Patent Application
20250041642
The present disclosure relates generally to suppression of fires in normally occupied areas, and more particularly to a fire suppressing gas generators, systems, and arrangements.
For regulatory approval, in most countries, devices for fire suppression using inert gas generators are required to be below a certain surface temperature once the gas generator is actuated. Devices which activate a sodium azide and iron oxide mixed pressed grain to generate nitrogen gas, tend to create substantial surface heat, but only after discharge and until the gas generator body (inner housing component) cools to ambient temperature. In most cases, such devices are enclosed especially for transportation. There is a need for a fire suppressing gas generator that meets health and safety standards, especially for transportation, but that does not impede the expulsion of fire suppressing gas, does not have or impart substantial thrust bias, and that has an exterior surface that can be maintained within regulated temperatures.
There is also a need for fire suppressing gas generator systems and arrangements that are useful for retaining and/or actuating multiple gas generators.
In accordance with an aspect, there is provided a fire suppressing gas generator comprising: a housing structure comprising: an inner housing component comprising an array of discharge ports distributed thereon; an outer housing component encapsulating the inner housing component and comprising an array of openings distributed thereon; and spacing structure extending between the inner housing component and the outer housing component to maintain the inner housing component and the outer housing component in a fixed spaced relationship; and a fire suppression subsystem comprising: a filter disposed within the inner housing component and spaced from an interior wall of the inner housing component; a plurality of propellant grains inside the filter, the plurality of propellant grains comprising at least one column of stacked propellant grains, each of the propellant grains comprising a pressed mixture of sodium azide and iron oxide; and at least one ignition device associated with the propellant grains, wherein the propellant grains when ignited by the ignition device generate a fire suppressing gas which passes through the filter and out of the discharge ports of the inner housing component; wherein the distributions of the discharge ports of the inner housing component and the openings of the outer housing component provide substantial thrust neutrality to the fire suppressing gas generator when the fire suppressing gas passes out of the housing structure.
In accordance with another aspect, there is provided a fire suppression system comprising: a fire suppression portion comprising a plurality of the fire suppressing gas generators; and an actuation portion causing staged actuation of the plurality of the fire suppressing gas generators.
In accordance with another aspect, there is provided a fire suppression arrangement comprising: a fire suppressing gas generator; and a frame physically retaining the fire suppressing gas generator.
In accordance with another aspect, there is provided a fire suppression system comprising: a stack of multiple of the fire suppression arrangements.
In accordance with another aspect, there is also provided a fire suppressing gas generator comprising: a housing structure comprising an inner housing component having an array of discharge ports distributed thereon; a fire suppression subsystem hermetically sealed within the inner housing component and comprising: a filter disposed within the inner housing component and spaced from an interior wall of the inner housing component; a plurality of propellant grains inside the filter, the plurality of propellant grains comprising at least one column of stacked propellant grains, each of the propellant grains comprising a pressed mixture of sodium azide and iron oxide; and at least one ignition device associated with the propellant grains, wherein the propellant grains when ignited by the ignition device generate a fire suppressing gas which passes through the filter and out of the discharge ports of the inner housing component; and at least one inert test gas sealed within the inner housing component; and at least one normally closed valve extending from an exterior of the inner housing component to the interior of the inner housing component for, when caused to be opened, extracting a quantum of the inert test gas thereby to confirm the hermetic sealing of the fire suppression subsystem.
In accordance with another aspect, there is also provided a fire suppressing gas generator comprising: a housing structure comprising a cylindrical inner housing component having an array of discharge ports distributed thereon; a fire suppression subsystem within the cylindrical inner housing component and comprising: a cylindrical filter disposed within the inner housing component and spaced from an interior wall of the cylindrical inner housing component; a plurality of propellant grains inside the filter, the plurality of propellant grains comprising at least one column of stacked propellant grains, each of the propellant grains comprising a pressed mixture of sodium azide and iron oxide; and at least one ignition device associated with the propellant grains, wherein the propellant grains when ignited by the ignition device generate a fire suppressing gas which passes through the filter and out of the discharge ports of the cylindrical inner housing component; a ring at each of opposite ends of the cylindrical inner housing component for centering respective ends of the cylindrical filter within the cylindrical inner housing component; an end cap connectable to each of opposite ends of the cylindrical inner housing component for retaining the fire suppression subsystem within the cylindrical inner housing component; and a gasket within a respective ring at each of the opposite ends of the cylindrical inner housing component and between a respective end cap and the cylindrical filter, wherein prior to connecting of the end caps and the cylindrical inner housing component each gasket extends beyond the respective ring and is compressible between the respective end cap and the cylindrical filter.
