Method for covering a lens blank with a protective plastic film

摘要

A method and apparatus are disclosed for covering the face of a blank of mineral or organic glass with a protective plastic film. Before pressing the protective film onto the surface of the blank, the blank and film are positioned a certain distance from each other by means of separate holding devices and held so that the edge of the blank and the film do not touch. The film is then heated so that the center of the film surface attains a higher temperature than the outer edge. Pneumatic pressure is then applied to the film surface so that more pressure is exerted at the center of the film than at the outer edge. The protective film is forced on to the surface of the blank from the center radially outward by the applied air pressure, forcing gas trapped between the block and the film to escape from between the blank and the film toward the outer edge of the film as the film makes contact with the blank. Finally, additional pressure is applied to the film to complete the bonding of the film to the blank.