EP1787724B1 - Device and method for powdering or dusting printing material - Google Patents

Abstract

Device has container (17), whereby air, preferably propellant air mixture can be inserted into container over an air intake opening (18). Air from container is executable over air discharge opening (22), whereby air intake opening with inlet air supply (19) is coupled with air discharge opening with discharge opening air supply (23). An air intake current and an air discharge opening current over discharge opening air supply is adjusted such that a pressure in for instance an ambient pressure, prevails in the container. A propellant particle (16) is executed over a propellant discharge opening and is arranged on powdering and dusting printing material, which convey electro-less air. An independent claim is also included for the method.

Description

The invention relates to a device for powdering or dusting of substrates. Furthermore, the invention relates to a method for powdering or dusting of substrates.

In printing technology, it is already state of the art to powder printed substrates with powder or to dust. In sheet-fed printing machines, the powdering or pollination of printed printed sheets serves to prevent blocking of the printed sheets in the area of the delivery arm. Furthermore, the powder applied to the printing sheets can facilitate the drying of the applied printing ink. In the state of the art, powdering or dusting of printing materials is carried out in such a way that powder is directed onto a printed printing material with the aid of compressed air. This is what the DE 196 35 830 A1 as well as the DE 198 36 014 A1 each devices for dusting or powdering of substrates, in which the powder is directed with the aid of a jet of compressed air to the substrates. This known from the prior art approach has the disadvantage that the transport of the printed substrate, in particular the transport of printed sheets, can be adversely affected by the compressed air. Furthermore, with such known from the prior art devices usually far too much powder directed to the substrates, the excess powder can be freely distributed or uncontrolled in a printing and can be inhaled by working in the printing people. This represents a significant health risk for working in a printing people.

On this basis, the present invention based on the problem of creating a novel device and a novel method for powdering or dusting of substrates.

The aforementioned problem is solved by a device for powdering or dusting substrates according to claim 1. The inventive device has at least one container, wherein at least air, preferably a powder-air mixture, is insertable into the container via at least one air inlet opening, wherein at least air from the container via at least one air outlet opening is executable, wherein the or each air inlet opening with an inlet air supply and the or each air outlet opening is coupled to an outlet air supply, via which an air inlet flow and an air outlet flow are adjustable so that a pressure prevailing in the container corresponds approximately to an ambient pressure, and wherein the powder particles executable on at least one powder outlet opening and on a to be powdered or to be pollinated printing material conveying air flow can be directed.

With the device according to the invention, the powder particles to be conveyed onto a printing substrate can be moved on the printing substrate on the basis of the kinetic energy adhering to the powder particles, without the presence of a conveying air flow. Accordingly, the powder particles are thrown, so to speak, in the direction of the printing material or shot, without a conveying air flow in the form of a compressed air jet being used for transporting the same in the direction of the printing material. When powdering or dusting the substrates, therefore, the transport of the same is not affected. Furthermore, it is avoided that directed in the direction of the powdered to be powdered or to be printed substrate powder particles in the printing press uncontrolled. This reduces the health risk for people working in a printing company.

The or each air inlet port is configured to allow powder particles to be moved past an inner surface of a wall of the container and to be electrostatically charged by friction on the inner surface of the container. The powder particles directed onto the printing substrate are therefore electrostatically charged.

According to an advantageous development of the invention, the or each air inlet opening is integrated into a wall of the container such that via the or each air inlet opening air, preferably the powder-air mixture, tangentially to the wall of the container in the same is inserted.

According to a further advantageous development of the invention, the container is surrounded by a housing such that electrostatically charged powder particles can be directed via at least one powder outlet opening of the container into the housing and via at least one powder outlet opening of the housing onto the substrate to be powdered or dusted, wherein the or each Puderauslassöffnung of the housing is integrated in a wall of the housing such that an exit direction of the powder particles from the housing on the one hand approximately tangential to the wall of the housing and on the other hand approximately perpendicular to the substrate to be powdered.

The inventive method for powdering or dusting of substrates is defined in the independent claim 11.

