WO2020067895A1

WO2020067895A1 - Spray device, nozzle unit and nozzle body

Info

Publication number: WO2020067895A1
Application number: PCT/NL2019/050645
Authority: WO
Inventors: Wilhelmus Petrus Johannes De Kruijf; Cornelis Johannes Maria Van Rijn; Wietze Nijdam; Henri Joseph Van Egmond
Original assignee: Medspray B.V.
Priority date: 2018-09-25
Filing date: 2019-09-25
Publication date: 2020-04-02
Also published as: NL2021704B1

Abstract

Spray device A spray device has a spray nozzle unit, comprising a nozzle body (10) with a cavity (40) for receiving a pressurized liquid. A perforated nozzle wall (20) having at least one orifice (21) extending throughout a thickness thereof releases a jet of said pressurized liquid during operation. A fluid flow path from an inlet of the device to said nozzle wall (20) imposes a first fluid flow resistance on said pressurized liquid that is greater than a second fluid flow resistance of air flowing from said cavity (40) through said at least one orifice (21).

Description

Spray device, nozzle unit and nozzle body

The present invention relates to a spray device having at least one spray nozzle unit, said nozzle unit comprising a nozzle body with a cavity for receiving a pressurized liquid and with a perforated nozzle wall having at least one orifice extending throughout a thickness thereof in fluid communication with said cavity, said orifice releasing a jet of said pressurized liquid at a spray side of said nozzle body, wherein said spray nozzle unit is provided with a fluid inlet that receives said pressurized liquid from a container and passes said liquid to said cavity. A micro-jet spray may emanate from many emitting jets, in which each jet will initially breakup into a mono disperse primary droplet train according to the so-called Rayleigh breakup mechanism. As a result, consecutive primary droplets have a same size and propagate from the nozzle orifice in a same direction, typically the diameter of the primary droplet Is 1,85-2,0 times the diameter of the nozzle orifice. Often the corresponding nozzle orifices are provided in a planar substrate yielding jets all directed in a same spraying direction.

A spray device of the type as described in the opening paragraph is known from US patent application 2008/0006719. This patent application describes, particularly with reference to figure 7 of Its drawing, a spray nozzle body comprising a substrate and a front nozzle wall that are formed as a single piece of plastic material. The nozzle wall of this known device is relatively thin and elastically deformable for adopting an overall curved profile once exposed to the pressure of said pressurized liquid yielding jets directed in different spraying directions.

According to this US application the orifices that generate said jets are all of approximately a same size to deliver a mono-disperse spray pattern of droplets that are equally of

approximately a same size.

For specific applications such as cosmetics, perfume, wafer cleaning, fuel injection, spray dryers, medical sprays, however, specific varying characteristic spray patterns may be required and an particular variation within the droplet size distribution of the generated spray is warranted. For pharmaceutical applications, for Instance, a spray providing small droplets with a narrow size distribution can be efficiently targeted at different sections of the lungs, provided that the micro-jet spray can be adequately controlled and reproduced. A spray providing larger droplets, however, may at the same time target the oral cavity to provide a desired flavour. Also a droplet train leaving the nozzle along the normal to a planar nozzle wall, i.e. without deflection, may Impose a larger impact on a target and, hence, be sensed differently than droplets of a same mass and velocity that are released under an angle relative to said normal in both and other cases it may hence be desirable to launch droplets of different size. The generation of droplets of different size, from within a common nozzle body or from different nozzle bodies of a common nozzle unit having cavities that experience a similar Inlet pressure of the liquid to be sprayed, in practice, may give a disturbed or otherwise irregular start-up behaviour of the spray. As a result some orifices may tend starting earlier to spray than others.

