Automated screener

In a screener in which a chase for framing a stencil screen is pivotally secured at a rear edge for rotatable movement upwardly relative to a table surface, from an open position permitting a workpiece that is to be placed on, or withdrawn from, the table surface to a closed position in which the screen will be in contact during a print stroke with a workpiece whereby, in the closed position, printing fluid on a first end of the screen can be spread by a squeegee and applied to the workpiece through the screen during a print stroke, and whereby thereafter the chase can be rotated upwardly from the closed position and the print fluid can be swept back by a squeegee to the first end during a flood stroke, the improvement according to which operation of the screener is automated, comprising:

• means for moving the chase to and from the open and closed position;
• an axial shaft below the rear edge of the chase and extending along at least a portion thereof;
• a pair of clamp members rigidly securing the chase to the axial shaft;
• a cylindrical bearing bar extending across the rear edge of the chase, rigidly secured to the clamp members and spaced from the top surface of the chase;
• a partially cylindrical bearing slidably and pivotally disposed on the bearing bar;
• an arm extending across the chase rigidly secured to the partially cylindrical bearing so as to slide in translation across the chase to pivot about the bearing bar whereby the arm is rotatable to an obtuse angle with respect to the table when the chase is in the open position;
• a drive chain extending along the rear edge of the chase;
• a motor connected to drive the chain;
• a pin-bearing member carrying on its upper surface at least one pin for linking with the chain;
• means for hingedly connecting the pin-bearing member to the top rear surface of the arm whereby as the arm is rotated upwardly, the pin bearing member moves in a vertically downward direction, while remaining horizontal for release from the chain;
• means for supporting a print squeegee and a flood squeegee;
• means for securing the print squeegee over the screen, comprising a pneumatic cylinder secured to the arm and having a piston shaft extending downwardly therefrom and connected to said print squeegee, and means for adjusting the height of the front and rear edges of the print squeegee, whereby the print squeegee is movable above and below the bottom edge of the flood squeegee and is retractable after a print stroke and whereby when the chase is in the closed position, the bottom edge of the print squeegee is in contact with the screen;
• switch means responsive to the end of a print stroke for actuating the pneumatic cylinder to retract the print squeegee;
• adjustable spring-loaded means for supporting the flood squeegee over the screen spaced therefrom when the chase is in the closed position whereby contact between the flood squeegee and the chase can be made by raising the chase a first predetermined distance which is a minor fraction of the distance from the table surface to the open position, the adjustable supporting means being formed to permit the front of the flood squeegee to be at a higher position than the rear of the flood squeegee relative to the table so that the angle formed by the bottom of the flood squeegee relative to the table corresponds to the angle defined by raising the chase said first distance;
• a first limit member rigidly dependent from the arm, having a follower on its lower edge for contacting the top surface of the follower edge of the chase when the chase is raised said first distance;
• a second limit member rigidly dependent from the arm downwardly past the edge of the chase and formed with a follower;
• and
• a channel member parallel to the direction of translation of the arm, formed to receive the follower of the second limit member and disposed to limit vertical movement of the arm during the print and flood strokes, thereby limiting upward movement of the chase to said first distance where the chase contacts the follower of the first limit member, the channel member having a discontinuous portion at a region corresponding to the end of the flood stroke to release the second limit member thereat, permitting the chase to be raised to the open position to enable removal of said workpiece.