Abstract:
A flashlight having a main power circuit and a barrel is disclosed. The main power circuit includes a light source and a portable power source for supporting the light source. The barrel is not within the main power circuit. The flashlight also has a ball for holding the light source. The light source is fit and in contact with the inner surface of the ball. The outer circumference of the ball has an array of fin-like protrusions for effectively dissipating heat from the light source.

Description:
TECHNICAL FIELD 
       [0001]    The present invention relates to portable lighting devices, including for example, flashlights and headlamps, and their circuitry. 
       BACKGROUND 
       [0002]    Various hand held or portable lighting devices, including flashlights, are known in the art. Such lighting devices typically include one or more dry cell batteries having positive and negative electrodes. The batteries are arranged electrically in series or parallel in the battery compartment or a housing. The battery compartment also sometimes functions as the handle for the lighting device, particularly in the case of flashlights where a barrel contains the batteries and is also used to hold the flashlight. An electrical circuit is frequently established from a battery electrode through conductive means which are electrically coupled with an electrode of a light source, such as a lamp bulb or a light emitting diode (“LED”). After passing through the light source, the electric circuit continues through a second electrode of the light source in electrical contact with conductive means, which in turn are in electrical contact with the other electrode of a battery. Typically, the circuit includes a switch to open or close the circuit. Actuation of the switch to close the electrical circuit enables current to pass through the lamp bulb, LED, or other light source—and through the filament, in the case of an incandescent lamp bulb—thereby generating light. 
         [0003]    In metal flashlights, it has also been conventional to use the barrel and the tail cap as a portion of the conductive means of the electrical circuit. However, in order to increase corrosion resistance and aesthetics of aluminum flashlights, the head, barrel, and tail cap are usually anodized. As a result, either a skin cut to remove anodizing on the inner mating surfaces of the barrel and the tail cap are required to provide a conductive path between the barrel (and the tail cap) and the other portion(s) of the electrical circuit, or the relevant contacting portions must be masked prior to anodizing so that they are not anodized in the first place. Either approach requires additional manufacturing steps, which in turn increases manufacturing costs. Further, the unprotected portions of aluminum or aluminum alloy are more susceptible to corrosion. 
         [0004]    Some flashlights designs have proposed the use of a ball to hold the light source of the flashlight within a ball housing to allow the light source to be adjusted with respect to the principal axis of a reflector. Such flashlights, however, do not provide a configuration that suitably addresses the thermal management issues created by today&#39;s high power, high brightness LEDs. 
         [0005]    Some advanced portable lighting devices provide multiple functions for different needs. For example, a power saving mode and/or an SOS mode may be implemented in a flashlight or other portable lighting devices in addition to the normal “full power” mode. In such portable lighting devices, the user typically elects the desired mode of operation by manipulation of the main power switch. For example, when the flashlight is in the normal mode or the power save mode of operation, the flashlight may be transitioned to another mode of operation, such as an SOS mode by manipulating the main power switch to momentarily turn off and then turn back on the flashlight. 
         [0006]    Typically the functionality of multi-mode portable lighting devices of this sort is provided by a microcontroller, which remains powered by the batteries at all times. As a result, the volatile memory of the microcontroller may be used to store the current mode of the flashlight, and thus determine which mode to transition into in the event that a user enters the proper command signal. However, if the portable lighting device—particularly in the case of larger flashlights—is accidentally hit against, or dropped on, a hard surface, the inertia of the battery or batteries may cause the battery or batteries to disconnect from one of the battery contacts for a short period of time. This disconnection will also cause a power loss to the microcontroller, thereby causing the microcontroller to lose track of the mode the flashlight or other lighting device was in prior to the power loss. As a result, the microcontroller will reset the flashlight or other lighting device to its default mode, which is typically off, rather than automatically returning to the prior mode of operation. Resetting under such circumstances is undesirable and potentially hazardous. 
         [0007]    Portable lighting devices that include advanced functionality typically include a printed circuit board with a microcontroller or microprocessor to provide the desired functionality. A need exists, however, for a push button switch assembly that includes an integral circuit board that may be readily employed in a variety of portable lighting devices to provide multiple levels of functionality to the same. 
         [0008]    In view of the foregoing, a need exists for an improved portable lighting device that addresses or at least ameliorates one or more of the problems discussed above. 
       SUMMARY 
       [0009]    It is an object of the present invention to address or at least ameliorate one or more of the problems associated with flashlights and/or portable lighting devices noted above. Accordingly, in a first aspect of the invention, a portable lighting device with a light source and a portable power source for powering the light source is provided. 
         [0010]    In one embodiment, the portable lighting device has a portable power source having an anode and a cathode, a light source having a positive electrode and a negative electrode, a first spring, a second spring, and a housing for holding the portable power source. The first spring may be located between the light source and the portable power source for forming a first portion of a first electrical path between the positive electrode of the light source and the cathode of the portable power source. The second spring may be located between the light source and the portable power source for forming a first portion of a second electrical path between the negative electrode of the light source and the anode of the portable power source. The housing of the portable lighting device preferably does not form part of the first or second electrical paths. 
         [0011]    In another embodiment, the portable lighting device has a main power circuit, a first spring, a second spring, and a barrel. The main power circuit includes a portable power source and a light source. The portable power source has an anode and a cathode. The light source has a positive electrode and a negative electrode. The first spring is within the main power circuit and electrically connects the positive electrode of the light source and the cathode of the portable power source. The second spring is within the main power circuit and electrically connects the negative electrode of the light source and the anode of the portable power source. While the barrel is configured to hold the portable power source, it does not form part of the main power circuit. 
         [0012]    In a second aspect, a portable lighting device with a light source and an adjustable ball for holding the light source is provided. 
         [0013]    In one embodiment, the portable lighting device comprises a main power circuit including a portable power source, a reflector, a light source, and an ball assembly including a metal ball for adjustably holding the light source relative the principal axis of a reflector. The outer surface of the ball includes one or more cooling fins for dissipating heat from the light source. In another embodiment, a plastic adjustment ring is preferably molded around the ball to form a unitary ball assembly for adjusting the light source relative to the principal axis of a reflector. 
         [0014]    In another aspect, an adjustable ball assembly for a portable lighting device is provided. In one embodiment, the adjustable ball assembly has a metal tubular housing, a ball assembly, a lighting module, a funnel spring and a ball retainer. The metal tubular ball housing may have a forward end, a rearward end, and a slot on the rearward end. The ball assembly is configured to fit within the forward end of the metal tubular ball housing. A ball of the ball assembly preferably has an annular hollow region, sized to receive the lighting module. The retainer is configured to fit within the aft end of the metal tubular ball housing. The retainer may have an annular channel region that is configured to receive a tail end of funnel spring there through. A head end of the funnel spring is larger in diameter than the annular channel region of the retaine and is interposed between the retainer and the forward contact cup. 
         [0015]    In another embodiment, the adjustable ball assembly for portable lighting devices has a metal tubular ball housing, a ball assembly, a lighting module, a retainer, a insulator, and a funnel spring having a head. The metal tubular ball housing has a front end and a rear end. The ball assembly has an annular hollow region in which the assembly slideably fits. The ball assembly includes a central through hole. The lighting module can be partially fit within the adjustable ball assembly. The retainer can have a through hole and a front open mouth. The diameter of the front open mouth is smaller than that of the annular hollow region of the ball assembly. The retainer can be fit within the rearward end of the metal tubular ball housing so that the front open mouth of the retainer defines a rear-most position. The insulator can be located between the lighting module and the retainer. The insulator can have a cup-shaped receiving area to receive the head of the funnel spring. The receiving area defines a front-most position. The diameter of the head of the funnel spring is larger than the front open mouth of the retainer. The head of the funnel spring can be confined between the front-most position and the rear-most position. 
         [0016]    Further aspects, objects, and desirable features, and advantages of the invention will be better understood from the following description considered in connection with the accompanying drawings in which various embodiments of the disclosed invention are illustrated by way of example. It is to be expressly understood, however, that the drawings are for the purpose of illustration only and are not intended as a definition of the limits of the invention. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0017]      FIG. 1  is a top view of a portable lighting comprising a flashlight according to one embodiment of the present invention. 
           [0018]      FIG. 2  is a cross-sectional view of the flashlight of  FIG. 1  taken along the plane indicated by  402 - 402 . 
           [0019]      FIG. 3  is an enlarged cross-sectional view of the forward section of the flashlight of  FIG. 1  taken through the plane indicated by  402 - 402 . 
           [0020]      FIG. 4  is an exploded perspective view of the flashlight of  FIG. 1 . 
           [0021]      FIG. 5A  is an enlarged exploded perspective view of a portion of the head assembly of the flashlight of  FIG. 1 .  FIG. 5B  is an enlarged exploded perspective view of the adjustable ball assembly portion of the flashlight of  FIG. 1 .  FIG. 5C  is an enlarged exploded perspective view of the switch assembly portion of the flashlight of  FIG. 1 .  FIG. 5D  is an enlarged exploded perspective view from the forward end of the flashlight of  FIG. 1  illustrating how the front barrel and rear barrel of the flashlight are assembled together with the circuit board and charge rings.  FIG. 5E  is an enlarged perspective view of the ball housing, switch housing and battery pack (with the front and rear barrels been removed) of the flashlight of  FIG. 1  for illustrating the ground path of the flashlight of  FIG. 1 . 
           [0022]      FIGS. 6A through 6C  are different cross-sectional views illustrating one relative position between the skirt lock ring and head.  FIGS. 6D through 6F  are different cross-sectional views illustrating a second relative position between the skirt lock ring and head.  FIGS. 6G through 6I  are different cross-sectional views illustrating a third relative position between the skirt lock ring and head. 
           [0023]      FIG. 7  is a circuit diagram illustrating the relationship of the electronic circuitry according to one embodiment of the invention. 
           [0024]      FIGS. 8A-E  are schematic circuit diagrams of different components of the circuit shown in  FIG. 7 . 
           [0025]      FIG. 9  is a power profile diagram. 
       
