AU737341B2 - Smoke detector - Google Patents

Description

AUSTRALIA

Patents Act 1990 COMPLETE SPECIFICATION FOR A STANDARD PATENT Name of Applicant: CLIFFORD DAVIS Actual Inventor: CLIFFORD DAVIS Address for Service: Chrysiliou Moore Martin CMC Centre 143 Sydney Road Fairlight Sydney NSW 2094 Invention Title: Smoke Detector The following statement is a full description of this invention, including the best method of performing it known to me/us: e:\jh\2823.dockr \\server\e\docs\patents\comp\8431 b.doc SMOKE DETECTOR This invention relates to smoke detectors and to an improvement to make them more acceptable in use to the public.

Smoke detectors comprise a smoke sensor, an alarm and a power source. When the detector detects more than a threshold value of smoke it triggers the alarm until the detected value of smoke falls below the threshold value.

Smoke detectors are normally mounted on the ceiling of a room, since smoke from a fire will collect at the top of the room. Thus, the smoke detector is normally out of reach of most people and is accessible only by standing on a ladder, chair or the like.

Smoke detectors are intended to be active all of the time and so do not have an on/off switch. Usually, the only user accessible parts of a smoke detector are a "test" button and the compartment for the battery.

S9 Smoke detectors installed in kitchens generally have a high number of false alarms when normal cooking activities create more smoke than the smoke detector's threshold value. Typical activities which cause false alarms include burning toast, grilling and frying cuts of meat at high temperatures. Owners may remove the battery with the intention of replacing it when the smoke subsides or resort to hitting the unit. Either way the unit may not be operative when a real fire occurs.

.e The present invention aims to ameliorate the problems of present smoke detectors by providing a disabling mechanism which temporarily interrupts the activation of the alarm and which reactivates the alarm after a preset time without user intervention, where the disabling mechanism can only be activated once an alarm condition has been sensed, ie, it is not possible to deactivate the alarm when the smoke detector is merely in a passive "sensing" mode.

The disabling means may disable the smoke sensor unit or it may disable the alarm unit, or both.

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\\server\e\docs\patents\comp\8431 b.doc Preferably, the disabling means disables the smoke sensor unit and/or the alarm unit by cutting off the power supply.

Preferably, the disabling means connects between the battery and the smoke sensor unit and alarm unit and uses the smoke alarm's battery.

Preferably, the disabling means includes an infra red detector and an electronic timer. Preferably, the infra red detector, on receiving an appropriate signal causes the power to be cut to the smoke sensor unit and/or alarm unit and activates the timer unit to reconnect the power after a preset time.

Preferably, the infra red sensor is responsive to normal household infra red transmitters, such as remote control units fo" televisions, radios and the like.

Whilst infra red triggering is preferable, the invention includes within its scope provision of a manually activated disabling switch or activation by electro e. magnetic radiation of other frequencies and ultrasonic sound.

Whilst the invention has particular appeal to use in smoke alarms, it will be S" 15 appreciated that it may be used in other applications. Accordingly, in one broad form, the invention provides a detector unit including: sensing means for detecting a predetermined condition and for generating an alarm signal in response thereto; indication means, responsive to the alarm signal for providing an indication 20 identifying said condition; disabling means responsive to the alarm signal and only then operable to disable at least one of said sensing means, said indication means and the transmittal of said alarm signal to said indication means, for a preset time in response to receipt of disabling means.

The invention also provides a disabling means for use with a detector unit which includes a sensing means for detecting a predetermined condition and for generating an alarm signal in response thereto and indication means responsive to the alarm signal for providing an indicator identifying said condition, said disabling means responsive to the alarm signal and only then operable to disable I 30 at least one of said sensing means, said indication means and the transmittal of \\server\e\docs\patents\comp\8431 b.doc said alarm signal to said indication means, for a preset time in response to receipt of a disabling means.

