The invention pertains to a nozzle head for a spray device according to the preamble of claim 1.
Such nozzle heads are commonly used on spray devices for the hydrostatic, pneumatic or combined hydrostatic and pneumatic atomization of paints, varnishes, adhesives or other liquid substances, particularly in paint spray guns.
In the nozzle heads of such spray devices, the air ring nozzle has the function of discharging the compressed air supplied to the device in the form of a high-energy air jet that draws material from another central nozzle, atomizes this material and forms a spray jet containing said material. Horn air nozzles usually are directed at the spray jet obliquely and equidirectionally to the outflow direction in laterally arranged horns of the nozzle head that point forward in the spray jet direction such that the air jets being discharged from these nozzles can respectively deform or form the spray jet. Due to the lateral deformation/formation, a more or less large flat jet or flat jet and round jet is created in dependence on the flow energy (air quantity, air pressure, flow speed, etc.).
In order to achieve an optimal work result, the spray jet needs to be adapted, among other things, with respect to the jet width, the material distribution, the material type and the droplet size. The adaptation is essentially carried out in dependence on the physical boundary conditions (supply air pressure, air quantity, etc.) in the form of a constructive adaptation of the openings of the central air ring nozzle and the horn air nozzles. In order to achieve sufficiently homogenous spray jets, one, two, three or more horn air nozzles that interact with the central opening of the central nozzle are typically used per horn. Paint spray guns with one, two or more horn air nozzles are known from practical applications and ensure a sufficient jet formation and atomization based on the criteria mutual distance, diameter, angle and distance from the paint nozzle opening, as well as the number thereof. In this case, the horn air nozzles are arranged in an air cap that is mounted on the paint spray gun body, usually screwed thereon by means of mounting rings. The central air nozzle may also be directly screwed, clipped or similarly mounted on the paint nozzle or on the paint spray gun body. A nozzle head of this type is known, for example, from German Utility Model G 90 01 265.8. The paint nozzle openings and the horn air nozzle openings are conventionally realized in the form of round bores.
In practical applications, the diameters of the horn air nozzles are realized differently depending on the supply pressure and the individually desired shape of the spray jet. The effect of the individual horn air nozzles is dependent on the supply pressure. Splitting of the jet may occur at higher supply pressures. An undesirably coarse atomization with small jet width may occur at excessively low supply pressures. In addition, the material throughput and other material properties (e.g., viscosity, rheology, etc.) are also highly dependent on the supply pressure and the arrangement of the horn air nozzles. When using one or more smaller horn air nozzles or unfavorable bore angles, back-misting problems may occasionally arise on the opening surfaces of the nozzles due to the suction effect occurring at smaller nozzle or bore diameters.
Small control openings or auxiliary atomizer openings that contribute to the jet formation and the atomization are usually arranged around the central nozzle. In order to transform the pre-formed jet emerging from the cylindrical tube of the central air nozzle opening into a different shape or, for example, to convert a round jet into a flat jet, large amounts of energy from the jet formation bores and the horn bores are required, which ultimately lead to high energy losses and limit the jet formation.
One significant disadvantage of this jet formation method can be seen in that a large part of the energy for the jet formation and the post-atomization is already blown out into the surrounding air through the narrow bores and multiple outlets (large shear planes on the surface in connection with significant fluctuations in speed).
Modified nozzle heads with possibly deviating spraying parameters and geometries frequently need to be used for slightly different paint or varnish materials in order to achieve a flawless spray pattern and therefore the desired result of the paint application, varnish application or other material application.
It is the objective of the invention to improve a nozzle head in such a way that the flow energy of the compressed air can be optimally converted into jet formation, flow speed and therefore into atomization work.
This objective is attained with a nozzle head with the characteristics of claim 1. Due to the formation of the central jet with the aid of at least one non-cylindrical nozzle, particularly at least one non-cylindrical horn air nozzle, it is also possible to significantly reduce the amount of energy required for the jet formation.
The invention is based on the fact that the required adaptation of cylindrical nozzles to the individual requirements can only be realized by varying the diameter sizes, the length and the inclination of the cylindrical bores, their mutual distance and the distance from the other nozzle openings. Non-cylindrical nozzles can be fluidically optimized and adapted to the individual task in an easier fashion.
It goes without saying that the internal shape, particularly the opening of the nozzles, should be non-cylindrical in this case. The external shape of the nozzles usually is unimportant for the jet formation.
Advantageous embodiments of the invention are disclosed in the remaining claims.
In an enhancement of the invention, a variable design of the control bores is proposed in order to achieve an efficient jet formation.
This applies analogously to the shaping of the flow regions of the air nozzle. Consequently, the round jet can be pre-formed due to a special shaping in such a way that less horn air is required for the formation of the broad jet and arbitrary jet shapes can be realized.
It is proposed, in particular, to utilize nozzles with an elliptical or at least approximately oblong hole-shaped cross section.
The atomization process can be additionally improved with a nozzle opening that widens in the direction of the spray jet.
It is also possible to provide grooves, lamellae, air guide vanes or the like in order to guide the air in the nozzle openings.
