Abstract:
A parachute flare igniter assembly includes a novel safety for arresting the motion of a slider when subjected to external forces, but allows slider motion when subjected to intended cable actuation forces. The igniter safety includes a housing, a slider, a cable and a sleeve. The slider, connected to the cable, is slidably received within the housing. The cable moves the slider by applying a cable force conventionally obtained by actuation of a parachute associated with the flare and connected to an end of the cable opposite an end connected to the slider. The sleeve is connected to the cable and is disposed between the housing and the slider, so that the sleeve will arrest the slider with respect to the housing when the cable force is not present. A flare and a method of providing a safety in an igniter assembly is also provided.

Description:
[0001]    This invention was made with Government support to Contract Numbers W52P1J-04-C-0002 and FA8213-04-C-0026. The Government has certain rights in this invention. 
     
    
     FIELD OF THE INVENTION 
       [0002]    This invention, in various embodiments, relates to a novel igniter assembly for igniting combustible compositions in a highly reliable manner and, in particular, to an igniter assembly which includes a safety for preventing inadvertent ignition while allowing a combustible illuminant composition to be actuated by deployment of an associated parachute. Embodiments of the invention also relate to devices comprising the novel igniter assembly, such devices including, by way of example, illuminating flares. 
       BACKGROUND OF THE INVENTION 
       [0003]    Among the various environments in which illuminating flares are used, perhaps the most common environment for the use of flares involves the illumination of military battle grounds. In such applications, the flares are launched above ground or water areas where enemy personnel and vehicles are suspected to be present. Essentially, the illumination provided by the flare facilitates visual detection of the enemy personnel and vehicles, providing more precise identification of target locations at which to aim ordnance. The illuminating effect provided by the flare is conventionally enhanced by equipping the flare with a parachute, which increases the flight time by slowing the rate of descent for the illuminating flare and, upon deployment thereof, provides a force for actuating an igniter housed in the flare. 
         [0004]    The use of flares to ascertain the precise location of enemy targets can provide obvious military advantages. However, the availability and widespread use of military flares has negated this advantage somewhat, since there is an increased likelihood of opposing military forces also possessing flares. Thus, in order to gain a military advantage from the flares, it is paramount that the flares operate in a highly reliable and dependable manner, since flare failure can provide the opposing military force additional time to launch their own flares and ordnance. 
         [0005]    An example of an illuminating flare that is reliable by conventional standards, e.g., about 87% of the time is shown in  FIGS. 5-7  herein. It is believed that one of the largest contributors, if not the largest contributor, to failed firing of this illuminating flare is the misfiring of the flare igniter. The flare, which is generally designated by reference numeral  200  in  FIG. 5 , comprises an aluminum casing  202  partitioned into two compartments. The forward compartment is the larger of the two compartments, and contains an energetic material in the form of a solid illuminant fuel  204  designed to enhance nighttime vision and an igniter assembly  206  for initiating burning of the illuminant fuel  204 . In the illustration, the aft compartment is the smaller of the two compartments, and contains a parachute  208  and a timing device (unnumbered). The timing device, inserted at an aft end of the casing  202 , detaches from the flare casing  202  at a predetermined time to create a passageway through which the parachute  208  can deploy. Upon deployment through the passageway, the parachute  208  slows the rate of descent of the flare  200 , extending the time during which the burning illuminant fuel  204  is maintained at an elevated position. In this manner, the illuminating effect provided by the burning illuminant fuel  204  is enhanced. 
         [0006]    A conventional igniter is disclosed in U.S. Pat. No. 4,155,306 and illustrated in  FIGS. 6 and 7  herein. Referring to  FIG. 6 , the igniter  206  includes a housing  212  formed of a molded piece of LEXAN® polycarbonate or other polycarbonate, or light-weight metal. The housing  212  has longitudinally extending internal walls  213  and ridge  213   a , which are receivable into an aluminum cap (not shown). The internal walls  213  and the ridge  213  a define upper and lower hollow compartments  215 , and a diametrically extending raceway  214  interposed between the upper and lower compartments  215 . The raceway  214  is defined in part by the ridge  213   a  of the internal wall  213 . The ridge  213   a  has a depth less than that of the remainder of the internal walls  213 . For convenience, the ridge  213   a  is shaded. The function of the ridge  213   a  is explained in further detail below. 
