EP0520145B1 - Device for dust removal - Google Patents

Abstract

The invention relates to a device for the removal of dust adhering to film-like material webs (2) - for example paper, plastic or textile webs - or sheets and continuous webs, having at least one first discharge electrode (3) and having a first and second suction chamber (4, 5), which is characterised in that first disturbance openings (6) are arranged on the side of the material web (2) directed towards the suction chambers (4, 5), in that first disturbance openings (6) are arranged downstream of the first discharge electrode (3) and upstream of the first suction chamber (4) in the direction of travel of the material web, in that the first disturbance openings (6) open into a first gap (9) formed between the first disturbance openings (6) and the material web (7), in that the air current passing through the first disturbance openings (6) is directed onto the material web surface and in that the first suction chamber is designed such that the dust-laden air is sucked in at an angle alpha to the surface of the material web. d

Description

The invention relates to a device for removing dust that adheres to sheet-like material webs - for example paper, plastic or textile webs - or plates and endless webs.

A device for removing dust is already known (DE-39 14 310 A1) which serves to pick up and remove the dust accumulating in the area of turning bars. The known device has, among other things, a discharge electrode, suction chambers and a guide element over which the material web is moved. The guide element is a turning bar in the known device.

With the known device, the cutting dust that arises when cutting paper webs should be removed so that the system no longer has to be shut down for mechanical cleaning and to reduce the risk of a dust explosion. The suction chambers provided for this purpose are arranged in a semicircle around the turning bar and absorb the dust released by the blowing air of the turning bar and the centripetal acceleration. In addition, is on the side facing away from the suction chambers the paper web is provided with a suction nozzle, as well as discharge electrodes which reduce electrostatic adhesive forces by electrostatically neutralizing the dust particles and the product web by a corresponding supply of positive and negative ions in the surrounding air.

A disadvantage of the known device, which has proven itself in general, however, is that, owing to the arc-shaped suction chambers, it can only be arranged on turning bars in the deflection area of the material web and only achieves a dedusting effect which no longer meets the increased requirements for dedusting.

EP-A-0 245 526 discloses a device for removing dust that adheres to sheet-like material webs (1), for example paper, plastic or textile webs, or plates and endless webs, with at least one first discharge electrode (10) and with one first suction chamber (13), blowing openings (11) being arranged on the side of the material web (1) facing the suction chambers (13).

From US-A-4 454 621 a device for removing dust adhering to the sheet-like material webs (S), for example paper, plastic or textile webs, or plates and endless webs, with at least one first discharge electrode (10) and with A first suction chamber (30) is known, wherein blowing openings (38a) are arranged on the side of the material web (1) facing the suction chambers (30).

Fault openings that are not connected to an air pressure source are not mentioned in these documents.

The invention is therefore based on the object of providing a device for removing dust according to the preamble of the main claim, in which the dedusting effect is increased compared to the known device.

The object underlying the invention is achieved in a device according to the preamble of the main claim (DE-39 14 310 A1) by its characterizing features.

For this purpose, first fault openings are arranged on the side of the material web facing the suction chambers in the direction of material web movement behind the first discharge electrode and in front of the first suction chamber. Through these first fault openings, the additional air is sucked into the gap between the suction chamber and the opposite guide element, so that faults are generated in the air layer on the material web, a larger proportion of dust is entrained and taken up by the first suction chamber arranged behind the first fault openings in the material web movement direction can. In addition, the fault openings reduce the risk of the product web being sucked in. By A suitable polarity of the discharge electrode, the guide element and the first suction chamber and, if appropriate, further suction chambers, the dust removal is further improved. It is particularly advantageous to place the discharge electrode at a high DC voltage potential with + and - at alternating tips or at a rectangular AC voltage, the guide element being grounded at the same time.

Advantageous further developments and refinements of the invention are shown by the subclaims. In particular, the arrangement of second fault openings behind the first suction chamber increases the dedusting effect, in particular when the air flow sucked in through the second fault openings and the gap is directed at the area of the material surface in which the first suction chamber is arranged. Because of this air flow, an impingement flow is built up against the air layer arranged closely above the material web surface, which in cooperation with the negative pressure emanating from the first suction chamber brings about a particularly good dedusting, which can be caused by the flow separating from the material web surface.

In a special embodiment, a second suction chamber sucks off further dust particles and thereby increases the dedusting effect. To improve the effectiveness, third fault openings can also be arranged, which are arranged behind the second suction chamber in the direction of material movement.

In order to improve the flow conditions, in particular to increase the flow speed, a first gap, which is formed between the first fault openings and the guide element, is tapered. As a result, with a constant volume flow in the gap, the flow velocity in the direction of material web movement is increased, so that a higher proportion of dust particles is entrained. A A comparable effect is achieved if the second gap arranged between the second fault openings and the guide element is widened in the direction of material web movement. This is because the air flow takes place in this area against the direction of material movement due to the suction effect of the suction chambers.

