GB1102362A - Process for drafting staple fibres and improved web produced according to such process - Google Patents

Abstract

1,102,362. Drafting fibres. PAVENA A.G. 10, Feb., 1965 [15. Feb., 1964], No. 5829/65. Headings D1D and D1F. A method of drafting staple fibres between a pair of feed rollers and a pair of delivery rollers, comprises the steps of passing a non- twisted "stable band" (i.e. one in which the fibres are adhesively bonded together by a setting-agent) through the feed rollers, gripping in turn one or more individual fibres by means of a pair of delivery rollers so that each fibre or group so gripped is subjected to a high tensional load increasing up to the failure of the bond between the fibre or group and the adjacent fibres, and withdrawing the fibre or group substantially without force by means of the delivery rollers. The method aims to avoid the use of fibre control means, such as aprons, in the drafting zone (although a guide may be employed in the drafting zone which merely smooths away projecting fibres and does not compress the material), and to promote "cross-sectional stability" and "transverse stability" of the material undergoing drafting, thereby preventing "drafting waves" i.e. irregularities, appearing in the drafted material. "Cross-sectional stability" is defined as meaning that the band retains its cross-sectional configuration before and after entering the feed nip; "transverse stability" is defined as meaning that when a fibre enters the delivery-nip and is subjected to a high tensile load, as described below, the load is distributed throughout the remaining fibres so that it is not substantially elongated, although an elongation arising merely from the aligning of the molecular chains of the fibre may result. The method may be applied to preparatory and final drafting; in the former, two or more slivers may be doubled. Further the method may be used in two-stage drafting. The distance between the nips of the delivery and feed rollers may exceed the stable length of the fibres. In Fig. 2, a band consisting of fibres bonded together as described in Specification 1102363, is shown approaching the nip plane EK of delivery rollers. The fibres, being arranged naturally at random, project beyond one another, and are gripped in the nip one at a time. Fibre c, being bonded to adjacent fibres is subjected to a pull K c which increases until the bond fails, at which point the pull falls almost to zero and the fibre is carried away by the delivery rollers with practically no force. The pull is of short duration and the elongation of the fibre, i.e. its "lengthwise stability", minimal, thereby reducing the possibility of irregular drafting. The other fibres are held back by the fibres to which they are bonded. The lengthwise stability of the band may be tested by an instrument or by the readiness with which it breaks under its own weight.