Pollination device and operating procedures

Abstract

In a method for operating a device for dusting sheets (1) with powder (2) in a printing press, in a dusting mode an air-powder mixture is distributed by a distributor (8) onto spray nozzles (12) which are connected to outlets (10) of the distributor (8) via lines (11). In a cleaning mode the distributor (8) is operated without supplying powder (2) to the distributor (8) and is held in a switching position in which only a minority of the outlets (10) are connected to a compressed air source (14) in order to blow through those of the lines (11) which are connected to the minority of the outlets (10) at a flow rate of the compressed air from the compressed air source (14) which is increased compared to the dusting mode and thereby loosen powder deposits.

Description

[0001] The present invention relates to a method for operating a device for dusting sheets with powder in a printing press, wherein in a dusting mode an air-powder mixture is distributed by a distributor to spray nozzles which are connected to outlets of the distributor via lines.

[0002] Furthermore, the present invention relates to a device suitable for carrying out the method for dusting sheets with powder in a printing press, comprising a metering device, an injector which is connected downstream of the metering device, a distributor with valves and outlets, spray nozzles and lines for connecting the outlets to the spray nozzles.

[0003] Such a method and such a device are described in DE 10 2021 126 381 A1.

[0004] The disadvantage of this state-of-the-art technology is that powder deposits can accumulate and become trapped in the lines. Cleaning the lines is only possible manually and requires partial disassembly of the device. This results in long press downtimes and high maintenance costs. In practice, manual cleaning is usually not performed regularly due to the associated effort, but only when the complications resulting from clogging of the lines, particularly the depositing of ink in the delivery pile, become clearly visible to the operating personnel. Another disadvantage is that clogging of the lines leads to a gradual increase in powder consumption and, as a result, to severe contamination of the printing press and its surroundings.

[0005] The object of the invention is to provide a more maintenance-friendly operating method for a pollination device corresponding to the type mentioned at the outset and to create a pollination device suitable for carrying out the method.

[0006] The object is achieved by a method for operating a device for dusting sheets with powder in a printing press, wherein in a dusting mode an air-powder mixture is distributed by a distributor onto spray nozzles which are connected to outlets of the distributor via lines, characterized in that in a cleaning mode the distributor is operated without supplying powder to the distributor and is held in a switching position in which only a minority of the outlets are connected to a compressed air source in order to blow through those of the lines which are connected to the minority of the outlets with a flow rate of the compressed air from the compressed air source which is increased compared to the dusting mode and thereby loosen powder deposits.

[0007] The object is further achieved by a device for dusting sheets with powder in a printing press, comprising a metering device, an injector which is connected downstream of the metering device, a distributor with valves and outlets, spray nozzles and lines for connecting the outlets to the spray nozzles, characterized in that the injector has a first flow channel for primary air from a compressed air source and a second flow channel for secondary air sucked in from the environment, and that a shut-off valve is provided for closing the second flow channel in a cleaning mode.

[0008] One advantage of the invention is the increased process stability and reliability of the printing operation. Waste caused by ink settling in the delivery pile and heavy contamination of the printing press and its surroundings by powder are avoided. Powder consumption is reduced. The invention shortens service-related machine downtimes and lowers maintenance costs. A further advantage of the invention is that it enables partially or fully automated cleaning.

[0009] The following developments of the method according to the invention are possible: The compressed air source can deliver an air pressure in cleaning mode that does not exceed a maximum pressure delivered by it in dusting mode.

[0010] In an injector upstream of the distributor, primary air from the compressed air source can be mixed with secondary air drawn in from the environment via a flow channel of the injector in the dusting mode, and in the cleaning mode the flow channel can be kept closed.

[0011] The distributor can be switched to the switching position in the cleaning mode by opening each of the valves of the distributor associated with the minority of outputs and closing each of the valves of the distributor associated with the remaining outputs of the distributor.

[0012] The minority of outputs may comprise a maximum of one third of all outputs of the distributor.

