RU2626753C1 - Fire/overheat signaling detector with built-in remote operation checking device - Google Patents

Abstract

FIELD: physics.

SUBSTANCE: it is possible to use in various industries for signaling overheat and fire temperatures on different types of engines, compressors and other devices. In the fire or overheat signaling detector including a housing, in which, at least, two miniature absolute pressure indicators are located, each of the alarm devices comprises a membrane with an electrical contact located in front of it, enclosed in one common miniature chamber; a heat-sensitive tube filled with a gas with a metal core located therein capable of reversibly releasing and absorbing hydrogen with a temperature change, the open end of which communicates with the cavity of the housing communicating with the cavity of the miniature chambers by means of capillary tubes, a module of switches, the contacts of which are connected to the signaling detector contacts. According to the solution, signaling detectors with a clapping diaphragm are selected as signaling devices, which are set to the preset pressure threshold due to the choice of the membrane thickness. The core is placed in a braid made of silica thread, while the inner cavity of the housing and the static cavities of the miniature absolute pressure detectors are evacuated.

EFFECT: increasing the reliability of the signaling device and reducing the complexity of manufacturing, while providing a remote performance check.

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Description

The invention relates to fire alarm devices based on the pneumatic principle of operation, and is intended for use both in aerospace engineering and in other areas where early detection and prevention of foci of ignition is required. It can be used in various industries for signaling temperatures of overheating and fire on various types of engines, compressors and other devices.

One of the most well-known types of fire alarm sensors used in aeronautical engineering are sensors that contain a tube-shaped sensing element, the pressure change in which, caused by an increase in temperature, is transmitted to a pressure regulator that generates an alarming electric signal. A temperature-sensitive substance is placed in the sensitive tube, capable of emitting large volumes of gas with increasing temperature. Substances capable of saturation and evolution of gas include metal hydrides and pseudohybrids. The substance is in the form of a powder or granules that are saturated with hydrogen in the manufacture of the sensor. A characteristic feature of this substance is the ability to saturate with gas at low temperatures and the avalanche-like evolution of absorbed gas with increasing temperature, and with decreasing temperature, the released volume of gas is absorbed again. The sensor generates an electrical signal proportional to the change in pressure. The pressure regulator can be made in the form of one or more chambers, with a fixed metal membrane and with an electrode located opposite it. Due to the flexibility of the metal membrane under the action of pressure in the sensitive tube is able to bend and interrupt the electrical contact (see DE19927841, IPC G01K5 / 34; US513627, IPC G08B17 / 04).

The disadvantages of the known technical solutions are direct contact of the powder particles with the walls of the sensitive tube, which at high temperatures can lead to the welding of particles to the walls of the tube and reduce the sensitivity of the sensor by reducing the area of the inner surface of the tube in contact with the powder particles.

A pneumatic pressure sensor is known (see US5691702, IPC G08B17 / 04), which discloses the construction of a pneumatic pressure sensor using a single wire as a signal conductor between the control electronics and the switch assembly. The second path in the circuit between the two main components of the system is formed by a ground loop made by a ground connection to the control electronics unit and another ground connection to the sensor assembly. The completion of this path in the circuit is achieved through the general ground loop of the aircraft. The device contains two diaphragms in one module, switching contacts and a set of resistors in the electronic module of the sensor. This design eliminates the need for a second wire, which would serve as a return conductor passing between the control electronics unit and the sensor assembly, and also provides an additional opportunity to detect a short circuit to ground throughout the conductor between the two extreme points of the sensor circuit.

A pneumatic pressure sensor is also known (see US5136278, IPC G08B17 / 04) / The sensor contains a cylindrical container equipped with a gas tight chamber, on one end of which an alarm device is installed, and on the other end is an integrity control device. The alarm device contains a deformable membrane that normally has no electrical contact. The integrity control device contains a deformable membrane, normally having electrical contact with the second contact. The membrane of the integrity monitoring device and the membrane of the alarm device are located adjacent to each other, forming a gas-tight cavity, which is connected to the sensor tube at the same gas pressure. The membrane of the integrity control device responds to reduced gas pressure, moving away from the second contact and providing an indication of a malfunction. This configuration saves space and reduces weight.

