System for early detection, warning and prevention of chimney fires

Abstract

The invention describes a system for the early detection, warning and prevention of a chimney fire, where the system comprises a chimney fire extinguisher (1) which is triggered when a chimney fire parameter reaches a trigger threshold value, a chimney fire sensor (20) to measure a chimney fire parameter in the chimney flue (7) and an air supply stopper (25) for a wood burner (23) to stop the air supply to the wood burner. Furthermore, the system includes a communication unit (27) which receives a signal from the chimney fire sensor (20) and transmits an early warning signal when the chimney fire parameter reaches the warning threshold value, so that unnecessary triggering of the chimney fire extinguisher (1) can be prevented by adjusting the draft on the basis of the warning signal.

Description

[0001] Title: System for early detection, warning and prevention of chimney fires

[0002] Description

[0003] Field of invention

[0004] The present invention relates to a system and a method for detecting, warning and preventing chimney fires where the system is used together with a chimney fire extinguisher.

[0005] Background

[0006] It is a challenge to create a system to detect, warn and prevent chimney fires that can handle the external influences in the form of weather, heat, soot and smoke over time without triggers, signaling devices or sensors becoming defective or triggering because of errors.

[0007] It is usually accumulated soot that burns in a chimney fire. Improper burning or raw wood causes soot to accumulate in the chimney and is usually the cause of chimney fires. Other causes can be poor draft, incorrect installation or old and bad chimney flue or lack of sweeping of the chimney flue.

[0008] Previously patented solutions often have high complexity in the trigger mechanism, which makes it vulnerable to external influences over time, and the production costs are high, which has made them unsuitable. Others have made triggers based on electronics where the lifespan of batteries and power supply make regular testing and maintenance necessary. Fully electronic extinguishing systems also require more frequent maintenance.

[0009] The inventor has previously described a chimney fire extinguisher in patent application 20220569. In order to prevent the triggering of this or another chimney fire extinguisher, it is desirable to have a detection and warning system that intervenes automatically before the chimney fire extinguisher is triggered or that gives the user the opportunity to take fire-preventing actions, which would typically be to close the draft in the wood burner or close a damper in the chimney.

[0010] The purpose of the invention is to provide a system for detecting, warning and preventing chimney fires which can withstand external influences and is simple and cheap to produce.

[0011] Furthermore, there is a purpose to prevent unnecessary triggering of the chimney fire extinguisher. A further purpose is that it has so few components that it will not be affected to the same extent over time by external factors such as e.g. corrosion, soot coating, heat, water, UV radiation or wind.

[0012] Brief summary of the invention

[0013] In a first aspect, the invention describes a system for the early detection, warning and prevention of a chimney fire in a chimney flue having one or more wood burners attached, wherein the system comprises a chimney fire extinguisher which is triggered when a chimney fire parameter reaches a trigger threshold value and a chimney fire sensor to measure a chimney fire parameter in or above the chimney flue, in a connection pipe between a wood burner and the chimney flue or in the one or more wood burner or in an air supply to the wood burner. Furthermore, the system includes an air supply stopper for the wood burner to stop the air supply to the wood burner and a communication unit that receives a signal from the chimney fire sensor and conveys an early warning signal when the chimney fire parameter reaches the warning threshold value, so that unnecessary triggering of the chimney fire extinguisher can be prevented by adjusting the draft on the basis of the warning signal.

[0014] The chimney fire sensor may comprise at least one of chimney temperature sensor, gas sensor, particle sensor, optical sensor and air flow sensor.

[0015] The system may comprise an early warning unit configured to be triggered by the warning signal from the communication unit, wherein the early warning unit gives a chimney fire warning in the form of an audio signal or light signal that can be perceived by a user of the wood burner.

[0016] The air supply stopper may be an ordinary draft regulation mechanism supplied with the wood burner to be operated by a user when the user perceives the chimney fire warning.

[0017] The air supply stopper may comprise a releasable closing mechanism which closes the air supply on receipt of the warning signal from the communication unit.

