EP2303765B1 - Method for producing three-dimensional shapes from assembled pieces having distinct elasticity-properties, and leathercraft article - Google Patents

Description

The present invention relates to a method for producing a three-dimensional shape of a bag or article of leather goods from two pieces intended to be assembled and having characteristics of different elasticities, including a piece of leather. It also relates to an article of leather goods, such as bags made from this process. The invention is particularly applicable to leather goods at least partly made of leather.

The field of the invention is that of the industry of processing substantially flat materials for the purpose of making three-dimensional shapes. In the present application, the term "form" is to be considered not only in the proper sense (geometrical form), but it also designates, figuratively, an object or a set having the evoked geometrical properties (producing a "three-dimensional shape") .

Consider the field of leather goods, which interests us particularly. Currently, when a leatherworker wishes to make a leather bag with a three-dimensional shape, he is currently forced to use specific pieces of structure or frame, to form a sort of framework of the bag on the basis of which pieces of leather. leather will be assembled and held in a desired shape. The structural or reinforcing parts condition the final shape of the bag. This results in a complexity of realization (multiplicity of elements, assembly, etc.) and therefore additional costs. Moreover, once the bag is assembled and shaped, it is not easy to obtain shape variations, slightly deviating from a predefined nominal shape, due to the presence of structural or reinforcing parts which opposes the deformations. Or it may be useful to easily deform a bag having a predefined nominal shape, for reasons of space, storage etc., while retaining the ability to resume its original nominal form. (See for example DE641614 C .)

The object of the present invention is to provide a method for obtaining a three-dimensional shape of a bag or an article of leather goods, which does not imply the use of specific structural parts or armature.

This object is achieved with a method for producing a three-dimensional shape from two pieces to be assembled having distinct elasticity characteristics, including a leather piece, comprising the steps described in claim 1.

Thus, with the method according to the invention, it is possible to obtain a three-dimensional equilibrium shape having both strength and flexibility characteristics. The outfit is due to the self-supporting properties of the structuring piece of leather, which is the body of the three-dimensional shape. The structuring piece however has a certain flexibility, and lends itself to deformations, mainly in flexion.

In a particular version of the invention, structural and deforming parts made in webs or skins are used in the process, having reduced thicknesses relative to their other dimensions.

In another version of the invention, the method further comprises a step of cutting at least one of the two pieces after obtaining the three-dimensional shape.

In another version of the invention, the method further comprises a step of cutting at least one of the two parts prior to the tensioning of the deforming part.

The bonding step comprises spraying an adhesive having characteristics of resistance to moisture, on the structuring part and on the deforming part.

It is advantageous to provide a zone delimitation of the structuring part to be glued.

The invention also relates to a process having all of the preceding features and further comprising assembling said two assembled parts with other structural parts.

According to yet another aspect of the invention, there is provided an article of leather goods, such as a bag, according to claim 8.

• la figure 1 illustre les différentes étapes du procédé de réalisation selon l'invention ; et
• la figure 2 est une vue en coupe de l'enveloppe complexe obtenue avec le procédé selon l'invention.

Other advantages and characteristics of the invention will appear on examining the detailed description of an embodiment which is in no way limiting, and the appended drawings in which:

• the figure 1 illustrates the different steps of the production method according to the invention; and
• the figure 2 is a sectional view of the complex envelope obtained with the method according to the invention.

We will now describe, with reference to the figure 1 the different steps of the production process according to the invention, together with the technical means used in this process.

Are intended to be assembled in the process according to the invention, two pieces forming skins, sheets or layers, in that they have a reduced thickness relative to their other dimensions. Both pieces have distinct elasticity characteristics. The piece having the highest elasticity characteristics and the "structuring part" the piece having the weakest elastic characteristics, because of their respective function in the assembly to be produced, will be called "deforming part".

The structuring piece is leather. This structuring part is particularly sought for properties of mechanical strength and rigidity, essentially in tension / compression in the plane of its surface (when flat) or in the directions tangent thereto. The structural part also resists deformation under the effect of stresses exerted perpendicularly to its surface. On the other hand, it is sought for this structural part a relatively high bending ability. The structuring part thus has combined qualities of transverse mechanical strength and flexibility of the material. These notions of mechanical strength, strength and rigidity, are to be considered relatively to the deforming part, which has in comparison with the characteristics of elasticity greater than the structuring part.

Firstly, a deforming piece 1 was prepared and cut such as "Bengaline Lycra®" or elastane®-based. This piece deforming will form a lining, which may have been woven with decorative or fancy patterns.

In a first step (I), the deforming part 1 is cut beforehand according to a predetermined template according to the desired three-dimensional shape, that is to say as a function of the deformation that it will cause on the structuring part.

The deforming part 1 is then placed in a tensioning machine comprising two mechanical parts 10, 11 in which are inserted and locked the edges of the part 1 which is held in tension with a tension force F determined according to the characteristics of the deforming part used (stage II) and in particular its elasticity.

This tensioning force F must ensure a tension lower than the breaking force of the deforming part.

One of the faces of the deforming part 1 is then subjected to a spray application of glue by means of a suitable equipment 12 arranged facing the deforming part 1 (step III). The adhesive used is preferably a strong adhesive and having a minimum sensitivity to environmental conditions and in particular humidity levels and temperature variations. It must not be retractable with water and heat; It may be Neoprene® or equivalent, but should preferably be environmentally and health friendly.

