Abstract:
A flashlight is disclosed for use in environments with relatively high levels of vibration forces acting along a predominant axis of light emission of the flashlight. The flashlight includes a lamp having a pair of leads extending rearwardly from the lamp parallel to the predominant axis of light emission and a printed circuit board disposed perpendicular to the predominant axis of transmission. The flashlight further includes a pair of receptacles disposed in the printed circuit board and adapted to receive the pair of leads of the lamp and a conductive adhesive disposed within the receptacles to secure the leads of the lamp within the receptacles of the printed circuit board.

Description:
FIELD OF THE INVENTION  
         [0001]    The present invention relates generally to flashlights, and more particularly to flashlights that in use are subjected to substantial reversible shock forces acting generally longitudinally of the flashlight.  
         BACKGROUND OF THE INVENTION  
         [0002]    The concept of mounting flashlights on guns is a relatively recent innovation. Prior art flashlights used lamps that were inefficient and required relatively large batteries. Past efforts to mount flashlights on guns have resulted in combinations that were cumbersome and prohibitively heavy. Further, the market for flashlights mountable on guns is limited. For example, sportsmen involved in hunting are typically not allowed to hunt after dusk. Consequently, a flashlight mounted on a sport gun is of little value to a sportsman.  
           [0003]    In contrast, military and law enforcement agencies are frequently called upon to operate at night and under a variety of environmental conditions. However, when used in combat or law enforcement situations, the failure of a gun-mounted flashlight could result in serious endangerment to the user. For example, if a soldier or law enforcement officer were to attempt to illuminate a target while arming his weapon, but before firing his flashlight malfunctioned or operated intermittently, any momentary illumination from the flashlight could reveal the soldier&#39;s or officer&#39;s position and cause the soldier or officer to become the target of return fire.  
           [0004]    Recent advances in weapons technology have provided a number of relatively light, reliable, hand-holdable rapid firing weapons either of an automatic fire pistol or “machine gun” type. Light illumination sources have also been developed for use with the new weapons technology that provide a high ratio of light ray output to weight. In general, any combination of lithium, NiCd or air-cell batteries used in conjunction with halogen or xenon lamps provide a relatively high light output to weight ratio. When combined with aluminum or strong plastic housings and fittings, the result is a lightweight, relatively durable combination.  
           [0005]    One successful combination includes the use of lithium batteries and xenon lamps. Xenon lamps may be constructed of a high pressure glass. Unlike quartz lamps, xenon lamps may be handled and easily replaced within conventional flashlights. To replace a xenon lamp, a user may simply remove a lens ring and take out a reflector assembly. The reflector assembly may include the reflector and a lamp assembly. The lamp assembly generally includes an adjuster that holds the xenon lamp. Typically, the xenon lamp has a pair of leads that are inserted into the adjuster. The adjuster may then be screwed into the reflector assembly. The distance that the adjuster is screwed into the reflector may be used to control focus.  
           [0006]    While such combinations have been somewhat successful, they have generally failed to meet the harsh requirements of military or law enforcement applications. When combined with rapid fire automatic weapons, conventional flashlight technology often fails due to factors such as vibration forces. Accordingly, a need exists for flashlight technology that is both lightweight and also resistant to shock forces.  
         BRIEF SUMMARY OF THE INVENTION  
         [0007]    In carrying out the present invention, a flashlight is provided for use in environments wherein the flashlight is subjected to relatively high levels of vibration forces acting along a predominant longitudinal axis of light ray emission of the flashlight. The flashlight includes a light source in the form of a high pressure, high intensity, incandescent lamp having a pair of leads extending rearwardly from the lamp generally parallel to the predominant axis of light emission rays. A printed circuit board is disposed generally transverse to the predominant axis of light transmission. The flashlight further includes a pair of receptacles disposed in the printed circuit board and adapted to receive the leads of the incandescent lamp. A conductive adhesive is disposed within one or both of the receptacles to secure the leads of the lamp within the receptacles of the printed circuit board. Alternatively, the conductive adhesive may be injected into one or both of the receptacle after the leads of the lamp have been installed. In general, the steps of the process may be practiced in any order. In this manner, the LED leads are not displaced from the circuit board when subjected to high reciprocating forces as experienced with prior flashlights having their leads inserted into receptacles in the circuit board but not fixedly secured therein.  
           [0008]    Accordingly, one of the primary objects of the present invention is to provide a technique for securing the leads of an incandescent lamp light source to a printed circuit board in a flashlight so as to prevent dislodgement of the leads from the circuit board when the flashlight is subjected to high reciprocating forces acting substantially in the direction of the light rays emitted from the flashlight.  
           [0009]    Another object of the present invention is to provide a flashlight that employs a printed circuit board disposed generally transverse to the longitudinal axis of the flashlight and has the leads of an incandescent lamp secured in receptacles in the circuit board by an adhesive so as to prevent the leads dislodgement from the circuit board when subjected to significantly high shock forces acting on the leads in a direction generally normal to the circuit board.  
