Patent Application
20110079333
The present invention is directed to a tire tread, and more specifically, to a tire tread with a treadwear indicator.
The use of treadwear indicators is not new and the use of treadwear indicators is mandated by law in many countries. A variety of such indicators are known. Once such type employs colored means, such as colored rubber or colored fibers, below the tread for a visual indicator of wear. Other types use tie-bar type elements in the tread grooves. Under US law, the upper surface of a treadwear indicator must be located at a height of 1/16″ (1.6 mm) from the base of a groove in which the treadwear indicator is located.
A practical problem with the colored indicators is that there is no way for the operator to determine the level of wear until the tire is worn. When the tire employs the tie-bar type wear indicator, since the treadwear indicator is the same color as the remaining part of the tread, it can be difficult to determine the level of wear. Another practical problem is that a treadwear indicator constructed at one height for one country's requirements may not meet the standard heights required by other countries. Thus, a different construction may be required for each different country, leading to manufacturing and other assorted organizational costs.
A tire tread in accordance with the present invention includes at least one tread element and a treadwear indicator. The tread element projects from a base of the tire tread. The tread element has a radially outermost surface for contacting a road surface. The treadwear indicator includes a first step and a second step radially offset from the first step. The first step has a first surface which is disposed radially inward of the outermost surface of the tread element. The second step is disposed radially inward of the outermost surface of the tread element.
According to another aspect of the present invention, the second step is disposed radially inward from the first step and the outermost surface of the tread element.
According to still another aspect of the present invention, the first and second steps define planes generally parallel with the outermost surface of the tread element.
According to yet another aspect of the present invention, the first step includes an insignia and the second step includes an insignia for informing an operator that the wear condition of the tire tread is acceptable.
According to still another aspect of the present invention, the first step is rectangular.
According to yet another aspect of the present invention, the first step is circular.
According to still another aspect of the present invention, the first step is rectangular and the second step is circular.
According to yet another aspect of the present invention, the first step is circular and defines a recess radially inward from the second step.
According to still another aspect of the present invention, the second step is circular and extends radially away from the second step.
According to yet another aspect of the present invention, the second step is rectangular.
A treadwear indicator in accordance with the present invention includes a first step and a second step radially offset from the first step. The first step has a first surface disposed radially inward of an outermost surface of a road contacting tread element. The second step is disposed radially inward of the outermost surface of the road contacting tread element.
According to another aspect of the present invention, the second step is disposed radially inward from the first step and the outermost surface of the road contacting tread element.
According to still another aspect of the present invention, the first and second steps define planes generally parallel with the outermost surface of the road contacting tread element.
According to yet another aspect of the present invention, the first step includes an insignia and the second step includes an insignia for informing an operator that the wear condition of the tire tread is acceptable.
According to still another aspect of the present invention, the first step is rectangular.
According to yet another aspect of the present invention, the first step is circular.
According to still another aspect of the present invention, the first step is rectangular and the second step is circular.
According to yet another aspect of the present invention, the first step is circular and defines a recess radially inward from the second step.
According to still another aspect of the present invention, the second step is circular and extends radially away from the second step and the first step is rectangular.
The following definitions are applicable to the present invention.
“Annular” means formed like a ring.
“Axial” and “axially” are used herein to mean lines or directions that are parallel to the axis of rotation of the tire.
“Circumferential” means lines or directions extending along the perimeter of the surface of the annular tire parallel to the Equatorial Plane (EP) and perpendicular to the axial direction.
“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 sub classified as “wide”, “narrow”, or “slot”. The slot typically is formed by steel blades inserted into a cast or machined mold or tread ring therefor. In the appended drawings, slots are illustrated by single lines because they are so narrow. 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 from 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 tread surface area occupied by a groove or groove portion, the width of which is in question, divided by the length of such groove or groove portion; thus, the groove width is its average width over its length. Grooves, as well as other voids, reduce the stiffness of tread regions in which they are located. Slots often are used for this purpose, as are laterally extending narrow or wide grooves. Grooves may be of varying depths in a tire. The depth 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 groove are of substantially reduced depth as compared to wide circumferential grooves which they interconnect, they are regarded as forming “tie bars” tending to maintain a rib-like character in the tread region involved.
“Inner” means toward the inside of the tire and “outer” means toward its exterior.
“Lateral” means an axial direction.