         [0007]    A sliding cartridge (also referred to herein as a slider)  216  is disposed in the raceway  214  and is slidable along the raceway  214 . The slider  216  comprises a spring-loaded striker arm  218 , a torsion spring (located at position  220 ), and a pistol primer (containing a small amount of explosive)  222 . The striker arm  218  is depicted in a loaded or cocked position in  FIG. 6 . The torsion spring  220  urges the striker arm  218  to pivot about pin  224  and toward the position shown in  FIG. 7 , in which the striker arm  218  rests against the primer  222 . A cam surface  225  of the housing  212  obstructs the striker arm  218  from moving toward the primer  222  and, in combination with the urging force of the spring  220 , prior to actuation maintains the slider  216  in the position depicted in  FIG. 6 . 
         [0008]    Located below the raceway  214  is a pellet cavity  226  containing an ignitable composition, such as boron potassium nitrate (BKNO 3 ) pellets. The pellet cavity  226  is in communication with the solid illuminant fuel  204  through an orifice (not shown). 
         [0009]    The slider  216  is operatively connected to the parachute  208  via cable or lanyard  230 , which extends along a cable raceway (not shown) formed in the aluminum casing  202 . The cable  230  contains a first swage ball  232  accommodated within recess  234  for securing the cable  230  to the slider  216 . The recess  234  is in communication with a slot  236 , which is sufficiently wide to permit passage of the cable  230 , but to obstruct passage of the first swage ball  232 . At the end of the cable  230  is a second swage ball (not shown, but positioned behind the first swage ball  232  in  FIG. 6 ). The cable  230  extends between the first swage ball  232  and the second swage ball along an axial direction, that is, perpendicular to the portion of the cable  230  passing through the slot  236  (i.e., into the sheet on which  FIGS. 6 and 7  are shown). The second swage ball is encapsulated into the internal wall  213 . The encapsulation of the second swage ball in the internal wall  213  serves as a safety mechanism to protect against unintentional firing by preventing tension in the cable  230  from prematurely moving the slider  216  along the raceway  214 . 
         [0010]    In operation, the igniter assembly  206  is actuated by the force generated upon parachute  208  deployment. Upon actuation of the parachute  208 , the deploying parachute pulls the cable  230  toward the aft end of the flare  200 . When properly operated, the force imparted on the cable  230  by the deploying parachute  208  is sufficient to dislodge the second swage ball from the housing  212  and move the slider  216  in tandem with striker arm  218  and the primer  222  across the raceway  214  with sufficient force to overcome the fictional resistance between the cocked striker arm  218  and the cam surface  225 , as well as the frictional resistance between the slider  216  and the raceway  214 , thus passing the striker arm  218  under the cam surface  225 . 
         [0011]    After the slider  216  has moved a sufficient distance for the striker arm  218  to clear the cam surface  225 , the urging force of the torsion spring  220  pivots the striker arm  218  about pin  224  and toward the primer  222 , which is now located over the cavity  226  containing the ignitable BKNO 3  pellets. Impact of striker arm  218  against the primer  222  detonates the primer  222 . The heat and flames generated by the detonation of the primer  222  pass through an orifice and ignite the BKNO 3  pellets in cavity  226 , which in turn ignites a wafer, which in turn ignites the solid illuminant fuel  204 . Because the ridge  213   a  of the internal wall  213  extends in depth only a portion of the way across the depth of the raceway  214 , a clearance is defined (between the ridge  213   a  and the opposing cap surface) through which the striker arm  218  can pass as the striker arm  218  pivots toward the primer  222 . 
         [0012]    Although effective by conventional standards, flares possessing the igniter assembly  206  function correctly only approximately 87% of the time. In the majority of the cases in which failure occurred, the slider mechanism  216  was found to have traveled only part of the way down the raceway, with the cable found either broken or intact. The reasons for these failures are believed to be as follows. The deployment of the parachute  208  imparts an instantaneous shock force to the cable  230 , causing the second swage ball to dislodge from the slider wall in which the second swage ball is encapsulated. However, the remaining force imparted to the cable  230  by parachute deployment is not always sufficient to overcome additional frictional forces at the slider/raceway interface and the interface between the cocked striker arm  218  and the cam surface  225 . These frictional forces can prevent the slider  216  from moving sufficient distance to clear the cam surface  225  and reaching and striking the primer  222 . One reason for the high fictional force at the slider/raceway interface is that the cable does not pull at the center of the slider  216 . Another reason is that the ridge  213   a  defining the top of the raceway  214  does not extend along the full depth of the slider  216  (in order to provide a clearance for passage of striker arm  218  as the striker arm  218  pivots from the cocked state to the firing state). The presence of this clearance is believed to allow the slider  216  to rotate somewhat about its longitudinal axis in the raceway  214  during sliding movement, thus increasing fictional forces. 
