FR3124095A1 - FOAM PROJECTION NOZZLE - Google Patents

Abstract

This nozzle comprises a nozzle body (22) ending on a nozzle (26) for ejecting the foam, which has been previously formed by mixing its liquid and gaseous constituents in a mixer located preferably just upstream of the nozzle, in the nozzle body (22). The ejection passage (25) passing through the mouthpiece has oblong sections whose main sides are everywhere at least 2.5 mm apart from each other, and it gradually widens towards the outlet. A plume (27) of flattened and widening foam is obtained. Application to devices for spraying foams, in particular viscose, onto external surfaces. Figure for abstract: Figure 2.

Description

FOAM PROJECTION NOZZLE

The present invention relates to a nozzle for spraying a foam.

It will find utility in particular in decontamination or depollution work, in which foams must be projected on vast surfaces which can be strongly inclined or vertical, belonging for example to buildings or other immobile structures, possibly not easily accessible, and maintain on these surfaces for a time long enough to act on the pollutants, without running or otherwise degrading.

We appreciate for this the so-called viscose foams, that is to say enriched with a gelling agent which increases the physical stability of the foams and makes them less able to flow on even very inclined or vertical surfaces. These two characteristics allow the foam to act for a sufficient time on the surface to be treated that they cover. Examples are given in FR 2 841 802 A1. One of their disadvantages is that they are difficult to manufacture from a foaming solution in a liquid state, precisely because of the high viscosity of this solution. Foam generating devices are generally intended for conventional foams, and they are not suitable for viscose foams. In particular, they do not make it possible to guarantee in a sustainable manner a high expansion of the foam produced, that is to say a low liquid fraction in the foam (for example less than 10% by volume); a lower expansion has the particular disadvantage of using an excess of liquid products with the same volume of foam, and of giving fewer small, longer lasting bubbles.

It has in particular been observed that, even when foams with high expansion are produced, they are generally degraded by passing through the ejection nozzle of the devices, which cause part of the bubbles to burst, and dissipate part of the gas included, this which increases the liquid fraction of the modified foam as well as the diameter of the remaining bubbles.

A typical foam spray nozzle is described in WO 2005/025755 A; it includes a passage for projecting a jet of liquid to foam, then a nozzle with fine and multiple openings which divide the jet and thus form the foam just at the outlet of the device. However, it is not certain that this device makes it possible to produce foams with high expansion, or even that the expansion can be regulated or stabilized.

An object of the invention is to spray foams, in particular special high-viscosity foams, which retain a satisfactory degree of expansion when leaving a lance of a spraying device, without being degraded when passing through a nozzle. ejection from the device.

Other objects of the invention are to easily and reliably produce foams having the desired degree of expansion from their liquid and gaseous constituents, and to pass these foams directly into the mouthpiece, while minimizing their paths to eject them out of the nozzle and the rest of the device.

In a general form, the invention relates to a nozzle for spraying a foam, through which passes a passage having a central axis corresponding to a flow direction of the foam or constituents of the foam from an upstream to a downstream, the nozzle comprising a foam ejection nozzle, the nozzle containing an end of the passage downstream of the direction of flow, characterized in that the end of the passage has cross sections, perpendicular to the central axis, comprising two opposite main sides and interconnected by connection sides that are shorter than the main sides, the main sides being at least 2.5 mm apart everywhere. It clearly differs from the design of WO 2005/025755 A, where the ejection nozzle comprises an upstream part with a wide opening through which the liquid passes without change of state, then a downstream part with fine openings, to form the foam . The tip of the nozzle of the invention, on the contrary, has a wide opening to avoid as much as possible breaking the foam bubbles and thus reducing the expansion.

It was found that this particular shape of the nozzle tip avoided significantly degrading the viscose foams which passed through the tip, by limiting the bursting of the bubbles thanks to the sufficient width offered to their passage.

According to some optional enhancements:

- the main sides of at least some of the cross sections are curvilinear and diverge from each other towards the middles of the main sides, where they are at least 4mm apart;

- the end of the passage widens downstream of the direction of flow, at angles of no more than 30° between a wall of the end of the passage and the central axis.

