Prodn. of moulded plastic pointer - by thermo-forming transparent plastic film to shape, and injecting shot of polymer, with provision for illumination if necessary

摘要

Injection moulded transparent plastic pointer is produced by first thermoforming a plastic film into the shape of the exterior of the pointer and then injecting the transparent polymer into this. ADVANTAGE - The process and prod. are esp. inexpensive. In one example, a flat sheet of plastic film is thermoformed to shape after it has been printed with a coating appearing black externally but white internally. The polymer shot is then injected into this shape. At the same time the shaft is also moulded. A bore is also formed above the shaft; and this provides two surfaces for illumination. The principle of the pointer can be used e.g. for a flat dial type pointer. The illumination makes it useful in the dark etc