U.S. patent number 3,841,215 [Application Number 05/303,862] was granted by the patent office on 1974-10-15 for method and apparatus for control of the supply of ink for offset duplicating machines.
This patent grant is currently assigned to Ricoh Co., Ltd.. Invention is credited to Toru Hasegawa.
United States Patent |
3,841,215 |
Hasegawa |
October 15, 1974 |
**Please see images for:
( Certificate of Correction ) ** |
METHOD AND APPARATUS FOR CONTROL OF THE SUPPLY OF INK FOR OFFSET
DUPLICATING MACHINES
Abstract
A method and an apparatus obviating the problem of how to supply
an optimum quantity of ink to a master plate to be duplicated by
offset duplicating machines. The method consists in automatically
controlling the quantity of ink supplied to the master plate by
measuring the ratio of the area of image regions of the plate to
the whole area of the plate or the image area ratio or by reading
the code marks superposed on the plate for indicating the image
area ratio. Measurement of the image area ratio is carried out by
scanning the image surface of the plate by means of a scanning
head.
Inventors: |
Hasegawa; Toru (Yabe-machi,
JA) |
Assignee: |
Ricoh Co., Ltd. (Tokyo,
JA)
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Family
ID: |
26971300 |
Appl.
No.: |
05/303,862 |
Filed: |
November 6, 1972 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
Issue Date |
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299596 |
Oct 20, 1972 |
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Current U.S.
Class: |
101/148;
101/350.1; 101/484 |
Current CPC
Class: |
B41L
27/14 (20130101); B41L 39/00 (20130101) |
Current International
Class: |
B41L
27/14 (20060101); B41L 39/00 (20060101); B41L
27/00 (20060101); B41l 025/00 () |
Field of
Search: |
;101/349,350,148,365,363,147,426 |
References Cited
[Referenced By]
U.S. Patent Documents
Primary Examiner: Fisher; J. Reed
Attorney, Agent or Firm: Cooper, Dunham, Clark, Griffin
& Moran
Parent Case Text
CROSS REFERENCE TO RELATED APPLICATION
This application is a continuation-in-part of applicant's copending
application Ser. No. 299,596, now abandoned, executed Oct. 12, 1972
and filed Oct. 20, 1972 for "Method of Control of the Supply of Ink
for Offset Duplicating Machines," Attorney's Docket No. 9779.
Claims
What I claim is:
1. A method of control of the supply of ink for offset duplicating
machines comprising the steps of producing read-out pulses by
scanning the image surface of a master plate and reading image
regions of the master plate, supplying said read-out pulses to an
AND circuit together with pulses of a predetermined frequency
produced by a transmitter, actuating a counter while the AND
circuit is operative so as to count the ratio of area of image
regions of the plate to the whole area of the plate, and
automatically controlling the quantity of ink supplied to the
master plate in accordance with said ratio.
2. A method as set forth in claim 1 wherein scanning of the image
surface of a master plate in the step of producing read-out pulses
is carried out by moving a scanning head axially of a master
cylinder on which the master plate is mounted while the master
cylinder is rotated.
3. A method as set forth in claim 1 wherein scanning of the image
surface of a master plate in the step of producing read-out pulses
is carried out by means of a scanning head while the master plate
is placed on a master plate feed tray.
4. A method as set forth in claim 1 wherein automatic control of
the quantity of ink in the step of automatically controlling the
quantity of ink supplied to the master plate in accordance with
said ratio is effected by varying the amount of angular rotation of
an ink fountain roller.
5. A method as set forth in claim 4 wherein the amount of angular
rotation of the ink fountain roller is varied by means of a pulse
motor.
6. A method as set forth in claim 4 wherein the amount of angular
rotation of the ink fountain roller is varied by means of a
solenoid.
7. A method as set forth in claim 1 wherein automatic control of
the quantity of ink in the step of automatically controlling the
quantity of ink supplied to the master plate in accordance with
said ratio is effected by varying the speed of an electric motor
for driving the duplicating machine.
8. In a method of offset-printing a copy sheet with an image from a
master plate, the steps of
a. detecting the ratio of the area of the image to the total area
of the master plate;
b. producing a control signal determined by the magnitude of the
value of said ratio; and
c. controlling the application of ink to the copy sheet in
accordance with the control signal for varying the amount of ink
applied in direct relation to the value of said ratio,
wherein the ratio-detecting step comprises
i. scanning the master plate for producing readout pulses of
duration determined by the magnitude of image areas scanned,
ii. generating reference pulses of constant predetermined
frequency, and
iii. applying said readout pulses and reference pulses to an AND
circuit for producing output pulses, of a number determined by the
cumulative duration of said readout pulses;
and wherein the signal-producing step comprises
i. counting said output pulses, and
ii. producing a control signal determined by the counted number of
said output pulses.
