Textiles: weaving – Fabrics – Drier felts
Reexamination Certificate
1999-12-08
2002-01-01
Silverman, Stanley S. (Department: 1731)
Textiles: weaving
Fabrics
Drier felts
C139S38300A, C139S358000, C162S903000, C162S902000, C162S358200, C162S358100, C442S181000
Reexamination Certificate
active
06334467
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates to a flat woven papermaker's forming fabric having a paper side layer and a machine side layer interconnected by weft binder yarns. Each weft binder yarn in sequence interweaves with the paper side layer warp yarns in segments of the weft yarn path so as to complete the paper side layer weave pattern, and to contribute to the properties of the paper side surface of the paper side layer. Each weft binder yarn interlaces with a machine side layer warp yarn, to bind the paper and machine side layers together. Within the overall fabric weave pattern, the number of weft yarns between pairs of weft binder yarns in the paper side layer is irregular.
BACKGROUND OF THE INVENTION
Flat woven papermaker's forming fabrics in which so-called “intrinsic” weft binder yarn pairs are used to interconnect the weave structures of the paper and machine side layers are well known. Various arrangements have been described, for example by Wilson, U.S. Pat. No. 5,518,042; Vohringer, U.S. Pat. No. 5,152,326; Quigley et al., U.S. Pat. No. 5,520,225; Ostermayer et al., U.S. Pat. No. 5,542,455; Wright, U.S. Pat. No. 5,564,475; Wilson, U.S. Pat. No. 5,641,001; Ward, U.S. Pat. No. 5,709,250; Seabrook et al., U.S. Pat. No. 5,826,627; and Wilson, U.S. Pat. No. 5,937,914. Many others are known.
One feature that is common to all of these known forming fabric designs is that they are essentially “regular” and “even”. The spacing of the intrinsic weft binder yarn pairs is regular there being the same number of paper side layer weft between each binder yarn pair, and the interlacing points of each member of the intrinsic weft binder pair into the machine side layer are evenly spaced in both the machine direction and cross-machine direction, within the fabric weave pattern repeat. Thus there is always one, or two, or even three wefts in between each intrinsic weft binder yarn pair.
These references also teach, for example in Seabrook et al. and in the two Wilson disclosures, that the two members of a weft binder yarn pair can occupy a single weft path in the paper side layer such that when one of the members interweaves into the paper side layer thus occupying one segment of the weft path, the other interlaces with a warp in the machine side layer. These disclosures also teach that there can be none, one, two, or three paper side layer warp yarns in between successive segments of the weft path.
As used herein, the following terms have the following meanings.
The term “weft binder yarn” refers to each yarn of a pair of yarns which together occupy a single unbroken weft path in the paper side layer, and which separately interlace with a machine side layer warp yarn.
The term “interweave” refers to a locus at which a yarn forms at least one knuckle with another yarn in the paper side layer.
The term “segment” refers to a locus at which a weft binder yarn interweaves with at least one paper side layer warp.
The term “interlace” refers to a point at which a yarn wraps about another yarn in the machine side layer to form a single knuckle.
The term “float” refers to that portion of a yarn which passes over, or under, a group of other yarns in the same layer of the fabric without interweaving or interlacing with them. The associated term “float length” refers to the length of a float, expressed as a number indicating the number of yarns passed over. A float can be exposed on the machine side or paper side of each of the paper side layer and the machine side layer. The term “internal float” thus refers to a float exposed between the two layers, either on the machine side of the paper side layer, or on the paper side of the machine side layer.
The terms “regular” and “irregular” refer to the number of wefts in between successive weft binder yarns in the paper side layer within the fabric weave pattern repeat. In a regular fabric, the number of intervening wefts is constant; in an irregular fabric the number of intervening wefts is not constant.
The terms “symmetry” and “asymmetry”, and the associated terms “symmetrical” and “asymmetrical”, refer to the shape of the path occupied by a weft binder yarn as it exits the paper side layer, interlaces with a machine side layer warp, and returns to the paper side layer. The path is symmetrical when the interlacing point is located substantially at the middle of the path.
The terms “even” and “uneven” refer to the location of the interlacing points between a weft binder yarn and a machine side layer warp in the machine side layer within the fabric weave pattern repeat. In an “even” fabric the points are all the same distances apart in each of the machine direction and the cross machine direction and form a coherent pattern; in an “uneven” fabric the points are not necessarily all the same distances apart in the machine direction and do not form a coherent pattern.
The notation such as 3/2, for example, in reference to a fabric design refers to the number of warp, or machine direction yarns, over and under which a weft, or cross machine direction yarn, floats within the weave pattern. Thus 3/2 means that a weft yarn floats over three warp yarns and then under two warp yarns within the weave pattern.
Prior to the present invention, the basic approach in fabrics of this type has been to limit the designs chosen for each of the paper side layer and machine side layer to those which were compatible for interconnection with each other. For the two chosen designs to be compatible, two criteria were considered to be important.
First, it must be possible to weave the complete fabric incorporating the designs chosen for the paper side layer and the machine side layer, and including the weft binder yarns which interconnect the two layers together, on one loom. Generally, the number of sheds required to weave the machine side layer when divided by the number of sheds required to weave the paper side layer is an integer, typically 1, 2 or 3. Occasionally, this ratio will be a fraction, such as ½, when a 3-shed machine side layer design is combined with a 6-shed paper side layer design. In general, the number obtained by dividing the higher shed number by the lower one will be an integer.
Second, the paper side layer and machine side layer weave designs must provide internal weft floats (paper side layer) and internal warp floats (machine side layer) which can be interlaced to interconnect the two layers without creating any significant stresses which will distort the planarity of either or both layers. As noted above, this approach resulted in fabrics which are both regular and even. It was also believed that other properties of a forming fabric, such as planar fibre support and wire marking, would be adversely affected if the weft binder pairs were irregularly spaced.
It was generally believed that these limitations would maximise fabric stability, reduce or even eliminate sleaziness (the movement of one of the two layers relative to the other) and reduce the occurrence of fabric delamination caused by both internal and external abrasion of the weft binder yarns.
It is thus apparent that a great deal of experimental and design effort had to be expended in order to find compatible combinations of paper and machine side layer weave designs capable of interconnection by means of weft binder yarns, because the number of compatible paper and machine side layer weave design combinations available for use in forming fabrics of this type has been restricted by the criteria noted above.
BRIEF SUMMARY OF THE INVENTION.
This invention is based on the discovery that regularity is not a necessity in forming fabrics of this type. From this it follows that weft binder yarn pairs can be irregularly arranged in the paper side layer, so that within the weave pattern repeat the number of weft between each weft binder yarn pair is not always the same. Since the locations of the internal floats in the weft binder yarns within the paper side layer pattern repeat will determine the interlacing locations, it also follows that the interlacing points
Barrett Rex
Johnson Dale B.
Stone Rick
AstenJohnson, Inc.
Halpern M.
Silverman Stanley S.
Wilkes Robert A.
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