The present invention has inter alia for its object to provide a spray device having a design freedom of creating any desired spray pattern with droplets of any particular size, within one or more narrow or at least well defined droplet size distributions, without substantially affecting the start-up characteristics of the nozzle unit. The present invention particularly aims, inter alia, to provide such a spray device that generates a micro-jet spray retaining any desired droplet size distribution or variation of micro-jets and droplets obtained via the Rayleigh breakup mechanism. in order to achieve said object a spray device as described in the opening paragraph, according to the invention, is characterized in that a fluid flow p path from said inlet to said nozzle wall Imposes a first fluid flow resistance on said pressurized liquid that is greater than a second fluid flow resistance, said second fluid flow resistance being that of air flowing from said cavity through said at least one orifice. The Invention Is thereby based on the recognition that a disturbed start-up behaviour of a nozzle Is Influenced by air captured inside the cavities flowing out of larger orifices more easily and quickly than from more narrow orifices.

On start-up, said air is expelled by the fast advancing pressurized liquid that is filling the cavities. By tuning both flow resistances such that the fluid flow resistance encountered by said liquid Is at a level beyond that of the air flowing out of the cavity via the nozzle orifices, said latter phenomenon is no longer the decisive factor for a specific orifice to start spraying instead the liquid is decelerated by the first flow resistance and air is allowed sufficient time to escape both through narrow as well as larger orifices. The orifices, as a result, experience a similar pressure drop and start spraying substantially simultaneously, regardless their specific size or number. In this respect a specific embodiment of the device according to the invention is characterized in that said nozzle body comprises a first cavity in fluid communication with at least one first orifice and at feast one further cavity in fluid communication with at least one further orifice, said at least one first orifice and said at least one further orifice having mutually different dimensions.

To yield a uniform Initial spray in a gentle manner it has been found advantageous to tune the dimensions of each cavity with the size and number of orifices in the nozzle wall. When initially priming the spray nozzle unit with the pressurized liquid, air that is initially still inside the spray nozzle unit will be expelled through the nozzles orifices in the nozzle wall with a relatively high velocity. The liquid may in that case cause a rather high and not very well controlled shock wave on the nozzle wall, which In turn may introduce Initially uncontrolled jet velocities and uncontrolled coalescence effects on spray jets emanating from neighbouring orifices and cavities. The additional resistance imposed on the liquid entering the cavity will also reduce such uncontrolled high velocity of air escaping through the orifice.

With preference the fluid flow resistance of the flow path from said inlet to said nozzle wall Is at least between 0.1 and 10 percent of the total flow resistance of all orifices that communicate with the particular cavity. This ratio depends amongst others on the viscosity ratio between the liquid and air. Taking Into account a difference In viscosity of the order of at least a factor 100-

1000 between a typical liquid and air. this means that air will experience a flow resistance that is of the order of a factor 100-1000 less than liquid flowing through the same flow path. By tailoring the first flow path to have a flow resistance between 0.1 and 10 percent of that of the orifices, the desired tuning is obtained of the hydrodynamical behaviour of the advancing liquid to the aerodynamic behaviour of the expelled air.

When the liquid reaches the nozzle wail it wiil experience the full flow resistance of the flow path that it followed, which will roughly have Increased by the liquid-air viscosity ratio compared to the airflow resistance of the air that passed through the same flow path. The resulting deceleration of the liquid will also lead to a significant reduction of the air speed through the nozzles. Correspondingly, also the pressure impact of the priming liquid on the nozzle wall will be significantly reduced once it reaches the nozzle wall. An Increased resistance of the liquid flow path for the liquid compared to that of the air leaving the cavities may be realized en implemented in several ways. In a first embodiment a spray device according to the invention, In this respect, Is characterized in that said first fluid flow resistance is locally increased by restricting a cross section of said fluid flow path. A local constriction of the cavity or of the flow path leading to the cavity may impose sufficient flow resistance on the liquid to exceed that of the orifices concerned as experienced by said air.

A further specific embodiment of the spray device according to the invention in characterized in that said fluid flow path comprises at least one constriction means that disturbs said fluid flow path of said pressurized liquid. Such constriction means will impose a further flow resistance to the flow path such that the total resistance will exceed the desired level. In a particular embodiment the spray device according to the invention, in this respect, Is characterized in that said constriction means comprises at least one rim underneath said nozzle wall adjacent to said orifice, said rim extending into said fluid flow path through said cavity and surrounding said orifice.