The disabling means preferably includes a disabling signal receiving means and cut out means which actually disables the sensing means or the indication means. A timer is also preferred which issues a restore signal to the cut out means. The disabling signal receiving means, timer means and cut out means are preferably only active when required and for this purpose an alarm signal detector is preferably provided. Preferably activation means is provided which activates and deactivates the various components. Preferably the disabling signal receiving means is only activated when an alarm signal is detected and the timer means only activated when a disabling signal is received. The timer may pass a signal to the activation means to deactivate the disabling signal receiving means and itself after a restore signal is generated by the timer.

The disabling means may be placed in series, between a power source and the active components of the detector and merely cut power to the detector for a pre- •set time.

o Fig. 1 is a block diagram of an embodiment of the invention in relation to a conventional smoke detector; Fig. 2 is a side view of an embodiment of the invention.

Fig. 3 is a block diagram of the shutdown circuitry of an embodiment of the invention.

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Fig. 4 is a detailed circuit diagram of the fig. 3 embodiment.

Referring to the drawings, there is provided a standard smoke alarm 10, which includes a smoke sensor unit 12 and an alarm unit 14. The smoke alarm 10 is powered by a battery 16, normally a long life 9 volt battery. The alarm unit 14 is activated by the smoke sensor 12 when the amount of smoke sensed exceeds a preset threshold.

In addition to the battery 16, smoke sensor 12 and alarm 14, there is provided a shutdown unit 18 located in series between the battery 16 on one hand and the smoke sensor 12 and alarm unit 14 on the other hand. The shutdown unit 18 is o:\patents\comp\8431.doc housed in an opaque domed housing which, preferably, attaches to the underside of the smoke detector 10. The shutdown unit is operable to disconnect/connect the battery 16 to the smoke sensor and alarm units. The shutdown unit 18 operates from the smoke detectors battery 16 and so overcomes the problem of supplying two separate power sources. By using a single battery the smoke detector's low battery indicator indicates the state of the combination in total.

The principle of operation is best understood by reference to the block diagram of Fig. 3. When power is applied to the system the low power shutdown and status circuit 20 sets the circuit operation up in the following manner: the electronic switch 22 is turned on sending power to the smoke alarm 10 and the alarm detection circuit 24. Power to the 14 stage shutdown timer 26 is turned off and the one second oscillator 28 is disabled. All other circuits are turned off which allows the circuit to operate in a very low current standby mode (less than one micro amp). When the smoke sensor 12 senses an unacceptable level of smoke the alarm unit 14 is activated. The alarm unit 14 typically makes a continuous beepbeep sound. Each sound causes a high current pulse. The high current pulses generated by the smoke alarm activate the alarm detection circuit 24. Alarm S" detection circuit 24 turns the I.R. detector switch on\off circuit 30 on which in turn powers up the I.R. 5 volt power regulator 32. The 5 volt regulator 32 now supplies i 20 the correct current to operate the infra red detector 34.

When a user transmits a signal from an infra red remote control, pulses arriving from the remote control are detected by the infra red detector 34 and are used to activate the low power shutdown and status circuit 20. This circuit 20 switches the electronic switch 22 off and removes power from the smoke alarm 10. It also turns the timer 26 on and activates the one second oscillator 28.

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The timer 26 can be set to any of the 14 timer outputs ranging from seconds to over one hour. When the timer has timed out it sends a signal to the low power S:shutdown and status circuit 20, which in turn switches the smoke alarm 10 back on and places the system back to its low power mode as previously described.

While the timer 26 is activated it only draws 300 micro amps from the battery.

Typically the timer 26 is set to time out after about 10 minutes.

o:\patents\comp\8431.doc Normal smoke alarms include circuitry to monitor the battery condition and include signalling means to indicate when battery power is low. Such monitor circuitry also usually includes means to indicate when power is connected and to confirm the battery is in good condition, such as when the battery is replaced.

This is usually by causing the alarm unit to emit a series of short beeps. Since the disabling circuitry disconnects power to the smoke alarm to disable it, when power is reconnected to enable the alarm it will emit the power on series of beeps, so letting a user know it has been reactivated.

