Abstract:
An electrical terminal including a base pad for soldering to a surface. The base pad has a curved perimeter, and top and bottom surfaces. The electrical terminal also includes a securement portion having a deformable member for deforming around a conductor wire to capture and secure the conductor wire directly to the securement portion. The securement portion is configured relative to the base pad such that forces exerted by the conductor on the base pad are directed to a central region of the base pad.

Description:
RELATED APPLICATION 
     This application is a continuation of U.S. application Ser. No. 09/671,035, filed Sep. 27, 2000, now U.S. Pat. No. 6,406,337, issued Jun. 18, 2002, the entire teachings of which are incorporated herein by reference. 
    
    
     BACKGROUND 
     The windshield and/or rear window of automotive vehicles often have an electrical device such as an antenna or defroster formed on or in the glass. In order to electrically connect the electrical device to associated equipment, for example, a radio, telephone, or defroster control, an electrical terminal is first soldered to the glass in electrical communication with the electrical device. An electrical cable extending from the associated equipment is then secured to the electrical terminal for providing electrical communication therebetween. A problem with some current electrical terminals is that the terminals can be easily separated from the glass by peeling if accidental pulling forces are exerted on the electrical cable. In addition, some electrical terminal designs are prone to cause cracking of the glass during soldering because of heat related stress concentrations formed on the glass by the footprint of the terminal. 
     SUMMARY 
     The present invention provides an electrical terminal which is less readily separated from glass by accidental pulling forces than current terminal designs. In addition, the present invention electrical terminal has a design which causes little or no cracking of glass during soldering. The present invention is directed to an electrical terminal which includes a base pad for soldering to a surface. The base pad has a curved perimeter, and top and bottom surfaces. The electrical terminal also includes a securement portion having a deformable member for deforming around a conductor wire to capture and secure the conductor wire directly to the securement portion. The securement portion is configured relative to the base pad such that forces exerted by the conductor on the base pad are directed to a central region of the base pad. 
     In preferred embodiments, the base pad is formed of sheet metal and is generally circular in shape. The bottom surface of the base pad has a layer of solder thereon. In one embodiment, the securement portion includes a deformable strap located at the central region of the base pad formed by two opposed slits in the base pad. The slits allow the insertion of the conductor wire therethrough for capture between the top surface of the base pad and the strap. 
     In another embodiment, the securement portion includes an arm having proximal and distal ends extending from the central region of the base pad for directing forces exerted by the conductor wire to the central region. The proximal end extends from the central region and is defined by two opposed slots formed in the base pad extending from the perimeter of the base pad to the central region. The distal end has opposed crimping tabs for securing directly to the conductor wire. A portion of the arm is bent upwardly at an angle at about the perimeter of the base pad for absorbing forces exerted on the arm by the conductor wire. The distal end of the arm is bent to be parallel with the base pad. 
     The present invention also provides an electrical terminal assembly which enables easy soldering of multiple terminals with proper spacing therebetween. The terminal assembly includes at least two terminals, each having a base pad for soldering to a surface. Each base pad is secured to a conductor wire. A carrier strip is attached to the base pads by breakable regions. 
     The present invention further provides a method of soldering multiple electrical terminals to a surface, including providing an electrical terminal assembly having at least two terminals, each having a base pad for soldering to the surface. The base pads are secured to respective conductor wires and are attached to a carrier strip by breakable regions. The base pads are soldered to the surface with the carrier strip providing the proper spacing between the base pads. Once the base pads are soldered, the carrier strip is separated from the base pads by bending the carrier strip upwardly, thereby breaking the breakable regions. 
     In the present invention electrical terminal, by directing forces exerted by the conductor to the central region of the base pad, the strength of the solder joint between the base pad and the underlying surface, typically glass, is maximized. As a result, the terminal is not readily separated from the glass by accidental pulling forces. In addition, by having a generally circular base pad, the base pad of the present invention forms little or no heat related stress concentrations on the glass during soldering so that little or no cracking of the glass occurs. Consequently, the present invention provides a terminal that may be soldered to glass in a reliable manner and remain soldered thereto during normal use. Finally, the present invention electrical terminal assembly allows multiple electrical terminals to be quickly and easily soldered with the proper spacing therebetween, thereby allowing the manufacturing process to be conducted more quickly. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     The foregoing and other objects, features and advantages of the invention will be apparent from the following more particular description of preferred embodiments of the invention, as illustrated in the accompanying drawings in which like reference characters refer to the same parts throughout the different views. The drawings are not necessarily to scale, emphasis instead being placed upon illustrating the principles of the invention. 
