GB1575027A

GB1575027A - Pneumatic tyres

Info

Publication number: GB1575027A
Application number: GB1551/77A
Authority: GB
Original assignee: Firestone Tire and Rubber Co
Current assignee: Bridgestone Firestone Inc
Priority date: 1976-01-21
Filing date: 1977-01-14
Publication date: 1980-09-17
Also published as: AT358409B; DE2700479A1; JPS5291203A; CA1035682A; ATA27677A; IT1086810B; NO770117L; ES455217A1; BE850390A; PT66074A; CH619401A5; SE7700387L; PT66074B; FR2338813A1

Abstract

A conventional tyre carcass with a radial reinforcement inlay (15, 16) in the crown area of the radial tyre is provided with an additional reinforcement material layer (20, 21) comprising a flexible sheet-like structure with quadratic or rhombic bonding without a calendered-on rubber coating. This sheet-like structure can be subjected to pretreatment with a resorcinol/formaldehyde solution in order to ensure adhesion to the tyre rubber. Alternatively, an adhesive can be used for this purpose. The sheet-like structure can either be in the form of a prefabricated, cap-shaped overlay and can extend over the entire belt reinforcement, or can be applied as separate strips over the side edges of the belt reinforcement. The sheet-like structure, which has higher elasticity than the belt cord, enables the design of an appropriately reinforced, flexible transition region between the belt reinforcement inlay and the flexible regions at the sides of the tyre. <IMAGE>

Description

(54) IMPROVEMENTS RELATING TO PNEUMATIC TIRES (71) We, THE FIRESTONE TIRE & RUBBER COMPANY, a corporation organized under the laws of the State of Ohio, United States of America, of 1200 Firestone Parkway, Akron 44317, State of Ohio, United States of America, do hereby declare the invention, for which we pray that a patent may be granted to us, and the method by which it is to be performed, to be particularly described in and by the following statement: This invention relates to belted pneumatic tires. It is directed to the reinforcing tread ply area (belt area) in this type of tire and concerns tires having either a radial or bias body.

In a radial tire, the reinforcing cords in the body run in a substantially radial direction (that is, at an angle of the order of 75" to 90 to the circumferential centerline of the tire tread) Such tires contain a relatively stiff, inextensible hoop of reinforcing material known as the reinforcing belt structure. This structure is located between the body and the tread in the crown area of the tire. A radial ply tire constructed in this manner may be characterized as containing an annular, relatively stiff, inextensible hoop or belt which is connected to the tire beads, and the resulting rim and vehicle, by a supple, flexible sidewall. The tire operates as a rolling hoop; as such, the tread area of the tire provides low rolling resistance which results in better fuel economy and very little tread motion, which results in longer tread life.

A reinforcing belt structure may also be employed with a tire body in which the cords in the body are biased (a belted-bias tire). The belt structure is similar to that used in a radial tire but the cords in the body plies are usually placed to form an angle between 20 and 40 with the circumferential centerline of the tire tread.

Tire constructions of the belted-bias type and the radial type are well known.

According to the invention there is provided a pneumatic tire having either a radial or bias tire body, a reinforcing belt structure comprising one or more reinforcing belt plies of cord material having a high modulus of elasticity overlying the tire body in the crown area of the tire, a tread member of rubber having a low modulus of elasticity radially outward of the belt structure, each of the lateral edges of the belt structure having a layer of flexible non-calendered fabric disposed at a location radially between the tire body and the tread member and radially outward of the belt ply or a belt ply of the belt structure the said fabric comprising cord material of an intermediate modulus of elasticity with the cords extending in two directions transverse to each other.

By non-calendered fabric we mean a fabric which has no rubber calendered on to it.

In preferred constructions according to the invention the fabric is a square-woven non-calendered fabric. Such a material allows the dissipation of air around the belt edges in the tire manufacturing process thereby eliminating the possibility of any trapped air in this area. A calendered, square-woven fabric would not yield this result. During the curing operation, the non-calendered square-woven material permits the surrounding rubber to flow through the openings in the square-woven fabric.

This results in a strong union between the square-woven fabric and its surrounding material which is resistant to the forces working on this area during the operation of the tire.

