LOW PERMEABILITY FABRIC

Abstract

A tubular stuffer element for a plurality of coiled monofilaments interweaved and interconnected with pintels and having open spaces therebetween to form a fabric which is heat set. Tubular stuffer elements are inserted in the space between the coiled monofilaments. The glass transition temperature Tg of the material for the tubular stuffer elements is selected to be at approximately the heat set temperature for the coiled monofilaments so that the stuffer elements are deformed to fill the central portions of the coiled monofilaments.

Description

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a coil link fabric, and, more particularly, to such a fabric having stuffers inserted into open areas to reduce the permeability of the fabric.

2. Description of the Related Art

Fabrics wound with coiled filaments that require lower permeability such as used in dryers, PMC, and other non-woven industries are stuffed with fibers of the monofilament or multifilament type to fill the open spaces in the coils of the fabric. These stuffers may be braided or extruded, and in a variety of elongated solid geometric shapes. When significantly lower permeability is required, it is difficult to seal all the openings in the fabric. This is because the fabric needs to be stuffed and then heat set to a high temperature to shrink the coiled fabric onto the stuffer and close the open spaces in the fabric structure. The complex geometric shapes used in the past are difficult to insert in the open spaces. Even with the elaborate procedure to fill the open spaces, the resultant permeability is still not low enough because the stuffers do not conform to the curved and intricate shapes of the coiled monofilaments.

What is needed in the art is a fabric of the above type having a significantly lower permeability and which is made using a simplified process.

SUMMARY OF THE INVENTION

The invention, in one form, is directed to a fabric having a plurality of coiled monofilaments arranged in side-by-side intermeshing relationship and having elongated pintles extending through intermeshed portions of the coils. Elongated tubular stuffer elements extend through central portions of each of the coils. The monofilaments are heat set to form the fabric and the stuffer elements are formed from a material having a glass transition temperature at around the temperature at which the monofilaments are heat set so that the stuffer elements deform to fill voids between the coil elements.

The invention, in another form, is directed to a method for forming a low permeability fabric having the steps of arranging a plurality of coiled monofilaments in side-by-side intermeshing relationship. Pintles are extended through intermeshed portions of the coiled monofilaments and tubular stuffer elements are extended through central portions of the coiled monofilaments. The monofilaments are heat set at an elevated temperature with the tubular stuffer elements formed from a material having a glass transition temperature at about the elevated temperature for the coiled monofilaments, whereby the tubular stuffer elements are deformed to fill the central portion of the coiled monofilaments.

BRIEF DESCRIPTION OF THE DRAWINGS

The above-mentioned and other features and advantages of this invention, and the manner of attaining them, will become more apparent and the invention will be better understood by reference to the following description of embodiments of the invention taken in conjunction with the accompanying drawings, wherein:

FIG. 1 is an enlarged side view of a coiled fabric showing a stuffer element in place in the coiled fabric;

FIG. 2 is a side view of the stuffer element of FIG. 1 after a heat setting process for the fabric;

FIG. 3 is an enlarged side view of the fabric of FIG. 3 after the heat set condition;

FIG. 4 is an enlarged plan view of the stuffer element in the heat set condition of FIG. 3 without the coiled fabric;

FIG. 5 is an enlarged side view of the stuffer element of FIG. 4; and,

FIG. 6 is an enlarged cross-section of an alternate tubular stuffer element for use in a coiled fabric.

Corresponding reference characters indicate corresponding parts throughout the several views. The exemplifications set out herein illustrate embodiments of the invention and such exemplifications are not to be construed as limiting the scope of the invention in any manner.

DETAILED DESCRIPTION OF THE INVENTION

Referring now to the drawings, and more particularly to FIG. 1, there are shown a plurality of tubular stuffers 10 in place in a fabric 12 formed from a plurality of coiled monofilaments 14 intermeshing to form a continuous loops in the MD (machine direction). The fabric 12 is formed to provide a belt and the elongated portion of the belt is in the MD. At the intersections 16 of the coiled filaments there are a series of pintles 18 which extend in a CMD (cross machine direction). As shown in FIG. 1 the CMD is at right angles to the plane of the figure. In other words, the CMD is crosswise to the elongated belt. The coiled monofilaments are made from a variety of polyester material such as [Name of Product] manufactured by [Name of Company]. It should be apparent that other materials may be employed for the coiled monofilaments with equal results. The materials for fabric 12 are selected so that they can be heat set to reduce the open spaces and decrease the permeability.

After the coiled monofilaments 14 are interweaved and the pintels 18 are inserted, the tubular stuffers 10 are inserted in a CMD fashion. The material of the stuffer element 10 is a polymer selected from a broad range of materials so that its glass transition temperature T_g is approximately at the temperature at which the polyester monofilaments are heat set. Examples of polymers used for this purpose may be polyethylene terephthalate (PET), PCTA, polyphenylene sulfide (PPS), flurolpolymers and nylons.

