Abstract:
A flashlight in accordance with the present invention includes a chamber, end cap, head assembly, and lamp holder assembly. The head assembly includes a reflector and a lens. In accordance with one embodiment of the present invention, the flashlight includes electrode connections that prevent the conduction of electrical energy from one or more batteries which are improperly aligned within the chamber. In another embodiment, the lamp holder assembly includes a lamp socket having a lamp guide and/or a fluorescent coating. In another embodiment, the flashlight comprises a head assembly attached to the chamber which is rotatable relative to the chamber to cause electrical coupling of the lamp and one or more batteries retained by the chamber.

Description:
[0001]    This application is a continuation of U.S. patent application Ser. No. 10/377,535, filed Feb. 27, 2003, now pending, which is a reissue application of U.S. patent application Ser. No. 09/100,527, filed Jun. 18, 1998, now U.S. Pat. No. 6,193,388, which is a continuation-in-part of U.S. patent application Ser. No. 09/013,078, filed Jan. 26, 1998, now U.S. Pat. No. 6,354,715. 
     
    
     FIELD OF THE INVENTION 
       [0002]    The present invention relates to the field of flashlights and more specifically to hand held portable battery operated flashlights. 
       BACKGROUND OF THE INVENTION 
       [0003]    Flashlights generally include a battery chamber having an end cap for retaining one or more batteries, a light bulb electrically connected to the one or more batteries and a reflector for reflecting the light from the light bulb in a particular direction. The electrical connection between the batteries and the light bulb usually includes a switch mechanism for selectively providing electrical energy from the batteries to the light bulb and, therefore enabling the flashlight to be turned on and off. The primary function of flashlights is to provide a convenient portable storable light source which is capable of projecting light in a particular direction. 
         [0004]    Some flashlights are capable of focusing and defocusing light projected by the flashlight by allowing the light bulb to be moved within the reflector along the reflector&#39;s optical axis. The reflector is typically a parabolic shaped reflector because such a reflector provides a theoretical focus of the light when the light bulb is positioned at the parabolic reflector&#39;s focal point. In this regard, light rays emanating from a light bulb positioned at the focal point of a parabolic reflector are reflected parallel to the parabolic reflector&#39;s optical axis. Referring to  FIG. 1A , a light beam dispersion is shown from a parabolic reflector with a light bulb positioned at the focal point of the parabolic reflector. In contrast, as shown in  FIG. 1B , when the light bulb is moved away from the parabolic reflector&#39;s focal point, light rays reflected by the parabolic reflector diverge (i.e., defocus) leaving a glaring light void about the center of the reflected light rays and decreasing the light gathered from the light bulb. 
         [0005]    The electrical energy to enable a flashlight to operate is usually provided by one battery, or two or more batteries in series arrangement, held within the battery chamber of the flashlight. When the charge in the batteries is depleted, a user will typically replace the batteries by removing the end cap, removing the old batteries from the battery chamber, inserting new batteries into the battery chamber, and replacing the end cap. However, when replacing multiple batteries in a flashlight, the possibility arises that a user may improperly position the batteries in a nonseries arrangement. For example, a user may improperly align the new batteries such that the positive poles of the batteries face each other, or may comingle the old batteries with the new batteries and misalign a new battery with an old battery. Misaligning the batteries may have undesired consequences, for example explosion causing physical injury, to a user of the flashlight. 
         [0006]    Additionally, batteries often naturally emit hydrogen gas. As such, when batteries are contained within the flashlight&#39;s battery chamber, the possibility arises that hydrogen gas emitted by the batteries may become trapped within the flashlight. In some circumstances, a defective battery will emit high quantities of hydrogen gas. As a consequence, hydrogen gas may accumulate within the flashlight, thus raising the possibility of undesired consequences to a user of the flashlight, for example explosion causing physical injury. 
         [0007]    Finally, parts of the flashlight sometimes require replacement. For example, the flashlight&#39;s light bulb will require replacement when the light bulb&#39;s filament burns out, which is often discovered when the flashlight is needed (e.g., when there are no other sources of light, including for example electrical power outages which occur at night or darkness when camping outdoors). Flashlights usually include a spare light bulb positioned on the interior of the end cap. Replacing a burned out bulb with a bulb positioned on the end cap is difficult, especially in low or no light conditions. For example, during a power outage, replacing the light bulb in a typical flashlight would require a user to remove the end cap, locate and grasp a small spare light bulb on the end cap without allowing the batteries to fall out of the flashlight, replace the end cap, remove the head assembly, replace the burned out bulb and replace the head assembly, all in darkness. 
       SUMMARY OF THE INVENTION 
       [0008]    It is an objective of the present invention to provide an improved flashlight having improved switching and focusing capabilities. 
         [0009]    It is another objective of the present invention to provide an improved flashlight which maximizes the light gathered from a light bulb, optimally focuses the gathered light into a projected light beam and minimizes the light void within the light beam throughout the range of focus. 
         [0010]    In accordance with one embodiment of the present invention, an improved flashlight is provided having an end cap, chamber, head assembly and lamp holder assembly. In one embodiment of the invention, the head assembly includes an elliptical reflector to increase the amount of light reflected by the flashlight when a light source is positioned within the elliptical reflector. Preferably, the elliptical reflector has an eccentricity value of no less than about 0.80 and no more than about 0.99. Preferably, the elliptical reflector has a vertex curvature value of no less than about 2.0 and no more than about 5.2. In one arrangement, the elliptical reflector has an eccentricity value of about 0.96 and a vertex curvature of about 3.1. 
