A PROCESS FOR REALIZING PLASTIC CAP ASSEMBLIES FOR CONTAINERS

Abstract: The process for realizing plastic cap assemblies comprises: a first forming stage wherein a plastic material is compressed to obtain a cap for opening and closing a container; a second forming stage wherein a plastic material is compressed to obtain a cap annular element, destined to function as a connecting organ between the cap and the container; an assembly stage of the two elements.

Description: Desc n pt i on . A Process for Realizing Plastic Cap Assemblies for Contai ners. Technical Field. The invention relates to a process for realizing plastic caps in the field of containers for water, soft drinks, and liquids in general. Background Art. For some time now caps have been in use which comprise, briefly, a cap for opening and closing the container and a device, usually a security strip, which evidences whether the container has in fact been opened at least once. The relatively low cost of each such cap assembly and the very high number of pieces utilized mean that even a small improvement, whether in cap shape or in the process for realizing the cap assembly, is extremely important; such small improvements can indeed lead to enormous savings in the production of the objects. Firstly metal caps were devised. but these have been gradually replaced by plastic caps, since they were expensive and brought about the need to perform mec anica 1 machining subsequent to their manufacture, such as for example edge-tapping for connection with the various components of the cap assembly, or adjustments during their attachment to the container. A first process for realizing plastic caps comprised an injection of fluid-state plastic into speci al 1y-snaped dies. Caps of various types could be obtained thus. This technology, nowever, presents a drawback: the machines for the injection of the plastic achieve only moderate production levels. which obviousy influences the cost of the final product. In the attempt to increase productivity, multiple dies are used, so that for each injection several caps are obtained. This increases productivity but at the same time adds to the complexity of the dies and thus to production costs. The prior art also teaches the technology of forming by compression and subsequent mechanical machining. This technology consists of introducing a small piece of plastic material into the matπx of a die and deforming the material by means of a punch which penetrates the matrix and causes the material to occupy all available space remaining between the punch and the matrix - which space obviously corresponds to the shape of the cap to be obtained. This stage of the process produces plastic caps with a single pressing operation, and also at the same time produces the security strip destined to detach from the cap when it is first removed from the container. Further mechanical operations realize the fracture line between the cap and the security strip and the tabs for constraining of the cap assembly to the container. In many cases a still further operation is performed to obtain a seal internally of the cap. An advantage of these machines is that the die is simple and can be installed in series in rotary machines comprising a large number of punch-matrix die groups These machines are extremely fast and therefore very highly productive. The disadvantage of this technology is that it provides caps which in some cases require a further forming stage to obtain the seal, and in all cases require further mechanica " ' operations It has been attempted to manufacture these caps using laterally-opening dies but the complication in the die construction has rendered this solution impracticable. The main aim of the present invention is to provide a process by which a plastic cap assembly can be manufactured at reduced costs. Disclosure of the Invention. This aim is achieved by the process, as it is characterised in the claims that follow the present descπ ption. The process, specifically intended for realizing plastic caps, comprises a first stage wherein a plastic mateπal is press-formed to obtain a cap for opening and closing a container for which it is destined. The process further comprises a second stage wherein a plastic material is press-formed to obtain an annular element for the cap, which element will be a connecting organ between cap and container. The annular element is conformed such that when the cap is first used a first annular part will remain constrained to the cap while a second annular part will fracture perceptibly. The annular element is also conformed such that tne first annular part and the second annular part have differing diameters and are interconnected bv means of easy-break ribs. Given the conformation of the annular element, the ribs extend radiallv and can easily be obtained by means of press-forming using simple dies In this second stage, the annular element can advantageously exhibit a third part destined to constitute a seal for the cap. This third part is obtained internally of the annular element and, before assembly of the cap, is connected to the annular element by means of easy-break ribs. The third part also extends radially and can easily be obtained by press-forming using simple dies. Finally, the process includes an assembly stage of the two cap elements, realized in such a way that the first part of the connecting organ is constrained to the cap If the annular element is provided with the third part, namely the seal , this is forced into the upper internal part of the cap. The proposed process does not i ntend to present a new type of cap, but to provide a new manufacturing process for both known and new caps, which process has the characteristic of improving the known manufacturing process of using press-forming only for making cap assemblies wherein the cap and the security strip are realised in a single piece which thereafter is subject to mechanical operations. The process described can advantageously be used for manufactuπng known-type caps, such as for example the cap described in GB patent GB 2,141,414 belonging to the present applicant, which comprises elements having a conformation and functional characteristics which are like those described in the present description. Obviously new- type caps can also be used, as long as their characteristics are compatible with those described herei n . The process enables productivity of known-type caps, previously obtained only by injection, to be considerably ι ncreased .

Claims: Cl ai ms . 1. A process for realizing plastic cap assemblies, characterized in that it comprises the following stages: a first forming stage wherein a plastic material is press- formed to obtain a cap for opening and closing a container; a second forming stage where a plastic material is press- formed to obtain an annular element of said cap assembly, destined to function as a connecting organ between the cap and the container and conformed in such a way that when the cap assembly is first used to open said container a first annular part of said annular element remains constrained to the cap and a second annular part thereof, having a different diameter to a diameter of the first annular part thereof, fractures perceptibly; an assembly stage of the cap and annular element wherein said annular part of said annular element is constrained 2. A process as in claim 1, characteπsed in that said second stage of press-forming of a plastic material is performed in order to obtain said annular element which, apart from being conformed in such a way that on first use of the cap assembly to open said container a first part of said second annular element remains constrained to the cap and a second part thereof fractures perceptibly, also exhibits a third part destined to constitute a seal for the cap. 3. A process as in claim 2, characterized in that during said assembly stage, said third part of the second annular element is forced into an upper internal part of the cap. 4. A process as in claim 1. characterized in that said first part and said second part of said second annular element obtained during the second press-forming stage are interconnected by means of easy-break ribs.

Inventors: MORINI EMILIO, MORINI, EMILIO
Applicants: BORMIOLI METALPLAST SPA, MORINI EMILIO, BORMIOLI METALPLAST S.P.A., MORINI, EMILIO
Application year: 1996
Main classification: B29C43
IPC codes: B29C43, B29C65