    
    
     DETAILED DESCRIPTION 
       [0026]    Embodiments of the invention will now be described with reference to the drawings. To facilitate the description, any reference numeral representing an element in one figure will represent the same element in any other figure. Further, in the description that is to follow, upper, front, forward or forward facing side of a component shall generally mean the orientation or the side of the component facing the direction toward the front end of the portable lighting device or flashlight. Similarly, lower, aft, back, rearward or rearward facing side of a component shall generally mean the orientation or the side of the component facing the direction toward the rear of the portable lighting device (e.g., where the tail cap is located in the case of a flashlight). 
         [0027]    Flashlight  400  according to one embodiment of the present invention is described in connection with  FIGS. 1-9  below. Flashlight  400  incorporates a number of distinct aspects of the present invention. While these distinct aspects have all been incorporated into the flashlight  400  in various combinations, it is to be expressly understood that the present invention is not restricted to flashlight  400  described herein. Rather, the present invention is directed to each of the inventive features of the flashlight  400  described below, both individually as well as collectively, in various embodiments. Further, as will become apparent to those skilled in the art after reviewing the present disclosure, one or more aspects of the present invention may also be incorporated into other portable lighting devices, including, for example, head lamps. 
         [0028]    Referring to  FIGS. 1-2 , flashlight  400  includes a head assembly  610 , a front barrel  508  a rear barrel  526 , a tail cap  506 , a switch  500 , and charging contacts  512  and  514 . In the present embodiment, the front barrel  508  and the rear barrel  526  are joined together near where the external charging contacts  512  and  514  are provided to form a uniform cylinder body. The aft end of the rear barrel  526  is enclosed by the tail cap  506  while the forward end of the front barrel  508  is enclosed by the head assembly  610 . 
         [0029]    Front and rear barrels  508 ,  526  are preferably made out of metal, more preferably aluminum. Rear barrel  526  may be provided with a textured surface  404  along a portion of its axial extent, preferably in the form of machined knurling. A portion of front barrel  508  extends beneath a head skirt  494  of the head assembly  610 . A hollow space  499  is formed within rear barrel  526  for housing a portable power source, such as a battery pack  501 . 
         [0030]    In the present embodiment, battery pack  501  comprises two lithium-ion batteries physically disposed in a series arrangement, while being electrically connected in parallel. The structure of one battery pack that may be used as battery pack  501  is more fully described in co-pending U.S. patent application Ser. No. 12/353,820, which is hereby incorporated by reference. 
         [0031]    Battery pack  501  has a front end  507  having a reduced diameter in comparison to the remainder of the battery pack  501 . This arrangement prevents battery pack  501  from being inserted in a reverser manner, thereby protecting battery pack  501  as well as the flashlight  400 . Further, as shown best in  FIG. 4 , a cathode (or positive electrode)  503  and an anode (or negative electrode)  505  are both provided on the front end  507  of the battery pack  501  for added safety. 
         [0032]    While a lithium-ion battery pack  501  is used as the portable power source for the illustrated embodiment of flashlight  400 , in other embodiments, other portable power sources may also be employed, including, for example, dry cell batteries, rechargeable batteries, or battery packs comprising two or more batteries physically disposed in a parallel or side-by-side arrangement, while being electrically connected in series or parallel depending on the design requirements of the flashlight. Other suitable portable power sources, including, for example, high capacity storage capacitors may also be used. 
         [0033]    Tail cap  506  is also preferably made out of aluminum and is configured to engage mating threads provided on the interior of rear barrel  526  as is conventional in the art. However, other suitable means may also be employed for attaching tail cap  506  to rear barrel  526 . A one-way valve  504 , such as a lip seal, may be provided at the interface between tail cap  506  and rear barrel  526  to provide a watertight seal while simultaneously allowing overpressure within the flashlight to expel or vent to atmosphere. However, as those skilled in the art will appreciate, other forms of sealing elements, such as an O-ring, may be used instead of one-way valve  504  to form a watertight seal. The design and use of one-way valves in flashlights is more fully described in U.S. Pat. No. 5,113,326 to Anthony Maglica, which is hereby incorporated by reference. 
         [0034]    In the present embodiment, spring  502  is seated in a spring seat  511  provided on the forward end of tail cap  506 . Spring  502  urges battery pack  501  forward so that electrodes  503 ,  505  on the front end  507  of battery pack  501  come into contact with cathode contact  523  and anode contact  525 , respectively, provided on the aft side of charger circuit board  520 . Contacts  523 ,  525  are preferably soldered to the aft side of charger circuit board  520 . 
         [0035]    If made out of aluminum, the surfaces of front barrel  508 , rear barrel  526  and tail cap  506  are preferably anodized to prevent corrosion. While in the present embodiment, barrels  508 ,  526  and tail cap  506  do not form part of the electrical circuit of the flashlight  400 , in other embodiments, one or more of the front barrel  508 , rear barrel  526 , or tail cap  506  may form part of the electrical circuit of the flashlight. In such embodiments, those surfaces used to make electrical contact with another metal surface should either not be anodized or a skin cut to remove anodizing should be made following anodization for purposes of establishing the electrical circuit in the assembled flashlight. 
         [0036]    External charging contacts  512  and  514  are provided at the rearward section of front barrel  508 . While charging contacts  512  and  514  are provided in the present embodiment in the form of charging rings to simplify the recharging procedure, in other embodiments charging contacts  512  and  514  may take on other forms. 
         [0037]    In the present embodiment, a charger circuit board  520  is interposed between charging contacts  512  and  514 . Charger circuit board  520  is configured to be in electrical communication with charging contacts  512  and  514 , while simultaneously isolating charging contacts  512  and  514  from direct electrical communication with one another through a short circuit. Electrical communication between charger circuit board  520  and charging contacts  512  and  514  may be established by providing a conductive trace on the charger circuit board  520 . 
         [0038]    Charger circuit board  520  may include, for example, a charge protection circuit, a charge control circuit, and a battery protection circuit. The charge protection circuit may be used to continuously monitor the battery voltage. The charge control circuit may be used to charge the battery pack  501 . The battery protection circuit may be used to further protect the battery pack  501  from over charging, over discharging, or over current. 
         [0039]    Referring to  FIGS. 1-4 , the present embodiment includes a head  420  to which a number of other components may be mounted, including, for example, skirt lock ring  426 , wave spring  422 , head skirt  494 , face cap  412 , lens  416 , and reflector  418  to form a head assembly  610 . Head  420 , skirt lock ring  426 , head skirt  494  and face cap  412  are preferably made from anodized aluminum. On the other hand, reflector  418  is preferably made out of injection molded plastic. The interior surface of reflector  418  is preferably metallized to enhance its reflectivity to a suitable level. 
         [0040]    In the present embodiment, head  420  is a hollow support structure comprising a front section  516 , a midsection  518  and an aft section  530 . Head  420  is internally disposed in the present embodiment in that head  420  is covered by face cap  412 , skirt lock ring  426 , and head skirt  494  when the flashlight  400  is fully assembled. In other words, in the present embodiment, head  420  does not comprise an external portion of the flashlight  400 . The front section  516  comprises a generally cup-shaped receiving area  532  for receiving reflector  418 . The midsection  518 , which extends rearward from the front section  516 , includes a generally cup-shaped receiving area  534 . And, the aft section  530 , which extends rearward from the midsection  518 , includes internal threads  536  which are configured to mate with external threads  497  on the forward end of front barrel  508 . Head  420  is locked to the front barrel  508  with a retainer  432 . Retainer  432  is externally threaded with threads  540  on its aft end and is outwardly tapered on its forward end. Retainer  432  is configured so that external threads  540  mate with internal threads  495  provided on the forward end of front barrel  508 . 
         [0041]    Because front barrel  508  includes opposing slots  411 , when retainer  432  is threaded into threads  425  of front barrel  508 , front barrel  508  is expanded as the tapered portion of retainer  432  contacts front barrel  508  and is then screwed further into the front barrel  508 . When retainer  432  is fully seated in front barrel  508 , head  420  is locked to the front barrel  508 . 
