Patent Application
20200378038
The present invention relates to a method for making elasticized yarns based on natural fibres, among which cotton, in particular such stiff natural fibres as linen, ramié, hemp, jute, bamboo. The invention also relates to fabrics products with the above elasticized yarns.
Since some decades, elasticized fabrics made from elastic thread yarns of many kinds are used. The advantage of these fabrics is a high deformability of the items made therefrom. In particular, garments are made that do not hinder the movements of the limbs of the user, or conform themselves to these movements, thus generating a comfort sensation. This is particularly useful in underwear clothing or in sport and gym clothes, for particular use, but is also appreciated in everyday life situations such as sitting in a car, walking and whenever the joints are bent. Moreover, elasticized fabrics are used to make bandages, dressings and garments for treating wounds, sprains, inguinal hernia and the like. Besides, elasticized fabrics are advantageous for making general-purpose gloves, as well as covers for sofas, armchairs and chairs, since rounded covers can be manufactured therefrom.
The features of an elasticized fabric depend on the high elasticity of the elasticized yarn used to make them. Methods are known to obtain elasticized yarns in which an inextensible yarn is arranged about a core comprising an elastic fibre.
For instance, documents WO 2008/130563 A1 and WO 2012/062480 A2 describe ring spun elastic composite yarns, in which an elastic core fibre is surrounded by a fibrous sheath consisting of a mass of synthetic or natural spun staple fibres, for instance cotton fibres. An inelastic filament, for example a polyester or polyamide or polyolefin filament, is arranged near the elastic core fibre, in order to improve the elastic recovery properties of the elasticized yarn obtained therefrom. This way, permanent or long-lasting deformation can be prevented in such article portions as tight elbow or knee garment portions, in particular, when the joints have been flexed and then extended.
In order to obtain a favourable trade-off between elastic elongation and low shrinkage properties, according to WO 2008/130563 A1 the yarn is spun maintaining predetermined stretch ratios of the elastic fibre and of the inelastic filament. On the contrary, according to WO 2012/062480 A2, the elastic fibre and the inelastic filament are connected to each other in a plurality of points, and the inelastic filament is made of polyester, in particular in a polyester copolymer.
Other elasticized yarns are obtained using coil-forming machines. In this case, a substantially inextensible covering yarn is arranged as a helix about the elastic core. If such an elasticized yarn is stretched, the coils of the helix moves away from one another. When the yarn is released, the coils and the helix tends to return to their previous configuration. This accounts for the elastic recovery of the yarn and of any fabric thereof.
Also these articles, manufactured from helicoidally wrapped yarns, suffer from the drawback that, when highly deformed, their elastic recovery is delayed and/or they are permanently deformed. This is the case, in particular, if the covering yarn is stiff, for example a linen, ramié, hemp, jute, bamboo yarn or the like. In this case, high friction occurs between the coils of the rigid covering yarn and the core elastic fibre.
In particular, WO2012/056436 discloses elasticized yarns in which the covering yarn comprises such a stiff material as linen, hemp or ramié, and the number of coils per length unit of the elasticized yarn is set within a predetermined range. In particular, the number of coils per length unit of the elasticized yarn is larger than a minimum value that depends on the linear mass density of the covering yarn. This prevent the so-called “orange skin” defect, i.e. small masses of material randomly arranged on the fabric surface.
US 2004/128973 A1 discloses a composite twist yarn produced by arranging a twisted spun yarn and at least one filament parallel to each other, and twisting them together in a direction reverse to the twisted direction of the spun yarn over an untwisted point of the spun yarn so that the twisted direction of the composite twist yarn is substantially the same as the spun yarn, until the number of twists of the composite twist yarn is larger than that of the spun yarn.
JP2008297646 (A) discloses a composite core spun yarn, with a core made of a piled yarn including at least two filament yarns and a sheath made of staple fibres. Preferably, the composite spun yarn is produced by doubling a piled yarn of at least two filament yarns with staple fibres and twisting them in a direction reverse to the twisting direction of the piled yarn.
Therefore, the present invention aims at providing a manufacture method for an elastic core yarn, in which a covering yarn made of a natural material, in particular such a stiff material as linen, ramié, hemp, jute or bamboo, is wound about a core in which, besides the elastic fibre an accompanying filament is introduced to modify the elastic properties of the elastic fibre, so that the elasticized fabrics made of this elastic core yarn, returns to an undeformed configuration without any significant delay or permanent deformation, after being stretched and then released.
