Field of the Invention

[0001 ] This invention relates to fire extinguisher monitoring systems and, more specifically, to a fire extinguisher discharge detection device.

Background of the Invention

[0002] Periodic maintenance of fire extinguishers essential to ensure the availability and operational adequacy thereof in the event of a fire. Fire extinguishers must be replaced after full or partial discharge.

[0003] Generally, inspection personnel periodically visually inspect fire extinguishers, such as by checking the pressure gauges thereof. However, the feasibility of such manual inspecting is poor given the time-consuming nature thereof.

[0004] As such, various automatic fire extinguisher detection devices have been proposed to automate the inspection process.

[0005] One such device uses an image sensor which captures images of a pressure gauge dial of the fire extinguisher to detect discharge of the fire extinguisher when the dial moves. Other devices employ load cells to detect changes in the weight of a fire extinguisher.

[0006] US 8842016 B1 (CAZANAS et al.) 23 September 2014 proposes a system which uses trigger activation and/or pressure loss detection to determine activation of the fire extinguisher.

[0007] The present invention seeks to provide a way which will overcome or substantially ameliorate at least some of the deficiencies of the prior art, or to at least provide an alternative.

[0008] It is to be understood that, if any prior art information is referred to herein, such reference does not constitute an admission that the information forms part of the common general knowledge in the art, in Australia or any other country.

Summary of the Disclosure

[0009] There is provided herein a fire extinguisher discharge detection system comprising a portable detection device. [0010] The device is preferably self-contained within portable housing for ready attachment directly to a fire extinguisher.

[0011 ] The housing forms an attachment face for direct attachment across a surface of a fire extinguisher canister to thereby form a tight acoustic coupling between the attachment face and the cylinder.

[0012] The device further comprises a microphone and a controller which analyses acoustic signals received from the microphone to detect discharging of the fire extinguisher.

[0013] The attachment face may magnetically attach to the canister.

[0014] To enhance the acoustic coupling, the attachment face may have a geometry maximising contact surface area with the canister. The attachment face may comprise one-dimensional curvature for attachment to one side of the canister or two- dimensional curvature for attachment to a base thereof. The attachment face forms sufficient contact surface area, preferably greater than 2 cm ² . The attachment face may occupy an entire rear of the housing. The device may comprise interchangeable attachment faces of different geometries, each of which may be installed depending on the geometry of the canister.

[0015] The device may be configured to remain operational for a year or more and, in this regard, the controller may default to a low-power sleep state and wake from the low-power sleep state when receiving an audio interrupt from the microphone.

[0016] When the controller is in the low-power sleep state, the microphone continuously determines whether acoustic signals exceed a threshold in the time domain.

[0017] The microphone is preferably a low-power high accuracy MEMS microphone which may further provide audio signal interrupts.

[0018] The controller may comprise a memory device comprising calibration settings and wherein the controller analyses the acoustic signals according to the calibration settings. The calibration settings may specify a time domain amplitude threshold, a frequency domain range and a frequency domain range amplitude. [0019] The device may comprise a data interface and the controller may be configured for receiving updated calibration settings via the data interface.

[0020] The system may further comprise a monitoring server in operable communication with the device and the device may transmit at least one of the acoustic signals and measured parameters thereof to the server. The server may analyse the parameters to adjusts the calibration settings to optimise detection accuracy to reduce or eliminate false positive detections.

[0021 ] The server may optimise detection accuracy by employing machine learning having as input at least one of historical parameters and calibration settings and which is trained using associated detection accuracy data to optimise the calibration settings.

[0022] The system may comprise different sets of calibration settings for different types of fire extinguishers, including those having different canister volumes and a different fire extinguisher agent (e.g., C02, powdered fire extinguisher agents and the like). The controller may be configurable with a type of fire extinguisher and the system may select the respective set of calibration settings accordingly.

[0023] The controller may perform time domain amplitude threshold analysis of the acoustic signals and frequency domain amplitude threshold analysis.

[0024] The frequency domain amplitude threshold analysis may comprise threshold analysis across a wide frequency range, such as greater than 10 kHz, or across discrete low and high frequency ranges such as more than 5 kHz apart.

[0025] The device further may comprise a motion sensor in operable communication with the controller and wherein the controller detects motion using motion signals received from the motion sensor.

