HK1142288A - Foam-generating device of a fire nozzle - Google Patents

Description

Foam generating device of fire nozzle

Technical Field

The present invention relates to the field of fire fighting nozzles of the foam nozzle type. The invention relates more particularly to a foam generating device for a fire fighting nozzle.

Background

A problem in the art of foam nozzles relates to insufficient and uneven expansion of the water/foam-producing agent and air pre-mixture before it is sprayed through the nozzle orifice.

In fact, insufficient and uneven expansion limits the effectiveness of foam extinguishment and the range of foam injection.

It is known to spray the water/foam-generating premix inside a conical tube from a valve ensuring the acceleration of the premix (see figure 7). The vent provided between the valve and the conical tube ensures that the outer surface of the premix spray is in contact with the outside air, which is driven by the viscosity inside the conical tube. However, in this device, the premix can only take up the very small proportion of air required to obtain a sufficiently expanded foam.

As shown schematically in fig. 8, the device can be modified by designing an orifice in the center of the valve, which orifice is connected to the outside air through a vent pipe connected to the outside of the valve. This solution allows external air to be sucked into the centre of the premix spray and increases the contact surface area between premix and air, so that the expansion can be doubled. The disadvantage of this method is that it is necessary to make an air delivery duct that is perpendicular to the axis of the jet in a first section and then rotated 90 ° in order to send air into the centre of the cone. Such a manufacture is therefore complex, expensive and only allows air to come into contact with the inner surface of the premixed injection.

In this case, it makes sense to propose a simpler and more efficient solution to introduce air to the centre of the top of the premix, to increase the expansion and to increase the range of foam injection.

Disclosure of Invention

The object of the present invention is to overcome these drawbacks of the prior art by proposing a foam-generating device for a fire fighting nozzle.

This object is achieved by a foam generating device for a fire fighting nozzle, wherein the device comprises:

-a nozzle lance consisting of a first end and a second end, the first end being a substantially cylindrical or slightly converging first conduit;

-a diffuser cone coaxially and uniformly laid within the second end of the nozzle spout; and

-an air inlet opening designed in the second end of the nozzle lance,

the device is characterized in that the diffuser cone has splined grooves and is mounted coaxially inside a second cylindrical duct, inside which a propagation front (propagation front) of the premixture of water and foam-generating agent propagates around the splined diffuser cone so as to produce a divergent and separated jet of premixture (dispersed and separated jets) at the outlet of the second cylindrical duct, the outlet of the second cylindrical duct being placed spaced apart from the first duct and the air inlet placed in the region of the second end of the nozzle spout being located upstream from the outlet of the second cylindrical duct with respect to the propagation direction of the premixture so as to allow the divergent and separated jet to be sprayed onto the inner surface of the first duct and to allow the external air to pass onto the outer surface of the jet and to allow the external air to pass between the jets, the divergence and separation of the jets producing, on the one hand, the effect of sucking the external air inside the first duct, on the other hand, the effect of mixing air with the premix in the separation region of the educts is also produced; the constantly generated sprays meet the inner surface of the first conduit to form an enclosed volume of premix into which the outside air is drawn.

According to another characteristic, the second cylindrical duct is held in axial direction by a radial spacer and in axial direction upstream from the first duct by a screw, the head of which will block the orifice of the spline diffuser cone and the shank of which passes through the middle of the radial spacer and projects into the threaded inner periphery of the orifice of the spline diffuser cone.

According to another feature, the second cylindrical conduit is coaxially secured within the second end of the nozzle spout by a flush-fitting socket fixedly secured to the outer peripheral edge of the second cylindrical conduit.

According to another feature, the support ring is coaxially mounted and firmly fixed around the second cylindrical duct downstream from the flush-fitting socket and upstream from the first duct of the nozzle spout, and has an outer diameter slightly smaller than the inner diameter of the second end of the nozzle spout, so as to keep the second cylindrical duct in a substantially axial direction by abutting against the inner wall of the second end, while not hindering the intake of outside air.

According to another feature, the section of the spline grooves of the diverging cone increases simultaneously with the section of the cone.

According to another feature, the thickness of the partitions forming the spline groove partitions determines the air infiltration space and the uniformity of the foam.

Drawings

Other features and advantages of the invention will become more apparent upon reading the following description and upon reference to the drawings in which:

FIG. 1 shows a perspective view of a spline diffuser cone;

FIG. 2 shows a longitudinal section through a nozzle spout fitted with a foam-generating device;

FIGS. 3 and 4 show transverse cross-sectional views of a nozzle spout fitted with a foam-generating device, respectively a cross-section comprising axis (BB) and a view from upstream to downstream and a cross-section comprising axis (AA) and a view from downstream to upstream;

FIG. 5 shows a perspective view of a nozzle spout and its end with an air inlet;

FIG. 6 shows a perspective view of a nozzle spout fitted with a foam generating device;

FIG. 7 shows a cross-sectional view of a first device of the prior art mentioned in the introduction for spraying a water/foam-generating premix;

FIG. 8 shows a cross-sectional view of a second improved apparatus for spraying a water/foam-generating premix known in the art as described in the introduction; and

figure 9 shows schematically a cross-section of the device according to the invention.

