JPH0628959B2 - Printing machine speed control method - Google Patents

Description

TECHNICAL FIELD The present invention relates to a speed control method for a printing press.

2. Description of the Related Art Generally, in a printing press, for example, a rotary printing press, an operator can arbitrarily set a printing speed at the time of printing, that is, a rotation speed at the time of printing of a plate cylinder. And when printing starts, after the rotation speed of the plate cylinder reaches the printing speed,
Alternatively, it is performed during the rising change until the rotation speed of the plate cylinder reaches the set speed.

However, when printing is started after the rotation speed of the plate cylinder reaches the printing speed, the time required for printing becomes long as a whole, and when printing is started while the rotation speed of the plate cylinder is changing, this speed change is Since it is a linear one that changes continuously from the initial stage of rotation until it reaches the set speed, there is a difference in the printing speed in one printed matter, and the image is dark at low speed areas and light at fast speed areas. As described above, there is a drawback that uneven density occurs in the image.

There is also a method of rotating the plate cylinder from the beginning at the printing speed set by the operator, but in this case, if the printing speed is high, the drive system is suddenly loaded, and if it is used repeatedly, Durability deteriorates due to deterioration of the system,
In the worst case, there was a drawback that the drive system was damaged.

SUMMARY OF THE INVENTION It is an object of the present invention to eliminate the above-mentioned conventional drawbacks, prevent the occurrence of density unevenness in a printed matter, and provide a control method for a printing press that does not impose an excessive load on a drive system.

The present invention for achieving the above object relates to a rotation speed of a plate cylinder, a rotation speed at the time of printing of the plate cylinder, a predetermined reference speed is provided, and a printing speed larger than that is different from the reference speed. When the speed is set, in the printing process, the rotation of the plate cylinder is started at a speed equal to or lower than the reference speed, and the rotation speed of the plate cylinder is printed in integer printing units until the rotation speed of the plate cylinder reaches the printing speed. A speed control method for a printing press is characterized in that the speed is raised stepwise at a timing other than during operation.

Embodiments shown in the drawings will be described below.

FIG. 1 shows a rotary transcription printing machine, in which 1 is a cylindrical plate cylinder on the outer peripheral surface of which a stencil sheet is wound with its tip locked by a clamper device 13 and which rotates around its own central axis. In addition, an ink supply roller 2 is provided in the plate cylinder 1 to supply ink to the inner wall of the plate cylinder 1 which is a porous structure. A press roller 3 is provided below the plate cylinder 1 at a position facing the ink supply roller 2 in a state of being supported by a support arm 4a and synchronized with the rotation of the plate cylinder 1 by a drive motor (not shown). It reciprocates around the shaft 4. The press roller 3 presses the printing paper 5 sent from a paper feeding device (not shown) against the outer peripheral surface of the plate cylinder 1, and transfers the ink, which has passed through the perforated portion of the stencil sheet wrapped around the outer circumference of the plate cylinder 1, to the printing paper. To form an image.

The paper discharge / conveyance device 6 includes several endless belts 7 and four rollers 8
It is configured to have an air suction box 14 inside thereof, and the printing paper 5 on which an image has been formed is conveyed to the paper ejection tray 9. In this embodiment, the four rollers 8 are rotationally driven by the same drive motor as that of the plate cylinder 1, and thereby the endless belt 7 is moved in the direction of the arrow in the figure, and the air suction box 14 is moved.
The printing paper 5 pressed against the endless belt 7 by the suction force is conveyed in the direction of the arrow in the figure.

The plate cylinder position detection sensor 10 detects when the rotational position of the plate cylinder 1 reaches a predetermined position. Printing pressure detection sensor 1
Reference numeral 1 denotes a sensor for detecting the state of the press roller 3, which detects when the press roller 3 is pressed against the plate cylinder 1. The paper trailing edge detection sensor 12 is a sensor for detecting that the trailing edge of the printing paper 5 transported on the endless belt 7 of the transport device 6 has passed therethrough.

FIG. 3 is a flow chart of speed control, FIG. 4 is a block diagram thereof, and FIG. 5 is a diagram showing an example of speed change. The speed control method will be described with reference to these.

