EP3554734B1 - Method and device for producing tear-off lids and tear-off lid - Google Patents

Description

Reference to related documents

This document claims the priority of the Swiss patent application 0536/17 , filed April 21, 2017.

Field of invention

The invention relates to a method for producing tear-open lids according to the preamble of claim 1. Furthermore, the invention relates to a device for producing tear-open lids according to the preamble of claim 9 and a tear-open lid according to claim 15.

background

Tear-off lids are known, for example from DE-U 298 17 592 or off DE-U 92 03 953 . If the container, which is closed with the tear-off lid, contains a liquid, corrosive product, such as salt water, the bare cut edge of the lid opening can corrode. In the case of a tear-off lid with a so-called retort-curl, the rolling of the area with the cut edge upwards and outwards and the overlap with the tear-off foil provide a certain protection against the influence of the product. The bare or possibly corroded cut edge is also not visible. However, depending on the aggressiveness of the product and the storage time of the filled container, traces of corrosion can still be visible. In EP-A-1 153 840 it is proposed that the tear-off film is also sealed onto the curl itself, whereby the cut edge is protected from the contents of the can by a seal. It turns out, however, that the sealing both on the sealing flange and also on the curling in production is difficult to master perfectly with a high manufacturing rate. WO-A 02/790041 mentions in passing that the gap created during the roll-up process can be filled with the heat-seal coating of the tear-off foil without explaining how this would actually be feasible in the industrial production of tear-off foils. Known tear-off foils are only provided with a very thin heat-sealing layer and it is not apparent to the person skilled in the art how this layer can be used to fill the gap when a heat-sealing known to the person skilled in the art is carried out. In the WO-A 02/790041 The option mentioned is therefore hardly feasible in practice. Out EP-B 2 055 736 it is known to provide an outward curl in a container at the mouth of the container, so that the cut edge does not come into contact with water. It is proposed to protect the cut edge there with a modified hotmelt material which contains a thermoplastic elastomer. Out WO 2015/164986 A1 a method and a device according to the preamble of the independent claims are known which enable effective protection of the cut edge. In rare cases, however, insufficient protection of the cut edge can occur even with this known method.

Presentation of the invention

The invention is based on the object of creating an improved method with which tear-off lids can be produced industrially at a very high rate and at low cost, and in which the number of faulty lids with inadequate cut edge protection practically approaches zero.

This object is achieved in the above-mentioned method for producing tear-open lids in that, after the free end of the collar has been rolled up, the rolled-up area is heated in such a way that at least a partial melting of the plastic material of the strip takes place.

The rolled-up area includes at least the actual retort curl, which adjoins the area of the cover ring that forms the sealing surface and in particular includes the entire area in which the strip of plastic material is present. By heating it is meant that the rolled-up area is brought to a temperature that enables the plastic material to melt, it being not mandatory, but preferred, that the entire rolled-up area is homogeneously brought to the same temperature. The melting of the plastic material does not mean that the entire plastic material of the strip has to be brought to the melting temperature. It can be sufficient if the material layer of the plastic material adjoining the cover material melts in order to ensure the adhesion of the plastic material to the cover ring material. The heating is also not restricted to the rolled-up area, it may be that the entire cover ring is heated, but heating is preferred that is essentially restricted or concentrated to the rolled-up area with the strip of plastic material. Any heat sources can be used for this.

It has been shown that by heating the rolled-up area and melting the plastic material of the strip, optimum adhesion of the plastic material to both sides of the cover ring can be achieved, both of which are adjacent to the plastic material of the strip in the rolled-up area. The rolled-up area is hermetically sealed against the contents of the container to which the tear-off lid is applied. Thus, the corrosion on the Cut edge in tear-off lids which have been produced according to the invention can be reliably avoided.

