IE41824B1

IE41824B1 - Pneumatic tyres

Info

Publication number: IE41824B1
Application number: IE1943/74A
Authority: IE
Original assignee: Dunlop Ltd
Priority date: 1973-09-22
Filing date: 1974-09-19
Publication date: 1980-04-09
Also published as: AU7349874A; LU70955A1; FI272674A; GB1483053A; DE2444860A1; JPS5082706A; DK497274A; BE820083A; ES430274A1; FR2244635B1; SE7411753L; NL7412407A; IE41824L; FR2244635A1; SE412346B

Abstract

1483053 Pneumatic tyres DUNLOP Ltd 16 Sept 1974 [22 Sept 1973 6 March 1974] 44539/73 and 10005/74 Heading B7C A heavy-duty pneumatic tyre, e.g. for commercial vehicles, comprises a carcass with a single ply 7 of substantially radially extending inextensible cords and a breaker assembly with three superimposed plies 2-4 of inextensible cords, the ratio of the radius of transverse curvature R of the radially outer surface of the tyre tread 1 to the axial width W of the tread lying in the range 2À75 : 1 to 3À5 : 1, and the cords of two of the breaker plies being disposed at equal and opposite cord angles with the cords of the third ply being disposed at a different cord angle to the cords of the other two plies. The cord angle of the two plies may be 10- 25 degrees and that of the third ply 40-70 degrees. The third, higher cord angle, ply may be the radially outermost one, in which case the breaker plies may progressively increase, Fig. 1, or decrease (Fig. 3b, not shown) in width from the outermost to the innermost or may be arranged such that the third ply is the widest one and the middle ply is narrower than the innermost ply (Fig. 3c, not shown). Alternatively (Fig. 3a, not shown), the higher cord angle ply may be the radially innermost ply and narrower than the middle ply which in turn is wider than the outermost ply. A layer of rubber may be interposed between two of the breaker plies in the central region of the breaker assembly. The maximum axial width B of the breaker assembly may be 90-110% of the tread width W. The cords of the carcass and breaker assembly may be of steel.

Description

PATENT APPLICATION BY (71) DUNLOP LIMITED, A BRITISH COMPANY, OF DUNLOP HOUSE, RYDER STREET, ST. JAMES’S, LONDON S.W.I., ENGLAND.

This invention relates to pneumatic tyres and. more particularly to heavy duty radial ply tyres, for example, those suitable for use on trucks and other commercial vehicles.

Known tyres of this type comprise a carcass reinforced 5 by a single plytof substantially radially extending inextensible cords, e.g. steel cords, and a tread supported by a breaker assembly made up of several plie3 of inextensible cords, two at least of which have a low bias angle, for example in the range 10° to 25°.

Current radial ply truck tyres of, for example, size .OO-R-POjhave tread widths of the order of 195 to 200 mm associated with radii of curvature of the tread radially outer surface in a meridian plane in the range 350 mm to 500 mm in the inflated but unloaded state.

We have now found however that in order to obtain a more uniform contact pressure distribution in the tyre ground contact -241824 area, and thus better grin and more even wear, the radius of the tread radially outer surface in a transverse plane should be greater i.e. this surface should have a flatter profile.

According to the present invention there is provided a 5 heavy duty radial ply pneumatic tyre comprising a carcass reinforced by a single ply of substantially radially-extending inextensible cords and a tread supported by a breaker assembly, the radius of the curvature of the radially outer surface of the tread in a meridian plane being such that the ratio of said 1q radius of curvature to the axial width of the tread of the tyre is in the range of 2,75 to 1 to 3.5 to 1, the breaker assembly comprising at least three superimposed plies of inextensible cords, the cords of two of the plies having equal and opposite bias angles relative to the mid-circumferential plane of the tyre and the cords of a third ply having an angle relative to the mid-circumferential plane different to the angle to said plane of the cords of the said two plies.

In this way the lateral stiffness of the breaker assembly and hence the overall tread life may be optimized. Advantageously ?0 the cords of said two plies have an angle of 1O°-25° preferably °-25°, and the cords of said third ply have an angle of 40°70°, preferably 4O°-5O°. It is advantageous that the high angle ply is the outermost ply for the reason that this enables the higher angle ply to act also as protection for the two lower angle plies,the latter being those'whioh are tensioned on in-341824 flation of the Gyro arid hence arc nubjccted to tho higher Load.

It WILL he appreciated that the stiffening function of the higher angle layer will not be seriously impaired, by damage to some of the cords therein e,g. by stone cutting when in use. In present radial ply truck tyres the higher angle ply is generally the innermost ply and a fourth breaker ply is frequently provided to carry out the function of protection of the low angle layers.

If desired the breaker assembly of the tyre of this in10 vnrition may not he fully triangulated across it3 whole Width but only in ita aide regions and not in the centre of' the breaker.