         [0042]    The face cap  412  retains lens  416  and reflector  418  relative to the head  420  and reflector  418 . In the present embodiment, face cap  412  is configured to thread onto external threads  238  provided on the front section  516  of the head  420 . In other implementations, however, other forms of attachment may be adopted. An O-ring  114  is provided at the interface between face cap  412  and lens  416  to provide a watertight seal. As best seen in  FIG. 3 , reflector  418  is positioned within the cup-shaped receiving area  532  of head  420  so that it is disposed forward of the head  420  and retainer  432 . The internal surface of the cup-shaped receiving area  532  together with the outer surface of reflector  418  and reflector flange  419  ensure the proper alignment of the principal axis of reflector  418  with the central axis of the front barrel  508 . The face cap  412  in turn clamps O-ring  414 , lens  416 , and reflector  418 , via reflector flange  419 , to head  420 . 
         [0043]    Head skirt  494  has a diameter greater than that of the front and rear barrels  508 ,  526 . Head skirt  494  is also adapted to pass externally over the exterior of the front and rear barrels  508 ,  526 . The forward end  542  of head skirt  494  is configured to mate with the outer surface of a skirt lock ring  426  at selected locations to properly position head skirt  494  relative to face cap  412  and head  420 . 
         [0044]    The locking mechanism of the head skirt  494  will now be described.  FIG. 5A  shows an exploded view of a portion of head assembly  610 . The outer surface of head  420  has a nominally smooth surface  566  with an annular groove  567  on the outer surface of aft section  530  and a plurality of protuberances  568  equally spaced from each other around the outer circumference of the midsection  518  of head  420 . 
         [0045]      FIGS. 6A through 6I  are cross-sectional views illustrating different relative positions between the head  420  and skirt lock ring  426 . The dimensions of the head  420  and skirt lock ring  426  in  FIGS. 6A through 6I  are not to scale. Nevertheless,  FIGS. 6A-6I  are helpful for the purpose of illustrating how the locking mechanism of head skirt  494  works in the illustrated embodiment. 
         [0046]    As best seen in  FIGS. 6C ,  6 F, and  6 I, a gap  531  is formed between each protuberance  568  and the front section  516  of head  420 . In the present embodiment, six protuberances  568  are used. Each of the protuberances  568  has a relief cut  569  on the front end such that each of the protuberances  568  have a reversed L-shaped cross-section in the longitudinal direction of flashlight  400  as seen in  FIG. 6C , for example. At the toe of the reversed L-shaped protuberances  568  is a lock member  570 . In the present embodiment, the number of protuberances  568  is six. In other embodiments, the number of protuberances  568  may be different. However, the number of protuberances  568  should be an integer number greater than or equal to three. 
         [0047]    As best seen in  FIG. 5A , The inner surface of skirt lock ring  426  has a front end  581 , an aft end  582  and a middle portion  583  in between. The inner surface of skirt lock ring  426  comprises a plurality of longitudinal channels  571  formed by a plurality of first indexing bumps  572  and second indexing bumps  575 . In the present embodiment, six first indexing bumps  572  are formed near the middle portion  583  of the inner surface of the skirt lock ring  426  and six second indexing bumps  575  are formed near the aft end  582  of the inner surface of the skirt lock ring  426 . Each of the first indexing bumps  572  comprises two high plateau regions  574  separated by a low plateau region  573 . Similarly, each of the second indexing bumps  575  comprises two high plateau regions  577  separated by a low plateau region  576 . 
         [0048]    In the present embodiment, some of the high plateau regions  577  of the second indexing bumps  575  have a hole  578  sized to receive a ball  428 . In the present embodiment, three holes  578  are equally spaced from each other around the inner circumference of skirt lock ring  426 . In the present embodiment, the number of first indexing bumps  572  is the same as the number of second indexing bumps  575 . In an alternate embodiment, the number of first indexing bumps  572  may be an integer multiple of the number of second indexing bumps  575 . In another embodiment, the number of first indexing bumps  572  is an integer factor of the number of second indexing bumps  575 . In the present embodiment, the number of second indexing bumps  575  is the same as the number of protuberances  568 . In other embodiments, the number of second indexing bumps  575  may be an integer multiple of the number of protuberances  568 . 
         [0049]      FIGS. 6A-C  show different cross-sectional views through the head  420  and skirt lock ring  426  when the skirt lock ring  426  has been rotated to a position which unlocks the head skirt  426  axially from the head  420 .  FIGS. 6A-6C  also show skirt lock ring  426  in a position (position A) relative to head  420  where their aft ends are aligned. Balls  428  now sits in annular groove  567  and the top end  579  of ball  428  is lower than the top surface  580  near the aft end of skirt lock ring  426 . Accordingly, head skirt  494  can be freely mounted to or dismounted from skirt lock ring  426  at this position. When every protuberance  568  of head  420  is aligned with a channel  571  of skirt lock ring  426  (as shown in  FIG. 6C ) by rotating skirt lock ring  426  to a suitable position, then the first indexing bumps  572  and the second indexing bumps  575  are aligned with the smooth surface  566  of skirt lock ring  426  (as shown in  FIGS. 6A-6B ). In this position, skirt lock ring  426  may be freely moved axially forward or rearward over head  420 .  FIG. 6A  more particularly shows where low plateau regions  573 ,  576  of skirt lock ring  426  are aligned with the smooth surface  566  of head  420 , and  FIG. 6B  more particularly shows where high plateau regions  574 ,  577  of skirt lock ring  426  are aligned with the smooth surface  566  of head  420 . When the skirt lock ring  426  is indexed to this position, it is in a position in which it may be moved forward or rearward relative to head  420  by an operative amount. However, skirt lock ring  426  cannot be rotated relatively to head  420  because protuberances  568  and high plateau regions  574  are next to each other so that high plateau regions  574  extend too far out from skirt locking ring  426  to pass over protuberances  568 . 
         [0050]    When skirt lock ring  426  and head  420  are aligned as illustrated in  FIGS. 6A-6C , skirt lock ring  426  may be pushed forward to position B against the spring force of wave spring  422 , as shown in  FIGS. 6D-6F . When skirt lock ring  426  is pushed forward in this manner protuberances  568  and high plateau regions  574  are no longer next to each other. As a result, skirt lock ring  426  can now be rotated relative to head  420  because high plateau regions will now pass through gap  531  between protuberance  568  and the front section  516  of head  420  as skirt lock ring  426  is rotated. Balls  428 , however, no longer sit in annular groove  567 , but instead are disposed on the smooth surface  566 . As a result, the top end  579  of ball  428  is now higher than the top surface  580  near the aft end of skirt lock ring  426 . If the head skirt  494  is mounted to the skirt lock ring  426 , the ball  428  will extend into annular groove  429  formed in the interior surface of head skirt  494 . However, because protuberances  568  remain aligned with channels  571 , the skirt lock ring  426  remains subject to being moved rearward to position A shown in  FIGS. 6A-6C  and thus the head skirt  494  is not axially locked to the head  420  at this point. 
         [0051]    When skirt lock ring  426  and head  420  are aligned as described in  FIGS. 6D-6F , skirt lock ring  426  can be rotated relatively to head  420 . If a user rotates skirt lock ring  426  30° in either direction and then releases the skirt lock ring  426  wave spring  422  will bias the skirt lock ring  426  rearward, and the relationship between skirt lock ring  426  and head  420  will be the position (position C) as shown in  FIGS. 6G-6I . Now, protuberances  568  are aligned with low plateau regions  573  (as shown in  FIG. 6I ). Further, the spring force of wave spring  422  pushes skirt lock ring  426  rearward until a corner of each low plateau region  573  fits into a space formed by relief cut  569  of an opposing protuberance  568  and lock members  570  are positioned under the low plateau regions  573 . In this manner, skirt lock ring  426  cannot be rotated relatively to head  420  because each side of lock member  570  of protuberances  568  is now next to a high plateau region  574 . In addition, balls  428  are still disposed on the smooth surface  566 , and, as a result, the top end  579  of ball  428  is still higher than the top surface  580  near the aft end of skirt lock ring  426 . Thus, if head skirt  494  is mounted, it will be axially locked by ball  428  to head  420  and cannot be dismounted (as shown in  FIGS. 2-3 ). 
         [0052]    When head skirt  494  is locked (as shown in  FIGS. 2-3 ), the skirt lock ring  426  and head  420  are aligned as illustrated in  FIGS. 6G-6I . To access adjusting ring  448  to adjust the alignment of the beam direction of the substantial point source of light, namely LED  445  of LED module  444  in the present embodiment, with the principal axis of the reflector, head skirt  494  must be unlocked and slid rearward over front barrel  508  at least far enough for the user to gain access to adjustment ring  448 . The procedure for accomplishing this is described below. 