It is a particular feature of the invention to provide such a manufacture method by which an elastic core yarn can be produced such that the accompanying filament does not protrude out of the helix through the coil of the covering yarn, when the elastic core yarn is stretched and then released, so as to preserve the elastic properties and the aspect of the fabrics made therefrom.
It is also particular feature of the invention to provide such a manufacture method by which an elastic core yarn can be produced from which fabrics can be made with no “orange skin” defect.
It is also a feature of the invention to provide an elasticized yarn and an elasticized fabric having the above indicated features.
These and other objects are achieved by a method as defined by attached claim 1. Exemplary specific embodiments of the invention are defined by the dependent claims. Such objects are also achieved by an elasticized yarn and a fabric as defined by claims 17 and 18, respectively.
In the description, the expression “metric count” is used to mean a unit of yarn linear density, which is the length, expressed in kilometres, of 1 Kg of yarn. Accordingly, the metric count is expressed in Km/Kg. An alternative yarn count measurement unit is tex, which is, inversely, the mass expressed in grams of 1 Km of yarn, or a submultiple of it, such as dtex (decitex). In particular, metric count Nm of the inextensible yarn is between 2 and 80.
In the description, the expression “number of torsions” or “of windings per metre” means the number of torsions that can be directly counted as the number of inverse torsions that is required for completely removing the windings on a predetermined length of a twisted yarn that has been arranged between two fixed points at a predetermined initial tensile stretch. In particular, the predetermined length and the initial tensile stretch are selected according to ISO 2061.
More in detail, a method for making an elastic core yarn include the steps of:
In the description, the expression “natural fibre” means a fibre obtained from such a material as cotton, wool, silk and so on, in particular the covering yarn can be made of a stiff natural material such as linen; hemp; ramié; bamboo; jute; a combination thereof.
This way, the core remains untwisted while the covering yarn is being wrapped about it. This is advantageous, since a sliding is admitted relatively between the core and the covering yarn wrapping the core, in order to avoid the defects of the fabrics made with the elastic core yarn, namely, the “orange skin” and permanent or long-lasting deformation defects of the fabric.
With respect to other yarn made according to the prior art, namely US 2004/128973 A1 or JP2008297646 (A), in which the core is twisted along with other yarn(s), and therefore no relative sliding is possible, with the invention such sliding is admitted, avoiding the above defects.
Before wrapping, the covering yarn as provided can initially have a “Z” twist direction, as it is normally available on the market. Then, the step of wrapping the core with the covering yarn is carried out by helically winding the covering yarn about the core, for instance, by a method using a hollow spindle. The twist direction of the helix is selected opposite to the initial twist direction of the covering yarn. In this case, during the step of wrapping, initially, the number of “Z” twists per metre decreases down to crossing the zero. Subsequently, the covering yarn takes “S” twists, i.e. it becomes twisted in a twist direction that is opposite to the initial twist direction. Of course, the same applies, mutatis mutandis, to the case where the covering yarn is initially “S”-twisted and finally becomes “Z”-twisted.
This way, during the wrapping step, the absolute number of twists per metre, i.e. regardless the twist direction, initially decreases down to an untwisted configuration, and then increases again (in the opposite direction). If, on the contrary, the step of wrapping were carried out in the same twist direction as the initial twist direction of the covering yarn as provided, the absolute number of twists would always increase during the whole wrapping step, and it could become too high, i.e. it could cause excessive internal stress in the covering yarn, which would become fragile, or even cause the covering yarn to break during the step of wrapping itself.
For example, if
On the contrary, if the wrapping step were carried out in the direction opposite to the decreasing direction of the invention, i.e. if the helically wrapping step were carried out by increasing the “Z” twists of the covering yarn, after forming only 300 coils of covering yarn about the core, which is far lower than the target value of 1100, the covering yarn would achieve the limit value of 400+300=700 twist per meter. In other words, the covering yarn would achieve this limit value, but the core would not be coated enough to provide such advantages as a quick and substantially complete elastic return and an absence of the “orange skin” defect.
