EP1519837B1 - Device for cleaning the surface of a rotating body driven in rotation - Google Patents

Abstract

The device comprises a round cylindrical ultrasound generator (5), adjustable relative to the rotating body with radial emission. The ultrasound generator (5) has a soft coating on the outer surface thereof which may be wetted with cleaning fluid (11.2). The above is driven in rotation about an axis (6) parallel to the axis (10) of the rotating body.

Description

The invention relates to a device for cleaning the surface of a driven in rotation about an axis, preferably circular-cylindrical body of revolution, in particular a roller or a cylinder of a printing press, with a vetraschallerzeuger, see, for. For example DE-A1-19902957.

There are generally known washing devices on offset printing machines, which are used for the cleaning of ink rollers, blanket or impression cylinders. Furthermore, systems are known, wherein the washing unit for the blanket cylinder is supplied via a pumping station with detergent and compressed air. At the heart of this system is a washing unit with four main components, consisting of a cleanser dispenser, a dirt winder, a squeegee with inflatable rubber lip, and spray nozzles to ensure an even distribution of water and detergent. By means of a microprocessor control all blanket cylinders can be cleaned simultaneously or individually. The washing programs required for this can be individually selected for each printing unit, depending on the degree of soiling of the blankets, via a central control unit. Depending on the washing program, a dosed amount of detergent with water can be rinsed onto the washing cloth via special nozzles.

It is also a washer for blanket cylinder of an offset printing machine known (G 91 15 948 U), which is equipped with a pressed against the blanket cylinder during the washing process washing device, which is associated with a reservoir for washing liquid. The scrubbing liquid is supplied after consumption via a return line to a return tank.

Furthermore, a washing device for blanket cylinder offset printing machines with an adjustable to the blanket cylinder by pivoting about a pivot axis housing is known (DE 40 10 957 C2), wherein the washing device is associated with a washing roller, with a Variety in the axial direction of adjacent spray nozzles is provided for spraying with a washing liquid. This device uses more solvent.

In addition, a washing device for inking units in printing machines is known (DE 41 21 017 A1), wherein the washing device is housed in a housing in which a variable speed driven rubber roller and a counter-driven and sprayable by means of nozzles and arranged in operative connection with the rubber roller polygonal roller arranged are. The housing is adjustable against the cleaning of the roller. The paint residues are collected in a so-called squeegee. Disposed beneath the polygonal roller and inside the housing is a detergent-filled tray, which is connected at its bottom to a vibrator and into which the surface of the polygonal roller is immersed. The vibrator rests on vibration isolators, which are connected to the bottom of the housing. The vibrator operates in the ultrasonic range and removes any residual paint remaining on the polygonal roller. The tub fills with cleaning agents and paint residues, which are supplied via the nozzle strips or via the polygonal roller. The liquid in the tub then overflows and is returned via the Waschmittelabführvorrichtung the cleaning circuit.

In contrast, the invention has for its object to optimize a cleaning device of the type mentioned with few structural means and to improve overall.

The cleaning device that achieves this object has a circular-cylindrical ultrasound generator with radial radiation that can be adjusted with respect to the rotating body to be cleaned. The ultrasonic generator has on its outer shell a wettable with cleaning liquid, soft coating. It can be driven in rotation about an axis parallel to the axis of the body of revolution.

Due to the advantageous design and arrangement of the cleaning device cleaning over the known devices is substantially improved and also intensified, can be done with a few structural means. Furthermore, it is cleaned more intensively and gently by this device. This allows the cleaning intervals increases and the service life of the components to be cleaned are extended. In addition, solvent can be saved significantly in the cleaning liquid.

In a preferred embodiment, the ultrasound generator can be pointed towards and away from the body of revolution. He can switch between working and non-working positions.

In a preferred embodiment, the ultrasonic generator can be adjusted on its axis or along its axis, preferably in a reciprocating positioning movement with a stroke of 1 mm to 50 mm and a stroke frequency of 100 s ^-1 to 10 min ^{- 1} . The axial adjustment of the ultrasound generator serves to equalize the cleaning effect, which results from the ultrasonic-induced reactions in the cleaning liquid.

