US3682221A

US3682221A - Tire construction with improved reinforcement

Info

Publication number: US3682221A
Application number: US807318A
Authority: US
Inventors: Alfred Marzocchi; Alfred Winsor Brown
Original assignee: Individual
Current assignee: Individual
Priority date: 1969-03-14
Filing date: 1969-03-14
Publication date: 1972-08-08
Anticipated expiration: 1989-08-08

Abstract

Tire construction featuring as the principal reinforcement a combination of chopped bundles or cords, each composed of an assembled plurality of glass filaments held together, and chopped discrete glass filaments distributed throughout the rubbery matrix generally uniformly, preferably at a level of about two to about thirty-five parts of glass per one hundred parts of rubber and preferably with the bundles exceeding the discrete filaments in amount on a weight basis.

Description

15] 3,682,221 1 51 Aug. 8, 1972 United States Patent Marzocchi et al.

[56] References Cited UNITED STATES PATENTS 2,056,012 9/1936 Madge et al. ..............l52/355 2,557,778 6/1951 Barry........................161/208 3,077,915 2/1963 Weber.......................152/355 3,398,045 8/1968 Clayton et al..........l52/330 X [22] Filed:

Primary Examiner-Drayton E. Hoffman Attorney-StacIin & Overman and Paul F. Stutz 211 App]. No.1 807,318

[57] ABSTRACT Tire construction featuring as the principal reinforce- Related US. Application Data [60] Continuation-in-part of Ser. No. 699,193

,Jan. 19 1968, abandoned, and a continuatiomm ment a combination of chopped bundles or cords, part of Set. NO. 622 588 March 13 1967 Pat. each assembled glass No. 3,433,689, whidh is a division 6r Ser: NO. mems l E and glass 450,790, April 26, 1965,Pat. N0. 3,315,722. d'smbuted hmughwt rubbery mam generally uniformly, preferably at a level of about two to about thirty-five parts of glass per one hundred 51.2.8]....................l52/357, 152/354, 152/9136; parts of rubber and preferably with the bundles ceeding the discrete filaments in amount on a weight basis.

[58] Field of Search......

11 Claim, 12 Drawing figures PATENTEDmc 8 I912 3.682.221" sum 2 0F 7 A r TOIPA/E KS minnows men 3.682.221

SHEET [1F 7 I Arramvera PATENTEBM B 81912 sum 5 or 7 INVENTORS MA flrrommrs v PATENTEDAUB 81972 3.5 2.221 SHEET 70F 7 INVENTORS ALFRED Nmzoocm PH 1' o RUWS TIRE CONSTRUCTION WITH IMPROVED REINFORCEMENT This is a continuation-in-part of application Ser. No. 699,193, filed Jan. 19, 1968, now abandoned, and application Ser. No. 622,588, filed Mar. 13, 1967, now U.S. Pat. No. 3,433,689; which latter application is a divisional application of application Ser. No. 450,790, filed Apr. 26, 1965, now U.S. Pat. No. 3,315,722; said applications being assigned to the same assignee as the present application.

The present invention relates to an improved tire construction employing a novel reinforcement system and, as well, a method of manufacturing such improved tire.

Over the years, a number of textile materials have been employed as reinforcement components in tire constructions. The earliest tires employed cotton in the form of a fabric; more recently, in the form of bias cut,

mutually parallel cords. More recently, tire manufacturers employed rayon and currently employ nylon as a reinforcing textile. In recent years, polyester, e.g., Dacron, fibers, yarns and strands, and even wire cords, have entered the picture, each contributing its own particular features of advantage. Glass fibers have also been suggested as a reinforcing component for tires. See, for example, the following U.S. Pat. Nos.: 2,184,326, 2,884,040 and 2,894,555.

Many of the textiles mentioned above, in addition to having their inherent advantages, have accompanying disadvantages. Cotton is deficient due to the inherent propensity to undergo moisture degradation. Rayon is not much stronger, is low in modulus and, in addition, is undesirable in certain respects because of its low strength per unit cross sectional area.

Nylon has found considerable acceptance by reason of its increased strength as compared to rayon, coupled with its toughness and high impact resistance which makes it extremely desirable in providing a tough carcass capable of withstanding considerable abuse. Another advantage of using fabric plies composed of synthetic linear filaments such as nylon in tire casings is that the filaments of nylon have a high tensile strength which makes it practical to manufacture heavy duty tires with relatively thin side walls and yet of relatively light weight, whereby less rubber is required and less heat is developed in actual case. Polyester as a reinforcing medium is not fully evaluated as yet, but appear to present some promise as a tire reinforcement.

Nylon, with all of its advantages, is possessed of at least one serious drawback by reason of its thermal character. Thus, nylon fabric, e.g., the nylon cords, tend to progressively and permanently become elongated when the tire is in service due to tension stresses to which the cords are subjected and the heat generated in the tire running under load. This characteristic of nylon cord causes the tire casings to increase in size, which sets up stresses in the treads which cause cracks to develop in the treads, greatly reducing the resistance of the tread to wear. Another ramification of the foregoing is the tendency of the nylon fabric reinforced tire to thump due to so-called flat spotting. This is generally evidenced to the user by the fact that, after parking overnight, the tire cord will, due to the normal temperature drop, become heat set in a somewhat flattened contour caused by the depression on the bottom of the tire in contact with the pavement.

This flat spot causes a noticeable thump" when the car is run again, which albeit gradually disappears as heat is developed due to the load on the tire and the operational speed. This particular phenomena has been greatly credited with the failure of nylon cord tires to be utilized by automobile manufacturers as original equipment.

Conventional fabrics used heretofore are also possessed of the drawback that tires, regardless of the care taken in manufacture, are of irreproducible constant diameter. This is to say that tires produced in difierent factories, even though utilizing the same specification, fabrics, rubber stock, building techniques and cure cycles, will rarely have the same overall dimension. Tires made with conventional fabric plies are also found to experience variable change in dimensions after a given period of road use. This is particularly undesirable in the field of truck tires, since such tires are desirably retreaded. As a consequence, tires to be mounted on dual wheels must be individually paired by the user according to size in order to get an even match which will give satisfactory performance.

conventional fabric (rayon, nylon, etc.) reinforcedv tires of the bias type are generally not as stable as would be desired, particularly on comering. This lack of cornering stability resides in the conventional technique practiced in the design of tires generally Thus, it is conventional in U.S. tire manufacturing to design the carcass construction [composed of a plurality of overlying bias plies], the tread, the side wall and the beads in such fashion that the whole structure functions integrally to define the optimum in wear properties of the tire. Under these design conditions, cornering stability of the tire suffers somewhat. On the other hand, tires of the Michelin type, employing radial cords with a reinforcing wire breaker strip just beneath the tread portion, provide a stability which is greater than tires of the bias type. However, this is accomplished only at a sacrifice in smoothness of ride, e. g., the ride is harsher.

Bias tires employing the conventional fabrics are also beset with the problem of tread movement or squirming as to that portion in contact with the road surface. This frequently results in the tread definition becoming distorted into a configuration inconsistent with that for which tread definition was designed.

With the foregoing general introduction, it may be stated that it is a general object of the present invention to provide a reinforcement system for pneumatic tires which provides features of advantage which in large measure overcome the drawbacks and deficiencies noted hereinabove.

It is another object of the present invention to provide a tire construction employing features of reinforcement which are novel, but yet readily adaptable into conventional tire manufacturing facilities.

It is yet another object of the present invention to provide a system of tire reinforcement which lends a happy marriage between improved wear, minimized flat spotting or thump and improved cornering properties.