     FIG. 1 is a plan view of an embodiment of the present invention electrical terminal which is secured to an electrical cable. 
     FIG. 2 is a side view of the electrical terminal of FIG.  1 . 
     FIG. 3 is a side view of the electrical terminal of FIG. 1 soldered to a piece of glass. 
     FIG. 4 is a plan view of a multiple terminal soldering assembly having a series of electrical terminals attached to a carrier strip which are secured to electrical cables. 
     FIG. 5 is a side view of the multiple terminal soldering assembly soldered to a piece of glass. 
     FIG. 6 is a plan view of another embodiment of the present invention electrical terminal which is secured to an electrical cable. 
     FIG. 7 is a side view of the electrical terminal of FIG.  6 . 
     FIG. 8 is a side view of the electrical terminal of FIG. 6 soldered to a piece of glass. 
     FIGS. 9 and 10 are plan and side views, respectively, of a series of the electrical terminals of FIG. 6 which are attached to a carrier strip. 
     FIG. 11 is a plan view of another multiple terminal assembly. 
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     Referring to FIGS. 1 and 2, terminal  11  is an electrical terminal that is typically soldered to the windshield or rear window of an automotive vehicle in electrical communication with an electrical device, such as an antenna or defroster formed on or in the glass, so that the electrical device may be electrically connected to associated equipment by an electrical cable  18 . Electrical terminal  11  includes a generally flat or planar base pad  12  formed of sheet metal having a continuously curved outer perimeter or edge  12   a . Typically, base pad  12  is generally circular in shape (FIG.  1 ). The bottom surface  12   c  of base pad  12  is precoated with a layer of solder (FIG. 2) for facilitating the soldering process. Two parallel slits  14   a  in the central region of base pad  12 , made by lancing, form a deflectable or deformable strap  14 . The strap  14  is centrally located relative to base pad  12 . This allows the inner conductor wire  18   a  of electrical cable  18  which extends beyond the outer insulation  18   b  to be inserted through the slits  14   a  and under strap  14  for assembly to base pad  12 . The diameter of the conductor wire  18   a  pushes and deforms the strap  14  slightly upwardly relative to base pad  12  so that the strap  14  extends around the top surfaces of conductor wire  18   a . The conductor wire  18   a  is thereby captured or pinched between the strap  14  and the top surface  12   b  of base pad  12 . The electrical terminal  11  and the cable  18  are typically preassembled in a cable/terminal assembly  10  before soldering. 
     In use, electrical terminal  11  is typically soldered to glass  34  (FIG. 3) by positioning terminal  11  in the desired position on the glass  34 , usually a metallic terminal pad coated on the glass  34 , and heating base pad  12  to melt the layer of solder  20  on the bottom  12   c  of base pad  12 . The solder  20  bonds base pad  12  to glass  34  as well as bonds conductor wire  18   a  to both the base pad  12  and the glass  34 . The curved outer perimeter  12   a  of the circular base pad  12  has no sharp corners and, as a result, forms little or no heat related stress concentrations on the glass during soldering. Typically, such stress concentrations, if formed, tend to cause cracks in the glass. Consequently, little or no cracking of the glass  34  occurs when electrical terminal  11  is soldered thereto. 
     Once terminal  11  is soldered to glass  34 , any accidental pulling forces F (FIG. 3) exerted on electrical cable  18  are transferred to about the center  16  of base pad  12  because the inner conductor  18   a  of cable  18  is secured to base pad  12  at the center  16 . This maximizes the ability of terminal  11  to resist separating from the glass  34  due to accidental pulling of cable  18 . The reason for this is that a greater pulling force is required to pull terminal  11  from glass  34  when directed at the center  16  than if directed at the perimeter  12   a , for example, if cable  18  were secured to base pad  12  near the perimeter  12   a . A pulling force directed at the perimeter  12   a would separate the base pad  12  from the glass  34  by first lifting an edge from the glass  34  and then progressively peeling the base pad  12  from the glass  34 . As a result, an edge directed pulling force does not act on the whole solder joint at once, but instead is directed on a small area along the moving peel line. Only a portion of the solder joint is acted upon by the pulling force at a particular time. In contrast, by securing cable  18  to the center  16  of base pad  12  and directing pulling forces F to the center  16  of base pad  12  rather than to the perimeter  12   a , the pulling forces F do not lift an edge of base pad  12  in a peeling type action. Consequently, the centrally directed pulling forces F at any particular moment in time are resisted by the entire solder joint which makes it more difficult to pull base pad  12  from the glass  34 . 
