GB2273910A

GB2273910A - Compensating for failure of an isolated zone metering device in an ink duct

Info

Publication number: GB2273910A
Application number: GB9400051A
Authority: GB
Inventors: Holger Dick; Jurgen Marschar; Gerhard Pannars
Original assignee: Heidelberger Druckmaschinen AG
Current assignee: Heidelberger Druckmaschinen AG
Priority date: 1993-01-05
Filing date: 1994-01-04
Publication date: 1994-07-06
Anticipated expiration: 2014-01-04
Also published as: JPH06238873A; JP3415665B2; DE4300071C2; DE4300071A1; GB9400051D0; GB2273910B

Description

2273910 Process and device for the control of zonal inking in a printing

unit The invention relates to a process and a device for the control of zonal inking in a printing unit of a printing press according to claim 1 and claim 8.

In order to cater for the differint ink demands in individual regions of a printed image, the ink is usually supplied zonally to a printing unit. Known already from DE 26 48 098 C3 is an apparatus for the zonal metering of a liquid medium on a roller in a printing press with zone-wide metering elements. These metering elements comprise supporting and metering regions in the axial direction of the roller. While the supporting regions are constantly in contact with the roller, the metering regions are set, independently of one another and depending on the ink demand, to a suitable gap with respect to the roller. According to one embodiment, the metering elements consist of cylinders rotatable in the circumferential direction, with the metering regions themselves being in the form of eccentric recesses. In a further embodiment, it is provided that the metering elements are in the form of flat pieces, said flat pieces being, with one side, in direct tangential contact with the roller as a supporting region, being tangentially displaceable with respect to the roller and comprising in their front region a skimming edge behind which starts, as a metering region, an obliquely inwardly extending recess. The setting of the metering elements with respect to the roller to which the ink is transferred is accomplished either manually or, alternatively, is automatically controlled through the intermediary of a motor with potentiometer feedback.

In the event of the failure of an adjusting mechanism for a metering element of a printing unit, for example because of a mechanical defect, it may be the case that, with the corresponding metering element incorrectly set, the printing unit can no longer be used or can be used only to a limited extent; that is, in the worst case, the printing press will stand idle until the defect has been remedied.

The object of the present invention is to propose a process and a device, said process and device ensuring an acceptable printed product even in the event of the failure of an ink-metering element.

The object of the invention is achieved by the characterizing parts of claim 1 and claim 9, respectively.

According to an advantageous embodiment of the process according to the invention, it is provided that, if using a continuous-feed inking unit, in which the ink is supplied directly from an ink-duct roller into the inking unit, the correct ink flow in the incorrectly set ink zone is regulated through the rotational speed of the ink-duct roller. If using a vibrator-type inking unit, in which a vibrator roller is disposed between ink-duct roller and one of the inking-unit rollers, the correct ink demand in the incorrectly set ink zone is regulated through the lift of the ink-duct roller. In either case, the ink supply is set such that the setpoint ink demand is achieved in the incorrectly set ink zone.

In order also to supply the setpoint ink demand to the other, originally correctly set ink zones, these ink zones, too, must be adjusted, with it being necessary to distinguish between two cases: the incorrectly set ink zone is too high or it is too low. In the former case, this reduces the ink flow in general; consequently, all adjustable ink zones must be set higher. In the second case, the situation is the opposite one - the ink flow is increased in general; consequently, all the originally correctly set ink-metering elements must be set lower. The positions of the ink-metering elements are corrected such that the setpoint ink demand is always supplied to the corresponding printing unit.

