Apparatus for controlling ink supply amounts of individual zones

An apparatus for controlling ink supply amounts of individual zones by independently controlling gaps between an ink fountain roller and blades, the zones being obtained by dividing an axial length of a printing plate, includes a stepping motor arranged to correspond to each blade, a pulse generator directly coupled to the stepping motor, a waveshaper consisting of two AND gates and arranged in correspondence with the pulse generator, and a control unit including a CPU, an interface, and a memory. The stepping motor increases or decreases the gap between each blade and the ink fountain roller. The pulse generator generates two-phase pulse-like signals upon rotation of the stepping motor. The waveshaper waveshapes the pulse-like signals into two-phase pulse signals in accordance with hysteresis characteristics. The control unit supplies drive pulses to the stepping motor and detects that a control error of the stepping motor occurs when the pulse signals are not normally generated by the waveshaper in response to the drive pulses.

BACKGROUND OF THE INVENTION 
The present invention relates to an apparatus for controlling ink supply 
amounts of individual zones obtained by dividing an axial length of a 
printing plate mounted on a plate cylinder in a printing press. 
In a conventional printing press, blades corresponding to the individual 
zones of the printing plate are disposed opposite to an ink fountain and 
an ink fountain roller which are used to continuously supply optimal 
amounts of ink to the printing plate mounted on the plate cylinder. Gaps 
between the ink fountain roller and the respective blades are 
independently adjusted in accordance with an image pattern on the printing 
plate, and the amounts of ink supplied to the individual zones are 
determined. This operation is performed by remote control. For this 
purpose, gap adjusting motors are arranged for the blades, respectively, 
and potentiometers are also arranged to convert gaps into electrical 
signals. Gap signals are supplied to feedback signals to a DC servo 
control circuit, thereby controlling the ink supply amounts of the 
individual zones. 
With the above arrangement, control precision and stability are 
insufficient due to durability of servo motors and potentiometers, their 
deterioration over time, variations in impedances of connecting wires, and 
electrical noise. 
In order to eliminate the above drawbacks, stepping motors and a digital 
control circuit can be used to perform open or closed loop control in 
place of the above analog control. 
In open loop control, however, when each stepping motor cannot be rotated 
in synchronism with drive pulses and becomes out of step, amounts of ink 
cannot be appropriately supplied. In the worst case, such control becomes 
inaccurate or impossible, resulting in defective printing. Therefore, it 
is necessary to use closed loop control. 
A control origin is detected by a sensor, and control is performed in 
accordance with the detected control origin. Alternatively, a gap between 
the blade and the ink fountain roller is detected as an electrical signal 
in the same manner as in the conventional technique, or a rotational 
condition of each motor is detected by a rotary encoder or the like, and a 
detection output is used as a feedback signal. 
In closed loop control, when the control origin is detected by the sensor, 
control values excluding the original control value are not given by 
closed loop control. The out-of-step state of the stepping motor cannot be 
detected. When the potentiometer is used, its durability is degraded 
because it has mechanical contacts. At the same time, detection precision 
is limited, and high-stability, high-precision control is impossible. When 
the rotary encoder or the like is used, the out-of-step state of the 
stepping motor causes rotational torque pulsation and hunting. A hunting 
pulse is generated by the rotary encoder or the like. A count of the 
rotary encoder becomes inaccurate, and a control error occurs. 
SUMMARY OF THE INVENTION 
It is an object of the present invention to provide an apparatus for 
controlling ink supply amounts of individual zones by using stepping 
motors, wherein an out-of-step state of each stepping motor can be 
accurately detected. 
It is another object of the present invention to provide an apparatus for 
controlling ink supply amounts of individual zones by using stepping 
motors, wherein a high-precision, high-stability control state can be 
obtained. 
