The present invention relates to a closeable opening device for a sealed packaging, which contains a flowable medium, wherein the device comprises a spout fitting having a pipe section and flange, said pipe section being furnished with an internal and an external thread, as well as to a cylindrical cutting element, the lower edge of which is equipped with one or a plurality of teeth and the internal jacket surface of which is furnished with driving dogs protruding in the radial direction that interact with driving dogs in a screw cap comprising a jacket wall and cover surface, wherein the spout fitting and the cylindrical cutting element are produced as a one-piece finished good connected to one another via predetermined breaking points.
A closeable opening device of the aforementioned type is taught by the European Patent Reference EP-A 1088764. In this case, a principle is used, which is common in closure technology, wherein multi-part closures are produced so that two parts are disposed on top of one another and are injection molded in one piece to be connected to one another via predetermined breaking points. In this connection, the expenditure for tools is on the one hand reduced and on the other hand the assembly is simplified because the parts connected to one another via predetermined breaking points are already disposed in their accurately aligned relative position to one another and have thus to be merely pushed together. This technology, which is sufficiently known per se, has also been used previously for the closures of interest here and is, for example, also taught by the European Patent Reference EP-A 1084060.
Both documents disclose a semi-finished good, which displays a one-piece production of a spout fitting including a flange together with a cylindrical cutting element. The cutting element according to the European Patent Reference EP-A 1084060 does not have a planar surface at the upper or lower edge, which is suitable for being connected in a revolving manner to an upper or lower edge of the spout fitting. A solution is thus necessarily disclosed in which the cutting element is produced in an intermediate position within the spout fitting as a semi-finished good connected to the lower edge of said spout fitting via predetermined breaking points.
In both solutions, the preassembly, during which the cutting element has to be inserted into the spout fitting, is not as trivial as it may appear. Sealed packagings made of laminates or plastic films, onto which the opening devices of interest here are mounted, are or contain a plastic film which is difficult to sever because the material is very tough and requires that the teeth correspondingly comprise a sufficient solidity. Nevertheless, said teeth cannot simply be designed arbitrarily robust because they also must be capable of piercing and cutting the material. Correspondingly said teeth must not be negatively impacted during assembly. This problem is solved by WIPO patent application WO 2007/051328. The solution consists of holding the cutting element and the spout fitting together such that a simple axial pressure can be applied to the upper edge, which runs flatly in a perpendicular plane with respect to the rotational axis. If this assembly is carried out, the screw cap must now be fitted so as to be correctly aligned in the axial direction. This is carried out to this point as a result of the screw cap being fitted practically in an arbitrary angular position with respect to the perforator and the screw cap being subsequently pressed with the internal thread thereof in a ratchet-like manner over the external thread on the spout fitting. This is not a problem per se with regard to the assembly. A problem has however become apparent in that the driving dogs on the screw cap and the corresponding driving dogs on the cutting element can now practically assume an arbitrary angular position with respect to each other. Because the tamper-evident band has to first be detached during the initial opening and in so doing a relatively large torque is required, the user tends to apply said torque in a sudden and jerky manner. This can now result in the driving dogs of the screw cap being able to jump over the driving dogs of the spout fitting.
In addition, the greatest torque is required when the teeth have to open the film of the sealed packaging. At this time, it is again possible that the driving dogs jump over one another. If this happens, a complete opening of the film is often no longer assured when the packaging is being initially opened.
In order to solve the first problem, assembly lines have partially been built, which have turned the screw cap into an exact angular position with respect to the cutting element and only then push the two parts together so that in the assembled state the driving dogs are already brought correctly to the position where said dogs approximately abut against each other. This has required corresponding positioning means on the screw cap as well as on the semi-finished product, which can be mechanically or optically scanned. This process is, however, associated with substantially higher assembly costs.
With regard to the second problem, a practical solution thereto has so far not been found.