EP1814695A2

EP1814695A2 - Nozzle for co2-snow/crystals

Info

Publication number: EP1814695A2
Application number: EP05797252A
Authority: EP
Inventors: Godehard Möller; Andreas Michalske
Original assignee: Venjakob Maschinenbau GmbH and Co KG
Current assignee: Venjakob Maschinenbau GmbH and Co KG
Priority date: 2004-09-28
Filing date: 2005-09-23
Publication date: 2007-08-08
Also published as: WO2006034824A2; KR20070063563A; RU2007109826A; WO2006034824A3; JP2008514394A; US20090197512A1; CA2579294A1; MX2007003396A

Abstract

The invention relates to a nozzle (1) for the oriented discharge of CO2-snow and compressed air. A central region (5) of the nozzle (1) comprises at least one first discharge opening (6) which is embodied in such a manner that it produces a central beam (2) of CO2-snow having a supersonic speed. The central region (5) of the nozzle (1) is surrounded by a peripheral area (7) which is provided with a plurality of second discharging openings (8) which are arranged about the first discharge opening (6) and embodied such that they can produce a covering beam (3) which is made of air, preferably compressed air, and which surrounds the central beam (2), and has a slower speed than the central beam (2). The covering beam (3) has the same direction as the central beam (2). The invention also relates to a method for treating, in particular cleaning, a work piece which is to be coated with CO2-snow, and a central beam (2) of CO2-snow having a speed greater than 200 m/s which is directed to the workpiece by means of the covering beam (3) which is made of air and/or compressed air and which surrounds the central beam, and the covering beam (3) has a slower speed than the central beam (2).

Description

NOZZLE FOR CO2 SNOW / CRYSTALS

The invention relates to a nozzle for CO2 snow. In particular, the invention relates to a nozzle for the directed ejection of CO2 snow, in particular for cleaning workpieces.

Before painting a workpiece, it is cleaned and freed from dirt. In the past, it has been considered to use CO2 snow or crystals as cleaning agents in a jet.

In DE 19926119 C2, a jet tool for generating a beam of CO2 snow for cleaning microsystems or precision engineering is described. In this jet tool, CO2 snow is generated in a capillary and admixed by a supersonic velocity support jet. The overall jet thus generated contains CO2 particles and is used for cleaning small parts such as a microchip.

The jet tool of the prior art can not be used to clean workpieces over a large area in a painting device. In particular, the capillary arrangement only allows a very low throughput of CO2 snow and is therefore not suitable for wide industrial application.

The object of the present invention was therefore to provide a nozzle for cleaning, with CO2 snow and air, which meets the requirements of industrial cleaning. It is another object of the invention to provide a method for treatment, in particular for cleaning a workpiece to be coated with CO2 snow.

The problem is solved by a nozzle for directional

Ejecting CO2 snow and compressed air being a central In the region of the nozzle, it has at least one first discharge opening, which is designed to produce a supersonic speed core jet having CO2 snow, wherein the central region of the nozzle is surrounded by a peripheral region, which is a plurality of second

Discharge openings, which are arranged (preferably symmetrically) around the first discharge opening and are designed to generate a core jet surrounding the jet stream of air, preferably compressed air at a lower speed than the core stream, wherein the cladding jet has the same direction as the core jet. By means of such a nozzle, a core jet of CO2 snow can be generated, which has a surrounding jet of air or compressed air surrounding it and can thus bring a cleaning jet onto a working area which is dimensioned sufficiently to be able to sustainably clean even larger areas. Preferably, the core jet is formed by CO2 snow being formed by relaxation of CO2 and generated by pressurized air within a CO 2 gun as a mixed jet of CO 2 and compressed air at high speed at the exit. Instead of compressed air, another gas can be used. A core jet produced in this way is then a mixed jet of CO2 snow and air or compressed air. This core jet is surrounded by a sheath jet of pure air, which shields the core against external influences. Particularly preferably, the second Eritladungsöffnungen are formed so that this air is sucked, which then form a cladding beam surrounding the core beam. This jacket jet can be generated by entraining air through the exiting core jet via the second discharge openings. Ambient air is particularly preferably used for this purpose, ie the second discharge openings are free with their distal end intended. As a result, the ambient air is preferably entrained by these slots, accelerated and sits evenly around the core jet. This effect can preferably be enhanced by an attached venturi. Furthermore, icing of the nozzle tip is prevented by a targeted approach of the ambient air to the nozzle outlet. Alternatively, a compressed air connection can be provided at these distal ends of the second discharge openings. In this way, it is possible to clean workpieces before a painting step, which are passed in a short time with a transport device on such a C02 gun with this nozzle.

