EP3554734A1

EP3554734A1 - Method and device for producing tear-off lids and tear-off lid

Info

Publication number: EP3554734A1
Application number: EP18703189.3A
Authority: EP
Inventors: Peter Taiana; Marcel Oberholzer
Original assignee: Soudronic AG
Current assignee: Soudronic AG
Priority date: 2017-04-21
Filing date: 2018-01-25
Publication date: 2019-10-23
Anticipated expiration: 2038-01-25
Also published as: ES2832878T3; EP3554734B1; WO2018191828A1; PT3554734T; US20200094308A1; JP2020517526A; TWI754004B; TW201841803A; CH713744A2; CN110366457A

Abstract

The invention relates to a tear-off lid (10) having a rolled-up region around the removal opening (15), which tear-off lid is formed in such a way that, before the rolled-up region is formed, a plastic strip (32) of small thickness is applied to the collar (4) of the lid ring. After the rolled-up region has been formed, the plastic strip (32) is melted in order to produce good adhesion of the plastic to the top side and the bottom side of the tear-off lid (10) in the rolled-up region. A practically hermetic seal of the cut edge (31) of the tear-off lid (10) is thus achieved economically and with the possibility of production at a high rate. The invention further relates to a method and to a device for producing such a tear-off lid.

Description

Method and device for producing rip-off covers and a rip-off lid

Note on related documents

This document claims priority to Swiss Patent Application 0536/17, filed on Apr. 21, 2017, the entire contents of which are hereby incorporated by reference.

Field of the invention

The invention relates to a method for the production of tear-open lids according to the preamble of claim 1. The invention further relates to a device for the production of tear-open lids according to the preamble of claim 9 and a tear-open lids according to claim 15.

background

Tear-off covers are known, for example from DE-U 298 17 592 or from DE-U 92 03 953. Contains the container, which is closed with the tear-open, a liquid, corrosive filling material, such as. Salt water, so the bare cut edge of the lid opening can corrode. In the case of a tear-open lid with a retort curl, the curling of the area with the cut edge upwards and outwards and with the covering by the tear-open foil provide a certain protection against the influence of the filling material. Also, the bare or possibly corroded cutting edge is not visible. However, depending on the aggressiveness of the contents and the storage time of the filled container, traces of corrosion may still be visible. In EP-A 1 153 840 it is proposed that the tear-open film is also sealed to the curl itself, whereby the cut edge of the can contents is protected by a seal. It turns out, however, that the seal is difficult to master perfectly both at the sealing flange and in addition to the rolling in the production with high manufacturing cadence. It is mentioned casually that WO-A 02/790041 mentions that the gap formed during the rolling-in process can be filled with the hot-seal coating of the tear-off film, without explaining how this can be done in the industrial production of. Tear-up films would actually be feasible. Known slips are only provided with a very thin heat-sealable layer, and it is not obvious to the person skilled in the art how this layer can be used for gap filling if a heat seal known to the person skilled in the art is carried out. The possibility mentioned in WO-A 02/790041 is therefore hardly practicable in practice. From EP-B 2 055 736 it is known to provide an opening to the outside of a container at the mouth of the container, so that the cutting edge does not come into contact with water. It is proposed to make there a protection of the cutting edge with a modified hotmelt material containing a thermoplastic elastomer. WO 2015/164986 A1 discloses a method and a device according to the preamble of the independent claims, which enable effective protection of the cut edge. In rare cases, however, inadequate protection of the cut edge can also occur with this known method.

Presentation of the invention

The object of the invention is to provide an improved method with which tear-open lids can be produced industrially in very high cadence and at low cost, and in which the number of defective lids having an insufficient cut edge protection practically approaches zero , This object is achieved in the above-mentioned method for the production of tear-open lids in that after rolling in the free end of the collar of the rolled-up area is heated so that at least a partial melting of the plastic material of the strip.