The circumferential, lateral edges of the reinforcing relatively stiff, belt structure in a radial tire are located in the shoulder area of the tire. This is the thickest area of the tire. As such, high temperature may be generated in this area of the tire as the result of the flexing. It is well known that tire strength decreases as a function of running temperature so that tires are always designed to generate as low a running temperature as possible.

The reinforcing belt structure is relatively stiffer than the adjacent parts of the tire.

The edges of this belt structure create a hinge point in the tire and it is thought that as these edges are subjected to forces in operation the edges may react to these forces by moving radially outwardly in the softer adjacent parts of the tire. This motion may be detrimental to tire performance.

The incorporation of the novel cap ply structure combats these forces and holds the belt edges firmly onto the tire body or carcass. This is a result of the improved adhesion which results from the construction of this invention and the inherent strength characteristic of the fabric which has reinforcing cords running in two directions, as opposed to reinforcing cords running in only one direction with standard tire body fabrics.

Constructions according to this invention result in the provision of an intermediate modulus material i.e. the cords of the fabric in the area between a high modulus material of the belt i.e. the cords of the belt structure and a surrounding low modulus rubber material and thus mitigates the sharpness of the change of modulus.

Various specific structural features may be utilized to accomplish this result, namely (1) a full cap ply of the fabric, located on top of the reinforcing belt structure and under the tread, which extends laterally, completely across the reinforcing belt structure; (2) separate narrow plies of the fabric which are located over the lateral edges of the belt structure; (3) plies of the fabric which are wrapped around the lateral edges of the belt structure to envelop these edges; or (4) any combination of these constructions. The axially outer edge of the cap ply fabric may be located over the lateral edge of the reinforcing belt structure or any ply edge in the belt structure, or it may be located axially outwardly of the lateral edge of the belt structure.

The fabric may be made from nylon, polyester, rayon, cotton, fiberglass of low denier, or aramid (such as Kevlar -- Regi- stered Trademark), and any workable combination thereof, such as, nylon in the circumferential direction and Kevlar in the radial directions. When nylon or polyester are used, the cords and/or yarns in the fabric may be monofil or multifil. When rayon, cotton or aramid are used in the fabric, the cords and/or yarns may be multifil. The term cords will be used herein to include yarns. When stiffer materials are used as the cord in the fabric the cords and the resulting fabric must be flexible and adequate flexibility may be provided by using a low denier or small gauge material. It is preferred to use a nylon multifil material as the cord in the fabric.

The fabric may have equal or substantially equal strength in both cord directions.

One of the cord directions in the fabric may be circumferentially disposed around the tire (parallel to the circumferential tread centerline of the tire), the other cord direction being radial (assuming a 90 degree angle between the cords). Alternatively, the cords may be angled in relation to the circumferential tread centerline.

The angle between the cords is preferably 90 degrees but the use of smaller angles is within the scope of this invention. The fabric may be obtained by weaving or knitting processes. In weaving the cord angle with the fabric is usually 90 degrees whereas knitting permits other angles and fabric configurations.

The invention applies to belted tires of either the radial or bias body types, whether they be designed for passenger, truck, farm, off-the-road, military, motorcycle, industrial, or airplane vehicles.

The fabric is preferably subjected to a prior treatment with a resorcinol-formaldehyde solution to facilitate adhesion of the surrounding rubber compound in the tire.

An additional treatment of applying a cement prior to incorporation into the tire may also be utilized.

Some embodiments of the invention will now be described by way of example with reference to the accompanying drawings in which: Figure 1 is a top view of a square-woven fabric, Figure 2 is a cross-sectional view of a radial ply tire illustrating two embodiments of this invention; Figures 3 to 8 are diagrammatic illustrations of further embodiments of this invention, each of Figures 3 to 6 illustrating two such embodiments.

In Figure 1, the fabric is shown at 1 and has a set of warp cords 2, in one direction and a set of weft cords 3, in the other direction. The angle between these cords is shown as 90 degrees defining a square between the cords, but it is understood that the angle may vary depending on the process used to manufacture the fabric. The fabric shown was woven, but it may also be knitted. The fabric is devoid of any layers of rubber skim calendered onto it such as is at present standard practice for fabric used in the tread area of a pneumatic tire. The fabric in Figure 1 may be dipped in an adhesive solution to provide tackiness curing building and adhesion in the cured state of the tire.