Therefore, the process according to the invention makes it possible to form a larger number of coils per length unit of the elastic core yarn, without reaching or excessively approaching a limit value beyond which the covering yarn can become fragile or even break due to the excessive absolute number of twists per metre. This is particularly important for such stiff materials as linen, hemp, or the like, since this limit value is lower than in the case of other conventional natural fibres.
The process according to the invention allows therefore to reach a large number of coils per length unit of the elastic core yarn product. The coils have therefore a very tight arrangement, which obliges the coils to return to their initial configuration and relative position once the elastic core yarn has been stretched and then released. This is possible even if the elastic core yarn comprises such a stiff material as linen, hemp, jute, bamboo or the like. This way, the continuous yarn of the core does not protrude out of the covering yarn through the coils thereof, which would remarkably deteriorate the aspect and the mechanical features of any fabric made with the elastic core yarn.
Therefore, the invention makes it possible to successfully product elastic core yarns in which the elastic core comprises a continuous yarn in addition to the elastic yarn, even if the covering yarn comprises such a stiff material as linen, hemp, ramié, jute, bamboo, or the like.
The feature of having an untwisted core comprising a continuous yarn remarkably reduces the friction between the coils of the stiff covering yarn and the elastic fibre. This way, the elastic recovery of the wrapping coils is improved, and therefore the problem of the permanent or long-lasting deformation of conventionally manufactured fabric portions made of linen and other rigid materials is solved. Therefore, when a fabric made with the elastic core yarn of the invention is stretched and then released, which is the case, for instance, for tight elbow or knee garment portions, when these joints are flexed and then extended, no defects occur any longer.
The closed wrapping space according to the invention, i.e. the wrapping space enclosed in a container, provides a solution to the following problem. As described above, in the method according to the invention, the covering yarn loses the initial twists, and then is twisted in an opposite direction. Therefore, an intermediate zero-twist condition is crossed in which the natural discontinuous fibres of the elastic core yarn are untwisted, i.e. substantially parallel to one another. This is diagrammatically shown in
In a possible embodiment, the step of providing the core includes steps of mounting a first spool of the elastic fibre and a second spool of the continuous yarn on a hollow spindle machine, while the step of providing the covering yarn includes a step of mounting a third spool of the covering yarn coaxially to a hollow cylindrical body of the hollow spindle machine. The step of conveying the core comprises a step of stretching and unwinding the same, at a predetermined unwinding speed that is the same as the conveying speed of the elastic fibre and of the continuous yarn from the first spool and from the second spool, respectively, by means of a friction wheel to which the elastic fibre and the continuous yarn, before conveying them to a central recess of a rotating hollow cylindrical body. The step of conveying the core can also comprise a step of stretching the core now wrapped with the covering yarn at the outlet of an orifice, and a step of collecting the elastic core yarn on a fourth spool or collection bobbin, at such a collecting speed to cause a predetermined stretch ratio of the elastic fibre.
The above described method can be actuated by a well-known hollow-spindle machine to, such as a Hamel type hollow-spindle machine providing a protected wrapping space enclosed in a container.
In particular, the predetermined minimum value T0, for any value of the linear mass density Nm indicated in a respective line of the table 1 is value T0 written in the same line of table 1; for values lying between two adjacent linear mass density Nm values given in respective contiguous lines of table 1, the minimum value T0 is obtained by linearly interpolating the values T0 written in the same contiguous lines of table 1. With this number of coils can be obtained a coil arrangement tight enough to allow a substantially immediate and complete elastic recovery of the elastic core yarn. This way, the accompanying filament of the core is prevented from protruding out of the helix through the coil of the covering yarn, when the elastic core yarn is stretched and then released. This would deteriorate the elastic properties and the aspect of the fabric manufactured from the elastic core yarn, when in use.
In particular, the coil number T per length unit of the elastic core yarn is lower than a maximum value T1; for each linear mass density value Nm indicated in a respective line of table 2, this minimum value is the value T1 written in the same line of table 2; for values lying between two adjacent linear mass density Nm values given in respective contiguous lines of table 2, the maximum value T1 can be obtained by linearly interpolating the values T1 written in the same contiguous lines of table 2. This makes it possible to obtain a not too stiff elastic core yarn, which would be the case if the coils were arranged too tight beside one another.
