NZ213134A

NZ213134A - Pneumatic tyre:tread relief pattern coated with crack resistant film

Info

Publication number: NZ213134A
Application number: NZ21313485A
Authority: NZ
Inventors: K Takehara
Original assignee: Sumitomo Rubber Ind
Priority date: 1984-08-17
Filing date: 1985-08-16
Publication date: 1986-12-05
Also published as: AU4626685A; JPS6139604U

Description

<div class="application article clearfix" id="description"> 2 f 3 ) 3 4 Priority D?te(s): .../. 7. Complete Specification Filed: {£: Class: .&£?.<:((/?.& DEC'{986 Publico t-cn Dste: ....... P.0. Jcurn ?!, Ko* ^^...•»# I PATENTS FORM NO. 5 NEW ZEALAND PATENTS ACT 195 3 COMPLETE SPECIFICATION "PNEUMATIC TIRE" ■if WE SUMITOMO RUBBER INDUSTRIES, LTD., a Japanese company of No.1-1, Tsutsuicho 1-chome, Chuo-ku, 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:- -1- (followee1 by page I A.) 2 13 5 This invention relates to a pneumatic tire suitable for cruising and capable of preventing cracks in the tread part. Generally, when new tires are set on a vehicle, they are required to cover about 1,000 km of break-in cruise before they begin to acquire stability of travelling performance. During this break-in cruise, any operation at a relatively high speed under harsh conditions must be avoided. This break-in cruise is extremely important for most automobile users of ordinary skill. Thus, there have been worked out devices for displaying completion of the break-in cruise. One device resorts to forming letters or symbols raised to a height of not more than 1 mm from the surface of the tread and assuming complete disappearance of such letters or symbols by wear as a sign indicative of completion of the break-in cruise. Another device utilizes a rubber layer of distinct color buried at a prescribed depth in the tread part in estimating the cumulative distance of break-in cruise on the basis that the progress of wear of the tread part is discernible against the distinct color of the buried rubber layer. These devices are invariably aimed at displaying the completion of the break-in cruise. After completion of the break-in cruise, 'the tires of these devices assume the same construction as other ordinary tires and, therefore, are used in entirely the same way. 1A 2 13 4 ^P| An object of a preferred embodiment of the invention is to provide a pneumatic tire possessing a tread construction capable of displaying the completion of break-in cruise similarly to the conventional tire and, even after completion of the break-in cruise, protecting the tread grooves against cracking. According to one embodiment the present invention thus provides a pneumatic tire, characterized by the fact that the outer surface of a tire tread part having a relief pattern formed therein is inseparably coated along the contour thereof with a thin film having a uniform thickness in the range of 0.1 to 1mm and excelling in crackproofness. Brief Description of the Drawings: Fig. 1 is a righthand half of the cross section of a pneumatic tire of the present invention and Figure 2. is an enlarged cross section of tread grooves. In the figures, 1 stands for a bead core, 2 for a carcass, 3 for a belt layer, 4 for a tread part, and 5 for a thin film. Now, one embodiment of this invention will be described below with reference to the accompanying drawings. As illustrated in Fig. 1, a pneumatic tire T comprises a carcass 2 having the opposite ends thereof folded back around O -2- — .1 v 2 t 3134 #» bead cores 1 and fastened thereto, a belt layer 3 having cords arrayed as inclined relative to the circumferential direction of tire by a relatively narrow angle, and a tread part 4 having a relief pattern formed therein. In the tread part 4, tread grooves G1, G2 are formed in the surface thereof. A thin film 5 of a uniform thickness in the range of 0.1 to 1 mm is formed along the contour of the tread surface. The thin film 5 is made of relatively soft rubber different from the rubber of the tread part 4 and excellent in crackproofness. The thin film 5 has rigidity of 45 to 55 degrees on the JIS rigidity scale. It may be made of rubber of substantially the same quality as side walls or of rubber tinted in a color other than black. When the aforementioned thin film is formed along the contour of the surface of the tread as described above, this thin film remains on the surface of the tread exposed to the road surface until the cumulative distance of the break-in cruise reaches about 1,000 km. Thus, the user of the tire is enabled to tell the time when the break-in cruise is completed. After completion of the break-in cruise, the thin film 5 survives only on the surface of the tread grooves Gl, G2. Since this thin film excels in crackproofness, the remaining thin film effectively curbs occurrence of cracks in the tread groove bottoms owing to the repeated deformation which the tire is suffered to undergo during the travel. The wall thickness of this thin film is required to be fixed from the standpoint that the portion of the thin film exposed to direct contact with the road wears out after about 1,000 km of travel and the - 3 - 213134 portion remaining in the grooves retains sufficient crackproof-ness intact. Thus, it falls in the range of 0.1 to 1 nun, preferably 0.2 to 0.3 mm. The formation of the thin film of the aforementioned prescribed thickness on the surface of the tread is accomplished by preparing a thin film of rubber vulcanized or partially vulcanized in advance, applying this thin film on the surface of the tread rubber in an unvulcanized state, and subjecting the tread rubber and the applied thin film to vulcanization in a metal die. This invention can be embodied on tires of all categories without reference to the choice between the constructions of radial tire and bias tire. It is adopted particularly advantageously to radial tires for passenger cars; The pneumatic tire of the present invention has a thin film excellent in crackproofness formed along the contour of the surface of the tread part and, therefore, enables the user thereof to tell the time of completion of break-in cruise by complete wear of the thin film in the portion of the tread part exposed to direct contact with the road surface. This thin film surfaces on the inner surfaces of tread grooves and warrants effective prevention of cracks in the tread groove bottoms. 4 </div>

Claims

<div class="application article clearfix printTableText" id="claims"> 213134 What we claim is: (1) A pneumatic tire, characterized by the fact that the outer surface of a tire tread part having a relief pattern formed therein is inseparably coated along the contour thereof with a thin film having a uniform thickness in the range of 0.1 to 1 mm and excelling in crackproofness. (2) A pneumatic tire according to Claim 1, wherein the thickness of said thin film falls in the range of 0.2 to 0.3 mm. (3) A pneumatic tire according to Claim 1, wherein said pneumatic tire is a radial tire for a passenger car. (4) A tire substantially as hereindescribed with reference to the accompanying drawings. BALOV/CJ, -:r)M :it OAHiEY A r~« </div>