In a preferred embodiment, the ultrasonic generator moves in its emission direction, in the longitudinal ultrasonic wave direction, or transversely to its axis, preferably in a reciprocating positioning movement with an amplitude of 1 μ to 240 μ, preferably at a half amplitude of 10 μ to 100 μ. This movement of the ultrasonic generator leads to a homogenization and intensification of the ultrasonic effect on the cleaning process. The frequency at which the movement is carried out corresponds to the selected ultrasonic frequency. The movement is z. B. in welding sonotrodes produced by the piezoceramic disks or piezoceramic packages. In a preferred embodiment, there are also relative movements transversely to the emission direction, in the transverse direction of the wave, or here along the axis of the ultrasonic generator. These movements are performed with a half amplitude of up to 5 μ. All movements of this kind can be set by parameter changes.

In a preferred embodiment, a cam mechanism or a swash plate mechanism or a linear drive is provided for the adjustment of the ultrasound generator or the ultrasound generator is accommodated in a holder which is mounted pivotably about an axis.

In a preferred embodiment, the ultrasound generator is clocked in one or more of its movements and / or its ultrasound emission.

In a preferred embodiment, the ultrasonic generator can be pressed against the rotating body.

In a preferred embodiment, the ultrasonic generator is spring-loaded against the rotation body.

In a preferred embodiment, one or more nozzles are provided for supplying cleaning fluid to the pad of the ultrasonic generator. With only one nozzle, the outlet opening thereof should extend over approximately the entire length of the rotary body and / or ultrasound generator. But there are also several, preferably arranged in a row nozzles into consideration.

In a preferred embodiment, the pad of the ultrasonic generator is formed as a shell thereof. The lining may also be a self-contained band that passes over the ultrasonic generator and at least one other roller.

In a preferred embodiment, a scraper element is provided which acts against the lining of the ultrasound generator. In the case of a band-shaped covering, it is advisable to arrange the scraper element on the other roller.

In a preferred embodiment, the stripping element is rotatably mounted.

In a preferred embodiment, at least one respective nozzle for cleaning liquid is provided on both sides of the wiping element.

The coating of the Ulraschallerzeugers may be brush-like and / or made of foam and / or made of fabric. Preference is given to a net-like and / or net-gummed fabric which is penetrated by bristles. A preferred fabric for the covering is terry or molton. But there are also other, cleaning fluid receiving and ultrasonic cleaning materials in the cleaning liquid into consideration.

In a preferred embodiment, a web of cleaning cloth passes over the ultrasonic generator and comes from a cleaning cloth roll to be wound up into a dirty cloth roll.

In a preferred embodiment, the web can be wetted on the ultrasound generator side with cleaning liquid, in particular sprayed with one or more nozzle (s). Wetting "from the inside" prevents cleaning fluid from entering the printing press.

In a preferred embodiment, the ultrasound generator is designed as an intensity-modulated and / or amplitude-modulated and / or frequency-modulated and / or pulsed ultrasound transmitter.

The ultrasound generated by the ultrasonic transmitter is preferably in a frequency band between 2 x 10 ⁴ s ^-1 and 2 x 10 ⁶ s ^-1 or in a frequency band between 2 x 10 ⁴ s ^-1 and 10 ⁵ s ^-1 or in a frequency band between 4 x 10 ⁴ s ^-1 and 2 x 10 ⁵ s ^-1 .

In a preferred embodiment, the ultrasound generator, if necessary in conjunction with its sheathing, effects only one preliminary stage of cavitation. This is to be understood that cavitation bubbles can already form, but they do not reach their actual required size for imploding themselves, and thus do not implode, or implode prematurely with such a large impact, but rather disintegrate. It can therefore also form no Sonolumineszenz.

In a preferred embodiment, a welding sonotrode is used as the ultrasonic generator. The latter conventionally comprises a converter, an amplitude transformation piece and a radiating sonotrode head.

In a preferred embodiment, the ultrasonic generator comprises piezoelectric transducers distributed with axial offset over the circumference of the ultrasonic generator. This measure serves to even out the effect of ultrasound.

In a preferred embodiment, the outer jacket of the ultrasound generator consists of a layer material whose surface hardness is less than the surface hardness of the base body.

