Multiple combustion sensing device with false alarm prevention

NORWAY

Explanation No. 124751

Int. Cl. G 08 b 17/00 KI. 74a-30 i

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Patent Application No. 4480/69 Filed

12.11.1969

BOARD

FOR INDUSTRIAL JUSTICE

Løpedag

Application widely available from

The application is laid out and the pamphlet is published

14.5.1970

29.5.1972

Priority requested from: Nov. 13, 1968, United States, No. 775,484

BRK- ELECTRONICS, INC.,

525 Rathbone Avenue, Aurora (Kane County), Ill., USA. Inventors: Wilbur L. Ogden, 911, Watson Street and

Clarence Glenn Henderson, 2230 Gettysbourg Drive, both: Aurora (Kane County), Ill., USA.

Prosecutor: Civil. Per Onsager.

Combustion Detector.

BACKGROUND OF THE INVENTION The present invention relates to a combustion detector comprising two or more combustion sensing devices, each adapted to provide an electrical signal in the event of combustion, and an alarm triggering device which does not respond to each signal, but only to the sum of two or more of the signals.

Generally, a fire comprises and goes through four phases: first the initial phase in which only invisible combustion products are released and the fire cannot be recognized by humans because there is no smoke, flames or noticeable heat generation, second the smoke phase, the third flame phase and the fourth heat phase caused of the flames. The initial or initial stages usually have a duration of, that is, hours, days or weeks, and in themselves pose virtually no danger to people or property. As soon as the fire enters the rst phase, it develops, it develops very quickly, and in the course of minutes and even seconds it is characterized by smoke, flames and heat, which each pose a great danger, causing great damage to property and puts human life at risk.

From now on, various devices are known for detecting each fire phase, such as resistance bridges for detecting a fire in any phase, i.e. primarily in its initial phase, ionization-type foils for detecting a fire in its initial phase (see US Pat. 2,465,377, 2,702,898, 2,759,174, 3,078,450), of pre-darkening or photocell type for smoke detection (see U.S. Pat. 2,278,920), of the photocell type for detecting flames or radiation (see United States Patent No. 2,553,420) and the thermocouple or thermistor type for detecting heat (see United States Patents 2.9Ο1 · 74θ ° g 3 · θ38.1θ6).

The smoke, flame, and heat detectors are of course valuable, but by the time the onset of combustion they are designed to detect, act, the fire has evolved to a high level of danger where it causes property damage and puts human lives at risk.

Accordingly, attention is focused on foil devices for detection of fire in its initial phase, that is, the resistance broth and the ionization type. Both types are sensitive to the invisible gaseous combustion products produced at the first stage of the fire, the type of ionization detecting solid particles that are larger than usual but still so small that they are invisible as well as smoke, while the resistance bridge type detects these same particles and the water vapor emitted as a product of combustion.

However, a significant difficulty encountered in detecting fires in the initial phase is in false alarms caused by factors other than combustion. All fire detectors are sensitive to atmospheric conditions other than combustion products, for example, ion: atomizers are very sensitive to air movement, ozone, dust and various chemical vapors, while resistance brochures are extensible for rapid periodic changes in humidity.

Therefore, despite a number of useful suggestions, there is no complete solution to the problem of early fire detection, or rather, early fire detection is constantly suffering from accidental malfunctions, especially false alarms.

The present invention solves the problem of false alarms caused by factors other than combustion and provides an improved early detection fire detector with far greater sensitivity and reliability than known constructions.

The invention is based on the use of two or more combustion detection principles at a pre-selected or given fire phase, in such a way that each of them compensates for the limitations of the others, that is to say, combining sensing functions for conditions whereby they which is common to all and does not result from combustion, rarely or never occurs simultaneously in nature.

Specifically, the invention is first and foremost to design a combustion detector of the kind initially provided so that the two foil devices both respond to the change in a given ambient state that occurs during combustion, but are sensitive to mutually different states, of false alarm, and that they respond to mutually different environmental state changes that are not due to combustion and which will rarely occur at the same time.