Various examples are described.
Examples will now be described more fully with reference to the accompany drawings, in which:
In a first end of the outer housing component 14 is a centrally-positioned hole 35, the edge of which accommodates and supports a washer 36. Hole 35 and washer 36 are sized to enable electrical access to an initiator assembly (not shown in
In the second end of the outer housing component 14 is a centrally-positioned hole, the edge of which accommodates and supports a washer 22. This hole and washer 22 are sized to enable physical access to a valve 66 that is supported within an end cap 68 of inner housing component 12 and extends out of the interior inner housing component 12 to an exterior of inner housing component 12 when generator 10) is assembled. Valve 66 is normally closed. Access to valve 66 enables one or more inert test gas such as Helium to be injected through valve 66 when temporarily opened into an otherwise hermetic sealed gas-tight assembled inner housing component 12. Insertion of an inert test gas to be retained within inner housing component 12 creates a small positive pressure within the sealed inner housing component 12 that serves to inhibit ingress of ambient air/moisture, and allows for subsequent periodic checks of the hermetic seal integrity of inner housing component 12 to be conducted. For example, at defined intervals, a small quantum of the previously-inserted inert test gas (for clarity, the test gas is not inserted in sufficient quantities to itself serve as an effective fire suppressing gas, but just as a seal integrity “indicator”) may be drawn via valve 66 out of inner housing component 12 to confirm its manufactured hermetic seal is maintained, by this inert test gas being retained and thus having not since leaked out of inner housing component 12 to be replaced with ambient air and moisture. In the event that, during a particular check, the particular inert test gas is detected, the gas-tight hermetic seal integrity of inner housing component 12 can be confirmed. If the particular inert test gas is not detected, then it may be decided that the inner housing component 12 has lost integrity such that the reliability of the rest of the components housed within inner housing component 12 to generate a fire suppressing gas (i.e., the propellant grains; the initiator grain; etc.) cannot be confirmed. This may lead to replacement or refurbishment of the generator 10), in accordance with appropriate rules and regulations. One or multiple such valves may be provided in a given fire suppressing gas generator.
In this example, valve 66 is a Schrader valve. In other examples, a valve of a different type could be deployed, such as a Presto valve.
Inner housing component 12 may be inserted into outer housing component 14 via the open second end, as will be described. The multi-piece mesh also has a cap 28, itself including bars and supported on first end ring 30 of the spacing structure so as to together form a closure 26. Screws 32 and 34 enable fastening of closure 26 against the outside of sleeve 46.
The generally-uniform distribution of the openings 18 on outer housing component 14 facilitates negligible thrust bias to outer housing component 14 when a fire suppressing gas passes out of openings 18. For example, thrust from a given quantum of gas exiting from one of the openings 18 and that would tend to propel outer housing component 14 in a particular direction is generally counteracted by thrust from another quantum of gas exiting another one of the openings 18 that is opposite outer housing component 14 from the one opening 18. In order to reduce the chance that a person or an object may come into contact with inner housing component 12 while fire suppressing gas is being generated, openings 18 may be sized smaller than, for example, the typical human finger, while being of sufficient size to enable the egress of fire suppression gas from within outer housing component 14 without undue internal pressure after ignition, and in a thrust neutral manner.
