EP0041952B1 - Danger detection device with detector - Google Patents

Abstract

In a detection arrangement comprising a central processing unit (E) and signalling devices (M) remotely located, the energy transmission from a radiation source (Q) and the signal return takes place exclusively optically by means of radiation conductor elements, so called optical conductors (L1, L2), through which the signalling devices are connected to the processing unit (E). The signalling devices (M) contain a detector (F), preferably with a high ohmic capacity, e.g. a smoke sensitive ionisation chamber (8) fed by a solar sensor (7) exposed to a radiation via an optical conductor and of which the output signal is sent back to the processing unit (E) by an electric transformer with a high ohmic capacity (T) and by an optical conductor (L2). This type of detection arrangement is preferably used for indicating the presence of a fire, smoke, a rise of temperature, or for the protection against house breaking, and it is particularly suitable for an area where there is a danger of explosion or electrical break-down.

Description

The invention relates to a hazard reporting unit with a status sensor element which changes its output voltage when a hazardous status to be reported occurs, whereby a reporting signal is generated.

Such reporting units can be used to report dangerous conditions, for example to report a fire, to report dangerous gases or vapors, to increase temperature undesirably, or to protect against burglary or theft. The message signal can be used to alarm or to initiate protective or countermeasures when the undesired state occurs.

The sensor elements used in the reporting units are matched to the condition to be detected and are designed, for example, as fire, smoke, gas, radiation, temperature or intrusion detectors. The invention can be used with particular advantage where sensor elements with high electrical resistance are required, for example ionization chambers when used as fire detectors.

In the case of previously known signaling systems, the voltage supply from an evaluation unit to the individual signaling unit arranged at a distance therefrom and the signal return from these signaling units to the signaling center generally takes place by means of electrical lines, possibly also by wireless electrical transmission. However, such a transmission is very susceptible to interference and unreliable. Electrical interference often occurs during line transmission, e.g. B. network pulses or induced in the lines electrical voltages that lead to an incorrect response of the signaling units and to an incorrect signal transmission. For similar reasons, telephone connections with a modulated laser beam have been proposed, as described in "The Bell System Technical Journal 58 (1979)". The known detectors have further disadvantages, which are listed below. The supply voltage fluctuates due to the voltage drop in the lines, so that complex stabilization devices are required. The components of the signaling unit are also exposed to environmental influences, e.g. B. temperature-dependent, so that complex compensation measures must be taken. For special uses, especially in potentially explosive atmospheres, special protective measures are necessary when voltage is supplied via electrical cables. By using a wireless transmission and a special explosion-proof design of the signaling units, the last-mentioned disadvantage can be overcome, but as is known, wireless transmission is even more susceptible to faults and unreliable because of the various interferences.

US Pat. No. 3,805,066 shows an optical smoke detector in which the individual smoke chambers arranged in series are connected to one another by light guides. The optical connection between the smoke chambers has nothing to do with the above-mentioned reasons, namely the exchange of an electrical connection by an optical connection, because it only connects purely optical sensors that work according to the light barrier principle, without the sensor element having to be supplied with an electrical voltage, and therefore neither an optical-electrical nor an electrical-optical converter are provided.

The object of the invention is to provide a hazard alarm unit that has low power consumption and works sensitively, reliably, without interference, stably, precisely and independently of voltage over longer periods. The hazard detection unit is particularly suitable for use in potentially explosive atmospheres and / or under the influence of electrical interference.

This object is achieved in the hazard notification unit specified in the preamble of claim 1 by the feature defined in the characterizing part of claim 1.

• Figur 1 zeigt ein Beispiel einer Meldeanlage mit parallel angeschlossenen Meldeeinheiten.
• Figur 2 zeigt den Prinzipaufbau eines Brandmelders.
• Figur 3 zeigt den Prinzipaufbau eines lonisations-Brandmelders.
• Figur 4 zeigt ein Brand-Sensorelement.
• Figuren 5 bis 7 zeigen verschiedene Ausführungsformen.
• Figur 8 zeigt den konstruktiven Aufbau eines lonisations-Brandmelders.

The invention is described on the basis of the exemplary embodiments shown in the figures.

