The patent badge is an abbreviated version of the USPTO patent document. The patent badge does contain a link to the full patent document.
The patent badge is an abbreviated version of the USPTO patent document. The patent badge covers the following: Patent number, Date patent was issued, Date patent was filed, Title of the patent, Applicant, Inventor, Assignee, Attorney firm, Primary examiner, Assistant examiner, CPCs, and Abstract. The patent badge does contain a link to the full patent document (in Adobe Acrobat format, aka pdf). To download or print any patent click here.
Patent No.:
Date of Patent:
May. 16, 1995
Filed:
Oct. 22, 1993
Po-Ling Shiao, Hsinchu, TW;
Chien-Tsung Wu, Taichung Hsien, TW;
Chi-Shen Tuan, Taipei, TW;
Tzong-Ming Yeh, Taipei, TW;
Industrial Technology Research Institute, Hsinchu, TW;
Abstract
An improved injection/compression molding process for the manufacturing of high quality concave optical lenses of thin thickness. A thermoplastic material is injected into a mold cavity of an injection/compression molding machine, the mold cavity is designed to have adjustable thickness and is initially set at a thickness greater than the lens to be produced. After the amount of the plastic injected fills the enlarged cavity, the thickness of the cavity is gradually reduced by exerting a compressional force on the thermoplastic material inside the mold cavity. During the compression stage, the injection continues and the excess thermoplastic material is squeezed into an overflow pocket inside the injection/compression mold. The injection apparatus can be switched into a pressure holding mode during and after the compression stage to prevent any backflow and post-injection shrinkage. The process disclosed in the present invention offers many significant advantages over prior art processes, including avoidance of the commonly encountered weld line and birefrigence problem, substantially improved quality control, elimination of external heating or cooling needs, increased production rate, and reduced production cost.