EP0789635B1 - Method and apparatus for removing dust particles from a relatively moving material web - Google Patents

Abstract

PCT No. PCT/CH95/00196 Sec. 371 Date Mar. 6, 1997 Sec. 102(e) Date Mar. 6, 1997 PCT Filed Sep. 6, 1995 PCT Pub. No. WO96/07460 PCT Pub. Date Mar. 14, 1996According to a method to remove dust particles from a stable material web which moves relative to a contact-free operating de-dusting device, a blower unit of the de-dusting device is provided at a specified first distance (d) and a grounded potential surface at a second distance (d) from the surface of the material web. The velocity and the pressure between the surface of the material and the potential surface of the ultrasonic gas flow existing from the blower unit is adjusted so that the product of the pressure and of the second distance (d) according to Paschen's law makes a discharge of the dust particles on the surface of the material feasible relative to the grounded potential surface. Furthermore, the adhesive forces (van der Waals forces) are overcome by the ultrasonic gas flow. Thus, these dust particles attached to the surface of the material are picked up by the ultrasonic gas flow without using electrically biased discharge electrodes, requiring electrical energy, and are removed by suction by at least one suction unit. The high operating expenses, required for equipment with electrically biased discharge electrodes, become superfluous with the described method.

Description

The invention relates to a method according to the preamble of Claim 1 and a device according to the preamble of Claim 4.

The construction of dedusting systems for moving material webs, also called web cleaning systems, can be roughly non-contact, and divided into those working with brush support become. In the latter dedusting systems, the dust particles with rotating brush roller or stationary brush grater mechanically detached from the material web and then suctioned off. The brush quality, as well as its thickness, material and design the bristles were going to the properties of the cleaning material surface. Such non-generic Dust collectors are in the Bundesverband Druck e.V., Postfach 1869, Biebricher Allee 79, D - 6200 Wiesbaden 1, "Technical Information Service", II / 1985, pp. 1 to 20, as well as in the WO87 / 06527.

Dedusting systems that operate without contact have a blowing unit on which a gas jet on the web to be cleaned led, as well as a suction unit with which the dust particles absorbing gas was sucked off again. With the blowing unit together or in the vicinity, discharge electrodes were used for discharging the dust particles located on the material web. Such dedusting systems are from the EP-A 0 245 526, EP-A 0 520 145, EP-A 0 524 415, the EP-A 0 395 864 and CH-A 649 725 are known.

Another route was followed in EP-A 0 084 633. Here a turbulent gas flow was applied to one to be dedusted Directional fabric web and this through the turbulent flow in Vibration is offset, which removes the dust particles from the fabric surface were replaced. However, this type of dedusting could be only apply to thin material webs that are seen through caused the gas jet to vibrate.

A non-generic cleaning system for removing one on a moving belt, especially a rolled belt adhering liquid is described in DE-A 4 215 602. The problems that arise with a dedusting system also include particles adhering to the surface due to electrostatic forces did not result here.

If at all in the dust extraction systems listed above a fluidic design of the nozzle outlets of the blowing units, they are considered to be Material web inclined channels with constant channel cross-section in the area of the nozzle outlet opening, e.g. in EP-A 0 245 526, EP-A 0 520 145 and DE-A 4 214 602 is shown. Only in EP-A 0 084 633 and in an embodiment variant DE-A 4 215 602 was an outlet channel cross section described the nozzle with a changing cross section. In EP-A 0 084 633 the gas flow was opened vertically guided the fabric web. In DE-A 4 215 602 a mistakenly referred to as Laval nozzle with an after a constriction widening pear-shaped and narrowing again Cross section used.

The invention solves the task of dedusting a moving, stable, which cannot be vibrated for dedusting To carry out material web in which dispenses with discharge electrodes can be.