Besides creating excess flow resistance such barrier may also cause a controlled deflection of the emanating spray jet to deliver any desired spray profile. In a preferred embodiment, the spray device according to the invention is characterized in that said rim at least substantially surrounds said orifice eccentrically, and particularly is circular or semi-circular. The eccentric positioning of the orifice with respect to the rim will create a net lateral momentum that is believed to be responsible for a deflection of the ray emanating from said orifice in order to provide sufficient strength and integrity to such rim, a further preferred embodiment of the spray device according to the invention is characterized in that said rim is an integral extension of said nozzle wall.

Such barrier that surrounds said orifice and hangs down from the nozzle layer, tends to divide the cavity into separate regions that are both adjacent said nozzle wail A first region, in which said jet orifice is located, lies downstream of said barrier, while a second region, more remote of the orifice, is situated upstream of said barrier !n order to facilitate proper hydrodynamics in both regions of the cavity a spray device of the type as described in the opening paragraph, according to a further aspect the invention is characterized in that said cavity comprises a first region adjacent said nozzle wall, said at least one orifice being provided at the area of said first region, in that said cavity comprises a second region adjacent said nozzle wall, said second region being separated by a barrier from said first region, and in that said nozzle wall is provided with a least one further orifice extending throughout the thickness of said nozzle wali at the area of said second region. This at least one further orifice is not intended to deliver a s micro-jet but allows air to enter the second region of the cavity after operation of the nozzle.

To that end, a specific embodiment of the spray device according to the invention is characterized In that said at least one further orifice is smaller than said at least one first orifice, particularly at least ten times smaller. All liquid may in that case effectively drain from the cavity to provide a stable, identical initial configuration and set-up each time the spray device is being re used.

Although a spray device may be manufactured In a wide variety of ways and of a wide variety of materials, a preferred embodiment of the spray device according to the present invention is characterized In that said nozzle body comprises a silicon substrate and In that said nozzle wall comprises a silicon nitride layer overlying said nozzle body. The use of these materials enables the manufacture of the nozzle device with a great precision in this respect a further preferred embodiment of the spray device according to the invention is characterized in that said nozzle body is formed using MEMS or semiconductor technology delivering said at least one cavity and said at least one orifice with photo-lithographic precision.

The invention moreover relates to a nozzle unit and a nozzle body as applied in the afore mentioned spray device and will now be described in greater detail with reference to certain specific explanatory embodiments and an accompanying drawing in the drawing:

Figure 1 shows a schematic cross section of a typical spray device according to the

25 invention;

Figure 2 Is a cross section first example of a spray nozzle unit in an embodiment of a spray device according to the invention;

Figure 2A,B are respectively a cross section and a top view of a spray nozzle body as applied

In the spray nozzie unit of figure 2;

Figure 3A, B are respectively a cross section and a top view of a constriction body as applied

In the spray nozzle unit of figure 2;

Figure 4A,B are respectively a cross section and a top view of a second embodiment of spray nozzle body In a spray device according to the invention; Figure 5A,B are respectively a cross section and a top view of a third embodiment of spray nozzle body in a spray device according to the invention;

Figure 6A,B are respectively a cross section and a top view of a fourth embodiment of spray nozzle body in a spray device according to the invention; and Figure 7A,B are respectively a cross section and a top view of a fifth embodiment of spray nozzle body in a spray device according to the invention.

It should be noticed that the drawings are drafted purely schematicalfy and not to scale. In particular, certain dimensions may have been exaggerated to a lesser or greater extent for sake of clarity and understanding. Corresponding parts have been identified with same reference numerals throughout the drawing.

Figure 1 shows a typical example of a spray device. The spray device is used as a dispenser for a certain fluid to be sprayed and comprises a container 100 for holding a quantity of a fluid to be sprayed. The spray device 100 may be in any suitable form like a spray can or Inhaler, and may be fitted with automatic dosing means dispensing a certain, predetermined quantity of the liquid at a time in figure 1 a spray can of for instance a metal like aluminum, glass or plastic is depicted with a contents of typically between a few millilitre and few hundreds millilitre.