An important feature of the nozzle proposed here is that it very favorably comprises a mixer of the constituents of the foam, forming the foam and connected to the nozzle, upstream of the nozzle in the direction of flow. This construction where the nozzle and the mixer are adjacent allows the foam to pass directly or almost directly into the nozzle as soon as it has been formed, which further reduces the risk of it being degraded.

Particularly advantageous:

- the mixer comprises a cage limited by a tube, two obstacles at two opposite ends of the tube and arranged in succession along the central axis, and at least one solid body freely movable in the cage and retained in the cage by the obstacles ;

- the at least one solid body consists of at least one rigid ball;

- the obstacles are grids.

This integration of the mixer with the nozzle comprising the tip is greater, and therefore more favorable, if the nozzle comprises a nozzle body encompassing the tip and a tubular part forming the tube of the cage and in which the obstacles are placed; and more advantageously still if the tubular part of the nozzle body contains a cylindrical and rectilinear bore belonging to said passage, connected directly to the end of the passage, the cross section of the end of the passage being geometrically inscribed, at the place of connection , in a cross section of the bore; and if the bore is rectilinear, with a circular section, and the passage has a uniform and rectilinear direction in the nozzle body.

And the integration of the nozzle with the rest of a device for manufacturing or generating foam, making it possible to obtain a possibly large flow rate of the foam, is better if the tubular part has a connecting thread to a supply conduit into the constituents of the foam.

Another aspect of the invention is the application of the nozzle according to any one of the preceding claims to processes for spraying viscose foam onto exterior surfaces.

The invention will now be described in its various aspects, characteristics and advantages, by means of the following figures, which illustrate a particular embodiment thereof, given for purely illustrative purposes:

- the is a diagram of a foam projection apparatus equipped with an embodiment of the invention;

- the , the projection nozzle body according to section II-II of the ;

- the represents the mixer;

- the represents the end of the projection lance;

- the represents the nozzle body according to the VV section of the ;

- the shows the nozzle ejection tip viewed from the front.

Referring to the , a foam generating apparatus to which the nozzle is added is disclosed; the nozzle could of course be placed on other devices. This comprises a tank 1 of foaming solution in the liquid state, a bottle 2 of compressed air, a pressure gauge 3, a main regulator 4, a pneumatic pump 5, a mixer 6, a foam ejection nozzle 7 (which is therefore the subject of the invention), a frame 8. A first duct 11 connects an outlet orifice of the tank 1 and passes through the pneumatic pump 5. A second duct 14 connects an outlet orifice of the bottle 2 to the regulator 4 main, then merges with the first conduit 11 at a junction 15 downstream of the discharge port of the pneumatic pump 5. The air flowing in the second conduit 14 is slightly compressed at constant pressure (7 bars for example). The pressure gauge 3 is connected by a pressure tapping conduit 20 to the second conduit 14, upstream of the main regulator 4, and it therefore makes it possible to measure the pressure of the gas at the outlet of the bottle 2 and to evaluate the filling of that -this.

The frame 8 carries the reservoir 1, the bottle 2, the main regulator 4, the pneumatic pump 5, the first conduit 11 and the second conduit 14. The chassis 8 can be vertical and belong to a backpack carried by the operator of the device; the frame 8 can also be a trolley, for example. The foam ejection nozzle 7 is not attached to the frame 8, but is located at the end of a flexible lance 21, held by the operator. The lance 21 is connected to the first conduit 11 and to the second conduit 14 at the location of the junction 15. We will see that the mixer 6 is not necessarily separated from the nozzle 7, but that it can on the contrary be placed in it: the mixer 6 is then not fixed to the frame 8 either and it is located downstream of the lance 21.

According to , the nozzle 7 is formed of a unitary nozzle body 22, in the shape of a cylinder, which is traversed right through by a passage 23. The passage 23 comprises a main part, which is a cylindrical bore 24, which is immediately followed downstream by a passage end 25 of more complex shape which will be described later. The bore 24 is formed in a tubular part of the nozzle body 22. The mixer 6 can be placed in the bore 24 and occupy all or part of its length. The foam or its constituents pass through the passage 23 in a flow direction from left to right on the , represented by the arrow on a central axis XX of the nozzle body 22 and of the passage 23, and the nozzle 7 comprises at its downstream end a nozzle 26, which contains the end of the passage 25. The foam is ejected from the nozzle 7 by the tip 26 by forming a plume 27 preferably in the shape of a flattened cone, capable of covering large widths of surfaces to be treated by flaring outwards.

