FOAM PROJECTION NOZZLE

Abstract

This nozzle comprises a nozzle body (22) terminating in a foam ejection tip (26). The foam has been previously formed by mixing its liquid and gaseous components in a mixer preferably located just upstream of the tip, within the nozzle body (22). The ejection passage (25) through the tip has oblong sections, the principal sides of which are at least 2.5 mm apart throughout, and it gradually widens towards the outlet. A flattened and flared plume (27) of foam is obtained. Application to foam spraying devices, particularly for viscosified foams, on exterior surfaces. See Figure 2 for abbreviations.

Description

Title of the invention: Foam Projection Nozzle

[0001] The present invention relates to a foam projection nozzle.

[0002] It will be useful in particular in decontamination or pollution control work, in which foams must be projected onto large surfaces which may be highly inclined or vertical, belonging for example to buildings or other fixed structures, possibly difficult to access, and remain on these surfaces for a long enough time to act on the polluting products, without running or degrading in any other way.

[0003] Viscose foams are valued for this purpose; that is, foams enriched with a gelling agent that increases their physical stability and makes them less prone to flowing over even highly inclined or vertical surfaces. These two characteristics allow the foam to act for a sufficient time on the surface being treated. Examples are given in FR 2 841 802 A1. One of their drawbacks is that they are difficult to manufacture from a liquid foaming solution, precisely because of the high viscosity of this solution. Foam-generating devices are generally designed for conventional foams and are not suitable for viscose foams.In particular, they do not allow for a sustained high overrun of the foam produced, i.e. a low liquid fraction in the foam (for example less than 10% by volume); a lower overrun has the disadvantage of using an excess of liquid products for the same volume of foam, and of producing fewer, more durable small bubbles.

[0004] In particular, it has been observed that, even when foams with high expansion are produced, they are generally degraded when passing through the ejection nozzle of the devices, which causes some of the bubbles to burst and some of the gas contained to dissipate, thereby increasing the liquid fraction of the modified foam as well as the diameter of the remaining bubbles.

[0005] A typical foam projection nozzle is described in document WO 2005 / 025755 A; it comprises a jet of the liquid to be foamed, followed by a nozzle with multiple fine openings that divide the jet and thus form the foam just as it exits the apparatus. 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.

[0006] An object of the invention is to project foams, in particular special high-viscosity foams, which retain a satisfactory degree of expansion at the exit of a nozzle of a projection device, without being degraded by passing through a device ejection nozzle.

[0007] 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 nozzle, minimizing their paths to eject them from the nozzle and the rest of the apparatus.

[0008] In general terms, the invention relates to a foam projection nozzle, through which passes a passage having a central axis corresponding to a flow direction of the foam or foam constituents from upstream to downstream. The nozzle comprises a foam ejection tip, the tip containing an end of the passage downstream of the flow direction. The nozzle is characterized in that the end of the passage has cross-sections, perpendicular to the central axis, comprising two opposing principal sides connected by connecting sides shorter than the principal sides, the principal sides being at least 2.5 mm apart at all times. It differs markedly from the design of WO 2005 / 025755 A, where the ejection nozzle has an upstream portion with a wide opening through which the liquid passes without a change of state, and then a downstream portion with fine openings to form the foam.The nozzle tip of the invention, on the contrary, has a wide opening to avoid breaking the foam bubbles as much as possible and thus reduce overspreading.

[0009] It has been observed that this particular shape of nozzle tip prevented significant degradation of viscosified foams which passed through the tip, by limiting the bursting of bubbles thanks to the sufficient width offered for their passage.

[0010] According to certain optional improvements:

[0011] - the main sides of at least some of the cross-sections are cur viline and diverge from each other towards the midpoints of the main sides, where they are at least 4mm apart;

[0012] - the end of the passage widens downstream of the flow direction, at angles of plus 30° between a wall at the end of the passage and the central axis.

