Abstract:
An electrical cord locking connector joins electrical cords in series and presents a streamlined profile that minimizes interference in restricted spaces through which the cords must be fed to service a job site. The connector joins the ends of successive cords utilizing the outwardly projecting shoulder provided on the female socket of one cord in cooperation with a latch member on the male end of the connecting cord to lock the two cords together. A cord provided with a female end terminating in a replacement cord cap is provided with a socket presenting a generally circular face and an outwardly projecting shoulder at the face for engaging a releasable latch member of a mating plug, thereby preventing separation of the plug and socket under force until the latch member is disengaged.

Description:
This application is a continuation-in-part of application Ser. No. 12/070,020, filed Feb. 14, 2008. 

   FIELD OF THE INVENTION 
   This invention relates to locking connectors for electrical extension and power cords to prevent separation of series-connected cords during use. 
   BACKGROUND OF THE INVENTION 
   In the construction of buildings and other structures a live electrical outlet is often remote from the area where workmen require electric power to operate power tools of various types. A typical example is a carpenter utilizing a power tool in a multi-floor structure or single floor areas having a long horizontal expanse. In these common construction environments electrical power tools are supplied with electricity using long extension cords connected in series, which may span long horizontal distances as well as vertically through several floors. When power cords separate under stress, time is lost and the broken connection may be difficult to locate and reestablish. 
   Also, in a construction environment, a series of extension cords are often threaded through openings, around corners and, under stress, separate at the weakest point which is usually where they are joined end to end. Separation at the union of two cords or at the power cord of a tool is not uncommon, thereby causing a complete shut down of electrically-powered equipment. Although locking devices have been proposed and used at the interconnection between two cords to assist in preventing separation, such devices may project radially and thus increase the transverse dimension of the cords at the connection, thereby presenting an obstacle to passing the connected cords through an opening or around a corner. When this occurs, the cords cannot be advanced until fed by hand through or around the turn or other obstacle, also resulting in lost time. 
   Furthermore, safety regulations in construction environments may require that a locking connector be used at the joinder of electrical cords in series in order to preclude separation under longitudinal stress and possible exposure of workers to electric shock. This could be caused, for example, by an uncoupled end of an extension cord being exposed to moisture at a construction site. This further evidences the need for an improved locking connector that provides a minimum of interference with handling and movement of serially connected electrical cords in a construction environment. 
   SUMMARY OF THE INVENTION 
   In an embodiment of the present invention an electrical cord locking connector presents a streamlined profile and does not project radially outwardly at the junction of two interconnected cords, thereby minimizing interference in tight spaces through which the extension cords must be fed to service the job site. The connector joins the ends of the successive cords utilizing the outwardly projecting shoulder provided on the socket end of one cord, the socket cooperating with a latch member on the male end of a connecting cord to lock the two cords together at the mating ends without utilizing laterally projecting components that would prevent the normal feeding of the interconnected cables around corners and through openings and other restricted spaces. 
   In another aspect of the invention, a first electrical cord has an end provided with a plug having at least three prongs, one of which is connected to the grounding conductor of the cord, and a second cord has an end provided with a socket having at least three openings therein for receiving corresponding prongs of the first cord. The socket has an outwardly projecting shoulder for preventing improper mating of the prongs and openings, and the plug has a releasable latch member projecting therefrom which engages the shoulder when the plug and socket are properly mated to prevent separation of the plug and socket during use of the cords. 
   In another aspect of the present invention, the latch member comprises a plate element having an opening therein for receiving the shoulder on the female socket when the plug and socket are mated and, in a further aspect of the invention, the plate element flexes as the plug and socket are mated to clear the shoulder until the opening in the plate element registers therewith. 
   In another aspect of the present invention a latch member is flexed as the cords are connected and shifts to a locking position receiving the shoulder when the opening in the plate registers therewith. Furthermore, in an alternative arrangement the latch member is provided with a lip for engaging the shoulder when the plug and socket are mated. 
   In yet another aspect of the present invention a replacement cord cap assembly is provided with a radially outwardly projecting shoulder at the face of the socket adjacent the two openings in the socket that receive corresponding current-carrying prongs of a male plug. The shoulder is received by a latch member on a connecting cord to prevent separation of the plug and socket. 
   Other advantages of this invention will become apparent from the following description taken in connection with the accompanying drawings, wherein is set forth by way of illustration and example, embodiments of the present invention. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
       FIG. 1  is a perspective view of one embodiment of the present invention showing the mating ends of two extension cords connected together and locked. 
       FIG. 2  is a view similar to  FIG. 1  but exploded to reveal the parts prior to the inserting the plug into the socket to connect the two extension cords together. 
       FIG. 3  is a plan view of the male plug with the latch plate removed. 
       FIG. 4  is an exploded, side elevational view of the plug and latch parts. 
       FIG. 5  is a perspective view of a second embodiment of the present invention showing electrical cords connected to a multiple outlet socket assembly wherein each shoulder is continuous over the top of the respective socket face. 
       FIG. 6  is a detail, plan view of a latch plate having a depending lip. 
       FIG. 7  is a side elevational, detail view showing the depending lip of the latch plate of  FIG. 6  engaging a shoulder. 
       FIG. 8  is a partial, enlarged perspective view of the second embodiment showing the latch plate of  FIG. 6  in its locked position. 
       FIG. 9  is a perspective view of a third embodiment of the present invention showing the mating ends of two extension cords connected together and locked, the female end being provided with a replacement cord cap. 
       FIG. 10  is a view similar to  FIG. 9  but exploded to reveal the parts prior to inserting the plug into the socket to connect the two extension cords together. 
       FIG. 11  is a front view of the replacement cord cap showing the face of the socket. 
       FIG. 12  is a side elevational view of the female replacement cord cap. 
   