[0026] The motion sensor may be a low power and sensitive gas shock sensor. [0027] The device may also wake from the low power sleep state when receiving an interrupt from the motion sensor. The device may be configured for only analysing the acoustic signals after detecting motion to conserve power.

[0028] The controller may be configured for acoustic signal-based discharge detection verification by analysing the motion. [0029] For example, the motion sensor may comprise an accelerometer and wherein the verification may comprise detecting acceleration greater than a threshold.

[0030] The motion sensor may comprise a multiaxial accelerometer and wherein verification may comprise detection acceleration greater than a threshold in more than one axis or two axes.

[0031] The device further may comprise a data interface and wherein the controller transmits discharge detection information via the interface.

[0032] The controller may be further configured for analysing the acoustic signals to determine the duration of discharge.

[0033] The device further may comprise a short-range communication interface operably interfacing the controller and wherein the controller is configured for communicating with an electronic device.

[0034] The short-range communication interface may transmit a controller ID to the electronic device.

[0035] The short-range communication interface may make periodic beacon transmissions encoding the controller ID.

[0036] Other aspects of the invention are also disclosed.

Brief Description of the Drawings

[0037] Notwithstanding any other forms which may fall within the scope of the present invention, preferred embodiments of the disclosure will now be described, by way of example only, with reference to the accompanying drawings in which:

[0038] Figure 1 shows a detection device for a fire extinguisher in accordance with an embodiment; and

[0039] Figure 2 illustrates exemplary utilisation and processing of the detection device.

[0040] Figure 3 shows an exemplary frequency domain acoustic signal amplitude waveform;

[0041] Figure 4 shows exemplary time domain triaxial acceleration waveforms;

[0042] Figure 5 shows an acoustic signal-based discharge detection verification process; [0043] Figure 6 illustrates the attachment of the device to a base of a fire extinguisher; and

[0044] Figure 7 shows a rear perspective view of the device in accordance with an embodiment.

Description of Embodiments

[0045] Figure 1 shows a dramatic representation of a portable fire extinguisher detection device 100 for a fire extinguisher 101.

[0046] As shown in Figure 6, the device 100 may be attached directly to a canister 139 of the fire extinguisher 101. As shown in figure 6, the device 100 may be concealed by being attached to a base 140 of the canister 139.

[0047] As shown in Figure 7, the device 100 is self-contained within portable housing

141. In this regard, the device 100 comprises the requisite componentry for the portable operation thereof entirely contained within the housing 141 , such as battery power supply, controllers, sensors and the like, so as to be operably portable and readily attachable directly to the canister 140 of the fire extinguisher 101.

[0048] The housing 140 may expose an operational user interface including operational pushbuttons 150 and LED status indicators 151.

[0049] The device 100 forms an attachment face 142 for direct attachment to the canister 139 to thereby form a sufficient acoustic coupling 120 with the canister 139. [0050] The attachment face 142 may comprise a magnetic pad 143 which magnetically attracts metallic cylinders 139.

[0051 ] The attachment face 142 may have geometry maximising the contact surface area with the canister 139. In one embodiment, the attachment face 142 has one dimensional curvature to attach to the side of the canister 139. Flowever, in embodiments shown in Figure 7, the attachment face 142 comprises two-dimensional curvature (i.e., is substantially concave) so as to conform in the interface a convex base 140 of the cylinder 139.

[0052] In embodiments, the device 100 comprises interchangeable attachment faces

142, each of which may be installed depending on the geometry of the canister. [0053] The attachment face 142 is further preferably sufficiently large, such as greater than 2 cm ² . In the embodiment shown in Figure 7, the attachment face 142 may occupy the entire rear of the housing 141 to maximise the contact surface area thereof [0054] in this way, the device 100 may be attached to the fire extinguisher 101 so as to achieve good acoustic coupling therewith and which may be left in place for an extended duration of time for detecting discharge of the fire extinction 101 .

[0055] The device 100 comprises a controller 105. The controller 105 may be a ESP32 series low-cost, low-power system on a chip microcontroller with integrated Wi-Fi and dual-mode Bluetooth.

[0056] The controller 105 comprises a processor 106 for processing digital data. A memory device 107 is in operable communication with the processor 106 via a system bus 108. The memory device 107 stores digital data including computer program code instructions. These computer program code instructions may be logically divided into a plurality of computer program code instruction controllers 109. In use, the processor 106 fetches these computer program code instructions and associated data 1 10 for interpretation and execution of the functionality described herein.