[0013] The following developments of the device according to the invention are possible: The valves in the distributor can be formed by a first perforated disc with a first number of first holes and a second perforated disc with a second number of second holes, the second number being unequal to the first number. The second number may be smaller than the first number. The second number may be at least two-thirds of the first number. The first perforated disc can be mounted to rotate relative to the second perforated disc in different rotational positions, wherein in each of the rotational positions a different group of the second holes can be closed by the first perforated disc. The dosing device, the injector shut-off valve and the valves of the distributor can be controlled in such a way that in the cleaning mode the dosing device is deactivated, the shut-off valve is closed and only a minority of the valves of the distributor are open.

[0014] Further developments of the invention will also become apparent from the following description of embodiments and the accompanying drawings.

[0015] Showing: Fig. 1 a pollination device in schematic representation with a first embodiment of a distributor of this pollination device, Fig. 2 an injector of the pollination device Fig. 1 as a detail, Fig. 3 and Fig. 4 a second embodiment of the distributor of the pollination device from Fig. 1 in a pollination mode, Fig. 5 and Fig. 6 the distributor of the second embodiment when changing the valve switching position, Fig. 7 and Fig. 8 the distributor of the second embodiment in a cleaning mode and Fig. 9 to 11 different valve switching positions of the distributor of the second embodiment.

[0016] Fig. Figure 1 shows a diagram of a device for dusting sheets 1 with powder 2 in a printing press. The device comprises a dosing line 3 for zoneless dusting and a dosing line 4 for zonal dusting. The dosing lines 3, 4 are connected to a powder reservoir 5. Each dosing line 3, 4 comprises a dosing device 6. An injector 7 is connected downstream of the dosing device 6. Furthermore, each dosing line 3, 4 comprises a distributor 8 with valves 9 and outlets 10. The outlets 10 are connected to spray nozzles 12 via lines 11. A different one of the lines 11 is connected to each outlet 10. In dosing line 4, a valve 9 is connected upstream of each outlet 10. In dosing line 3, only the outlets that can be deactivated during format width adjustment have valves upstream of them, but not the outlets in between. Otherwise, dosing lines 3 and 4 are identical.The dosing device 6 and the valves 9 are controlled by an electronic control device 13. The injectors 7 of the two dosing lines 3, 4 are connected to a common or separate compressed air source 14.

[0017] Fig. Figure 2 shows the injector 7 of the dosing line 4 in detail. The injector 7 comprises a first flow channel 15 for primary air 16 from the compressed air source 14 and a second flow channel 17 for secondary air 18 drawn in from the environment. A check valve 19 is inserted into the second flow channel 17 and can be controlled manually or by the control device 13. The check valve 19 is a ball valve. In the embodiment according to Fig. 1, the valves 9 of the distributor 8 are solenoid valves.

[0018] The device is operated in a dusting mode during printing and in a cleaning mode during maintenance.

[0019] In dusting mode, the dosing device 6 of the dosing line 4 is activated by the control device 13. The dosing device 6 doses the powder 2 from the powder reservoir 5, for example, by rotating a dosing roller of the dosing device 6. The dosed powder 2 is conveyed by gravity from the dosing device 6 into the injector 7, where it is mixed with the primary air 16 and the secondary air 18 to form an air-powder mixture 20. The shut-off valve 19 in the injector 7 is open. The air-powder mixture 20 flows from the injector 7 into the distributor 8. In the distributor of the dosing line 3, the air-powder mixture is evenly distributed to all outlets connected to spray nozzles located within the format width of the sheet 1.

[0020] In the distributor of the dosing line 3, the outlets which are connected to spray nozzles located outside the format width of the sheets 1 are shut off by a corresponding switching of the valves.

[0021] In the distributor 8 of the dosing line 4, the valves 9 are switched depending on the print image on the sheet 1. As a result, outputs 10 connected to spray nozzles 12 located in zones with increased powder demand are activated, and other outputs 10 connected to spray nozzles 12 located in zones with lower powder demand are deactivated.