In a further advantageous embodiment of the present invention, a tempering device for

Controlling the temperature of the sheath jet of compressed air and or the core jet of CO2 snow provided. By controlling the temperature, in particular of the jacket jet, it is possible to influence the geometry of the core jet. A temperature of the cladding beam of less than 1O ⁰ C is preferred particularly preferably of less than 4 ⁰ C.

In a further advantageous embodiment of the present invention, a control device is provided for adjusting the speed of the mantle jet of compressed air and / or the core jet of CO2 snow, in particular independently of one another. By adjusting the speed of the cladding jet, the geometry of the core beam and thus the focus and the working range of the core beam can also be varied.

In a further advantageous embodiment of the present invention, the first discharge opening for the core jet is designed as a Laval nozzle. By choosing the Laval nozzle allows the CO2 snow to very high speeds, especially preferred

Supersonic speed, be accelerated and leave the nozzle with it. The combination of this very high speed of the core jet on the one hand and the surrounding jet stream of compressed air on the other hand, which prevents disturbing influences from the core jet, allow the application of the core beam to the working area of a workpiece to be cleaned over long distances, thereby also cleaning

Profile parts and three-dimensional bodies is possible.

In a further advantageous embodiment of the present invention are supplies for the compressed air within the nozzle in a section in front of the

Discharge openings provided parallel to feeders for the CO2 snow led. By this constructive measure a lower height of the nozzle is possible. In addition, the forces are ideally absorbed in the nozzle and preferably aligned with the exit direction of the two beams.

The object is also achieved by a carousel support for receiving at least one nozzle according to the invention comprising a rotating device, which is designed such that the at least one nozzle is movable in rotational movements over a working range. Through the use of a carousel support, as described for example in the utility model DE 29814293 Ul the applicant for another application, the cleaning is even more workable even with workpieces with undercuts. On such a carousel carrier, preferably at least one nozzle is arranged on a rotatable hub, so that upon rotation of the rotating device by the cleaning jet a circle or an ellipse in a plane on the working area is described. Particularly preferably, the nozzle is made obliquely, so that also undercuts cleaned can be, since the beam in the rotating movement of the rotating device describes a conical section in space and not just a cylinder. This oblique orientation of the individual nozzle so that the workpiece not only frontally but also in the undercut area cleaned from the side. Particularly preferably, the rotating device is (co-) driven by recoil forces of the jet emerging from the nozzle. In this way it is possible to save an additional drive for the rotating device. However, it is also advantageously possible to provide a special speed or speed curves for the rotating device via a corresponding control device for the rotating device, with which special geometries can then be cleaned particularly efficiently. Particularly preferred are on the Karusseiträger or the rotating device a plurality of nozzles, more preferably 3 nozzles provided. In addition, it is advantageous to form the rotating device or the carousel itself again transversely to the conveying direction of the workpiece to be machined, so that the carousel or the rotator perpendicular or oblique to the conveying direction, for example, a conveyor belt on which the workpieces are stored back and can be moved. In this way a very complete workspace is described. Preferably, the angle of attack of the individual nozzle of the carousel support will be set differently, so that by the rotational movement of the individual, nozzles on the one hand and the transverse movement of the entire Krausseiträgers on the other hand, a large

Work area can be extensively and evenly coated.

