Apparatus for dusting printed pages

Abstract

The invention relates to a device for powdering printed sheets (15), comprising a powder distributor with a valve for an air-powder mixture. The valve is configured as a throttle (21, 22) with an adjustable flow cross section, which comprises a first throttle (21) and a second throttle (22). The throttles (21, 22) are actuated by a control device (23) according to a first mode and a second mode. The flow cross section of the first throttle (21) is adjusted to be smaller than the flow cross section of the second throttle (22) in the first mode and to be larger than the flow cross section of the second throttle (22) in the second mode.

Description

TECHNICAL FIELD

[0001] The invention relates to a device for powdering printed sheets, comprising a powder distributor, which has valves for an air-powder mixture. BACKGROUND

[0002] A device is described in DE 199 37 090 B4, in which a powder-air mixture is conveyed in an annular distributor and distributed there onto a plurality of single lines, through which the mixture is guided to individual output nozzles. The single lines can be closed by valves, which can be actuated by electromagnets, for example. SUMMARY

[0003] It is the task of the invention to provide a further device for powdering printed sheets.

[0004] The task is solved by a device for powdering printed sheets, comprising a powder distributor, which has valves for an air-powder mixture, characterized in that the valves are configured as throttle valves with an adjustable flow cross section, the throttle valves comprising a first throttle valve and a second throttle valve. The throttle valves are actuated by a control device according to a first mode and a second mode and the flow cross section of the first throttle valve is adjusted to be smaller than the flow cross section of the second throttle valve in the first mode and to be larger than the flow cross section of the second throttle valve in the second mode.

[0005] An advantage of the invention is that with the invention it is possible to achieve that different amounts of powder are ejected with each powdering nozzle of a nozzle row.

[0006] Different further embodiments are possible:

[0007] The throttle valves can be configured as pinch valves.

[0008] Each pinch valve has a resilient hose and an actuator for squeezing the hose.

[0009] The powder distributor is an annular distributor, wherein the throttle valves are arranged annularly.

[0010] The control device actuates the throttle valves according to data from a prepress stage.

[0011] The data are associated with an ink amount distribution of the printed sheets to be powdered. BRIEF DESCRIPTION OF DRAWINGS

[0012] Further embodiments result from the following description of preferred embodiments and the associated drawings, in which:

[0013] Figure 1 a general view of a powdering device is shown,

[0014] Figure 2 Fig. 3b shows a schematic view of a powder distributor of a powdering device in a different operating mode;

[0015] Figure 3a Fig. 3b shows a schematic view of a powder distributor of a powdering device in a different operating mode;

[0016] Figure 4a Fig. 4b shows a schematic view of a throttle valve of a powder distributor with an enlarged flow cross section;

[0017] Figure 5a Fig. 5b shows a schematic view of a throttle valve with a reduced flow cross section;

[0018] Figure 6 Fig. 6 shows a schematic view of a powder amount distribution caused by a powdering device; and

[0019] Figure 7 Fig. 7 shows a schematic view of an ink amount distribution according to pre-press data. DETAILED DESCRIPTION

[0020] Figure 1 The powdering device shown in Fig. 1 is arranged in a delivery stack of a planographic printing press and serves to powder printed page sheets. The printed page sheets are conveyed by a chain conveyor of the delivery stack past the powdering device while being powdered and are deposited on a delivery stack of the delivery stack after being powdered.

[0021] The powdering device comprises a reserve container 1 which has a powder reserve 2 therein. The reserve container 1 is funnel-shaped or conical and the powder reserve 2 forms a build-up column. A meter 3 with a metering roller 4 is connected to a lower end of the reserve container 1. The powder in the powder reserve 2 is conveyed by gravity into the meter 3 and is metered there by the metering roller 4. The metered powder reaches a jet 5 which is connected to the meter 3. In the jet 5, the powder is mixed with pressure air from a pressure air line 6 to form an air-powder mixture.

[0022] The air-powder mixture from the jet 5 reaches a powder distributor 10 via a connecting line 8, which has one distributor input 9 and a plurality of distributor outputs 11. The connecting line 8 is connected to the distributor input 9 and a supply line 7 is connected to the distributor outputs 11.

[0023] A spray bar 12 is arranged in the transport path of the printed sheet 15 and includes a row of powder nozzles 18, which are arranged on nozzle heads 13. The air-powder mixture is sprayed onto the printed sheet 5 in the form of spray cones 14. The spray bar 12 is connected to a powder distributor 10 via a bundle of supply lines 7. A different nozzle head 13 is connected to each supply line 7. In the powder distributor 10, the total flow GS of the air-powder mixture is divided into sub-flows TS, the number of which corresponds to the number of distributor outputs 11. Each sub-flow TS flows out of the powder distributor 10 through a different distributor output 11. Figure 1 The diagram only schematically illustrates the division of the total flow GS into sub-flows TS. A number of throttle valves 21, 22, corresponding to the number of distributor outputs 11, are arranged in the powder distributor 10, with a different throttle valve 21, 22 connected upstream of each distributor output 11. The sub-flows TS flow into the distributor outputs 11 through the throttle valves 21, 22. Each sub-flow TS flows through a different throttle valve 21, 22. Figure 1 The throttle valves 21 and 22 are not shown in the diagram.

[0024] Figure 2 According to Figure 1 The cross-sectional view along section line II-II shown in the diagram illustrates the interior of the powder dispenser 10. It can be seen that the powder dispenser 10 is an annular dispenser, wherein throttle valves 21 and 22 are arranged annularly. The throttle valves 21 and 22 are configured as pinch valves, wherein each throttle valve 21 and 22 has a flexible hose 19 and an actuator 20 for squeezing the hose 19. The actuator 20 is controlled by a control device 23 based on data from the prepress stage.