[0013] An important feature of the nozzle proposed here is that it very favorably incorporates a foam constituent mixer, which forms the foam and is 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 degradation.

[0014] In a particularly advantageous way:

[0015] - the mixer comprises a cage limited by a tube, two barriers at two ex opposite ends of the tube and arranged in succession along the central axis, and at minus a solid body freely moving in the cage and held in the cage by the obstacles;

[0016] - at least one solid body consists of at least one rigid ball;

[0017] - the obstacles are grids.

[0018] This integration of the mixer into the nozzle including the tip is greater, and therefore more favorable, if the nozzle includes a nozzle body encompassing the tip and a tubular part forming the cage tube and in which the obstacles are placed; and even more advantageously if the tubular part of the nozzle body contains a cylindrical and straight 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 point of connection, in a cross-section of the bore; and if the bore is straight, with a circular cross-section, and the passage has a uniform and straight direction in the nozzle body.

[0019] And the integration of the nozzle with the rest of a foam manufacturing or generation apparatus, allowing to obtain a potentially large flow rate of the foam, is better if the tubular part has a thread for connection to a supply conduit for the constituents of the foam.

[0020] Another aspect of the invention is the application of the nozzle according to any one of the preceding claims to methods of projecting viscosified foams onto external surfaces.

[0021] 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 purely for illustrative purposes:

[0022] - [Fig. 1] is a diagram of a foam projection apparatus equipped with a publication of the invention;

[0023] - the [Fig.2], the projection nozzle body according to section II-II of the [Fig.6];

[0024] - [Fig.3] represents the mixer;

[0025] - [Fig.4] represents the end of the projection lance;

[0026] - [Fig.5] represents the nozzle body according to section VV of [Fig.6];

[0027] - [Fig.6] represents the nozzle ejection tip viewed from the front.

[0028] Referring to [Fig. 1], a foam-generating apparatus to which the nozzle is added is described; the nozzle could obviously be placed on other apparatus. This apparatus comprises a reservoir 1 of liquid foaming solution, a compressed air cylinder 2, a pressure gauge 3, a main pressure regulator 4, a pneumatic pump 5, a mixer 6, a foam ejection nozzle 7 (which is therefore the subject of the invention), and a frame 8. A first conduit 11 connects an outlet port of the reservoir 1 and passes through the pneumatic pump 5. A second conduit 14 connects an outlet port of the cylinder 2 to the main pressure regulator 4, and then joins the first conduit 11 at a Junction 15 is located downstream of the pneumatic pump 5's discharge port. The air flowing in the second conduit 14 is slightly compressed at a constant pressure (7 bar, 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 thus allows the gas pressure at the outlet of cylinder 2 to be measured and its fill level to be assessed.

[0029] 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 frame 8 can be vertical and belong to a backpack worn by the device operator; the frame 8 can also be a rolling cart, for example. The foam ejection nozzle 7 is not fixed to the frame 8, but is located at the end of a flexible lance 21, which is held by the operator. The lance 21 connects to the first conduit 11 and the second conduit 14 at the junction 15. We will see that the mixer 6 is not necessarily separate from the nozzle 7, but can instead be located within it: the mixer 6 is then also not fixed to the frame 8 and is located downstream of the lance 21.

[0030] According to [Fig. 2], the nozzle 7 is formed of a unitary nozzle body 22, cylindrical in shape, through which a passage 23 passes. The passage 23 comprises a main part, which is a cylindrical bore 24, immediately followed downstream by a more complex-shaped end of the passage 25, which will be described later. The bore 24 is formed in a tubular portion 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 flow through the passage 23 in a left-to-right direction in [Fig. 2], as represented by the arrow on a central axis XX of the nozzle body 22 and the passage 23, and the nozzle 7 comprises at its downstream end a tip 26, which contains the end of the passage 25.The foam is ejected from the nozzle 7 through the tip 26, forming a plume 27 preferably in the shape of a flattened cone, suitable for covering large widths of surfaces to be treated by flaring outwards.