The non-cylindrical nozzles may be produced in metallic parts by means of machining. The non-cylindrical nozzles can be manufactured in a particularly simple fashion from plastic, particularly from a plastic that can be injection-molded. Such nozzles may likewise be realized in plastic inserts and mounted in nozzle heads of metal.
In addition, other advantageous effects can be achieved due to the combination of cylindrical, conical and other non-cylindrical nozzle openings.
Other advantageous details and embodiments of the invention are illustrated in the figures described below.
In these figures:
The nozzle head for a paint spray gun illustrated in
The horn air nozzles 15, 16 and 17, 18 are fluidically optimized in such a way that the round jet is subjected to a homogenous jet formation and the desired jet width is achieved without splitting the spray jet. According to
In the present exemplary embodiment, the paint needle 4 is hollow and features an opening 4a that is realized cylindrically along its longitudinal axis and through which a vacuum or an overpressure can be generated in the spray jet. In one particular variant, another varnish component is injected into the spray jet via the hollow needle 4. For this purpose, the inlet opening of the needle 4 is connected to corresponding material-containing devices. In a special embodiment, the opening 4a may be realized non-cylindrically such as, e.g., with an oval cross section or with any other non-cylindrical shape.
The opening 4a may be connected to compressed air or to a vacuum.
On the other hand, the paint needle 4 may also be realized in the form of a solid body rather than in a hollow fashion. In this case, the needle 4 advantageously is always realized such that its external shape corresponds to the internal shape of the paint nozzle 3 at the sealing point or contact surface with this nozzle and sealing pairings are realized.
In the variant according to
In the variant illustrated in
In the variant according to
The horn air nozzles described so far have the same internal size anywhere in the longitudinal direction. However, it is also possible to utilize horn air nozzles that are widened or tapered in the longitudinal direction.
The flow surface 22 of the horn air nozzle 17d or another horn air nozzle could also have a corrugated, nubby, fluted or spiral-shaped design or be realized in a different way.
In the variant according to
The insert 23 could also be bonded into the opening in the sidewall 19 of the horn 14.
A variant of
A variant of a portion of the embodiment according to
It would also be possible to provide lamellae, nubs or the like instead of the transverse grooves 24 or longitudinal grooves.
In the variant according to
Special fluidically optimized channels for the horn air are created with the above-described cross-sectional shapes of the horn air nozzles. It would naturally also be possible to realize other cross-sectional shapes and combinations thereof.
In the last two variants, the round jet is pre-formed due to the special shaping in such a way that less horn air than usual is required for the formation of the broad jet.
Other embodiments of the nozzle head with a different air cap or even without [an] air cap are conceivable; in the context of the invention, the non-cylindrical openings in the nozzle head are of essential importance.
The nozzle head 1a illustrated in
Arbitrary combinations of the described nozzle variants naturally are possible and may lead to particularly advantageous spraying results.
All combinations of cylindrical and non-cylindrical nozzles are conceivable in dependence on the desired work result and fall under the scope of the present invention.
The invention naturally is not limited to the above-described nozzle heads. It can also be advantageously utilized in other nozzle heads.
The proposed non-cylindrical nozzles naturally can be produced in a particularly simple fashion in nozzle heads or parts of nozzle heads that are made of plastic, particularly injection-molded. In nozzle heads that are entirely or partially made of metal (usually special steel), non-cylindrical nozzles can be realized by means of lost-wax casting or with the aid of inserts.
In other embodiments, the air nozzle/air ring nozzle may also be directly attached, clipped or screwed on the paint nozzle or installed or mounted thereon in a different way. The air nozzle and the paint nozzle may also be realized in one piece.
The entire nozzle device could be directly connected to a gun body with or without additional carrier device.
In another embodiment, the nozzle device respectively is directly connected to the compressed air network and a material supply.
In another embodiment, the nozzle device may also represent part of the air supply or the material supply.
The external shape of the nozzle device may also have arbitrary geometric shapes in the circumferential direction; in one particular embodiment, the entire spray device may have arbitrary geometric shapes.
The openings for the jet formation, as well as the horn air nozzles or horn outlet openings, do not necessarily have to be provided in projecting horns, but may also be arranged, for example in the plate 9, in lateral elevations, in tubes or in a circumferential ring around the plate.
The number of openings in the horns, as well as for the jet formation, is basically arbitrary; several openings may be combined in segments and arranged, for example, in areas that lie opposite one another (90 degrees, 45 degrees, 30 degrees, . . . ). In this case, particular jet shapes can be realized by means of individual openings, several or many openings.
Due to the described and other conceivable fluidically optimized nozzle openings, the energy of the compressed air can be more optimally utilized, the jet can be formed in a superior fashion and the atomization can be improved. In addition to achieving finer droplets, this also makes it possible to improve the droplet distribution in the jet and to realize a more uniform droplet distribution center. It is likewise possible to reduce the dependence of the jet on other parameters such as, e.g., the supply pressure, the material viscosity and manufacturing tolerances, and to diminish the noise by reducing the discharge speed and the compressed air demand.
Number | Date | Country | Kind |
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20 2010 007 355.3 | May 2010 | DE | national |
Filing Document | Filing Date | Country | Kind | 371c Date |
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PCT/EP2011/002544 | 5/21/2011 | WO | 00 | 11/16/2012 |