Control of an applicator roll of a printing machine

Abstract

In a method for controlling an application roller of a printing press, the peripheral speed of the application roller is changed relative to the peripheral speed of a form cylinder such that a fluid film disturbance (18) transferred from the form cylinder to the application roller and, after one revolution of the application roller, transferred back from the application roller to the form cylinder, is transferred to the form cylinder at the immediately following revolution of the form cylinder at least two millimeters offset relative to the previous transfer, and that the fluid film disturbance (18) is transferred back at the same circumferential angle location of the form cylinder no earlier than after three revolutions of the form cylinder.

Description

[0001] The present invention relates to a method and devices for controlling an application roller of a printing press.

[0002] Application rollers are used to apply a fluid to a forming cylinder, on which the application roller rolls. There are printing forming cylinders and coating forming cylinders.

[0003] For example, the prior art according to DE 10 2004 042 265 A1 and DE 10 2011 010 720 A1 describes methods in which dampening agent is applied to a printing cylinder, here called a plate cylinder, using a dampening roller.

[0004] In DE 197 33 644 A1 a printing machine is described whose form cylinder is driven by a first drive and whose application roller is driven by a second drive, wherein the ratio of the circumferential speeds of the form cylinder and the application roller can be continuously adjusted to each other.

[0005] EP 0 653 302 A1 describes a speed control system in which the speeds of an ink application roller and a forming cylinder are recorded and transferred to a computer to calculate a speed compensation for the ink application roller.

[0006] In DE 10 2015 209 521 A1 an offset printing machine is described whose inking unit is connected to a form cylinder via a planetary gear drive.

[0007] The invention arose from the following background: An inking roller projects a "ghost image" of the printing form onto its surface, which, after one rotation of the inking roller, is transferred back to the printing cylinder and can thus be transferred as a disruptive feature onto the substrate. These disruptions can have edges running in the printing direction or around the cylinder's circumference, as well as edges running perpendicular to the printing direction. To eliminate disruptions with edges running in the printing direction, the inking rollers of offset printing presses traverse axially. This laterally displaces the disruption picked up by the inking roller, thereby reducing the contrast of the disruption. To reduce disruptions with edges running perpendicular to the printing direction, several inking rollers with different diameters are used in offset inking units.However, the use of multiple application rollers is generally not possible in a dampening system or a coating system due to cost and space constraints.

[0008] The invention is based on the objective of specifying a further method for controlling an application roller of a printing press and of creating at least one device for carrying out the method.

[0009] The problem is solved by a method according to claim 1, namely a method for controlling an application roller of a printing press, characterized in that the peripheral speed of the application roller relative to the peripheral speed of a forming cylinder is changed by a corresponding control of a motor or by a correspondingly dimensioned gearbox such that a fluid film disturbance transferred from the forming cylinder to the application roller and, after one revolution of the application roller, transferred back from the latter to the forming cylinder, is transferred to the forming cylinder at the immediately following revolution of the forming cylinder at least two millimeters offset relative to the previous transmission, and that the fluid film disturbance is transferred back at the same circumferential angle of the forming cylinder no earlier than after three revolutions of the forming cylinder.

[0010] An advantage of the method according to the invention is that it significantly reduces the contrast of disturbances running perpendicular to the printing direction. It prevents such disturbances from being transferred to the same position on the circumferential surface of the printing cylinder with each revolution. The circumferential displacement of the disturbance from revolution to revolution prevents the formation of a sharp, stationary contrast edge in the fluid film on the printing cylinder, thereby greatly reducing the visual perception of the disturbance in the printed image.

[0011] The stated limits apply to the common format sizes of printing presses.

[0012] Several further developments of the inventive method are possible: A repetition rate - that is, the number of revolutions of the forming cylinder until the application roller unwinds again at the same circumferential angle point of the forming cylinder - can be set.

[0013] A speed difference between the peripheral speed of the application roller and the peripheral speed of the forming cylinder can be set.

[0014] The problem underlying the invention is further solved by a device according to claim 4, namely a device for controlling an application roller of a printing press, characterized in that a motor is connected to the application roller via a planetary gear, wherein the motor is controlled in such a way that the peripheral speed of the application roller is changed relative to the peripheral speed of a forming cylinder such that a fluid film disturbance transmitted from the forming cylinder to the application roller and, after one revolution of the application roller, transmitted back from the latter to the forming cylinder, is transmitted to the forming cylinder at the immediately following revolution of the forming cylinder at least two millimeters offset relative to the previous transmission and is transmitted back to the forming cylinder at the earliest after three revolutions of the forming cylinder at the same circumferential angle of the forming cylinder.

