Measuring and testing – Sheet – woven fabric or fiber
Reexamination Certificate
2000-09-29
2002-06-04
Williams, Hezron (Department: 2856)
Measuring and testing
Sheet, woven fabric or fiber
C073S007000, C073S009000
Reexamination Certificate
active
06397672
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention generally relates to a method for determining the frictional properties of materials, such as textiles, to better quantify values such as skin-feel, hand, and texture of the materials. While the invention is presented as being applied to textiles, the invention is also applicable to polymer films, paper sheets, and other surfaces.
2. Description of the Prior Art
Of the major aesthetical attributes of fabrics, the handle attribute is probably the most difficult to quantify. The handle or “hand” of a fabric refers to the suppleness, softness, smoothness, flexibility, and thickness of a fabric, and relates to a complex mechanism involving physical, psychological, and neurological concepts, which combine to produce a perceived quality of the fabric. The most common method for evaluating the hand of a fabric is a subjective analysis accomplished by a person rubbing the fabric between a thumb and forefinger. However, this method is far from ideal, and the subjective nature of the test makes it difficult to establish common industry-wide parameters regarding the hand of fabrics.
F. T. Peirce (“The Handle of Cloth as a Measurable Quantity”,
J. Textile Inst
, 21, T377-T416 (1930)) pioneered attempts to explain the hand of fabrics in terms of their physical properties, and stressed the importance of the surface properties of the fabric. Pierce did not attempt to study and measure the surface properties, but the characterization of the frictional properties of textile materials has occupied other textile researchers for many years. For example, J. A. Morrow (“The Frictional Properties of Cotton Materials”,
J. Textile Inst
., 22, T425-T440 (1931)) measured the frictional properties of fabrics at different normal loads, areas of contact and speeds of testing, and proposed an empirical relationship of the form:
F=mP+kA (1)
where F is the frictional force, P is the pressure, and A is the area of contact. It is immediately apparent from this equation that the commonly accepted Amontons Law for the coefficient of friction (&mgr;=F/N), first set forth by Guillaume Amontons, would not fit Morrows data. E. C. Dreby (“A Friction Meter for Determining the Coefficient of Kinetic Friction of Fabrics”,
J. Research Nat. Bur. Standard
, 31, 237-246 (1943)) confirmed this conclusion, and a later investigation by H. G. Howell (“Inter-Fiber Friction”,
J. Text Inst
., 42, T521-T535 (1951)) provided further evidence that Amontons laws are not valid with respect to the frictional properties of fabrics.
Fundamental work by Howell and Mazur (“Amontbns Law and Fibre Friction”,
J. Text lnst
., 44, T59-T69 (1953)) suggested that a more suitable relationship for the frictional properties of fabric was of the form:
F=CP
n
(2)
where n is a frictional index O<n<1, F is the frictional force per unit area of contact, P is the normal force per unit area of contact, and C is a frictional constant. A thorough experimental investigation of this relationship was carried out by D. Wilson (“A Study of the Fabric-on-Fabric Dynamic Friction”,
J. Textile Inst
., 54,143-155 (1963)) that confirmed its suitability. More recently Carr et al. (“Frictional Characteristics of Apparel Fabrics”,
Textile Res. J
., 58,129-136 (1988)) and J. O. Ajayi (“Fabric Smoothness, Friction and Handle”,
Textile Res. J
., 62, 52-59 (1992)) have studied the effects of weave, fabric weight, direction of rubbing, etc. on the frictional properties of woven fabrics.
All of the foregoing authors attempted to define the hand quality or other properties of fabrics based upon friction constants, and with reference to Equation (2), the C value has become a well-known friction constant for quantifying the properties of fabrics. However, referring to earlier papers (Carr et al., 1988; Ajayi, 1992), where F and N are measured in physical pressure units (i.e., Pascals, which are Newtons/m
2
, hereinafter “Pa”), and when solving Equation (2) for physical units, it is evident that n has no unit. However, the friction constant C has a unit Pa
(1-n)
. Thus, it is evident from the foregoing discussion that the friction constant C is dependent on n. This dependency causes difficulty in comparing the C values of different fabrics. Furthermore, because n is a measure of the physical characteristics of the material, n values tend to vary from material to material. Thus, it is not logical to compare and characterize the frictional properties of two different textile materials using the C values. Accordingly, it is desirable to establish a new method and apparatus for quantifying the quality of a fabric or other material.
SUMMARY OF THE INVENTION
In the preferred form, the invention sets forth a method for determining the quality of a fabric or other material. The invention establishes a new constant value to be applied to this determination. The constant value is referred to as the Quality Energy Value (hereinafter the “QE value”) of a material. The QE value takes into account the reciprocatory motion actually used when rubbing a piece of cloth with a finger, and utilizes a testing apparatus which somewhat simulates this to and fro motion. The QE value also advantageously takes into account the velocity at which the frictional properties of the fabric are measured. As will be demonstrated in more detail below, it has been found that the lower the QE value, the better the quality of the fabrics. Accordingly, using the method of the invention, a range of QE values may be established for a plurality of fabrics, and, thereby, the relative qualities of the fabrics may be compared.
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Joseph O. Ajayi, “Fabric Smoothness, Friction, and Handle,” Textile Research Journal, 52-59, Department of Pure and Applied Chemistry, University of Strathclyde, Scotland
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R. Chattopadhyay and S. Banerjee, “Th
Garber C D
Jones Tullar & Cooper PC
Texas Tech University
Williams Hezron
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