Patent GB-758630-A (GB)
Title: Improvements relating to methods of and corresponding apparatus for the butt-splicing of articles composed of uncured rubber
IPC: B29C65/00
Filed: 1954-12-30
Abstract: 758,630. Jointing rubber. PIRELLI SOC. PER AZIONI. Dec. 30, 1954 [Dec. 30, 1953], No 37712/54. Class 70 [Also in Group VIII] In a method of butt splicing the two ends of a pneumatic tyre inner tube or of a solid ring or other article of uncured natural or synthetic rubber, wherein the two ends of a tube or other article are flattened and clamped in two clamps movable towards and away from one another in a splicing machine, each end being positioned to project slightly beyond that side face of its clamp which is toward the opposite clamp a part of each projecting portion being trimmed off by a cut parallel with said side face and the clamps brought together to abut the said ends to form a splice, the trimming operation is effected by two heated knives each moved through a projecting portion along a rectilinear path parallel to said side face of the relative clamp and also to the clamping faces of said clamp, each knife being shaped in the cutting zone thereof, and in section in a plane perpendicular to its path of movement, to correspond to the desired profile of the cut end portion, while supporting said portion in a direction perpendicular to the planes of the clamping faces of said clamp, and maintaining a pushing action on said portion opposed to the thrust of the knife. Apparatus for carrying the method into effect comprises two trimming devices associated respectively with two clamps, at least one clamp being movable towards and away from the other, the said trimming devices each comprising a knife shaped and movable in the manner set forth above, and means effective to support each portion against deflection in a direction perpendicular to the planes of the clamping faces of its clamp, and to maintain a pushing action upon said portion in opposition to the thrust of the knife. The two flattened ends of an inner tube 1, Fig. 1, to be spliced are placed in the lower jaws 2, 3 of clamps A, B, the lateral folds of the tube ends being accommodated in cylindrical channels 8, Fig. 2, in each lower jaw, and portions 9 of the tube ends projecting from the side faces 10 of the clamps A, B. Two knives 11 mounted on a common carriage (not shown), are movable in the direction of the arrow C to trim the portions 9. Each knife 11 is associated with mechanically driven rollers 12, 13 which bear upon the upper and lower surfaces of one of the portions 9, and support the latter against deflection in a direction perpendicular to the clamping faces as the knife passes through said portion. The rollers 12, 13 rotate in opposite directions at peripheral speeds in excess of the speed of traverse of the knife, and push the portion 9 towards the knife 11 in opposition to the thrust of the latter. The cutting zone of each knife in longitudinal section in a plane perpendicular to its path of traverse is arcuate so that the cut surfaces of the flattened tube ends are convex. In side elevation the cutting zone of each knife is V-shaped, the aperture in the V facing in the direction of the cutting movement. When the cutting operation is completed the carriage returns to its initial position and the clamps are approached to press the cut surfaces of the tube ends together.