US 3256130 A
Description (OCR text may contain errors)
United States Patent O 3,256,130 MULTI-BREAK FABRIC .lohn L. Nisbet and Hubert C. Woodall, Jr., Winston- Salem, N.C., assignors to Carolina Insulatiug Yarn Company, Winston-Salem, N.C., a corporation of North Carolina Filed Aug. 3, 1961, Ser. No. 129,081 2 Claims. (Cl. 161-89) The present invention relates to a system of lfibers having controlled strength and stretch characteristics. More specifically the present invention provides an arrangement of fibers such as glass fibers which are disposed in a predetermined pattern so as to constitute a mat or fabric having a predictable stretch and strength characteristic in all or in predetermined directions.
It is well known that many fibers, both organic and inorganic have characteristics which make such fibers desirable for incorporation' as reinforcement in impregnated or laminated materials. Metal fibers, for example, have high strength but low elasticity characteristics. The present invention provides a fabric and method of forming an elastic material using nonelastic reinforcement. While glass fibers are used in the specific example given herein it will be recognized that other fibers possess similar characteristics and could be used in like manner.
Glass fibers have many desirable characteristics for certain purposes. They possess good electrical insulating properties, high strength to weight ratio, high thermal resistivity and are resistant to oils, acids and corrosive atmospheres. Glass fibers do not, however, possess any appreciable elasticity and hence, fabric woven from such fibers will not stretch in order to conform to shapes having, for example, double curvatures. This characteristic presents a problem when fabrics are made up of woven glass fiber inmpregnated with rubber or any other material. strong and possess good electrical insulating characteristics but do n-ot conform to shapes having curvatures requiring stretchability.
It is also desirable to provide a material in the form of a mat or fabric providing a multi-break material which will give or -break certain fibers on initial tension and will maintain its continuity through the medium of a second set of fibers until a predetermined percent of elongation is reachedwhereupon a third set of fibers is relied upon for strength and continuity. In this manner material may be fabricated having predictable stretch characteristics in which an initial impact will cause the material to give by breaking a certain set of fibers but in which the impact will be contained by ahigh strength, controlled elasticity final set of fibers. Additional sets of fibers may be provided if desired.
Materials have :been designed heretofore utilizing woven glass fiber impregnated with rubber or other suitable compound. In order to give such materials some degree of stretchability the glass fiber-fabric is inserted on the bias. This type of material has a degree of flexibility but the fabric usually must be spliced along its length because of the bias fabric, also the width of the fabric decreases -appreciably when the material is elongated.
According to the present invention there is provided a mat or fabric comprising a first system of glass fiber yarns which are arranged in a curved pattern with a second system of warp yarns knitted to retain the glass fiber yarns in their predetermined pattern Within the mat or fabric. The third warp yarn system may be of a different material containing less geometric extensibility and different strength characteristics than the fibers used in the first system. The elongation of the fabric can be controlled during impregnation or coating and when Such fabrics, if not biased, are unusuallyY is shown in FIG. 1.
3,256,130 Patented June 14, 1966 the material must be stretched to conform to a desired shape certain of the warp yarns will break to permit the material to assume the desired configuration. The ultimate strength of the material is not adversely affected by this breaking of certain warp yarns since the glass fibers forming the first system and constituting the principal strength of the reinforcement are still' present in continuous form. Furthermore, the warp yarns, while broken and not continuous over great lengths of the fabric, are present and do add to the overall strength of a coated or impregnated material. Thus, the present invention provides a means whereby the desirable characteristics of glass fibers may be incorporated in a material having the additional desirable characteristic of stretchability at the desired time.
The present invention finds application as a laminating media where it is desirable that the fabric give slightly under an initial impact but that the ultimate strength of the material be high to prevent penetration by the impacting object. The formability of the invention lends itself to products having double curvatures.
A11 object of the present invention is to provide a fabric or mat having multiple break characteristics.
Another object of the present invention is to provide a fabric or mat having a plurality of systems of fibers including glass bers, the various systems of fibers having varying strength and elastic characteristics so that one set `of fibers yields under a predetermined tension Without adversely affecting the ultimate strength of the material.
Still Vanother object of the present invention is to provide an insulating material having .a plurality of systems of fibers impregnated or coated therein, including glass fibers, the material being stretchable by virtue of breaking one or more sets of fibers, the glass fibers forming the ultimate strength of the reinforcement remaining in continuous form.
Other objects and many of the attendant advantages of the present invention will becomemore fully apparent upon consideration of the following detailed specification in -connection with the accompanying drawings wherein:
FIG. 1 is a plan view of one embodiment of a fabric according to the present invention and,
FIG. 2 is a knitting diagram of the fabric shown in FIG. 1.
The present invention comprises a plurality of individual systems of fibers which are arranged in a predetermined pattern so as to constitute a mat of set pattern and having controlled strength and elongation characteristics.