The rolled-up area is preferably heated before the tear-off film is sealed onto the cover ring, so that this is a separate work step in the production of the cover. As a result, the heating and melting of the plastic material can be carried out separately from the introduction of heat during the sealing of the tear-open film and the influence of the heating of the rolled-up area on the seal can also be avoided. Cooling of the cover ring can also be provided between the heating of the rolled-up area and the sealing, for example by means of an air stream, so as not to influence the seal or the sealing parameters for the sealing of the tear-off film on the cover ring.

An inductive heating means is preferably used to heat the rolled-up area. This creates eddy currents in the metallic cover material, which cause it to be heated. The heating can affect the entire lid ring. Provision can be made for the arrangement of the inductive heating means and, if necessary, a concentration of the field lines of the inductive heating by means of pole pieces to generate the eddy currents mainly in the rolled-up area. The inductive heating of the metal material of the cover ring can cause the plastic material to be heated very quickly to the temperature at which the plastic material is melted. Inductive heating means have long been used in the industrial environment for heating workpieces and are known to those skilled in the art and are also commercially available. Alternatively, the heating can also take place with infrared radiation or hot air.

Alternatively or additionally, it is also possible to heat the rolled-up area while the tear-off film is being sealed. In this case a heating means contacting the rolled-up area is preferably provided in the sealing tool so that a direct heat transfer takes place from the heating means to the rolled-up area. In this way, the heating of the rolled-up area can be carried out separately from the sealing of the tear-off film on the cover ring, so that the sealing is not influenced in a disruptive manner by the heating of the rolled-up area. It is possible to carry out the heating in two stages both outside the sealing tool, in particular inductively, and also inside the sealing tool.

When sealing the tear-off foil on the lid ring, it is known to heat up twice so that the tear-open foil is first pre-sealed on the lid ring, and in a second step the main sealing of the tear-off foil on the lid ring takes place, the temperature of the pre-sealing being lower than the temperature of the main seal. In this case it is preferred that the heating of the plastic material of the strip or of the rolled-up area takes place in the second step during the main sealing of the tear-off film. In this way it can be avoided that the pre-sealing at the lower temperature is influenced by an additional heat input by heating the rolled-up area. Such a heat input can be managed well with the main seal with the higher sealing temperature.

The term plastic material of the strip in the present case includes that the strip comprises or consists of a polymer or a resin, and that the heating of the rolled-up area takes place at least to the melting temperature of the plastic material of the strip. In particular, that the rolled-up area is heated to a temperature in the range from 100 ° Celsius to 200 ° Celsius and in particular to a temperature in the range from 140 ° to 180 ° Celsius. This is for the case is particularly advantageous that the top of the lid blank forming the heat-sealable sealing surface for the tear-off film is or comprises a polypropylene-modified lacquer system, or is a polypropylene laminated coating, or is another coating containing polypropylene, and that the underside of the lid blank has a coating of a can interior lacquer with polyester or acrylic or epoxy or polyvinyl chloride. The named choice of material for the strip made of plastic and the named areas for the heating result in a particularly good connection between the named coatings of the cover blank or cover ring and the plastic strip.

A foaming agent can be added to the plastic material of the strip so that when the rolled-up area is heated, foaming occurs which can enlarge the area or the surface of the adhesion.

The invention is also based on the object of creating a manufacturing device for tear-open lids, by means of which tear-open lids can be manufactured at high speed and inexpensively, which have practically fault-free protection of the cut edge of the tear-open lid against corrosion.

This object is achieved in the device mentioned at the beginning with the characterizing features of claim 9.

Through the at least one further processing station, which is provided in the conveying direction after the third processing station, which is designed to heat at least the rolled-up area of the tear-off lid ring to at least the melting temperature of the plastic strip, the device is used to heat the rolled-up area and melt the Plastic material of the strip ensures optimal adhesion of the plastic material to both sides of the cover ring can be achieved, both of which adjoin the plastic material of the strip in the rolled-up area. In the case of the tear-off lid produced with it, the device achieves a hermetic seal between the rolled-up area and the contents of the container to which the tear-open lid is applied. In this way, the corrosion of the cut edge in the case of tear-off lids which have been produced on a device according to the invention can be reliably avoided.

