GB1047921A - Improvements in or relating to pneumatic tyres - Google Patents

Abstract

1,047,921. Pneumatic tyres. DUNLOP RUBBER CO. Ltd. Jan. 20, 1964 [Jan. 31, 1963], No. 3933/63. Heading B7C. A tubular pneumatic tyre comprises at least one carcass ply and a base region 15 for seating upon a wheel rim, said base region being provided at each of its axially outer portions with a substantially inextensible annular reinforcement 18 for gripping the wheel rim, those portions of the or each carcass ply lying adjacent each annular reinforcement being radially disposed solely on one side of the reinforcement. Each reinforcement 18 comprises at least one layer formed from a plurality of convolutions of steel cord extending substantially circumferentially around the tyre. The reinforcements 18 may join to form a single reinforcement across the base region. The carcass plies 4, 5 are spaced from the reinforcements 18 by a layer of rubber 19 extending across the base region and terminating in radially outwardly extending tapered portions 20 which separate the radially innermost portions of the sidewall rubber from the carcass. The base region 15 comprises an axially central portion 16 flanked by two axially outer portions 17 which extend radially inwards at an angle of 15 degrees to the axis of rotation of the tyre. The reinforcements 18 are provided on the radially inner surface of the portions 17. A chafer strip 21 of vulcanized rubber is applied to the radially inner surfaces of the reinforcements 18. An inflation valve extends through the base region 15 into the tyre. Building the tyre.-The tyre carcass is built in cylindrical form on a radially collapsible tyre building drum 23 and on two coaxial supporting members 24, one at each end of the drum 23 and axially spaced therefrom. The drum 23 in uncollapsed condition has a diameter substantially equal to that of the base region of the finished tyre and is shaped to provide an axially central portion flanked by two frustoconical portions 26 corresponding to the profile of the base region 15. Each annular reinforcement 18 is constructed by wrapping a chafer strip 21 around the uncollapsed drum 23, and then superimposing convolutions of steel cord in that part of the chafer strip supported on a portion 26 of the drum. The annular rubber layer 19, the outer carcass ply 5, the inner carcass ply 4 and an inner liner 2 are then wrapped, in that order, around the reinforcements with the ends of the plies and liner extending in axially staggered positions across the members 24. The radially outer surface of the liner 2 is coated with shellac powder to prevent adhesion. Two rubber locating rings 30 are placed around the portions 32 of the plies which bridge the gaps between the drum and supporting members so as to draw these portions radially inwards until they engage cylindrical extension 28 provided at the ends of the drum. The portions of the carcass supported on the drum and members 24 are held against axial movement by gripping rings 31. The air pressure on the radially inner surface of each carcass portion 32 is reduced below ambient atmospheric pressure. The rings 30 are then removed and the supporting members advanced until the radially outermost portions 29 thereof grip the portions 32 against the drum 23. An inflation valve is then inserted through the carcass and the base region 15. The ends of the plies are turned over by means of inflatable bags on the members 24. The carcass is then in tubular form with the ply and liner ends in staggered overlapping relationship. A tread 13 and breaker plies 11, 12 are formed into an annulus which is located coaxially and symmetrically around the carcass. The carcass is inflated into engagement with tread and breaker and subsequently the sidewall rubbers are added. In a second embodiment the liner and plies are turned over individually to form the tubular carcass. The inflation valve is inserted in the radially outer carcass wall and the carcass is then rolled in an axial direction so that the overlapped portions of the plies and the valve are positioned over the base region 15.