In one example of such a construction a discoupling layer of rubber is positioned in the centre region of the breaker assembly between two of the plies as described in British U Patent Specification No. 1,327,195. In this way the stiff support may be provided where it is most needed, adjacent the tyre shoulders^ and the centre of the tyre tread may be more flexible to ensure good impact resistance.

Preferably the maximum axial width of the breaker assembly PO is in the range 90$ to 110$ of the axial width of the tread.

Although at the present time it is preferred that the inextensible cords are steel cords it is anticipated that as -441824 other inextensiblo materials are developed they may become equally satisfactory for the purpose of this invention.

The invention will' now be described by way of example with reference to the accompanying drawings of which:5 Figure 1 is a cross-sectional view of a tyre having a triangulated breaker assembly; Figure 2 is a perspective cut-away view of the breaker assembly plies of the tyre of Fig. 1 showing their relative bias angles, and Figures 3a,b and c show diagrammatically alternative breaker assembly ply arrangements.

As shown in Figure 1 a 10.00-R-20 tyre consists of a tread supported by a breaker assembly consisting of three breaker plies 2, 3 and 4, beads 5 and sidewalls 6, a carcass ply 7 of radially orientated steel cords extending from bead to bead.

The radius of curvature R of the radially outer surface of the tread of the tyre in a meridian plane is 660 mm, and the axial width W of the tread is 215 mm whilst the maximum axial width B of the breaker assembly is 200mm. The ratio of breaker PQ width to tread width is thus 93$ and the ratio of tread radius to width is 3.02 to 1.

As shown more clearly in Figure 2 the breaker ply 2 consists of parallel steel cords at a bias angle of 45° to the mid-541824 circumferential plane of the tyre,,whilst the breaker plies 3 and 4 consist of similar parallel steel cords and have equal and opposite bias angles of 18° to the mid-circumferential plane of the tyre, the ply 3 being biassed in an opposite sense from the ply 2.

In the tyre shown in Figures 1 and 2 referred to above the breaker assembly consists of breaker plies in which the widest ply is innermost and the narrowest ply is the outermost.

Figures 3a-c illustrate other arrangements of breaker plies 10 which may be utilized if desired. In Figures 3a,b and c the letter Ή’ is used to denote the ply of high bias angle (40° to 70°) and the letter ’L’ to denote the plies of lower bias angle (10° to 25°)..

In Fig. 3a, the ply H is the radially innermost ply, the 15 width arrangement being that the radially outermost ply L’ is the narrowest and the adjacent ply I is the widest.

In Fig. 3b, the ply H is the radially outermost ply and the widths progressively, decrease radially inwardly, i.e. 2Q In Fig. 3c the ply H is again the radially outermost and widest ply, and the adjacent ply L’ is the narrowest ply.

Claims

1. A heavy duty radial ply pneumatic tyre comprising a carcass reinforced by a single ply of substantially radially-extending inextensible cords and a tread supported by a breaker assembly, the radius of the curvature 5 of the radially outer surface of the tread in a meridian plane being such that the ratio of said radius of curvature of the radially outer surface of the tread to the axial width of the tread of the tyre is in the range of 2.75 to 1 to 3.5 to 1, the breaker assembly comprising at least three superimposed plies of inextensible cords, 10 the cords of two of the plies having equal and opposite bias angles relative to the mid-circumferential plane of the tyre and the cords of a third ply having an angle relative to the mid-circumferential plane different to the angle to said plane of the cords of the said two plies. axial

2. A tyre according to Claim 1 wherein the maximumytoidth of the 15 breaker assembly supporting the tread of the tyre is in the range 90% to 110% of the axial width of the tread.

3. A tyre according to Claim 1 or 2 wherein the angle of the cords of said two plies to said plane is in the range 10° to 25°.

4. A tyre according to Claim 3 wherein said range is 15° to 25°. 20 5. a tyre according to any preceding claim wherein the angle of the cords of the third ply to said plane is in the range 40° to 70°C,

5. Other across the full width of the assembly.

6. A tyre according to Claim 5 wherein said range is 40° to 50°.

7. , A tyre according to any preceding claim wherein said third layer is the radially outermost layer of the assembly. - 7 41824

8. A tyre according to any preceding claim wherein the plies of the breaker assembly are not directly superimposed on each

9. < A tyre according to claim 8 wherein said plies are not directly superimposed in the centre of the assembly.

10. A tyre according to claim 8 or 9 wherein a discoupling layer of rubber is disposed between two of the plies in the •,0 central region of the assembly.

11. · A tyre according to any preceding claim wherein the innermost ply of the assembly is narrower than at least one of the ' other plies.

12. A tyre according to claim 11 wherein the outermost ply 15 is the widest ply.

13. A tyre according to any one of the preceding claims wherein the inextensible cords of at least the ply or plies of the breaker assembly are steel cords. -841824

14. A tyre according to claim 1 substantially as described herein with reference to, and as illustrated in, Figures 1 and 2 of the accompanying drawings. 15 · A tyre according to claim 1 substantially as described 5 herein with reference to, and as illustrated in, any one of Figures 3a,h and c of the accompanying drawings.