Abstract:
An ignition unit for a fire extinguishing assembly has an ignition unit housing with a firing pin disposed within the housing. A spring is coupled to the firing pin, and a restraining device holds the pin in place in the housing, A formed eutectic holds the restraining device in place such that when the eutectic deforms, the firing pin is released and moved by the spring in a desired direction.

Description:
BACKGROUND 
       [0001]    Fire extinguishing aerosol devices generally have a housing with a discharge opening, a charge for producing a fire-extinguishing aerosol, and an ignition unit. When the ignition unit is operated, the pyrotechnic or solid-fuel charge is ignited, and the gaseous combustion products thereof form the fire extinguishing aerosol that passes through the discharge opening into the fire region and extinguishes the fire. In some prior devices, the ignition unit comprises an igniter positioned on or in the pyrotechnic that ignites when electrically activated or heated to a high temperature, such as that caused by a fire. One problem in causing ignition in this manner is that the igniter must be inside the housing, thus requiring that the container itself reach a high temperature prior to ignition. 
         [0002]    Another shortcoming is the necessity to connect electrically operated units to suitable detection devices and releasing panels (cost, maintenance, reliability issues.) In some prior devices, a fuse, such as one composed of cordite extends outside of the container. Such fuses, while igniting in response to a desired temperature, are prone to damage and potential malfunction (fuse is limited to one, high activation temperature—significant damage occurs prior to activation). It is also dangerous to ship fire extinguishing devices which can be undesirably activated during shipment. 
         [0003]    In one existing device, a bulb is used to hold a spring loaded pin in place. At a prespecified temperature, the bulb breaks, releasing the pin which ignites the pyrotechnic. 
       SUMMARY 
       [0004]    An ignition unit for a fire extinguishing assembly has an ignition unit housing with a firing pin disposed within the housing. A spring is coupled to the firing pin, and a restraining device holds the pin in place in the housing, A formed eutectic holds the restraining device in place such that when the eutectic deforms, the firing pin is released and moved by the spring in a desired direction. 
         [0005]    In further embodiments, a fire extinguishing assembly includes a thermal ignition unit and an aerosol generating unit. The ignition unit in one embodiment comprises a spring loaded piston that is held under spring tension by a formed eutectic, which deforms at a predetermined temperature. When such temperature is reached, the piston is released, and strikes a primer to ignite a desired pyrotechnic in the aerosol generating unit. In a further embodiment, the eutectic is held in place by a restraining clip, which when removed, also releases the spring loaded piston to ignite the pyrotechnic. In one embodiment, the piston strikes a primer, which ignites an ignition mix, which further ignites the pyrotechnic. The ignition mix may be formed of the same material as the pyrotechnic. The primer may be a simple pistol primer in one embodiment, or other means of igniting the ignition mix. 
         [0006]    The ignition unit may be releasably engaged with a canister that contains the pyrotechnic. In one embodiment, it is formed with threads for mating with threads on the canister. The ignition unit and canister may ship in an unassembled state, and then be easily assembled at a desired location of use to form the fire extinguishing assembly. Many different size canisters may use the same ignition unit. The inclusion of a restraining clip allows actuation of the extinguishing assembly either mechanically, or in direct response to heat 
         [0007]    In one embodiment, the aerosol generating unit comprises a canister having a housing with aerosol exit ports. A cooling material is supported within the housing above the exit ports. A combustion chamber is provided within the housing above the cooling material. The aerosol forming composition is supported within the housing above the combustion chamber. An ignition mix extends into the aerosol forming composition for igniting the aerosol forming composition. 
     
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0008]      FIG. 1  is a cross section of an ignition unit mounted on an aerosol delivery canister according to an example embodiment. 
           [0009]      FIG. 2  is a top view of a firing pin for use in the ignition unit of  FIG. 1  according to an example embodiment. 
           [0010]      FIG. 3  is a top and side view of a retaining clip for retaining a formed eutectic according to an example embodiment. 
