Patent Publication Number: US-6217356-B1

Title: Electrical terminal with arc arresting region

Description:
FIELD OF THE INVENTION 
     This invention relates to electrical connectors and more particularly to electrical terminals having a region to accommodate deterioration owing to electrical arcing. 
     BACKGROUND OF THE INVENTION 
     Electrical connectors are sometimes used in applications wherein the connectors need to be mated and unmated without first disconnecting the power source. When an electrical potential exists between the terminals of the connectors, arcing can occur as they are mated and unmated, thus causing deterioration of the terminals. Various approaches have been used to reduce such deterioration or to fabricate terminals that can withstand deterioration. 
     U.S. Pat. No. 5,176,528 discloses a pin and socket connector assembly in which each of a pair of power lines is connected to a pair of mating terminals such that one of each pair of mating terminals are allowed to deteriorate or be “sacrificed” while the integrity of the other of the pair is maintained. The use of a pair of “sacrificial” terminals for each power line increases the number of terminals that must be included in a connector housing and the overall dimensions of the connector. 
     U.S. Pat. No. 5,591,039 discloses the use of an arc arresting or sacrificial ring located near the opening of each socket terminal in the connector. The mating pin terminal engages the ring, which receives any electrical arc before the pin terminal engages the socket terminal. This approach requires an extra member for each receptacle terminal and additional steps to assemble the connector. 
     It is desirable and more cost effective, however, to have an electrical terminal that can provide a sacrificial function as well as maintain the integrity of the electrical connection. 
     SUMMARY OF THE INVENTION 
     The present invention is directed to a socket terminal that overcomes the problems of the prior art. The electrical terminal includes a body having first and second connecting portions. The first connecting portion is adapted to mate with a pin terminal and includes two beams extending substantially parallel to one another from an edge of the body and defining a terminal-receiving slot therebetween. Each beam has a primary contact surface spaced inwardly form leading ends of the beams and extending orthogonally into the terminal-receiving slot. At least one of the beams includes a secondary or sacrificial contact surface proximate the leading end thereof. The primary and secondary contact surfaces on the at least one beam are spaced both vertically and horizontally from each other. The corresponding primary contact surfaces of the two beams are substantially opposed to each other. Upon inserting a pin terminal into the terminal-receiving slot, the secondary or sacrificial contact surface engages the pin terminal at at least one first location thereon. Upon further insertion of the pin, the pin engages the primary contact surfaces at second locations thereon, the second locations being spaced at least horizontally from the at least one first location on the pin. The secondary or sacrificial contact surface on the at least one beam and the at least one first locations on the pin terminal define an electrical arc arresting region thereby preventing deleterious electrical arcing between the pin terminal at the second locations and the primary contact surfaces on the beams. 
     For purposes of illustrating the invention, the terminal is being shown in a terminal block for use in a control panel. 
     It is an object of the invention to provide an electrical terminal that includes a structure that provides at least one electrical arc-arresting region and a separate region for electrical connection when the connectors having the terminals are fully mated. 
     It is another object of the invention to provide an electrical terminal having the above capabilities that is cost effective to manufacture. 
     It is a further object of the invention to provide electrical terminals for terminating to stripped wire ends that prevent the wires from entering the socket that is to be mated to a pin terminal. 
     Embodiments of the invention will now be described by way of example with reference to the accompanying drawings. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 is an isometric view of a terminal block with a terminal made in accordance with the invention exploded therefrom. 
     FIG. 2 is a cross-sectional view of the terminal block of FIG.  1 . 
     FIG. 3 is an isometric view of a terminal made in accordance with the invention. 
     FIG. 4 is a plan view of a cross-section of the terminal block of FIG. 1 illustrating the position of terminals in the terminal-receiving passageways. 
     FIGS. 5 and 6 are sectional views of the terminal block illustrating a pin terminal engaging the leading end of a terminal made in accordance with the invention. 
     FIGS. 7 and 8 are sectional views similar to those of FIGS. 5 and 6 illustrating the position of the two terminals after the terminals have been fully mated. FIG. 9 is a fragmentary portion of a terminal block having an alternative embodiment of the electrical terminal exploded therefrom. FIG. 10 is a cross-sectional plan view of the terminal block assembly of FIG.  9 . 
     FIG. 11 is a fragmentary portion of a terminal block having a further embodiment of the terminal exploded therefrom. 
     FIG. 12 is a cross-sectional plan view of the terminal block assembly of FIG.  11 . 
    