         [0053]    First, when head skirt  494  is axially locked to the head  420  by the skirt locking ring  426 , the skirt lock ring  426  and head  420  are aligned as illustrated in  FIGS. 6G-6I . Further, skirt lock ring  426  cannot be rotated relative to head  420 . However, the head skirt  494  is free to rotate about the skirt locking ring  426  and front barrel  508  to axially translate the light source along the axis of the reflector as discussed more fully below. Further, the skirt lock ring  426  together with the head skirt  494  may be pushed forward against wave spring  422  to unlock skirt lock ring  426  from head  420 . By rotating the skirt lock ring  426  30° in either direction, the skirt lock ring  426  and head  420  are aligned as illustrated in  FIGS. 6D-6F , and, as a result, the head skirt  494  is axially unlocked from the head member  494  and thus may be removed from the flashlight  400 . This is because skirt lock ring  426  is now free to move from position B to position A, and once skirt lock ring  426  and head  420  are aligned in position A, as shown in  FIGS. 6A-6C , balls  428  will fall into trench  567  and the top end  579  of balls  428  will no longer be higher than the top surface  580  near the aft end of skirt lock ring  426 . Accordingly, head skirt  494  may continue to be moved rearward and dismounted and no longer locked by ball  428  and head skirt  494  can now be dismounted. However, cam  488  will block skirt lock ring  426  from moving rearward beyond its position in position A. 
         [0054]    If it is desired to mount head skirt  494  back to have a complete flashlight assembly, the following procedure can be used. First, head skirt  494  is slid forward over the flashlight front barrel  508  until it abuts skirt lock ring  426 . Once head skirt  494  abuts skirt lock ring  426 , head skirt  494  together with skirt lock ring  426  may be pushed forward to position B against the spring force of wave spring  422 , as shown in  FIGS. 6D-6F . Balls  428  are now disposed on the smooth surface  566  and the top end  579  of ball  428  is higher than the top surface  580  near the aft end of skirt lock ring  426  so as to extend into annular groove  429  in head skirt  494 . 
         [0055]    Once in position B, skirt lock ring  426  may be rotated 30° in either direction and then released. Wave spring  422  will bias the skirt lock ring  426  rearward so that the skirt lock ring  426  and head  420  are placed in position C as shown in  FIGS. 6G-6I . At this point, skirt lock ring  426  can no longer be rotated because lock members  570  of protuberances  568  are now locked by high plateau regions  574 . Because balls  428  are now disposed on the smooth surface  566 , as shown in  FIG. 6H  and skirt lock ring  426  cannot be rotated, head skirt  494  is axially locked to the head  420  and cannot be dismounted (as shown in  FIGS. 2-3 ). 
         [0056]    Referring back to  FIGS. 3-4 , one-way valves  424  and  430 , such as a lip seal, are preferably provided at the interface between face cap  412  and skirt lock ring  426  and also at the interface between head skirt  494  and skirt lock ring  426  to provide a watertight seal and to prevent moisture and dirt from entering head and switch assembly  406 . 
         [0057]    As noted above, a portion of front barrel  508  is disposed under head skirt  494  when it is mounted to the flashlight  400 . The forward most portion of the front barrel  508  is interposed between, and threadably attached to, the aft section  530  of the head  420  and retainer  432  as explained above. As a result of the foregoing construction, with the exception of the external surface formed by switch cover  500 , all of the external surfaces of the flashlight  400  according to the present embodiment may be made out of metal, and more preferably aluminum. 
         [0058]    Front barrel  508  is provided with a hole  544  through which a seal or switch cover  515  of switch  500  extends. The outer surface of front barrel  508  surrounding switch cover  515  may be beveled to facilitate tactile operation of flashlight  400 . Front barrel  508  may also be provided with a groove  546  about its circumference at a location forward of the trailing edge  548  of head skirt  494  for positioning a sealing element  496 , such as an O-ring, to form a watertight seal between the head skirt  494  and front barrel  508 . Similarly, switch cover  515  is preferably made from molded rubber. As best illustrated in  FIG. 3 , switch cover  515  is preferably configured to prevent moisture and dirt from entering the head and switch assembly  406  through hole  544 . 
         [0059]    Referring to  FIG. 5B , the components of an adjustable ball assembly  513  according to the present embodiment are illustrated. In the present embodiment, a lamp or other light source, such as LED  445  of LED module  444 , is mounted within head and switch assembly  406  so as to extend into reflector  418  through a central hole provided therein. In particular, LED module  444  is mounted on adjustable ball assembly  612 , which in turn is slideably mounted within front barrel  508 . The adjustable ball assembly  612  is prevented from sliding out of front barrel  508  by retainer  432 , head  420 , and cam assembly  488 ,  490  and cam follower assembly  435 . In the present embodiment, cam follower assembly  435  includes a cam follower screw  434 , a cam follower roller  436 , and a cam follower bushing  438 . 
         [0060]    An LED module that may be used for LED module  444  is described in co-pending U.S. patent application Ser. No. 12/188,201, filed Aug. 7, 2008, by Anthony Maglica et al., the contents of which is hereby incorporated by reference. 
         [0061]    Referring to  FIGS. 3 and 5B , when adjustable ball assembly  612  is positioned inside front barrel  508  and the cam follower assembly  435  is positioned in one of the axial slots  411  the radial arms of adjusting ring  448  will extend through the opposing slots of front barrel  508 . Further, the reflector  418  is sized so that the LED module  444  held by the adjustable ball assembly  612  is positioned adjacent the central opening in the aft end of reflector  418 . 
         [0062]    Still referring to  FIG. 3 , the moveable cam assembly  488 ,  490  is sized to fit around the outer diameter of the front barrel  508 . Front cam half  488  and rear cam half  490  form the cam assembly  488 ,  490  which is generally a barrel cam with a curved cam channel  550  that extends around the inner circumference of the cam assembly  488 ,  490 . The cam assembly  488 ,  490  is also sized such that when installed, the cam follower roller  436  of the cam follower assembly  435  engages with cam channel  550 . Accordingly, the cam channel  550  is able to define the axial rise, fall, and dwell of the adjustable ball assembly  612 . This is because the cam follower assembly  435  is able to slide in the curved cam channel  550  of the cam assembly  488 ,  490  when cam assembly  488 ,  490  is rotated. 
         [0063]    The cam assembly is held longitudinally in place between the aft end of head  420  and snap ring  492 . Because the curved cam channel  550  is disposed transverse to the axis of the flashlight  400 , when cam assembly  488 ,  490  is rotated, ball housing  440  (along with LED module  444 ) will move forwards and backwards along the longitudinal direction of flashlight  400 , changing the dispersion of light created by the flashlight from spot to flood and then from flood to spot. 
         [0064]    In the present embodiment, front barrel  508  preferably includes a groove  552  about its circumference for positioning external snap ring  492  to keep the cam assembly  488 ,  490  from moving toward the rear direction of the flashlight  400 . 
         [0065]    Cam assembly  488 ,  490  is preferably a two piece construction so that the separate halves may be fitted over the outer diameter of the flashlight front barrel  508  and the cam follower assembly  435 . The tow pieces of the moveable cam assembly  488 ,  490  may be secured together by any suitable method. Preferably, the respective cam halves are formed to snap together. 
         [0066]    Referring to  FIGS. 3 and 4 , longitudinal locking ribs are provided on the outer diameter of the cam assembly  488 ,  490 . Preferably the locking ribs are equally spaced around the outer circumference of the cam assembly. Corresponding longitudinal locking slots are provided on the interior surface of the head skirt  494 . As a result, when head skirt  494  is mounted on the flashlight  400  and it is rotated about the axis of the front barrel  508 , cam assembly  488 ,  490  will also be caused to rotate about the front barrel  508 . Rotation of the cam assembly  488 ,  490  in turn will cause the adjustable ball assembly  612  to axially displace along the inside of reflector  418 . In this way, the LED module  444  or other light source may be caused to translate along the reflector axis. 
         [0067]    One of the electrode contacts, the negative electrode  556 , in the present embodiment, of LED module  444  is configured to make electrical connection with the surface of through hole  545  of ball  442 , which is preferably made out of metal. As previously described, the ball  442  is slideably mounted via ball housing  440 , which is also preferably made out of metal, within front barrel  508 . 
         [0068]    Another electrode contact, the positive electrode  554 , in the present embodiment, of LED module  444  is in electrical communication with funnel spring  456  via contact cup  450 . 
         [0069]    The surface of through hole  545  of ball  442 , in the present embodiment, is shaped to operatively receive and hold LED module  444  so that the negative electrode  556  of LED module  444  is in contact with as much surface area of ball  442  as possible, thereby not only forming an electrical path between the negative contact  556  of LED module  444  and ball  442  but also providing an efficient thermal dissipation path between the LED module  444  and ball  442 . 