The rolled-up region comprises at least the actual retort curl, which adjoins the region of the lid ring which forms the sealing surface, and in particular comprises the entire region in which the strip of plastic material is present. By heating, it is meant that the curled portion is brought to a temperature which will permit the plastic material to be melted, although it is not mandatory, but it is preferred that the entire curled portion be brought homogeneously 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 may be enough if the on _. the material of the plastic material adjacent to the lid material melts in order to ensure the adhesion of the plastic material to the lidding material. The heating is also not limited to the rolled-up area, it may be that the entire lid ring is heated, but is preferably a heating, which is limited or concentrated on the rolled-up area with the strip of plastic material substantially. For this purpose, any heat sources can be used.

It can be seen that with the heating of the rolled-in area and the melting of the plastic material of the strip, an optimal adhesion of the plastic material to the two sides of the cover ring can be achieved, which in the rolled-up area both on the plastic material of the Bordering the strip. A hermetic seal of the rolled-up area with respect to the contents of the container on which the tear-off lid is applied is achieved. Thus, the corrosion at the Cutting edge in tear-open, which have been prepared according to the invention, be safely avoided.

The heating of the rolled-up area is preferably carried out prior to the sealing of the tear-off film on the cover ring, so that this is a separate working step in the manufacture of the lid. As a result, the heating and melting of the plastic material can be performed separately from the heat input, in the sealing of the tear film and it can also be an influence of the heating of the rolled area on the seal avoided. It may be provided between the heating of the rolled-in area and the seal also a cooling of the cover ring, for. Example by an air flow, üm the sealing or the sealing parameters for the sealing of the tear-open film on the cover ring not to influence.

Preferably, an inductively operating heating means is used to heat the rolled-up area. This produces eddy currents in the metallic de-deco material which cause it to heat up. The heating can act on the whole lid ring. It can be provided by the arrangement of the inductive heating means and possibly a concentration of the field lines of the inductive heating by means of pole pieces to produce the eddy currents mainly in the rolled-up area. By the inductive heating of the metal material of the cover ring, a very rapid heating of the plastic material to the temperature can be effected, at which the melting of the plastic material takes place. Inductive heating agents have long been used in the industrial environment for the heating of workpieces and are known to the person skilled in the art and are also commercially available. Alternatively, the heating can also be done with infrared radiation or hot air.

Furthermore, it is alternatively or additionally possible to carry out the heating of the rolled-up area during the sealing of the tear-off film. In this case For example, a heating means contacting the curled area is preferably provided in the sealing tool so that a direct transfer of heat from the heating means to the rolled-in area takes place. Thus, the heating of the rolled-up area can be performed separately from the seal of the tear-open film on the lid ring, so that the seal is not troubled 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 additionally within the sealing tool.

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

The term plastic material of the strip herein means that the strip comprises or consists of a polymer or a resin and that the heating of the rolled-up area is at least at the melting temperature of the plastic material of the strip. In particular, that the heating of the rolled-up area to a temperature in the range of 100 ° Celsius to 200 ° Celsius, and in particular to a temperature in the range of 140 ° to 180 ° Celsius. This is for Particularly advantageous is the case that the upper side of the lid blank forming the heat-sealable sealing surface for the tear-off film is or comprises a polypropylene-modified paint system, or is a polypropylene-laminated coating, or another polypropylene coating is, 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. Said choice of material of the plastic strip and the areas mentioned for the heating result in a particularly good connection between the mentioned coatings of the lid blank or lid cover and the plastic strip.

A foaming agent may be added to the plastic material of the strip, so that when the rolled-up area is heated, foaming takes place which increases the area or surface area of the adhesion.

The invention is also the task

Basically to create a manufacturing device for tear-open, through which tear-open in high cadence and inexpensive to produce, which have a virtually flawless protection of the cutting edge of the tear-open against corrosion.

This object is achieved by the aforementioned device with the characterizing features of claim 9.