[0015] One advantage of the technical solution with the planetary gearbox is that a small motor can be used, which is cost-effective and requires little installation space.

[0016] The problem is also solved by a device according to claim 5, namely a device for controlling an application roller of a printing press, characterized in that two meshing gears are provided for driving the application roller, the gears being eccentrically mounted on shafts, so that the circumferential speed of the application roller is changed relative to the circumferential speed of a forming cylinder in such a way that a fluid film disturbance transmitted from the forming cylinder to the application roller and, after one revolution of the application roller, transmitted back from the latter to the forming cylinder, is transmitted to the forming cylinder at the immediately following revolution of the forming cylinder at least two millimeters offset relative to the previous transmission, and the fluid film disturbance is transmitted back at the same circumferential angle of the forming cylinder no earlier than after three revolutions of the forming cylinder.

[0017] One advantage of the alternative solution with the gears and eccentric shafts is that no additional motor is required for the application roller, which is cost-effective.

[0018] The problem is also solved by a device according to claim 6, namely a device for controlling an application roller of a printing press, characterized in that a motor is connected to the application roller for drive purposes, that a gear train is provided for driving a form cylinder, that the motor is not connected to the gear train, wherein the motor is controlled in such a way that the peripheral speed of the application roller is changed relative to the peripheral speed of the form cylinder,that a fluid film disturbance transferred from the forming cylinder to the application roller and, after one revolution of the application roller, transferred back from the latter to the forming cylinder, is transferred to the forming cylinder at the immediately following revolution of the forming cylinder offset by at least two millimeters relative to the previous transfer, and that the fluid film disturbance is transferred back to the forming cylinder at the same circumferential angle point of the forming cylinder no earlier than after three revolutions of the forming cylinder.

[0019] One advantage of this solution with the separate motor of the application roller, which is present in addition to a main motor that drives the forming cylinder via the gear train, is that no complex gearbox is required.

[0020] The method and devices according to the invention are particularly advantageous in applications where the application roller is a single dampening roller in an offset printing unit or a single coating roller in a coating unit. In this case, the offset printing unit comprises no other dampening roller besides the single dampening roller, and the coating unit comprises no other coating roller besides the single coating roller.

[0021] Constructively and functionally advantageous further developments of the invention result from the following description of exemplary embodiments and the associated drawing.

[0022] It shows: Figure 1 shows an application roller slip-mold cylinder revolutions diagram, Figure 2 shows an application roller unwind-mold cylinder revolutions diagram, Figure 3 shows an application roller control device with a planetary gear, Figure 4 shows an application roller control device with gears with eccentric shafts, and Figure 5 shows an application roller control device with an application roller separate motor.

[0023] In the Figures 3-5 The same elements are designated with the same reference symbols, so that no repeated descriptions of these elements are necessary.

[0024] This is in the Figures 3-5Each figure schematically depicts an offset printing unit of a sheet-fed printing press. The offset printing unit comprises a printing cylinder 1 and a dampening unit with a single application roller 2 and a dampening roller 3. During printing, the application roller 2 rolls along the printing cylinder 1 to apply the dampening solution. Preferably, the diameter of the application roller 2 is smaller than the diameter of the printing cylinder 1. The rotation of the printing cylinder 1 is driven by a main motor of the sheet-fed printing press via a gear train 4, which includes a gear 5 that is coaxially and rotationally fixed to the printing cylinder. The rotation of the application roller 2 is driven by circumferential friction through the dampening roller 3, which bears against the printing cylinder 2.