         [0070]    In the present embodiment, the outer surface of ball  442  comprises a plurality of cooling fins  447  which increase the surface area of the ball  442  and its heat dissipation rate. In other embodiments, cooling fins  447  may be omitted or other forms of cooling fins may be employed. 
         [0071]    In the present embodiment, a plastic adjusting ring  448  is molded around metal ball  442  to form a unitary ball assembly  443 . Adjusting ring  448  may be used to slightly adjust the axial direction of LED module  444 , and hence LED  445  within adjustable ball assembly  612 . Although, in other embodiments, the adjusting ring  448  and ball  442  may be separate components, providing adjusting ring  448  and ball  442  as a co-molded ball assembly  443 , as in the present embodiment, simplifies manufacturing. 
         [0072]    LED module  444  is pressed forward within through hole  545  of ball  444  until a flared portion of LED module  444  comes into contact with a corresponding shaped region of reduced diameter within through hole  545 . Front contact cup  450  is in electrical communication with the front end of a funnel-shaped spring  456 , which is preferably made out of a spring metal, such as phosphor bronze. The rear end of the funnel shaped spring  456  is held by a rear contact cup  462 , which is preferably made out of metal. In the present embodiment, front contact cup  450  includes a pointed region, which is configured to extend into the back of LED module  444  to contact positive electrode  554 , which is recessed from the back of LED module  444 . 
         [0073]    Insulator  446 , which includes a through hole on its forward end, is provided to prevent the front contact cup  450  from coming in electrical contact with the ball  442 . During assembly, insulator  446  would be inserted into through hole  545  after LED module  444 . The front contact cup  450  would then be inserted so that the pointed portion of contact cup  450  extends through the central through hole formed in insulator  446 . Insulator  446  is preferably made out of non-conductive material, such as plastic. 
         [0074]    The widest portion of funnel-shaped spring  456  is received within front contact cup  450  so as to make physical and electrical contact therewith, and so that the narrower portion of funnel-shaped spring  456  extends rearward beyond the aft end of ball housing  440 . 
         [0075]    A ball retainer  454  having a through hole  455  shaped to accommodate funnel-shaped spring  456  is used to push ball assembly  443  forward within the through hole  545 . Ball retainer  454  includes, on a forward facing surface  457  thereof, a ball engagement surface  459  configured to operatively mate with the aft end of ball  442  so that ball  442  may be adjusted slightly within ball housing  440 . 
         [0076]    In general, the forward curved surface  441  of ball  442  and the rearward curved surface  449  of ball  442  are preferably have a spherical profile to facilitate the adjustment of ball  442  within ball housing  440 . Likewise, the ball engagement surface  451  of ball housing  440  and the ball engagement surface  459  of ball retainer  454  preferably have mating angled surfaces. 
         [0077]    Ball retainer  454  also includes a cylindrical projecting portion  453 , which is sized to fit within forward contact cup  450 . Based on this configuration, the widest portion of funnel-shaped spring  456  is mechanically interposed between forward contact cup  450  and the forward end of the cylindrical projecting portion  453  of ball retainer  454 . 
         [0078]    In the present embodiment, the inner surface at the rear portion of ball housing  440  has a groove to support a snap ring  458 . A wave spring  452  is further interposed between the snap ring  458  and ball retainer  454 . Wave spring  452  biases ball retainer  454  forward so that ball engagement surface  459  engages with the aft end of ball  442 , which in turn biases ball  442  forward until the forward end of ball  442  engages with the ball engagement surface  451  of ball housing  440 . Further, in addition to biasing ball retainer  454  into the aft end of ball  442 , wave spring  453  biases ball retainer  454  so that the cylindrical projecting portion compresses the forward end of funnel-shaped spring  456  against contact cup  450 , which in turn biases LED module  444  forward within through hole  545  of ball  442  until the flared portion of LED module  444  comes in contact with the wall of through hole  545 . As a result, negative electrode  556  of LED module  444  is in intimate physical and electrical contact with ball  442 . 
         [0079]    The forgoing construction provides a simplified adjustable ball assembly  612 , which may be pre-assembled before inclusion in flashlight  400  or another flashlight or portable lighting device. It also allows the use of a single funnel-shaped spring  456  between the front contact cup  450  and the rear contact cup  462 , without the need of using contact sleeves to retain a biasing member such as a coil spring, therefore simplifying the manufacturing process and reducing manufacturing costs. 
         [0080]    Rear contact cup  462  is frictionally held by main switch housing  476  so that the aft end of rear contact cup  462  is in electrical communication with L-shaped contact  562  on lower switch housing  478 . Further, once adjustable ball assembly  612  is included in flashlight  400 , funnel-shaped spring  456  is compressed between front contact cup  450  and rear contact cup  462 , thereby forcing rear contact cup  462  into intimate physical and electrical contact with L-shaped contact  562  on lower switch housing  478 . As a result, funnel-shaped spring  456  is able to maintain electrical contact between front and rear contact cups  450 ,  462  as ball housing is axially moved forward and backwards within barrel  508  due to the operation of cam assembly  488 ,  490 . 
         [0081]    In the present embodiment, a compressible spring probe  460 , which is preferably made out of metal, is provided to establish a ground path between ball housing  440  and ground contact  486 . The spring probe  460  includes a barrel  461 , a plunger  463  and a spring (not shown) therebetween within the barrel  461  for biasing the plunger  463  away from barrel  461 . Spring probe  460  is sized so that as ball housing  440  axially slides forward and backwards within front barrel  508  due to the operation of assembly  488 ,  490 , spring probe  460  remains compressed between ball housing  440  and ground contact  484 , thereby maintaining electrical contact between the ball housing  440  and ground contact  484  at all times. 
         [0082]    Referring to  FIGS. 3 ,  4 ,  5 B,  5 C, and  5 E, the barrel  461  end of spring probe  460  is inserted through a hole provided in the switch housing  476  to make electrical contact with the downward extending leg  485  of ground contact  484 . As best seen in  FIG. 5E , the plunger  463  of spring probe  460  contacts the rear wall  439  of ball housing  440 . Therefore, an electrical communication between the ground contact  484  within the switch housing  476  and the ball housing  440  is established and maintained throughout operation of flashlight  400  by spring plunger  460 . 
         [0083]    Referring to  FIGS. 3 ,  4  and  5 C, the components of switch assembly  614  will now be described. Switch assembly  614  preferably includes a main switch housing  476  and a user interface, which is a switch cover  500  in the present embodiment. Main switch housing  476  encloses an upper switch housing  466 , an actuator  468 , a snap dome  470 , an assembled circuit board  472 , a snap in contact  474 , a lower switch housing  478 , a switch spring  480 , a set screw  482 , a ground contact  484 , and a hex nut  486 . In the present embodiment, snap in contact  474 , switch spring  480 , set screw  482 , ground contact  484 , and hex nut  486  are preferably made out of metal while main switch housing  476 , upper switch housing  466 , actuator  468 , and lower switch housing  478  are preferably made out of non-conductive material, such as plastic. 
         [0084]    Referring to  FIG. 5C , in the present embodiment, the snap dome  470  has four legs with one leg  582  shorter than other three legs  583 ,  584 ,  585 . The legs  583 ,  584 ,  585  are used to contact to ground pads  586 ,  587 ,  588  on assembled circuit board  472  while the short leg  582  is used to contact with a momentary pad  589  on assembled circuit board  472 . A ring-shaped latch pad  590  is placed in the middle of the assembled circuit board  472 . In the present embodiment, the momentary pad  589  is closer to the center of assembled circuit board  472  than other three pads. 
         [0085]    When switch  500  is not depressed, short leg  582  is not in contact with any portions on assembled circuit board  472 . In this situation, both latch pad  590  and momentary pad  589  on assembled circuit board  472  are not in contact with ground pads  586 ,  587 ,  588  on assembled circuit board  472 . 
         [0086]    When switch  500  is depressed half way down, actuator  468  pushes snap dome  470  toward assembled circuit board  472 . In this situation, short leg  582  makes contact with momentary pad  589  even though the central body of snap dome  470  remains out of contact with latch pad  590  of assembled circuit board  472 . Because the whole snap dome  470  is made of metal, the momentary pad  589  is now connected to ground, while the latch pad  590  is not. 
         [0087]    When switch cover  515  is further depressed, actuator  468  pushes snap dome  470  further down until snap dome  470  collapse such that the body of snap dome  470  is in contact with latch pad  590 . Now, not only momentary pad  589  is connecting to ground, latch pad  590  is also connecting to ground. 