The invention is based on the 1st surprising finding, that just by choosing a gas stream, especially its pressure on an area of a material web surface to be dedusted as well as the selection of the distance of this area Efficient dedusting is possible from a grounded surface. It is now assumed that efficient dust removal only is then possible if on the area to be dedusted generated gas pressure of the gas stream is so great that the product from the gas pressure and the above distance according to the law of Paschen's corresponding critical stress is less than that electrostatic voltage (charge) of the dust particles, which this mainly adheres to the surface of the material web. I.e. under these conditions the self-discharge takes place Dust particles. You will be neutralized. You are now only liable due to the significantly smaller Van der Waals force and others not electrostatic forces. The gas velocity of the Conditions of the gas flow generating Paschen's law is now still so high to include only the slightly adhering dust particles to remove.

The discharge effect (Paschen's law) is still affected by the Balloelectricity effect (waterfall electricity, Lenard effect) supports, as it through the narrowing nozzle cross-section arises. This is done at least partially Ionization of the gas flowing through, here air, without use any ionization unit requiring electrical energy.

The second surprising finding is based on the fact that through the Special design of the suction unit the gas flow at a deflection angle is deflected and thus the necessary suction effect of the Conveys dust particles into the suction unit.

Based on these findings, there are for the specialist a variety of design options, but here only a small selection can be shown.

The almost daily removal process for cleaning the high-voltage electrodes and their subsequent exact adjustment when reinstalling are thus eliminated in accordance with the invention constructed devices.

The required gas flow is preferably through the Design of the blowing unit and / or the suction unit, such as it is or are described in the dependent claims, reachable.

Fig. 1

eine schematische Darstellung der Kräfte, welche Staubpartikel auf einer Materialbahn halten,

Fig. 2

des Paschen-Gesetz,

Fig. 3

einen Querschnitt durch die Entstaubungsvorrichtung,

Fig. 4a und 4b

einen Teilquerschnitt und eine Draufsicht in Richtung IVb auf eine Einblaseinheit der Entstaubungsvorrichtung mit schlitzförmigem Gasaustritt,

Fig. 5a und 5b

eine zu den Figuren 4a und 4b analoge Darstellung für einen in einer Düsenreihe angeordneten Gasaustritt,

Fig. 6

einen Querschnitt durch eine Variante der Entstaubungsvorrichtung mit zwei auf der gleichen Seite der Materialbahnoberfläche angeordneten Einblaseinheiten,

Fig. 7

einen Querschnitt durch eine weitere Variante der Entstaubungsvorrichtung, bei der die zu entstaubende Materialbahn umgelenkt wird,

Fig. 8

einen Querschnitt durch die in Figur 3 dargestellte Entstaubungsvorrichtung, jedoch mit Strömungsbeeinflussungselementen in der Einblas- und Absaugeinheit,

Fig. 9

eine Draufsicht in Blickrichtung IX in Figur 8 auf die Strömungsbeeinflussungselemente der Einblaseinheit,

Fig.10

eine Draufsicht in Blickrichtung X in Figur 8 auf die Strömungsbeeinflussungselemente der Absaugeinheit,

Fig.11

einen Längsschnitt durch eine Variante einer Einblas- und Absaugeinheit und

Fig.12

eine schematische Darstellung einer Entstaubungsvorrichtung mit der in Figur 11 dargestellten Einblas- und Absaugeinheit zur Entstaubung von blattförmigem Gut.

Examples of the method according to the invention and of the devices which can preferably be used to carry out the method are described in more detail below with reference to the drawings. In addition to the nozzle arrangements and constructions described here, other embodiments can of course also be used, provided the conditions described below for discharging the dust particles and overcoming their holding forces on the material web are achieved without using high-voltage electrodes that require electrical energy. Further advantages of the invention result from the following description text. Show it:

Fig. 1

a schematic representation of the forces that hold dust particles on a material web,

Fig. 2

the Paschen law,

Fig. 3

a cross section through the dedusting device,

4a and 4b

2 shows a partial cross section and a plan view in the direction IVb of an injection unit of the dedusting device with a slot-shaped gas outlet,

5a and 5b

3 shows a representation analogous to FIGS. 4a and 4b for a gas outlet arranged in a row of nozzles,

Fig. 6

2 shows a cross section through a variant of the dedusting device with two blowing units arranged on the same side of the material web surface,

