WO2000029228A1

WO2000029228A1 - Tread/tire with improved groove design

Info

Publication number: WO2000029228A1
Application number: PCT/US1998/024636
Authority: WO
Inventors: Daniel Edward Schuster; William Samuel Rossi
Original assignee: The Goodyear Tire & Rubber Company
Priority date: 1998-11-18
Filing date: 1998-11-18
Publication date: 2000-05-25
Also published as: AU1463599A

Abstract

An improved tire tread has a net-to-gross ratio greater than 50 %, and a plurality of grooves, each defined by a base spaced between road contacting ribs. The improved tread has at least one circumferentially extending radially deep groove (30) having a discontinuous circumferential penetration protector (12) in the base of the groove. The penetration protector is spaced from the adjacent road contacting ribs (40, 40a). The penetration protectors may be connected to each other and/or the adjacent ribs. Areas of discontinuity in the circumferentially extending penetration protectors are preferred areas for measuring the non-skid of the tire.

Description

TREAD/TIRE WITH IMPROVED GROOVE DESIGN Background of the Invention This invention relates to an improvement in circumferential groove design for tire treads. The invention applies to new tires and replacement treads having circumferential grooves containing penetration protectors, also known as stone ejectors. The design is particularly well suited for truck tires. The groove improvement makes easier the measurement of the non-skid in such tires. The rubber treads of pneumatic tires are commonly provided with one or more transversely spaced circumferentially continuous anti-skid grooves to increase the traction properties of the tire. These grooves are generally straight or zigzag.

The spaced grooves define solid ribs, rib lugs or rib blocks (i.e., rows of blocks or lugs) of the road contacting surface of the tire. The grooves extend radially inward from the ground- contacting surface to a base, the base of the groove extending between the walls of adjacent ribs or blocks.

The grooves of such tires tend to pick up and retain objects, such as stones. Such stones can be forced into contact with the base of the groove, potentially cutting or penetrating the base of the groove. If the penetration is deep enough, the wire reinforcement in the breaker or belt structure of the tire can be exposed. Such exposure can lead to oxidation or rusting of the wire reinforcement.

A pneumatic tire with transverse crossbars or buttresses is described in U. S. Patent 3, 706,334 granted December 19, 1972.

A pneumatic tire with a rib occupying the majority of the base of a groove is described in French Patent 1 , 163 ,341.

Early attempts to protect the base of the circumferential groove from rock penetration relied on rather large projections that occupied a high percentage of the groove void area.

U.S. Patent 5,115,850, issued May 26, 1992 ('850) provides a stone penetration barrier which minimizes the amount of space used to provide such a barrier. Also the barrier is designed to give a visual indication of occurrences of rock penetration damage in the area of the base of the groove.

While the design of the '850 patent works well to protect the base of the groove, it has been found difficult to measure the wear of the tire by measuring the non-skid (the distance between the top of a block or rib and the base of a groove) because of interference from the penetration protectors.

Accordingly, it is an object of this invention to provide a tire that is resistant to stone penetration, yet provides a means for easily and accurately measuring the non-skid of the tire.

Other objects of the invention will be apparent from the following description and claims.

Summary of the Invention This invention relates to an improved tire tread having a net to gross ratio greater than

50% and a plurality of grooves. The tread has at least one circumferentially continuous groove, having a base extending between road contacting ribs. The improved tread has a discontinuous row of circumferential penetration protectors in the base of the groove. The penetration protectors are axially spaced from the adjacent road contacting ribs. The designed discontinuities in the row of penetration protectors may be used for measuring the non-skid depth of the tread.

A penetration protector has a height measured from the base of the groove radially outward 3/32 inch to the height of the tread, a width of 1/16 inch to the width of the groove, and a length of 1/8 inch to substantially the circumference of the tire. The discontinuities in the circumferentially extending penetration protectors may be placed in preferred locations for measuring the non-skid manually. Brief Description of the Drawings

Fig. 1 illustrates a plan view of a tire with the improved tread.

Fig. 2 illustrates a plan view of a portion of the tread having a circumferential groove with penetration protectors and bracing.

Fig. 3 is an enlarged sectional view of the tread.