According to a further embodiment of the process according to the invention, it is proposed that the ink flow to the incorrectly set ink zone is corrected through the lateral deflection of at least one ink distributor roller of the inking unit of the corresponding printing unit. Whereas, in the aforementioned embodiments, the ink supply to the incorrectly set ink zone is correctly set by changing the rotational speed of the ink-duct roller or by changing the lift of the ink-duct roller, with all other ink zones being adapted to the changed ink supply, this further embodiment involves the respective ink demand in the adjacent zones being determined by means of an iterative process. The required ink demand in the individual zones is successively calculated such that the surplus ink is transported out of the incorrectly set ink zone or such that the missing quantity of ink is transported into the incorrectly set ink zone. In particular, the ink demand in the ink zones directly adjacent to the incorrectly set ink zone is calculated by means of the following formula:

4 &E(.-m3 and a (1-2b) E... c..x-bE (c-2.3 -bE czcm 3 AE The individual variables have the following significance:

x denotes the incorrectly set ink zone; AE(.-., and AE(,m3 represent the change in position of the adjacent zones (x+l) and (x-1); denotes the setpoint value of the incorrectly set ink zone; and denotes the actual value of the set ink zone x; E(,c-m3 and E(-,.m) stand for the original setpoint values of ink zones (x+l) and (x-1) directly adjacent to the incorrectly set ink zone x; factor a represents the distribution of the influence of the two ink zones (x+l) and (x-1) directly adjacent to the incorrectly set ink zone x; and b denotes the percentage of ink transport from the adjacent zones (x+l) and (x-1) to the incorrectly set ink zone x.

As already mentioned, the setpoint ink demand for the printing unit is calculated by means of an iterative process. In a further development of the process according to the invention, it is proposed that the ink zones (x+l) and (x-1), for which the corrected ink demand has been calculated, are defined as the nonsettable ink zone x. Then, using the aforementioned formula, the setpoint ink demand is determined in zone (x-2) or in zone (x+2). This process is continued until the correct ink demandhas been determined for all the ink zones of the printing unit.

Since factor a in the aforementioned formula, which describes the distribution of the inffuence of the two ink zones directly adjacent to the incorrectly set ink zone, is subject to certain parameters, an advantageous embodiment of the process according to the invention proposes the following: First, an approximation to the desired ink demand in the incorrectly set ink zone is achieved by changing the rotational speed of the ink-duct roller or by changing the ink-duct-roller lift of the inking unit. Then, the respectively required ink demand in the individual ink zones is calculated using the aforementioned formula.

According to an advantageous further development of the process according to the invention, it is proposed that the percentage b of the ink volume transferred from the adjacent zones to the incorrectly set ink zone is determined experimentally or arithmetically as a function of the lift of the ink distributor roller.

The invention is explained in greater detail with reference to the following drawings, in which:

Fig. 1 shows a longitudinal section through a printing press with two printing units; Fig. 2 shows a longitudinal section through an ink duct of a printing unit; Fig. 3a shows the zonal setpoint ink demand, the actual ink demand and the corrected ink demand for an incorrectly (too high) set ink zone, according to a first embodiment of the process according to the invention; Fig. 3b shows the zonal setpoint ink demand, the actual ink demand and the corrected ink demand for an incorrectly (too low) set ink zone; Fig. 4a shows the zonal setpoint ink demand, the actual ink demand and the corrected ink demand for an incorrectly (too high) set ink zone, according to a further embodiment of the process according to the invention; and Fig. 4b shows the zonal setpoint ink demand, the actual ink demand and the corrected ink demand for an incorrectly (too low) set ink zone.

Fig. 1 shows a longitudinal section through two printing units 2 of a printing press 1. Each printing unit has the usual cylinder configuration, consisting of plate cylinder 3, rubber-blanket cylinder 4 and impression cylinder 5. A storage drum 6 is disposed between the impression cylinders 5 of the two printing units 2. Ink 10 and damping solution are supplied to the plate cylinder 3 via the inking unit 7 and the damping unit 8, respectively. The inking unit 7 consists of a multiplicity of individual rollers, of which the rollers 16 are in the form of ink distributor rollers. Said ink distributor rollers 16 execute a lateral motion, with the so-called distributor-roller lift being automatically adjusted by means of a feedback-control apparatus.

Fig. 2 shows a longitudinal section of an ink duct 9 of a printing unit 2. The ink 10 is transferred, zonally metered, from the inking unit 9 onto the ink-duct roller 11 and from there into the inking unit 7 (not separately shown). In the case s6wn, the ink is transferred through the intermediary of a so-called continuous-feed inking unit, i.e. the roller 15 is constantly in contact with the ink-duct roller 11.