In this example, inner housing component 12 includes an open-ended cylindrical sleeve 46 that is formed of steel, and which includes arrays of discharge ports 48 distributed across its surface and each extending from its exterior to its interior. In this example, the discharge ports are arranged in multiple rows. The distribution of discharge ports 48 provides substantial thrust neutrality (i.e. facilitates negligible thrust bias) to the inner housing component 12 when a fire suppressing gas passes out of the discharge ports 48. In particular, discharge ports 48 are positioned on sleeve 46 in locations such that as fire suppressing gas is exiting from discharge ports 48 under pressure, inner housing component 12 does not tend substantially to be physically propelled in any particular direction. For example, thrust from a given quantum of gas exiting from one of the discharge ports 48 that would tend to propel inner housing component 12 in a particular direction tends to be counteracted by thrust from another quantum of gas exiting another one of the discharge ports 48 that is opposite inner housing component 12 from the one discharge port 48. Multiple discharge ports 48 are provided, and are sized, positioned and of a sufficient number to enable the egress of fire suppression gas from within inner housing component 12 without undue internal pressure after ignition, and in a thrust neutral manner.
End cap 68 has, at its periphery, threads which match the inside diameter threads of sleeve 46, and when screwed together, end cap 68 comes into contact with the top of a filter-pad-centering-ring 72. Filter-pad centering-ring 72 provides the benefit of maintaining the plenum spacing (discussed in further detail below) at its end of a filter pad 52 after assembly, as well as disciplining the positioning of a gasket 74 to be inserted between an end of filter pad 52 and end cap 68. Gasket 74 is thicker than the height of filter-pad-centering-ring 72 in that it extends beyond filter-pad centering-ring 72 when sitting atop of an end of a filter-pad 52 inserted within sleeve 46. As such, when the surface of end cap 68 presses down against gasket 74 a good seal is created against the internal propellant grain to block by-product (gas; particulate) from bypassing filter-pad 52 during actuation. In this example, gasket 74 is a silicone gasket, placed inside filter-pad-centering-ring 72, inserted atop respective end filter-pad 52 and sleeve 46 to retain components within sleeve 46. Similarly, an end cap 38 has, at its periphery, threads that match inside diameter threads of sleeve 46 and when screwed together, end cap 38 comes into contact with the top of a filter-pad-centering-ring 64. Filter-pad centering-ring 64 provides the benefit of maintaining the plenum spacing at its end of filter pad 52 after assembly, as well as disciplining the positioning of a gasket 62 to be inserted between the respective end of filter pad 52 and end cap 38. Gasket 62 is thicker than the height of filter-pad-centering-ring 64 in that it extends beyond filter-pad centering-ring 64. As such, when the surface of end cap 38 presses down against gasket 62 a good seal is created against internal propellant grain to block by-product (gas: particulate) from bypassing filter-pad 52 during actuation. In this example, gasket 62 is a silicone gasket, placed inside filter-pad-centering-ring 64, inserted atop respective end filter-pad 52 and sleeve 46 to retain components within sleeve 46. End cap 38 has a centrally-positioned bore 40) enabling electrical access to initiator assembly 60 which, as will be described, interfaces with propellant grains and can ignite the propellant grains within filter-pad inner housing component 12 when sufficient electrical power is applied to initiator assembly 60. Initiator assembly 60 may be a squib.
As explained briefly above, spacing structure extends between inner housing component 12 and outer housing component 14 to maintain inner housing component 12 and outer housing component 14 in a fixed spaced relationship. It is preferable that when inner housing component 12 is encapsulated within outer housing component 14, external objects—whether inanimate or animate—are not generally able to easily come into contact with inner housing component 12, as inner housing component 12 will tend to become quite hot when fire suppression is being generated inside of it. The spacing structure serves primarily to physically and thermally separate outer housing structure 14 from inner housing structure 12 so that heat imparted to inner housing structure 12 during generation of fire suppressing gas is not substantially transferred to outer housing structure 14. It will be appreciated that some of the heat carried by the fire suppressing gas itself may indeed be imparted to outer housing component 14 as the fire suppressing gas passes through openings 18, but this is expected to be a far lower amount of heat than would be borne by inner housing component 12. Furthermore, due to the size of openings 18 relative to the size of the bars of the cage, heat transferred to outer housing component 14 from fire suppressing gas can, in turn, be transferred to the ambient very quickly and efficiently after the rapid passage of the fire suppressing gas.