Fig. 4 is an enlarged sectional view of an alternative tread pattern having penetration protectors. Definitions The invention also may be better understood in the context of the following definitions which are applicable to both the specification and to the appended claims.

"Aspect ratio" of the tire means the ratio of section height to section width. "Axial" or "axially" are used herein to refer to lines or directions that are parallel to the axis of rotation of the tire. "Block" or "lug" refers to lands of rubber in the tread delineated by substantially circumferential and substantially lateral grooves in the tread. A block or lug can be square, rectangular, or have other geometric or irregular shapes depending on the groove angle and the path of the groove.

"Compensated tread width" means the tread width multiplied by the aspect ratio. "Circumferentially" as used herein means a plane parallel to the equatorial plane of a tire.

"Equatorial Plane (EP)" means the plane perpendicular to a tire's axis of rotation, passing through the center of its tread. "Footprint" means the contact patch or area of contact of the tire tread with a flat surface at zero speed under normal load and pressure.

"Groove" means an elongated void area in a tread that may extend circumferentially or laterally about the tread in a straight, curved, or zigzag manner. Circumferentially and laterally extending grooves sometimes have common portions and may be subclassified as "wide", "narrow", or "slot". The slot typically is formed in a tread by steel blades inserted into a cast or machined mold.

A "slot" is a groove having a width in the range from about 0.2% to 0.8% of the compensated tread width, whereas a "narrow groove" has a width in the range of about 0.8% to 3 % of the compensated tread width and a wide groove has a width greater than 3 % thereof. The "groove width" is equal to the tread surface area occupied by a groove or a groove portion, the width of which is its average width over its length. Grooves, as well as other voids, reduce the stiffness of the tread regions in which they are located. Slots are often used for this purpose, as are laterally extending narrow or wide grooves. Grooves may be of varying depths in a tire. The depths of a groove may vary around the circumference of the tread, or the depth of one groove may be constant but vary from the depth of another groove in the tire. If such narrow or wide grooves are of substantially reduced depth as compared to wide circumferential grooves with which they interconnect, they are regarded as forming "tie bars" tending to maintain a rib-like character in the tread region involved.

"Net-to-gross ratio" means the ratio of the area of the tire tread which normally makes contact with a paved road surface while in the footprint, divided by the area of the tread in the footprint, including non-contacting portions such as the inner tread surface.

"Radial" and "radially" are used to mean directions radially toward or away from the axis of rotation of the tire.

"Rib" means a circumferentially extending strip of rubber on the tread which is defined by at least one circumferential "wide groove" and either a second such groove or a lateral edge of the tread, the strip of rubber being laterally undivided by full depth narrow or wide grooves. As used herein a rib may be defined to include solid ribs, or lugs or blocks arranged circumferentially around a tire.

"Tread" means that portion of a tire that comes in contact with the road when the tire is normally inflated and under normal load.

"Tread width" means the arc length of the tread surface in the axial direction, that is, in a plane passing through the axis of rotation of the tire. Detailed Description of the Invention With reference now to Fig. 1, a tire (10) is provided having a tread (20). The tread has a circumferentially continuous groove (30) spaced between ground contacting ribs (40,40a), and a plurality of narrow grooves (50), and groove segments (52) spaced between ground contacting tread blocks (60). The illustrated tread pattern is of a rib-block type configuration.

Fig. 2 is an enlarged plan view of a portion of the tread (20) illustrating the circumferentially continuous groove (30) located in the center of the tread. The groove has a row of discontinuous circumferential penetration protectors (12) shown in the base (22) of the groove. A penetration protector (12) is approximately axially centered in the base (22) of a groove (30), and is spaced substantially equidistant from the walls (42,42a) of the adjacent ribs. A plurality of radially extending flashes (14) are shown. The flashes (14) connect the penetration protectors (12), and some flashes (14a) extend therefrom, and may be connected to the walls (42, 42a) of adjacent ribs (40, 40a).

The flash (14,14a) is the result of the venting of the tire in the tire mold, and those skilled in the art will recognize that different venting procedures can be used that will result in the absence of flash. In the illustrated embodiment, the flash (14,14a) is directed to specific locations that make implementation of the invention easier. Those skilled in the art will recognize that the invention may be practiced using alternative implementations that give similar results.