In order to achieve the above objects of the present invention, there is 
provided an apparatus for controlling ink supply amounts of individual 
zones by independently controlling gaps between an ink fountain roller and 
blades, the zones being obtained by dividing an axial length of a printing 
plate, a stepping motor, arranged to correspond to each blade, for 
increasing/decreasing the gap between each blade of the ink fountain 
roller, a pulse generator, directly coupled to the stepping motor, for 
generating two-phase pulse-like signals upon rotation of the stepping 
motor, a waveshaper, arranged in correspondence with the pulse generator, 
for waveshaping the pulse-like signals into pulse signals in accordance 
with hysteresis characteristics, and control means for supplying drive 
pulses to the stepping motor and detecting that a control error of the 
stepping motor occurs when the pulse signals are not normally generated by 
the waveshaper in response to the drive pulses. 
When each stepping motor is rotated in response to drive pulses, two-phase 
pulse-like signals are generated by the pulse generator. The pulse-like 
signals are waveshaped into two-phase pulse signals by the waveshaper. 
Therefore, normal rotation of each stepping motor can be detected by these 
two-phase pulse signals. In addition, since the waveshaper has hysteresis 
characteristics, the out-of-step state of each stepping motor does not 
cause hunting in the output pulses from the waveshaper even if hunting 
occurs in the pulse-like signals from the pulse generator. In this case, 
the signals from the waveshaper are two-phase pulses, so that a rotational 
direction of the stepping motor can be detected. A wrong rotational 
direction can be accurately detected, and a control error of the stepping 
motor can be immediately detected.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
The present invention will be described in detail with reference to a 
preferred embodiment in conjunction with the accompanying drawings. 
Referring to FIG. 1, blade gap adjusting switches 11.sub.l to 11.sub.n 
respectively corresponding to zones obtained by dividing an axial length 
of a printing plate are arranged in an operation panel (to be referred to 
as an OP hereinafter) 1. Indicators 12.sub.l to 12.sub.n such as bar 
indicators are arranged above the switches 11.sub.l to 11.sub.n so as to 
oppose the switches 11.sub.l to 11.sub.n, respectively. The indicators 
12.sub.l to 12.sub.n indicate gaps between the ink fountain roller and the 
blades. A main control unit (to be referred to as an MCT hereinafter) 2 
connected to the OP 1 includes a processor such as a microprocessor (to be 
referred to as a CPU hereinafter) 21 as a major component, a memory (to be 
referred to as an MM hereinafter) 22 consisting of a ROM (Read-Only 
Memory) and a RAM (Random Access Memory), and interfaces (to be referred 
to as I/Fs hereinafter) 23 to 25, all of which are connected through a bus 
26. The CPU 21 executes instructions stored in the ROM in the MM 22 and 
performs predetermined data processing while storing/reading out necessary 
data in/from the RAM in the MM 22. 
A subcontrol unit (to be referred to as an SCT) 3 connected through the I/F 
24 in the MCT 2 includes a CPU 31 similar to the CPU 21, an MM 32 similar 
to the MM 22, and I/Fs 33 to 36. The CPU 31, the MM 32, and the I/Fs 33 to 
36 are connected through a bus 37. The CPU 31 performs predetermined 
control in the same operations as in the CPU 21. 
Drive units (to be referred to as DRVs hereinafter) 4.sub.l to 4.sub.n are 
arranged for the blades of the ink fountain, respectively. These DRVs 
4.sub.l to 4.sub.n correspond to the indicators 12.sub.l to 12.sub.n, 
respectively. The DRVs are represented by the DRV 4.sub.l, as shown in 
FIG. 1. The DRV 4.sub.l includes a stepping motor (to be referred to as an 
STM hereinafter) 41 for controlling a gap between the ink fountain roller 
and a corresponding blade, and a pulse generator (to be referred to as a 
PG hereinafter) 42 directly connected to the STM 41. When a selection 
signal MC output from the I/F 36 in the SCT 3 is supplied to the DRV 
4.sub.l through a buffer 43, AND gates 46 to 52 are turned on. A driver 
(to be referred to as a DR hereinafter) 54 is driven by a forward or 
reverse rotation pulse PF or PR output from the SCT 3 through the I/F 35 
in the SCT 3 in accordance with an excitation signal generated by an 
excitation pattern generator (to be referred to as an EPG hereinafter) 53. 
