A radial ply tire comprises a tread, sidewall and bead regions. At least the region of severe flexing of the sidewall when the tire is run in a deflated or substantially under-inflated condition comprises a rubber compound which has a rebound resilience of at least 87 percent, and more preferably of at least 90 percent, measured by the Lupke Dunlop pendulum method according to B.S. 903/1950 and a hardness in the range of 45- 65 Shore A.
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1. A radial ply pneumatic tire comprising a tread, a pair of sidewalls each terminating in a tire bead and a carcass of substantially radial cords extending from one tire bead to the other, each sidewall having a highly resilient region disposed axially inwardly and axially outwardly of the carcass and extending radially outwardly from a point radially inward of the maximum width of the tire to the radially outer extremity of the sidewall, the highly resilient region being formed of a high resilient rubber compound having a rebound resilience of at least 87 percent measured by the Lupke Dunlop pendulum method according to British Standard 903/1950 and a hardness in the range of 45-65 Shore A.
15. A radial ply pneumatic tire comprising a tread, a pair of sidewalls each terminating in a tire bead with the tread width being greater than the distance between the beads when mounted on a rim and a carcass of substantially radial cords extending from one tire bead to the other, each sidewall having a highly resilient region disposed axially inwardly and axially outwardly of the carcass and extending radially outwardly from a point radially inward of the maximum width of the tire to the radially outer extremity of the sidewall, the highly resilient region being formed of a high resilient rubber compound having a rebound resilience of at least 87 percent measured by the Lupke Dunlop pendulum method according to British Standard 903/1950 and a hardness in the range of 45-65 Shore A.
14. In a pneumatic radial tire and wheel assembly capable of being run in a deflated condition having a wheel rim with a pair of opposed annular flanges and means to prevent the tire from becoming dislodged from the wheel when run in a deflated condition; the tire having a pair of sidewalls each terminating in a tire bead and a carcass of substantially radial cords extending from one bead to the other, the improvement comprising means to permit sidewall flexing with low temperature build-up while operating in deflated or low inflation condition, said means comprising two layers of highly resilient material in each sidewall, one layer being disposed axially inwardly and the other being disposed axially outwardly of the carcass, said layers extending radially outwardly from a point radially inward of the maximum axial width of the tire to the radially outer extremity of the sidewall, the layers being formed of a high resilient rubber compound having a rebound resilience of at least 87 percent measured by the Lupke Dunlop pendulum method according to British Standard 903/1950 and a hardness in the range of 45-65 Shore A.
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This invention relates to pneumatic tires.
According to the present invention a radial ply pneumatic tire comprises a tread, sidewalls and beads, at least the region of severe flexing of the sidewall when the tire is run in a deflated or substantially underinflated condition comprising a rubber compound having a rebound resilience of at least 87 percent measured by the spring
The tire consists of a tread 1, sidewalls and beads 3 and as shown in the drawings, is mounted on a wheel rim 4 (shown schematically) which has a width between flanges less than the width of the tread 1 of the tire. The tire also includes a carcass 5 of radial cords turned up around the beads 3 and a pair of breaker plies 6 extending beneath substantially the full width of the tread.
As shown on one sidewall of the flattened tire in FIG. 1, the zone of severe flexing of the sidewall 2 is the region of the sidewall between the lines A and B. On the other sidewall of the tire of FIG. 1 the lines E and F show the position of the high resilience rubber in the tire illustrated.
As shown more clearly in FIG. 2 the tire contains a rubber of resilience at least 90 percent in the region 7 of the sidewall between the line E and the line F so that the high resilience rubber extends from a point close to but radially outwardly of the rim flange to the base of the tread pattern wearable rubber.
Tests have been carried out to investigate the effect on temperature build-up in the tire sidewall produced by varying the resilience of the sidewall compound.
Textile radial ply tires (size 185/60 × 13) in which the rubber in the sidewall region between E and F (see FIG. 2) and in the inner liner of the tire was of various levels of hardness and resilience. The temperature generated in the tire sidewall was measured on three different tires run at the same speed and conditions with the tire totally flat and mounted on a 31/2 inches wide crimped rim. The results are tabulated below:
| ______________________________________ |
| Resilience of S/W cpd |
| Hardness of S/W cpd |
| Temp. |
| ______________________________________ |
| 70% 61 Shore A 120° C |
| 90% 61 Shore A 90° C |
| 95% 51 Shore A 95° C |
| ______________________________________ |
Similar tests were carried out to compare a compound of 90 percent resilience and 60/61 Shore A hardness with a similar compound of 87 percent resilience and similar hardness. These tires were the same size as the tires mentioned above, but were run (in the same position on the same car) at an inflation pressure of 4 psi. The results were as follows:
| ______________________________________ |
| S/W cpd. S/W cpd Temp. |
| resilience Hardness (50 mls. at 4 psi) |
| ______________________________________ |
| 90% 61 Shore A 87° C |
| 87% 60 Shore A 108° C |
| ______________________________________ |
From this test it appears that for compounds of this hardness level (which give better results than softer compounds) the resilience value is extremely critical in the region of 90 percent a small difference in resilience producing a markedly different result. The compound of 87 percent resilience was adequate if some inflation pressure is present and modest performance standards are set, but was inferior to the higher resilience compound.
In all the tests mentioned above the temperature measurement was carried out by inserting a suitable thermocouple into the mid-sidewall region of the tire sidewall i.e., the position of maximum width of the tire.
In the tire of FIG. 3 a cushion 8 of high resilience compound is provided inside the tire carcass to thicken the tire in the shoulder region and further reduce flexing. Numeral 9 refers to alternative buttresses as previously discussed.
| Patent | Priority | Assignee | Title |
| 6044884, | May 30 1997 | Continental Reifen Deutschland GmbH | Pneumatic vehicle tire having reinforced sidewalls for improved emergency running properties |
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| Executed on | Assignor | Assignee | Conveyance | Frame | Reel | Doc |
| Feb 23 1976 | Dunlop Limited | (assignment on the face of the patent) | / |
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