The zonal metering of the ink 10 is effected by metering elements 13. Said metering elements are in the form of cylinders comprising supporting regions and metering regions. The supporting regions are in the edge regions of the cylindrical metering elements 13 and are constantly in contact with the ink-duct roller 11. The metering regions are in the form of eccentric recesses, with the result that the transfer of ink onto the inkduct roller 11 can be controlled by rotation of the cylinders about their own axis. The adjustment of the metering elements 13 is accomplished either manually or automatically by means of a motor with potentiometer feedback.

In the case of a continuous-feed inking unit, the quantity of ink supplied to a printing unit is regulated through the rotational speed of the ink-duct roller. Conventionally, the ink-duct roller is associated with a separate drive. In the case of a vibrator-type inking unit, the lift of the ink-duct roller is likewise regulated by a separate drive. Both instances of regulation serve to regulate the supply of ink to the respective printing unit 2.

Fig. 3a shows the zonal setpoint ink demand, the actual ink demand and the corrected ink demand for an incorrectly (too high) set ink zone x. The setpoint ink demand of the printing unit exhibits a uniform distribution, i.e. all ink-metering elements 13 supply the same proportion of ink to the printing unit 2.

Since the adjusting mechanism of ink zone x is defective, the quantity of ink supplied to ink zone x is too high. In order, nevertheless, to obtain an optimal printed product, the quantity of ink supplied to the printing unit 2 is reduced through control of the ink duct roller 11 or of the ink-duct-roller lift in such a manner that ink zone x receives the setpoint ink demand In order now to ensure that all other ink zones are capable of covering the setpoint ink demand, it is necessary for the corresponding ink- metering elements to be opened further. The correction value E=... is calculated by means of a comparison of the setpoint ink demand E_r_..:L, c_ with the actual ink demand in the corresponding printing unit 2.

Fig. 3b shows the opposite case: Through an incorrect setting of the defective zone x, too little ink is supplied to that zone. The setpoint ink demand is supplied to the defective ink zone x by adjusting the inkduct roller 11 or by changing the operating frequency of the vibrator roller 12. In order also to ensure that the setpoint ink demand Emmt-r,, =úrit- of the inking unit 2 will continue to be met, all further ink zones are set lower accordingly.

Fig. 4a and 4b show a further embodiment of the process according to the invention. Whereas, according to the first embodiment of the process according to the invention, the ink demand in the defective ink zone x is corrected by changing the ink supply in such a manner that it conforms to the setpoint ink demand of said ink zone x, the further embodiment of the process according to the invention makes use of lateral distribution-and thus of interzonal ink transport.

Fig. 4a shows the positions of the ink-metering elements 13 with the ink zone x incorrectly (too high) set, whereas Fig. 4b shows the situation for an incorrectly (too low) set ink zone x. The actual ink demand E 2.

of the adjacent zones (x-1) and (x+l) to the defective ink zone x is calculated using the aforementioned formula I. As soon as the actual ink demand E..,_. for zones (x-1) and (x+l) is known, said ink zones are defined as non- adjustable ink zones x; then, the calculation is performed for ink zones (x-2) and (x+2). This process is performed successively for all ink zones n of the printing unit 2. The ink transport from one ink zone to another can also be influenced, for example, by the lift of the ink distributor rollers 16.

In certain extreme cases, the setpoint ink demand in the printing unit 2 cannot be covered by lateral distribution. According to an embodiment of the process according to the invention, a combination of the first and second embodiments is provided, i.e. first, the setpoint ink demand in the incorrectly set ink zone x is approximately achieved by changing the rotational speed of the ink-duct roller 11 or by changing the ink-duct-roller lift; then, the precise, corrected ink demand in the individual ink zones n is calculated by calculating the ink flow between the individual ink zones as a result of lateral distribution.

