Controlled tension fabric and a method of making same

Abstract

A controlled tension fabric (100) is provided comprising a membrane (10) including knitted fabric or woven fabric with weft and warp, and at least one yarn (1) bound to the membrane (10) and including a first filament (2) including elastic material, a second filament (3) wound around the first filament (2) with a predetermined pitch or developing parallel to said first filament (2) and including heat-shrinkable and / or water-shrinkable material defining, when subjected respectively to a heat source or a water dosage sufficient to shrink the second filament (3), a second maximum plastic linear expansion, and wherein the first filament (2) is pre-tensioned and defines a first elastic linear expansion stably maintained at least until the second filament (3) is subjected to the heat source and / or water dosage.

Description

[0001] DESCRIPTION

[0002] CONTROLLABLE TENSION FABRIC AND METHOD FOR MAKING SAID FABRIC

[0003] The present invention relates to a controllable tension fabric, and the related method for making said fabric, of the type specified in the preamble of the first claim.

[0004] In particular, the present invention relates to a fabric comprising a preferably knitted membrane to which a composite yam defining controllable elastic properties is bound, particularly suitable for use in making seats or backrests of chairs, such as an entire fabric surface of the seat or fabrics that generally require controlled elasticity preferably lower than the elasticity of the fabric.

[0005] As is known, in recent years, the use of heat-shrinkable yarns has been widely disseminated and successful in the textile sector.

[0006] Heat-shrinkable yarns are essentially composite yams that have the ability to shrink when heated; this capability is similar to the commonly used materials for heatshrink tubing.

[0007] Specifically, unlike the tubing technique where the tubular element undergoes constrictions, heat-shrinkable yams are configured to reduce their length when approached by a heat source.

[0008] The heat-shrinkable yam is particularly useful when introduced into the weft within a fabric, whether it is a fabric made of weft and warp or even a knitted fabric. The shrinkage capability of the yam allows, in fact, to locally tension the fabric on command so as to control the mechanical characteristics of the fabric itself in the area where the yam is woven.

[0009] More specifically, generally, the heat-shrinkable yam consists of a first filament, or core, and a second heat-shrinkable filament wound around the first filament or a single composite yarn. The entire composite can also be woven in warp or weft direction.

[0010] This heat-shrinkable yam has, particularly recently, been used to make knitted fabrics, wherein the yarn is uniformly knitted, to create seats or backrests of chairs that can be tensioned through the application of heat, such as in an oven or with hot steam.

[0011] An example of such a fabric is marketed under the name Camira knit™.

[0012] The known technique described has some significant drawbacks.

[0013] In particular, when the heat-shrinkable yarn in knitting undergoes the shrinkage process, it tends to become excessively loose and, therefore, can form excessively soft areas or wrinkles in areas like the seat or backrest of a chair to which the fabric with heat-shrinkable yam is applied.

[0014] Therefore, especially in the area of the backrest, the fabric does not maintain the desired shape, and it is not possible to fully control the conformation of the support areas. Moreover, a fabric that is uniform in terms of properties does not allow for the variation of its characteristics locally, that is, at specific areas.

[0015] In this situation, the technical task underlying the present invention is to devise a controllable tension fabric, and the related method of making it, capable of substantially overcoming at least part of the aforementioned drawbacks.

[0016] Within the scope of this technical task, an important object of the invention is to provide a controlled tension fabric, and the related method of making it, which allows complete control over the shape and tension imposed on a seat or backrest of a chair, once used on the seat or backrest of the chair. Another important object of the invention is to make a controlled tension fabric, and the related method of making it, that can support a user comfortably and effectively when used on a chair.

[0017] Furthermore, an additional task of the invention is to create a controlled tension fabric, and the related method of making it, that allows for an aesthetically pleasing, uniform appearance without fractures between areas of different functionality, for example, with different applied tensions, and that presents controllable lines in the shape in which there are no wrinkles or other undesirable sagging areas.