Advantageously, the coil number T per length unit of the elastic core yarn, for any value of the linear mass density Nm, is provided by the equations:
T
1=
K
1
N
m
0.42, if Nm<20 Km/Kg;
T
1=
K
2
N
m
0.42, if Nm≥20 Km/Kg,
where K1 is a number set between 82 and 348 and K2 is a number set between 118 and 308. Preferably, K1 is a number set between 120 and 240. More preferably, K2 is a number set between 140 and 220.
Most preferably, the coil number T per length unit of the elastic core yarn is set between −10% and +10% of a reference value T2; for each linear mass density value Nm indicated in a respective line of table 3,
this reference value is the T2 value written in the same line of table 3; for values lying between two adjacent linear mass density Nm values given in respective contiguous lines of table 3, the reference value T2 can be obtained by linearly interpolating the values T2 written in the same contiguous lines of table 3.
Advantageously, the steps of conveying the core and the covering yarn comprise:
The elastic fibre can be made of a synthetic elastomeric material having a linear mass density set between 22 dtex and 940 dtex. In particular, the linear mass density is selected among 22, 44, 78, 100, 156, 310, 470, 620, 940 dtex. In particular, the elastomeric material is selected from the group comprised of a polyurethane and a polyether-polyurea copolymer. For example, the elastic fibre can comprise at least the 85% of segmented polyurethane. In particular, the synthetic elastomeric fibre can be a fibre commercially known as Lycra® or Elastan®.
Preferably, the step of conveying the elastic fibre is carried out by stretching the elastic fibre according to a stretch ratio between 2 and 7, i.e. up to 2 to 7 times its length n a natural (non-stretched) state. In the case of a Lycra® 156 dtex elastic fibre, the stretch ratio is about 3.4.
As an alternative, the elastic fibre can be a natural rubber fibre having a linear mass density set between 22 dtex and 1300 dtex.
Preferably, the continuous yarn is made of a material selected from the group comprised of:
The continuous yarn, in particular a T400 yarn, can have a linear mass density set between 22 dtex and 660 dtex. In particular, the linear mass density is selected among 22, 44, 83, 167, 330, 660 dtex.
The continuous yarn can have a parallel arrangement along the elastic fibre, i.e. it can be arranged parallel to the elastic fibre.
As an alternative, the continuous yarn can have an interconnected arrangement along the elastic fibre, i.e. it can have connection points to the elastic fibre at predetermined distances from one another.
As an alternative, the continuous yarn can have a wrapped arrangement, where the continuous yarn forms a covering about the elastic fibre.
It falls within the scope of the invention also an elasticized yarn obtained in the way above described, as well as a elasticized fabric containing at least one part of elasticized yarn above described obtained in the way above described.
The invention will be now shown with the following description of exemplary embodiments and examples thereof, exemplifying but not limitative, with reference to the attached drawings, in which:
With reference to
In order to obtain elastic core yarn 50, a step is performed of covering, i.e. helically wrapping covering yarn 40 about core 30. To this purpose, steps are carried out of conveying core 30 and covering yarn 40, at respective speeds vA, vC. Core 30 is conveyed towards a collecting bobbin 51 through a wrapping space 35, and covering yarn 40 is conveyed in wrapping space 35, where it reaches core 30 laterally, i.e. tangentially, according to a predetermined angle α between the direction of core 30 and the direction of covering yarn 40, in order to form a substantially helical covering about core 30.
As shown in
In an exemplary embodiment, before reaching wrapping space 35, core 30 passes through a central recess 63 of a first cylindrical body 61 turning at a predetermined high speed about its own axis 63′. In other words, core 30 follows a substantially linear path. On the contrary, covering yarn 40 is conveyed along an outer surface 62 of first cylindrical body 61, preferably along a guide arranged thereon. Preferably, first cylindrical body 61 is integrally and coaxially housed in a second hollow cylindrical body 64, cylindrical bodies 61, 64 forming a conveying unit 60. Bobbin 41 of covering yarn 40 is fixed inside second cylindrical body 64, therefore covering yarn 40 is conveyed through a gap 65 between bobbin 41 and the outer surface of first cylindrical body 61.
