Patent GB-727576-A (GB)
Title: Improvements in tire building machine
IPC: B29D30/32
Filed: 1951-10-23
Abstract: 727,576. Building pneumatic tyres. GENERAL TIRE & RUBBER CO. Oct 23, 1951 [Nov. 2, 1950], No. 24791/51. Class 144 (1). In building a pneumatic tyre by forming a plurality of fabric plies into a flat band on a building drum D the tyre beads 69 are disposed by bead placing means 36 over the end portions of the band and the said end portions are then expanded radially against the beads to hold them in position and allow withdrawal of the beadplacing means 36. The end portions of the band are then turned and stitched round the beads by turnover fingers 44 after which a tread strip is wrapped round the band and stitched thereon by a beating hammer H. As shown, an expandable drum D is fixed on a hollow shaft 1 which is mounted cantilever fashion in bearings 2, 3 on a frame F and driven by a motor 105 through an air clutch 6. The frame F supports also fixed guide rods 155 on which the bead placing means 36 are slidably supported, and a rotatable shaft 138 to which is fixed an arm 85 supporting the tread stitching hammer H. Drum assembly. The drum D, Fig. 5, comprises a central support member 7 fixed to the shaft 1 and axially movable end support members 8 which are simultaneously adjustable by a right- and left-hand screwthreaded rod 16 journaled in the central support 7. The end support members 8 are relatively wide and each supports a pair of inflatable bands 21 on which rest a'plurality of arcuate-section members 26 which together form the periphery of the drum ends. The members 26 are bent radially inwardly at their ends and formed with hook portions 25 to receive garter springs 24 which resiliently retain the periphery members 26 in position. The central support member 7 supports a plurality of periphery members 27 which overlap the periphery members 26 on each side and are retained in position by a rubber band 29 seated in a corrugation 28, formed centrally in each member 27, which engages in a circumferential groove 10 in the support member 7. Slotted end cylinders 19 supporting the turnover fingers 44 are bolted to the outer ends of the end support members 8 to leave an annular space in the region of each drum shoulder containing the garter springs 24. In this space is arranged a plurality of bead-centring blocks 63, one for each turnover finger 44, which engage the garter spring 24 to expand therewith and are formed with a stepped band-engaging surface 66, 67 and a bevelled cam surface for engagement by the co-operating turnover finger. The bands 21 are inflated to cause radial expansion of the drum D and blocks 63 by air supplied to connections 22 via the hollow shaft 1 from a supply main 96, Fig. 25. Bead-placing means. The bead-placing means comprise a bead-setting ring 36 for each end of the drum pivoted in a support frame 147 or 148 axially slidably mounted on fixed guide rods 155. Each ring 36 carries a plurality of resilient bead supporting tongues 37 projecting axially inwards from the inner periphery of the ring. The outboard ring support frame 148 is pivoted to its slide mounting and is keyed to a quadrant gear 41 which engages a rack 40. A rack 39 fixed to the inboard ring support 147 and the rack 40 engage a common fixed rotary pinion 38 and the ring support 147 is fixed to a rod 130 which is operated by an air piston 129, Fig. 25. In the inoperative position the outboard ring 36 lies horizontal, clear of the drum end, to allow a bead ring to be placed over the drum on to the inboard setting ring 36. On initial movement of the inboard ring by rod 130 into bead placing position, rack 40 is moved to rotate the quadrant gear 41 and swing the outboard ring 36 up over the drum end, this movement being limited by a pin 42 on the ring frame 148 engaging in a guide slot 43 in a fixed part of frame F. Further movement of rack 40 pulls the outboard setting ring 36 into bead-placing position. Ply turnover means. The slotted end cylinders 19 each support a plurality of turnover fingers 44 arranged in slots 34 equi-spaced around the cylinder periphery. The fingers 44, Figs. 16-18, each have a nose roller 47 and a series of stitching rollers 48 on the underside, and they are interconnected by a garter spring 49, engaging in the nose portion of each finger, to pull them radially inwards. Each finger 44 is pivoted to one end of a link 45 which has a pin 52 engaging in an arcuate slot 51 in a triangular