| 摘要 |
754,438. Wheel tyres. FIRESTONE TIRE & RUBBER CO. Jan. 18, 1954 [Oct. 22, 1953], No. 1424/54. Class 144 (2). A tyre tread comprises circumferential ribs 13-19 at least some of which are divided into road contacting blocks 32 by narrow grooves 9 which extend completely across the ribs and have parallel but offset end portions connected at adjacent ends thereof by relatively short centre portions. As shown, the tread comprises continuous shoulder ribs 14, 15, a continuous central rib 13 and intermediate ribs 16, 17 and 18, 19. All the ribs have serrated lateral faces and the intermediate ribs are traversed by deep, narrow, diagonally extending grooves 9 so that the ends of the blocks 32 so formed overlap circumferentially. The serrations 26, 27 on the outer faces of the shoulder ribs 14, 15 have bases 36, 33 which extend radially inwardly deeper than the shoulder ribs to provide for better vulcanisation of the tread shoulder. The serrations on the inner faces of the shoulder ribs are double in number those on the confronting faces of the intermediate ribs 16, 19, and disposed so that the ridges of the intermediate rib serrations are aligned with alternate valleys of the shoulder rib serrations, the intervening circumferential grooves 20, 25 being narrow in these regions so that under load the respective rib portions abut to leave recesses 28. The abutting (under load) rib portions are undercut as at 2, 3, 5, 6 to provide air and water outlets in use. Flexibility of the shoulder ribs 14, 15 is provided by deep narrow grooves 30, 31 which extend, at intervals, diagonally half way into the ribs from the adjacent grooves 20, 25. The grooves 9 in the intermediate ribs are directed as shown to converge, in oppositely directed senses respectively, on the circumferential grooves 21, 24 between the pairs of ribs 16, 17 and 18, 19. The depth of each groove 9 is greatest at its centre portion 1, Fig. 4, the end portions being shallower to provide braces 7, 8 between adjacent blocks 32 to stiffen the overlapping end portions thereof.
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