US2073204A - Method and apparatus for producing fire extinguishing foam - Google Patents

Description

March 9, 1937. w. FRIEDRICH 2,073,204

METHOD AND APPARATUS FOR PRODUCING FIRE EXTINGUISHING FOAM Original Filed Dec. 5, 1933 2 Sheets-Sheet l INVENTOR WlLHELM FR\EDRICH ATTORNEY March 9, 1937. w FRlEDRlcH 2,073,204

METHOD AND APPARATUS FOR PRODUCING FIRE EXTINGUISHING FOAM Original Filed Dec. 5, 1933 2 Sheets-Sheet 2 INVENTOR WILH ELM FRIEDRKH A TORNEY Patented Mar. 9, 1937 METHOD AND APPARATUS FOR PRODUC- ING FIRE EXTINGUISHING FOAM Wilhelm Friedrich, Berlin-Charlottenbnrg,

Germany Original application December 5, 1933, Serial No.

Divided and this application April 11,

1935, Serial No. 15,894. In Germany December 8 Claims.

This invention refers to a method and apparatus for producing fire extinguishing foam.

This application is a division of my copending application Ser. No. 701,069, filed December 5,

1933, for a Method and means for producing foam for fire extinction, (issued as U. S. Patent 2,003,184, dated May 28, 1935).

The present invention is a solution of the problem of generating air foam by the use of a 10 fire engine or pump for liquid without the use of gas under pressure.

For this purpose an auxiliary device 1. e. a foam generator is interposed on the suction side between the pump and'the conduit supplying water. This foam generator (1. e. the apparatus) is so constructed, that turbulence together with the entry of external air is produced by the water entering under a certain pressure, with which a foam forming agent (i. e. a chemical substance) 1 has been mixed in any suitable way, this turbulence resulting in the production of foam which is directed to the seat of the fire through hose pipes by means of the fire engine pump. To produce turbulence it is necessary for the water to flow in a thin stream under a certain pressure which, however, need not be very high (about half an atmosphere will sufiice). For fine subdivision of the water let it can be led into the auxiliary apparatus in the form of a thin film or band or in the form of separate jets. The jets are directed longitudinally of the generator but they can also be directed inclined to the iongitudinal axis of the apparatus so that they strike one another and produce violent eddying. The

36 subdivision can be carried to the fineness of mist.

It is further necesary for the total cross section of the foam outlet to be many times as great as the crosssection of the liquid inlet. As for the production of foam about 8 to 15 volumes of air 40 are required per volume of water and as the water preferably flows at a greater speed than the air entrained thereby, a high ratio of cross-section of the air-inlet to the water inlet is necessary.

It has also been found advantageous for the interior of the foam generator in which the foam is produced to be of conical form narrowing in the direction of flow, so that the air entrained by the jets of water gradually increases in speed in the direction of fiow until atthe actual formation of the foam it has reached the speed of the water.

It has also been found by experiments with the apparatus that for good results in foam formation, the properties of the foam forming agent are not unimportant. By way of example the The above described foam generator" is partic- 5 ularly adapted for interposition in the suction pipe of a pressure pump. But in another form it'can be used as a nozzle set upon the end of. the hose, the water under pressure supplied by the fire engine pump having the foam former 10 added, at any suitable place. The foam formation then takes place directly in the nozzle at the place of the fire, air being drawn in by the Jet of liquid and worked into foam in the nozzle.

It will readily be understood that to increase the 15 turbulence it is desirable to make the nozzle as long as possible since the walls of the nozzle cooperate in the foam formation which is promoted by the turbulence. But further means can be used to increase the turbulence in such foam 0 generators or nozzles: for example longitudinally extending partition walls can be provided.

When a foam generator in the form of a nozzle is used, it is possible to supply a large number of such nozzles with water from a single fire 25 engine and discharge the resulting air foam.

The foam generator according to the invention is extremely simple and it can be constructed in innumerable ways provided the above prescribed requirements are fulfilled namely the formation 30 of fine jets or a thin band of liquid or atomization of the liquid, the flow of the jet substantially longitudinally or inclined thereto, the admission of the air which is entrained by the turbulence of the liquid and the production of 35 turbulence by longitudinal walls or other means which are further described below.

As regards the openings for the liquid it has been found that the use of fine, pointed apertures say of star, cross or the like form are ad- 40 vantageous. Such apertures are particularly emcient if the material in which they are formed is not too thick so that the Jets of liquid in their passage through the apertures are guided only over the shortest possible length and after 45 such passage can spread.

