Note: Descriptions are shown in the official language in which they were submitted.
`EIDELBERG / ~-359 ~ f~ March 1983
The invention relates to a method of determining the area
coverage of a printing original or printing plate for
printing presses by means of a measuring device equipped
with a number of sensors in which each individual sensor
is calibrated with the aid of at least one calibration
strip with both minimum and maximum area coverage.
A syst~m for predetermining the settings for the ink zone
adjusting screws on printing presses is known from US
patent speciEication 3,958,509. With the aid of an elec-
tronic camera the area coverage of two calibration plates,
one for the 0 ~ calibration and the other ~or the 100 ~
calibration, is measured and these va~ues are stored. In
a further measuring operation the area coverage of the
printing plate is measured, and these measured values are
brought into agreement with the measured values of the
two previously measured calibration plates. Thereupon
the corrected measured values are stored. The ink zone
adjusting screws are set in accordance with these corrected
measured values.
In addition, DE-OS 29 50 606 describes a device for the
zone-wise optoelectronic measurement of the area coverage
of a printing original. The brightness distribution of
a printing original is ~neasured by recording elements and
supplied to a computer which then supplies appropriate
signals for setting the ink zone screws.
A disadvantage of this system for predetermining the
settings for the ink zone adjus-ting screws is that there
is no automatic calibration of the measuring device in
order to compensate for fluctuations of the illumination
device and the receiver elements as well as of the entire
analogue electronics and the different reflection con-
ditions of the plates being measured. Furthermore, if
illumination is by means of fluorescent tubes, the fluctua-
tion in intensity which is dependent on the mains fre-
quency has a very disadvantageous effect with regard to a
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scanning measuring run which should be as fast as pos-
sible. Moreover, this system is most inconvenient for
the operator since it is difIicult to take account of
the different formats and types of plate. Furthermore,
the designs are usua]ly very elaborate, expensive and
complex with the result that the cost of their imple-
mentation bears no sound economic relation to the desired
savings in waste and set-up times by presetting the ink-
ing control on the printing presses.
The object of the invention is to develop a method of
determining the area coverage of printing plates, images
of the printing plates, printed colour separations,
films etc., and thus to be able to calculate the respec- ~"
tive ink requirement.
The technical object of the invention is achieved by the
characterizing clauses of Claims ~ and 10.
The intention of the invention is to provide simpler
operation and reproducibility when measuring area coverage
pro~iles o~ printing originals. Furthermore, gr.eat flexi-
bility is to be guaranteed with regard to types of printing
original and formats of printing original, which leads to
considerable savings in cost. Moreover, reliable preset-
ting of the press i5 obtained through the high accuracy.
A particular advantage which becomes apparent is the cor-
rection calibration by way of a special calibration field
which is on the printing original in which several refer-
ence points are scanned in the calibra-tion area.
An advantageous evaluation takes place via the automatic
status recognition which is composed of several cornponents:
. Verification of the presence, exact position and cor-
rect length of a calibration strip,
2. Detection of the calibration field on the printing
plate and/or printing original, and
3. Scanning of the type and format of the printing plate
and/or printing original.
To obtaln high measuring accuracy and thus to improve ~he
quality of the prese-tting, if there is no calibration
area on the printing plate and/or printing original, the
minimum and the maximum values of the area coverage of
the printing plate and/or printing original are advantageously
measured by the sensors of the measuring device, and there
is a subsequent normalization to these values.
It is practical to design the measuring device such that
inside there is an illumination device consisting of fluorescent
tubes whose fluctuations in intensity are smoothed, as a
result of which high measuring speeds can be obtained.
The lenses in front of the ill~lmination device are for
the improved, i.e. more homogeneous, illumination of the
e.g. ink-zone-width areas of the printing plate. Disturb-
ing shining effects can be suppressed by the use of
polarization filters and dispersion films in the measuring
head.
A preferred embodiment of the invention consists in that
the receiving means are composed of sensors, and via a
multiplexer the signals of the individual sensors are
supplied to an amplifier for amplification and are digitized
by an analogue/digital converter for storage. Control
and calculation functions are performed by a computer
which is integrated in the control panel.
The safety rollers fitted to the measuring device are
a particular advantage since they prevent any damage to
the printing original which may possibly rest uneven.
Calibration field masks are provided to facilitate the
making of the measuring field on the different types of
printing plate.