[0018] Moreover, an additional object of the invention is to create a controllable tension fabric, and the related method of making it, that allows control of the padding volume when the latter is present in relation to the tension imposed on the fabric, maintaining residual elasticity after shrinkage.

[0019] In conclusion, a task of the invention is to create a controlled tension fabric that can be made entirely in a single production process.

[0020] The technical task and the specified objects are achieved by a controlled tension fabric, and the related method of making it, as claimed in the attached claim 1 . Preferred technical solutions are highlighted in the dependent claims.

[0021] The features and advantages of the invention are clarified below by the detailed description of preferred embodiments of the invention, with reference to the accompanying drawings, wherein:

[0022] Fig. 1 shows a sequence diagram of a process for making a controllable tension fabric according to the invention;

[0023] Fig. 2 illustrates a sequence diagram of the sub-phases of tensioning and covering of the pre-tensioning phase of a process for making a controllable tension fabric according to the invention;

[0024] Fig. 2a is an example of a yarn for making a fabric having a controllable tension according to the invention wherein the second filament is wound around the first filament with a predetermined pitch and the layer covers both filaments;

[0025] Fig. 2b represents an example of a yam for making a fabric having a controllable tension according to the invention wherein the second filaments develop parallel to the first filament and the layer covers both filaments;

[0026] Fig. 3a is a cross-sectional view of a backrest of a chair on which a controllable tension fabric according to the invention is installed, and in which the yam has undergone the shrinkage process, but the first filament is still pretensioned;

[0027] Fig. 3b represents a cross-sectional view of the backrest of Fig. 3a in which the yam has undergone the shrinkage process and the first filament has undergone elastic return, thus compensating for thermal shrinkage, and is tensioned so as to form the fabric area of the backrest wherein it is woven;

[0028] Fig. 4 shows an example of a controllable tension fabric according to the invention, wherein a padding layer is present;

[0029] Fig. 5 illustrates a schematic sketch of a controllable tension fabric according to the invention, and wherein a padding layer is present, and the yam is English- hooked between the front and back of the fabric and integrated into the padding;

[0030] Fig. 6 is a further example of a controllable tension fabric according to the invention, English-hooked at both the ends of the fabric and at a face of the membrane;

[0031] Fig. 7a illustrates a detailed schematic view of a controllable tension fabric according to the invention, including a padding layer within which the yam is placed already shrunk but still pre-tensioned;

[0032] Fig. 7b represents a view of the fabric of Fig. 7a in the phase of elastic release of the yam, and wherein the fabric is thinned so as to allow the padding layer to increase its thickness and the first filament has lost its pre-tensioning; and

[0033] Fig. 7c shows a view of the fabric of Figs. 7a-7b subjected to tensioning, and wherein the yam can elastically deform by an amount of elastic deformation equal to the maximum shrinkage capacity of the second filament, which acts substantially as a block to elastic deformation.

[0034] In this document, measurements, values, shapes, and geometric references (such as perpendicularity and parallelism), when associated with words like "about" or similar terms such as “approximately” or "substantially," are to be understood as subject to measurement errors or inaccuracies due to production and / or manufacturing errors and, especially, to slight deviations from the value, measurement, shape, or geometric reference to which they are associated. For example, such terms, if associated with a value, preferably indicate a deviation not exceeding 10% of the value itself.

[0035] Additionally, when used, terms like "first," "second," "upper," "lower," "main," and "secondary" do not necessarily identify an order, priority of relationship, or relative position, but may simply be used to more clearly distinguish between different components.

[0036] Unless otherwise specified, as can be seen from the following discussions, it is considered that terms such as "treatment," "computing," "determination,"

[0037] 'calculation," or similar refer to the actions and / or processes of a computer or similar electronic computing device that manipulates and / or transforms data represented as physical, such as electronic quantities in the registers of a computer system and / or memories into other data similarly represented as physical quantities within computer systems, registers, or other storage, transmission, or display devices.

[0038] The measurements and data reported in this text are to be considered, unless otherwise indicated, as made in International Standard Atmosphere ICAO (ISO 2533:1975).

