| 摘要 |
639,279. Pneumatic tyres. FIRESTONE TIRE & RUBBER CO. Nov. 26, 1947, No. 31311. Convention date, Dec. 24, 1946. [Class 144 (ii)] A tyre tread is formed with closely-spaced circumferential ribs 13 ... 21 of serrated form, the facing edges of adjacent ribs having a tooth-pitch ratio of two-to-one so that under load the teeth 23 of larger pitch enter alternate notches between the smaller-pitch teeth of the adjacent ribs. Air, water &c. trapped in the intervening pockets 6 escapes along the bottoms of the grooves between the ribs to prevent the formation of suction-cups and to preserve the non-slip character of the ground-engaging portion of the tread.
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