Automatic peel control mechanism

In a screen printing press, the combination of:

• a press frame,
• a screen,
• a screen frame supporting the screen,
• a printing bed fixed to the press frame for supporting the screen frame and a sheet of stock during printing,
• a squeegee which slides across an upper surface of the screen during printing,
• a traveling carriage which transports the squeegee in reciprocating motion between a front end and a rear end of the screen during a printing cycle,
• carriage driving means for imparting the reciprocating motion to the carriage,
• a pivoted printing head having a rearward end pivotally mounted on the press frame to support the carriage and screen frame relative to the press frame, and
• an automatic peel control mechanism which raises a front end of the screen frame at a controlled rate during a printing cycle, the automatic peel control mechanism comprising:
• a rotatable cam means located at the rearward end of the printing head,
• means for rotating the cam means in timed relation to the travel of the carriage, and
• a mechanical linkage extending from the cam means at the rearward end of the printing head to the front end of the screen frame including elongated, reciprocating rigid members extending along the sides of the printing head and being pushed and pulled by said cam means, and lifters at the forward ends of the elongated members, rotation of the cam moving the linkage to lift the front end of the screen frame,
• said cam means comprising a scroll cam having a spirally configured peripheral camming surface,
• said mechanical linkage further comprising a lever mechanism positioned near the rear of the printing head to be driven by the cam means, the rigid members being connected at their rearward ends to the lever mechanism so that the lever mechanism applies longitudinal force to them, the lifters including bell cranks to translate the longitudinal movement of the rigid members into the upward movement of the front end of the screen,
• said lever mechanism including means for varying both the initial off contact position and the rate at which the front end of the screen is raised relative to the rate at which the carriage travels.