A known version of the sensor described in patent CH371021, IPC A62C3 / 08 (also published as patent US3122728, patent GB961143). The sensor contains an actuator unit connected to the sensing tube. The executive unit is made in the form of one (or several) chambers, limited by a metal membrane with an electrode located opposite it, moreover, the membrane comes into contact with the electrode under the influence of pressure changes in the sensitive tube and breaks the contact.

The open end of the sensing tube is connected to the cavity of the chamber (s) of the actuator unit, with a fixed metal membrane, the sensing tube itself is made of metal and is filled with a substance that can be saturated with hydrogen at low temperatures and adsorb it with increasing temperature, and the substance is made in the form of a thread saturated hydrogen during the operation of manufacturing the sensor and entwined with a metal tape in the form of a spiral that protects the thread from welding to the walls of the sensitive tube at high rates Aturi.

In the known design, it is possible that the sensor is triggered with a delay due to a spirally rolled metal strip that lowers the temperature threshold of the sensor sensitivity.

A known fire alarm sensor described in patent US5691702, IPC G08B17 / 04. A distinctive feature of the known sensor is the filling of a sensitive tube containing a substance capable of saturation with hydrogen, an inert gas, such as helium. The presence of inert gas allows you to generate an alarm signal in case of mechanical violation of the integrity of the sensitive tube. In order to generate an alarm signal about a violation of the integrity of the tube, a separate chamber is provided in the executive unit connected to the tube in which the metal membrane is in constant contact with the opposing electrode. If the tube is damaged, an inert gas leaks in the chamber, accompanied by a decrease in pressure with the membrane disconnected from the electrode and the formation of the corresponding signal.

A known sensor described in patent RF2438184, in which the sensitive tube is made of metal and filled with a substance capable of saturating with hydrogen at low temperatures and absorbing it when heated in a given temperature range, the substance is made in the form of a zirconium filament saturated with hydrogen during the manufacture of the sensor . The thread is placed in a braid made of basalt threads, and the sensitive tube is filled with helium.

In the known construction, there is a possibility of false alarms of the signaling device (not in a given temperature range) due to the relatively low thermal conductivity of the basalt thread, which reduces the temperature threshold of the sensitivity of the signaling device. The roughness and brittleness of a basalt thread creates technological difficulties when pulling a basalt braided thread into a heat-sensitive tube, since the length of the tube for aircraft can range from 7 m to 12 m. At the same time, the presence of a large number of micropores and reactive metal oxides in the basalt fiber can lead to absorption a certain amount of hydrogen released from the metal filament, reducing the alarm pressure. Zirconium is a relatively expensive material and, in terms of its ability to saturate with hydrogen, is inferior to other metals capable of being saturated with hydrogen, which limits the possibilities of its use in fire alarm sensors.

Closest to the proposed technical essence and the achieved result is a pneumatic pressure sensor for use in an overheat or fire warning system with a switch module, comprising a gas-tight manifold functionally connected to a sensitive tube filled with gas; alarm supply switches located directly adjacent to each other across the collector and responsive to an increase in gas pressure in said sensing tube to indicate an appropriate heating condition; each of these alarm triggers consists of a first flexible membrane, typically not in contact with an external surface, with a first electrical contact located outside the collector. This first flexible membrane responds to increased pressure from the manifold and moves toward the first contact to indicate overheating status. The sensor contains a failure signaling switch for indicating an emergency situation when the pressure of the gas in the sensor tube drops, which consists of a second flexible membrane, usually touching its external surface with a second electrical contact located outside the collector. This second flexible membrane responds to a decrease in gas pressure and moves away from the second contact to indicate a malfunction. And the collector, the first and second membranes mentioned, and the corresponding first and second electrical contacts form a switching module. The switching module further comprises a corresponding forming tube for each flexible membrane. This forming tube has a first end opening into a sealed gas-tight compartment located behind the corresponding membrane to transfer enough pressure to deform the membrane (see application US2009 / 0236205, IPC H01N35 / 24).

