NZ212617A - Motorcycle tyre with axially spaced sets of circumferentially extending groove components - Google Patents

Description

2 126 1 7 Patents Form No. 5 NEW ZEALAND PATENTS ACT 1953 COMPLETE SPECIFICATION "TIRE FOR MOTORCYCLES" -i-zWE SUMITOMO RUBBER INDUSTRIES, LTD., of No. 1-1, Tsutsuicho 1-chome, Chuo-ku, Kobe-shi, Hyogo, Jaoan, a Japanese company O hereby declare the invention, for which-5/we pray that a patent may be granted to-He/us, and the method by which it is to be performed, to be particularly described in and by the following statement 2. 2 126 17 The present invention relates to an improved tire especially but not exclusively for motorcycles.

It is an object of an embodiment of this invention to provide a tire for motorcycles which is superior in stability and gripping performance as the motorcycle or other vehicle travels a straight line or in a curved line.

The present invention will be hereinafter described particularly with regard to motorcycles but it is to be understood that the invention has application to other types of vehicles or movable devices and not only those with two-wheels.

Motorcycle tires come into contact with the ground at a steep angle when the motorcycle corners. Therefore, it is necessary that the tread be constructed such that the edges of the tread extend near to the ends of the maximum width of the carcass profile, so that the tire exhibits good road gripping performance at any inclined angle. In addition, the motorcycle tires should have stable travelling performance and gripping performance when the motorcycle travels in a straight line at a high speed. Up to now, rib-pattern tires have been common for high speed travelling on the paved roads and block-pattern tires have been generally employed for off-road travelling.

According to one embodiment of the invention there is thus provided a tire for motorcycles which comprises at least three lengthwise groove components in the circumferential direction within the range of bank angle 0° to 50°, said lengthwise groove components having a length corresponding to at least 20% of the circumference, and linear crosswise 2 126 f T 3. grooves that connect said lengthwise groove components to one another.

An embodiment of this device is now described with reference to the accompanying drawings wherein: Figure 1: shows very diagrarrunatically a part plan view of a tire according to one embodiment of the invention; and Figure 2: shows very diagrarrunatically a cross-sectional view of the tire of Figure 1.

The tire (1) has a linear lengthwise groove (2) which is formed along the tire equator (C) and linear crosswise grooves (3) which extend from the lengthwise groove (2) toward the edges of the tread. The angle (a) formed between the lengthwise groove (2) and the crosswise groove (3) is 20° to 90°, and preferably 45° to 70°. The angle (a) should preferably be acute for the stability in travelling in a straight line and the water exclusion in high-speed travelling. On the other hand, it should preferably be obtuse for the gripping performance on wet roads. Thus the angle (a) is established according to the performance required. According to the embodiment of the invention shown the linear lengthwise groove component (4) which extends circumferentially of the tire is formed in the range of bank angle about 15°. This lengthwise groove component (4) is interrupted or connected in the circumferential direction of the tire by at least one crosswise groove (3)-Another linear lengthwise groove component (5) that extends in the circumferential direction of the tire is formed in the range of bank angle about 30°. Similarly, the linear groove component (6) that extends in the circumferential direction of the tire is formed in the range of bank angle about 50°. These lengthwise groove components are connected to the crosswise groove (3).

The bank angle is defined by the angle (r) formed between a tangential line which touches the tread at point P and a plane M parallel to the rotating axis of the tire. As the point P comes near the edge of the tread, the bank angle becomes greater. When a motorcycle corners in an inclined position, the maximum bank angle is about 50°. Therefore, it is necessary to form the linear lengthwise groove component (6) in the range of bank angle 50° or at the part of the tire which comes into contact with the ground when the motorcycle runs in an inclined position. This is important for stable travelling and wet road gripping.

The lengthwise groove components (4), (5), and (6) each should have a length equivalent to a least 20% of the circumference at their respective positions. The percentage should preferably be greater for the lengthwise groove component in the range of small bank angle. Thus the percentage may be greater than 30% for the lengthwise groove component in the range of bank angle 0° to 20°.

In this embodiment, the lengthwise component (4) in the range of bank angle 15° and the lengthwise component (5) in the range of bank angle 30° are connected by the first crosswise groove component (7), and the lengthwise component (4) in the range of bank angle 15° and the lengthwise component (6) in the range of bank angle 50° are connected by the second crosswise groove component (8). These crosswise groove 2 126 t 7 . components are arranged alternately in the circumferential direction on both sides of the crosswise groove (3).

This embodiment of the invention is seen to have a tread of arrowhead pattern formed by the linear lengthwise groove components (4), (5), and (6), the linear crosswise groove (3), and the crosswise groove components (7) and (8). In addition, each of the lengthwise groove components are arranged in a particular range of specific bank angle. On account of this unique structure, the tire according to the present invention provides an improved travelling stability and gripping performance in both straight travelling and cornering.

Although this invention has been described by way of example and with reference to one possible embodiment thereof it is to be understood that modifications or improvements may be made thereto without departing from the scope of the invention as defined in the appended claims. -* 212617

Claims (7)

WHAT WE CLAIM IS:

1. A tire for motorcycles which comprises a continuous linear groove on the tire equator and at least two axially spaced sets of groove components each side wherein the components in each set are aligned in the circumferential direction, each set lying within the ground contacting tread of a motorcycle bank angle 0° to 50°, the total length of all components in each set corresponding to at least 20% of the circumference, the groove components of the sets being interconnected by linear crosswise grooves wherein the crosswise grooves include linear grooves which extend from the continuous linear groove to the edge of the tread on either side thereof and at the same angle thereto.

2. A tire as claimed in Claim 1 wherein the set of groove components farthest from said continuous linear groove has less total length than the closest set does.

3. A tire as claimed in claim 2 wherein a set of groove components in the bank angle range 0° to 20° has a total length extending to at least 30% of the circumference.

4. A tire as claimed in any one of the preceding claims wherein the linear crosswise grooves extending to the edge of the tread alternate sequentially in the circumferential direction with crosswise grooves—ex-teirding between ' components of the sets only. o\ /'* AA 312817 - 7 -

5. A tire as claimed in Claim 1 or any one of Claims 2 to 4 when dependant upon Claim 1 wherein the said same angle is between 20° and 90°.

6. A tire as claimed in Claim 5 wherein the said same angle is between 45° and 70°.

7. A tire substantially as hereindescribed with reference to the accompanying drawings. SUMITOMO RUBBER INDUSTRIES LIMITED By their attorneys Baldwin, Son <Sc Carey