Patent GB-931981-A (GB)
Title: Improvements in or relating to the manufacture of pneumatic tyres
Inventor: HURST NORMAN ASHCROFT
IPC: B29D30/06
Filed: 1959-01-10
Abstract: 931,981. Venting pneumatic tyre plies. DUNLOP RUBBER CO. Ltd. Dec. 31, 1959 [Jan. 10, 1959], No. 967/59. Classes 144 (1) and 144 (2). A machine for piercing the sidewalls of a tyre, to vent the carcase plies thereof, comprises a table 2 for supporting the tyre 40 horizontally, and a set of arms 13 disposed in a circle and projecting through radial slots 4 in the table to centralize the tyre with respect to needle holders 18 carried one by each arm 13, the arms 13 being movable radially to engage a bead of the tyre, and the needle holders 18 being movable so that their respective needles 26 pierce the sidewall of the centred tyre to a controlled depth, the arms 13 and needle holders 18 being subsequently retractable for removal of the tyre. As shown, a central vertical pillar 5 projects through the table 2 and terminates in a circular guide plate 7, the lower end of the pillar having an inner sleeve 8 slidable thereon under the action of a bell-crank 37, 36 actuable by a motor-driven cam 35. An outer sleeve 11 is slidably mounted on the sleeve 8 and has an annular groove 12 in its lower end to engage the ends of lovers 15 integral one with the lower end of each arm 13 where said arm is pivoted to frame brackets 14. Each arm 13 projects through a radial slot in a flange plate 10 extending from the upper end of the sleeve 8, and is urged radially outwardly of the table 2 and plate 10 by a spring 16, such outward movement being limited, however, by abutment of the sleeve 11 against the plate 10, or by contact of the arms with the tyre bead. An adjustable stop 17 depending from the table 2 and extending through the plate 10 serves to limit upward movement of the sleeve 11 in the event of plate 10 being raised in the absence of a tyre from the table 2. Each needle holder 18 is slidably guided in upper and lower brackets 19 on its associated arm 13 and is urged upwardly by a spring 20 acting between the lower bracket 19 and an abutment 21 on the holder, upward movement being limited by a holder bracket 22 engaging the underside of plate 10. The upper end of each holder 18 has a recess 23 housing a needle 26 which is anchored at its lower end to a base 25, 25a and is guided at its upper end by a guide shroud 3 slidably secured in the recess by a cap nut 29. A compression spring 27 within the recess 23 acts between the needle base 25 and the lower end of the guide 30, compression of the spring by telescoping of the guide within the holder to project the needle 26 being limited by engagement of the guide with the base portion 25a. In operation, a tyre is placed on the table 2 to surround the plate 7, and the motor 32 is operated to rotate the cam-shaft 33. The cam 35 is thereby rotated to permit the sleeve 8 to rise on the pillar 5 under the action of the springs 16 (through arms 13, levers 15, sleeve 12 and plate 10) and the springs 20. The arms 13 move radially outwardly until stopped by the tyre bead, whereupon the sleeve 8 continues to rise, within the sleeve 12, under the action of the springs 20, such movement continuing after the needle guides 30 have been arrested by the tyre sidewall, so that the needles are projected by the holders 18 to effect the desired piercing of the sidewall. Subsequent rotation of the cam 35 actuates the bell-crank 36, 37 to retract sleeve 8 and thence, through the plate 10, the sleeve 12 to restore the arms 13 and needle holders 18 to the inoperative positions, whereupon a second cam 38 operates a microswitch 39 to switch-off the motor 32.