# US 7,461,677 B2 · Pneumatic tire having bell shaped wide width main grooves

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- Number: US 7,461,677 B2
- Document ID: US7461677B2
- Status: Granted
- Kind: B2
- Application number: 11/226,309
- Filed: 2005-09-15
- Published: 2006-03-23
- Granted: 2008-12-09
- Earliest claimed: 2004-09-17
- Assignees: Bridgestone Corporation
- Inventors: Youji Noguchi; Akira Yagi
- Web page: https://patentgrep.com/patent/US7461677B2

## CPC

- B60C 19/001: {Tyres requiring an asymmetric or a special mounting}
- B60C 11/0302: {directional pattern, i.e. with main rolling direction}
- B60C 11/0332: {by the footprint-ground contacting area of the tyre tread}
- B60C 11/13: characterised by the groove cross-section, e.g. for buttressing or preventing stone-trapping
- Y10S 152/904: Specified tread pattern for front tyre and rear tyre
- B60C: VEHICLE TYRES; TYRE INFLATION; TYRE CHANGING; CONNECTING VALVES TO INFLATABLE ELASTIC BODIES IN GENERAL; DEVICES OR ARRANGEMENTS RELATED TO TYRES
- Y10S: TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS

## Abstract

A pneumatic tire suitable for competitive sports has a specified tread pattern comprising a central region and both shoulder regions, in which a plurality of bell-shaped wide-width main grooves each extended substantially bell-shapedly into both sides approximately centering on an equator of the tire are disposed in the tread at a given interval in the circumferential direction of the tire wherein the bell-shaped wide-width main groove has specified inclination angles in the central region and the shoulder region and specified groove width and groove depth, and a width of a connecting land portion at a position coming the bells-shaped wide-width main grooves closest to each other is not less than 1.5 mm, and the tire has a given negative ratio at the central region.

## Claims

### Claim 1

A pneumatic tire having a central region corresponding to TW80×35% and both shoulder regions when TW80 is a ground contact width of a tread in the tire mounted onto a rim of 4.5-5 inches under an internal pressure of 100 kPa and a load of 784 N, in which no wide-width main groove continuously extending in a circumferential direction is existent in the central region and the shoulder regions, characterized in that a plurality of bell-shaped wide-width main grooves each extended substantially bell-shapedly into both sides approximately centering on an equator of the tire are disposed in the tread to form a plurality of land parts each comprised of a center land portion, a shoulder land portion and a connecting land portion viewing from a front face of the tire in which an inclination angle with respect to the circumferential direction is 90-10° in the central region and 10-90° in the shoulder region and a groove width is 7-13% of TW80 and a groove depth is 65-90% of a rubber thickness of the tread, and an interval (d1) on the equator between the bell-shaped wide-width main grooves adjoining to each other in the circumferential direction is 4.0-5.5% of a tire peripheral length and a width (d2) of the connecting land portion at a position coming the bells-shaped wide-width main grooves closest to each other is not less than 1.5 mm, and a negative ratio at the central region is 50-80%;
wherein the bell-shaped wide width main grooves are substantially symmetric with respect to the equatorial plane,
wherein at least one sub-groove is arranged in the shoulder land portion formed in the shoulder region between the adjoining bell-shaped wide-width main grooves to render the shoulder land portion into a fork shape, and a groove width of the sub-groove is 15-60% of the width of the main groove and a groove depth of the sub-groove is 30-100% of the depth of the main groove.

### Claim 2 (depends on 1)

A pneumatic tire according to claim 1, wherein in at least the vicinity of the connecting land portion, a radius of curvature (R1) of a curved part connecting to a top (R0) of the bell-shaped wide-width main groove at a leading side is not more than 35 mm and a radius of curvature (R2) of a bottom portion of the bell-shaped wide-width main groove at a trailing side is not more than 80 mm.