Fig. 1:

eine schematisierte Darstellung einer erfindungsgemäßen Vorrichtung zum Bepudern bzw. Bestäuben von Bedruckstoffen nach einem ersten Ausführungsbeispiel der Erfindung;

Fig. 2:

die erfindungsgemäße Vorrichtung zum Bepudern bzw. Bestäuben von Bedruckstoffen in einer gegenüber Fig. 1 um 90° gedrehten Ansicht in Blickrichtung II gemäß Fig. 1;

Fig. 3:

ein Detail der erfindungsgemäßen Vorrichtung zum Bepudern bzw. Bestäuben von Bedruckstoffen gemäß Fig. 1 und 2; und

Fig. 4:

eine schematisierte Darstellung einer erfindungsgemäßen Vorrichtung zum Bepudern bzw. Bestäuben von Bedruckstoffen nach einem zweiten Ausführungsbeispiel der Erfindung in einer Ansicht analog zu Fig. 2.

Preferred embodiments of the invention will become apparent from the dependent claims and the description below. Embodiments of the invention will be described, without being limited thereto, with reference to the drawings.
Showing:

Fig. 1:

a schematic representation of an inventive device for powdering or dusting of substrates according to a first embodiment of the invention;

Fig. 2:

the device according to the invention for powdering or dusting of substrates in one opposite Fig. 1 rotated by 90 ° view in viewing direction II according to Fig. 1 ;

3:

a detail of the device according to the invention for powdering or dusting of substrates according to Fig. 1 and 2 ; and

4:

a schematic representation of a device according to the invention for powdering or dusting of substrates after a second embodiment of the invention in a view analogous to Fig. 2 ,

Hereinafter, the present invention will be described with reference to FIG Fig. 1 to 4 using the example of powdering or pollination of sheet in more detail. However, the invention can also be used for powdering or dusting web-like substrates.

Fig. 1 to 3 show very schematically a first embodiment of a device according to the invention for powdering or dusting of printed sheet 10, wherein for powdering or dusting the sheet 10, the same are moved past the device according to the invention. Fig. 1 illustrates the transport direction of the sheet 10 along a transport path 11 with the arrow 12, wherein the sheets to be polled 10 are detected at a leading edge of a sheet transport device 13 and moved in the direction of the arrow 12 along the transport path 11. During transport of the printed sheets 10 along the transport path 11, the transport of the printed sheets 10 is stabilized via suction / blowing devices 14. In Fig. 1 is schematized the length of the sheet to be powdered 10 recognizable, in Fig. 2 but the width of the same.

In the embodiment of Fig. 1 to 3 the device according to the invention for powdering or dusting of substrates via a plurality of modules 15, which are positioned transversely to the transport direction (arrow 12) of the sheet 10 over the width of the same with distance from each other. Over each of the modules 15 powder particles 16 can be applied to the substrate 10, wherein each of the modules 15 thereby, as in Fig. 3 shown, is formed. Fig. 3 shows a cross section through a module 15 along the cutting direction III-III in Fig. 1 ,

Each of the modules 15 of the device according to the invention for powdering or dusting the printed sheet 10 has according to Fig. 3 via a container 17, which preferably has a frusto-conical contour. In the container 17 is via an air inlet opening 18 which is coupled to an inlet air supply 19, air or a powder-air mixture inserted.

The air inlet opening 18 is in such a way integrated into a wall 20 of the container 17, that the air or the powder-air mixture can be introduced tangentially to the wall 20 of the container 17 in the container 17. Accordingly, the air inlet opening 18 is designed as a tangential air inlet opening, wherein powder particles can be moved past an inner surface 21 of the wall 20 by the tangential introduction of the air or of the powder-air mixture into the container 17. The powder particles 16 are in the sense of a cyclonic flow on the inner surface 21 of the wall 20 of the container 17 movable past.

