INDEPENDENT DEVICE FOR GENERATING A VISCOUBLE FOAM

Description

[0001] The present invention relates to a self-contained device for generating viscosified foam.

[0002] It will be useful in particular in decontamination or depollution work, in which foams must be applied to large surfaces which may be steeply inclined or vertical, for example belonging to buildings, or in almost closed spaces which may be difficult to access, and must remain on these surfaces for a long enough time to act on the polluting products, without running or degrading in any other way.

[0003] For this purpose, so-called viscosified foams are appreciated, i.e., those enriched with a gelling agent that increases the physical stability of the foams and makes them less likely 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 the 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 viscosified foams.In particular, they do not guarantee a high expansion of the foam produced in a sustainable manner, i.e. a low liquid fraction in the foam (for example less than 10% by volume); a lower expansion has the disadvantage of using an excess of liquid products for the same volume of foam, and of producing fewer small, more durable bubbles.

[0004] An example of a foam generating device is described in WO 2013 / 067401 A2; this device is partly portable, but is designed for ordinary fire-fighting foams.

[0005] US5623995 A, US2010 / 175897 A1 and CN110251865 A describe other foam generation and projection devices.

[0006] FR2889085 A1 and WO2019 / 011513 A1 describe mixers of the foam constituents, capable of producing the latter in projection devices such as those in the documents mentioned above. These mixers comprise beds of solid bodies composed of superimposed layers; the foam constituents are forced to flow through the beds, and they mix in the interstices of the solid bodies, forming the foam. The compact beds described in these documents are nevertheless not very suitable for producing foams with high expansion.

[0007] An object of the invention is to manufacture foams, in particular special high-expansion foams, reliably, at a high flow rate, by means of a suitable generator whose operation is stable.

[0008] Other objects of the invention are: to be able to transport the device without difficulty to places that are difficult to access and without any source of supply, for example water or electricity; to offer certain safety advantages to the operator.

[0009] According to a general definition, the invention relates to a foam generation device, comprising: ∘ a reservoir of a foaming liquid, ∘ a bottle of compressed gas, ∘ a first conduit exiting the reservoir and passing through a pneumatic pump while being connected to suction and discharge ports of said pneumatic pump, ∘ a second conduit exiting the bottle and passing through a pressure reducer, the first conduit and the second conduit joining at a junction, ∘ a conduit for transporting a mixture of the foaming liquid and the compressed gas extending between the junction and a foam ejection end, ∘ a mixer of the foaming liquid and the compressed gas, in which the foam is formed, and located on the conduit for transporting the mixture between the junction and the ejection end, the second conduit comprising a bifurcation leading to an orifice for starting the pneumatic pump, characterized in that the mixer comprises: ∘ a cylindrical wall open at both axial ends and traversed by the mixture between said axial ends, ∘ a cage formed in the cylindrical wall, and ∘ at least one solid body free to move in the cage, the at least one solid body consisting of 1 to 40 balls, constructed of rigid materials, and in that the cage is 10 to 400 mm long, 10 to 100 mm in diameter, and the balls are 2 to 20 mm in diameter, a filling of the cage by the balls being such that the balls do not form, at rest, superimposed layers, the diameter of the balls being 2 to 10 times smaller than the diameter of the cage, preferably 4 to 8 times smaller than the diameter of the cage.

[0010] This device, where compressed gas is used both to produce the foam and to suck the foaming liquid out of its tank, eliminates the need for a power supply to the device, which would require either the use of an external supply via cables or a heavy battery. The flow rate of the sucked liquid, conditioned by the energy supplied to the pump, is proportional to the pressure of the compressed gas, and the flow rate of the compressed gas used to produce the foam is also proportional to this pressure. The stability of the foam expansion, i.e. the value of its liquid fraction, is therefore guaranteed without any adjustment. The mixer integrated into the device is well suited to producing a foam with the required qualities.The balls being in small number in the cage and of much smaller dimensions than it, do not form superimposed layers but on the contrary remain free and accomplish independent and significant movements, capable of giving a high expansion of the foam.

