Abstract:
A removable cap for an associated battery compartment housing at least one battery, whereby battery compartment forms a portion of a night vision device which is powered by the battery. The cap includes a one-piece contact that can be attached to the cap in a single operation. The contact includes a unitarily formed leaf-spring which makes mechanical and electrical contact with the battery when the cap is installed on the battery compartment.

Description:
FIELD OF THE INVENTION 
     The present invention relates generally to battery compartment caps and more specifically to a removable battery compartment cap having a one piece contact assembly. 
     BACKGROUND OF THE INVENTION 
     Battery compartments for housing batteries used in powering various electronic devices such as night vision goggles, flash lights, camera light meters, etc., are well known in the art. Such battery compartment designs include removable battery compartment caps which enable the battery or batteries contained within the compartment to be removed and replaced with a new or recharged battery or batteries. 
     Referring to FIG. 1A, there is shown a AN/PVS-7B night vision goggle device  58  (illustrated by the dotted lines) which includes a horizontally oriented PVS-7B battery compartment  50  closed by a removable prior art PVS-7B battery compartment cap  10 . The battery compartment cap is tethered to the night vision goggle device by a retainer strap  57 . As can be seen in FIG. 1C, the battery compartment  50  is loaded with either Lithium Sulfur Dioxide BA-5567/u batteries  52  (only one is shown) or two (2) AA batteries. 
     FIG. 1B is an exploded perspective view of the removable battery compartment cap  10  of FIG.  1 A. As shown, the battery compartment cap  10  generally comprises a cap member  12 , the retainer strap  57 , a retainer link  59 , an o-ring  48  and a contact assembly  28 . The cap member  12  includes a circular top  14  and an annular skirt  24  depending from the periphery of the circular top  14 . The compartment side surface of the circular top  14  includes a centrally disposed contact locating post  16  surrounded by an annular contact seating flange  18  and a circumferential lip  20 . The circumferential lip  20  in conjunction with the annular skirt  24  define a groove  22  for receiving the o-ring  48  that seals the battery compartment cap  10  to the battery compartment  50 . The exterior surface of the circular top  14  defines a centrally disposed projection  15  with an enlarged end  17  for coupling the battery compartment cap  10  to the retaining strap  57 . The retaining strap  57  is coupled to the night vision goggle device  58  by a retainer link  59 . A thread arrangement  26  for securing the battery compartment cap  10  to the battery compartment  50  is provided on the inner surface of the annular skirt  24 . 
     Still referring to FIG. 1B, the contact assembly  28  includes a stamped metal contact  30 , a washer  38 , a circular retaining clip  40  and a conical-shaped coil spring  42 . The contact includes a hub  32  portion with a centrally disposed aperture  33 . Three spoke members  34  extend radially from the periphery of the hub portion  32 . In between any two of the three spoke members is a tab  36 . Each tab  36  extends axially in the direction of the spring  42  from the periphery of the hub portion  32 . The circular retaining clip  40  that retains the contact  30  to the contact locating post  16  includes sharp projections  41  which cut into the locating post  16 . The coil spring  42  includes a large diameter end  44  and a small diameter end  46 . 
     Each component of the contact assembly  28  must be separately assembled to the cap member  12  as follows. First, the contact  30  of the contact assembly  28  is assembled to the cap member  12  so that the hub  32  portion engages the annular seating flange  18  while the contact locating post  16  extends through the aperture  33  of the hub portion  32 . Next, the washer  24  is installed onto the contact locating post  16  so that it rests against the hub portion  32  of the contact  30 . The retaining clip  40  is then press-fitted to the contact locating post  16 . Additional retention is sometimes provided by heat staking the free end of the contact locating post  16  after the retaining clip  40  is press fitted thereto. Finally, the coil spring  42  is non-removably secured to the contact  30  by the three tabs  36 . This is accomplished by bending each tab  36  around a portion of the first coil of the large diameter end  44  of the coil spring  42  to mechanically secure the coil spring  42  to the contact  30 . Then, each tab  36  is soldered to the coil to ensure electrical continuity between the coil spring  42  and the contact  30 . 