         [0013]    U.S. Pat. No. 6,412,417, the disclosure of which is incorporated by reference herein, discloses an inventive igniter assembly which overcomes at least one of the above discussed problems, for instance by reducing sticking of the slider or by providing a motion restricting bridge (replacing the encapsulated swage ball mentioned above) feature for preventing the unintentional firing and ignition of the illumination composition when subjected to a static force of up to 90 lbs. However, the igniter will be rendered inoperable if the static force required to release or break the bridge is sufficiently high enough to prevent against all inadvertent or unintentional firings, because the parachute, by way of the cable, will not provide reliable requisite force to break the bridge. Also, as the force requirement increases for the bridge, the resultant resistance force upon the cable, along its path, junctions or bends to the parachute attachment, undesirably increases. 
         [0014]    The illumination composition ignition sensitivity for the above mentioned patent is dependent upon circumferential clocking of the igniter assembly. In this regard, the above mentioned patents due not provide against the unintended ignition of the illumination composition when the igniter assembly is subject to an impact or impulse force when dropped in a zero degree orientation, i.e. in the direction of the slider&#39;s motion. 
         [0015]    Therefore, it is desirable to provide an igniter assembly wherein the illumination composition ignition sensitivity is substantially independent of circumferential clocking. It would also be of advantage to provide an igniter assembly that resists ignition of the illumination composition when subjected to an impact or impulse force, particularly when the force is applied generally in the zero degree orientation or in the direction of the sliders motion. 
       BRIEF SUMMARY OF THE INVENTION 
       [0016]    Accordingly, in one embodiment, an igniter assembly overcoming the above-discussed problems includes a safety for preventing inadvertent ignition while allowing a combustible illuminant composition to be actuated by deployment of an associated parachute. An advantage provided by embodiments of this invention is an igniter assembly wherein the illumination composition inadvertent ignition sensitivity is substantially independent of circumferential clocking. Another advantage provided by embodiments of this invention is an igniter assembly that resists ignition of the illumination composition when subjected to an impact or impulse force, particularly when the force is applied in the zero degree orientation or in the direction of the slider&#39;s motion. 
         [0017]    In one embodiment of the invention, a parachute flare igniter assembly includes a safety for arresting the motion of a slider when subjected to external forces, but allows slider motion when subjected to intended cable forces. The igniter safety includes a housing, a slider, a cable and a sleeve. The slider, connected to the cable, slides in a track provided in the housing allowing the slider to be slidably received therein. The cable moves the slider by applying a cable force as may be obtained by actuation of a parachute. The sleeve is connected to the cable and is disposed between the housing and the slider, the sleeve being configured and positioned to arrest the slider with respect to he housing when the cable force is not present. 
         [0018]    In another embodiment, an apparatus for initiation of an energetic material and including an igniter assembly is provided. 
         [0019]    In another embodiment, the invention includes a method of providing a safety in an igniter assembly. 
         [0020]    Other advantages and features of the invention will become apparent when viewed in light of the detailed description of the various embodiments of the invention when taken in conjunction with the attached drawings and appended claims. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS  
         [0021]      FIG. 1  shows a plan, partially phantom view of an igniter assembly having a safety in accordance with a first embodiment of the invention, depicting a slider and striker arm of the igniter assembly in a loaded state. 
           [0022]      FIG. 2  shows a plan, partially phantom view of the igniter assembly of  FIG. 1 , but depicting the slider and striker arm in a firing state. 
           [0023]      FIG. 3  shows an isolated, perspective view of the slider of the igniter assembly in accordance with the first embodiment. 
           [0024]      FIG. 4  shows an exploded perspective view of the igniter assembly in accordance with the first embodiment. 
           [0025]      FIG. 5  shows a partially sectioned view of a known flare in which an embodiment of the igniter assembly of the invention may be used. 
           [0026]      FIG. 6  shows a plan, partially phantom view of the known igniter assembly of  FIG. 5 , depicting a slider and striker arm of the igniter assembly in a loaded state. 
           [0027]      FIG. 7  shows a plan, partially phantom view of the known igniter assembly of  FIG. 6 , depicting the slider and striker arm in a firing state. 
           [0028]      FIG. 8  shows a top plan view of a cartridge depicting the striker arm in a fired position. 
           [0029]      FIG. 9  shows a side sectional view of the cartridge of  FIG. 8 . 
           [0030]      FIG. 10  shows a plan, partially sectioned view of an igniter assembly having a safety in accordance with a second embodiment of the invention. 
           [0031]      FIG. 11  shows a cross-sectional side view of the igniter assembly in accordance with the second embodiment. 
           [0032]      FIG. 12  shows a partial cross-sectional view of the safety in accordance with the second embodiment. 
           [0033]      FIG. 13  shows a partial cross-sectional view of a sleeve suitable for use with a safety in accordance with a third embodiment of the invention. 
       
