US 4,589,336 AGranted

Screen printing method and apparatus

OwnerGerhard Klemminventor

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Abstract

A screen printing machine has a reciprocable printing screen and below it a counter-pressure roller. Above the screen a squeegee unit is movable relative to the screen and has two vertically displaceable parallel squeegees. During movement of the screen in one direction, one of the squeegees forces ink through the screen and the other squeegee is retracted. During reverse movement the one squeegee is retracted and the other one pushes the ink pool over the screen back to the starting position. In the starting position, the one squeegee is lowered again and the other squeegee is retracted. The transfer of the ink pool from the other squeegee to the one squeegee takes place directly above the printing line which is defined by the screen in conjunction with the counter-pressure roller. The screen printing machine is provided with a control device for coordinating the movements of the squeegee unit with the movements of the printing screen.

In a screen printing machine, a combination comprising

(1) a substantially flat printing screen having a first side arranged to be contacted by a pool of a printing medium and a second side;
(2) a counter-pressure roller located at the second side of said printing screen and defining with the second side of said printing screen a printing line;
(3) means for reciprocating said printing screen in predetermined directions relative to said counter-pressure roller between spaced-apart first and second positions;
(4) a squeegee unit disposed at said first side of said printing screen and including
(4a) a printing squeegee and a drag squeegee,
(4b) means for positioning said printing squeegee to force the printing medium of said pool through said printing screen in the region of said printing line and against a running workpiece web, which overlies said counter-pressure roller, while said screen moves from said first to said second position,
(4c) means for selectively displacing said squeegees toward and away from said first side of the printing screen so that said printing squeegee is disengaged from the printing screen upon completion of movement of said printing screen from said first to said second position, so that said drag squeegee is moved into contact with the screen during the initial stage of movement of said screen to said first position and so that said printing squeegee reengages the screen not later than at the time said screen starts to move from said first position back toward said second position with said flood squeegee disengaged from said screen;
(4d) means for shifting said squeegee unit in said predetermined directions independently of said printing screen, said shifting means moving said squeegees as a unit counter to the direction of movement of said screen as the screen returns to the first position so that said drag squeegee shifts the pool relative to said print line followed by shifting said squeegees in the direction of movement of said screen toward said second position for positioning the printing squeegee for another printing on said workpiece web;
and
(5) guide means for said squeegee unit.

7 more elements

Abstract

Claims14