An embodiment of the invention is explained with refer-
ence to the following drawings.
Fig. 1 shows an arrangement of the calibration strip and
the printing plate on the printing plate support
surface with measuring device.
Bii5
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Fi~. 2 shows a vertical section through the measuring
device.
Fig. 3 shows the operator keyboard for the printing plate
reader.
r
Fig, 4 shows the components of the rneasuring device.
Fig. 5 shows a film for making the calibration strip.
Fig. 6 shows a calibration field.mask with window slipped
over a negative plate (negative copyl. r~r'
Fig. 7 shows a calibration field mask without window
slipped over a positive plate (positive copy).
Fig. 1 shows the printing plate support surface 1 with
the measuring device 7 which is attached thereto and which
runs in guide tracks 62. On the printing plate support
sur~ace -1 there is a stop bar 10 whi.ch is at right angles
to the scale strip 12. The horizontal stop bar 10 is,
or example, divided into thirty-two measuring zones 11,
corresponding to the ink duct zones of a certain press
format, and the vertical scale strip 12 is, for example,
divided into twenty-two measurinq zones 11, corresponding
to the number of sensors. ~he printing plate 2 with the
register and clamping rail stampings 63 is aligned at the
stop bar 10 on the printing plate support surface 1 and
is centralized with respect to the scales in the region
of the printing plate 2. On the surface of the printing
plate 2 are the ink-carrying surface 3 and the calibration
~ield 4 as well as the calibration area 20 with the
meaSuring track 46. ~urthermore, disposed on the printing
plate support surface 1 left of the vertical scale strip
12 is the calibration strip 6~ which is subdivided such
that the left-hand field 6 is pro~ided for the minimum
calibration and the right-hand field 5 or the maximum
calibration of the ink control.
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Inside the measurin9 device 7, as shown in Fig. 2, there
. are twenty~two sensors 9 and an additional sensor 8 which,
in the course of a measuring run, determine the ink
values of the calibration strip 64, the ink-carrying
surface 3, the calibration field 9 and the calibration
area 20 of the printing pla-te 2.
Inside the measuring device 7 there are illumination de-
vices 14 with two fl.uorescent tubes 51 which are attached
by holding devices 65. In the path of radiation of the
fluorescent tubes 51 towards the printing plate support
surface 1 there are lenses 15 which may also be in the
form of polarization filters ~. The sensors 9 are dis- /.
posed above a focussing lens 18 directly over the measuring
slit 19 and are coupled to a matching electronics 47.
Also in t.his path of rays are polari~ation filters 58
and dispersion films 39. The areas of the printing plate
2 and of the calibration strip 6~ which are to be measured
by the sensors 8 and 9 are laid down by the measuring
slit 19 and the partitions 29 of the light shafts. The
measuring device 7 i5 driven by a motor (not shown) via
a toothed belt and is guided in guide tracks 62. Disposed
underneath on the measuring device 7 are safety rollers
16 which are attached to it by means of brackets 17.
Fig. 3 shows the individual controls (output possibilities
and information on operator control) 21 to 55 which are
situated on the desk panel 13 of the printing plate reader
in order to perform.-the measuring operation. The s-teps
of the method are performed, for example, in the fol~
lowing order:
The calibration strip 64, made preferably of the same
material as the printing plate, is placed on the printing
plate support surface 1 left of the printing plate 2.
Thereupon the unit is put into operation by means o the
on/off switch-25. ~i.th the aid of the button 30 a vacuum
is set up in the area of the format~dependent vacuum slits
38 which are in the printing plate support surface 1.
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~his vacuum first of all draws i~ the calibration strip
64. The printing plate 2 is placed in position such
that the register and clamping rail stampings 6~ are at
the upper edge of the printing plate support surface 1
and are aligned with the stop bar 10 in such a way that
the left-hand edge of the printing plate 2 is inside the
first measuring zone 11 and is centered between the
first and final measuring zones. Aligning is made easier
by line markings 32 for the nominal width of Heidelberger
Druckmaschinen standard plates.
Thereupon a preselection is made of the desired output,
log and reset modes by the operator by pressing the
buttons for output selection 52, log selection 53 and ,~
reset selection 54. The opera-tor can choose between a
numeric, a graphic and a test log. sy means of the output
button 24 the operator can have the log strip 23 printed
out by the log printer 22.