The device has insufficient sensitivity to the effects of temperature when a specified temperature interval is reached. In addition, it does not provide the ability to provide remote health checks.

The technical problem of the invention is the creation of a fire / overheating detection device that works reliably under vibration and temperature extremes, typical for operating conditions of aircraft, which has a higher sensitivity to temperature when a specified temperature interval is reached, with adjustable hysteresis.

The technical result consists in increasing the reliability of the signaling device and the reduced complexity of manufacturing while providing remote verification of performance.

The problem is solved in that in a fire / overheating detection device, including a housing in which at least two miniature absolute pressure sensors are located, each of the indicators contains a membrane with an electrical contact located opposite it, enclosed in one common miniature camera; a heat-sensitive tube filled with gas with a core made of metal capable of reversibly releasing and absorbing hydrogen when the temperature changes, the open end of which communicates with the cavity of the housing, communicating with the cavity of the miniature chambers using capillary tubes, a switch module, the contacts of which are connected to the contacts of the signaling devices , according to the solution, signaling devices with a popping membrane are selected as signaling devices, the membranes are configured to a predetermined pressure response threshold by selecting t membrane thickness, the core is placed in a braid made of silica filament, while the inner cavity of the body and the static cavity of miniature absolute pressure alarms are evacuated.

The signaling device further comprises a signaling device operability checker made in the form of a nichrome wire, helically wound along the length of the heat-sensitive tube over a silica braid 0.2-0.3 mm thick with a winding pitch of 1-1.2 mm, while the ends of the nichrome wire are brought into the signaling device housing through the hermetic outlet and output to the connector in the housing cover for supplying voltage.

Hydrogen is selected as the gas. As the core used titanium thread. The number of miniature cameras can be three.

The invention is illustrated by drawings, in which Fig. 1 shows a diagram of a fire / overheat detection signaling device, in Fig. 2 is a design of a fire / overheating detection device, FIG. 3 is a miniature absolute pressure chamber; FIG. 4 - heat-sensitive tube. The positions in the drawings indicate the positions:

1. Heat-sensitive tube;

2. Executive unit;

3. Cover;

4. The ring;

5. Capillary tubes;

6. Sleeve;

7. Mounting plate;

8. Hairpin;

9. Miniature pressure signaling device ("FAILURE");

10. Miniature pressure signaling device ("OVERHEAT");

11. Miniature pressure signaling device ("FIRE");

12. The board with resistors;

13. The insulator;

14. Casing;

15. Contact screw;

16. Connector;

17. Wire;

18. Germovyvod for connecting a device for checking the operability of the signaling device;

19. Dynamic cavity;

20. Membrane;

21. Static cavity;

22. Electrical contact;

23. Germovyvod cameras;

24. The metal shell;

25. Titanium thread;

26. A silica filament braid;

27. Nichrome wire.

The proposed fire / overheating detection device (Fig. 1) comprises an actuating unit 2 connected to a heat-sensitive tube 1, as well as two (or more) miniature absolute pressure sensors and an integrated remote operability check device. The executive unit 2 includes a housing, two or more miniature absolute pressure detectors 9, 10, 11, a board with three resistors 12, a contact screw 15, a connector 16 for connecting a health check device, a leak-out terminal 18 for connecting a health check device for a signaling device.

Miniature absolute pressure switches 9, 10, 11 (Fig. 2), are mounted in the actuator block on the studs 8 installed in the ring 4 using the sleeve 6 and the mounting plate 7. Three capillary tubes 5 are welded into the ring 4 for communication with the dynamic cavity 19 of the corresponding miniature absolute pressure switch (figure 3). Thus, the dynamic cavity of each miniature absolute pressure switch, limited by the membrane 20 (Fig. 3), communicates with the cavity of the heat-sensitive tube through the corresponding capillary tube. The composition of the miniature absolute pressure switch (Fig. 3) includes a membrane 20, which is able to move under the influence of a pressure change and contact with the opposite electrical contact 22, isolated from the housing by means of a chamber pressure seal 23, thereby breaking or shorting the electrical circuit depending on its provisions regarding contact.