[0057] The memory device 107 may store configuration settings, including those used for acoustic signal analysis as will be described in further detail below.

[0058] The controller 105 may have an audio interface 1 11 interfacing the acoustic coupling 102. The controller 105 interfaces a microphone 1 12, preferably a MEMS (Micro-Electro-Mechanical System) microphone which offers high signal-to-noise ratio (SNR), low power consumption, good sensitivity and which are available in small packages. The audio interface 100 receives acoustic signals 1 13 from the microphone 1 12.

[0059] The microphone 112 is preferably attached directly to the interior face of the attachment face 142.

[0060] In embodiments, the controller 105 receives an audio interrupt 1 14 from the microphone 1 12 when the microphone 1 12 detects audio.

[0061 ] For extended operational duration, the controller 105 may default to a low- power sleep state and wake from the low-power sleep state when receiving an audio interrupt from the microphone 112 when the microphone 112 detects exceeding a threshold. When waking from the low-power sleep state, the controller 105 may commence analysis of acoustic signatures received from the microphone 1 12. In this way, the controller 105 saves computational power to preserve the battery power supply thereof.

[0062] In embodiments, the device 100 may further comprise a sensor to detect proximity of the canister 139 at the attachment face 142 (such as a magnetometer) and wherein the controller only enters and operational state when the proximity sensor detects that the device is attached to canister 139.

[0063] The controller 105 may comprise a motion sensor 115. In one embodiment, the motion sensor 105 is a gas shock sensor which is used given the good sensitivity thereof.

[0064] The motion sensor 1 15 may comprise a multiaxial accelerometer, such as the MMA8452Q programmable 3-Axis 8-bit/12-bit digital accelerometer.

[0065] The controller may comprise a short-range communication interface 1 16 for short-range communication with an electronic device 117. The short-range communication interface 116 may be a Bluetooth, Bluetooth low energy, NFC, RFID short-range communication interface and the like.

[0066] The controller 105 may further comprise a data network interface 118 for sending and receiving data across a data network 119.

[0067] The data network interface 1 18 may be a Wi-Fi interface in communication with a Wi-Fi router for sending and receiving data across the Internet.

[0068] Figure 2 shows exemplary utilisation and processing 120 of the device 100 in accordance with an embodiment.

[0069] Step 121 may comprise attachment of the detection device 100 to the fire extinguisher 101 and the registration thereof. The attachment face 142 of the device 100 may be affixed to the metallic cannister 103 of the fire extinguisher 101 using the magnetic coupling 104. The device 100 may be affixed to the side of the cannister or concealed under the base thereof as shown in Figure 7. [0070] Registration of the device 100 may comprise recording details of the device 100 and/or the fire extinguisher 101 in a database of a server. The device 100 may be preconfigured with the unique controller ID. Various information may be stored in the database in relation to the controller ID, including location, type of fire extinguisher and the like.

[0071 ] In embodiments, the device 100 may receive over-the-air (OTA) updates at step 122. For example, the controller 105 may receive software and/or firmware updates and/or updated data parameters 1 10. As will be described in further detail below, the controller 105 may receive updated calibration settings for more accurately analysing audio and/or motion signals for detecting discharge of the fire extinguisher 101.

[0072] At step 124, the controller 105 enters the aforedescribed low-power sleep state to preserve power. Preferably, the device 100 comprises sufficient battery supply to remain sleeping for more than one year.

[0073] At step 127, the controller 105 receives an audio interrupt from the microphone 112 and wakes at step 129. More specifically, at step 123, the MEMS microphone 112 may continuously analyse acoustic signals 1 13 to determine if the acoustic signals exceed a threshold and, if so, generate an audio interrupt 1 14 at step 125. As can be appreciated, the power consumption of the mems microphone 112 for detecting audio exceeding a threshold is much less than that consumed by the controller.

[0074] In embodiments, the motion sensor 115 may similarly analyse motion signals at step 128 and generate a motion interrupt at step 126 accordingly. Where the motion sensor 115 is a gas shock sensor or the like, the motion sensor 115 may generate the interrupt when any motion is detected. In the embodiment where the motion sensor 1 15 is an accelerometer, the motion sensor 115 may generate the interruption of the acceleration detected thereby exceeds a threshold.