During assembly of fire suppressing gas generator 10, second end ring 70 of the spacing structure may be placed inside cylindrical cup portion 16 of the multi-piece cage prior to insertion of inner housing component 12 and against the inward-facing portion of its closed first end. Second end ring 70 is dimensioned to correspond in shape and size to the cylindrical shape of outer housing component 14, and in its inward-facing surface (opposite its outward-facing surface) has an annular shelf 71 forming an annular region spaced inwardly from its periphery for receiving and supporting a respective end of inner housing component 12. The amount that annular shelf 71 is spaced inwardly from its periphery corresponds to the fixed spaced relationship between inner housing component 12 and outer housing component 14.
Similarly, first end ring 30 of the spacing structure is also dimensioned to correspond in shape and size to the cylindrical shape of outer housing component 14. During assembly of fire suppressing gas generator 10), first end ring 30 may be placed atop a respective end of inner housing component 12 after inner housing component 12 has been inserted into outer housing component 14 and received by second end ring 70. First end ring 30 is at least partially inserted into the interior of outer housing component 14 until it rests against a respective end of inner housing component 12. More particularly, like second end ring 70, on its inward-facing surface (opposite its outward-facing surface), first end ring 30) of the spacing structure also has an annular shelf (not shown) forming an annular region spaced inwardly from its periphery for receiving and supporting the respective end of inner housing component 12. Similarly, the amount that the annular shelf of first end ring 30 is spaced inwardly from its periphery corresponds to the fixed spaced relationship between inner housing component 12 and outer housing component 14.
Each of first end ring 30 and second end ring 70 is formed of a material that is a poor heat conductor, but that can also maintain its physical rigidity even when exposed to pressure and heat from fire suppressing gas. In this example, the components of first end ring 30 and second end ring 70 that contact inner housing component 12 are formed of wood, pre-coated with a fire retardant paint. Other materials for rings 30, 70 could be used that provide sufficient structural rigidity while also resisting buckling/melting/combustion before, during, or after fire suppression. With wood in particular, wood combustion and even charring requires oxygen which will not substantially be present after ignition due to the primarily nitrogen content being forced into the region on combustion of the propellant grains. Furthermore, generally wood tends to combust at around 750 F (Fahrenheit), whereas during tests it has been found that the inner housing components such as those described herein reach only about 500 F after discharge such that wood in the vicinity would, at most, slightly char and would not combust. Again, other material options for rings 30 and 70, and for other embodiments of spacing structures, may be chosen.
In turn, filter pad 52 surrounds a plurality of propellant grains 56. Each propellant grain 56, in this example, is a disk/puck shaped grain and is stacked against others in a cylindrical format. In this example, there is a single stack of propellant grains 56. Furthermore, in this example, each propellant grain 56 is a pressed mixture of sodium azide and iron oxide. For its part, filter pad 52 functions to inhibit escape of particulates from the interior of inner housing component 12 when grains 56 are ignited, and also to absorb some of the heat generated upon ignition of the grains 56. In this example, propellant grains 56 each include a number of small bores therethrough for providing greater overall surface area of the grains 56 and thus greater overall exposure to oxidation of the sodium azide and iron oxide of which they are made, facilitating faster ignition. It will be appreciated that, in other examples, propellant grains may not have any of these smaller bores or “pin holes”, in which case, all other things being equal, the propellant grains would not ignite as quickly due to having less initial exposed surface area. Therefore, in general it will be appreciated that overall timing of gas production and its duration can be at least partially controlled through the grain production process, in particular by producing grains that have a higher or lower exposed surface area. This may be done using different overall shape envelopes or through the provision of the smaller bores. It will also be appreciated that some grains in a given fire suppressing gas generator may have such bores, and others may not, or still others may have slightly larger bores and/or different overall shape envelopes, in order to provide the manufacturer with control over the speed and duration of production of fire suppressing gas upon ignition. It will be appreciated, however, that generally puck-shaped grains are straightforward to make and to stack, do not have sharp edges that can easily break off of the whole during assembly, transportation, and installation, and can be made to provide a useful surface area to volume combination.
