EP1023178B1 - Screen printing installation - Google Patents

Description

The present invention relates to a screen printing unit with a Circular sieve with squeegee arranged in it, a counter pressure surface for the circular screen, drive means and a device for the controlled Lift off the squeegee according to the printing process Preamble of claim 1.

Screen printing units of this type are known, and their circular screens are for discontinuous web running or for sheet printing intended. A screen printing unit of this construction is e.g. in EP-A-0 723 864.

With these printing processes, discontinuous web running is said to be the distance from the end of the print to the start of the next print Printing should be as small as possible (because of expensive printing materials). Accordingly, the distance from the leading edge of the paper should be used for sheet printing be as small as possible at the start of printing.

To optimally solve such tasks with ever higher ones Print speeds make the squeegee more difficult with very short cycle times (10 msec). The system needs in interaction with different colors and motifs (i.e. different color requirements) an extraordinary Dynamics that are not easy to master. in addition comes that the color comes through at a standstill with the rotary screen the sieve runs (open spaces; the motif is all over Scope).

The complex task could now be carried out with a screen printing unit initially defined type according to the invention by a construction be solved according to the characterizing part of claim 1.

Even the highest cycle rates with short movement times can be thanks the solution according to the invention, i.e. about the setting of the cams according to the invention will be realized. Thanks to this mechanical control can Mass forces of the squeegee are strong due to suitable constructions be reduced.

Thanks to the cam, the (adjustable) squeegee pressure becomes mechanical generates what in comparison e.g. of pneumatic Controls allow a significant increase in speeds.

The cam is running at the circumference at the start of printing adjustable to the smallest possible distance from To reach the end of printing at the beginning of printing. Thanks to this adjustability can compensate for the influences of color and the decrease in color become. The adjustability or adjustability of the phase is solved via a helical toothing (Adjustment within synchronization).

The circular sieve can be a closed zone in the zero position have so that no color can leak. Preferably a color level control is used so that as little as possible Color in the sieve is necessary.

Particularly advantageous embodiments of the subject matter of the invention are defined in the dependent claims.

Fig. 1:

rein schematisch ein Siebdruckwerk integriert auf ei-ner Bogendruckmaschine;

Fig. 2:

eine ähnliche Darstellung wie Fig. 1 mit einem Rotationssiebdruckwerk auf einer Rollendruckmaschine mit Pilgerschritt-Bahntransport;

Fig. 3:

schematisch ein Rotationssiebdruckwerk integriert auf Körperdruckmaschine mit ebenen oder zylindrischen Körpern;

Fig. 4:

eine rein schematische Darstellung eines synchronisierten Antriebs eines Rundsiebes mit gesteuerter Rakel und dem Gegendruckzylinder als mechanische Ausführung (eine Maschinenseite) und

Fig. 5:

ebenfalls rein schematisch ein Rotationssiebdruckwerk mit diskontinuierlichem Rakeldruck (bei fehlendem Gegendruck).

The screen printing unit according to the invention is explained in more detail below with reference to the drawing. It shows:

Fig. 1:

schematically a screen printing unit integrated on a sheet-fed printing machine;

Fig. 2:

a representation similar to Figure 1 with a rotary screen printing unit on a web printing press with pilgrim web transport.

Fig. 3:

schematically a rotary screen printing unit integrated on a body printing machine with flat or cylindrical bodies;

Fig. 4:

a purely schematic representation of a synchronized drive of a rotary screen with a controlled doctor blade and the impression cylinder as a mechanical design (one machine side) and

Fig. 5:

also schematically a rotary screen printing unit with discontinuous doctor blade printing (in the absence of counter pressure).

Figures 1 to 3 of the drawing illustrate the principle of various Rotary screen printing method.

Fig. 1 shows a rotary screen printing unit integrated on a Sheetfed press. The circular sieve 1 can be with or without indentation 1 '. The doctor blade arranged inside the sieve 2 is equipped with a device for controlled lifting of the Doctor blade 2 coupled (not shown here). On the impression cylinder 3 is a sheet 5 that can be gripped by a gripper 4. With the above gripper 4 in the pit zone of the impression cylinder the circular sieve 1 is provided with an indentation 1 ' (e.g. in the form of a cross bar with exemption for the above Gripper 4 on the impression cylinder 3). With the gripper sunk 4 (not shown) there is no indentation in the circular sieve needed. In both cases, the squeegee 2 must be above the indentation 1 'or the pit zone with the gripper 4 lowered become.

