Control system for rotary printing screens

In a machine for printing a recurrent composite pattern on a substrate, comprising transport means for continuously advancing said substrate along a predetermined path and a set of cascaded printing units with rotary screens overlying said path, said set being divided into several groups for the printing of complementary portions of said pattern, each group including a plurality of printing units for the printing of different color components of the respective pattern portion, each printing unit being provided with a drive member for rotating the screen thereof and with an elevatable mounting having lifting means for raising said screen off said substrate during an idling phase of a printing cycle, the combination thereofwith:

• common drive means coupled with said transport means for imparting rotation to the screens of all printing units;
• a differential gearing for each printing unit having an input element coupled to said common drive means and a first output element coupled to said drive member, said differential gearing being further provided with a second output element;
• retractable detent means individual to each printing unit for arresting said second output element during a working phase of a printing cycle;
• and
• timing means coupled with said transport means for generating staggered operating signals defining said printing cycle, said operating signals including first signals commanding the actuation of said lifting means at the end of said working phase and second signals commanding the retraction of said detent means in said idling phase.

In a machine for printing a recurrent composite pattern on a substrate, comprising transport means for continuously advancing said substrate along a predetermined path and a set of cascaded printing units with rotary screens overlying said path, said set being divided into several groups for the printing of complementary portions of said patterns, each group including a plurality of printing units for the printing of different color components of the respective pattern portion, each printing unit being provided with a drive member for rotating the screen thereof at a peripheral velocity identical for all said printing units and with an elevatable mounting having lifting means for raising said screen off said substrate during an idling phase of a printing cycle followed by a working phase, the combination therewith of:

• transmission means linking said transport means with each drive member for correlating the substrate speed with said peripheral velocity, said transmission means including a speed changer adjustable to vary the ratio of said peripheral velocity to said substrate speed;
• stop means individual to each printing unit for deactivating the drive member thereof from said transmission means to arrest the respective screen in said idling phase in a predetermined rotational position;
• first sensing means coupling with said transport means for measuring said substrate speed;
• second sensing means coupled with said speed changer for measuring said peripheral velocity;
• programming means controlled by said second sensing means for generating operating signals for said lifting means and said stop means of each printing unit in a predetermined sequence defining a printing cycle;
• and
• timing means controlled by said first sensing means and connected to said programming means for distributing said operating signals to the several printing units of each group at intervals determined by said substrate speed;
• said transmission means including a differential gearing for each printing unit having an input element coupled with said speed changer and a first output element coupled with said drive member, said differential gearing being further provided with a second output element, said stop means including retractable detent means for arresting said second output element during said working phase.