AU463568B2 - Improvements in or relating to pneumatic tyres - Google Patents

Description

30.207 71 This invention relates to pneumatic tyres.

When a pneumatic tyre.is punctured, loss of

interior walls air can occur to the extent that opposite localised pressure of the tyre come into contact with high severely and the tyre adjacent.to the contact patch is

flexed and buckled. This creates very high stresses in the tyre the rubber and the reinforcing materials within

and can lead to tyre failure, e.g. by fatigue, in in the particular since there are flexing movements during tyre of very great amplitude which are repeated

each rotation of the tyre. According to the present invention there is

provided a pneumatic tyre having in the outer region of rubber each of the sidewalls an annular layer of soft -aplied- the rubber of tc i.w.l aid Soft run0

having a hardness of 45 B.S.I. or softer.

If desired the modulus of elasticity.of the

rubber may also be low e.g. less than 450 lbs./square

measured at 300 extension but rubbers of considerably

higher modulus may also be used. The sidewall of a tyre is considered, in this

specification, to be that portion of a tyre which extends from the edge of the tread which forms the limit of the ground contacting surface to the position of on the tyre corresponding to the radially outer limit the flange of a standard wheel rim to which the tyre would norually be fitted. The outer region of each of the tyre sidewalls, of soft adjacent to the tread, to which the annular layer rubber is applied may extend from the edge of the tread

which forns the liuit of the ground contacting surface,

2. 46356

30,207 7t radially inwardly to the mid-sidewall region i.e. that

region of the tyre of maximum width measured on the

moulded tyre, though th3 region may be smaller and lying

between the above-mentioned limits.

The layer of soft rubber is preferably located

substantially radially outwardly of a point lying

radially outwardly of the mid-sidewall by an amount of

about of the total sectional height of the moulded tyre

measured from the bead base to the peak of the crown of

the tyre tread.

The maximum thickness of the annular layer of

soft rubber may lie between 1 mm and the total thickness

of rubber down to the topping compound on the cords of

the tyre casing. The annular soft rubber layer may be located

outwardly or inwardly of the carcass sidewall i.e. on the

inner liner side but preferably, in either case the outer

region of each of the sidewalls of the tyre are devoid

of deep grooves or any other such pattern features which

may lead to concentration of stresses during severe

flexing.

In a tyre in accordance with the invention,

the provision of the soft rubber layer serves to reduce

the very high stresses in the rubber and the reinforcing

material within the tyre under deflated running conditions

compared with tyres having no such layer by the dis-

tribution of the strains in the structure. Thus early

structural failure can be avoided and a deflated tyre

according to the invention uay be driven an increased

distance compared with a conventional tyre not in

accordance with the invention, without serious damage, a

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eventually being fitted. replacement tyre and wheel assembly to tyres This invention is applicable in particular can be applied to carcasses having carcasses of radial cords but to be run safel: of cross-bias cords. Since the tyre is designed of the tyre is prefer under deflated conditions the aspect ratio cent and particularly betwe< ably low, e.g. between 30 and 75 per the tyre is pre and 70 per cent and the width of the tread of flanges of the rim of the ferably greater than the width between wheel for which the tyre is designed. conjunction with The present invention may be used in 1,359,467, 1,359,46 inventions of our United Kingdom Patent Nos. 1,359,461, 1359,462 and 1,359,463. in The invention applies to tyre and wheel assemblies e.g. where the rim ii which the tyre can be removed from the rim the tyre is not removable a split rim or, alternatively, when for example, therefrom, i.e. the two form a permanent assembly, after assemblyof the when the rim is swaged over the tyre beads tyre and rim. be describ Several examples of the invention will now to the accompanying drawi by way of example only with reference in which:- a tyre having ther Figure 1 shows in section a sidewall of a veneer of soft rubber in the outer region; a tyre having a is Figure 2 shows in section a sidewall of of thicker soft rubber in the outer region; tyre Figure 3 shows in section a sidewall of a

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having thereon a thin layer of soft

rubber inside the carcass in the outer

sidewall region;

Figure 4 shows in section a sidewall of a tyre

having a thicker layer of soft rubber

inside the carcass in the outer sidewall

region.

As shown in Figure 1, a 185/60-13 radial ply

tyre consists of a carcass 1, containing a textile radial

cord reinforcing ply and bead assemblies, several breaker

layers 2, tread rubber 3 and sidewall rubber 4, and a

chafer strip

The tread rubber 3 is of a usual type and has a

hardness in the range 63 to 73 B.S.I. whereas the sidewall

rubber is softer having a hardness in the range 53-57

B.S.I.