[0025] Figure 3a The device is shown in a first mode, such as during a first printing task. Here, the flow cross-section 24 of the first throttle valve 21 is adjusted to be smaller than the flow cross-section 25 of the second throttle valve 22. Therefore, less powder flows out from the distributor output terminal 11 connected downstream of the first throttle valve 21 than from the distributor output terminal 11 connected downstream of the second throttle valve 22.

[0026] Figure 3b The device is shown in a second mode, for example, in a second printing task. Here, the control device 23 adjusts the flow cross-section 24 of the first throttle valve 21 to be larger than the flow cross-section 25 of the second throttle valve 22. Therefore, in the second mode, more powder flows out from the distributor output terminal 11 connected downstream of the first throttle valve 21 than from the distributor output terminal 11 connected downstream of the second throttle valve 22. Figure 3a and 3bThe flow cross-section of the remaining throttle valves, which are arranged in the circuit together with the first throttle valve 21 and the second throttle valve 22, is not shown in

[0027] All throttle valves 21, 22 of the powder dispenser 10 are identical in construction, so that only the first throttle valve 21 will be described later on. This first throttle valve 21 is shown in Figure 4a in a view corresponding to Figure 2 and in Figure 4b in a view orthogonal thereto (side view). The hose 19 is flexible and permanently elastic, and the actuator 20 (for example in the form of a plunger or piston rod) bears against the circumferential surface of the hose 19. In Figure 4a and 4b the adjustment of the first throttle valve 21 corresponds to the first mode shown in Figure 3a Here, the actuator 20 is not moved out or only slightly moved out and therefore does not squeeze or only slightly squeezes the hose 19, so that the hose does not contract or only slightly contracts.

[0028] Figure 5a and 5b the adjustment of the first throttle valve 21 corresponds to the second mode shown in Figure 3b Here, the actuator 20 is moved out to a greater extent and squeezes the hose 19 to a greater extent, so that the hose contracts more strongly. By contracting more strongly, a reduced flow cross-section of the first throttle valve 21 is obtained in Figure 5a and 5b relative to Figure 4a and 4b .

[0029] Figure 6 The powder quantity distribution over the print width is shown in a bar chart. The print width is divided into a row of zones A to G and the powder spreading device spreads powder onto the print sheet 15 according to the powder distribution curve shown. The powder quantity in each zone A to G is ejected by a different spray head 13, respectively.

[0030] Figure 7 A bar chart is shown with the ink quantity distribution on the print sheet 15. It can be seen that there are different amounts of ink in the zones A to G, which are represented by data stored in the pre-press stage (which the control device 23 calls up). The powder distribution curve in Figure 6 compared with Figure 7 it can be seen that the powder distribution curve in Figure 6 corresponds to the ink quantity distribution curve in Figure 7 .

[0031] Reference sign table

[0032] 1 reservoir container

[0033] 2 powder reserve

[0034] 3 meter

[0035] 4 metering roller

[0036] 5 injector

[0037] 6 compressed air line

[0038] 7 supply line

[0039] 8 connecting line

[0040] 9 dispenser input

[0041] 10 powder dispenser

[0042] 11 dispenser output

[0043] 12 spray bar

[0044] 13 spray head

[0045] 14 spray cone

[0046] 15 printed sheet

[0047] 16 powder quantity dispensing

[0048] 17 ink quantity dispensing

[0049] 18 powder nozzle

[0050] 19 hose

[0051] 20 actuator

[0052] 21 first throttle

[0053] 22 second throttle

[0054] 23 control device

[0055] 24 flow cross section

[0056] 25 flow cross section

[0057] A-G zones

[0058] GS total flow

[0059] TS subflow

Claims

1. An apparatus for powdering a printed page (15), comprising: Powder distributor (10) with a valve for an air-powder mixture and a reserve container (1) for a powder reserve (2), on which a metering device (3) is connected, characterized in that the metering device (3) has a metering roller (4) for metering powder from the powder reserve (2), on the metering device (3) a jet (5) is connected, in which the metered powder is mixed with pressure air to form an air-powder mixture, and the jet (5) is connected to the powder distributor (10) by a connecting line (8), wherein the air-powder mixture from the jet (5) reaches the powder distributor (10) through the connecting line (8), the valve is configured as a throttle valve (21, 22) with an adjustable flow cross section (24, 25), the throttle valve comprises a first throttle valve (21) and a second throttle valve (22), wherein the throttle valves are arranged in the powder distributor and respectively upstream of different distributor outlets (11) of the powder distributor (10); in the powder distributor (10) the total flow (GS) of the air-powder mixture is divided into a number of partial flows (TS), the number corresponding to the number of distributor outlets (11), wherein each partial flow (TS) flows out of the powder distributor (10) through a different throttle valve (21, 22) and a different distributor outlet (11), respectively, the throttle valves (21, 22) are actuated by a control device (23) according to a first mode and a second mode; and the flow cross section (24) of the first throttle valve (21) is adjusted to be smaller than the flow cross section (25) of the second throttle valve (22) in the first mode and to be larger than the flow cross section (25) of the second throttle valve (22) in the second mode, wherein the throttle valves (21, 22) are configured as pinch valves, each having a resilient hose (19) and an actuator (20) for squeezing the hose (19), and the powder distributor is a ring distributor, wherein the throttle valves (21, 22) are arranged annularly.

2. The apparatus of claim 1, wherein, The control device (23) actuates the throttle valves (21, 22) according to data from a pre-press stage.

3. The apparatus of claim 2, wherein, The data are associated with an ink amount distribution (17) of a printed sheet (15) to be dusted. The data are associated with an ink amount distribution (17) of a printed sheet (15) to be dusted.

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