         [0011]    In accordance with another embodiment of the present invention, a flashlight having an elliptical reflector is matched with either a negative or concave lens, or a flat or planar lens. In this regard, the focusing and light gathering characteristics of the flashlight are optimized when the flashlight&#39;s elliptical reflector is matched with a negative or flat lens. Preferably, the flashlight&#39;s elliptical reflector is matched with a lens having an effective focal length no greater than about −2.5″. In one arrangement, an elliptical reflector having an eccentricity value of about 0.96 and a vertex curvature of about 3.1 is matched with a lens having an effective focal length of about 0″. 
         [0012]    In accordance with another embodiment of the present invention, the head assembly includes a hyperbolic reflector to increase the amount of light reflected by flashlight when a light source is positioned within the reflector. Preferably, the hyperbolic reflector has an eccentricity value of no less than about 1.01 and no more than about 1.25. Preferably, the hyperbolic reflector has a vertex curvature value of no less than about 2.0 and no more than about 7.0. In one arrangement, the hyperbolic reflector has an eccentricity value of about 1.04 and a vertex curvature of about 3.3. 
         [0013]    In accordance with another embodiment of the present invention, a flashlight having a hyperbolic reflector is matched with either a positive or convex lens, or a flat or planar lens. In this regard, the focusing and light gathering characteristics of the flashlight are increased when the flashlight&#39;s hyperbolic reflector is matched with a positive or flat lens. Preferably, the hyperbolic reflector is matched with a lens having an effective focal length no less than about 2.5″. In one arrangement, a hyperbolic reflector having an eccentricity value of about 1.04 and a vertex curvature of about 3.3 is matched with a lens having an effective focal length of about 0″. 
         [0014]    It is another objective of the present invention to provide a flashlight with an improved electrical connection between the batteries and the light source. In accordance with another embodiment of the present invention, the flashlight includes electrode connections which substantially reduce the likelihood that electrical energy will be conducted from batteries which are improperly aligned within the flashlight. In this regard, the electrode connection intended to contact the negative pole of the battery includes a non-conductive portion at the center of the electrode connection and a conductive portion at the perimeter of the electrode connection. As such, in the circumstance wherein a battery is inserted into the flashlight with the positive pole facing the electrode connection, the positive pole will only contact the non-conductive portion, and not the conductive portion, of the electrode connection. Additionally, the electrode connection intended to contact the positive pole of the battery includes a conductive spring having a nonconductive coating. As such, in the circumstance wherein a battery is inserted into the flashlight with the negative pole facing the electrode connection, the negative pole only will contact the nonconductive coated portion. 
         [0015]    It is another objective of the present invention to provide a flashlight with a light holder assembly that facilitates lamp bulb replacement. In one embodiment of the present invention, the lamp holder assembly includes a lamp socket having a lamp guide which provides a guide for installing lamp bulbs into the lamp socket and also provides a secure position for the lamp bulb. In accordance with one embodiment of the present invention, the guide facilitates replacing lamps in less than desirable light conditions, as well as protects the lamp from receiving impact shocks when the flashlight is jarred. 
         [0016]    It is another objective of the present invention to provide a flashlight capable of maintaining a spare lamp bulb in close proximity to the flashlight&#39;s light bulb thus providing for the efficient and easy replacement of the lamp bulb when needed. In accordance with one embodiment of the present invention, the flashlight includes a lamp holder assembly which includes a notch for receiving and holding a spare lamp. As such, a spare lamp is easily accessible by simply removing the head assembly from the chamber and all that is required to replace the lamp bulb is removal of the lamp bulb in the lamp socket, removing the spare lamp, and inserting the spare lamp into the lamp socket. Preferably, the lamp holder assembly further includes a fluorescent coating or additive which illuminates light in otherwise dark conditions, thereby facilitating lamp bulb replacement in less than desirable light conditions. 
         [0017]    In another embodiment, the flashlight comprises a chamber for retaining one or more batteries, a lamp, electrical coupling for holding said lamp and selectively electrically coupling the lamp and one or more batteries, and a head assembly attached to the chamber and rotatable relative to the chamber to cause the electrical coupling to selectively electrically couple the lamp and one or more batteries retained by the chamber. In this regard, the lamp holder assembly moves inside the chamber when the flashlight is turned “off” or “on.” The lamp holder assembly includes a lamp holder, a conductive spring, a switch plate, a detent lever, a detent ball, a switch contact, a spring contact, a conductive strip, and a strip support. When assembled, the lamp holder assembly is secured axially and rotatable relative to the chamber. The head portion of the flashlight is assembled to the chamber by attaching the assembled head assembly to the chamber such that the lamp is positioned within the first central opening of the reflector. As a consequence, the head assembly is removably attached to the chamber. When fully seated, the head assembly engages the switch plate, and the rotation of the head assembly will cause the lamp holder assembly to rotate. The lamp holder assembly is rotatable among three detents. The first occurs when the head assembly is removed or attached to the chamber. The second occurs when the head assembly is in the “off” position. The third occurs when the head assembly is in the “on” position. The detents are caused by the detent ball being positioned in one of three slots formed on the outer edge of the chamber. As a result, the flashlight is moveable between the “on” and “off” detent positions by the radial movement of the head assembly. The switch contact does not contact the conductive strip in the “off” position. The switch contact contacts the conductive strip in the “on” position. The “on” detent occurs when the detent ball rolls to a second slot on the outer edge of the chamber. Notably, the detent mechanism is physically separated from the switching mechanism. 
         [0018]    In another embodiment of the flashlight, the spare lamp is held secure by the lamp holder assembly until the user of the flashlight rotates the lamp holder assembly to align a spare lamp opening with the spare lamp. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0019]      FIG. 1A  shows a light beam dispersion from a parabolic reflector with a light source positioned at the focal point of the reflector. 
           [0020]      FIG. 1B  shows a light beam dispersion from a parabolic reflector with a light source defocused ⅓ the distance from the focal point to apex of the reflector curvature. 
           [0021]      FIG. 2  is a perspective view of a flashlight in accordance with the present invention. 