The object is also achieved by a method for the treatment, in particular cleaning, of a workpiece to be coated with CO2 snow with a core jet of CO2 snow at a speed of more than 200 m / s with a jet stream of air surrounding the core jet, preferably compressed air, is directed onto the workpiece, wherein the jacket jet has a lower velocity than the core jet. By such a method in which the core jet at high speed from CO2 snow is again surrounded by a slower mantle jet of compressed air, the core beam can be well defined and constantly applied over a longer distance on a workpiece. By combining a slower jet of compressed air, all disturbing influences that would alter the geometry of the core jet are discouraged. In this way, the defined core beam of CO2 snow can be generated with constant parameters over long distances and can thus be foreseeably applied to workpieces which have larger undercuts or different distances to the cleaning nozzle.

In a further advantageous method of the present invention, the jacket jet has a speed of less than 80%, preferably less than 75%, more preferably less than 50% of the speed of the core jet. It has surprisingly been found that the cladding jet, even at significantly lower speeds than the core jet a high

Shielding effect against disturbing external influences and contributes to the stabilization of the core beam. Thus, the core jet can act again undisturbed on the workpiece.

In a further advantageous method of the present invention, the ratio of the velocity of the cladding jet to the velocity of the core jet is adjustable. By choosing the ratio of the velocity of the cladding jet to the velocity of the core beam, the geometry of the core beam is affected. In this way it is possible to carry out the beam shaping of the core beam. In another advantageous method of the present invention, the core jet has a velocity of more than 333 m / s. By choosing the supersonic range for the core beam, it is possible to achieve particularly high cleaning effects.

In a further advantageous method of the present invention, the core jet has a diameter of 30 mm. Particularly preferably, the diameter of 30 mm is generated about 80 mm behind a nozzle end and kept constant at this diameter for a further 200 to 300 mm. A variation of the diameter of the beam focus is possible for example by changing the speed of the sheath current and / or the choice of the temperature gradient between sheath current and core current.

In a further advantageous method of the present invention, the cladding jet has an outer diameter of about 200 to 250% of the diameter of the core jet.

In a further advantageous method of the present invention, the geometry of the core beam can be adjusted by varying the speed of the jacket jet.

In a further advantageous method of the present invention, the jacket jet of compressed air at a higher temperature than the core jet of CO2 snow.

In a further advantageous method of the present invention, the workpiece is painted after processing.

Advantageous embodiment and further embodiments are explained in the accompanying drawings. Hereby shows: Fig. 1 is a sectional view of an embodiment of the nozzle according to the invention;

Fig. 2 is an external view of an embodiment of the nozzle according to the invention;

3 is a view of a second embodiment of the nozzle according to the invention in four partial views.

4 shows a view of a third exemplary embodiment of the nozzle according to the invention in four partial views;

5 shows a schematic representation of the core jet and the jacket jet after emerging from a nozzle according to the invention; and

Fig. 4 is a view of an inventive

Carousel carrier with nozzles according to the invention.

FIG. 1 shows a section along the points A'A of a nozzle according to the invention as well as in FIG. 2. The nozzle 1 has a central conveying region for CO2 snow along the arrow shown. This channel opens into a first discharge opening 6, which is located in a central region 5 of the nozzle 1. This central area is circular, as is the first discharge opening. Adjacent to this, a peripheral region 7 of the nozzle 1 is arranged in a circle around the central region 5 of the nozzle 1. In this peripheral region a plurality of slot-like second discharge openings 8 are provided, from which then compressed air can be conveyed. The delivery lines for the compressed air are routed in the middle section of the nozzle parallel to the central conveyor area for CO2 snow.

In use, it is now possible, along the arrow shown to promote CO2 snow, over the first Discharge opening 6, which is shown in the figure as a Laval nozzle is supersonic speed from the nozzle 1 in the central region of the nozzle 5 exit. Compressed air is conveyed out of the peripheral region 7 of the nozzle 1 through the various slots 8 and thus forms a jacket jet around the core jet which escapes in the central region.