The infra red detector 34 is responsive to an infra red signal in the frequency band(s) normally used by household remote control units such as television, radio, garage remote control units or the like. These remote control units normally transmit coded signals at a single frequency, with different codes corresponding to different commands. However, in this application it is preferable for the sensor to respond to the presence or absence of an infra red signal in the relevant frequency band(s), irrespective of any coding of the signal. Thus, it is not normally necessary for the unit to be supplied with an infra red transmitter any household remote control unit will activate the infra red sensor.

Referring to fig. 4 there is shown a circuit diagram which corresponds to the functional block diagram of fig. 3. When the battery is first applied to the circuit, 20 capacitor C4 starts to charge via resister R6 to the positive potential supplied by the 9 volt battery. At the same time capacitor C10 starts to charge via resisters R12, R9, and the isolation diode D5. The time constant of the C4/R6 combination is less than that of the C10O/R9/R12 combination so the bistable circuit made up of CMOS Schmitt trigger Nand gates U1C and U1D will be set so that pin 11 of U1D will be at a high voltage and pin 10 of U1C is at zero voltage. This part of the circuit represents the low power shutdown and status circuit 20 shown in the block diagram of Fig. 3. In this configuration the electronic switch Q5 is turned on :via its gate resistor R10. The output pin 1 of Q1 is connected to the smoke alarm and so allowing the smoke alarm to be switched on. Pin 10 of UC is connected to positive power input pin 16 of U3, the 14 stage timer IC (the connection to pin is not shown in fig. In this state no power is consumed by the timer circuit U3. Pin 10 UC is also connected to input gate pinl of U1A. U1A, resistor R3 and o:\patents\comp\8431.doc capacitors C1 and C2 form an oscillator, which oscillates at 1 Hz when a positive voltage is applied to pin 1 of U1 C. This part of the circuit is the equivalent of the one second oscillator 28 of fig. 3. Since pin 10 of U1C is at zero voltage, this deactivates the one second oscillator 28. This set of conditions allows the circuit to operate in a low current state thus presenting a minimal drain, usually less than one micro amp, on the battery.

The alarm detection circuit 24 of fig. 3 consists of components C13, R13, D6, and D7. While the smoke alarm is switched on but in its sensing state, the battery consumption is very low, only about 9 to 10 micro amps, producing a voltage of around 10 millivolts across R13. However, a short pulse of current is presented by the smoke alarm circuit approximately once every minute. This pulse is used to sense the battery condition and sound a single beep from the alarm when the battery is getting low. Under these circumstances the single pulse will develop around 100 millivolts across this circuit due to the large value of C13. This small voltage drop will only subtract from the total battery condition in a very small way.

However when an alarm condition is present the alarm unit 14 draws a series of high current pulses. These rapid high current pulses generated by the alarm .i quickly charge C13 until 06 and D7 clamp the voltage across C13 at 1.2 volts.

This clamp voltage has two functions. One is to prevent the voltage rising across 2 C13 to the point where the voltage supplied to the alarm will not allow it to .*function and the second is to allow the voltage to rise above 600 millivolts to activate the disabled circuit component. The positive side of C13 is connected to the base of transistor Q3. The I.R. detector switch 30 circuit consists of Q3 and Q4. When the clamp voltage rises above 600 millivolts the NPN transistor Q3 turns on, pulling its collector voltage to ground. This action pulls the base of PNP transistor Q4 negative via R15 turning Q4 on and bringing Q4's collector voltage close to the +9 volt rail. The collector of Q4 connects to the base of Q1 via R1 and when at a high voltage turns Q1 on. Transistor Q1 represents the I.R. power regulator 32 of fig. 3. When the collector of Q4 is at +9 volt, the voltage at the base of Q1 is clamped to 6.2 volts by the action of Zener diode D2. With a base voltage of 6.2 volts and a voltage drop across the base emitter junction of Q1 of about 600 millivolts, a supply of 5.6 volts is presented to the supply pin of the infra red detector U2 (34 in fig. When a hand held I.R. remote control is o:\patents\comp\8431 .doc pointed at the I.R. detector and activated, the output pin of U2 produces a stream of one millisecond pulses approximately 5.6 volts in amplitude. Transistor Q2 acts as an in phase voltage translator to bring the amplitude of the pulses closer to 9 volts.