By the at least one further processing station, which is provided in the conveying direction after the third processing station, which is designed for heating, at least the rolled-up region of the tear-open lid ring to at least the melting temperature of the plastic strip, with the. Device with the heating of the rolled-up area and the melting of the plastic material of the strip an optimal adhesion of the plastic material on the two sides the lid ring can be achieved, which both adjoin the plastic material of the strip in the rolled-up area. By the device is a hermetic in the tearing covers thus produced. Tightness of the rolled-in area relative to the contents of the container is achieved, on which the tear-open lid is applied. Thus, the corrosion cut edge in tear-open, which have been produced on a device according to the invention, can be safely avoided.

The rolled-up area is usually a retort curl, which adjoins the area of the lid ring that forms the sealing surface. By the heating that can be achieved with the processing station, it is meant that the rolled-up area lies on one side Temperature is brought, which allows melting of the Kunststoffmateri- as, - where it is not mandatory, but it is preferred that the entire, rolled-up area is brought to the same homogeneous 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 may be sufficient if the material layer 'of the plastic material adjacent to 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 lid ring is heated, but a heating is preferred which is essentially concentrated in the rolled-up area. Any heat sources can be used for this purpose.

An induction heating means is preferably provided in the further processing station as the heat source. 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 of plastic. Thus, even with the additional processing station, the high production cadence for tear-open covers can be retained. The another processing station can be provided at any point along the conveying path of the device between the processing station which produces the rolled-in 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 cools off the cover rings up to the sealing station. At most, an additional cooling station can be used for cooling, which cools the cover rings, for example with an air flow. Cooling in front of the sealing station has the advantage that the sealing parameters are not influenced by the previous heating up 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 contacting the rolled-up region in the sealing tool. In a device which has two sealing stations successively 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 region in the temperature range from 100 ° C. to 200 ° C., and in particular, in the range from 140 ° to 180 ° C. Furthermore, it is preferred that the application station for applying the strip-shaped plastic strip is designed so that a strip with a substantially uniform thickness, in particular a thickness in the range of 0.05 mm to 0.5 mm and in particular with a thickness of about 0.1 mm, can be generated. The small thickness of the strip is advantageous for the rapid achievement of the melting temperature.

Furthermore, the invention relates to a tear-open lid, comprising a circumferential attachment portion, a sealing flange with a sealed on this Tear-open film, and a rolled around the sealing flange, rolled-up area laterally delimits the removal opening, wherein the rolled-up. Edge a seal made of a plastic, which term means a polymer or a resin has, which is adhesively bonded by melting the plastic in the rolled-up area with the top and bottom of the tear-open. This cover has the. mentioned advantages. Brief description of the drawings

Further embodiments, advantages and applications of the invention will become apparent from the dependent claims and from the following description with reference to the figures. Showing:

FIGS. 1 to 5 vertical sectional views through a cover blank, a cover ring and a tear-open lid to explain processing steps in the formation of a tear-open lid;

FIG. 6 shows a vertical sectional view of a lid ring in the manufacture of a tear-open lid according to the invention;

Figure 7 is an enlarged view of a portion of the cover ring of Figure 6;

FIG. 8 shows the cover ring of FIG. 7 after

Curling the edge of the removal opening to form the rolled-up portion of the cover ring;

Figure 9 is an enlarged view of a portion of the cover ring of Figure 8;

Figure 10 is a plan view of the lid ring of a tear-open;

Figure 11 is a schematic side view of a device according to the invention for the production of Äuf- rissdeckeln. with a cut edge sealed according to the method of the invention; Figure 12 is a vertical sectional view of a portion of a sealing tool for effecting heating of the curled portion in the sealing tool; and

FIG. 13 shows a perspective view of the vertically cut sealing tool of FIG. 12.