9. In a method of offset-printing a copy sheet with an image from a
master plate, the steps of
a. detecting the ratio of the area of the image to the total area
of the master plate;
b. producing a control signal determined by the magnitude of the
value of said ratio; and
c. controlling the application of ink to the copy sheet in
accordance with the control signal for varying the amount of ink
applied in direct relation to the value of said ratio,
wherein the ratio-detecting step comprises
i. determining said ratio, and
ii. forming, on a non-image portion of said master plate, scannable
code marks representative of the determined value of said
ratio;
and wherein the signal-producing step comprises
i. scanning said non-image portion of said master plate for
detecting said code marks, and
ii. producing a control signal in response to the detected presence
of said code marks, and representative thereof.
10. Offset printing apparatus including in combination,
a. a master plate bearing an image to be printed;
b. a rotary master cylinder for carrying said plate;
c. means for supplying ink to said plate on said master
cylinder;
d. a printing couple including a blanket cylinder for transferring
an inked image from said plate to a copy sheet; and
e. means for rotatably driving said printing couple to advance the
copy sheet therethrough;
wherein the improvement comprises:
f. means for movably scanning said master plate to direct the ratio
of the area of the image thereon to the total area of the plate and
for producing a first output signal in response to the detected
ratio;
g. means for controlling the application of ink to the copy sheet
in response to a control signal; and
h. means for converting said first signal to a control signal for
said controlling means for varying the application of ink to the
copy sheet in direct relation to the detected magnitude of said
ratio,
wherein said master plate bears, on a non-image-bearing portion
thereof, code marks representative of the value of said ratio; and
wherein said scanning means comprises means for scanning said
non-image-bearing portion of said plate to detect said code marks
and produce a first signal representative thereof.
11. Apparatus as defined in claim 10, wherein said
ink-application-controlling means comprises means for adjusting
said ink-supplying means in response to said control signal to vary
the supply of ink to said plate in direct relation to the detected
value of said ratio.
12. Apparatus as defined in claim 10, wherein said
ink-application-controlling means comprises means for adjusting
said driving means in response to said control signal to vary the
velocity at which said printing couple is driven in inverse
relation to the detected value of said ratio.
13. Offset printing apparatus including, in combination,
a. a master plate bearing an image to be printed;
b. a rotary master cylinder for carrying said plate;
c. means for supplying ink to said plate on said master
cylinder;
d. a printing couple including a blanket cylinder for transferring
an inked image from said plate to a copy sheet; and
e. means for rotatably driving said printing couple to advance the
copy sheet therethrough;
wherein the improvement comprises:
f. means for movably scanning said master plate to detect the ratio
of the area of the image thereon to the total area of the plate and
for producing a first output signal in response to the detected
ratio;
g. means for controlling the application of ink to the copy sheet
in response to a control signal; and
h. means for converting said first signal to a control signal for
said controlling means for varying the application of ink to the
copy sheet in direct relation to the detected magnitude of said
ratio,
wherein said scanning means comprises means for successively
scanning parallel linear portions of said plate and producing a
first signal comprising a succession of readout pulses of number
and duration determined by the magnitude of the area of scanned
image on said plate; and wherein said converting means comprises
means for generating reference pulses of constant predetermined
frequency, an AND circuit to which said readout pulses and said
reference pulses are supplied for producing output pulses, at said
predetermined frequency, of a number determined by the cumulative
duration of said readout pulses, and means for counting said output
pulses to produce a control signal representative of the counted
number of said output pulses.
14. Apparatus as defined in claim 13, wherein said
ink-application-controlling means comprises means for adjusting
said ink-supplying means in response to said control signal to vary
the supply of ink to said plate in direct relation to the detected
value of said ratio.
15. Apparatus as defined in claim 13, wherein said
ink-application-controlling means comprises means for adjusting
said driving means in response to said control signal to vary the
velocity at which said printing couple is driven in inverse
relation to the detected value of said ratio.
16. An offset printing device having a master plate bearing an
image and a controllable ink supply for printing said image,
wherein the improvement is in a device for controlling the ink
supply as a function of the density of the image on the master
plate, comprising:
means for scanning the master plate in a succession of relatively
narrow scan lines and for generating a first type read-out signal
while traversing an area of the master plate which bears said image
and for generating a second type read-out signal while traversing
an area of the master plate which does not bear an image;
means for generating a clock pulse train of transmission
pulses;
means for counting said transmission pulses; means connecting the
scanning means, the generating means and the counting means for
applying said transmission pulses to the counting means to be
counted therein only while a first type read-out signal is being
generated by the scanning means, whereby the count accumulated in
the counting means at any particular time represents the ratio of
the image area to the total scanned area up to that time; and
means connecting the counting means and the ink supply for
controlling the ink supply as a function of the count accumulated
in the counting means.