It may be stated here parenthetically that stability is also evidenced in a tire in terms of uniform footprint, as it were. In conventional tire constructions employing bias cut ply reinforcement, the footprint of the tire, that the variation in load due to imperfections in the road surface, valleys and crests of the road, cracks in the road,- foreign objects, etc., which all serve to shift the load; On the other. hand, what is more important is the character of the footprint as the tire corners, as it were. Here, a variation in the area of contact, in effect, changes the dynamic relationship of the center of gravity of the automobile and the road. This phenomenon explains why skids occur on cornering, resulting in accidents." Thus, the contour of the footprint changes, particularly in inclement weather, moisture, wet roads,

damp roads, etc. Ideally, on cornering, the footprint should remain the same; namely, describing a generally square outline or, in any event, of rectangular contour. Where one of the sides of the footprint becomes curvilinear, for example, by the wayof opposed intersecting catenary curves, then an unstable condition exists which can prove uncomfortable and even disastrous to the driver, depending upon the speed of the vehicle, the weight of the vehicle and, of course, the condition of the pavement, etc.

It is an object of the present invention to, provide a pneumatic tire including novel and improved reinforcement systems which provides features of advantage in manufacturing as well as service capabilities as compared to conventional tires known heretofore.

It is still another object of the present invention to provide a tire construction which, while representing a considerable departure from conventional reinforcement, is adapted for manufacture in conventional tire I manufacturing facilities.

It is a particular object of the present invention to provide a tire construction featuring a reinforcement which allows elimination of the conventional carcass plies composed of continuous mutually parallel cords of one material or another. I

It is still another particular object of the present invention to provide a tire construction featuring an elastomeric matrix which is possessed static as well as dynamic properties which are larger than conventionally reinforced rubber stocks.

It is a-particular object of the present invention to provide a tire which is possessed of improved traction under icy, snowy and wet conditions.

It is likewise another object of the present invention to provide a tire construction which is relatively inexpensive, albeit the advantages enumerated hereinabove.

It is yet another object of the present invention to provide a tire construction featuring an elastomeric of the mold cavity in which vulcanization takes place.

It is also an object of the present invention to provide a reinforcement system for pneumatic tires which, in conjunction with conventional bias cord reinforcement, permits the attainment of the optimum reinforcement by the cords by reason of an achievement of. a transfer of stresses from the cords in one ply to'the cords in an adjacent ply.

It is also anobject of the present invention to provide.

a tire construction featuring as the principal elastomeric stock reinforcement an amount of glass in chopped form; some of it being in the form of chopped discrete fibers and some, usually the greater amount, in the form of chopped cords.

It is a particular object of the present invention to provide tires which featurerandomly distributed short lengths of glass fibers and short lengths of glass bundles in the tread region to lend resistance to chunking as well as resistance to cut through from foreign objects in the tire path. I 7

It is also an object of the present invention to provide a unique method of producing a tire featuring constructional features in accordance with the presentinventron.

It is still another object of the present invention to provide a tire construction featuring as a reinforcement, alone or in combination with carcass and/or belt plies, an amount of glass in chopped form, either as individual filaments, strands, yarns, cords, or combinations thereof; preferably the latter.

The foregoing, as well as other objects of the present invention, will become apparent to those skilled in the art from the following detailed description taken in conjunction with the annexed sheets of drawings on which there are presented, for purposes of illustration only, several embodiments of the present invention.

The invention will be described in greater detail with particular reference to the annexed sheets of drawings in which:

FIG. 1 is a generally three-quarter perspective view of a tire with the outer rubber ply broken away for purposes of showing the interior reinforcing construction representing a preferred embodiment of the present invention;

FIG. 2 is a view similar to FIG. 1, showing an alternative construction in accordance with another embodiment of the present invention;

' FIG. 3 is a perspective view with a portion broken away, but showing a reinforcing band or belt representing .a component of the reinforcement system illustrated in FIGS. 1 and 2;

FIG. 4 is a view similar to FIG. 3, but showing a modified construction of the reinforcing band in accordance with another embodiment of the present invention;

FIG. 5 is a view similar to FIGS. 3 and 4, but showing yet another alternative variant construction in accordance with yet another embodiment of the present invention;

FIG. 6 is a schematic side elevational view illustrating a manner of performing one method in accordance with the present invention;

FIG. 7 is a top plan view of the apparatus schematically illustrated in FIG. 6;

FIG. 8 is a perspective view of a particular cord construction constituting an assembly of strands composed of different filaments as representing a variant embodiment of the reinforcing system for pneumatic tires in accordance with the present invention;

FIG. 9 is a perspective view similar to FIGS. 1 and 2 and illustrating an alternative construction embodying a reinforcing system in accordance with another embodiment of the present invention; and

FIG. 10 is a schematic side elevational view illustrating one manner of assembling a restrictive band construction representing one embodiment of the present invention.

FIG. 11 is a three-quarter perspective view of a U cross-sectional segment of a tire featuring a reinforcement system in accordance with the present invention;

FIG. 11A is a perspective view of a segment of rubber sheet good illustrating another embodiment of the present invention;

FIG. 12 is a similar view of a segment of a tire representing an alternative embodiment of the present invention; and

FIG. 13 is a greatly enlarged view of a segment of the cross-sectional face of the tire of FIG. 12.

In accordance with one embodiment of the present invention, a tire construction embodies, as essentially the sole reinforcement (other than carbon black and the like) a chopped glass reinforcement; a proportion of which is in the form of bundles composed of an assembled plurality of individual filaments held in bundle configuration by an elastomeric impregnant and a proportion composed of a plurality of discrete individual filaments of glass of extremely short length.

In accordance with another embodiment of the present invention, the rubber composition or elastomeric composition containing the combination of bundles and filaments is incorporated into a tire construction in particular regions. For example, when present in the tread region, the elastomeric composition containing both bundles and fibers imparts to the tire the capabilities of improved traction and, as well, wear and endurance.

In accordance with another embodiment representing a broad scope of the present invention, a tire features as essentially the sole reinforcement (other than carbon black and the like) an amount of glass in the form of relatively short length of either filaments, strands, yarns, cords, bundles, or the like, preferably bearing an anchoring agent and most preferably, additionally, an elastomeric coating.

In a further embodiment of the present invention, a tire construction, composed of a bias ply carcass featuring mutually parallel cords and one or more belt plies situated between the carcass plies and the tread and coextensively therewith, contains, in addition, in adjacent proximity to the bias plies and the belt plies, a layer which contains a combination of the chopped glass, a proportion of which consists of bundles of assembled filaments and a proportion of which consists of discrete individual filaments, all distributed relatively uniformly throughout the layer concerned.

At this point, definition of terms appears in order.

A filament of glass is an individual fiber or solid rod, as it were. A strand, on the other hand, is a collection of a great plurality of individual filaments, usually varying from a grouping numbering in the neighborhood of 104, 208, and even up to SOS-2,000 individual filaments gathered together in a manner well-known in the art and technology of glass fiber manufacture.

A cord, bundle or cable, on the other hand, comprises a plurality of strands, for example, 2 to 30, and even up to 50 strands, plied or assembled together continuously. The strands may be possessed of twist, reverse twist, or no twist. Further, a number of strands of several ply constructions, e.g., three strands, may be combined to yield an ultimate cord having a total number of strands equal to the product of the number of strands in the first assembly and the number of these assemblies that are combined to make up the final cord. As can be appreciated, a cord will be composed of a large number of individual filaments, say in the neighborhood of 300 to 2,000. By way of illustration, a cord construction may feature three strands of continuous filaments gathered together with or without twist. Additionally, 10 of the just-foregoing three-ply strand assemblies may be joined together with or without twist to form, in effect, a 30-strand assembly, each strand being composed, for example, of perhaps a to 200 filaments yielding a 3,000 to 6,000 filament cord", cable or bundle assembly. A 30,000 filament assembly cord is achieved by (l) forming a lO-strand assembly; (2) combining five of these to form a SO-strand assembly; and (3) finally combining three of the latter to yield a ISO-strand cord. The cord designation for the latter is l0/5/ 3.