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
       [0034]    An example of a basic design of the illuminating flare with which the igniter of this invention is compatible is shown in  FIG. 5  and discussed above. In the interest of brevity, and because the design of known illuminating flares is within the purview of one of ordinary skill in the art, the following discussion will be limited to embodiments of the novel igniter assembly having a safe configured in accordance with the present invention. 
         [0035]    Referring to  FIG. 1 , the igniter assembly, or “igniter,”  106  includes a housing  112  formed of a molded piece of LEXAN® or other polycarbonate and a safe  100 . The housing  112  has longitudinally extending internal walls  113 , which are receivable into an aluminum cap  150  ( FIG. 4 ) of the casing so that peripheral portion  112   a  of the housing  112  abuts the periphery of the aluminum cap  150 . Groove  112   b  may be used to assist in aligning the housing  112  and the aluminum cap  150  with the flare body. The internal walls  113  define a first hollow compartment  115   a , a second hollow compartment  115   b , and a diametrically extending slider raceway  114 . Although the compartments  115   a  and  115   b  are optional, their presence is preferred in order to lower material costs and provide a venting feature discussed in greater detail below. A sliding mechanism (also referred to herein as a slider)  116  is disposed in the raceway  114  and is slidable along at least a portion of the raceway  114 . In one embodiment, the slider  116  is sized and configured for sliding about 0.5 inches (about 1.27 cm) along the raceway  114 . Each of the internal walls  113  defining the raceway  114  has a depth (perpendicular to the plane of  FIG. 1 ) set substantially equal to the depth of the sliding mechanism  116  without impairing movement of the latter. 
         [0036]    The slider  116  is movable between a loaded state depicted in  FIG. 1  and a firing state depicted in  FIG. 2 . Referring to  FIG. 1 , the slider  116  has a pocket  116   a  substantially centrally located therein, constructed and arranged to receive a stationary cartridge  117 . (Although not shown in the figures, the cartridge  117  may be provided with a pin hole and pin for retaining the striker arm  118  in the cocked position during assembly.) The slider  116  comprises a motion restricting bridge  128  positioned at an open end of the pocket  116   a . A cutter  140  of the stationary cartridge  117  is positioned in the pocket  116   a  in contact with the motion restricting bridge  128 . Although not shown, the region of the motion restricting bridge  128  contacted by the cutter  140  may include a notch to facilitate fracture of the bridge  128 . When in the loaded state depicted in  FIG. 1 , contact between the motion restricting bridge  128  and the cutter  140  obstructs the slider  116  from sliding toward the firing position depicted in  FIG. 2 , unless a sufficient force is applied to the slider  116  to break the bridge  128  along cutter  140  and as concentrated thereby. The slider  116  also has incorporated therein a pellet cavity  126  and striker pin clearance slot (also referred to herein as the striker arm clearance slot)  119 , the purpose of which will be explained in greater detail below. An aluminum strip (not shown) lines a portion of the pellet cavity  126  through which the explosion from the primer  122  penetrates during actuation. The aluminum strip serves to protect the pellets from accidental ignition in the event that the primer material undergoes undesired ignition by means other than the striker arm. The pellet cavity  126  is movable into communication with a wafer (not shown), which is in communication with solid illuminant fuel. The pellet cavity  126  contains an ignitable composition, such as boron potassium nitrate (BKNO 3 ) pellets. In one embodiment, pellet cavity  126  is sized and configured for receiving at least eleven BKNO 3  pellets. (The pellets, for safety, may be loaded into the cavity  126  after the igniter assembly has been assembled. Since the pellet cavity  126  moves, an oblong hole is provided in the base of the housing to allow pellet loading through the housing, as well as communication between the pellet cavity  126  and the wafer over the entire path of movement of the pellet cavity  126 .) The size of the slider  116  is determined by taking into account the diameter of the pellet cavity  126  and the clearance slot  119  needed for passage of the spring-loaded striker ann  118 . 
         [0037]    As shown in  FIGS. 8 and 9 , the body of cartridge  117  is generally of a known construction and provides a mounting for the spring-loaded striker arm  118 , a torsion spring  120 , and a pistol primer  122 . The body of cartridge  117  can be either formed separately from the housing  112  or be injection molded into the housing  112  during formation of the housing  112  so that the cartridge  117  and housing  112  are integral. The striker arm  118 , the torsion spring  120 , and the pistol primer  122  are then assembled in the cartridge  117 . In the loaded state illustrated in  FIG. 1 , the torsion spring  120  urges the striker arm  118  to pivot about pin  124  toward the position shown in  FIG. 2  in which the striker arm  118  is seated against the primer  122 . However, when the slider  116  is in the loaded state, a cocking wall portion  124  of the slider  116  obstructs the striker arm  118  from moving from its cocked position toward the primer  122 . 