The warp and weft cords may be of the same material or the warp cords may be of one material and the weft of another. The cords in one direction, either warp or weft, may be alternated from one type to another; such as, nylon, Kevlar, nylon, Kevlar, etc. or one Kevlar, four nylon, one Kevlar, four nylon, etc.

Referring to Figure 2, a radial pneumatic tire is shown generally as 10 having inextensible bead rings 11; body plies 12 and 13; sidewalls 14; reinforcing belt structure con taining belt plies 15 and 16; road-engaging tread surface 17 and narrow cap plies 20 and 21. The bead, body, tread and reinforcing belt plies in this tire are of any known standard construction. This invention is particularly useful in constructions having steel cords in the reinforcing belt plies; however, the reinforcing cords in the belt structure may be of the known tire reinforcing materials which are utilized in this area; such as glass cords or Kevlar. The cords in these belt plies for angles to the circumferential centerline of the tread ranging from 15 to 40". The angle of cords in adjacent plies may vary and the cords in adjacent plies may change the directions of their angle. The cords in the body may be any of the known tire reinforcing cords which have been utilized in this area of the tire; such as rayon, polyester, glass, nylon, steel or Kevlar. The cords in these body plies are substantially radial, forming an angle of 90 degrees to the circumferential centerline of the tread.

The narrow cap ply 20, illustrated on the right-hand side of Figure 2 is a squarewoven, non-calendered nylon multifilament of 840/1 nylon in both directions. In this embodiment the axially inner edge of the cap ply is located axially inwardly of the edge of the reinforcing belt structure and the axially outer edge of the cap ply is located axially outwardly of the edge of the reinforcing belt structure. It is understood that both edges of the belt structure may have this construction.

The embodiment illustrated as a narrow cap ply 21 in the left-hand side of Figure 2 has its axially outer edge corresponding to the outermost edge of the reinforcing belt structure.

It is understood that each of Figures 2 to 6 illustrates two embodiments of this invention. The invention includes within its scope symmetrical tires which utilize the same construction on both of the lateral edges of the reinforcing belt structure, and tires which are asymmetrical and utilize any combination of the different constructions shown in Figures 2 to 6.

In Figures 2 through 8 the reinforcing belt structure is diagrammatically illustrated as plies 15 and 16. The various cap ply embodiments in these figures are illustrated as plies 23 through 37. Figures 2 through 6 illustrate cap ply embodiments wherein separate, narrow cap plies are utilized in the area of the lateral edges of the reinforcing belt structure. Figures 7 and 8 illustrate embodiments wherein full cap plies are used which extend across the entire width of the reinforcing belt structure.

The right-hand side of Figure 3 illustrates an embodiment wherein a narrow cap ply, 23, is located between the edges of the tread plies and extends axially outwardly of the ends of the cap plies. The left-hand side of Figure 3 illustrates an embodiment wherein narrow cap plies (24 and 25) are located on top of both of the edges of the tread plies in the reinforcing belt structure and extend axially outwardly beyond the edges of the reinforcing belt structure.

The right-hand side of Figure 4 illustrates an embodiment wherein narrow cap plies, 26 and 27, are located on top of the lateral edge of each of the tread plies, respectively, and end above the lateral edge of each tread ply. The left-hand side of Figure 4 illustrates an embodiment wherein one of the narrow cap plies, 28, is located on top of the edge of a belt ply and extends axially beyond the edge of the belt ply and another cap ply, 29, is located on top of a belt ply and extends to the edge of the belt ply. It is understood that these plies, 28 and 29, may be reversed so that the wide cap ply is on the outside belt ply and the narrower cap ply is on the inside belt ply.

An additional narrow cap ply, 37, is illustrated in the right-hand side of Figure 4 located between the body and the reinforcing belt structure at the edge of the belt structure. It is understood that the axially outer edge of ply 37 may end axially outwardly of the edge of the belt structure similar to the location of ply 23 in Figure 3. It is also understood that a narrow cap ply similar to 37 may be used with any of the embodiments illustrated in the Figures.

