This invention relates to a method and apparatus for the production of vehicle tires having the usual crown portion, carcass and sidewalls by means of a combination injection molding and vulcanization device.
Inflatable vehicle tires are conventionally produced by labor-intensive processes which have been known for many years. The carcass and sidewalls are usually fabricated and prevulcanized on a tire mounting machine using raw rubber, whereafter the separately produced and prevulcanized crown portion (without tread) is placed on the carcass. This assembly is then placed in a vulcanizing press which completes the vulcanization process and simultaneously forms the tread configuration. The crown portion can be placed on the carcass as a finite strip or as an endless ring. With the latter alternative the crown portion is expanded during final vulcanization. The separately produced crown portions are kept in readiness in an intermediate storage area and are removed therefrom according to production requirements. This conventional tire production process is labor-intensive and time consuming owing to the multitude of operations which must be at least partially carried out manually. Furthermore, the finished vehicle tire is frequently non-uniformly shaped which results in balancing problems, particularly in the area of the relatively large crown portion.
The production of vehicle tires by injection molding or casting is disclosed in German Pat. No. 2,514,973, according to which the rubber crown portion and sidewalls are formed in a specially designed injection mold into which the carcass and possibly a reinforcing belt resting on a core are placed. The production or finishing of the tire is effected in two injection cycles. In the first cycle, the tire sidewalls are injection molded in adjacent cavities, whereafter the mold is restructured and the crown portion is then injection molded and simultaneously joined to the sidewalls.
The tire produced by this process is characterized by thicker than usual sidewalls since the conventional canvas support or reinforcement is eliminated, and the sidewalls must thus be thickened to provide a sufficient tensile load capability. The vehicle tire produced in this manner thus has different characteristics and behavior as compared with conventional tire designs.