The consequence of this combination is that if a non-combustion condition occurs and triggers a detector device to emit an alarm signal, the same condition will not trigger the other detector device and no false alarm signal is emitted ·, by matching the two detector devices in such a way that one compensates or counteracts the other's limitations, that is the other's sensitivity to conditions other than combustion; the probability of any false alarm will be reduced by many orders of magnitude if not removed completely, since at least two different and critical conditions which are not critical for combustion detector devices must be present simultaneously to cause false alarms.

The invention specifically provides a fire detector which serves for early warning, resp., Warning of the initial phase of a fire, and comprising a ^tt0G "port coupling with a combination of a detector device where both said foil devices can respond to invisible combustion products emitted in the initial phase of a fire, and both foil devices can respond to the change in combustion air electrical conductivity occurring and where one of the foil devices comprises a resistance bridge which is sensitive to the change in combustion of the electrical conductivity of the air during combustion; and wherein the second foil device comprises an ionization type combustion detector means.

As previously mentioned, the resistance brotype has been obstructed by an unfortunate embrace for rapid changes in the water vapor content of the atmosphere, while the type of ionization has been obstructed by adverse consequences of chemical vapors, dust, eons and strong air currents. However, Bet has been found that the ionization type is largely susceptible to changes in

124751 ⁴ the water vapor content of the atmosphere and the resistance bridge type are largely undefined. equal to air flow and, when properly compensated, for chemical vapors, ozone and dust. By combining two such detector devices in an "AND" gate system in which the sum of their alarm signals can emit an alarm sensor, while their individual signals cannot, each detection device will counteract or compensate the other's weaknesses.

In this combination, a rapid change in the water vapor content of the atmosphere will trigger the resistance bridge but not the ionizer, while dust particles, air flow or ozone may trigger the ionizer but not the resistance bridge. However, when one fire breaks out, both of these devices, even in the initial phase of the fire, will respond to the same signs of fire, namely the combustion products and the change in their electrical conductivity caused by the fire. In particular, the ionizer will rapidly detect the small, invisible particles of combustion products, and the resistance bridge will quickly detect these small particles and / or the rapid increase in the water vapor content, and the sum of the two resulting signals will trigger the alarm already in the fire phase.

Thus, to a large extent, if not completely, the causes of false alarms are compensated in both units, so that false alarms are practically eliminated without impairing the ability of each unit to detect a fire quickly.

In reality, these devices have previously been operated far below the limit of their detection or decay capability only because of the problem of false alarms, that is, the detectors had to be made relatively impolite to reduce the number of false alarmsΠΊ

Due to the fact that the problem of false alarms is largely eliminated, the resistance bridge and the ionization detector and, in combination with these, also additional detector devices, which also include a third firing device having a combustion-type combustion detector means, can be operated with a far greater sensitivity than what was previously possible, in reality with maximum sensitivity, thereby providing a detector which is more sensitive and fast acting than known detectors and at the same time far more reliable.

Furthermore, the invention provides an improved resistance bridge type detector device comprising a single decay grating and an automatic electronic compensation circuit for this grating, this circuit continuously sensing or monitoring the electrical conductivity of the decolouring grating and, with a predetermined delay, automatically compensates for all changes in the conductivity of the grid ⁵ 124751 so that a constant voltage drop across the grid is maintained except when there is a certain change in the conductivity of the grid at a rate greater than corresponding to the preselected delay. In the latter case, the grid becomes sufficiently conductive and the bridge sufficiently out of balance to output a signal that triggers an alarm signal.

Because the compensation circuit senses a change in conductivity and the consequent voltage change and automatically sets the voltage to the preselected value within the constraints given by the selected delay, the circuit automatically compensates for slowly occurring and irrelevant changes, not only in the atmosphere, but also in the atmosphere itself. -detektorgitteret. Accordingly, the initial sensitivity of the device will be fully maintained even though the electrical characteristics of the grille change significantly over a period of time due to accumulation of coatings, fingerprints and / or other causes.

Thus, a resistance bridge device is provided which is advantageous in that it reduces the number of foil grids to one, substantially eliminates the prior need for testing and mating of grids, reduces the frequency and extent of maintenance work, reduces the adverse effects of ambient conditions and prolonged maintenance work. the grating as well as maintains the selected sensitivity of the device throughout its lifetime.

The invention provides instructions for both self-contained, battery-operated detectors for domestic and commercial use and mains-operated detectors for installation in larger numbers in alarm systems with main station for commercial and industrial use.

