US3395744A - Reinforcing fabric for tires - Google Patents

Description

6, 1968 a. M. WOLF ET AL REINFORCING FABRIC FOR TIRES Filed Feb. 4, 1966 United States Patent f 3,395,744 REINFORCING FABRIC FOR TIRES Burton Myer Wolf, Wadsworth, and Jerry Karl Reber and Robert Charles Purcell, Akron, Ohio, assiguors to The Firestone Tire & Rubber Company, Akron, Ohio,

a corporation of Ohio Filed Feb. 4, 1966, Ser. No. 525,069 6 Claims. (Cl. 152-358) ABSTRACT OF THE DISCLOSURE This disclosure relates to a novel reinforcing fabric construction which contains warp cords and weft threads with the warp cords comprised of standard cord material, such as rayon, nylon and polyesters, and with the weft threads comprised of unoriented linear crystalline resinous material, such as nylon, having an elongation greater than 50% and which is particularly well suited for use as a reinforcing fabric in vulcanizable articles, specifically in pneumatic tires.

This invention relates to woven fabric containing warp cords and weft threads, and specifically to the type of fabric used in the manufacture of tires.

The weft threads may also be referred to as pick or filling threads, but for convenience we will use the term weft thread throughout. The sole function of the weft threads is to hold the Warp cords in their proper places, keeping the warp cords uniformly spaced and from touching one another. However, in order to retain the relative strength of the fabric in a direction longitudinally along the warp axis, the weft threads must, of necessity, be relatively small, frail threads as compared to the warp cords. The weft threads must be strong enough to hold the warp cords in place and yet not so strong as to cause the fabric to lose its directional strength or to cause sawing of the warp by the weft.

This type of weak weft fabric described above is the major type of fabric used in the manufacture of tires. Two of the major problems encountered in the use of this weak weft fabric in the manufacture of tires are: (1) the loss in the processing (calendering, dipping, etc.) of the edges of the fabric due to the breakage of the weft threads caused by the crimping -or folding over of the fabric edges; and (2) the breakages of the weft threads resulting from the lateral expansion of the fabric during the tire shaping process prior to the molding and curing of the tire. The failure in both cases is the breakage of the weft threads, resulting in the loss of control It over the warp cords and consequent non-uniform distribution of the warp cords. In the first case, the sections of the fabric which contain broken weft threads must be segregated and scrapped as they are unacceptable for use. In the latter case, the entire tire must be scrapped due to the non-uniform distribution of the warp cords.

It is an object of this invention to eliminate these two defects caused by weft breakage, that is, the fabric edg loss in processing and the tire loss in shaping.

Although the breaking of weft threads during expansion of a green tire (uncured tire) is not uncommon during the manufacture of tires embodying conventional fabric bias angles, this problem has become serious in the production of tires of the radial ply type. This problem is particularly troublesome in connection with the manufacture of radial tires of large section Widths passenger tires of 7.50 inches section Width and larger, and truck tires, and otf-the-road tires. In the building of such tires the lateral expansion demanded of the fabric plies is very severe. The conventional weft threads are not adequate and frequently break, resulting in a non- 3,395,744 Patented Aug. 6, 1968 ICC uniform end count of the warp cords. When the weft cords break, instead of the tire fabric expanding uniformly with an even distribution of the warp cord end count, the fabric merely splits at the break, resulting in gaps in the fabric at these breaks and unwanted high concentrations of warp cords in the unbroken weft areas, because the weft still restrains the warp cords in these areas,

In the acocmpanying drawing:

FIG. 1 is a plan view of a portion of a sheet of fabric embodying the present invention;

FIG. 2 is a cross-sectional view of a portion of a calendered sheet of fabric used for the manufacture of tires embodying the present invention;

FIG. 3 is a cross-sectional view of a tire embodying the present invention.

Referring to FIG. 1, a tire-reinforcing fabric 10 contains warp cords 11 and weft threads 12.

Referring to FIG. 2, the warp cords 11, shown in cross-section, are held in spaced, parallel relation by weft thread 12. Both the warp cords and weft threads, as well as the fabric comprising them, are encased in and coated by a rubber skim coat 13, which is applied to the fabric by any known process, as by calendering; as by spreading a plastic rubber composition onto the fabric followed by consolidation of the coating into and onto the fabric by heating and/ or pressing; or as by dipping the fabric in a suitable fluid rubber composition followed by consolidation of the resulting coating into and onto the fabric.

Referring to FIG. 3, a tire 14 is comprised of two annular wire beads 15, sidewalls 16, a tread 17 and fabric body plies 18. The tire may, optionally, contain tread plies 19. The fabric of this invention is employed in body plies 18, and also, optionally, may be used in tread plies 19. The disclosure of four body plies and two tread plies is not intended in any way to limit the scope of the invention, as it is common in the art to use various numbers of plies, both body and tread, depending on the size and intended use of the tire. Optionally a tire of the invention may omit one or both side-walls, or it may be a peg-leg tire with only one sidewall.

As has been stated, the sole function of the weft threads is to hold the warp cords fixed so the warp cords will be and remain evenly spaced and not touch one another. In the past, weft threads have been very frail cotton or rayon threads. The usual cotton weft threads are 30s in the cotton numbering system, and have an elongation at break of approximately 12 percent, and a normal tensile of 285 grams, both under standard laboratory conditions. The weft thread of rayon is usually of denier of continuous filament and has an elongation of approximately 15 percent at break and a normal tensile of 200 grams, both under standard laboratory conditions.

