Dwell time control system and method with automatic pressure switch point adjustment

A system for operating a plunger in a blank mold to mold a parison from a glass gob, the plunger being driven by a piston in a cylinder to which a source of a pressurized medium may be applied at selected pressures, the system comprising:

• a position sensor configured to monitor the position of the plunger in the blank mold versus time during a parison forming cycle beginning at a time t1 and ending at a time t4;
• and
• a control system programmed to detect a nonlinearity in the movement of the plunger during the monitored parison forming cycle that is indicative of an upper part of the blank mold having been filled with glass from the glass gob at a time t2;
• wherein the control system is programmed to detect a movement-related characteristic of the plunger during the monitored parison forming cycle that falls below a preselected level at a time t3, the movement related characteristic falling below the preselected level being indicative of the glass from the glass gob having been distributed throughout the blank mold to fill the blank mold;
• and
• wherein the control system is programmed to apply a first pressure from time t1 to time tp2, a second pressure from time tp2 to time tp3, and a third pressure from time tp3 to time t4 during a parison forming cycle subsequent to the monitored parison forming cycle, after a gob is loaded into the blank mold;
• wherein the control system is programmed to determine the time interval between time t1 and time tp2 to be a first predetermined percentage of the time interval between time t1 and time t2;
• and
• wherein the control system is programmed to determine the time interval between time t1 and time tp3 to be a second predetermined percentage of the time interval between time t1 and time t3.

A system for operating a plunger in a blank mold to mold a parison from a glass gob, the plunger being driven by a piston in a cylinder to which a source of a pressurized medium may be applied at selected pressures, the system comprising:

• a position sensor configured to monitor the position of the plunger in the blank mold versus time during parison forming cycles each beginning at a time t1 and ending at a time t4;
• and
• a control system programmed to determine a time t2 in each monitored parison forming cycle at which an upper part of the mold has been filled with glass from the glass gob;
• wherein the control system is programmed to determine a time t3 in each monitored parison forming cycle at which the glass from the glass gob has been distributed throughout the entire blank mold to completely fill it;
• and
• wherein the control system is programmed to apply a first pressure from time t1 to time tp2, a second pressure from time tp2 to time tp3, and a third pressure from time tp3 to time t4 during each parison forming cycle, after a gob is loaded into the blank mold;
• wherein the control system is programmed to determine the time interval between time t1 and time tp2 to be a first predetermined percentage of a time interval based upon the time interval between time t1 and time t2 for one or more previous parison forming cycles;
• and
• wherein the control system is programmed to determine the time interval between time t1 and time tp3 to be a second predetermined percentage of a time interval based upon the time interval between time t1 and time t3 for one or more previous parison forming cycles.