Further objects and advantages of the invention will become apparent from the following description in connection with the drawing.

Fig. 1 is a simplified diagram illustrating the principle of the present invention.

Fig. 2 is a coupling screen for an advantageous embodiment of a detector for commercial and industrial use, designed for grid operation and for transmitting a signal to a central alarm station.

FIG. 3 is a wiring diagram of an advantageous embodiment of a fully self-contained, battery-operated fire detector and detector, specially designed for domestic use.

Fig. 4 shows, from the underside, a particular embodiment of a self-contained detector and with the cover partially removed to reveal the individual elements.

Fig. 5 shows an enlarged section through the combustion sensor components taken along line 5 "5 of Fig. 4".

FIG. 6 is a vertical section through the detector along line 6 - 6 of FIG. 4.

In the following, preferred embodiments of the invention will be described.

In accordance with the invention, in an AND ”gate circuit, a pair of combustion-sensing devices are combined which can respond to the same sign of fire or to the change that occurs during combustion in the same ambient state, but which are sensitive to mutually different states that may occur. random and prone to cause false alarms, which are of such a nature that they would rarely occur at the same time; the combination will thus emit an alarm signal when a given condition or environmental change is caused by a fire, but not when a condition which would tend to cause a false alarm but not due to combustion occurs and which other sensing device may react. In this way, each of the foil devices compensates for the other's deficiencies, and each of them can thus be made more sensitive than previously possible. The essential main combination is a pair of foil devices that respond to the initial phase of a fire. To this main combination can be added additional types of foil devices with ”0G^Mgate set to respond to the sum of the alarm signals from two, three or more of the sensing devices.

The latter is illustrated schematically in FIG. 1, wherein a resistance bridge 10 includes an ionizing device 20, a heat detecting device 30 »a smoke detecting device 4θ, and^one flame detection device 50 is connected in parallel to a suitable energy source.

The resistor device 10 comprises a variable impedance grid R exposed to the atmosphere, a compensation circuit CR connected in bridging with the grid, and a primary trigger device PT, e.g. a so-called^,,MOSFET "transistor (metal oxide silicon field effect transistor), connected to the bridge's center outlet. This circuit will be described in more detail below.

The ionizing device 20 consists mainly of an ionizing chamber I and a primary release device PT. Among the important advantages obtained by the ionizing device of the invention are (1) that no complete saturation is required in the ionization chamber, and (2) that the number of ionization chambers can be reduced to one instead of two, and (3) that the amount of radioactive material required as an ionization source can be reduced. In fact, the total amount can

In ϊ 124751 radioactive material is reduced to less than one microcurie, which is less than the amount usually found on a luminescent dial. In the coupling shown, the ionization chamber I is connected in bridge coupling with a balancing means BI, e.g. a fixed resistor, and the primary trigger is connected to the bridge's center outlet.

The heat sink 30 is generally a common detector which detects the rate of rise, and comprises a thermistor H exposed to the atmosphere and a compensating thermistor GH which is shielded against the atmosphere, the two being connected in bridge coupling with a primary discharge device PT connected to the center outlet of the bridge. As will be seen from the following, the heat detector can be made several orders of magnitude more sensitive than hitherto possible since it is part of the invention's multi-port system.

The smoke sensor 40 may be a mold refraction detector comprising a light source L and a photocell S which becomes conductive as smoke darkens the light beam, the photocell being connected to a primary trigger PT. Here again, it should be noted that the photocell does not need to be compensated so that it acts as a rate of change organ, as has been the case so far, but can be used to provide a positive target for any determined degree of degradation.

The flame sensor 50 may conveniently comprise a photocell F adapted to respond to a barking flame, or a device sensitive to the flame radiation, and is likewise coupled to a primary burner PT without compensation, although compensation may in some cases be beneficial.

The outputs of all the primary trigger devices PT are connected to a gate circuit or selective circuit DN which is designed to remain inoperative at signal input from any of the primary triggers individually, but to respond to the sum of signals emitted simultaneously from a predetermined number of primary triggers greater than one, This circuit is in turn connected to an alarm trigger AT which is arranged to be conductive when the gate DN receives the aforementioned sum of signals, and shown here as a single coupling means coupling a bracket, light or other alarm device A to the power source.

