GB1591019A - Fabric testing - Google Patents

Description

(54) FABRIC TESTING (71) We, I.W.S. NOMINEE COM PANY LIMITED, a British Company of Wool House, Carlton Gardens, London, S.W.1., do hereby declare the invention, for which we pray that a patent may be granted to us and the method by which it is to be performed, to be particularly described in and by the following statement: This invention relates to an improved method and apparatus for the testing of abrasion resistance of textile fabrics.

In order to test new or modified fabrics to ascertain whether they will stand up adequately to abrasion in use, it is common to subject samples to an artificial, accelerated abrasion test. Various apparatus is available to perform this kind of test, and one such is the Martindale Abrasion Tester. In this a sample of the fabric under test is mounted on a resilient pad on an arm. The arm is driven so as to rub the sample against a stationary standard fabric until such time as the operator determines that the sample is worn through to end-point. The test result is usually expressed as the number of rubs to end-point.

This method suffers from a number of disadvantages. One is that the standard abradant fabric may vary, but possibly more important is that determination of the endpoint by the operator is very subjective.

One method used requires examination of the sample at intervals during the wear cycle to ascertain when two yarns not being adjacent to one another are broken. The accuracy of this technique is dependent on the frequency of inspection intervals adopted and the perception of the operator.

Another method involves allowing wear to proceed until a noticeable change in fabric appearance occurs. Again this is subjective and depends on the number of times the operator inspects the sample.

One type of apparatus employs a pin which projects through the fabric sample and makes electrical contact when the fabric is worn. However, the pin itself often gives rise to uneven wear and hence to inconsistent results.

The invention seeks to provide an improved testing apparatus which gives more consistent results and is less dependent on subjective operator assessments.

In accordance with this invention, an abrasive testing apparatus comprises an abradant and a sample carrier movable relative to one another to cause the abradant to rub a fabric sample on the carrier, at least the surface of the abradant and of the carrier being electrically conductive and adapted to be connected to an electrical test completion indicating circuit. The samplebearing surface of the carrier preferably comprises a flexible electrically conductive film. The completion indicating circuit may cause the machine to stop, flash a light, call the operator, provide a display of the test result or perform other useful operations.

The method of the invention comprises placing a fabric sample on an electrically conductive surface of a sample carrier and rubbing the sample with an electrically conductive abradant surface until the carrier surface makes electrical contact with the abradant surface.

The standard abradant used in testers of the type described is a woven cross-bred woollen fabric. In the modified apparatus of the invention this is replaced by a metal abradant, preferably a mesh. A stainless steel woven mesh has been found particularly useful.

The sample is normally mounted on a resilient pad on the sample carrier. A foam pad is commonly used. In the apparatus of the invention the surface of the pad beneath the sample must be conductive. We have found that metal foils will provide the necessary conducting surface. However, such foils alone tend to be fragile and may tear, interfering with the abrasion result.

Accordingly, we prefer to use metal foils supported on a flexible plastics material, whether by lamination or otherwise. A lamination of metal foil and a cellulosic material sheet has given especially good results. For availability and cheapness an aluminium foil is preferred. It is preferred to bond the foil to the foam pad, e.g. with adhesive, although it may be held in place mechanically.

The electrically conductive abradant should be insulated from the main body of the machine, while the electrically conductive sheet on the carrier may be 'earthed' to the machine body. An electrical lead is connected to the abradant, and one may be connected to the machine body. These leads form the connections to an external circuit capable of performing the desired operation or operations.

The invention will be described further, by way of example, with reference to the accompanying drawings, in which : Figure 1 is an exploded diagrammatic section of a sample carrier of abrasion testing apparatus modified according to the invention; Figure 2 is a diagrammatic section of the modified abradant-mounting system of the apparatus of Figure 1; Figure 3 is a diagram of a suitable circuit for use with the apparatus; and Figure 4 is a graph showing the relationship between abrasion tests carried out on the modified apparatus and on the standard apparatus.

As shown in Figures 1 and 2, a standard Martindale abrasion tester sample carrier comprises a main body 10 connected by a rod 12 to the machine drive (not shown).