An end grain 58, which may also be a pressed mixture of sodium azide and iron oxide, has a central bore 59 dimensioned to receive a portion of an initiator assembly 60. Initiator assembly 60 itself serves as an ignition device that sparks when sufficient electrical current is imparted via a wire 61 and thereby ignites the end grain 58 with which it is associated thereby to set off a chain reaction of ignition of the propellant grains 56 in the cylindrical stack. Ignition of the pressed sodium azide and iron oxide in the propellant grains 56 causes a very rapid chemical reaction resulting in the release of a fire suppressing gas.
Also shown in
In some implementations it may be useful to, when a fire is detected, cause simultaneous ignition of all of the respective initiator assemblies of all of the generators of fire suppression system 490. However, in this example, actuation portion 600 contains components that cause staged—or sequential—actuation of the multiple generators 200, thereby to cause staged emission of fire suppression gas into the dwelling. Staged actuation includes relaying ignition power individually to respective ones of the fire suppressing gas generators at spaced intervals i.e., at different times, thereby to cause respective ignitions of the generators at different times. Enabling the fire suppressing gas generators to be actuated sequentially may provide lower magnitude overall pressure shock to a dwelling as compared with that which may occur if simultaneously actuating multiple fire suppressing gas generators. For example, a first of a series of spaced actuations may increase pressure within the dwelling temporarily for a short time and, upon the pressure dropping again as air/fire suppressing gas is able to exit through dwelling vents and the like, a second actuation may be conducted causing the pressure in the dwelling to again rise before dropping again, and so forth. Providing an actuation portion 600 that can be configured to provide staged actuation may be very useful for enabling the overall fires suppression system 490 to be configured to suit a particular dwelling's dimensions and ventilation configuration. In this example, actuation portion 600 includes an electronic circuit 600 itself including a number of components, that interfaces with a signal line 580 that is electrically connected or in communication with a detector (not shown) and/or with a fire suppression control panel (not shown) that sends an actuation signal to electronic circuit 600 upon detection of a fire. Electronic circuit 600 also interfaces with an electrical power supply (not shown) via power line 590) that conveys sufficient power to electronic circuit 600 that can, in turn, be relayed by electronic circuit 600 to generators 200.
More particularly, electronic circuit includes a signal interface 650 in communication via signal line 580 with a detector (not shown) and/or a fire suppression control panel (not shown). Signal interface 650), in turn, is in electrical communication with a central processor 640. Upon receipt by signal interface 650) of a fire detection signal from a fire detector and/or a fire suppression control panel, which signal may be of a particular format, signal interface 650 may in turn provide a digital ignition signal to central processor 640 via line 655. Responsive to receiving the digital ignition signal via line 655, central processor 640) may cause a digital signal on line 645 to switch from high to low (i.e., from 1 to 0) or from low to high (i.e., from 0 to 1). Line 645, in this example, is connected to the TRIGGER input pin on all of multiple timer integrated circuits (IC) T of a timer subsystem. In examples, of IC T may be a 555-type Timer IC available from Texas Instruments of Dallas, Texas. U.S.A. With a 555-type Timer IC, timing intervals can be established by electrically arranging a respective external R-C (Resistor-Capacitor) circuit with respect to its input pins, such that a respective time interval passes between the moment the specified signal reaches its TRIGGER input pin thereby triggering a start of each respective countdown and the moment its OUTPUT pin in turn causes a signal to be placed on line 645. It will be appreciated that alternative timer ICs and configurations of same may be employed.
In this example, each of ICs T is configured through with a respective different countdown time, after which an IC T will trigger the closing of a respective relay (not shown) to connect power from the power supply on line 590 to a respective generator 200 via a respective electrical conduit 540, 550, 560, 570. For example, a first of the ICs T may be configured to have a countdown time of 2 seconds, a second of the ICs T may be configured to have a countdown time of 8 seconds, a third of the ICs T may be configured to have a countdown time of 14 seconds, and a fourth of the ICs T may be configured to have a countdown time of 20 seconds. As such, after central processor 640 promulgates a signal on line 645, such that all ICs T receive the signal on line 645 simultaneously power from power line may be routed via electrical conduit 540 in 2 seconds thereby to actuate the initiator assembly of the first of the generators 200, may be routed via electrical conduit 550 in 8 seconds thereby to actuate the initiator assembly of the second of the generators 200, may be routed via electrical conduit 560 in 14 seconds thereby to actuate the initiator assembly of the third of the generators 200, and may be routed via electrical conduit 570 in 20 seconds thereby to actuate the initiator assembly of the fourth of the generators 200.