[0011] According to various optional improvements to this design: the device comprises a pressure gauge for measuring the pressure of the compressed gas in the bottle; the mixture transport conduit comprises a flexible lance; the device comprises a single control lever, arranged on the lance, for opening the lance and ejecting the foam; the cage is delimited by two grids following one another in the cylindrical wall; - the device is mounted on a portable chassis or a rolling trolley, and completely independent, in service, of external supplies, in particular electricity or fluids.

[0012] The invention is well suited to the generation of foams containing a gelling agent.

[0013] The invention will now be described in its various aspects, characteristics and advantages, by means of the following figures, which illustrate a particular embodiment, given for purely illustrative purposes: there Figure 1 is a diagram of an embodiment of the invention; the Figure 2 represents the mixer; the Figure 3 represents the end of the projection lance; the Figure 4 illustrates a concrete arrangement of the realization.

[0014] Referring to the figure 1 , the apparatus 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 end 7, and a chassis 8. A first conduit 11 connects an outlet orifice of the tank 1 to a suction orifice 12 of the pneumatic pump 5; it leaves the pneumatic pump 5 through its discharge orifice 13, passes through the mixer 6 and ends at the end 7. A second conduit 14 connects an outlet orifice of the bottle 2 to the main regulator 4, then flows into the first conduit 11 at a junction 15 made between the discharge orifice of the pneumatic pump 5 and the mixer 6. A branch 16 of the second conduit 14 ends at an orifice 17 for setting the rotor of the pneumatic pump 5 in motion (possibly via a second regulator 43 to independently adjust the pressure at this location).The branch 16 leaves the second conduit 14 just downstream of the main regulator 4 and therefore transports slightly compressed air 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 the latter.

[0015] The chassis 8 carries the tank 1, the bottle 2, the main regulator 4, the pneumatic pump 5, the first conduit 11 and the second conduit 14. As shown in the figure 4 , the frame 8 may be vertical and belong to a backpack carried by the operator of the device; the frame 8 may also be a rolling trolley, for example. The foam ejection end 7 is not fixed to the frame 8, but is located at the end of a flexible lance 21, which the operator holds. The lance 21 extends between the end 7 on the one hand, and the junction 15 on the other hand.

[0016] The mixer 6 is located on the path of the mixture of liquid and compressed air between the junction 15 and the end 7, and it is shown in figure 2 . It comprises two flat grids 28 following one another in the bore 24 of a cylindrical wall and occupying its entire section, two seals 29 to which the grids 28 are respectively fixed and which serve as support for the wall of the bore 24, and spherical and rigid balls 30 free to move between the grids 28. The seals 29 serve to hold the grids 28 in place and to form between them a cage 31, still 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.

[0017] This type of mixer comprising balls, or more generally solid bodies, free in a cage crossed by the previously mixed fluids has proven to be very effective in producing foams whose expansion is well determined and possibly high, that is to say with a low liquid fraction. It is particularly suitable for the manufacture of viscosified foams. The cage 31 can be 10 to 400 mm long, 10 to 100 mm in diameter, and the balls 30 2 to 20 mm in diameter. Free and independent movements, of large amplitude, of the balls 30 being sought to give a high expansion, a very low filling of the cage 31 by the balls 30 is sought. According to the invention, the balls 30 do not form superimposed layers at rest. They are 1 to 40 in number, with a diameter 2 to 10 times smaller than the diameter of the cage 31; more advantageously, 4 to 8 times smaller than this diameter; and at best, about 5 times smaller.

[0018] There figure 3 shows that the end 7 is attached to the front end of a barrel of a gun 32 held by the operator, the rear end of which is joined to the lance 21. The operator opens the lance 21 and triggers the projection of foam by pressing a trigger 35 of the gun 32.

[0019] There figure 4 illustrates a possible arrangement of the equipment on chassis 8, where a spare tank 1' is still shown, used when the first (tank 1) has been emptied.

