METHOD AND APPARATUS FOR CONTROL OF THE SUPPLY OF INK FOR OFFSET DUPLICATING MACHINES
United States Patent 3841215
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.
US Patent References:
/1275642.html
Rechman - August 1918 - 1275642
Apparatus for indicating changes in ink
Crosfield - January 1961 - 2968988
Colour printing
Crosfield et al. - January 1961 - 2969016
Method and means for measuring ink film thickness
Bradford et al. - February 1961 - 2971461
Method and apparatus for predetermining settings for ink fountain keys
Norton - May 1965 - 3185088
/1275642.html
Rechman - August 1918 - 1275642
Apparatus for indicating changes in ink
Crosfield - January 1961 - 2968988
Colour printing
Crosfield et al. - January 1961 - 2969016
Method and means for measuring ink film thickness
Bradford et al. - February 1961 - 2971461
Method and apparatus for predetermining settings for ink fountain keys
Norton - May 1965 - 3185088
Application Number:
05/303862
Publication Date:
10/15/1974
Filing Date:
11/06/1972
View Patent Images:
Export Citation:
Assignee:
Ricoh Co., Ltd. (Tokyo, JA)
Primary Class:
Other Classes:
101/350.100, 101/484
International Classes:
B41L27/14; B41L39/00; B41L27/00; B41L25/00
Field of Search:
101/349,350,148,365,363,147,426
US Patent References:
| 3329087 | Regulation of repetitive pattern repeat length on a web | July 1967 | Sandor et al. | |
| 3439175 | MEASURING DEVICE FOR MEASURING A LAYER OF LIQUID ON A SURFACE | April 1969 | Kammuller et al. | |
| 3562491 | MASTER CONTROLLED COPY COUNT METHOD AND APPARATUS | February 1971 | Branfield | |
| 3567923 | SYSTEM FOR MONITORING AND CONTROLLING THE COLOR DENSITY OF INK DURING PRINTING | March 1971 | Hutchison | |
| 3584579 | SENSING PROBE AND CONTROL FOR PRESS INKER EMBODYING SAME | June 1971 | Rothenberg | |
| 3585928 | PRINTING PLATE MAKING MACHINE | June 1971 | Kaneko | |
| 3650204 | REPROGRAPHY MACHINE CONTROLLED BY INFORMATION ON MASTER | March 1972 | Burger et al. | |
| 3707123 | APPARATUS FOR DETECTING CHANGES IN THE THICKNESS OF AN INK FILM ON THE ROLLER SYSTEM OF A PRINTING PRESS | December 1972 | Heasman et al. |
Primary Examiner:
Fisher, Reed J.
Attorney, Agent or Firm:
Cooper, Dunham, Clark, Griffin & Moran
Parent Case Data:
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
9. In a method of offset-printing a copy sheet with an image from a master plate, the steps of
10. Offset printing apparatus including in combination,
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,
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:
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:
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.
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
9. In a method of offset-printing a copy sheet with an image from a master plate, the steps of
10. Offset printing apparatus including in combination,
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,
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:
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:
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 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 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 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 n , R n -1 . . . R n -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 n -k to R n are flip-flops Q n -k to Q 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 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 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.
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 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 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 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 n , R n -1 . . . R n -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 n -k to R n are flip-flops Q n -k to Q 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 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 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.