The present invention envisions a restrictive band featuring the employment of an elastomeric stock system which includes therein both filamentized short lengths of glass fibers and, additionally, unfilamentized or unseparated bundles or cords of glass fibers. Most desirably, the reinforcing fibers and cords are selected of a given range of lengths. It is additionally envisioned that the elastomeric stock system, forming a restrictive band in accordance with the present invention, may contain continuous mutually parallel lengths of strands or cords separated one from the other and perhaps proceeding in spiral fashion or filament-wound fashion about the periphery of the tire radially outwardly of the reinforcement fabric, yet beneath the tread portion. In some cases, the continuous strands are arranged so that they extend into the tread portion where such would be desirable.

To illustrate the potentiality of glass fiber as a reinforcing component of tires in dynamic application, the properties of a single filament of glass fiber are listed in Table I.

TABLE I GLASS FIBER SINGLE FILAMENT PROPERTIES Tensile Strength psi 500,000 Tenacity gpd 15.3 Ultimate Elongation 4.8 Elastic Recovery 100 Toughness psi 1 1,900 Modulus psi 10,500,000 Coefficient of Thermal Expansion 2.8 X l0'F. Water Adsorbency 0.3 Moisture Regain 0.0

While the glass fibers in the form of fibers, strands, cords or bundles can be introduced into the elastomeric stock as is, so to speak, it is most effective for the glass fibers to be first treated or sized, as it were, to provide a protection against interfilament destructive acsubsequent impregnation of the strands or cords as they 4 are formed, usually simply by introducing the gathered filaments into a pool of the treating liquid while simultaneously distorting the strand filaments to efiect penetration into the zones between fibers, thereby insuring complete impregnation. Following impregnation, the coated strands or cords are given a mild heat treatment to set the treating agent. A system of treatment for glass fibers may involve a first surface treatment embodying an anchoring agent which enhances the bonding relationship between the glass fiber surface and the ultimately used elastomeric material. A suitable anchoring agent is represented by the amino silanes such-as gamma-aminopropyltriethoxy silane or by a similar silane having a carboxyl group in the organic group attached to the silicon atom or an amino or carboxyl group in the carboxylato group of a Werner complex compound. These may be applied to the glass fiber surfaces or incorporated as a component of a size composition and applied to the glass fibers as they are gathered together in the formation of strands, yarns or the like; all of which is more fully described in the copending application Ser. No. 406,501 filed Oct. 26, 1964, entitled Glass Fibers Treated For Combination With Elastomeric Materials And Method, now US. Pat. No. 3,39l,052. A desired strong bonding relationship can also be achieved by the impregnation of the strands or other multi-filament glass fiber structure with a composition formulated to contain, in addition, an elastomeric material, preferably in an uncured or an unvulcanized state as described in the aforesaid copending application Ser. No. 406,501, as will hereinafter be illustrated by way of examples.

For purposes of comparison, the following table lists the reinforcement cord properties comparing glass cords with organic cords.

TABLE II REINFORCEMENT CORD PROPERTIES The properties appearing in the foregoing Table II speak generally for themselves. They generally demonstrate the toughness and impact strength of glass fiber cords. This, coupled with their high dimensional stability, demonstrates their great utility. Additionally, this, coupled with their relatively inert character to temperature or humidity changes, makes them a desirable and, in fact, an ideal tire reinforcement material when used in the manner disclosed herein. The problem, of course, has been in converting the well-known static properties of glass fibers into a construction which would endure dynamic stresses. The present invention solves this dilemma by reason of the novel conjoint employment of filamentized short length filaments, unseparated chopped bundles, strands or cords and, in a preferred embodiment, employment in the same band of elastomeric stock of mutually parallel strands, cords or bundles of a continuous nature. I

The following are representative of size compositions which may be applied to the glass fibers in forming.

EXAMPLE 1 0.5-2.0 percent by weight gamma-aminopropyltriethoxy silane 0.3-0.6 percent by weight glycerine Remainder water EXAMPLE 2 8.0 percent by weight partially dextrinized starch 1.8 percent by weight hydrogenated vegetable oil 0.4 percent by weight lauryl amine acetate (wetting agent) 0.2 percent by weight non-ionic emulsifying agent 1.0 percent by weight glycylato chromic chloride Remainder water EXAMPLE 3 3.2 percent by weight saturated polyester resin 0.1 percent by weight polargonate amide solubilized with acetic acid 0.1 percent by weight tetraethylene pentamine stearic acid 0. 1 percent by weight polyvinyl alcohol 3.0 percent by weight polyvinyl pyrrolidone 0.3 percent by weight gamma-aminopropyltriethoxy silane 7 0. 1 percent by weight acetic acid 93.1 percent by weight water The size composition is merely applied to the glass fiber filaments as they are gathered together and the strand of sized glass fibers is allowedto dry in ambient air.

In the foregoing examples, the gamma-aminopropyltriethoxy silane can be replaced as an anchoring agent with other amino silanes such as gamma-aminopropylvinyldiethoxy silane, n(gamma-triethoxysilylpropyl)propylamine, beta-aminoallyltriethoxy silane, aniline silane derivatives, etc.

While it is not essential to impregnate the strand or bundle of glass fibers before cutting or chopping to the lengths desired for admixture with the elastomeric material in forming the molding compound, it is preferred to impregnate the bundle of glass fibers for fuller separation of the fibers one from the other in the bundle and to incorporate an elastomeric system into the interior of the glass fiber bundle whereby the fibers can more efiectively become anchored in the elastomeric system.

For this purpose, the strand oryarn of glass fibers is simply unwound from a supply drum and advanced submergedly into a bath of the elastomeric impregnant.

Thence, the impregnated yarn is pulled through a wiping die which works the impregnating liquid into the innermost regions of the bundle or strand and also serves to wipe off excess material.

The following are a few representative liquid compositions containing an elastomeric material which may be used to impregnate the bundle or strand of glass fibers:

EXAMPLE 4 100 parts by weight neoprene rubber 4 parts by weight powdered magnesium oxide 5 parts by weight powdered zinc oxide parts by weight Channel Black 1 part by weight Thiate B (trialkyl thiourea accelerator) The above ingredients after being mixed on a mill are combined with sufficient of an appropriate rubber solvent to form a liquid impregnant bath.

EXAMPLE 5 100 parts by weight Paracril C rubber (Buna N) 25 parts by weight SRF carbon black 5 parts by weight powdered zinc oxide 0.5 parts by weight Aminox (reaction product of diphenyl amine ester) 1 part by weight stearic acid 40 parts by weight dicumyl peroxide The above ingredients after being mixed on a mill are combined with sufficient of an appropriate rubber solvent to form a liquid impregnant bath.

EXAMPLE 6 60 parts by weight Lotol 5440U. S. Rubber Company Lotol 5440 is a 38 percent dispersed soiids system including a butadiene-styrene-vinyl pyridine terpolymer latex, a butadiene styrene latex and a resorcinol-formaldehyde resin.