Functional connection with the alarm system and the issuance of signals “FAILURE”, “FIRE”, “OVERHEAT” occurs through a board with resistors 12 and a contact screw 15. The voltage supply and disconnection of the device for checking the operability of the signaling device are carried out using the connector 16 and the pressure relief 18.

The cavity of the miniature absolute pressure switch is divided by a membrane 20 into a dynamic 19 and a static 21. The dynamic cavity 19 is communicated using a capillary tube 5 with a cavity of the heat-sensitive tube 1, the static cavity is evacuated. The fire / overheating detection device detects three types of temperature / pressure status, which correspond to the three values of the output resistance, and generates the corresponding alarm signals, and also has a built-in remote operability check device. If the temperature of the environment surrounding the heat-sensitive tube increases or the heat-sensitive tube undergoes intense heating, the internal pressure in the heat-sensitive tube and, accordingly, in the dynamic cavities of the miniature pressure transmitters of the absolute pressure of the actuator unit starts to increase in proportion to the temperature increase. When the pressure inside the heat-sensitive tube reaches the set value, the membrane is activated and closes the electrical contact in the miniature absolute pressure switch 10 responsible for the alarm "OVERHEAT" in the Executive unit. This leads to switching current in the electrical circuit for the passage of the signal “OVERHEAT” through the board with resistors 12 and the contact screw 15 to the alarm system. The board with resistors contains three resistors 12 (Fig. 1), each of which is in electrical communication with the electrical contact of the corresponding miniature absolute pressure switch 9, 10, 11 ("FAILURE", "OVERHEAT", "FIRE"), switching current when closing / opening the corresponding electrical contact. Another type of temperature / pressure state occurs when a flame is exposed to a high-intensity section of a heat-sensitive tube for a short period of time or when the overall significant excess of the ambient temperature is above the set limits (above the temperature at which the “OVERHEAT” signal is averaged over the length of the signaling device). In this case, a rapid release of a large volume of gas from the titanium filament occurs. In the miniature absolute pressure switch 11, an increase in pressure occurs, as a result of which the membrane moves and closes the electrical contact, switching the electric current in the circuit to pass the “FIRE” signal. The third, pressure-sensitive miniature absolute pressure switch 9, which is part of the pressure control unit, is under constant pressure (the membrane is closed with an electrical contact), which is maintained in the heat-sensitive tube and capillary tubes. In the event of a violation of the integrity of the heat-sensitive tube, a gas leak occurs, accompanied by a decrease in pressure with the membrane disconnected from the electrical contact and the formation of the corresponding “FAILURE” signal. In the above example, all three miniature absolute pressure switches included in the Executive unit have a static 21 and dynamic cavity 19 (figure 3). The dynamic cavity is bounded by a membrane. Moreover, the response pressure of the membranes of miniature absolute pressure detectors responsible for the output of the “FIRE” and “OVERHEAT” signals is controlled by the thickness of the membranes, selected so that each of them occurs at a pressure corresponding to the achievement of a predetermined range of positive temperatures. The thickness of the membrane of the miniature absolute pressure signaling device responsible for issuing the “FAILURE” signal is selected so that the pressure of the gas filling the heat-sensitive tube, capillary tubes, and the dynamic cavity of the specified miniature absolute pressure sensor keeps the membrane closed with an electrical contact. The advantage of the applied membranes is the possibility of regulating the hysteresis, which ensures the accuracy of their operation upon reaching a predetermined pressure value.

As such membranes, flapping membranes can be used, for example, according to the patent of the Russian Federation 2293298, providing the necessary accuracy of operation.