The rolled-up area is usually a retort curl that adjoins the area of the cover ring that forms the sealing surface. The heating that can be achieved with the processing station means that the rolled-up area is brought to a temperature that allows the plastic material to melt, although it is not mandatory, but preferred, that the entire rolled-up area is homogeneous on the same Temperature is brought. The melting of the plastic material does not mean that the entire plastic material of the strip has to be brought to the melting temperature. It can be sufficient if the material layer of the plastic material adjoining the cover material melts in order to ensure the adhesion of the plastic material to the cover ring material. The heating is also not limited to the rolled-up area; it may be that the entire cover ring is heated, but heating is preferred that is essentially concentrated on the rolled-up area. Any heat sources can be used for this.

An induction heating means is preferably provided as a heat source in the further processing station. This allows a particularly rapid heating of the cover ring, and in particular of its rolled-up area, to the desired temperature, which is required for melting the strip made of plastic. This means that the high production rate for tear-off lids can also be maintained with the additional processing station. The further processing station can be provided at any point along the conveying path of the device between the processing station which produces the rolled-up area and the sealing station. It can be arranged before or after a turning station of the device. The arrangement in front of the turning station is advantageous because it allows the cover rings to cool down again up to the sealing station. An additional cooling station, which cools the cover rings with an air stream, for example, can serve for cooling. The cooling before the sealing station has the advantage that the sealing parameters are not influenced by the previous heating of the cover ring.

However, it can also be provided that the further processing station is integrated in the at least one sealing station and has a heating means that contacts the rolled-up area in the sealing tool. In the case of a device which has two sealing stations one after the other in the conveying direction in order to carry out a pre-sealing of the tear-open film and the main sealing, the further processing station is preferably integrated in the second sealing station.

The further processing station is designed in particular for heating the rolled-up area in the temperature range from 100 ° Celsius to 200 ° Celsius and in particular in the range from 140 ° to 180 ° Celsius. It is also preferred that the application station for applying the band-shaped plastic strip is designed in such a way that a strip with a substantially uniform thickness, in particular a thickness in the range from 0.05 mm to 0.5 mm and in particular with a thickness of approx , 1 mm, can be generated. The small thickness of the strip is advantageous for the rapid reaching of the melting temperature.

The invention further relates to a tear-open cover, comprising a circumferential fastening section, a sealing flange with a sealing flange Tear-off film, and a rolled-up area that runs around the sealing flange and laterally delimits the removal opening, the rolled-up edge having a seal made of a plastic, which term means a polymer or a resin, which is made by melting the plastic in the rolled-up area with the top and the underside of the tear-off lid is adhesively connected. This cover has the advantages mentioned.

Brief description of the drawings

• Figuren 1 bis 5 vertikale Schnittansichten durch einen Deckelrohling, einen Deckelring und einen Aufreissdeckel zur Erläuterung von Bearbeitungsschritten bei der Bildung eines Aufreissdeckels;
• Figur 6 eine vertikale Schnittansicht eines Deckelrings bei der Herstellung eines Aufreissdeckels gemäss der Erfindung;
• Figur 7 eine vergrösserte Ansicht eines Teils des Deckelrings von Figur 6;
• Figur 8 den Deckelring von Figur 7 nach dem Einrollen des Randes der Entnahmeöffnung zur Bildung des eingerollten Bereichs des Deckelrings;
• Figur 9 eine vergrösserte Ansicht eines Teils des Deckelrings von Figur 8;
• Figur 10 eine Draufsicht auf den Deckelring eines Aufreissdeckels;
• Figur 11 eine schematische Seitenansicht einer Vorrichtung gemäss der Erfindung zur Herstellung von Aufreissdeckeln mit gemäss dem Verfahren der Erfindung abgedichteter Schnittkante;
• Figur 12 eine Vertikalschnittansicht eines Teils eines Siegelwerkzeugs zur Durchführung der Erhitzung des eingerollten Bereichs im Siegelwerkzeug; und
• Figuren 13 eine schaubildliche Ansicht des vertikal geschnittenen Siegelwerkzeugs von Figur 12.

