GB2256812A - Admixing device of a fire-extinguishing device or vehicle - Google Patents

Description

21 2 -, 0 S 'I z Admixing device of a f ire-exting[gishing device The

invention relates to an admixing device of a fire-extinguishing device, in particular a firefighting vehicle, for admixing a foam-forming or film5 forming addition agent with the fire-fighting agent e.g. water.

Such devices are provided in order to improve the control of the admixture and the unavoidable inaccuracy of the mixture ratio.

Foaming agent-admixing arrangements are known for this purpose, in which arrangements the fire-fighting water flow is measured with mechanical means and the result of measurement is transmitted to movable flaps or the like. This measuring technique results in a high pressure loss in the extinguishing agent line and leads to inaccurate results of measurement.

Furthermore, a foaming agent-admixing arrangement is known (DE-OS 28 35 468) which is operated by means of an electronically controlled control loop. This arrangement requires a high level of capital expenditure which is not always justified, in particular in the case of comparatively small extinguishing units.

The underlying object of the invention is to provide a simple admixing device with which the pressure loss in the extinguishing agent line experienced in the prior art is reduced and with which the foaming agent is admixed with the fire-fighting water in a quantity which remains constant in terms of percentage, even in the case of fluctuation in the through-flow quantity of the extinguishing agent.

According to a f irst aspect of the present invention there is provided an admixing device adapted for use in a f ire-extinguis.hing device for admixing a foam-forming or film-forming additive with a firefighting agent which is conveyed krom a fire-fighting 1 agent source to one or several consumers through a main conveying line by means of a fire-fighting agent pump, which admixing device comprises: a container for the additive; 5 a line for the additive; a premixer pump to which the additive line is guided; and a by-pass line in which the premixer pump is arranged which by-pass line is connected to the main conveying line and by-passes the fire-fighting agent pumpP wherein a ball valve having an adjusting lever is provided in the additive line in front of, i.e. upstream of, the premixer pump the setting of which determines the amount of additive introduced into the premixer pump, and a venturi is arranged in the main conveying line, associated with which venturi there is a control piston which is controllable by the venturi directly as a function of the through-flow of fire-fighting agent through the fire- extinguishing device, which control piston is connected to the adjusting lever of the ball valve so as to be able to control its setting.

In the case of the device according to the invention, the through-flow quantity is determined by the quantity removed by the consumers. This throughflow generates, in the venturi, the effective pressure which is transmitted to the piston which operates, for example, in opposition to a spring force and acts on the adjusting lever, for example by way of a piston rod with which the control piston is provided. This adjusting lever opens or closes the ball valve to adjust its setting.

A quantity of foaming additive which remains constant in terms of percentage is to be constantly admixed with the fire- fighting agent. The percentage 51 admixture can vary according to need. In order to meet this requirement, it is proposed, furthermore, that the ball valve be provided with mechanical means for preadjustment by means of which a variety of initial settings can be achieved so that the opening angle of the ball valve is directly- i.e. linearly- proportional to the admixture quantity of the foaming additive introduced into the premixer pump. The ball valve can be connected with the control piston by means of the adjusting lever via a connecting rod, with the adjusting lever having several points.of connection for its securement to the connecting rod.

The points of connection, for example bore holes for a screw connection, may be provided in such a way that an initial setting results which corresponds, for example, to a 1, 2, 3% or greater admixing rate of foaming additive.

The control piston may be spring-loaded and the characteristic line of the spring may be set in such a way that the stroke of the piston is linearlyproportional to the through- flow of the extinguishing, i.e. fire-fighting, agent. In this connection, the control piston can be provided with a spring assembly which is connected with an upper piston rod and consists of plate springs. On account of this measure, the piston always produces the same stroke so that the through-flow quantity of extinguishing agent corresponds to the stroke. This means that with a 100 % through-flow quantity the stroke travel is likewise 100 %. If the through-flow quantity is reduced on account of less removal by the consumers, for example to 70 %, the stroke travel likewise amounts to just 70 In many cases, consumers with different capacities are provided. If one of the consumers is switched off, the quantity removed and, with that, the through-flow quantity of extinguishing agent is reduced.

The quantity of extinguishing agent that can be removed at the consumers may be in a range of 1: 7. Other ranges may also be used.

The admixing device may be provided with a nonreturn valve in the additive line upstream of the premixer pump, which may take the form of a jet pump.

According to a second aspect of the present invention there is provided a fire-extinguishing device including an admixing device according to the first aspect of the invention.

An exemplary embodiment of the invention is represented in the drawing and is described in greater detail in the following.

The admixing device 1 is associated with a fire- extinguishing device which is not denoted in greater detail. From an extinguishing agent source 2, which is not represented in greater detail and which can be a hydrant, a fire-fighting water container or the like, there issues lines 3 and 4 with shut-off valves 5 and 6 which run into a main conveying line 7. The latter is guided to a fire-fighting agent pump 8 from which the extinguishing agent line 9 is guided by way of a venturi 10 to the consumer 11. There branches off from the extinguishing agent line 9 a branch line 14 from which lines 15 and 16 are guided to the consumers 12 and 13. Valves 17 to 19 are provided in front of the consumers 11 to 13. A foaming additive container is denoted by 20. Other addition agents, for example wetting agents or the like, can also be stored here. Going off from the container 20 there is an additive line 21 which is guided to a premixer pump 47. The latter consists of a water jet pump 29 which is connected with a ball valve 24. Fitted to the ball, which is not represented, there is an adjusting lever 25 by means of which a mechanical pre-adjustment can be M.

