PNEUMATIC TIRE WITH SEALANT

Abstract

The present invention is directed to a pneumatic tire comprising a tread portion having (i) circumferential grooves and (ii) circumferential ribs or rows of tread blocks; an inner surface defining a tire cavity; and a sealant material layer at least partially covering the inner surface radially below the tread portion within the tire cavity. The sealant material layer comprises elevations of sealant material, wherein an elevation of sealant material is provided radially below each of at least two of the circumferential grooves, and wherein the sealant material layer has a larger radial thickness in said elevations than in areas radially below the circumferential ribs or rows of tread blocks.

Claims

1. A pneumatic tire comprising a tread portion having (i) circumferential grooves and (ii) circumferential ribs or rows of tread blocks; an inner surface defining a tire cavity; and a sealant material layer at least partially covering the inner surface radially below the tread portion within the tire cavity, the sealant material layer comprising elevations of sealant material, wherein an elevation of sealant material is provided radially below each of at least two of the circumferential grooves, and wherein the sealant material layer has a larger radial thickness in said elevations than in areas radially below the circumferential ribs or rows of tread blocks.

2. The pneumatic tire according to claim 1, wherein each elevation has an axial width within a range of 70% to 130% of an axial width of a bottom of a circumferential groove radially above the respective elevation.

3. The pneumatic tire according to claim 1, wherein a radial thickness of an elevation of two neighboring elevations, measured from the inner surface of the tire to the radially innermost surface of the respective elevation, is one or more of: at least 15% larger than a radial thickness of the sealant material layer in the middle between the two neighboring elevations; and at most 100% larger than a radial thickness of the sealant material layer in the middle between the two neighboring elevations.

4. The pneumatic tire according to claim 1, the tire comprising at least three circumferential grooves and at least four circumferential ribs or rows of tread blocks.

5. The pneumatic tire according to claim 1, wherein an elevation of the sealant material is provided radially below each of said circumferential grooves.

6. The pneumatic tire according to claim 1, wherein the largest radial thickness of the elevations is within a range of 3 mm to 9 mm, measured from the inner surface of the tire to the radially innermost surface of the respective elevation.

7. The pneumatic tire according to claim 1, wherein a radial thickness of the sealant material layer in the middle between two neighboring elevations is within a range of 2 mm to 6 mm.

8. The pneumatic tire according to claim 1, wherein a difference between i) a radial thickness of the sealant layer in the middle between two neighboring elevations and ii) a largest radial thickness of one of the neighboring elevations, is at least 0.5 mm.

9. The pneumatic tire according to claim 1, wherein the sealant material layer extends in an axial direction over at least 90% of the width of said tread portion.

10. The pneumatic tire according to claim 1, wherein the sealant material comprises one or more of: a butyl rubber-based composition, a polyisoprene-based composition, a natural rubber-based composition, a polyurethane-based composition, a polybutene-based composition, an emulsion styrene-butadiene rubber-based composition, an EPDM-based composition, and a silicone-based composition.

11. The pneumatic tire according to claim 1, wherein the sealant material layer comprises one of: (i) axially adjacent sealant material strips extending circumferentially about an axis of the tire and along the inner surface of the tire, and (ii) one or more sealant material strips spirally wound about an axis of the tire and along the inner surface of the tire.

12. The pneumatic tire according to claim 11, wherein the sealant material strips form the elevations and the areas of the sealant material layer radially below the circumferential ribs or rows of tread blocks, and wherein at least multiple sealant material strips are one or more of: radially thicker in areas radially below the circumferential grooves than in the areas radially below the circumferential ribs or rows of tread blocks so as to form the elevations in the sealant material layer; arranged on top of one another so as to form the elevations in the sealant material layer.

13. The pneumatic tire according to claim 1, wherein the tread portion has two shoulder portions and a center portion axially between the two shoulder portions, and wherein each shoulder portion comprises a circumferential shoulder rib or row of shoulder tread blocks, and the center portion comprises at least three circumferential ribs and at least four circumferential grooves, and wherein each shoulder rib is delimited by one of the at least four circumferential grooves.