At the same time or previously, a structuring piece 2 made of leather or a similar material has been prepared and cut. This material will constitute both the body and the outer shell of the three-dimensional shape. The structuring part is subjected (step IV) on one of these faces intended to be applied to the deforming part, to a glue application identical to that used to glue the deforming part 1. The application of the glue is carried out from preferably on the so-called "velvet" side.

The deforming part 1 and the structuring part 2 previously glued are then superimposed and glued (step V), the deforming part 1 is always maintained in tension (step V).

Once the setting time of the glue has elapsed, the tension force F is removed and the complex piece 1 + 2 thus produced is released, which instantly takes on a three-dimensional curved shape (step VI). Being freed from the tension force F, the deforming piece 1 which was previously stretched retracts to return to its nominal shape. However, it does not find exactly its initial shape given the resistance that the structural part 2 sets against it. The curvature of the complex part 1 + 2 is induced by the difference of the tension forces exerted respectively on the structuring part 2 of rigid feature, and on the deforming piece 1 of elastic characteristic, and the fact that the two pieces form layers 1.2 firmly bonded to each other. Given the stress exerted by the deforming part 1 on the structuring part 2, the curved shape is such that the structuring part 2 is located on the convex side, while the deforming part is located on the concave side.

Note also that the structuring piece plays a role of spring, when it works in bending.

This complex piece 1 + 2 is then completed (step VII) by assembling other structural parts. This assembly is carried out by known techniques, such as sewing, gluing, etc. In the particular application of leather goods, where the structural part 2 is leather, it takes for example a generally cylindrical shape, which is completed by other pieces of leather 22 closing the ends of the cylinder, so as to constitute a bag 20. Accessories such as handles 21 and closures are then mounted on the bag 20.

The production steps that have just been described can be automated from current industrial manufacturing techniques. The various equipment used for cutting, tensioning, gluing, bonding layers, and assembly, can be provided with control means / numerical control and if necessary robotic. In particular the material used for the deforming part, such as fabric, can be a standardized material, which allows a certainty as to the result, that is to say the precise obtaining of the desired three-dimensional shape.

It will be noted that the method is suitable not only for small but also for large areas of structuring and deforming parts. The surface is actually a determining factor of the implementation.

In the aforementioned application to a leather article, the bag 20 thus obtained then has a permanent three-dimensional shape without the need to include specific stiffening or holding parts to form a structure or frame. With reference to the figure 2 , the maintenance is carried out directly by the leather layer 2 (structuring part) whose flower 23 constitutes the outer face of the envelope. The deformation was caused by the fabric layer 1 with elastic properties (deforming part), one side of which will constitute the lining of the bag, a layer of glue 3 having been applied between the pile of the leather layer 2 and the facing face. a benefit of the invention lies in the fact that each of the structuring and deforming parts provides three functions: a first function is mechanical, in terms of resistance (for the structuring part) and of retraction (for the deforming part), in order to obtain the desired three-dimensional shape. A second function is to jointly form an envelope for a container (wall of the bag). A third function is to constitute the style (made visual, tactile) outside or inside the bag. It is remarkable that these three functions are assured only by two pieces contiguous to one another.

Of course, the invention is not limited to the examples which have just been described and many adjustments can be made to these examples without departing from the scope of the invention as described in claims 1-8.

Claims (8)

1. A method for producing a three-dimensional shape of a bag or leather article (20) from two parts (1, 2) to be assembled and having different elasticity characteristics, including a part made of leather, characterized in that it comprises the following steps:

   applying tension and maintaining tension to the part, said the deformable part, having relatively higher elasticity characteristics;

   a bonding of the leather part, said the structural part, having the weakest elasticity characteristics, on the deformable part maintained in tension;

   a suppression of the tension applied to the deformable part, which then exerts stresses on the structural leather part, so as to deform it into bending and to obtain a complex part (1 + 2) formed of said deformable and structural parts assembled, said complex part having the desired three-dimensional shape, said three-dimensional shape being curved such that the structural leather part (2) is positioned on the convex side, and the deformable part (1) is positioned on the concave side.
2. The method according to claim 1, characterized in that the structural part and the deformable part are formed in a sheet or skin shape having reduced thicknesses relative to their other dimensions.
3. The method according to claim 1 or 2, characterized in that it further comprises cutting at least one of the two parts after obtaining the three-dimensional shape.
4. The method according to claim 1 or 2, characterized in that it further comprises cutting at least one of the two parts before tension is applied to the deformable part.
5. The method according to one of the preceding claims, characterized in that the bonding comprises spraying a moisture-resistant adhesive on the structural leather part (2) and the deformable part (1).
6. The method according to one of the preceding claims, characterized in that it further comprises a zone delineation of the structuring leather piece to be bonded.
7. The method according to any one of the preceding claims, further comprising further comprising assembling said complex piece (1 + 2) with other structuring pieces (22).
8. A leather article (20), such as a bag, at least a portion of which is made from two assembled parts (1, 2) having distinct elasticity characteristics, in which a part (1), said the deformable part, has the highest elasticity characteristics, and a part (2) made of leather, said the structural part, has the lowest elasticity characteristics, said leather structural part being bonded to the deformable part which exerts stresses on the leather structural part so that the two parts have a three-dimensional curved shape such that the leather structural part is positioned on the convex side, while the deformable part is positioned on the concave side.

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