undertaken. The additive line 21 is introduced into the ball valve 24. A non-return valve 23 and a valve 22 are installed, furthermore, in the additive agent line 21. There further pertains to the admixing device 1 a control piston 32 which is controlled as a function of the through- flow of extinguishing agent and which consists of a housing 33, a piston 34 with lower piston rod 35 and upper piston rod 39. A connecting rod 36 is connected with the piston rod 35 by way of an articulated connection 38, which connecting rod 36 is provided at the other end with an opening 37. The adjusting lever 25 is likewise provided with bore holes 26 to 28, one of which is connected with the opening 37 of the connecting rod 36 by means of a screw connection. On account of the different connections, with the same length of stroke H of the piston 34 there result different angles of adjustment alpha 1, alpha 2, alpha 3 and, with that, different opening cross sections in the ball valve 24. The control piston 32 is provided with a spring assembly 40 between the upper piston rod 39 and a fastening 42, which assembly, in the exemplary embodiment, consists of plate springs 41. The piston space below the piston 34 is connected with the venturi 10 by way of a line 44. Moreover, a line 43 is guided from the extinguishing agent line 9 into the space above the piston 34. A rinsing line 45 with valve 46 is guided into the additive line 21.

In the exemplary embodiment, a large consumer 11 and two smaller consumers 12 and 13 are provided. The capacities of these consumers can be designed in the following manner: for the consumer 11, 2000 litres per minute and for the consumers 12 and 13 in each case 400 litres per minute of extinguishing agent. If all three consumers are in use, a total through-flow quantity of 2800 litres results. If, on the other hand, the two consumers 11 and 12 are switched off so that only the consumer 13 is in use, the quantity of extinguishing agent now removed is in a ratio of 1: 7 to the total quantity of extinguishing agent which can be removed. The fire-extinguishing device can thus remove different quantities of extinguishing agent. The effective pressure in the system is adjusted as a function of the quantity of extinguishing agent removed and controls the stroke travel H of the piston 34 by way of the control lines 43 and 44 in connection with the spring assembly 40. The stroke travel is thus adjusted as a function of the through-flow quantity.and causes constantly, in terms of percentage, the same quantity of foaming additive to be admixed with the firefighting agent. If the admixing rate is to be changed, the connecting rod 36 is either connected with the opening 27 or with the opening 28 of the adjusting lever 25. Each of these openings 26 to 28 corresponds to an admixing rate for the foaming agent. Thus ja 1, 2 or 3 or greater admixing rate can be set. Once the admixing rate is set, it remains constant until there is another adjustment in the case of each through-flow quantity removed. This means that with an adjusted additive rate of 2 and a quantity of extinguishing agent, which has been removed, of 2800 litres per minute, per minute 56 litres of additive are admixed with the fire- fighting agent by way of the jet pump 29.

1 claims 1. Admixing device adapted for use in a fireextinguishing device, in particular a fire-fighting vehicle, for admixing a foam-forming or film- forming additive with a fire-fighting agent which is conveyed from a fire- fighting agent source to one or more consumers through a main conveying line by means of a fire-fighting-agent pump, which admixing device comprises:

a container for the additive; line for the additive; premixer pump to which the additive line is guided; and a by-pass line in which the premixer pump is arranged, which by-pass line is connected to the main conveying line and by-passes the fire-fighting agent PUMP, wherein a ball valve having an adjusting lever is provided in the additive line in front of, i.e.

upstream of, the premixer pump the setting of which determines the amount of additive introduced into the premixer pump, and a venturi is arranged in the main conveying line, associated with which venturi there is a control piston which is controllable by the venturi directly as a function of the through-flow of fire-fighting agent through the fire-extinguishing device, which control piston is connected to the adjusting lever of the ball valve so as to be able to control its setting.

2. Admixing device according to claim 1, wherein the ball valve is provided with mechanical means for preadjustment, by means of which a variety of initial settings of the ball valve can be achieved.

3. Admixing device according to claim 2, wherein the control piston has a first piston rod to which the adjusting lever of the ball valve is adjustably 1 connected via a connecting rod.

4. Admixing device according to claim 3, wherein the adjusting lever has several points of connection for the connecting rod.

5. Admixing device according to any one of claims 1 to 4, wherein the control piston is spring-loaded in such a way that the stroke of the control piston is directly- i.e. linearly- proportional to the throughflow of the fire-fighting agent.

6. Admixing device according to claim 5, wherein the spring-loading of the control piston is provided by a spring assembly which comprises plate springs.

7. Admixing device according to claim 6, wherein the control piston is provided with a second piston rod to which the spring assembly is connected.

8. Admixing device according to any preceding claim, wherein consumers having different capacities are provided.

9. Admixing device according to claim 8, wherein the quantity of extinguishing agent which can be removed at the consumers can be varied, preferably within a range of 1: 7 of the maximum amount that can be removed.

10. Admixing device according to any preceding claim, wherein the premixer pump takes the form of a jet pump. 11. Admixing device according to any preceding claim, wherein there is provided in the additive line upstream of the premixer pump a non-return valve. 30 12. A fire-extinguishing device including an admixing device according to any one of claims 1 to 11. 13. An admixing device or a fire-extinguishing device substantially as hereinbefore described with reference to and as illustrated in the accompanying drawing.

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