EP0007487B1 - Sealed can and preformed closure element therefor, as well as method and apparatuses for manufacturing them - Google Patents

Description

The invention relates to a sealed can with an internally laminated fuselage and a can opening, a membrane which is provided as a guarantee seal and is thermoformed from a sheet of film with a membrane part which spans the can opening and is optionally provided with a pull-out member and a membrane collar which is laminated to the inside of the can opening Can wall is glued and extends from the plane of the film part to the edge of the opening, with its upper collar edge ending below the opening edge, while a covering part produced from the same sheet film is flanged over the opening edge and on the inside of the surrounding the can opening Can wall ends with its lower inner edge over the upper edge of the collar.

• (a) in die Dosenöffnung eine durch Tiefziehen vorgeformte Verschlußmembran mit einem zum Überspannen der Öffnung der Dose bestimmten, mit einem Herausziehglied versehenen oder zu versehenden Folienteil und einem Membrankragen, welcher zum Verkleben mit der Innenseite der die Dosenöffnung umgebenden Dosenwandung bestimmt ist, sowie einem peripheren, als Überdeckungsteil für den Rand der Dosenöffnung bestimmten, den Membrankragen umgebenden Umfangsbereich eingesetzt wird und
• (b) das Überdeckungsteil über den Öffnungsrand der Dose gebördelt wird wobei ein den Membrankragen und den an ihn anschließenden Bereich des Überdeckungsteils umfassender Versiegelungsbereich zur Anlage an die Innenseite der die Öffnung umgebenden Dosenwandung kommt.

The invention also relates to a method for sealing a can with a laminated inner wall, in which

• (a) in the can opening a pre-formed sealing membrane with a drawing part intended for spanning the opening of the can, provided with a pull-out member or to be provided and a membrane collar which is intended for gluing to the inside of the can wall surrounding the can opening, and a peripheral , is used as a covering part for the edge of the can opening, surrounding the membrane collar, and
• (b) the covering part is flanged over the opening edge of the can, a sealing area comprising the membrane collar and the region of the covering part adjoining it coming to bear against the inside of the can wall surrounding the opening.

Furthermore, the invention also relates to a preformed closure element which is used in the manufacture of a can according to the invention and which consists of a thermoformed membrane made from a sheet of film with a film part intended for spanning the opening of the can, optionally with a pull-out member, and a membrane collar, the sum of which Adhesion is determined with the inside of the can wall surrounding the can opening, and there is a peripheral circumferential area intended as a covering part for the edge of the can opening, and a method for its production by permanent deformation of the closure membrane under pressure only in the area of the predetermined breaking point between two, compared with the closure membrane hard pressing surfaces moving past each other in the direction of the membrane axis.

Finally, the invention also relates to a first device which can be used in the production of the above-mentioned preformed closure element according to the invention, and a second device for producing a sealed can according to the invention, preferably using the preformed closure element according to the invention.

For food cans, among others it is common not only to seal them with a lid but also under the lid with a tear-off aluminum foil. Such foils are usually arranged a few millimeters below the upper edge of the can and with their edge zone, also called a collar, pulled up against the inner edge of the can up to the edge of the can. To tear off the film, it is provided with a flap, the film being provided with a predetermined breaking point on the can wall. The predetermined breaking point can be provided in the flat film part spanning the can opening or in the corner forming the transition to the collar or in the edge zone itself. In the case of round cans, the predetermined breaking point is a circular groove which weakens the film cross section. It is known to make the groove mechanically by scratching, which has the disadvantage that the film cross section is weakened very unevenly. Furthermore, the wedge-shaped groove base causes tension peaks which lead to an undesired breakage when the can is struck during transport. Furthermore, it is known to crimp a groove as a predetermined breaking point in the collar of the film drawn high on the can wall. The associated weakening of the material is so slight that when the film is removed it tears off next to the predetermined breaking point.

In a known device, a membrane between two hard pressing surfaces, which are harder than the membrane, is only permanently deformed in the area of a predetermined breaking point, in particular with complete separation into two parts.

A deformation of the membrane only in the area of the predetermined breaking point between two hard pressing surfaces already takes place with the can closure according to DE-A-2 061 497 by Zeiler AG, in which the side wall, i.e. the collar, of a deep-drawn membrane is glued to the can body and cut through thereon is formed, whereby two membrane parts are formed with along the interface with butt edges.

However, it is practically impossible to make the cut with such an exact depth that only the membrane, but not the lamination present in practically all cans, is cut through, so that the cut is made down to the material of the can wall itself. that this material consists of sheet iron or cardboard or cardboard, in any case, the violation of the lamination of the same is highly undesirable for hygienic reasons. This is because, in particular in the case of a can wall made of cardboard, residues of liquid contents of the can seep into the cardboard and dry there with the formation of crusts and possibly decompose; with metallic cans can use electrochemical processes, especially when laminated with another metal, which can change the taste of the can.

The known methods have the common disadvantage that the attachment of the predetermined breaking point is time-consuming and requires a high level of work accuracy. Another disadvantage is that it is difficult with films for square cans to make the groove in the can corners with the desired accuracy.

The object of the present invention is therefore to create a sealed can in which these disadvantages are avoided and the lamination of an internally laminated can body remains intact even after the membrane has been removed.

In addition, the invention aims to implement methods and devices to simplify and reduce the cost of manufacturing such sealed cans with undamaged lamination.

It is already known for easy removal of the film part and membrane collar from one of these parts of the membrane, a pull-out member, e.g. a tab or tongue. The attachment of this pull-out member is known.

Further problems which the invention is intended to solve occur when parts of the sealing or sealing membrane are glued to the can wall.

Devices with an anvil or piston and a stamp covering them are preferably used to deform such membranes. The above object is achieved according to the invention in a sealed can of the type described in the introduction that an uncovered and undamaged ring strip of the lamination is present on the inside of the can wall surrounding the can opening between the lower inner edge of the covering part and the upper collar edge of the membrane collar, whereby when the film part is removed from the can opening by means of the pull-out member, the entire membrane collar is removed together with the film part while leaving the complete lamination on the inside of the can wall.

