Press bending of glass sheets

Claim 1

Method of bending a glass sheet to a required curvature, comprising heating the glass sheet to a temperature within the bending temperature range of the glass, locating the heated glass sheet between a first bending die of open form for contacting a minor portion only of one surface of the sheet and an opposed complementary second bending die for contacting a major portion of the other surface of the sheet, moving the dies relatively towards each other to bend the heated glass sheet to the required curvature, and heating the second bending die to adjust the rate of heat loss from said other surface of the sheet substantially to the rate of heat loss from said one surface of the glass sheet during the bending operation to effect a balance between the respective overall heat losses from the two surfaces of the glass sheet.

Claim 8

The method of forming a glass sheet to provide respectively concave and convex opposite surfaces thereon having selected curvatures, which comprises the steps of: a. heating the sheet while flat to a selected temperature within the bending temperature range of the glass; b. contacting a minor portion only of one surface of the sheet while at said selected temperature with a concave bending die whereby heat transfer from said one surface occurs at a particular rate due in part only to contact with said concave bending die; c. simultaneously with (b), contacting at least a major portion of the other surface of said sheet with a convex bending die whereby heat transfer from said other surface occurs at least predominantly through heat loss to said convex bending die; d. controlling the temperature of said convex bending die to adjust the rate of heat transfer from said other surface of said sheet substantially to said particular rate at which heat is transferred from said one surface of said sheet whereby to obtain substantial equality of temperatures for the convex and concave surfaces of said sheet formed respectively by steps (b) and (c); and e. removing said bending dies from contact with said sheet while the substantial equality of temperatures specified in step (d) prevails whereby said convex and concave surfaces of the sheet retain said selected curvatures thereof as imparted by said bending dies.

Claim 9

The method of forming a glass sheet to provide respectively concave and convex opposite surfaces thereon having selected curvatures, which comprises the steps of: a. heating the sheet while flat to a selected temperature within the bending temperature range of the glass; b. contacting a minor portion only of one surface of the sheet while at said selected temperature with a concave bending die whereby heat transfer from said one surface occurs at a particular rate due in part only to contact with said concave bending die; c. simultaneously with (b), contacting at least a major portion of the other surface of said sheet with a convex bending die whereby heat transfer from said other surface occurs at least predominantly through heat loss to said convex bending die; d. controlling the temperature of said convex bending die to adjust the rate of heat transfer from said other surface of said sheet substantially to said particular rate at which heat is transferred from said one surface of said sheet whereby to obtain substantial equality of temperatures for the convex and concave surfaces of said sheet formed respectively by steps (b) and (c); and e. removing said bending dies from contact with said sheet while the substantial equality of temperatures specified in step (d) prevails whereby said convex and concave surfaces of the sheet retain said selected curvatures thereof as imparted by said bending dies.