If the gate DN was set to allow the sum of two arbitrary output signals to pass through, simultaneous activation of any of the devices 10, 20, 30, 40 and 50 would give an alarm signal. In the event of a slow-moving spontaneous combustion, the resistance bridge 10 and the ionizer 20 would quickly detect the situation and cause an alarm signal. If there was a dangerous build-up of heat which started to give rise to annealing, the combination of the heat detector 30 and In or both of the devices 10 and 20 would cause alarm. If a flammable appliance or firefighter started a fire, the smoke detector ¢ 0 and flame detector 5θ together with the devices would quickly trigger the alarm signal. In this way, there would be a complete fire detection.

Nevertheless, the various phenomena that are not due to combustion, and for which some of the detectors are sensitive, would normally not cause a false alarm. A flickering light bulb can trigger the flame detector 50, but without any combustion product that can be discharged by one or more of the other detectors, there is no alarm. The same is true of dust, dust, strong air currents, chemical vapors, ozone, sudden changes in temperature, etc. The likelihood of two such voidable conditions not due to combustion occurring at the same time in nature is extremely low, and the device is therefore virtually free of the problem of false alarms,. Because the combination is thus free of false alarms, each of the detector units can be effectively utilized at approximately maximum sensitivity. From a practical point of view, the usable sensitivity of known fire detectors has been heavily dependent on the problem of false alarms. All of the detector units are capable of working with great sensitivity, which, however, were largely unused previously due to the numerous false alarms that would occur if the units were set to an excessive sensitivity, and the systems were therefore necessarily operated far below their performance. By using two or more detector devices in an 'OC' port system, the problem is solved with a significant and important sensitivity socking.

It will be appreciated that the gate DN can be set so that alarm is triggered when three, four or all five detector units are triggered, and any of - or all - detector units 3θ&gt; 4 ° and 5 ° can be omitted from the circuit, depending on the the ability to detect as desired.

In the preferred embodiments of the invention, the detector advantageously consists only of the resistor bridge 10 and the ionizer 20, since these detector units are sensitive to the initial phase of a fire, the change in the conductivity of the air upon occurrence combustion, and the small invisible combustion products, i.e._M which constitute products of practically every naturally occurring fire as well as of instigated fires, and they are capable of detecting fires in their initial stages before life and property are threatened by smoke, flames and heat.

Referring now to FIG. 2, in which an embodiment of the invention is shown. The device shown is network-operated and arranged to short-circuit the supply line to give an alarm, this detector being intended for use in systems with multiple detectors in commercial buildings or industrial buildings. In such environments, it is common to connect a variety of detector heads to a common supply line from a central alarm station. For example, there may be twenty or thirty detector heads connected on a single line connected to an alarm unit covering a particular part of the building, other parts of the building being covered by each of a number of other alarm units, all of which are monitored by a guard who by observing an alarm condition that is visible and / or audible at the central station, may investigate what precautions are required, such as hand-off, fire department calls, evacuation of the area, etc. In order to simplify this kind of system and also allow for easy mounting and replacement of the detector heads, a fitting socket is connected to the line for each detector head, as shown in the lower right corner of FIG. 2. To cooperate with this socket, each head is provided with a corresponding stop portion 61 with pins 5 and 7 for power supply to the head. A pair of resistors R9 and R10 are arranged to adapt the circuit to either 120 or 24 volt systems, both resistors being used at 120 volts and the resistor R10 being shunted with a short circuit at 24 volts.

A resistor bridge 10 and an ionizer are connected in parallel to the power source. Resistance bridge 10 comprises a detector or foil means R comprising a cam-like conductive grid disposed on a glass carrier, which will be discussed later in connection with FIG. 4 · The organ forms a variable impedance which is fsensible for rapid shear in the conductivity of the air at the onset of a fire, in particular caused by water vapor and the more than normally large but even invisible particles formed by other combustion products. This variable impedance is compensated for naturally occurring ambient changes with a compensation circuit CR which essentially acts as a delayed high-voltage voltage regulator to normally maintain a constant voltage drop across the grid R. The circuit preferably comprises a means Q2 whose resonant impedance can be controlled from a very low value to a very high value, e.g. a MOSFET ”transistor, a resistor R2 and a capacitor C1. This circuit serves to maintain a balanced state of the bridge, consisting of the self and the lattice R, except when the lattice resistance or conductivity changes with a certain value over a specified period of time. By appropriately dimensioning the resistor R2 and the capacitor C1, change and time can be varied to achieve a carefully regulated compensation rate, depending on the type of fire to be detected and the prevailing atmospheric conditions.