           [0010]    A feature of the present invention lies in providing a flashlight as aforedescribed that facilitates attachment to a weapon, such as a machine gun, and that is constructed to withstand significantly high reciprocating forces acting in the axial direction of the light source leads during operation of the machine gun.  
           [0011]    Further objects, features and advantages of the present invention will become apparent from the following description of a preferred embodiment of the invention when taken in conjunction with the accompanying drawings wherein like reference numerals designate like elements throughout the several views. 
       
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0012]    [0012]FIG. 1 is a side elevational view of a gun having a flashlight made in accordance with the present invention mounted thereon;  
         [0013]    [0013]FIG. 2 is an exploded elevational view of the flashlight of FIG. but with internal power source batteries being shown in phantom;  
         [0014]    [0014]FIG. 3 depicts a lamp holder assembly of the type employed in the flashlight of FIG. 2, portions being shown in longitudinal section for clarity;  
         [0015]    [0015]FIG. 4 is an exploded view of the lamp holder assembly of FIG. 3; and  
         [0016]    [0016]FIG. 5 depicts, on an enlarged scale, a lamp assembly as employed in the lamp holder assembly of FIG. 4. 
     
    
     DETAILED DESCRIPTION  
       [0017]    Referring now to the drawings, FIG. 1 depicts a flashlight  10  employing a vibration resistant light source in accordance with the present invention attached to a machine gun  12 . As illustrated, the flashlight  10  is attached to the machine gun  12  so that a predominant axis of light ray emission  16  from the flashlight is substantially parallel with the direction of gunfire from the machine gun  12 .  
         [0018]    As the machine gun  12  fires, the detonation of the gunpowder inside each cartridge fired imparts a backward impulse to the machine gun  12  that must be overcome by the user (not shown). Further, in the case of a gas-operated breech, the firing of each cartridge causes the breech to automatically open and close as each spent cartridge is ejected and each new cartridge is loaded. The net effect of firing the machine gun  12  is to impart significant vibration forces  14  to the flashlight  10  acting in a direction substantially parallel to the axis of light ray emission from the flashlight.  
         [0019]    As shown in FIG. 2, the flashlight  10  includes a generally tubular body  20  that houses one or more batteries such as 1.5-volt alkaline batteries  22 ,  24 , a switch  26  and a light assembly  28 . The light assembly  28  also includes a lamp holder assembly  32 , a reflector assembly  30  and a retaining ring  34 . The lamp holder assembly  32  includes a generally tubular-shaped impulse housing  50  made of a suitable electrically conductive material, a lamp assembly  52 , an electrically conductive spacer  56 , and an electrically nonconductive insulating collar  54  as illustrated in FIGS. 3 and 4.  
         [0020]    Referring to FIG. 4, the housing  50  has a stepped internal cylindrical passageway defining a lamp receiving portion  58  and a printed circuit PC board receiving portion  60  separated by an annular shoulder  62 .  
         [0021]    As illustrated in FIG. . 5 , the lamp assembly  52  includes a lamp  70  and a PC board assembly  92 . The lamp  70  is preferably a high pressure, high intensity incandescent lamp having a filament  72 , first and second leads  74 ,  76 , and an elastomeric sheath  78 . The elastomeric sheath  78  surrounds the outer circumference of the lamp in which filament  72  is embedded and functions to cushion the quartz or high temperature envelope of the lamp from transverse vibrations.  
         [0022]    The PC board assembly  92  includes a circular-shaped fiberglass board  84  having parallel planar external surfaces  84   a  and  84   b . First and second electrically conductive receptacles  80  and  82 , that may be formed as tubular-shaped brass fittings, are secured to the board  84  by pre-drilling suitable size cylindrical holes equidistant from the center of the board  84  so as to lie on a common diameter and press fitting or swaging the receptacles  80 ,  82  into the pre-drilled holes. The tubular receptacles  80 ,  82  define center passageways or apertures for receiving the leads  74 ,  76  of the lamp  70 .  
         [0023]    The PC board  84  has conductive coatings  86  and  88  formed on its opposite surfaces  84   a  and  84   b , respectively, by appropriate known technology such as plating, lamination, etc. The conductive coating  86  is formed so as to make electrical contact with the first receptacle  80  without contacting receptacle  82 , and the conductive coating  88  is formed to make electrical contact with the second receptacle  82  on the opposite side of the board  84  without contacting receptacle  80 .  
         [0024]    To form the lamp assembly  52 , a suitable amount of an electrical conductive and flexible adhesive resin (glue)  90 , such as available from Loc Tite under its Part No. 3882, is injected into each of the apertures passing through the receptacles  80 ,  82 . Following injection of the adhesive  90 , the leads  74 ,  76  are pressed into the apertures within the receptacles  80 ,  82  and the adhesive resin  90  allowed to cure by the application of heat or otherwise.  
         [0025]    After the adhesive resin  90  has cured, the lamp assembly  52  may be assembled to the housing  50  (FIG. 3). The lamp receiving portion  58  and PC board receiving portion  60  of the housing  50  need only be slightly larger in diameter than an outer diameter of the elastomeric sheath  78  and PC board  84 , respectively. Once the lamp assembly  52  has been inserted into the housing  50 , the conductive coating  86  forms an electrical contact with the housing  50 . Electrical contact with the conductive coating  88  is formed through the electrically conductive spacer  56 .  