In place of such star shaped apertures, narrow preferably crescent shaped slots can be used which cause the liquid to emerge in the form of thin films or fan-like jets.

In generators of large size it may be of advantage to use several concentrically arranged generating chambers. n

In another embodiment of the foam generator which can be constructed equally well for u interposition in a pipe line through which foam is to pass or as a nozzle, instead of a large number of fine jets of liquid, a small number of thicker jets of liquid is used; by causing these jets to strike one another breaking up of the liquid into very fine particles is effected, foam L ;ing formed with the air entrained in the direction of the Jets, the foam in its course drawing inmore air which increases the foam formation. a

This mode of foam formation has several advantages. The foam can be generated by a supply of water under pressure in a foam tube which at the same time can be constructed as a nozzle for discharging the foam. Jets inclined towards one another strike together in the foam tube, it not being necessary for the liquid to flow in the form of fine jets as jets of larger diameter can be used. It is only essential thatv the jets should meet one another at a small angle at a point preferably. in the axial direction of the tube, so that at the meeting point the jets break up whereby with a foam former present foam is generated. It is therefore possible to usewater containing a considerable proportion of foreign bodies, without its being necessary to employ fine strainers which are liable to be rapidly choked. In practice three nozzles directed towards one another at small angles canbe used for the liquid supply, with, in some cases, a fourth central nozzle which lies axially of the tube and directs a part of the liquid against the vertex of the solid angle formed by the ets from the three inclined nozzles. When such nozzles are used in this manner then for example for a foam tube which generates around 1 cubic meter of air foam per minute, four nozzles each of say 4 mm. diameter can be used, so that the mesh of the strainer can be 3 mm.

, The foam tube is further constructed so that it can be provided at its discharge end with a bend serving as a pouring head while together with the water supply pipe it can be set upon or coupled to a long carrying pipe, so that this foam pouring nozzle can be directed by means of the carrying pipe overthe edge of a high tank or vessel in order to supply the tank along its wall with the air foam.

A hand foam nozzle can be provided with a multi-way cock and a water nozzle so that by manipulating the cook it is possible to direct water under pressure to the foam nozzle or to the water nozzle, in order .to direct either foam or water on to a fire at will.

The invention further extends to the solution of the problem of supplying the foam former to the water under pressure as uniformly as possible and regulatably and of obtaining inti mate mixture of the foam former with the water.

The solution of foam former can be mixed with the water under pressure at any desired. point in the supply pipe, for example on the suction side of the pump; it can, however, also be led directly into the foam generator where it mixes with the inflowing water! To introduce the foam former into the main water current before the pump, that is on the suction side, according to the invention a mixing device is provided by which the foam former solution is drawn in by the pump simultaneously with the water and incorporated in the latter. This device consists of a pipe branch which can be connected to the water pipe, and which is connected to a suitable container holding the The introduction of foam forming solution into the nozzle and its mixing with the water under pressure therein can according to the invention be effected in various ways; it is essential, firstly that the foam former shall already have been mixed as thoroughly as possible with water and introduced therefore as a solution at a certain not too high concentration. This is important because a highly concentrated foam former solution owing to its high'viscosity could not at the great speeds at which the mixing takes place in the generator become sufficiently uniformly and completely distributed through the water under pressure.

Secondly according to the invention care must be taken that when the foam former solution is introduced into the generator constructed as a nozzle it is as finely divided as possible so that it can mix as rapidlyand uniformly as pos- -sible with the water entering the nozzle in tin jets.

For this purpose in the foam generator according to the invention in addition to apertures for the entry of water under pressure there may be one or more separate apertures for the foam former solution.

To introduce the foam former solution into the jets of water under pressure a spraying nozzle projecting into the foam generator or a plurality of single apertures can be provided which can be constructed in the same manner as the apertures for the water under pressure.

In order to fulfill the first requisite, namely to supply an already thoroughly mixed foam former solution, according to the invention a separate operation is employed which consists in feeding a strongly concentrated foam former solution out of a container by means of water under pressure and a suitable Jet apparatus, the solution at the same time being intimately mixed with the water and brought to the required degree of dilution by a regulating device. This operation has the further advantage that the diluted solution enters the foam generator dispersed under a certain pressure.

To carry out this operation according to the invention, for example a part of the water flowing under pressure can be led through a branch pipe to an ejector connected with the container where the water uniformly draws the foam former solution ofi and mixed therewith flows into the foam generator.