     A more detailed description of terminal  11  now follows. As shown in FIG. 1, base pad  12  is preferably circular. Slits  14   a  are formed through base pad  12  on opposite sides of the center  16  of base pad  12 . Slits  14   a  extend parallel to each other across the central region of base pad  12  on either side of center  16 , and terminate about halfway between the center  16  and the outer perimeter  12   a . Terminal  11  is formed in a stamping and forming process by a forming die having a succession of progressive stations. Typically, the forming process produces a series of terminals  11  which are attached to a continuous carrier strip  22 . FIG. 4 depicts a section of such a configuration. The cables  18  may be attached when the terminals  11  are formed, or at a later time. 
     In one embodiment, base pad  12  is formed of C260 brass and is about 8 mm in diameter by 0.318 mm thick. Base pad  12  is tempered ½ hard about 0.22 mm thick. Slits  14   a  are about 4 mm long and are located 1.5 mm apart from each other. Solder  20  is about 0.305 mm thick and contains about 25% Sn (tin), 62% Pb (lead), 10% Bi (bismuth) and 3% Ag (silver). Alternatively, solder  20  may contain about 30% Sn, 65% In (indium), 0.5% Cu (copper) and 4.5% Ag. The elements and percentages of solder  20  may be additionally varied to suit the situation at hand. Base pad  12  may also be formed of other suitable conductive metals such as copper or bronze. In addition, the length and spacing between slits  14   a  may be varied to accommodate different diameter conductor wires  18   a . Furthermore, the diameter and thickness of base pad  12  may be varied to suit different applications. 
     Referring to FIGS. 4 and 5, multiple terminal soldering assembly  30  includes a series of cable/terminal assemblies  10  which are attached to a carrier strip  22  by a series of breakable regions  26 . In use, the soldering assembly  30  is placed upon the glass  34  in the desired location. The cable/terminal assemblies  10  are then soldered to the glass  34  while still attached to the carrier strip  22 . The cable/terminal assemblies  10  are attached to carrier strip  22  at the same distance apart from each other that is required when soldered on the glass  34 . Consequently, proper spacing of the terminals  11  on the glass  34  is consistently achieved. Once the terminals  11  are soldered to the glass  34 , the carrier strip  22  is separated from the terminals  11  by bending the carrier strip  22  upwardly and downwardly in the direction indicated by arrow  32  (FIG. 5) until the breakable regions  26  break along lines  28 . Thus, multiple cable/terminal assemblies  10  are quickly and easily soldered to glass  34  with the proper spacing therebetween. 
     Since terminals  11  are typically attached to carrier strip  22  when formed, the formation of soldering assembly  30  subsequently only requires attaching the electrical cables  18  to the terminals  11  and cutting the carrier strip  22  to a length that contains the desired number of terminals  11 . The spacing of terminals  11  relative to each other on carrier strip  22  may be selected to suit particular applications. Although six cable/terminal assemblies  10  are shown attached to carrier strip  22  in FIG. 4, any number of cable/terminal assemblies  10  may be employed depending upon the application at hand. Typically, carrier strip  22  is attached to at least two cable/terminal assemblies  10 . 
     Referring to FIGS. 6 and 7, electrical terminal  50  is another embodiment of the present invention. Terminal  50  may be preassembled with an electrical cable  18  to form a cable/terminal assembly  40 . Terminal  50  has a base pad  42  that is generally or substantially circular in shape. The outer perimeter or edge  42   a  of base pad extends continuously in a circular manner for about 270° before being interrupted by an arm  48  having a proximal end  48   a  extending from the center  16  of base pad  42  and which is defined by a pair of parallel slots  46  formed within base pad  42  (FIG.  6 ). Arm  48  extends beyond the outer perimeter  42   a  of base pad  42  for crimping to cable  18 . The slots  46  extend from the outer perimeter  42 , inwardly about halfway to the center line  17  of base pad  42 , thereby forming two wings  52  thereof. The arm  48  has an intermediate portion  48   b  which is bent upwardly at an angle from the proximal end  48   a  at about the outer perimeter  42   a . The distal end  48   c  of arm  48  includes a crimping portion  44  having two opposed crimping tabs  44   a  for crimping to the inner conductor wire  18   a  of cable  18 . Arm  48  is bent between the intermediate portion  48   b  and the distal end  48   c  so that the distal end  48   c  is positioned parallel to and laterally offset from the base pad  42  as well as above the top surface  42   b . A layer of solder  20  coats the bottom surface  42   c  of base pad  42 . 