The guide element can either be a turning bar known per se or a deflection roller, but a plate with an essentially flat surface can also be provided. In the case of material webs with low inherent rigidity (thin paper webs, foils, fabrics), the arrangement of a shaft is imperative, since only the tensile stresses in the material web can prevent it from being sucked into the suction chambers. A guide element can also be dispensed with for material webs with a sufficiently high inherent rigidity. There is then a gap between the fault openings and the material web. In any case, it is possible to provide blow holes in the guide element to reduce friction between the material web and the guide element. In the event that a cylinder, for example a turning bar, is provided as the guide element, the second suction chamber can be arranged such that the dust particles detaching tangentially from the material web due to the deflection of the material web are taken up by the second suction chamber. A maximum linear amplification of the two effects is to be achieved by a linear alignment of the force effect due to the suction and the effect of the inertia of the dust particles.

It was thought to justify the particularly good results with the dedusting by disturbing the stationary parallel flow over the material web. The interactions between the first and second suction chambers, the first and possibly second and third fault openings and the tapering gap make the stationary air ingested through the fault openings Parallel flow superimposed small two-dimensional disturbances, which are built up from partial vibrations of different wavelengths.

The alignment of the first fault openings is such that the air flow passing through them is directed essentially perpendicular to the surface of the material web. The arrangement of the first suction chamber in the area in which the detachment of a boundary layer formed by air on the material web surface is possible also promotes the dedusting effect. For this reason, the angle alpha at which the first suction chamber sucks in the air should also be adapted to the angle of a separation flow line.

Figur 1

eine erste Ausführungsform der erfindungsmäßen Vorrichtung in einem Schnitt;

Figur 2

eine zweite Ausführungsform der erfindungsgemäßen Vorrichtung abgebrochenen in einem Schnitt;

Figur 3

eine dritte Ausführungsform der erfindungsgemäßen Vorrichtung abgebrochen in einem Schnitt;

Figur 4

eine vierte Ausführungsform der erfindungsgemäßen Vorrichtung in einem Schnitt.

Figur 5

eine fünfte Ausführungsform der erfindungsgemäßen Vorrichtung in einer teilweise geschnittenen Darstellung von oben;

Figur 6

die Vorrichtung gemäß Fig. 5 in einem Schnitt; und

Figur 7

die Vorrichtung gemäß Fig. 1 mit zusätzlich angeordneten Zuluftrohren.

The invention is explained in more detail below with reference to the drawing. In this shows:

Figure 1

a first embodiment of the device according to the invention in a section;

Figure 2

a second embodiment of the device according to the invention broken off in a section;

Figure 3

a third embodiment of the device according to the invention broken off in a section;

Figure 4

a fourth embodiment of the device according to the invention in a section.

Figure 5

a fifth embodiment of the device according to the invention in a partially sectioned view from above;

Figure 6

the device of Figure 5 in a section. and

Figure 7

1 with additionally arranged supply air pipes.

A preferred first embodiment of the device according to the invention is shown in FIG. 1. In this, a guide element 7 is designed as a cylinder. The cylinder is shown in a section perpendicular to its longitudinal extent, with first and second suction chambers 4, 5 and first and third fault openings 6, 14 extending essentially parallel to the cylinder axis. A material web 2 is partially guided around the cylinder and is moved essentially in the circumferential direction of the cylinder. A first and a second suction chamber 4, 5, also shown in section, and first and third fault openings 6, 14 open into a common surface. The fault openings are suitable arrangements or rows of spaced-apart bores or breakthroughs, their spacing and air passage cross section and the associated amount of air which disturbs stationary flow. In this case, first discharge openings 6, then the first suction chamber 4, then the second suction chamber 5 and finally third fault openings 14 are arranged behind a discharge electrode 3 in the direction of the material web. This arrangement effects the supply air flow to the first and the second suction chamber illustrated by the arrows 13 in FIG. 1 4, 5 out. A first gap 9 formed by first fault openings 6 and the guide element 7 or the material web is designed in such a way that it tapers in the direction of material movement, as a result of which the air sucked therein is accelerated towards the first suction chamber 4. It should be noted that the air drawn in through the suction chambers reaches flow velocities of more than 50 m / s in the gap, so that even normal material web speeds of 15 m / s can be neglected.

