Measuring and testing – Sheet – woven fabric or fiber
Patent
1995-10-10
1997-01-28
O'Shea, Sandra L.
Measuring and testing
Sheet, woven fabric or fiber
73830, G01L 504
Patent
active
055969011
DESCRIPTION:
BRIEF SUMMARY
The invention relates to a method according to the pre-characterizing clause of Patent claim 1.
In textile technology, the measurement of the tearing strength of textile fibres yields important information on the problems to be expected in spinning and on the achievable yarn strength.
Classic methods for determining the tearing strength on the individual fibre are already known. However, there are no measuring instruments of wider application for these methods on the market. One example of such a method is described in U.S. Pat. No. 5,167,150 SHOFNER ET AL.
The measuring instruments commonly found on the market are based on the measurement of the bundle tearing strength. The most important instruments are known by the trade names Pressley, Stelometer and HVI.
In the measurement of the so-called Pressley index, a well combed-out and parallelized fibre bundle is gripped in the jaws of two clamps. There is no clearance between the two clamps. The fibres projecting beyond the clamps are cut off. A sliding weight on a load arm increases the force until the fibre bundle is torn apart. The load at tear can thereupon be read off on a load arm. The fibre bundle is subsequently weighed. The Pressley index is then calculated from the weight and the load at tear.
The Stelometer functions in the same way as the Pressley instrument. However, the clearance between the clamps is not 0, but 1/8 inch. Statements can consequently also be made on the elongation of the fibres.
The HVI are largely based on the Stelometer arrangement. In these fully automatic measuring instruments, the fibre bundle cannot be weighed for various reasons. In the tensile test, a force sensor measures the maximum tearing force at this point. The location of the constant mass point within the fibre tuft is established by means of an additional sensor. This mass-point measurement does not yield any absolute indication of the number of fibres, the fibre weight or the fibre cross-section. The constant mass point is calibrated by means of a calibrating cotton, of which the tearing force in g/tex (grams per tex/according to DIN standards 60905, 60910) is known. The dispersion of the calibrating cotton and the accuracy in the measurement of the desired values influence the dispersion between the measuring instruments and the reproducibility of the individual measuring instruments. The fibre tuft is moved between the detection of the mass point and the actual tearing-strength measurement. At the same time, the fibre tuft can vary according to the fibre properties, thus leading to increased dispersions as a result of mass-point deviations. The calibration constitutes considerable expenditure of time which is an important factor in these measuring instruments trimmed for speed. The functioning of the HVI is already known from various measuring instruments.
In all the known methods for measuring the bundle tearing strength, the actually torn fibre cross-section is approximated only indirectly. Wide dispersions of the measurement results occur thereby. A further disadvantage is that the crimping of the fibres is not eliminated, that is to say the point in time of the fibre break is greatly influenced by the individual crimping of each fibre. The measured bundle tearing strength is therefore closely associated with the particular crimping.
The invention is intended to remedy this. The object on which the invention is based is to provide a method for measuring the tearing strength of fibres, especially of textile fibres, which is based on an absolute measuring method.
The invention achieves the set object by means of a method which has the features of claim 1.
The method according to the invention eliminates the disadvantages of the state of the art and is characterized by an absolute measuring method which avoids the use of calibrating cotton.
Further advantageous embodiments of the invention are characterized in the dependent claims.
The invention and developments of the invention are explained in more detail below by means of the partially diagrammatic represe
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Dougherty Elizabeth L.
O'Shea Sandra L.
Zellweger Luwa AG
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