Apparatus to measure the bending length and bending rigidity of fabrics

An apparatus to measure the bending length and bending rigidity of a piece of fabric comprising a generally planar surface upon which the plate of fabric is moved. The surface terminates at one end with an edge over which a leading end of the fabric passes. An optical device defines a plane extending downwardly from the surface edge at approximately 41.5 degrees. The optical device detects when the plane is intersected by the leading end of the fabric when, after a sufficient length of the piece of fabric has passed beyond the surface edge to cause bending of the fabric piece, the leading edge of the fabric intersects the plane.

BACKGROUND OF THE INVENTION 
The present invention relates to apparatus to measure the bending length 
and bending rigidity of fabric. 
PRIOR ART 
The recent introduction to the garment manufacturing industry of 
sophisticated instruments for measuring fabric mechanical and physical 
properties has raised the awareness of the textile industry to the 
usefulness of objective measurement for quality control and product 
development. However, apart from being expensive, the currently available 
instruments require a skillful and devoted operator. These are the main 
reasons for the reluctance of most tailors to adopt fabric objective 
measurement for quality control. 
OBJECT OF THE INVENTION 
It is the object of the present invention to overcome or substantially 
ameliorate the above disadvantages. 
SUMMARY OF THE INVENTION 
There is disclosed herein an apparatus to measure the bending length and 
bending rigidity of fabrics, said apparatus comprising: 
a generally horizontal planar surface terminating at one end with an edge, 
upon which a strip of fabric is placed and along which it is moved, a 
distance transducer mounted adjacent said surface to detect the distance 
moved by said strip; 
a detector to determine when a leading edge of said strip passes the edge 
of said surface; and 
an optical sensor to detect when said leading edge intersects a plane 
extending downwardly from said surface edge at an acute angle to the 
horizontal.

DESCRIPTION OF THE PREFERRED EMBODIMENT 
A preferred form of the present invention will now be described by way of 
example with reference to the accompanying drawing, which schematically 
depicts in perspective view an apparatus to measure the bending length and 
bending rigidity of fabric. 
In the accompanying drawing there is schematically depicted an apparatus 10 
(flexometer) to measure the bending length and bending rigidity of 
fabrics. 
The apparatus 10 includes a body 11 having an upper horizontal surface 12 
provided with an aperture 13 having a straight edge 14. Extending in a 
direction generally normal to the edge 14 is a guide bar 15 along which a 
length of fabric is moved toward the edge 14. 
Mounted adjacent the surface 12 is a displacement transducer 16 which 
measures the distance travelled by the fabric strip. Located adjacent the 
edge 14 is a reflective sensor 17 to determine when the leading edge of 
the strip passes thereby. 
Mounted within the body 11 is a photodetector 18 which detects when the 
leading edge of the strip intersects a plane extending downwardly from the 
edge 14 at an acute angle of between 40.degree. and 45.degree., preferably 
about 41.5.degree., to the horizontal. 
A digital readout 19 shows the length of the fabric extending between the 
edge 14 and the point of intersection with the leading edge of the fabric 
with the abovementioned plane. 
The above apparatus 10 measures two bending properties of a fabric, that is 
the fabric bending length which is related to the ability to drape a 
material, and the fabric bending rigidity which is related to the quality 
of stiffness when a fabric is handled. The bending rigidity is 
particularly critical in the tailoring of lightweight fabrics as a very 
flexible fabric (low bending rigidity) may cause seam puckering while a 
high bending rigidity fabric can be more manageable in sewing and produce 
a flat seam. 
A photodetector 18 is used to detect the point where the overhanging part 
of a rectangular strip of fabric bends and reaches a plane inclined at 
41.5.degree. to the horizontal. The bending length (LB) is displayed 
automatically with the use of an electronic encoder, thus the error due to 
the operator's judgement is eliminated. This bending legth is combined 
with the cloth mass M (g/cm.sup.2) to give the fabric bending rigidity (B) 
as shown in the following relations: 
EQU B=0.10M LB3(mg.cm) 
Initial measurements with the apparatus 10 show good correlation in the 
bending rigidity between this instrument and the KES-F Bending Tester A 
correlation coefficient of 0.98 was found for 10 worsted fabrics covering 
a variation in fabric weight from 113 g/m.sup.2 to 453 g/m.sup.2, both 
warp and weft directions were measured. This is shown in the FIG. 2. 
Despite the high correlation, the KES-F values are significantly lower 
than those given by the Stiffness Meter. This is because measurements were 
done on the KES-F Bending Tester prior to the modification of the 
instrument's clamps by the manufacturer which raises the measured bending 
rigidities to values approximately equivalent to the apparatus 10.