[0075] In further embodiments, where the motion sensor 1 15 is a multiaxial accelerometer, the controller 105 may analyse acceleration signals across more than two axes thereof before generating the interrupt. For example, monitoring the acceleration signals across more than two axes may detect when the fire extinguisher 101 is lifted upwardly and move sideways, such as when acceleration in more than two axes exceeds a threshold.

[0076] Where the controller 105 comprises the motion sensor 115, the controller 105 may only wake at step 129 if and interrupt is received from both the audio interface 11 1 and the motion sensor 1 15. Alternatively, the controller 105 may wake with the audio interrupt 1 14 and then analyse the signals received from the motion sensor 1 15 to determine if the fire extinguisher 101 is being moved.

[0077] At step 131 , the controller 105 analyses the acoustic signals 130 received from the microphone 112.

[0078] At step 132, the controller 105 may determine if acoustic signal amplitude exceed a threshold in the time domain. As alluded to above, the microphone 1 12 itself may determine if the acoustic signal amplitude exceeds the threshold.

[0079] At step 130, the controller 105 may perform frequency domain analysis of the acoustic signals 1 13. For example, the controllers 109 may comprise a Fast Fourier Transform (FFT) controller which converts the acoustic signals from the time domain to the frequency domain. Thereafter, the controller 105 may analyse frequency domain amplitude within frequency bands thereof to detect acoustic signals indicative of the fire extinguisher 101 being discharged.

[0080] Figure 3 shows an exemplary frequency domain waveform 144 having frequency on the X-axis and amplitude of the Y-axis. The waveform 144 shows a wide frequency spread characterised by white noise-like audio signals generated by the fire extinguisher 101 when being discharged.

[0081 ] Frequency domain analysis may comprise determining whether the amplitude exceeds a threshold T across a wide frequency range FR1 such as a range wider than 10 kFIz.

[0082] Alternatively, frequency domain analysis may comprise determining whether the amplitude exceed the threshold T both at a lower frequency range FR2 and a higher frequency range FR3, such as which I more than 5 kFIz apart. [0083] In embodiments, volume of the canister 139 and/or the fire extinguishing agent therein (i.e. C02, powder fire agents and the like) may affect the acoustic singles exhibited by the fire extinguisher 101 during discharge, including the ranges and the frequency domain.

[0084] As such, during the registration stage 121 , the type and/or sizing of the cannister 103 of the fire extinguisher 101 may be recorded within the data 110 of the controller 105 so that, when analysing the acoustic signals at step 131 , the controller 105 may use a set of calibration settings according to the type of fire extinction 101 to analyse the acoustic signals.

[0085] As alluded to above, the controller 105 may receive over the air updates 122, including audio and/or motion analysis calibration settings for more accurately detecting discharges.

[0086] In embodiments, a plurality of detection devices 100 are in operable communication with a server via the network 119. The device 100 may transmit the acoustic signals (and in embodiments, the motion signals), or statistics thereof (such as threshold, frequency domain amplitude and the like) to the server.

[0087] The server may analyse the data from various devices to optimise the configuration settings accordingly to avoid false positive detections. Updated configuration settings may be transmitted to the devices 100 across the network 119. [0088] In embodiments, the server employs machine learning wherein a trained machine (such as a neural network) is optimised by a machine learning algorithm (such as one which updates the weightings of neurons thereof). The trained machine may output the optimised audio and/or motion detection parameters.

[0089] The machine learning algorithm may be trained using historical data, including historical audio and motion readings and discharge determinations.

[0090] At step 137, the controller 105 may transmit information of the detection of the discharge via the network 119 at step 138 which may trigger an inspection and/or replacement. Where the fire extinguisher 101 is replaced, the detection device 100 may be reset. [0091] Figure 5 shows a process 145 which may be used by the device 100 for verifying acoustic signal-based discharge detection.

[0092] The process 145 may comprise an acoustic signal-based discharge detection stage comprising the aforedescribed acoustic signal analysis 131 for acoustic signal- based discharge detection 146. As alluded to above, the acoustic signal analysis 131 may involve the aforedescribed time domain amplitude thresholding 132 and frequency domain analysis 130.

[0093] Upon acoustic signal-based discharge detection at step 146, the process 145 may then verify the discharge detection by analysing the motion signals at step 128. [0094] The motion signal analysis may involve time domain thresholding wherein the acoustic signal-based discharge detection 146 is verified only if motion is detected by the motion sensor 115.

