Forming station and method for forming a hot glass sheet with transverse curvature

Abstract

A glass sheet press forming station ( 32 ) and method for press forming hot glass sheets with transverse curvature is performed by initially limiting the central forming of a glass sheet (G) between its end portions upon pickup from a roll conveyor to an upper mold ( 38 ) and prior to press forming with an associated lower mold ( 66 ) to prevent central area optical distortion of the press formed glass sheet.

1 . A forming station for forming a hot glass sheet having a pair of spaced end portions with distal extremities and also having an intermediate portion extending between its end portions, the forming station comprising:
 a housing having a heated chamber;   a roll conveyor for conveying the hot glass sheet into the heated chamber of the forming station along a plane of conveyance;   an upper mold located within the heated chamber of the forming station above the roll conveyor and having a downwardly facing surface that has a downwardly convex shape with curvature in transverse directions, and the upper mold being movable between an upper position spaced above the roll conveyor and a lower position adjacent the roll conveyor;   a vacuum source for drawing a vacuum at the downwardly facing surface of the upper mold;   a gas lift jet array located in the forming station below the plane of conveyance of the glass sheet to supply upwardly directed gas lift jets that provide the sole impetus for lifting the glass sheet upwardly from the roll conveyor to the upper mold in its lower position and contacting the intermediate portion of the lifted glass sheet with the downwardly facing surface of the upper mold for less than 50% of the distance between the distal extremities of the end portions of the glass sheet, whereupon the upper mold and the glass sheet are moved upwardly to the upper position of the upper mold;   a lower mold having a ring shape that faces upwardly with a concave shape in transverse directions complementary to the downwardly convex shape of the downwardly facing surface of the upper mold, the lower mold being movable horizontally within the heated chamber of the forming station at a location above the roll conveyor to below the upper mold in its upper position with the glass sheet supported on the upper mold by the gas lift jet array, whereupon the upper mold is moved downwardly and the vacuum source is operated to draw a vacuum at the downwardly facing surface of the upper mold and press form the glass sheet between the upper and lower molds to provide curvature of the glass sheet in transverse directions, and the upper mold then being moved upwardly to its upper position with the press formed glass sheet supported on the upper mold by the vacuum drawn at its downwardly facing surface;   a delivery mold that is then moved to below the press formed glass sheet on the upper mold in its upper position whereupon the vacuum drawn at the upper mold by the vacuum source is terminated to release the glass sheet from the upper mold onto the delivery mold which is then moved out of the forming station for delivery of the press formed glass sheet; and   a controller for operating the roll conveyor, the upper mold, the vacuum source, the gas lift jet array, the lower mold, and the delivery mold to provide the press forming of the glass sheet and its delivery.   
     
     
         2 . A forming station as in  claim 1  wherein the controller terminates the operation of the gas lift jet array providing the upwardly directed gas lift jets before completion of the press forming of the glass sheet between the upper and lower molds. 
     
     
         3 . A forming station as in  claim 2  wherein the controller terminates the operation of the gas lift jet array providing the upwardly directed gas lift jets as the downward movement of the upper mold with the glass sheet supported thereon begins the press forming of the glass sheet between the upper and lower molds. 
     
     
         4 . A forming station as in  claim 1  wherein the gas lift jet array includes a pair of end portions for lifting the end portions of the glass sheet and a central portion for lifting the intermediate portion of the glass sheet, and the gas lift jet array also includes a control for controlling pressure of gas supplied to the end portions and to the central portion of the gas lift jet array. 
     
     
         5 . A forming station as in  claim 1  further including a pair of positioners movable under the operation of the controller to blocking positions below the upper mold prior to operation of the gas lift jet array to limit upward movement of the end portions of the glass sheet toward the downwardly facing surface of the upper mold and thereby limit the extent of the intermediate portion of the glass sheet that contacts the downwardly facing surface of the upper mold, and the controller subsequently moving the pair of positioners from their blocking positions to unblocking positions to permit the subsequent press forming of the glass sheet between the upper and lower molds. 
     
