Safety System This invention relates to safety systems, and particularly,
but not exclusively, to a system for switching off domestic appliances upon detection of an impending fire, and/or for triggering multiple alarm signals in response to such detection.
Studies have shown that 69% of domestic fires originate accidentally by electrical sources, such as electric cookers and deep fat fryers. Studies have shown that over 80% of homes are now fitted with smoke detectors providing an alarm output, and it is well established that these can save lives as well as provide an early indication of a fire hazard to reduce damage to property.
There are, however, still a large number of fires producing fatalities within houses with smoke alarms fitted. A nonnal smoke alarm does not provide any automatic preventative action, and automatic sprinkler systems are too expensive to be used widely in a domestic environment.
There is therefore a need for a system which responds to the detection of an impending fire or a fire hazard, and which provides preventative action, but with low equipment and installation cost.
New buildings in the UK are now required to have mains powered smoke detectors, and furthermore the detection of smoke in the vicinity of one smoke alarm is required to trigger operation of all installed smoke alarms, to ensure that all occupants hear the warning. For this purpose, mains operated smoke detectors may incl ude a communications port, and the multiple smoke detectors in a building are wired together through the wiring infrastructure of the building. It is more difficult to provide this communication between smoke alanns in an existing building.
The benefits of mains powered smoke alarms over battery operated devices are obvious. Various adapters have been developed which enable a smoke detector to be fitted between a light socket and a light bulb, so that a mains operated device can be installed without any wiring changes and without needing any socket dedicated solely to the smoke alarm. Again, there remains a difficulty in providing communication between multiple smoke detectors when installed in this way.
According to a first aspect of the invention, there is provided a safety system comprising: a sensor for detecting a fire detection device alarm signal and producing an interrupt signal m response to the fire detection device alarm signal; and an interrupt device controlled by the interrupt signal for interrupting the operation of a domestic appliance.
The fire detection device will typically be a smoke alarm, although heat sensors can also be used for fire detection purposes.
The invention enables a standard smoke alarm (or other fire detection device) to be fitted, and the alarm signal of the device is used to trigger an interrupt device. This may interrupt electrical power (for example to an electric cooker) or a gas supply (for example to a gas cooker) or oil supply for an oil burning device. This enables a cooker to be switched off when a fire detection signal is generated. There is however, no need for any hard-wired installation, although the sensor can be hard wired if desired, and can then be mains powered rather than battery powered. The system can be low cost and have low (or no) installation costs.
In one example, the sensor comprises a sound sensor for detecting a smoke or other fire alarm audible output signal.
The sound sensor can then comprise a hand held control device. This control device can be mounted within range of the smoke alarm audio output, and can then send an intemupt signal to one or more power or gas supply points around the house.
This intemupt signal is preferably then a wireless signal, for example audio, again so that no wiring is required, and the intemupt device then comprises a receiver for receiving the wireless signal.
The use of a control device enables a plurality of interrupt devices to be controlled. A corresponding plurality of interrupt signals can be provided, each for controlling a different interrupt device for interrupting a different domestic appliance power supply.
Alternatively, a number of appliances can be controlled by the same interrupt signal. s
In another embodiment, the sensor comprises an electrical sensor for detecting a control signa] for the fire detection device alarm signal, for example an electrical sensor for detecting when electrical power is provided to the alarm.
lO In response to the fire detection device alarm signal, a modulator may be used to modulate a mains power supply line which supplies power to the fire detection device with the interrupt signal, and the interrupt device then comprises a demodulator for detecting the interrupt signal from the modulated mains power supply.
This arrangement enables multiple mains powered fire detection devices to be in communication with each other as well as with the interrupt device, again without needing any additional wiring. Such an arrangement is therefore suitable for adaptor type smoke alarms which are fitted into existing buildings.
The interrupt device can be integrated into a domestic power supply socket, for example a domestic electric cooker power supply socket. The installation of the system then simply involves changing a plug socket for one which includes a power interrupt.
The interrupt device can comprise a circuit breaker, and the system can be integrated into a miniature circuit breaker.
According to a second aspect of the invention, there is provided a control device for use in a safety system, comprising: a sound sensor for detecting a specific audible input; a transmitter for transmitting a wireless control signal for activating or deactivating all appliance in response to detection of the audible input.
This control device recognises an audible output, for example a smoke alarm output, and generates a control signal for deactivating electric appliances which may be the cause, or for activating other appliances for automatic preventative action, such as extractor fans, warning indicators or mobile phones for sending alert messages.
