EP0263290B1 - Electronically controlled automatic mixing apparatus for fire engines - Google Patents

Description

The invention relates to a device for fire-fighting vehicles with an automatic, electronically controlled admixer, with which a foam agent is sucked in from a storage container and the fire water is mixed behind the fire water pump in a predetermined amount, the dosage of the amount of foam agent provided by a in the foam agent line a control element actuated by a control unit in connection with several flow measuring devices in the extinguishing agent lines, the extinguishing water-foam medium mixture being fed via lines to a consumer, where a control valve is provided as the control element, and that the extinguishing water-foam medium mixture and the foam agent are passed through the flowmeters are recorded quantitatively and both measured values are fed to the control unit, the dosage of the foam agent taking into account the current flow rate of extinguishing water and foam agent mixture and the set dosage values s automatically by controlling the control valve, resulting from a target / actual comparison.

In the case of an electronically controlled admixer for a fire truck (DE-A 3038 334), a volumetric metering pump which is speed-controlled by a control unit is provided. In this method, a speed is assigned to a certain volume flow according to the pump characteristic and the admixing depends on the proportionality and reproducibility of the admixing characteristic, or the flow must be measured and the speed corrected in the event of deviations. Such speed controls are relatively easy to implement in the case of an AC power supply via the frequency, a relatively large outlay having to be carried out on vehicles because of the DC power supply.

Electronically controlled admixers have already been used in stationary installations (DE-A 28 35 468). The pure admixing function was carried out by a normal pre-mixer, which works on the principle of a water jet pump. This proportioning device is built into the bypass of a water pump, between the pump outlet (pressure side) and pump inlet (suction side).

In addition to these pump premixers, mixing devices are also known which operate using a foam agent pump based on the differential pressure principle, or with speed-controlled volumetric metering pumps, or in which the signal of the water flow is converted mechanically to control the foam agent flow.

The known admixers have the disadvantage that e.g. the amount of motive water cannot be used to operate the bypass as an extinguishing agent, the pressure losses in the differential pressure principle are relatively high and, in the case of speed-controlled metering pumps, there is a dependency on the pump characteristic and its reproducibility. The known systems also have the disadvantage that they work with satisfactory accuracy only in a relatively small flow range (1: 7 to 1:10).

Because of the disadvantages outlined above, it is difficult to use automatic mixers for mobile systems and at the same time to achieve a high mixing accuracy over larger flow ranges.

The invention has for its object to provide an automatic admixing device for mobile systems with which the known Disadvantages are avoided and can be used with very high accuracy in a large flow range.

This object is achieved in that the foam agent is mixed in behind the fire water pump; that the extinguishing water-foam agent mixture is fed to several consumers via branch lines, that the quantitative detection of the extinguishing water-foam agent mixture takes place in two partial streams, the partial streams optionally being detected by means of a flow meter and / or by means of a pressure measurement, and both values are added via an adder Control unit are fed.

With this measure, the water flow is continuously measured in the partial flows and the foam medium is fed to the water with the foam medium pump via the flow meter and the control valve.

The extinguishing water-foam agent mixture is measured and processed in each partial flow. The measured values are sent as electrical signals to a computer which compares them with the signal from the foam agent flow meter, taking into account the set dosage, and eliminates differences by correspondingly controlling the control valve. By dividing it into two partial flows, the flow measurement can be carried out without pressure loss in the thrower supply and a smaller flow measuring device, which then works more precisely in this area and is less expensive, can be used in the second partial flow. Both partial flows can optionally be measured by means of a pressure meter or a flow meter or vice versa.

Another advantage of the invention is the fact that a speed control in favor of a much simpler control for changing the cross section in the control element is omitted can. Furthermore, according to the invention, a very simple centrifugal or impeller pump can be used instead of the volumetric pump, which only has to bring the maximum flow rate and a minimum pressure level, but can otherwise run at a constant speed. Compared to conventional pump pre-mixers, the invention does not show any loss in performance due to pump circulation. Larger pressure drops can also be processed. After that, the whole system according to the invention becomes less susceptible to faults. Pipes can be dimensioned smaller and a flow meter with a higher pressure loss can be used. If the foaming agent is seen in the direction of flow, introduced before the extinguishing water pump, the advantage is that the foaming agent pump can run with a weaker drive.

In order to ensure a precisely metered admixture of the extinguishing agent in all operating states of the extinguishing device, it is further proposed that between the foam agent pump and the control valve there is a return provided with an overflow valve or an orifice, with which the foam agent conveyed by the foam agent pump and not required for metering is provided is returned to the foam concentrate container. This feedback has the advantage that the foam operation can be carried out intermittently without the Foam agent pump is switched off or an undesirable pressure increase occurs.

In order to give the operator an overview of the foam agent still available, a signal is taken from the flow meter for the foam agent, which is processed to indicate the level of the foam agent and consequently can always be provided for sufficient foam agent.

Fig. 1

die Schaltung eines automatischen Zumischers mit einem Hydranten,

Fig. 2 bis 4

unterschiedliche Durchfluß- und Druckmessungen.

