Ophthalmic lens manufacturing equipment includes lens die assemblies constructed to accommodate fragile, high quality glass lens dies. The lens die supports of the assemblies provide a series of grooves of critically small widths on their interface surfaces to apply vacuum pressure from an external source...http://www.google.com/patents/US5620635?utm_source=gb-gplus-sharePatent US5620635 - Ophthalmic lens manufacturing equipment and method