     
         6 . A forming station as in  claim 4  wherein the pair of positioners have respective pivotal connections providing support thereof on the upper mold for their movement between the blocking and unblocking positions under the operation of the controller. 
     
     
         7 . A forming station as in  claim 1  that is used with a system having a quench station to which the delivery mold moves the press formed glass sheet for quenching under the operation of the controller. 
     
     
         8 . A forming station for forming a hot glass sheet having a pair of spaced end portions with distal extremities and also having an intermediate portion extending between its end portions, the forming station comprising:
 a housing having a heated chamber;   a roll conveyor for conveying the hot glass sheet into the heated chamber of the forming station along a plane of conveyance;   an upper mold located within the heated chamber of the forming station above the roll conveyor and having a downwardly facing surface that has a downwardly convex shape with curvature in transverse directions, and the upper mold being movable between an upper position spaced above the roll conveyor and a lower position adjacent the roll conveyor;   a vacuum source for drawing a vacuum at the downwardly facing surface of the upper mold;   a gas lift jet array located in the forming station below the plane of conveyance of the glass sheet and having a pair of end portions and a central portion for providing upwardly directed gas lift jets that provide the sole impetus for lifting the glass sheet respectively at its pair of end portions and intermediate portion upwardly from the roll conveyor to the upper mold in its lower position and contacting the intermediate portion of the lifted glass sheet with the downwardly facing surface of the upper mold for less than 50% of the distance between the distal extremities of the end portions of the glass sheet, whereupon the upper mold and the glass sheet are moved upwardly to the upper position of the upper mold;   a lower mold having a ring shape that faces upwardly with a concave shape in transverse directions complementary to the downwardly convex shape of the downwardly facing surface of the upper mold, and the lower mold being movable horizontally within the heated chamber of the forming station at a location above the plane of conveyance of the roll conveyor to below the upper mold in its upper position with the glass sheet supported on the upper mold by the gas lift jet array, whereupon the upper mold is moved downwardly and the vacuum source is operated to draw a vacuum at the downwardly facing surface of the upper mold and press form the glass sheet between the upper and lower molds to provide curvature of the glass sheet in transverse directions, and the upper mold then being moved upwardly to its upper position with the press formed glass sheet supported on the upper mold by the vacuum drawn at its downwardly facing surface;   a delivery mold that is then moved to below the press formed glass sheet on the upper mold in its upper position whereupon the vacuum drawn by the vacuum source at the upper mold is terminated to release the glass sheet from the upper mold onto the delivery mold which is then moved out of the forming station for delivery of the formed glass sheet;   a quench station to which the delivery mold moves the press formed glass sheet for quenching; and   a controller for operating the roll conveyor, the upper mold, the vacuum source, the lift jet array, the lower mold, and the delivery mold and quench station to provide the press forming of the glass sheet and its delivery for quenching.   
     
     
         9 . A forming station as in  claim 8  wherein the controller terminates the operation of the gas lift jet array providing the upwardly directed gas lift jets as the downward movement of the upper mold begins the press forming of the glass sheet between the upper and lower molds. 
     
     
         10 . A forming station as in  claim 8  further including a pair of positioners pivotally movable on the upper mold under the operation of the controller to blocking positions below the upper mold prior to operation of the gas lift jet array to limit upward movement of the end portions of the glass sheet toward the downwardly facing surface of the upper mold and thereby limit the extent of the intermediate portion of the glass sheet that contacts the downwardly facing surface of the upper mold, and the controller subsequently pivotally moving the pair of positioners from their blocking positions to unblocking positions to permit the subsequent press forming of the glass sheet between the upper and lower molds. 
     