14. The pneumatic tire according to claim 1, wherein the elevations in the sealant material layer and areas of the sealant material layer having a radial thickness smaller than the radial thickness of said elevations alternate along an axial direction of the tire.

15. The pneumatic tire according to claim 1, wherein said areas of the sealant material layer having a radial thickness smaller than the radial thickness of said elevations have an axial width within a range of 60% to 120% of the radially outermost surface of the respective rib or respective row of tread blocks radially above.

16. The pneumatic tire according to claim 1, wherein at least one foam element is attached to a radially inner surface of at least two axially neighboring elevations such that at least one air cavity is formed between said axially neighboring elevations, a radially outer surface of the foam element and a radially inner surface of the sealant material layer between said axially neighboring elevations.

17. The pneumatic tire according to claim 16, wherein the foam element is a foam strip extending in a circumferential direction along a circumferential length corresponding to at least 50%, preferably at least 80%, of an inner circumference of the tire, measured along the inner surface at an axial center of the tire.

18. The pneumatic tire according to claim 16, wherein the axial width of the foam element is within a range of 20% to 50% of a maximum axial width of the sealant material layer.

19. The pneumatic tire according to claim 16, wherein the foam element is free of a coating or foil facing the sealant material layer.

20. The pneumatic tire according to claim 16, wherein the foam element comprises one or more of: a noise dampening material; a polymeric foam material; a polyurethane foam material; a strip shape; and a material having a density within a range of 0.01 g/cm.sup.3 to 1 g/cm.sup.3.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0082] The structure, operation and advantages of the invention will become more apparent upon contemplation of the following description taken in conjunction with the accompanying drawings, wherein:

[0083] FIG. 1 shows a schematic cross section of a prior art tire comprising a sealant material layer;

[0084] FIG. 2 shows a schematic cross section of an embodiment of a sealant tire in accordance with the present invention;

[0085] FIG. 3 shows a schematic cross section of a prior art tire comprising a foam material strip attached to a sealant material layer; and

[0086] FIG. 4 shows a schematic cross section of a noise dampened sealant tire in accordance with an embodiment of the present invention.

DETAILED DESCRIPTION OF THE EMBODIMENTS

[0087] FIG. 1 is a schematic cross-section of a tire 1′ in accordance with the prior art. The example tire 1′ has a tread portion 10, two bead portions 3, and two sidewalls 2 joining outer axial edges of the tread portion 10 with the respective bead portions 3. The tread portion 10 has a plurality of circumferential grooves 9 and ribs 8. Such pneumatic tire constructions are generally known in the tire art. The tire 1′ has an inner surface defining a tire cavity 6. A sealant material layer 5′ is provided on the inner side or surface of the tire 1′ in an area opposite to the tread portion 10. The thickness of the sealant material layer 5′ is essentially constant over the axial width and circumference of the tire F. For the sake of an improved intelligibility, reference signs (numerals) 2, 3, 6, 8, 9, and 10 are used for the same elements as described herein below in the description of FIGS. 2 to 4.

[0088] FIG. 2 shows a tire 1 in accordance with a first embodiment of the present invention. Similar to the tire 1′ shown in FIG. 1, tire 1 has sidewalls 2, bead portions 3, a tread portion 10, a tire cavity 6, optionally delimited by an inner liner of the tire 1, circumferential grooves 9 (or in other words circumferential main grooves) as well as circumferential ribs 8.