           [0022]      FIG. 3  is an exploded perspective view illustrating the assembly of the flashlight of  FIG. 2 . 
           [0023]      FIG. 4  is an exploded side view of the end cap, chamber, lamp holder assembly and head assembly. 
           [0024]      FIG. 5  is a cross-section view of the flashlight down the center of the flashlight of  FIG. 2  as taken through the plane indicated by  2 - 2 . 
           [0025]      FIG. 6A  is an exploded perspective view of the interior of the end cap. 
           [0026]      FIG. 6B  is a cross-section view of the end cap through the plane indicated by  2 - 2 . 
           [0027]      FIG. 7A  is an exploded perspective view of the head assembly. 
           [0028]      FIG. 7B  is a partial cross-section of the head assembly of  FIG. 7A  as taken through the plane indicated by  7 - 7 . 
           [0029]      FIG. 8A  is an exploded view of the lamp holder assembly. 
           [0030]      FIG. 8B  is a partial cross-section of the lamp holder assembly of  FIG. 8A  as taken through the plane indicated by  8 - 8 . 
           [0031]      FIGS. 9A and 9B  are cross-section views of the flashlight of  FIG. 2  as taken through the plane indicated by  2 - 2  showing aligned and misaligned batteries, respectively. 
           [0032]      FIG. 10  is a perspective view of the lamp holder assembly positioned within the chamber. 
           [0033]      FIG. 11  is partial cross-section of the head portion of the flashlight of  FIG. 2 , as taken through the plane indicated by  2 - 2 , showing the flashlight in the “off” position. 
           [0034]      FIG. 12  is partial cross-section of the head portion of the flashlight of  FIG. 2 , as taken through the plane indicated by  2 - 2 , showing the flashlight in the “on” position. 
           [0035]      FIGS. 13A and 13B  show the results of simulations for a variety of eccentricity values. 
           [0036]      FIG. 14A  shows the lamp prior to being inserted into the lamp socket. 
           [0037]      FIG. 14B  shows the lamp inserted into the lamp socket. 
           [0038]      FIG. 14C  shows a spare lamp removed from the notch which holds the spare lamp. 
           [0039]      FIG. 15A  is a front view of the lamp holder assembly when the head assembly is removed from the chamber. 
           [0040]      FIG. 15B  is a front view of the lamp holder assembly when the head assembly is attached to the chamber. 
           [0041]      FIG. 16  is an exploded perspective view illustrating the assembly of the flashlight of  FIG. 2  having the alternative lamp holder assembly. 
           [0042]      FIG. 17  is an exploded side view of the end cap, chamber, alternative lamp holder assembly and head assembly. 
           [0043]      FIG. 18  is a cross-section view of the flashlight, having the alternative lamp holder assembly, down the center of the flashlight of  FIG. 2  as taken through the plane indicated by  2 - 2 . 
           [0044]      FIG. 19  is a partial cross-section of the head assembly of  FIG. 7A  as taken through the plane indicated by  7 - 7 , showing a different shaped guide to accommodate the alternative lamp holder assembly. 
           [0045]      FIG. 20  is an exploded view of the alternative lamp holder assembly. 
           [0046]      FIG. 21  is a partial cross-section of the lamp holder assembly of  FIG. 20  as taken through the plane indicated by  20 - 20 . 
           [0047]      FIG. 22A  is a perspective view of the alternative lamp holder assembly positioned within the chamber with the detent lever and switch plate shown apart from the lamp holder assembly. 
           [0048]      FIG. 22B  is a perspective view of the alternative lamp holder assembly fully assembled to the chamber. 
           [0049]      FIG. 22C  is a side view of the perspective view shown in  FIG. 22A . 
           [0050]      FIG. 23  is a front view of the alternative lamp holder assembly (without the switch plate) at the second end of the chamber, showing the position of the alternative lamp holder assembly when the head assembly is capable of being attached or removed from the second end of the chamber. 
           [0051]      FIG. 24  is a front view of the alternative lamp holder assembly (without the switch plate) at the second end of the chamber, showing the position of the alternative lamp holder assembly when the flashlight is in the “off” position. 
           [0052]      FIG. 25  is a front view of the alternative lamp holder assembly (without the switch plate) at the second end of the chamber, showing the position of the alternative lamp holder assembly when the flashlight is in the “on” position. 
           [0053]      FIG. 26  is a front view of the alternative lamp holder assembly (without the switch plate) at the second end of the chamber, showing the position of the alternative lamp holder assembly which exposes the spare lamp. 
           [0054]      FIG. 27  is a perspective view of the alternative lamp holder assembly positioned within the chamber with the detent lever and switch plate shown apart from the lamp holder assembly. 
       
    
    
     DETAILED DESCRIPTION 
       [0055]    Referring to  FIGS. 2 through 5 , a flashlight  10  in accordance with one embodiment of the present invention is shown having a chamber  20 , end cap  30 , head assembly  40  and lamp holder assembly  50 . The chamber  20  includes an interior portion for holding two batteries  60 ,  62  in a series arrangement, openings at a first end  210  and a second end  220 , a first o-ring  230  positioned at the first end  210 , and a second o-ring  240  positioned at the second end  220 . Referring additionally to  FIGS. 6A and 6B , the end cap  30  includes a bowed tripod portion  310  to facilitate standing the flashlight  10  on a flat surface, interior threads  320  and a conductive disk  330 . Referring additionally to  FIGS. 7A and 7B , the head assembly  40  includes a head piece  410 , a first o-ring  420 , a bezel  430 , a reflector  440 , a second o-ring  450  and a lens  460 . The head piece  410  includes a first end  411 , a circular tab  412  located within the head piece  410  at the first end  411 , guides  413 , a second end  414  and lugs  415  located within the head piece  410  at the second end  414 . The reflector  440  includes a reflective surface on the reflector&#39;s  440  interior, a first central opening  442 , a second central opening  444  substantially opposite the first central opening  442 , wings  446 , and outer threads  448 . Preferably, the reflector  440  consists of a durable synthetic material, such as that offered by General Electric Company under the name ULTEM. The bezel  430  includes a first end  431 , inner threads  432  at the first end  431  which thread to the reflector&#39;s  440  outer threads  448 , a recessed circular tab  433  at the first end  431 , a second end  434 , and a circular tab  435  at the second end  434 . The lens  460  is positioned at the perimeter of the first end  431  of the bezel  430 . The exterior of the flashlight  10  consists of a metal or durable synthetic material. For example, the exterior of the flashlight  10  can consist of a polycarbonite, or acrylonitrile-butadiene-styrene, or the polycarbonite offered by General Electric Company under the name CYCOLOY. 