In Fig. 3, an enlarged sectional view of the groove (30), with a row of penetration protectors (12) and base (22), is illustrated. In the illustrated embodiment, the penetration protectors (12) are axially centered in the base of the groove (30), and radially extend outward from the base (22) of the groove (30). The flashing (14), as illustrated, has a radial height equal to the radial height of a penetration protector.

In a prior art tire, penetration protectors were spaced apart from each other about 0.1 inch (2.5 mm) and were interconnected by a narrow flash of rubber about 0.02 inch (0.5 mm) wide. In the illustrated tire of the invention, the penetration protectors (12) are spaced from each other by about 0.15 inch (4 mm) at measuring locations (16,16a). Also, around measuring locations (16,16a), the flashes (14a) are thinner than flashes (14), and are directed from the side of a penetration protector (12), toward a block wall (42 or 42a).

Measuring locations (16,16a) are free of flash and any other obstruction that may hinder access to the groove base (22), i.e. to the full depth of the groove.

Fig. 4 illustrates an alternative tread design which may employ the penetration protectors (12) of the invention, having the spacing described.

The measuring locations (16,16a) are located in circumferential groove (30), between walls (42,42a) of adjacent blocks or ribs (40,40a). With reference to Figs. 3 and 4, in a preferred embodiment, preferred measuring locations (16) are placed in a position that relates to the centers (15,15a) of adjacent blocks, which are on opposite sides of groove (30). For example, the proximity of the center of block (40) may be determined by estimating the mass center, area center or geometric center of the block. Likewise, the proximity of the center of block (40a) can be estimated. A preferred measuring location (16) can then be established in the proximity of a line (17) that connects the center (15) of a block (40) and the center (15a) of a block (40a).

With reference again to Figs. 2 and 3, in an embodiment where lugs are staggered relative to each other in adjacent rows, a further limitation may be added wherein a line (17) will be drawn between the centers (15,15a) of adjacent blocks (40,40a) only where blocks (40) and (40a) overlap axially with each other by 50% or more.

These preferred measuring locations (16) provide the best reference points for measuring non-skid when using manual non-skid measuring tools. The reference shoulder of a measuring tool can be placed on two adjacent blocks, one on each side of a groove (30), in line with the centers of the adjacent blocks (40,40a), where it is believed that the most consistent measurements are obtained using such a tool.

Those skilled in the art will recognize that non-skid can be measured using machine vision, or other non-contact measuring devices. When machine vision is used, for example, a beam of laser light may be used to locate a measuring location (16,16a) in a groove (30) and a block center (15,15a), measuring the difference in height between each location. When such a non-skid-measuring device is used, the placement of measuring locations (16,16a) relative to the blocks (40,40a) is not critical since the measuring points may be located independent of each other.

In the illustrated embodiment, to help assure that the preferred measuring location is used to obtain non-skid measurements, especially when manual measuring devices are used, the flashes (14) in non measuring locations are widened to about 0.03 inch (0.75 mm) to make it difficult for a non-skid measurements to be obtained in such locations. This assures accurate measurements of non-skid are obtained since the preferred measuring locations (16) are placed, as described above, where the most consistent measurements will be obtained when using manual non-skid measuring tools.

In the illustrated embodiment, the penetration protectors (12) are buttons of rubber having a length of 1/4 to 3/4 inch, a width of 1/8 inch, and a height of 1/8 inch as measured from the base (22) of a groove (30) to the top of a penetration protector (12). Although the exact measurements or design of the penetration protectors used are not critical to the invention, depending on the size of the tire, preferred penetration protectors will have a length of 1/4 inch to continuous around the circumference of the tire except for a measuring location, a width of 1/16 inch to the width of the groove, and a height of 2/32 inch to the height of a rib or block. A tire according to the present invention was made in a 285/75 R245 size truck tire.

The base of the groove had a full 0.152 inch radius contour that extended to the walls of adjacent ribs. The walls of the ribs were each inclined at a 10° slope outwardly from the groove base. The groove depth was 0.75 inch. The groove included a penetration protector with a 0.125 inch height and a 0.125 inch width, and a length that varied depending on the location in the tire from 1/4 inch to 3/4 inch, and flashing (14) of the same height as the penetration protector. The tire had a tread width of about 8.0 inches, an aspect ratio of 75 % .