In the area of the ring strip, the can wall and the lamination covering it can have at least one self-contained longitudinal groove. At least one of the two side walls of the longitudinal groove can be formed by the correspondingly indented lower inner edge region of the covering part or the correspondingly indented upper edge region of the membrane collar. In particular, the upper of the two side walls of the longitudinal groove can be formed by the correspondingly indented lower inner edge region of the covering part and the lower of the two side walls by the correspondingly indented upper edge region of the membrane collar.

Finally, in a further embodiment there may be an upper and a lower longitudinal groove, of which the upper side wall of the upper longitudinal groove is formed by the correspondingly indented lower inner edge region of the covering part and the lower side wall of the lower longitudinal groove is formed by the correspondingly indented upper edge region of the membrane collar, while the lower side wall of the upper and the upper side wall of the lower longitudinal groove are formed by corresponding indentations in the strip between the two grooves of the inside of the can wall covered with undamaged lamination.

Often, the sheet film from which the above-mentioned preformed sealing element is produced by deep drawing can be coated on its lower side facing the inside of the can with a more or less thick layer of a material which is adhesive when heated but not adhesive at room temperature, in particular a thermal varnish .

If this layer is relatively thick, because of its elasticity it makes it difficult to separate the covering part of the membrane from the membrane collar and from the film part surrounded by the latter. A grooving or posting at the predetermined breaking point is then not sufficient. In this case, a clean separation and flawless formation of the uncovered ring strip between the two membrane parts is particularly easy when using a preformed closure element of the type described at the outset, which is characterized according to the invention in that the membrane collar is connected in at least one parallel to the connection to the film part, a ring zone forming a predetermined breaking point has a perforation.

Such a preformed sealing membrane can be produced particularly easily with the aid of the manufacturing method described at the outset, which is characterized in that when the sealing membrane is deformed in the area of the predetermined breaking point, contact with one of the two pressing surfaces is interrupted at regular intervals on the circumference of the predetermined breaking point, as a result of which the membrane is perforated at the interruptions.

The perforation of the preformed closure membrane can, however, also be produced in a simple manner by treating the membrane still on the anvil of the device for producing the predetermined breaking point, instead of using a stamp, with an externally acting pressure roller which, while the anvil is rotating, is used to treat the perforation A predetermined breaking point is created and, in the case of the roll being provided with corresponding projections (teeth), the perforations are also made at the same time.

• (i) vor, während oder nach einem der Schritte (a) und (b) mindestens eine Sollbruchstelle im zur Anlage an die Innenseite der Dosenwandung bestimmten Bereich des Überdeckungsteils oder des Membrankragens durch formveränderndes Drücken erzeugt wird, und
• (ii) auf den genannten Versiegelungsbereich in oder neben der Sollbruchzone von dem innerhalb der Dosenöffnung oberhalb der Membran gelegenen Raum her ein Druck mit einer in mindestens einer parallel zum Folienteil verlaufenden Ebene radial nach außen gerichteten Komponente ausgeübt wird, und dabei die Membran im Versiegelungsbereich erwärmt wird, wodurch der an der Innenseite der Dosenwandung anliegende Bereich des Uberdeckungsteils einerseits und der Membrankragen in der betroffenen Druckebene voneinander getrennt und jeder an der Dosenwandung angeklebt wird, während zwischen dem unteren Innenrand des Überdeckungsteils und dem oberen Kragenrand des Membrankragens ein unbedeckter und unverletzter Ringstreifen der Kaschierung verbleibt.

The sealed can according to the invention is produced by the method described at the outset, which is characterized according to the invention in that

• (i) before, during or after one of the steps (a) and (b) at least one predetermined breaking point in the System against the inside of the can wall certain area of the covering part or the membrane collar is generated by shape-changing pressing, and
• (ii) a pressure is exerted on the said sealing area in or next to the predetermined breaking zone from the space located inside the can opening above the membrane with a component directed radially outwards in at least one plane running parallel to the film part, and the membrane is heated in the sealing area is, whereby the area of the covering part on the inside of the can wall on the one hand and the membrane collar in the affected pressure plane are separated from each other and everyone is glued to the can wall, while between the lower inner edge of the covering part and the upper collar edge of the membrane collar there is an uncovered and undamaged ring strip Lamination remains.

The predetermined breaking zone can be generated prior to step (a) in a manner known per se by exerting a shearing pressure on the zone in question in the sealing region of the membrane, so that an annular strip which is thinner than the thickness of the deep-drawn membrane is produced. In this case, a self-contained groove can additionally be pressed into the predetermined breaking zone, or the membrane, optionally also in or below the groove, can be provided with at least one circumferential scoring in the predetermined breaking zone.

As said, however, the membrane is preferably provided with at least one circumferential perforation in the predetermined breaking zone, in particular if it is provided with a thicker thermal lacquer or similar coating on its inside.

In a preferred application of the method according to the invention, the radial pressure component is dimensioned so strongly that a longitudinal groove is formed in the relevant plane in the uncovered ring strip of the lamination without damaging the lamination.

The first device described at the outset, which can be used in the manufacture of the preformed closure element according to the invention, and which comprises an anvil with a head part carrying a front face and a stamp, which two parts can be moved axially with respect to one another by force, and wherein the one press surface on the circumference of the cylindrical or prism-shaped anvil head part is arranged, at the other end of the pressing surface of the anvil a pressing edge is provided, above which the side wall of the anvil is chamfered towards the anvil end face facing the die, and the other pressing surface through the outer surface of a tapering recess away from the anvil in Stamp is formed according to the invention, characterized in that axial grooves are provided in the bevelled side wall of the anvil above the press edge, which extend to the press edge. These axial grooves are preferably evenly distributed over the entire circumference of the pressing edge and preferably have their deepest point in the area of the latter.