         [0056]    The chamber  20 , which is shown in  FIG. 5  holding two batteries  60 ,  62 , is enclosed at the first end  210  by the end cap  30  and at the second end  220  by the head assembly  40 . Referring to  FIGS. 4-8 , the end cap  30  is removably attached to the chamber  20  at the first end  210  to selectively uncover the interior portion of the chamber  20  for inserting or removing the batteries  60 ,  62 . In this regard, the chamber  20  includes threading  250  on the exterior surface at the first end  210  of the chamber  20  for engaging the interior threads  320  on the end cap  30 . The first o-ring  230  provides a snug attachment when the end cap  30  is threaded to the chamber  20 . 
         [0057]    The lamp holder assembly  50  includes two embodiments. In either embodiment, the lamp holder assembly  50  is positioned at the second end  220  of the chamber  20 . In the first embodiment, the lamp holder assembly  50  does not move inside the second end  220  of the chamber  20  when the flashlight  10  is turned “off” or “on.” In this regard and referring to  FIGS. 8A and 8B , the lamp holder assembly  50  includes a lamp holder  510 , a conductive spring  520 , a switch lever  530 , a second lever  540 , a switch spring  550 , a switch contact  560 , a second spring  570 , a spring holder  580 , a conductive strip  590  and a strip support  592 . The spring holder  580  includes a spring tab  582 , first tab  584 , second tab  586 , and a first conductive contact  588 . Preferably, the spring holder  580  includes a notch  589  wherein a hydrogen catalyst can be placed to absorb hydrogen gas emitted by the batteries  60 ,  62 . As shown in  FIG. 10 , when assembled to the chamber  20 , the lamp holder assembly  50  does not extend beyond the second end  220  of the chamber  20 . Referring to  FIGS. 3 ,  4 ,  8 A,  8 B and  10 , the lamp holder assembly  50  is assembled to the chamber  20  by first attaching the conductive spring  520  to the spring holder  580 . The spring holder  580  includes a spring tab  582  which engages and retains a portion of the conductive spring  520 . The spring holder  580  and conductive spring  520  are next attached to the second end  220  of the chamber  20 . In this regard, the spring holder  580  includes a first tab  584  and a second tab  586  for engaging the second end  220  of the chamber  20 . The chamber  20  includes an end guide  260 , and the end guide  260  includes a first recessed tab  262  for engaging the first tab  584 , and a second recessed tab  263 , for engaging the second tab  586 . Referencing  FIG. 10 , attachment of the spring holder  580  and conductive spring  520  to the second end  220  occurs by inserting the spring holder  580  and attached spring  520  in the first end  210  of the chamber  20  and moving the spring holder  580  toward the second end  220  of the chamber  20  until the first recessed tab  262  engages the first tab  584  and the second recessed tab  263  engages the second tab  586 . 
         [0058]    The lamp holder  510 , with the switch lever  530  and second lever  540  assembled on the lamp holder  510 , is next inserted into the second end  220  of the chamber  20 . The lamp holder  510  includes tabs  511 , a switch slot  512  and a second slot  513 . The switch lever  530  includes tabs  532  and slots  534 , and the second lever  540  includes tabs  542  and slots  544 . The switch lever&#39;s  530  slots  534  mate with the switch slot  512  to allow the switch lever  530  to slide along the switch slot  512 . The second lever&#39;s  540  slots  544  mate with the second slot  513  to allow the second lever  540  to slide along the second slot  513 . Referencing  FIGS. 3 ,  5 ,  8 A,  8 B and  10 , the lamp holder  510  is next partially inserted into the second end  220  of the chamber  20  by aligning the switch slot  512  with the first slotted opening  264  of the end guide  260 , and the second slot  513  with the second slotted opening  266  of the end guide  260 . Once partially inserted, the switch lever  530  and second lever  540  are spring loaded onto the lamp holder  510  by inserting the switch spring  550  and second spring  570 , and aligning and engaging the switch lever&#39;s  530  slots  534  with the switch slot  512  and aligning and engaging the second lever&#39;s  540  slots  544  with the second slot  513 . With the switch lever  540  and second lever  550  depressed, the lamp holder  510  is fully seated into the second end  220  of the chamber  20 . As a result, as shown in  FIG. 10 , the switch lever&#39;s  530  tabs  532  and the second lever&#39;s  540  tabs  542  engage the chamber  20  at points  514 . As shown in  FIG. 5 , the lamp holder&#39;s  510  tabs  511  engage the interior of the chamber  20 . Referencing  FIGS. 3 ,  8 A and  10 , the switch slot  512  engages the recessed tab  265  of the end guide  260  and the second slot  513  engages the recessed tab  267  of the end guide  260 . Preferably, the lamp holder assembly  510  snap fits to the chamber  20 . Referencing  FIG. 11 , the lamp holder  510  encloses the spring tab  582 , further securing the conductive spring  520  to the spring holder  580 . Referencing  FIG. 11 , the spring holder  580  does not contact the interior of the chamber  20 . Referencing  FIG. 10 , the lamp  70  extends from the second end  220  of the chamber  20  when the lamp  70  is installed into the lamp holder assembly  50 . 