[0018] The releasable closing mechanism may comprise a biased closing plate which is released and closes the air supply to the wood burner upon receipt of an early warning signal from the communication unit.

[0019] The air supply may go through a air supply channel with an air intake on the outside of the building.

[0020] The air supply stopper may comprise a damper in the air supply channel of the wood burner. The chimney fire sensor may comprise an air flow meter which comprises measurement of the air supply for combustion in the wood burner.

[0021] The chimney fire sensor may comprise a chimney temperature sensor placed in the chimney flue above the uppermost inlet from the one or more wood burner or just above the chimney flue.

[0022] The trigger threshold value may be 350 degrees Celsius and the warning signal is emitted from the communication unit at 250 degrees.

[0023] In a second aspect of the invention, a method is described for preventing unnecessary triggering of a chimney fire extinguisher which is triggered at a trigger threshold value of a chimney fire parameter, where the method comprises the steps: a. to measure a chimney fire parameter in a chimney flue or air supply, b. to send an early warning signal to a communication unit when a measured value of the chimney fire parameter reaches the warning threshold value, c. to send a regulation command from the communication unit based on at least the measurements of the chimney fire parameter.

[0024] The method may comprise: step a. may further comprise measuring the temperature in the chimney flue using the temperature sensor and measuring the temperature in the connection pipe or the wood burner using the secondary temperature sensor, step b. may further comprise the measured value of the chimney fire parameter being the difference between the temperature sensor and the secondary temperature sensor, and step c. may further comprise sending the regulation command from the communication unit to an early warning unit based on temperature differences

[0025] The method may further comprise sending the regulation command from the communication unit to an early warning unit which emits an audible or visible signal so that a user can regulate or close a manual air supply stopper for the wood burner, thus preventing release of the fire extinguisher or a chimney fire.

[0026] The method may further comprise sending the regulation command from the communication unit to a releasable closing mechanism.

[0027] Brief description of the figures To facilitate the understanding of the invention, we have attached some drawings where the same features have the same respective reference numbers in all the figures.

[0028] Figure la shows a cross-section of a chimney fire extinguisher in the charged / closed state as integrated in a chimney cap.

[0029] Figure lb shows a cross-section of the chimney fire extinguisher in the charged / closed state as integrated in the chimney cap where the signaling mechanism is an electronic device that alerts via digital signals or sound.

[0030] Figure 2a shows a cross-section of the chimney fire extinguisher shown in fig. la in released / open condition.

[0031] Figure 2b shows a cross-section of the chimney fire extinguisher shown in fig. lb in released / open condition.

[0032] Figure 3 shows a cross-section of an extinguisher bag rolled up with a line.

[0033] Figure 4 shows an embodiment where the system includes a traditional wood burner, a chimney fire sensor, a communication unit and an early warning unit.

[0034] Figure 5 shows an embodiment where the system includes an air supply channel with access to air outside the house.

[0035] Figure 6 shows temperature development over time in a chimney fire.

[0036] Figure 7 shows an embodiment of a fire extinguisher base and support with biasing means.

[0037] Detailed description

[0038] A system for early detection, warning and prevention of chimney fires is described. The system comprises a chimney fire extinguisher 1 which is triggered when a chimney fire parameter reaches a trigger threshold value.

[0039] As shown in fig. 4, the system for detecting, warning and preventing chimney fires comprises a chimney fire sensor 20 to measure a chimney fire parameter primarily in, or just above, the chimney flue. The chimney fire sensor 20 can be, for example: a chimney temperature sensor 21, a gas sensor, a particle sensor, optical sensor and an air flow sensor. All these sensors will be able to detect a chimney fire with a high degree of certainty. The chimney temperature sensor 21 will detect that the temperature in the chimney flue rises rapidly by several hundred degrees. The gas sensor will detect that the gas composition changes because it is mainly soot and pitch that is burned in a chimney fire. The particle sensor will detect an increased flow of particles in the chimney flue and the airflow meter will detect increased air flow in the chimney flue. The chimney fire sensor may be positioned above the top inlet from a wood burner 23 to the relevant chimney flue and the chimney fire sensor must be placed in the chimney flue or just above the chimney flue, such as at or on the chimney cap 8. If the chimney fire sensor is an air flow sensor the air flow meter may be positioned in the chimney flue or perhaps more preferable in a air supply channel 24 supplying air to the wood burner 23 and also in a connection pipe 33 between the wood burner 23 and the chimney flue.