The first suction chamber 4 is arranged so that it sucks in the air at an angle α from the surface of the material web. The angle α is acute to the surface of the web guide element 7 and to the web movement direction. The angle α is approximately 30 ° to the tangent to the surface of the material web guide element 7. The second suction chamber 5, in contrast, is arranged so that it sucks the air at an angle β to the tangent to the material web surface, the angle β being acute to the surface of the material web guide element 7 and to the material web guiding direction and is dimensioned such that the dust particles detached from the material web surface by inertial forces and flow effects are maximally accelerated. The deflection of the material web on the guide element also causes the product to be broken open and thus to release bound dust particles. The second suction chamber 5 is therefore arranged in the area in which the inertial forces which act on the guide element 7 due to the material web deflection. The third fault openings 14 cause a comparable disturbance of the parallel flow caused by the first fault openings 6 and are arranged such that the air flow emanating from the third fault openings 14 is directed at the area of the material web guiding element 7 in which the second suction chamber 5 is arranged.

A particularly good dedusting is achieved by the interaction of the various fault openings 6, 14 and the suction chambers 4, 5 and the discharge electrode 3. In particular, fine dust with particle sizes smaller than 25 »m can be removed. It is also contemplated to design the guide element 7 as a turning bar.

The second embodiment of the device according to the invention shown in a section perpendicular to the longitudinal extent of the device in FIG. 2 has first fault openings 6, the first suction chamber 4, the guide element 7 and the discharge electrode 3. The material web 2 is guided between the discharge electrode 3, the first fault openings 6 and the suction chamber 4, on the one hand, and the guide element 7, which is designed as an essentially flat plate, on the other hand. The movement of the material web takes place at an angle, preferably at right angles to the longitudinal extent of the device, the longitudinal extent of the device being predetermined by the longitudinal extent of the fault openings of the suction chambers and the discharge electrode.

The discharge electrode 3 is arranged in front of the first fault openings 6 in the material web movement direction. The first suction chamber 4 is arranged in the material web movement direction behind the first fault openings 6 in such a way that it sucks in the air from the material web surface at an angle alpha. This angle alpha is dimensioned such that the dust particles detached from the surface of the material web by flow effects and the electrostatic neutralization are additionally accelerated by the suction effect of the extracted air.

A third embodiment of the device for removing dust according to the invention is shown in a section in FIG. 3 and, in addition to the discharge electrode 3, the first fault openings 6 and the first suction chamber 4, has second fault openings 10 through which air additionally flows against the material web surface. The guide element 7 is arranged opposite the first fault openings 6, the first suction chamber 4 and the second fault openings 10, the material web 2 being located between them. From the drawing it can be seen that on the one hand the first fault openings 6 with the material web or the guide element 7 the first gap 9 and, on the other hand, the second fault openings 10 with the material web 2 or the guide element 7 form the second gap 11. Both columns 9, 11 have an essentially unchanged cross section. The first fault openings 6 are arranged such that they point essentially perpendicular to the surface of the material web. In the interaction of the second fault openings 10 with the first suction chamber 4, very extensive dedusting is achieved, in particular also for dust particles below 25 »m. The first suction chamber 4 is arranged in such a way that it accelerates the dust particles, which are released from the material web surface by flow effects and the electrostatic neutralization, in order to be able to suction them safely.

Fig. 4 shows a fourth embodiment of the device according to the invention. The first fault openings 6, the first suction chamber 4 located behind them and the second fault openings 10 located behind them open into a common surface. The guide element 7 is located opposite this surface. While the guide element 7 is embodied as a substantially flat plate in this embodiment, the common surface is shaped such that the first gap 9 formed by the first fault openings 6 with the guide element 7 is in one another Material movement direction tapers and that the second gap 11 formed by the second fault openings 10 and the guide element 7 widens in the material web movement direction. The first suction chamber 4 is arranged in the region of the smallest cross section of the gaps formed by the first and second fault openings or the common surface and the material web or the guide element 7. The orientation of the first suction chamber 4 and the second fault openings 10 essentially corresponds to the embodiment shown in FIG. 3. A discharge electrode 3 is also provided in this arrangement.

The design of the first and second gap 9, 11 ensures that the air that is sucked in by the first suction chamber 4 is accelerated toward the first suction chamber 4.

5 shows a further embodiment of the device according to the invention. The material web 2 is guided around a cylindrical guide element 7 and is moved in the direction of the arrows M. In the material web movement direction M, the first fault openings 6 are located behind the discharge electrode 3, which has alternating positive and negative direct voltage potentials or AC electrodes at their tips. Behind the first fault openings 6 there is the first suction chamber 4. Arranged last in the material web movement direction M, there are the second fault openings 10. The arrows 13 illustrate the supply air flow in the material web movement direction M upstream of the device in the material web movement direction M and in the material web movement direction M behind the device the material web movement direction M flows. The supply air flow is essentially parallel in front of and behind the device. The disturbances illustrated by the arrows 15 are superimposed on this supply air flow. The first and second fault openings 6, 10 have bores or openings which, among other things, prevent the danger of the material web 2 being drawn in by the suction chamber 4.