    
     DETAILED DESCRIPTION OF THE DRAWINGS 
     Referring first to FIGS. 1 through 8, electrical terminal  20  includes a body  22  having first and second connecting portions  30 ,  50 . The first connecting portion  30  includes two beams  32  that extend from body edge  24  to leading ends  34 , each beam further including a C-shaped bend  36  intermediate the leading end  34  and terminal body  22 . Beams  32  are essentially parallel to each other and define a terminal-receiving slot  44  therebetween. Each beam  32  includes a primary contact surface  38  on the C-shaped bend. At least one of the beams  32  includes a secondary or sacrificial contact surface  40  proximate the leading end  34  thereof. In the embodiment shown, both of the beams  32  include secondary contact surfaces  40 . It is to be understood that only one of the beams needs the sacrificial contact surface. The primary and secondary contact surfaces  38 ,  40  of each beam extend orthogonally into slot  44  and are spaced both vertically and horizontally from one another. The primary and secondary contact surfaces  38 ,  40  of one of the two beams  32  are opposed to the corresponding primary and secondary contact surfaces of the other of the two beams  32 . 
     Terminal  20  is stamped from an iron copper alloy or other suitable metal stock having a thickness of about 0.5 millimeters and is selectively plated at the contact surfaces with a noble metal such as a gold alloy, as known in the art. The beams of terminal  20  generate a sufficient normal force to interconnect to signal carrying terminals and the terminal has sufficient thickness and current carrying capability to transmit power. 
     FIGS. 1,  2 , and  4  illustrate the position of terminals  20  in terminal-receiving passageways  62  of a terminal block housing  60 . Body  22  of terminal  20  includes barbs  28  extending from side edges  26  for securing the terminal  20  in the passageway  62 . For purposes of illustration, terminal block housing  60  is of the type disclosed in U.S. patent application Ser. No. 08/899,458. It is to be understood that terminal  20  may be used in other connector housings and terminal block configurations. As can be seen in these Figures. the primary contact surfaces  38  are adjacent one side of passageway  62 , the secondary contact surfaces  40  are adjacent the opposite side of passageway  62 , and slot  44  is open to the mating face  63  of the housing. 
     The second connecting portion  50  of terminal  20  is shown as a flat member extending orthogonally from body  22 . Portion  50  includes aperture  52  and is adapted to be received on an upper surface of the housing  60  and secured thereto with screw  64  and nut  66 , or other devices as known in the art. The collar  65  of screw  64  is adapted to engage a stripped end of a wire (not shown), as known in the art. 
     FIGS. 5 through 8 illustrate the mating sequence of a pin terminal  70  in housing  78  with the socket terminal  32  in housing passageway  62 . For purposes of illustration the portions of beams  32  underlying pin terminal  70  are shown in phantom. As the leading end  72  of pin terminal  70  enters passageway  62 , it is received in terminal-receiving slot  44  and is moved into physical and electrical engagement with secondary or sacrificial contact surfaces  40  of terminal  30  at first locations  74  on two sides of pin terminal  70 , as shown in FIGS. 5 and 6. Upon further insertion of the pin terminal  70  into slot  44 , the pin terminal  70  engages primary contact surfaces  38  at second pin locations  76 , as shown in FIGS. 7 and 8. As can best be seen in FIGS. 5 and 7, the first and second pin locations  74 ,  76  are along opposite edges of pin terminal  70  and are at least spaced horizontally from one another. The secondary or sacrificial contact surfaces  40  and first pin terminal locations  74  define electrical arc-arresting regions that receive any arcing that may occur as the respective terminals  20 ,  70  are mated or unmated while power is applied to the connector assembly. The electrical arc-arresting regions prevent deleterious electrical arcing between the pin terminal at second locations  76  and primary contact surfaces  38 . The two beams  32  of the socket terminal  20  provide multiple points of contact at each of the locations  74 ,  76 , which is desirable for carrying power. FIGS. 9 and 10 illustrate another embodiment  120  of a terminal made in accordance with the invention. In this embodiment, the first connecting portion  130  is identical to that of terminal  20 . The second connecting portion  150  is adapted to cooperate with a spring clamp  154  of the type disclosed in U.S. patent application Ser. No. 09/092,473. FIG. 10 illustrates one wire  80  mated with a terminal  120 . The body  122  of second connecting portion  150  is configured to be received in a terminal-receiving passageway  162  of terminal block housing  160  such that body  122  provides a stop surface for the stripped end  82  of wire  80 , thereby preventing the bare wire from being inserted too far into the passageway and into the first connecting section. FIGS. 11 and 12 illustrate a further embodiment  220  of a terminal made in accordance with the invention. In this embodiment the first connecting portion  230  is identical to that of terminal  20 . The second connecting portion  250  is a cage design, as known in the art. FIG. 12 illustrates one wire  80  mated with a terminal  220 . As best seen in FIG. 12, the body  222  of second connecting portion  250  and terminal-receiving passageway  262  of terminal block housing  260  are configured such that passageway surface  263  provides a stop surface for the stripped end  82  of wire  80 , thereby preventing the bare wire from being inserted too far into the passageway and into the first connecting section. 
     The present invention has the advantage of providing two separate electrical connecting areas for each mating pair of terminals. The initial connection at a first location defines an arc-arresting region that protects the integrity of the electrical connection between the pair at a second location. The terminal has the capability to transmit power as well as signals. 
     It is thought that the electrical terminal of the present invention and many of its attendant advantages will be understood from the foregoing description. It is apparent that various changes may be made in the form, construction, and arrangement of the parts thereof without departing from the spirit or scope of the invention, or sacrificing all of its material advantages.