Tyre

Abstract: A tyre which is provided on a sidewall with an embossed mark (3) , the embossed mark has an indent portion (5) and an outline portion (6), the outline portion has a top surface (6A) having a light colour different from a dark colour of the light colour different from a dark colour of the sidewall surface (2S) ,the bottom (5A) of the indent portion is provided with a rough surface to have a less lustre than the sidewall surface, and preferably, the radial height of the mark is in the range from 15 mm to 60 mm, and the bottom of the indent portion is provided with a cross mesh pattern whose mesh pitches are 0.01 to 0.1 times the radial height H of the mark.

Description: The present invention relates to a tyre having an embossed mark on the surface of the tyre sidewall. In general, a tyre is provided in the sidewall portions with embossed marks to indicate, for example its trade mark, tyre size, pattern and the like. In order to improve the visibility of such a mark, white rubber has been used, wherein as shown in Fig.8, the whole of the embossed mark (a) is made of white rubber protruding from the outer surface (b) of the tyre sidewall. White colour contrasts with the black rubber sidewall, and thus the visibility is improved in comparison with black embossed marks. However, as the white mark has a glossy flat top surface similar to the tyre sidewall, the mark often becomes invisible at some view angle or direction and the tyre appearance becomes unattractive. It is therefore, an object of the present invention to provide a tyre which is provided in a sidewall portion with a mark improved in visibility and attractiveness. A tyre according to the preamble of claim 1 is known from EP-A-0 253 557. According to one aspect of the present invention, a tyre comprises a tread and sidewalls extending radially inwardly from the tread edges, at least one of the sidewalls provided on the outer surface thereof with an embossed mark, wherein the embossed mark has an indent portion and an outline portion the outline portion protruding from the sidewall outer surface and extending along the outline of the indent portion, the outline portion being provided with a top surface having a light colour different from the dark colour of the sidewall, the indent portion having a bottom indented from the top surface of the outline portion, and the bottom being provided with a rough surface to have a lower lustre than the sidewall. Preferably, the roughness is formed by a cross mesh pattern whose mesh pitches are 0.01 to 0.1 times the radial height H of the mark, and the radial height H of the mark is from 15 mm to 60 mm. Embodiments of the present invention will now be described in detail in conjunction with the accompanying drawings, in which: Fig.1 is an enlarged partial perspective view of a tyre according to the present invention showing an embossed mark in the sidewall thereof; Fig.2 is a cross sectional view of the mark; Fig.3 is an enlarged cross sectional view of the surface of the indent portion of the mark showing the mesh pattern; Figs.4(a) and 4(b) are views showing other examples of mesh pattern; Fig.5 is an enlarged plan view of another marked part of the sidewall showing other embossed marks; Figs.6 and 7 are cross sectional views explaining a method of making the mark; and Fig.8 is a partial perspective view of a tyre according to the prior art. In this embodiment, the tyre 1 is a pneummatic tyre 1 comprising a tread portion, a pair of axially spaced bead portions and a pair of sidewall portions 2 extending from the tread edges to the bead portions. The sidewall portions 2 are each provided with embossed marks 3. Fig.1 shows one of the marks 3, which mark represents a letter "T". The mark 3 comprises an indent portion 5 and an outline portion 6. The outline portion 6 protrudes from the outer surface 2S of the tyre sidewall portion 2, and extends around the T-shaped indent portion 5. In this example, therefore, the outline portion 6 extends continuously along the outline of the mark 3. The outline portion 6 is made of a white rubber compound 11A. The white rubber compound 11A is exposed at least at the top surface 6A of the outline portion 6 to present preamble a white colour (other light colours may be used). In this embodiment, the outer side surface 6B and inner side surface 6C of the outline portion 6 are covered by a thin layer of a black rubber compound 11B to show a black colour (other dark colours may be used ). The indent portion 5 is a hollowed out part of the mark 3 having a bottom surface 5A indented from the top surface 6A of the outline portion 6. The bottom surface 5A is provided with a mesh pattern (P) to provide roughness. In this embodiment, the mesh pattern (P) is formed by a first group (A) of equispaced parallel straight lines 9 extending in a radial direction and a second group (B) of equispaced parallel straight lines 10 extending at right angles to the above- mentioned radial direction so as to cross the radial lines 9. The mesh pitches or the line spacings (t) in this example are constant in each of the groups (A, B) and the same value therebetween. More particularly, the mesh pattern (P) in this example is formed by a number of small size indents of a right pyramid shape as shown in Figs.2 and 3. The above-mentioned parallel straight lines 9 and 10 are the ridge lines formed between the adjacent indents. As shown in Fig.3, each indent has smooth sides (S1, S2) inclined at an angle (alpha, beta) in the range from 30 to 65 degrees with respect to the normal direction to the sidewall surface, and the opposed sides (S1 and S2) intersect each other at the bottom so as to form a V-shaped cross section. In this example, the inclination angle (alpha) of one of the opposed sides (S1 and S2) is the same as the inclination angle (beta) of the other side, hut they may be different from each other. The bottom surface 5A of the indent portion 5 is completely covered by a thin layer of the above-mentioned black rubber compound 11B to present a black colour a dark colour. This layer is continued from the above-mentioned layer covering the inner side surface 6C of the outline portion 6. In the above-explained example, the mesh pattern (P) is formed by a number of small size indents which are arranged in a number of rows in each of the two different directions, a radial direction and a direction crossing the radial direction at a right angle. However, the mesh pattern (P) can be formed by a number of continuous narrow indents or grooves which comprises a first group (A) of equispaced parallel grooves 9 extending in a direction, for example a radial direction, and a second group (B) of equispaced parallel grooves 10 extending in a direction crossing the above-mentioned direction at for example a right angle. In this case, each of the grooves 9 and 10 has a pair of opposed sides (S1 and S2) inclined at angles (alpha and beta) in the same manner as the above-explained example. Accordingly, the bottom surface 5A diffuses the incident light. For visibility of the mark and attractiveness of the tyre view, it is preferable that the height H of the mark 3 measured radially between the radially inner most point to the radially outer most point of the mark is 15 mm to 60 mm, and the mesh pitch (t) is 0.01 to 0.1 times the mark height H. If the height H is more than 60 mm, cracks are liable to occur between the outline portion 6 and the tyre sidewall rubber when the sidewall is subjected to bending deformation. For the same reason, the amount (h) of protrusion of the outline portion 6 from the sidewall surface 2S is preferably less than 5 mm. The outer side surface 11B of the outline portion 6 is inclined at an angle (theta) from 5 to 10 degrees with respect to the normal direction to the sidewall surface 2S towards the inside or centre of the mark of the indent portion from the base to the top. The corner between the outer side surface 11B and the sidewall surface 2S is rounded by a radius of curvature R of more than 1 mm. The bottom surface 5A or the outermost point level thereof is the same level as or a higher level than the outer surface 2S. Fig.4(a) shows another example of the mesh pattern, wherein the pattern (P1) is substantially same as the above-mentioned pattern (P), but both the first group of straight lines 9 and the second group of straight lines 10 are inclined with respect to the radial direction. Fig.4(b) shows still another example of the mesh pattern, wherein the cross lines forming the mesh are curved such that a circle is revolved at regular pitch angles around a point defined thereon. As explained above, those two examples of the mesh pattern (P) can be formed by either arranging a number of dependent small size indents or arranging a number of continuous grooves in two different directions. Fig.5 shows other embossed marks 3, which represent letters "D" and "U". Figs.6 and 7 shows a method of forming the mark 3. The method comprises the steps of 1) forming a depression (M) at the place in a raw sidewall rubber strip 12 where the mark is formed; 2) putting a block of a raw white rubber compound 13 in the depression (M) so that the white rubber protrudes from the depression (M); 3) completely covering the white rubber block 13 by a thin strip 15 of 4 black rubber compound which is the same compound as the sidewall rubber strip 12; 4) vulcanising the assemble 16 of those raw rubber materials or layers 12, 13 and 15 while pressing a negative impression 19 against the outside surface of the assemble 16, the negative impression 19 comprising a protruding portion 17 with a negative mesh pattern corresponding to the indent portion 5 and a depressed portion 18 corresponding to the outline portion 6; and 5) removing the thin black rubber layer 15 at only the top of the formed protruding part (K) which corresponds to the outline portion 6 so that the white rubber 13 appears, after the vulcanisation has been done, by for example buffing to the level (L) shown in Fig.7. This method is incorporated into a conventional tyre making method in which an assembly of raw tyre compounds for example a tread rubber strip, sidewall rubber strips, a carcass, bead rubber strips and the like, is vulcanised using a mould having an inside face with a negative impression of the tyre.