Mixer 6 is shown in . It comprises two planar grids 28 succeeding each other in the bore 24 and occupying its entire section, two seals 29 to which the grids 28 are respectively fixed and which serve as their support for the wall of the bore 24, and two spherical balls 30 and rigid free to move between the grids 28. It has been found that the balls 30, being both mobile and small in number, were capable of efficiently producing viscose foams thanks to the low pressure drops and the intensity of the agitation they produce in the liquid constituents. The seals 29 serve to hold the grids 28 in place and to form between them a cage 31, further delimited by the wall of the bore 24, and in which the balls 30 are retained. They also force all the fluids circulating in the bore 24 to pass through the interior of the cage 31. The mixer 6 thus defined can occupy the entire volume of the bore 24 or almost, that is to say that the grid 28 in upstream is close to the entrance to bore 24, and grid 28 downstream rests on the rear face of end piece 26.

Alternatively, the mixer 6 could be separate from the nozzle 7, have an unchanged construction except that it would include its own cylindrical wall, instead of that of the nozzle body 22, to close the cage 31; and the nozzle would be roughly reduced to the nozzle 26. In order to avoid destruction of the foam by the explosion of some of its bubbles, the mixer would then preferably be connected to the nozzle, which would be placed immediately downstream of him.

The shows that the lance 21 is joined to a rear end of a barrel 33 of a gun 32 held by the operator of the apparatus. The opposite end of barrel 33 carries a thread 34 to which nozzle body 22 is screwed. The operator opens the lance 21 and triggers the projection of foam by pressing a trigger 35 of the gun 32.

The is a sectional representation of the nozzle body 22, which completely illustrates the passage 23 and notably shows an internal thread 36 which is used to screw the nozzle 7 onto the thread 34 at the end of the barrel 33.

We will now describe the tip 26 particularly by means of the . The end of the passage 25 is approximately conical, widening continuously downstream of the direction of flow with a moderate slope: its wall preferably makes angles less than approximately 30° with the central axis XX, as represented by FIGS. 2 and 5. The cross-sections (perpendicular to the direction of flow of the fluids in the nozzle 7, in the central axis XX) of the end of the passage 25 are oblong, that is to say greatly elongated in a transverse direction (vertical to the ) with respect to the other transverse (horizontal) direction.

The represents the contour of an internal cross section Si of the end of the passage 25, by which the end of the passage 25 is connected to the bore 24, and the contour of an external cross section Se, by which it opens on a face front 37, directed towards the surface to be covered with foam, of the nozzle 7. The cross sections such as Si and Se (with progressive variations of shapes for the intermediate cross sections) are generally composed of two main sides Li or Le, d globally vertical orientations to the , which are connected by roundings Ri and Re. The main sides, such as Li or Le, are all arranged symmetrically with respect to the central axis XX. Their shape is purely curvilinear, which is the case of the main sides Li of the internal cross-section Si, or partially or completely rectilinear, which is the case of the main sides Le of the external cross-section Se. The opposite main sides are always spaced apart by a distance greater than about 2.5 mm (here 3 mm to 5 mm at the ends and in the center of the side sides Li of the inner cross section Si, which is the narrowest), in order to provide a sufficient passage width for the foam bubbles and to avoid, as much as possible, that they burst when leaving the nozzle 7. In addition, the contour of the internal cross section Si is geometrically inscribed, that is i.e. included, in the contour of the hole 24.

In accordance with the invention, the foam is formed not far from the outlet of the device by the mixing of the air and the foaming solution, crossing the mixer 6. The grids 28, and especially the balls 30, are very effective in obtaining a foam with high expansion, that is to say with a low liquid fraction. The end of the passage 25 in the endpiece 26 has a shape which gives the flattened and widening plume 27, therefore able to easily cover entire strips of the surface by a simple sweep of the lance 21. It also has a width opening and conditions of direct connection with the bore 24 which reduce to very little the proportion of foam bubbles which burst after leaving the mixer 6 and produce a degradation of the foam by increasing its liquid fraction. The high expansion of the foam, favored by the mixer 6 and maintained by the nozzle 7 as well as by the brevity of the journey of the foam to the outlet of the nozzle 26, is sought among other things for viscose foams.

