Corning Incorporated

Robert M Menihan

Richard Bruce Pitbladdo

Jackson P Trentelman

Jason S Watts

Kevin Bruce Sterner

Edwin Q Giles

Ronald Alan Davidson

Martin J Schad

William W Blakeslee, Deceased

David L Naylor

This invention contemplates a near net-shape method of making thin glass-ceramic articles possessing substantially uniform thickness and parallel opposing surfaces comprising the steps of: (a) heating the receiving and opposing molding surfaces of a mold to predetermined different temperatures; (b) bringing the receiving and opposing molding surfaces of the mold into close proximity to each other to press a delivered charge of molten glass to fill said mold, while thermally providing and maintaining a substantially parallel fit between the receiving and opposing surfaces of the mold, to achieve substantially uniform thickness in the pressed charge, (c) pressing the glass charge for a time sufficient to remove enough heat from the glass charge that the temperatures of the molding surfaces and the glass article surfaces are all nearly at equilibrium, wherein the press time and mold temperature differential combine to result in symmetric heat removal thereby causing all the aforementioned temperatures to reach equilibrium at nearly the same time, (d) removing the glass article from the mold; (e) covering the opposing surfaces of the glass article with a refractory insulating material; (f) heat treating the covered glass article at a temperature and for a time sufficient to cause the glass article to crystallize in situ to a glass-ceramic article; and (g) cooling the covered glass-ceramic article to room temperature and removing the covering therefrom.

Method for forming flat glass-ceramic articles

In a mold apparatus, the receiving molding surface and the opposing molding surface are each mounted coaxially and in sliding fashion within an alignment means. Both of these alignment means have an equal number of spaced apart alignment pads which are positioned such that opposing pads will be in cooperable engagement with each other during pressing. Utilizing the disclosed apparatus, a method for molding precisely shaped articles, such as magnetic memory disc substrates which require precisely parallel, opposite molded surfaces, is described. Simply stated, the method utilizes the alignment pads' thermal expansion characteristics to induce a controlled level of thermal distortion to obtain pad lengths which result in parallel opposing molding surfaces. There are two methods for accomplishing this pad length required for parallel molding surfaces: the first method, controlled heating, consists of introducing heat to a pad to cause it to expand, thereby extending the length thereof; the second method, controlled cooling, consists of introducing cooling to a pad to cause it to contract, thereby shortening the length thereof. Once pad lengths are adjusted and thus the molding surfaces are parallel, the glass article may be pressed. This method is suitable for press molding any glass article which requires parallel opposing surfaces, regardless of the article's thickness.

Method and apparatus for parallel alignment of opposing mold surfaces by

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Corning, NY, United States of America

Robert M Menihan