[0040] Preferably, the chimney fire sensor 20 is a chimney temperature sensor 21. The chimney temperature sensor 21 can e.g. sit in the chimney cap or at an upper part of the chimney flue above the uppermost inlet from a wood burner of a plurality of wood burners attached to the chimney flue in question. The chimney temperature in normal use is typically between 50 and 250 degrees C. In the event of a chimney fire, the temperature will typically be over 300 degrees C.

[0041] The system further comprises an air supply stopper 25 for the wood burner 23 which can stop the air supply. In one embodiment, the air supply stopper 25 comprises a draft regulation mechanism 26 which is supplied with the wood burner 23 and is operated by a user when the user wants more or less heat or when the user hears or sees a warning about a possible chimney fire.

[0042] The system further comprises a communication unit 27 which receives a signal from the chimney fire sensor 20. The purpose of the chimney fire sensor 20 is to detect whether the measured values of the chimney fire parameter approach a trigger threshold value for the chimney fire extinguisher 1 or more precisely; reaches a warning threshold value, which is lower than the trigger threshold value. The communication unit 27 conveys an early warning signal when the chimney fire parameter reaches the warning threshold value for the chimney fire extinguisher I, preferably at a predetermined warning value of the chimney fire parameter. The communication unit 27 may trigger an early warning unit 30 that gives an early warning in the form of an audio signal or light signal that can be perceived by a user of the wood burner 23 causing the user to reduce the draft for preventing possible triggering of the chimney fire extinguisher or a chimney fire in worst case.

[0043] In a preferred embodiment, the chimney fire parameter is temperature, and the temperature is measured by a chimney temperature sensor 21 because temperature is the most stable and predictable way to detect a chimney fire. It is also on temperature that there is the most data and where the instrumentation is most reliable in the environment found in a chimney flue during startup of a chimney fire. In the aforementioned preferred embodiment, a chimney temperature sensor 21 measures whether the chimney temperature Tc approaches a trigger value of the chimney temperature TT for triggering the chimney fire extinguisher 1. At an early warning temperature Tw, which is slightly below the trigger temperature TT, an early warning signal is given. Fig. 6 shows a typical temperature development at the startup of a chimney fire. If the air supply is shut off if the chimney temperature exceeds 250 degrees C in the upper part of the chimney flue of a one-story residential building, this will in most cases be enough to prevent the full development of a chimney fire. The choice of temperature for sending the warning signal depends on the length of the chimney flue, the number of wood burners connected to the chimney flue 7, the sizes of the wood burners and where the temperature sensor 21 is located. Experiments has shown that choosing 280 degrees C as warning temperature and 380 degrees C as trigger temperature functions well.

[0044] In an embodiment the system further comprises a secondary temperature sensor 34 measuring the temperature in the wood burner 23 or the connection pipe 33 between the wood burner and the chimney flue and being connected to the temperature to the communication unit 27 as indicated in fig. 4. This embodiment enables detection of chimney fires based on the difference between the chimney temperature measured by the temperature sensor 21 and the temperature in the connection pipe 33 or wood burner measured by the secondary temperature sensor 34. If the chimney temperature is higher than the temperature in the connection pipe or wood burner a chimney fire is probably taking place. The secondary temperature sensor will also pick up excessive heat from the wood burner much faster than the temperature sensor in the chimney flue 7.

