Blocking piece and method for vacuum blocking a lens blank

Abstract

A blocking piece for vacuum blocking a lens blank is disclosed. The blocking piece includes a blank contacting element formed of a rigid fluid-permeable material having an upper surface for contacting the lens blank. The blocking piece further includes a support element having an upper part tightly enclosing the blank contacting element on a peripheral surface of the blank contacting element and a lower part adapted to engage with a clamping device for clamping the blocking piece. The lens blank is fixed to the upper surface of the blank contacting element by applying a vacuum within the blocking piece to provide suction through essentially the entire upper surface of the blank contacting element. The disclosure further relates to a method for blocking a lens blank and a use of an element formed of a rigid fluid-permeable material as a part of a blocking piece.

Dependencies are inferred from the claim text.