39 parts by weight water EXAMPLE 7 2 parts by weight resorcinol formaldehyde resin l part by weight Formalin (37 percent solution) 2.7 parts by weight concentrated ammonium hydroxide 25 parts by weight vinylpyridine terpolymer (42 percent latex) 41 parts by weight neoprene rubber latex (50 percent solids) 5 parts by weight butadiene latex (60 percent solids) 0.05 parts by weight sodium hydroxide 1 part by weight gamma-aminopropyltriethoxy silane 1 part by weight vulcanizing agent 1,100 parts by weight water The impregnated cord or strand may be chopped to different sized lengths and thence incorporated into the elastomeric stock material in order to produce the vulcanizable restrictive band referred to earlier herein. Any type of commercial cutter may be employed to automatically cut the strands into lengths ranging from 6 to 3 inches in length. One cutter which has been utilized is called a Brenner cutter and is manufactured by Brenner Machine Company of Newark, Ohio. Another suitable cutter is manufactured by Turner Machine Company of Danbury, Conn.

To produce a glass reinforced elastomeric system in accordance with the present invention, a conventional rubber formulation, e.g., recipe, is introduced onto a mill and worked to a proper workable viscosity; care being taken not to scorch the elastomeric stock material. Then, 2 parts per hundred parts of rubber [hereinafter referred to as phr] of treated impregnated glass cords or strands are gradually introduced to the mill which is set with the roll surfaces spaced apart about 0.055 inches. The stock on the millis repeatedly cut and crossed to work the glass fiber such that the bundles or strands separate into individual filaments and thereby become intimately and homogeneously diffused throughout the mass. Next, anywhere from 5 to phr of additional lengths of chopped impregnated cord having a length of about A to 3 inches are introduced to the mill at the same setting or slightly smaller setting ranging down to 0.035 inches. When this addition has been completed, the material is allowed to stay .on the mill for only a couple passes so that the bundles, strands or cords do not become separated into individual filaments, but substantially retain their bundle or cord indentity. The material is then removed from the mill and cut to a band width, generally corresponding to the shoulder to shoulder dimension of the tire to which it is to be affixed. The band width on examination will be found to contain both individual filaments of glass ranging from one sixty-fourth to one-quarter inches in length and lengths of strand or cord assemblies measuring from 5 4 to 3 inches in length. The short lengths of individual filaments result from the working and breaking up of the initial addition of 2 phr of glass bundles. A band, as just described, is circumferentially wrapped about a nylon cord carcass ply construction on a tire building machine just prior to application of the tread stock strip. The mating edges can be chamfered in accordance with routine practice and the lateral edges can also be biased or feathered for smooth incorporation into the tire construction. Thereafter, the tire construction proceeds with the arrangement of the tread stock, setting of the beads and finally the vulcanization of the tire, yielding a finished tire embodying the present invention.

Referring now more particularly to the drawings, there is shown in FIG. 1 a tire ll composed of spaced parallel circular bead wires 13 and 15 connected by the carcass portion 17 extending in torroidal configuration from one bead to the other. The beads are adapted to engage spaced rim flanges (not shown) on a vehicle wheel. The tire includes an outer peripheral tread portion 19 which serves as the ground contacting component of the tire. From the inside out, the carcass is composed of an inner cushion ply 21 extending from bead to bead and successively plies 22, 24, 26 and 28 of bias cut nylon fabric in which the principal cords C and C' are mutually parallel with the same cords in the same ply and are at an acute angle to the peripheral center line 29 of the tire which is coincident with the peripheral rolling axis of the tire. The cords C in the carcass plies 22 and 26 describe the same angle, while the cords C' in carcass plies 24 and 28 define an angle opposite to that of the cords C. The alternate reverse arrangement of the bias cut plies lends dynamic stability to the tire carcass considered as a whole. The carcass plies extend from bead to bead and then are wrapped bead area in the interest of simplicity of illustration.

In accordance with the present invention, a restrictive band 31 is situated peripherally about the outer bias cut nylon cord ply 28 and beneath the tread 19 extending transversely from shoulder 32 on the left to shoulder 33 on the right; the latter being the smooth curve of juncture between the tread stock and the outer rubber ply 35. In the embodiment of FIG. 1, the restrictive. reinforcing band 31 extends one complete wrap about the periphery of the tire with the mating edges chamfered and overlapping, although not shown, in a manner similar and customary in the splicing of the tread ply in conventional tire building operations.

The reinforcing band 31 is shown somewhat enlarged in FIG. 3 and, as can be seen, is composed 'of an elastomeric stock 31 having embedded therein discrete fibers 31b of glass fiber in essentially filament form and bundles or strands 31c of unseparated fibers. The lateral edges 31d and 3le of the restrictive band 31 are desirably feathered for more uniform and unified integral joining with the other tire components during building and vulcanization. The unseparated bundles contained in the restrictive band of elastomeric stock (rubber) can vary in amount from a minimum of about phr to as much as about 75 phr. Preferably, the range is to 50 phr and the optimum in reinforcing value is achieved where the amount is about 30 to 35 phr.

Referring now to FIG. 2, the tire 11 is composed of parts bearing the same reference numeral as the tire 11 in FIG. 1. The tire 11 of FIG.,2 is substantially identical to thetire ll of FIG. 1 with the exception that the restrictive reinforcing band 31 is situated between bias cut nylon fabric plies 26 and 28; The tire construction employing the reinforcement system as described in either of the embodiments of FIG. 1 or FIG. 2 is capable of being built in accordance with conventional tire building techniques in the tire manufacturing industry. The restrictive band 31 in each case extends transversely from shoulder to shoulder.

The restrictive band 31 including the reinforcing filaments and reinforcing bundles or strands can be produced, in general, by milling, calendering and/or extrusion; although the latter is less desirable since the distribution of the, reinforcing system is not as uniform as with either milling or calendering. The restrictive band may vary in thickness from about 0.020 inches to about 0.125 inches. A thickness of 0.050 is ideal for passenger tire constructions. Tires constructed in accordance with either of the embodiments of FIGS. 1 and 2 were found to minimize flat spotting or thumping" due to the nylon cord bias plies propensity to set at the deflected condition on exposure to low temperatures. A number of tires embodying the construction illustrated in FIGS. 1 and 2 were measured and found to be considerably more uniform in diameter at the same inflation pressure varying by as little as one fourth to three-eighths inch.

A restrictive reinforcing band in accordance with the present invention, but representing a variant embodiment, is illustrated in FIG. 4 and identified by the numeral 41. Like the band construction 31 of FIG. 3, the

band 41 contains individual discrete, extremely short lengths of glass fiber filaments 41b and also a plurality of unseparated strands, bundles or cords 410. The band 41 additionally includes a plurality of mutually parallel cords or strands 42 composed of assembled filaments, either twisted or untwisted. In each case, it is most preferred that the cords, strands or bundles 42 include an impregnation system as described hereinbefore in Examples 4-7. The band 41 can be manufactured by first drawing a plurality of strand or cord assemblies-71 (FIG. 10) from a plurality of rotatable supply spools 72 held in a creel arrangement 73 as in-conventional textile practice, directing the strand or cord assemblies through a comb 74 and thence training the strands under and over an array of rollers arranged to direct the strands into a pool of impregnant 75, thence through a hot air oven 76 and finally through a calendar 77 composed of a three roll stack; an elastomeric stock being fed to the top and middle rolls 78 and 79,

respectively, while the strands are fed through the mid die and bottom rolls 79 and 80, respectively, whereby the strands are combined with elastomeric stock to yield the assembly shown in FIG. 4. Alternatively, a restrictive band construction as shown in FIG. 4 can be formed by hand layup or by a laminating technique wherein two sheets of elastomeric stock have sandwiched therebetween a given number of mutually parallel strands of glass fiber.