The fluid inside the container 100 may be pressurized already, for instance under influence of a propellant, residing under pressure in said container, or it may be pressurized under influence of a mechanical or manual action that forces the liquid out of the container, for instance as a result of a pumping or suction action. These pumping means typically comprise pumping means that deliver a pressure of the order of a few Par to a few tenths of bars and may be manually driven or motorized. Alternatively the pressurizing means may also consist of a mouthpiece of an Inhaler which allows the user to exert pulmonary suction.

On top of the container is a spray nozzle unit (SNU) 1 according to the invention. In between is a spring valve arrangement 105 that closes off the container 100 or, alternatively, opens a flow path for the contained fluid from the container to and through the spray nozzle unit 1 In order to deliver a fine mist of liquid, often referred to as aerosol or spray. A skilled person is supposed to be very well familiar with this art. Figure 2 gives a more detailed cross section of the spray nozzle unit 1 that is applied In the spray device of figure 1. The spray nozzle unit comprises a spray nozzle body 10 that is sealed in an enclosure body 110 to be fitted on or to valve and/or pressurizing means 105 that connect to the reservoir 100, holding the liquid to be sprayed. The enclosure body may be made of any suitable plastic and provides a liquid tight seal to both the container 100, 105 and the spray nozzle body 10. The spray nozzle body 10 may for Instance be fitted by means of ultra sone welding techniques and the plastic enclosure body may be press fitted onto the container. In order to avoid Inadvertent particles Inside the fluid from entering and possibly clogging the spray nozzle device 10, a filter body 9 is fitted upstream of the nozzle body 10 inside the spray nozzle unit 1. Both the nozzle body and the filter body are manufactured from a semiconductor material using u ltra-precise semiconductor wafer technology. In this example silicon Is used as semiconductor material which allows photo-lithographic deposition and etching techniques to be used to create nozzle orifices and filter pores respectively In the nozzle body 10 and filter body 9 with extreme precision as custom in nowadays integrated circuit semiconductor technology. A porous absorber body 3 of a suitable polymer, for instance polyethylene or polypropylene, Is placed upstream of the filter body to adsorb dissolved chemicals, like oils, and to serve as a pre-filter that preserves filter capacity the filter body 9.

According to one embodiment of the invention, a constriction body 7 Is moreover fitted in the enclosure body. This constriction body 7 provides a localized constriction 5 and corresponding added flow resistance within the spray nozzle unit In a flow path between the inlet 2 of the spray nozzle unit and the spray nozzle body 10. The constriction body 7 is piaceci at a d istance d relative to a filter body 9. Said distance d may vary from a few millimetre to zero, thereby creating more or less fluid buffer In between in the depicted case, the constriction body is placed upstream of the filter body 9. Alternatively, however, the constriction body might as well be positioned in between the filter body 9 and the nozzle body 10.

Figure 3A and 4A show respective cross sections of the nozzle body 10 and the constriction body 7, while figure 3B and 4B provide corresponding top views. The nozzle body comprises a silicon substrate 10 that is cut out mono-crystalline silicon wafer, having a thickness of the order of a few hundred micron. Shown is merely a surface portion of the nozzle body where a cavity 40 Is formed at a main surface that will receive the liquid concerned at an appropriate pressure. Overlying the substrate 10 is a nozzle wall 20 that is formed by a silicon nitride layer covering said main surface and spanning the cavity 40 to create an Individual island. The nitride layer 20 typically has a thickness of a few microns and has been deposited on a thin silicon oxide layer 15. Said oxide layer serves as a stress relief in between the substrate and the nitride layer and moreover could advantageously be used as an etch stop during manufacturing of the device. The nozzle body has been created by means of conventional high precision

semiconductor or MEMS technology, including photolithography, (vapour)deposition, oxidation and etching. Using these techniques one or more orifices 21 are photo-iithographicai!y etched throughout the thickness of the nitride layer 20 at each cavity 40. In total the nozzle body will comprises a (large) number of these islands, each having one or a few nozzle orifices 21 communicating with the cavity 40 below, In order to provide a spray nozzle generating a large number of concurrent micro spray lets, as shown in figure 3B.