[0031] The mixer 6 is shown in [Fig. 3]. It comprises two flat grids 28 arranged successively within the bore 24 and occupying its entire cross-section, two sealing gaskets 29 to which the grids 28 are respectively fixed and which support them against the wall of the bore 24, and two rigid, spherical balls 30 free to move between the grids 28. It has been found that the balls 30, being both mobile and few in number, are suitable for efficiently producing viscous foams due to the low pressure drop and the intensity of the agitation they produce in the liquid constituents. The sealing gaskets 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 fluids circulating in the bore 24 to pass through the inside of the cage 31. The mixer 6 thus defined can occupy almost the entire volume of the bore 24, that is to say that the grid 28 upstream is close to the entrance of the bore 24, and the grid 28 downstream rests on the rear face of the nozzle 26.

[0032] Alternatively, the mixer 6 could be separate from the nozzle 7, have an unchanged construction except that it would have its own cylindrical wall, instead of that of the nozzle body 22, to close the cage 31; and the nozzle would be approximately reduced to the tip 26. In order to avoid destruction of the foam by explosion of some of its bubbles, the mixer would then preferably be connected to the tip, which would be placed immediately downstream of it.

[0033] Figure 4 shows that the lance 21 is attached to the rear end of a barrel 33 of a gun 32 held by the operator of the device. The opposite end of the barrel 33 has a thread 34 onto which the nozzle body 22 is screwed. The operator opens the lance 21 and triggers the foam projection by pressing a trigger 35 of the gun 32.

[0034] Fig. 5 is a cross-sectional representation of the nozzle body 22, which fully illustrates the passage 23 and notably represents an internal thread 36 which serves to screw the nozzle 7 onto the thread 34 at the end of the barrel 33.

[0035] We will now describe the nozzle 26 particularly by means of [Fig. 6]. The end of the passage 25 is approximately conical, widening continuously downstream of the flow direction with a moderate slope: its wall preferably makes angles of less than about 30° with the central axis XX, as shown in Figures 2 and 5. The cross-sections (perpendicular to the direction of fluid flow 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 one transverse direction (vertical to [Fig. 6]) with respect to the other transverse direction (horizontal).

[0036] Figure 6 shows the outline of an internal cross-section Si of the end of the passage 25, through which the end of the passage 25 connects to the bore 24, and the outline of an external cross-section Se, through which it opens onto a front face 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 in shape for the intermediate cross-sections) are generally composed of two main sides Li or Le, with orientations that are generally vertical to Figure 6, which are joined by rounded edges 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, as is the case for the main sides Li of the internal cross-section Si, or partially or completely rectilinear, as is the case for the main sides Le of the external cross-section Se.The main opposite sides are always spaced more than approximately 2.5 mm apart (here 3 mm to 5 mm at the ends). and at the center of the lateral sides Li of the inner cross-section Si (which is the narrowest), in order to provide sufficient passage width for the foam bubbles and to prevent, as far as possible, them from bursting when leaving the nozzle 7. In addition, the contour of the inner cross-section Si is geometrically inscribed, that is to say included, in the contour of the bore 24.

[0037] According to the invention, the foam forms near the outlet of the device through the mixing of air and the foaming solution as it passes through the mixer 6. The grids 28, and especially the beads 30, are very effective in obtaining a high-expansion foam, i.e., one with a low liquid fraction. The end of the passage 25 in the nozzle 26 has a shape that produces the flattened and flared plume 27, thus easily covering entire sections of the surface with a simple sweep of the lance 21. It also has an opening width and direct connection conditions with the bore 24 that greatly reduce the proportion of foam bubbles that burst after exiting the mixer 6 and cause foam degradation by increasing its liquid fraction.The high foam expansion, facilitated by the mixer 6 and maintained by the nozzle 7 as well as by the short distance the foam travels to the outlet of the nozzle 26, is desirable, among other things, for viscosified foams.

