Print head assembly, screen printing system and method
AssigneeDTG International GmbH
InventorJeffrey Richard Willshere
Life of this patent
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Abstract
A print head assembly (119) for printing a print medium (PM) onto a workpiece (W) through a printing screen (105) which includes a screen element having a pattern of printing apertures therein, the assembly comprising: first and second carriages (141) which are in use movably supported on respective ones of first and second guides (117); and first and second print head units (143, 145) which are mounted in adjacent, parallel relation to and between the carriages, wherein the print head units each comprise first and second print head actuators which are mounted on respective ones of the carriages, and a support member (151) which extends between the print head actuators, such as to be movable vertically thereby, and in use supports a printing element.
Claims35
A print head assembly for printing a print medium onto a workpiece through a printing screen which includes a screen element having a pattern of printing apertures therein, the assembly comprising:
- first and second carriages which are in use movably supported on respective ones of first and second guides;
- and
- first and second print head units which are mounted in adjacent, parallel relation to and between the carriages, wherein the print head units each comprise first and second print head actuators which are mounted on respective ones of the carriages, and a support member which extends between the print head actuators to be movable vertically thereby;
- wherein the support members of the print head units each have a squeegee blade attached thereto, and the assembly is movable in first and second oppositely-directed print strokes, such that, in the first print stroke, the print head actuators of the first print head unit are controlled to bring the squeegee blade attached thereto into operative contact with the screen element and apply a required downward force thereto for printing and the print head actuators of the second print head unit are controlled to raise the squeegee blade attached thereto just clear of the screen element, and, in the second print stroke, the print head actuators of the first print head unit are controlled to raise the squeegee blade attached thereto to a position just clear of the screen element and the print head actuators of the second print head unit are controlled to lower the squeegee blade attached thereto into operative contact with the screen element and apply a required downward force thereto for printing;
- wherein a cavity between the squeegee blades is maintained with a volume of print medium which is such that the print medium extends across the cavity and in contact with each of the squeegee blades in each of the first and second print strokes.
A method of screen printing a print medium onto a workpiece through a printing screen which includes a screen element having a pattern of printing apertures therein, the method comprising the steps of:
- providing a print head assembly comprising:
- first and second carriages which are movably supported on respective ones of first and second guides;
- and first and second print head units which are mounted in adjacent, parallel relation to and between the carriages, wherein the print head units each comprise first and second print head actuators which are mounted on respective ones of the carriages, and a support member which extends between the print head actuators to be movable vertically thereby;
- attaching a squeegee blade to each of the support members of the print head units;
- operating the assembly to print on a workpiece which is supported below the printing screen, wherein the print head assembly operating step comprises the steps of:
- controlling the print head actuators of the first print head unit to bring the squeegee blade attached thereto into operative contact with the screen element and apply a required downward force thereto for printing;
- controlling the print head actuators of the second print head unit to raise the squeegee blade attached thereto just clear of the screen element;
- driving the assembly over the surface of the screen element in a first direction to print deposits of the print medium onto the workpiece which is supported below the printing screen;
- controlling the print head actuators of the first print head unit to raise the squeegee blade attached thereto to a position just clear of the screen element;
- controlling the print head actuators of the second print head unit to lower the squeegee blade attached thereto into operative contact with the screen element and apply a required downward force thereto for printing;
- driving the assembly over the surface of the screen element in a second, opposite direction to print deposits of the print medium onto the workpiece which is supported below the printing screen;
- and
- maintaining a cavity between the squeegee blades with a volume of print medium which is such that the print medium extends across the cavity and in contact with each of the squeegee blades in each of the first and second print strokes.
Dependencies are inferred from the claim text.