[0025] In the exemplary embodiment in Figure 3Gear 5 is engaged with gear 6, which is coaxially and rotationally fixed to a ring gear 7. Gears 5 and 6 have helical teeth. A sun gear 9 is fixedly mounted on the shaft of an electric motor 8, while gear 10 is rotatably mounted. This gear 10 engages with gear 11, which is coaxially and rotationally fixed to the friction roller 3 via a shaft 15. Gear 10 eccentrically carries a planetary gear 12, which, together with ring gear 7 and sun gear 9, forms a planetary gear set 13. Gear 10 forms the rotating hub of the planetary gear set 13. The planetary gear set 13 has two inputs and one output and is therefore a superimposed gear set. One input (ring gear 7) is driven by the main motor via the gear train 4, and the other input (sun gear 9) is driven by the motor 8. The rotational speed of the output (gear 10) results from the superposition of the rotational speeds of the two inputs.The advantage is that a significant portion of the output torque, and thus the torque of the application roller 2, is supplied by the main motor, and only a small portion by motor 8, which is why the latter can be small. Motor 8 is program-controlled in such a way that the... Figure 1 The speed profile of the application roller 2 is shown. The main motor runs at a constant speed.

[0026] In the exemplary embodiment in Figure 4Gears 6, 10, and 11 are also present, with gear 6 being non-rotatably connected to gear 10 via a shaft 14. Gears 10 and 11 are each mounted off-center on shafts 14 and 15, respectively. An eccentricity e exists between a central axis M and the shafts 14 and 15 of the respective gears 10 and 11. This eccentricity e results in a change in the gear pitch circle, causing the friction roller 3, and consequently the application roller 2, to continuously change their speed relative to the speed of the forming cylinder 1. The eccentricity e is dimensioned such that a sinusoidal speed profile of the application roller 2 results. This sine curve, like the sawtooth curve in Figure 1A period of three revolutions of the forming cylinder 1. The amplitude of the sine curve corresponds to the peak value of the sawtooth curve. The rotation of the application roller 2 is driven exclusively by the main motor, which also drives the rotation of the forming cylinder 1.

[0027] In the exemplary embodiment in Figure 5 The rotation of the application roller 2 is driven by an electric motor 16, which is present in addition to the main motor, which also drives the rotation of the forming cylinder 1 via the gear train 5. The motor 16 is coupled to the shaft 15 via a coupling 17, which is rotationally fixed to the friction roller 3. Here, the motor 16 is arranged coaxially with the friction roller 3 as a direct drive. The motor 16 is program-controlled such that the Figure 1 The speed profile of the application roller 2 is shown. The main motor runs at a constant speed.

[0028] The in the Figures 3-5 The presented design solutions can be transferred from the offset printing unit to a coating unit with minor adjustments. For example, when transferring the embodiment from Figure 5 In a coating unit, the friction roller 3 is omitted and the motor 16 is arranged coaxially with the application roller 2 as a direct drive and is connected to the application roller 2 via a coupling and a shaft.

[0029] Figure 1 shows a diagram on whose ordinate the relationship between the circumferential speed of the application roller 2 from the Figures 3-5 and the speed difference (slippage) existing in percent for the circumferential speed of the form cylinder 1 is specified, and on its abscissa the number of revolutions of the form cylinder 1, which correspond to the number of printed sheets, is specified.

[0030] Figure 2The diagram shows the ordinate of which indicates the development of the circumferential surface of the application roller 2 in millimeters, and the abscissa of which indicates the number of revolutions of the printing cylinder 1, corresponding to the number of printed sheets. In the Figure 1 and 2 In the example shown, the application roller 2 has a diameter D = 64 mm (see...). Figures 3-5 ) on the forming cylinder 1. The application roller 2 changes its peripheral speed by -1% per revolution of the forming cylinder 1 for two revolutions and then returns to its initial speed, which is 10% lower (-10%) than the peripheral speed of the forming cylinder 1. This results in an offset of the development of the application roller 2 relative to the forming cylinder 1 of: D × π × 1 % = 64 mm × π × 0 , 01 = 2 , 01 mm ≈ 2 mm Versatz pro Umdrehung des Formzylinders 1 .