When voltage is first applied to the circuit, Cl has no charge, and the base of transistor Q2 is on the emitterpot a Hal,

Depending on the resistance of the detector grid, there is some voltage between the collector and the emitter at Q2. It can be assumed to facilitate understanding that the lattice R has the same resistance as R2. At the moment when the voltage is applied, one half of the applied voltage lies over the grid R and the other half over the collector and emitter of the transistor Q2. Cl is instantaneously charged at a predetermined rate determined by its capacity and by the resistance R2. As the charge on Cl Oker, the voltage between the collector and the emitter of the transistor Q2 rises, and the voltage across the detector R decreases. As the voltage across C2 approaches the threshold voltage of transistor Q2, Q2 begins to change its resistance, and it continues to change its collector-emitter resistance until the collector-emitter voltage becomes equal to the voltage across C1. This leads to a decrease in the collector-emitter voltage for Q2 and a decrease in the voltage on the detector grid. This voltage is kept constant because one has $ 100 negative feedback by R2 being connected between collector and base. Because of this feedback, any change in voltage drop from collector to emitter causes a corresponding change in base voltage, which in turn causes a reset of the collector-emitter resistance and a regulation of the collector-emitter voltage.

The above description is fully applicable to the coupling of FIG. 3 and likewise the coupling of FIG. 2 as far as detector compensation is concerned. If the central circuit of the alarm circuit using the device of FIG. 2 is such that the detectors are disconnected from the source by alarm, it may be necessary to supplement the coupling to facilitate the initial charge of Cl, but such a complement will be obvious to those skilled in the art and will not mean any change in the characteristics of Q2, R2 and Cl in terms of voltage compensation.

The above-described resetting of the voltage with a view to maintaining a constant collector-emitter voltage does not occur instantaneously, but at a certain rate determined by the time constant of R2 and Cl. Therefore, when the grid is hit by combustion products that occur in sufficient quantity and appear faster than the RC circuit can compensate them, the collector-emitter voltage of the transistor will rise and bring the current from an amplifier Q1 to. To send and transmit a predetermined signal to an alarm trigger Qj.

Should the detector grid at any time assume a different resistance than its original, the transistor Q2 will adapt to the new resistance value by changing its resistance to a new value appropriate to maintain a constant voltage drop from collector to emitter.

Furthermore, because of the $ 100 negative feedback, the circuit is freed from the influence of temperature changes.

If desired, professionals in the field will be able to further improve the link. For example, in parallel with or instead of R2, another transistor may be provided, the base of which is controlled by an RC network so that at the time of switch-on there will be a low impedance connection which causes Cl to be charged faster and the base of Q2 reaches the operating point earlier. After the RC network reached its charge point, this other transistor would be blocked and form a high resistance for R2. From that point on, the circuit would work as described above. Under certain conditions, it may be advantageous to let R2 be a resonant impedance.

In the event of a fire, the grid's conductivity changes faster than the circuit can compensate, and the bridge formed by the grid and circuit is sufficiently out of balance to cause readout of the primary discharge device Q1. The device Q1 preferably comprises a MOSFET transistor with the emitter connected to the network over a sensitivity regulator which comprises a diode chain D with a base connected to the center terminal of the grating bridge and with output to the alarm generator Q5 over a resistor R3. Q1 is preferably so biased that it generally does not have a current flow, and the resistor R3 is selected so as to limit the current flow to a predetermined value, e.g. 130 / uA, when Q1 is made conductive by the detector grid R.