17. An offset printing device as in claim 16 wherein the means for
controlling commences controlling the ink supply before the
scanning of the master plate is completed.
18. An offset printing machine as in claim 17 wherein the
controlling means include means for increasing the output of the
ink supply by a preset amount each time the counting means
accumulates a preset number of counts while the master plate is
being scanned.
19. An offset printing device as in claim 18 wherein the
controlling means include a pulse motor, means for pulsing the
motor in response to the accumulation of a preset count of pulses
in the counting means, and means for driving the ink supply with
the pulse motor to increase the output of the ink supply with each
motor pulse while the master plate is being scanned.
20. An offset printing device as in claim 16 wherein the
controlling means include a solenoid connected to the ink supply
and energizable to increase the output of the ink supply and means
responsive to the accumulation of a preset number of pulses in the
counting means to energize the solenoid.
21. An offset printing device as in claim 16 wherein the offset
printing device includes a variable speed motor defining printing
speed and wherein the improvement includes means for controlling
the speed of the motor as a function of the count accumulated in
the counting means after scanning of the master plate is
completed.
22. An offset printing device as in claim 21 including means for
incrementally increasing the output of the ink supply in response
to defined incremental increase in the count accumulated by the
counting means while the master plate is being scanned.
23. A method of operating an offset printing device having a master
plate bearing an image and an ink supply whose output is
controllable comprising the steps of:
scanning the master plate in a succession of relatively narrow scan
lines and generating a first type read-out signal while traversing
an image area on the master plate and generating a second type
read-out signal while traversing an area of the master plate does
not bear an image;
generating a clock pulse train of transmission pulses;
counting only the transmission pulses which occur while a first
type read-out signal is being generated whereby the count of
transmission pulses at any particular time is indicative of the
ratio of image area versus total scanned area of the master plate;
and
controlling the output of the ink supply in accordance with the
accumulated count of pulses.
24. A method as in claim 23 wherein the controlling step includes
controlling the ink supply while the master plate is being
scanned.
25. A method as in claim 23 wherein the controlling step includes
incrementally increasing the output of the ink supply upon the
accumulation of a defined increment of counted transmission pulses
while the master plate is being scanned.
26. A method as in claim 25 wherein the offset printing device
includes a variable speed motor defining the speed of printing
copies of said master plate and wherein the controlling step
includes controlling the speed of the motor in accordance with the
accumulated count of transmission pulses.
Description
BACKGROUND OF THE INVENTION
This invention relates to a method and apparatus for control of the
supply of ink which permits the quantity of ink supplied to a
master plate in an offset duplicating machine to be adjusted
automatically.
Duplication of a master plate by an offset duplicating machine is
generally performed by the following process: a master plate is
mounted on the master cylinder and ink is applied by an inking
device to the image regions of the plate after an ink repellent
etching solution is applied to the plate; the ink image of the
plate is transferred to the blanket cylinder and one copy sheet
after another is brought into pressing engagement with the blanket
cylinder to print the image of the plate on the copy sheets; and
the plate on the master cylinder is ejected when the image of the
plate is printed on a predetermined number of copy sheets and the
ink image on the blanket cylinder is removed by a cleaning device,
thereby finishing all the steps for duplicating one master
plate.
Supply of ink to a master plate is effected by rotating the ink
fountain roller through a suitable angle. This angular rotation of
the ink fountain roller takes place each time one copy sheet is
supplied between the blanket cylinder and the impression
cylinder.
Generally, a number of master plates are used for carrying out
duplication successively, and one plate differs from another in the
area of image regions or the ratio of the area of image regions of
the plate to the whole area of the plate. Thus, if a constant
quantity of ink is supplied from the ink fountain irrespective of
the types of master plates mounted successively on the master
cylinder, the images printed on copy sheets will contain excess ink
when the image regions of the plate occupy a small area on the
plate and the images printed on copy sheets will be lighter in
color than is necessary when the image regions of the plate occupy
a large area on the plate.
It is thus necessary to set the angular rotation of the ink
fountain roller at a suitable level to control the quantity of ink
supplied to the master plate in accordance with the area of image
regions of the plate when the plate is mounted on the master
cylinder. It has hitherto been customary to effect the
aforementioned setting of the rotational angle of the ink fountain
roller by manual operation. It has also been customary to perform
trial printing of a number of copy sheets to adjust the quantity of
ink supplied till an optimum quantity is determined.