[0022] In cleaning mode, the dosing device 6 of the dosing line 4 is deactivated by the control device 13. In the example of the dosing device 6 being designed as a dosing roller, this means that it does not rotate. Thus, in cleaning mode, no powder 2 is fed into the injector 6 and the distributor 7. The shut-off valve 19 of the injector 6 is kept closed in cleaning mode. Thus, in cleaning mode, the primary air 16 from the compressed air source 14 cannot escape into the environment via the second flow channel 17. In cleaning mode, the valves 9 of the distributor 8 are held in switched positions by the control device 13 so that only a minority of the outlets 10 are connected to the compressed air source 14. In cleaning mode, the compressed air source 14 supplies an air pressure of the primary air 16 that does not exceed a maximum air pressure supplied by the compressed air source 14 in dusting mode.This ensures energy-saving cleaning of the piping system.

[0023] Those lines 11 connected to said minority of outlets 10 are blown through with compressed air from the compressed air source 14 at a higher flow rate than in the dusting mode, thereby dislodging powder deposits in these lines 11. The distributor 8 is thus switched to a switching position in the cleaning mode by opening each of the valves 9 of the distributor 8 associated with the minority of outlets 10 and closing each of the valves 9 of the distributor 8 associated with the remaining outlets 10 of the distributor.

[0024] The minority of outlets 10 can comprise a maximum of one-third of all outlets 10 of the distributor 8. If the minority of outlets 10 comprises, for example, exactly one-third of all outlets 10 of the distributor 8, first the first third of the existing lines 11 are blown clean, then, after switching the valves 9, the second third of the existing lines 11 are blown clean, and finally, after switching the valves 9 again, the remaining third third of the lines 11 are blown clean.

[0025] Likewise, it can be provided that the minority of the outlets 10 comprise only a single outlet 10. In this case, in each switching position of the distributor 8 in cleaning mode, a different one of the outlets 10 with a connected line 11 is blown clean with compressed air. In each of the successively set switching positions of the distributor 8, a different one of the valves is open. The control device 13 can, according to a program running within it for the cleaning mode, briefly open one of the valves 9 in sequence and then close them again, so that all lines 11 are gradually blown clean.

[0026] The smaller the said minority of outlets 10, the higher the flow velocity of the compressed air in the line 11 or lines 11 that is / are cleared per cleaning step. If the minority comprises only one outlet 10, only one line 11 is cleared per cleaning step, achieving a particularly high flow velocity, which under practical conditions can be 3 to 4 times the flow velocity in dusting mode.

[0027] In the Fig. 3 to 11, a modification is shown in which the valves 9 of the distributor 8 are not designed as solenoid valves, but instead are formed by a first perforated disc 21 and a cooperating second perforated disc 22. Otherwise, the embodiment according to the Fig. 3 to 11 of the previously described embodiment according to the Fig. 1 and Fig. 2.

[0028] Fig. Figure 3 shows that the first perforated disc 21 and the second perforated disc 22 are arranged coaxially with each other. The first perforated disc 21 is mounted so as to be rotatable about a geometric axis 23 relative to the second perforated disc 22 in various rotational positions, which are shown in the Fig. 9 to 11. The rotation of the first perforated disc 21 serves to set the various switching positions, which correspond to the rotational positions, and is driven by a drive 24, which is controlled for this purpose by the control device 13. The drive 24 is an electric motor and drives the first perforated disc 21 via a pinion 25 that engages with an external toothing of the first perforated disc 21.

[0029] Fig. 4 shows the distributor 8 from Fig. 3 in a section. The first perforated disk 21 has a first number m of first holes 26, 27, which in the given example is nine. (m - 1) of the first holes 26 are evenly distributed around the axis 23, with a first hole 26 being arranged every 45° in the example shown. The additional first hole 27 is arranged at an intermediate position between two of the evenly distributed first holes 26. The second perforated disk 22 has a second number n of second holes 28, which are evenly distributed around the axis 23. The following applies: m > n ≥ ⅔ m In the given example, n is eight. The first holes 26, 27 and the second holes 28 are through holes. For better visibility, the second holes 28 are shown in the drawing with a slightly smaller diameter than the first holes 26, 27.

