6 cause until the intermediate ring 15 the Layer that contacts sheet or film of plastic material. The thickness e of the intermediate ring 15 is dimensioned so. that the sum H of the thickness e of the ring 15 and the depth P of the recess 13 of the die is greater than the height H * of the projection 13 of the patrix.

The operation of this device is then as follows. As with a common thermoforming process, a thin layer is created a plastic material which is brought to a temperature above its softening temperature, of the

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Holding elements 16 held while the actuators F Push the patrix 5 upwards until the projection 11 is at the level of the holding elements 16 for the layer 12 has exceeded. Subsequently, a negative pressure or a vacuum is generated inside the male mold.

The part of the plastic layer pulled against the projection 11 is then close to this projection and takes on the initial shape, which is hereinafter referred to as so-called. "Memory form" referred to shall be.

The tensions that develop in this "memory form" through thermoforming are eliminated by one the The shape anneals, so to speak, you leave it in contact with the warm protrusion for a sufficient period of time, for example, about 5 seconds at a temperature of 60 ° C, in the event that the cover is based on a polyvinyl chloride layer, for example, is made of PVC films of 250µ thick.

After this time has elapsed, the actuator can be used F, F 'the die 6 down until the intermediate ring 15 comes into contact with the part of the layer 17 which is based on the Projection rests. Due to the thickness of the intermediate ring, the bottom 14 of the recess 13 does not come with the part of the Plastic film 17 in contact, which rests on the flat surface of the projection.

In this phase (see FIG. 4 in this regard), the intermediate ring 15 thermally isolates the cold mattress 6 from the warm layer parts of the plastic material with which the ring is in contact and thereby enables an abrupt cooling of this part the layer 17 is avoided. In addition, the

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Intermediate ring in this way the seal between the die and that adopted by the layer 17 on the projection Memory form of the available volume.

In the course of the further manufacturing process, the following steps are done at the same time: The between the Die and the memory shape of the layer 17 existing air is sucked in and it is between the projection 11 and the Memory form a short overpressure is generated.

In this way, the memory form becomes sudden and abrupt stretched, especially at its circumference and pressed against the inner cold wall of the patrix, thereby causing it resulting contact is deterred.

Afterwards it is only necessary that the relief-like Impression of the cover 18 having layer can be seen from the mold and the cover for example by means of a hole punch cut out.

In Fig. 5 a possible shape of the cover produced by cutting out of the formed shape is shown, it is the cutting operation has been carried out so that a tongue 23 has been left for tearing open the lid.

The cover produced in this way has a flat part 19 which is surrounded by a depending edge part 20. The diameter of the flat upper part is greater than the diameter of the opening 2 of the container on which the lid is attached should be so that it is possible to easily place it on the container (see Fig. 2).

In the course of the expansion process of the memory shape, the central area 21 of the flat area 19 has radial stresses

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assumed, however, of an amplitude that is significantly weaker than the tangential stresses assumed by the downwardly extending edge portion 20.

The lid produced in this way allows the closure of containers whose opening diameter is between the diameter the shape of the memory and the diameter of a capsule element, as shown in dashed lines in FIGS is.

To close the container, it only needs to be inserted into a heat tunnel with the lid on, whose heating elements attached to the ceiling deliver less thermal energy than the side heating elements. Under Due to the influence of the heat energy, the lid shows the tendency to take on the geometric shape of the memory shape again. Included The central part 21 of the flat area 19 of the lid, which only shrinks slightly, contracts only a little and retains it hence its planar shape, while the peripheral zone 22 and the downwardly extending edge 20, which in the course of the deformation-quenching process, a large amount of heat shrinkage have acquired ability to contract strongly and therefore the top of the container and the "bead 3, like shown in Fig. 2, tightly and tightly enclose; thereby has the heat shrinkage capacity of the downward extending Edge has a strong tangential component (see arrows f * in Fig. 5) and causes the fixed application of the edge, the

SOWXG

neither shifts nor rises / the airtightness and securely attaching the lid to the container.

Depending on the dimensions of the manufacturing molds, it is possible to obtain lid molds with a heat shrinkability, depending on the circumstances of use (type and form of the

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closing lid) and the handling are adapted, both in terms of the lid itself and that of these lids to be closed containers.