In order for the operator to obtain a printed matter, the rotation speed of the plate cylinder 1 is set by a speed setting key provided on an operation unit (not shown), and when the printing machine is operated, the control unit 15 sets the reference speed and operator set in advance. Is compared with the printing speed set by, and a command for rotating the plate cylinder 1 is issued.
6 and the plate cylinder 1 starts to rotate.

If the printing speed set by the operator is lower than the reference speed, the plate cylinder 1 starts to rotate at the speed set by the operator.
Speed, printing speed greater than 80 rpm, for example 5 speed (120
When setting the rpm), first set the second speed (6
The plate cylinder 1 starts rotating at 0 rpm. The rotation start speed of the plate cylinder 1 may be the first speed (40 rpm) or the third speed of the reference speed.

With the start of rotation of the plate cylinder 1, the printing paper 5 passes between the plate cylinder 1 and the press roller 3, and the press roller 3 is pressed toward the plate cylinder 1 by a cam (not shown) for printing.
The printing paper 5 is conveyed to the paper ejection tray 9 by the conveying device 6.
When the press roller 3 is pressed against the plate cylinder 1,
When the support arm 4a of the press roller 3 is rotated upward, the printing pressure detection sensor 11 is turned on, and the press roller 3 is pushed down due to the continued rotation of the plate cylinder 1, the support arm 4a is rotated downward. As a result, the printing pressure detection sensor 11 is turned off. The OFF signal of the printing pressure detection sensor 11 is input to the control unit 15, and the control unit 15 controls the drive motor 1
A command signal is sent to 6, and the rotation speed of the plate cylinder 1 is switched from the 2nd speed to the 3rd speed. Such speed conversion is performed every one rotation of the plate cylinder 1, that is, every time one sheet is printed, and the rotation speed of the plate cylinder 1 is increased stepwise until the printing speed set by the operator is reached. The speed conversion may be performed every time the plate cylinder 1 rotates a plurality of times, that is, every time a plurality of sheets are printed.

When the printing machine is not used for a long time and is used again after that, the ink to be supplied to the plate cylinder 1 is kneaded, and the idling operation for supplying the ink is performed. In this case, since the printing paper 5 is not sent, the printing pressure detection sensor 1
1 does not turn ON / OFF, and the signal is not input to the control unit 15. In this case, a signal from the plate cylinder position detection sensor 10 that generates a pulse each time the plate cylinder 1 makes one rotation is input to the control unit 15, which sends a command signal to the drive motor 16.
The rotation speed of the plate cylinder 1 can be controlled in the same manner as described above.

By the way, in general, before the printing process as described above, in order to ensure the close contact of the stencil sheet to the outer periphery of the plate cylinder 1 and to further ensure the transfer of the ink from the plate cylinder to the printing paper, it is called a plate making operation. The process is performed. This is performed by applying printing pressure by the press roller 3 while feeding the printing paper 5 at a speed considerably lower than the normal printing speed (for example, 10 rpm at the plate cylinder rotation speed). In this plate attaching operation, the slower the sheet conveying speed is, the more the cylindrical plate cylinder 1 of the stencil sheet becomes.
It is known that the adherence to the sheet is ensured and the rising of the image in the next printing process is improved.

The printing paper with the plate is conveyed to the paper ejection tray 9 by the paper ejection conveying device 6 in the same manner as in the printing process. The four rollers 8 of the conveying device 6 are driven by the plate cylinder 1 in this embodiment. Since it is the same as the drive source of the above, the printing speed becomes slower than that at the time of normal printing. Therefore, the printing paper with the plate on the endless belt 7 is conveyed at a low speed. In some cases, as shown in FIG. 2, there is a problem in that the sheet is stopped before it is completely placed on the sheet discharge tray 9. When the next printing process is started in this state, the plate-shaped paper is jammed and the subsequent paper discharge becomes jumbled.

Therefore, in this embodiment, the transport speed of the endless belt 7 of the transport device 6 is changed from the middle in order to reliably discharge the sheet transported by the plate-forming operation at the ultra-low speed onto the sheet discharge tray.