According to the invention the container for the foam former solution can be in the form'of a haversack which the manipulator of the nozzle can carry on his back. Such an arrangement has the advantage that the nozzle manipulator can independently carry out all the necessary operations for regulating the production of foam without reference to the space conditions at the seat of the fire and without the help of assistants. He is also in a position by cutting off the supply of foam former to project water instead of foam.

If the foam nozzle is provided with a multi-way cock for the water under pressure, the cock can also serve for shutting off the foam former. The foam former is advantageously supplied through an interior or exterior nozzle concentric with the water nozzle so that the projecting water jet draws out the foam former by suction while mixing therewith and projects it into the meeting point where the jets are broken up.

It has already been proposed to produce air, foam by means of a Jet of liquid having foam former added to it, which in a jet pump sucks in air and works it into foam. The use of water jet pump is not at all suitable for obtain ng the desired results Water jet pump works with a single solid water jet which flows through a. narrow nozzle. Since the turbulence produced by a powerful solid water jet is too small and since too little air is sucked in (about 1 to 1 /2 volume of air to 1 volume of water) such a jet pump does not yield foam suitable for fire fighting. Only with the present invention is an air foam with sufficient toughness, stiffness and fineness of the' bubbles produced.

Some examples of constructions for carrying.

out the method of the invention are illustrated in the accompanying drawings.

Figure 1 shows a foam generator in the form of a suction jet pipe in axial section, which is connected to the suction side of a pump, for example a fire engine pump.

Figure 2 shows an elevation of the complete foam generator interposed between a hydrant and a pump.

Figures 3 and 4 show axial sections of two foam generating nozzles which by themselves generate foam if water under pressure containing a foam former is supplied to them.

Figure 5 is a section on the line V--V of Figure 3.

Figure 6 shows a foam generator in the form of a nozzle in combination with a portable foam former container and devices for feeding and premixing the foam former.

Figure 7 shows a multiple way cock for shutting off the supply of water and foam former, in section on an'enlaged scale.

Figure 8 is a sectionon the line VIII-VIII of Figure 7.

The foam generator shown in Figure 1 consists of a chamber l in the form of a conical tube which is connected to the suction side of the pump by a coupling 2 at the pump entry end.

Into the flared opening projects a feed pipe 5 connected to a supply of water by a coupling 3 and preferably provided with a control cock 4, which pipe has apertures for example slots 5 at its outlet end discharging into the hollow space I surrounding the pipe 5. This hollow space leads into the direction of fiow into a narrow annular slit 8 out of which the water flowing through the pipe 5, slots 6 and space I is projected in the form of a thin tubular band and strikes the wall of the chamber I at a small angle.

Air which flows freely into the opening 9 is drawn in by the jet of water emerging from the slit 8, and is accelerated in the chamber i so that at the instant it meets the water jet it already has a substantial speed.

The necessary foam former in the form of a solution of suitable concentration is supplied through a pipe l0 laterally connected to the pipe 5. The foam former solution flows through the pipe ii to a small hollow space l2 which also has an outlet in the form r a fine slit l3 which is immediately adjacent the slit 8. In this way the projected foam former solution is caused to mix withthe water projected from the slit 8. To increase the turbulence two oppositely rotating screw wheels l4 and I5 are provided which break up the air and liquid mixture and increase the foam formation.

Figure 2 shows the generator I illustrated in Figure 1 in combination with a pump I! which further works up the entering foam and forces 75 it through the hose l8 from which the foam can be directed upon a fire through an ordinary plain nozzle. The water is in this case supplied from a hydrant l9 and led to the generator through a hose 20. The foam former solution is fed from a container 2i by -a suitable suction or pressure device not shown.

For fine regulation of the water supply a device is provided which enables the section of the slit 8 (Figure 1) to be regulated. For this purpose an annular sleeve 22 is arranged on the pipe 5 which can be advanced or retracted by a screw thread 23 and the slit width thus varied.

The nozzle shown in Figure 3 is a foam generator which can be set on any desired water supply under pressure, for example at the end of a fire engine hose. f

The water under pressure, with which the foam former can be mixed at any suitable place in the supply pipe, flows through a lateral connection 24 and thence through a narrow annular slit 25 in the form of a band jet into the nozzle along the conically contracting wall 26, mixing with the air drawn through the flared opening 21. To increase the turbulence longitudinal partition walls 28 and 29 can be provided inside the nozzle, their cross section being shown in Figure 5.