The constriction body 7 is less critical and may be formed using simple mechanical means like puncturing a solid, for instance metal or plastic, body to create one or more localized restrictions 5. To realize a more controlled and reproducible flow path resistance, however, in this example use is made of a silicon body for the constriction body 7 as well. This body is processed in a similar fashion as the nozzle body 10 to create one or a few openings 75 in the nitride layer 20 overlying a individual cavities 70 that are etched in the constriction body 7. These openings have typicaily a total surface area ||l|li|l||ll||l|ll|lithe total surface area of the total surface area occupied by the nozzle orifices 21 of the nozzle body and may particularly be of equal cross sectional size as the cavity 70 Itself. The resulting constriction body 7, se figure 4B, will impose a fluid flow resistance on the pressurized liquid that Is greater than a fluid flow resistance of air flowing from a cavity 40 through the corresponding one or more orifices 21.

The fluid flow resistance that is exerted on the pressurized liquid once it fills the cavity of the nozzle body 10 may also be greater than a fluid flow resistance of air flowing from a cavity 40 through the corresponding one or more orifices 21 by modifying the nozzle body itself. This is the case in a second embodiment of the spray device according to the invention, whose spray nozzle body is shown in figures 4A en 4B respectively in cross section and top view. The nozzle body 10 and further details are similar to those of the first embodiment except that a flow path from an inlet 48 to a cavity 40 has been confined by a relatively small entrance opening 45. This constriction 45 and relatively shallow cavity 40 Imposes additional flow resistance to the fluid entering the cavity. By properly dimensioning the length and width (overlap) of this entrance 45 together with the depth of the cavity 40 this added resistance may be tailored to a desired level. A separate constriction body 7, like in the first embodiment, may in that case be avoided s or combined to meet the flow resistance window according to the invention.

The embodiment of figure 4A,B may be realized, using conventional silicon semiconductor technology. Starting with a mono-crystalline silicon body 10, the main surface is oxidized or silicon oxide is deposited, for instance using chemical vapour deposition, to form a relatively re thick silicon oxide layer 15 having a thickness of a few micrometre. Next a silicon nitride layer

20 is deposited onto the oxide layer 15 and a nozzle orifice 21 is created in this nitride layer by means of photo lithographic masking and etching techniques that aiiow for a extremely precise positioning and dimensioning of the orifice 21 that may have a size of between 0,5 and 10-20 micron. The oxide layer 15 Is etched through this orifice by wet etching to create the cavity 40. is Finally the cavity 40 is opened by dry plasma etching the back side of the silicon body, using a mask, to create the entrance 48 and overlap 45.

Besides statically, embedded in the configuration of the nozzle body or in a separate constriction body upstream of the nozzle body, an added flow resistance may also be created so dynamically. An example thereof is provided by a third embodiment of the spray device

according to the Invention, whose spray nozzle body is shown in figures 5A en 5B respectively In cross section and top view. This nozzle body comprises a silicon substrate 10 that is cut out mono-crystalline silicon wafer, having a thickness of the order of a few hundred micron. Shown is merely a surface portion of the nozzle body where a cavity 40 is formed at a main surface 25 that will receive the liquid concerned at an appropriate pressure. Overlying the substrate 10 is a nozzle wall 20 that is formed by a silicon nitride layer covering said main surface and spanning the cavity 40. The nitride layer 20 typically has a thickness of a few microns and has been deposited on a thin silicon oxide layer 15. Said oxide layer serves as a stress relief In between the substrate and the nitride layer and moreover could advantageously be used as an etch stop so during manufacturing of the device. The nozzle body has been created by means of

conventional high precision semiconductor or MEMS technology, including photolithography, (vapour)deposition, oxidation and etching. Using these techniques one or more primary orifices 21 are etched throughout the thickness of the nitride layer. Figure 5A shows merely a single primary orifice 21 that is associated with the cavity 40 but in practice more than one primary orifice 21 could have been created in the nitride layer spanning the cavity 40. Moreover, in practice the nozzle body will comprise several cavities 40 at the main surface, each of which having one or more of those primary orifices of a same or different dimension.

