Patent Publication Number: US-9853396-B1

Title: Electrical plug having a flexible terminal retention feature

Description:
TECHNICAL FIELD OF THE INVENTION 
     The present invention relates generally to electrical plugs and, more particularly, to electrical plugs having flexible terminal retention features. 
     BACKGROUND OF THE INVENTION 
     Electrical plugs are used to connect electrical devices with electrical sockets. There are several issues that may arise in the use of these plug/socket combinations. As shown in  FIG. 1 , an operator  1  may attempt to remove the plug  3  from the socket by grasping the electrical cord  5  attached to the plug  3  and pulling on the cord  5  rather than properly grasping the plug  3 . As shown in  FIG. 2 , this may cause the plug  3  to rotate in the socket and cause damage to the terminals  2  that result in increased electrical resistance and resulting in higher terminal temperatures in use or could cause a terminal to facture. This is particularly true of plugs conforming to the National Electrical Manufacturers Association (NEMA) 5-15P standard connected within sockets conforming to the NEMA 5-15S standard. These plugs have two blade style terminals (neutral and hot) that are aligned with the direction of rotation and one round pin terminal (ground). The blade terminals can easily rotate within their rectangular sockets, but the round terminal is constrained within its round socket and is more likely to bend or break. 
     Similar rotation of the plug  3  in the socket may also be caused by an electrical device  6 , such as an electric vehicle battery charger, also known as electric vehicle service equipment (EVSE), hanging from an outlet  7  where the socket  8  is oriented such that the cord exits the top of the plug and then curves outwardly to extend to the EVSE as shown in  FIG. 3 . 
     Although this problem of plug rotation may more acutely affect angled plugs  3  having a 90 degree cord  5  to terminal  2  relationship as in the plugs shown in  FIGS. 1-3 , a straight plug  9  having a 180 degree relationship between the terminals  2  and the cord  5  as shown in  FIG. 4  may also experience rotation in the socket that could damage the plug terminals if the cord or plug is pulled or yanked in an upward or downward direction. 
     Therefore, a needs exists for an electrical plug designed to inhibit damage to plug terminals caused by rotation of the plug terminals in the socket. 
     The subject matter discussed in the background section should not be assumed to be prior art merely as a result of its mention in the background section. Similarly, a problem mentioned in the background section or associated with the subject matter of the background section should not be assumed to have been previously recognized in the prior art. The subject matter in the background section merely represents different approaches, which in and of themselves may also be inventions. 
     BRIEF SUMMARY OF THE INVENTION 
     In accordance with an embodiment of the invention, an electrical plug, such as those used with an electrical vehicle battery charger, is provided. The electrical plug includes a first plug terminal, a second plug terminal, third plug terminal, and a terminal retainer configured to secure the first, second, and third plug terminals within the electrical plug. The terminal retainer defines a flexible structure in which the first plug terminal is secured, thereby allowing the first plug terminal to move independently of the second and third plug terminals. 
     The first plug terminal may have a round cross section and the second and third plug terminals may have a rectangular cross section. The second and third plug terminals may be aligned on a first lateral axis while the first plug terminal is aligned on a second lateral axis different than the first lateral axis such as those conforming to conform to NEMA 5-15P standards. The terminal retainer may consist of a single piece of injection molded plastic. 
     The flexible structure is in the form of a cantilever beam and wherein the first plug terminal is secured in a location proximate a free end of the cantilever beam. The first plug terminal may define a circumferential flange. 
     The electrical plug may further include a housing in which the terminal retainer is disposed. The housing may be formed of a polymeric material and may be over-molded on the terminal retainer. The electrical plug may further include a first, second, and third electrical wire interconnected with the first, second, and third plug terminals respectively. The electrical plug is interconnected by the first, second, and third electrical wires to an electric vehicle battery charger. A portal may be defined in the housing that is configured to allow the first, second, and third electrical wires to exit the housing. This portal is located closer to the first plug terminal than the second and third plug terminals. The first, second, and third electrical wires may exit the housing along an axis that is substantially perpendicular to a longitudinal axis of the first plug terminal. 
     The foregoing and other objects, features, and advantages of the invention will be apparent from the following detailed descriptions of embodiments of the invention the accompanying drawings of these embodiments. 
    
    
     
       BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWING 
       The present invention will now be described, by way of example with reference to the accompanying drawings, in which: 
         FIG. 1  is a side view of an operator improperly removing an electrical plug from an electrical socket according to the prior art; 
         FIG. 2  is a side view of rotation of a ninety degree electrical plug in the electrical socket according to the prior art; 
         FIG. 3  is a perspective view of an electrical device hanging from an electrical plug in an electrical socket according to the prior art; 
         FIG. 4  is a side view of rotation of a straight electrical plug in an electrical socket according to the prior art; 
         FIG. 5  is a perspective cut away view of an electrical plug having a flexible structure in which a plug terminal is secured according to an embodiment of the invention; 
         FIG. 6  is a side cut away view of an electrical plug having a flexible structure in which a plug terminal is secured according to an embodiment of the invention; 
         FIG. 7  is a bottom perspective view of a plug terminal retainer configured to secure the first, second, and third plug terminals within the electrical plug of  FIG. 5  having a flexible structure in which the first plug terminal is secured according to an embodiment of the invention; 
         FIG. 8  is a top perspective view of the plug terminal retainer of  FIG. 6  according to an embodiment of the invention; 
         FIG. 9  is a side view of the first plug terminal of the electrical plug according to an embodiment of the invention. 
     