The most important type of output of the printing plate
reader is an automatically readable data carrier, e 7 g ~
a cartridge 55, The measured values of a complete plate
set can be stored on this cartridge 55. This cartridge 55
is then preferably read by an input unit,in the control
panel of the printing press. The data ~or the ink require-
ment are then converted into press presetting values.
The format of the printing plate 2 i5 set at the encoding
switches 26 which are identified by the symbols for format t
width 27 and format length 28. Those figures are set which
are covered by the printing plate 2 as it rests on the stop
bar 10 and the scale strip 12. The format width which is
input determines the travel of the measuring device 7.
The format which is set at -the encoding switches 26 is
stored by pressing -the forrnat input bu-tton 45.
The colour separation of the printing plate 2 is selected
with the aid of the colour separation selector b,utton 31,
a~
_ 7
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e.g. black, cyanl magenta, yellow or X and ~ ~or two
additional colours. The suction air for the printing
plate 2 is activated by means of the vacuum button 30
whereby the suction air is limited to the format-dependent
vacuum slits 38. The measuring run is started by pressing
the start button 33.
The measuring run begins with the measuring of the field
6 for minimum calibration and the field 5 ~or maximum
calibration. This is followed by the measurement on the
printing plate 2 beginning with the first measuring ~one
11 up to that measuring zone which corresponds to ~he set
format width of the printing plate 2. '~
The measuring device 7 glides back at high speed over the
printing plate support sur~ace 1 to its starting point.
After the output button 24 has been pressed, the selected
output is initiated. It is a]so possible beforehand to
measure further printing plates 2 with other colour separa
tions. The paper feed button 21 is ~or the paper feed
of the log strip 23 on the log printer 22. ~Irther func-
tions which are useful for the operator are activated
by the selective actuation of the emergency stop button
37, restart button 36 and cancelling button 35 (for
colour separation selection and/or calibration field
switch-of~). The special additional sensor 8 can be
switched off via the calibration sensor switch-off button
34.
Fig. 4 shows in diagrammatic form the flo~ of signals
within the rneasuring device 7. The individual components
are the focussing ]enses 18, sensors 8 and 9, matching
electronics 47, multiplexer 48 and amplifier 49. The
measuring device 7 is driven by a motor (not shown) which
is connected to a gear unit. By means, for example, of
an inductive measuring pickup the basis is established
for determining the position of the measuring device 7
on the printing plate support surface 1. The positions
of the measuring device 7 are determined via a counter
which accep-ts the pulses received by a pulse disc and via
a comparator The measurementS take place during the
continuous run of the measuring device 7 over the
printing plate support surface 1. The measured values
are supplied to the A/D converter 50 which is in the
processing electronics of the unit.
The light reflected by the printing plate 2 is received
via focussing lenses 18 by sensors 8 and 9, processed
by the matching electronics ~7 and supplied via a multi-
plexer 48 to an amplifier 49 and then to an A/D converter
50. To make optimum use of the resolution capability of
the A/D converter 50, the amplification factor of the
amplifier 49 is matched to the maximum signal of the
sensors 9 of the field for minimum calibration 6 of
the calibration strip 64. If a minimum number of steps
o~ the usable converter range is fallen below, then the
offset circuit of the amplifier ~9 is changed via the
measured values o~ the fields for maximum calibration
5 of the calibration strip 64. In the event of a reaction
between offset setting and amplifier setting, the ampli-
fier circuit is r~-optimized. This may necessitate a
new calibration run before the actual measuring run.
In general, the calibration run and the measuring run
run into one another, at any rate within a printing plate
set after the ~irst printing plate.
The individual sensors B and 9 are calibrated on the cali-
bration strip 64. The additional sensor 8 determines the
contrast conditions between calibration strip 64 and
printing plate 2 via the calibration field 4 and the
calibration area 20 on the printing pla-te 2. By means of
special mathematical operations the previously established
characteristics of the sensors ~ and 9 are matched to
the conditions of the printing plate 2.
If an area coverage value less than 0~ is found in a
measuring zone on the printing plate, then there is a
calibration error as a result of defective calib~ation
measuring areas. The minimum calibration is to be replaced
by this value, i.e. the negative measured value is to be
set equal to zero.
To have ~s low a difference as possible between the con-
trast conditions of the prin-ting plate 2 and those of
-the calibration strip 64` the calibration strip 64 should
be made of the sarne material as the printing plate 2.