During operation a pressurized liquid is fed to an inlet of the nozzle body 10 (outside the area of the drawing) and is freely flowing into the cavity 40. The cavity 40 comprises an annular rim 25 that hangs down from the nitride layer 20 and is formed integral therewith in a common manufacturing process step. This rim 25 provides a constriction body that Interferes with the liquid flowing towards the main surface with the orifice 21. The liquid Is forced to where the primary orifice 21 is located while the barrier 25 narrows down the cross section of the flow path toward this orifice 21. As a result, an increased flow resistance is experienced by the liquid. The flow channel, for the liquid concerned, from an inlet of the device to the orifice(s) 21 may be modified this way to have an increased flow resistance such that the total flow resistance for the liquid to said orifice(s) 21 exceeds the flow resistance of air that was initially In the cavity 40 and that Is escaping through said orifice(s) 21 once the liquid enters the cavity. This air may moreover be partly trapped in a second region 42 of the cavity 40 that is underneath the nozzle wall 20 and behind the barrier rim 25 to form air cushions that further avoid liquid from entering the same space.

As can been seen in figure 5B said rim 25 entirely surround s said orifice 21 and, as a result, divides the cavity 40 In a first region 41 adjacent at the main surface in open communication with said orifice and said further region 42 beyond said rim 25. A further, smaller orifice 22 may be provided at the area of said further region 42 in order to secure a proper evacuation and draining of the liquid from this area of the cavity 40 once the supply of liquid is terminated. This secondary orifice 22 is considerably smaller than the primary orifice and as such provides too much flow resistance to really take part in the spraying process by releasing a spray jet Itself

As shown in figure 5A and 5B, the orifice 21 lies eccentric relative to the cavity 40, while the rim 25 is concentric with the circular cavity 40. This will give rise to certain deflection of the micro spray jet emanating from the orifice 21 due to a net lateral momentum. Conversely, the orifice 21 might as well be placed in the middle, as shown in figure 2k, while the rim is positioned shifted from the centre of the cavity to attain a similar effect. By varying the distance between the orifice 21 and the rim 26 as well as by configuring the dimensions and position of the rim 26, a deflection angle may be tailored precisely for each cavity individually to suit a particular s desired spray pattern Additional secondary orifices 22 may be placed in the second region 42 to further facilitate a swift evacuation of liquid once the supply Is dropped. instead of creating additional flow resistance in the flow path such that It will exceed the flow resistance imposed on the air flowing through out of the cavity 40 on start-up of the device, re also the latter resistance may be reduced. This has been applied in a third embodiment of the spray device according to the invention, whose spray nozzle body is shown in figures 6A en 6B respectively in cross section and top view. In this case the primary orifice 21 Is surrounded by a number of considerably smaller further orifices 23 that reduce said out-flow resistance of air but that do not produce a separate micro-jet spray during operation of the device. These is further orifices 23 have a crosse section that is of the order of ten times smaller than that of the primary orifice 21 that they surround. Any leakage from these orifices may be taken up by the micro let ray emanating from the primary orifice 21 by coalescence and might give rise to an Increased droplet size. The nozzle body 10 comprises silicon, while the orifices 21,23 are etched in a silicon nitride layer 20 the same way as described with reference to the preceding so embodiments of the invention.

A combination of the rim 25 hanging down from the nitride layer 20, surrounding the primary orifice, and a number of further orifices In the first region 41 of the cavity adjacent said primary orifice is also possible. This is shown In figures 7A and 7B as a further example of the device 25 according to the Invention. Besides, this embodiment shares the features of the previous embodiments, described hereinbefore.

Although the invention has been describes to merely a few specific embodiments in the preceding, it will be clear that the Invention Is by no means limited to that example. Instead may alternatives and variations are feasible for a skilled person without departing from the true scope and spirit of the present invention, as Indicated by the foliowing claims.