• FIG. 1 shows an example of an alarm system with alarm units connected in parallel.
• Figure 2 shows the basic structure of a fire detector.
• Figure 3 shows the basic structure of an ionization fire detector.
• Figure 4 shows a fire sensor element.
• Figures 5 to 7 show different embodiments.
• Figure 8 shows the construction of an ionization fire detector.

In the alarm system shown in FIG. 1, a central evaluation unit E is provided, which has a radiation source Q and a radiation receiver R. The radiation source Q is fed by a signal circuit S, while the output signal of the radiation receiver R is fed back to the signal circuit S. As soon as a predetermined difference between emitted and received radiation is determined, the signal circuit S emits an alarm signal to an alarm unit A or causes z. B. via EDP the initiation of protective or countermeasures. Corresponding signal circuits are e.g. B. in large numbers from the technology of optical condition detectors, for. B. smoke detectors, known.

The radiation from the radiation source Q is referred to by a first radiation-conducting element Lτ, also known as fiber optics, hereinafter referred to as light guide for the sake of brevity, to a plurality of signaling units M _i , M ₂ , M ₃ , ... ver arranged away from the evaluation unit E. shares that have sensors for the condition to be detected. The coupling and decoupling of the radiation for the individual signaling units takes place in a manner known in light guide technology, with branching elements V ₁ , V ₂ , ... or W ₁ , W ₂ , ... suitable training, likewise the connection to the individual reporting units via suitable known connections. The radiation is taken from the individual signaling units M ₁ , M ₂ , M3,... And returned to the receiver R in the evaluation unit E via a second light guide L ₂ . The individual signaling units M _i , M ₂ , M ₃ , ... are therefore connected in parallel via a light guide L ₁ and L ₂ to the evaluation unit E in a group. The entire group can be closed behind the last signaling unit by an end element T, which is used to monitor the functioning of the light guides.

It is noted that further such groups of signaling units connected in parallel can be connected to the radiation source Q and the radiation receiver R via further light guides (L ₁ ', L21

The light guides used can either consist of a single fiber or can be made of several, ie as a light guide bundle. Supply line L ₁ and return line L ₂ can also be combined into a single bundle. The type of light guide can be selected as required and in coordination with the signaling units of various types.

In principle, any suitable lamp, a light or infrared emitting diode or a LASER can be used as radiation source Q, the spectral distribution being broadband, monochromatic, multimonochromatic. However, it is expedient to select the spectrum of this radiation source Q such that it is adapted to the transmission properties of the light guides when using single-mode light guides and to the properties of the radiation receiver R. It may be appropriate to use the radiation source intermittently or in pulses, e.g. B. to operate at a frequency of 30 Hz or to design the branching elements in a known manner so that the individual signaling units receive radiation sequentially at different times in the manner of an optical multiplex.

The radiation receiver R is expediently matched to the radiation source Q and can, for. B. as a photoconductor (Si, GaAs, PbSe, InSb), as a pyroelectric element (LiTa0 ₃ , TGS, PVF ₂ ) or as a bolometer.

FIG. 2 shows a signaling unit M with a high-resistance sensor element F, which requires a voltage supply of a few volts for operation, but only has a very low power consumption. The sensor element F contains a sensor 8, the electrical resistance of which changes when exposed to a state variable to be detected, which is connected in series with a reference element 9. In such an arrangement, the voltage drop at the sensor 8 and thus the output potential U of the sensor element changes when the state parameter to be monitored changes. For the voltage supply of the series-connected elements 8 and 9, one or more solar cells, for. B. silicon diodes, which receive radiation from a branch L _{3 of} the light guide L. If the resistance of the sensor element F is large enough and the power consumption is correspondingly low, the voltage generated by these solar cells or silicon diodes 7 is sufficient to operate the sensor element F.

