The present invention relates to a slide fastener having a pair of opposed tapes, each including a strip made of a flexible material folded on itself around an elongate core member, in particular a flexible cord, so as to form a teeth-carrying edge onto which a respective row of coupling teeth is fastened.

The invention also relates to a method for the manufacture of such a slide fastener.

Slide fasteners of that type are disclosed for instance in US-A-1 933 290 and EP-1 384 412 A1.

The manufacture of slide fasteners having stringer tapes made of a flexible material, in particular thin soft natural or artificial skin or leather, faces the problem that with said materials it is very difficult, if not almost impossible, to obtain tapes having the required strength and dimensional stability. Tapes made of such materials are in fact relatively weak and prone to yield under stress. Difficulties can thus be involved in maintainining the correct relative positions of the coupling teeth which are affixed thereto, which is a necessary condition for the proper functioning of a slide fastener.

An object of the present invention is to provide an improved slide fastener and a method for the manufacture thereof, which allows to overcome the above-outlined inconveniences of the prior art.

This and other objects are achieved according to the invention by a slide fastener and a method according to claim 1 and claim 8, respectively.

The stringer tapes of a slide fastener manufactured in accordance with the present invention exhibit a superior strength and an optimal dimensional stability, allowing to reliably maintain the correct relative positions of the coupling teeth affixed thereto.

Further features and advantages of the invention will become apparent from the detailed description which follows, provided purely by way of a non-limiting example, with reference to the accompanying drawings, in which:

• figure 1 is a partial front view of a slide fastener manufactured in accordance with the present invention;
• figure 2 is a partial top plan view showing a phase of the manufacture of a stringer tape for a slide fastener according to the invention;
• figure 3 is a cross-sectional view along the line III-III of figure 1; and
• figure 4 is a cross-sectional view along the line IV-IV of figure 1.

Referring to the embodiment illustrated in figure 1, a slide fastener generally designated by the reference numeral 1 comprises a pair of oppositely disposed stringer tapes 2, each carrying a respect row of discrete fastener elements or coupling teeth 3. Said fastener elements or coupling teeth 3 are affixed to a longitudinal edge of each of said tapes 2, and are disposed so as to be taken into and out of engagement by a slider 4 which is manually operable by means of a pull-tab 5.

Each stringer tape 2 includes a strip 6 (figure 2) made of a flexible material, such as a woven or non-woven or knitted material. The strips 2 can be in particular made of natural or artificial skin or leather, having a thickness comprised between 0.20 and 0.35 mm, preferably between 0.25 and 0.30 mm.

As shown in figure 2, onto the inner surface or face 6a of the strip 6 there is applied a correspondingly shaped strip 7 of a reinforcing sheet material. The reinforcing strip 7 is conveniently made of a plastic material (preferably nylon) or metal or woven or non-woven or knitted film or tape, having a thickness of preferably between 0.05 and 0.15 mm, and very preferably of 0.10 mm, and is applied to the strip 6 by means of an adhesive, such as a glue or mastic.

After the reinforcing strip 7 has been applied to the strip 6, a layer of adhesive, preferably the same interposed between said strips, is applied onto the reinforcing strip 7. Thereafter, the thus obtained composite strip is folded on itself, around an elongate core member 8, such as a flexible cord, and is pressed for a predetermined period of time, for instance by passing through a rolling guide.

According to an alternative, a strip 7 of reinforcing material is folded and sticked by an adhesive on itself around the core member 8, and thereafter a strip 6 of a flexible material, such as a natural or artificial skin or leather, is wrapped around and sticked by an adhesive to the thus obtained semifinished product.

In either case, a thus manufactured stringer tape 2 has a cross-sectional shape such as that shown in figure 3.

The core member 8 and the fold of the stringer tape 2 form a teeth-carrying bead or edge, onto which a respective row of fastener elements or coupling teeth 3 can be reliably affixed.

As shown in figure 4, for each tooth 3 a hole 9 can be stamped or punched in the corresponding tape 2, and the tooth 3 has an anchoring portion 3a extending through said hole 9. The teeth 3 can be formed for instance by injection moulding a plastic material, or crimping metal elements.

In the manufacture, the composite strips 6, 7 described above can be obtained by cutting into strips a composite sheet obtained by applying a relatively large sheet of reinforcing material to a corresponding sheet of flexible material, with an interposed adhesive. As an alternative, the said composite strips can be obtained by applying a previously cut strip 7 of reinforcing material to a previously cut strip 6 of flexible material, with an interposed adhesive.

The stringer tapes of a slide fastener manufactured in accordance with the present invention exhibit a superior strength and an improved dimensional stability, even though the material forming the strips 6 is inherently weak.

Obviously, without modifying the principle of the invention, the embodiments and the constructional details may be widely varied with respect to what has been described and illustrated purely by way of a non-limiting example, without thereby departing from the scope of the invention as defined in the accompanying claims.