[0030] The said minority of the outputs 10 is one in the given example, but can be larger in modifications and, for example, amount to two, with two additional first holes 27 being arranged at two intermediate positions between the equally distributed first holes 26.

[0031] The minority (m - n) of the outlets 10 or the lines 11 connected to them to be blown out simultaneously comprises at most one third of all outlets 10 of the distributor 8, so that: (m - n) ≤ ⅓ n This follows: m≤43 n

[0032] Fig. 5 shows that the distributor 8 has one or more actuators 29 for setting the second perforated disc 22 away from the first perforated disc 21 and one or more return springs 30 for setting the second perforated disc 22 against the first perforated disc 21. In the illustrated setting position ( Fig. 5) the first perforated disc 21 is rotated relative to the second perforated disc 22 to change the valve switching position. In the setting position ( Fig. 3 and Fig. 7) either the dusting of sheets 1 ( Fig. 3) or blowing out the lines 11 ( Fig. 7). In Fig. 6, the rotation 31 of the pinion 25 and the rotation 32 of the first perforated disc 21 are indicated by arrows.

[0033] In the Fig. 3 and Fig. Figure 4 shows the dusting mode, with the air-powder mixture 20 flowing through all of the first holes 26 except the additional first hole 27. The first holes 26 are aligned with the second holes 28, and the additional first hole 27 is closed from below, or on the outlet side, by the second perforated disc 22, so that the additional first hole 27 forms a kind of blind hole. Therefore, the air-powder mixture 20 flows into the additional first hole 27 from above, or on the inlet side, but not through the latter into any second hole 28.

[0034] In the Fig. 7 and Fig. Figure 8 shows the cleaning mode, where the secondary air 18 flows through the additional first hole 27 and the second hole 28 aligned with the latter. All other first holes 26 are not aligned with any second hole 28 and are closed by the second perforated disc 22, forming a kind of blind hole. Likewise, those of the second holes 28 that are not aligned with the additional first hole 27 are closed by the first perforated disc 21, which Fig. 8 (and analogously in the Fig. 9 to 11) is illustrated by a representation of the closed second holes 28 with a broken line.

[0035] In the Fig. Figures 9 to 11 show three different valve switching positions of the distributor 8, in each of which a different one of the lines 11 is blown clean. The valve switching positions are adjusted successively by gradually rotating the first perforated disc 21 relative to the second perforated disc 22.

[0036] The position according to Fig. 9 corresponds to that in the Fig. 8. In this position, the first of the lines 11 is blown clean. To get out of the position according to Fig. 9 into the position according to Fig. 10, the first perforated disc 21 is rotated by the drive 24 by 45° clockwise relative to the second perforated disc 22, which is stationary at the same time. Before the rotation, the second perforated disc 22 is separated from the first perforated disc 21, as shown in Fig. 5, and after turning, the second perforated disc 22 is positioned against the first perforated disc 21.

[0037] The second of the lines 11 is then blown clean and is connected to the second hole 28, which is now aligned with the additional first hole 27, via one of the connections 10.

[0038] In order to blow clean the third of the lines 11, the additional first hole 27 must be rotated into alignment with the next second hole 28 in the circular row of second holes 28, so that the position according to Fig. 11 is reached.