         [0059]    Referring to  FIGS. 7A and 7B , the head assembly  40  is assembled by first inserting the reflector  440  into first end  431  of the bezel  430  and threading the reflector&#39;s  440  threads  448  to the bezel&#39;s  430  inner threads  432 . The second o-ring  450  is next inserted into the circular recessed tab  433  and the lens  460  is fixedly attached to the bezel  430  by pressing the lens  460  into the circular recessed tab  433 . The o-ring  450  allows for secure attachment between the lens  460  and the bezel  430 . Preferably, the lens  460  snap fits to the bezel  430 . The first o-ring  420  is next placed over the circular tab  435  at the second end  434  of the bezel  430 , and the second end  434  of the bezel  430  is inserted into first end  411  of the head piece  410  with the wings  446  of the reflector  440  aligned with the guides  413  of the head piece  410 . When the second end  434  of the bezel  430  is fully inserted into the first end  411  of the head piece  410 , the bezel&#39;s  430  circular tab  434  engages the head piece&#39;s  410  circular tab  412 , and the wings  446  of the reflector  440  engage the guides  413  of the head piece  410 . As a result, the bezel  430  is only allowed to rotate relative to the head piece  410  (i.e., radially) and cannot move away from the head piece  410  (i.e., axially). Preferably, the bezel  430  snap fits to the head piece  410 . As a result of the wings  446  of the reflector  440  engaging the guides  413  of the head piece  410 , the reflector  440  moves within the bezel  430  axially when the bezel  430  is moved radially. 
         [0060]    The head portion of the flashlight  10  is assembled by attaching the assembled head assembly  40  to the chamber  20 , having the lamp holder assembly  50  assembled in the chamber  20 , such that the lamp  70  is positioned within the first central opening  442  of the reflector  440 . In this regard, the head assembly  40  is removably attached to the chamber  20  at the second end  220 .  FIGS. 10 and 15A  show the lamp holder assembly  50  assembled in the chamber  20  when the head assembly is removed from the chamber  20 . The chamber  20  includes the end guide  260  formed on the exterior surface at the second end  220  of the chamber  20 . Referencing  FIGS. 3 and 10 , the end guide  260  includes paths  261  which engage the lugs  415  on the head piece  410 . The lugs  415  are aligned with paths  261 , and the head assembly  40  is guided in the direction  287  until the head assembly  40  is fully seated on the second end  220  of the chamber  20 . The head assembly  40  is then rotated in the direction  288  to a first detent, which is caused by the switch lever  530  being positioned between two of the guides  413 . The flashlight  10  is in the “off” position at this position. In this position, the head assembly  40  is only permitted to rotate relative to the chamber  20  (i.e., radially) and cannot move away from the chamber  20  (i.e., axially). The second o-ring  240  provides a secure attachment between the head assembly  40  and the chamber  20 . 
         [0061]    When fully assembled and holding batteries  60 ,  62  in proper alignment, the flashlight  10  is capable of selectively electrically coupling the lamp  70  to the batteries  60 ,  62 . The chamber  20  includes a conductive strip  590  along the length of the chamber  20 , between the first end  210  and the second end  220 . The conductive strip  590  is supported at the first end  210  of the chamber  20  by the strip support  592 . Referring to  FIGS. 6A and 6B , the end cap  30  includes a nonconductive area  340 . Referencing  FIG. 8 , when the end cap  30  is attached to the chamber  20 , the conductive disk  330  is electrically connected to the conductive strip  590  at point  593 . The conductive disk  330  electrically connects the negative contact of the battery  60  to the conductive strip  590  when the battery  60  is properly aligned in the chamber  20  as shown in  FIG. 9A . The nonconductive area  340  prevents electrical connection when the battery  60  is improperly aligned in the chamber  20  as shown in  FIG. 9B . In this regard, the positive contact of an improperly aligned battery  60  only contacts the nonconductive area  340  and does not contact the conductive disk  330 , due to the opening  331 , as shown in  FIG. 6A . 
         [0062]    The lamp holder assembly  50  selectively electrically connects the lamp  70  to properly positioned batteries  60 ,  62  in accordance with the radial movement of the head assembly  40 . Referencing  FIG. 11 , the flashlight  10  is shown in the “off” position. Referencing  FIGS. 3 ,  10  and  12 , the flashlight  10  is moved to the “on” position by rotating the head assembly  40  in the direction  288 . The head portion of the flashlight  10  can be disassembled by rotating the head assembly  40  from the “off” position in a direction opposite  288  and disengaging the head assembly  40  from the chamber  20  along paths  261 . 
         [0063]    Referring to  FIGS. 8-12 ,  14 A,  14 B,  14 C and  15 , the lamp holder  510  includes a lamp socket  515  for holding a lamp  70  having a first pin  72  and second pin  74  and a lamp guide  516 . When the head portion of the flashlight  10  is assembled, the lamp guide  516  does not contact the reflector  440 . In this regard, the reflector  440  is prevented from contacting the lamp guide  516  by stop  436  as shown in  FIG. 11 . The lamp guide  516  is a guide which facilitates aligning the first pin  72  and second pin  74  of the lamp  70  with the lamp socket  515  when the lamp  70  is being installed. The lamp guide  516  also provides a secure position for the lamp  70  by supporting a part of the outer portion of the lamp  70  when the lamp  70  is installed. As such, the lamp guide  516  facilitates replacing a lamp  70  in less than desirable light conditions, as well as protects the lamp  70  from receiving impact shocks from the reflector  440  when the flashlight  10  is jarred. Additionally, the lamp holder  510  is capable of receiving and holding a spare lamp  71 . In this regard, the lamp holder  510  includes a notch  517  which is capable of receiving a spare lamp  71 . 
