Process for the fabrication of interconnecting elements for a slide fastner

Abstract

Method for manufacturing interconnecting elements for a slide fastener, comprising the steps of producing interconnecting half-elements provided with a predetermined three-dimensional shape, by means of punching of said half-elements from a sheet, and forming said interconnecting elements by joining together respective pairs of half-elements.

Description

FIELD OF APPLICATION[0001]The invention relates to the manufacture of interconnecting elements for a slide fastener (zip fastener). The invention in particular relates to the manufacture of interconnecting elements which have a complex shape, for aesthetic purposes or for personalization of the slide fastener.PRIOR ART[0002]A slide fastener as known comprises essentially two flanking strips which carry respective rows of interconnecting elements, commonly called teeth or tines, and a slider for engaging and disengaging the aforementioned elements. The fastener may also comprise a top stop and a bottom stop for stopping the slider.[0003]Punching is a widely used technique for manufacturing interconnecting elements, especially if they are made of a metallic material. The prior art in the field essentially envisages that each element is punched as a single piece from a flat metal sheet, also termed plate. Punching is generally performed in several stages; prior to punching and associat...

AI Technical Summary

Benefits of technology

The invention allows for the creation of interconnecting elements with complex three-dimensional shapes using the punching process, which is high-productivity and low-cost. These shapes include inclined surfaces, curved surfaces, and parts tapered from bottom to top. The half-elements can be made with a flat strip and then joined together, resulting in interconnecting elements with double the size of prior art without the need for a shaped sheet. This expands the possibilities of aesthetic personalization of the slide fastener while maintaining a low industrial cost and a proven and reliable process.

Problems solved by technology

Moreover, there are some materials, such as brass, which are unsuitable for other processes (e.g. injection moulding) and for which punching is particularly suitable.

Production by means of punching from a flat sheet still has, however, a major drawback being unsuitable for making interconnecting elements with a complex shape.

Moreover, the various drawing, coining and other machining steps are easily performed only on the two parallel faces of the sheet, and do not allow obtention of complex three-dimensional shapes.

Subsequent machine-finishing of the teeth is not convenient because it would require processing one-by-one a large number of parts with small dimensions of the order of a few millimetres.

A partial solution to the problem would consist in starting from a shaped sheet, but this solution is not appealing because it would involve very high plant costs.

For these reasons, in the prior art, production of a complex three-dimensional shape by means of punching is not considered to be feasible.

Other machining techniques are known (e.g. machine-tool processing, precision casting, etc.) which can obtain elements of various shapes, but these techniques do not have the production capacity of punching and involve higher costs.

Another limitation of punching consists in the difficulty of punching a strip with a large thickness.

In the prior art punching is used normally for a small thickness, usually not greater than about 1-1.5 mm; punching from a strip of large thickness (e.g. >2 mm) is difficult and may cause deformation of the teeth.

This deformation may be unpleasant and / or may adversely affect operation.

Production by means of punching is not considered able to meet this market demand in a satisfactory manner.

Moreover, as mentioned above, a processing as seen in FIG. 9 is applicable in practice only when the plate thickness is small (about 1 mm), thus having a limited versatility.

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