The main body carries an insert 14 covered by a foam pad 16 over which a sample 18 of fabric is placed. The insert/pad/sample assembly is held in the carrier by a screwthreaded base 20 which engages the main body 10. The carrier modified in accordance with the invention has, in addition to the above components, a cellulose film/aluminium foil laminate 22 between the pad 16 and the sample 18. The conductive side (i.e.

the aluminium foil) faces downward, and makes electrical contact with the base 20 and the main body 10 which are metallic.

The foil laminate 22 is adhesively bonded to the pad 16.

An abradant mounting system comprises a base 24 to which is fixed a 33 gauge wire woven stainless steel mesh (1296 holes/ sq.in.) 26 by means of mounting rings 28, 30 secured to the machine by bolts 31. The mesh 26 is insulated from the body of the machine by electrically insulating sheets 32, 34.

The modified apparatus is operated in an identical manner to the standard machine, i.e. the sample on the carrier assembly is rubbed against the abradant in a circular motion. However, the end-point is determined differently, and far more consistently, in the following manner.

Figure 3 shows a typical circuit for controlling the modified apparatus of the invention. The foil laminate 22 and mesh-26 act as a switch, closing the circuit when the sample 18 wears through. Twp NAND logic units 36 are connected in a flip-flop circuit such that when contact is made between the mesh 26 and the laminate 22, a transistor driven light emitting diode 38 is switched on, and the machine motor is turned off through a relay 40. Since a tester will normally have four sample carrier/abradant units working from the one motor, the light tells the operator which sample has worn through and he may then start the machine again by depressing a reset switch 42 which turns off the diode 38 and restarts the motor. The test then -proceeds until all four samples have failed, when the mean number of rubs is calculated.

Figure 4 illustrates the comparison of the modified test of the invention against the standard test (IWS Test Method 112). The relationship is non-linear but nevertheless smooth, and it can be seen that the number of rubs (and hence the time taken) to the end-point is considerably reduced, so enabling results.to be obtained more quickly.

Furthermore, we have found that the coefficient of variation of the test results of the modified apparatus of the invention is between 5% and 10% whereas the coefficient for the standard test varies from 9% to 14%.

Thus the apparatus of the invention gives more consistent results.

In the tests illustrated in Figure 4, point 1 was obtained with barathea, point 2 with serge dyed with a premetallized dye, point 3 with serge dyed with an acid levelling dye, point 4 with serge which was flat set and dyed with a premetallized dye, the points 5 with - a woven woollen and point 6 with flannel. In the case of the test on woven woollen fabric the two -points Sa and Sb show the variation in results obtained from successive conventional tests.

WHAT WE CLAIM IS: 1. Abrasion testing apparatus suitable for testing textile fabrics which comprises an abradant and a sample carrier movable relative to one another to cause the abradant to rub a fabric sample on the carrier, at least the surface of the abradant and of the carrier being electrically conductive and adapted to be connected to an electrical test completion indicating circuit.

2. Apparatus according to claim 1 wherein the sample-bearing surface of the carrier comprises a flexible conductive

**WARNING** end of DESC field may overlap start of CLMS **.

Claims (7)