The output potential U of the sensor element F controls a likewise very high-resistance electrical-optical converter T. This can consist of an LCD element with electrically controllable radiation permeability or reflection, e.g. B. a suitable liquid crystal, which is attached to a reflective surface R _o . Radiation is fed to this transducer T via a branch L _{4 of} the light guide Li and removed again from the light guide L ₂ . Normally, as long as the liquid crystal is opaque to radiation, no signal is returned via this light guide L ₂ . However, if the output voltage U of the sensor element F and thus the control voltage of the converter T exceeds a certain threshold for a certain change in state, the liquid crystal becomes transparent so that the radiation supplied via the light guide L _{4 is} reflected by the reflector R _o and the evaluation unit via the Light guide L ₂ receives radiation. Such LCD elements are known from watch technology.

FIG. 3 shows a detection unit designed as an ionization fire detector. The sensor 8 is designed as an air-accessible ionization chamber and the reference element 9 as a less air-accessible or smoke-insensitive ionization chamber. Both ionization chambers contain radioactive sources for ionizing the air in the chambers. In this arrangement, the potential U at the junction of the two ionization chambers changes in accordance with the smoke density in the air-accessible ionization chamber 8.

Of particular advantage in the design of the sensor as an ionization chamber is the extraordinarily high internal resistance and thus the particularly low power consumption, so that the radiation power supplied by the evaluation unit is sufficient to operate a large number of signaling units connected in parallel.

In this exemplary embodiment, it may be expedient not to supply the output potential U of the sensor element directly to the electrical-optical converter T, but via a field-effect transistor FET serving as an impedance converter and threshold switch, the gate of which is connected to the connection point of the two ionization chambers 8 and 9 and its source and drain via contr Stands 1 and 2 are connected to connections 3 and 4 of the sensor element.

It is noted that instead of the ionization chambers 8 and 9, other high-resistance condition sensors can also be used, which react to other condition parameters to be detected, for example to certain gases or vapors, to changes in humidity, temperature or pressure, etc.

FIG. 4 shows, as a high-resistance sensor F, a semiconductor element, for example a MOSFET, a MOS capacitance or a Schottky diode with a gas, temperature, moisture, smoke or pressure-sensitive active layer A1. For example, a pressure and temperature sensitive MOSFET structure is known as POSFET ("Science" 200 [1978], p. 1371), in which the active layer AI consists of polarized polyvinylidene fluoride. Another example is the "charge flow" transistor (CFT, "IEEE of Solid-State Circuitsa, vol. SC-14 [1979], p. 753), in which the active layer consists of poly (p-aminophenylacetylene) , the characteristic of which changes as a function of moisture, and which is applied to a silicon dioxide layer SIO. Another example is the hydrogen-sensitive MOSFET structure, in which the active layer AI consists of palladium metal ("Vacuum" 27 [1976], p. 245). Sensors of the type described thus represent high-resistance controllable semiconductors in which the insulator layer of a gas, temperature, moisture, pressure or smoke-sensitive insulator layer Al, for. B. from a PVF ₂ (polyvinyl difluoride) layer corresponds. The bias voltage at the gate electrode EG is set approximately to the threshold value for the conductivity between the source electrode Es and the drain electrode ED. This conductivity changes when exposed to ambient conditions.

Furthermore, the electrical-optical converters used are not limited to the example shown with a liquid crystal, but other such elements can also be used. For example, FIG. 5 shows an electrical-optical converter with electrically controllable radiation deflection, for example of the LiNb0 ₃ type. Such a converter T has a chip EO, which has the property that when an electrical voltage U is applied, the light irradiated via an optical fiber L _{4 is} deflected in different directions depending on the voltage. The light guide L ₂ which absorbs the radiation is now arranged at a point which corresponds to an output voltage of the sensor element F and thus an input voltage U of the converter at which an alarm message is to be given.

FIG. 6 shows an electro-optical converter in which the beam path in the air space between the two light guides L ₄ , L ₂ through a piezoelectric element PB, for example through a multilayer polyvinyl difluoride (PVF ₂ ) structure which has become known as a »bimorph structure is changed, which is arranged in a gap between the light guides L ₄ and L ₂ covered with a cladding CL and is provided on both outer sides with electrodes EL.