Ionizer 20 comprises a bridge coupling containing an ionization chamber R5 with a small amount of radioactive material, under a microcurie, and a balancing resistor R4 for this chamber. The chamber R5 can be of any suitable known embodiment, and the amount of radioactive material is chosen so that the chamber is not saturated with ions. This causes the chamber to have a very high impedance, which is found advantageous. Operation of the ionization chamber under unsaturated conditions is not sensitive to atmospheric pressure, and it will operate at all atmospheric pressures up to a height of 7600 m without change in fertility. Moreover, because of the fewer ions produced by the radioactive material, a smaller amount of combustion products will be required to change the electron current. This makes it possible to use a fixed resistance R4 for balancing and gives very generous detection of a very safe amount of radioactive material. The ionization bridge is coupled to the base of a primary trigger, preferably in the form of a MOSFET ** transistor Q3&gt; whose output, like the output of Q1, is connected to the alarm trigger Q5 over a resistor R ?. The resistor R7 serves, in the same way as the resistor R3, to limit the current through Q5 when open, to a certain value, e.g. 130 / UA. The emitter of transistor 3 is connected to a sensitivity regulator via a voltage regulating silicon transistor Q4, shown here in the form of an adjustable resistor R8. To provide normal energization, transistor Q3 is biased to a relatively nominal current, such as 50 µA,

The alarm output Q5 suitably comprises a so-called SCR "transistor (silicon controlled rectifier transistor") whose base current is stronger than the output current of each of the MOSFET ^ transistors yl and Q3 but less than the sum of these currents, e.g. 200 / uA in the example cited so far. Accordingly, only the ionization chamber is conductive, the output of its trigger Q3 is limited by the resistor R7 to 130 µA, and the transistor Q5 is not opened. When the lattice R alone is sufficiently conductive to activate the trigger Q1, the total current supply to Q5 will be the sum of the 130 / uA from Q1 and the 50 / uA normal current from, Q3, which is still not sufficient to trigger Q5. However, if a fire breaks out, each of the primary trippers Q1 and Q3 will produce a current of 130 / uA, giving a sum of 260 / uA. When this occurs, the voltage drop across the resistor R5 becomes sufficient to conduct the transistor Q5 so that it short-circuits the supply lines and causes a significant power supply that can be recorded in a remote alarm station to energize an alarm device.

A lamp L1 is connected to the transistor to, when lit, indicate the particular detector head that caused the alarm, in the case that a plurality of heads are connected to a common supply line. Preferably, there is a connection line from the lamp circuit to terminal 4 P &amp; stop 61 to allow for remote notification should this be desired, then appropriate circuit elements are connected to terminal 4 P &amp; adapter socket 60.

In addition, conductors preferably move from different points in the circuit to pins 1, 2, 3 θ of the stop 61 to make it easier to determine voltage and current values ​​during maintenance work on the detector.

The described coupling enables a very fissile early warning with little or no propensity for false alarm under commonly occurring ambient conditions. The consequence is an improved and virtually foolproof fire detector which has greatly improved sensitivity and reliability, yet is compatible with conventional detector systems and alarm systems.

Referring now to FIG. 3 in which there is shown a battery-operated embodiment of the fire detector according to the invention. The coupling is basically similar to the one described above, except that it is battery operated and has its own alarm sensor.

The coupling, as before, comprises a resistance bridge 10 with detector grid R and output Q1, an ionizer 20 with ionization chamber R5 and output Q3&gt;, and an alarm trigger which in this case is connected in series with a horn H and a primary battery B1.

The energy of the system is supplied by a 10.7 volt mercury battery B1 which provides the weak bias current which drives the detector device, and also provides the current needed for operation of the horn by alarm.

When the transistor Q5 is opened, current passes through the horn H from the battery B1 and an alarm signal is emitted. The capacitor C3 serves to supply the starting current to the horn and thus relieves the battery.

In this connection, the battery B1 is continuously monitored by means of a monitoring battery B2 via an adjustable voltage divider Ril. When the current from the battery B1 begins to decrease at the start of the battery life, the voltage of the battery B1 is overcome by the battery B2, after which a capacitor C4 recharges via a resistor R12 to a point where a programmable dual base transistor - a so-called unijunction or PUT transistor - Q6, switches on and thus in turn releases a silicon controlled transistor Q7 · When Q7 is opened, it connects battery B2 to horn H, which, with the aid of a capacitor C5, emits an alarm signal. Transistor Q7 can only remain open as long as it receives base current from transistor Q6. Q6 remains open until capacitor C4 is discharged through the transistor, after which Q6 closes, causing Q7 car to shut down and interrupt the alarm signal. At this point, the C4 starts to recharge over the resistance Ril from the battery B2, and after a period of about five minutes, the process is repeated. Thus, every five minutes the horn will emit a stab for one to two seconds to signal that the battery B1 is empty and must be replaced.