It is within the purview of the present invention that the mutually parallel strands 42 may be the same or'dif-- ferent fibers. Thus, instead of all being fiber glass, a proportion of the strandsmay be fiber glass and the balance nylon, rayon, cotton or polyester. It is also within the purview of the present invention to form the cords, strands or cables 42 by employing a mixture of fibers representing three or more different materials, e.g., glass, cotton, rayon, nylon, polyester, etc. Another variant embodiment for the restricting band embodying a reinforcement system in accordance with a further aspect of the present invention is illustrated in FIG. 5 wherein a band 51 (partially broken away) is shown. The band 51 employs discrete, extremely short lengths of glass filaments 51b and a somewhat greater proportion of unseparated cords or strands somewhat greater in length as described hereinbefore and being identified by the reference numeral 516. These are in the form of impregnated strands, bundles or cords. In place of the mutually parallel strands 42 as in the embodiment of FIG. 4, the embodiment of FIG. 5 employs a woven fabric 52 embedded in the elastomeric stock component of the restrictive band 51. The fabric 52 is composed of woof strands 52a and cross or warp strands 52b. The fiber making up these should preferably be different where one is glass. Thus, most preferably, the

strands

52a and 52b are not both glass strands. The

warp and

woof strands

52a and 52b may be strands of glass, nylon, rayon, cotton, polyester (Dacron) and any of the other alternative constructions mentioned hereinbefore. It is within the scope of the present invention to employ two or more of the candidate fibrous strand constructions to weave the fabric 52. As in the case of the mutually parallel strands 52, the fabric may be combined with the restrictive band in any one of the several ways described herein. Preferably, a calendering combination as described previously is employed,

although a laminating technique, under certain circumstances, may prove most beneficial.

FIG. 8 illustrates a cord construction 60 in accordance with this invention; said cord employing

twisted strands

61, 62, 63, 64, 65, 66 and 67. Each of the strands is composed of a plurality of assembled filaments. The cord 60 is shown assembled from a combination of strands of differing materials. Thus, certain of the strands 61-67 may be glass, a number of them may be cotton and a number of them may be nylon, rayon polyester (Dacron) or the-like. It goes without saying, of course, that the cord or cable 60 may be made up of strands 61-67, all of the same filamentary material. Ideally, they are impregnated (see Examples 4-7) in a manner as described (in connection with FIG. 10), particularly where a glass strand is in assembly therewith. The cord or cable 60 may be employed in fabricating the restrictive belt or band 41 and, in which case, it would be substituted for the strands 42. Where different fibers, both organic and inorganic, are employed, a considerable versatility and flexibility in combination of properties is imparted to the restrictive band and correspondingly to the tire construction. It will also be appreciated that the cable 60 may be employed as one or the other or both of the

strands

52a and 52b in the fabric in the restrictive band 51 in the embodiment of FIG. 5.

In FIGS. 6 and 7, there is disclosed, somewhat schematically, a process and apparatus for retreading a tire in accordance with another embodiment of the present invention. Thus, a tire 90 is mounted on a flanged hub 91, carried rotatably on a shaft 92 mounted on either side in

journals

93 and 94 respectively mounted on like supports 94 and 95. A pulley 96 is mounted at one end of the shaft 92 driven by a belt 97 mounted on pulley 98 driven via shaft 99 by a motor 100 connected to a source of electrical power, not shown. The tire mounted, as just discussed, may be rotated at any desired speed. In accordance with the present invention, a supply spool 100a containing a continuous length of previously impregnated glass cord or strand is mounted in spaced parallel relationship with the tire. The shaft 101 of this spool 100a is parallel to the shaft 92. A continuous length of the strand or cord is drawn from the spool and is fed through a traversing eyelet 102 mounted for to and fro travel on a threaded shaft 103, reversably turned by a motor 104 operating via a pair of pulleys 10S and 106 connected by a belt 107. The threading of shaft 103 and governing travel of eyelet 102 arrangement can be selected in order to give any desired spacing between the length of cord as it is fed peripherally onto the tire, as illustrated by the reference numeral 108 (FIG. 7), yielding a filament wound or spiral wound reinforcing strand as the tire 90 rotates along with the supply spool 100a. Another supply spool 110 contains a continuous supply of restrictive band stock material, such as that illustrated in either FIGS. 3, 4 or 5. Usually, the construction of FIG. 3, namely, the band 31, will suffice since the spiral wound continuous strand will take the place of the strands 42 in the restrictive band construction 41 of FIG. 4. The breaklines 111 illustrate that a band length 112 can be peripherally wrapped about the previously independently applied spiral strand or cord of glass. Of course, the band construction, as a very thin member,

may be continuously wound about the tire contemporaneously with the applied filament wound strand or cord. A further supply spool 120, shown in dotted outline in FIG. 6, represents that two or more strands of glass may be wound about the tire at the same time; care being taken, of course, to employ a separate eyelet traversing rod arrangement, as shown in FIG. 7. Once sufficient continuous glass strands have been spirally wrapped about the carcass, a final wrap of restrictive band 112 may be put about the structure and then the tread stock applied as in conventional retreading operations. The restrictive band alone may be wound about the carcass instead of in combination with the spiral or filament wound cord. Skive knives, although not shown, are usually employed to trim excess rubber from the tire, whereby molding is easier and dynamic stability of the ultimate retread is improved. It goes without saying that the tread, of course, is first buffed off of the tire to be retread, and the reference numeral 90 represents a tire from which the tread has been removed by bulfing in a truing and dynamically balanced apparatus.

Although not shown, it is within the purview of the present invention to employ a technique as generally illustrated schematically and described hereinabove in connection with FIGS. 6 and 7 for the original manufacture of tires; in other words, in the tire building process. Thus, it is within the framework of the present invention to adopt the procedure just described to a tire building operation generally similar to'that employed in building radial tires. In such a technique, the tire components are built up on a drum or mandrel fitted with bead seal adapters permitting the partially built tire to be pneumatically expanded to a tire configuration whereupon the glass cord can be spirally wound about the crown of the carcass prior to application of the tread strip. Provision can be made for convenient supply rolls of glass cord together with apparatus including a traversing eyelet for feeding the glass cord assembly spirally onto the carcass in the crown region. As in the embodiment shown in FIGS. 6 and 7, we may employ one or more restrictive band members 112. This will tend to further insure isolation and separation of the strands, thereby precluding any interfilament, interstrand or intercord destruction. In any event, when sufficient wraps of the continuous spiral wound cord have been applied together with an optional cushioning layer of the restrictive band stock material 112, the supply rolls can be pivoted away and the tread stock applied in routine fashion followed by vulcanization in an appropriate mold.

The construction provided by this technique yields a tire possessed of considerable inherent stability just beneath the tread region by reason of the layer of spirally wound glass cords as described. The construction, as just described, finds particular utility in a bias ply cut nylon cord tire, since the continuous plies lend dimensional uniformity in so far as the tire diameter is concerned and additionally prevent growth of the tire due to any inherent thermal deficiency of the nylon cords.

Whether the tire, constructed in accordance with the present invention and the techniques just described, be a new tire manufactured on tire building equipment as just described or whether the tire be a retread tire buffed and constructed as just described, it is found that it is inherently a much more stable tire than known heretofore. Even with the added .stability, however, it is found that the harshness of ride is not a necessarily accompanying factor as in the case of wire breaker strip tires of the Michelin type.

Retreading operations employing the technique as just described results not only in a restrictive band in terms'of tiresize, but also in the creation of a shield which resists penetration by foreign objects frequently found on the air strip as described early in the present application.