         [0038]    The slider  116  is operatively connected to the parachute via cable (or lanyard)  130 , which extends through a cable slot  104  and along an axial channel (not shown) contained in the flare body. The cable  130  is attached to the slider  116  via a swage ball  132 , which is accommodated within recess  134  of the slider  116  for securing the cable  130  to the slider  116 . The recess  134  is in communication with a slider slot  136 , which is sufficiently wide to permit passage of the cable  130 , but sufficiently narrow to obstruct passage of the swage ball  132  therethrough. The cable  130  may be aligned with the longitudinal axis (center) of the slider  116 . Instead of using a roller pin to redirect the cable  130  near the end of the flare, a LEXAN® or other polycarbonate molded surface  108  having a relatively large radius can be used to redirect the cable  130  from along the cable slot  104  (shown extending to the right in  FIG. 1 , but when the cap  150  is connected onto the housing  112  the cable  130  extends through and along the cable slot  104 , i.e. into the drawing figure) and toward the longitudinal axis of the slider  116 . Enlarging of the turn radius for cable redirection reduces the friction upon the cable  130 . 
         [0039]    The safety  100  includes, by way of example, an aluminum sleeve  102  selectively coupled to the cable as shown in  FIG. 1 . The sleeve  102  may comprise a draw, round  3003  aluminum tube having a wall thickness of 0.040 inch. When the cap  150  is assembled to the housing  112 , the cable  130  is directed through the cable slot  104  such that the ends of the sleeve  102  provide a mechanical lock-out between the slider  116  and the inside wall (not shown) of the cap  150 , which will be discussed below in greater detail in the second embodiment of the invention. This mechanical lock-out or safety  100  substantially eliminates the possibility of accidental illumination composition ignition by providing the sleeve  102  cooperatively associated with the cable  130  to minimize movement of the slider  116  when subjected only to accidental shock or impulse force, such as would be experienced by dropping the igniter  106 . 
         [0040]    The sleeve  102  is designed to provide a comparatively rigid material structure in its axial, longitudinal direction and further includes either a designed “soft” structure, a relatively weak material structure, a brittle material structure or a combination of such features in a normal or radial direction to the longitudinal axis of the sleeve. The material structure of the sleeve  102  in the axial direction, parallel to cable  130  as sleeve  102  is initially disposed in igniter assembly  106  is sufficiently strong under columnar loading so as to prevent slider movement in the event of an accidentally applied force. Moreover, the material structure of the sleeve  102  in the normal, i.e., radial, direction is designed to cause the sleeve  102  to bend, break, comply or yield when subjected to a sufficient yet relatively small lateral force, such as when the parachute pulls upon the cable  130  via the cable slot  104 . By providing the designed material and/or structural characteristics into the sleeve  102 , the sleeve  102  may rigidly support the cable  130  when subjected to accidental loadings to provide a mechanical lock-out of slider movement, but will allow the cable to give or bend when subjected to intended loadings, allowing slider movement. 
         [0041]    As noted above, the sleeve  102  in this embodiment is a round aluminum tube having an axial, drawn hole therethrough for selectably and positionably receiving the cable. The wall thickness of the sleeve  102  is sufficiently thin to provide the designed “soft” structure as described herein without impairing its functionality under axial loading. It is recognized that other shapes may be used to advantage, particularly a square sleeve, without limitation. Moreover, the sleeve  102  may be made out of other materials compatible with the above-mentioned design characteristics, including for example, without limitation, glass, ceramic, wood, plastic and other metals and alloys. Optionally, the sleeve  102  may be integral with or form an integral part of the cable, instead of being a separate component. Also, the sleeve may be permanently secured to the cable, as by crimping, and need not necessarily allow the cable to slide to any substantial degree therein. 
         [0042]    In operation, the igniter  106  is actuated by the force generated upon parachute deployment. Upon actuation of the parachute, the cable  130  is pulled by the deploying parachute. When properly operated, the force imparted on the cable  130  by the deploying parachute is sufficient to cause the cable  130  to pull through the cable slot  104  and apply a small fracture force (normal or radial force) sufficient to bend, break, comply or yield the sleeve  102 , disabling the mechanical lock-out, or safety. With the disabling of the safety, the cable  130  pulls the slider  116  from its loaded state to its firing state while simultaneously breaking the optional motion restricting bridge  128  along the cutter  140 . After the bridge  128  has been broken, the bridge segments (designated by reference numerals  128   a  and  128   b  in  FIG. 2 ) flare over the cutter  140  and keep the slider  116  from moving backwards (i.e., toward its loaded state position). The cutter  140  is preferably designed with a small radius on the tip rather than a sharp edge, so that over time the edge of the cutter  140  will not wear through the bridge  128  due to normal vibrations experienced during transportation of the flare. It is recognized that the optional bridge provides resistance to slider motion or cable tension. However, the optional bridge is not designed to mechanically lock-out the sliders motion when subjected to an impact force primarily directed in the zero degree orientation of the igniter assembly. Table 1 provides an acceptance table for a slider when subjected to an as indicated force (the first row assesses the conventional igniter assembly not having the safety according to an embodiment of the invention, the second through fourth rows assess the inventive igniter assembly having the inventive safety.) 
         [0000]    
       