         [0088]    When momentary pad  589  or latch pad  590  are connected to ground are received as signals to the assembled circuit board  472 , which in turn passes or disrupts the energy flow from the batteries in the hollow space  499  to the aft end of rear contact cup  462 . In this way, head and switch assembly  406  can turn the flashlight  400  on or off. The assembled circuit board  472  may additionally include circuitry suitable for providing functions to the flashlight  400  which will be described in more detail later. 
         [0089]    Snap in contact  474  is configured to include curved springs or biasing elements to ensure electrical contact is maintained with positive contact pin  596  and L-shaped contact  560 . 
         [0090]    Lower switch housing  478  includes two L-shaped contacts  560 ,  562 . L-shaped contact  560  is used to form electrical connection with a positive contact of the assembled circuit board  472  while also electrically contacting one of the biasing elements of snap in contact  474 . L-shaped contact  562  is used to electrically contact with another positive contact of the assembled circuit board  472  while also electrically contacting with the aft end of rear contact cup  462 . 
         [0091]    Ground contact  484  is secured by hex nut  486  so that it is in electrical communication with set screw  482 , which in turn is electrically coupled to switch spring  480 , which in turn is electrically coupled to a ground contact of the assembled circuit board  472 . 
         [0092]    Ground contact  484  includes a downwardly extending leg portion  485  (shown in  FIG. 5C ) for establishing electrical contact with the aft end of the spring probe  460 . Ground contact  484  also has an upwardly bent leaf spring portion  487  (shown in  FIG. 5C ) for contacting ground contact pin  598 . A wall of main switch housing  476  is disposed between downwardly extending leg portion  485  and upwardly bent leaf spring  487  so that both are provided with structural support in the axial direction. 
         [0093]      FIG. 5D  is an enlarged exploded perspective view from the forward end of the flashlight of  FIG. 1  illustrating how the front barrel  508  and rear barrel  526  of the flashlight  400  are assembled together with the circuit board  520  and charge rings  512  and  514 . 
         [0094]    Cathode contact  523  and anode contact  525  are preferably mounted to charger circuit board  520  using solder. Cathode contact  523  has a spring element  527  formed therein. Anode contact  525  has spring elements  529  formed therein. When battery pack  501  is installed in the hollow space  499  of barrel  526 , the spring element  527  of the cathode contact  523  are in contact with the cathode  503  of battery pack  501  while the spring elements  529  of anode contact  525  are in electrical contact with the anode  505  of battery pack  501 . 
         [0095]    Referring to  FIGS. 3 ,  4  and  5 D, the positive contact pin  596  is preferably swaged and soldered to a central via  597  extending through the charger circuit board  520 . The rearward end of positive contact pin  596  is in electrical contact with the cathode contact  523 . The ground contact pin  598  is preferably swaged and soldered to an outer via  599  extending through the charger circuit board  520 . The rearward end of ground contact pin  598  is in electrical contact with the anode contact  525 . 
         [0096]    As best seen in  FIG. 5E , ground contact pin  598  extends through a hole formed in the aft end of the main switching housing  476  to contact the upwardly bent leaf spring  487  of ground contact  484  and thereby form an electrical path between ground contact  484  and anode contact  525 . As seen in  FIG. 3 , positive contact pin  596  also extends through a hole formed in the back of main switch housing  476  to control snap in contact  474  and compress the same, thereby forming an electrical path between the snap in contact  474  and cathode contact  523 . 
         [0097]    When battery pack  501  is installed into the hollow space  499 , in the present embodiment, a circuit path for supporting the charger circuit board  520  and for recharging the battery pack  501  is formed from the cathode  503  of battery pack  501  to the cathode contact  523 , a positive contact pad (not shown) on charger circuit board  520 , to the charger circuit board  520 . The ground path can be formed from the ground pad (not shown) on the charger circuit board  520 , to the anode contact  525 , and then to the anode  505  of battery pack  501 . 
         [0098]    Electrical current for powering the assembled circuit board  472  flows from the cathode  503  of battery pack  501  to the cathode contact  523 , positive contact pin  596 , snap in contact  474 , L-shaped contact  560 , and to the positive power pad (not shown) on the assembled circuit board  472 . The ground path for return current flow from the electronics of the assembled circuit board  472  to battery pack  501  extends from the ground pad (not shown) on the assembled circuit board  472  to switch spring  480 , set screw  482 , ground contact  484 , ground contact pin  598 , anode contact  525 , and finally, the anode  505  of battery pack  501 . 
         [0099]    Electrical current for powering the load (LED module  444 ) flows from the cathode  503  of battery pack  501  to the cathode contact  523 , positive contact pin  596 , snap in contact  474 , L-shaped contact  560 , a first positive power pad (not shown) on the assembled circuit board  472 , a second positive power pad (not shown) on the assembled circuit board  472 , L-shaped contact  562 , aft contact cup  462 , funnel-shaped spring  456 , front contact cup  450 , to the positive electrode  554  of LED module  444 . The ground path of the load includes the negative electrode  556  of LED module  444 , ball  442 , ball housing  440 , spring probe  460 , ground contact  484 , ground contact pin  598 , anode contact  525 , and anode  505  of battery pack  501 . 
         [0100]    In other words, in the present embodiment, neither the front barrel  508  nor the rear barrel  526  is used as a part of the electric path for charging the battery pack  501 , powering the assembled circuit board  472 , or powering the LED module  444 . Likewise, in the present embodiment, tail cap  506  is not used as a part of the electrical path for charging the battery pack  501 , powering the assembled circuit board  472 , or powering the LED module  444 . The configuration of the embodiment described above in connection with  FIGS. 1-5E  provides several advantages. First, it simplifies the manufacturing process and manufacturing cost by eliminating the head, barrel, and tail cap from the electrical circuits of the flashlight. Further, the adjustable ball housing is simplified. 
         [0101]    Assembled circuit board  472  will now be described in connection with FIGS.  7  and  8 A- 8 E. For the purpose of simplification, assembled circuit board  472  is described in connection with flashlight  400 . However, it is to be understood that assembled circuit board  472  as well as switch assembly can also be used in other flashlights or portable lighting devices.  FIG. 7  is a block diagram illustrating the relationship of the electronic circuitry of assembled circuit board  472 . In the embodiment of  FIG. 7 , assembled circuit board  472  includes a microcontroller circuit  808 , a reverse battery protection circuit  802 , a linear regulator circuit  804 , a first mode memory device  810 , a second mode memory device  812 , a third mode memory device  814 , a bypass switch  806 , a MOSFET driver  820 , an electric load switch  822 , a momentary pad  589 , a latch pad  590 , and a cell count test point  824 . Detailed electrical circuit schematics of assembled circuit board  472  are shown in  FIGS. 8A-8E . 
         [0102]      FIG. 8A  shows a preferred circuit schematic diagram of reverse battery protection circuit  802 . In the present embodiment, the reverse battery protection circuit  802  takes the voltage  702  from the cathode of a battery of a battery pack  501  and electrically connects it to an electronic load switch, such as a p-channel metal-oxide-semiconductor field-effect transistor (PMOS)  712 . The gate of PMOS  712  is connected to ground  714  while the drain of PMOS  712  is connected to an internal voltage supply  704  for assembled circuit board  472 . With this reverse battery protection circuit  802 , when the battery or battery pack is installed in reverse order, no current will flow through current paths of the flashlight. 
         [0103]    Referring to  FIG. 8B , microcontroller circuit  808  includes a microcontroller  720  and connections. Microcontroller  720  receives input signals through signal lines ADC_MODE_CAP 1   722 , ADC_MODE_CAP 2   724 , ADC_MODE_CAP 3   726 , MISO  730 , MOMENTARY_SWITCH  736 , MAIN_SWITCH  738 , and RESET  742 . Microcontroller  720  also delivers output signals through signal lines ADC_MODE_CAP 1   722 , ADC_MODE_CAP 2   724 , ADC_MODE_CAP 3   726 , BYPASS_LDO  734 , and LAMP_DRIVE  740 . Accordingly, signal lines ADC_MODE_CAP 2   722 , ADC_MODE_CAP 1   724 , ADC_MODE_CAP 3   726  are bi-directional. In one embodiment, the microcontroller  720  is a commercial microcontroller having embedded memory, such as, for example, ATtiny24 which is an 8-bit microcontroller manufactured by Atmel Corporation of San Jose, Calif. In another embodiment, the microcontroller  720  can be a microprocessor. Yet in other embodiments, the microcontroller  720  can be discrete circuits. 
         [0104]    Microcontroller  720  has a power supply source  708  to provide a voltage input. Typically, microcontroller  720  cannot accept a power supply having a voltage higher than a predefined value, for example, 5.5 volts. However, assembled circuit board  472  is configured to be useable in a flashlight containing two, three or four dry cell batteries or cells electrically connected in series (depending on the length of rear barrel). Thus, battery voltage source  702  (and also  704 ) range from 3.0 volts to 6.0 volts. If a flashlight is designed to be used with four batteries connected in series, depending on the particular implementation, voltage from the battery voltage source  702  cannot be used to supply the microcontroller  708  directly. 