         [0064]    As shown in  FIG. 15B , the spare lamp  71  in the notch  517  is covered by the switch lever&#39;s  530  tab  532  when the head portion of the flashlight  10  is assembled. As shown in  FIG. 15A , the spare lamp  71  in the notch  517  becomes uncovered by the switch lever&#39;s  530  tab  532  when the head assembly  40  is disassembled from the chamber  20 . As such, as shown in  FIGS. 10 ,  14 A,  14 B,  14 C,  15 A and  15 B, the spare lamp  71  is easily accessible by removing the head assembly  40  from the chamber  20 , thereby making the spare lamp  71  held by the lamp holder  510  accessible. In this regard, all that is required to replace the lamp  70 , is removal of the lamp  70  from the lamp socket  515 , removing the spare lamp  71  from the notch  517 , and installing the spare lamp  71  into the lamp socket  52 . Preferably, the insulated lamp holder  510  includes a phosphorescent coating or additive, which illuminates light in otherwise dark conditions, thereby facilitating lamp replacement in less than desirable light conditions. 
         [0065]    Referencing  FIGS. 8A ,  8 B,  9 A and  9 B, the first pin  72  is electrically connected to the switch spring  550  by conductive contact  551 , and the second pin  74  is electrically connected to the spring  520  by the first conductive contact  588 , when the lamp  70  is positioned in lamp holder assembly  50 . The conductive spring  520  includes an portion  521  having a nonconductive coating and a tail  522 . As shown in  FIG. 9A , the tail  522  contacts the positive pole of the battery  62  when the battery  62  is properly aligned in the chamber  20 . As shown in  FIG. 9B , the portion  521  having a nonconductive coating prevents electrical contact with an improperly aligned battery  62 . In this regard, the negative pole of an improperly aligned battery  62  only contacts a nonconductive portion of conductive spring  520  and does not contact a conductive portion, thereby preventing electrical connection and removing the possibility of a catastrophic event due to reverse polarization. 
         [0066]    Referring to  FIGS. 5 ,  8 A,  8 B,  11  and  12 , the switch lever  530  is moveable between the “on” and “off” positions when the head portion of the flashlight  10  is assembled. The switch lever  530  includes a switch contact  560  having an edge  561 . The switch contact  560  is electrically connected to the switch spring  550 . Referencing  FIG. 11 , the flashlight  10  is shown in the “off” position. In this position, the switch lever  530  is fully extended due to the switch lever  530  being positioned between two of the guides  413  within the head piece  410 . As a consequence, the switch lever  530  does not electrically connect the edge  561  to the conductive strip  590  at point  594 . Moreover, the switch lever  530  in fully extended position provides a detent to maintain the flashlight  10  in the “off” position until flashlight  10  is moved to the “on” position. Referencing  FIG. 12 , the flashlight  10  is in the “on” position. In this position, the switch lever  530  is compressed due to the switch lever  530  contacting one of the guides  413  within the head piece  410 . As a consequence, the switch lever  530  electrically connects the edge  561  to the conductive strip  590  at point  594 . In the “on” position, the second lever  540  is positioned between two of the guides  413  within the head piece  410 . In this regard, as the head assembly is turned in the direction  288  from the “off” position, the second lever  540  will no longer contact one of the guides  413 , and will become fully extended due to the second lever  540  being positioned between two of the guides  413  within the head piece  410 . The second lever  540  becoming fully extended provides a detent to maintain the flashlight  10  in the “on” position until flashlight  10  is moved to the “off” position. Preferably, the head assembly  40  is rotatable about thirty degrees between the “off” and “on” positions. 
         [0067]    The movement of the lamp  70  within the reflector  440  to focus and defocus the light emanating from the lamp  70  is independent from the radial movement of the head assembly  40  to turn the flashlight  10  “on” or “off.” When assembled, as shown in  FIGS. 11 and 12 , the lamp  70  is positioned within the interior of the reflector  440  through the first central opening  442  of the reflector  440 . As such, rotating the bezel  430  relative to the head piece  410  causes the reflector  440  to move within the bezel  430  axially relative to the head piece  410 . As a result, the reflector  440  moves relative to the lamp  70 , and such movement allows for the light emanating from the lamp  70  to be focused by positioning the lamp  70  at the reflector&#39;s  440  focal point, or defocused by positioning the lamp  70  away from the reflector&#39;s  440  focal point. 
         [0068]    As indicated above and with reference to  FIGS. 16-27 , the lamp holder assembly  50  includes a second embodiment, the lamp holder assembly  500 , which moves inside the second end  220  of the chamber  20  when the flashlight  10  is turned “off” or “on.” Referencing  FIG. 20 , the lamp holder assembly  500  includes a lamp holder  610 , a conductive spring  620 , a switch plate  630 , a detent lever  640 , a detent ball  650 , a switch contact  660 , a spring contact  670 , a conductive strip  690 , and a strip support  692 . The lamp holder assembly  500  is assembled to the chamber  20  by first attaching the conductive spring  620  to the lamp holder  610 . The lamp holder  610  includes a spring tab (not shown) which engages and retains a portion of the conductive spring  690  and holds the conductive spring  690  in contact with the spring contact  670 , as is shown in  FIG. 21 . The lamp holder  610  and attached conductive spring are next positioned at the second end  220  of the chamber  20 . Referencing  FIG. 18 , the lamp holder  610  includes a tab  612  for contacting a portion of the interior of the chamber  20  near the second end  220  at area  614 . Positioning of the lamp holder  610  and attached conductive spring  620  occurs by inserting the lamp holder  610  and attached spring  620  in the first end  210  of the chamber  20  and moving lamp holder  610  toward the second end  220  of the chamber  20  until the tab  612  engages the interior of the chamber  20  at the at area  614 . The lamp holder  610  further includes a tab (not shown) which is aligned with a corresponding slot (not shown) in the interior of the chamber  20  to ensure that the lamp holder  610  and attached spring  620  are properly positioned at the second end  220  of the chamber  20 . The lamp holder  610  is shown positioned at the second end  220  of the chamber  20  in  FIGS. 22A and 27 . 