'The different calibra-tion strips 69 can be kept in a special
calibration strip store which is, for example, in the
measuring desk.
By means of a visual comparison between printing plate 2
and callbration strip 64 the printer should select the
best possible calibratio~ strip 64 and place it in the
measuring position on the measuring desk. This ensures
that the receiving rneans is calibrated in the later work-
ing range of -the printting plate 2. In con~unction with re-
calibration this leads to OptiTTIUTII resolution and measuring
accuracy. This is of particular importance if, owing to
the possible absence of the calibration field 4 or a de-
fective calibra-tion area 20 and/or calibration field 9,
the additional sensor 8 has to be switched off by pressing
the calibration sensor switch-off button 34.
Fig. 5 shows the film 56 for rnaking the calibra-tion strips
64. The two fields 41, 92 correspond to the minimum and
maximum area c~verage. The marking lines 43 are for
trimming to the different plate lengths. The identification
corner 94 of the film 56 is, e.g. in the case of aluminium
plates, cut off, and is retained in the case of multi- ¦
metal plates. When workin~ without automatic plate--type
recognition, a microswitch in the printing plate support
surface 1 in the region of the calibration strip 69 is
actuated by the calibration strip 69 with the aid of which
th~ type of plate is recognized.
The calibration Eield mask 60 showll in Fig. 6 has a window
59 for the copy of the calibration field 9 in t:he case of
negative copies. I'he calibration field mask 57 shown in
Fiy. 7 is used for making the calibration field 9 in the
case of positive copies. The calibrattion field masks 57
and 60 are made of any material; calibration field masks
made of sheet metal have proved particularly effective.
For the dimensionally correct copying of the calibration
field ~ on the printing plate 2, the appropriate cali-
bration field mask 57 or 60 is, in this special design,
slipped over the right-hand top corner of the printing
plate 2, i.e. at the end of printing since there are no
stamped holes there.
The copying of the calibration strip 64 in the printing
direction of the plate is particularly important in the
case of printing plates 2 with a pronounced direction of
shine (brushed, etc.). In principle, it would also be
possible to integrate shine-reducing measures within the
measuring device 7, e.g. dispersion films 39 or the use
of polarization filters 40 in the measuring slit 19 and/
or in the path of the illumination and receiving rays.
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In contrast to aluminium printing plates, much light is
reflected by the ink-carrying parts of the plate in the
case of multi-metal printing plates. This makes it
necessary for the measuring signal to be inverted. This
is cornmunicated to the unit either by automatic actua-
tion of a special microswitch when the calibration strip
is placed in position, or automatically by the above-
described plate type recognition.
The additional sensor ~i is preferably of the type which
can be switched off by means of the calibration sensor ii
switch-off button 34 in case the calibration field 4 is
deEective or entirely missing.
In an embodiment which is different from the above-
described input via encoding swi.ches 26, it is also
possible to specify the forma-t automatically in that the
jump in contrast from the printiny plate support surface
1 to the printing plate 2 is measured by the sensors 9
in the vertical (plate length~ direction and by the sensors
8 or 9 in the horizontal (plate width) direction.
The result of the measurement of the measuring device 7
are area coverages per zone. The area determined by
zone width and number of sensors serves as a basis in
this connection. In general, the format-dependent
printing length is not identical with this basic area.
Therefore, there is an automatic correction of the measured
value for normalization to 100%. This is done by multi- ;
plying the result with the format-dependent, fixed
factors.
These area coverage values do not yet permit the direct
presetting of the inking control in the printing unit
of a printing press. Depending on the type of press and
the ink, the area coverage values must now be used to
calculate the presetting of the ink duct (zone opening)
and the ductor (ink strip width~. This is done prefer-
ably in the control desk of the printing press, but can,
in principle~ also be performed with the computer of
the printing plate reader.
The use of a special presetting computer is also possi~le.
By means of such a presetting computer with appropriate
presetting programs it is possible to obtain the universal
operation of all machines with presetting data insofar as
they are in the format range. This presetting computer
could also convert the zone intervals and ~one widths
which are dependent on the ink duct and are fixed-programmed
in the printing plate reader so that they can be used ~or
other ink ducts.
From the area coverage data it is possible -to calculate
also the ink requirement per sheet, or in the case of
web-fed presses, per section length by including the ink
film thickness on the sheet. Thus, it is possible to
estimate the ink requirement for the production run in
advance.