Further refinements, advantages and applications of the invention emerge from the dependent claims and from the description that follows based on the figures. Show:

• Figures 1 to 5 vertical sectional views through a cover blank, a cover ring and a tear-open cover to explain processing steps in the formation of a tear-open cover;
• Figure 6 a vertical sectional view of a cover ring in the production of a tear-open cover according to the invention;
• Figure 7 an enlarged view of part of the cover ring of FIG Figure 6 ;
• Figure 8 the cover ring from Figure 7 after the edge of the removal opening has been rolled up to form the rolled-up area of the cover ring;
• Figure 9 an enlarged view of part of the cover ring of FIG Figure 8 ;
• Figure 10 a plan view of the cover ring of a tear-open cover;
• Figure 11 a schematic side view of a device according to the invention for producing tear-open lids with a cut edge sealed according to the method of the invention;
• Figure 12 a vertical sectional view of a part of a sealing tool for performing the heating of the curled area in the sealing tool; and
• Figures 13 FIG. 13 is a perspective view of the vertically cut sealing tool of FIG Figure 12 .

Way (s) for carrying out the invention

With reference to the Figures 1 to 11 the production of tear-off lids known to the person skilled in the art can be briefly explained according to the prior art. Figure 1 shows a cover blank 1. At the beginning of the transport path of a manufacturing device 20 ( Figure 11 ) a stack 12 is shown which contains a large number of such lid blanks, which are individually stacked and processed along the transport path by different processing stations, whereby lid rings are first formed from the lid blanks and these are then processed further to the finished tear-off lid. The cover blanks are, for example, round disks made of coated metal and thus protected against corrosion, for example made of coated tinplate. The coating of the in Figure 1 upper underside is usually different from that in Figure 1 underlying coating of the top of the blanks 1. These blanks have, for example, a diameter of 11 cm and have already been preformed at their edge 6 by a processing machine (not shown) and the formation of the edge 6 is later used to attach the finished tear-off lid to a container or a can through a folded joint. This is known to the person skilled in the art and is not explained further here. The lid blank 1 in Figure 1 and the cover rings 2 in the Figures 2 to 4 are, as mentioned, shown with their underside upwards, while the finished tear-off lid is in Figure 5 is shown with its top and thus the tear-off film 8 facing upwards. The machining in the device can initially be in the location of the Figures 1 to 4 respectively, after which a turning station 26 follows, which the cover rings for sealing the tear-off film 8 on the respective cover ring in the position of Figure 5 brings.

The conveying device 22, which conveys the lid blanks, the lid rings and the tear-off lid in the manufacturing device 20 along the transport path in the direction of the arrow A from one processing station to the next processing station, is formed in particular by two toothed belts running in parallel, on which receptacles for the lid blanks or Cover rings are provided, as will be apparent to those skilled in the art WO 2006/017953 known. This is also not explained further here. At the processing stations known to those skilled in the art and only shown schematically here, the blank to be processed is lifted off the conveyor 22 and processed by the respective processing station and returned to the conveyor 22. This is indicated with arrows pointing up and down at the processing stations. In the case of the machining stations, the drive of the machining stations is indicated below the conveyor. This is used to raise and lower the blanks and cover rings and to carry out the respective processing steps.

In a punching processing station 23, a cover ring 2 is first formed from the cover blank 1 by cutting out a central part 30 of the blank and disposing of it as waste. This forms the removal opening of the tear-open cover, which is closed with the tear-off film in a later manufacturing step. A sealing flange 7 remains adjacent to the removal opening 15. The metal material lies bare at the cut edge 31 or the sheet metal of the cover ring 2 is no longer protected there by the coating or coatings. In a processing station 24, the edge of the removal opening is pulled upwards to form a collar 4 and this collar is rolled in a further processing station 25, so that a so-called retort curl 5 is formed. The shape of the curl or the retort curl can be different. The curling which forms the edge of the removal opening ensures that the user of the can is protected from the sharp-edged cut edge 31 when removing the contents of the can.