         
               
               
               
               
             
           
               
                 TABLE 1 
               
               
                   
               
               
                   
                 Intended 
                   
                   
               
               
                 Force 
                 Slider Motion 
                 Lock-out 
                 Acceptable 
               
               
                   
               
             
             
               
                 No sleeve with applied axial impact force 
                 No 
                 No 
                 No 
               
               
                 (conventional condition including a bridge) 
               
               
                 Sleeve with applied axial impact force, i.e., a 
                 No 
                 Yes 
                 Yes 
               
               
                 force applied in the zero degree direction 
               
               
                 Sleeve with applied cable force, i.e., a force 
                 Yes 
                 No 
                 Yes 
               
               
                 applied by actuation of a parachute 
               
               
                 Sleeve with simultaneously applied cable 
                 Yes 
                 No 
                 Yes 
               
               
                 force and axial impact force 
               
               
                   
               
             
          
         
       
     
         [0043]    Movement of the slider  116  into the firing state depicted in  FIG. 2  moves the striker arm  118  out of contact with cocking wall portion  124  and aligns the striker ann  118  with striker pin clearance slot  119 . As shown in  FIG. 3 , the cocking wall portion  124  can contain a guide slot  124   a  for receiving the striker pin (unnumbered) at the distal end of the striker arm  118 . Provision of this guide slot  124   a  prevents the tip of the striker pin from becoming embedded in the wall portion  124 , thus further enhancing the reliability of the igniter The striker arm  118  is hence permitted to move through the striker pin clearance slot  119  (due to the urging force imparted by the torsion spring  120 ) until the striker ann  118  strikes against the primer  122 . 
         [0044]    Movement of the slider  116  into the firing state depicted in  FIG. 2  also moves the cavity  126  to align the cavity  126  with primer  122 . Thus, detonation of the primer  122  starts an ignition sequence by which the BKNO 3  pellets, the wafer, and the illuminant composition are sequentially ignited. 
         [0045]    Optionally, the bridge  128  provides a variable safety feature for controlling the force required to move the slider  116 . The stress on the bridge  128  is equal to force over area. By increasing the height of the bridge  128 , more stress is required to break the bridge  128 . In one embodiment, the bridge  128  height was set at about 0.0305 cm (0.12 inch) to 0.356 cm (0.14 inch) to prevent backward movement of the slider  116  and provide a minimum pull force requirement of at least 50 lbs force and, more preferably, 90 lbs force to move the slider  116  into the firing state shown in  FIG. 2 . As mentioned above, the bridge  128  can be provided with a notch to facilitate fracture of the bridge  128  with cutter  140 . However, while the bridge  128  provides a resistance force, it fails to provide the necessary lock-out or other preventative measures to insure against inadvertent ignition, or movement of the slider  116  causing ignition. While the bridge  128  is not necessarily required, it may be included not only to provide the aforementioned minimum pull force requirement but also to facilitate assembly of the cocked striker arm  118  by holding the slider  116  in its cocked or loaded position. 
         [0046]    Another optional safety feature is the provision of one or more holes  121  through the portions of walls  113  defining the raceway  114  so that, if by some mishap the primer  122  were to unintentionally ignite before the slider  116  is moved to its firing state, the gases generated by ignition of the primer  122  can be vented to one or both of the outside compartments  115   a  and  115   b  to prevent ignition of the BKNO 3  pellets. 