[0039] With reference to the Figures, the controllable tension fabric according to the invention is globally denoted by the number 100.

[0040] The fabric 100 is substantially a thin element developing predominantly in a space along two predominant directions compared to the third.

[0041] The fabric 100 comprises, as a whole preferably at least one membrane 10.

[0042] The membrane 10 is substantially formed by a thin element defining a two- dimensional surface. The membrane 10 can thus be made of knitted fabric or alternatively from woven fabric with weft and warp. Preferably, the membrane 10 is made of knitted fabric.

[0043] Moreover, the fabric 100 preferably comprises at least one yam 1.

[0044] The yarn 1 is a thin, elongated element, developing in space predominantly along a preponderant direction compared to the third.

[0045] Specifically, the yam 1 comprises at least one first filament 2 and one second filament 3.

[0046] The first filament 2 is substantially a thread-like element, thus defining its own opposite ends and its own length. In particular, the first filament 2 comprises elastic material. The first filament 2 may also include additional materials. In the preferred embodiment, the first filament 2 is made of elastic material.

[0047] Even more specifically, the elastic material is preferably of the silicone type. In fact, this material has the advantage of being heat resistant.

[0048] The second filament 3 is also a thread-like element. Therefore, the second filament 3 also defines its own opposite ends and its own length.

[0049] Furthermore, the second filament 3 comprises a heat-shrinkable and / or water- shrinkable material. The heat-shrinkable material is a material that, as is known, when subjected to an adequate heat source, plastically shrinks.

[0050] Similarly, a water-shrinkable material, also known as water-shrink, is a material that, as is known, when subjected to an adequate water dosage, and preferably at controlled temperature, plastically shrinks.

[0051] Therefore, the second filament 3 defines, when subjected to a heat source and / or a water dosage sufficient to shrink the second filament 3, a second maximum plastic linear expansion. By linear expansion is meant substantially the variation in the length of the second filament 3, that is, the variation in distance between the ends. Moreover, when referring to maximum expansion, it is intended to indicate the expansion limit beyond which the second filament 3 cannot go. Clearly, the second filament 3 undergoes shrinkage or retraction when subjected to a heat source and / or a water dosage. Therefore, preferably, the second expansion is negative.

[0052] The water dosage is preferably at a temperature between 25 °C and 60 °C, particularly preferably between 25 °C and 35 °C, for example, approximately equal to 30 °C. In fact, the temperature variation can lead to a variation in the shrinkage factor of the second filament 3.

[0053] In this sense, it should be noted that the second filament 3 may include alternatively heat-shrinkable and water-shrinkable material or material that includes both characteristics, i.e. , a thermo-hydro-shrinkable material. For example, in fact, the material can shrink when subjected to a water dosage, also acting as a heat source, which impresses on the material an expansion variable with the water dosage temperature. In this sense, therefore, both contributions determine the second maximum plastic linear expansion.

[0054] At the same time, the second filament 3 could also expand in section, for example defining diameter increments while shrinking.

[0055] The second filament 3 could also include additional materials.

[0056] Similarly to the first filament 2, however, in the preferred embodiment, the second filament 3 is made of heat-shrinkable and / or water-shrinkable material.

[0057] Even more specifically, the heat-shrinkable material can be of polymeric type, for example even more specifically polyester or polyolefin or even polyvinyl chloride.

[0058] Therefore, in summary, the yarn 1 thus realized can be subjected to length variations at least between 10% and 60%, possibly between 10% and 60%, which correspond preferably to permanent recesses of the yam 1 after heating the yarn, for example in an oven, at temperatures preferably between 90°C and 120°C.

[0059] Structurally, within the yam 1 , the second filament 3 is wound around the first filament 2 or develops parallel to it.

[0060] In an embodiment with a heat-shrinkable second filament 3 and a silicone first filament 2, it is advantageously possible to deform the yam 1 , particularly the second filament 3, by subjecting it to a heat source without the heat itself impacting the integrity of the first filament 2.

