NZ214118A

NZ214118A - Tyre with circumferential grooves flanked by deeper sipes

Info

Publication number: NZ214118A
Application number: NZ21411885A
Authority: NZ
Inventors: Takeuchi Akihiro
Original assignee: Sumitomo Rubber Ind
Priority date: 1984-11-09
Filing date: 1985-11-08
Publication date: 1987-10-30
Also published as: AU4949385A; DE3539530A1; NZ214119A; AU578756B2; JPS6185503U

Description

2 141 18 >r!oriry D<Jte(si". .

Con.plcta Specification Filed: .U CfeKS ) Publication Dr | P.O. Journal, ?*i 3 0 OCT 1987 patents Form No. 5 NEW ZEALAND PATENTS ACT 1953 COMPLETE SPECIFICATION "TIRE HAVING SIPINGS IN GROOVE BOTTOMS" £,WE SUMITOMO RUBBER INDUSTRIES, LTD. a Japanese company t of No. 1-1, Tsutsuicho 1-chome, Chuo-Jcu, Kobe-shi, Hyogo, Japan hereby declare the invention, for which i/we pray that a patent may be granted to me/us, and the method by which it is to be performed, to be particularly described in and by the following statement (followed by p»ge I A.) 2 141 18 TIRE HAVING SIPINGS IN GROOVE BOTTOMS BACKGROUND OF THE INVENTION The present invention relates to a tire having sipings formed in its tread surface and an effective siping function even at the end of the service life of the tread portion.

In general, spiked tires have been widely used for running on a snowy or icy road. However, in the case where the spiked tires run on a normal pavement, the spiked tires involve problems such as particle pollution and damage of the pavement. Therefore, much effort has been made in developing and researching spikeless or studless tires in order to improve braking and snow*/ performances thereof to the same extent as those of the spiked tire. Also, it is necessary to improve wet gripping property and reduced local wear of the tread in a normal road. To improve these performances, sipings S extending in an axial or transverse direction of the tire along the circumferential groove of the tread, for example. Each of such sipings has a width of lmm or less and a depth equal to or less than that of the circumferential groove of the tread. The tread rubber is subjected to a flexibility so as to sufficiently follow a deformation upon contacting with the ground or road, thus I* V > enhancing the braking effect and the wet gripping performance. However, since the conventional sipings have a depth equal to or less than that of the circumferential aroove of the tread as described above, the sipings do not perform their function at the end of the wear service life of the tread. SUMMARY OF THE INVENTION The present invention provides as an object a tire having sipings which perform their function from the beginning to the end of tread wear of wear of the tire without any reduction in various performances such as braking effect, wet gripping property, wear resistance and the like.

The present invention is characterized in that sipings are formed in the tread surface, the sipings being each connected at one end to a circumferential groove extending in a circumferential direction of a tire, a depth of each siping is greater than that of the circumferential groove, and each siping extending up to a bottom of the circumferential groove.

BRIEF DESCRIPTION OF THE DRAWINGS Fig. 1 is a plan view of a part of a tread of a tire on the left half side, according to the present invention; Fig. 2 is a cross-sectional view taken along the line II-II of Fig. 1; and Figs. 3 and 4 are cross-sectional views showing other embodiments of sipings. 2 141 18 DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will now be described with reference to the accompanying drawings.

A tread T is provided on each side of the circumferential centerline of a tire with an outer side longitudinal or circumferential groove G1 and an inner side longitudinal or circumferential groove G2. These grooves G1 and G2 are provided symmetrically with respect to the centerline. Sipings S extending in an axial or transverse direction are provided at a constant interval in the tire circumferential direction on both sides of the longitudinal grooves G1 and G2. As shown in Fig. 2, each siping is formed so that its cross-section extends to the bottom of the longitudinal groove Gl. More specifically, a depth DS of each siping is greater than a depth DG of the longitudinal groove G to cut the bottom of the longitudinal groove. The siping S may terminate at the center of the bottom of the longitudinal groove.

On the other hand, the siping SI may be formed throughout the bottom of the longitudinal crroove as shown in Fig. 3. Furthermore, it is possible to form the siping S2 so as to extend to both sides of the longitudinal groove as shov/n in Fig. 4.

It is preferable that the depth DS of the f 2 1411 siping be in a range over 100% to 130% of the depth DG of the longitudinal groove.

As has been apparent from the foregoing description, since the siping has a depth greater than a depth of the longitudinal groove and extends to the bottom of the longitudinal groove, a tread rubber may have mobility even in the end of tread wear. This makes it possible to reduce its rigidity, thus maintaining good braking performance, wet gripping property and wear risistance.

Claims

WHAT WE CLAIM IS;

1. A tire having a tread with at least one longitudinal groove extending in a circumferential direction of the tire and a number of sipes each connected at one end to the longitudinal groove and each being of a depth greater than the depth of said longitudinal groove.

2. The tire according to claim 1, wherein each of said sipes extend in a transverse direction of the tire and terminate at a central portion of said longitudinal groove.

3. . The tire according to claim 1, wherein each of said sipes extend in a transverse direction of the tire through the bottom of said longitudinal groove.

4. The tire according to claim 1, wherein each of said sipes extends along both sides and the bottom of said longitudinal groove. .

5. The tire according to any one of preceding claims, whrein the depth of each of said sipes is equal to or less than 130% of the depth of said longitudinal groove.

6. A tire substantially as herein described with reference to Figures 1 and 2 or Figures 1 and 3 or Figures 1 and 4 of the accompanying drawings. ' BALDWIN, SON' & CAFicY 5 » WW—iNMft,.