As with the coupling shown in FIG. 2, energizing a single detector device as a result of conditions not due to combustion will not result in the release of transistor Q5, while the onset of a fire will cause both devices to be energized, Q5 opened and the horn energized.

In this device, the coupling is such that Q5 when it is exposed will remain released until reset. For resetting, a switch SW is provided which shuts at its output the transistor Q5 at its end so that its load is removed and the transistor is thereby returned to non-conductive or off state, whereupon the alarm is switched off until the rate of change in ambient conditions again becomes such (or remains so) to the device is triggered again.

By connecting the shunt to the switch contacts in such a way that the primary energy source B1 is connected directly to the horn H, the switch simultaneously provides an appropriate opportunity for manual control of the operation of the device and for the condition of the battery B1.

During normal operation, there is no draining of the monitoring battery B2, and this battery will therefore last as long as it can be stored, which is currently two years. The weak current discharged from the primary battery B1 during normal operation gives this battery a service life of at least one year, provided that the unit is not put into alarm mode for any extended period this year. At the end of the year, or earlier if the elk have been in business frequently, the primary battery B1 should be removed and the monitoring battery B2 put on the primary battery. place. A new battery should then be put in the place of the monitoring battery as soon as possible, if not monitoring is lost.

In any case, the cross-monitoring circuit (assuming a battery is inserted into the monitoring circuit) will always inform the homeowner or user of the fact that the primary battery should be replaced when its performance falls below a certain value. Under normal operating conditions. Replacements are replaced with one battery per year, since other maintenance is practically not required.

The dual-gate system shown is thus shown to be just as applicable for commercial fire detection as for residential fire detection, provides a very solid and reliable warning system that can respond to all stages of fire, but especially in the initial phase, and virtually eliminates the problem of false alarms. .

For practically all fire detection systems for commercial and residential use will ⁿThe AND gate combination of the resistor bridge 10 and the ionizer 20 provide optimal results. However, any other detector device may be added to the circuit for special purposes. For example, the resistance bridge is fertile for any type of fire, while the ionizer only responds to incomplete combustion. If it is desired to detect fires where complete combustion takes place, which is a rarity, an additional detection device may be provided such that the alert signal is triggered whenever any two of the three detection devices respond to a fire. Such a third detection device would preferably comprise a detector which is very sensitive to the rate of temperature rise and has a very small fble thermistor with low heat capacity. In view of the security of the multi-port system, the sensitivity of such a heat sink can be set at a rate as low as 0. 5 - 0.6 ° C per day. mine, which is a far greater sensibility than you could have used with any heating fixtures in the past. This device would be in the form of an electric bridge with the detecting thermistor exposed to the atmosphere and with a low heat time constant, while the other thermistor, the reference thermistor, would have a much larger heat time constant by having a larger physical mass or being attached to a body with high heat capacity.

FIG. 2 and 3 show preferred embodiments of the invention, it will thus be possible to make various changes, exchanges and modifications within the scope of the invention.

In any of its embodiments, the multi-port system of the invention may conveniently be mounted in the housing shown in FIG. 4-6.

The detector components are transistorized and miniaturized as far as is technically and economically feasible at present, and all are confined to a mounting plate 21, as illustrated somewhat schematically and, for example, in Figures 4 and 6. The top side of the plate bears a printed connection as is well known in the art. the electrical connections between the components form, and the components are mounted on the underside of the plate, where the horn H, switch SW and batteries B1 and B2 are marked for the connections.

The detector R of the device 10 is preferably formed by a two-conductor comb-shaped grid mounted on a glass support 22 mounted in a substantially triangular ceramic holder 26. The holder has three through holes, one at each corner, two of which are provided with conductive linings 31 and support washers 32 which serve to hold the carrier in the holder and to electrically connect with the cam-shaped grid sample on the carrier.

The support is preferably a thin square piece of modified borosilicate glass of high purity, and the lattice pattern is preferably tin oxide applied to the support according to known tin oxide technology, while the two substrates 32 are in physical and electrical contact with the respective parts of the lattice pattern.