         [0069]    Referencing  FIGS. 22A ,  22 B,  22 C and  27 , with the lamp holder  610  exposed at the second end  220  of the chamber  20 , the lamp holder assembly  500  is assembled. In this regard, the detent ball  650  is positioned on the lamp holder  610  at the guide  611  and the detent plate  640  is next positioned onto the lamp holder  610  with the detent plate ball opening  642  positioned on the detent ball  650  and the slots  644  aligned with the threaded openings  612  on the lamp holder  610 . The switch plate  630  is next positioned with openings  631  aligned with the threaded openings  612 . The lamp holder assembly  500  is completely assembled by inserting screws (not shown) through the openings  631 , threading the screws to threaded openings  612 , and securing the switch plate  630  to the lamp holder  610 . As a result, the lamp holder assembly  500  is secured axially and rotatable at the second end  220  of the chamber  20 . 
         [0070]    As described above and with general reference to  FIG. 18 , the head portion of the flashlight  10  is assembled by attaching the assembled head assembly  40  to the chamber  20  having the lamp holder assembly  500  assembled in the chamber  20 , such that the lamp  70  is positioned within the first central opening  442  of the reflector  440 . In this regard, the head assembly  40  is removably attached to the chamber  20  at the second end  220 .  FIG. 22B  shows the lamp holder assembly  500  assembled in the chamber  20  when the head assembly  40  is removed from the chamber  20 . The chamber  20  includes the end guide  260  formed on the exterior surface at the second end  220  of the chamber  20 . The end guide  260  includes paths  261  which receive and guide the lugs  415  on the head piece  410  when the head assembly  40  is attached to and removed from the chamber  20 . The lugs  415  are aligned with paths  261 , and the head assembly  40  is guided in the direction  287  until the head assembly  40  is fully seated on the second end  220  of the chamber  20 . Detachment of the head assembly  40  occurs by moving the head assembly  40  in the direction opposite  287  until the head assembly  40  is removed.  FIG. 23  shows the position of the lamp holder assembly  500  (without switch plate) when the head assembly  40  is capable of being attached to or removed from the chamber  20 . Referencing  FIGS. 23 and 27 , the lamp holder assembly is positioned at a first detent, which is caused by the detent ball  650  being positioned in a first slot  652  on the outer edge of the chamber  20  at the second end  220 . 
         [0071]    When fully seated, the guides  413  of the head assembly  40  engage the slots  634  on the switch plate  630 , and the rotation of the head assembly  40  will cause the lamp holder assembly  500  to rotate. The head assembly  40  is then rotated in the direction  288  to a second detent, which is caused by the detent ball  650  being positioned in a second slot  652  on the outer edge of the chamber  20  at the second end  220 . The flashlight  10  is in the “off” position at this position.  FIG. 24  shows the position of the lamp holder assembly  500  (without switch plate) when the head assembly  40  is in the “off” position. In this position, the head assembly  40  is only permitted to rotate relative to the chamber  20  (i.e., radially) and cannot move away from the chamber  20  (i.e., axially). The head portion of the flashlight  10  can be disassembled by rotating the head assembly  40  from the “off” position in a direction opposite  288  to the first detent, and disengaging the head assembly  40  from the chamber  20  along paths  261 . 
         [0072]    When fully assembled and holding batteries  60 ,  62  in proper alignment, the flashlight  10  is capable of selectively electrically coupling the lamp  70  to the batteries  60 ,  62 . Referencing  FIG. 20 , the chamber  20  includes a conductive strip  690  along the length of the chamber  20 , between the first end  210  and the second end  220 . The conductive strip  690  is supported at the first end  210  of the chamber  20  by the strip support  692 . The lamp holder assembly  500  selectively electrically connects the lamp  70  to properly positioned batteries  60 ,  62  in accordance with the radial movement of the head assembly  40 . Referencing  FIG. 21 , the first pin  72  is electrically connected to the switch spring  620  by spring contact  670 , and the second pin  74  is electrically connected to the switch contact  660 , when the lamp  70  is positioned in lamp holder assembly  500 . Referring to  FIGS. 16-22 , the flashlight  10  is moveable between the “on” and “off” positions by the radial movement of the head assembly in the direction  288 . As shown in  FIG. 24 , the switch contact  660  does not contact the conductive strip  690  in the “off” position. As shown in  FIG. 25 , the switch contact  660  contacts the conductive strip  690 . In this regard, as the head assembly  40  is rotated in the direction  288 , the lamp holder assembly  500  is rotated as well. The “on” detent occurs when the detent ball rolls to a third slot  652  on the outer edge of the chamber  20  at the second end  220 . Notably, the detent mechanism is physically separated from the switching mechanism. Preferably, the head assembly  40  is rotatable about thirty degrees between the “off” and “on” positions. The movement of the lamp  70  within the reflector  440  to focus and defocus the light emanating from the lamp  70  is independent from the radial movement of the head assembly  40  to turn the flashlight  10  “on” or “off” as described previously. 