- 10

Claims

CLAIMS:

1. Process for the control of zonal inking in a printing unit of a printing press in the event of the failure of at least one adjusting mechanism for an ink-metering element associated with an ink zone, c h a r a c t e r i z e d i n t h a t the actual ink demand supplied to the printing unit (2) in the case of incorrect setting of the ink-metering elements (13), and the setpoint ink demand supplied to the printing unit (2) in the case of correct setting of the ink metering elements (13), are calculated, in that the actual ink demand is compared with the setpoint ink demand and in that the actual settings of the adjustable ink-metering elements are corrected such that the setpoint ink demand is supplied to the printing unit (2).

2. Process according to claim 1, c h a r a c t e r i z e d i n t h a t if using a continuous-feed inking unit, in which the ink (10) is supplied directly from an ink-duct roller (11) into the inking unit (7), the correct ink flow in the incorrectly set ink zone (x) is regulated through the rotational speed of the inkduct roller (11).

3. Process according to claim 1, c h a r a c t e r i z e d i n t h a t if using a vibrator-type inking unit, in which a vibrator roller (12) is disposed between ink-duct roller (11) and.one of the inking-unit rollers, the correct ink flow in the incorrectly set ink zone (x) is regulated through the lift of the ink-duct roller.

4. Process according to claim 1, c h a r a c t e r i z e d i n t h a t the ink flow to the incorrectly set ink zone (x) is corrected through the lateral deflection of at least one ink distributor roller (16) of the inking unit (7) of the corresponding printing unit (2).

5. Process according to claim 4, c h a r a c t e r i z e d i n t h a t the change in the position of the ink-metering elements (13) associated with the ink zones (x+l, x-1) directly adjacent to the incorrectly set ink zone (x) is calculated by means of the following formula:

AE(,m) and b where the individual variables have the following significance:

X Incorrectly set ink zone that cannot be adjusted; AE(._jL) Change in position of the adjacent zones and AEc..%) x+l and x-l; Setpoint value of the incorrectly set ink zone x; Actual value of the incorrectly set ink zone x; Original setpoint values of ink zones x+l and E(...%) and x-1 directly adjacent to the incorrectly set ink zone x; a, where Distribution of the influence of the two 0 < a <1 ink zones x+l and x-1 directly adjacent to the incorrectly set ink zone x; b Percentage of ink transport from the adjacent zones x+l and x-1 to the incorrectly set ink zone x.

6. Process according to claim 5, c h a r a c t e r i z e d i n t h a t the factor a is subject to printing-press-specific parameters and in that, outside of the preselected limits, the ink quantity (E<.,,-m) or E(...,, ) transferred from or to the incorrectly set ink zone (x) is changed by changing the rotational speed of the ink-duct roller (11) or the operating frequency of the vibrator roller (12) of the inking unit (7).

7. Process according to claim 5, c h a r a c t e r i z e d i n t h a t the percentage b of the ink quantity (Ec.,.%) or E(.,_my) transferred from the adjacent zones (x+l or x-1) to the incorrectly set ink zone (x) is determined experimentally or arithmetically as a function of the lift of the ink distributor roller (16).

8. Process according to claim 5, c h a r a c t e r i z e d i n t h a t iteratively, the calculated position of each inkmetering element (13) of the ink zone (x+m or x-m, m>2) is defined as a non-settable zone (x) and in that the changes in the setting of the ink-metering elements (13) of the adjacent zones (x+n or x-n, where n = m+l) are then calculated.

Device for the control of zonal inking in a printing unit of a printing press in the event of the failure of at least one adjusting mechanism for an ink-metering element associated with an ink zone, c h a r a c t e r i z e d i n t h a t a computing/control apparatus (17) is provided, said computing/control apparatus (17) calculating the actual ink demand supplied to the printing unit (2) in the case of incorrect setting of the ink-metering elements (13), and the setpoint ink demand supplied to the printing unit (2) in the case of correct setting of all ink metering elements (13), with said computing/control apparatus (17) comparing the actual ink demand with the setpoint ink demand and correcting the actual settings of the adjustable ink-metering elements (13) such that the setpoint ink demand is supplied to the printing unit (2).