According to a third aspect of the invention, there is provided a safety system compnslng: a plurality of mains powered safety alarm devices, a plurality of control circuits, each associated with one of the safety alarm devices, each control circuit comprising: a sensor for detecting a safety alarm device alarm signal; a modulator for modulating a mains power supply line which supplies power to the safety alarm device with an alert signal; a demodulator for detecting the alert signal from the mains power IS supply; and a circuit for activating the safety alarm device alarm, wherein the alarm of each of the safety alarm devices is activated in response to an alarm signal produced at any one of the safety alarm devices.
This aspect of the invention provides communication between multiple safety alarm devices using modulation of the power supply to the devices using superposition of an alert signal. This alert signal provides a communication link between the multiple devices so that an alarm generated at one device can trigger all the others to provide an alarm output. The system requires access only to the mains power lines within a building and does not need any dedicated wiring. As a result, the system can be installed in existing buildings using adapter type alarm devices.
Each safety alarm device may comprises a fire detection device such as a smoke alarm, but the invention may also be used with other alarm devices such as burglar alarms.
The system may also have an interrupt device controlled by the alert signal for interrupting the operation of a domestic appliance. s
In a system with multiple smoke alarms, each smoke alarm (or its control circuit) can be provided with a light indicator for indicating correct operation of all smoke alarms of the system. This enables easy testing of the complete installation.
Where the system includes one or more interrupt devices, these may also be provided with a light indicator for indicating correct operation of all smoke alarms of the system.
For example, the interrupt device may be a circuit breaker m the domestic fuse box, and the correct installation and operation of the smoke alarm system can be determined by examining a control box located at the location of the circuit breaker.
According to a fourth aspect of the invention, there is provided 28. A device for activating or deactivating an appliance, wherein the device is controlled by a control signal generated in response to the generation of an alarm signal by a fire detection device.
The control signal can be generated in response to detection of the generation of the alarm signal of a smoke alarm, for example in response to audio detection of the smoke alarm output or the electrical detection of the alarm drive signal.
The device is preferably integrated into a domestic power supply socket, so that it operates to interrupt the electric power supply.
The invention also provides a method of controlling the power supply to a domestic appliance, comprising: detecting a fire detection device alarm signal; producing an interrupt signal in response to the fire detection device alarm signal; and interrupting the power supply for a domestic appliance in response to the interrupt signal.
The invention also provides a method of controlling a plurality of mains powered safety alarm devices, comprising: detecting a safety alarm device signal for each device; modulating a mains power supply line which supplies power to the safety alarm device with an alert signal in the event of detection of a safety alann device signal; demodulating the mains power supply to detect any alert signal; and activating each of the safety alarm devices in response to an alarm signal produced at any one of the safety alarm devices.
An example of the invention will now be described in detail with reference to the accompanying drawings, in which: Figure 1 shows a system of the invention; Figure 2 shows the controller used in the system of the invention; Figure 3 shows the interrupt device used in the system of the invention; and Figure 4 shows a second example of system of the invention.
Figure 5 shows a mains powered smoke alarm which can be used in another system of the invention; Figure 6 shows in more detail a mains powered smoke alarm adapted for use in a system of the invention; and Figure 7 shows an interrupt device for use in a system using the smoke alarm of Figure 6.
A first aspect of the invention relates to the automatic interruption of the operation of devices which may be the cause of a fire in the event of a smoke detector providing an alarm signal.
Figure 1 shows one example of an implementation of the system of this aspect of the invention. The system is for use with a conventional smoke detector 10, which produces an audible output 12 when smoke is detected. In the UK, most smoke detectors satisfy British Standard BS 5446 - Part l the specification being sound output of minimum 85dBA at 3 metres with a frequency to be in the range of 2200/2800Hz.
The system of the invention uses a sensor 14 for detecting the audible alarm output of the smoke detector. The sensor 14 can therefore be freestanding and does not need to be hardwired. When the smoke detector output is detected, an interrupt signal 16 Is provided, and this is detected by an interrupt device 18 which interrupts the power supply to a domestic appliance, such as an electric cooker 20.
The invention thus enables a standard smoke alarm to be fitted, and the audio output of the smoke alarm is used to trigger a power interrupt device 18. The system switches offthe cooker when smoke is detected by the conventional smoke detector.
In the example shown in Figure 1, the sensor 14 is provided within range of the smoke alarm, and the interrupt signal may have a longer range to activate plug sockets which supply power to electric appliances around the home. The signal 16 is wireless, and may comprise a radio or infra red signal. However, a preferred low cost option is to use a different audio signal as the interrupt signal 16.