     A completed electrical circuit is provided when the battery compartment cap  10  is installed on the battery compartment  50  loaded with batteries  52  as shown in FIG.  1 C. The electrical circuit is created by the mechanical and electrical contact between the small diameter portion  46  of the coil spring and the negative end of the battery  52 , and the solder connections between the coil spring  42  and the contact  30 . The circuit is completed by the physical touching of the contact  30  to a ground sleeve  54  in the battery compartment  50 . 
     Although the battery compartment cap  10  of FIGS. 1A-1C operates in a generally satisfactory manner, there exists certain disadvantages which reduces its utility. One disadvantage is that the contact assembly  28  is comprised of four (4) separate components which must be assembled in a process which involves three bending operations and three soldering operations which add complexity to the manufacturing of the battery compartment cap  10 . Another problem with the battery compartment cap  10  is that it presents difficulties when the batteries  52  are changed. More particularly, when the battery compartment cap  10  is applied to the battery compartment, the relatively long free length of the uncompressed coil spring  42  (represented in FIG. 1C as dotted lines) causes it to contact the battery  52  before the thread  26  of the battery compartment cap  10  engages the thread  56  of the battery compartment  50 , thereby requiring a significant compression force to apply the battery compartment cap  10 . This causes difficulty when changing batteries, especially under adverse circumstances. Still another problem with the above design concerns the possibility of missed contact when loading certain types of batteries. In particular, certain types of batteries have diameters which are significantly small than the diameter of the battery compartment. If such batteries are loaded into the battery compartment when the battery compartment is oriented horizontally, the batteries tend to sit in an off-centered manner within the battery compartment. Consequently, when the battery compartment cap is applied to the battery compartment the small diameter end of the spring may not contact the batteries. 
     It is, therefore, a primary object of the present invention to provide an improved battery compartment cap with a one-piece contact assembly that substantially overcomes the disadvantages associated with prior art battery compartment caps. 
     SUMMARY OF THE INVENTION 
     A removable cap for closing an associated battery compartment housing at least one battery. The cap comprises a cap member and contact means attached to the cap member for completing an electrical circuit with the at least one battery housed within the battery compartment. The contact means includes a unitarily formed sliding biasing member for making mechanical and electrical contact with the at least one battery. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     For a detailed understanding of the present invention, reference should be made to the following detailed description taken in conjunction with the accompanying drawings wherein: 
     FIG. 1A is a perspective view of an exemplary night vision device shown by dotted lines. The night vision device is powered by batteries housed in a battery compartment which includes a prior art battery compartment cap; 
     FIG. 1B is an exploded partial cross-sectional view of the prior art battery compartment cap of FIG. 1A; 
     FIG. 1C is a cross-sectional view through the prior art battery compartment cap and battery compartment of FIG. 1A; 
     FIG. 2A is an exploded partial cross-sectional view of an exemplary embodiment of the battery compartment cap of present invention; 
     FIG. 2B is a bottom plan view of the contact assembly used in the battery compartment cap of the present invention; 
     FIG. 2C is side cross-sectional view through the contact assembly of FIG. 2B; and 
     FIG. 2D is a cross-sectional view through the battery compartment cap of the present invention installed on a battery compartment. 
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     Referring to FIG. 2A, there is shown an exploded perspective view of an exemplary embodiment of a removable battery compartment cap made according to the present invention denoted by the numeral  60 . As shown, the battery compartment cap  60  generally comprises a cap member  62 , a retainer strap  102 , a retainer link  104 , an o-ring  100  and a one piece contact assembly  78 . The components of the battery compartment cap  60  can be manufactured from any well known conventional materials. For instance, the cap member  62 , the retainer strap  102 , and retainer link  104  can be manufactured from any suitable plastic or metal material. The o-ring  100  can be manufactured from any elastic material such as rubber. The contact assembly  78  can be manufactured from any suitable metal such as beryllium copper or stainless steel. 
     As can be seen in FIG. 2A, the structure of the cap member  62  employed in the battery compartment cap  60  of the present invention is similar to the prior art cap member of FIGS. 1A-1C, and thus, includes a circular top  64  and an annular skirt  74  depending from the periphery of the circular top  64 . The compartment side of the circular top  64  includes a centrally disposed contact locating post  66  surrounded by an annular contact seating flange  68  and a circumferential lip  70 . The circumferential lip  70  in conjunction with the annular skirt operate to define a groove  72  for receiving the o-ring  100  that seals the battery compartment cap  60  to an associated battery compartment  106  (FIG.  2 D). It should be understood, however, that any other technique for sealing the battery compartment cap  60  to the battery compartment can be used. For example, if the cap member is manufactured from a plastic material, the o-ring  100  can be replaced with one or more a unitarily formed sealing ribs to further reduce the assembly costs of the battery compartment cap. 