FIG. 7 shows, as a further example, an electro-optical converter in which the beam path in the air space between the two light guides L ₄ , L _{2 is changed} by an electrostatic semiconductor switch SI. In this, for example, a silicon oxide layer SIO is moved into the beam path by an applied voltage V ₁ , V ₂ between the electrodes EL. This element SIO-EL also acts as a bimetal, so that a fire detector provided with it is sensitive to both smoke and temperature. The semiconductor switch can also be constructed like the stepper motors used in clock technology.

In the manner described, a signaling unit can be created in which both the transmission of the power required to operate the sensor element and the signal transmission back to the evaluation unit take place in a purely optical way. The selection of the sensor elements is by no means limited to the components mentioned, but any, with particular advantage high-resistance sensors for any state variables can be used, for. B. thin layers, semiconductors, in particular high-resistance transistors of the MOS type, or piezoelectric elements that change their properties under the influence of the ambient conditions and react, for example, to a fire phenomenon.

FIG. 8 shows the structural design of a detection unit designed as an ionization fire detector, which operates according to the functional principle explained with reference to FIGS. The ionization chambers can be constructed, for example, according to Swiss patent 551 057 or US Pat. No. 3,908,957.

The fire detector contains an outer ionization chamber 8 and an inner ionization chamber 9, which are arranged on the two sides of an electrically insulating carrier plate 10. The first ionization chamber 8, which serves as a sensor element, has an outer electrode 11 designed as a metal grid, through which air can penetrate into the interior of the chamber. The outer electrode of the other ionization chamber 9 serving as a reference chamber, on the other hand, is equipped with a largely air-impermeable metal hood 13 as the outer electrode. A metal disk 12 and 14, which are conductively connected to one another with a metallic stamp 15 and which each carry a radioactive source 16 and 17 for ionizing the interior of the chamber, serve as counter electrodes in the chambers 8 and 9. If there is an electrical voltage between the outer electrodes 11 and 13, a certain ion current therefore flows through the series-connected ionization chambers 8 and 9, ie between the electrodes 11 and 12 and 13 and 14, a certain potential U being established at the connection point 15. As soon as Smoke penetrates into the air-accessible ionization chamber 8, its electrical resistance changes and thus also the ion current and the potential U at the connection point 15.

The carrier plate 10 is mounted in a housing 20 which has a base plate 21, an adjoining cylinder part 22 and a cover 23. In this case, an annular opening 24 is provided between the cylinder part 22 and cover 23 for the air to enter the smoke-sensitive ionization chamber 8.

The housing 20 can be connected to a base part 30 which is fastened, for example, to the room ceiling. This connection can be made, for example, with a snap lock, with projections 26 of a plurality of snap springs 25 provided on the housing 20 sliding over an annular web 31 on the base part 30 and locking there.

The base part 30 is connected to a central evaluation unit via light guides Li and L ₂ . These light guides end in a plug S ₁ on the underside of the base part 30. The base plate 21 contains a matching light guide socket S ₂ as a counterpart. Light guide connections of this type are commercially available and known. European patent publications 6 662 and 8 709 are mentioned from the large number of publications. For example, a "Connector" C-21 from Hughes Aircraft Co. can be used for this.

As already described with reference to FIG. 2, the radiation arriving via the light guide Li is directed via a branch L ₃ to the optical-electrical converter 7, for example a solar cell battery, which is connected to the two outer electrodes 11 and 13 of the ionization chambers 8 and 9 is connected and the series circuit of the two chambers supplies a voltage. The plunger 15 connecting the counterelectrodes 12 and 14 is connected to the electrical-optical converter T, which receives radiation via the other branch L _{4 of} the light guide L ₁ and whose retroreflection is removed from the light guide L ₂ and via plug connection S ₂ , S ₁ and the Base part 30 is returned to the evaluation unit.

An ionization fire detector designed in this way has all the advantages of conventional ionization fire detectors with regard to optimal smoke sensitivity and a particularly early response to the slightest trace of smoke, but avoids the disadvantages associated with the need for power supply and signal return via electrical lines. Such an ionization fire detector can be used with particular advantage when electrical interference in the lines is to be expected or in an explosive environment.