A fabric according to one embodiment of the invention, It can be seen that this fabric is composed of warp yarns 1 and 2 which form a support for the sinusoidally curved yarns 3.
yThe particular fabric shown is made on a warp knitting machine and the knitting diagram for -this particular fabric is shown in FIG. 2. It can be seen that the yarn 1 is knitted, being wrapped around the needles alternately in opposite directions. The yarn 2 is passed on either side of the needle in each course. The yarn 3 is laid in the warp yarns and is shifted laterally in each course in alternate directions so as to have a sinusoidal form as shown. In the particular example disclosed the yarn 1 is 40 denier polyester, the yarn 3 is /2/ 2 glass fiber and the yarn 2 is 900/1/2 glass fiber. The fabric disclosed in FIG. l may be impregnated with a material such as a silicone rubber when used as a tape. Since the fibers are of a controlled thickness and the pattern of fibers is generally uniform throughout the length of the fabric, the tape'will be of uniform thickness throughout. When such a material is wrapped around an irregularly shaped object, the yarn 2 will initially break for the reason that, in the particular fabric disclosed, these fibers are glass and in this design have a straighter configuration whereas the fibers 1 are of polyester and possess greater elasticity. Thus, the yarns 2 comprise a first system of bers which break to give the reinforced material a degree of elasticity. If greater extensibility is required than is derived from a breaking7 of the yarns 2, the yarns 1 of polyester may also break and the reinforced tape may be stretched until the fibers 3 are extending substantially longitudinally of the tape. The strength characteristics of the impregnated material are not adversely affected by the breaking of the warp yarns since these yarns are still in the tape and the ultimate strength of the tape is based on the presence of the glass fibers 3.
It should be recognized that the specific pattern of the fabric may be varied to suit'varying operational requirements. It is possible to utilize yarns of different size and materials in place of the yarns 1 and 2. The glass fiber yarns 3 may be arranged in any suitable pattern and it is only necessary that these yarns be supported by the knitted warp yarns and be disposed in a pattern to give the resulting fabric the desired ultimate strength and extensibility characteristics.
It will be noted that none of the yarns in this disclosed embodiment extend across the entire width of the material. This prevents wicking occurring across the width of any fabric so constructed and where slit or coated it does not destroy the integrity of the material.
it is also possible to construct a fabric in accordance with the present invention wherein the yarns used to retain the ultimate strength fibers in place during manufacture of the impregnated material may be subsequently removed from the material. That is to say, the yarns 1 and 2 which retain the yarns 3 in a predetermined pattern may be made of a material which by subsequent chemical treatment will be dissolved so that the fabricated material will contain only the yarns 3. It is also within the realm of the present invention to thermally fuse the warp yarn after the material is impregnated so as to provide a material having substantial elasticity and possessing the strength characteristics of tape reinforced with glass fiber.
It is also possible according to the present invention to break the yarns 2 by passing the impregnated tape between a pair of differential rollers, the second pair being driven at a greater speed than the first pair so that the tape is tensioned therebetween. This controlled tension will break the yarns 2 and give the tape the desired degree of elasticity.
It can be seen that the present invention provides a fabric in the nature of a mat wherein the strength and elongation characteristics are controlled and readily predictable. According to this general embodiment one or more systems of warp yarns are used to retain one or more sinusoidally or otherwise disposed systems of glass fibers in place and these retaining systems break under tension, thereby providing the material with a certain elasticity and the ability to conform to shapes requiring stretch in more than one direction. The remaining unbroken yarns provide the ultimate strength of the material and these yarns are maintained in continuous form up to the ultimate strength points of the material.
Obviously many modifications and variations of the present invention are possible in light of the above teachings.
What is claimed as new and desired to be secured by Letters Patent is:
1. An impregnated material having at least three systems of fibrous material, a first set of nonelastic high strength fibers forming a first set of yarns running warpwise of the fabric, a second set of elastic relatively low strength fibers forming a second set of yarns knitted in separate courses, a third set of nonelastic high strength fibers forming a third set of yarns extending in a zigzag pattern warpwise of the fabric, said second set of yarns knitted to retain said first and third sets of yarns and said first set of yarns maintaining said third set of yarns in said zigzag pattern, said first set of yarns of the impregnated material adapted to be disrupted so as to permit the impregnated material to stretch to the length of the third set of yarns.
2. A tape comprising an impregnated fabric, the fabric including a first set of yarns extending warpwise of the fabric, said first set of yarns comprising nonelastic high strength glass fibers, a second set of yarns knitted in separate courses, said second set of yarns comprising relatively elastic low strength synthetic fibers, and a third set of yarns extending in a zig-zag pattern through the separate knitted courses of the second set of yarns, said third set of yarns comprising non-elastic high strength glass fibers, said first set of yarns adapted to be disrupted so that said tape is extensible to the elastic limit of the second set of yarns, said second set of yarns adapted to be disrupted so that the tape is extensible to the full length of the zig-zag third set of yarns.
References Cited by the Examiner UNITED STATES PATENTS 2,142,908 1/1939 Mendel 66-193 2,539,301 1/1951 Foster 28-72 2,587,117 2/1952 Clay 23-7 2,831,235 4/1958 Taylor 28--7-1r 2,879,581 3/1959 Evans et al. 28-80 2,913,801 11/1959 Kessler et al. 28-74 2,956,331 10/1960 Whitehead 28-80 2,967,415 1/1961 Ford et al 66-193 3,106,079 10/1963 Kohl 66-193 3,127,306 3/1964 Turton et al 66-202 X FOREIGN PATENTS 273,935 8/1951 Switzerland.
ROBERT R. MACKEY, Acting Prima/'y Examiner.
RUSSELL C. MADER, DONALD W. PARKER,
H. G. GARNER, P. C. FAW, Assistant Examiners.