The production of the sealed can according to the invention is carried out most simply by means of a novel device, which has a table with an annular flange which projects around the circumference of the table above the table level and is attached to the edge of the table, a fixed upright support element at its upper end, which is arranged in the center of the table the table is slidably supported against bias, on the table a pushing device expandable laterally away from the support element against a bias with an expanding ring or preferably at least two pushing surfaces on each of their outer sides facing away from the supporting element and a counter pushing surface indicated on the pushing surfaces Includes inner surface of the ring flange.

The upper end of the carrier element preferably has a side jacket which is tapered towards the top. Each segment of the pressing device preferably has adjusting means facing the carrier element, by means of which the distance of the pressing surfaces from the axis of the carrier element is adjusted as a function of the downward displacement of the table on the carrier element. The setting means can have beveled contact surfaces which lie axially displaceably on the beveled side jacket of the carrier element.

The purpose of the present invention is further to create a method with which the predetermined breaking point can be produced quickly and with good accuracy and regardless of the shape of the can cross-section.

According to the invention, this purpose is achieved in that the membrane is permanently deformed under pressure only in the area of the predetermined breaking point between two hard surfaces relative to the membrane.

This has the advantage that the stamp required to carry out the method can be easily adapted to any can cross-sectional shape with the associated anvil.

Another advantage of the invention is that very thin films of e.g. only 0.06 mm can be processed quickly and without rejects. Another advantage of the invention is that differences in thickness of the film in the range of the usual manufacturing tolerances do not affect the effectiveness of the predetermined breaking point.

Finally, a further advantage of the method according to the invention is that the predetermined breaking point can be applied both in the film part spanning the can cross section and in the film collar lying against the inside wall of the can.

• Fig. 1 und Fig. 2 schematisch die Behandlung einer tiefgezogenen Membran in einem ersten Schritt des Verfahrens nach der Erfindung zeigen;
• Fig. 3 zeigt eine Teilansicht, teilweise im Axialschnitt, einer Vorrichtung zur Herstellung eines vorgeformten Versiegelungselements nach der Erfindung,
• Fig. 4 zeigt eine Ansicht, in Perspektive und teilweise aufgeschnitten, der Vorrichtung von Fig. 3;
• Fig. 5 zeigt im Schnitt eine Teilansicht des durch die Behandlung nach Figuren 1 und 2 erhaltenen vorgeformten Versiegelungselements;
• Fig. 6 zeigt eine perspektivische Teilansicht, zum Teil im Schnitt, eines mit Hilfe der in Figuren 3 und 4 gezeigten Vorrichtung hergestellten Versiegelungselements;
• Fig. 7 zeigt in Perspektive und teilweise aufgeschnitten eine Ausführungsform der Vorrichtung nach der Erfindung zur Herstellung einer Dose, deren Versiegelung in Figuren 10 bzw. 11 gezeigt ist;
• Fig. 8 zeigt einen Querschnitt durch die linke Seite des in Fig. 7 gezeigten Vorrichtungstisches mit vorgeformter Membran und offenem Dosenende während des Einführens der letzteren in drei verschiedene Stadien, die beiden ersten Stadien sind strichpunktiert gezeigt.
• Fig. 9 zeigt einen Querschnitt ähnlich demjenigen der Fig. 8, aber mit Membran und offenem-Dosenende fertig verklebt, mit dem einen Segment der Vorrichtung nach Fig. 7 in Drückstellung;
• Fig. 10 zeigt eine Teilansicht einer ersten Ausführungsform des oberen Endes einer Dose mit einer Membran, wie sie durch das Verfahren nach der Erfindung erhalten wird, im Längsschnitt durch die Dose;
• Fig. 11 zeigt eine ähnliche Teilansicht einer anderen Ausführungsform eines oberen Dosenendes;
• Figuren 12 und 13 zeigen Ausschnitte aus der Dosenwandung und einem Membrankragen in zwei weiteren Ausführungsformen;
• Fig. 14 ein erstes Ausführungsbeispiel einer Vorrichtung zur Durchführung des erfindungsgemäßen Verfahrens zur Erzeugung einer Sollbruchstelle;
• Fig. 15 ein zweites Ausführungsbeispiel einer Vorrichtung zur Durchführung des letztgenannten Verfahrens;
• Fig. 16 ein drittes Ausführungsbeispiel einer Vorrichtung zur Durchführung desselben Verfahrens und
• Fig. 17 ein viertes Ausführungsbeispiel zur Durchführung desselben Verfahrens.

Further details of the invention are explained in connection with the accompanying drawings, in which

• Figures 1 and 2 show schematically the treatment of a deep-drawn membrane in a first step of the method according to the invention;
• 3 shows a partial view, partly in axial section, of a device for producing a preformed sealing element according to the invention,
• Fig. 4 shows a view, in perspective and partially cut away, of the device of Fig. 3;
• 5 shows in section a partial view of the preformed sealing element obtained by the treatment according to FIGS. 1 and 2;
• 6 shows a perspective partial view, partly in section, of a sealing element produced with the aid of the device shown in FIGS. 3 and 4;
• Fig. 7 shows in perspective and partially cut away an embodiment of the device according to the invention for producing a can, the sealing of which is shown in Figures 10 and 11;
• FIG. 8 shows a cross section through the left side of the device table shown in FIG. 7 with a preformed membrane and an open can end during the insertion of the latter into three different stages, the first two stages being shown in broken lines.
• FIG. 9 shows a cross section similar to that of FIG. 8, but with the membrane and open can end glued, with one segment of the device according to FIG. 7 in the pressing position;
• Fig. 10 shows a partial view of a first embodiment of the upper end of a can with a membrane, as obtained by the method according to the invention, in longitudinal section through the can;
• Figure 11 shows a similar partial view of another embodiment of an upper can end;
• Figures 12 and 13 show sections of the can wall and a membrane collar in two further embodiments;
• 14 shows a first exemplary embodiment of a device for carrying out the method according to the invention for producing a predetermined breaking point;
• 15 shows a second exemplary embodiment of an apparatus for carrying out the latter method;
• Fig. 16 shows a third embodiment of an apparatus for performing the same method and
• 17 shows a fourth exemplary embodiment for carrying out the same method.

Preferably, membranes made of laminated aluminum foil are used in these embodiments.

