GB1120036A - Improved fabrics - Google Patents

Abstract

Pilling is eliminated or reduced by at least 50% in woven or knitted fabrics made from spun yarns containing high tenacity synthetic fibres which cause pilling, by treating the fabric with at least one ultrasonic beam to attach at least some of the synthetic fibres to the same or to other fibres in the spun yarn and thereby to eliminate or reduce the pilling by preventing p teasing out and migration of the synthetic fibres to the surface of the fabric during testing or in wear. In one embodiment, the fabric is treated with ultrasonic vibratory apparatus comprising a head excited by a magnetostrictive or piezoelectric transducer. The fabric passes between the head piece in the form of a strip, roller or bar and an anvil. In a second embodiment, the anvil is replaced by a second head piece vibrated in synchronism with the first head piece. The head piece(s) may be cooled internally and maintained below the melting temperature of the synthetic fibres. Preferably, the fabric is treated in narrow rows at right angles to one another and the spacing of the rows is chosen so that the majority of the fibres which give rise to pilling are held in at least one spot along their length in the yarn. Alternatively, the fibres may be attached to other fibres in a pre-selected pattern. The or each head is preferably an exponential horn made of silver steel. The head(s) may be spring-loaded and have the shape of a chisel, a round tip, a wheel, a bar, a sphere or other convex shape. To treat the entire width of the fabric the head(s) may be of strip form, the anvil being a rotating roller if only one head is provided. If the strips are wider than 6" several transducers are mounted along the length thereof. A relay circuit may be provided to interrupt power whenever the head and the anvil or the two heads touch. The power may be controlled by a micro-switch which is held in the "on" position by the fabric entering the apparatus or by hand or foot control. The fabric may be fed through the apparatus at a speed of 10-60 cm. per sec. by feed and delivery rollers or by a claw and presser assembly. The gap between the head and the anvil or the two heads varies between 100% and 50% of the fabric thickness. A specified fabric contains 67% polyethylene terephthalate crimped fibres and 33% viscose rayon.