| 摘要 |
1310624 Pneumatic tyres FIVEREL SOC CIVILE D'ETUDES ET DE RECHERCHES 23 Dec 1970 [9 June 1970] 61228/70 Heading B7C [Also in Division D1] A tyre has a carcass including cords each comprising a plurality of glass filaments each of which are enclosed in a sheath of elastomeric material, and having a corrected primary coefficient of twist greater than 90, and a corrected secondary coefficient of twist greater than 130, and an elongation to rupture of less than 3À5%. The tyre may have either a radial ply carcass (5, Fig. 1, not shown), or a discontinuous carcass 5a, 5b having the cords symmetrically interrupted about the median plane of the tyre. In the latter embodiment the tyre may include a substructure comprising a reinforcing ply radially inward of the interruption, and/or a bracing layer beneath the tyre tread. The substructure may consist of a reinforcing ply of rayon and nylon cords, and bracing layer may consist of one or more plies of rayon, nylon or steel cords. For glass filament cords, the formula is given where C is the coefficient of twist, T is the twist in turns per metre and N m is defined as 1000 divided by linear mass in tex units. Applied to a glass cord of 680 x 3 x 3 d.tex with Z350/S300 twists the formula is said to give a primary coefficient of twist C 1 = 124 and a secondary coefficient of twist C 2 = 183. A method of producing glass cords comprises coating a plurality of glass threads each cbmprising a plurality of continuous filaments with a resin which covers each filament individually, and slightly polymerizing the resin to form an elastomeric sheath about each filament. The threads are then twisted together to form a strand having C 1 greater than 90. Finally several identical strands are twisted together in the opposite sense to form a cord with C 2 greater than 130. Tyres incorporating carcass plies of glass cords may be tested in the following ways:- (a) By rolling against a wheel 1 metre in diameter under a load of 550 kg, the wheel having a protrusion 61 mm. above the periphery and inclined at 45 degrees to the wheel radius, the ambient temperature being maintained at 30‹ to 32‹ C. and the tyre being examined periodically until it bursts. (b) By mounting on the rear of a normallyloaded vehicle travelling along a cement track at 35 km./hour, the track having obstructions formed by steel angles 11¢ cm. high at 30 degrees to the track, the number of shocks causing the tyre to burst being measured. (c) By mounting on a vehicle running at an average speed of 100 km./hour for a specific distance on a track with severe bends to cause tyre wear. (d) By rolling against a wheel as in (a) but without the protrusion, at various loadings to destruction. |