Fig. 1

die seitliche Teilansicht einer Vorrichtung zum Reinigen von Gummituchzylindern für eine Offsetdruckmaschine mit einem verstellbar gelagerten Ultraschallerzeuger;

Fig. 2

eine schematische Darstellung des Gummituchzylinders mit dem darunter angeordneten Ultraschallerzeuger in einer Vorderansicht quer zu Fig. 1;

Fig. 3

ein weiteres Ausführungsbeispiel einer Reinigungsvorrichtung in einer Seitenansicht ähnlich der von Fig. 1, wobei Düsen für Reinigungsflüssigkeit beidseits eines Abstreifelements vorgesehen sind;

Fig. 4

eine Teilansicht der inneren Schicht einer Ummantelung des Ultraschallerzeugers;

Fig. 5

eine vordere Teilansicht des Ultraschallerzeugers mit der Ummantelung; und

Fig. 6

und Fig. 7 seitliche Teilansichten weiterer Reinigungsvorrichtungen mit einem zusätzlichen Reinigungstuch.

The invention is explained below with reference to exemplary embodiments illustrated in the drawing. Show it:

Fig. 1

the partial side view of an apparatus for cleaning blanket cylinders for an offset printing machine with an adjustably mounted ultrasonic generator;

Fig. 2

a schematic representation of the blanket cylinder with the ultrasonic generator arranged underneath in a front view transverse to Fig. 1;

Fig. 3

a further embodiment of a cleaning device in a side view similar to that of Figure 1, wherein nozzles are provided for cleaning liquid on both sides of a scraper;

Fig. 4

a partial view of the inner layer of a jacket of the ultrasonic generator;

Fig. 5

a front partial view of the ultrasonic generator with the sheath; and

Fig. 6

and FIG. 7 shows lateral partial views of further cleaning devices with an additional cleaning cloth.

In the drawing, 1 denotes a device in Fig. 1, which is used for cleaning blanket cylinders 3 of an offset printing machine 2. In the drawing, only the essential parts are indicated schematically. The drive of the blanket cylinder 3 is carried out according to arrow 3 '. The blanket cylinder 3 is associated with a cleaning device 4, which consists of at least one ultrasonic generator 5, which is arranged with its axis of rotation 6 to a rotation axis 10 (Fig. 2) of the blanket cylinder 3 running parallel.

The ultrasound generator 5 or ultrasound transmitter generates high-frequency sound waves which, for example, generate small, initially growing bubbles in liquids, which finally implode and locally develop a tremendous heat for a short time. These extreme conditions create an unusual environment for chemical reactions. During compression, for example, a positive pressure is exerted on the fluid that pushes the molecules together. On the other hand, expansion creates a negative pressure that pulls them apart. During the expansion phase, a sound wave can be enough generate high-intensity bubbles. In order for a blister to form, so much negative pressure must occur during the expression phase of the sound wave that it overcomes the tensile strength of the fluid. The decrease in bubble size with increasing frequency causes the duration of collapse to decrease. As a result, the mechanical effects of the collapse decrease as it decreases due to the shorter duration of severity. Therefore, a relatively strong mechanical action takes place in the frequency range from 2 × 10 ⁵ s ^-1 to 6 × 10 ⁵ s ^-1 . Above about 1 x 10 ⁶ s ^-1 , these effects decrease significantly. The advantageous design of the ultrasonic generator allows use even under extreme conditions such as dust, dirt, high temperatures and moisture. The surface of the ultrasound processor or ultrasound generator 5, which radiates the ultrasound, consists of materials such as stainless steel or coated stainless steel, wherein the layer material has a lower surface hardness than the steel.

The ultrasound generator 5 with its converter 5.1 shown in FIGS. 1 to 3 has on both sides of its end bearing journals 6.1, which are rotatably received in spaced-apart side parts or wall parts of a holder 14. The holder 14, which is indicated only schematically in Fig. 1, superimposed on an axis 16 and can be moved in the direction of the surface of the blanket cylinder 3 and thus pressed against the surface as shown in FIG. The adjustment of the ultrasonic generator 5 via a not shown in the drawing adjusting device, wherein the movement of the adjustment of the holder 14 is controlled by a processor in a certain clock frequency. The drive of the ultrasonic generator 5 via a with 9 in Fig. 2 schematically indicated drive device, which may be formed as a cam gear or swash plate mechanism and causes the ultrasonic generator 5 moves with its axis of rotation 6 as shown in FIG. 6.3 axis parallel to the axis 10 of the blanket cylinder 3. Further, the drive device 9 is designed so that also a cycled movement of the ultrasonic generator 5 in the direction of the surface of the blanket cylinder 3 and opposite thereto, so that the surface of the blanket cylinder 3 comes into contact only briefly with the surface of the ultrasonic generator 5.