Way (s) for carrying out the invention

With reference to the. Figures 1 to .11, the known in the art manufacturing of tear-open lids according to the prior art will be briefly explained. 1 shows a cover blank 1. At the beginning of the transport path of a production device 20 (Figure 11) is a stack shows overall 12, holds the corresponds a plurality of such lid blanks ^"which are stacked and processed individually along the transport path of various processing stations, The lid blanks are, for example, round disks made of coated metal and thus protected against corrosion, for example of coated white sheet The underside lying above is generally different from the coating of the upper side of the blanks 1 located at the bottom in FIG. 1. These blanks have, for example, a diameter of 11 cm and are already preformed at their edge 6 by a processing machine (not shown) and the formation of the edge 6 is later used to attach the fer tiger on a container or a can through a rabbeted connection. This is known to the person skilled in the art and will not be explained further here. The cover blank 1 in Figure 1 and the cover rings 2 in Figures 2 to 4 are, as mentioned, with its bottom up Darge ^¬ presents, while the finished tear-open lid is shown in Figure 5 with its top and thus the tear-open 8 upwards , The processing in the device can initially take place in the position of FIGS. 1 to 4, after which a turning station 26 follows, which the cover rings for sealing the. Tear-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-open lids in the production device 20 along the transport path in the direction of the arrow A from one processing station to the next processing station, becomes in particular of two parallel running. Timing belts, formed, on which receptacles are provided for the cover blanks or cover rings, as known to those skilled in WO 2006/017953. Again, this will not be explained further here. In the processing stations which are known to the fan operator and are shown here only schematically, 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 in the. Processing stations with up and down arrows. At the processing stations, the drive of the processing stations is indicated below the conveying means. This serves to raise and lower the blanks and cover rings and to carry out the respective processing steps.

In a punching processing station 23, first of all, the lid blank 1 is inserted. Cover ring 2 is formed by ^' a middle part 30 of the blank is cut out and disposed of as waste. Thus, the removal opening of the tear-open lid is formed, which in a later production step is closed with the tear-open film. At the cutting opening 31, the metal material lies bare 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 up to 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 curls can be different. The curl, which forms the edge of the removal opening, ensures that the user of the can is protected from the sharp-edged cutting edge 31 when removing the contents of the can.

If the production steps, as illustrated, are carried out with the sealing flange 7 facing downwards, the turning station 26 which turns the cover rings follows, s.ö that during further processing, the sealing flange 7 after the turning station in the conveyor 22nd and up in the processing stations.

Thereafter, the tear-open film 8 is sealed onto the sealing flange, which can take place 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 will not be explained further here. It may be followed by further processing stations, in which an embossing of the sealing foil takes place, the tear-open tab is positioned and a leak test of the seal takes place. This is also. The person skilled in the art and will not be explained further here. At the end of the lifting device 20, finished tear-open lids 10 (FIG. 5) are dispensed whose removal opening 15 is covered by a tear-open foil 8, which is sealed on the sealing flange 7. The edge of the removal opening 15 is formed by a (in the position of the cover according to FIG 5) upwardly and outwardly bent retort curl 5. The finished tear-open lid 10 can be secured by means of its seam edge 6 on a can jacket (which is indicated in Figure 5 only with a wall portion 11) and thus closes the can. This takes place in the filling operation in which the can has been filled with a filling material. The filled can can be opened later by the tear-off film is torn away from the Dedkel- ring means of their tear tab 18, whereby the removal opening 15 is open. The procedure known from WO 2015/164986 A1 for applying a strip of plastic material to the rolled-in area and the procedure according to the present invention will be described below, reference being made to the known, previously explained production steps or the known production device if necessary.

Figures 6 and 7 show a lid ring in which the processing step of "pulling the edge of the removal ^" opening to form the collar 4 has already taken place. This has been done in the processing station 24. In the preferred example shown here (or in a separate step) an inward curvature has been generated at the upper end 34 of the collar 4, which facilitates the subsequent introduction into the formation of the retort curl. It has also been applied in a single step on the inside 40 of the collar 4, a plastic strip 32. The application of this plastic layer takes place in a separate processing station 29, which is arranged between the drawing station 24 and the curling station 25.