“Leading” means a portion or part of the tread that contacts the ground first, with respect to a series of such parts or portions, during rotation of the tire in the direction of travel.
“Lugs” means discontinuous radial rows of tread rubber in direct contact with the road surface.
“NSK” means non-skid depth of a tread (i.e., the radially innermost, outer surface usually at the base of the grooves).
“Outer” means toward the tire's exterior.
“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.
“Tie-Bar” means an extra thickness of rubber at the bottom of a slot such that, in the location where the extra rubber is present, the slot depth is less than the slot depth at all other locations. Tie-bars stabilize a lug by limiting the independent movement of two portions of a lug that are separated by slots, while traction properties that are inherent in the use of slots are provided.
“Trailing” means a portion or part of the tread that contacts the ground last, with respect to a series of such parts or portions during rotation of the tire in the preferred direction of travel.
“Tread” means a molded rubber component which, when bonded to a tire casing, includes that portion of the tire that comes into contact with the road when the tire is normally inflated and under normal load.
The invention will be described by way of example and with reference to the accompanying drawings in which:
The following language is of the best presently contemplated mode or modes of carrying out the invention. This description is made for the purpose of illustrating the general principals of the invention and should not be taken in a limiting sense. The scope of the invention is best determined by reference to the appended claims.
Commercial tires must comply with local regulations in place in their destination countries. In general, there are two major treadwear indicator (TWI) standards which are incompatible. First, the DOT standard of USA requires a TWI height above NSK of 1/16″ with a tolerance of (+ 1/64″, −0″). In mm, this is a TWI at a height above NSK of between 1.59 mm and 1.98 mm. Second, the CCC standard of China requires a TWI height above NSK of at least 2.0 mm. Therefore, conventional TWIs cannot economically meet both standards with a single mold design.
A TWI in accordance with the present invention may include multiple levels, each one being in compliance with a different specific standard. As an example, current demand typically requires a TWI in compliance with DOT and CCC standards. However, in accordance with the present invention, the TWI may be expanded to additional standards, such as GCC (India-Indonesia), etc. Further, in accordance with the present invention, different shapes may be used to show a second (and third, fourth, . . . ) level of treadwear. The example TWI of
As an alternative feature, the name of each standard may be engraved/molded on outer surface of each corresponding step of the TWI. As shown, but not limited in the FIGS., one step may correspond to DOT and another step to CCC. Consequently, the multi-level TWI in accordance with the present invention may allow sale and use of a single tire for different markets, where the laws do not permit overlap in the TWI heights. Further, the use of the same molds, rather than separate molds, for multiple markets/regions may be permitted. Additionally, warehousing of the tires, production planning, and other commercial aspects may be enhanced, as well as costs minimized.
Conventional TWIs mainly offer gimmicks aimed to provide more information to a user regarding the remaining height of the design. However, these do not allow a single tire to comply with multiple regulatory requirements.
A portion of an example tire tread 1 for use with the TWI 100 of the present invention is illustrated in
Located within the groove 10 is at least one treadwear indicator 100 in accordance with the present invention. As shown in the detail of
When the example tire 1 is unworn, the steps 111, 122 both clearly show the undamaged insignias 115, 125 and may inform the operator that the wear condition of the tread 1 is acceptable according to DOT and CCC standards. As the tread 1 wears, the radially outer second step 122 will eventually reach the same radial level as the worn outer surface of the ribs 12. At this time, the CCC insignia 125 will also be worn away so that it will be clear that the tread 1 has reached its wear limit according to the CCC standard. If the tread 1 is being utilized in a CCC jurisdiction, the tire has reached the limit of its use and should no longer be used. If the tread 1 is being utilized in a DOT jurisdiction, this is of no account and the tire may continue to be used.
As the tread 1 wears further, the radially inner first step 111 will eventually reach the same radial level as the more worn outer surface of the ribs 12. At this time, the DOT insignia 115 will also be worn away so that it will be clear that the tread 1 has reached its wear limit according to the DOT standard. If the tread 1 is being utilized in a DOT jurisdiction, the tire has reached the limit of its use and should no longer be used. Thus, a single tire with a TWI 100 in accordance with the present invention may be used in either a DOT or a CCC jurisdiction while complying with both standards simultaneously.
Variations in the present invention are possible in light of the description of it provided herein. 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. It is, therefore, to be understood that changes can be made in the particular embodiments described which will be within the full intended scope of the invention as defined by the following appended claims.