### Claim 3 (depends on 1)

A pneumatic tire according to claim 1, wherein in the connecting land portion at the position coming the bell-shaped wide-width main grooves closest to each other in the circumferential direction is formed a recess communicating both the adjoining bell-shaped wide-width main grooves, and the recess has substantially a streamline shape at a section in which a height of the connecting land portion is gradually decreased in the thickness direction of the tread and a length of the recess formed in the connecting land portion at a zone at least ranging from an outer surface of the tread to 20% of the depth of the main groove is 80-200% of the width of the main groove and a depth of the recess at a position deepest from the outer surface of the tread is 60-100% of the depth of the main groove.

### Claim 4 (depends on 1)

A pneumatic tire according to claim 1, wherein a sipe communicating with the bell-shaped wide-width main groove is arranged substantially in a center of the center land portion in the circumferential direction, and a width of the sipe is 0.5-2 mm and a depth of the sipe is 30-80% of the depth of the main groove.

### Claim 5 (depends on 1)

A pneumatic tire according to claim 1, wherein said tire is a front tire of a racing cart.

### Claim 6

A pneumatic tire having a central region corresponding to TW110×35% and both shoulder regions when TW110 is a ground contact width of a tread in the tire mounted onto a rim of 7-5 inches under an internal pressure of 100 kPa and a load of 1078 N, in which no wide-width main groove continuously extending in a circumferential direction is existent in the shoulder regions, characterized in that a wide-width main groove extending straight in the circumferential direction and having a see-through width corresponding to 5-9% of TW110 and a groove depth corresponding to 65-90% of a rubber thickness of the tread is disposed on an equator of the tire and a plurality of bell-shaped wide-width main grooves each extended substantially bell-shapedly into both sides approximately centering on an equator of the tire are disposed in the tread to form a plurality of land parts each comprised of a center land portion, a shoulder land portion and a connecting land portion viewing from a front face of the tire in which an inclination angle with respect to the circumferential direction is 90-10° in the central region and 10-90° in the shoulder region and a groove width is 7-13% of TW110 and a groove depth is 65-90% of the rubber thickness of the tread, and an interval (d3) on the equator between the bell-shaped wide-width main grooves adjoining to each other in the circumferential direction is 4.0-5.5% of a tire peripheral length and a width (d4) of the connecting land portion at a position coming the bells-shaped wide-width main grooves closest to each other is not less than 1.5 mm, and a negative ratio at the central region is 55-65%;
wherein the bell-shaped wide width main grooves are substantially symmetric with respect to the equatorial plane,
wherein at least one sub-groove is arranged in the shoulder land portion formed in the shoulder region between the adjoining bell-shaped wide-width main grooves to render the shoulder land portion into a fork shape, in which a groove width is 30-65% of the width of the main groove and a groove depth is 40-100% of the depth of the main groove.

### Claim 7 (depends on 6)

A pneumatic tire according to claim 6, wherein viewing from the connecting land portion at the position coming the bell-shaped wide-width main grooves closest to each other, an angle (α1) of the center land portion defined between the bell-shaped wide-width main grooves is set to not less than 25° and an angle (α2) of the shoulder land portion defined between the bell-shaped wide-width main grooves is set to not less than 25°.

### Claim 8 (depends on 6)

A pneumatic tire according to claim 6, wherein in the connecting land portion at the position coming the bell-shaped wide-width main grooves closest to each other in the circumferential direction is formed a recess communicating both the adjoining bell-shaped wide-width main grooves, and the recess has substantially a streamline shape at a section in which a length of the recess formed in the connecting land portion at a zone at least ranging from an outer surface of the tread to 20% of the depth of the main groove is 80-200% of the width of the main groove and a depth of the recess at a position deepest from the outer surface of the tread is 60-100% of the depth of the main groove.

### Claim 9 (depends on 6)

A pneumatic tire according to claim 6, wherein a sipe communicating with the bell-shaped wide-width main groove is arranged substantially in a center of the center land portion in the circumferential direction in which the sipe has a width of 0.5-2 mm and a depth corresponding to 40-80% of the depth of the main groove.

### Claim 10 (depends on 6)

A pneumatic tire according to claim 6, wherein said tire is a rear tire of a racing cart.