Detailed Description

The following description refers not only to the attached drawings, but also proposes to follow the propagation front of the premix, from entering the foam-generating device until it is ejected through the orifice of the first duct (1a) of the nozzle spout, so as to clearly express the features and advantages of the invention.

Of course, the propagation front of the premix reaches the fire nozzle by means of a hose. The inner diameter of the hose is equal to the outer diameter of the second cylindrical pipe (3) projecting slightly beyond the fire nozzle, so that the end of the hose fits onto the periphery of the second projecting cylindrical pipe (3). Thus, through the first end of the second cylindrical conduit (3), the propagation front of the premix reaches the fire fighting nozzle.

As shown in fig. 6, the propagation front propagates inside the second cylindrical pipe (3) through the radially connected spacers (4) in the second cylindrical pipe (3). These spacers (4) divide a cylindrical area at the center thereof with the same axis as the second cylindrical pipe (3). The length and the radius of the cylindrical area are respectively smaller than those of the second cylindrical pipe (3), and the length and the radius of the cylindrical area are suitable for the screw rod to pass through but not suitable for the head of the screw (5) to pass through. Thus, the propagation front propagating inside the second cylindrical duct (3) not only passes through the radial spacers (4), but also surrounds the screw (5) positioned on the axis of the second cylindrical duct (3), the head of the screw (5) abutting against the central end of the spacers (4) and the shank of the screw (5) passing through the centre of the radial spacers in order to reach the complementary threaded inner periphery of the orifice (2b) of the splined diffuser cone (2). The radial spacers (4) and the screws (5) allow the spline diffuser cone (2) to be held on the axis inside the second cylindrical duct (3); the central end of the radial spacing piece (4) is clamped between the head of the screw (5) and the spray hole (2b) of the spline diffusion cone (2) from the upstream to the downstream of the propagation front edge.

After the propagation front of the premix, as shown in fig. 2 and 3, has passed between the radial spacers (4) and around the screws (5), it propagates generally not only to the inside of the second cylindrical duct (3), but also around the diffusion spline cone (2). Due to the divergence of the spline cone (2), the available space for the premix flow inside the second cylindrical duct (3) decreases gradually with the continuous propagation of the propagation front, so as to decrease at the outlet of the second cylindrical duct (3) to the separate space delimited by the spline grooves (2a) of the diffusion cone (2). The device of the invention thus ensures not only a gradual acceleration of the premix, which is proportional to the power with which it is sprayed, but also a separation of the diffused sprays produced.

Briefly, the propagation front is a mutually separated high efficiency (powerfull), dispersed jet due to the propagation of the front around the diffusion spline cone (2) and at the outlet of the second cylindrical pipe (3).

These premixed jets are then injected onto the inner surface of a cylindrical or slightly converging first duct (1a) located at the first end of the nozzle lance (1).

As shown in fig. 5 and 2, the nozzle spout (1) further comprises a second end (1b) located upstream from the first conduit (1a) and into which a flush-fitting socket (6) of suitable dimensions for secure fixing can be fitted and approximately at half the outer periphery of the second cylindrical conduit (3), so that the second cylindrical conduit (3) is held centrally of the second end (1b) in the direction of the axis of the nozzle spout (1) and engages into the second end (1b) for a sufficient selected distance depending on the divergence of the spray leaving the second cylindrical conduit (3); the divergence is closely related to the divergence of the spline cone (2).

In practice, said distance between the outlet of the second cylindrical duct (3) and the inlet of the first duct (1a) of the nozzle lance (1) should be chosen to be large enough to let outside air enter inside the first duct (1a) of the nozzle lance (1) from the air inlet (1ba) provided at the second end (1b), but small enough so that the premixed spray leaving the second cylindrical duct (3) is sprayed on the inner surface of the first duct (1a) and not on the air inlet (1 ba).

Thus, the mutually separated, highly efficient, dispersed sprays leaving the second cylindrical conduit (3) and being sprayed on the inner surface of the first conduit (1a) not only allow the external air to be transferred due to viscosity onto the outer surface of the sprays and to pass between the separated sprays as far as inside the first conduit (1a) of the nozzle spout (1), but also allow the air and premix to mix first in the separation region of the sprays. On the one hand, the action of drawing external air between the separated jets inside the first duct (1a) is created due to the divergence and separation of the jets. On the other hand, the suction is enhanced by the fact that the jet is constantly added to meet the inner surface of the first duct (1a) creating a closed premix space upstream of the orifice of the first duct (1a) of the nozzle spout (1), as shown for example by the axis (AA) in fig. 2 and 4.

As shown in fig. 1, since the section of the spline of the diffuser cone (2) is increased simultaneously with the section of the cone (2), and the thickness of the spacer (2c) forming the spline groove partitions determines the uniformity of the air permeation space and the foam, the closed space is more easily generated.

