GB1353903A - Methods and apparatus for treading tyres or wheels - Google Patents

Abstract

1353903 Extruded tyre tread BARWELL ENG Ltd and J H BARWELL 30 April 1971 [7 May 1970] 22154/70 Heading B5A [Also in Division B7] A rubber tread 52 is extruded, by an intermittent or continuously operated piston extruder, or by a screw extruder, around the periphery of a member, e.g. a wheel, a solid orinflated tyre, or a tyre carcase from an extrusion outlet which is partly defined by the member, and during rotation of the member. In the Fig. 1 embodiment, a tyre 13 is mounted for rotation on a hub 9, by a variable speed motor, at a slow rate during extrusion and, prior thereto, at a slower rate for removal by cutting of the worn tread by a gauge 25, which is reciprocated transversely of the rotating tyre, from a crank 22 and threaded shaft 21, during which the required profile is determined by a replaceable template 28 against which is urged, by a wheel rotated threaded shaft 29, a follower 27 to which the gauge 25 is connected. The extrusion die, Fig. 3, comprises a head 40 having a rectangular flow passage to which is bolted, by a member 35 and bolts 36, a die housing and frame 42, the passage whereof contains a member restricting flow at the passage base and a surrounding screen which may be shaped to increase flow at the screen extremities. The extrusion outlet of the die is defined by elements which are replaceable for different size tyres; a plate having a contour 47a corresponding to the periphery to which is applied the tread; a plate 49 corresponding to that of the tread; and side plates 48, 50. In the Fig. 3 embodiment, intermittent, continuous, zig-zag tread channels 52a, Fig. 1, are formed during extrusion by the rounded, or rectangular, fingers 54 of a slider 53 which is mounted to the ends of a bar 55, reciprocated by a double acting piston, via a lever connection to lugs 56 thereof. Rotary asymmetric fingers may alternatively be provided. At the commencement of extrusion, the tread is bevelled at 52b by a cutter, e.g. an electrically heated wire, and excess material in the region 52b, resulting as the tyre is drawn away from the die, is similarly removed, the channels 52a being connected at this location by cutting after vulcanizing in a steam autoclave. A tread pattern as in Fig. 5, is formed by a pair of fingers which are reciprocated transversely across the die outlet by pistons. The fingers 54 of the Fig. 3 embodiment, may be maintained stationary to form straight channels, or may be reciprocated intermittently to form tortuous channels. Where an unchannelled tread is extruded, the tread channels may be cut by cutters downstream of the die, or after curing of the tread. Patterns may be embossed on the tread sides or shoulders by patterned rollers located at the die or downstream thereof. In a modification of the Fig. 3 embodiment, the slider 53 and plate 49 may comprise a single element reciprocable in an arcuate path corresponding to the tread surface.