In order to ensure the plate attaching operation, it is preferable that the printing paper is conveyed at an ultra-low speed while the press roller 3 is pressed against the outer peripheral surface of the plate cylinder 1. Therefore, it is conceivable to detect this at the moment when the press roller 3 is separated from the outer peripheral surface of the plate cylinder 1 by the printing pressure detection sensor 11 and increase the driving speed of the conveying device 6 from this moment. By doing so, in the case of a large print paper (for example, B4 size), the discharge conveyance speed of the print paper 5 becomes high immediately after being released from the press roller 3, so that even the plate-making paper is discharged onto the discharge tray. 9 will be reliably discharged. However, in the case of smaller print paper, the press roller 3
At the moment when the paper is separated from the plate cylinder 1, the already printed printing paper has already passed through the transport device 6 or has reached the end point thereof, so even if the discharge transport speed is increased from there. It has no effect.

Therefore, in this embodiment, when the sheet trailing edge detection sensor 12 detects the trailing edge of the printing sheet 5, the sheet discharging and conveying speed of the conveying device 6 is increased from that moment (for example, at the plate cylinder rotation speed).
(30 to 40 rpm) makes it possible to reliably discharge the plate-making sheet onto the sheet discharge tray 9 even in the case of a small size sheet.

FIG. 6 is a flow chart for performing such control. When the plate cylinder 1 has passed the plate cylinder position detection sensor 10, the leading edge of the printing paper has already passed on the paper trailing edge detection sensor 12, so it can be determined that there is paper. If the paper trailing edge detection sensor 12 detects the paper trailing edge,
From that moment, the drive speed of the transport device 6 is changed to a higher value. If the paper is particularly large (for example, A3 size), the press roller 3 is separated from the plate cylinder 1 before the paper rear edge detection sensor 12 detects the paper rear edge. 11 is the press roller 3
The drive speed of the transport device 6 is changed to a high value from the moment when it is detected that the paper is separated from the plate cylinder 1.

Effect As described above, according to the present invention, when a predetermined reference speed is provided and a printing speed different from the reference speed and higher than the reference speed is set, in the printing process, the plate cylinder is rotated at a speed equal to or lower than the reference speed. Since the rotation of the plate cylinder is started and the rotation speed of the plate cylinder reaches the printing speed, the rotation speed of the plate cylinder is gradually increased for each integer printing unit at a timing other than during the printing pressure operation. To be printed by 1
The rotation speed does not change for printed materials one by one, so that density unevenness does not occur, and the drive system is not suddenly overloaded and the strength of the drive system parts can be reduced. Therefore, the manufacturing cost can be reduced.

[Brief description of drawings]

The drawings show one embodiment of the present invention, FIG. 1 is a schematic view of a rotary copying printing machine, FIG. 2 is a schematic view showing only a sheet discharging and conveying device, and FIG. 3 is a flow chart for speed control of a plate cylinder, FIG. 4 is a block diagram of the same as above, FIG. 5 is a graph showing an example of the speed change of the plate cylinder, and FIG. 6 is a flow chart for controlling the discharge conveyance speed. 1 ... Plate cylinder, 2 ... Ink supply roller, 3 ... Press roller, 5 ... Printing paper, 6 ... Discharging / conveying device, 7 ... Endless belt, 8 ... Roller, 9 ... Discharging table, 10 ... Plate cylinder position detection sensor 11 ... Printing pressure detection sensor, 12 ... Paper rear edge detection sensor 15 ... Control unit, 16 ... Drive motor

Claims (1)

[Claims] 1. When the printing speed of the plate cylinder is set to a predetermined reference speed and a printing speed different from the reference speed is set, a speed equal to or lower than the reference speed is set in the printing process. Characterized in that the rotation of the plate cylinder is started, and the rotation speed of the plate cylinder is increased stepwise at a timing other than during the printing pressure operation for each integer printing unit until the rotation speed of the plate cylinder reaches the printing speed. Speed control method for printing machine.