[0045] In one embodiment shown in fig. 5, the system comprises an air flow meter 22 in an air supply to the wood burner 23. The air flow meter 22 can comprise an anemometer which is placed in the air supply channel (24) to the wood burner 23. The air supply channel to the wood burner 23 can be a dedicated air supply channel 24 which draws air from outside the building as in modern building as shown in fig. 5 or simply the air intake of a traditional wood burner. An anemometer will be able to provide a relatively accurate measure of the amount of air supplied to the combustion, which is sufficiently accurate to detect the increased draft that occurs when a chimney fire starts.

[0046] When the airflow meter 22 exceeds a warning threshold value, an early warning signal is sent to the communication unit 27. The warning threshold value for the airflow meter must be adapted / calibrated to the wood burner in question and the chimney flue in question.

[0047] The warning signal can be communicated to a user by a light signal or an audio signal indicating the danger of a chimney fire. The user then has the option to close the draft if the user is at home.

[0048] In another embodiment, the early warning signal can go to an air supply stopper 25 which comprises a closing mechanism 28 which closes the air supply on receipt of the warning signal from the communication unit 27. The closing mechanism 28 can comprise a biased stop plate 29 which, when triggered, stops the air supply.

[0049] In one embodiment, the chimney fire extinguisher 1 is a heat-releasable chimney fire extinguisher 1. The chimney fire extinguisher comprises, in an embodiment shown in fig. 1-3 a fire extinguisher base 11 for attachment to a chimney cap or upper parts of the chimney flue. The chimney fire extinguisher 1 further comprises a support 2 which is releasably attached under the base 11. The support 2 can in one embodiment be a hinged lid 2. Other designs can e.g. be a plate or a net which is releasably attached to the fire extinguisher base 11. The fire extinguisher base 11 can be made up of the chimney cap itself.

[0050] As shown in fig. la and lb, the chimney fire extinguisher 1 further comprises an extinguisher holder 6 with extinguishing agent where the extinguishing agent holder 6 is supported by the support 2, and a fire signaling mechanism 31 to notify of a chimney fire. In one embodiment, the fire signaling mechanism 31 is a pretensioned arm with a flag 32, as shown in fig. la and 2a.

[0051] In one embodiment, the chimney fire extinguisher 1 comprises a heat-releasable unit 4, for example a wire which melts when exposed to heat at a trigger temperature TT as shown in Figs la and lb. If the heat-releasable unit 4 is triggered, the support 2 will fall and the extinguishing agent holder 6 will spread the extinguishing agent in the chimney flue 7 as indicated in fig. 2a, 2b and fig. 3. At the same time, the pretensioned arm 31 will spring up and a warning will thus take place.

[0052] The heat-releasable unit 4 may comprise a heat-releasable wire 4 which is fixed in a pre-tensioned arm with a flag 32 which is connected directly to the support 2 which keeps the fire extinguisher closed inside the chimney fire extinguisher 1, as shown in Fig. la. In case of chimney fire and high temperatures towards the support 2, this wire or the point where the wire is connected to the support 2 will melt and break the connection between the support 2 and the wire 4. The temperature TT can typically be 350 - 400 degrees Celsius. This means that a tin alloy can function as a heat-releasable wire 4.

[0053] In one embodiment (as shown in Figs la and 2a) the signaling mechanism 3 1 can be a pretensioned arm with a flag 32. Then the flag, which is pre-tensioned, will pop up and signal at the same time as the support 2 falls down and releases the fire- extinguishing agent in the chimney flue. In a version of this invention (as shown in Figs lb and 2b), the pretensioned flag is supplemented or replaced by an electronic fire alarm 3. Then the mentioned heat-releasable wire 4 can act as a circuit that breaks at a melting point and trigger the electronic signaling mechanism 31.

[0054] As shown in Figs lb and 2b, the fire extinguisher can further comprise a heat- releasable unit 4 which connects the support 2 and a fire signal trigger 12 to the base 11, where the heat-releasable unit 4 is configured to detach the support 2 and the fire signal trigger 12 so that the extinguishing agent is distributed in the barrel at the same time as the fire signaling mechanism 31 is activated.