In addition to the air inlet opening 18, the container 17 has an air outlet opening 22, which is coupled to an outlet air supply 23. Air can be carried out from the container 17 via the air outlet opening 22, wherein an air inlet flow flowing into the container 17 via the air inlet opening 18 into the container 17 and an air outlet flow flowing out of the container 17 via the air inlet opening 18 can be adjusted via the inlet air supply 19 and the outlet air supply a pressure prevailing in the container 17 corresponds approximately to the ambient pressure of the respective module 15. The pressure provided by the inlet air supply 19, prevailing in the region of the air inlet opening, is greater than the ambient pressure, the pressure provided by the outlet air supply 23 and prevailing in the region of the air outlet opening 22 is less than the ambient pressure.

Due to the above-described flow conditions in the container 17, the powder particles on the inner surface 21 of the wall 20 of the container 17 contacting moving and preferably charged by friction on the inner surface 21 of the wall 20 of the container 17 electrostatically or triboelectrically. Via a powder outlet opening 24 of the container 17, the preferably electrostatically charged powder particles 16 pass from the container 17 into a housing 25 surrounding the container 17, starting from the housing 25, the preferably electrostatically charged powder particles 16 via a Puderauslassöffnung 26 of the housing 25 from the housing 25 executable and can be directed to the sheet 10.

In the housing 25 prevails due to the flow conditions described above, a pressure which corresponds approximately to the pressure in the container 17 and thus approximately the ambient pressure of the module 15. This ensures that no air flow takes place in the area of the powder outlet opening 26, so that the powder particles 16, which are preferably charged with electrostatic charge, leave the housing 25 via the powder outlet opening 26 solely on account of their kinetic energy. The preferably electrostatically charged powder particles are thus directed förderluftstromlos on the sheet to be powdered 10 and thus thrown so to speak in the direction of the sheet 10.

It should be noted at this point that the modules need not have a housing. Rather, the powder particles electrostatically charged in the container 17 can be directed via a corresponding powder outlet opening of the container directly onto the printed sheets to be powdered. In this case, the powder outlet opening introduced into the container is then designed analogously to the powder outlet opening 26 of the housing 25, the powder outlet opening 24 of FIG Fig. 3 is then closed or not available.

In the embodiment of Fig. 1 to 3 in which the containers 17 of the modules 15 are each surrounded by a housing 25, the already mentioned powder outlet opening 26 is introduced into a wall of the housing 25. In this case, the powder outlet opening 26 of the housing 25 is integrated in a wall of the housing 25 in such a way that an exit direction of the powder particles from the housing 25, which in FIG Fig. 2 is shown by arrows 27, approximately tangential to the wall of the housing 25 and approximately perpendicular to the sheet to be powdered 10 runs. The preferably electrostatically charged powder particles 16 thus leave the modules 15 in an exit direction 27, which runs tangentially to a wall of the housing 25 and perpendicular to the printed sheet 10.

The powder outlet 24 of the container 17, which is surrounded in the embodiment shown by the housing 25, opens according to Fig. 3 in the axial direction in the housing 25th

If, on the other hand, the container is not surrounded by a housing but the powder particles preferably charged electrostatically in the container are directed directly over the container onto the sheet to be powdered, the powder outlet opening integrated in the container is designed analogously to the powder outlet opening of the housing.

For electrostatic or triboelectric charging of the powder particles 16 on the inner surface 21 of the wall 20 of the container 17, the inner surface 21 of the container 17 is formed of a conductive material or coated with such a material, said material to the material of the powder particles 16 a relatively large having electrostatic or triboelectric distance in a so-called triboelectric series. This ensures that the powder particles can be electrostatically charged by friction when contacting the inner surface 17 of the container 20. In the embodiment shown, the powder particles 16 are charged positively.

In addition to the inner surface 21 of the wall 20 of the container 17, an inner surface 28 of the housing 25 may be formed of such an electrostatically conductive material or coated with such a material. In this case, the powder particles 16 are then electrostatically charged by friction on the inner surface 28 of the housing 25 even during the contacting advancing movement.