It will be appreciated that ICs T may be configured with different timings than those set forth above, which timings are provided as examples for aiding with the explanation of actuation portion 600. For example, the time spacing(s) between ignitions as determined by the countdown timing to which ICs T are respectively configured, may be 0, 6, 12, and 18 seconds, may be 1, 4, 9, 12 seconds, or may be any other timing that is appropriate for the dwelling.
In alternative examples, a single IC may itself include multiple timing circuits, so that a signal to the single IC may initiate multiple countdowns with respective different countdown timings thereby to, in turn, cause actuation of multiple different generators 200.
In alternative examples, a first actuation of a first of generators 200 may not be conducted after a countdown of a IC T. For example, such a first actuation may be conducted by a signal on line 645 directly actuating a relay without an intervening IC T, for enabling power from power supply to be relayed to a generator 200 as a direct result of the signal on line 645.
In alternative examples, an electronic circuit for the actuation portion may include a cascade structure in which a first IC T may receive an initial signal on line 645, and may in turn trigger a respective relay at one time while also, after a delay, trigger an OUTPUT signal on another line that is, in turn, connected to the TRIGGER line of another IC T. Variations are possible.
Variations in the number of generators, and thus the structure of the electronic circuit of the actuation portion, are possible. For example, timed ignitions may be conducted for any number of generators 200 in a fire suppression system, such as two generators 200, three generators 200, five generators 200, and so forth, such that the electronic circuit should have corresponding timing circuits or routines for each. It will be appreciated that a given actuation may actuate multiple generators 200 using the same conduit extending from the electronic circuit but split closer to fire suppression portion 500 of fire suppression system 490.
Alternative configurations having respective advantages are contemplated. Some alternative configurations are disclosed in U.S. Pat. No. 8,413,732, the contents of which are incorporated herein by reference. For example.
A set of sodium-azide/iron oxide solid propellant grains is disposed inside of housing 1012. In this example, the propellant grain set comprises a central column 1018 of 36 (thirty-six) propellant grains including 34 (thirty-four) stacked cylinder-shaped “main” propellant grains 1022 capped on each of its ends with 1 (one) “end” grain 1024. Disposed generally in parallel with the central column and therearound are six outer columns 1020 each comprising 36 (thirty-six) stacked cylinder-shaped main propellant grains 1022. Between the central and outer columns of stacked propellant grains are silicone spacers 1026.
As can be seen, the end propellant grains 1024 in the center column 1018 each have a large bore therethrough sized to receive a portion of an ignition device such as a squib (not shown in
Disposed between the set of propellant grains and the housing is a filter pad 1030. In this example the filter pad 1030 comprises an inner coarse-screen steel mesh and an outer fine-screen steel mesh. Interposed between the coarse-screen mesh and the fine-screen mesh are layers of steel wool and preferably non-biopersistent (non-carcinogenic) ceramic “paper” material. In this example, the steel wool is a fine #000 steel wool, with a 35 micron fiber size. Preferably, the steel wool is an extra fine #0000 fiber size.
In this example the ceramic material is the UNIFRAX 1-2 micron fiber PC204 material, with a composition of 52% SiO2. 46% Al2O3, and 2% other material. Alternatives such as the UNIFRAX 2-4 micron fiber PC440 material may be used. The above-noted UNIFRAX materials are known as “Category 2” materials in the European Union's “FIBER DIRECTIVE”, otherwise known as Directive 97/69/EC. “Category 3” materials such as the following may be usable: an INSULFRAX 3.2 micron fiber, 64% SiO2, 30% CaO, 5% MgO, 1% Al2O3 material, an ISOFRAX 4 micron fiber. 75% SiO2, 23% MgO, 2% Other material, and a FIBROX 5.5 micron fiber, 47% SiO2, 23% CaO, 9% MgO, 14% Al2O3, 7% Other material. Thermal Ceramics Incorporated of Augusta. Ga., U.S.A. provides ceramic materials also that may be viable.
