A method is disclosed for making an elastic core yarn (50), wherein an elastic core (30) comprising a fibre (10) of natural rubber with metric count 200-1000 dtex is covered by a cotton-based covering yarn (40), comprises a step of conveying the elastic core (30) and the covering yarn (40) in such a way that the covering yarn (40) laterally attains a proximity of the elastic core (30) in a wrapping space (35); a step of helically wrapping the covering yarn (40) about the elastic core (30) in a wrapping space (35), wherein the conveying speed, and therefore the winding/unwinding speed, is selected such that the elastic core (30) is stretched up to a stretching ratio of at least 2, and such that, during this wrapping step, the covering yarn (40) becomes twisted with a final twist direction opposite to its initial twist direction, and forms a number T of coils per length unit of the elastic fibre (10) set between a predetermined minimum value T.sub.0 and a predetermined maximum value T.sub.1 both depending on the linear mass density Nm of covering yarn (40), the wrapping space (35) being enclosed by a container (67). An elasticised yarn obtained this way, and a fabric, in particular a denim type fabric, manufactured from this yarn.

The present invention relates to a composite yarn, a preparation method thereof and an elastic fabric, wherein the composite yarn comprises a core yarn and an outer wrapping yarn, wherein the core yarn further comprising at least one piece of elastic filament, and wherein the outer wrapping yarn is made of short fiber, wherein the outer wrapping yarn is spirally wrapped on the core yarn, wherein drafting ratio of the core yarn is 1-1.5 times.

A method is provided for manufacturing an elastic core yarn in which a core comprises an elastic fiber and a continuous yarn arranged along the elastic fiber, and in which a covering yarn of such a natural material as flax, hemp, ramié, bamboo, jute, is helically wrapped about the core. A step of helically wrapping the core with the covering yarn is carried out in such a way that a number T of coils covering yarn is formed about a length unit of the elastic fiber larger than a predetermined minimum value depending on the linear mass density Nm of covering yarn, and that the covering yarn becomes twisted with a final twist direction “S” or “Z” that is opposite to an initial twist direction “Z” or “S”, respectively. The step of wrapping is performed in a wrapping space enclosed within a container.

A machine for making covered elastic yarns, including a plurality of covering units, where each of the covering units has a spool for feeding an elastic yarn, a system for feeding a non-elastic yarn, a member for tensioning the covered elastic yarn and a bobbin for collecting the covered elastic yarn, where the system for feeding the non-elastic yarn has a microspindle which rotates about an axis and at least one bobbin for feeding the non-elastic yarn separated by and arranged upstream of the microspindle along the sliding path of the non-elastic yarn and arranged outside the rotation axis of the microspindle, the microspindle including a channel which is coaxial to the rotation axis for the passage of the elastic yarn.

A machine for making covered elastic yarns, including a plurality of covering units, where each of the covering units has a spool for feeding an elastic yarn, a system for feeding a non-elastic yarn, a member for tensioning the covered elastic yarn and a bobbin for collecting the covered elastic yarn, where the system for feeding the non-elastic yarn has a microspindle which rotates about an axis and at least one bobbin for feeding the non-elastic yarn separated by and arranged upstream of the microspindle along the sliding path of the non-elastic yarn and arranged outside the rotation axis of the microspindle, the microspindle including a channel which is coaxial to the rotation axis for the passage of the elastic yarn.

A method is provided for manufacturing an elastic core yarn (50) in which a core (30) comprises an elastic fibre (10) and a continuous yarn (20) arranged along elastic fibre (10), and in which a covering yarn (40) of such a natural material as flax, hemp, rami, bamboo, jute, is helically wrapped about the core (30). A step of helically wrapping the core (30) with the covering yarn (40) is carried out in such a way that a number T of coils covering yarn (40) is formed about a length unit of the elastic fibre (10) larger than a predetermined minimum value depending on the linear mass density Nm of covering yarn (40), and that the covering yarn (40) becomes twisted with a final twist direction S or Z that is opposite to an initial twist direction Z or S, respectively, the step of wrapping occurring in a wrapping space (35) enclosed within a container (67).

A method for making an elastic core yarn includes covering an elastic core having a fiber of natural rubber with metric count 200-1000 dtex with a cotton-based covering yarn. The elastic core and the covering yarn are conveyed such that the covering yarn laterally attains a proximity of the elastic core in a wrapping space. The covering yarn is helically wrapped about the elastic core. The conveying speed, and therefore the winding/unwinding speed, is selected such that the elastic core is stretched to a stretching ratio of at least two, and the covering yarn becomes twisted with a final twist direction opposite to its initial twist direction, and forms T coils per length unit of the elastic fiber set between a minimum value T0 and a maximum value T1. An elasticized yarn is thereby obtained, and a fabric, in particular a denim type fabric, is manufactured from this yarn.

An elastic thread yarn comprising linen and/or rami and/or hemp and an elastic thread, with a thread made of an elastomeric material, and a substantially inextensible yarn made of linen and/or rami and/or hemp helically wound about the elastomeric core at a predetermined number of windings per length unit of elasticized yarn, wherein, for each metric count Nm, the number of windings substantially inextensible yarn of the elasticized yarn, is set between two values indicated by two curves (12, 13) which can be expressed according to exponential laws, for example, with the same exponent, i.e. according to equations of the form T=K N.sup.0, 327 where K is 20 and 50, respectively. In particular, an intermediate curve 11 is such that, by choosing for a given metric count a number of windings proximate to curve 11, this best feature balance is obtained. In an exemplary embodiment, the core comprises a bare elastic thread, i.e. an elastic thread that is not coated by other fibers. In another exemplary embodiment, the core comprises an elastic thread coated with a natural fiber as cotton or viscose, or with a combination thereof. The elastic thread yarn according to the invention provides elasticized fabrics containing linen and/or on rami, which has, in particular, a better surface regularity than well-known elasticized fabrics comprising linen, and which is comparable with the regularity of the elasticized fabrics comprising natural fibers such as cotton, wool, etc. and synthetic fibers, and also allows using ramie and hemp yarns to make elastic thread yarns and fabrics, for example, for making cloth items.

Embodiments of the present invention are directed to a tri-core yarn including a core including an elastomeric filament, a first cover, and a second cover, and a fiber sheath covering the core, wherein the first cover and the second cover are each wrapped around the elastomeric filament.