Fig. 7

3 shows a cross section through a further variant of the dedusting device, in which the material web to be dedusted is deflected,

Fig. 8

3 shows a cross section through the dedusting device shown in FIG. 3 , but with flow influencing elements in the blowing and suction unit,

Fig. 9

8 shows a plan view in viewing direction IX in FIG. 8 of the flow influencing elements of the blowing unit,

Fig. 10

8 shows a top view in the viewing direction X in FIG. 8 of the flow influencing elements of the suction unit,

Fig. 11

a longitudinal section through a variant of a blowing and suction unit and

Fig. 12

is a schematic representation of a dedusting device with the blowing and suction unit shown in Figure 11 for the dedusting of sheet-like material.

In Figure 1 , the electrostatic and Van der Waals forces E and W acting on dust particles S are shown schematically. The dust particles S are often also held in place by liquid bridges F. The gas flow G acting on the dust particles S occurs on the right side B of FIG. 1 . The gas stream G is drawn off on the left side A.

In Figure 2, the Paschen's law is - the dependence of the critical voltage U / crit p from the product of pressure and distance d for different gases - is entered. Figure 2 is a copy of Figure 6.20 from K. Simonyi, "" Physikalische Elektronik ", Verlag BG Teubner Stuttgart, 1972, page 526. The law of Paschen is in the book just cited here on pages 524 to 526 and in Ch. Gertsen, "Physik" Springer-Verlag 1960, p. 303. This law specifies the critical electrical voltage U / crit at which a discharge "ignites" between two flat electrodes, where p is the pressure in the gas flow between the electrodes. The pressure-distance product p · d is given on the abscissa of Figure 2 in Torr · cm, where 1 Torr is 133 Pa at 0 ° C.

According to the invention, the law of Paschen is now used for the dedusting of a material web 1 . The dust particles S adhere to them due to their electrical charge. According to the invention, an injection unit 3a / b of the dedusting device with an earthed potential area is arranged at a distance d from the material web surface, and the speed and pressure between the material surface and the potential area of the supersonic gas stream G emerging from the injection unit 3 are set such that the Voltage caused by the charged dust particles S is equal to the critical voltage U / crit in Paschen's law. The product p · d required for the critical voltage U / crit can now be selected from FIG . Now the gas pressure between the material surface carrying the dust particles S and the grounded potential area is set in such a way that, given a given structural distance d between the material surface and the grounded potential area, the value of the product p · d sought above is approximated. With the help of an electronic field meter, it can be determined how high the electrical charge is. This enables an optimization of the product p · d during the assembly and adjustment of the dedusting device.

The required conditions can be achieved with the supersonic gas flow G. The discharged dust particles S are then picked up by the ultrasonic gas flow G without the use of electrically biased discharge electrodes and sucked off with a suction unit 7 . The high maintenance costs that are required for systems with electrically biased discharge electrodes are therefore eliminated here.

The injection unit as well as the suction unit 3a / b or 7a / b are made of metal and grounded. It is therefore the distance of the blowing unit 3a / b from the surface of the material web 1 equal to the distance d of the grounded potential area from it. In order to obtain good electrical conductivity, the surfaces of the blowing unit and the suction unit 3a / b or 7a / b facing the material web 1 can be coated with an electrically conductive layer. For aluminum, for example, an anodizing process would be used to obtain good electrical conductivity.

In the dedusting device shown in cross section in FIG. 3 , both the upper and lower sides 9a and 9b of the material web 1 can be dedusted. For this purpose, one blowing-in 3a and 3b and one suction unit 7a and 7b are arranged above the top and also below the bottom 9a and 9b . The movement of the material web 1 takes place in the direction of the arrow 11 . The conveying speed of the material web 1 is 4.75 to 15 m / s in the exemplary embodiment described here. The conveying speed has no influence on the efficiency of the dedusting device.