         [0105]      FIG. 8C  shows a circuit schematic diagram of one embodiment of a linear regulator circuit  804 . The illustrated linear regulator circuit  804  takes the internal voltage supply  704  from reverse battery protection circuit  802  as an input voltage and converts it into digital voltage output source  708  for supplying the microcontroller  708  through two different paths. The first path is through a low drop-out (LDO) linear voltage regulator  716  and the second path is to bypass the LDO linear voltage regulator  716  and pass through a PMOS  750 . 
         [0106]    When a flashlight is designed for receiving four or more batteries or cells electrically connected in series, internal voltage supply  704  cannot be used to supply microcontroller  720  directly. Accordingly, signal line BYPASS_LDO  734  would be turned low by microcontroller  708 . Thus, bipolar transistor  806  with built-in resistors will not conduct. As a result, PMOS  750  also will not conduct, therefore, resulting in internal voltage supply  704  being converted to digital voltage output source  708  through LDO linear voltage regulator  716 , which will provide an output voltage that is lower than the input voltage supply. In an embodiment in which four batteries or cells are connected electrically in series, the LDO linear voltage regulator  716  is preferably configured to drop the input voltage by about 1.0 volt. 
         [0107]    If flashlight  400  is designed for receiving two or three batteries in series, or if flashlight  400  is powered by battery pack  501 , internal voltage supply  704  may be used to supply microcontroller  720  directly. In these situations, signal line BYPASS_LDO  734  would be turned high by microcontroller  708 . In this situation, bipolar transistor  806  with built-in resistors would be closed so as to conduct, and, therefore, PMOS  750  would also be closed and thereby conduct. Internal voltage supply  704  would, therefore, be converted to digital voltage output source  708  through PMOS  750 , and bypass the LDO linear voltage regulator  716 . 
         [0108]    In the embodiment of  FIG. 8C , internal voltage supply  704  may be coupled to digital voltage source  708  first through a resistor  744  before passing through the LDO linear voltage regulator  716  or the PMOS  750 . Resistor  744  and capacitor  746  constitute an RC filter that filters out noises, for example, noise due to the switching of PMOS  780  (see  FIG. 8D ). This RC filter helps reduce errors when microcontroller  720  is making analog-to-digital conversions. In the present embodiment, resistor  744  may be set at 18 Ohms, for example, while capacitor  746  may be set at 1.0 micro Farad, for example. 
         [0109]    Microcontroller  720  can be programmed during manufacturing of a flashlight or other portable lighting device to input number of battery cell information, such as battery cell count, through cell count test point  824  (shown in  FIG. 7 ) to decide whether to turn signal line BYPASS_LDO  734  high or low. This battery cell count information is also stored in an embedded non-volatile memory, such as EEPROM, of microcontroller  720  for determining an appropriate power profile which will be described in more detail below. 
         [0110]      FIG. 8D  shows a circuit schematic diagram of MOSFET driver circuit  820  and a load switch  822 . In the embodiment of  FIG. 8D , electronic load switch  822  comprises PMOS  780 . The source of PMOS  780  is coupled to internal voltage supply  704  while the drain of PMOS  780  is coupled to voltage output pin  710 . Voltage output pin  710  may be coupled to the positive electrode of the LED  445  of flashlight  400 . The gate of PMOS  780  is coupled to a MOSFET driver  820 , which is implemented by a bipolar transistor  782 . The gate of PMOS  780  is also pulled-up to internal voltage supply  704  by a resistor  778 . Accordingly, when the base of bipolar transistor  782  is driven high by signal LAMP_DRIVE  740 , bipolar transistor  782  is closed and begins to conduct, which in turn causes PMOS  780  to close and conduct. Therefore, electric power can flow from internal voltage supply  704  to voltage output pin  710  thereby completing the circuit to power LED  445 . 
         [0111]    With the switch assembly design described above, as long as the battery pack or batteries are installed so that the cathode of the batteries of battery pack is in electrical communication with the snap in contact  474  and the anode of the batteries or battery pack is in electrical contact with the ground contact  484 , the assembled circuit board  472  will be supported by power from the batteries or battery pack regardless whether the flashlight  400  is turned “on” or turned “off.” By default, microcontroller  720  is in a very low power stand-by mode to minimize drain on the batteries. When momentary pad  589  is grounded by snap dome  470 , microcontroller  720  wakes up from the low power stand-by mode and turns on to close the load switch  780 , which in turn powers the LED  445  of the flashlight  400 . As long as momentary pad  589  is grounded, the LED  445  will be in full power. Once the plunger  448  is released and momentary pad  589  is no longer grounded, microcontroller  720  will turn “off” load switch  780  and power to LED  445  will be cut off. Microcontroller  720  will then go back to low power stand-by mode. 
         [0112]    If switch plunger  468  is pressed sufficiently hard to cause both momentary pad  589  and latch pad  588  to be grounded, the LED  445  will remain powered until another full press is detected. 
         [0113]    Referring to  FIG. 8E , the three mode memory devices  810 ,  812 ,  814  will now be described together. The first mode memory device  810  has an input/output signal line ADC_MODE_CAP  1724  which is coupled to microcontroller  720 . Signal line ADC_MODE_CAP 1   724  is also coupled to one end of a charge resistor  754 . The other end of resistor  754  is coupled to an RC circuit comprising a bleed off resistor  756  connected in parallel with a capacitor  758 . The other end or the RC circuit is coupled to ground. This first mode memory device  810  can be used to store information in a temporary manner. Microcontroller  720  may be used to store information in mode memory device  810  by setting signal line ADC_MODE_CAP 1   724  to a high or a low signal. The high signal would be stored in the first mode memory device  810  for a short period of time, for example, 2 seconds, before it is decayed sufficiently that it is no longer recognized as a high signal. Microcontroller  720  can execute a read operation from signal line ADC_MODE_CAP 1   724  to retrieve data stored in the first mode memory device  810 . In one embodiment, the resistance of resistor  756  is 1.0 Mega Ohms while the capacitance of capacitor  758  is 1.0 micro Farad. Similarly, the second mode memory device  812  and the third mode memory device  814  can have the same configuration as that of the first mode memory device  810 . 
         [0114]    Flashlight  400  may be provided with a variety of modes of operation. In the present embodiment, controller  808  is configured to implement eight separate modes of operation. Accordingly, when the flashlight is switched on, microcontroller  720  reads mode information from an internal memory, for example, an embedded SRAM built in the microcontroller  720 . Microcontroller  720  increments the mode information by one to obtain current mode information and then stores the current mode information to the external mode memory devices  810 ,  812 ,  814 . Flashlight  400  also changes to the new mode of operation accordingly. 
         [0115]    For example, when plunger  468  is pressed sufficiently to cause snap dome  470  to deflect into the latch position while flashlight  400  is in the off mode, microcontroller  720  reads the previous mode information from the embedded SRAM. If the previous mode information is 0,0,0, microcontroller  720  increments it by one to obtain the current mode information, which is 0,0,1. In the present embodiment, a 0,0,1 mode information represent a full power mode. In accordance, flashlight  400  enters the full power mode. Microcontroller  720  then writes the current mode information into the three mode memory devices  810 ,  812 ,  814  by pulling signal lines ADC_MODE_CAP 3   726  and ADC_MODE_CAP 2   722  to low and pulling signal line ADC_MODE_CAP 1   724  to high. 
         [0116]    If the switch  500  is pressed sufficiently hard to cause switch assembly to enter into the latch position (both momentary pad  589  and latch pad  588  are grounded), while the flashlight  400  is in an operational mode other than the off mode, and then held for a period of time, for example, two seconds, in the present embodiment, microcontroller  720  interprets the received input as a command to change modes of operation. Microcontroller  720  reads the previous mode information from the embedded SRAM and increments it by one to obtain the new current mode information. If the previous mode information is 0,0,1, for example, then the new current mode information would be 0,1,0. Microcontroller  720  then writes the new current mode information into the three mode memory devices  810 ,  812 ,  814  by pulling signal lines ADC_MODE_CAP 3   726  and ADC_MODE_CAP 1   724  to low and pulling signal line ADC_MODE_CAP 2   722  to high. In the present embodiment, this 0,1,0 combination represents a 50% power save mode. 
         [0117]    In the present embodiment, an 0,1,1 combination stored in the three mode memory devices  810 ,  812 ,  814  represents that the current mode is a 25% Power Save mode. The rest of the operational modes for flashlight  400  are shown in Table 1. 
         [0000]    
       