SUMMARY OF THE INVENTION
This invention has as its object the provision of a method and an
apparatus for controlling the supply of ink for offset duplicating
machines wherein the image surface of the master plate is scanned
by a scanning head and the ratio of the area of image regions of
the plate to the whole area of the plate is measured and counted by
a counter or the ratio of the area of image regions of the plate to
the whole area of the plate is read from the code marks superposed
on the plate, and the amount of angular rotation of the ink supply
control cam or the number of revolutions of the electric motor for
driving the duplicating machine is controlled in accordance with
the image area ratio determined in this way. The method according
to this invention permits setting of the quantity of ink supplied
to the master plate to be performed automatically by eliminating
manual attention, and enables to do without the additional
operation of performing trial printing.
According to the invention, there is provided a method and an
apparatus for controlling the supply of ink for offset duplicating
machines which permit the ratio of the area of image regions of a
master plate to the whole area of the plate to be determined either
by scanning the image surface of the plate by a scanning head and
counting by a counter or by reading code marks superposed on the
plate for indicating the ratio of the area of image regions of the
plate to the whole area of the plate, and the quantity of ink
supplied to the plate is adjusted automatically instead of manually
as has hitherto been the case. The method and apparatus offer the
advantages of permitting the number of revolutions of the motor to
be controlled in accordance with the image area ratio determined in
this way so as to bring the shade of color of the printed images to
a desired level and keep the same at such level, and enabling trial
printing to be done without when the master plates are changed.
BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 is a schematic view of an offset duplicating machine
incorporating the present invention therein;
FIG. 2 is a perspective view of a master cylinder and a master
plate mounted thereon, showing one example of scanning of the
master plate;
FIG. 3 is a plan view of a master plate;
FIG. 4 is a perspective view of a master cylinder and a master
plate mounted thereon, showing a code superposed on the master
plate and means for reading such code;
FIG. 5 is a block diagram of one example of the ink supply control
device adapted to carry the method according to this invention into
practice;
FIG. 6 shows pulses used in the present invention;
FIG. 7 and FIG. 8 are front views of examples of the ink supply
control device;
FIG. 9 is a circuit diagram showing the manner of operation of a
flip-flop for one example of a control circuit;
FIG. 10 shows one example of pulses for operating the control
circuit;
FIG. 11 and FIG. 12 are circuit diagrams showing other forms of ink
supply control device which rely on the control of the number of
revolutions of the motor;
FIG. 13 shows variations in the input time constant of the trigger
element in relation to variations in the input wave form for the
armature;
FIG. 14 and FIG. 15 are pulse diagrams showing the read-out pulses
counted at two different levels; and
FIG. 16 is a block diagram of a device for carrying out the
counting shown in FIG. 14 and FIG. 15.
DESCRIPTION OF PREFERRED EMBODIMENTS
In FIG. 1, there is shown schematically an offset duplicating
machine in which a master cylinder 1, a blanket cylinder 2 and an
impression cylinder 3 rotate in the directions of arrows in
synchronism with one another as is well known. An inking device 4
comprises ink applying rollers 5 and 6, an ink form roller 7, a
ductor roller 8 and an ink fountain 9. The ink fountain 9 contains
a quantity of ink 11 therein, and an ink fountain roller 13 mounted
on a shaft 12 is disposed in the ink fountain 9, the ink fountain
roller 13 being adapted to rotate counterclockwise through a small
angle about the shaft 12 each time a copy sheet is supplied between
the blanket cylinder and the impression cylinder. Although not
shown, a water supply service for supplying water to the ink form
roller 7 is disposed adjacent the inking device 4.
A cleaning device 14 is disposed near the blanket cylinder 2 for
cleaning the peripheral surface of the blanket cylinder 2 when
duplication of one master plate on a predetermined number of copy
sheets is finished. The cleaning device 14 comprises an immersing
roller 17 immersed in a cleaning liquid 16 in a tank 15, and a
cleaning roller 18 maintained in pressing engagement with the
immersing roller 17.
A number of master plates 21 to be duplicated are placed in a stack
on a master plate feed tray 19, with the uppermost plate being
ready to be mounted on the master cylinder 1 when printing is
initiated. When a predetermined number of copy sheets are printed,
the used plate is automatically ejected onto an ejected master
plate receiving tray 22.
Copy sheets 24 placed on a sheet feed tray 23 are successively fed
between the blanket cylinder 2 and the impression cylinder 3 by a
sheet feed device (not shown) so as to duplicate the master plate
on the copy sheets. Printed copy sheets are ejected onto a printed
copy sheet receiving tray 25.
A code read-out means 26 and a scanning head 27 for scanning the
image surface of the master plate 21 mounted on the master cylinder
1 are disposed above the master cylinder 1. The scanning head 27 is
adapted to move axially of the master cylinder 1 or in the
direction of an arrow 28 in FIG. 2 at a low rate so as to measure
the area of image regions of the master plate 21. The code read-out
means 26 is adapted to read code marks 29 superposed on a non-image
region of the master plate 21 as shown in FIG. 4 and indicating a
quantity of ink desired to be supplied to the particular master
plate.