     In use, referring to FIG. 8, terminal  50  is soldered to glass  34  in a manner similar to terminal  11 . As with terminal  11 , base pad  42  is generally circular in shape (FIG. 6) and does not tend to cause heat related stress concentrations in glass  34 , and therefore, little or no cracking occurs. The proximal portion  48   a  of arm  48  lies along the same plane (FIG. 8) as the rest of base pad  42  such that slots  46  provide only minor interruptions in the circular shape of base pad  42 . Consequently, with regard to heat transfer from terminal  50  to glass  34 , base pad  42  is effectively circular in shape as shown by the dotted lines (FIG. 6) despite slots  46 . Once soldered, any accidental pulling forces F 1 /F 2  on cable  18  (FIG. 8) are transferred to the center  16  of base pad  42  because the proximal end  48   a  of arm  48  extends therefrom. Consequently, terminal  50  is resistant to being separated from glass  34  in a similar manner as with terminal  11 . In addition, the upwardly angled intermediate portion  48   b  at arm  48  is able to bend or deflect thereby absorbing forces exerted on terminal  50  by cable  18 . This may lessen the intensity of forces F 1 /F 2  exerted on base pad  42  by accidental pulling of cable  18 . For example, if a longitudinal pulling force F 1 was exerted on cable  18 , intermediate portion  48   b  would bend slightly to the left and absorb some of the force. In addition, if an upward pulling force F 2  was exerted on cable  18 , intermediate portion  48   b  would bend slightly upwardly and absorb some of the force. The angled intermediate portion  48   b  is also able to absorb forces that are in the opposite direction of forces F 1  and F 2 , for example, forwardly and downwardly directed forces. Furthermore, the proximal end  48   a  of arm may also bend or deflect to absorb forces. 
     In one embodiment, terminal  50  is formed of C260 brass and is about 8 mm in diameter by 0.381 mm thick. Base pad  12  is tempered ½ hard about 0.22 mm thick. Terminal  50  is about 13 mm in length. Slots  46  are about 8 mm wide and are spaced apart from each other to form a proximal end  48   a  of arm  48  that is about 2.5 mm wide. Intermediate portion  48   b  is bent at about a 45° angle to provide equal force absorbing capabilities for longitudinal and vertical forces. The distal end  48   c  is bent to be above the proximal end  48   a  about 1.5 mm. The crimping tabs  44  are about 4 mm wide. The same solder  20  used with terminal  11  may be employed with base pad  42 . As with terminal  11 , the dimensions of terminal  50  may be varied to suit particular circumstances. Although intermediate portion  48   b  is preferably bent, alternatively, intermediate portion  48   b  may be straight. In addition, the proximal end  48   a  may be bent instead of intermediate portion  48   b.    
     Terminal  50  is formed by a stamping and forming process in a similar manner as with terminal  11 . As seen in FIGS. 9 and 10, after being formed, terminals  50  are attached to a carrier strip  22  by breakable regions  26  extending from crimping portion  44 . The carrier strip  22  may be cut into sections in similar fashion to that shown in FIGS. 4 and 5 to form a multiple terminal soldering assembly, so that multiple terminals  50  may be soldered to glass  34  at the same time. Cables  18  may be crimped to terminals  50  before soldering. 
     FIG. 11 depicts another configuration of a multiple terminal soldering assembly  60  where terminals  50  are attached to the carrier strip  22  by breakable regions  26  extending from the base pad  42  instead of from crimping portion  44 . Cables  18  may be also crimped to terminals  50  before soldering. 
     While this invention has been particularly shown and described with references to preferred embodiments thereof, it will be understood by those skilled in the art that various changes in form and details may be made therein without departing from the scope of the invention encompassed by the appended claims. 
     For example, although particular terms have been used to describe the present invention such as upwardly, downwardly, forwardly, etc., these terms are not meant to limit the orientation of the present invention terminal. In addition, although the base pads  12  and  42  are preferably generally circular in shape, base pads  12 / 42  may be generally oval, or may be other suitable curved shapes which do not have sharp corners. Such curved shapes may include linear perimeter portions. Furthermore, although base pads  12 / 42  have been depicted as generally flat or planar, alternatively, the base pads may have contoured bottoms for mating with contoured surfaces such as a curved surface. Solder layer  20  may be omitted if desired. Also, the present invention terminal may be soldered to surfaces other than glass.