During manufacture, the outer fine-mesh screen and the steel wool and ceramic layers are rolled together and formed into a cylinder around the coarse-mesh screen to form the cylindrical filter pad 1030. If the steel wool and/or mesh screens being employed hold machine oil, then the filter pad 1030 is baked to burn off any machine oil attached thereto at this point. The burning off of the machine oil prior to use of the generator ensures that the machine oil does not get discharged along with the fire suppressing gas during use. It will be understood that, alternatively the steel wool and meshes could be baked prior to assembly.
The filter pad 1030 functions to inhibit escape of particulates from the interior of the generator 1000 when the grains 1022, 1024 are ignited, and also to absorb some of the heat generated upon ignition of the grains 1022, 1024.
More particularly, the ceramic fibers are considered the main filtration element, with the steel wool on the inner layers being the course filter element. The steel wool also advantageously inhibits or stops the tunneling that can occur otherwise if the ceramic material is locally attacked by sodium oxide (Na2O). The sodium oxide tends to cause the ceramic material to reach a lower melting point and as a result form holes in the filter. As such, when the sodium oxide hits the steel wool the local attack is blunted and spread out so that when it reaches the next ceramic layer is has a broad front. The outer fine steel mesh layer serves as a mechanical support, whereas the inner coarse mesh tube defines the inner diameter of the filter pad 1030.
Directly against the inner surface of the housing 1012 is a hermetic sealing layer (not shown) for preventing or significantly inhibiting ambient moisture from entering the housing 1012 through the discharge ports and being absorbed in the solid propellant grains. As shown in the figures, the discharge ports 1014 have a “figure eight” shape formed by drilling/punching two proximate and connected holes through the housing 1012. This shape of discharge port 1014 advantageously provides two sharp points at the midpoint of the discharge port 1014 against which the hermetic sealing layer is generally forced upon its expansion upon ignition due to internal pressure buildup. While preferably the hermetic sealing layer would be of such a material that would be ripped due to internal pressure alone, the sharp points provide increased chance of piercing of the hermetic sealing due to the increased internal pressure to allow the fire suppressing gas to escape. It will be understood that other shapes of holes could be provided that encourage piercing of the hermetic sealing layer in this manner.
Directly inside the hermetic sealing layer surrounding the filter pad is a plenum space formed by a spacer, which in this example is 1/16 inch wire 1032 that is wrapped around the filter pad 1030. The wire 1032 functions to provide the plenum space between the filter pad 1030 and the interior wall of the housing 1012 so that fire suppressing gas, generated upon ignition first at the ends of the housing 1012 and then progressively inwards from the ends, can exit from numerous additional discharge ports 1014 and not only those that are located directly adjacent the burning propellant grains 1022, 1024. Thus, internal pressure built up during ignition can be distributed through the plenum space assured by the wire 1032 across the set of discharge ports 1014, which serves to limit the buildup of internal pressure during use. The wire 1032 also beneficially functions to maintain the filter pad 1030) in a cylindrical shape for insertion of the propellant grains 1022, 1024 therein particularly during manufacture of the generator 1000. The wire 1032 also absorbs some of the heat generated upon ignition of the grains 1022, 1024.
A silicone sealing gasket 1034 is positioned at each end of the housing 1012 over each end of the cylindrical filter pad 1030. Also at each end of the housing 1012, a filter-pad centering ring 1036 extends past the ends of the housing 1012. With the sealing gasket 1034 in place, the end cap 1038 may be pressed against the gasket 1034, compressing gasket 1034 between filter pad 1030 and end cap 1038 as end cap 1038 meets filter-pad centering ring 1036. End caps 1038 may then be affixed in place, to seal the end of the housing 1012. Preferably, particularly in order to meet transportation safety and security regulations, the end caps 1038 are adapted to be crimped, screwed, or otherwise relatively permanently secured onto the end of an adapted housing 1012 so that the end caps 1038 cannot practically be removed.