[0061] Similarly, in a further embodiment with a water-shrinkable second filament 3 and a first filament 2 of any suitable material, it is advantageously possible to deform the yam 1 , particularly the second filament 3, by subjecting it to a water dosage without the dosage itself impacting the integrity of the first filament 2.

[0062] Furthermore, advantageously, the first filament 2 is preferably pre-tensioned in the absence of said heat source and / or water dosage.

[0063] Therefore, this means that the first filament 2 defines a first elastic linear expansion. Even more specifically, within the fabric 100, advantageously, the first filament 2 stably maintains the first elastic linear expansion at least until the second filament 3 is subjected to said heat source and / or water dosage, preferably at a controlled temperature.

[0064] The first elastic linear expansion also corresponds to the length variation of the first filament 2, that is, the variation in distance between the ends.

[0065] However, the first elastic linear expansion is not necessarily a maximum expansion. It can correspond to a partial expansion of the first filament 2 or, alternatively, even to the maximum elastic linear expansion that can be imposed on the first filament 2 in the absence of the heat source and / or a water dosage.

[0066] Additionally, the first expansion is given by an extension of the first filament 2 and is therefore positive. In addition, the first expansion is elastic, not plastic.

[0067] Advantageously, since the second filament 3 is wound around the first filament, at least part of the first elastic linear expansion can be stably maintained by the second filament 3. In fact, as the first filament 2 is linearly expanded, it defines, as obvious, sectional expansions, particularly shrinkages. The winding of the second filament 3 can prevent the sections of the first filament 2, in the absence of the heat source and / or water dosage, at least partly and locally from returning to the starting shape and therefore maintaining at least part of the first elastic linear expansion of the first filament 2.

[0068] Preferably, the second filament 3 is wound around the first filament 2 with a predetermined pitch, for example in Z or S. The pitch is defined by the segment of the first filament 2 run by a complete turn of the second filament 3 around the first filament 2 relative to the total length of the first filament 2.

[0069] The pitch can be varied to increase or decrease the stiffness of the yarn 1 given by the coupling of the filaments 2, 3.

[0070] In addition to the above, it may be advantageous to configure the yam 1 so that when the yarn 1 is subjected to the heat source and / or a water dosage sufficient to shrink the second filament 3, the total deformation of the yam 1 brings the first filament 2 to cancel the first elastic linear expansion.

[0071] In this regard, the second filament 3 can be configured so that the maximum plastic linear expansion imposes on the first filament 2 a length variation equal to the first elastic linear expansion when the yam 1 is subjected to the heat source and / or a water dosage. The activation of the yam 1 expansion can be achieved in an oven or with other tools such as, for example, a steam iron.

[0072] Or, in the case of water-shrinkable yam, the activation of the yam 1 expansion can be achieved by washing the yam 1 or, more generally, the fabric 100.

[0073] Naturally, being the yam 1 placed within the membrane 10, it can influence the overall behaviour of the fabric 100, as better specified below.

[0074] In any case, such a fabric 100 can be advantageously used in making chairs.

[0075] By the term chair is preferably meant a seat. However, the chair could be any device that allows a user to sit and can, depending on the configuration, also be constituted, therefore, by devices other than a seat such as an armchair or a small sofa.

[0076] For example, the chair can also be a vehicle seat, such as a car, or for other means such as trains or aircraft.

[0077] Additionally, the chair is not bound to a specific use and design but can be adapted, depending on convenience, to various uses such as home use, office, or other environments other than those mentioned, such as restaurants, hotels, conference rooms, study rooms, or others.

[0078] The chair generally defines at least one backrest and a seat. Moreover, the chair comprises a frame 101.

[0079] The frame 101 defines a supporting structure on which the fabric 100 can be stably bound. Preferably, the fabric 100 is integrally bound to the frame 101 at its ends.

[0080] Naturally, considering the uses for which it is intended, the fabric 100 may include additional features.

[0081] For example, as shown in Figs. 4-5, the fabric 100 may also include at least one padding layer 11. The padding layer 11 is preferably positioned at one face of the membrane 10, possibly between two membranes 10. Moreover, if the yarn 1 is not woven but English-hooked, or loop-hooked, or tubular with drop-needle stitch weave, at one face of the membrane 10, the padding layer 11 is preferably positioned at the face opposite the face including the yam 1 .

