Process for controlling a cylinder-type silk screen printing mac

Details Process for controlling a cylinder-type silk screen printing mac Process for controlling a cylinder-type silk screen printing mac

1996-02-20

1998-01-13

Yan, Ren

Printing

Stenciling

Processes

101124, B41M 112

Patent

active

057067228

DESCRIPTION:

BRIEF SUMMARY
FIELD OF THE INVENTION

The invention relates to a method for controlling a cylinder screen printing machine, where a printing cylinder, which takes up the material to be printed and is driven by a drive motor, and a screen carriage, which runs above it with a squeegee lowered onto the screen stencil, are moved at a synchronised speed during the printing cycle. The invention also relates to a cylinder screen printing machine with a printing cylinder which takes up the material to be printed and is driven by a drive motor, a screen carriage running above it, a squeegee which can be lowered onto the screen stencil and a device for synchronising the movement of the printing cylinder and the screen frame during the printing cycle, which operates according to the method described above.


BACKGROUND OF THE INVENTION

Two methods of this kind are known from the prior art, in which the printing cylinder and the screen carriage are moved synchronously by a single drive motor via a mechanical link. In both cases, the mechanical link is made via a gear wheel positioned on the end face of the printing cylinder which engages a toothed rack positioned on the corresponding side of the screen carriage. The printing path covered by the screen carriage corresponds exactly to one complete turn of the printing cylinder.
The first method employs a so-called swing cylinder, which has a single gear wheel on each end face which permanently engages the toothed rack mounted on the corresponding side of the screen carriage. Following the printing cycle, the cylinder returns to the starting position, where it takes up the next item to be printed, and the printing cycle starts again immediately from the beginning.
The disadvantage of this method is that the swing cylinder switches directly from one sense of rotation to the other without stopping, so that the newly fed item to be printed must be grasped instantly by the printing cylinder. In this context, it can happen that the item to be printed is not fed onto the printing cylinder correctly or optimally, thus impairing the printing quality.
The second known method attempts to avoid this disadvantage by controlling the synchronisation between the printing cylinder and the screen carriage during the forward and return passes via two gear wheels on each end face of the printing cylinder. During the printing cycle (forward pass), the first gear wheel engages the toothed rack positioned on the corresponding side of the screen carriage. At the end of the printing cycle, this gear wheel and the toothed rack are disengaged due to the fact that the teeth at the appropriate point on the gear wheel are recessed by milling. The toothed rack can return freely over the stopped gear wheel. The return pass of the screen carriage is achieved by a second gear wheel which engages the toothed rack mounted on the corresponding side of the screen carriage during the return pass. During the return pass, the first gear wheel is held still by a mechanical device. After the return pass has been completed, the first gear wheel starts rotating again and engages the toothed rack of the screen carriage, at which point a new printing cycle begins. The two gear wheels are driven by a single drive motor. Due to the fact that the printing cylinder linked to the first gear wheel always rotates in the same direction and stops during the return pass of the screen carriage, there is sufficient time to feed the material to be printed onto the printing cylinder, given an appropriate printing speed.
However, the disadvantage of the second method is the technically complex mechanical synchronisation of the two gear wheels. This also leads to correspondingly high susceptibility to failure and to relatively frequent servicing of the cylinder screen printing machine. In addition, the printing speed is limited by the mechanical elements. Every increase in the printing speed also leads to a decrease in the idle time of the printing cylinder during the return pass of the screen carriage, which impairs the accurate feeding of the

REFERENCES:
patent: 3945317 (1976-03-01), Brasa
patent: 5101722 (1992-04-01), Nagatani

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