The device shown in FIGS. 1 and 2 for producing a preformed closure element according to the invention comprises an anvil or piston 10 with a pressure surface 11a attached to its piston head 11 and an end face 11b, on the pressure surface 11a lies a piston ' 11 head pushed-on deep-drawn membrane 12 with its membrane collar 13, while the flat film part 14 of the membrane rests on the end face 11b of the piston head 11. The covering part 15 of the membrane 12 is directed away from the piston 10 in its shape obtained during deep drawing. On the outside 13a of the membrane collar 13, the roller 16 belonging to the device is now applied and, by means of a drive (not shown) and pressing elements (not shown), via the shaft 17 carrying it, in circulation around the metal collar 13 of the membrane in a direction relative to the longitudinal axis of the cylindrical pressing surface 11 guided radial plane and now produces in the outer side 13a, as shown in Fig. 2, a circumferential indentation or groove 18. Preferably, the roller 16 with projections, for example Provide teeth 19 which produce a perforation (holes 1 9a) in the membrane collar 13 when pressed sufficiently.

A plastic layer 21, in particular a thermal lacquer layer, which is preferably located on the side of the membrane 12 facing away from the piston 10, is not damaged during the treatment which is gentle on the surface in the described device, apart from a perforation. As already mentioned, this perforation is particularly advantageous if the membrane has a thicker layer of thermal lacquer. The side of the film part 14 of the membrane 12 that spans the inside of the can, which carries this plastic rail 21, faces the inside of the can in the sealed can.

In contrast to deformation only at the predetermined breaking point, the deformation in this treatment takes place over a wider zone above and below the predetermined breaking point, which protects the material of the membrane and the plastic layer carried by it.

In the manufacture of a sealed can according to the invention, a membrane can also be used as the preformed sealing element, as is produced in a device shown in FIGS. 3 and 4, which consists of a piston or anvil 30 and a stamp 31 surrounding it with an internal recess 32 consists. The punch 31 has a conical pressing surface 33a on the inner, slightly inwardly inclined side wall 33 of the recess 32. The piston head 34 has a circumferentially cylindrical wall surface 35, with an edge surface 37 which is bevelled conically towards the piston end face 36, as a result of which a pressing edge 38 is formed between the latter and the cylindrical wall surface 35. On such a device, a membrane 20 is deformed such that an outer indentation 24 facing the can wall and an inner indentation 25 are formed in the wall of the membrane collar 23, as shown in FIG. 5.

If the device shown in FIGS. 3 and 4 is provided on the circumference of the chamfered edge surface 37 of the piston head 34 with small axial grooves 39, which preferably have a deepest point 39a instead of the pressing edge 38 'and end in the wall surface 35, then in such a device 4 from membrane 12 produces a preformed sealing element 22 (FIG. 6) with a circumferential perforation 22a, the cross section of which is otherwise the same as that of the sealing element of FIG. 5.

A sealing element similar to that shown in FIG. 5 can also be produced if the piston 10 in FIGS. 1 and 2 instead of the head 11 carries a counter roller (not shown) which has the same shape as the roller 16, except that it is not included Teeth is provided and preferably has the same diameter in the radial direction as the piston head 11th

In Fig. 7 an apparatus for producing a sealed can according to the invention is shown, the essential components of which are a table 41 with an annular flange 43 projecting around the table circumference over the table plane, which is attached to the table edge 42 in a manner known per se, e.g. is fixed by welding or screwing, and comprise a fixed, upright support element 44. At the upper end of the carrier element 44, which is arranged in the center with respect to the table 41, the table 41 is slidably supported against bias. The preload is generated by a spring 49 which tends to hold the table 41 at the upper end of the support element 44. Provided on the table 41 along the plane of the table from the carrier element 44 to the outside against a pretension, a pushing device 45 with at least two segments 46, 46 ', the segments 46, 46' on their outer sides facing away from the carrier element 44 pressing surfaces 47, 47 ' wear.

The pretensioning of the pushing device is generated by means of tension springs 48, which endeavor to move segments 46, 46 ′ lying opposite one another on both sides of the longitudinal axis of the carrier element 44 towards the longitudinal axis and thus towards one another.

On the inner surface of the ring flange 43, a counterpressure surface 58 facing the pressure surfaces 47, 47 'and the segments 46, 46' is provided.

In the embodiment shown in FIG. 7, the carrier element 44 is designed as a column, the free, preferably upward-pointing end of which is tapered, that is to say has a side jacket 51 that narrows upwards.

Correspondingly, each of the segments 46, 46 'is assigned radial setting means in the form of transverse webs 52, 52', each of which has a beveled contact surface 53 on its end facing the carrier element 44, which lies axially displaceably on the beveled side jacket 51 of the carrier element 44.

The segments 46 and 46 ′ are preferably separated from one another by an obliquely directed gap 54. To guide the transverse webs 52, 52 'in the radial direction on the table 41, the latter carries guide pins 55, 55' which engage in corresponding elongated holes 56, 56 'in the transverse webs 52, 52'. Electrical heating elements 57 are provided both in the table 41 and in the ring flange 43 and can also be accommodated in the segments 46, 46 '.

The processing of a preformed sealing element similar to that shown in FIG. 2, which however only carries an indentation 25 on the side of the membrane collar 23 facing the interior of the can opening, for sealing a can according to the invention by means of the device shown in FIG of Figures 8 and 9 explained. In this case, the pressure surfaces 47, 47 'of the segments 46, 46' should be smooth, that is to say they do not have any annular bead segments 59. 8, a membrane 20 with its deep-drawn cup part consisting of the film part 26 spanning the opening, the membrane collar 23 and partly with the still undeformed cover part 27 is inserted into the opening of a can 50 and rests with the bent cover part 27 on the opening edge 50a of the can. The can 50 and the membrane 20 are now centered on the longitudinal axis of the carrier element 44, into the annular gap 60, which is open at the top and is located between the pressure surface 58 of the ring flange 43 and the pressure surfaces 47, 47 'of the segments 46, 46', whereby the outer end 27a of the covering part 27 is bent upwards at the upper rounded edge 61 of the ring flange 43 and flanged around the can edge 50a.