In Fig. 2, the nozzle of Fig. 1 is again shown in a schematic overall view. The slot-shaped second discharge openings 8 in the peripheral area 7 of the nozzle, which are arranged around the first discharge opening 6 in the central area 5 of the nozzle, can be seen here in particular. Through these slit-shaped discharge openings 8 a uniform jet surrounding the core jet is formed, which completely surrounds the CO2 snow core jet and can delimit against external influences.

In Fig. 3 is a view of a second embodiment of the nozzle according to the invention is shown in four partial views. In this nozzle, the peripheral portion 7 is formed of slit-shaped discharge holes 8 which, unlike the nozzle of Figs. 1 and 2, the air for the clad jet are formed so that the distal ends of the discharge holes 8 directly communicate with the ambient air. In this nozzle shape, it is provided that the air for the jacket jet from the ambient air is sucked in via the slot-shaped discharge openings 8 and is entrained by the core jet, which can exit via the first discharge opening, thus forming the jacket jet around the core jet. Preferably, this nozzle 1 has eight slot-shaped discharge openings 8, which are arranged in a star shape around the first discharge opening 6 of the nozzle or the central area 5 of the nozzle. The first discharge opening 6 in this case advantageously has a Laval nozzle to define the core jet. In Fig. 4 is a view of a third embodiment of the nozzle according to the invention is shown in four partial views. In this case, a channel having geometry for the second discharge openings 8 is provided. The second

Discharge openings are in this case arranged as channels symmetrically about the first discharge opening 6 and inclined to this at an angle of 26 degrees. Preferably, this angle is between 40 degrees and 5 degrees, more preferably between 20 degrees and 30 degrees. Preferably, eight channels are provided here. Slots, as in the nozzle form according to FIG. 3, may additionally be provided between the channels or alternatively as an alternative to individual channels (not shown).

In Fig. 5, the exiting core beam 2 and the surrounding cladding beam 3 is shown over a length L schematically. From the nozzle 1 emerges via the first discharge opening 6, a mixture of CO2 snow and compressed air as the core jet 2 at supersonic speed along the central, thick arrow shown. In addition, a jacket jet 3 is generated by compressed air in that compressed air emerges from the second discharge openings 8 at a lower velocity than the core jet 2 and forms a jacket jet 3 around the core jet 2. After a distance A from the nozzle head, preferably after about 80 mm, a region L forms over a length L in which the diameter of the core jet 2 is kept substantially constant and is surrounded by the jacket jet 3. The jacket jet 3 has a lower speed than the core jet 2. The length L is preferably about 200 to 500 mm, more preferably about 200 to 300 mm.

By choosing the speed ratio of the jacket jet 3 to the core jet 2, the geometry of the

Kernstrahl 2 are influenced as well as by the choice the temperature of the jacket jet 3 with respect to the temperature of the core jet.

FIG. 6 shows a carousel support 20 according to the invention, on which three nozzles 1 according to the invention are mounted.

A drive motor for the rotation forms the drive 22 whose force can be transmitted via a V-belt to a rotary tube 24. Through the rotary tube 24, the supply of the three nozzles 1.1 to 1.3 can be done via a rotary feedthrough for compressed air and liquid CO2.

The nozzles 1.1 to 1.3 consist of a Co2 snow blasting gun 29, which are provided via an inlet opening 27 for compressed air and a further inlet opening 28 for CO2, shown here with control valve. A gun mount 26 with integrated graduated scale is provided to perform reproducible adjustments of the beam direction.

