Textiles: cloth finishing – Expanding device for textile webs – Spreader
Patent
1997-03-31
1998-03-24
Vanatta, Amy B.
Textiles: cloth finishing
Expanding device for textile webs
Spreader
26105, D06C 306
Patent
active
057298785
DESCRIPTION:
BRIEF SUMMARY
TECHNICAL FIELD
The present invention relates to an apparatus for transversely spreading a web, such as a split web or a nonwoven fabric, so that the width of the web after spreading is equal to or greater than 1.2 times the width of the web before spreading.
BACKGROUND ART
A spread web obtained by transversely spreading a traveling web has been used in the field of a textile industry and a plastic film industry. For example, Japanese Examined Patent Publication (Kokoku) No. 53-38783 discloses the production of a cross-laminated nonwoven fabric (split fiber nonwoven fabric), by spreading a broad width uniaxially stretched split web or slit web. Also, U.S. Pat. No. 4,223,059 discloses the adjustment of the width and the transverse stretching of a nonwoven fabric. Japanese Examined Patent Publication (Kokoku) No. 4-36948 discloses the cross-lamination of webs stretched in the longitudinal direction. Also, a filament tow is often widened (this technique is referred to as a "tow-opening" in the textile industry) to be introduced into a Pacific converter or a tow cutter. Similarly, a tow-opening nonwoven fabric is well-known.
The web spreading of the present invention is used to increase the width of the web so that the width of the web after spreading is significantly larger than that of the web before spreading. A ratio of the width of the web after spreading to that of the web before spreading (resultant width to the original width) is referred to as the spreading ratio. The web spreading of the present invention means that the spreading ratio is 1.2 or more. Accordingly, the web spreading of the present invention is different from the correction or prevention of wrinkles and creases. In the correction or prevention of wrinkles and creases, the width of the web does not substantially change. Also, the web spreading of the present invention is different from transverse web stretching. While the object of transverse web stretching is to cause molecules to orientate in the transverse direction by the stretching, the web spreading only spreads the width of the web without any change in the molecular orientation. Although, in the case of spreading a nonwoven fabric, some of the filaments may be stretched and oriented, such orientation is very small on the whole.
In the prior art, a curved expander roll is used to prevent occurrence of wrinkles and creases in a traveling web, such as a paper, a film or a fabric. There may be a case wherein the width of the web is slightly enlarged during the use of the curved expander rolls. However, the spreading ratio is low in such a case and substantial web spreading is not effected. The spreading ratio becomes larger if a curvature of the expander roll increases or a tension of the traveling web increases, but a desired larger spreading ratio is not yet obtainable and the resultant web has the inferior uniformity.
Alternatively, it may be possible to increase the width of the web by using a screw roll. In such a case, the spreading ratio becomes larger than that when the expander roll is used, but the uniformity of the resultant web is deteriorated, such that the central zone of the web is widened to a greater extent, while the side edge zone has a lower spreading ratio. Thus, the screw roll is not used for spreading the web at a high spreading ratio.
To solve the above drawbacks, various spreading apparatuses have been proposed and disclosed in, for example, Japanese Examined Patent Publications (Kokoku) No. 46-43275, No. 50-40186, No. 51-30182 and No. 58-10507. The spreading apparatus disclosed in the above Kokoku No. 46-43275 uses a plurality of coil springs arranged in the web traveling direction at a certain pitch, each coil spring extending in the transverse direction. These coil springs are gradually transversely expanded while moving in the web traveling direction. The web is carried by the coil springs and transversely spread. This spreading apparatus has been used by the present applicant because the web can be uniformly spread at a higher spreading ratio. Howev
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Kurihara Kazuhiko
Kuroiwa Yuki
Murakami Shuichi
Yazawa Hiroshi
Nippon Petrochemicals Company Limited
Polymer Processing Research Instr., Ltd.
Vanatta Amy B.
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