         [0047]    Material selections for the igniter assembly parts, not mentioned herein, are considered to be well understood by a person of ordinary skill in the art and thus further mention is not necessary. 
         [0048]    Representative infrared illuminating compositions that may be used with embodiments of this invention are disclosed in U.S. Pat. Nos. 3,411,963, 5,056,435, 5,587,522, 5,912,430, and 6,123,789, the disclosures of each of which are incorporated herein by reference. 
         [0049]    Parachute deployment systems and conventional flare assemblies modifiable for use with embodiments of the igniter of this invention are disclosed in U.S. Pat. Nos. 5,386,781 and 5,347,931, the disclosures of each of which are incorporated herein by reference. 
         [0050]    Having described an embodiment of an igniter assembly above including an embodiment of the inventive safety, attention will now be turned primarily to other embodiments of the inventive safety with further discussion of the igniter assembly and its operation only as desirable to facilitate a more comprehensive understanding and appreciation of the invention. A second embodiment of the invention is shown in  FIGS. 10 ,  11  and  12  and described with respect thereto. 
         [0051]      FIG. 10  shows a plan, partially sectioned view of an embodiment of an igniter assembly  306  having a safety  300  in accordance with a second embodiment of the invention. Reference may be simultaneously made to  FIGS. 11 and 12 . The igniter assembly  306  includes a slider  316  that is sized and configured for travel along a slider pathway  314  within the housing  312  when properly urged by a cord or cable  330 , the cable having an end cap  332  and inserted into a channel  334  of the slider  316  as similarly described above. It is recognized that the cable  330  may be permanently affixed or connected to the slider  316  as would be recognized by a person having ordinary skill in the relevant art. The igniter assembly  306  further provides an optional, arcuate shaped bridge  328  for retaining the slider  316  in the loaded state upon a cutter  140 , where the cutter  140  may pierce or release the bridge  328  allowing the slider  316  to travel along the pathway  314  into the firing state. The bridge  328  provides some resistance to slider motion; however, it does not provide assurance of unintended motion when subjected to all external forces, as was described above, e.g. first row in Table 1. 
         [0052]    In order to prevent unintended slider motion accidental application of force, the igniter assembly  306  includes the safety  300 . Generally, the safety  300  provides a lock-out type of mechanism that prevents slider motion except when a particular “combination” of parameters is provided that allows the slider  316  to move as intended. Specifically, the so called “combination” is acquired by taking advantage of the material properties, the material geometry, the intended cable force and the unintended impact force. The required parameter combination is such that when there is a cable force the material geometry and the material properties will allow slider motion, but when the unintended impact force is present without the cable force then there is no slider motion. The impact force FI comprises generally any external force being applied to the igniter assembly  306  in any direction, particularly in the zero-degree direction as shown in  FIG. 11 . The cable force FC is the force applied to the cable  330  in a cable channel  304  when actuated by the deploying parachute. The force FC is generally shown in  FIGS. 11 and 12 . The channel  304  directs the force FC somewhat orthogonally to the travel direction of the slider  316 , however it is recognized that the Force FC may be oriented in any direction other than inline with the slider&#39;s motion and the impact force FI. 