Exemplary embodiments are shown in the drawing and are described in more detail below. It shows:

Fig. 1

switching an automatic proportioner with a hydrant,

2 to 4

different flow and pressure measurements.

The consumer denoted by 1 can represent a launcher tube and the consumer denoted by 2 can represent a connection for an extinguishing hose or the like or, as shown in the exemplary embodiment, for three extinguishing hoses 2a, 2b and 2c.

These can also represent a self-protection system, hand tubes or front throwers, for example.

The extinguishing agent consists of a mixture of water and foam. The water is taken from a hydrant 44. According to FIG. 1, the water is drawn in by means of a line 5 from a pump 6 and supplied to the consumer 1 and the consumer (s) 2 in the pressure mode. The foaming agent 12 is fed into the line 5 behind the pump 6 at 15a, as shown in FIG. 1.
In a branch line 7a leading to the consumer 1 there is a valve 8 for switching the consumer 1 on and off, and a changeover valve 10 for regulating the power of the consumption 1. The foam agent 12 is located in a closed storage container 11 with a feed 35 and is supplied by one Pump 13 sucked in through a line 14, pressurized there and mixed in at 15 of the extinguishing water line 5 and passed on in the mixture line 7. In the line 14 there is a shut-off valve 16, a control valve 17 and a flow meter 18, which can be designed, for example, as an impeller counter. From line 7, a branch line 20 branches off at 19, which is divided into lines 22 to consumers 2. In the line 7a is a pressure measuring device 9 for quantitative detection of the flow rate. In the line 20 of the extinguishing water-foam agent mixture there is a flow meter 21, which can be designed, for example, as a Woltmann meter. A control line 40 leads from the flow meter 21 and is introduced into a computer 36. With 23 shut-off valves for designated the consumer 2. At 26, a branch line 25 leaves the line 20, which ends at 24 in the branch line 14.

There is a pressure reducer 28 and a shut-off valve 27 in line 25. After the foam has been used, line 25 is used to flush the foam medium line 14.

To return the foaming agent not required for metering into the storage container 11, a branch line 30 is led from line 14 into the foaming agent container 11 at 29. A shut-off valve 31 for the container return and an overflow valve 32 are provided in line 30.

A computer, for example a microprocessor 36, is provided for the automatic admixing of the foaming agent, to which the corresponding control commands are supplied by a setpoint generator 37 via control lines 38. Of the Flow measuring devices 18 and 21 and from the pressure measuring device 9 go from control lines 39, 40 and 41, which are introduced into the computer 36. The values supplied to the computer 36 by the devices 9, 18 and 21 are processed in the ACTUAL / TARGET comparison. With the calculated result, the actuator 43 of the control valve 17 is actuated by means of the control line 42. A signal is taken from the flow meter 18 by means of a control line 34, which is fed to the fill level indicator 33, with which the amount of foam agent present is displayed.

With the measure according to the invention, a stream of extinguishing water is mixed in a selectable ratio of foaming agent, the percentage addition remaining constant regardless of the water flow and this constancy being achieved automatically.

Instead of the flow rate measurement 21 in line 20 and the pressure measurement 9 in line 7a, the measurements can be carried out, as shown in FIGS. 2 to 4. The pressure measurement 9 and the flow measurement 21 are arranged differently and can therefore be used optionally.

Claims (2)

1. Device for fire-fighting vehicles having an automatic, electronically controlled admixer, with which a foaming agent is drawn off out of a storage container by suction and is admixed with the fire-fighting water in a certain quantity, the dosage of the quantity of foaming agent occurring by means of a regulating element which is provided in the foaming agent line and is actuated by a control unit in connection with several through-flow measuring units in the extinguishing agent lines, with the fire-fighting water - foaming agent mixture being supplied by way of lines to a consumer, where a regulating valve is provided as the regulating element and the fire-fighting water - foaming agent mixture and the foaming agent are detected quantitatively by means of the through-flow measuring units and both measured values are supplied to the control unit, with the dosage of the foaming agent occurring automatically in consideration of the instantaneous fire-fighting water - foaming agent mixture through-flow and the adjusted dosing value by means of activation of the regulating valve, resulting from a comparison of actual and rated values, characterised in that the foaming agent is admixed after the fire-fighting water pump (6);
   in that the fire-fighting water - foaming agent mixture is supplied to several consumers (1 and 2) by way of branch lines (22);
   in that the quantitative detection of the fire-fighting water - foaming agent mixture occurs in two partial flows, with the partial flows being detected selectively by means of a through-flow measuring unit (21) and/or by means of a pressure measurement (9) and both values being supplied by way of an adder to the control unit (36).
2. Device according to claim 1, characterised in that provided between the foaming agent pump (13) and the regulating valve (17) there is a return line (30) which is provided with an overflow valve (31) or a restrictor and with which the foaming agent which is not required for dosing purposes can be supplied back into the foaming agent tank (11).

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