Therefore, the DR 54 causes a stepwise rotation of the STM 41. 
Upon rotation of the STM 41, the PG 42 is also rotated and generates 
two-phase pulse-like signals .phi. a and .phi.b having the same phase 
difference (90.degree. out of phase) as in a two-phase encoder. The 
two-phase pulse-like signals are waveshaped into two-phase pulse signals 
.phi.A and .phi.B by the AND gates 44 and 45 which serve as a waveshaper 
having hysteresis characteristics. The two-phase pulse signals .phi.A and 
.phi.B are supplied to the I/F 34 in the SCT 3. 
A resistor R is inserted in a power source return path of the DR 54. A 
voltage generated across the STM 41 upon supply of a drive current is 
output as an excitation detection signal H to the I/F 34 in the SCT 3 
through the AND gate 48. 
When an increase/decrease in gap between each blade and the ink fountain 
roller is designated by selectively using the switches 11.sub.l to 
11.sub.n in the OP 1, the input data is supplied to the CPU 21 through the 
I/F 23. The CPU 21 outputs through the I/F 24 data which designates the 
blade subjected to an increase/decrease in gap. This data is supplied to 
the CPU 31 through the I/F 33. The CPU 31 outputs the selection signal MC 
through the I/F 36 to select a DRV 4 to be controlled. The forward or 
reverse rotation pulses PF or PR, the number of which corresponds to an 
increase/decrease in gap, are output from the I/F 35. The STM 41 is driven 
through the EPG 53 and the DR 54. The STM 41 is rotated by the number of 
steps corresponding to the number of pulses and, therefore, the gap 
between the ink fountain roller and the corresponding blade can be 
adjusted. 
Upon rotation of the STM 41, the PG 42 is rotated to output the pulse-like 
signals .phi.a and .phi.b representing a state of rotation and outputs the 
detection signal H upon application of a drive current from the DR 54. 
When the pulse signals .phi.A and .phi.B through the I/F 34 are normally 
generated, the CPU 31 determines that the out-of-step state of the STM 41 
does not occur and a control state is normal. At the same time, the CPU 31 
determines using the detection signal H that a driving state is normal. 
The SCT 3 determines whether an error occurs. If an error occurs, the SCT 
3 sends an error signal to the MCT 2. The MCT 2 indicates an error in 
accordance with the error signal. 
A blade gap indication on the OP 1 is given by a value designated by each 
of the switches 11.sub.l to 11.sub.n. 
The above control is repeatedly and sequentially performed in an order of 
DRV 4.sub.l to 4.sub.n at high speed. Control for the DRV 4.sub.l to 
4.sub.n and indications on the indicators 12.sub.l to 12.sub.n are 
performed upon operations of the OP 1. 
The I/F 25 is used for data exchange with other portions, and its data 
processing is performed by the CPU 21. 
FIG. 2 is a perspective view showing a structure of the DRV 4. The STM 41 
is fixed on a mounting plate 61 through a reduction gear box 62. The PG 42 
is directly coupled to the STM 41. A known blade gap adjusting mechanism 
(not shown) is driven through a gear 63 and a gear 64 meshed therewith. 
The gear 63 is mounted on a shaft extending through the mounting plate 61 
of the gear box 62. 
A support member 65 is fixed on the mounting plate 61 at a position 
opposite to the STM 41 and is parallel to the STM 41 and the like. A 
printed circuit board 66 having respective circuits of the DRV 4 shown in 
FIG. 1 thereon is locked so as to face the STM 41. 