         [0053]    Returning to the embodiment shown in  FIGS. 11 and 12 , the safety  300  includes a cable  330  connected to a sleeve  302 , where the sleeve  302  arrests the motion of the slider  316  with respect to the igniter assembly  306  when subjected to the force FI by acting as a supporting column. The sleeve  302  has a slider end  302   a  and a housing end  302   b . The sleeve  302  provides structural support for the cable  330  primarily in its axial direction so that the proximately coupled ends  302   a  and  302   b  provide motion resistance between a slider end  316   a  of the slider  316  and (including an intervening segment of cable  330 ) an inside housing cover surface  350   b  of a housing cap or cover  350 , respectively. The cover  350  is part of the igniter assembly  306 . 
         [0054]    The sleeve  302  is sufficiently pliable that it may fracture, bend, flex, yield or otherwise give way when subjected to the cable force FC applied by the cable  330 , allowing the slider  316  to move as the cable  330  is drawn through the channel  304 . In this embodiment the channel  304  orthogonally transitions the motion of cable  330  to the direction of movement of slider  316 . To further facilitate designed failure of the sleeve  302  when subjected to the cable force FC, an impingement surface or point  308  is provided in the channel  304  of the igniter assembly  306 . 
         [0055]    The sleeve  302  may include one or more peripheral recesses or grooves  310 . The grooves  310  provide added structural relief in the non-axial direction for facilitating motion of the cable  330  when subjected to cable force FC, without appreciably diminishing the strength of the sleeve  302  in its axial direction when subjected to impact force FI. The grooves  310  in this embodiment are v-grooves; however, it is recognized that any other suitable shape, including without limitation slits, cuts or material fracture points, that facilitate relief may be used. 
         [0056]    In order to provide vibration protection to the sleeve  302  during storage and handling and to further secure the sleeve  302  between the slider  316  and the cover  350 , an optional sleeve bridge  360  may be included. The sleeve bridge  360  releasably secures the sleeve  302  (and the cable  330 ) to a wall  312   c  of the housing  312  with tacks  362 . The sleeve bridge  360 , the tacks  362  or a combination of the two are designed to give way allowing the cable  330  and sleeve  302  to propagate through the channel  304  when subject to the cable force FC. 
         [0057]    As described above with respect to the second embodiment, there are design attributes that improve the functionality of the sleeve. The sleeve may be “staked” into place to retain the sleeve within the assembly, but yet allow sleeve movement upon a load applied through the cable. Also, the polycarbonate housing  312  may have a radius having a very subtle, yet sharpened, corner within the assembly to further ensure the sleeve  302  or sleeve segments will fracture upon cable loading. Moreover, the polycarbonate-housing opening may be sized to allow the “fractured” sleeve to pass through the igniter assembly into channel  304 , providing additional space for slider or sleeve movement. Moreover, the sleeve  302  may include a plurality of “v” grooves in the wall thereof to a sufficient depth, given the sleeve wall thickness, to facilitate sleeve fracture upon cable loading. 
         [0058]    To summarize with respect to the described embodiments, embodiments of the sleeve are designed, with geometry and material selection, to stay in place, until sufficient and appropriately directed force releases the sleeve allowing for slider movement and flare ignition. Thus, the flare may ignite when operational loads are applied through a cable, but will resist flare ignition due to other loads applied to the flare. 
         [0059]    A third embodiment of a sleeve  402 , as depicted in  FIG. 13 , is a coil bound or tension spring. The coil bound or tension spring may surround a cable  430  in the same manner as mentioned above with respect to the first and second embodiments to provide high stiffness in the axial direction of the sleeve under columnar loading, but while allowing the cable to yield in the normal direction. In this regard, the spring forming sleeve  402  would have high spring rate K to resist external forces, but a low bending moment to allow the cable  430  to apply a cable force. 
         [0060]    While particular embodiments of the invention have been shown and described, numerous variations and other embodiments will readily occur to those of ordinary skill in the art. Accordingly, the invention is limited only by the appended claims.