Patent Publication Number: US-6984130-B2

Title: Electrical contact assembly for connecting a battery to a circuit

Description:
FIELD OF THE INVENTION 
   The present invention relates to an electrical contact assembly. More particularly this invention concerns such an assembly of the type used to connect a removable battery, e.g. in a cell phone, to an electrical circuit, e.g. a printed-circuit board. 
   BACKGROUND OF THE INVENTION 
   A standard contact assembly has a dielectric mounting block having inner and outer faces and at least one conductive contact unitarily formed of elastically deformable metal. This contact has a center web set in the block, an inner leg extending from the web past the inner face and elastically deflectable toward the inner face and toward the center web, and an outer leg extending from web and elastically deflectable from an outer position spaced well outward of the outer face and spaced from the web to an inner position closely juxtaposed with or even touching the web. 
   Such a contact assembly can be mounted, for example, in a wall of a cell phone, between the openable battery compartment and the interior compartment holding the phone&#39;s circuitry. Each inner leg bears on and makes permanent electrical contact with a trace of the printed-circuit board carrying this circuitry. Each outer leg can bear on a terminal of a removable battery, typically of the replaceable and rechargeable type. British patent 833,038 of R. Firman, German patent 3,338,080 of G. Muscaglione, and German patent 198 34 375 of K. Bauer describe typical such contact assemblies. Three contacts are provided normally on one mounting block to allow three electrical connections to be made to the battery. 
   In today&#39;s very small electronic equipment, in particular cell phones, it is important that every element be made as compact as possible. The above-described contact assemblies however cannot be reduced beyond a certain thickness, is as otherwise the outer leg at least will not bear with sufficient force against the battery terminals to form a good long-term electrical connection. The stroke of the outer leg must be maximized to ensure that it is deformed considerably in its inner contacting position, and this relatively long stroke takes up valuable space inside the device it is mounted in. 
   OBJECTS OF THE INVENTION 
   It is therefore an object of the present invention to provide an improved contact assembly. 
   Another object is the provision of such an improved contact assembly which overcomes the above-given disadvantages, that is which is extremely compact, yet which still forms a strong electrical connection. 
   SUMMARY OF THE INVENTION 
   A contact assembly has a dielectric mounting block having inner and outer faces, and a conductive contact unitarily formed of elastically deformable metal. The contact has a center web set in the block, an inner leg extending from the web past the inner face and elastically deflectable toward the inner face and toward the center web, and an outer leg extending from web and elastically deflectable from an outer position spaced well outward of the outer face and spaced from the web to an inner position extending at least partially inward past the web. 
   The ability of the outer leg to move inward past the web means that it has a substantial stroke and can therefore be built into a thinner mounting block. As a result, it can bear with quite some force on whatever it is connecting to, but still is of very compact dimensions. 
   The contact is further formed with inner and outer U-shaped bights connecting the respective legs to the web. In addition the bock is formed on the outer face with an inwardly directed abutment. The outer leg has a tip bearing outward on the abutment in the outer position. In fact the tip bears with prestress against the abutment so that even when only deflected slightly the outer leg will press with its prestress force on the terminal it is engaging. Unlike a tip which stands free, the outer contact according to the instant invention resists displacement from its outermost starting position with considerable force so that, even if just deflected inward a tiny bit, it will press with this considerable force on the battery terminal or other circuit element it is making an electrical connection with. 
   The web according to the invention is formed with a cutout through which the tip passes on movement of the outer leg from the outer position to the inner position. This cutout can be a laterally open notch, but according to a particular feature of this invention it is formed as a notch wholly bounded by the web, that is a hole. The web is substantially wider at the notch than the tip. 
   The bights in accordance with the invention are at opposite ends of the web and the legs extend oppositely toward each other from the respective bights. This gives the contact an S- or Z-shape. Since the two legs bend in from opposite ends, the web will not tend to cant or twist in the mounting block but instead will sit flatly therein when in use. 

   
     BRIEF DESCRIPTION OF THE DRAWING 
     The above and other objects, features, and advantages will become more readily apparent from the following description, reference being made to the accompanying drawing in which: 
       FIG. 1  is a perspective view of the contact assembly according to the invention; 
       FIG. 2  is an edge view of the contact assembly; 
       FIG. 3  is a cross section of the contact assembly; 
       FIG. 4  is a side view of-the contact assembly; 
       FIG. 5  is a perspective view of one of the contacts in the relaxed condition; 
       FIG. 6  is a view like  FIG. 5  but with the outer leg in the inner position; and 
       FIG. 7  is a sectional view illustrating the contact assembly in use. 
   

   SPECIFIC DESCRIPTION 
   As seen in  FIGS. 1 through 6 , a contact assembly  10  according to the invention basically comprises an injection-molded dielectric plastic mounting block  11  and three identical sheet-metal contacts  12 , typically made of copper- or gold-plated steel. Here as shown in  FIG. 7  the mounting block  11  is adapted to be set in a hole  33  in a wall  32  between a compartment holding a battery  35  and a compartment holding a circuit board  34 . The contacts  12  each connect a respective trace  34   a  of the circuit board  34  with a respective terminal  35   a  of the battery  35 . 
   Each contact  12  basically comprises a planar central web  15 , an outer leg  13  connected to one end of the web  15  via a U-shaped bight  20 , and an inner leg  14  connected to the opposite end of the web  15  by another U-shaped bight  28 , all unitarily formed with each other from a bent sheet-metal stamping. The web  15  has a widened portion  18  that fits tightly in a complementary region  19  of a notch  16  of the block  11 . In fact the widened portion  18  is such a tight fit that when it is forced in direction  17  ( FIG. 3 ) into the region  19 , it solidly locks the contact  12  in place. 
   The inner leg  14  is of fairly simple construction and has an inwardly (toward the web  15 ) concave outer end  29  that rides on the respective trace  34   a . It extends from the end of the web  15  formed with the widened portion  18  and when unstressed extends at a small acute angle to the web  15  as shown in  FIGS. 2 ,  3 ,  4 ,  5 , and  6 . When installed as shown in  FIG. 7  it extends almost parallel to the web  16  and barely projects past an inner planar face of the block  11 . 
   The outer leg  13  extends from the opposite end of the web  15  and has an inwardly concave contact portion  30  lying between a body portion  21  and an inwardly convex tip  27 . The contact portion  30  engages the battery terminal  35 . The tip  27  is only about one-third as wide as the contact portion  30  and as the web  15 . The web  15  according to the invention is formed with a full-length notch or slot  31  that is slightly wider than the tip  27  so that as described below the tip  27  can pass inward through this slot  31  when the leg  13  is pressed inward. 
   The mounting block is formed with an abutment pocket  25  having an inwardly directed surface  26  against which an outer face of the outer-leg tip  27  normally bears with some prestress. Thus as shown in  FIG. 3  before a battery  35  is installed the contact portion  30  projects well past the outer face of the block  11  and the tip  27  bears with quite some force on the abutment surface  26 . When a battery  35  is installed, the outer leg  13  moves inward as indicated by arrow  36  ( FIGS. 4 and 5 ), with the tip  27  moving away from the surface  26  and eventually passing through the slot  31  in the web  15  as shown in  FIG. 7 . 
   The prestressing of the tip  27  against the surface  26  ensures that even if only deflected inward slightly, the region  30  will bear with quite some force against the battery terminal  35   a . In addition the ability of the tip  27  to move inward past the web  15  means that the arm  12  can deform through a considerable stroke even through the entire assembly is of relatively modest thickness, measured perpendicular to the web  15 .