The tire shown in FIG. 9 illustrates a variant construction featuring a tire 121' composed of spaced

beads

122 and 123 connected by a carcass portion 124 which is a radial cord construction having mutually parallel cords 125 which proceed at an angle ,of 90 between

beads

122 and 123; the 90 being taken with reference to the peripheral center. line 126 of the tire. In accordance with the present invention, this radial cord may be nylon, wire or glass cords impregnated as described. The tire includes a tread portion 127 which serves as the ground contacting component of the tire.

I Inaccordance with the present invention, just beneath the tread portion 127 and extending generally from shoulder 128 to shoulder 129, there .is situated two restricting bands or

belts

130 and 131; both of which are constructed in accordance with the details of construction described hereinbefore, particularly in connection with FIGS. 3, 4 and 5. The

restrictive bands

130 and 131 may be individual separate bands which are positioned peripherally about the tire with chamfered overlapping ends offset one with respect to the other. Alternatively, the segments identified by the

reference numerals

130 and 131 may, in fact, represent different plies of a multiple wrap-around of an elongate strip or band of a reinforcing restrictive band member composed, for example, of a construction as identified as 31 in FIG. 3, 41 in FIG. 4, or 51in FIG. 5.

The tire construction embodying the constructional details identified in FIG. 9 ispossessed of greater stability dynamically than the conventional radial tire. Additionally, the tire embodying the constructional details of -FlG. -9 will not .impart to the'vehicle, upon which mounted, as harsh a ride as conventional radial tires of the Michelin type employing wire cords in the radial carcass ply and additionally wire reinforced elastomeric stock forming a belt or breaker strip assembly as, for example, noted in the patent to Bourdon U.S'. Pat. No. 2,894,555 mentioned earlier herein. It will be appreciated that the radial cords may extend from bead to head or it may extend from one bead up through one shoulder across the tread area and down into the opposite side wall, while the opposite radial ply proceeds reversely from the opposite bead. up through the shoulder area and down into the side wall area of the spaced

beads

213 and 215 connected by a toroidallygion of the toroidal carcass, there is integrally secured thereto a tread 223 which is the ground engaging part of the tire; the beads engaging the rim portion of the wheel. In accordance with the present invention, the elastorneric stock contains distributed therethrough a plurality of chopped bundles 227 situated randomly therethrough and, in addition, a plurality of discrete filaments 229. The bundles and the filaments are both formed of a mineral substance, preferably glass. In the embodiment of FIG. 11, the tire contains no conventional carcass reinforcement as, for example, radial or bias ply cords. By reason of the random uniform distribution of the discrete fibers and the short chopped bundles throughout the elastomeric matrix, the ground engaging surface of the tread contains a plurality of.v

strip or sheet 281 composed of an elastomeric material including principalreinforcement in theform of mutually parallel cords 283 formed'of synthetic material such as rayon or polyamide, e.g., nylon. Additionally, the elastomeric stock materialcontains chopped bundles 284 and short discrete individual filaments of glass 286 as described generally hereinbefore and in more detail hereinafter. I

In FIG. 12, there is illustrated a tire 251 composed of spaced beads 253-and 255 connected by the toroidal carcass 257 bearing integrally at the crown region a extending carcass 217. The beads contain interiorly thereof reinforcing rings 219 and 221. At the crown retread 259. Bead ring members 260 and 261 are situated interiorly of the beads 255 and 253, respectively. The tire includes carcass plies 265 and 267. The carcass plies extend from head to bead as shown and are wrapped about each bead in a conventional tumup. Additional reinforcement is provided by peripheral belt plies 269 and 271 located also in the crown region above and radially outwardly from the carcass plies but beneath the tread and generally laterally coextensive therewith.

The tread is composed of elastomeric material having distributed therethrough a proportion of chopped bundles 275, each composed of a plurality of filaments secured together, and a proportion of discrete fibers 277. The elastomeric stock between the belt plies 271 V and 269 and between the belt ply 271 and the outer carcass ply 267 is similarly composed. The nature of the discrete fibers and the chopped bundles is more clearly illustrated in the enlarged view of FIG. 13.

The tread stock thusly composed provides significantly improved tractive properties under snowy and icy conditions. This improvement is due to the combined effect of the particular modulus of the stock and the presence of discontinuities in the tread surface. in the form of bundle ends and fiber ends. Both the bundle'and fiber are securely held by the matrix proper in which the bundle orfiber is embedded'This securement is provided by means of appropriate impregnant coatings as will be described hereinafter.

The presence of the stock, containing both chopped bundles and short discrete filaments of glass, in the region between the outer tread reinforcing belts and the conventional carcass plies serves to unitize, as it were, the belt plies and the carcass plies. It is not uncommon to normally consider the belt plies and the carcass plies as separate independent members from the operational point of view. In previous tires, the belt plies are separated from the carcass plies by a region of the same rubber of which the remainder of the tire is composed. In accordance with the embodiment, however, the stresses to which the belt plies are subjected are partially borne by the cords of which the carcass plies are composed.

The elastomeric stock material, of which the tire illustrated in FIG. 1 l is composed and of which the tread stock and the stock surrounding the reinforcement plies of the embodiment of FIG. 12 is composed, may be prepared in a variety of ways. Thus, the glass may be combined with the rubber via Banbury mixing or preferably via mill mixing. The discrete fibers and the bundles composed of the assembled plurality of fibers may be added to the rubber stock and processed to sheet, strip or to other forms. The stock recipe should be well mixed on the mill before the addition of glass or, in the Banbury, the stock should be mixed first and the glass added as a later addition in order to avoid breakdown of the glass; that is, in order that the glass substantially retain its definition or identity as a bundle and/or fiber of given length. Too severe a mixing within the Banbury or the mill will tend to cause the glass bundles and fibers to deteriorate to essentially particle size, which phenomena is to be avoided.

Most preferably, the glass is added to the mixed stock in two separate and distinct stages and in the form of bundles, each composed of a plurality of from about 500 to about 30,000 filaments. Thus, in a mill mix, a first amount (the preferred amounts will be discussed more fully hereinafter) of bundles is added to the stock on the mill, preceded, of course, by a mill mixing of the particular recipe. The first amount of chopped bundles introduced on the mill will, after a number of passes, be found to become largely separated into individual discrete filaments which become uniformly distributed throughout the stock on the mill with some observable linear orientation in the direction of the moving stock. Subsequently and preferably just prior to the cessation of mixing, a second amount of chopped bundles or cords of glass is added to the stock. The mixing is allowed to proceed just sufficiently to distribute the chopped bundles throughout the mass with little or no separation into discrete filaments. The mass of the glass, inherent in the bundle form, coupled with the relatively high specific gravity leads to a rather rapid distribution of the bundles throughout the stock. Thus, usually from three to seven passes on the conventional rubber mill will suffice to distribute the chopped cords relatively uniformly without appreciable separation of the bundles or cords.