The right-hand side of Figure 5 illustrates an embodiment wherein a narrow cap ply, 30, envelops the edge of one of the belt plies in the reinforcing belt structure by being wrapped around the edge. The lefthand side of Figure 5 illustrates an embodiment wherein a narrow cap ply, 31 envelops all of the ply edges in the reinforcing belt structure by being wrapped around the entire edge of the belt structure.

The right-hand side of Figure 6 illustrates an embodiment wherein a narrow cap ply, 32, envelops the edge of the outermost tread ply in the reinforcing belt structure by being wrapped around this edge. The lefthand side of Figure 6 illustrates a combina tion of narrow cap plies, 30 and 32, showing all edges of the belt structure enveloped in separate, narrow cap plies, 33 and 34.

It is understood that it is necessary to apply a separate layer of rubber between the non-calendered cap plies in the areas where they will be immediately adjacent to another non-calendered cap ply to prevent cord to cord contact between the plies.

Specifically, such rubber gum strips would have to be placed between plies 24 and 25 in Figure 3 and plies 33 and 34 in Figure 6 in the areas where the cords of these plies would be in contact.

The fabric utilized in the invention may be first coated by a resorcinol/formaldehyde, rubber-based dip by immersing the fabric in a bath of the dip solution. A natural rubber-based, add-on cement may also be applied to this fabric, if desired, to improve its tack to adjoining rubber coated plies in the uncured tire. This cement has a natural rubber base and contains tackifying resins which are dissolved in a solvent media, such as toluene. This type of cement is applied to the fabric by immersing the fabric in a bath of the cement or by spraying.

Figure 7 illustrates a full cap ply 35, which extends axially beyond both of the lateral edges of the reinforcing belt structure. The full cap ply extends axially across the entire width of the reinforcing belt structure. It is understood that the ends of the cap ply may be wrapped around one or both of the ends of the belt plies in the manner illustrated in Figure 5.

Figure 8 illustrates an embodiment containing a full cap ply 36, which ends at the lateral edge of the belt ply structure.

In all the embodiments the cap ply or plies may be applied to the tire building drum when the tire is on the flat building drum or on an inflated drum by winding the cap ply around the drum in the proper location. In building a single layer cap ply embodiment, an overlap of the cap ply ends of up to one inch has been used. This overlap may result in a gap between the cap ply ends, a butt of the cap ply ends, or a slight overlap of the cap ply ends, in the cured tire. The small area of cord to cord contact which may occur when a slight overlap of the cap ply ends is present in the cured tire has not been detrimental to tire performance.

The preferred embodiments of the ones illustrated in the Figures are shown in Figure 2. It is also preferred that the cords in the fabric are perpendicular to each other but this is not necessary; they may be at a lesser angle to each other. As such, one set of cords may run circumferentially around the tire parallel to the circumferen tial centerline of the tire tread and the other set of cords will be short cords running radially of the tire parallel to the cords in the body ply of the radial tire and perpendicular to the- circumferential centerline of the tire. It is understood that the cords in the cap ply may be angled in relation to the circumferential tread centerline of the tire without departing from the novel scope of this invention.

Specifically, the embodiment illustrated by narrow cap ply 20 in Figure 2 has been utilized in an HR 78-15 radial tire. In this tire the body consisted of two plies of radial, polyester cords. The reinforcing belt structure consisted of two plies containing steel cord at an angle of 22 degrees to the circumferential tread centerline with the cords in each ply running opposite directions. The narrow cap plies consisted of two separate strips of square-woven, noncalendered fabric. This fabric was comprised of 840/1 nylon multifil in both directions with one set of the cords running circumferentially of the tire and the other set radially. The narrow cap plies are 1.625 inches wide and have their lateral edges located .375" beyond the outermost edge of the reinforcing belt structure. On an indoor drum test designed to fail the tire by a separation at the edge of the tread ply, experimental tires with this construction ran longer than experimental tires of an identical construction which did not contain the narrow cap ply embodiment.