A few additional indications, of a concrete nature, are given below to more fully describe a particular example of this embodiment of the device and its performance.

Mixer 6: diameter and length of cage 31: from 10 to 100 mm and from 10 to 400 mm;

Rigid balls 30: from 1 to 40, from 2 to 20 mm in diameter;

Nozzle body 22: outer diameter and length: 35mm and 100mm;

Hole 24: diameter and length: 25mm and 80mm;

Hole End Cross Sections ( ): A=25mm, B=31mm, C=2mm, D=15mm, E=5mm, F=3mm;

Foaming solution: water, with Glucopon 215UP [BASF] at 10g/l, and Xanthan Gum (G1253) [Sigma Aldrich] at 3g/l;

Layer projected on vertical surface: 10m ² , 1cm thick, in 120s; sliding speed less than 1cm/min. In the case where the foam is used to fill a volume, the foam holding time is at least 120 min;

Expansion of the foam obtained: approximately 16.7 (approximately 100 liters of foam produced for 6 liters of the foaming solution consumed).

A similar test with another nozzle, belonging to the known art, produced a much lower expansion foam.

The mixer 6 can be placed outside the nozzle 7 and upstream from it. The balls 30 could be replaced by another freely movable solid body in the cage 31, and their number could also be different, a single solid body being possible.

And the shapes of the tip 26 can also differ from those proposed here, the advantageous embodiments therefore comprising a sufficient opening width to avoid bursting of too many bubbles and moderately progressive evolutions of opening sections.

Claims (12)

Foam projection nozzle, traversed by a passage (23) having a central axis (X-X) corresponding to a direction of flow of the foam or foam constituents from upstream to downstream, the nozzle (7 ) comprising a nozzle (26) for ejecting the foam, the nozzle containing an end of the passage (25) downstream of the direction of flow, characterized in that the end of the passage (25) has cross sections, perpendicular to the central axis (X-X), comprising two opposite main sides (Li, Le) and interconnected by connection sides (Ri, Re) shorter than the main sides, the main sides being everywhere at a distance of at least minus 2.5mm. Foam spray nozzle according to Claim 1, characterized in that the main sides (Li) of at least some of the cross-sections are curvilinear and diverge from each other towards the middles of the main sides, where they are at least 4mm apart. Foam spray nozzle according to any one of claims 1 or 2, characterized in that the end of the passage (25) widens downstream of the direction of flow, at angles of at most 30° between a wall at the end of the passage and the central axis (X-X). Foam projection nozzle according to any one of Claims 1 to 3, characterized in that it comprises a mixer (6) of the constituents of the foam, forming the foam and connected to the endpiece (26), in upstream of the nozzle in the direction of flow. Foam projection nozzle according to Claim 4, characterized in that the mixer comprises a cage (31) bounded by a tube, two obstacles (28) at two opposite ends of the tube and arranged in succession along the axis central (X-X), and at least one solid body (30) freely movable in the cage and retained in the cage by the obstacles. Foam spray nozzle according to Claim 5, characterized in that the at least one solid body consists of at least one rigid ball. Foam projection nozzle according to any one of Claims 5 or 6, characterized in that the obstacles are grids. Foam projection nozzle according to any one of Claims 5 to 7, characterized in that the nozzle comprises a nozzle body (22) including the tip (26) and a tubular part (24) forming the the cage and in which the obstacles are placed. Foam spray nozzle according to Claim 8, characterized in that the tubular part of the nozzle body contains a cylindrical and rectilinear bore (24) belonging to the said passage, connected directly to the end of the passage, the cross section of the the end of the passage being geometrically inscribed, at the point of connection, in a cross section of the bore (24). Foam spray nozzle according to Claim 9, characterized in that the bore (24) is rectilinear, of circular section, and the passage (23) has a uniform and rectilinear direction in the nozzle body (22). Foam projection nozzle according to any one of Claims 8 to 10, characterized in that the tubular part has a thread (36) for connection to a conduit (33) for supplying the constituents of the foam. Application of the nozzle according to any one of the preceding claims to processes for spraying viscose foams onto external surfaces.