From the foregoing, it will be appreciated that the utilization of glass as a reinforcement of rubber products requires a consideration of the form of the glass, be it filament, strand, yarn, cord, or the like, as well as the properties of these different forms and, ad-

ditionally, the proper combination and location of the glass filament, strand, yarn, cord, or the like. By way of illustration, it has been disclosed earlier herein that the properties of a single glass filament include (a) essentially percent elasticity, (b) essentially no yield under stress, (c) excellent dimensional stability and (d) immunity to change in properties by reason of varying atmospheric conditions. The translation or the utilization of these properties as a tire reinforcement, however, requires the consideration of other properties of glass which are considerably different from the conventional organics. These properties include (1) stiffness (glass is 322 grams per denier [gpd] while nylon ranges from 18 to 23 gpd, the polyesters range from 11 to 21 gpd, the acrylics such as Acrilan and Orion 7 to 10 gpd and viscose rayon 11 to 25 gpd); (2) a low breaking elongation (glass is 3-4 percent whereas the polyesters range from 19-30 percent, nylon 1640 percent, acrylics, e.g., Acrilan, 36-40 percent and viscose rayon 9-30 percent); (3) a relatively high specific gravity (glass is 2.54 compared to 1.14 for nylon and the acrylics, 1.5 for rayon and 1.22 to 1.38 for the polyesters, e.g., Kodel and Dacron); and (4) toughness (on a denier basis, glass has a value of 0.07 compared to nylons 0.75, rayons 0.20, 0.5 for Dacron polyester, 0.37 for Kodel polyester and 0.4 for the acrylic Orlon).

From the above, it can be appreciated that the utilization of glass in any form, e.g., filament, strand or cord, as a reinforcement for rubber is not a matter of substitution but, to the contrary, entails a consideration of the overall properties and, as well, a determination of the ideal geometric location of the glass, alone and in combination with other materials, in order to achieve effective reinforcement.

By way of further explanation, it will be appreciated that filaments of glass are drawn in a molten state from a heated multi-orifice platinum bushing and gathered together into strand configuration contemporaneous with the spraying thereon of a size composition preferably containing an anchoring agent adapted to impart to the glass surface the ability to adhere to the ultimate rubber stock. Generally, 204 filaments are gathered together to form a strand, although a strand may be composed of 400, up to 900 and occasionally 2,000 filaments; in each case, drawn from a single bushing. The strands become cooled and solidified in the attenuation thereof at high rates of speed from the bushing and are wound after sizing onto a spool. The continuous strand wound about a spool can then be plied and combined with additional like strands to form multiple strand yarns. Additionally, the multiple strands and yarns can be plied and combined with like yarns with or without twist to form the cords or bundles as referred to earlier herein. As indicated, the glass filaments are preferably coated with a suitable size, for example, an amino silane; a variety of formulations for which are disclosed in application Ser. No. 406,501, filed Oct. 26, 1964, now US. Pat. No. 3,391,052 entitled Glass Fibers Treated For Combination With Elastomeric Materials and Method and being assigned to the assignee of the present application. One typical size composition is composed of 0.5-2.0 percent by weight of gamma-aminopropyltriethoxy silane, 0.30.6 percent by weight of a lubricant, such as glycerine, and the remainder composed of water. The strands or yarns "vinyl pyridine terpolymer latex, a butadiene styrene latex and a resorcinol-formaldehyde resin; said solids being dispersed in 40 parts by weight of water. A suitable commercial product is LOTOL 5440, a product marketed under that trade name by Uniroyal (formerly U.S. Rubber Company).

EXAMPLE 8 Four different neoprene stocks were prepared to determine the properties imparted by the inclusion therein of relatively short discrete glass filaments and short lengths of chopped cords or bundles; each composed of a plurality of assembled filaments. The glass cord was composed of filaments measuring 0.00036 inches in diameter. Three 204-filament strands were combined together; the filaments bearing a size as described above and the strands being impregnated as described just previously. The ultimate assembled impregnated cord was cut into V4 inch lengths and added to the neoprene stocks in the manner described hereinbelow.

A. The control neoprene stock has the formulation given in Table III below.

TABLE [II Neoprene GRT Stearic Acid Maglite D Polyethylene AC Neozone D SRF Black Zinc Oxide Paraflux Altax Total: I 8

Test specimens were prepared and retained for testing.

B. A stock as in (A) was mill mixed and to it was added an amount of V4 inch lengths of the chopped cord providing a level of l7 percent by weight. The stock was allowed to mix sufficiently that substantially all chopped bundles separated into individual filaments such that there were essentiallyno cords or bundles in the stock. The stock was removed and test specimens prepared and vulcanized at 300 F. for from 20 to 60 minutes, depending on size of the specimens.

C. A proportion of the same stock was mixed on the mill and 17 percent by weight of 36 inch chopped bundles as above were added, but the mixing was continued just sufficiently to disperse the bundles so that all of the glass contained in the neoprene stock was in the form of bundles and there were essentially no individual or discrete filaments present. Again, test specimens were prepared from the thusly prepared stock.

D. Another proportion of the same neoprene stock was mixed and 17 percentby weight of glass was added in this manner: 5 percent of the total chopped )4 inch cords were added and thoroughlyblended into the elastomer so that these cords became separated into individual filaments; 95 percent of the total glass cords or bundles were added and mixing continued just sufliciently to disperse the bundles so that the final stock contained a minor proportion (5 percent) of individual filaments and 95 percent of unseparated A inch cords or bundles. Again, test specimens were prepared.

The test specimens from the above stoclt formulations were tested in accordance with conventional rubber testing practice with the observed properties of each, that is, the tensile, the elongation, modulus, tear, hardness and resilience, being summarized in Table IV in which the vertical columns are labeled corresponding to the previous paragraphs, e.g., A, B, C and D.

As revealed in the above table, the tensile strength and the tear strength are highest in the stock formulation containing both the chopped bundles and the short discrete filaments. Composition B containing 17 percent of glass, all of which is in the form of extremely short lengths by reason of the longer mixing, shows a general overall degradation in properties. Composition C in which the glass reinforcement is entirely in the form of cords shows an improvement in that the tensile and tear strengths are improved over Composition B. As indicated, the best overall tensile and tear strengths are present in Composition D.

EXAMPLE 9 Various amounts of chopped glass bundles were added to a mill mixed tire tread compound to determine the effect. The compound was a /25 blend of butadiene styrene rubber and a cis-l,4 polybutadiene rubber. The recipe appears in Table V.

The glass bundles were composed of three 204-fi1ament strands assembled together. The individual filaments had a diameter of 0.00036 inches. The filaments were sized as previously described and the three-strand bundle was impregnated. The bundles were chopped into A inch lengths and added to the tire tread stock in varying amounts listed in Table V. The glass was added sequentially; that is, with a minor amount ranging from 5-10 percent of .the total added first to the stock so that it would defilamentize into discrete individual fibers.

The majority (90-95 percent) was added as bundles late in the mixing cycle so that it retained its bundle integrity. The level of glass reinforcement as seen in Table V and Table VI below was 0, 5, 10 or 20 percent. The percent glass reinforcement was calculated as the amount of glass divided by the amount of glass plus the amount of stock times 100. The variation in properties according to glass content is given in Table VI.

TABLE VI Glass 20 Tensile 3045 2175 2135 1785 Elongation 700 625 535 440 Modulus: 100% 195 305 425 595 200% 440 480 615 770 300% 870 785 985 1040 Shore A 65 67 70 74 Tear 235 240 260 265 EXAMPLE 10 Passenger vehicle tires (8.25 X 14) were built employing in the tread stock an amount of chopped bundles and an amount of discrete individual filaments. The tires were evaluated under snow and ice conditions in comparison with a standard tread stock; that is, not containing the glass filament reinforcement. Also evaluated were tires featuring the chopped bundles and chopped fibers containing tread stock and also glass cord reinforcing belts. The formulation for the glasscontaining tread stock and the control stock are contained in Table VII.

90% 86 inch chopped impregnated bundles, each composed of three 204-fi1ament strands plied together; 10% discrete inch filaments.