It is also possible in this way to obtain closures, for example cap closures and the like. In which the The height of the edge is important, as this guarantees the necessary hygienic conditions if the

to

send containers are intended at the same time, as outer packaging for a product intended for consumption and for direct

to serve consumption of this product by the buyer / \ as this in the event of containers that contain individual amounts of beverage, is the case. It should also be noted that the height of the edge of the lid or the closure capsule is practically the same as the height that extends downwards before it is put on Edge occupies after fastening the lid on the container to be closed.

It will be understood that the present invention is also applicable to the production of lids that close containers must whose shapes are not rotationally symmetrical, for example prismatic or parallelepiped containers. In the same way, covers can also be produced in the manner described, which are intended for closing containers are whose opening edge has no bead.

It is also understood that the device described for example can also be designed so that several covers are made from the same plastic film at the same time can and that in each case the geometry of the memory shape or the geometry of the shape memory acquired in this way, that each part of the plastic layer to be treated is communicated during the preforming process, the geometry can be adapted to the container opening.

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Claims (11)

A 39 483 m a - 149 April 18, 1972 New claims: 1. Lid for closing containers due to heat shrinkage Property, with a flat part surrounded by a downwardly extending edge, characterized in that, that the flat part (19) has a central area (21) with a weaker shrinkage capacity than the peripheral ' Area (22) of the flat part (19) and that the edge part (20) has a shrinkage capacity with a large tangential component disposes. 2. Lid according to claim 1, characterized in that the lid has an output shape memory which it only has a tendency to take under the influence of thermal radiation. 3. Lid according to claim 1 or 2, characterized in that the circumference of the downwardly extending edge part (20) larger than the circumference of the opening of the container to be closed (1) is. 4. Process for the production of a lid according to one or more of claims 1-3, characterized by the following Method steps that at least a part of a thermoplastic, softened plastic film is preformed in this way is that this part is given the preform of a lid, the preform having the same appearance and smaller Dimensions than those which the lid after opening 209847/0733 A 39 483 m ia. a - 149 ^AT April 18 , 1972 . - 2r - should have that the preform is made stress-free in a homogeneous manner by maintaining the assumed shape and that a rapid deformation including a radial expansion of this preform is then carried out, the deformation being associated with an immediate quenching process. 5. The method according to claim 4, characterized in that the preform in the rapid deformation is an analogous shape, but with larger dimensions than the shape that the lid has after application. 6. The method according to claim 4 or 5, characterized in that the preforming and the deformation including expansion the preform can be effected by thermoforming. 7. Device for performing the method according to one or several of claims 4-6, characterized in that to form a "preform of the same appearance, however smaller dimensions than after application to a container (1) having a lid ^ (2) made of at least a part of a thermoplastic layer material a male mold is provided, with arrangements (8) for the elimination of stresses (annealing) in a homogeneous manner and for a predetermined period of time and that for subsequent rapid deformation with radial expansion of the tension-free preform and immediate quenching of further facilities (die 6 with Cooling arrangements, ventilation passages 7) are provided. 8. Apparatus according to claim 7, characterized in that for preforming the thermoplastic layer material the male mold (5) of a thermofrom machine operating under vacuum is provided, and that the male mold has thermal elements 209847/0733 A 39 483 m ^ a - 149 AS April 18, 1972 (8) has to keep its temperature at one, above the softening temperature to keep the temperature of the thermoplastic material lying. 9 «Device according to claim 7 or 8, characterized in that that opposite the male mold (5) a female mold (6) with cooling arrangements is arranged to keep its temperature at a temperature below the patrix that between Ma- (5) trize (6) and patrix, as well as the thermoplastic layer material a thermally insulating area (intermediate ring 15) is arranged, the airtight contact between The male, female and plastic material secures, and that Means are provided between the preform in contact with the male mold (5) and the inner wall area suction of air located in the die (6) and at the same time between the outer surface of the die (5, 11) and to create an overpressure in the preform, 10, a device for closing a container with the aid of a lid having a heat-shrinkable capacity according to a or more of claims 1 - 3 {characterized in that ceiling heating elements and side heating elements are provided, whereby the lateral thermal elements emit stronger thermal radiation, 11. Containers with airtight lid corresponding to one or more the
Reren claims 1-3, characterized in that the lid is attached to the container opening due to a heat-shrinking process. 209847/0733