Method and apparatus for adjusting the position of a stencil relative to a printing table

A method and an apparatus for adjusting the position of a stencil relative to a printing table, characterized by PA1 (a) applying a transparent material to the printing table over a reference pattern, PA1 (b) transferring the stencil pattern onto the transparent material, e.g. by printing, PA1 (c) compensating for and eliminating any deviation between the printing pattern and the reference pattern by displacing the transparent material with the pattern printed thereon so that the pattern coincides with the reference pattern, and PA1 (d) adjusting the position of the stencil and a frame carrying the stencil in the same manner as the position of the transparent material was adjusted.

BACKGROUND OF THE INVENTION 
The present invention relates to a method of adjusting the position of a 
stencil relative to a printing table, and in particularly relative to a 
reference pattern applied to the printing table, and apparatus for 
carrying out the method. 
In silkscreen printing machines, the stencil with associated frame is fixed 
relative to the stand of the silkscreen printing machine. The printing 
table, which may be reciprocatingly movable, is also fixed relative to the 
stand of the printing machine. 
In silkscreen printing machines it is a prime desire that the pattern 
assigned to the stencil be precisely positioned in relation to the 
material fixedly oriented to the printing table via registering means. It 
is practically always necessary to adjust the stencil (or the printing 
table) before the pattern obtains its exact position on the material. This 
adjustment has been found to be complicated and, above all, time 
consuming. 
For the purpose of adjustment, it is previously known to apply a reference 
material to the registering means of the printing table and then move the 
printing table to the printing position and thereafter to apply the 
stencil pattern to the reference material. When the reference material is 
again moved back to the infeed position, it is possible to establish 
whether the stencil pattern deviates from the desired position, i.e. the 
pattern of the reference material, and if so by how much. In order to 
compensate for this deviation it is necessary to adjust the stencil 
pattern in relation to the material, since the material is fixedly related 
to the registering means with reference to a special position on the 
printing table. 
In order to enable the stencil pattern to be adjusted, it has previously 
been proposed to hold the stencil in a first frame which, in turn, is held 
by but rotatably and displaceably arranged in a further frame. This 
further frame is fixed relative to the machine stand. 
When a deviation has been established, it is necessary to adjust the first 
frame of the stencil relative to the other frame, this being effected by 
means of a plurality of setting devices. The setting devices are 
activated, however, "by instinct" and are set to such values that the 
stencil pattern can be assumed to be placed exactly on the material. 
Subsequent to actuating the setting devices, a further print is made on a 
reference material to establish whether the setting approaches the desired 
exact setting or not. This setting work has been found extremely 
complicated, perhaps primarily because the setting is not only oriented in 
the "x" and "y" direction, i.e. at right angle coordinates, but normally 
requires the stencil to be twisted. 
OBJECT OF THE INVENTION 
An object of the present invention is to enable the setting to be made in a 
much simpler manner than was previous possible with the use of simple 
means and to obtain said setting by normally one single adjustment.