If the manufacturing steps are carried out with the sealing flange 7 pointing downwards, as shown, the turning station 26 follows, which turns the cover rings, so that during further processing the sealing flange 7 is at the top after the turning station in the conveyor device 22 and in the processing stations.

The tear-off film 8 is then sealed onto the sealing flange, which can be done in two stages with a first sealing station or pre-sealing station 27 and a second sealing station or a main sealing station 28. The sealing process is also known to the person skilled in the art and is not explained further here. Further processing stations can follow in which the sealing film is embossed, the tear-off tab is positioned and the seal is tested for leaks. This is also known to the person skilled in the art and is not explained further here. At the end of the manufacturing device 20, finished tear-off covers 10 ( Figure 5 ) output whose removal opening 15 is spanned by a tear-off film 8 which is sealed on the sealing flange 7. The edge of the removal opening 15 is by a (in the position of the lid according to Figure 5 ) retort-curl 5 bent upwards and outwards. The finished tear-off lid 10 can be attached to a can jacket (shown in FIG Figure 5 is only indicated with a wall part 11) are attached and thus closes the box. This takes place in the bottling plant in which the can has been filled with a product. The filled can can be opened later by tearing the tear-off film away from the lid ring by means of its tear-off tab 18, with the result that the removal opening 15 is open.

This is what turns out to be WO 2015/164986 A1 known procedure for applying a strip of plastic material in the rolled-up area and the procedure according to the present invention described, reference being made to the known, previously explained production steps or the known production device, insofar as this is necessary.

Figures 6 and 7 show a cover ring in which the processing step of drawing the edge of the removal opening to form the collar 4 has already taken place. This took place in the processing station 24. In the preferred example shown here (or in a separate step) an inward curvature has been produced at the upper end 34 of the collar 4, which facilitates the subsequent curling to form the retort curl. A plastic strip 32 has also been applied to the inside 40 of the collar 4 in one work step. This plastic layer is applied in a separate processing station 29, which is arranged between the drawing station 24 and the rolling station 25.

The band-shaped strip 32 made of the plastic material forms a seal for the cut edge 31 when it is rolled up, which is shown below. The strip 32 consists of a plastic, which term here means a polymer or resin. Such plastics are commercially available and in particular also commercially available in qualities that reliably withstand the sterilization temperature during the sterilization of the filled container and thus do not melt again at the sterilization temperature, so that the seal formed by the strip is retained during the sterilization. As shown, the strip is preferably of uniform thickness over the entire height of the band. It is provided as a thin plastic strip, which preferably has a thickness d in the range from 0.05 millimeters to 0.2 millimeters, preferably a thickness of approximately 0.1 millimeters. The height H of the strip can be, for example, 1 to 3 mm.

The application is preferably carried out on the basis of the expert WO 2015/164986 A1 known way by spraying molten, liquid plastic material, with a relative movement of the nozzle and cover ring. Preferably, the cover ring is moved in a rotating manner in the processing station 29 and the inside 40 of the collar 4 is moved past the outlet opening of a spray nozzle which is statically arranged during application and from which the plastic emerges. The cover ring is thus raised at the processing station 29, set in rotation and the application is activated when the cover ring has reached the correct position in relation to the outlet opening. After at least one full revolution, when a continuous band or such a strip is formed on the inside, the cover ring is moved back down to the conveyor, whereby the rotation is stopped so that the cover ring is placed back on the receptacles of the conveyor can. Then it is conveyed to the roll-in station 25. The plastic of the band 32 cools down as soon as it is applied to the cover ring and solidifies so that the plastic does not flow during further conveyance and the band is stable in the form shown. At most, a coolant, for example in the form of a fan, can be provided in the application station or processing station 29.