[0039] The information relating to the Fig. The steps described in Figures 9 to 11 are repeated in the cleaning mode until every second hole 28 of the row has been in conductive connection with the additional first hole 27 into the primary air 16 and thus every line 11 has been blown clean. List of reference symbols 1 sheet 2 powders 3 Dosing line 4 dosing lines 5 powder storage containers 6 Dosing device 7 Injector 8 distributors 9 Valve 10 Exit 11 Line 12 spray nozzle 13 Control device 14 Compressed air source 15 first flow channel 16 Primary air 17 second flow channel 18 Secondary air 19 second flow channel 20 air-powder mixture 21 first hole disc 22 second hole disc 23 Axis 24 drive 25 pinions 26 holes 27 holes 28 holes 29 Actuator 30 return spring 31 rotations 32 rotations QUOTES CONTAINED IN THE DESCRIPTION

[0000] This list of documents submitted by the applicant was generated automatically and is included solely for the convenience of the reader. This list is not part of the German patent or utility model application. The DPMA assumes no liability for any errors or omissions. Cited patent literature

[0000] DE 10 2021 126 381 A1

[0003]

Claims

[1] Method for operating a device for dusting sheets (1) with powder (2) in a printing machine, wherein in a dusting mode an air-powder mixture (20) is distributed by a distributor (8) to spray nozzles (12) which are connected to outlets (10) of the distributor (8) via lines (11), characterized by that in a cleaning mode the distributor (8) is operated without supplying powder (2) into the distributor (8) and is held in a switching position in which only a minority of the outlets (10) are connected to a compressed air source (14) in order to blow through those of the lines (11) which are connected to the minority of the outlets (10) with a flow rate of the compressed air from the compressed air source (14) which is increased compared to the dusting mode and thereby loosen powder deposits. [2] Method according to claim 1, characterized bythat the compressed air source (14) in cleaning mode delivers an air pressure that does not exceed a maximum pressure delivered by it in dusting mode. [3] Method according to claim 1 or 2, characterized by that in an injector (7) upstream of the distributor (8), in the dusting mode, primary air (16) from the compressed air source is mixed with secondary air (18) sucked in from the environment via a flow channel (17) of the injector (7), and that in the cleaning mode the flow channel (17) is kept closed. [4] Method according to one of claims 1 to 3, characterized by that the distributor (8) is switched to the switching position in the cleaning mode by opening each of the valves (9) of the distributor (8) associated with the minority of outputs (10) and closing each of the valves (9) of the distributor (8) associated with the remaining outputs (10) of the distributor (8). [5] Method according to one of claims 1 to 4, characterized by that the minority of outputs (10) comprises at most one third of all outputs (10) of the distributor (8). [6] Device for dusting sheets (1) with powder (2) in a printing machine, for carrying out the method according to one of claims 1 to 5, comprising - a dosing device (6), - an injector (7) which is connected downstream of the metering device (6), - a distributor (8) with valves (9) and outlets (10), - spray nozzles (12) and - lines (11) for connecting the outlets (10) with the spray nozzles (12), characterized by , that the injector (7) has a first flow channel (15) for primary air (16) from a compressed air source (14) and a second flow channel (17) for secondary air (18) sucked in from the environment, and that a check valve (19) is provided for closing the second flow channel (17) in a cleaning mode. [7] Device according to claim 6, characterized by that the valves (9) in the distributor are formed by a first perforated disc (21) with a first number of first holes (26, 27) and a second perforated disc (22) with a second number of second holes (28), the second number being unequal to the first number. [8] Device according to claim 7, characterized by that the second number is smaller than the first number. [9] Device according to claim 7 or 8, characterized by that the second number is at least two-thirds of the first number. [10] Device according to one of claims 7 to 9, characterized bythat the first perforated disc (21) is rotatably mounted relative to the second perforated disc (22) in different rotational positions, wherein in each of the rotational positions a different group of the second holes (28) is closed by the first perforated disc (21). [11] Device according to one of claims 6 to 10, characterized by that the metering device (6), the shut-off valve (19) of the injector (7) and the valves (9) of the distributor (8) are controlled in such a way that in the cleaning mode the metering device (6) is deactivated, the shut-off valve (19) is closed and only a minority of the valves (9) of the distributor (8) are open.

Images