Finally, because of the pressure effect of the premix being injected into the hose and/or the operation of the balanced nozzle (which changes the orientation of the nozzle spout (1) relative to the flexible hose), the device may be subjected to an inconsiderable torque at the flush-fitting pocket (6), which may cause the second cylindrical conduit (3) to be too offset from the axis of the nozzle spout (1) until separation or failure of the flush-fitting pocket (6) results. To overcome this possibility and as shown in fig. 2 and 3, the invention proposes a support ring (7), the support ring (7) having an outer diameter (fig. 3) which is slightly smaller than the inner diameter of the second end (1b) of the nozzle lance (1), the support ring (7) being mounted coaxially and firmly on the outer periphery of the second cylindrical pipe (3) between the flush-fitting socket (6) upstream thereof and the first conduit (1a) of the nozzle lance (1) downstream thereof, so that the support ring (7) will abut against the inner wall of the second end in the presence of torsion to limit any deformation of the flush-fitting socket (6). Of course, it is required that the support ring (7) should be dimensioned so as to fulfill its function without hindering the intake of external air from the air port (1ba) provided in the second end (1b) of the nozzle spout (1).

The device according to the invention has two important advantages compared with the state of the art. The first advantage is that the expansion is enhanced by three phenomena combined together:

external air is forced inside and outside the jet, thus doubling the contact surface area between the premix and the air;

the external air entering the separation region of the spray is first mixed with the premix, and

-the jets coming out of the splined grooves (2a) are bonded on the inner surface of the first conduit (1a) by creating an efficient mixing between the air and the premix inside and outside the premix jets. A second advantage is the increase of the range of the foam jet, which is achieved by a continuous acceleration with respect to the gradual decrease of the premix propagation space between the second cylindrical duct (3) and the splined diffuser cone (2), on the one hand, and an improvement of the expansion, on the other hand.

It will be evident to those skilled in the art that the present invention may be embodied in many other specific forms without departing from the scope of the invention as set forth in the appended claims. The present embodiments are therefore to be considered as illustrative, but they may be modified within the scope defined by the scope of the appended claims and the invention should not be limited to the foregoing description.

Claims (6)

1. A foam generating device for a fire fighting nozzle, comprising:

-a nozzle spout (1) formed with a first end (1a) and a second end (1b), the first end (1a) being a substantially cylindrical or slightly convergent first conduit (1a),

-a diffusion cone coaxially and uniformly laid within the second end (1b) of the nozzle spout (1), and

-an air inlet (1ba) arranged in the second end (1b) of the nozzle spout (1),

said device being characterized in that said diffusion cone (2) has splined grooves (2a) and is mounted coaxially inside a second cylindrical duct (3), in which second cylindrical duct (3) a propagation front of a premix of water and foam-generating agent propagates around the splined diffusion cone (2) forming a diffused and separated jet of said premix at the outlet of said second cylindrical duct (3), said outlet of said second cylindrical duct (3) being spaced apart from said first duct (1a), and said air inlet (1ba) provided in the region of said second end (1b) of said nozzle tube (1) being located upstream of said outlet of said second cylindrical duct (3) with respect to the propagation direction of said premix, allowing said diffused and separated jet of said premix to be sprayed onto the inner surface of said first duct (1a) and external air to pass to said jet On the outer surface and allowing the passage of external air between the jets, the jet of diffused and separated jets on the one hand creating the effect of drawing the external air into the interior of the first duct (1a) and on the other hand allowing the mixing of air with the premix in the separation region of the jets; the jet is continuously added to meet the inner surface of the first conduit (1a) to form a closed premix space into which the external air is drawn.

2. The device according to claim 1, characterized in that the second cylindrical duct (3) is held in axial direction by a radial spacer (4) and in axial direction along the upstream of the first duct (1a) by a screw (5) whose head will block the spray holes (2b) of the spline diffuser cone (2) and whose shank passes through the middle of the radial spacer (4) and into the threaded inner periphery of the spray holes (2b) of the spline diffuser cone (2).

3. An arrangement according to any of claims 1-2, characterized in that the second cylindrical pipe (3) is fitted coaxially in the second end (1b) of the nozzle spout (1) by means of a flush-fitting socket (6) firmly fixed to the outer peripheral edge of the second cylindrical pipe (3).

4. A device according to any one of claims 1-3, characterized in that a support ring (7) is coaxially mounted and firmly fixed around the second cylindrical pipe (3) between downstream of the flush-fitting socket (6) and upstream of the first pipe (1a) of the nozzle spout (1), and has an outer diameter slightly smaller than the inner diameter of the second end (1b) of the nozzle spout, so that the second cylindrical pipe (3) is held approximately in the axial direction by abutment against the inner wall of the second end (1b) while the intake of outside air is not hindered.

5. A device according to any of claims 1-4, characterized in that the spline grooves (2a) of the diverging cone (2) have a cross-section that increases simultaneously with the cross-section of the cone (3).

6. The device according to any one of claims 1 to 5, wherein the thickness of the spacers (2c) forming the intervals of the spline grooves (2a) determines the air permeation space and the uniformity of foam.