Patent GB-1389250-A (GB)
Title: Pneumatic tyre
IPC: B60C9/22
Filed: 1972-03-08
Abstract: 1389250 Pneumatic tyres UNIROYAL 8 March 1972 [12 March 1971] 10734/72 Heading B7C A pneumatic tyre has a tread consisting of a central portion 7 with continuous circumferential grooves 11, and two shoulder portions 8, 8a, the tyre being constructed such that when in an inflated but unloaded state the ground contacting surface of one shoulder portion 8 lies radially inwardly of the projected profile (indicated by dotted lines in Fig. 1) of the ground contacting surface of the central portion 7 and, as viewed in radial section, is straight and makes an angle α of 10-30 with the tyre axis, the shoulder portion 8 being capable of contacting the ground, at least in part, when the tyre is run on non- yielding ground and an appropriate turning force is applied thereto. As shown in Fig. 1 the other shoulder portion 8a may be similarly constructed to that 8, its ground contacting surface making an angle # = a in the inflated and unloaded state. The shoulder portions 8, 8a may be separated from the central portion 7 by respective circumferential grooves 9, 9a which are wider than and at least as deep as the grooves 11. The widths b, c of the shoulder portions may be equal or unequal, and the shoulder portions may together make up 40% of the total width of the tread, the central portion 51%, and the two grooves 9, 9a the remaining 9%. The tyre may have a radial carcass 2 and a cord reinforced breaker 6, the cords of the carcass and breaker being made of glass, or metal, e.g. steel, or textile, e.g. rayon, nylon or polyester. The breaker may comprise two superimposed layers which may be transversely continuous as shown in Fig. 1 or alternatively the radially outermost, (Fig. 2, not shown), or both, Fig. 3A, the layers may be transversely discontinuous, each discontinuous layer being divided into a central element 26 and two side elements 27, 27a by spaces 28, 28a located beneath the grooves 9, 9a respectively. The cords in one breaker layer cross those in the other layer, and where a layer is transversely discontinuous the angle B made by the cords in a central element 26 with the mid-circumferential plane 10 of the tyre may be in the range 12- 18 degrees, and the angle A made by the cords in a side element 27, 27a may be in the range 20- 30 degrees. A further breaker layer with cords extending parallel to the plane 10 may be provided radially outward of the two breaker layers. The tread pattern on the central portion 7 may be the same as, or different to, that on one or both of the shoulder portions 8, 8a. Both the central and shoulder portions may have rectilinear circumferential grooves as shown in Fig. 3A. Alternatively (Fig. 8, not shown) the shoulder portions may have zig-zag circumferential grooves whilst the central portion has rectilinear grooves and anti-skid slots or ridges in or on the ribs between its grooves. In a further embodiment (Fig. 9, not shown) the central portion has alternate zig-zag and rectilinear circumferential grooves and the shoulders are provided with blocks similar to those 18 shown in Fig. 10, and in yet another embodiment (Fig. 11, not shown) the shoulders have chevron shaped configurations.