APPARATUS AND METHOD FOR THE ASSESSMENT OF IN-PLANE ANISOTROPIC LIQUID ABSORPTION IN NONWOVEN FABRICS
 

S. J. Russell, N. Mao
Nonwovens Research Group, School of Textile Industries
University of Leeds
Leeds, LS2 9JT, UK
 

An instrumental method is described that enables real-time measurement of in-plane anisotropic liquid absorption in nonwoven fabrics. The system uses variations in electrical capacitance to monitor changes in the liquid absorbed by a fabric as a function of time. In the computer-integrated system, multiple capacitance transducers are arranged equidistantly around a central point to allow separate measurements in up to eight different in-plane directions. The design features of the system, its theoretical basis and examples of measured results are presented.

DYNAMICS OF YARN TENSION ON KNITTING MACHINES

T. Pusch, I. Wünsch, P. Offermann
Institute of Textile and Clothing Technology
Dresden University of Technology
D-01062 Dresden, Germany
 

The submitted paper reports a study of investigation of the dynamics of yarn tension, i.e. to the time dependence of the yarn tension on large-diameter circular knitting machines (LCKM). The special feature of this study is the fact that predictions are made for the course of the yarn tension during a single stitch-forming process.

Only the yarn tension in the area of the yarn feeder and the yarn guide eye can be measured. Some results of such experimental investigations have already been published [1,2]. In this paper, additional results of theoretical model calculations are presented. In particular, by these calculations it will be possible to determine the structure of the yarn tensile force at the knitting point, i.e. in the region between knitting needles.

The calculation of the yarn tension required a numerical solution of a system of non-linear differential equations. The special difficulty lies in the formulation of the non-equilibrium state of the running yarn, especially in the formulation of the robbing-back effect.
 

FIBRE DYNAMICS IN THE REVOLVING-FLATS CARD,
PART I
A CRITICAL REVIEW
 

C.A. Lawrence, A. Dehghani, M. Mahmoudi, B. Greenwood and C. Iype
School of Textile Industries
University of Leeds
Leeds, LS2 9JT
 

The last several decades have seen significant developments to the revolving-flats card and much research has been published on the fundamentals of the carding process. There are still, however, contradictions in the detailed explanation of fibre behaviour during carding and in the effectiveness of certain developments widely accepted as beneficial. This paper presents a critical review of the literature concerning the way fibre mass is disentangled into individual fibres to form a card sliver and the effectiveness of principal machine components. Areas are indicated where further research is necessary to resolve contradictory views and further the understanding of the process.

FIBRE DYNAMICS IN THE REVOLVING-FLATS CARD
PART II
AN INVESTIGATION INTO THE OPENING, INDIVIDUALISATION, ORIENTATION AND CONFIGURATION OF FIBRES DURING SHORT-STAPLE CARDING
 

A. Dehghani, C.A. Lawrence, M. Mahmoudi, B. Greenwood, C. Iype
School of Textile Industries, University of Leeds, Leeds, LS2 9JT, England
 

High-speed photography was used to investigate the state of fibres during the short-staple carding process. Image processing was employed to investigate the flow uniformity and the degree of opening and fibre individualisation of the fibre mass. The results showed that there is a considerable mass flow variation at the taker-in stage and at the back of the cylinder. Due to the carding action between the cylinder and the revolving flats, most tuftlets are separated into individual fibres, but some remain as micro tuftlets and are transferred to the doffer. With the increased discretisation the fibre mass becomes more uniformly distributed at the front of the cylinder. However, on the doffer the mass flow variation increases, which suggests that the transfer is not a uniform action. The angle of orientation of fibres was measured at the taker-in, at the front of the cylinder after the revolving flats and at the doffer stage. It was found that the fibres are highly orientated at the front of the cylinder. However, after the transfer region the degree of orientation of the fibres on the doffer decreases. In order to establish an understanding of the state of individual fibres, the change in the crimp level of fibres during the process was studied. It may be assumed that crimp level is directly related to the forces applied to the fibres. The results showed that the fibres at the front of the cylinder are subjected to more tension as compared to the fibres at the taker-in stage. A study was also carried out on the effect of the boundary layer around the cylinder by directly measuring the speed of individual fibres at the front of the cylinder. This study showed that the majority of the fibres are hooked to the cylinder wires and travel at the speed of the cylinder surface.