During application, it is ensured that the distance between the application opening or the spray nozzle and the inside 40 of the collar 4 remains essentially constant when the liquid plastic is sprayed on, so that the thickness of the strip 32 is essentially constant and its small thickness is possible. This can be done on the WO 2015/164986 A1 known way. The procedure according to WO 2015/164986 A1 for producing the strip 32 is preferred. In the context of the present invention, however, the strip 32 can also be applied to the cover ring in other ways. So it is possible to have a insert prefabricated strips of plastic material in the collar of the cover ring. This can take place in a separate processing station or when pulling the collar in station 24 or when rolling in the collar in station 25. In these cases the station 29 shown would be omitted.

It can be seen that the strip 32 is positioned on the inside 40 of the collar 4 that it is closer to the plane of the sealing flange 7 than to the cutting edge 31. The positioning and dimensioning of the strip is approximately such that the strip 32 is the lower third of the Collar 4 to about the lower half of the collar 4 covered. A greater height H of the strip is possible, but then the cost of material for the plastic used increases without this being necessary for further processing or for protecting the cut edge. In practice, the height H will be approx. 1 mm to 3 mm.

According to the Figures 6 and 7 Lid ring provided with the plastic strip is provided with a retort curl 5 in the processing station 25 in a known manner. This station 25 works with the rolling tools known for this, so that this does not have to be explained in detail here, since this is known to the person skilled in the art. A modification which is obvious to a person skilled in the art may arise in the case of the tools if the collar 4 has already been pre-bent at its upper edge 34 for curling, which is preferred. It can be seen according to the Figures 8 and 9 which show the cover ring after the turning station 26, that during the formation of the retort curl 5 the strip 32 forms a seal which prevents the entry of liquid into the interior of the retort curl. Thus, the bare cut edge 31 is protected against the influence of a liquid in the can. It does not matter whether the curling takes place in such a way that the cut edge 31 is partially embedded in the strip 32, as shown, or whether it only rests on the strip 32. Also the opposite that the cut edge 31 cuts through the strip 32 and rests against the metal of the inside 40, the function of the strip 32 does not interfere. The usual manufacturing tolerances in the formation of the retort curl 5 therefore play no role. The top view of Figure 10 shows the cover ring as it is conveyed into the sealing station 27, in which the tear-off film is sealed over the removal opening 15.

In the example of Figure 11 The manufacturing device 20 for the tear-off lid comprises the processing station 29 for applying the tape 32 to the lid ring and the processing station 25 for rolling in the collar 4.

According to the present invention, the rolled edge area is heated in order to melt the strip 32 at least in the contact area with the metal of the lid or the coatings on it. The rolled-up edge area includes at least the retort-curl 5, as it is for example in Figure 9 can be seen and in particular the entire part of the tear-open cover covered by the strip 32. In a first exemplary embodiment, a processing station 35 is provided in front of the turning station 26, in which processing station 35 the rolled-up area is heated. This can be done in such a way that the cover is also lifted off the conveying means 22 at this processing station 35, followed by heating in the processing station and then placing on the conveying means. The cover ring or its rolled-up area can, however, also be heated in the processing station while it is on the conveying means 22, that is to say without being lifted off the conveying means. In the processing station 35 in front of the turning station, the cover ring is still lying with the retort curl or the rolled-up area pointing upwards, as in FIG Figure 4 shown. This enables the rolled-up area to be heated from above and, for this purpose, an induction heating device is preferably provided in the processing station 35, which is shown schematically as block 43. The design of a Such a heating device is known to the person skilled in the art and need not be explained in more detail here. Instead of an induction heating device, an infrared radiation source or a hot air source could also be provided.

