| 摘要 |
A print head assembly for and method of printing a print medium onto a workpiece through a printing screen (105) which includes a screen element (109) having a pattern of printing apertures (110) therein, wherein the assembly comprises first and second print head units (143, 145) which are mounted in adjacent, parallel relation to and between first and second carriages (141, 141), and wherein the print head units (143, 145) each comprise first and second print head actuators (147, 147) which are mountable on respective ones of the carriages (141, 141), and a support member (151) which extends between the print head actuators (147, 147), such as to be movable vertically thereby; wherein the support members (151) of the print head units (143, 145) each have a squeegee blade (181) 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 (147, 147) of the first print head unit (143) are controlled to bring the squeegee blade (181) attached thereto into operative contact with the screen element (109) and apply a required downward force thereto for printing and the print head actuators (147, 147) of the second print head unit (145) are controlled to raise the squeegee blade (181) attached thereto just clear of the screen element (109), and, in the second print stroke, the print head actuators (147, 147) of the first print head unit (143) are controlled to raise the squeegee blade (181) attached thereto to a position just clear of the screen element (109) and the print head actuators (147, 147) of the second print head unit (145) are controlled to lower the squeegee blade (181) attached thereto into operative contact with the screen element (109) and apply a required downward force thereto for printing; wherein a cavity between the squeegee blades (181, 181) 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 (181, 181) in each of the first and second print strokes. |