First, the film part 26 now meets the end faces 46a, 46a 'of the segments 46, 46' before the can opening edge 50a with the region of the covering part 27 of the membrane 20 which it supports on the ring shoulder 41 of the table 41 located at the bottom of the annular gap 60 has hit. When the can is pressed further down into the annular gap 60, the region of the membrane 20 between the covering part 27 and the membrane collar 23 is stretched and torn off there, in particular at the indentation 25, when the covering part 27 is flanged around the can opening edge 50a.

While the can edge 50a with the membrane area covering it strikes the annular shoulder 41 of the table 41 due to the pressure on the can, this pressure on the can 50 in the axial direction downwards causes the table 41 on the carrier element 44 to compress the spring 49 pressed down. Here, the contact surfaces 53 of the transverse webs 52, 52 'slide downward on the beveled side casing 51 of the carrier element 44 and are displaced radially outward from the latter, whereby they fasten the segments 46, 46 ', widening the gap 54 away from one another and moving onto the counter-back surface 58.

The membrane collar 23 and the covering part 27 which are pulled away from the membrane collar 23 by the flanging of the covering part 27 around the can opening edge 50a and which are separated from one another leave a membrane-free ring strip 62, in the area of which the undamaged lamination 61 of the can is revealed.

The pressing surfaces 47, 47 'now simultaneously press the membrane collar 23 and the area of the covering part 27 to be located on the inner wall of the can after the can edge 50a, in the direction of the counter-pressing surface 58, and firmly against the inner wall, and since the pressing surfaces 47, 47' of the segments 46, 46 'as well as the annular shoulder 41 a and the counter-back surface 58 are heated by the heating elements 57, the thermal lacquer layer covering the outside of the membrane softens and adheres to the can wall or to the liner 61 of the latter (FIG. 9) .

When the downward pressure on the can ceases, the spring 49 lifts the table 41, the springs 48 pull the segments 46, 46 'again inwards away from the counterpressure surface 58, and the can 50 which has been released in this way and is now sealed can now move upwards be lifted out of the device.

FIG. 10 shows a partial view of a first embodiment of the upper end of a can sealed according to the invention and removed from the device of FIG. 7, in which the same parts have the same numbering as in FIGS. 8 and 9.

As usual, a lid 65, which covers the sealing membrane in the can opening, is also inserted into the can.

The sealed can shown in FIG. 10 can also be produced by not only perforating but completely cutting through the membrane collar 13 in the membrane shown in FIG. 1. As a result, the covering part 15 falls down a short distance and comes to rest on an impact shoulder (not shown). Then the can wall 50 is placed from above over the membrane collar 13 held by the film part 14 resting on the piston head part 11 and down onto the horizontal section of the covering part 15 lying on the shoulder and now the separate parts of the membrane, namely membrane collar 13 and covering part 14, the latter with simultaneous flanging, glued to the can wall by heating the piston head and a flanging device brought up from the outside by softening the thermal lacquer layer 21 of the membrane.

On the pressing surfaces 47, 47 ', an annular bead 59 can also be provided near the end faces 46a, 46a', which is only interrupted by the gap 54 and which facilitates the tearing off of the covering part 27 from the membrane collar 23 by pressing on the latter.

If the pressing surfaces 47, 47 'of the segments 46, 46' now carry a thicker annular bead (not shown) below the annular bead 59, then in the processes described in connection with FIGS. 8 and 9, the membrane collar 23 and the covering part 27 are separated from one another separating ring strip 62 produces a deeper indentation 63 in the inner wall of the can, but is flattened such that it does not damage the lining 61 of the inside of the can wall. The upper side wall 63a of the indentation 63 is formed here by the inner edge region of the covering part 27 of the membrane 20, while the lower side wall 63b of the indentation 63 is formed by the upper edge region of the membrane collar 23 (FIG. 11). By fitting corresponding annular beads on the pressing surfaces 47, 47 'of the segments 46, 46' in the device of FIG. 7, in addition to the indentation 63, an indentation 64 running parallel to this can also be produced in the membrane collar 23 (FIG. 12), or two indentations 65 and 66 running parallel to one another can be produced, which are pressed in at the upper and lower edge of the lamination ring strip 62 not covered by the membrane, whereby the upper side wall of the upper indentation 65 is formed by the inner edge region of the covering part 27, while the lower one Side wall of the lower indentation 66 is formed by the upper edge region of the membrane collar 23 (FIG. 13).

These two embodiments of the seal also contribute to facilitating the complete clean separation of the membrane collar 23 and the film part of the membrane 20 which surrounds it and is formed in one piece with it and spans the can opening.

To form the two indentations 65 and 66 (FIG. 13), a double roller can be used, the axis of which extends parallel to the can axis and which is guided around on the inside of the membrane collar 13 already inserted into the can opening, or the axis of which is fixed, in which case the Can is rotated so that the double roller acts with each point of the can wall in the horizontal plane of deformation on the can wall to produce the two indentations.

The predetermined breaking point is preferably not placed in the vicinity of the transition zone between membrane collars 13 or 23 and the film part 14 spanning the can opening, but rather the membrane collar 13, 23 should have a certain height for better sealing. The predetermined breaking point should therefore be moved more upward, so that the membrane collar 13, 23 is longer than the downward-facing section of the covering part 15 covering the inside of the can wall. This also applies to the perforation shown in FIG. 6.

In any case, on the membrane, either on the membrane collar or preferably a pull-out member, for example a tab, is attached to the film part, by means of which the film part and membrane collar can be completely and cleanly pulled out of the can opening.