         [0026]    The diameter  68  (FIG. 4) of the spacer  56  may be slightly smaller (e.g.,  5  mils) than the inner diameter  69  of the insulated collar  54 . In contrast, the outer diameter  64  of the flange  66  on spacer  56  may be significantly smaller (e.g., 100 mils) than the inner diameter  63  of the housing  50 . The net effect of these differences in diameter is that the insulated collar  54  holds the spacer  56  in a centered position within the recess  60  in housing  50  such that the flange  66  only contacts the conductive surface  88  on the PC board  84  and cannot touch the adjacent inner cylindrical surface of recess  60  in housing  50 . A hollow, cylindrical space or recess  55  within the spacer  56  allows the flange  66  to surround the receptacles  80 ,  82  without coming into contact with them.  
         [0027]    To assemble the flashlight  10 , the lamp assembly  52  may first be inserted into the housing  50  as above described. The spacer  56  may then be inserted into the insulated collar  54  and a male thread  57  on the collar  54  screwed into a complementary female thread  53  within the housing  50  until the flange  66  bottoms against the conductive surface  88 . The lamp assembly  52 , spacer  56  and nonconducting, insulating collar  54  assembled into the housing  50  form the lamp holder assembly  32 .  
         [0028]    The lamp holder assembly  32  may then be assembled to the reflector  30 . To this end, a female thread  31  within the reflector  30  is screwed onto a male thread  51  on the housing  50  to form the light assembly  28 .  
         [0029]    The light assembly  28  is then assembled into the flashlight housing  20  by inserting the light assembly  28  into the enlarged diameter end  20   a  until the spacer  56  contacts the positive terminal  23  of the battery  22  after which the retaining ring  34  is placed over the reflector  30 . A female thread  33  within the retaining ring engages a male thread  19  on the flashlight body to complete assembly of the flashlight  10 . Once inserted into the flashlight body  20 , a flange  29  of the reflector  30  forms an electrical contact with a moveable contact  21 . The switch  26  then completes the circuit back to the negative terminal of the battery through a spring  27 .  
         [0030]    With the thus described flashlight  20  mounted on the machine gun  12  as illustrated in FIG. 1, the elements of the flashlight  10  cooperate to form a structure that is extremely resistant to vibration. For example, during detonation of a cartridge, the backward impulse causes the batteries to surge forward against the spacer  56 . However, the spacer flange  66  presses directly against the shoulder  62  through the periphery of the circuit board  84  transferring the impulse energy into the impulse housing  50 . The impulse housing  50 , in turn, transfers the energy to the reflector  30  and in turn to the body  20  via operation of the retaining ring  34 .  
         [0031]    The circuit board  84  does not receive any significant stress or vibrating impulse forces normal to the surfaces  84   a ,b (i.e. in the direction of light transmission) except for the weight of the lamp  70 . The lamp  70 , in turn, resists the impulse energy forces, and thus the tendency to pull the leads  74 ,  76  out of the circuit board  84 , because of the conductive glue  90  securing the leads  74 ,  76  into the receptacles  80 ,  82 .  
         [0032]    The use of the glue  90  in the flashlight  10  differs from the prior use of such glues for a number of reasons. For example, the prior uses of such glues have been in the context of a primary attachment and connection mechanism in the assembly and repair of flexible circuits or for electronic shielding. In contrast, the glue  90  of the flashlight  10  is used as an auxiliary mechanism for securing the leads of the lamp  70  to the receptacles  80 ,  82  and for maintaining electrical contact.  
         [0033]    Further, the glue  90  is used within the receptacles to resist shearing action. However, the mechanism that allows the glue  90  to perform so successfully is not limited exclusively to its ability to resist shear. For example, as with most mechanical devices, the receptacles  80 ,  82  are created with certain manufacturing tolerances, including variations in diameter and wall consistency along the length of the receptacle apertures. The leads  74 ,  76  are subject to the same variations. In effect the variations in diameter and wall surface consistency operate to create a large number of attachment points that directly resist lead pull-out and which can also contribute to a wedging effect. The glue  90  within the receptacle  80 ,  82  is believed to interact with the variations due to manufacturing tolerances to form an in-situ locking mechanism that would not exist in other contexts. The interaction of the glue  90  with the receptacles  80 ,  82  and leads  74 ,  76  results in a bonding mechanism that far exceeds the tensile and shear strengths of the glue  90  by itself.  
         [0034]    Still further, the flexibility of the glue  90  allows the glue to absorb the shock generated by gunfire without fracturing or separating. The result is an extremely durable bond between the leads  74 ,  76  and the receptacles  80 ,  82  that prevents the lamp leads from being ejected from the receptacles when subjected to the shock forces created by firing the machine gun.  
         [0035]    While a preferred embodiment of the present invention has been illustrated and described, it will be understood that changes and modifications may be made therein without departing from the invention in its broader aspects. Various features of the invention are defined in the following claims.