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     Presented herein is a description an electrical plug that includes a flexible structure in which one of plug terminals is secured, thereby allowing the first plug terminal to move independently of the other plug terminals and reducing the occurrence of damage to the terminals caused by improper removal of the electrical plug from an electrical socket. 
       FIGS. 5-9  illustrate a non-limiting example of an electrical plug  110  conforming to the National Electrical Manufacturers Association (NEMA) 5-15P standard, hereinafter referred to as a plug  110 . As shown in  FIG. 5 , the plug  110  includes a first plug terminal  112  in the form of a pin having a generally rounded cross section, hereinafter referred to as a ground terminal  112 , a second plug terminal  114  in the form of a blade having a generally rectangular cross section, hereinafter referred to as a neutral terminal  114 , and a third plug terminal  116  in the form of a blade having a slightly smaller rectangular cross section than the neutral terminal  114 , hereinafter referred to as a hot terminal  116 . The plug  110  further includes a terminal retainer  118  that secures the ground, neutral, and hot terminals  112 ,  114 ,  116  within the plug  110 . The terminal retainer  118  rigidly retains the hot and neutral terminals  114 ,  116  while having a flexible structure  120  in which the ground terminal  112  is retained. 
     As illustrated in  FIG. 6 , the neutral and hot terminals  114 ,  116  are free to rotate since the blades of these terminals  114 ,  116  are generally parallel to the corresponding sockets  122  while the round ground terminal  112  is substantially surrounded by the round ground socket  124 . This inhibits the ground terminal  112  from rotating in the ground socket. The flexible structure  120  allows the ground terminal  112  to move independently of the neutral and hot terminals  114 ,  116  so that the neutral and hot terminals  114 ,  116  can rotate in the neutral and hot sockets  122  of the outlet while the ground terminal  112  does not rotate in the ground socket  124 . 
     As best illustrated in  FIG. 7 , the flexible structure  120  is in the form of a cantilever beam  126  having a free end  128  and a fixed end  130 . The ground terminal  112  is secured to the terminal retainer  118  at the free end  128  of the cantilever beam  126 . The terminal retainer  118  and the flexible structure  120  are integrally formed of a single piece of injection molded plastic. 
     As shown in  FIG. 5 , the plug  110  further includes a housing  132  in which the terminal retainer  118  is disposed. The housing is formed of a polymeric material and is over-molded the terminal retainer  118 . A first, second, and third electrical wire  134 ,  136 ,  138 , hereinafter referred to as the ground wire, neutral wire, and hot wire  134 ,  136 ,  138  respectively, are interconnected to the interconnected with the ground, neutral, and hot terminals  112 ,  114 ,  116  respectively. A wire exit portal  140  is defined in the housing configured to allow the ground, neutral, and hot wires  134 ,  136 ,  138  to exit the housing. The portal is located closer to the ground terminal  112  than the neutral and hot terminals  114 ,  116 . The plug  110  illustrated here has a right angle or ninety degree configuration so that the ground, neutral, and hot wires  134 ,  136 ,  138  exit the housing along an axis (Y) that is substantially perpendicular to a longitudinal axis (X) of the ground terminal  112 . As used herein, substantial perpendicular means±10° of absolutely perpendicular. Other embodiments of the plug may be a straight configuration in which the ground, neutral, and hot wires exit the housing along an axis that is substantially parallel to a longitudinal axis of the ground terminal. As used herein, substantial parallel means±10° of absolutely parallel. 
     As best shown in  FIG. 9 , the ground terminal  112  includes a circumferential flange  142 . This flange  142  is captured within the flexible structure  120  by molding the terminal retainer  118  over the flange  142  as shown in  FIGS. 7 and 8 . Prior art embodiments of the ground pin originally had an undercut with serrations in the metal of the ground pin to facilitate grip between the ground terminal and the material forming the terminal retainer. This undercut design also had sharp corners that rendered the ground terminal more susceptible to fracture from bending forces. The ground terminal  112  and flange  142  do not include any metal serrations to facilitate grip. Rather, the flange  142  has a fillet  144  to facilitate grip of the material forming the terminal retainer  118  to the ground terminal  112  and provide increased resistance to bending forces in this region of the ground terminal  112 . 
     Accordingly, an electrical plug  110  having terminal retainer  118  with a flexible feature that allows at least one of the plug terminals  112  to move independently of the other plug terminals  114 ,  116  is presented. The flexible structure  120  allows one of the plug terminals  112  to be held in a fixed orientation in a socket  124  while the other plug terminals  114 ,  116  are rotated within their respective sockets  122 , for example by improper plug removal technique by an operator as shown in  FIG. 1  or equipment hanging from the plug as shown in  FIG. 3 . Allowing one or more fixed terminals  112  to move independently of other terminals  114 ,  116  reduces the likelihood of damage or breakage of that terminal  112  of the plug is improperly rotated during removal from or insertion into a corresponding electrical socket. 
     The illustrated embodiments conform to the NEMA 5-15P standard. However, other embodiments of the invention that conform to different technical standards, such as Europlug CCE 7/16, British Standard (BS) 1363, Australian/New Zealand Standard AS/NZS 3112, or Chinese PPCS-CCC technical standards, but especially to plugs having a mix of parallel blade terminals and round terminals, e.g. NEMA 5-15P, 6-15P, 6-30P, 6-50P, and 14-50P, may be envisioned that provide similar benefits. 
     While this invention has been described in terms of the preferred embodiments thereof, it is not intended to be so limited, but rather only to the extent set forth in the claims that follow. Moreover, the use of the terms first, second, upper, lower, etc. does not denote any order of importance, location, or orientation, but rather the terms first, second, etc. are used to distinguish one element from another. Furthermore, the use of the terms a, an, etc. do not denote a limitation of quantity, but rather denote the presence of at least one of the referenced items.