Abstract: The presence/absence of a core fiber in a core yarn is reliably detected to prevent production of a core fiber-free core yarn. In a method for producing a core yarn C by wrapping a fiber bundle S around a core fiber F, the core yarn C is spun with a core fiber F content being changed from that of normal spinning for a predetermined time period after the start of spinning, in order to detect whether the core fiber F is present. The core yarn C may be spun with a core fiber made of a drawn elastic yarn to detect whether the core fiber is present based on a thickness fluctuation of the core yarn that is caused by slackening the core yarn.

Abstract: The presence/absence of a core fiber in a core yarn is reliably detected to prevent production of a core fiber-free core yarn. In a method for producing a core yarn C by wrapping a fiber bundle S around a core fiber F, the core yarn C is spun with a core fiber F content being changed from that of normal spinning for a predetermined time period after the start of spinning, in order to detect whether the core fiber F is present. The core yarn C may be spun with a core fiber made of a drawn elastic yarn to detect whether the core fiber is present based on a thickness fluctuation of the core yarn that is caused by slackening the core yarn.

Abstract: An elastic core fiber is caught to prevent production of a core yarn having no elastic core fiber. In a method for producing a core yarn by supplying a sliver to a drafting device in a predetermined amount and merging a core fiber with the sliver, the sliver is supplied to the drafting device in an amount greater than the predetermined amount over a predetermined period of time after spinning is started, so as to merge with the core fiber, and thereafter, the sliver is supplied to the drafting device in the predetermined amount. Preferably, the amount of sliver that is supplied to the drafting device is changed in accordance with the rotational speed of predetermined draft rollers in the drafting device.

Abstract: An elastic core fiber is caught to prevent production of a core yarn having no elastic core fiber. In a method for producing a core yarn by supplying a sliver to a drafting device in a predetermined amount and merging a core fiber with the sliver, the sliver is supplied to the drafting device in an amount greater than the predetermined amount over a predetermined period of time after spinning is started, so as to merge with the core fiber, and thereafter, the sliver is supplied to the drafting device in the predetermined amount. Preferably, the amount of sliver that is supplied to the drafting device is changed in accordance with the rotational speed of predetermined draft rollers in the drafting device.

Abstract: When an unwinding device based on a friction roller system is used to unwind a yarn from a package while applying unwinding tension to the package, the package may collapse at the opposite ends of the package, resulting in inappropriate unwinding. An unwinding device includes a friction roller 3 that contacts with a peripheral surface of a winding package 1 to rotate the package 1 and a yarn guide roller 4 that guides an elastic yarn 5 unwound and drawn out from the package 1 in the radial direction of the package as a result of rotation of the friction roller 3. A friction belt 11 is provided on an axial part of the friction roller 3 so that the friction roller 3 contacts with only a central portion 1b of the package 1 which is located inside opposite axial ends 1a, 1a of the package 1 and which has a substantially fixed outer diameter, and the friction belt 11 has a larger diameter than a cylinder 10 and is located radially outside the cylinder 10.

Abstract: A core yarn manufacturing machine has a spinning unit including a hollow guide shaft member wherein the yarn passage is formed in the axis direction, and a nozzle applies a whirling flow to the tip section of the hollow guide shaft member. A core yarn is manufactured by winding the fiber bundle into the spinning unit, around the core fiber which is also fed, in the tip section of the hollow guide shaft member. The machine has a suction force producer for producing a suction force toward the interior of the yarn passage from the entrance of the hollow guide shaft member, and a core fiber feeding apparatus that feeds to the spinning unit. A control device controls the operation and non-operation of the whirling flow generating nozzle, the suction force producer and the core fiber feeding apparatus.

Abstract: The object of the present invention is to provide a core yarn manufacturing machine and a core yarn manufacturing method capable of carrying out automatic yarn pick-up of the core yarn like a true twist.