[0055] In one embodiment, the fire signal trigger 12 includes an electrical circuit that can be broken by the heat-releasable unit. The heat-releasable unit 4 may be a heat- triggered wire 4 which is fixed to the electronic fire alarm 3 (fig. lb and 2b) which is connected directly to the support 2 which keeps the extinguishing agent holder 6 closed inside the chimney fire extinguisher 1. In case of chimney fire and high temperatures against the support 2, this heat-releasable wire or the point where the wire is connected to the lid will melt and break the circuit that runs in the fire signal trigger 12. In the event of a disconnection of the electronic signal in the fire signal trigger 12, an electronic warning will be triggered from the fire signaling mechanism 31. In one embodiment, the fire signaling mechanism 31 may comprise an electronic fire alarm 3 which sends a fire alarm in the form of digital signals.

[0056] In one embodiment, the heat-releasable unit 4 comprises a solder point that connects the fire signal trigger 12 and the support 2. The solder point will be able to replace the heat-releasable wire that triggers and the connection between the support 2 and the fire signal trigger 12.

[0057] In an embodiment shown in Figs 2a and 2b, the extinguisher holder comprises an extinguisher bag 6. The extinguisher bag 6 can be attached to a line 5 which is in turn attached to a heat-releasable fire extinguisher 1 or chimney cap and which enables the extinguisher bag 6 to fall freely down the chimney when triggered of the holder 2. The extinguisher bag 6 can further be configured to tear due to the G- forces that occur when the extinguisher bag is stopped in its free fall by line 5 when it is fully extended as indicated in fig. 2a and b.

[0058] In an embodiment shown in fig. 3, the line 5 is spun around the extinguishing agent bag 6, which will spin when falling due to the G-forces that occur similar to a yo-yo that is spun out in a fall. This will cause the bag to release extinguishing agent when thread 5 is fully spun out. In a chimney fire, there is a large draft of hot air up the chimney. It is therefore important for successful extinguishing that the chimney is exposed to the extinguishing agent in the lower part of the fire. The draft in the chimney will then drag the extinguishing agent up the chimney with it.

[0059] In one embodiment, the line 5 is a flat band spun around the extinguishing agent bag 6 or extinguishing agent box having holes that is covered by the flat band.

[0060] During long-term heating with wood, a layer of soot can form on the support 2 and the base 11 and prevent release. To increase the probability of successful release when the heat release unit 4 is released, the support 2 can be biased towards an open position by means of biasing means such as a torsion spring 14 or coil spring, see fig. 7-

[0061] Within the framework of the invention, there is room for a wide range of variations and adaptations based on e.g. different chimney caps and what kind of material they are made of, as well as variations in warning mechanisms. The invention will therefore be described in further detail in the form of embodiment examples with reference to the attached drawings.