The ultrasonic generator 5 is coated with a cloth-like coating 7 or a stocking, which covers the outer surface of the ultrasonic generator 5. The cloth-like coating 7 may consist of a net-rubberized terry stocking so that the surface of the ultrasonic generator forms a brush-like stripping element.

The cleaning device 4 further includes a rotatably mounted scraper element, which is referred to below as a doctor blade 8. The doctor blade 8 can be started or driven by means of a drive device not shown in the drawing. The stripping element or the doctor blade 8 can consist of a square material or of a nip roll and is at least temporarily in contact with the surface of the ultrasound generator 5 and scrapes out dirt from the brush-like coating 7.

In the area of the surface to be cleaned of the blanket cylinder 3 is a cleaning device, wherein in the drawing, only the cleaning nozzle 11 of FIG. 1 or the further embodiment shown in FIG. 3 two cleaning nozzles 12 and 13 are provided on both sides of the doctor blade 8. Instead of a cleaning nozzle, a surface nozzle, slot nozzle or numerous juxtaposed nozzles can be provided.

The cleaning nozzle 11 of FIG. 1 is located above the point of contact between the surface of the blanket cylinder 3 and the surface of the ultrasonic generator 5. In the drawing of FIG. 1, the one nozzle 11 is shown, which may be formed, for example, as a surface nozzle and with its slot opening extends over the entire width of the blanket cylinder 3. Furthermore, it is possible that numerous juxtaposed cleaning nozzles 11 are provided according to FIG. 1 in front of the surface of the blanket cylinder 3. The nozzle 11 is connected via a line 11.1 with a reservoir not shown in the drawing, so that in this way washing liquid through the cleaning nozzle 11 of the surface of the blanket cylinder 3 and the ultrasound generator 5 can be supplied. The cleaning liquid 11.2 is returned via a 14 connected to a holder 14.2 via a return line not shown in the drawing in a return tank, which serves to hold the dirty washing liquid. The dirty washing liquid can be processed in the return tank via appropriate filter elements, so that it is then available again as a cleaning fluid.

In the embodiment according to FIG. 3, as already mentioned, the doctor blade 8 is surrounded by two cleaning nozzles 12 and 13, so that the cleaning liquid 11.2 is sprayed onto the surface of the ultrasonic generator 5 from below. The two nozzles 12 and 13 may also, like the nozzle 11, be connected via a line 11.1 with a return tank.

The distance between the outlet opening of the individual nozzles to the surface of the parts to be cleaned and the angle between the nozzle axis and the surface of the ultrasonic generator 5 is fixed in the embodiment. However, it is also possible to change the setting of the nozzles by a corresponding, not shown in the drawing device.

By means of the ultrasonic generator 5 with the liquid applied, cavitation is generated, as already described above. The extent and effect of cavitation depend in particular on the parameters of the ultrasonic field. So z. B. frequencies, amplitude and sound intensity of the ultrasonic generator 5 such as cavitation waves, size of the bubble radii, the strength of bubble collapse and spatial dimensions of cavitation are regulated. On the basis of a quantitative description of the ultrasound fields, cavitation processes can thus be optimized and ultrasound generators 5 can be modulated on the type of surfaces and contaminations.

For this purpose, the ultrasound generator 5 is designed as an intensity-modulated and / or amplitude-modulated and / or frequency-modulated and / or pulsed ultrasound transmitter. The ultrasound generated by the ultrasonic transmitter 5 is in a frequency band between 2 x 10 ⁴ s ^-1 and 2 x 10 ⁶ s ^-1 or in a frequency band between 2 x 10 ⁴ s ^-1 and 10 ⁵ s ^-1 or in a frequency band between 4 x 10 ⁴ s ^-1 and 2 x 10 ⁵ s ^-1 .