As Fig. 3 shows, the housing 25 and thus also the container 17 of each module 15 of the device according to the invention is connected to a ground potential 29. In this way, it can be ensured that in the case of the triboelectric charging of the powder particles the same positive charge carriers can be refilled in the area of the container 17 and of the housing 25, so that powder particles 16 can be charged safely electrostatically or triboelectrically over the entire operating period.

According to Fig. 1 At least one electrode 30, which is connected to a voltage source 31 and thereby charged opposite to the powder particles 16, is arranged in the region of the transport path 11 for the printed sheets 10 to be powdered on a side of the printed sheets 10 opposite the modules 15. Accordingly, in the embodiment shown, the or each electrode 30 is negatively charged. With the aid of the or each electrode, the powdering or pollination of the printed sheets 10 is assisted, since the or each electrode 30 attracts the charged powder particles 16 and thus moves in the direction of the printed sheets 10. In the embodiment of Fig. 1 to 3 Accordingly, the charged powder particles 16 are moved on the one hand by the kinetic energy of the same and on the other hand by the electrical attraction of the or each electrode 30 in the direction of the printed sheets 10. As already mentioned, no conveying air flow or compressed air jet is used.

For the purposes of the present invention, the powder outlet openings 26 of the housing 25 can be controlled or regulated in their open position. The size of the powder discharge openings 26 can be adjusted to adjust the amount of the powder particles 16 to be conveyed onto the printed sheets 10. In order to influence the size of the powder outlet openings 26, the same is associated with an adjustment mechanism (not shown).

By the above-described flow of the powder particles in the container 17, centrifugal forces act on the powder particles, thereby pushing large and heavy powder particles radially outward against the inner surface 21 of the wall 20 of the container 17, whereas relatively small and light powder particles remain radially inward. About the air outlet 22, the relatively small and light powder particles can be sucked or removed together with the air from the container 17, wherein the relatively small and light powder particles are preferably trapped or retained on a filter 32 in the region of the air outlet 22nd is positioned. This avoids that relatively light and small powder particles escape into the environment and can be inhaled by persons working in the printer. The danger of health impairments is thereby significantly minimized.

A powder-air mixture is preferably introduced into the container 17 via the air inlet opening 18. Alternatively, it is also possible to introduce only air via the air inlet opening 18 in the container 17, this air is then mixed with held in the container 17 powder to form the powder-air mixture within the container 17.

In the embodiment of Fig. 1 to 3 are across the width of the sheet to be dusted 10 several modules 15 spaced from each other. In contrast, it is also possible how Fig. 4 shows that the device according to the invention has only a single Modul.15, which then extends over the entire width of the printed sheet 10 to be dusted. With regard to all other details, the embodiment of the Fig. 4 with the embodiment of Fig. 1 to 3 match, so that reference may be made to the above statements.

In the exemplary embodiments shown, the powder outlet openings 26 each extend over the entire width of the housing 25 of the corresponding module 15. It should be noted at this point that the powder outlet opening 26 of the modules 15 can also have a smaller width than the housing 15. Furthermore, as seen across the width of the module, a plurality of powder outlet openings 26 can be integrated into the housing 25 of the module at a distance from one another.

LIST OF REFERENCE NUMBERS

10

sheet

11

transport distance

12

transport direction

13

transport means

14

Suction / blower

15

module

16

powder particles

17

container

18

Air inlet opening

19

Inlet air supply

20

wall

21

palm

22

air outlet

23

Auslassluftversorgung

24

Puderauslassöffnung

25

casing

26

Puderauslassöffnung

27

exit direction

28

palm

29

ground potential

30

electrode

31

voltage source

32

filter

Claims (11)