[0062] References

[0063] 1 Chimney fire extinguisher

[0064] 2 Support / Hinged lid

[0065] 3 Electronic fire alarm

[0066] 4 Heat-releasable unit / Heat-releasable wire

[0067] 5 Line

[0068] 6 Extinguishing agent holder / Extinguishing agent bag

[0069] 7 Chimney flue

[0070] 8 Chimney hat

[0071] 11 Fire extinguisher base

[0072] 12 Fire alarm trigger

[0073] 14 Torsion spring

[0074] 20 Chimney fire sensor

[0075] 21 Chimney temperature sensor

[0076] 22 Air flow meter

[0077] 23 Oven

[0078] 24 Air supply channel

[0079] 25 Air supply stopper

[0080] 26 Draft regulation mechanism

[0081] 27 Communication unit

[0082] 28 Closing mechanism

[0083] 29 Stop plate

[0084] 30 Early warning unit

[0085] 31 Fire signaling mechanism

[0086] 32 Pretensioned arm with a flag

[0087] 33 Connection pipe

[0088] 34 secondary temperature sensor

Claims

CLAIMS1. System for early detection, warning and prevention of chimney fires in a chimney flue having one or more wood burners (23) attached where the system comprises: a chimney fire extinguisher (1) which is triggered when a chimney fire parameter reaches a trigger threshold value, a chimney fire sensor (20) to measure the chimney fire parameter in or above the chimney flue (7), in a connection pipe (33) between a wood burner and the chimney flue (7) or in the one or more wood burner (23) and its air supply, an air supply stopper (25) for the one or more wood burner (23) to stop the air supply to the wood burner, a communication unit (27) which receives a signal from the chimney fire sensor (20) and transmits an early warning signal when the chimney fire parameter reaches an early warning threshold value below the trigger threshold value, so that unnecessary triggering of the chimney fire extinguisher (1) can be prevented by adjusting the draft on the basis of the warning signal.

2. System according to claim 1 where the chimney fire sensor 20 is at least one of chimney temperature sensor (21), chimney gas sensor, chimney particle sensor, chimney optical sensor and air flow sensor.

3. System according to claim 1 or 2, where the warning signal from the communication unit (27) triggers an early warning unit (30) which gives an early warning in the form of an audio signal or light signal that can be perceived by a user of the one or more wood burner (23).

4. System according to claim 3 where the air supply stopper (25) is a draft regulation mechanism (26) supplied with the wood burner to be operated by a user when the user perceives the early warning.

5. System according to claim 1 or 2, where the air supply stopper (25) is a releasable or adjustable closing mechanism (28) which closes the air supply on receipt of the early warning signal from the communication unit (27).

6. System according to claim 5 where the releasable or adjustable closing mechanism (28) comprises a pre-tensioned closing plate (29) which is released and closes the air supply to the one or more wood burner (23) upon receipt of an early warning signal from the communication unit (27).

7. System according to any of the preceding claims, where the air supply goes through a air supply channel (24) with air intake on the outside of the building and the air supply stopper (25) is a damper (26) in the air supply channel (24) to the wood burner (23).

8. System according to any one of the preceding claims, where the chimney fire sensor (20) is an air flow meter (22) positioned in or above the chimney flue (7), in a connection pipe between a wood burner and the chimney flue (7) or in a wood burner (23) or the air supply channel (24).

9. System according to any of the preceding claims 1 - 7, where the chimney fire sensor (20) is a chimney temperature sensor (21) positioned in or just above the chimney flue (7) above the uppermost inlet of the one or more wood burner (23) connected to the chimney flue.

10. System according to claim 9, where the trigger threshold value is 350 degrees Celsius and the early warning signal is sent out from the communication unit (27) at 250 degrees Celcius.

11. System according to claim 9 or 10 comprising a secondary temperature sensor (34) positioned on the wood burner or the connection pipe (33).

12. Method for preventing unnecessary triggering of a chimney fire extinguisher (1) which is triggered by a trigger threshold value of a chimney fire parameter, where the method comprises the steps: a. measuring a chimney fire parameter in or above the chimney flue (7), in a connection pipe (33) between the one or more wood burner and the chimney flue (7) or in the one or more wood burner (23) and its air supply by means of a chimney fire sensor (20), b. sending an early warning signal to a communication unit (27) when a measured value of the chimney fire parameter reaches the early warning threshold value, c. sending a regulation command from the communication unit based on at least the measurements of the chimney fire sensor (20).

13. Method according to claim 12 when dependent on claim 11, wherein: step a comprises measuring the temperature in the chimney flue using the temperature sensor and measuring the temperature in the connection pipe (33) or the wood burner (23) using the secondary temperature sensor (21), step b comprises the measured value of the chimney fire parameter being the difference between the temperature sensor and the secondary temperature sensor (34), andstep c comprises sending the regulation command from the communication unit (27) to an early warning unit (30) based on the chimney temperature sensor (21) and the secondary temperature sensor (34). 14 Method according to claim 12 or 13, where the method further comprises sending the regulation command from the communication unit (27) to an early warning unit (30) which emits an audible or visible signal so that a user can close a manual air supply stopper for the wood burner.

15. Method according to claim 12 or, where the method further comprises sending the regulation command from the communication unit (27) to a releasable or adjustable closing mechanism (28).

Images