In Figure 4 a similar nozzle is shown. In this the water-foam former mixture is not discharged through a continuous annular slit, but through numerous fine nozzles 30 in the longitudinal directlcn of the wall of the nozzle 26, through which the water is discharged in fine separate jets.

Another way of supplying the foam former in the nozzle is shown in Figure 6 in which a device is shown in which the foam former is drawn off by a by-passed portion of the water under pressure and gradually mixed with and diluted by such water, the dilute foam former solution then being led in finely divided form into the jets of water under pressure. Here the foam former container 52 can be carried on the back and is connected with the nozzle 3| by two hose pipes.

In the supply pipe for the water under pressure is'a multi-way cock 53 (see Figures 6, 7 and 8) which with the plug 54 in open position allows the main current of water to pass through the main plug passage 55 to the annular conduit 33 from whence the water is projected in jets through the apertures in the projections in the manner above described. A part of the water can flow into the hose pipe 58 through a lateral bore 56 in the plug 54 communicating with the main passage 55. This hose 58 leads to an ejector device 59, of which the jet nozzle 60 projects into the chamber 8|.

This chamber is regulatably connected with the interior of the foam former container 52 through a cook 52. The water projected through the nozzle 50 draws foam former from the container 52 through the outlet 53 from the cook 62, and the foam former is entrained by the water jet, becoming intimately mixed therewith. The outlet from the ejector 59 is connected to a second entry 65 to the plug 54 by a second hose 54. As Figures '7 and 8 show, with-the cook 53 in working position, the liquid coming from the ejector 59 flows through the hose 54, to the entry 65 and through a passage 66 to an outlet 61 on the other side; from here the dilute foam former solution through a bent tube 58 reaches an atomizing nozzle 69 through which the solution is projected in finely divided form between the jets of water under pressure emerging from the two rows of projections into the interior of the nozzle 3!. By this mode of supply very rapid and intimate intermixing of the foam former, already diluted, with the Jets of water is effected so that a considerable output of foam is obtainable with small consumption of foam former. The supply pipe 32 can at the same time serve as a handle for the foam generating nozzle. Ad-

vantageously the pipe 32 can run along the rear end of the nozzle at a certain distance from it, as

Figure 6 shows'so that the fingers can be accom- 10 modated in the space between.

What I claim is:

1. Method of producing a fire extinguishing foam which comprises ejecting one or more high velocity streams of liquid from a corresponding number of nozzles in such manner as to impart a high degree of turbulence to the body of said stream of liquid, thereby finely subdividing the same, and aspirating air from the atmosphere into and by means of the resulting stream-of subdivided liquid in the presence of a foam promoting agent.

2. Method of producing a fire extinguishing foam as defined in claim 1 in which the liquid is converted into a foam with a volume of air 26 amounting to at least seven times the volume of said liquid.

3. Method of producing a fire extinguishing foam as defined in claim 1 in which a substantially cylindrical solid stream of quenching liquid 30 is converted into a substantially tubular stream of film-like thickness.

4. Method of producing a fire extinguishing foam which comprises dividing a unitary stream of quenching liquid into a plurality of relatively small free flowing jets whereby said stream is transformedinto a stream of the liquidin finely divided form and aspirating air into and by means of said finely divided stream in the presence of a foam promoting agent. 5. Method of forming a fire extinguishing foam as defined in claim 1 in which the foam promoting agent is a member of the group consisting of sulfonated fatty alcohols, salts of aromatic alkylated sulfovacids and salts of alkyl naphthalene sulfo acids.

.6. Apparatus for the production of fire extinguishing foam comprising a tube having an entrance end and an open discharge end, a conduit for quenching liquid, at least one nozzle located adjacent the entrance end of the tube and communicating with said conduit for finely subdividing the quenching liquid delivered by --said conduit and projecting the resulting stream of finely subdivided quenching liquid through the tube toward the discharge end thereof, and

means for mixing a foam promoting agent with .the quenching liquidv comprising a conduit for foam promotingagent, and at least one nozzle located adjacent the entrance end of the tube and adapted to project a stream of finely subdivided liquid delivered by said last named conduit through and toward the discharge end of said tube, and inlet means adjacent the entrance end of said tube opening to the atmosphere.

7. Apparatus as defined in claim 6 in which a nozzle communicating with the conduit for quenching liquid and a nozzle communicating with the conduit for foam promoting agent are annular and substantially concentric.

8. Apparatus as defined in claim 6 in which a plurality of nozzles communicate with each of the conduits for quenching liquid and for foam forming agent.

WILHELM FRIEDRICH.

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