TABLE VIII Glass Containing Control Properties Tread Compound Stock Tensile 1 600 23 80 Elongation 440 550 Modulus at 300% 1 135 1095 Tear (Die C) 230 247 Hardness (Shore A) 66 61 Specific Gravity 1.16 1.14

a. A pair of control tires were formed utilizing the nonglass filled tread compound of Table VII. The tread matrix employed a snow tread design known as a snow cap". A pair of essentially identical tires were formed, but using the tread compound of Table VII containing bundles chopped to V4 inch length and individual filaments chopped to V4 inch length; the tread also employing the snow cap" tread configuration. A third pair of tires were fabricated identical to the second pair except that, in addition, the tire featured a pair of belt plies beneath the tread and above the carcass. These belts were formed of mutually parallel cords of glass as described in Example X of U.S. Pat. No. 3,311,152. The tires were mounted on test vehicles and run over packed snow, wet ice and dry ice courses. The vehicles were equipped with instruments enabling a measuring evaluation of tractive performance of the tires. The

, results are tabulated in Table IX below.

The physical properties of the glass containing compound are listed in Table VIII below together with properties of the control compound.

TABLE 1X Dynamic Traction Rating Lbs. Lbs. Lbs. Lbs. At Max. at 40% at at 200% at 400% Drawbar Wheel Wheel Wheel Wheel Code Lbs. I Slip Slip Slip Slip 180 PSI Compaction A 100 100 100 100 100 B 104,105 104,105 100,103 98,103 99,100 C 111,111 111,111 112,112 109,109 106,108

Dry Ice A 100 100 100 100 100 B 114,112 114,112 114,112 114,112 119,114 C 103,104 103,104 103,104 105,106 105,106

Wet Ice A 100 100 100 100 100 B 113,105 113,105 112,105 109,105 105,105

' A-Control tire-molded of control stock (Table VII, Column 2) B-Tire with tread stock containing glass bundles and discrete filaments C-Belted tire with tread stock containing glass bundles and discrete filaments Bmkin Distance to stop control tire gm l)isi.anco to stop experimental tire The results are given in Table X below.

c. The same tires as in (a) were evaluated on test vehicles to determine their braking capabilities in terms of average deceleration rate (ft/sec). The formula used in the determination is:

S t f Dcceleration rate (ft./sec. W

' d. The same tires were evaluated on test vehicles to determine lateral traction capability on wet ice. Two dynamometer units were employed; one positioned at 90 from the test vehicle and hooked to the rear axle end and the other dynamometer unit being attached behind the test vehicle. The maximum directional force at zero lateral resistance was measured by the test vehicle imposing a force against the second dynamometer unit until excessive directional slip was produced. The maximum lateral resistance at zero directional force was measured by the first dynamometer unit imposing a force-until excessive lateral slip was produced. Having determined maximum directional force and maximum lateral resistance,'the directional force was increased incrementally and the resultant lateral resistance measured.

The results are given in Table Xll below.

TABLE Xll Wet lce Dynamic Lateral Traction Rating at 70 m. at 140 Lbs. at 210 Lbs. Code Direct. Force Direct. Force Direct. Force A 100 100 100 B 129 140 172 c 137 I60 249 See Table 1x As can be seen from the foregoing, the tires featuring treads containing glass, both in the form of filaments and in the fonn of chopped bundles, demonstrated considerably improved tractive performance under snow and ice conditions. The tires employing additionally the reinforcing belt between the carcass plies and the tread demonstrated the highest ratings. By wayof summary, in .the 180 PSI compaction, the glass. belted tire containing glass in the tread showed about 9-l2 percent improved traction. Under wet ice" conditions, the improvement was about 15 percent. Lateral traction rating of the test tires'demonstrated improvement, up to 72 percent for tires with the glass containing tread, and up to percent for the tires with glass containing tread and employing the belt plies.

EXAMPLE 1 l A neoprene stock was prepared in accordance with the formulation of Table III. A proportion of this com pound was mixed on a mill. To it was added 30 parts of glass in the form of A inch chopped bundles of glass filaments held together by an impregnant. 28.5 parts of the total chopped bundles were added first, which defilamentized intodiscrete individual filaments. The remainder of the bundles was added and mixed only enough to distribute the bundles through the stock. The tensile strengths of neoprene control stock and the glass filled stock were determined employing die cut dumbbell specimens measuring l X% X 0.075 inches. Tensile tests were also run on the glass containing stock having a single cord of a given material disposed interiorly and centrally of the sample during vulcanization. Similar tensile specimens were prepared with three parallel cords centrally and interiorly disposedQ-The test cords included a rayon cord, a nylon cord and a glasscord; the latter being composed of five 408-filarnent strands. The individual filaments were sized with aminopropyltriethoxy silane size and the ultimate cord was impregnated with LOTOL 5440". The results are given in Table Xlll below.

' S strands of 408 filaments plied together with essentially no twist.

The glass filled stock (tested alone-no cords) demonstrated a tensile strength of 142 pounds. Referring to the strength values achieved with the specimen containing the three parallel cords in addition to the glass filaments and bundles contained in the matrix demonstrates an increase in strength over that expected; such increase believed due to a more effective transfer of stresses from one cord to the other due to the presence of the filaments and bundles.

Exactly why an elastomeric compound containing both chopped bundles and chopped individual filaments demonstrates improvedphysical properties and, as well, improved dynamic performance, that is, when incorporated into a vehicle tire,-is not known. It is suspected that the individual filaments and the

Claims

1. A tire construction of elastomeric material comprising: spaced annular bead members adapted to engage the rim portions of a wheel, said bead members each including an interiorly disposed reinforcing ring, a body member extending toroidally between and connecting said bead members, a ground contacting tread carried by said body member at the crown thereof, said elastomeric material extending throughout said tire, said elastomeric material including carbon black as a reinforcement, and, as essentially the sole additional reinforcement, a plurality of chopped glass bundles ranging from about 1/8 to about 3 inches in length, said bundles each including an assembled plurality of individual filaments held in bundle configuration by an elastomeric impregnant and a plurality of discrete individual filaments of glass ranging up to about one-fourth inch in length, said bundles and filaments being distributed throughout the tire.

2. A tire construction as claimed in claim 1, wherein said filaments and bundles constitute in aggregate about 2 to about 35 parts of glass per hundred of elastomer.

3. A tire construction as claimed in claim 2, wherein the amount of bundles exceeds the amount of filaments.

4. A tire construction as claimed in claim 3, wherein said impregnant includes a substance having a bonding affinity for the glass and an elastomeric component having a vulcanizing compatibility with the principal elastomeric material of said tire.

5. A tire construction as claimed in claim 4, wherein said chopped bundles each include from 500 to 30,000 individual filaments.

6. A tire construction as claimed in claim 3, wherein the amount of bundles is about five times the amount of discrete filaments.

7. A tire construction as claimed in claim 6, wherein the amount of filaments is about 2 parts per hundred of elastomer and the amount of bundles is about 10 parts per hundred of elastomer.

8. A tire construction including means for removable attachment to a wheel rim, a carcass extending toroidally from said means, said carcass including at least one ply of mutually parallel cords, and a tread carried at the crown of said carcass, said tire construction further including an elastomeric matrix extending throughout said tire holding said components together, said matrix including, distributed generally randomly throughout, a plurality of lengths of chopped glass bundles measuring from about 1/8 to about 3 inches in length and each comprising an assembled plurality of individual filaments held together by an elastomeric impregnant.

9. A tire construction as claimed in claim 8, wherein said matrix further includes a plurality of indiviDual chopped filaments of glass ranging up to about one-fourth inch in length.

10. The tire construction as claimed in claim 8, wherein said chopped glass bundles constitute from about 2 to about 35 parts per hundred parts of elastomer.

11. A tire construction as claimed in claim 8, wherein said carcass includes a plurality of plies, each comprising mutually parallel cords.