Three pins 34 are projected from mounting plate 21^a&gt; 34b and 34c, two of which, as shown in FIG. 5 »forms connection leads for the grid. The holder 26 Akyves suitably attaches to these pins for mounting the detector unit. Specifically, the holder is positioned so that the carrier 22 remains with the grid bearing surface facing down and exposed. Deposits on the pins 34 t-bars to keep the carrier away from the mounting plate to provide a shielded space for mounting the ionization chamber R5 of the detector device 20.

The chamber R5 is formed by a rudder 23 which is putty or otherwise attached to the underside of the mounting plate 21 with a screw 24 which is axially located in the spring and is adjustably inserted in retracted position in a nut 25 attached to the plate 21, as well as a small piece of radioactive material. material placed on the lower end of the screw. This amount is so small that it cannot be shown in the drawing. The rudder and screw are placed a short distance above the container 26, so that the atmosphere has free access to the interior of the tube.

The detector components are all placed on the mounting plate in a single layer, except for the placement of the detector devices R and R5 on top of each other, and are selected with the least practical height, so that the apparatus has a very low cross-section.

The entire circuitry is then placed in a shallow, downwardly open rectangular or square pan 44 of metal plate with low sidewalls 46. The assembly is preferably carried out by passing three or four metal screws 4θ through the mounting plate and suitable spacers 51 screwed into the pan so that the plate remains in the plate. distance from the surface of the pan. In order to make the mounting rigid, it is also preferred to screw or otherwise attach the switch SW to one of the pan side walls 4θ ·

The pan is in turn arranged for mounting in the ceiling of a room or on the heavy wall of an enclosure or hallway. With the self-contained unit according to FIG. 3 illustrated in FIG. 4 - θι, the pan can be mounted by means of a pair of screws passing through suitable holes 52 which are cut into its upwardly facing bottom and are nickel-hole shaped to facilitate releasable mounting of the pan to the ceiling. With the coupling shown in FIG. 2, the pan can simply be mounted by the plug connection 60,61.

A level below all detector components protrudes from opposite side walls 46 ^of the pan down a pair of brackets designed to readily accommodate a pair of bolts 5θ that protrude from the inside of the detector cover 58 · The cover is made of one piece of metal or a suitable plastic and with an appealing exterior (ie, the underside and exterior of the side walls) . The cover is generally pan-shaped and larger than the pan 44 so that its protruding sidewalls lie outside the sidewalls 46 of the pan. The cover side walls extend up to a level below the upside down of the pan, so that when the apparatus is mounted, they are spaced from the ceiling surface and preferably end slightly above the bottom edge of the side walls 46, thereby concealing the detector components. In the center of its bottom, the cover has 5θ^oneseries of small sealed holes 59 located just below the grid of the lower carrier 22.

Combustion products will rise to the ceiling by natural circulation and then spread horizontally along it. In the embodiment shown ·. together, the space between the cover end walls and the roof and the pan as well as the holes 59 together will provide a path for highly efficient and effective circulation of the combustion products through the housing "over the detector unit R and into the detector unit R5 regardless of the natural circulation direction of the products. Combustion products from a fire occurring under the detector will rise through holes 59 and extend sideways through the gap between the boiler, cover and roof, ensuring that detector units R and R5 contact the products quickly and completely. If a fire occurs far from the detector, the products will rise to the ceiling and spread horizontally along it, after which the spaces between cover and ceiling together with the low profile of the detector components will more or less appear to sweep the "combustion products slightly down towards the detector units R and R5, which in turn ensures quick and thorough flushing of the detectors with the products.

In a practical embodiment, the detector with all its advantages and special features is only 18 cm in square and 4 »5 cm high. In this model, the handle of the switch SW protrudes slightly from the side wall of the cover to facilitate operation with a broom shaft or the like, so that the occupants of the house do not need to climb a ladder or a chair to reset or test its functionality.

The commercial or industrial models of the detector whose coupling are shown in FIG. 2, can similarly be mounted in a two-piece housing of this embodiment, except that the batteries B1 and B2, the horn H and the switch SW are slbyfes and the plug or plug 61 will be exposed on the upper side of the pan 44- to facilitate connection with an outlet 60 in the ceiling.