The band-shaped strip 32 made of the plastic material forms a seal for the cutting edge 31 during the curling, which is shown below. The strip 32 is made of a plastic, which term here means a polymer or resin. Such plastics are commercially available and in particular also commercially available in qualities which 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 preserved during the sterilization. The strip is, as shown, preferably formed uniformly thick 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 mm to 0.2 mm, preferably a thickness of approximately 0.1 mm. The height H of the strip may be, for example, 1 to 3 mm. The application is preferably carried out in a manner known to the person skilled in the art from WO 2015/164986 A1 by spraying molten, liquid plastic material, whereby a relative movement of the nozzle and the cover ring takes place. Preferably, the cover ring is moved in rotation in Be ^¬ processing station 29 while the inner side 40 of the collar 4 at the outlet opening of a statically arranged during the application spray nozzle moves past, from which the plastic emerges .. The cover ring is thus at the processing station 29th lifted, rotated and the application is activated when the cover ring has reached the correct position relative to the outlet opening. After at least one complete revolution, when a continuous band or strip is formed on the inside, the lid ring is again moved downwards to the conveyor, whereby the rotation is stopped, so that the lid ring rests again on the receivers of the conveyor can be discontinued. The plastic of the belt .32 then cools on application to the cover ring and solidifies, so that no further flow of the plastic takes place during the further conveyance and the belt is stable in the form shown. At best, a coolant, for example in the form of a blower, can be provided in the application station or processing station 29.

It is ensured in the application that the distance of the discharge opening or the spray nozzle to the inside 40 of the collar 4 during the spraying of the liquid plastic remains substantially constant, so that the thickness of the strip 32 is substantially constant, and its small thickness becomes possible. This can be effected in the manner known from WO 2015/164986 A1. 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 a different manner. So it is possible one This can be done at a separate processing station or when pulling the collar in the station 24 or when rolling the collar in the station 25. In these cases, the station 29 shown would be omitted.

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

The lid ring provided with the plastic strip according to FIGS. 6 and 7 is provided in the processing station 25 in a known manner with a retort curl 5. This station 25 works with the known rolling-in tools, so that this need not be explained in detail here, since this is known to the person skilled in the art. A modification that is obvious to the person skilled in the art may arise in the case of the tools when the collar 4 has already been pre-bent at its upper edge 34 for insertion, which is preferred. As can be seen in FIGS. 8 and 9, which show the lid ring after the turning station 26, the strip 32 forms a seal during the formation of the regular curl 5, 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 curl occurs in such a way that the cut edge 31 is partially embedded in the strip 32, as shown or if it rests only on the strip 32. Also the opposite, that the cutting edge 31 cuts through the strip 32 and rests against the metal of the inner side 40, does not disturb the function of the strip 32. Thus, usual manufacturing tolerances play no role in the formation of the retort curl 5. The plan view of FIG. 10 shows the cover ring as it is conveyed into the sealing station 27, in which the tear-open film is sealed over the removal opening 15.

In the example of FIG. 11, the tear-open lid manufacturing device 20 comprises the processing station 29 for applying the band 32 to the lid ring and the processing station 25 for curling the collar 4.

According to the present invention, the rolled-up edge region is heated in order to melt the strip 32 at least in the contact region to the metal of the cover or the coatings thereon. The rolled-in edge region comprises at least the retort curl 5, as can be seen for example in FIG. 9, and in particular the entire part of the tear-open lid 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 heating of the rolled-up area takes place. This can be done so that even with this processing station 35 a lifting of the lid from the conveyor 22 takes place and then the heating in the processing station and then the depositing on the conveyor. However, the cover ring or its rolled-up region can also be heated in the processing station on the conveyor 22, ie without lifting it off the conveyor. In the processing station 35 in front of the turning station, the lid ring is still facing up with the retort curl or the curled area, as shown in FIG. This makes it possible to heat the rolled-up area from above and preferably an induction heating device is provided in the processing station 35, which is shown schematically as block 4.3. The design of a Such a heater is known in the art and need not be explained in detail here. Instead of an induction heating device could also be a. Infrarotstrahlungs- source or a hot air source can be provided.