Fig. 2 shows schematically a rotary screen printing unit, which on a web press with pilgrim train transport is integrated. Here is next to the rotary screen 1 with squeegee 2 (with coupled, not shown device for controlled Lifting the squeegee) an impression cylinder 3 with release zone 3 'available. Here the squeegee 2 each because of the Retreat (pilgrimage) over the exemption zone 3 'of the Impression cylinder 3 are raised.

Fig. 3 shows the principle of a rotary screen printing unit, which is integrated on a body pressure machine. This is also here Round screen 1 is provided with a squeegee 2 which can be raised in a controlled manner. The bodies to be printed (counter pressure surfaces) can be flat bodies 3 (e.g. glass plates) on a conveyor belt 4 or cylindrical Body 5 (e.g. bottles).

The bodies 3 and 5 to be printed form the counter pressure surface. The squeegee 2 must be raised between the individual bodies become.

Fig. 4 shows the synchronized drive of the rotary screen 1, the Doctor blade 2 and the impression cylinder 3 (here impression cylinder with exemption zone of a pilgrim step machine) of a screen printing unit.

The synchronized drive is on one side of the Printing unit. On the other side of the circular sieve 1, however, could another cam with lever to control the squeegee 2 may be provided.

The synchronized drive of rotary screen 1, squeegee 2 and impression cylinder 3 essentially takes place via the following elements: The gears 4, 5, driven by the motor 7, serve to drive of rotary screen 1 and impression cylinder 3.

The motor 7 is used here to drive the printing unit. in principle the drive could also be from a main machine shaft respectively.

About the gears 6 to 10 is a gear 11 with helical teeth driven which part of the control device for the Squeegee 2 forms.

About another gear 12 with helical teeth, which over an adjusting mechanism 13 is mounted transversely the cam 14 driven. With the adjusting mechanism 13 the phase of the cam disc 14 can be set (also during the barrel), thanks to the helical teeth with high precision.

The cam disc 14 can have a fixed or a variable contour (e.g. thanks to the construction of two adjacent, rotatable disks).

Via a roller 15 and the squeegee lever 16 (e.g. a kind Rocker arm, held at point 16 ') is finally the Squeegee controlled (lifted off). By storage in point 16 ' the squeegee pressure can be adjusted. With two cams (see Fig. 5) the holder and control of the squeegee 2 is much more precise, and the contact pressure can be regulated better.

The squeegee 2 must always be lifted when there is no counter pressure is present, otherwise the circular sieve 1 will be damaged can.

Claims (5)

1. Screen printing apparatus comprising a circular screen (1) with a doctor blade (2) arranged within it, a counterpressure surface (3) for said circular screen (1), drive means (7) and a device for a controlled lifting of the doctor blade (2) during the printing operation, wherein said control device (13 - 16) for the doctor blade (2) comprises at least one cam disk (14) for moving the doctor blade (2) during operation by means of a blade lever (16) into any desired position and whereby said circular screen (1), the counterpressure surface (3) and said at least one cam disk (14) for a controlled lifting of the doctor blade (2) are in a synchronous driving connection by the intermediary of a mechanical driving gear (4 - 6, 8 - 12), characterized in that the setting of the phase of said cam disk (14) is performed by means (13) for lateral displacement of two intermeshing helical gear wheels (11, 12) in said driving gear for the shaft of the cam disk.
2. Screen printing apparatus according to claim 1, characterized in that for each doctor blade (2) there are provided two identically shaped cam disks (14) which are mounted parallel to each other on a common shaft in order to actuate two blade levers (16) which engage the doctor blade (2) from both sides of the circular screen drum (1).
3. Screen printing apparatus according to claim 1 or 2, characterized by means (16') for adjusting the application pressure of the doctor blade in its position of normal operation.
4. Screen printing apparatus according to any of claims 1 to 3, characterized in that each of said cam disks (14) has an invariable contour.
5. Screen printing apparatus according to any of claims 1 to 3, characterized in that each of said cam disks (14) has variable contour, e.g. by a basic structure in the form of two disks adapted to be rotated relative to each other.

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