Cold rolling of glass preforms

A method for making cylindrical glass preforms with convex, optical quality end surfaces comprising the steps of:

• (a) placing a glass ball preform having an optical quality surface on a heated lower platen;
• (b) raising the temperature of the glass ball preform to a temperature above the glass transition temperature of the glass ball preform;
• (c) engaging the glass ball preform with an upper platen;
• and
• (d) moving at least one of the upper and lower platen to cause a gap between the upper and lower platen to narrow to a predetermined dimension and simultaneously to cause the glass ball preform to roll between the upper and lower platen to form a cylindrical preform having a predetermined diameter, the cylindrical preform having convex, optical quality end surfaces.

A method for making cylindrical glass preforms with convex, optical quality end surfaces comprising the steps of:

• (a) placing a glass ball preform having an optical quality surface on a heated lower platen;
• (b) lowering the viscosity of the glass ball preform to be in a range of from about 104 to about 108 poise;
• (c) engaging the glass ball preform with an upper platen;
• (d) effecting relative lateral movement between the upper platen and the lower platen;
• (e) effecting relative vertical movement between the upper platen and the lower platen to cause a gap between the upper platen and the lower platen to narrow to a predetermined dimension;
• and
• (f) rolling the glass ball preform between the upper and lower platen to form a cylindrical preform having a predetermined diameter, the cylindrical preform having convex, optical quality end surfaces.

A method for making cylindrical glass preforms with convex, optical quality end surfaces comprising the steps of:

• (a) placing a glass ball preform having an optical quality surface on a heated lower platen;
• (b) raising the temperature of the glass ball preform to a temperature above the glass transition temperature of the glass ball preform;
• (c) engaging the glass ball preform with an upper platen;
• (d) effecting relative lateral movement between the upper platen and the lower platen;
• (e) effecting relative vertical movement between the upper platen and the lower platen to cause a gap between the upper platen and the lower platen to narrow to a predetermined dimension;
• and
• (f) rolling the glass ball preform between the upper platen and the lower platen to form a cylindrical preform having a predetermined diameter, the cylindrical preform having convex, optical quality end surfaces.

An apparatus for making cylindrical glass ball preforms with convex, optical quality end surfaces comprising the steps of:

• (a) a lower platen on which a glass ball preform having an optical quality surface is placed;
• (b) an upper platen which is generally parallel to the lower platen, the upper and/or lower platen being movable relative to one another in a vertical direction and a horizontal direction;
• (c) means for heating the glass ball preform to above a glass transition temperature thereof;
• and
• (d) means for setting a final gap between the upper platen and the lower platen, the final gap controlling the diameter of the cylindrical glass ball performs, relative vertical movement between the upper and lower platen allowing the glass ball preform to be engaged between respective rolling surfaces of the upper platen and the lower platen, relative horizontal movement between the upper platen and the lower platen causing the glass ball preform to roll between the respective rolling surfaces of the upper platen and the lower platen.