Claims (16)

1. An alarm device for signalling dangers comprising a condition sensor element (F) which upon occurrence of a dangereous condition which is to be reported alters its output voltage (U) in order to initiate giving of an alarm signal, an op- to-electrical transducer (7) receiving electromagnetic radiation through at least one radiation-conducting element (L_i, L₃) and thereby delivering an electrical potential for the voltage supply of the sensor element (F) and an electro-optical transducer (T), which generates an optical signal upon change of the output voltage (U) of the sensor element (F), which signal is transduced through at least one further radiation-conducting element (L₂) and is evaluated for generating an alarm signal, characterized in that the electro-optical transducer (T) is constructed as a passive element.

2. Alarm device according to claim 1, characterized in that the sensor element (F) contains an element (8) which is sensitive to a combustion phenomenon.

3. Alarm device according to claim 2, characterized in that the element which is sensitive to a combustion phenomenon is constructed as an air accessible ionization chamber (8).

4. Alarm device according to claim 3, characterized in that the air accessible ionization chamber (8) is connected in series with an ionization chamber (9) which is less accessible to air and in series with output means (3, 4) of the opto-electrical transducer (7).

5. Alarm device according to any of claims 2 to 4, characterized in that the sensor element (F) is contained in a housing (20) which is accessible to the ambient air which housing (20) is removable connected with a socket portion (30) that the optical contact between the light-conducting elements (Li, L₂) in the housing (20) and in the socket portion (31) is achieved by a light-conducting connection means (Si, S₂) and that the opto-electrical transducer (7) and the electro-optical transducer (T) are arranged at that face of the light-conducting connection part (S₂) being opposite to the socket portion (31).

6. Alarm device according to claim 5, characterized in that the opto-electrical transducer (7) and the electro-optical transducer (T) are arranged at a support plate (10) which carries at its lower face the air accessible ionization chamber (8) and at its upper face the less air accessible or smoke-insensible ionization chamber (9) which support plate (10) is arranged below a base plate (21) comprising the light-conducting connection part (S₂).

7. Alarm device according to claim 4, characterized in that the connection terminal of both the ionization chambers (8,9) are connected with the gate (G) of a field-effect transistor (FET) and that the source or drain electrode of the field-effect transistor (FET) is connected with the control connection (R_o) of the electro-optical transducer (T).

8. Alarm device according to claim 1, characterized in that the sensor element (F) comprises a high-ohm semiconductor element having an active insulation layer being sensitive to gas, moisture, pressure, smoke or temperature.

9. Alarm device according to any of claims 1 to 8, characterized in that the opto-electrical transducer (7) comrises at least one solar cell.

10. Alarm device according to any of claims 1 to 9, characterized in that the electro-optical transducer (T) contains a liquid cristal device (LCD) having electrically controllable optical permeability or electrically controllable optical reflection.

11. Alarm device according to any of claims 1 to 9, characterized in that the electro-optical transducer (T) contains an element (EO) having electrically controllable radiation deflection that the element (L₂) conducting back the radiation is mounted with its radiation receiving surface such that it receives radiation in the presence of a predetermined input voltage of the electro-optical transducer (T).

12. Alarm device according to any of claims 1 to 9, characterized in that the electro-optical transducer (T) is constructed as a multi-layer PVF₂ bimorphous structure (PB) arrranged in a gap of the light-conducting elements (L₂, 1₄) and being provided with two electrodes.

13. Alarm device according to any of claims 1 to 9, characterized in that the electro-optical transducer (T) is structured as an electrostatic semiconductor layer (SIO) arranged in a gap of the light-conducting elements (L₂, L₄) and having a layer which is movable by the action of an electrical potential and/or by the temperature.

14. Alarm device according to claim 10, characterized in that the liquid cristal device (LCD) is electrically controlled by the output voltage (U) of the sensor element (F) such that upon occurrence of an condition which is to be reported it alters its degree of optical reflection or of optical transmission.

15. Alarm device according to claim 14, characterized in that radiation is transmitted to the liquid crystal device (LCD) through an additional radiation-conducting element (L₄) and that a reflecting surfache (Ro) is provided at which there is reflected the infed radiation after passing the liquid crystal element (LCD), as a function of its degree of optical reflection or of optical transmission and such reflected radiation is removed by an additional radiation-conducting element (L₂).

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