CROSS REFERENCE TO RELATED APPLICATIONS

This application is a national stage application under 35 U.S.C. 371 of PCT Application No. PCT/EP2017/061474 having an international filing date of 12 May 2017, which PCT application claimed the benefit of European Patent Application No. 20170165040 filed 5 Apr. 2017, the entire disclosure of each of which are hereby incorporated herein by reference.

TECHNICAL FIELD

The present invention relates to a metallic can lid having a reclosable opening, in particular for beverage cans and for containers for storing foods and other liquid, pasty, powdery and/or solid products.

INTRODUCTION

A can lid having a reclosable opening is known from EP 1 607 341 A1 in which an opening is introduced in the metallic can lid and the margin of this opening is beaded to provide an anchorage possibility for a prefabricated plastic closure part. The plastic closure part encloses a base part which is to be connected to the bead margin of the can opening and in which an opening closed by a flat stopper is formed. The flat stopper is connected to the opening margin via a plastic tear seam so that the flat stopper connected to a tear tab can be released from the plastic base part via the tear tab by exertion of a pull and can be pivoted into an open position. The opening can be temporarily closed again by pressing in the flat stopper which is preferably conical at its lower side.

Reclosable can lids are furthermore described in DE 10 2010 013 531 A1 and EP 2 354 022 B1, for example.

Finally, a reclosable can lid is known from DE 10 2015 112 428 A1 of the applicant on which the present invention is based and which is intended to be substantially improved by the invention.

SUMMARY

It is therefore the object of the invention to design the known reclosable can lid such that its production is possible in an even more economic manner, the construction design is simplified, material savings can be achieved and the function is in this respect simultaneously improved.

This object is substantially satisfied by a metallic can lid having a microgap which extends peripherally, which is provided in the metallic lid surface and which is sealed off at an inner lid side by a film; having a weakening line extending adjacent to said microgap in the film; having a sealing frame composed of a plastic material which is connected to the fixed lid surface and which surrounds the opening region; having a closure unit composed of a plastic material which is connected to the metallic lid region which is disposed within the microgap and which can be pivoted open, said closure unit being pivotably attached to the fixed lid surface and being provided with a tear-open member disposed diametrically opposite the pivot bearing region, wherein the sealing frame and the closure unit cooperate via sealing and latching ribs and associated receiving grooves and the metallic lid region disposed within the annular microgap is received and held in the opening region of the lid, in particular in a shape matched and/or force transmitting manner and in particular without a toothed arrangement; and wherein the film provided at the inner lid side and covering the microgap consists of a molded part, in particular a deep-drawn molded part, which reproduces the lower side structure of the can lid forming a continuous metallic surface; and wherein both the sealing frame is connected to the fixed lid surface in a bonded manner and the closure unit is connected to the metallic lid region that can be pivoted open in a bonded manner, in particular by a thermal process using an adhesive lacquer layer which is preferably suitable for use with food and/or has lubricating properties.

Due to the interplay of the individual features of the can lid in accordance with the invention, it becomes possible to accommodate and to fasten both the sealing frame and the closure unit in a space saving manner and preferably in a recess of the can lid surface at the upper side of the can lid and thus to avoid the apertures of the can lid surface required in known designs. This also brings about advantages with respect to hygiene, in particular in connection with the further special feature of the invention which comprises that the closure unit has at its total outer periphery a sealing apron which extends up to the fixed lid surface and which is preferably connected to the fixed lid surface in a bonded manner via the adhesive lacquer layer.

It can be ensured in this manner that the plastic elements disposed at the outer lid side cannot be infiltrated by contaminants and the like.

The lower side of the metallic can lid disposed at the inner can side and formed by a practically continuous metal surface only including the microgap is in turn connected in a bonded manner via the adhesive lacquer layer to the molded plastic film part which ensures the sealing off of the microgap, with it being important that no plastic parts belonging to the closure unit or to the sealing frame extend through the metallic lid material and, accordingly, only two components come into contact with one another and have to be connected at the lower lid side, namely the metallic lid, on the one hand, and the molded plastic part, on the other hand.

The preferred use of a joining together of the lid region that can be pivoted open without a toothed arrangement and/or without undercuts is furthermore of advantage, said lid region first being punched out from the lid surface and then being pressed back into the lid surface again, wherein the recognition is used that the punching out process can be designed such that a conical expansion can be achieved in the lid material over a part region of the material thickness, said conical expansion enabling a shape matched and/or force transmitting connection between a fixed lid surface and a punched out lid region with a formation of the desired microgap.

The bonded connection can in particular comprise a plastic weld connection, with the adhesive lacquer serving for an adhesive promotion between the plastic and the metal, or a so-called hot melt connection.

The sealing frame, the closure unit and the molded film part are preferably exactly mutually aligned with respect to the metallic lid surface by means of positioning studs which are preferably point-shaped and associated recesses which are in particular cup-shaped.