The blowing device 3a or 3b described below is designed in such a way that an ultrasound gas stream, here an ultrasound air stream G, emerges from it. The gas stream G emerging from the blowing device 3a / b hits the surface of the material web 1 at an angle α between 20 ° and 100 °, preferably between 30 ° and 55 °, against its direction of movement 11 . The suction of the dust particles S lifted off the material surface takes place downstream in the flow direction 25 of the outflowing gas G at a first angle σ between 20 ° and 70 °, preferably below approximately 45 ° and again at a second point approximately perpendicular to the material surface. This second suction acts in particular on dust particles S lying in depressions and holes.

The blowing unit 3a / b has a two-part nozzle structure, described below. Starting from a pressure channel 13 as a gas supply unit, there is a continuously tapering nozzle cross-section 15 which, after a constriction 17, merges into a continuously expanding nozzle cross-section 19 up to the nozzle outlet 20 . The width of the constriction 17 is between 0.02 mm and 0.08 mm, preferably less than about 0.04 mm. The opening angle at the nozzle outlet 20 is between 3 ° and 15 °, but preferably between 5 ° and 10 °. The surface line lying on the left in the cross section of FIG. 3 in the widening nozzle cross section 19 is curved, while the opposite surface line is a straight line 21 . This straight line 21 extends at an angle α to the plane of the material web 1 . The angle α is between 20 ° and 100 °, preferably between 30 ° and 55 °. The edge point 22 of this straight line 21 at the nozzle outlet 20 has the smallest distance d from the material web 1 , which is between 0.5 and 2 mm, depending on the material to be dedusted. This distance d corresponds to the distance d of the Paschen's law. The opening 23 between the two blowing units 3a and 3b is designed in the direction of movement 11 as a triple-widening "V", the leg angle of which increases at each transition step 24a and 24b . The gas emerges from the nozzle opening 20 , as indicated by an arrow 25 in FIG. 3 , obliquely onto the material web 1 against its direction of movement 11 in the direction of the relevant suction unit 7a or 7b ,

The edge point 22 is designed as a sharp edge. As a result of this sharp edge 22 , when the supersonic flow G emerges from the nozzle outlet 20, a flow vortex region is created, the turbulence of which removes the dust particles S discharged according to the Paschen law from the surface 9a or 9b of the material web 1 against the Van der Waalschen Forces W supports. The blowing units 3a and 3b are made of metal and are grounded by a schematically illustrated electrical grounding analogous to the suction unit 7a and 7b . The nozzle outlet 20 lies in a plane 6 which intersects the material web 1 at an angle between 25 ° and 65 °, preferably below 45 °.

Analogous to the two blowing units 3a and 3b, there are also two suction units 7a and 7b . The two suction units 7a and 7b are arranged and formed symmetrically to one another. Each of the two suction units 7a and 7b has two suction channels 27 and 29 , which open into a suction chamber 30 . The inputs of the suction channels 31a and 31b are arranged in a plane 33 , which is at a constant distance from the top or bottom 9a or 9b of the material web 1 . The plane 33 is at the same time the upper side of the suction unit 7a or 7b opposite the upper or lower side of the material. The suction units 7a and 7b are preferably made of electrically conductive material (metal). However, if other material is used or if the metal can coat with a non-conductive corrosion coating over time, this surface, like that of the injection units 3a and 3b , must be provided with an electrically conductive layer, as already explained above. As shown in FIG. 3 , the plane 33 is set back in relation to the nozzle outlet 20 . This reset can also be smaller. The level 33 could also be arranged directly after the nozzle outlet 20 .

The suction channel 27 has a funnel-shaped tapering suction mouth 35 which is inclined towards the surface of the material web 1 . The inclination of the suction mouth 35 is directed towards the nozzle outlet 20 . The surface line 36a of the funnel-shaped suction mouth 35 facing the nozzle outlet 20 has an angle β that is as flat as possible to the surface of the material web 1. The angle β is between 15 ° and 30 °. The other surface line 36b of the suction mouth 35 opposite the surface line 36a is steeper and points to Surface of the material web 1 at an angle σ between 20 ° and 70 °. Since the suction mouth 35 should in any case be funnel-shaped, it is of course forbidden that the two extreme angle values of 30 ° can be used together at the angles β and σ.