DETAILED DESCRIPTION OF A PREFERRED EMBODIMENT 
The method according to the invention of adjusting the position of a 
stencil 1 relative to the position of a printing table 2 is based on the 
fact that the stencil 1 is held tensioned in an inner first frame 3 which, 
in turn, is held by and placed in an outer, second frame 4. The inner 
frame 3 can be moved to different positions relative to the outer frame 4 
by three setting devices 5, 6 and 7. By simultaneously actuating the 
setting means 5 and 6 equally, the inner frame 3 is moved relative to the 
outer frame 4 in the direction of the coordinate "x", while actuation of 
the setting means 7 causes the inner frame 3 to move in the direction of 
the coordinate "y" relative to the outer frame 4. Different degrees of 
actuation of the setting means 5 and 6 causes the frame 3 to be twisted in 
the outer frame 4. By means of this arrangement it is thus possible to 
adjust each small deviation, irrespective of how it occurs. 
The structural design of the setting means 5, 6 and 7 is previously known 
and does not form any part of the present invention. 
The outer frame 4 is capable of being raised and lowered but is, 
nevertheless, fixedly related to the stand of the printing machine, of 
which stand only supports 1b and 1c are illustrated in FIG. 1. The 
printing table 2 is reciprocatingly movable but is, nevertheless, fixedly 
related to the stand 1b and 1c of the printing machine. 
In the infeed position of the printing table 2 there is applied to said 
table a material 8 exhibiting a reference pattern 8a. The material 8 is 
provided with a pattern 8a which is an exact replica of the pattern 1a 
exhibited by the stencil 1, namely "R". The stencil pattern is referenced 
1a while the pattern of the material 8 is referenced 8a. The reference 
pattern 8a is fixed relative to the printing table 2 via a plurality of 
registering means 9. It is an object of the present invention to ensure 
that the pattern "R" of the stencil 1 obtains an exact position in 
relation to the pattern "R" on the material 8 during a printing operation. 
It is here suitable to assume that the stencil pattern 1a (R) printed on 
the material 8 gives a pattern which deviates from the position of the 
pattern 8a (R) and that it is therefore necessary to displace the stencil 
pattern 1a in the second frame 4 in a manner such that, when printing, the 
pattern 1a will be placed exactly over the pattern 8a. 
In order to facilitate this adjustment procedure there is placed over the 
material 8 having the reference pattern 8a a transparent material 10 
which, via registering means 11, is fixed relative to and held to the 
printing table 2. The registering means 11 are placed on a beam 12 joined 
to the printing table, the nature of which beam will be described in more 
detail hereinafter. 
When the printing table 2 is moved to the printing position, i.e. 
immediately beneath the stencil 1 and the stencil pattern 1a is applied to 
the transparent material 10, it can be established when moving the table 2 
to the infeed position, i.e. the position shown in FIG. 1, whether there 
is any deviation between the reference pattern 8a and the print or pattern 
which has been obtained from the stencil 1, namely the pattern 10a. 
In FIG. 1 it has been shown that the deviation necessitates displacement of 
the print or pattern 10a in the direction of the coordinate "y" and also 
in the direction of the coordinate "x". By displacing the transparent 
material 10 via setting means 13, 14 and 15, in a manner such that the 
printed pattern 10a is located immediately above the reference pattern 8a, 
the setting position of the setting means 13, 14 and 15 can be read off 
and a corresponding setting can be transferred directly to the setting 
means 5, 6 and 7. Naturally, it is a prerequisite that displacement of the 
transparent material 10 by maneuvering the setting means 13, 14 and 15 
takes place in the same manner as displacement of the stencil 1 in the 
frame 4 by maneuvering the setting means 5, 6 and 7. Thus, if the setting 
means 13, 14 and 15 are graduated in the same manner as the setting means 
5, 6 and 7 and the setting means 5, 6 and 7 are set to that graduation 
measured on the setting means 13, 14 and 15 when the printed pattern 10a 
is located immediately above the pattern 8a, the inner frame 3 with the 
stencil pattern 1a can thus be moved by the setting means 5, 6 and 7 in 
exactly the same manner. Thus, there is hereby ensured an exact 
relationship of the stencil pattern 1a with the reference pattern 8a. 
FIG. 2 is a horizontal view of the edge surface of the printing table 2 
with setting means 13, 14 and 15. The setting means 13, 14 co-act with the 
edge surface 2a of the table and are arranged to cooperate with a beam 12 
carrying the registering means 11 for the transparent material 10. 
Conveniently the setting means 13 and 14 are rotatably mounted in beams 1e 
and a part 13b and 14b provided with screw threads extend into the edge 
surface 2a of the printing table and mesh with a respective nut mounted in 
a groove extending parallel with the edge surface 2a, said groove guiding 
movement of the nuts in the direction of the "y" coordinate. By actuating 
the setting means 13 and 14 to an equal extent and in the same direction 
the transparent material 10 is moved in the direction of the direction of 
"x" coordinate, while rotation or actuation of the setting means 15, which 
also cooperates with the beam 12 in the manner described above but via an 
angled part 12a, causes the transparent material to be moved in the 
direction of the "y" coordinate. This means that if the reference pattern 
8a has a point located in "A" while the transparent material obtains a 
corresponding printed point located at "A'" it is only necessary to 
actuate the setting means 15. If, on the other hand, the reference pattern 
has a point located at "B" it is necessary to actuate the two setting 
means 13 and 14 equally in order to move the point "B'" immediately above 
the point "B". If, on the other hand, the reference pattern has a point 
"C" while the stencil pattern provides a print on the transparent material 
10 at point "C'", it is not only necessary to displace in the "y" 
direction and "x" direction but also to rotate the transparent material, 
this being effected by actuating the setting means 13 and the setting 
means 14, and possibly also the setting means 15. 
Since setting of the means 13, 14 and 15 is effected whilst visually 
observing how the printed pattern 10a is slowly moved to correspond with 
the reference pattern 8a, the degree to which the setting means 13, 14 and 
15 need be actuated is not too complicated. 
The great advantage afforded by the present invention lies in the fact that 
the setting value of the setting means 13, 14 and 15 when the reference 
pattern and the transparent material coincide exactly can be transferred 
directly to the setting means 5, 6 and 7 for the stencil 1. 
The method according to the invention, which is intended to adjust the 
position of a stencil relative to a printing table, or more specifically 
to a pattern on a material resting on the printing table, thus comprises 
the steps of first applying the stencil 1 to the inner frame 3, which in 
turn is movably arranged relative to the frame 4. A reference pattern 8a 
is then placed on the printing table 2. A transparent sheet of material 10 
is then applied to the printing table over the reference pattern and is 
registered by means 11 in a beam 12 fixed to the printing table. The 
printing table 1 is moved to the printing position and the stencil pattern 
is transferred and applied (printed) to the transparent material 10. By 
means of this method it is possible to discern the difference or deviation 
between the printed pattern 10a and the reference pattern 8a in a simple 
manner and to compensate for and to eliminate any difference or deviation 
by displacing the printed pattern 10a on the transparent material 10 to 
coincide with the reference pattern 8a. This movement is then transferred 
to the stencil by causing the frame 3 carrying the stencil to be displaced 
to a corresponding degree in relation to the machine stand or the outer 
frame 4. Displacement of the printed pattern 10a to the reference pattern 
8a is effected by actuating three setting means and when the printed 
pattern 10a coincides exactly with the reference pattern 8a, the positions 
of the setting means are read off and these settings transferred directly 
to the setting means for the frame of the stencil. 
The invention is not restricted to the aforedescribed exemplary embodiments 
but can be modified within the scope of the inventive concept. 
Respective setting means 5, 6, 7 and 13, 14, 15 are provided with markings 
13a, 14a, 15a and have the form of spindles, micrometer spindles.