[0031] In Figure 2It can be seen that the fluid film disturbance 18, located at 221 mm during the first rotation of the forming cylinder 1, is located at 223 mm during the second rotation of the forming cylinder 1, resulting in the offset calculated above (223 mm - 221 mm = 2 mm). After the speed of the application roller 2, and thus the slippage, was reduced by 1% for each of two rotations of the forming cylinder 1, i.e., to -12%, and then increased again to the initial value of -10% for one rotation of the forming cylinder 1, the cycle begins again, so that the fluid film disturbance is transferred back to the forming cylinder 1 at the same circumferential angle every three rotations of the forming cylinder 1. Reference symbol list

[0032] 1. Forming cylinder 2. Application roller 3. Friction roller 4. Gear train 5. Gear 6. Gear 7. Ring gear 8. Motor 9. Sun gear 10. Gear 11. Gear 12. Idler wheel 13. Planetary gear 14. Shaft 15. Shaft 16. Motor 17. Clutch 18. Fluid film disturbance Diameter e Eccentricity M Central axis

Claims

1. Method for controlling an applicator roller (2) of a printing press, characterized in that the circumferential speed of the applicator roller (2) relative to the circumferential speed of a form cylinder (1) is changed by a corresponding actuation of a motor (8, 16) or by a correspondingly dimensioned transmission (18) in such a way that a fluid film disturbance (18) transmitted from the form cylinder (1) to the applicator roller (2) and retransmitted by the applicator roller (2) to the form cylinder (2) after one revolution of the applicator roller is transmitted to the form cylinder (1) offset by at least two millimeters relative to the preceding transmission during the immediately following revolution of the form cylinder (1), and that the fluid film disturbance (18) is repeatedly retransferred at the same circumferential angle point of the form cylinder (1) at the earliest after three revolutions of the form cylinder (1).

2. Method according to claim 1, characterized in that a repetition rate - i.e. the number of revolutions of the form cylinder (1) until the applicator roller (2) reaches the same circumferential angle point of the form cylinder (1) again - is set.

3. Method according to claim 1, characterized in that a speed difference is set between the circumferential speed of the applicator roller (2) and the circumferential speed of the form cylinder (1).

4. Device for controlling an applicator roller (2) of a printing press, for carrying out the method according to claim 1, characterized in that a motor (8) is drive-connected to the applicator roller (2) via a planetary gear (13), the motor (8) being actuated in such a way that the circumferential speed of the applicator roller (2) is changed relative to the circumferential speed of a form cylinder (1) in such a way, that a fluid film disturbance (18) transferred from the form cylinder (1) to the applicator roller (2) and retransferred from the latter to the forming cylinder (1) after one revolution of the applicator roller (2) is transferred to the form cylinder (1) offset by at least two millimeters relative to the previous transfer during the immediately following revolution of the form cylinder (1) and the fluid film disturbance (18) is repeatedly retransferred at the same circumferential angle point of the form cylinder (1) at the earliest after three revolutions of the form cylinder (19).

5. Device for controlling an applicator roller (2) of a printing press, for carrying out the method according to claim 1, characterized in that two meshing gear wheels (10, 11) are provided for driving the applicator roller (2), the gear wheels (10, 11) being seated eccentrically on shafts (14, 15), so that the circumferential speed of the applicator roller (2) is changed relative to the circumferential speed of a form cylinder (1) in such a way that a fluid film disturbance transferred from the form cylinder (1) to the applicator roller (2) and retransferred by the applicator roller (2) to the form cylinder (1) after one revolution of the applicator roller is transferred to the form cylinder (1) offset by at least two millimeters relative to the previous transfer during the immediately following revolution of the form cylinder (1) and the fluid film disturbance is retransferred repeatedly at the same circumferential angle point of the form cylinder (1) at the earliest after three revolutions of the form cylinder (1).

6. Device for controlling an applicator roller (2) of a printing press, for carrying out the method according to claim 1, characterized in that a motor (16) is drive-connected to the applicator roller (2), that a gear train (4) is provided for driving a form cylinder (1), that the motor (16) is unconnected to the gear train (4), the motor (16) being controlled in such a way that the circumferential speed of the applicator roller (2) is changed relative to the circumferential speed of the form cylinder (1) in such a way that a fluid film disturbance transferred from the form cylinder (1) to the applicator roller (2) and retransferred by the applicator roller (2) to the form cylinder (1) after one revolution of the applicator roller is transferred to the form cylinder (1) offset by at least two millimeters relative to the previous transfer during the immediately following revolution of the form cylinder (1) and the fluid film disturbance is retransferred repeatedly at the same circumferential angle point of the form cylinder (1) at the earliest after three revolutions of the form cylinder (1).

7. Device according to one of the claims 4 to 6, characterized in that the applicator roller (2) is a dampening applicator roller in an offset printing unit.

8. Device according to claims 4 to 6, characterized in that the application roller (2) is a varnish application roller in a coating unit.

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