[0020] Here is how the operation of the device and its advantages can be described. Since the device is free from any servitude, that is to say, any supply from the outside, the operator can put it on or transport it without constraint to remote or inaccessible places. He grasps the lance 21 by the gun 32 and presses the trigger 35 when he is in front of the surface to be covered with foam. The opening of the lance 21 allows the compressed air to flow through the second conduit 14. Part of the flow passes through the pneumatic pump 5, starts it up and is used to suck an invariable flow, proportional to the air flow passing through the pump 5, of the foaming solution from the tank 1. The pumped foaming solution and the main flow of compressed air, which is directed towards the lance 21, converge at the junction 15, upstream of the mixer 6.Here too, the flow rate of the foaming solution and that of the compressed air which mixes with it are proportional and therefore have an invariable ratio, determined by the physical characteristics of the fluids and the device. The foam is formed by the mixing of air and the foaming solution, passing through the mixer 6, which is very effective for obtaining a high expansion foam, sought among other things for viscosified foams.

[0021] Some additional indications, of a concrete nature, are given below to describe more fully a particular example of this realization of the device and its performances. Bottle 2: capacity of 3l, starting pressure of 300 bars; Tanks 1 or 1': capacity of 8l each; Main regulator 4: reduces the pressure to 7 bars; Second regulator 43: reduces the pressure to 4 bars; 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; 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. If the foam is used to fill a volume, the foam holding time is at least 120 minutes.

[0022] Expansion of the foam obtained: approximately 16.7 (approximately 100 liters of foam produced for 6 liters of foaming solution consumed).

[0023] The balls 30 could be replaced by another solid body freely movable in the cage 31, and their number could also be different, only one solid body being possible.

Claims

1. A foam-generating device, comprising: - a reservoir (1) of a foaming liquid, - a compressed gas cylinder (2), - a first pipe (11) out of the reservoir and passing through a pneumatic pump (5) while being connected to suction (12) and discharge (13) ports of said pneumatic pump, - a second pipe (14) out of the cylinder (2) and passing through an expansion valve (4), the first pipe and the second pipe being joined at a junction (15); - a pipe (21) for transporting a mixture of the foaming liquid and the compressed gas extending between the junction (15) and a foam ejection end (7); - a mixer (6) of the foaming liquid and the compressed gas, in which the foam is formed, and located on the pipe (21) for transporting the mixture between the junction (15) and the ejection end (7); the second pipe comprising a bifurcation (16) leading to a port (17) for starting the pneumatic pump, characterised in that the mixer (6) comprises : - a cylindrical wall open at the two axial ends and through which the mixture passes between said ends axial, - a cage (31) formed in the cylindrical wall, - and at least one solid body (30) which is free to move in the cage, the at least one solid body consisting of 1 to 40 balls, constructed of rigid materials, and in that the cage is 10 to 400 mm in length, 10 to 100 mm in diameter, and the balls are 2 to 20 mm in diameter, a filling of the cage with the balls being such that the balls do not form, at rest, superposed layers, the diameter of the balls being 2 to 10 times less than the diameter of the cage, preferably less than 2 to 8 times less than the diameter of the cage.

2. The foam-generating device according to claim 1, characterised in that it comprises a pressure gauge (3) for measuring the pressure of the compressed gas in the cylinder (2).

3. The foam-generating device according to any one of claims 1 or 2, characterised in that the pipe (21) for transporting the mixture comprises a flexible nozzle.

4. The foam-generating device according to claim 3, characterised in that it comprises a single control lever (35), disposed on the nozzle (21), for opening the nozzle and ejecting the foam.

5. The foam-generating device according to any one of generations 1 to 4, characterised in that the cage is delimited by two gates (28) succeeding each other in the cylindrical wall.

6. The foam-generating device according to any one of claims 1 to 5, characterised in that it is mounted on a portable frame (8), and completely independent, in service, of external supplies, in particular of electricity or fluids.

7. An application of a device according to any one of the preceding claims to the manufacture and the spraying onto a surface of a foam containing a gelling agent.