Claims

Claims:

1. Spray device having at least one spray nozzle unit, said nozzle unit comprising a nozzle body with a cavity for receiving a pressurized liquid and with a perforated nozzle wall having at least one orifice extending throughout a thickness thereof in fluid communication with said cavity, said orifice releasing a jet of said pressurized liquid at a spray side of said nozzle body, wherein said spray nozzle unit is provided with a fluid inlet that receives said pressurized liquid from a container and passes said liquid to said cavity, characterized in that a fluid flow path from said inlet to said nozzle wall imposes a first fluid flow resistance on said pressurized liquid that is greater than a second fluid flow resistance of air flowing from said cavity through said at least one orifice.

2. Spray device according to claim 1. characterized in that said first fluid flow resistance is locally increased by restricting a cross section of said fluid flow path between said inlet of said nozzle unit and said at least one orifice that releases said jet of said pressurized liquid at a spray side of said nozzle body.

3. Spray device according to claim 2, characterized in that said cross section of said fluid flow path is restricted by a constriction body that is provided between said inlet and said nozzle body of said nozzle unit, said constriction body having at least one passage of reduced cross section for carrying said fluid flow path of said pressurized liquid.

4. Spray device according to claim 3, characterized in that said constriction body Is placed adjacent said nozzle body.

5. Spray device according to anyone of the preceding claims, characterized in that said cross section of said fluid flow path is restricted by a constriction means inside said cavity having at least one passage in open fluid communication with said at least one orifice.

6. Spray device according to claim 5, characterized in that said constriction means comprises at least one rim underneath said nozzle wall adjacent to said orifice, said rim extending into said fluid flow path through said cavity and surrounding said orifice.

7. Spray device according to claim 6, characterized in that said rim at least substantially surrounds said at least one orifice eccentrically and particularly is circular or semi-circular.

S. Spray device according to claim 6 or 7, characterized in that said rim is an integral portion of said nozzie wail.

9. Spray device according to anyone of the preceding claims. characterized in that said nozzle body comprises at least one further cavity in fluid communication with said fluid Inlet, said further cavity being bounded by a nozzle wall having at least one further orifice extending throughout a thickness thereof, wherein said at least one first orifice and said at least one further orifice have mutually different dimensions

10. Spray device having at least one spray nozzle unit, said nozzle unit comprising a nozzle body with a cavity for receiving a pressurized liquid and with a perforated nozzle wall having at least one orifice extending throughout a thickness thereof in fluid communication with said cavity, said orifice releasing a jet of said pressurized liquid at a spray side of said nozzle body, wherein said spray nozzle unit is provided with a fluid inlet that receives said pressurized liquid from a container and passes said liquid to said cavity, characterized in that said cavity comprises a first region adjacent said nozzle wali, said at least one orifice being provided at the area of said first region, in that said cavity comprises a second region adjacent said nozzle wall, said second region being separated by a barrier from said first region, and in that said nozzle wall is provided with a least one further orifice extending throughout the thickness of said nozzie wail at the area of said second region.

11. Spray device according to claim 10, characterized in that said at least one further orifice is smaller than said at least one first orifice, particularly at least 10 times smaller.

12. Spray device according to claim 10 or 11, characterized In that said barrier comprises a rim, hanging down from said nozzle wall and extending into said cavity.

13. Spray device according to claim 12, characterized in that said rim at least substantially surrounds said orifice, and particularly is circular or semi-circular.

14. Spray device according to claim 12 or 13, characterized in that said rim is an integral extension of said nozzle wal!.

15. Spray device according to anyone of the preceding claims, characterized in that said nozzle body comprises a silicon substrate and in that said nozzle wall comprises a silicon nitride layer overlying said nozzle body.

16. Spray device according to anyone of the preceding claims, characterized in that said nozzle body is formed using MEMS or semiconductor technology delivering said at least one cavity and said at least one orifice with photo-lithographic precision.

17. Nozzle unit as applied in the spray device according to claim 9.

18. Nozzle body as applied in the nozzle unit according to claim 17.