As the pulse from the I.R. Detector goes to a negative voltage, the emitter of transistor Q2 is pulled with it. The base of Q2 is connected to the 5.6 volt supply via R4 causing Q2 to conduct. The collector of Q2 is pulled down from 9 volt to the 5.6 volt supply and then continues to follow the negative pulse at its emitter toward the negative rail. When the pulse goes positive the emitter of Q2 reaches the 5.6 volt power supply and turns off. The voltage of collector of Q2 rises via to 9 volts. The collector of Q2 is connected to input pins 5 and 6 of U1B. This rising voltage is now large enough to pass through the 1.5 volt minimum to 7 volt maximum hysteresis points of the U1B input gates which causes U1B to output a sharp clean 9 volt pulse at its output pin 4.

To prevent any false tripping of the U C, U1D bistable circuitry due to power up or stray pulses arriving from the I.R. detector, the output of U1B is fed to a charge pump circuit consisting of C3, C4, D3, D4, R6. C3 has a smaller value than C4, S'"i preferably about 1 to 5. This circuit allows the voltage across C4 to be discharged to ground on receipt of a train of pulses generated by U1B when the I.R. remote S 20 control is pressed. However individual stray pulses will not discharge C4. This is necessary to prevent the false operation of the timer circuit.

When C4 is discharged sufficiently, this trips the state of the U1C, U1D bistable so that pin 10 of UIC is set to a high voltage. Pin 10 is connected to pin 16 (not shown) of U3 and the timer U3 is turned on by applying the high voltage at the 25 output pinl0 of UlC to its positive power pin 16. At the same time pin 11 of U1D 9 goes to a low voltage, turning the gate voltage off at Q5, which in turn switches off the smoke detector. When pin 10 of UlC goes high, it turns on the oscillator U1A, which generates a 1Hz output at pin 3. Pin 3 is connected to timer U3 at pin and commences U3 counting. Timer U3 has a series of output pins 1-7, 9 and 12- 15 which each output a negative voltage when the respective required number of input pulses have been received. The chosen output pin (in the figure it is 13) is o:\patents\comp\8431.doc connected to pin 13 of U1D via capacitor C5. When a negative pulse is applied to pin 13 of U1D, this causes the bistable circuit to switch (reset) to set output pin low and pin 11 high, so turning the smoke detector on again and turning the rest of the circuit off as previously described.

It will be appreciated by those skilled in the art that many modifications and variations may be made to the embodiments described without departing from the spirit or scope of the invention.

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Claims (22)

1. A detector unit including: sensing means for detecting a predetermined condition and for generating an alarm signal in response thereto; indication means, responsive to the alarm signal for providing an indication identifying said condition; disabling means responsive to the alarm signal and only then operable to disable at least one of said sensing means, said indication means and the transmittal of said alarm signal to said indication means, for a preset time in response to receipt SZ of disabling means.

2. The detector unit of claim 1 wherein the disabling means includes: disabling signal receiving means for receiving a disabling signal and for generating a cut-off signal in response to receipt thereof; ii cut-off means responsive to said cut off signal for disabling at least one of said i: sensing means, said indication means and the transmittal of said alarm signal to said indication means.

3. The unit of claim 2 wherein the disabling means further includes a timer means, said timer means for receiving said cut-off signal and for generating a restore signal a predetermined time after receipt of said cut-off signal.

4. The unit of claim 3 wherein the cut-off means receives said restore signal and ceases to disable said sensing means, said indication means or the transmittal of the alarm signal to said indication means. The unit of any one of claims 2 to 4 wherein the disabling signal receiving means has an active state, in which it generates said cut-off signal on receipt of a disabling S9 Iclains.doc dd signal and an inactive state in which said cut-off signal is not generated on receipt of a disabling signal.

6. The unit of any one of claims 2 to 5 wherein the cut-off means has an active state, in which it is capable of disabling the sensing means, the indication means or the transmittal of the alarm signal and an inactive state in which it is not so capable.