The device shown in Fig. 7 can not only be used for cylindrical cans with a preferably circular cross-section, but with appropriate adaptation of the shape of the table, the ring flange and the segments also for sealing cans of prismatic shape. For example, a box of square cross-section with rounded prism edges is sealed on a device similar to that shown in Fig. 7 if the pushing device contains four segments, each of which is an isosceles triangle, the tip of which faces the longitudinal axis of the support column, while the base of each triangle corresponds to one side of the square. If the table, which is preferably square in this case, is moved downwards on the support column, the triangles are pushed radially outward from the support column and separate and seal the membrane collar and overlapping part of the membrane in the same manner as shown in FIGS. 8 and 9. If the box is provided with sharp prism edges instead of the rounded one, then the sealing at the angle formed on each sharp prism edge can be accomplished by a special slide piece, which is moved outwards along a diagonal and the gap that occurs between two adjacent triangle segments when expanding fills out. The tip of the slider entering this gap has two end faces which form a right angle with one another and are at an angle of 45 ° to the diagonal along which the slider is guided. They can penetrate so completely into the angle of 90 ° that is present on the inside between the two sides of the square prism that meet on a longitudinal edge of the square prism that a perfect seal can be achieved even at this difficult point.

In FIG. 14, reference number 1 denotes a film with the film part 14 spanning a can cross-section, the film collar 13 directed against an upper can edge and abutting against an inner wall of the can and the end part 15 which is to be bent outwards via an upper can edge preferably already deep-drawn film 1 placed on an anvil 30 with a head 34 and a carrier 34a. The diameter of the carrier 34a is smaller than that of the head 34, so that the film 1 has only a relatively small contact area with the head 34, as a result of which it is easier to plug on or remove from the anvil 30. Vent channels 8 arranged in the anvil 30 allow the air trapped between the film and the head 34 to escape when the film 1 is plugged on. At the free end, the head 34 is provided with rounded edges so that its outer surface lies against the film 1. A plunger 31 is slidable up and down axially to the stationary anvil 30. The drive device of the plunger 31, not shown, can effect a hydraulic, pneumatic or mechanical drive, not shown. The punch 31 is provided with a conical recess 32 on the side facing the anvil 30. The cone angle a is chosen so that the recess 32 comes into contact with the film when the punch 31 is lowered with an annular surface 33a. The annular surface 33a is also opposite an annular surface 37 on the head 34 of the anvil 30. Both the punch 31 and the anvil 30 are made of a much harder material than the film 1. If the punch 31 is moved suddenly or gradually against the anvil 30 with great force, the film 1 is only deformed between the annular surfaces 33a and 37 , wherein the force to be applied by the punch 31 must be so great that the film 1 undergoes permanent deformation. In order to remove the air trapped between the film 1 and the stamp 31, ventilation channels 31 b are arranged in the stamp 31 through which the air located above the film 1 can flow out. The predetermined breaking point along which the film part 14 is torn off when the can is opened arises in the plastically deformed film area.

15, the film 1, the anvil 30 and the stamp 31 are basically the same. The only difference is that the cone angle α of the recess 32 is more acute than in the device example according to FIG. 14. This more acute cone angle causes the annular surface 33a with which the recess 32 contacts the film 1 when the punch 31 is lowered, in Area of the film collar 13 is. If the film stamp 31 is suddenly or gradually lowered with a correspondingly large force, a plastic reduction in the thickness of the film 1 is created in the film collar 13 between the annular surfaces 33a and 37, and accordingly the predetermined breaking point 3 in the film collar 13 occurs in this zone. that the outside of the film collar 13 can be welded to the inner wall of the can, so that transport damage occurring at the predetermined breaking point 3 has no adverse effects. Another advantage is that when the can is opened, i.e. when tearing off the film part 14 along the predetermined breaking. place no rough or sharp protrusions or edges on the film part remaining on the can, thereby avoiding the risk of injury otherwise.

In the example of the device according to FIG. 16, the cone angle ce is even more acute than in the example of the device according to FIG. 15. As a second difference to the example of the device described above, the head 34 of the anvil 30 is tapered at the end facing the die 31. As a result, the annular surfaces 33 and 37 touch the film 1 approximately in the middle of the film collar 13. If the punch 31 is lowered with force or gradually onto the anvil 30, the plastic deformation of the film 1 takes place in the film collar 13, where subsequently the predetermined breaking point 3rd lies. In this embodiment, the film 1, as indicated by dash-dotted lines, is slightly conically deformed. This does not result in a disadvantage, since this deformation is reversed when the film is inserted into the can. When the film part 14 is torn off, the remainder of the film collar 13 remaining on the can also does not form any inwardly directed edges or projections which represent a risk of injury to the user. In this exemplary embodiment too, the outside of the film collar 13 can be welded to the inner wall of the can, as a result of which damage in transit at the predetermined breaking point 3 remains without disadvantage.

17 is on the underside of the stamp. an annular rib 32a is arranged, the comb or ridge area of which likewise forms an annular contact surface 32b with the film 1, the annular surface 32b touching the film 1 on the part 14 spanning the can cross section. Opposite the surface 32b, the end face 36 of the anvil 30 forms the annular counter surface. When the punch 31 is suddenly or gradually lowered, the plastic deformation of the film 1 takes place between the annular surfaces 32a and 36 in the area of the film part 14, so that the predetermined breaking point comes to rest in this part.

In all four execution devices, vent and blown air channels directed against the film 1 can be provided in the anvil 30, so that the film 1 can easily be placed on the anvil 30 and the film 1 can be lifted off by a blast of air after the predetermined breaking point has been attached.

In all exemplary embodiments, the production of the tool parts 30 and 31 in accordance with a round or polygonal film shape is relatively simple and therefore inexpensive. By simply limiting the stroke on the punch 31, it is easily possible to process thin films of 0.06 mm and less. This allows differences in thickness in the film to be compensated for without disadvantage.

According to an embodiment not shown, the annular surfaces 33 and 37 can be provided with small serrations, beads, knurling or the like, so that more or less deformed points alternate in the area of the predetermined breaking point.

The method according to the invention has the advantage that the predetermined breaking point can be easily attached to the finished film. A further advantage is that when a can is opened, the material 14 that is torn out does not produce any material dust that falls into the can.

After the predetermined breaking point has been applied in the film 1 and before the latter has been inserted into the can, the film 1 is preferably covered with an elastic plastic layer which seals off any transport damage at the predetermined breaking point.

