Plastics spectacles designed to be moulded in single shot - with balanced flow across lenses and the frames

摘要

The depth profiles of the integral lenses and frames of a pair of spectacles are matched so that plastics material injected at one end of the frame flows to arrive at the bridge and at the far end of the frame with approx. a plane frontal flow. The process avoids air entrapment or distortion due to orientation by flow eddies during moulding of the lenses. The main feature is a broad deep profile across the centres of the lenses to induce extra drag on the material flowing alone the borders beside the material in the thicker channels of the frame rims.