Similar testing results were obtained in indoor drum tests on tires containing the embodiment (narrow cap ply, 21) illustrated as the left-hand side of Figure 2. Also, similar testing results were obtained on indoor drum tests on tires containing the embodiment illustrated in the right-hand side of Figure 2 (narrow cap ply, 20) wherein all the cords in the cap plies formed an angle of 45 degrees to the circumferential tread centerline.

WHAT WE CLAIM IS: - 1. - A pneumatic tire having either a radial or bias tire body, a reinforcing belt structure comprising one or more reinforcing belt plies of cord material having a high modulus of elasticity overlying the tire body in the crown area of the tire, a tread member of rubber having a low modulus of elasticity radially outward of the belt structure, each of the lateral edges of the belt structure having a layer of flexible non-calendered fabric disposed at a location radially between the tire body and the tread member and radially outward of the belt ply or a belt ply of the belt structure, the said fabric comprising cord material of an intermediate modulus of elasticity with the cords extending in two directions transverse to each other.

2. A tire as claimed in claim 1, wherein

**WARNING** end of DESC field may overlap start of CLMS **.

Claims

**WARNING** start of CLMS field may overlap end of DESC **.

tion of narrow cap plies, 30 and 32, showing all edges of the belt structure enveloped in separate, narrow cap plies, 33 and 34.

It is understood that it is necessary to apply a separate layer of rubber between the non-calendered cap plies in the areas where they will be immediately adjacent to another non-calendered cap ply to prevent cord to cord contact between the plies.

Specifically, such rubber gum strips would have to be placed between plies 24 and 25 in Figure 3 and plies 33 and 34 in Figure 6 in the areas where the cords of these plies would be in contact.

The fabric utilized in the invention may be first coated by a resorcinol/formaldehyde, rubber-based dip by immersing the fabric in a bath of the dip solution. A natural rubber-based, add-on cement may also be applied to this fabric, if desired, to improve its tack to adjoining rubber coated plies in the uncured tire. This cement has a natural rubber base and contains tackifying resins which are dissolved in a solvent media, such as toluene. This type of cement is applied to the fabric by immersing the fabric in a bath of the cement or by spraying.

Figure 7 illustrates a full cap ply 35, which extends axially beyond both of the lateral edges of the reinforcing belt structure. The full cap ply extends axially across the entire width of the reinforcing belt structure. It is understood that the ends of the cap ply may be wrapped around one or both of the ends of the belt plies in the manner illustrated in Figure 5.

Figure 8 illustrates an embodiment containing a full cap ply 36, which ends at the lateral edge of the belt ply structure.

In all the embodiments the cap ply or plies may be applied to the tire building drum when the tire is on the flat building drum or on an inflated drum by winding the cap ply around the drum in the proper location. In building a single layer cap ply embodiment, an overlap of the cap ply ends of up to one inch has been used. This overlap may result in a gap between the cap ply ends, a butt of the cap ply ends, or a slight overlap of the cap ply ends, in the cured tire. The small area of cord to cord contact which may occur when a slight overlap of the cap ply ends is present in the cured tire has not been detrimental to tire performance.

The preferred embodiments of the ones illustrated in the Figures are shown in Figure 2. It is also preferred that the cords in the fabric are perpendicular to each other but this is not necessary; they may be at a lesser angle to each other. As such, one set of cords may run circumferentially around the tire parallel to the circumferen tial centerline of the tire tread and the other set of cords will be short cords running radially of the tire parallel to the cords in the body ply of the radial tire and perpendicular to the- circumferential centerline of the tire. It is understood that the cords in the cap ply may be angled in relation to the circumferential tread centerline of the tire without departing from the novel scope of this invention.

Specifically, the embodiment illustrated by narrow cap ply 20 in Figure 2 has been utilized in an HR 78-15 radial tire. In this tire the body consisted of two plies of radial, polyester cords. The reinforcing belt structure consisted of two plies containing steel cord at an angle of 22 degrees to the circumferential tread centerline with the cords in each ply running opposite directions. The narrow cap plies consisted of two separate strips of square-woven, noncalendered fabric. This fabric was comprised of 840/1 nylon multifil in both directions with one set of the cords running circumferentially of the tire and the other set radially. The narrow cap plies are 1.625 inches wide and have their lateral edges located .375" beyond the outermost edge of the reinforcing belt structure. On an indoor drum test designed to fail the tire by a separation at the edge of the tread ply, experimental tires with this construction ran longer than experimental tires of an identical construction which did not contain the narrow cap ply embodiment.