After lowering the ambient temperature, the internal gas pressure in the heat-sensitive tube drops and the contacts of the miniature absolute pressure switches “FIRE” and “OVERHEAT” open, the indicator returns to its normal state (the contact of the “FAILURE” indicator remains closed). During normal operation of the detector, the cycle is repeated many times.

In order to increase the reliability of the fire / overheating detection device under vibration and temperature differences typical of the operating conditions of aircraft, the static cavity of all three miniature absolute pressure sensors and the internal cavity of the actuator unit (housing), in which the miniature absolute pressure sensors are located, is evacuated.

To reduce the complexity of manufacturing a fire / overheat detection alarm and to increase the accuracy of operation upon reaching a predetermined interval of positive temperatures, the composition of the gaseous medium filling the heat-sensitive tube is homogeneous and does not contain inert gas. A homogeneous gas environment consisting entirely of hydrogen provides a higher degree of absorption of hydrogen by titanium filament when filling the heat-sensitive tube with gas and a complete release of absorbed gas when the specified temperature range is reached, thereby ensuring the necessary pressure in the heat-sensitive tube and reliable operation of the corresponding miniature absolute pressure switch .

In a specific example, the metal shell 24 of the heat-sensitive detector tube (Fig. 4) is made of stainless steel, the thread 25 is made of titanium and placed in a braid of silica thread 26. The choice of titanium as the material for the manufacture of the thread is due to its high ability to absorb hydrogen in a given positive temperature range.

The result is achieved due to the higher ability of the titanium filament to saturate with hydrogen, increased thermal conductivity of the silica filament braid, which provides efficient heat transfer from the walls of the sensitive tube to the titanium powder, into which the titanium filament turns when it is saturated with hydrogen and facilitates the process of drawing the silica filament with a titanium filament into heat-sensitive tube due to flexibility, smooth shape of silica filament, lack of pores and roughness on its surface (unlike ba alto threads), the presence of health check unit.

The heat-sensitive tube (figure 4) is made of stainless steel, the outer diameter of the tube is 1.5mm-2mm, the wall thickness is 0.2-0.5mm. The length of the tube, depending on the design features of the aircraft, is from 7 to 12 m. The thickness of the silica yarn in the braid is 0.1 mm, the number of threads in the braid is eight. With the specified number of threads, the greatest technical result is achieved. The thermal conductivity of the braid increases with increasing number of threads due to an increase in the contact area with the inner surface of the tube. However, the increase in the number of filaments in the braid is limited by the thickness of the titanium filament, the magnitude of which is 0.6-0.8 mm.

The fire / overheat detection device with an integrated remote operability check device is arranged as follows (Fig. 2).

A heat-sensitive tube 1 with a titanium braided thread made of silica thread, over which a nichrome wire is helically wound, is connected through the cap 3 through the channels of the ring 4 with capillary tubes 5 connected to the dynamic cavities of miniature absolute pressure transmitters 9,10,11 through one end. The second end of the heat-sensitive tube communicates with the line for degassing and filling the tube with hydrogen. After degassing and heating, hydrogen is pumped into the heat-sensitive tube. A titanium filament in a silica filament braid placed in a heat-sensitive tube is saturated with hydrogen and turns into titanium hydride - a powdery substance held in a thermosensitive tube by a silica filament braid and preventing sintering of powder particles from the inner surface of the tube when heated to high temperatures, as well as providing effective heat transfer from the walls of the tube to titanium hydride powder. Then the second end of the heat-sensitive tube is welded and the detector is ready for operation.

The design of the signaling device is additionally equipped with a built-in remote device for checking its operability, simulating the actual process of overheating of the heat-sensitive signaling tube, which is implemented as follows (Fig. 4).

Along the length of the heat-sensitive tube over the silica braid 26, into which the hydrogenated titanium thread 25 is placed, nichrome wire 27 is helically wound with a diameter of 0.2-0.3 mm with a winding pitch of 1-1.2 mm. Due to the elasticity of the silica braid, the nichrome wire is wound over the silica braid with a certain tightness to facilitate the process of pulling the titanium filament in a silica braid with a nichrome wire into the shell of a heat-sensitive tube.