The inventors have found the elongation, not the tensile strength, to be the critical property required to obviate weft thread breakage. The objects of this invention are accomplished by use of a weft thread capable of a uniform elongation to at least 50 percent (the estimated lateral expansion in a radial tire) of its original length without breakage, and preferably of elongation to about 300 percent. Through use of a weft thread of this nature, the invention results in decreasing the amount of defective fabric edges during processing, because the new weft thread does not break when the fabric edges are folded over, but merely elongates or gives, thereby permitting the edges to be unfolded without breakages of the weft thread. Also the new weft thread does not break during the high lateral expansion demanded in tire manufacture, but due to its high elongation the thread merely elongates uniformly, thereby obviating any loss due to weft thread breakage during tire expansion. This latter advantage of the invention has allowed the manufacture of large section radial tires free from the previous persistent defect of uneven warp cord end count.

The materials useful as weft threads in this invention are filaments or threads comprising unoriented or partially unoriented linear crystalline resins possessing a high degree of elongation (greater than 50 percent).

A form of nylon, commonly referred to by the art as unoriented (undrawn) nylon has been found to be particularly successful in this invention. The nylon is of the type described in US. Patents Nos. 2,071,250, 2,071,253, 2,130,523 and 2,241,321. The material is usually used as 100 denier yarn or threads and typically has an elongation at break of 500 percent and a normal tensile of 180 grams (as compared to the 200 gram normal tensile of the prior art). The critical property is the elongation. An acceptable weft material may have tensile strengths varying over a wide range as long as it is adequate to control the warp cords and possesses the necessary minimum elongation.

The weft threads of the invention can consist essentially of other linear crystalline resins possessing the proper elongation property required in this invention when in an unoriented state. Examples of suitable resins are, without intending to limit:

(A) polyester of the type described in US. Patent No.

(B) blends of nylon and linear polyester;

(C) polyethylene of the type described in US. Patent (D) polypropylene of the type described in US. Patent Nos. 3,112,300 and 3,112,301;

(E) polyvinylidene chloride of the US. Patent No. 2,183,602; and

(F) polyurethanes.

It is understood that the problem of adhesion to rubber may be encountered with the use of the polyurethanes.

The weft threads of the invention are suitably formed of any one or more of the resins disclosed above as appropriate for use in the invention. Specifically, the weft threads may be made of one of the above-identified materials or a blend of one of the aboveddentified materials with another of the above-identified materials. The weft threads can be a single filament. or it can be formed of multiple filaments or yarns. Other thread sizes than the 100 denier threads disclosed above are useful in the invention, for example, threads in the range of about 50 to 200 denier.

type described in The warp cords employed in this invention may be any of the known high-strength tire cords of synthetic fibers such as rayon, nylon, linear polyesters, blends of nylon and polyesters, polyurethanes, etc.

Other modifications will be obvious to persons in the art without departing from the scope of this invention.

We claim:

1. A tire comprising a tread, two annular beads, and a body portion, the body portion comprising a reinforcing fabric resistant to breakage of weft threads, said fabric comprising warp cords and Weft threads, said weft threads having an elongation of at least 50% and comprising at least partially unoriented, crystalline linear resinous material.

2. The tire of claim 1, wherein the at least partially unoriented, crystalline linear resinous material is selected from the group consisting of a nylon, a polyester, a blend of a nylon and a polyester, a polypropylene, a polyethylene, a polyvinylidine chloride, and a polyurethane.

3. The tire of claim 1, wherein the at least partially unoriented, crystalline linear resinous material is nylon.

4. A vulcanizable rubber article having a vulcanizable rubber coated reinforcing fabric resistant to breakage of weft threads, said fabric comprising warp cords and weft the .at least partially unoriented, crystalline linear 50% and comprising at least partially unoriented, crystalline linear resinous material.

5. The vulcanizable rubber article of claim 4, wherein the at least partially unoriented, crystalline linear resinous material is selected from the group consisting of a nylon, a polyester, a blend of a nylon and a polyester, a polypropylene, a polyethylene, a polyvinylidine chloride, and a polyurethane.

6. The vulcanizable rubber article of claim 4, wherein the at least partially unoriented, crystalline linear resinous material is nylon.

References Cited UNITED STATES PATENTS 2,475,588 7/ 1949 Bierman.

3,207,654 9/1965 Reilly 57140 XR 3,305,911 2/1967 Chapman et a1. 2872 FOREIGN PATENTS 610,171 10/ 1948 Great Britain.

JOHN PETRAKES, Primary Examiner.

UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTION Patent No. 3,395,744 August 6, 1968 Burton Myer Wolf et a1.

It is certified that. error appears in the above identified patent and that said Letters Patent are hereby corrected as shown below:

Column 4, line 26, "the at least partially unoriented, crystalline linear" should read threads, said weft threads having an elongation of at least Signed and sealed this 30th day of December 1969.

(SEAL) Attest:

Edward M. Fletcher, J r.

Attesting Officer Commissioner of Patents WILLIAM E. SCHUYLER, JR.

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