As is illustrated in the drawings, a marker (24) may be provided to help the technician locate the preferred measuring location (16). In the illustrated embodiment the marker (24) is a set of arrows pointing to preferred measuring location (16). Those skilled in the art will recognize that other types of markers can be used. For example, a projection may be provided on the side of a rib wall (42,42a) at a preferred measuring location (16), or different colored markers may be used at such locations. Other means of marking the preferred measuring locations (16) will be apparent to those skilled in the art.

While the invention has been variously illustrated and described, those skilled in the art will recognize that the invention may be variously modified and practiced without departing from the spirit of the invention. The invention is limited only by the scope of the following claims.

Claims

1. An improved tire tread (20) having a net-to-gross ratio greater than 50% having at least one groove (30) defined by a base (22) between road contacting ribs (40,40a) characterized by: the at least one circumferentially extending groove (30) having a discontinuous row of circumferential penetration protectors (12) in the base (22) of the at least one groove (30), the penetration protector being axially spaced from the adjacent road contacting ribs (40,40a), and a measuring location (16) separating penetration protectors (12) at specified locations.

2. The tread of claim 1 wherein flashing (14a) is perpendicular to a penetration protector

(12).

3. The tread of claim 1, wherein flashing (14) connects adjacent penetration protectors (12).

4. The tread of claim 1, wherein the width of a penetration protector (12) is substantially equal to its radial height.

5. The tread of claim 1 wherein a penetration protector (12) has a height, measured from the base (22) of a groove (30) radially outward, of less 0.125 inch and a width of 0.125 inch.

6. The tread of claim 1, wherein the length of a penetration protector (12) is 1/4 to 3/4 inch.

7. The tread of claim 1 wherein preferred measuring location (16) is located in the proximity of a line (17) that connects the centers (15,15a) of adjacent blocks (40,40a) on opposite sides of groove (30), wherein blocks (40) and (40a) overlap each other axially by 50% or more.

8. The tread of claim 1 wherein the thickness of a flash (14) located between two penetration protectors (12) is about 0.03 inch (0.75 mm), and the thickness of a flash (14a) is about 0.02 inch (0.5 mm).

9. The tread of claim 7 wherein preferred measuring location (16) has a width between two penetration protectors (12) of about 0.15 inch (4 mm).

10. The tread of claim 1 wherein a marker (24) indicates the position of a preferred measuring location (16).

11. An improved pneumatic tire having a tread with a net-to-gross ratio greater than 50% and a plurality of grooves defined by a base spaced between road contacting ribs, the improvement characterized by: a tread having at least one circumferentially extending groove (30) having a discontinuous row of circumferential penetration protectors (12) in the base (22) of the at least one groove (30), the penetration protector being axially spaced from the adjacent road contacting ribs (40,40a), and a measuring location (16) separating penetration protectors (12) at specified locations.

12. The tire of claim 11 wherein flashing (14a) is perpendicular to a penetration protector (12).

13. The tire of claim 11 wherein flashing (14) connects adjacent penetration protectors.

14. The tire of claim 11 wherein the width of a penetration protector (12) is substantially equal to its radial height.

15. The tire of claim 11 wherein a penetration protector (12) has a height measured from the base (22) of a groove (30) radially outward of 0.125 inch, and a width of 0.125 inch.

16. The tire of claim 11 wherein the length of a penetration protector (12) is 1/4 to 3/4 inch.

17. The tire of claim 11 wherein a preferred measuring location (16) is located in the proximity of a line (17) that connects the centers (15,15a) of adjacent blocks or rib portions (40,40a) on opposite sides of groove (30), wherein blocks (40) and (40a) overlap each other axially by 50% or more.

18. The tire of claim 11 wherein the thickness of a flash (14) located between two penetration protectors (12) is about 0.03 inch (0.75 mm), and the thickness of a flash (14a) located near a preferred measuring location (16) is about 0.02 inch (0.5 mm).

19. The tire of claim 11 wherein preferred measuring location (16) has a width between two penetration protectors (12) of about 0.15 inch (4 mm).

20. The tire of claim 11 wherein a marker (24) indicates the position of a preferred measuring location (16).