About the drive 22, the rotary tube 24 and thus the entire carousel is brought into rotation, so that the three nozzles 1.1 to 1.3 come to rotate about the axis of rotation of the rotary tube. By adjusting the jets that emerge from the nozzle, the jet direction can preferably be set via the gun holder 26 so that the area to be machined on the workpiece is traversed optimally. By the provided between the drive motor 22 and the rotary tube V-belt, the rotational speed is controlled directly by the drive motor 22. It would also be conceivable to provide a coupling in such a way that only one basic speed is imparted via the drive motor 22 and further speed components are assisted by a repulsive behavior of the jet out of the nozzle. Particularly preferably, it is possible again, for example, the entire carousel support transversely over the workpiece or in Direction of the workpiece along the arrows shown so that in addition to the rotational movement of the Karusseiträgers a transverse movement, such as a reciprocating motion over the workpiece and / or on the workpiece takes place, so that the three rotating cleaning beams again evenly and more comprehensive the area of the workpiece distributed can be applied.

By this invention, a nozzle for the directed ejection of CO2 snow and compressed air for cleaning

Workpieces and a method provided for this purpose, on the industrial scale over constant working areas towards a high cleaning performance, preferably for the pretreatment of workpieces in a painting, can be achieved.

LIST OF REFERENCE NUMBERS

Nozzle Core jet Jacketed jet Central area of nozzle First discharge opening Peripheral area of nozzle Second discharge opening Tempering device Speed control Carousel carrier Drive Rotary pipe for supply lines Rotary feedthrough Pistol inlet Air inlet CO2 CO2 snow gun

Claims

1. nozzle (1) for the directed ejection of CO2 snow and compressed air, characterized in that a central

Area (5) of the nozzle (1) has at least one first discharge opening (6), which is designed to produce a CO2 snow having core jet (2) at supersonic speed wherein the central region (5) of the nozzle (1) of a peripheral area

(7), which has a plurality of second discharge openings

(8), which are arranged around the first discharge opening (6) and are designed to generate a jet stream (3) surrounding the core jet (2) from air at a lower speed than the core stream (2). 3) has the same direction as the core beam (2).

2. nozzle (1) according to claim 1, wherein a tempering device (10) for controlling the

Temperature of the sheath jet (3) from air and / or the core jet (2) is provided from CO2 snow.

3. nozzle (1) according to any one of the preceding claims, wherein a control device (12) for adjusting the

Speed of the sheath jet (3) from air and / or the core jet (2) of CO2 snow, in particular independently of each other, is provided.

4. nozzle (1) according to any one of the preceding claims, wherein the first discharge opening (6) is designed as a Laval nozzle.

5. nozzle (1) according to any one of the preceding claims, wherein feeds for the air within the nozzle (1) are provided in a section in front of the discharge openings parallel to leads for the CO2 snow out.

6. carousel for receiving at least one nozzle (1) according to one of the preceding claims comprising a rotating device, which is designed so that the at least one nozzle is movable in rotational movements over a working area.

7. A method for the treatment, in particular cleaning, of a workpiece to be painted with CO2 snow wherein a core jet (2) of CO2 snow at a speed of more than 200 m / s with a surrounding the core jet jet stream (3) of air on the Workpiece is steered,. characterized in that the jacket jet (3) has a lower velocity than the core jet (2).

8. The method of claim 7, wherein the cladding jet (3) has a speed of less than 80%, preferably less than 75%, more preferably less than 50% of the velocity of the core jet (2).

9. The method according to any one of the preceding method claims, wherein the ratio of the velocity of the jacket jet to the

Speed of the core beam (2) is adjustable.

10. The method according to any one of the preceding method claims, wherein the core beam (2) has a speed of more than 333 m / s.

11. The method according to any one of the preceding method claims, wherein the core jet (2) has a diameter of 30 mm.

12. The method according to any one of the preceding method claims, wherein the sheath jet (3) a Outside diameter of 200 to 250% of the diameter of the core jet (2).

13. The method according to any one of the preceding method claims, wherein the geometry of the

Core beam (2) by varying the speed of the cladding jet (3) is adjustable.

14. The method according to any one of the preceding method claims, wherein the cladding jet (3) from

Air has a higher temperature than the core beam (2) of CO2 snow.

15. The method according to any one of the preceding method claims, wherein the workpiece is painted after processing.

16. Use of a nozzle (1) according to one of claims 1 to 5 for carrying out a method according to claims 7 to 15.