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.

A method for starting a spindle of a cabling or two-for-one twisting machine, wherein a yarn reserve is formed on a take-up package, the machine has a workstation having a spindle pot for holding a first feed package and having a spindle rotor with a lateral outlet below the spindle pot, an outer yarn from one feed package is wound around an inner yarn from another feed package and the outer yarn is guided through the spindle shaft and its lateral outlet in a balloon orbiting the spindle pot to a yarn-guiding device above the spindle which merges the two yarn supplies, and a winding device in which the produced twist is wound onto the take-up package. A ratio of the take-up speed of the twist to the rotation speed of the spindle rotor is increased in comparison with the production data is used during creation of the yarn reserve.

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.

A method for starting a spindle of a cabling or two-for-one twisting machine, wherein a yarn reserve is formed on a take-up package, the machine has a workstation having a spindle pot for holding a first feed package and having a spindle rotor with a lateral outlet below the spindle pot, an outer yarn from one feed package is wound around an inner yarn from another feed package and the outer yarn is guided through the spindle shaft and its lateral outlet in a balloon orbiting the spindle pot to a yarn-guiding device above the spindle which merges the two yarn supplies, and a winding device in which the produced twist is wound onto the take-up package. A ratio of the take-up speed of the twist to the rotation speed of the spindle rotor is increased in comparison with the production data is used during creation of the yarn reserve.

Methods for fabricating coiled polymer fibers and yarns (high-spring-index coiled fibers and yarns). Methods include inserting twist separately into individual fibers or yarns, plying the fibers or yarns by inserting plying twist, setting the ply structure without permanently binding together the fibers or yarns of different plies so that the ply structure is substantially stable against untwist when torsionally untethered, and then unwrapping the plied fibers or yarns so that a high-spring-index fiber or yarn can be obtained. In some embodiments, the unwrapped fibers or yarns are further set so that these are further stabilized. The methods can eliminate the need for a mandrel, and can be quickly applied for applications where high-spring-index thermally-driven artificial muscles are presently employed, such as for presently commercialized comfort-adjusting jackets.