The suction mouth 35 then merges into a narrowed channel piece 37 , one surface line of which is the extension of the surface line 36b . This channel piece 37 extends to a further channel piece 39 , which then opens into the suction chamber 30 .

The distance h from the intersection of the shell line 36b with the plane 33 from the edge 22 (= the one lower end of the straight line 21 ) is ten to twenty-five times the distance d .

By arranging the blowing unit 3a or 3b , the suction channel 27 is flushed away from dust particles S which may be adhering to it.

The suction channel 29 is also funnel-shaped, but its surface line 40a facing the nozzle outlet 20 extends perpendicular to the surface of the material web 1 , while the surface line 40b lying opposite it runs slightly inclined to the surface of the material web 1 .

The suction chamber 30 has a profiling 44 on at least one of its opposite walls. This profile 44 is used to hang flow baffles, not shown. The flow baffles are necessary so that approximately the same pressure conditions prevail in the suction chamber 30 over all mouths of the channels 27 and 29 .

To remove dust from the material web 1 moving at a speed of up to 30 m / s, air G is blown with the blowing unit 3a and 3b at an air speed of up to a maximum of 550 m / s. In order to achieve this outflow speed, a pressure of approximately 2 bar prevails in the pressure channel 13 . Depending on the selected supersonic gas speed, a pressure of 50 to 100 mbar then results on the surface of the material web 1 . The dust particles S located on the surface of the material web 1 are now neutralized on the basis of the above-described laws of Paschen in a dark discharge, which is in principle a glow discharge at very low current intensities. At the same time, the dust particles S are lifted off by the supersonic air flow G , supported by the swirling, caused by the edge 22 against the Van der Waals forces acting on them. The dust particles S are sucked off through the suction channels 27 and 29 , the channel 29, which runs almost perpendicular to the surface of the material web 1 , mainly serving to receive dust particles S from depressions and holes.

The air blown in through the blowing unit or units 3a and 3b and the suction power of the suction unit or units 7a and 7b is in the temperature range from 18 ° C. to 23 ° C. The room in which the dedusting device is located prevails Overpressure.

The nozzle outlet 20, as well as the inputs to channels 27 and 29 can now, as shown in Figure 4a and 4b once enlarged in cross section and is shown in a top view in longitudinal slots 41 and once as nozzles rubbing 43 as shown in Figures 5a and 5b is shown to be trained.

To improve the absorption process of the dust particles S in the supersonic gas flow G , flow influencing elements 49 , 50 and 51 can be arranged in the expanding nozzle cross section 19 of the injection unit 3a and 3b , as well as in the two suction channels 27 and 29 , as indicated in FIG .

The flow influencing elements 49 arranged in the nozzle area 19 on the wall 21 are narrow longitudinal webs, as are shown in a plan view in viewing direction IX in FIG. 9 . Each longitudinal web 49 lies in a plane running parallel to the direction of movement 11 , which is at an angle of 82 ° to the material web 1 . In the example described above, the longitudinal webs 49 have a width of 1 mm and a mutual spacing of 15 mm.

The rows of webs 50 and 51 arranged in the suction channels 27 and 29 are narrow longitudinal webs, as shown in a plan view in the viewing direction X in FIG. 10 . Each longitudinal web 50 and 51 lies in a plane also parallel to the direction of movement 11 , which extends at an angle of 60 ° to the material web 1 . In the example described above, the longitudinal webs 50 and 51 have a width of 2 mm and a mutual spacing of 30 mm.

In addition to the blowing units 3a and 3b arranged in FIG. 3 , a further blowing unit, as shown in FIG. 6 , can also be arranged on each side of the suction unit or units 7a and 7b .

Instead of flat material webs 1 , material webs 46 deflected by a deflection unit 45 can also be dedusted. The position of the blowing unit, as well as that of the suction unit, is then, as shown in FIG. 7 , adapted to the course of the material web 46 . The angle of detachment of the material web 46 from the deflection unit 45 is preferably between 15 ° and 20 ° in order not to cause an unnecessary increase in electrical charging due to charge exchange and charge separation.