By means of the ultrasound generator 5, as already mentioned, an ultrasound cleaning is effected, with the waves of the ultrasound being transmitted to the ultrasound generator Cause formation of gas bubbles. As a result, a periodic compression and expansion of the gas bubbles is generated. The gas in the bubbles can reach a high temperature and the implosion of the bubbles creates a targeted pressure. As a result, an advantageous ultrasonic cleaning of the blanket cylinder 3 to be cleaned is effected. The cleaning effect is significantly improved by the advantageous embodiment of the surface of the ultrasonic generator 5. Due to the advantageous arrangement and arrangement of the ultrasonic generator 5 with the advantageous placement of the cleaning nozzles can be cleaned rollers and cylinders of the printing presses in the installed state. Likewise, this can create the possibility of performing the cleaning largely without solvents, so that the risk of explosion can be turned off. As a result, the risk potential is reduced because no or almost no solvent vapors occur. By the metered supply of the cleaning liquid 11.2 in conjunction with the ultrasonic generator 5, a direct cleaning with ultrasound is carried out very thoroughly. The time intervals between the cleaning processes can be changed depending on the paper insert and the color.

By this cleaning device, it is possible to accommodate this space-saving in the smallest space, which is not possible with band cloth cleaning.

In Fig. 4 and Fig. 5, the sheath of the brush is illustrated in more detail. The ultrasound generator 5 may have a very hard surface, for example made of stainless steel or other suitable material. The ultrasound generator 5 is surrounded according to FIG. 4 and FIG. 5 by a mesh grid 18, in which numerous brush hairs 19 are firmly connected to the mesh grid 18 according to FIG. 5. The mesh grid 18 completely surrounds the surface of the ultrasound generator 5 and serves to receive the individual bristle hairs 19 or bundled bristle hairs according to FIG. 5. The individual bundles of bristle hairs 19 are arranged at a distance from each other according to the mesh size of the mesh grating 18 and extend with respect to FIG Surface of the cylinder-shaped ultrasonic generator 5 radially outward. The rotary body or the ultrasonic generator 5 and thus the brushes 19 are completely surrounded by a casing 20. The sheath or the fabric-like coating 20 may consist of a close-meshed fabric.

The surface of the ultrasound generator 5 has a layer material whose surface hardness is less than the surface hardness of the base body of the ultrasound generator 5. The surface of the ultrasound generator 5 may, as already mentioned, consist of a metal surface, stainless steel surface or another, very hard material.

In the cleaning device according to FIG. 6, an internally toothed brush belt 19b passes over an ultrasound generator 5 and a further roller, which, like the ultrasound generator 5, is provided with a complementary external toothing 25. Furthermore, an additional cleaning cloth is passed over the ultrasonic generator 5 with the brush belt 19b through the gusset between the cylinder 3 to be cleaned and the ultrasonic generator 5. The cylinder 3 is an impression cylinder with grippers 24. The additional cleaning cloth is unwound from a cleaning cloth roll 21 and wound onto a dirty cloth roll 22.

In the cleaning device according to FIG. 7, an additional cleaning cloth is guided over an ultrasonic transmitter, which is covered with a brush 19c.

List of reference numbers

1

Device for cleaning blanket cylinders

2

Offset

3

Cylinder, blanket cylinder, rotating body

3 '

Arrow for part 3 drive

4

cleaning device

5

Ultrasonic generator, ultrasonic transmitter

5.1

converter

6

Rotary axis of the ultrasound generator

6.1

pivot

6.2

wall part

6.3

Arrow from part 5

7

cloth-like cover, stocking

8th

rotatably mounted scraper element, doctor blade

9

Drive device, such as swash plate drive

10

Axle, axis of rotation of the blanket cylinder

11

Cleaning nozzles, surface nozzle, slot nozzle (= liquid supply device)

11.1

management

11.2

cleaning fluid

12

Cleaning nozzles, surface nozzle, slot nozzle, numerous nozzles arranged next to each other

13

Cleaning nozzles, surface nozzle, slot nozzle numerous juxtaposed nozzles

14

bracket

14.1

Arrow pivoting direction of bracket 14

14.2

container

16

axis

18

grid display

19

Brush hair, brush

19b

brush belt

19c

brush coating

20

Sheath, cloth-like coating

21

Clean cloth roller

22

Dirty cloth roll

23

Internal toothing of the brush belt

24

grab

25

External toothing of the roller

Claims (28)