     Referring still to FIG. 2A, the exterior of the circular top  64  defines a centrally disposed protection  65  having an enlarged end  67  for coupling the battery compartment cap  60  to one end of the retaining strap  102 . The other end of the retaining strap  102  is coupled to a retainer link  104  which attaches the battery compartment cap  60  to a night vision goggle device similar to the one shown in FIG.  1 A. The retaining strap and link cooperate to tether the battery compartment cap to the night vision goggle device when the battery compartment cap is removed from the battery compartment. 
     Still referring to FIG. 2A, a thread arrangement  76  is provided on the inner surface of the annular skirt  74 . The thread  76  coacts with a corresponding thread  108  on the battery compartment  106  (see FIG. 2D) to removably secure the battery compartment cap  60  thereto. 
     Referring now to FIG. 2B, the contact assembly  78  preferably comprises an x-shaped one-piece stamped and formed metal contact  79  having a centrally disposed aperture  88  and a low profile leaf-spring  92  having a flat portion  94  and an arcuate portion  96 . The one piece contact assembly  78  eliminates the separate spring, washer and circular clip components and the six tab bending/soldering operations which are associated with the prior art battery compartment cap of FIGS. 1A-1C. The x-shaped of the contact  79  is made up of four extensions  80 ,  82 ,  84 , and  86  which are symmetrically positioned at approximately 90° increments around the centrally disposed aperture  88 . The extensions  82  and  86  operate to laterally stabilize the contact assembly  78 . In another embodiment of the present invention, the extensions  82  and  86  can be eliminated altogether if desired to reduce the complexity of the stamping die that is used in forming the contact assembly. 
     As shown in FIG. 2C, one end of the leaf-spring  92  is unitarily formed with extension  80 . The flat portion  94  of the spring  92  projects away from the extension  80  at a preferred angle of approximately 33° and then merges with the arcuate portion  96 . The arcuate portion  96  curves back toward the extension  84  where it terminates in a lip or bend  98  that enables the free end of the spring  92  to slide along the surface of extension  84 . The broad and planar surface area of the leaf-spring  92  provides more than twice the contact area when compared to the prior art coil spring described earlier in the background of the invention. Accordingly, the problem of missed contact with the batteries as described earlier with regard to the prior art battery compartment cap is substantially reduced. Moreover, the leaf-spring  92  has a significantly lower uncompressed profile as shown with dotted lines in FIG. 2D, when compared with the uncompressed profile of the prior art spring of FIGS. 1A-1C. This allows the thread  76  of the battery compartment cap  60  to engage the thread  108  of the battery compartment  106  prior to the spring  92  engaging the battery  110 . This makes changing the batteries substantially easier when compared with the prior art battery compartment cap of FIGS. 1A-1C, especially during adverse conditions which often require one-handed battery changes. 
     Referring again to FIG. 2B, the aperture  88  includes a plurality of unitarily formed locking projections  90  which extend radially inward from the periphery of the aperture  88  and operate to cut into the contact locating post  66  to lock and retain the contact assembly  78  to the cap member  60  when the cap member is assembled  60 . The unitarily formed locking protections  90  and the unitarily formed spring  92  of the contact assembly  78  enables it to be assembled to the cap member  62  in a single operation which substantially reduces the cost of manufacturing the battery compartment cap  60  when compared with the prior art cap of FIGS. 1A-1C. 
     Although the battery compartment cap  60  of the present invention is especially suited for use with the battery compartment of a AN/PVS-7B night vision goggle device as shown in FIG. 1A, it can be easily adapted to fit in many other applications. 
     It should be understood that the embodiment described herein is merely exemplary and that a person skilled in the art may make many variations and modifications to the embodiment utilizing functionally equivalent elements to those described herein. Any and all such variations or modifications as well as others which may become apparent to those skilled in the art, are intended to be included within the scope of the invention as defined by the appended claims.