In all of the exemplary embodiments shown, the anvil 30 and / or the punch 31 can be supported or suspended by an adjustable three-point bearing so that the two tool parts can be easily adjusted to one another.

Claims (28)

1. Can having a can body the wall of which is internally lined with a protective coating and a top opening, a membrane (12, 20) deep drawn from a foil, serving as a warranty seal, with a foil part (14) stretched across the top opening and a membrane collar (13, 23) glued to the coating on the inside of the can wall (50), surrounding the top opening, which collar part extends from the plane of the foil part toward the rim (50a) of the top opening, ending with its upper collar edge inside of the opening rim (50a) while a covering part generated from the same foil is crimped about the opening rim (50a) and ends, on the inside of the can wall surrounding the can opening, with its lower inner edge above the upper collar edge, characterized in that, on the inside of the can wall surrounding the can opening,

an uncovered and intact annular strip (62) of the coating is provided between the lower inner edge of the covering part (15,27) and the upper collar edge of the membrane collar (13, 23), whereby, when removing the foil part (14) by pulling it out of the can opening, also the entire membrane collar (13, 23) is removed, together with the foil part (14), leaving the complete internal lining on the inside of the can wall intact.

2. Can according to claim 1, characterized in that, in the range of the annular zone (62) the can wall (50) and the coating (61) covering the same are provided with at least one endless circumferential groove (63).

3. Can according to claim 2, characterized in that at least one of the two sidewalls of the circumferential groove (65, 66) is constituted by the correspondingly bent-in lower inside edge portion of the covering part (15, 27) or by the correspondingly bent-in upper edge portion of the membrane collar (13, 23).

4. Can according to claim 3, characterized in that the upper one of the two sidewalls (63a) of the circumferential groove (63) is consituted by the correspondingly inwardly bent lower inside edge portion of the covering part (15, 27) or by the correspondingly inwardly bent upper edge portion of the membrane collar (13, 23).

5. Can according to claim 2, wherein an upper (65) and a lower circumferntial groove (66) are present, of which the upper sidewall of the upper circumferential groove (65) is constituted by the correspondingly bent-in lower inside edge portion of the covering part (15, 27) and the lower sidewall of the lower circumferential groove (66) is constituted by the correspondingly bent-in upper edge portion of the membrane collar (13, 23), while the lower sidewall of the upper (groove) (65) and the upper sidewall of the lower circumferential groove (66) are constituted by corresponding indentations in the annular strip (62) between the two grooves of the inside of the can wall covered by intact coating.

6. Preformed closure element for producing a can according to claim 1, which consists of a membrane (22) deepdrawn from a leaf foil with a foil part (14), destined for covering the opening, of the can, and a membrane collar (23) destined to be glued to the inside of the can wall (50), surrounding the can opening, as well as, optionally, a periperhal annular reach (15) destined for the rim (50a) of the can opening, characterized in that the membrane collar (23) is provided, in at least one annular zone (25), parallel to the junction of the same (membrane collar) with the foil part and containing a desired rupturing line, with a lesser thickness than the remaining membrane of a perforation (22a).

7. A process for manufacturing a rupturing line in a closure membrane (22) destined for sealing a can according to Claim 1, characterized in that

(a) the closure membrane (22) is permanently formed by deep drawing from a leaf foil (1), in a manner known per se, with a foil part (14) destined for covering the opening of the can, and with a membrane collar (23), destined for being glued to the inside of the can wall (50) surrounding the can opening, as well as optionally with a peripheral annular reach destined as covering part (15) for the rim of the can opening, and

(b) hereupon permanently reducing the thickness of the deep-drawn closure membrane (22) only in the reach of the desired rupturing line (3) between two pressure faces (11, 12) which are hard compared with the closure membrane by moving the two pressure faces with pressure past one another in the direction of the membrane axis; whereupon

(c) the introduction of the closure membrane (22) into the can opening takes place.

8. Process according to claim 7, characterized in that during deforming of the closure membrane (22) in the zone of the desired rupturing line (3), the contact with one of the two pressure faces (11, 12), is interrupted at regular distances, about the circumference of the desired rupturing line (3), whereby the membrane (22) is perforated at the interruptions (39).

9. Process for sealing a can according to claim 1 having an inner wall which is lined with a protective coating, wherein

(a) a closure membrane deformed by deep drawing, with a foil part (14) destined for covering the opening of the can and a membrane collar (13, 23) destined to be glued to the inside of the can wall (50) surrounding the can opening, as well as with a periperhal annular reach surrounding the membrane collar (13, 23) and destined as covering part (15, 27) for the rim (50a) of the can wall surrounding the can opening, is introduced into the can opening, and

(b) the covering part (15, 27) is crimped about the opening rim (50a) of the can (50), whereby a sealing reach comprising the membrane collar (13, 23) and the zone of the covering part (15, 27) adjacent to the membrane collar is brought to lie against the inside of the can wall (50) surrounding the can opening, characterized in that

(i) prior to or concurrently with or after one of steps (a) and (b), there is generated, by shape-alter-: ing pressure treatment, at least one desired rupturing zone in the reach, destined for contact with the inside of the can wall (50), of the covering part (15, 27) or of the membrane collar (13, 23); and

(ii) pressure is exerted on the said sealing region in or adjacent a desired rupturing zone, from the space located within the can opening above the membrane, with a component directed radially outwardly in at least one plane parallel to the foil part (14), and with a component directed axially with regard to the membrane; and concurrently therewith the membrane is heated in the sealing region, whereby the portion of the covering part (15, 27) which lies against the inside of the can wall, on the one hand, and the membrane collar (13, 23) in the respective pressure plane are severed from one another, and each is glued to the can wall, while an uncovered and intact annular strip (62) of the coating remains between the lower inside edge of the covering part (15, 27) and the upper collar edge of the membrane collar (13, 23).

10. Process according to Claim 9, characterized in that the desired rupturing zone is produced prior to step (a) in a manner known per se by exertion of a shearing pressure on the respective zone of the sealing region of the membrane, so that an annular strip is generated which is thinner than the thickness of the deep-drawn membrane.