In this exemplary embodiment, wrapping space 35 is defined between the outlet end 69 of first cylindrical body 61, at which core 30 enters into wrapping space 35, and an orifice 66, preferably arranged on axis 63′, through which elastic core yarn 50 leaves wrapping space 35 and is drawn to collecting bobbin 51. Container or wall 67 enclosing wrapping space 35 is preferably axisymmetric and converges from the inner surface of second hollow cylindrical body 64 to orifice 66. [0052] The direction of the rotation of conveying unit 60 is selected so that the twist direction of the helix is opposite to the initial twist direction of covering yarn 40 and therefore covering yarn 40 becomes twisted with a final twist direction, e.g. “S”, opposite to the initial twist direction, e.g. “Z”, in the step of helically wrapping core 30.
Conveying speeds of core 30 and covering yarn 40, as well as the rotation speed of conveying unit 60 are selected so that a number of coils T of covering wrapper 40 is wound on each length unit of elastic core yarn 50 as manufactured, the number T being larger than a predetermined minimum value T0 that depends on the linear mass density Nm of covering yarn 40.
Wrapping space 35 is enclosed in a container 67, in order to avoid friction between free air, on the one hand, and the conveyed materials, and elastic core yarn 50 being formed, on the other hand. As discussed above, covering yarn 40 would lose its consistence, and could even break, while turning from initial twist direction to opposite final twist direction.
In particular, the material of covering yarn 40 is a stiff material, for example one among linen, hemp, ramié, bamboo, jute, or a combination thereof.
The diagram of
Advantageously, the coil number T per length unit of elastic core yarn 50, for any value of the linear mass density Nm of covering yarn 40, is provided by the equations:
T
1=
K
1
N
m
0.42, if Nm<20 Km/Kg;
T
1=
K
2
N
m
0.42, if Nm≥20 Km/Kg,
where K1 and K2 can range between a minimum value, respectively 82 and 118, and a maximum value, respectively 308 and 348. Curves 83 and corresponds to the couples of values (K1,K2)=(82,118) and (K1,K2)=(308,348), respectively. Preferably, K1 is set between 120 and 240, and K2 is set between 140 and 220.
The diagram of
In some exemplary embodiments, elastic fibre 10 of core 30 is a natural rubber fibre having linear mass density Nm set between 22 dtex and 1300 dtex.
In other exemplary embodiments, elastic fibre 10 of core 30 is a fibre made of a synthetic elastomeric material having linear mass density Nm set between 22 dtex and 940 dtex. In particular, linear mass density Nm can be selected among 22, 44, 78, 100, 156, 310, 470, 620 and 940 dtex. The elastomeric synthetic material is preferably a polyurethane or a polyether-polyurea copolymer.
Continuous yarn 20 can be a polyamide yarn, or a polyester such as polyethylene terephthalate, polybutylene terephthalate, and polytrimethylene terephthalate. In this case, continuous yarn 20 can be made of a single polyester or of a combination of these polyesters, in particular a combination of polyethylene terephthalate and polytrimethylene terephthalate commercially known as “T400”.
Such a combination of polyethylene terephthalate and polytrimethylene terephthalate used to make continuous yarn 20 has preferably a linear mass density Nm set between 22 dtex and 660 dtex, in particular, linear mass density Nm is selected among 22, 44, 83, 167, 330, 660 dtex
As an alternative, continuous yarn 20 can be an ultra-high molecular weight polyethylene yarn. Finally, continuous yarn 20 can comprise any combination of the above-mentioned materials. Each of these yarns can be smooth or texturized.
Moreover, even if the
It falls within the scope of the invention also an elastic core yarn 50 obtained through the method described above, as well as an elasticized fabric, not shown, made at least in part at least of elastic core yarn 50 obtained through the method described above. More in detail, elastic core yarn 50 can be used for either warp or weft yarn.
The foregoing description of embodiments and of examples of the invention, and of the way of using the apparatus, will so fully reveal the invention according to the conceptual point of view, so that others, by applying current knowledge, will be able to modify and/or adapt for various applications such embodiment without further research and without parting from the invention, and, then it is therefore to be understood that such adaptations and modifications will have to be considered as equivalent to the specific embodiment. The means and the materials to realise the different functions described herein could have a different nature without, for this reason, departing from the field of the invention. It is to be understood that the phraseology or terminology employed herein is for the purpose of description and, therefore, not of limitation.
| Number | Date | Country | Kind |
|---|---|---|---|
| 102018000002808 | Feb 2018 | IT | national |
| Filing Document | Filing Date | Country | Kind |
|---|---|---|---|
| PCT/IB2019/051343 | 2/19/2019 | WO | 00 |