Similar testing results were obtained in indoor drum tests on tires containing the embodiment (narrow cap ply, 21) illustrated as the left-hand side of Figure 2. Also, similar testing results were obtained on indoor drum tests on tires containing the embodiment illustrated in the right-hand side of Figure 2 (narrow cap ply, 20) wherein all the cords in the cap plies formed an angle of 45 degrees to the circumferential tread centerline.

WHAT WE CLAIM IS: - 1. - A pneumatic tire having either a radial or bias tire body, a reinforcing belt structure comprising one or more reinforcing belt plies of cord material having a high modulus of elasticity overlying the tire body in the crown area of the tire, a tread member of rubber having a low modulus of elasticity radially outward of the belt structure, each of the lateral edges of the belt structure having a layer of flexible non-calendered fabric disposed at a location radially between the tire body and the tread member and radially outward of the belt ply or a belt ply of the belt structure, the said fabric comprising cord material of an intermediate modulus of elasticity with the cords extending in two directions transverse to each other.
2. A tire as claimed in claim 1, wherein

the fabric is a woven fabric.
3. A tire as claimed in claim 1 wherein said non-calendered fabric has equal strength in both of said directions.
4. A tire as claimed in claim 2 or claim 3, wherein said non-calendered fabric has its cords extending in one of said directions disposed parallel to the circumferential centerline of said tire tread, the cords extending in the other direction being parallel to reinforcing cords in said tire body.
5. A tire as claimed in claim 2 or claim 3 wherein both said directions extend at an angle of 45" to the circumferential centerline of said tread.
6. A tire as claimed in any one of claims 3 to 5, wherein the cords extending in one of said directions are of a different material from those extending in the other direction.
7. A tire as claimed in any one of claims 3 to 5, wherein alternate cords extending in one of said directions are made frdm a different material from other cords or yarns extending in said one direction.
8. A tire as claimed in any one of claims 1 to 7, wherein the reinforcing belt structure comprises two or more reinforcing belt plies, said fabric being disposed radially outward of the outer or, as the case may be, the outermost belt ply.
9. A tire as claimed in any one of claims 1 to 7, wherein the reinforcing belt structure comprises two or more reinforcing belt plies, said fabric being disposed between the lateral edge portions of adjacent plies.
10. A tire as claimed in claim 9, wherein said fabric is further disposed radially outward of the outer or, as the case may be, the outermost belt ply.
11. A tire as claimed in any one of claims 1 to 7, wherein said fabric is disposed radi ally between the reinforcing belt structure and the tread member and extends across the full width of the reinforcing belt structure.
12. A tire as claimed in any one of claims 1 to 11, wherein said fabric extends laterally beyond the lateral edges of the reinforcing belt structure.
13. A tire as claimed in any one of claims 1 to 12 wherein a layer of said fabric is disposed between the tire body and a lateral edge portion of said belt structure.
14. A tire as claimed in any one of claims 1 to 7, wherein at least one lateral edge portion of the reinforcing belt ply or one of the reinforcing belt plies has said fabric folded about it.
15. A tire as claimed in any one of claims 1 to 7, wherein the reinforcing belt structure comprises two or more reinforcing belt plies and wherein said fabric is folded about at least one of the lateral edge portions of the belt structure.
16. A tire as claimed in any one of claims 1 to 15, wherein said non-calendered fabric is a square woven fabric.
17. A tire as claimed in any one of claims 1 to 16, wherein said non-calendered fabric is made from nylon cord.
18. A tire as claimed in claim 1, wherein said non-calendered fabric is a knitted fabric.
19. A pneumatic tire substantially as hereinbefore described with reference to and as illustrated in any one of Figures 2 to 8 of the accompanying drawings.