Scanning of the image regions of a master plate may be performed
after the plate is mounted on the rotating master cylinder as
aforementioned. Alternatively, scanning may be carried out while
the master plate is still placed on the master plate feed tray 19
by moving a scanning head 27a (FIG. 1) in the direction of the
arrow 28 (FIG. 2). When this is the case, an illumination means 30
comprising a light source and lenses for illuminating the master
plate 21 also moves in the direction of the arrow 28 together with
the scanning head 27.
When scanning of the image surface of the master plate 21 is
carried out while the plate is mounted on the rotating master
cylinder 1, scanning takes place lengthwise of the master plate 21
as shown by dashes designated 31 in FIG. 3. When the scanning head
27a alone is moved in the direction of the arrow 28 while the
master plate 21 remains stationary on the master plate feed tray
19, scanning takes place across the width of the master plate 21 as
shown by dashes designated 32 in FIG. 3. In the present invention,
scanning may take place in either direction.
Scanning of a master plate may be carried out in a plate-making
machine (not shown) in which plates are made. When this scanning
process is adapted, the image surface of a master plate is scanned
after the plate is made so as to determine the ratio of the area of
the image regions of the plate to the whole area of the plate
(hereinafter referred to as an image area ratio), and the ratio
thus determined is indicated in the form of code marks 29 in a
non-image region of the master plate 21 as shown in FIG. 4. The
code marks 29 are read by the read-out means 26 shown in FIG. 4
when the master plate is mounted on the master cylinder 1, and the
quantity of ink supplied by the inking device 4 is adjusted in
accordance with the value read by the read-out means 26.
Regardless of what processes may be followed in scanning the master
plate 21, synchronizing means 33 shown in FIG. 5 produces gate
pulses for controlling the initiation of scanning and the
termination of scanning of the image surface of the plate.
Scanning of the master plate 21 by the scanning head 27 results in
the production of read-out pulses 34 shown in FIG. 6 which
correspond to the area of image regions of the plate. Scanning
causes a transmitter 35 shown in FIG. 5 to produce transmission
pulses 36 of uniform frequency as shown in FIG. 6. The gate pulses
(not shown) from the synchronizing means 33, the read-out pulses 34
from the scanning head 27 (or 27a) and the transmission pulses from
the transmitter 35 36 are supplied to an AND circuit 37 shown in
FIG. 5. When the aforementioned three types of pulses are supplied
simultaneously to the AND circuit 37, counted pulses 38 shown in
FIG. 6 are produced and supplied to a counter 39.
The counter 39 comprises flip-flops which are n in number for
counting 2.sup.n pulses by a binary notation system. Assuming that
the master plate 21 has 150 scanned lines and the number of pulses
36 per one scanned line is 100, then all the pulses 36 produced for
one plate are 15,000 in number. That is, if image regions occupy
all the area of the master plate and the read-out pulses 34 are
continuously at a high level, a maximum of 15,000 pulses will be
produced in total. If a counter comprises 13 flip-flops, the
counter will be capable of counting the aforementioned maximum
number of pulses. Preferably, the maximum number of pulses produced
by scanning a master plate and counted by a counter and the ability
of the counter for counting the number of pulses are at high level
as much as possible so that the read-out of the image regions may
be performed as closely as possible.
Assuming that the quantity of ink supplied to the master plate on
the master cylinder is to be adjusted so that it is varied from one
to another of eight different levels, the counter 39 can produce
and supply an operation command 41 to the inking device 4 if an
output is taken out of one flip-flop when a pulse motor or solenoid
is employed and if an output is taken out of each of three
flip-flops when a variable speed drive motor is employed. The
command 41 is supplied to a pulse motor 42 or a solenoid 43 to
energize the same to set the quantity of ink supplied to the master
plate at a certain level, or supplied to a main motor 44 for
driving the duplicating machine so as to control the rate of
revolutions of the duplicating machine.
FIG. 7 and FIG. 8 illustrate examples of the ink supply control
device in which like reference characters designate similar parts.
In the device shown in FIG. 7, a ratchet wheel 45 is shown as being
secured to the shaft 12 on which the ink fountain roller 13 is
mounted as shown in FIG. 1, so that the ratchet wheel 45 and the
ink fountain roller 13 act conjointly. An adjusting member 46 and a
timing gear 47 substantially integral with the member 46 are
pivotally mounted on the shaft 12, the timing gear 47 being
connected through a timing belt 51 to another timing gear 49
mounted on the pulse motor 42.