The above-mentioned division of the injection unit 3a or 3b into two parts with the parts 3 ' and 3'' allows a simpler manufacture compared to a one-piece design. The division takes place along line 47 , which merges into straight line 19 . Sealing takes place via a sealing ring 48 , the course of which is laid depending on the use of the row of nozzles 43 or the longitudinal slot 41 . Due to the division of the injection unit 3a or 3b , a simple production of the flow influencing elements 49 is only possible.

The blowing unit 3a and 3b , as well as the associated suction units 7a and 7b are preferably designed as blocks, which can be attached to one another in parallel to the movement of the material web 1 , in order to be able to adapt the width of the dedusting device to the respective material web width to be dedusted.

Instead of moving the web of material, of course also moved the dedusting device over the material web become. Usually, however, the material web is or between the nozzle exits and inlets.

With the dedusting device described above not only material webs are dusted, but also plates and bows.

The dedusting device described above can be used for dedusting of any sheet-like and plate-like material, such as press chipboard, blockboard, plastic, paper, Cardboard tapes, glass, general foils, metal and medical foils, Textiles, printed circuit boards, industrial braids, film and magnetic strips etc. can be used.

Instead of the blowing unit 3a and 3b shown in FIGS. 3 to 10 , a unit 53 shown in FIG. 11 can also be used, which represents a union of a blowing with a suction unit. Furthermore, in contrast to the blowing units 3a and 3b , the flow velocity in the subsonic area is used; however, it is also possible to work in the area of the speed of sound. Analogous to the blowing units 3a and 3b , the unit 53 is also made up of two grounded nozzle parts 54a and 54b and has a constriction 55 of the nozzle channel cross section 56 . Starting from a pressure channel 57 designed analogously to the pressure channel 13 , this nozzle also has a tapering nozzle cross-section 59 (analogous to FIG. 15 ). In contrast to the blow-in units 3a and 3b , however, the narrow constriction 55 which has straight surface lines is advanced to the nozzle outlet 60 and is therefore significantly longer. This means that there is a stronger ionization effect (balloeloctricity) on the flowing stream. The axis of the constriction 55 has a preferred angle δ of approximately 51 ° with the tangent 68 to the material surface 71 . Other values for the angle δ between 20 ° and 100 ° and in particular between 30 ° and 55 ° can also be used. However, the value listed in the exemplary embodiment permits optimal work, in particular with regard to low air consumption and good pressing of the material web 71 to be dedusted against the drum 74 (pressure cylinder).

Analogous to the above blowing units 3a and 3b, this unit 53 also has a flow widening nozzle cross-section, which is now formed here by the space 61 in front of the nozzle outlet 60 . In contrast to the above injection units 3a and 3b , here the edge 63 of the one nozzle channel side, which is designed analogously to the lower edge 22, is outwards by an edge height a of 0.1 mm to 0.9 mm, here by 0.6 mm extended. This extension causes on the one hand a nozzle channel expansion and on the other hand a deflection of the escaping stream, as indicated by arrow 64 . This stream thus produces a suction effect, which conveys the dust particles into the suction unit 65 , which ultimately ensures the flow direction through an arranged row of webs in the suction channel and, lastly, has a very important role for the conveyance of dust particles up to the suction hose.

The width b of the constriction 55 is adjusted together with the gas pressure in the pressure channel 57 in such a way that optimal dedusting takes place with the lowest possible air consumption. In the embodiment variant described here, the width of the constriction is 0.04 mm at a pressure of 1.5 bar in the pressure channel 57 and a distance d / 53 of 4 mm to 7 mm, preferably 5 mm. The inclination of the narrowed nozzle channel 55 with respect to the tangent 68 to the material web 71 is here, for example, 51 °.