         
               
             
               
               
               
             
               
               
               
             
               
               
               
               
             
           
               
                 TABLE 1 
               
             
             
               
                   
               
               
                 Operation Modes and Code 
               
             
          
           
               
                   
                 Mode Name 
                   
               
             
          
           
               
                   
                 Current mode 
                 Next mode 
               
               
                   
                   
               
             
          
           
               
                   
                 Off 
                 0, 0, 0 
                 0, 0, 1 
               
               
                   
                 Full Power 
                 0, 0, 1 
                 0, 1, 0 
               
               
                   
                 50% Power Save 
                 0, 1, 0 
                 0, 1, 1 
               
               
                   
                 25% Power Save 
                 0, 1, 1 
                 1, 0, 0 
               
               
                   
                 10% Power Save 
                 1, 0, 0 
                 1, 0, 1 
               
               
                   
                 Blink 
                 1, 0, 1 
                 1, 1, 0 
               
               
                   
                 Beacon 
                 1, 1, 0 
                 1, 1, 1 
               
               
                   
                 SOS 
                 1, 1, 1 
                 1, 1, 1 
               
               
                   
                   
               
             
          
         
       
     
         [0118]    As long as the user continues to hold the switch  500  in the latch position, the flashlight  400  will transition through the lists of modes above. Every time a predetermined period of time, for example, two seconds, passes, the mode count will be incremented. 
         [0119]    Flashlight  400  may face a power interruption while the flashlight  400  is turned on or turned off. For example, when there is a need for battery replacement, flashlight  400  (and also the microcontroller  720 ) could experience a relatively long period of power interruption. When the flashlight is accidentally dropped on the ground or hit against a hard surface from one of its ends, the inertia of the batteries or battery pack could cause the batteries or battery pack which is sufficient to disconnect from one of the battery contacts for a short period of time, which is sufficient to cause a short period of power interruption to the controller  808 . 
         [0120]    In the present embodiment, after flashlight  400  has experienced a power interruption, no matter if it is a relatively long period or a short period, when the power is turned back on, microcontroller  720  runs a power up routine, which includes reading from the voltages stored on the three mode memory devices  810 ,  812 ,  814  through signal lines ADC_MODE_CAP 3   726 , ADC_MODE_CAP 2   722 , ADC_MODE_CAP 1   724 . Accordingly, flashlight  400  enters the mode indicated by the mode memory devices  810 ,  812 ,  814 . 
         [0121]    For example, after a battery replacement, the mode information indicated by the mode memory devices  810 ,  812 ,  814  should be 0,0,0 since the charge stored on each of capacitors  758 ,  764 ,  770  should have decayed by the time microcontroller  720  is again powered. Microcontroller  720  then reads from the three mode memory devices  810 ,  812 ,  814  and obtains 0,0,0 as the previous mode information. Accordingly, flashlight  400  enters the off mode. 
         [0122]    On the other hand, if the flashlight is accidentally dropped on the ground or is hit against a hard surface from one of its ends, the inertia of the batteries or battery pack could cause the batteries or battery pack to disconnect from one of the battery contacts for a short period of time, which is sufficient to cause a short period of power interruption of typically shorter than 0.5 seconds to the controller  808 . If the mode of operation right before the power interruption was, for example, the SOS mode, the charge, after the short power interruption, stored on each of capacitors  758 ,  764 ,  770  would continue to be retained until sufficiently after power is restored that microcontroller  720  will read 1,1,1 when it reads from the three mode memory devices  810 ,  812 ,  814 . Accordingly, flashlight  400  will enter the SOS mode, which was the operating mode before the power interruption. In other words, the flashlight  400  has immunity from such temporary power interruptions, due to accidental droppings of the flashlight or otherwise. 
         [0123]    The power immunity from interruption of flashlight  400  also applies to the condition when the flashlight  400  is in the off mode. When the flashlight  400  is switched off, microcontroller  720  writes 0,0,0 to the three mode memory devices  810 ,  812 ,  814 , and microcontroller  720  enters a low power stand-by mode. Therefore, regardless of whether a short power interruption or a long power interruption is experienced, after the power is restored, microcontroller  720  will read from the three mode memory devices  810 ,  812 ,  814  and obtain 0,0,0 as the previous mode information. Accordingly, flashlight  400  will enter the off mode. 
         [0124]    The electronic switch  822  is preferably controlled by controller  808  to supply power to LED  445  at different duty cycles to maximize battery life over a discharge cycle. Microcontroller  720  includes an internal memory for storing data concerning battery count information and the power profile such as included in  FIG. 9  for batteries or a battery pack that can be installed in flashlight  400 . As seen in  FIG. 9 , for most of the battery life, electronic switch  822  provides full power (100% duty cycle) to LED  445 . As the batteries are depleted, however, battery voltage  702  will drop which is monitored by microcontroller  720 . Microcontroller  720  uses the power profile stored in memory for a particular battery arrangement to determine when to reduce the duty cycle and when to maintain it at 100%. 
         [0125]    Each battery arrangement has a corresponding power map that includes at least a high voltage period and a voltage depletion period. Some battery arrangements, particularly for dry cell batteries, may also include a plateau region at the low voltage end of the power profile, corresponding to a constant low voltage period. When battery voltage  702  is in the high voltage period, microcontroller  720  provides a high duty cycle signal, typically 100%, to the lamp drive output pin  740  for MOSFET driver  820  to provide a power supply  710  to LED  445  with a high duty cycle. When battery voltage  702  is in the voltage depletion period, microcontroller  720  gradually declines the duty cycle signal to the lamp drive output pin  740  for MOSFET driver  820  to provide a declining power supply  710  to LED  445  with a gradually declining duty cycle. In battery arrangements that have a power profile that includes a low voltage plateau period, then when battery voltage  702  detects the low voltage period, microcontroller  720  provides a generally constant low duty cycle signal to the lamp drive output pin  740  for MOSFET driver  820  to provide a power supply  710  to LED  445  with a generally constant low duty cycle.  FIG. 9  is a power profile for battery pack  501 . By controllably reducing the duty cycle towards the end of a battery pack or a battery&#39;s life as set forth herein, the usable life time of battery pack or the battery can be significantly extended. 
         [0126]    While various embodiments of an improved flashlight and its respective components have been presented in the foregoing disclosure, numerous modifications, alterations, alternate embodiments, and alternate materials may be contemplated by those skilled in the art and may be utilized in accomplishing the various aspects of the present invention. For example, the power control circuit and short protection circuit described herein may be employed together in a flashlight or may be separately employed. Further, the short protection circuit may be used in rechargeable electronic devices other than flashlights. Thus, it is to be clearly understood that this description is made only by way of example and not as a limitation on the scope of the invention as claimed below.