Pneumatic tire wear indicating tread pattern

Abstract

A pneumatic tire and moulding matrix therefore, the tire tread incorporating a traction pattern which changes distinctively when only a predetermined amount of tread rubber remains, thus warning the tire user that his tire is approaching the legal or safe limit and will soon have to be replaced or retreaded.

Having now described my invention what I claim is: .[.1. A pneumatic tire comprising a tread provided with at least one main drainage groove and a first, radially outer, and a second, radially inner, pattern each comprising at least one tread element selected from the group consisting of slots, sipes, grooves, incisions and the like, the first pattern changing to the second pattern at a level situated radially inwardly of and substantially parallel to the tread ground contacting surface of the tire, said level being a predetermined amount less than the depth of the main drainage groove, the second pattern being distinctively different from the first and being located immediately radially inwardly of and in radial alignment with said first pattern..]. .[.2. A pneumatic tire according to claim 1 wherein the second pattern is substantially undetectable from the exterior of the tire until at least a portion of the tread equal in depth to the first pattern has been worn away..]. .[.3. A pneumatic tire according to claim 1 wherein the second pattern is in the form of at least one warning word..]. .[.4. A pneumatic tire according to claim 1 wherein the second pattern is in the form of at least one warning word repeated around the tire circumference..]. .[.5. A pneumatic tire according to claim 1 wherein the second pattern is in the form of at least one warning word repeated across the tire tread width..]. .[.6. A pneumatic tire according to claim 1 wherein the second pattern comprises a plurality of chambers..]. .[.7. A pneumatic tire according to claim 1 wherein the second pattern is at least partially filled with a material distinctively different from the tread rubber..]. .[.8. A pneumatic tire according to claim 7 wherein the said material comprises a rubber or plastics material of a color different from the tread rubber..]. .[.9. A pneumatic tire according to claim 7 wherein said material has an abrasion resistance different from that of the tread rubber..]. .[.10. A pneumatic tire according to claim 1 wherein the second pattern changes to at least one subsequent pattern radially-inwardly thereof..]. .[.11. A pneumatic tire copmrising a tread provided with at least one main drainage groove and a first, radially outer pattern of no particular visual significance and a second, radially inner, pattern having visual significance, each pattern comprising at least one tread element selected from the group conisting of slots, sipes, grooves, incisions and the like, the first pattern changing to the secnd pattern at a level situated radially inwardly of and substantially parallel to the tread ground-contacting surface of the tire, said level being a predetermined amount less than the depth of the main drainage groove, the second pattern having a lesser number of tread elements than the first pattern with all of the second pattern tread elements being in radial alignment with corresponding elements of the first pattern and located immediately radially inwardly of similar tread elements in the first pattern so that when the first pattern 
     
        is worn away the second visually significant pattern is exposed..]. 12. A pneumatic tire comprising a tread provided with at least one main drainage groove and a first, radially outer, and a second, radially inner, pattern each comprising at least one tread element selected from the group consisting of slots, sipes, grooves, incisions and the like, the first pattern changing to the second pattern at a level situated radially inwardly of and substantially parallel to the tread ground contacting surface of the tire, said level being a predetermined amount less than the depth of the main drainage groove, the second pattern being distinctively different from the first, being located immediately radially inwardly of and in radial alignment with said first pattern, and being in the form of 
     
     
        at least one warning word. 13. A pneumatic tire comprising a tread provided with at least one main drainage groove and a first, radially outer, and a second, radially inner, pattern each comprising at least one tread element selected from the group consisting of slots, sipes, grooves, incisions and the like, the first pattern changing to the second pattern at a level situated radially inwardly of and substantially parallel to the tread ground contacting surface of the tire, said level being a predetermined amount less than the depth of the main drainage groove, the second pattern being distinctively different from the first, being located immediately radially inwardly of and in radial alignment with said first pattern, and being in the form of at least one warning word repeated 
     
     
        around the tire circumference. 14. A pneumatic tire comprising a tread provided with at least one main drainage groove and a first, radially outer, and a second, radially inner, pattern each comprising at least one tread element selected from the group consisting of slots, sipes, grooves, incisions and the like, the first pattern changing to the second pattern at a level situated radially inwardly of and substantially parallel to the tread ground contacting surface of the tire, said level being a predetermined amount less than the depth of the main drainage groove, the second pattern being distinctively different from the first, being located immediately radially inwardly of and in radial alignment with said first pattern, and being in the form of at least one warning word repeated across the tire tread width.