FIG. 3 is a flow chart showing control procedures mainly executed by the 
CPU 31 in the SCT 3. Step 101 "ERROR FLAG OF GIVEN MOTOR SET? " is 
executed. If N (NO) in step 101, the selection signal MC is output and 
step 102 "SELECT GIVEN MOTOR" is executed. Step 111 "OUTPUT PF OR PR BY 
ONE STEP" is executed. Only the drive pulses, the number of which is 
required to rotate the STM 41 by one revolution, are output. Step 112 
".phi.A AND .phi.B NORMAL? " is executed to determine whether the pulse 
signals .phi.A and .phi.B through the AND gates 44 and 45 are normal. 
If Y (YES) in step 112, step 121 "UPDATE PRESENT POSITION DATA BY ONE STEP" 
is executed to update the data in the MM 32. Step 122 "STOP SELECTING 
GIVEN MOTOR" is executed by disabling the selection signal MC. The same 
operations after step 101 are performed for the next STM 41 through "END". 
However, if N in step 112, the pulse signals .phi.A and .phi.B are not 
normally generated, and the STM 41 is set in the out-of-step state. Step 
131 "SET ERROR FLAG OF GIVEN MOTOR" is executed. At the same time, data 
representing an error is sent to the MCT 2, and step 132 "DISPLAY ERROR OF 
GIVEN MOTOR" is executed. Flickering or a change in indication color of a 
corresponding indicator 12 on the OP 1 is performed, thereby signaling a 
control operation failure to an operator. 
Since the out-of-step state of the STM 41 can be immediately and accurately 
detected and can be immediately signaled to the operator, an appropriate 
procedure can be taken prior to production of a large amount of defective 
printed matter caused by a control error in ink supply amounts. 
Since the PG 42 generates the two-phase pulse-like signals .phi.a and 
.phi.b, the out-of-step state of the stepping motor can be accurately 
detected even if a hunting pulse is generated. 
The two-phase pulse signals .phi.A and .phi.B are used for detection of 
only the out-of-step state of the stepping motor. Therefore, this control 
scheme is not open loop control, and no control errors caused by noise or 
the like are generated. Even if the STM 41 is forcibly rotated by an 
external force, the pulse signals .phi.A and .phi.B represent a rotational 
direction and a rotational angle. Therefore, a positional error can be 
obtained by comparing the detected rotational direction and angle with 
preset data in the MM 32, thereby arbitrarily correcting the positional 
error. 
The STM 41 does not have any brush, and the PG 42 does not have any 
mechanical contacts unlike in a potentiometer or the like. Durability and 
stability of the apparatus as a whole can be improved, and high 
reliability can be assured. 
If gap control is accurate due to use of the STM 41 and the number of steps 
of the STM 41 is 10 times or more a minimum command unit, control 
precision and reproducibility can be improved. At the same time, the 
control origin of the DRV 4 does not have any mechanical limitations. 
Therefore, a control origin can be set independently of the blade gap 
adjusting mechanism. 
Since the PG 42 is directly coupled to the STM 41, generation of the 
pulse-like signals .phi.a and .phi.b upon rotation of the STM 41 is not 
delayed, and high-speed detection based on these pulse-like signals can be 
achieved. 
The STM 41 may be an ultrasonic driven motor, and the PG 42 may be a 
photoelectric pulse encoder to obtain the same effect as in the above 
embodiment. The printed circuit board 66 in FIG. 2 may be omitted, and a 
printed circuit board may be incorporated in the SCT 3 in FIG. 1. Various 
changes and modifications of the arrangements in FIGS. 1 and 2 can be made 
in accordance with selected conditions. 
The present invention is also applicable to plate registration and paper 
size presetting in a printing press with slight modifications. 
According to the present invention as has been described above, when the 
ink supply amounts of individual zones are controlled by the stepping 
motors on the basis of the gaps between the ink fountain roller and the 
blades, the out-of-step states of the stepping motors can be independently 
detected, and the high-precision, high-stability control state can be 
achieved. Various effects can be obtained in control for ink supply 
amounts of the individual zones in various printing presses.