1. Device for cleaning the surface of a rotating mechanism, preferably a rotating body, particularly a roller or cylinder (3) in printing machines comprises a round cylindrical ultrasonic generator (5) with radial emission, adjustable relative to the rotating body. The ultrasonic generator (5) has a soft coating on the outer surface thereof which may be wetted with cleaning fluid (11.2). The above is driven in rotation around an axis (6) parallel to the axis (10) of the rotating body.
2. Device according to claim 1 is characterised that ultrasonic generator (5) can be adjustable relative to the rotating body and of it suppressible.
3. Device according to claim 1 or 2 is characterised that ultrasonic generator (5) is adjustable in parallel to its axis (6), preferably in a bidirectional actuation in the range of 1 to 50 mm.
4. Device according to claim 1 to 3 is characterised that ultrasonic generator (5) is adjustable in parallel to its essential radial emission direction, preferably in bidirectional actuation in longitudinal wave direction in the range of 1 µ to 240 µ preferably 10 µ to 100 µ.
5. Device according to claim 1 to 4 is characterised that the adjustment of the ultrasonic generator (5) can be adjusted by a cam mechanism or is yoke driven, or a linear drive is designed, or the ultrasonic generator (5) is pivoted in a holder.
6. Device according to claim 1 to 5 is characterised that the ultrasonic generator (5) is pulsed in one or more movements.
7. Device according to claim 1 to 6 is characterised that the ultrasonic generator (5) is pressed against the rotating body.
8. Device according to claim 1 to 7 is characterised that the ultrasonic generator (5) is spring-mounted against the rotating body.
9. Device according to claim 1 to 8 is characterised that there are one or more nozzle(s).designed for the supply of cleaning liquid to the coat of the ultrasonic generator (5)
10. Device according to claim 9 is characterised as a nozzle with its outlet spanning the full length of rotating body and / or ultrasonic generator (5).
11. Device according to claim 9 is characterised as several nozzles (11, 12, 13) in a row.
12. Device according to claim 1 to 11 is characterised that the coating (19c, 20) of the ultrasonic generator (5) is designed as a jacket.
13. Device according to claim 1 to 11 is characterised that the coating of the ultrasonic generator (5) is an endless tape (19b) running along the ultrasonic generator (5) and at least another roller (25).
14. Device according to claim 1 to 13 is characterised that a scraper (8) affect the coat of the ultrasonic generator (5).
15. Device according to claim 13 and 14 is characterised that a scraper (8) is located at another roller (25).
16. Device according to claim 1 to 15 is characterised that the scraper (8) is pivoted.
17. Device according to claim 1 to 16 is characterised that on both sides of the scraper (8) at least one nozzle (12, 13) is provided for the cleaning liquid.
18. Device according to claim 1 to 17 is characterised that the coating of the ultrasonic generator (5) is a brush coating (19, 19b, 19c) and / or made of foamed material and / or fabric coating (20).
19. Device according to claim 1 to 18 is characterised that the coating of the ultrasonic generator is net-like and / or net-rubberized fabric (20) with bristle.
20. Device according to claim 1 to 19 is characterised that the coating of the ultrasonic generator (5) is towelling or molleton.
21. Device according to claim 1 to 20 is characterised that a web of cleaning cloth (21) runs to a dirty cloth roll (22) along the ultrasonic generator (5).
22. Device according to claim 21 is characterised that the web on the ultrasonic generator side is wettable with cleaning liquid, particularly with one or more nozzle(s) for spraying.
23. Device according to claim 1 to 23 is characterised that the ultrasonic generator (5) is designed to be an intensity modulated and / or amplitude modulated and / or frequency modulated and / or pulse modulated ultrasonic sender.
24. Device according to claim 1 to 23, is characterised that the ultrasonic sender (5) generates ultrasound in a wave band between 2 x 10⁴ s^-1 and 2 x 10⁶ s^-1 or in a frequency band between 2 x 10⁴ s^-1 and 10⁵ s^-1 or in a frequency band between 4 x 10⁴ s^-1 and 2 x 10⁵ s^-1.
25. Device according to claim 1 to 23, is characterised that the ultrasonic generator (5) generates only one preliminary stage of cavitations in the cleaning liquid during at least one cleaning interval.
26. Device according to claim 1 to 25, is characterised that at least one welding sonotrode is used as ultrasonic generator (5).
27. Device according to claim 1 to 26, is characterised that the ultrasonic generator (5) features piezoelectric transformers (converters), which are distributed with axial offset along the ultrasonic generator (5).
28. Device according to claim 1 to 27, is characterised that the outer coating of the ultrasonic generator (5) consists of coating material which surface hardness is less than the one of the body material.

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