Title: Improved Test Method and Apparatus The present Invention relates to
a test method and apparatus. In particular, the inventionre]ates to a test method and apparatus for simulating the stretch and recovery characteristics of fabrics, in particular stretch fabrics, during their normal use.
5 Proprietary devices are known which are sold for the purpose of measuring stretch in fabncs.
these devices, the test fabric is cut into strip form and therefore the raw knitted or woven edge is unsupported during testing, with the result that slippage in the fabric structure is possible. Dunng testing in the known devices, the fabric is stretched only once and then allowed to relax, as opposed to the fabric being repeatedly stretched and relaxed a predetermined number of times, in 10 all directions, as would occur in actual wearer use.
It is an obj ect of the present invention to provide a test method and an apparatus for carrying out this test method in which the above disadvantages are reduced or substantially obviated.
The invention provides a method fordetermining the stretch and recoverycharacteristics offabncs, in particular stretch fabrics, which method comprises the steps of 1 5 (a) mounting a fabric test piece into a clamping Moraine, supporting the frame and test piece horizontally and measuring the amount of pre-test deformity (d') in the fabric test piece due to gravity; (b) mounting the clamping frame together with its fabric test piece in a stretching device and defonTung the fabric to be tested by flexing the fabric test piece apre-determined number oftirnes 20 at a pre-determined speed with a pre-detennined stroke; (c) measuring the amount of post-test deformity (d:) the fabric test piece whilst still clamped in its frame, by repeating the measurement of step (a) above, shortly after stretching and (d) comparing the measurements resulting from steps (a) and (c).
l Comparison of the two measurements resulting from steps (a) and (c) thereby gives a quantifiable (d/d:) value for stretch end recovery characteristics in the fabric, producing acomparisonbetween the pre-test deformity and the extra deformity due to the constant flexing carried out in step (b).
The measurements before and after deformation may be carried out by either a contact or non 5 contact method dependent on the degree of control and accuracy required.
A suitable contact measuring device comprises an attachment which is separate to the test apparatus and comprises a gravityweightwithaslidingrod onto which the clamping device with the test piece of fabric is placed. Measurements are taken by the device before and after stretching by allowing the same weight to make contact with the fabric and it is a comparison on these 10 measurements do and d: which determines the result.
If a more delicate method of measurement was required, for example for a verylight weight fabric, then a non-contact method could be employed by using a laser distance measuring device, or similar optical method.
The present invention further provides an apparatus for simulating the stretch and recovery 15 characteristics of fabrics, in particular stretch fabrics, which apparatus comprises a clamping device to retain and support a test piece offabric; ahemisphericalblock and a "eared motor and crank arrangement adapted to move the hemispherical block laterally.
The apparatuspreferablyfiuthercomprisesadigitalcounterto determine the number ofcycles and a switching device linked to the digital counter.
20 The clamping frame is preferablyremovable from the apparatus and is preferably circular in shape.
It is particularly preferred that the apparatus further comprises means for varying the stroke of the crank arrangement dependent upon the inherent stretch in the fabric.
The measurements before and after deformation may be carried out by either a contact or non-
contact method dependent on the degree of control and accuracy required.
The invention will now be further described with reference to the accompanying drawings, in which Figure 1 is a longitudinal view of an embodiment of a test apparatus, and Figure 2 is a longitudinal 5 view of a contact measurement device.
As can be seen from Figure 1, the test apparatus shown generally at 10 comprises a clamping frame 2, a hemispherical block 4, a geared motor shown schematically at 6 and a crank arrangement 8 mounted on a drive shaft (not shown) from the motor 6. A shah 12 is provided between the crank arrangement 8 and the hemispherical block 4 to transfer drive from the motor 6 via the crank 10 arrangement 8 to the hemispherical block 4. A guide block 14 includes a through hole (not shown) for receipt and guiding of the shaft 12 and is located between the crank arrangement 8 and th hemispherical block 4. The clamping frame 2 is removably supported on amount 16 and secured by screw means 18. A support base 20 is provided, on which the guide block 14 and mount 16 are supported.
15 A digital counter 22 with start and stop buttons 24, 26 is connected to the motor by means of cabling passing through a conduit 28.
A fabric test piece 30 is shown mounted in the clamping frame 2.
As can be seen from Figure 2, a contact measuring device shown generally at 40 comprises a linear scale 32, weight 34 and measuring arm 36. A cursor line 3 8 is marked on the measuring arm 36, 20 which is attached to the weight 34. A guide 42, with a through hole (not shown) sized to receive the measuring arm 36 in sliding engagement is attached to the linear scale 32 and is adapted for releasable mounting on the frame 2 ofthe test apparatus 10. Clamp morns 46 is provided for securing the frame 2 of the test device 10 to the base 44 of the contact measuring device 40 In operation, the fabric test piece 30 is mounted in the clamping frame 2 and supported horizontally
byclamping the flame to thebase ofthe contact measuring device40 by means ofthe clamp means 46. The pre-test deformation (d I) due to gravity is measured by allowing the weight 34 to fall under gravity until it comes to rest supported by the fabric test piece 3 0. The position of the cursor line 3 8 on the linear scale 32 is then read and recorded. The clamping frame 2 with fabric test piece 5 30 is then removed from the contact measuring device 40 and transferred to the test apparatus 10.
The fabric test piece should be inserted into the Warns in a fullyrelaxed condition and therefore it is preferred that all tests are carried out after the fabric has been fully conditioned under standard laboratory conditions for aperiod of not less than 24 hours. The conditions would typicallybe 20-
22 C and 50-55% Relative Humidity. Other variations are compensated forbythe fact that the 10 weight employed to measure the amount of deflection is the same before and after stretching.
The frame 2 is then supported on the mount 16 and secured by screw means 18. The fabric test piece 30 is then deformed by flexing apredeternunednumberoftimes, at apre-determined speed bythehemispherical block4. The block 4 contacts the fabric test piece 30 with apredetermined force, which force is controlled by the stroke of the crank arrangement 8.
1 5 The feline 2 is then removed from the mount 16 and supported horizontallyin the measuring device.
The post-test deformation (d2) is measured by the same technique used to measure the pre-test deformation (d').
The post test deformation (d:) can then be compared with the pre-test deformation (do), in order to predict the stretch and recovery characteristics of the fabric in normal use.
20 The test method and apparatus according to the invention are particularly useful for testing fabrics where a degree of stretch and the maximum amount of recovery are desirable to enhance comfort and wear life, such as fabrics to be used in hosiery and sportswear, where the test method can simulate the effect of such fabrics being worn around an arm or a leg and being stretched by constant flexing of an elbow or knee. The number of flexing cycles, speed of flexing and force to 25 be applied, for examples of fabrics of these types, and the deformation observed, are shown by
wayofillustration only, in the following table. In practice, thenumberofflexing cycles, speed of flexing and force to be applied would be selected by the operator for a particular fabric or range of fabrics.
Fabric Type Number of Pre-test Post-test Lost recovery Cycles deformation do deformation do (d-d: _.. _ 5Knitted Fabric 350 11.14 mm 21.82 mm 10.68 mm _ Woven Fabric 350 6.64 mrn 25.80 mm 19.16 mm