Resilient tires and wheels – Tires – resilient – Cushion and pneumatic combined
Reexamination Certificate
1999-05-05
2001-01-09
Johnstone, Adrienne C. (Department: 1733)
Resilient tires and wheels
Tires, resilient
Cushion and pneumatic combined
C152S517000
Reexamination Certificate
active
06170545
ABSTRACT:
BACKGROUND OF THE INVENTION
1 . Field of the Invention
The present invention relates to a safety pneumatic tire, in particular, a safety pneumatic tire (tire assembly) which is greatly improved in both run-flat durability and riding comfort characteristic. More particularly, the present invention is concerned with a safety pneumatic tire which is equipped with a side-reinforcing layer and is filled with specific elastic foam in the internal hollow portion encompassed by a tire shell and a rim.
2. Description of the Related Arts
A number of proposals for a safety pneumatic tire have heretofore been made in order to enable the tire to continue running for the time being even in the case where the tire is deprived of pneumatic pressure by reason of puncture, flattening or the like. For instance, there is known a pneumatic tire which comprises a tire shell and closed cell-based foam which is filled into the internal hollow portion of the assembly composed of the tire shell and a rim which fits the above-mentioned tire to itself (refer to Japanese Patent Application Laid-Open Nos. 127207/1994(Hei-6), 183226/1994(Hei-6), 186610/1995(Hei-7), 332805/1996(Hei-8) and the like.
However, any of the tires disclosed therein is limited mainly to a special tire or a small-sized tire such as a tire for agricultural or tillage use, a rally tire, a tire for a two-wheeled vehicle, a bicycle tire and the like. In addition, there have heretofore been proposed a variety of safety pneumatic tires such as a tire of double-wall structure, a tire equipped inside with a load-supporting apparatus, and a side-reinforced tire. Of these, an example of the most general tire in practical service at the present time, is so-called a side-reinforced tire which is equipped with a side-reinforcing layer composed of relatively hard rubber lying inside of the side wall portion and extending over both the shoulder portion and the bead portion . Such kind of tire is used principally for a run-flat tire having an aspect ratio of at most 60%. Moreover, in the case of a pneumatic tire having a relatively large height and an aspect ratio of at least 60% , there is known a run-flat tire with such a structure that supports the load at the time of puncture or flattening by mainly fixing a tire-supporting member into a rim in order to avoid the heat build-up in the side wall portion due to relatively long-distance running with a high speed.
On the other hand, the requirements For the performance of a run-flat tire tend to be more and more enhanced, and thus it is the actual situation that further improvement in a possible run-flat distance of the tire is eagerly desired. In particular, in the case of a safety pneumatic tire with an aspect ratio of at least 60% , the tire is desired to exhibit satisfactory riding comfort characteristic under normal condition as well as sufficient run-flat durability. However, the problems in conventional side-reinforced tires still remain unsolved in that the run-flat durability is improved to some extent, but is not yet sufficiently improved, the riding comfort characteristic and the rolling resistance are markedly worsened, and in addition the tire weight is unfavorably increased.
SUMMARY OF THE INVENTION
Under such circumstances, a general object of the present invention is to provide a safety pneumatic tire which is remarkably improved in run-flat durability, is excellent in both run-flat durability and riding comfort characteristic, has a relatively light weight, and further is excellent in rolling resistance.
Other objects of the present invention will be obvious from the text of this specification hereinafter disclosed.
In view of the foregoing, intensive research and investigation were made by the present inventors in order to solve the above-mentioned problems. As a result, it has been found that the run-flat durability of a pneumatic tire is drastically enhanced by arranging a side-reinforcing rubber layer in the internal surface of a side wall portion and at the same time, filling closed cell-based foam comprising butyl rubber or halogenated butyl rubber in the internal hollow portion encompassed by a tire shell and the tire rim. The present invention has been accomplished by the above-mentioned findings and information.
It has been recognized in the course of the aforestated research and investigation by the present inventors that in the case of the conventional side-reinforced tire and the tire filled in with foam, the run-flat durability of a tire, that is, the possible run-flat distance of a tire after the puncture or flattening thereof, is closely related to the amount of the deflection of the tire. The above-mentioned findings can be seen, for instance, from the results of Comparative Examples 1 to 6 (refer to Table 1) in which testing was carried out by the present inventors through the use of the conventional side-reinforced tires. The findings can also be seen from the results of Reference Examples 1 to 4 (refer to Table 3 and
FIG. 4
) in which testing was carried out by the use of the conventional tires that were filled in with butyl rubber foam, but were not equipped with a side wall-reinforcing layer. The actual load ranges of the tires in Reference Examples 1 to 4 correspond to the tire deflection rate in the range of about 35 to 40%.
It has also been recognized in the course thereof by the present inventors that, in the case of butyl rubber or halogenated butyl rubber being employed in particular as the constructional material for the above-mentioned closed cell-based foam, an increase in the tire deflection rate due to flat-run is suppressed at a given level. Thereafter the tire deflection rate is decreased to some extent as the case may be, rather than is increased, whereby the tire deflection rate reaches a steady state (refer to Table 4 of Reference Example 5). The reason for the foregoing is thought as follows: Butyl rubber or halogenated butyl rubber is such rubber that has not only excellent gas-impermeability but also relatively high heat-build-up property, and therefore the pressure inside the closed-cell foam is raised by the self-heat generation, thereby suppressing the tire deflection. On the one hand, the decreased tire deflection decreases the self-heat generation of the foam of the tire. As a result, the temperature rise of the tire is ceased, so that the tire is brought to a steady state (the load-supporting mechanism of the foam). The above-mentioned phenomenon is a peculiar phenomenon which can not usually be seen in any of the conventional tires such as a side wall-reinforced tire and a tire inside of which is merely filled with elastic foam.
The present invention, which has been developed on the basis of the foregoing findings and information for the purpose of exhibiting the working effect in the actual load range, provides a safety pneumatic tire comprising a tire shell which is equipped with a toroidal carcass extending over a pair of bead portions and also functioning as a reinforcing material for a side wall portion connected to said bead portions and further for a tread portion, and which has a side-reinforcing layer on the internal surface of said side wall portion; a rim which hermetically seals and supports said bead portions of said tire shell; and closed-cell-based elastic foam which is filled in the internal hollow portion encompassed by said tire shell and said rim, wherein the constructional material of said elastic foam is butyl rubber or halogenated butyl rubber. The present invention also provides the safety pneumatic tire according to the aforestated constitution, wherein said tire has an aspect ratio of at least 60% , and at the same time, provides a tubeless pneumatic tire according to the aforestated constitution.
REFERENCES:
patent: 3195601 (1965-07-01), Travers
Kobayashi Kazuomi
Matsuo Kenji
Nishikawa Tomohisa
Bridgestone Corporation
Johnstone Adrienne C.
Sughrue Mion Zinn Macpeak & Seas, PLLC
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