**WARNING** start of CLMS field may overlap end of DESC **. tear, interfering with the abrasion result. Accordingly, we prefer to use metal foils supported on a flexible plastics material, whether by lamination or otherwise. A lamination of metal foil and a cellulosic material sheet has given especially good results. For availability and cheapness an aluminium foil is preferred. It is preferred to bond the foil to the foam pad, e.g. with adhesive, although it may be held in place mechanically. The electrically conductive abradant should be insulated from the main body of the machine, while the electrically conductive sheet on the carrier may be 'earthed' to the machine body. An electrical lead is connected to the abradant, and one may be connected to the machine body. These leads form the connections to an external circuit capable of performing the desired operation or operations. The invention will be described further, by way of example, with reference to the accompanying drawings, in which : Figure 1 is an exploded diagrammatic section of a sample carrier of abrasion testing apparatus modified according to the invention; Figure 2 is a diagrammatic section of the modified abradant-mounting system of the apparatus of Figure 1; Figure 3 is a diagram of a suitable circuit for use with the apparatus; and Figure 4 is a graph showing the relationship between abrasion tests carried out on the modified apparatus and on the standard apparatus. As shown in Figures 1 and 2, a standard Martindale abrasion tester sample carrier comprises a main body 10 connected by a rod 12 to the machine drive (not shown). The main body carries an insert 14 covered by a foam pad 16 over which a sample 18 of fabric is placed. The insert/pad/sample assembly is held in the carrier by a screwthreaded base 20 which engages the main body 10. The carrier modified in accordance with the invention has, in addition to the above components, a cellulose film/aluminium foil laminate 22 between the pad 16 and the sample 18. The conductive side (i.e. the aluminium foil) faces downward, and makes electrical contact with the base 20 and the main body 10 which are metallic. The foil laminate 22 is adhesively bonded to the pad 16. An abradant mounting system comprises a base 24 to which is fixed a 33 gauge wire woven stainless steel mesh (1296 holes/ sq.in.) 26 by means of mounting rings 28, 30 secured to the machine by bolts 31. The mesh 26 is insulated from the body of the machine by electrically insulating sheets 32, 34. The modified apparatus is operated in an identical manner to the standard machine, i.e. the sample on the carrier assembly is rubbed against the abradant in a circular motion. However, the end-point is determined differently, and far more consistently, in the following manner. Figure 3 shows a typical circuit for controlling the modified apparatus of the invention. The foil laminate 22 and mesh-26 act as a switch, closing the circuit when the sample 18 wears through. Twp NAND logic units 36 are connected in a flip-flop circuit such that when contact is made between the mesh 26 and the laminate 22, a transistor driven light emitting diode 38 is switched on, and the machine motor is turned off through a relay 40. Since a tester will normally have four sample carrier/abradant units working from the one motor, the light tells the operator which sample has worn through and he may then start the machine again by depressing a reset switch 42 which turns off the diode 38 and restarts the motor. The test then -proceeds until all four samples have failed, when the mean number of rubs is calculated. Figure 4 illustrates the comparison of the modified test of the invention against the standard test (IWS Test Method 112). The relationship is non-linear but nevertheless smooth, and it can be seen that the number of rubs (and hence the time taken) to the end-point is considerably reduced, so enabling results.to be obtained more quickly. Furthermore, we have found that the coefficient of variation of the test results of the modified apparatus of the invention is between 5% and 10% whereas the coefficient for the standard test varies from 9% to 14%. Thus the apparatus of the invention gives more consistent results. In the tests illustrated in Figure 4, point 1 was obtained with barathea, point 2 with serge dyed with a premetallized dye, point 3 with serge dyed with an acid levelling dye, point 4 with serge which was flat set and dyed with a premetallized dye, the points 5 with - a woven woollen and point 6 with flannel. In the case of the test on woven woollen fabric the two -points Sa and Sb show the variation in results obtained from successive conventional tests. WHAT WE CLAIM IS:

1. Abrasion testing apparatus suitable for testing textile fabrics which comprises an abradant and a sample carrier movable relative to one another to cause the abradant to rub a fabric sample on the carrier, at least the surface of the abradant and of the carrier being electrically conductive and adapted to be connected to an electrical test completion indicating circuit.

2. Apparatus according to claim 1 wherein the sample-bearing surface of the carrier comprises a flexible conductive

sheet.

3. Apparatus according to claim 2 wherein the sheet is a metal foil supported by a flexible plastics material.

4. Apparatus according to claim 1, 2 or 3 wherein the abradant is a stainless steel woven mesh.

5. A method of testing the abrasion resistance of a textile fabric which comprises placing a fabric sample on an electrically conductive surface of a sample carrier and rubbing the sample with an electrically conductive abradant surface until the carrier surface makes electrical contact with the abradant surface.

6. A method according to claim 5 wherein electrical contact between the carrier and abradant surfaces completes an electrical circuit giving an indication of the completion of the test.

7. Abrasion testing apparatus substantially as described with reference to Figures 1 to 3 of the accompanying drawings.