Patent GB-778478-A (GB)
Title: Method of and apparatus for rebuilding pneumatic tyres
IPC: B29D30/58
Filed: 1955-07-13
Abstract: 778,478. Retreading tyres. RAWLS, Y. July 13, 1955, No. 20260/55. Class 144 (1). Worn pneumatic tyre casings are retreaded by stretching the prepared peripheral surface of the casing and stitching tread stock thereto whilst in the stretched condition. As shown the retreading is effected on a machine comprising a frame 20 from which projects a rigid hollow horizontal support 31 carrying a rigid upstanding casing 32 at its end. The support 31 and casing 32 house shaft and chain transmission 36, 47 for a pair of hemi-spherical tyre support rollers 56 projecting laterally from each side of the top of casing 32, the,shaft 36 being driven by a motor and variable speed mechanism housed within the frame 20 and controlled by a hand lever 75. The support rollers 56 fit within the sectional cavity of the tyre 30 and serve to provide stitching pressure reaction and to rotate the tyre about its axis. To guide the tyre during its rotation a pair of rollers 88 are carried by an arm 91 projecting from the casing 32 to engage the inner periphery of the tyre at a point spaced from the rollers 56. Stretching of the peripheral surface of the tyre is effected by a pair of flanged bead-engaging rollers 27 which are mounted respectively on spaced cranked arms 25 carried on shafts 21, 22 projecting from the frame 20 for swinging movement in opposite directions, diverging from the support 31, so that the tyre is pulled tightly against the support rollers 56. This stretches, and opens up the lacerations in, the prepared surface in the region of the rollers 56 to allow the tread stock to penetrate into the lacerations during the stitching operation. The shafts 21, 22 are mechanically linked within the frame 20 for simultaneous operation by a fluid pressure piston and cylinder arrangement controlled by a valve 87. Each shaft 21, 22 has a further cranked member 24 rigidly connected therewith to carry tyre mounting rollers 26 which normally lie spaced from and outside the tyre. For mounting a heavy tyre on the machine, the shafts 21, 22 are operated to swing rollers 26 towards each other to provide a seat for the tyre at a height which allows the tyre beads to rest on the rollers 56. The shafts 21, 22 are then operated in reverse to swing rollers 27 down against the beads and thereby pull the tyre against the rollers 56 so that the beads are spread to allow the rollers 56 to enter the tyre cavity. For demounting the tyre, the rollers 26 are again swung into engagement with the tyre to lift it up past the rollers 56. Camelback is fed on to the tyre periphery by a hand operated roller 93 on which the camelback liner is wound up. The roller 93 is mounted on an arm 94 which is pivotally mounted on the top of the frame 20 for horizontal swinging movement into latched rest or operative positions. To facilitate central application of the camelback, a centre index 101 is horizontally and vertically adjustably mounted on an arm 102 which is swingable vertically into rest or operative positions. The arm 102 is spring biassed into rest position but may be pulled down into operative position where it is latched. The latch is releasable by a pedal 113 for spring return of the arm 102 to rest position. Stitching of the camelback is effected by a roller 121 which is mounted for swivelling about a vertical axis on a hand lever 120, swivelling of the roller 121 being controlled by a further hand lever 126. The lever 120 is curved to overlie the tyre periphery and is mounted at its end on an arm 133 for universal movement about three mutually perpendicular axes 128, 132 and 133, Fig. 5. The arm 133 is in turn pivoted vertically on the frame 20 and provided with latch means, controlled by a pedal 148, to lock it in rest or operative positions. The universal movement of the lever 120, and the swivelling of the roller 121 permit progressive stitching and if necessary, shaping, of the camelback from the centre line outwardly on each side.