[0038] Some additional details, of a concrete nature, are given below to describe more fully a particular example of this realization of the device and its performance.

[0039] Mixer 6: diameter and length of cage 31: from 10 to 100 mm and from 10 to 400 mm;

[0040] Rigid balls 30: from 1 to 40, from 2 to 20 mm in diameter;

[0041] Nozzle body 22: outer diameter and length: 35mm and 100mm;

[0042] Drilling 24: diameter and length: 25mm and 80mm;

[0043] Cross sections of the end of the drilling ([Fig.6]): A=25mm, B=31mm, C=2mm, D=15mm, E=5mm, F=3mm;

[0044] Foaming solution: water, with Glucopon 215UP [BASF] at 10g / l, and Xanthan Gum (G1253) [Sigma Aldrich] at 3g / l;

[0045] Layer projected onto a vertical surface: 10m2, 1cm thick, in 120s; sliding speed less than 1m / min. In the case where the foam is used to fill a volume, the foam retention time is at least 120min;

[0046] Foaming of the foam obtained: approximately 16.7 (approximately 100 liters of foam produced for 6 liters consumed of the foaming solution).

[0047] A similar test with another nozzle, belonging to the known art, produced a foam of much lower expansion.

[0048] The mixer 6 can be placed outside and upstream of the nozzle 7. The balls 30 could be replaced by another freely movable solid body in the cage 31. and their number could also be different, only one solid body being possible.

[0049] And the shapes of the nozzle 26 can also differ from those proposed here, the advantageous embodiments therefore including a sufficient opening width to avoid the bursting of too many bubbles and moderately gradual changes in opening sections.

Claims

Demands

1. A foam projection nozzle, traversed by a passage (23) having a central axis (XX) corresponding to a flow direction of the foam or foam constituents from an upstream to a downstream, characterized in that it comprises a nozzle body (22) encompassing a mixer (6) of the foam constituents, forming the foam, and a nozzle (26) downstream of the mixer, the nozzle containing an end of the passage (25), belonging to the passage (23), downstream of the flow direction; the end of the passage (25) having cross-sections, perpendicular to the central axis (XX), comprising two opposite principal sides (Li, Le) connected to each other by connecting sides (Ri, Re) shorter than the principal sides, the principal sides being everywhere separated by at least 2.5mm; the end of the passage (25) widening downstream of the direction of flow, at angles of at most 30° between a wall of the end of the passage and the central axis (XX);the mixer (6) being placed in a bore (24) belonging to the passage (23), connected directly to the end of the passage (25); the cross-section of the end of the passage being geometrically inscribed, at the point of connection, in a cross-section of the bore (24).

2. Foam projection nozzle according to claim 1, characterized in that the main sides (Li) of at least some of the cross sections of the end of the passage (25) are curvilinear and diverge from each other towards midpoints of the main sides, where they are separated by at least 4mm.

3. Foam projection nozzle according to any one of claims 1 or 2, characterized in that the bore (24) is cylindrical and straight.

4. Foam projection nozzle according to any one of claims 1 to 3, characterized in that the mixer comprises a cage (31) limited by a tube, two obstacles (28) at two opposite ends of the tube and arranged successively along the central axis (XX), and at least one solid body (30) freely movable in the cage and retained in the cage by the obstacles.

5. A foam projection nozzle according to claim 4, characterized in that at least one solid body consists of at least one ball rigid.

6. Foam projection nozzle according to any one of claims 4 or 5, characterized in that the obstacles are grids.

7. Foam projection nozzle according to claim 3, characterized in that the bore (24) has a circular cross-section, and the passage (23) has a uniform and straight direction in the nozzle body (22).

8. Foam projection nozzle according to any one of claims 1 to 7, characterized in that the passage (23) has, at one end, a thread (36) for connection to a conduit (33) for supplying the constituents of the foam.

9. Application of the nozzle according to any one of the preceding claims to methods of projecting viscosified foams onto exterior surfaces.

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