5 is shown in section in FIG. 6. The suction chamber 4 is located between the first and the second fault openings 6, 10. The discharge electrode 3 neutralizes the electrostatic attractive forces that exist between dust particles and the material web 2. Because the material web 2 is guided around the guide element 7 and because tensile stresses in the material web 2 pretension it in the direction of the guide element 7, it is possible to use a very high suction speed to work even with material webs 2 with low inherent rigidity.

7 shows a device according to the invention in accordance with the first preferred embodiment, the supply air, which is illustrated by the arrows 13, being supplied through supply air pipes 16. This ensures that as little ambient air as possible, which may be contaminated, is sucked in in the case of critical products, for example medical film. A supply of germ-free air can also be made available under certain circumstances by the supply air pipes 16, so that the high purity requirements can be met for many products.

The supply air supplied through supply air pipes 16 can, however, also be cleaned fresh air, or the extracted air is filtered and made available again. In the case of larger systems, such an arrangement also makes sense due to the energy balances, since it does not excessively disrupt existing heating and air-conditioning devices.

Claims (13)

1. Device for removing dust clinging to film-like material webs (2) - for example, paper, plastic or textile webs - or sheets and continuous webs by means of at least one first discharge electrode (3);
   having at least one surface, in which a first extraction chamber (4) disposed in the direction of movement of the material web opens;
   a material web guide element (7), which is situated opposite said surface;
   the direction of movement of the material web being defined as the direction in which the first extraction chamber (4) is disposed downstream of the first discharge electrode (3);
   characterized in
   that first disturbance openings (6) are disposed in the surface in which the first extraction chamber (4) opens, and that said first disturbance openings (6) contained in the surface and said material web guide element (7) form a first gap (9), into which said disturbance openings open,
   that the first disturbance openings (6) are disposed - in the direction of movement of the material web - downstream of the first discharge electrode (3) and upstream of the first extraction chamber (4),
   that the first disturbance openings (6) are disposed in such a way that additional air is sucked through said disturbance openings into the gap (9), and
   that the first extraction chamber is so constructed that it sucks in the dust-laden air at an acute angle (α) to the surface of the material web guide element (7) and to the direction of movement of the material web.
2. Device according to claim 1, characterized in that second disturbance openings (10) are disposed - in the direction of movement of the material web - downstream of the first extraction chamber (4) in such a way as to form a second gap (11) between the second disturbance openings (10) and the material web guide element (7).
3. Device according to claim 2, characterized in that the second interference openings (10) are disposed in such a way that the air stream emanating from the second disturbance openings (10) is directed towards the region of the material web guide element (7) in which the first extraction chamber (4) is disposed.
4. Device according to claims 1 to 3, characterized in that disposed - in the direction of movement of the material web - downstream of the first extraction chamber (4) is a second extraction chamber (5), which extracts the air above the material web guide element (7) at an acute angle (β) to the surface of the material web guide element (7) and to the direction of movement of the material web.
5. Device according to claim 4, characterized in that third disturbance openings (14) are disposed, viewed in the direction of movement of the material web, downstream of the second extraction chamber (5) in such a way that the air stream emanating from the third disturbance openings (14) is directed towards the region of the material web guide element (7) in which the second extraction chamber (5) is disposed and the third disturbance openings (14) together with the material web guide element (7) form the second gap (11).
6. Device according to one of claims 1 to 5, characterized in that the first gap (9) between the first disturbance openings (6) and the material web guide element (7) tapers in the direction of movement of the material web.
7. Device according to one of claims 2 to 5, characterized in that the second gap (11) between the second and third disturbance openings (10, 14) and the material web guide element (7) widens in the direction of movement of the material web.
8. Device according to one of claims 1 to 7, characterized in that the guide element (7) comprises blow-holes for reducing friction at the guide element (7).
9. Device according to one of claims 1 to 8, characterized in that the guide element (7) is a plate having a substantially flat surface.
10. Device according to one of claims 1 to 8, characterized in that the guide element (7) is a cylinder.
11. Device according to one of claims 1 to 10, characterized in that the air stream passing through the first disturbance openings (6) is directed substantially vertically onto the surface of the material web guide element (7).
12. Device according to one of claims 1 to 11, characterized in that the acute angle (α) at which the first extraction chamber (4) sucks in the air is approximately 30° to the tangent of the surface of the material web guide element (7).
13. Device according to one of claims 1 to 12, characterized in that the first and the second extraction chamber (4, 5) as well as the disturbance openings (6, 10) open into a common surface, which with the surface of the material web guide element (7) forms a gap which initially tapers and then widens in the direction of movement of the material web.

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