           [0011]      FIG. 4  is a side view of the firing pin of  FIG. 2 , and including the retaining clip of  FIG. 3  for retaining a formed eutectic according to an example embodiment. 
           [0012]      FIGS. 5A and 5B  illustrate a eutectic pellet in raw form and after it has been formed for use in the firing pin of  FIG. 2  according to an example embodiment. 
       
    
    
     DETAILED DESCRIPTION 
       [0013]    In the following description, reference is made to the accompanying drawings that form a part hereof, and in which is shown by way of illustration specific embodiments which may be practiced. These embodiments are described in sufficient detail to enable those skilled in the art to practice the invention, and it is to be understood that other embodiments may be utilized and that structural, logical and electrical changes may be made without departing from the scope of the present invention. The following description is, therefore, not to be taken in a limited sense, and the scope of the present invention is defined by the appended claims. 
         [0014]      FIG. 1  shows a cross section of a fire extinguishing assembly indicated generally at  100 . The fire extinguishing assembly comprises a canister  110  for coupling with an ignition unit  115 . The canister  110  includes a container  120  that may be lined with a desired material  122 , such as ceramic paper, or insulative material such as cardboard. Ceramic paper may produce fewer toxic gases such CO and unwanted odors as compared to other materials. Container  120  contains a bottom piece  125  with exit ports  127 . A sealant  128 , such as a poly sealant, may be used over the bottom piece  125  to provide an almost hermitic seal for contents inside container  120 . A cross member spacer  130  formed of mild steel in one embodiment is positioned within the container  120  between the bottom piece  125 . A first screen  133  is positioned adjacent the cross member spacer  130 , and supports a cooling material  135 , such as pieces of activated alumina, zeolite, marble chips, lava rock etc. In one embodiment, the pieces are approximately ⅛ th  inch to ¼ inch. Many other sizes and types of cooling material may also be used. 
         [0015]    A second screen  137  is positioned on top of the cooling material  135 , such that the first and second screens hold the cooling material  135  in position. The screens may be formed of stainless steel or other material compatible with the temperatures and other materials used in the canister. Spacer ring  140  formed of mild steel in one embodiment, is positioned on top of the second screen  137 , and provides a combustion chamber  142 . The spacer ring may be formed of other materials in further embodiments. 
         [0016]    The spacer ring  140  also supports a pellet  143  comprising a pressed aerosol forming composition when ignited. The pellet  143  is formed with a hole or opening  145  that contains an ignition mix  147  that is supported within a bushing  150  fastened at a top end of the canister  120 . In one embodiment, the cap is sealed with the canister by means of an annular sealant or sealing ring  152 . An ignition primer cap  155  is supported by the bushing  150  above the ignition mix  147  for igniting the ignition mix when struck. In a further embodiment, the pellet  143  may be formed without the ignition mix, and directly ignited by the primer cap. 
         [0017]    The bushing  150  has an ignition unit receiving portion  160  that extends from the cap and contains a threaded inner portion for receiving a threaded mating outer portion  161  of the ignition unit  115 . The receiving portion  160  and mating portion  161  may couple to each other in other ways, such as friction or snap fit. Such coupling may be permanent or releasable in various embodiments. 
         [0018]    The ignition unit  115 , which in one embodiment is generally cylindrical in shape, has a firing pin  165  slideably mounted within it. The firing pin is coupled to a spring  167  that is compressed against a ledge  170  within the ignition assembly. The firing pin is formed with a detent, groove or annular depression  172  for receiving a restraining device, such as a ball bearing  175  held within a portion  176  of the ignition unit extending generally transverse to the firing pin. Detent  172  may be annular in one embodiment to allow ease of manufacture, removing the need to properly align the pin  165  prior to insertion of the ball bearing  175 . In further embodiments, only a portion of the pin has the detent. 