At least one of the end caps 1038, and typically in practical implementations only one of the end caps 1038, has a central bore 1040 therethrough for receiving a squib barrel in a strong snap- or threaded fit. The squib barrel extends through the end cap 1038 and extends at least partially into the central bore of the end propellant grain 1024. The sealing gasket 1036 held in place by the end cap 1038 functions to substantially prevent the exit of generated fire suppressing gas through the ends of the filter pad 1030) and out of the housing 1012. This ensures that the generated fire suppressing gas escapes through the discharge ports 1014 of the housing 1012 via the filter pad 1030.
While examples have been described, alternatives are possible.
For example, while fire suppressing gas generators described herein are cylindrical, alternative generator “envelope” shapes and formats are possible, provided that the fire suppressing gas may be released in a thrust neutral manner.
Also, while the outer housing component of fire suppressing gas generators described herein are formed primarily as a steel cage, alternative examples may include an outer housing component with a cage that formed of another kind of metal or other material suitable for inhibiting access to or contact of the inner housing component it encapsulates. Alternatively, an alternative outer housing component may have characteristics that are less like a cage and more like an outer sleeve. An alternative outer housing component may have an outer form factor that is not cylindrical, despite encapsulating (for example) a cylindrical inner housing component.
In other examples, cooperation between the inner housing component and the outer housing component may together provide overall thrust neutrality of a fire suppressing gas generator. For example, examples may be considered wherein distribution of the discharge ports on an inner housing component provides substantially thrust bias to the inner housing component when the fire suppressing gas passes out of the discharge ports, while the distribution of the openings on the outer housing component provides substantially thrust neutrality to the outer housing component when the fire suppressing gas passes out of the openings.
In examples described herein, the inner housing component and the outer housing component are maintained in a fixed spaced relationship using rigid rings. Other structures for maintaining these components in a fixed spaced relationship and that, like the rigid rings, withstand vibration testing and other rigorous tests to ensure overall integrity, may be employed as alternatives.
While shapes of propellant grains described herein may be regarded as cylindrical “pucks”, other form factors are possible.
Unless otherwise explained, all technical terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this disclosure belongs. Although any methods and materials similar or equivalent to those described herein can be used in the practice for testing of the present invention, the typical materials and methods are described herein. In describing and claiming the present invention, the following terminology will be used.
It is also to be understood that the terminology used herein is for the purpose of describing particular aspects only and is not intended to be limiting. Patent applications, patents, and publications are cited herein to assist in understanding the aspects described. All such references cited herein are incorporated herein by reference in their entirety and for all purposes to the same extent as if each individual publication or patent or patent application was specifically and individually indicated to be incorporated by reference in its entirety for all purposes. To the extent publications and patents or patent applications incorporated by reference contradict the disclosure contained in the specification, the specification is intended to supersede and/or take precedence over any such contradictory material.
In understanding the scope of the present application, the articles “a”, “an”, “the”, and “said” are intended to mean that there are one or more of the elements. Additionally, the term “comprising” and its derivatives, as used herein, are intended to be open ended terms that specify the presence of the stated features, elements, components, groups, integers, and/or steps, but do not exclude the presence of other unstated features, elements, components, groups, integers and/or steps. The foregoing also applies to words having similar meanings such as the terms. “including”. “having” and their derivatives.
It will be understood that any aspects described as “comprising” certain components may also “consist of” or “consist essentially of,” wherein “consisting of” has a closed-ended or restrictive meaning and “consisting essentially of” means including the components specified but excluding other components except for materials present as impurities, unavoidable materials present as a result of processes used to provide the components, and components added for a purpose other than achieving the technical effect of the invention.
It will be understood that any component defined herein as being included may be explicitly excluded from the claimed invention by way of proviso or negative limitation.
In addition, all ranges given herein include the end of the ranges and also any intermediate range points, whether explicitly stated or not.
Terms of degree such as “substantially”. “about” and “approximately” as used herein mean a reasonable amount of deviation of the modified term such that the end result is not significantly changed. These terms of degree should be construed as including a deviation of at least ±5% of the modified term if this deviation would not negate the meaning of the word it modifies.
The abbreviation, “e.g.” is derived from the Latin exempli gratia, and is used herein to indicate a non-limiting example. Thus, the abbreviation “e.g.” is synonymous with the term “for example.” The word “or” is intended to include “and” unless the context clearly indicates otherwise.
While examples have been described, alternatives are possible.