The ends of the nichrome wire (see figure 2) are introduced into the body of the signaling device through a pressure terminal 18 and output to the connector 16, through which the device is supplied with voltage. When voltage is applied to the nichrome wire, it is heated to a temperature of 650-700 ° C, sufficient to start the process of hydrogen evolution in the heat-sensitive tube from the hydrogenated titanium filament. The evolution of hydrogen increases the internal pressure in the heat-sensitive tube, and accordingly in the dynamic cavity of the miniature detector, responsible for the alarm "OVERHEAT" and leads to the issuance of the corresponding signal to the contact screw 15.

At the beginning, the evolution of hydrogen as a result of heating the nichrome wire increases the internal pressure in the heat-sensitive tube, and, accordingly, in the dynamic cavity of the miniature signaling device responsible for the “OVERHEAT” signaling and leads to the output of the “OVERHEAT” signal to the contact screw 15.

As a result of further heating of the nichrome wire and an increase in the internal pressure in the heat-sensitive tube, the pressure in the dynamic cavity of the miniature detector responsible for the “FIRE” alarm increases, which leads to the generation of the “FIRE” signal to the contact screw 15.

The output of “OVERHEAT” and “FIRE” signals indicates the serviceability and operability of the fire / overheat signaling device.

Immediately after the “FIRE” alarm is triggered, the supply voltage supplied to the health check device is turned off. At the same time, the temperature in the heat-sensitive tube with the nichrome wire wound decreases, the pressure in the tube, and accordingly in the miniature warning devices “FIRE” and “OVERHEAT”, drops, the output of the signals “FIRE” and “OVERHEAT” stops.

The built-in remote health check device allows you to check the operability of the fire / overheat signaling device throughout the entire life of the signaling device.

In the implemented design of the built-in remote device for checking the operability of the fire / overheat signaling device, the thickness of the nichrome wire was 0.3 m, the spiral winding pitch was 1.2 m. With this combination of device parameters, the required speed and temperature of heating of the heat-sensitive tube are ensured, which ensures the completeness and reliability of the operation test .

Thus, in addition to the device for monitoring the integrity of the sensing element built into the detector, there is an external operational diagnostic device that allows testing the functioning of the detector as a whole. Testing takes place remotely and does not require the intervention of technical services, which reduces the time required for pre-flight diagnostics of the aviation object as a whole.

Claims (5)

1. A fire or overheating detection device, comprising a housing in which at least two miniature absolute pressure sensors are located, each of the sensors contains a membrane with an electrical contact located opposite it, enclosed in one common miniature camera; a heat-sensitive tube filled with gas, with a core of metal placed inside it, capable of reversibly releasing and absorbing hydrogen when the temperature changes, the open end of which communicates with the cavity of the housing, communicating with the cavity of miniature chambers using capillary tubes, a switch module, the contacts of which are connected to the contacts signaling devices, characterized in that signaling devices with a popping membrane are selected as signaling devices, the membranes are configured to a predetermined pressure threshold by selecting A membrane of thickness, the core is placed in a braid made of silica filament, while the internal cavity of the body and the static cavities of miniature absolute pressure detectors are evacuated. 2. The signaling device according to claim 1, characterized in that it contains a device for checking the operability of the signaling device, made in the form of a nichrome wire, helically wound along the length of the heat-sensitive tube over a silica braid with a thickness of 0.2-0.3 mm with a winding pitch of 1–1, 2 mm, while the ends of the nichrome wire are brought into the body of the signaling device through a pressure seal and output to the connector in the housing cover to supply power. 3. The detector according to claim 1, characterized in that hydrogen is selected as the gas. 4. The signaling device according to claim 1, characterized in that a titanium wire is used as the core. 5. The fire detector according to claim 1, characterized in that the number of miniature cameras is three.

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