Figure 2 shows one implementation of the sensor 14. A microphone 30 receives the audio smoke alarm output 32. The audio signals received by the microphone 30 are filtered by filter 34 to enable the characteristic smoke alarm output to be detected. This filtering may be performed in the analogue domain, or else digital filtering may be employed after A/D conversion. The filtering is used to detect the specific combination of frequencies which is characteristic of the smoke detector output, as stipulated by BS 5446.
A processor 36 receives the signal representing the detection of the smoke alarm output from the filter 34, and drives a loudspeaker 38 in response to that signal, in order to output the audio interrupt signal 16.
In a preferred implementation, the processor 36 and filtering components 34 are implemented as an integrated circuit chip, and digital signal filtering is used. However, the circuit could be implemented purely using analogue components. The sensor 14 is a battery operated device.
The sensor 14 also has an input key arrangement 40. This provides a reset function to enable power to the electrical appliances to be resumed after the cause of the smoke alarm activation has been investigated. The processor 36 recognises the key inputs and generates a control signal at the output which resumes power to the cooker 20. The input key arrangement also enables the correct functioning of the system to be tested, by generating a test interrupt signal 16. Of course, the system may also be tested by activating the smoke detector audio output.
Figure 3 shows one implementation of the power interrupt device 18. The interrupt signal 16 is detected by a microphone 42, and a filter 44 is again used in combination with a processor 46 to detect the specific combination of frequencies unique to the interrupt signal 16. The processor 46 provides a control signal for a relay 50.
Figure 3 shows the interrupt device integrated into a plug socket. A switch 52 of the plug socket is provided in the path of the mains live wire 54, and the relay 50 is in series with the switch 52. The relay is a bistable device, so that a control signal is required to open the relay, and a further control signal is required to reset the device and close the relay switch. The interrupt device may instead be integrated into a plug rather than into a plug socket, in a similar manner or provided in- line in a mains cable.
The filter and processor 44,46 are powered by the uninterrupted mains input to the plug socket, and are again implemented as an integrated circuit.
In the example above, the sensor 14 is remote from the plug socket 18. However, the sensor may be part of the plug socket. In this case, the sensor 14 simply converts the audio smoke alarm signal into a control signal suitable for operating the relay 50 of the interrupt device 18. In this case, the interrupt signal is the electrical signal for directly controlling the relay 50.
Alternatively, the sensor may be provided as part of the smoke detector] 0. The sensor will then detect the smoke detector audio output, and generate an interrupt signal, for example with longer range so that devices (i.e. plug sockets) all around the home can be controlled.
The example above shows only a cooker 20. The invention may be used to control the supply of power to other electrical devices, such as an electric deep fat fryer, a fan heater, an iron, a toaster or many other electrical appliances. The plug sockets for each of these electrical devices may respond to the same interrupt signal 16 so that the devices are all disabled together. Alternatively, each plug socket may have a dedicated interrupt signal, so that the sensor 14 can be configured to disable a desired selection of electrical appliances.
In all examples described above, the system is for interrupting power to an electric device. As mentioned above, one of the main causes of fires is electric cookers. Gas cookers are clearly also a cause of a large number of fires, and the invention can also be applied to a gas cooker. In this case, the system interrupts the gas supply, and the interrupt device can then comprise a shut-off valve activated by the interrupt signal.
The interrupt device is then positioned in the gas supply path to the cooker (gas cooker, bob or oven) rather than in the electrical supply path. The invention may in this way also be used to interrupt operation of a gas fire.
The system may operate with a combination of gas and electric devices. For example, a number of interrupt devices are provided, some (typically only one) for gas appliances and others for electric appliances.
In the system described above, the sensor 14 is used to interrupt power (electric or gas) supply to a domestic appliance. The sensor 14 can additionally or alternatively be used to provide control signals for activating other devices.
For example, the output signal from the sensor 14 (whether audio, radio frequency or infra red) may be used to illuminate a display panel with a visual warning indicator.
The signal may also be linked to other devices such as mobile phones, security alert call centres or directly to the emergency services. The output signal from the sensor 14 can also be used to switch on (instead of off) devices, such as extraction fans and shutters.
As mentioned above, a British Standard dictates the characteristics of the audio output of smoke alarms. In other countnes, a different standard may apply, or else the system may need to be sold in combination with a smoke alarm having an output matching the sensor circuitry.
If the detection of the smoke alarm output of a BS 5446 smoke detector output is prone S to accidental triggering by other sound sources, it may be preferred in any case to provide a smoke alamm with a more precisely known output, which can then be detected with a reduction or elimination of accidental triggering of the interrupt.