The coiled polymer monofilaments 14 have a heat set temperature around approximately 420° to 460° F. The glass transition point is defined as T_g is the temperature below which molecules have little relative mobility. Above T_g, secondary non-covalent bonds between polymer chains become weak in comparison to thermal motion and the polymer becomes rubbery and capable of elastic or plastic deformation without fracture. The glass transition temperature T_g is below the melting temperature T_m. It is the selection of a material with a glass transition temperature T_g to deform and fill the voids in the coiled monofilaments to more effectively reduce permeability during the heat set process of the fabric 12. Because the stuffer elements 10 are tubular, they are much more able to be deformed in the machine direction (MD) then a solid stuffer would be.

This is shown in FIGS. 2 and 3 which are highly magnified views of the fabric 12 of FIG. 1. It can be seen that the stuffer element 10 has greatly expanded in the machine direction (MD) to almost completely fill the voids between the coils of the coiled monofilaments. The tubular stuffer 10 has deformed to the point that it essentially closes the interior central portion of the tube. By providing the stuffer 10 in tubular form it more readily flattens to fill up the central portions of the coiled monofilaments 14.

FIGS. 4 and 5 show the ultimate form of the stuffer elements 10 after experiencing the heat setting of the coiled monofilament fabric 12. The width in the machine direction (MD) in FIG. 4 is greatly increased relative to the original circular shape shown in FIG. 1 and has lands 22 to more intimately conform to the coiled monofilaments. The side view shown in FIG. 5 shows that the stuffer element 10 expands to embrace the individual monofilaments in the direction that is a measure of thickness of the belt so that a series of recesses 24 are formed in stuffer element 10. Such an application of the tube stuffer 10 enables reductions in permeability significantly greater than previously accomplished enabling a permeability of around 60 CFM compared to permeability of around 175 CFM with prior art stuffers.

The configuration of the tubular stuffer element 10 may be circular in cross-section or have an oval shape 20 as shown in FIG. 6 and other cross-sections to fill the voids between the coiled monofilaments 14. The thickness of the tube may be selected from a wide range including a thick or thin wall tubing as needed for the particular application.

While this invention has been described with respect to at least one embodiment, the present invention can be further modified within the spirit and scope of this disclosure. This application is therefore intended to cover any variations, uses, or adaptations of the invention using its general principles. Further, this application is intended to cover such departures from the present disclosure as come within known or customary practice in the art to which this invention pertains and which fall within the limits of the appended claims.

Claims

1. A fabric comprising:

a plurality of coiled monofilaments arranged side-by-side in intermeshing relationship;

elongated pintles extending through intermeshed portions of said coil; and

elongated stuffer elements extending through central portions of each of said coils in between adjacent pintles, said stuffer elements being tubular, said monofilaments being heat set to form said fabric, said stuffer elements being formed from a material having a glass transition temperature at around the temperature at which said monofilaments are heat set whereby said stuffer elements deform to fill voids between said coiled monofilaments.

2. A fabric as claimed in claim 1, wherein said tubular stuffer elements are formed from a polymer.

3. A fabric as claimed in claim 1, wherein said coiled monofilaments are polyester.

4. A fabric as claimed in claim 1, wherein said tubular stuffing elements are selected from the group consisting of polyethylene terephthalate, PCTA, polypheylene sulfide, fluorpolymers and nylon.

5. A fabric as claimed in claim 1, wherein said tubular stuffer element has a thin wall.

6. A fabric as claimed in claim 1, wherein said tubular stuffer element has a circular cross section.

7. A fabric as claimed in claim 1, wherein said tubular stuffer element has a non-circular cross-section.

8. A fabric as claimed in claim 7, wherein said tubular stuffer element has an oval cross section.

9. A fabric as claimed in claim 1, wherein said fabric is in an elongated belt and said tubular stuffer elements extend crosswise relative to said belt.

10. A method for forming a low permeability fabric comprising the steps of:

arranging a plurality of coiled monofilaments in side-by-side intermeshing relationships;

extending pintles through intermeshed portions of said coiled monofilaments;

extending tubular stuffer elements through central portions of said coiled monofilaments in between adjacent pintles;

heat setting said monofilaments at an elevated temperature, said tubular stuffer elements being formed from a material having a glass transition temperature at about the elevated temperature for said coiled monofilaments whereby said tubular stuffer elements are deformed to fill the central portions of said coiled monofilaments.

11. A method as claimed in claim 10, wherein said tubular stuffer elements are formed from a polymer.

12. A method as claimed in claim 10, wherein said monofilaments are formed from polyester.

13. A method as claimed in claim 10, wherein said tubular stuffer elements are formed from the group consisting of polyethylene terephthalate, PCTA, polypheylene sulfide, fluorpolymers and nylon.

14. A method as claimed in claim 10, wherein said tubular stuffer elements have a thin wall.

15. A method as claimed in claim 10, wherein said tubular stuffer elements have a circular cross-section.

16. A method as claimed in claim 10, wherein said tubular stuffer elements have a non-circular cross-section.

17. A method as claimed in claim 16, wherein said tubular stuffer elements have an oval cross-section.

18. A method as claimed in claim 10, wherein said monofilaments are arranged to form an elongated belt and said tubular stuffer elements extend crosswise relative to said belt.