Tyre tread for use on soft sand or snow - has series of grooves sepd. by ridges which have hemi-spherical recesses with total area within specific ratios to total contact area

摘要

A tyre has a tread profile with a number of ridges sepd. by a number of grooves. The outermost face of the ridges has a number of recesses; the ratio of the total open area of the recesses to the contact area of the profile is between 10 and 30%. The contact area is the area in contact with a hard road surface when inflated to IATMA standard. The figure shows the plan view of part of the tread for use in e.g. a desert. Its profile has three main circumferential grooves (2) and a large number of ancillary grooves (3) running diagonally across the width. The main groove (2) along the centre line is straight but the other main grooves (2) are zigzag. Each intermediate ridge (5) has many recesses (6); each is circular in plan and hemispherical in relief. Those (6) in the shoulder areas are e.g. larger than those at the centre line area. They do not need to be circular. They can additionally be in the base of the various grooves. Their effect is to compress the e.g. sand entering them and so form rigid relief patterns which provide a good grip for the tyre. ADVANTAGE - The design has a high tractive grip both on soft sand and soft snow.