     
         11 . A method for forming a hot glass sheet having a pair of spaced end portions with distal extremities and also having an intermediate portion extending between its end portions, the method comprising:
 conveying the hot glass sheet on a conveyor into a heated chamber of a forming station to below an upper mold that is located above the conveyor and has a downwardly facing surface that has a downwardly convex shape with curvature in transverse directions;   moving the upper mold downwardly from an upper position to a lower position adjacent the glass sheet on the conveyor and operating a gas lift jet array to provide upwardly directed gas lift jets as the sole impetus for lifting the glass sheet from the conveyor and contacting the intermediate portion of the glass sheet with the downwardly facing surface of the upper mold for less than 50% of the distance between the distal extremities of the end portions of the glass sheet, and then moving the upper mold and the glass sheet upwardly to the upper position of the upper mold;   then moving a lower mold having a ring shape, that faces upwardly with a concave shape in transverse directions complementary to the downwardly convex shape of the downwardly facing surface of the upper mold, horizontally within the heated chamber to a location above the conveyor and below the upper mold in its upper position with the glass sheet supported on the upper mold and subsequently moving the upper mold downwardly and drawing a vacuum at the downwardly facing surface of the upper mold to press form the glass sheet between the upper and lower molds and provide curvature of the glass sheet in transverse directions, whereupon the upper mold is moved upwardly to its upper position with the press formed glass sheet supported on the upper mold by the vacuum drawn at its downwardly facing surface; and   then moving a delivery mold to below the press formed glass sheet on the upper mold in its upper position whereupon the vacuum drawn at the upper mold is terminated to release the glass sheet from the upper mold onto the delivery mold which is then moved out of the forming station for delivery of the press formed glass sheet.   
     
     
         12 . A method for forming a hot glass sheet as in  claim 11  wherein the operation of the gas lift jet array is terminated before completion of the press forming of the glass sheet between the upper and lower molds. 
     
     
         13 . A method for forming a hot glass sheet as in  claim 11  wherein the operation of the gas lift jet array is terminated as the downward movement of the upper mold with the glass sheet supported thereon begins the press forming of the glass sheet between the upper and lower molds. 
     
     
         14 . A method for forming a hot glass sheet as in  claim 11  wherein gas pressures are respectively supplied to the end portions and to the intermediate portion of the glass sheet and are controlled to limit the extent of the intermediate portion of the glass sheet that contacts the downwardly facing surface of the upper mold. 
     
     
         15 . A method for forming a hot glass sheet as in  claim 14  wherein a lesser gas pressure is supplied to the end portions of the glass sheet than to the intermediate portion of the glass sheet. 
     
     
         16 . A method for forming a hot glass sheet as in  claim 15  wherein the gas pressure supplied to the end portions of the glass sheet is 50 to 75% of the gas pressure supplied to the intermediate portion of the glass sheet. 
     
     
         17 . A method for forming a hot glass sheet as in  claim 11  wherein a pair of positioners are moved to blocking positions below the upper mold prior to operation of the gas lift jet array to limit upward movement of the end portions of the glass sheet toward the downwardly facing surface of the upper mold and thereby limit the extent of the intermediate portion of the glass sheet that initially contacts the downwardly facing surface of the upper mold, and the pair of positioners subsequently being moved from their blocking positions to unblocking positions to permit the subsequent press forming of the glass sheet between the upper and lower molds. 
     
     
         18 . A method for forming a hot glass sheet as in  claim 17  wherein the pair of positioners are moved between the blocking and unblocking positions about respective pivotal connections thereof on the upper mold. 
     
     
         19 . A method for forming a hot glass sheet as in  claim 11  wherein the press formed glass sheet is moved on the delivery mold from the forming station to a quench station for quenching. 
     
     
         20 . A method for forming a hot glass sheet as in  claim 11  wherein gas pressures are respectively supplied to the end portions and to the intermediate portion of the glass sheet and are controlled to limit the extent of the intermediate portion of the glass sheet that contacts the downwardly facing surface of the upper mold, a lesser gas pressure being supplied to the end portions of the glass sheet than to the intermediate portion of the glass sheet, wherein the operation of the gas lift jet array is terminated as the downward movement of the upper mold with the glass sheet supported thereon begins the press forming of the glass sheet between the upper and lower molds, and wherein after the press formed glass sheet is moved on the delivery mold from the forming station to a quench station for quenching.