The suction unit integrated in the unit 53 consists of a suction channel 65 which is approximately similar to the suction channel 35 , 37 and 39 , with the one channel wall being formed here only by a correspondingly shaped sheet metal 67 which can be attached, in a simpler design. Here too, analogous to the one already described above, the inlet of the suction channel 65 has an acute angle Φ in the transport direction 70 of the material web. The angle Φ should have a value between 20 ° and 50 ° and should preferably be between 33 ° and 39 °. The edge of the inlet opening of the suction channel 65 facing away from the nozzle outlet 60 is located at a distance e , which is 17 mm in the exemplary embodiment.

In order to minimize the air consumption required for dedusting, the pressure channel 57 is divided into individual subchannels in the direction transverse to the material web 71 . These sub-channels, which are not explicitly shown and which are identical in FIGS. 11 and 12 with the reference number 57 , are each connected to a supply chamber 69 via a supply channel which can be closed by a piston (not shown). The supply ducts have slightly changing flow cross-sections to equalize the pressure. The pistons can be adjusted via a mechanism (not shown) such that one supply channel after the other and thus also one partial channel after the other can be separated from the air supply and thus from the supply chamber 69 starting from the outer periphery. This allows adaptation to the web width that is actually to be cleaned. Only the required number of subchannels is supplied with compressed air and thus the air consumption is optimized, ie minimized.

The arrangement of the blowing / suction unit 53 in a dedusting device for sheet-like material 71 is shown in FIG . 12 . The sheets 71 to be cleaned are each held and held with a clamp 72 on a first drum 73 (feed cylinder). The transfer to a second drum 74 (printing cylinder) takes place in its approach location 76 with adjacent clamps 72 and 75 , the clamp 72 being opened synchronously with one another and the clamp 75 being closed for sheet acceptance. The illustration in FIG. 12 shows the good 71 already gripped by the clamp 75 with the clamp 72 open, a part of the sheet-like good 71 still resting on the drum 73 and being pulled onto it. The blow-in / suction unit 53 is assigned to the drum 74 , on which safety rollers 77 are arranged in the transverse direction to the width of the goods 71 , which should ensure that the sheet-like goods 71 are guided in the event of an air flow failure or a faulty sheet transfer.

Due to the high rotational speeds used for the drums 73 and 74 , the arcs 71 (good) tend to knock out or detach from the drum surface. With the devices according to the invention, this lift-off in addition to the dedusting can now be set satisfactorily by adjusting the air pressure. However, if the air pressure is set in such a way that only perfect dust removal is achieved, this may be too low for the "fixation" of the sheets. In this case, the security roller 77 takes over the desired hold-down.

Claims (13)