[0082] Generally, in a preferred embodiment, the yarn 1 is woven within the padding 11 . In this regard, it could also be English-hooked or wrapped around a bobbin to one or more filaments of an internal face of the membrane 10, that is, to a face adjacent to the padding so that the yarn 1 is internal to it, as shown, for example, in Figs. 7a-

[0083] 7 c. The padding layer 11 can thus be configured to thin or increase its thickness in relation to the tension applied locally to the yarn 1 and, therefore, to the membrane 10.

[0084] As shown in Figs. 7a-7c, in fact, depending on the shrinkage or stretching applied to the yarn 1 and, therefore, to the membrane 10, it is possible to modify the thickness and stiffness of the padding 11 with consequent variation of the local properties of the fabric 100.

[0085] Naturally, since the yam 1 , and therefore globally the fabric 100, defines a length, the padding layer 11 can advantageously be oversized compared to the yam 1 , and thus also to the fabric 100 and / or the membrane 10, so as not to undergo thickness reductions due to the length variations of the yam 1 .

[0086] The operation of the fabric 100 previously described in structural terms is as follows. Substantially, the behaviour of the fabric 100 is influenced by the yam 1 .

[0087] As described, the tension and expansion of the yam 1 can be controlled simply by subjecting the yam 1 itself, particularly the second filament 3, to a heat source and / or a water dosage sufficient to shrink the second filament 3. Naturally, the degree of expansion depends on the transmitted heat and / or the transmission time of the same heat as well as the chemical composition of the yam 1 itself. Alternatively, the degree of expansion depends on the water dosage and / or the wetting time of the yam 1 as well as the chemical composition of the yam 1 itself or, again, on the temperature of the water dosage.

[0088] Therefore, the second plastic linear expansion impressed on the second filament 3 may not be maximum, for example, if the heat or water is applied for a short time.

[0089] In any case, the first filament 2 is kept under tension at least until the second yam 3 is deformed and prevents the yam 1 from starting to deform undesirably. Thus, once the second filament 3 is retracted, the yarn 1 forms wrinkles that make the yam 1 itself and also the membrane 10 deformed undesirably. However, by removing the pre-tensioning state of the first filament 2 and thus allowing the second filament 2 to shorten to recover the elastic deformation, it is possible to bring the yam 1 to a tension state so that the wrinkles are removed.

[0090] The invention also includes a new method for making the controllable tension fabric 100.

[0091] In particular, the method comprises at least one winding or parallel arrangement phase. In the winding or parallel arrangement phase, the second filament 3 is essentially wound around or arranged parallel to the first filament 2 to make the yam 1 , as previously described.

[0092] Furthermore, the method also includes a binding phase. In the binding phase, the yam 1 is substantially bound to the membrane 10.

[0093] In the binding phase, the yam 1 can, in detail, be woven into the membrane 10 or English-hooked on a face of the membrane 10, preferably facing the inside of the fabric 100, or loop wrapped around one or more filaments of the membrane 10. Moreover, the yam 1 could continue to be woven peripherally around an English- hooked slider, or loop wrapped, or defining a tubular element with drop-needle stitch weave.

[0094] Furthermore, in the binding phase, it could also be provided to integrally bind reciprocally ends of the yam 1 at respective opposite ends of the membrane 10.

[0095] In any case, advantageously, the method includes a pre-tensioning phase preceding the winding or parallel arrangement phase. In the pre-tensioning phase, the first filament 2 is tensioned to define the first elastic linear expansion.

[0096] Moreover, the pre-tensioning, and thus the first elastic linear expansion, is stably maintained at least until the yarn 1 is bound to the membrane 10, and the second filament 3 is subjected to the heat source and / or water dosage.

[0097] Then, the method includes a removal phase. In the removal phase, the pretensioning state is removed to cancel the first elastic linear expansion.

