Rotary screen printing apparatus and process

A rotary screen printing device comprising:

• a reservoir to hold a coating material;
• a first heater to heat and liquefy the coating material held in the reservoir;
• a first heat sensor coupled to the reservoir;
• a rotatable cylindrical screen having an internal volume and an array of apertures there through;
• a squeegee fixedly disposed in the internal volume of the cylindrical screen so that the squeegee does not rotate within the cylindrical screen when the cylindrical screen is rotated;
• a conduit providing fluid communication of the coating material between the reservoir and the internal volume of the rotatable cylindrical screen;
• a second heater to heat the conduit;
• a second heat sensor to detect one of the temperature of the conduit, the temperature of the liquefied coating material passing through the conduit or the temperature of the liquefied coating material discharged from the conduit to the internal volume of the rotary cylindrical screen;
• a controller in communication with the first and second heat sensors and the first and second heaters to control the first heater so that the temperature of the coating material held in the reservoir has a predetermined temperature (TR) above the liquification point of the coating material and to control the second heater so that the coating material maintains a second predetermined temperature (TC) above the solidification point of the liquefied coating material as it passes through the conduit.

A rotary screen printing process, comprising:

• releasing a liquefied coating material at a pre-determined temperature (TR) above the liquification point of the coating material into a conduit which provides fluid communication to an internal volume of a rotating cylindrical screen, wherein
• the released liquefied coating material passes along the conduit and is introduced into the internal volume of the rotating cylindrical screen;
• and,
• the introduced liquefied coating material first contacts an internal surface of the rotating cylindrical screen and is then brought into contact with a squeegee which acts to impel the liquefied coating material through an array of apertures provided in the rotating cylindrical screen, the squeegee being fixedly disposed in the internal volume of the cylindrical screen so that the squeegee does not rotate within the cylindrical screen as the cylindrical screen is rotating;
• determining one of the temperature of the conduit, the temperature of the liquefied coating material passing through the conduit or the temperature of the liquefied coating material discharged from the conduit to the internal volume of the rotary cylindrical screen using a second heat sensor;
• using a heater, heating the conduit so that the coating material maintains a second predetermined temperature (TC) above the solidification point of the liquefied coating material as it passes through the conduit;
• contacting a printable substrate with an external surface of the rotating cylindrical screen so that liquefied coating material impelled through the apertures is transferred to the substrate;
• and,
• solidifying the transferred coating material on the substrate.