In another exemplary embodiment, the processing station can ^'be provided heating of the eingeroll- th region after the turning station and is in the example shown in broken lines as a processing station 35' to the illustrated .. In this processing station of the rolled-up range is below and is correspondingly it is preferred if the heat source acts from below, so that it may be more advantageous to design the processing station 35 'in such a way that the lid ring is lifted off the conveyor 22 in order to carry out the processing with the heat source. Also in this case, an induction heater be provided or another type of heating, which is shown only schematically as block 43.

After heating the rolled-up area, cooling may be provided, for example by a blower. This is particularly advantageous if the processing station 35 'is present after the turning station 26. and a pre-sealing station 27 is provided for pre-peeling the tear-open film 8 on the sealing flange 7. Otherwise, heating the rolled-up area may result in an undesirable influence on the temperature for the pre-seal.

As an alternative to, or in addition to, heating in a processing station 35 or 35 ', the heating of the rolled-up region may be provided in the sealing tool of the sealing processing station. In the case of presetting with the processing station 27 and the main sealing of the tear film with the processing station 28, it is preferred that the heating of the rolled-up area takes place in the main sealing station 28. Figures 12 and 13 show the structure by way of example a sealing tool for the sealing of the tear film and for heating of the rolled-up area. FIG. 12 shows a. Detailed illustration of the lower part 36 of the sealing tool, on which a lid ring 2 rests, which has been lifted from the sealing tool 22 by the sealing tool. FIG. 13 shows the lower sealing tool in a perspective view and already after the sealing step with the tear-open foil 8 on the lid ring 2 In the known sealing step, which will not be explained further here, a suitable side gel foil is then placed on the lid ring and fixed by means of the upper sealing tool (not shown) on the sealing flange 7 by the sealing process, after which the Laying the tear-open on the conveyor 22 is carried out. 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 heat the heating means 38 into the rolled-up area for heating the same and melting it To bring in strip 32. The heat energy for the heating means 38 is provided in this example by the heating elements 39, which also serve for the heating of the lower sealing tool below the sealing flange 7. These heating elements 39, which are electrically heated, are in direct communication with the sealing tool and are in heat flow communication with the heating means 38 via a heat transfer layer 42. This is a preferred example, but it will be apparent to those skilled in the art that it is the Heat generation for the heating means 38 for the rolled-up area can also be provided in another way. After leaving the sealing station 28 is thus not only the tear film. On the tear-open lid, the adhesion of the strip 32 to the two surfaces of the tear-open lid has also been improved by the melting of the strip 32.

According to the invention, a tear-open lid 10 with a rolled-up region of the removal opening 15 is thus formed such that, prior to the formation of the rolled-up area Area a plastic strip 32 is applied to the collar of the lid ckelrings. After formation of the rolled-in area, the plastic strip is melted to give good adhesion of the plastic to the top and bottom of the tear-open lid in the rolled-up area. This results in a cost-effective manner and with the possibility of production with high cadence a practically hermetic sealing of the cutting edge 31 of the tear-open.

While preferred embodiments of the invention have been described in the present application, it is to be understood that the invention is not limited thereto and may be embodied otherwise within the scope of the following claims.

Claims

1. A method of making tear-open covers (10) in which

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

the edge of the extraction opening is formed by pulling to a collar (4) projecting away from the sealing flange (7);

- On the inside (40) of the collar, a strip (32) made of plastic is applied;

- The collar (4) at its free end (34) is rolled and comes to rest in the strip of plastic _. ; and

- On the sealing flange (7) a Aufreissfo- lie (8) is sealed;

characterized in that

- After rolling the. Free end of the collar (4) of the rolled-up area is heated so that at least a partial melting of the plastic material of the strip (32).