Claims: A tyre (1) comprising a tread and sidewalls (2) extending radially inwardly from the tread edges wherein, at least one of the sidewalls (2) is provided on the outer surface (25) thereof with an embossed mark (3) whereby said embossed mark (3) has an indent portion (5) and an outline portion (6) said outline portion (6) protrudes from the sidewall surface (25) and extends along the outline of the indent portion (5), the indent portion (5) having a bottom (5A) indented from the top surface (6A) of the outline portion, characterised in that the outline portion (6) being provided with a top surface (6A) having a light colour different from the dark colour of the sidewall surface (25), and said bottom (5A) is provided with a rough surface to have a lower lustre than the sidewall surface (25). A tyre according to claim 1 characterised in that the radial height of said mark (3) is in the range of 15 mm to 60 mm, and the roughness of the bottom surface (5A) of the indent portion is provided by a cross mesh pattern (P) whose mesh pitches are 0.01 to 0.1 times the radial height H of the mark (3). A tyre according to claim 2 characterised in that said mesh pattern (P) is formed by a first group of parallel straight lines and a second group of parallel straight lines crossing said first group. A tyre according to claim 2 characterised in that said mesh pattern (P) is formed by curved lines. A tyre according to claim 1 characterised in that the bottom surface (5A) of the indent portion is provided with a number of small flat portions inclined at an angle (alpha, beta) in the range from 30 to 65 degrees with respect to the normal direction to the sidewall surface (25). A tyre according to claim 1 characterised in that the bottom surface (5A) of the indent portion is completely covered by a rubber layer having a dark colour different from said light colour. A tyre according to claim 1 characterised in that the outline portion (6) has an outer side surface (6B) and an inner side surface (6C) each of which are covered by a thin rubber layer to present a dark colour. A tyre according to claim 7 characterised in that said dark colour of the outer side surface (6B) of the outline portion is the same as the tyre sidewall surface (25).

Inventors: YAMASHITA FUMIKAZU, YAMASHITA, FUMIKAZU
Applicants: SUMITOMO RUBBER IND, SUMITOMO RUBBER INDUSTRIES LIMITED
Application year: 1992
Main classification: B60C13
IPC codes: B29K9, B60C13, B29D30