An oscillating lever 53 adapted to oscillate as shown by an arrow
52 each time a copy sheet is fed is pivotally connected at its base
to the shaft 12 and has a feed pawl 54 pivotally connected at its
base through a shaft 55. The feed pawl 54 is urged to move
counterclockwise in FIG. 7 by the biasing force of a compression
spring 56 connected at one end to the oscillating lever 53 and at
the other end to the pawl 54, so that a front end 54a of the pawl
54 is maintained in engagement with the peripheral surface of the
adjusting member or cam 46.
If the oscillating lever 53 moves counterclockwise, then the front
end 54a of the feed pawl 54 is released from engagement with the
peripheral surface of the adjusting member 46 and brought into
engagement with the ratchet wheel 45 so as to angularly rotate the
same counter clockwise. As a result, the ink fountain roller 13
acting conjointly with the ratchet wheel 45 angularly rotates
counterclockwise into a position in which a portion of its
peripheral surface to which the ink 11 adheres is juxtaposed to the
ductor roller 8.
The quantity of ink transferred by the ink ductor roller 8 from the
fountain roller 13 to the ink form roller 7 may vary depending on
the amount of angular rotation of the ink fountain roller 13. The
amount of angular rotation of the roller 13 and hence the amount of
angular rotation of the ratchet wheel 45 in FIG. 7 may vary
depending on the time at which the front end 54a of the feed pawl
54 is brought into engagement with the ratchet wheel 45. Thus it is
possible to adjust the quantity of ink supplied to the master plate
on the master cylinder by rotating the adjusting member 46 through
a suitable angle.
It has hitherto been customary to rotate the adjusting member 46
angularly manually by the operator so as to adjust the quantity of
ink supplied to the master plate in accordance with the area of
image regions of the plate. In the mechanism shown in FIG. 7,
however, the pulse motor 42 is rotated through a suitable angle by
a command signal from the counter 39 so as automatically to set the
amount of angular rotation of the adjusting member 46 or the
quantity of ink supplied to the master plate at a suitable
level.
In the device shown in FIG. 8, the solenoid 43 is used in place of
the pulse motor 42 for setting the angular rotation of an adjusting
member 57 at a suitable level. The adjusting member 57 is formed on
one portion of its peripheral surface with ratchet teeth 57a with
which are maintained in engagement a return rotation stop pawl 59
pivotally secured at its base to an immovable member and a feed
pawl 62 pivotally secured at its base to a feed lever 61. The feed
lever 61 is pivotally connected at its base to the shaft 12 and has
a free end which is connected to an actuating lever 43a of the
solenoid 43 and to one end of a return spring 63 secured at the
other end to an immovable member.
A command signal to the solenoid 43 or pulse motor 42 is given from
an adjusting circuit of the counter 39 shown in FIG. 5. If, for
example, an adjusting circuit 64 which comprises an R.sup.th
flip-flop as shown in FIG. 9 is turned on at high level, then its
output is differentiated by a differentiation circuit 65 and
supplied to the base of a transistor 66. This fires the transistor
66 and actuates the pulse motor 42 or energizes the solenoid 43 for
an instant. As a result, the feed lever 61 shown in FIG. 8 pivots
counterclockwise and causes the adjusting member 57 to rotate in
the same direction, or the adjusting member 46 shown in FIG. 7 is
caused to rotate clockwise.
The amount of angular rotation of the adjusting members 57 and 46
or the number of times the pulse motor 42 is actuated and the
solenoid 43 is energized may vary depending on the number of
adjusting circuits of the counter 39 which are actuated. The number
of adjusting circuits which are actuated depends on the number of
pulses 38 to be counted as shown in FIG. 6 or the ratio of the area
of image regions of the plate to the whole area of the plate.
If the total number of pulses produced by one master plate is set
at 15,000 and the quantity of ink supplied to the master plate is
to be adjusted such that it is varied from one to another of seven
different levels, the adjusting circuit of the counter 39 producing
a command signal will only have to be selected by switching from
one adjusting circuit to another each time 2,000 pulses are
counted. Since 2.sup.11 = 2048, an output will be produced each
time 2,048 pulses are counted as shown in FIG. 10 if the output of
the eleventh flip-flop is taken out (the output is taken out as by
differentiation when the flip-flop is switched from low to high
level), and the adjusting circuit can be switched from one to
another. Each time the output is produced, the command signal 41 is
produced by the counter 39 and supplied to the pulse motor 42 or
solenoid 43. By this arrangement, the number of flip-flops in the
counter 39 will be reduced to 11.
The counter 39 is designed such that the minimum number of
adjusting circuits to be provided or the number of counted pulses
38 to be introduced into the counter 39 before the command signal
41 is produced is decided by taking into consideration the amount
of angular rotation of the pulse motor produced by one command
signal or the pitch of the ratchet teeth of the adjusting cam
57.