[0089] The sealant material layer 5 according to the embodiment shown in FIG. 2, extends in a circumferential direction c and in an axial direction a along the inner surface of the tire 1. The sealant material layer 5 has four elevations 19, wherein each elevation 19 is axially positioned radially below a groove 9. In other words, the sealant material layer 5 has thicker portions at the axial positions of the grooves 9 than in areas of smaller radial thickness 18 arranged at axial positions radially below the ribs 8. As a consequence, the thicker sealant material in areas radially inside of the grooves, improves the sealing performance of the tire 1 in areas where the tread rubber material is relatively thin compared to the areas of relatively thick tread rubber material at the axial position of the ribs 8. This arrangement provides an advanced compromise between sealability and weight impact of the sealant material. In particular, large amounts of sealant material result in a higher weight of the tire 1 and can thus lead to inferior ride and handling properties. Cost efficiency is improved as well compared to the tire 1′ as shown in FIG. 1. In addition, the fact of having a sealant material thickness which is smaller in the areas radially below the ribs 8 improves heat conductivity and/or avoids heat build-up in these areas, in particular for improved high speed performance and frequent cornering maneuvers. It is noted that the relative thickness of the depicted elevations 19 or in other words protrusions or ridges of sealant material in the radially inner direction is shown in FIG. 1 schematically. Preferable absolute and relative thickness values have been mentioned herein above. In a non-limiting embodiment, the thickness of the sealant material layer 5 is about 3.6 mm in areas 18 between the elevations 19 whereas the largest thickness of the sealant material layer 5 in the elevations 19 is about 4.5 mm.

[0090] For the sake of better comprehensibility, the axial direction a, the circumferential direction c and the radial direction r have been indicated in FIG. 2 as commonly used in the description of tire geometries. The term direction shall not be limited to a certain orientation unless otherwise indicated herein. An axial direction a may be understood as a direction in parallel to the rotation axis of the tire 1. The circumferential direction c is concentric to the rotation axis of the tire 1 and the radial direction r extends radially from the latter as commonly understood in the tire art.

[0091] FIG. 3 shows a prior art tire 1″ with elements 2, 3, 6, 8, 9, 10 as already described in relation to FIGS. 1 and 2 above, but includes a sealant material layer 5″ carrying a noise dampening element 7″. Such a noise dampening element 7″ may be used to dampen or reduce the noise generated in the tire cavity 6 when driving. A drawback of such an arrangement consists in a relatively large heat build-up radially above the noise dampening element 7″ which is acting together with the sealant material layer 5″ as a thermal insulator. This may negatively impact tire performance and/or stability. Moreover, it has been found that such noise dampening elements 7″ may negatively affect the performance of the sealant material by hindering the free flow of the sealant material into a puncture hole in the tread. Therefore, such an arrangement typically requires a relatively thick sealant material layer 5″ which has again a negative impact on costs, weight and heat conductivity, and therefore also on tire performance.

[0092] According to the preferred embodiment of the invention, in the form of a tire 11 as shown in FIG. 4, using again same reference signs as in the previously discussed Figures where applicable, a foam element, such as a circumferential foam strip 7 is attached to a sealant material layer 5. The sealant material layer 5 has, by way of non-limiting example, the same shape as in the embodiment of FIG. 2 so that it comprises elevations 19, radially below the grooves 9 and areas of smaller sealant material thickness 18 radially below the ribs 8. The foam strip 7 is attached to two elevations 19 so as to form an air cavity 16 between the sealant material layer 5 and the foam strip 7. Thus, the foam strip 7 is not directly contacting the sealant material layer 5 over its whole axial width. Heat build-up below the foam strip and also in the area of the ribs is reduced. Moreover, sealant material flow into puncture holes radially above the foam strip 7 is ensured due to relatively large sealant material thickness in positions where the sealant material contacts the foam strip 7 and due to the air cavity 16 in an area between the two neighboring elevations 19 covered by the foam strip 7. In addition, the relatively large sealant material thickness radially below the circumferential main grooves 9 provides an improved security feature. Sealant material is saved in the areas 18 so as to reduce overall weight and improve heat conductivity.

[0093] While a foam strip 7 has been described in this embodiment as one example of a foam element, it is also possible that multiple foam strip segments are provided behind each other in the circumferential direction or multiple foam blocks are provide along the circumferential direction and attached to at least two axially neighboring elevations.

[0094] It is preferred that foam elements such as the circumferential foam strip 7 are positioned at an axial center of the tire 11 or in other words along the equatorial plane EP of the tire 11 as shown in FIG. 4. Such an arrangement improves tire balance.

[0095] While certain representative embodiments and details have been shown for the purpose of illustrating the subject invention, it will be apparent to those skilled in this art that various changes and modifications can be made therein without departing from the scope of the subject invention.