1. Process for removing dust particles (S) from a relatively moving, especially stable material web surface (1; 71) with a dedusting device that operates without contact, characterized in that a grounded potential surface area (6, 33; 54a, 54b) that faces material web surface (1; 71) of an injection unit (3a, 3b; 53) of a dedusting device is arranged at a distance (d; d/53) from material web surface (1; 71), the speed and pressure (p) between a material web surface area that is to be dedusted in each case and potential surface (6, 33; 54a, 54b) of flow of gas (G) that exits from injection unit (3a, 3b; 53) are to be adjusted in such a way that the critical voltage (U/crit) that is associated with the product of pressure (p) and distance (d; d/53) according to Paschen's Law lies below electrostatic voltage (E) of dust particles (S) on material web surface (1; 71) so that they are neutralized, and thus the holding forces (E/W) of the dust particles on the material web surface are overcome and the latter (S) are picked up only by flow of gas (G) without an ionization unit that requires electrical energy and are suctioned off by at least one suction unit (7a, 7b; 65).
2. Process according to claim 1, wherein the flow of gas, especially a flow of air (G), is blown at an angle (α, σ) of between 20° and 100°, preferably between 30° and 55°, onto material web surface (1; 71) and is suctioned off by at least one suction unit (7a, 7b; 65) that is downstream with regard to the direction of gas flow, i.e., upstream in the direction of travel of the material (11; 70).
3. Process according to claim 2, wherein dust particles (S) that are lifted by flow of gas (G) from the material web surface are picked up by a first suction opening (27; 65) that is inclined at an angle (σ, ) of between 20° and 70°, preferably at 45° from direction of gas flow (25), and preferably are picked up by an additional second suction opening (29) that is appoximately perpendicular to material web surface (1).
4. Dedusting device for carrying out the process according to one of claims 1 to 3 with an injection unit (3a, 3b; 53) that is connected to a supply unit (13; 57), as well as a suction unit (7a, 7b; 65), wherein injection unit (3a, 3b; 53), starting from supply unit (13; 57), has a continuously tapering nozzle cross-section (15; 59), which turns into a widening cross-section (19; 61) after a narrowing (17; 55), injection unit (3a, 3b; 53) has an electrically conductive surface area (6, 33; 54a, 54b) that is grounded and faces a material web surface area (1; 71) that carries dust particle (S), whereby the gas pressure in supply unit (13; 57), as well as distance (d; d/53) of grounded surface area (6, 33; 54a, 54b) from the material web surface area (1; 71) that is to be dedusted continuously in each case can be adjusted in such a way that dust particles (S) can be removed here without any use of ionization unit that can be connected to an electrical energy source to ionize the gas flow and can be suctioned off by suction unit (7a, 7b; 65).
5. Device according to claim 4, wherein the gas pressure in supply unit (13; 57), the distance (d; d/53) of grounded potential surface (6, 33; 54a, 54b) from material web surface area (1; 71) that is to be dedusted and the configuration of the nozzle cross-section (15, 17, 19; 59, 56, 55, 61) and its position up to the area to be dedusted are adjusted in such a way that, depending on the product of distance (d, d/53) and second gas pressure (p) that can be produced by injection unit (3a, 3b; 53) by the gas pressure in supply unit (13; 57) between grounded surface area (6, 33; 54a, 54b) and material web surface area (1; 71) that is to be dedusted and in each case is to be pulled continuously past, the critical voltage (U/crit) of Paschen's Law lies below electrostatic voltage (E) that holds dust particles (S), etc., in the area.
6. Device according to claim 4 or 5, wherein the nozzle outlet is arranged in such a way that its exiting flow of gas strikes the latter opposite direction of travel (11; 70) of material web (1; 71).
7. Device according to one of claims 4 to 6, wherein the axis of nozzle channel (21; 55) of injection unit (3a, 3b; 53) lies in a plane that lies at angle (α, σ) of between 20° and 100°, preferably between 30° and 55°, with respect to material web (1; 71) or its tangent (68).
8. Device according to claim 7, wherein the wall of the nozzle of injection unit (3a, 3b; 53) has at least one asymmetrically designed wall area on its is, especially in the area of opening (20; 60), whereby one of the nozzle channel surface lines of injection unit (3a, 3b; 53) is a straight line (21; 55), which lies in a plane that runs at an angle angle (α, σ) of between 20° and 100°, preferably between 30° and 55°, with respect to material web (1; 71).
9. Device according to claim 8, wherein straight nozzle channel surface line (21; 55) ends in a sharp edge (22; 63) at nozzle outlet (20; 60) to produce an area of turbulent flow extending from here toward the material web surface.
10. Device according to one of claims 4 to 9, wherein suction opening (35) of suction unit (27; 65) is tapered like a funnel starting from suction opening (31a), whereby one of nozzle surface lines is a first straight line (36a), which runs in a plane that lies at an angle (β, ) to material web (1; 71) of between 15° and 50°, especially between 33° and 39°,
11. Device according to one of claims 4 to 10, wherein injection unit (3a, 3b; 53) is made of at least two partial pieces (3, 3''; 54a, 54b) and preferably separating line(s) (47) run(s) through straight line (21; 55) of the nozzle channel surface line.
12. Device according to one of claims 4 to 11, characterized by a division into blocks preferably parallel to relative direction of movement (11; 70) of material web (1; 71) in order to be able to match the device width to the width of material web (1; 71) in a way that is simple to design.
13. Device according to one of claims 4 to 12, characterized by a first and a second injection unit (3a) that are arranged at a distance from one another in relative direction of movement (11) of material web (1), on both sides of which injection unit are arranged suction unit (7a), whereby the axes of the injection nozzle channels of the first and the second injection units are directed against one another.

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