Textiles: manufacturing – Thread finishing – Surface modification of running length
Reexamination Certificate
1998-04-28
2001-11-06
Cole, Elizabeth M. (Department: 1771)
Textiles: manufacturing
Thread finishing
Surface modification of running length
28, C026S087000, C026S102000
Reexamination Certificate
active
06311377
ABSTRACT:
BACKGROUND OF THE INVENTION
The present invention relates to the production of more uniform fabrics, and in particular, to the spreading of fibrous tows or zero-twist yarns used in producing woven and non-woven fabrics. In the fabric industry, particularly the reinforcing and structural fabric industry, rovings and zero twist yarns are used in weaving or stitching fabrics. Such fabrics then are used in many ways, including reinforcement of polymers or the creation of honeycomb reinforcements or supports.
Methods have long been sought to weave lighter weight webs of materials to reduce weight and cost. However, conventional production processes are limited in their ability to create lightweight webs of generally uniform areal weight. Several such processes disclosed in U.S. Pat. Nos. 4,556,440 and 4,667,831 dispose segments of a roving side by side to make a layer of material in a reinforcement fabric. However, the fabric varies randomly in areal weight along its length depending on how uniformly the fibers in the roving are spread across the weaving machine. Improvements which more uniformly spread the fibers of rovings used in fabrics would desirably reduce weight and cost, and more efficiently use the strength of the fibers. Such reinforcement fabrics are further used in the production of honeycomb materials which would similarly benefit from more uniformly spread fibers in the fabric layers which make up the honeycomb.
Fiber spreading processes are known in which rovings or zero twist yarns (both also referred to as tows) are resin impregnated and passed over a series of highly polished rolls to spread the width of the tow. Such methods for spreading fibers rely on the impregnant providing greater lubricity between fibers in the tow. Other methods of pneumatically opening fibrous tows are known in the art. However, the fibers so opened are only temporarily spread to permit the addition of a coating or other material, and are recombined into a tow.
Accordingly, the need exists to provide apparatuses and processes to more uniformly spread the fibers in a tow for use in existing apparatuses, processes and products.
SUMMARY OF THE INVENTION
The present invention satisfies that need with a fiber spreading process and apparatus which is capable of spreading a tow to provide a tow, web or ribbon of spread fibers having a lower areal weight. Input rovings or zero-twist yarns may be spread in-line in weaving or other fabric forming operations, or off-line in preparation for weaving or other fabric forming operations. In any event, spread fiber tows, webs or ribbons produced in accordance with the present invention will permit the production of fabrics having lower areal weight.
In accordance with the present invention, a process for spreading fibers is disclosed comprising the steps of moving an input tow of fibers generally in a machine direction along a tow path, contacting the tow with a plurality of spaced pins and moving the pins in the machine direction with the tow, then varying the spacing of the pins relative to the machine direction, and spreading the tow of fibers from a first areal density to a second areal density. After spreading the tow, the pins are removed from contact with the tow, which remains in a more uniform, spread condition.
A fiber spreader apparatus is further disclosed in accordance with the present invention. The fiber spreader spreads a tow of fibers moving in a machine direction, and comprises a plurality of spaced pins, where the spacing between the pins is variable relative to a machine direction, and the position of the pins is variable relative to the machine direction. The spacing and position of the pins are variable when the pins are moved generally in the machine direction. As a result, a tow moving in the machine direction along a tow path defined through the apparatus may be contacted by the pins, and spread by varying the spacing of the pins during such contact into a more uniform tow.
In addition, the present invention further includes a tow having a second areal density spread from a first input tow, where the second areal density is a lower, more uniform areal density. In accordance therewith, the spread fiber tow may also be a generally flat ribbon, or a web which is coated, treated or pre-impregnated, or may be adhered to a web of other material.
These and other objects and features of the present invention will become apparent from the drawings and detailed description below.
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Cole Elizabeth M.
Eckert Inger H.
Owens Corning Fiberglass Technology, Inc.
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