[0098] Performing the pre-tensioning phase before winding and maintaining the pretensioning implies that, advantageously, once the second filament 3 is retracted, the first filament 2 can elastically recover to regain the original tension of the entire yarn 1 and remove the wrinkles formed by the shrinkage of the second filament 3 on the pre-tensioned and thus extended first filament 2.

[0099] Pre-tensioning can be achieved through the use of special machinery that helps to perform the subsequent winding on the tensioned first filament 3 without difficulty. The machinery capable of performing such operations, as known, generally includes a feeder that feeds the first filament 2, keeping it tense thanks to end conveying means, while at the same time, a winder feeds the second filament 3 around the first filament 2.

[0100] Generally, the feeder and the conveying means are coordinated to avoid generating undesirable tensions on the first filament 2.

[0101] However, it is possible to reduce feeder feed speed at will to generate tensions on the first filament 2 during feeding, resulting in the first elastic linear expansion.

[0102] Alternatively, without using such machinery, it is possible to resort to particular formation processes.

[0103] Specifically, therefore, the manufacturing method can include additional phases. Specifically, the method can include a covering phase and a dissolving phase.

[0104] In the covering phase, at least the first filament 2 is covered, while it is tensioned, with a layer 4. Optionally, both the first filament 2 and the second filament 3 can be covered. The layer 4 is advantageously configured to maintain the first elastic linear expansion. Therefore, the layer 4 prevents the first filament 2 from experiencing an elastic return before winding and behaves essentially like a sort of corset for the first filament 2.

[0105] Layer 4 can be made in various ways.

[0106] In the preferred embodiment, layer 4 includes a tape containing polymeric material. Thus, for example, the covering phase can be achieved simply by winding the first filament 2, possibly also the second filament 3, tensioned by the tape.

[0107] Even more specifically, the polymeric material is of the thermoplastic type, such as PMMA or PVA.

[0108] In the dissolving phase, the layer 4 is essentially dissolved and, therefore, is no longer part of the yam 1 . Advantageously, dissolution occurs after the binding of yam 1 and membrane 10 and before subjecting the second filament 3 to the heat source and involves the activation of the second filament 3 if it is water-shrinkable. Thus, the dissolution of layer 4 releases the second filament 2, which can recover from the pre-tensioning state and shorten to regain its original length, preferably compensating for the reduction given by the second filament 3, and restore an initial usable length of the yam 1 .

[0109] The fabric 100 according to the invention achieves significant advantages.

[0110] In fact, the controllable tension fabric 100, and the related method of making it, once used on a seat or backrest of a chair, allows complete control over the shape and tension imposed on it, that is, the level of comfort and responsiveness of the chair.

[0111] In addition, the controllable tension fabric 100, and the related method of making it, can support a user comfortably and effectively when used on a chair.

[0112] As for the use of fabric 100 on a chair equipped with frame 101 , it is important to note that, as long as the second filament 3 is not subjected to a heat source and / or a water dosage, yam 1 is in a maximum extension state that allows easy assembly of fabric 100 onto frame 101 itself.

[0113] With particular reference to Fig. 7a, when yarn 1 is subjected to a heat source and / or a water dosage, the second filament 3 shrinks, causing a wrinkling of the first filament 2 and, thus, of the entire yam 1 .

[0114] As shown in Fig. 7b, however, when the pre-tensioning state is removed, and the first filament 2 undergoes elastic return, fabric 100 is tensioned since yam 1 , shortening, brings the fabric 100 surface under tension and allows the removal of wrinkles.

[0115] Naturally, as shown in Fig. 7c, fabric 100 can still be elastically deformed, particularly at least within the limits defined by the first filament 2 with particular reference to the maximum elastic deformation achievable, and / or by the second filament 3, which can also define a maximum elastic deformation. In this sense, the second filament 3 could also act as a block for the elastic expansion of the first filament 2, and thus the entire yam 1 , present in fabric 100, also defining the maximum deformation to which a seat or backrest of a chair can be subjected.