In another exemplary embodiment, the processing station for heating the rolled-up area can be provided after the turning station and is shown in the illustrated example with broken lines as processing station 35 '. In this processing station, the rolled-up area is at the bottom and accordingly it is preferred if the heating source acts from below, so that it can be more advantageous to design the processing station 35 'in such a way that the cover ring is lifted off the conveyor means 22 in it to allow processing with the heating source. In this case too, induction heating or another type of heating, which is only shown schematically as block 43, can be provided.

After the rolled-up area has been heated, cooling can be provided, for example by means of a fan. This is particularly advantageous if the processing station 35 ′ is present after the turning station 26 and a presealing station 27 for presealing the tear-open film 8 on the sealing flange 7 is also provided. Otherwise, the heating of the rolled-up area can have an undesirable effect on the temperature for the pre-sealing.

As an alternative to heating in a processing station 35 or 35 'or in addition to this, the heating of the rolled-up area in the sealing tool of the seal processing station can be provided. In the case of pre-sealing with the processing station 27 and the main sealing of the tear-off film with the processing station 28, it is preferred if the rolled-up area is heated in the main sealing station 28. Figures 12 and 13 show an example of the structure of a sealing tool for sealing the tear-off film and for heating of the curled area. Figure 12 shows a detailed representation of the lower part 36 of the sealing tool, on which a cover ring 2 rests, which has been lifted from the conveying means 22 by the sealing tool. Figure 13 shows the lower sealing tool in a diagrammatic representation and already after the sealing step with the tear-off film 8 on the lid ring 2. In the known sealing step, which is not explained further here, a suitable sealing film is then placed on the lid ring and using the upper sealing tool - not shown attached to the sealing flange 7 by the sealing process, after which the tear-off cover is placed on the conveyor means 22. In the figure it can be seen that the sealing tool has a special heating means 38, which directly contacts the rolled-up area and in particular the retort-curl 5 in order to bring the heat of the heating means 38 into the rolled-up area to heat the same and to melt the strip 32. In this example, the thermal energy for the heating means 38 is provided by the heating elements 39, which also serve to heat the lower sealing tool below the sealing flange 7. These heating elements 39, which are electrically heated, are in direct connection with the sealing tool and are in heat flow connection with the heating means 38 via a heat transfer layer 42. This is a preferred example, but it is obvious to a person skilled in the art that it generates heat for the heating means 38 can also be used in other ways for the rolled-up area. After leaving the sealing station 28, not only is the tear-off film 8 sealed onto the tear-open cover, but the adhesion of the strip 32 to the two surfaces of the tear-open cover has also been improved by the melting of the strip 32.

According to the invention, a tear-open cover 10 with a rolled-up area of the removal opening 15 is thus formed so that before the rolled-up cover is formed Area a plastic strip 32 is applied to the collar of the cover ring. After the rolled-up area has been formed, the plastic strip is melted in order to ensure good adhesion of the plastic to the top and bottom of the tear-open cover in the rolled-up area. This results in a practically hermetic sealing of the cut edge 31 of the tear-open cover in a cost-effective manner and with the possibility of production at high rates.

While preferred embodiments of the invention are described in the present application, it should be clearly pointed out that the invention is not restricted to these and can also be carried out in other ways within the scope of the following claims.

Claims (15)

1. Method for manufacturing peel-off lids (10), for which

   - a lid ring (2) with a central extraction opening (15) surrounded by a seal flange (7) is formed from a lid blank (1) by a punching process;

   - the edge of the extraction opening is formed by drawing towards a collar (4) protruding away from the seal flange (7);

   - a strip (32) made of plastic is applied onto the inner side (40) of the collar;

   - the collar (4) is rolled in at its free end (34) and comes to lie in the strip made of plastic; and

   - a peel-off foil (8) is sealed onto the sealing flange (7);
   characterized in that