1. A device for the powdering or dusting of substrates, particularly printing sheets, with at least one tank (17), wherein at least air, preferentially a powder-air mixture can be introduced into the tank (17) via at least one air inlet opening (18), wherein at least air can be output from the tank (17) via at least one air outlet opening (22), wherein the or each air inlet opening (18) is coupled to an inlet air supply (19) and the or each air outlet opening (22) is coupled to an outlet air supply (23) and wherein powder particles (16) via at least one powder outlet opening can be exported and directed onto a substrate (10) to be powdered or to be dusted in a manner free of a conveying air stream, characterized in that via the air inlet opening (18) an air inlet flow and via the air outlet opening (22) an air outlet flow can be adjusted, in that a pressure prevailing in the tank (17) approximately corresponds to an ambient pressure and in that the powder particles (16) can be moved past the inner surface (21) of the tank (17) in the sense of a cyclonic flow.
2. The device according to Claim 1, characterized in that the or each air inlet opening (18) is designed in such a manner that the powder particles (16) can be moved past an inner surface (21) of a wall (20) of the tank (17) in a contacting manner and in the process can be electrostatically charged through friction on the inner surface (21) of the tank (17).
3. The device according to Claim 1 or 2, characterized in that the or each air inlet opening (18) is designed as tangential air inlet opening which is integrated in a wall (20) of the tank in such a manner that via the or each air inlet opening (18) air, preferentially the powder-air mixture, can be introduced tangentially to the wall of the tank (17) into the latter.
4. The device according to any one or a plurality of the Claims 1 to 3, characterized in that the tank (17) comprises at least one tangential powder outlet opening which is integrated in a wall of the tank (17) in such a manner that a discharge direction of the powder particles from the tank (17) on the one hand runs approximately tangentially to the wall of the tank (17) and on the other hand approximately perpendicularly to the substrate to be powdered, so that electrostatically charged powder particles via the or each powder outlet opening of the tank can be directed directly onto the substrate.
5. The device according to any one or a plurality of the Claims 1 to 3, characterized in that the tank (17) is surrounded by a housing (25) in such a manner that electrostatically charged powder particles via at least one powder outlet opening (24) of the tank (17) can be directed into the housing (25) and via at least one powder outlet opening (26) of the housing (25) can be directed onto the substrate to be powdered or dusted.
6. The device according to Claim 5, characterized in that the or each powder outlet opening (26) of the housing (25) is designed as tangential powder outlet opening which is integrated in a wall of the housing (25) in such a manner that a discharge direction of the powder particles from the housing (25) on the one hand runs approximately tangentially to the wall of the housing (25) and on the other hand approximately perpendicularly to the substrate to be powdered, so that electrostatically charged powder particles via the or each powder outlet opening (26) of the housing (25) can be directed onto the substrate.
7. The device according to Claim 5 or 6, characterized in that the or each powder outlet opening (24) of the tank (17) in axial direction terminates in the housing (25).
8. The device according to any one or a plurality of the Claims 1 to 7, characterized in that the inner surface (21) of the tank (17) and/or an inner surface (28) of the housing (25) surrounding the tank (17) if applicable is formed of a conductive material or coated with such a material, which has a relatively large electrostatic or triboelectric spacing to the material of the powder particle.
9. The device according to any one or a plurality of the Claims 1 to 8, characterized in that the inlet air supply (19) and the outlet air supply (23) can be controlled or regulated in such a manner that a pressure prevailing in the tank (17) and if applicable the pressure prevailing in the housing (25) surrounding the tank (17) approximately corresponds to the ambient pressure, so that the electrostatically charged powder particles because of their kinetic energy and consequently can be transported in the direction of the substrate to be powdered or dusted free of a conveying air stream.
10. The device according to any one or a plurality of the Claims 1 to 9, characterized by at least one electrode (30) which is positioned on a side of the substrate to be powdered located opposite the tank (17), wherein the or each electrode attracts the electrostatically charged powder particles and thus supports the powdering or dusting of the substrate.
11. A method for the powdering or dusting of substrates, particularly of printing sheets, wherein powder particles via a cyclonic air flow prevailing in a tank (17) are moved past an inner surface of the tank (17), and wherein a pressure prevailing in the tank (17) approximately corresponds to an ambient pressure, so that the powder particles are output from the tank (17) and are directed onto a substrate to be powdered or dusted free of a conveying air stream.

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