The examples above relate to domestic applications. There are of course numerous non-domestic applications in which the invention may be employed. In addition, the sensor may be used in applications other than for fire detection or prevention. For example specific sounds may be detected to indicate failure of engine components or bearings in an aircraft. The sensor of the invention can detect these sounds and generate control signals for illuminating warning dials.
In another example, the interrupt device may be used to trip a ring mains circuit, so that a single interrupt device can be used to disable a number of appliances plugged in at different locations around the home.
Figure 4 shows an example of the device of the invention integrated into a miniature circuit breaker (M CB). As shown, the MCB 60 has an acoustic sensor 62 for receiving the smoke alarm output. The circuit of the invention is provided as a PCB 64 within the MCB housing (which is shown partially cut away at 66). The MCB has standard mountings68, and the circuit of the invention operates to toggle the switch 70 as shown by arrow 72.
In this design, there is no control unit, and the MCB is mains powered by means of the consumer board.
The examples above provide implementations of the invention using sensing of an acoustic alarm signal from a smoke sensor. The invention may also be implemented using electrical detection of the activation of a smoke alamm signal.
Figure 5 shows a mains powered smoke alarm 70 which is designed as an adapter which fits between a light socket 72 on a ceiling 74 and a bulb 76. Smoke alarms of this type are widely available.
Within the smoke alarm 70, there will of course be access to the electrical signal which drives the smoke alarm, and this electrical signal can then be used as the basis for generating the interrupt signal. The audio detection system described above can be used for this type of smoke alann, but the mains power lines providing power to the smoke alarm 70 provide an alternative way of communicating with the interrupt device, which may be at the fuse box and/or in plug sockets as described above.
Figure 6 shows a smoke alarm adapted for the invention. The smoke alarm 70 has an input 82 which receives smoke SO, and a detector 84 performs a smoke detection operation. This generates an alarm output for driving a speaker 86 in conventional manner. In accordance with the invention, this alarm output is also used to operate a modulator/demodulator 88 which superposes a modulation signal onto one of the mains wires 90. This superposed signal will typically be a low amplitude signal at a much higher frequency than the mains frequency, and can encode information using one of a number of conventional modulation techniques.
The use of mains signals as a carrier for overmodulated data is well known and there are various commercially available systems for performing the modulation and demodulation operations.
This invention in one aspect uses overmodulation onto the mains signals to communicate from the smoke alarm to the interrupt device. This overmodulation technique results in information being provided on the mains signal within all of a building, but also onto the mains supply of other buildings in the vicinity. For this reason, each complete system will have a unique identity, and the components of one system (multiple smoke detectors and one or more interrupt devices) will be able to communicate only with each other and not with other systems. This is already a function provided by existing available systems.
The interrupt device will have a different design, as no acoustic sensing is then required. Instead, the interrupt device will have a corresponding demodulator to enable detection of the communication signals sent by the smoke detectors.
Figure 7 is a schematic example of the circuit breaker interrupt device for use in a system having the smoke detectors of Figure 6. The same reference numerals are used as in Figure 4.
In addition to nonmal switching based on current overload, the circuit breaker has a demodulator 94 which derives the system communications signals 95 from the mains supply to the circuit breaker. In response to these signals, an interrupt signal (a voltage) is generated which operates a solenoid 96 which trips the interrupt device.
Thus, there are two separate mechanisms for the circuit breaker to operate.
IS In practice, each component of the system will have modulation and demodulation capability. Furthermore, the communications signals between the components will not only be the alarm signal. In addition, diagnostic and other system information can be shared, and the operation of the system will also involve a handshaking operation between the components.
This functionality can be useful for system testing and maintenance. For example, each smoke alarm, plug socket and/or interrupt device can be provided with a light indicator for indicating correct operation of all smoke alanns of the system.
The invention has been described above with the smoke alarm signal used to interrupt a power (or gas) supply to a domestic appliance. The use of a modulated mains supply may also be of benefit in a system having multiple smoke alarms, but without the interrupt functionality.
The system then enables the alarm signal of one smoke detector to be used to trigger the audio output of all the other smoke detectors in a building. The use of the mains system to do this can also enable a fire in one apartment of a block to be used to trigger alarm signals in all other apartments in the building. The invention enables this to be achieved with no additional wiring and therefore can be implemented with adapter type smoke alarms.
The invention has been described in detail with reference to smoke alarms. The invention is applicable to other fire detection devices, and such devices include optical as well as chemical smoke detection, but also heat sensors.
Furthermore, the mains based system above providing communication between alarms can also be extended to other safety devices, such as burglar alanns.
The specific implementation of the circuitry has not been described in detail. This will be routine to those skilled in the art of acoustic signal processing.