While the studs for the plastic parts positioned at the outer side of the can lid are preferably formed at this plastic part, the cup-shaped recesses for receiving the studs of the sealing frame at the lower side or inner side of the lid simultaneously act as studs for positioning the molded plastic part which has correspondingly complementary recesses.

The finished can lid preferably comprises a composite material in the form of a sheet metal layer, in particular composed of aluminum or tin plate, which is coated at both sides by an adhesive lacquer and which is connected at the inner side to the film molded part via the adhesive lacquer layer, wherein the mechanical strength of the film component in the composite material is expediently selected such that, while ensuring the required overall strength of the composite material, the material thickness of the metallic component can be reduced, in particular by at least 1%, in comparison with a film-free component.

In view of the huge volume of can lids produced in practice, such a saving of material, even if only amounting to 1%, for example, already plays a comparatively large role under economic aspects and accordingly represents a corresponding advantage.

In accordance with a further embodiment of the invention, the molded film part of the composite material extends up to and into the bead margin which is provided for connecting the lid to a can and which acts there as a sealing material and as corrosion protection.

Since additional sealing material is typically required in the region of the bead connection in conventional cans, a practically relevant saving and a cost reduction can in turn be achieved by the measure in accordance with the invention.

The pivot bearing region molded at the closure unit has, between its fastening region and the pivot part, a hoop region which is closed at the lid side, which expands in a gusset-like manner at both sides, which acts as a tilt spring and which enables a bistable positioning of the closure unit. This arrangement ensures that the closure unit is moved to an opening angle of more than 130° and is held open in this position when an opening angle of approximately 90° is exceeded, whereas the closure unit snaps back from the open position to an opening angle position of less than 30° on a falling below of an opening angle of approximately 90°. From this position, the closure unit can again be pressed into the sealing closed position without problem. This process can be carried out reversibly in both directions a multiple of times.

The configuration of this region, acting as a tilt spring, closed at the outer side is also important in this respect since the gaps which are frequently present in conventional solutions and which are prone to contamination are thereby avoided.

The embodiment of the sealing frame and the closure unit is of particular significance for the function of the reclosable can lid in accordance with the invention. The sealing frame and the closure unit cooperate via an inwardly disposed sealing rib and an outwardly disposed latching rib which engage into corresponding receiving grooves. A predefinable sealing pairing of slanted surfaces is in this respect provided between the sealing rib and a wall of the associated receiving groove, with the selection of the slant being dependent on which inner can pressure has to be maintained after the reclosing of the can has taken place, wherein it must simultaneously be taken into consideration that the opening process is not thereby made more difficult in a disruptive manner.

The latching rib is provided with a short slanted surface lug which cooperates with a counter-latch of the associated receiving groove, with a predefinable clearance being provided between the two cooperating surfaces when the can opening is closed.

This small clearance can be used to enable an excess pressure reduction during the opening movement of the closure unit without the lid already being opened so far in this phase that there would be a risk of a spurting out of liquid.

A further special feature of the invention that is important with respect to the constantly sought reduction of the production costs of can lids is that the can lid at least substantially comprises the same aluminum alloy as the container part connected to it; and the metallic material thickness of the can lid is substantially equal to the material thickness of the container part and preferably at least does not exceed twice the value of the material thickness of the container part, with the material thickness of the container part being in a range of approximately 0.1 mm and less.

Known cans, in particular beverage cans, comprise aluminum alloys, with it being typical to use an aluminum alloy of the 3000 series for the cylindrical can part and to use an aluminum alloy of the 5000 series for the lid part to take account of the different technical demands with respect to the can part and the lid part. So far, it has only been possible to reduce the wall thickness of the can wall to approximately 0.09 mm, and indeed by using an aluminum alloy of the 3000 series which is less expensive than the aluminum alloy of the 5000 series which is typically used as the lid material. The wall thickness of the lid material has to be at least twice as large as the material thickness of the can wall to ensure the necessary compression strength of the can despite the notch to be formed in the lid material in known lids for providing a tear-open groove. This notch has a depth which typically corresponds to approximately half the material thickness of the can lid. However, all the demands on the can lid with respect to the opening criteria and the leak tightness can be satisfied by the use of the higher-quality alloy series Aluminum 5000.

In addition to the saving of production costs achieved by the material selection or by the embodiment of the composite material and by weight reduction, it is of considerable importance that, also due to the specific microgap design, it is no longer necessary to use a specific material such as an aluminum alloy of the 5000 series, in particular 5182, for the lid material since an inexpensive aluminum of the 3000 series can now also be used for the metallic lid material.

The invention furthermore relates to a method of manufacturing a sealed opening, which can be torn open or pressed in and can preferably be reclosed, in an areal sheet metal material, in particular in a can lid which is configured as reclosable or which corresponds to a standard can lid in which the opening region can either be torn open or can be pressed into the can interior.

Further details and advantages of the invention are set forth in the dependent claims and will be explained in the following description of an embodiment with reference to the drawing.