tail portion 50 of the finger. The other end of the link 45 is pivoted to an operating ring 46 which is slidable axially on the shaft 1 and is operated, via a rack 55 or 56 and pinion 57 in the shaft 1, by a piston rod 58. The link 45 has stop portion 53 to abut the ring 46 at one limit of its pivoting movement thereon. A guide ring 60 axially adjustable on the end cylinder engages the tail portion 50 of each finger 44 to prevent radially outward movement of the tail portion on initial turnover movement of the fingers. In operation, as the rings 46 are moved axially inwards, the links 45 pivot thereon until the tail portions 50 of the fingers 44 abut the guide ring 60. This causes the fingers 44 to be pushed forwards, the nose rollers 47 sliding radially outwardly on the cam surfaces 65 on the bead-centring blocks 63, Figs. 16 and 17. When the finger tails 50 are free of the guide rings 60, Fig. 17, the links 45 will pivot about the fingers until the pins 52 engage the axially inner ends of the slots 51 and on further movement of the rings 46 will pivot thereon to move the fingers with the ply end portions thereon, radially outwardly against the bias of garter springs 49, until the link stop-portions 53 abut the rings 46. In this position the fingers 44 are then advanced, Fig. 18, to stitch the fabric plies up over the bead. The garter spring 49 exerts the stitching pressure and effects the turnover of those portions of the plies in between the turnover fingers. Tread stitching means. The tread stitching hammer H, Figs. 22, 24, comprises a plurality of beaters 73 journaled on a series of eccentrics 74 keyed to a shaft 75 supported parallel to the drum axis on a support arm 85 and rotated via chain and pulley transmission by a motor 109. The beaters 73 each have a hammer head 87 resiliently bolted thereto to define a guide slot which co-operates with a fixed rod 90 to constrain - the hammer head to the desired movement. The eccentrics 74 are so relatively angularly arranged that on each side of the central hammer the hammers beat the tread in succession from the centre outwardly. The point of contact of each hammer head, which is serrated, with the tread strip describes a part-oval path and this causes the drum, which is in slip-drive during the tread stitching operation, to be rotated slowly so that the tread is stitched throughout its circumference. Operation. With a bead ring 69 positioned on each setting ring 36, the drum D is set in rotation by operation of a foot-pedal 103, Fig. 25, controlling the motor 105 and a number of plies are wrapped around the drum to give a tapered or stepped arrangement at each end portion. A hand switch 136 is then closed to operate an air valve 131 controlling the piston rod 130 to move the bead setting rings 36 into bead placing position, Fig. 14. The drum is then expanded, together with the bead-centring blocks 63, by closing a switch 117 operating an air valve 119 controlling the supply of pressure air to the inflatable bands 21 via the hollow shaft 1. The bead-centring blocks press the ply end portions radially against the inner periphery of the beads, Fig. 15, the stepped surface of the blocks preventing the resilient tongues 37 on the rings 36 from being clamped between the plies and the beads. The bead-setting rings 36 are then withdrawn and a hand switch 128 closed to operate an air valve 126 controlling movement of the piston rod 58 to move the operating rings 46 carrying the turnover fingers 44. The end portions of the plies are turned and stitched round the beads 69 by the fingers 44, Figs. 16-18, after which the fingers are retracted and a tread strip wrapped round the plies on the drum. The drum is then put into " slip drive by closing a switch 141 which operates an air valve 139 to effect movement of a piston rod 97 and thereby a lever 98 which operates a valve 101 controlling the air clutch 6. The lever 98 is fixed to the hammer support shaft 138 which is thus rotated on movement of the lever 93 to bring the hammer H into operative position shown in broken lines in Fig. 2. At the same time, a lug 142 on the lever 98 closes a switch 108 causing the hammer drive motor 109 to operate the hammers to stitch the tread to the plies. On completion of the tread stitching operation the hammer is moved to inoperative position, shown in full lines in Fig. 2, and the drum expanding bands 21 deflated to collapse the drum and allow removal of the tyre for shaping and moulding.