In the outer sidewall region of the tyre is

positioned a thin layer 6 of soft rubber having a hardness 2 of 43 B.S.I. and a modulus at 300% extension of 800 lbs/in.

The layer of soft rubber extends from a point positioned

of the radial sectional height of the tyre radially

outwardly of the mid-sidewall to a point high on the tyre

shoulder and has a maximum thickness 1 Im.

In the example shown in Figure 2 the tyre is of

similar construction to that shown in Figure 1 except that

a layer 7 of the soft rubber replaces substantially all the

sidewall rubber radially outwardly of a point positioned

of the section height (Ii) of the tyre radially outwardly of

the id-sidewall.

In the example shown in Figure 3 the tyre is

again of similar cons*ruction to that shown in Figure 1

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30.207 /7t

(xcept that a layer 8 of the soft rubber having a

naximum thickness of 1 mm. is located radially inwardly

of the carcass plies. The layer 8 extends radially

outwardly to beneath the tread edge from between the

mid-sidewall and a point positioned j of the section

height of the tyre radially outwardly of the mid-sidewall. In the example shown in Figure 4 the tyre is

similar to that shown in Figure 3 except that a thicker

layer 9 of- the soft rubber is provided radially inwardly

of the carcass plies. The layer 9 has a maximum thickness

equal to the thickness of sidewall rubber 4 at the mid-

sidewall and extends from the mid-sidewall to a region

radially inwardly of the tread edge.

An example of a soft rubber suitable for use

in the invention is given in the table below, all amounts

of ingredients being given in parts by weight TABLE

Natural rubber 50 Insoluable sulphur 2

Neoprene WRT 50 MBTS 0.7

Lampblack 20 Nonox ZA 1.25

HAF black 10 BLE 25 1.75

Light Cal.Nag. 2

Pine Tar 3 Coumarone Indene resin 3 Hardness 40 to 43 B.S.I.

Zinc Oxide 4

The soft rubber used in the tyres of this invention is

preferably a rubber having a high resistance to flex

cracking, particularly at temperatures of the order of

100°C. to 1400 C.

4635. 6

Claims (3)

2 7171 THE CLAIMS DEFINING THE INVENTION ARE AS FOLLOWS:-

1. A pneumatic tyre having in the radially outer region of

each of the sidewalls an annular layer of soft rubber having a

hardness of 45 B.S.I. or softer.

2. A pneumatic tyre according to claim 1 in which the layer

of soft rubber is located substantially radially outwardly of a

point lying radially outwardly of the mid-sidewall by the amount

of about 1/8 of the total sectional height of the inflated tyre

measured from the bead base to the peak of the crown of the tyre tread.

3. A pneumatic tyre according to claim 1 or 2 in which the

maximum thickness of the annular layer of soft rubber is not less than 1 mm.

4. A pneumatic tyre according to claim 1, 2 or 3 in which

the annular layer of soft rubber is located outwardly of the carcass sidewall. A pneumatic tyre according to claim 1, 2 or 3 in which

the annular layer of soft rubber is located axially inwardly of the carcass sidewall.

6. A pneumatic tyre according to any one of the preceding

claims having an aspect ratio between 30% and

7. A pneumatic tyre according to claim 7 in which the as-

pect ratio is between 55% and

8. A pneumatic tyre according to any one of the preceding

claims in which the width of the tread of the tyre is greater than the width between the bead heels when the tyre is mounted on a

wheel rim for which the tyre is designed and inflated to its normal

302 07/71

working pressure. 9. A pneumatic tyre according to any one of the preceding claims in which the soft rubber is resistant to flex cracking at temperatures in the range 100 0 C. to 140 0 C. A pneumatic tyre substantially as described herein with

reference to and as illustrated in Figure 1 or 2 of the accompany ing drawings.

11. A pneumatic tyre substantially as described herein with

reference to and as illustrated in Figure 3 or 4 of the accompany ing drawings.

Dated this 17th day of June, 1971.

DUNLOP AUSTRALIA LIMITED.

EDWD. WATERS SONS, PATENT ATTORNEYS, RUSSELL STREET, MELBOURNE, AUSTRALIA.

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FIG.I.

FIG.2.

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FIG.3.

FIG .4.

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