[0095] In further embodiments, where the motion sensor 115 comprises an accelerometer, the discharge detection 146 may only be verified if the measured acceleration exceeds a threshold.

[0096] In embodiments, the device 100 may more accurately verify discharge detection using the aforedescribed multi-axis accelerometer by detecting whether measured acceleration exceeds a threshold across more than one axis, preferably two axes.

[0097] Figure 4 shows exemplary time domain acceleration waveforms 149 with the X-axis representing time and the Y-axis representing amplitude.

[0098] The waveforms may comprise an X-axis acceleration waveform 149A, Y-axis acceleration waveform 149B and a Z axis acceleration waveform 149C.

[0099] As shown in Figure 5, the verification process 145 may comprise corresponding X-axis thresholding 147A, Y-axis thresholding 147B and Z axis thresholding 147C. More specifically, with reference to Figure 4, the controller 105 may determine whether the acceleration waveforms 148 exceed a positive threshold T or negative threshold -T. [0100] According to the example of Figure 4, acceleration is detected in all three axes exceeding the threshold T or -T and therefore the acoustic signal-based discharge detection 146 is verified at step 148.

[0101 ] In embodiments, maintenance personnel may use electronic devices 1 17 to inspect and maintain fire extinguishers 101. In embodiments, the short-range communication interface 116 is a Bluetooth low energy interface which periodically transmits Bluetooth beacons at step 135. Each beacon transmission may comprise an ID of the controller 105. The electronic device 1 17, which may take the form of a mobile communication device, may execute a software application thereon. Receiving the beacon transmission may cause an operational system interrupt to launch the software application thereon.

[0102] The electronic device 117 may connect to controller 105 at step 136. For example, the electronic device 170 may communicate via Bluetooth, Wi-Fi and or NFC with the controller 105.

[0103] The software application may comprise user interface indicating whether the fire extinguisher has been discharged. In embodiments, the interface may indicate the volume of discharge.

[0104] Once the fire extinguisher 101 has been inspected, the controller 105 or the electronic device 117 may transmit an indication of such via the network 119 to the central server.

[0105] Depending on the analysis of the acoustic signals at step 131 , the controller 105 may detect and record the discharge of the fire extinguisher at step 134. In embodiments, the controller 105 may analyse motion signals from the motion sensor 115 to detect movement of the fire extinguisher 101 and/or discharge of the fire extinguisher 101 .

[0106] In embodiments, at step 133, the controller 105 may determine the discharge amount 133. For example, the controller 105 may initiate a timer during which the controller 105 detects acoustic signals indicative of the fire extinguisher being discharged. As such, the controller 105 may determine the remaining capacity of the fire extinguisher. For example, a fire extinguisher may be discharged for a period of 20 seconds wherein, during a discharge, the controller 105 may record that the fire extinguisher 101 was discharged for five seconds, thereby indicative that three quarters of retardant remains within the cannister 103.

[0107] In embodiments, the controller 105 is configured for analysing the acoustic signals to determine the duration of discharge. For example, the controller 105 may analyse the acoustic signals in the time domain to detect when the amplitude thereof exceeds a threshold and then when the amplitude falls back beneath a threshold and measuring a time period therebetween.

[0108] In embodiments, the controller 105 is configured for detecting a volume of fire extinguishing agents dispensed according to a known volume of the canister and the time period. Furthermore, the controller may be configured for calculating a remaining volume of fire extinguishing agent.

[0109] In further embodiments, the controller 105 is only configured for transmitting discharge notification when the remaining volume of fire extinguisher agent falls beneath a threshold.

[0110] The foregoing description, for purposes of explanation, used specific nomenclature to provide a thorough understanding of the invention. Flowever, it will be apparent to one skilled in the art that specific details are not required in order to practise the invention. Thus, the foregoing descriptions of specific embodiments of the invention are presented for purposes of illustration and description. They are not intended to be exhaustive or to limit the invention to the precise forms disclosed as obviously many modifications and variations are possible in view of the above teachings. The embodiments were chosen and described in order to best explain the principles of the invention and its practical applications, thereby enabling others skilled in the art to best utilize the invention and various embodiments with various modifications as are suited to the particular use contemplated. It is intended that the following claims and their equivalents define the scope of the invention.