The ink supply control devices shown in FIG. 7 and FIG. 8 operate
such that the pulse motor is actuated or the solenoid is energized
in accordance with the number of pulses produced by measuring the
area of image regions of a master plate to set the amount of
angular rotation of the adjusting members 46 and 57 at a certain
level so as to thereby automatically adjust the quantity of ink
supplied to the plate. Alternatively, it is possible to control the
tone of color of the printed image on copy sheets by varying the
number of revolutions of the electric motor for driving the
duplicating machine while keeping constant the amount of angular
rotation of the ink fountain roller 13 for each master plate.
It is known that the quantity of ink adhering to a sheet will be
reduced if the number of revolutions of the motor is increased and
the time interval during which the sheet is in contact with the
blanket cylinder is reduced, and that conversely a printed copy
sheet of an image dark in color can be obtained by reducing the
number of revolutions of the motor. FIG. 11 and FIG. 12 show ink
supply control devices which rely on controlling the number of
revolutions of the electric motor for driving the duplicating
machine by a comand signal from the counter 39.
In FIG. 11, resistors R.sub.n, R.sub.n.sub.-1 . . . R.sub.n.sub.-k
which are R+1 in number are each connected to a diode and one of
the adjusting circuits or flip-flops in the counter 39. The device
shown operates such that, when the counted pulses 38 are supplied
to the counter 39 and the selected flip-flop serving as the
adjusting circuit is turned on and off, the base current of a
transistor 71 is controlled and the current following to a motor
coil 72 is controlled, thereby automatically controlling the number
of revolutions of the motor 44.
The higher the image area ratio, the greater is the need to reduce
the number of revolutions of the motor. Thus, one has only to
reduce the number of revolutions of the motor in accordance with
the number of times a flip-flop of the high level is turned on.
In FIG. 11, the flip-flops F/F connected to the resistors
R.sub.n.sub.-k to R.sub.n are flip-flops Q.sub.n.sub.-k to Q.sub.n
whose Q outputs are reversed. When the number of pulses counted is
small, these flip-flops are at high level, so that no current flows
to the resistors and the quantity of the base current of the
transistor 71 is increased. This increases the quantity of a
current flowing to the coil 72, thereby increasing the number of
revolutions of the motor 44. If the number of pulses counted
increases and the flip-flops F/F are turned on, the Q outputs will
be converted to low level and a current will flow through the
resistors. Thus the base current of the transistor 71 is reduced in
quantity and the number of revolutions of the motor 44 is also
reduced.
Since Qn = 2 Qn-1, the image area ratio when the Q outputs are
converted to low level is the same as when 2Qn-1 is converted to
low level. Thus, the relation 1/Rn = 2/Rn-1 or its approximate will
be required for Rn-k to Rn. Also, it is required to provide for the
supply of the base current of the transistor to permit the motor 44
to rotate even when all the Q outputs are converted to low level.
If the quantity of ink supplied to a master plate is to be varied
from one to another of seven different levels as aforementioned,
the outputs of only three flip-flops F/F11, F/F12 and F/F13 will
have to be connected to the motor. In other words, the adjusting
circuits can be provided for eight different levels, since 2.sup.3
= 8.
By the aforementioned arrangement, a current flowing to the motor
44 will be reduced gradually as the number of pulses counted by the
counter 39 increases or the area of image regions of the master
plate increases, with the result that the number of revolutions of
the motor is reduced. Thus the rate at which the images are printed
on copy sheets can be automatically controlled in accordance with
the image area ratio of the plate even if a constant quantity of
ink is supplied to the plate. This is conducive to the production
of printed copy sheets of stabilized tone of color of the printed
images.
The circuit shown in FIG. 12 is such that the time at which a
thyristor is turned on is controlled by connecting the counter 39
to different capacitors of varying capacity so as to vary the
capacitor-resistor time-constant as shown in FIG. 13, thereby
controlling the number of revolutions of the motor 44. The numeral
81 designates an AC power source, and the numeral 82 a rectifier. A
pulsating current subjected to half-wave rectification flows
between lines 83 and 84.
An armature 85 of the motor is connected in series with the line
83, and a variable resistor 86 is connected in shunt with the line
83, with a plurality of capacitors 87, 88 and 89 being connected in
shunt with the variable resistor 86. The capacitors 87, 88 and 89
are each connected to one of the flip-flops serving as the
adjusting circuits in the counter 39. The capacity of each
capacitor increases in going from the capacitor 87 of lower level
to the capacitor 89 of higher level. That is, the time constant of
each capacitor and the variable resistor gradually increases as
shown in FIG. 13. The numeral 91 designates a pulse element
actuated by a voltage of a predetermined level, and the numeral 92
designates a thyristor adapted to be operated by the pulse
element.