2. The method of claim 1, wherein the heating is performed prior to sealing the tear-open film on the sealing flange.

3. The method of claim 1 or 2, wherein an inductively operating heating means is provided for heating.

4. The method according to any one of claims 1 to

3, wherein the heating of the rolled-up area during the sealing of the. Tear-off film (8) on the sealing flange (7) by a heating means (38) contacting the rolled-up region in the sealing tool (36).

5. The method of claim 4, wherein the seal of the tear film is a two-step process which comprises first a pre-seal and in a second step the main sealing of the tear-off film on the lid ring, and wherein the heating of the plastic material of the strip at the main sealing of the tear-open foil takes place.

6. The method according to any one of claims 1 to

5, wherein the plastic material of the strip comprises or consists of a polymer or a resin _/ and that the heating takes place at least to the flow temperature of the plastic material of the strip, in particular that the heating in the range of 100 ° Celsius to 200 ° Celsius, and in particular in the range of 140 ° to 180 ° Celsius.

7. The method according to any one of claims 1 to

6, characterized in that the sealing surface for the tear-open film forming the upper side of the lid blank has a heat-sealable, consisting of polypropylene or polypropylene-containing coating, and that the underside of the lid blank has an existing interior cans or can interior coating containing coating.

8. The method according to any one of claims 1 to 6, characterized in that the plastic material of the strip, a foaming agent is added.

9 .. An apparatus (20) for the production ^'of rice up lids (10) comprising a conveyor (22) for cover blanks (1) ,. Declcel rings (2) and tear-open lids (10) as well as processing bars (23-28) which are provided in the conveying direction (A) successively for processing the lid blanks, lid rings and tear-off covers, wherein a first processing station (23) serves as a stamping station for forming a lid ring (2) from a lid blank (1), a second processing station (24) for forming a protruding from the underside collar (4) of the cover ring (2) and a third processing station (25) are provided, which third processing station for Forming a rolled-up area is configured from the collar, and wherein at least one sealing station (27, 28) is provided, which is designed to seal a tear-off film (8) on a sealing surface (7) of the respective cover ring, wherein Conveying direction between the second. Processing station (24) and the third processing station (25) an applicator station (29) is provided, which is designed for applying a circumferential, endless plastic strip (32) on the inside (40) of the collar (4), and in that the third processing station (25) is configured such that the rolled-up area (5) comes into contact with the plastic strip (32), characterized in that at least one further processing station (35; 35 '; A) is provided after the third processing station (25), which is configured for heating at least the rolled-up area to at least the melting temperature of the Kunststoffstrei- fens (32).

10. Apparatus according to claim 9, wherein the further processing station comprises induction heating means (43).

11. Device according to one of claims 9 or 10, wherein the further processing station is integrated in the at least one sealing station and the one having rolled-up area in the sealing tool contacting heating means (38).

12. The apparatus of claim 11, wherein two sealing stations are provided successively in the conveying direction, and wherein the further processing station is integrated in the second sealing station.

13. Device according to one of claims 9 to 10, characterized in that the further processing station for heating the rolled-up area in the temperature range of 100 ° Celsius to 200 ° Celsius and in particular in the range of 140 ° to 180 ° C is designed ,

14. The device according to one of claims 9 to 13, characterized in that the application station (29) for applying a band-shaped plastic layer (32) is configured, which has a substantially uniform thickness, in particular, a thickness in the range of 0.05 mm to 0.2 mm and in particular with a thickness of about 0.1 mm.

15. tear-open lid, comprising a circumferential fastening section (6), a sealing flange (7), with a tear-open foil sealed on the latter and a rolled-up area (5) surrounding the sealing flange (7), which holds the removal opening (15) laterally delimited, characterized in that the rolled edge has a seal (32) made of a plastic, in particular of a polymer or resin, which by melting the plastic in the rolled-up area, with the upper side, and the Bottom of the tear-off lid is connected.