   - after rolling in the free end of the collar (4), the rolled-in section is heated up in such a way that at least a partial melting of the plastic material of the strip (32) occurs.
2. Method according to claim 1, wherein the heating up is carried out before the sealing of the peel-off foil onto the sealing flange.
3. Method according to claim 1 or 2, wherein a heating means working inductively is provided for heating up.
4. Method according to one of the claims 1 to 3, wherein the heating up of the rolled in section is done during the sealing of the peel-off foil (8) on the sealing flange (7) by a heating means (38) contacting the rolled-in section in the sealing tool (36).
5. Method according to claim 4, wherein the sealing of the peel-off foil is a two-stage process, comprising firstly a pre-sealing and in a second step the main sealing of the peel-off foil onto the lid ring, and wherein the heating up of the plastic material of the strip is done during the main sealing of the peel-off foil.
6. Method according to one of the claims 1 to 5, wherein the plastic material of the strip comprises a polymer or a resin or consists of it, and the heating up is done at least to the flow temperature of the plastic material of the strip, particularly wherein the heating up is done in the range from 100° Celsius to 200° Celsius and in particular in the range from 140° Celsius to 180° Celsius.
7. Method according to one of the claims 1 to 6, characterized in that the upper side of the lid blank forming the sealing surface for the peel-off foil has a heat-sealing-suitable coating consisting of or containing polypropylene, and in that the underside of the lid blank has a coating consisting of interior varnish for cans or containing interior varnish for cans.
8. Method according to one of the claims 1 to 6, characterized in that a foaming agent is added to the plastic material of the strip.
9. Device (20) for manufacturing peel-off lids (10), comprising a transport installation (22) for lid blanks (1), lid rings (2) and peel-off lids (10), as well as processing stations (23 - 28), which are provided in transport direction (A) in succession for processing the lid blanks, lid rings and peel-off lids, wherein a first processing station (23) is provided as punching station for forming a lid ring (2) from a lid blank (1), a second processing station (24) is provided for forming a collar (4) of the lid ring (2), which protrudes away from the underside, and a third processing station (25), wherein the third processing station is adapted to form a rolled-in section from the collar, and wherein additionally at least a sealing station (27, 28) is provided, which is adapted for sealing a peel-off foil (8) onto a sealing surface (7) of the respective lid ring, wherein an application station (29) is provided in transport direction between the second processing station (24) and the third processing station (25), which is adapted to apply a circumferential, endless plastic strip (32) onto the inner side (40) of the collar (4), and the third processing station (25) is adapted such that the rolled-in section (5) comes into contact with the plastic strip (32), characterized in that at least a further processing station (35; 35'; 28) is provided in transport direction (A) after the third processing station (25), which is adapted for heating up at least the rolled-in section to at least the melting temperature of the plastic strip (32).
10. Device according to claim 9, wherein the further processing station has induction heating means (43) .
11. Device according to one of the claims 9 or 10, wherein the further processing station is integrated in the at least one sealing station and has a heating means (38) contacting the rolled-in section in the sealing tool.
12. Device according to claim 11, wherein two sealing stations are provided one after the other in transport direction, and wherein the further processing station is integrated in the second sealing station.
13. Device according to one of the claims 9 to 10, characterized in that the further processing station is adapted to heat up the rolled-in section in the temperature range from 100° Celsius to 200° Celsius and particularly in the range from 140° Celsius to 180° Celsius.
14. Device according to one of the claims 9 to 13, characterized in that the application station (29) is adapted to apply a band-shaped plastic layer (32) having a substantially uniform thickness, particularly a thickness in the range from 0.05 mm to 0.2 mm and particularly with a thickness of about 0.1 mm.
15. Peel-off lid comprising a circumferential attachment section (6), a sealing flange (7), with a peel-off foil sealed onto the latter and a rolled-in section (5) extending circumferentially around sealing flange (7), which limits the extraction opening laterally, characterized in that the rolled-in edge has a sealing (32) made of a plastic, particularly of a polymer or resin, which is connected in an adhering way to the upper side and the underside of the peel-off lid by melting the plastic in the rolled-in section.

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