[0116] In conclusion, the controllable tension fabric 100, and the related method of making it, allow for an aesthetically pleasing appearance and have controllable lines as there are no wrinkles or other undesirable release areas. The invention is susceptible to variations within the scope of the inventive concept defined by the claims.

[0117] Within this scope, all details are replaceable by equivalent elements, and the materials, shapes, and dimensions can be any.

Claims

C LA I M S1. The controlled tension fabric (100) comprising:- a membrane (10) including knitted fabric or woven fabric with weft and warp, and- at least one yam (1 ) bound to said membrane (10) and including:- a first filament (2) including elastic material,- a second filament (3) wound around said first filament (2) with a predetermined pitch or that develops parallel to said first filament (2) and including heat-shrinkable and / or water-shrinkable material defining, when subjected respectively to a heat source or a water dosage sufficient to shrink said second filament (3), a second maximum plastic linear expansion, or and characterized by the fact that- said first filament (2) is pre-tensioned and defines a first elastic linear expansion stably maintained at least until said second filament (3) is subjected to said heat source and / or said water dosage.

2. A fabric (100) according to claim 1 , wherein said yam (1 ) is woven into said membrane (10) or English-hooked on a face of said membrane (10) or loop wrapped to one or more filaments of said membrane (10) or tubular with drop-needle stitch weave at a face of said membrane (10).

3. A fabric (100) according to any preceding claim, wherein said yam (1 ) is integrally bound to opposite ends of said membrane (10) at respective opposite ends.

4. A fabric (100) according to any preceding claim, wherein said first filament (2) is made of said elastic material.

5. A fabric (100) according to any preceding claim, wherein said elastic material is silicone.

6. A fabric (100) according to any preceding claim, wherein said second filament (3) is made of said heat-shrinkable and / or water-shrinkable material.

7. A fabric (100) according to any preceding claim, wherein said first elastic linear expansion is equal to the maximum elastic linear expansion that can be imposed on said first filament (2) in the absence of said heat source and / or said water dosage.

8. A fabric (100) according to any preceding claim, wherein said second filament (3) is configured so that said second maximum plastic expansion imposes on said first filament (2) a length variation equal to the first elastic linear expansion when said yam (1 ) is subjected to said heat source and / or said water dosage.

9. The chair defining a backrest and a seat and comprising at least one frame (101 ) and a fabric (100) according to any preceding claim.

10. The method for making a controllable tension fabric (100) and comprising:- winding or arranging parallel a second filament (3) including heat-shrinkable and / or water-shrinkable material defining, when subjected to a heat source and / or a water dosage sufficient to shrink said second filament (3), a second maximum plastic linear expansion around or parallel to a first filament (2) including elastic material with a predetermined pitch so as to create a yarn (1 ),- binding said yarn (1 ) to a membrane (10) including knitted fabric or woven fabric with weft and warp and characterized by the fact that it further comprises- pre-tensioning said first filament (2) to define a first elastic linear expansion before said winding and stably maintaining said first elastic linear expansion at least until said yam (1 ) is bound to said membrane (10) and said second filament (3) issubjected to said heat source and / or said water dosage,- removing said pre-tensioning to cancel said first elastic linear expansion.

11. The method according to claim 10, wherein in said binding phase said yam (1 ) is woven into said membrane (10) or English-hooked on a face of said membrane (10) or loop-hooked around one or more filaments of said membrane (10).

12. A method according to any of claims 11 -12, further comprising:- covering at least said first filament (2) with a layer (4) configured to maintain said first elastic linear expansion while said first filament (2) is tensioned, and- dissolving said layer (4) after binding said yam (1 ) to said membrane (10) and before subjecting said second filament (3) to said heat source and / or said water dosage.

13. The method according to the preceding claim, wherein said layer (4) comprises a tape including polymeric material, and said covering phase is carried out by wrapping the first filament (2) tensioned with said tape.

14. The method according to the preceding claim, wherein said polymeric material is of the thermoplastic type.

15. A method according to any of claims 10-14, wherein said water dosage is at a temperature of approximately 30 °C.

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