         [0019]    The groove  172  may have angled edges, allowing the ball bearing  175  or other stiff structure to move transversely away from the firing pin when no longer held against it. A restraining clip  177  fastened in the transverse extending portion of the ignition unit holds a formed eutectic  180 , against the restraining device  175 . The eutectic  180  is selected to deform at a desired temperature, releasing the restraining device  175 , allowing the spring  167  to drive the firing pin into the ignition primer cap  155 . The primer cap  155  will then fire, igniting the ignition mix  147  and in turn the pellet  143 . Aerosol from the pellet  143  passes through the screens and cooling material  135 , and cross member spacer  130 , breaks open the sealant  128  and exits via exit ports  127 . In one embodiment, the ignition temperature of the pellet is approximately 270 to 300° C., or other desired temperature which is a function of the chemical composition and method of preparation of the pellet. 
         [0020]    In one embodiment, the bushing  150  is part of the ignition unit, and couples to the canister. The bushing  150  includes the primer and ignition mix, and may be shipped separately from the canister, and assembled when ready to use. 
         [0021]    In one embodiment, the pellet  143  is formed of a composition comprising potassium nitrate (67-72), dicyandiamide (9-16), phenolformaldehyde resin (8-12), and potassium benzoate, bicarbonate or hexacyanoferrate (4-12) in various percentages by mass as indicated in parentheses. Various other compositions may be used, some of which are described in U.S. Pat. Nos. 6,042,664 and 6,264,772. 
         [0022]    The size of the canister may be varied significantly to provide different amounts of aerosol producing material. In one embodiment, the mating threaded portions where the canister and ignition unit attach are the same size for the various sizes of canisters. Thus, a canister designed for inside a cabinet may be fairly small, such as smaller than a can of soda. Canisters designed for larger applications, such as retarding fires in a room, may be very large, All the canisters may use the same size ignition unit provided they are designed to attach to each other through the use of mating threaded portions, or other physical coupling mechanisms. 
         [0023]    A top view of the ignition unit  115  is shown in  FIG. 2  at  200 . Several grooves may be cut into the top portion of the ignition unit as indicated at  205  to reduce the amount of material in the ignition unit  115 , and thereby increase the responsiveness of the ignition unit to temperature changes.  FIG. 2  also better illustrates a slot  210  for retaining clip  177 . 
         [0024]    The slot is positioned to hold the retaining clip, shown in detail in  FIG. 3  with side and top views, in a desired position as illustrated in a side view of the ignition unit with clip  177  installed in  FIG. 4 .  FIG. 3  shows the retaining clip formed with a middle flat portion having a hole  310  formed therein. As seen in  FIG. 4 , hold  310  lines up with the formed eutectic  180 , and provides a passage for the eutectic to flow through when heated, without allowing it to flow through when below the deformation temperature. Further holes may be formed in portions of the clip as desired to allow attachment of cords or string for manual pulling of the pin.  FIGS. 5A and 5B  illustrate the eutectic prior to installation at  510  and shaped for installation at  515  respectively. Shaping of the eutectic may be done with a ball bearing under pressure. In one embodiment, suitable eutectic pellets  510  may be obtained from Cerro Metal Products Co., Bellefonte Works, P.O. Box 388, Bellefonte, Pa. 16823, or from other sources as desired. Available example melting temperatures include but are not limited to 158, 174, 198 and 203° F. In further embodiment, the eutectic deform at temperatures in the range of approximately 70° C. or lower, or much higher, such as 270 to 300° C., and just about anywhere between. 
         [0025]    With the eutectic  180  formed or shaped as shown in  FIG. 1 , and a ball bearing  175  of substantially the same shape and diameter as the opening, the eutectic is prevented from further deforming at temperatures lower than its melting point, as there is no route available to it to deform into. The hole  310  in the clip is small enough to prevent significant flow, thus securing the pin in place until the eutectic  180  reaches a melting temperature. At that time, the eutectic flows through the hold in the clip, allowing the ball bearing to move away from the detent in the firing pin, and releasing the firing pin to ignite the pellet  143 . 
         [0026]    The Abstract is provided to comply with 37 C.F.R. §1.72(b) to allow the reader to quickly ascertain the nature and gist of the technical disclosure. The Abstract is submitted with the understanding that it will not be used to interpret or limit the scope or meaning of the claims.