11. Process according to Claim 10, characterized in that a closed-upon itself groove (18) is impressed into the desired rupturing zone.

12. Process according to Claim 9 or 10, characterized in that the membrane is provided with at least one circumferential scoring in the desired rupturing zone.

13. Process according to Claim 9 or 10, characterized in that the membrane is provided in the desired rupturing zone with at least one circumferential series of perforations (22a).

14. Process according to Claim 9, characterized in that the radial pressure component is so strong that a continuous groove (63) is gernated in the uncovered annular strip (62) of the protective coating (61) in the respective plane without injuring the coating (61).

15. Process according to Claim 14, characterized in that at least one of the two sidewalls of the continuous groove (63) is constituted by the correspondingly bent-in lower inside edge region of the covering part (15, 27) or by the correspondingly bent-in upper edge region of the membrane collar (13, 23).

16. Process according to Claim 15, characterized in that the upper one (63a) of the two sidewalls of the continuous groove (63) is constituted by the correspondingly bent-in lower inside edge region of the covering part (27) and the lower one (63b) of the two sidewalls is constituted by the correspondingly bent-in upper edge region of the membrane collar (23).

17. Process according to Claim 14, characterized in that an upper (65) and a lower continuous groove (66) are generated, of which the upper sidewall of the upper continuous groove (65) is constituted by the correspondingly bent-in lower inside edge portion of the covering part (15, 27) and the lower sidewall of the lower continuous groove (66) is constituted by the correspondingly bent-in upper edge portion of the membrane collar (23), while the lower sidewall of the upper (65) and the upper sidewall of the lower continuous groove (66) are constituted by corresponding impressions in the strip (62), between the two grooves, of the inside of the can wall (50) covered with intact coating (61).

18. Apparatus for producing a desired rupturing zone in a deep-drawn membrane (22) for a preformed closure element according to claim 6, which has a foil part (14) destined to cover an opening of a can, and a membrane collar (23) which is destined to be glued to the inside of the can wall (50) surrounding the can opening, as well as, optionally, a peripheral region destined as covering part (15) for the rim (50a) of the can opening, characterized by an anvil (30) and a mortar (31) which have pressure faces (33a and 35, 37), as well as by drive means which axially move with power the anvil (30) and mortar (31) toward one another, leaving an annular gap betwen the pressure faces (33a and 35, 37), whereby the annular gap is subjected to narrowing, so that the thickness of a foil (1) placed between the pressure faces is reduced in the region of the desired rupturing zone (3).

19. Apparatus according to Claim 18, characterized in that the anvil (30) comprises a cylindrical or prism-shaped head (34), and one of the pressure faces (35, 37) is constituted by the outer face or at least a circumferential region of the latter, and that the mortar member (31) has a frontal face, facing toward the anvil (30), and in the latter face a cavity (32) the sidewall (33) of which is tapered with decreasing diameter away from the anvil (30) and comprises or constitutes the other one of the two pressure faces (33a).

20. Apparatus according to Claim 19, characterized in that the diameter of the anvil head (34) decreases from the region of the pressure face (35, 37) toward its end facing toward the interior of the cavity (32) of the mortar (31).

21. Apparatus according to Claim 18, characterized in that the mortar (31) has a flat frontal face (31 a) and the anvil (30) possesses a head (34) with a flat end face (36) turned toward the frontal face (31 a), and containing one of the pressure faces (35, 37), and that the frontal face (31 a) of the mortar (31) bears an annular rib (32a), the crest of which constitutes the other pressure face (33a).

22. Apparatus for the manufacture of a pre-formed closure element according to Claim 6, in which a membrane is permanently deformed, only in the region of a desired rupturing zone, between two hard pressure faces which are harder than the membrane, wherein the apparatus comprises an anvil (30) with a head part (31) bearing a frontal face (36), as well as a mortar (31), which two parts are axially movable with power one toward the other, and wherein one of the pressure faces (35, 37) is arranged at the circumference of the anvil head part (34) being of cylindrical or prismatic shape, a rounded-off pressure edge (38) being provided at the upper end of the pressure face of the anvil, above which the sidewall of the anvil (30) above said pressure edge zone is beveled toward the frontal anvil face (36) turned toward the mortar (31), and the other pressure face (33a) is constituted by the mantle surface (33) of a recess (32) in the mortar (31) the diameter of which recess decreases away from the anvil (30), characterized in that in the sidewall (35, 37) of the anvil (30) above the rounded-off pressure edge (38) there are provided axial grooves (39) which extend across the pressure edge (38).

23. Apparatus according to Claim 22, characterized in that the axial grooves (39) are uniformly distributed about the entire circumference of said rounded-off pressure edge (39).

24. Apparatus for the manufacture of a sealed can according to claim 1, characterized in that it comprises a table (41) with an annular flange (43) fastened to the table rim (42) and protruding about the circumference of the latter upwardly above the table plane, a stationary upright carrier element (44) at the upper end of which, disposed centrally relative to the table (44), the table (44) is carried axially and downwardly displaceable against bias, pressure means (45) on the table (41) being expandible against bias along the table plane laterally away from the carrier element (44) toward the outside, with at least one pressure face (47, 47'), and a counterpressure face (58) on the inner face of the annular flange (43).

25. Apparatus according to Claim 24, characterized in that the upper end of the carrier element (44) is provided with a conically bevelled, upwardly narrowing sidewall (51).

26. Apparatus according to Claim 24 or 25, characterized in that the pressure means (45) comprise at least two segments (46, 46') each of which bears a pressure surface (47,47') on its outer sides facing away from the carrier element (44).

27. Apparatus according to Claim 26, characterized in that each segment (46, 46') of said pressure means comprises adjusting means (52, 52') facing toward the carrier element (44) by means which the distance of the pressure surface (47, 47') from the axis of the carrier element is adjusted dependent upon the downward displacement of the table (41) along said carrier element.

28. Apparatus according to Claim 25 or 26, characterized in that the adjusting means (52, 52') have sloped contact faces (53, 53') which rest axially displaceably on the bevelled sidewall (51) of the carrier element (44).

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