         [0073]    The spare lamp  71  is held secure by the switch plate  630 , until the user of the flashlight  10  rotates the lamp holder assembly  500  to align the spare lamp opening  632  with the spare lamp  71 . Referencing  FIG. 23 , the lamp holder assembly  500  (without switch plate) is shown in the position when the head assembly  40  is removed from the chamber  20 . From this position, the spare lamp opening  632  is aligned with the spare lamp  71  by rotating the lamp holder assembly in the direction opposite direction  288 .  FIG. 26  shows the position of the lamp holder assembly  500  (without switch plate) when the spare lamp opening  632  is aligned with the spare lamp  71 . Once aligned, the spare lamp  71  is removable from the lamp holder assembly  500 . 
         [0074]    Notably, the reflector  440  and lens  460  combination accomplishes one of the objectives of the present invention, namely to provide improved light gathering from the lamp  70 , optimum focus spot and minimal light void within the light projected by the reflector  440  throughout the range of the lamp&#39;s  70  movement within interior of the reflector  440 . In this regard, one embodiment of the present invention uses conic reflectors  440  other than a parabolic reflector. 
         [0075]    The vertex curvature (i.e., the actual shape) of the reflector  440  is determined using the following equation for a Vertex Cartesian coordinate system: 
         [0000]        f ( r )= Cr   2 /(1+√(1− SC   2   r   2 )), 
         [0000]    wherein C is the vertex curvature, r is the radial distance from the cylindrical center of the optic, and S is equal to unity minus the square of the eccentricity. In this regard, it was discovered that the use of nonparabolic reflectors minimized the light void which is apparent when a parabolic reflector was used, as shown in  FIG. 1B . Additionally, it was also discovered that matching nonparabolic reflectors with an appropriate lens curvature optimized the direction of the rays emanating from the nonparabolic reflector. For elliptical reflectors (i.e., 0&lt;eccentricity&lt;1), it was determined that the use of a negative or a flat lens caused a more uniform and intense ray pattern when the light source was placed at the optimum optical focal point. For hyperbolic reflectors (i.e., eccentricity&gt;1), it was determined that the use of a positive or flat lens caused a more uniform and intense ray pattern when the light source was placed at the optimum optical focal point. 
         [0076]    Referring to the table shown in  FIGS. 13A and 13B , a series of simulations were run using the equation 1.1, wherein the eccentricity ranged from 0.8 to 1.25. The criteria for the results shown in  FIGS. 13A and 13B  were as follows: (i) a reflector aperture (i.e., the size of the reflector&#39;s  44  second central opening  49 ) of 1.4375″; (ii) a reflector opening (i.e., the size of the reflector&#39;s  44  first central opening  48 ) of 0.19″; (iii) a maximum lighted spot size of 29″ to be illuminated by the flashlight  10  at a distance of 120″; (iv) a minimum light void throughout the range of focus (i.e., the movement of the lamp  70  along the reflector&#39;s  440  optical axis from about the reflector&#39;s  440  focal point to the point the lamp  70  exits the reflector  440  at either the first central opening  442  for a elliptical reflector or the second central opening  444  for a hyperbolic reflector); (v) a maximum range of motion of the lamp  70  throughout the range of focus of no greater than about 0.25″; (vi) a minimum angle of subtended light gathered by the reflector of about 100 degrees; and (vii) a lens with effective focal length of no less than about +2.5″ or no greater than −2.5. 
         [0077]    For each given eccentricity and lens combination, the vertex curvature was adjusted to attain the minimum focused spot size and void throughout the range of focus and the maximum subtended angle of light gathered by the reflector  440 . This was performed for each value of eccentricity by taking a sample of lenses with effective focal lengths of no less absolute value than about 2.5″, running simulations wherein the vertex curvature was increased until no void appeared when the lamp  70  was completely defocused (i.e., the lamp  70  exits the reflector  440  at either the first central opening  442  for a elliptical reflector, or the second central opening  444  for a hyperbolic reflector). The value of vertex curvature was not increased beyond what which was reasonably necessary to remove the void, because increasing the vertex curvature further reduced the potential magnification of the lamp&#39;s  70  light beam as the lamp  70  was moved away from the focal point of the reflector  440 . 
         [0078]    In view of the simulations and the criteria specified, the elliptical reflector, preferably has an eccentricity value of no less than about 0.80 and no more than about 0.99. Preferably, the elliptical reflector has a vertex curvature value of no less than about 2.0 and no more than about 5.2. In one arrangement, the elliptical reflector has an eccentricity value of about 0.96 and a vertex curvature of about 3.1. In one embodiment of the present invention, a flashlight  10  having an elliptical reflector is matched with a negative or flat lens. Preferably, an elliptical reflector is matched with a lens having an effective focal length of no greater than about −2.5″ and no more than about 0″. In one arrangement, an elliptical reflector  44  having an eccentricity value of about 0.96 and a vertex curvature of about 3.1 is matched with a lens  45  having an effective focal length of about 0″. 
         [0079]    In accordance with another embodiment of the present invention, the head assembly  40  includes a hyperbolic reflector. Preferably, the hyperbolic reflector has an eccentricity value of no less than about 1.01 and no more than about 1.25. Preferably, the hyperbolic reflector has a vertex curvature value of no less than about 2.0 and no more than about 7.2. In one arrangement, the hyperbolic reflector has an eccentricity value of about 1.04 and a vertex curvature of about 3.3. In another embodiment, a flashlight  10  having a hyperbolic reflector is matched with a positive or flat lens. Preferably, a hyperbolic reflector is matched with a lens having an effective focal length no less than about 2.5″. In one arrangement, a hyperbolic reflector  440  having an eccentricity value of about 1.04 and a vertex curvature of about 3.3 is matched with a lens  460  having an effective focal length of about 0″. 
         [0080]    The foregoing description of the present invention has been presented for purposes of illustration and description. The description is not intended to limit the invention to the form disclosed herein. Consequently, the invention and modifications commensurate with the above teachings and skill and knowledge of the relevant art are within the scope of the present invention. It is intended that the appended claims be construed to include all alternative embodiments as permitted by the prior art.