Assuming that the n-k.sup.th flip flop F/F is turned on and its
output Qn-k is connected to the capacitor 87, the pulse element 91
will be turned on after lapse of a predetermined time interval and
supply a trigger pulse to the thyristor 92. With the thyristor 92
being turned on, the pulsating current from the rectifier 82 is
supplied to the armature 85. The phase angle at which the thyristor
92 is turned on may vary depending on the time constant which is
determined by the variable resistor 86 and capacitor 87.
As the number of pulses counted by the counter 39 increases and the
flip-flops of higher level are successively turned on, the
flip-flops of the counter 39 are connected to the capacitor of
larger capacity, so that the capacitor-resistor time-constant is
increased. The increase in time-constant delays the production of a
trigger pulse by the pulse element 91 when the capacitor is turned
on, and hence delays the phase of current supply to the thyristor
92. This causes a reduction in the quantity of average current
supplied to the armature 85 of the motor 44 as shown in FIG. 13,
thereby reducing the number of revolutions of the motor 44.
According to this invention, it is possible automatically to
control the number of revolutions of the motor for driving the
duplicating machine in accordance with the image area ratio by
connecting the counter 39 to different capacitors of varying
capacity in accordance with the number of pulses counted by the
counter so as to thereby vary the capacitor-resistor time-constant
and control the time at which the thyristor is turned on.
As aforementioned, code marks of any suitable identifying system
for indicating the image area ratio of a master plate may be
superposed in a non-image region of the master plate beforehand
during plate making or at any other suitable time, in place of
scanning the image surface of the plate by means of a scanning
head. When this is the case, a command signal may be issued to the
solenoid 43, pulse motor 42 or electric motor 44 as follows: When
the command signal is given to the solenoid 43 or pulse motor 42,
the code marks are read or counted and the same number of pulses as
the code marks are supplied to the solenoid 43 or pulse motor 42.
When the number of revolutions of the drive motor 44 is to be
varied, the code marks are introduced to the inputs of three
flip-flops F/F of the counter 39 each time they are read and the
number of revolutions of the drive motor is varied as the
flip-flops are turned on and off, it being understood that the
motor speed is to be varied from one to another of eight different
levels.
Code marks may be superposed on the master plate as follows: When
the total number of pulses for one master plate is 15,000, a mark
is printed or otherwise superposed in a non-image region of the
plate each time 2,048 pulses are counted or the flip-flop F/F11 is
turned on. Marks may be printed by a number of or 7 marking members
(not shown) provided as in a plate-making machine and adapted to be
actuated by means of a solenoid.
As aforementioned, the tone of color of the images printed on copy
sheets can be kept constant by automatically adjusting the quantity
of ink supplied to the master plate in accordance with the image
area ratio or by automaticaly controlling the number of revolutions
of the motor for driving the duplicating machine while keeping the
supply of ink to the plate constant. According to the invention, it
is possible automatically and simultaneously to control the supply
of ink to the master plate and the number of revolutions of the
motor for driving the duplicating machine by providing two suitable
levels A and B differing from each other in the outputs of an
amplifier of read-out means for reading image regions of the plate
and separately taking out pulses above the A level and pulses above
the B level to measure the tone of color of the images.
Read-out pulses 93 shown in FIG. 14 are produced by amplifying by
an amplifier 95 shown in FIG. 16 signals read by a read-out means
94. It will be seen that the pulses 93 are of different heights and
shapes depending on the shade of color of the images. Two levels A
and B differing from each other in height are provided in the
read-out pulses 93, and pulses higher than the A level and pulses
higher than the B level are selected by selectors 96 and 97
respectively. The selector 96 produces pulses 101 while the
selector 97 produces pulses 102 shown in FIG. 15. The pulses 101 of
the A level are supplied to a counter 98 similar to the counter 39
while the pulses 102 of the B level are supplied to a counter 99,
so that the pulses are counted separately by the two counters for
controlling the quantity of ink supplied to the plate and the
number of revolutions of the drive motor in accordance with the
numbers of pulses counted.
For example, the counter 98 may be used to control the quantity of
ink supplied to the master plate by the process described with
reference to FIG. 7 and FIG. 8, and the counter 99 may be used to
control the number of revolutions of the motor 44 for driving the
duplicating machine by the process described with reference to FIG.
11 and FIG. 12, so as to maintain the tone of color of the image
printed on the copy sheets at an optimum level at all times.
By counting the difference between the pulses of the A level and
the pulses of the B level, it is possible to obtain the value for
image regions of the plate which are low in tone of color. If the
value obtained with image regions of the plate which are high in
tone of color is added to this value, it will be possible to adjust
more strictly the quantity of ink to be supplied to the plate in
accordance with the tone of color of the image in addition to the
image area ratio.
It is to be understood that the invention is not limited to the
features and embodiments hereinabove specifically set forth but may
be carried out in other ways without departure from its spirit.
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