7. The unit of any one of claims 3 to 6 wherein the timer means has an active state, in which it is capable of generating a restore signal and an inactive state in which it is not.

8. The unit of any one of claims 1 to 7 wherein the disabling means includes an alarm signal detection means detecting the alarm signal for generating an activation signal upon detection of the alarm signal.

9. The unit of claim 8 wherein the disabling means further includes activation means, e S.said activation means activating said disabling signal receiving means upon receipt of an activation signal. oeo f The unit of claim 8 or claim 9 wherein the activation means receives the cut out signal and places the timer means in the active state in response thereto.

11. The unit of any one of claims 8 to 10 when dependent on claim 3 wherein the activation means also receives the restore signal and places the timer means and/or Sothe disabling signal receiving means in the inactive state in response thereto.

12. The unit of any one of claims 1 to 11 wherein the disabling signal is an infra red pulse signal having a frequency or frequency band falling anywhere in the range of frequencies normally transmitted by household remote control units capable of generating an infra red pulse signal.

13. The unit of claim 12 wherein the disabling means is responsive to any of the infra red pulse signals. s.doc dd

14. A disabling means for use with a detector unit which includes a sensing means for detecting a predetermined condition and for generating an alarm signal in response thereto and indication means responsive to the alarm signal for providing an indicator identifying said condition, said disabling means responsive to the alarm signal and only then operable to disable at least one of said sensing means, said indication means and the transmittal of said alarm signal to said indication means, for a preset time in response to receipt of a disabling means. The disabling means of claim 14 including: disabling signal receiving means for receiving a disabling signal and for generating a cut-off signal in response to receipt thereof; ee cut-off means responsive to said cut off signal for disabling at least one of said sensing means, said indication means and the transmittal of said alarm signal to said indication means. 0. 0:

16. The disabling means of claim 14 or claim 15 further including a timer means, said timer means for receiving said cut-off signal and for generating a restore signal a predetermined time after receipt of said cut-off signal.

17. The disabling means of claim 16 wherein the cut-off means receives said restore signal and ceases to disable said sensing means, said indication means or the 0 4 S transmittal of the alarm signal to said indication means.

18. The disabling means of any one of claims 15 to 17 wherein the disabling signal receiving means has an active state, in which it generates said cut-off signal on receipt of a disabling signal and an inactive state in which said cut-off signal is not generated on receipt of a disabling signal.

19. The disabling means of any one of claims 15 to 18 wherein the cut-off means has an active state, in which it is capable of disabling the sensor means, the indication means or the transmittal of the alarm signal and an inactive state in which it is not so capable. The disabling means of any one of claims 16 to 19 wherein the timer means has an active state, in which it is capable of generating the restore signal and an inactive state in which it is not.

21. The disabling means of any one of claims 14 to 20 wherein the disabling means includes an alarm signal detection means detecting the alarm signal for generating an activation signal upon detection of the alarm signal.

22. The disabling means of claim 21 further including activation means, said activation means activating said disabling signal receiving means upon receipt of an activation signal. S. 23. The disabling means of claim 21 or claim 22 wherein the activation means receives the cut out signal and places the timer means in the active state in response thereto.

24. The disabling means of any one of claims 21 to 23 when dependent on claim 16 wherein the activation means also receives the restore signal and places the timer means and/or the disabling signal receiving means in the inactive state in response thereto. The disabling means of any one of claims 14 to 21 wherein the disabling signal is an infra red pulse signal having a frequency or frequency band falling anywhere in the range of frequencies normally transmitted by household remote control units capable of generating an infra red pulse signal.

26. The disabling means of claim 22 wherein the disabling means is responsive to any one of the infra red pulse signals.

27. A detector unit substantially as hereinbefore described with reference to the drawings. 12 \\servere\docs\patents\ciai m\8431claims.doc dd

28. A disabling means substantially as hereinbefore described with reference to the drawings. Dated 2 2 nd June, 2001 Clifford W. Davis By his Patent Attorneys CHRYSILIOU LAW 13 \\server\e\docs\patents\clainis\843 I claimsadoc dd