   DETAILED DESCRIPTION 
   Referring initially to  FIGS. 1 and 2 , the mating ends of two extension cords  10  and  12  are shown connected together in  FIG. 1  and separated in  FIG. 2  in alignment with each other to show the male and female parts aligned prior to connecting cords  10  and  12  together. The end of cord  10  illustrated is provided with a male plug  14  which, in  FIG. 2 , is shown aligned with but withdrawn from a female socket  16  on the corresponding end of cord  12 . It should be appreciated that cords  10  and  12  may extend 50 feet or more from the mating plug and socket illustrated in  FIGS. 1 and 2  where the remote end of cord  10  would be provided with a socket, and the remote end of cord  12  would be provided with a plug. Accordingly, at a construction site where extension cords are used to connect power tools to a current source, series connected cords may extend hundreds of feet. 
   Referring also to  FIGS. 3 and 4 , plug  14  is typically provided with three prongs  18 ,  20  and  22 . Extension cords for a two-wire, grounded source, such as a 110 volts AC, are illustrated herein, but it will be appreciated that the teachings of the present invention are equally applicable to other applications where a series of extension cords are required to reach a site remote from the power source. As shown in  FIGS. 3 and 4 , a hot wire  24  is connected to prong  18 , a grounded wire  26  is connected to prong  20 , and a grounding wire  28  is connected to prong  22  in the conventional manner. The prongs  18 ,  20  and  22  are received by the socket  16  at openings  32 ,  34  and  36  respectively in the conventional manner. 
   In order to prevent inadvertent improper mating of the plug  14  and socket  16  such that the grounding prong  22  would not be received in opening  36 , the socket  16  is typically provided with a shoulder  38  which would prevent such a misconnection because it would be engaged by the grounding prong  22  and thus the prongs  18  and  20  could not be inserted. In the present invention, a latch plate  40  of a resilient plastic material is secured to the body of plug  14  by a non-metallic, self-threading screw  42  and has an opening  44  therein which receives shoulder  38  when plug  14  and socket  16  are united as shown in  FIG. 1 . The latch plate  40  is of a generally T-shaped configuration presenting a head  46  terminating in an upwardly curved lip  47 , and an integral stem  48  through which the screw  42  extends to secure the latch plate  40  to the body of the plug  14 . As the plug  14  is mated with the socket  16 , the shoulder  38  engages head  46  and flexes the plate  40  upwardly as viewed in  FIGS. 1 and 2  until it registers with the opening  44  and is received therein as shown in  FIG. 1  in its final position. The lip  47  assists the user in manually flexing the head  46  upwardly until it clears the shoulder  38 . Accordingly, force applied to the cords  10  and  12  in normal use that could cause the plug  14  and socket  16  to separate are resisted in the present invention by the interengagement of the latch plate  40  and shoulder  38 , which prevents separation of plug  14  from socket  16 . Therefore, the present invention locks the two cords  10  and  12  together to prevent separation under stress conditions. It should be understood, however, that the latch plate  40  does not affect use of the plug in a normal wall socket as the latch plate can be rotated 180 degrees to a non-interfering position. 
   Utilization of the self-tapping screw  42  facilitates adding the locking feature of the present invention to existing extension cords. Referring to  FIGS. 3 and 4 , a hole  50  bored in plug  14  receives screw  42  which extends through a hole (not visible) in stem  48  and tightly secures the latch plate  40  to the plug  14 . Note in  FIG. 4  that hole  50  is between hot wire  24  and grounded wire  26  and does not reach grounding wire  28 . As seen in the exploded view of  FIG. 4 , a washer  52  receiving screw  42  may be disposed between the stem  48  and the underlying surface of plug  14 . 
   It should also be noted that the latch plate  40  prevents a two-prong male plug from being inserted improperly into a socket. If this is attempted, the plate  40  engages the socket at the projection that presents the grounding opening  36 . 
   Referring to  FIGS. 5-8 , the present invention may also be utilized with extension cords having multiple socket faces, as illustrated in  FIG. 5  where a triple socket  54  on one end of a cord  56  is illustrated. It should be noted that each socket face  57  presents a longer upper shoulder  58  than in the single ended extension cords  10  and  12  shown in  FIGS. 1 and 2 . To lock an extension cord  60  to a corresponding shoulder  58 , a latch plate  62  having a depending lip  64  is utilized as best seen in  FIGS. 6-8 . More particularly, latch plate  62  has a central opening  66  therein from which lip  64  depends at the forward end thereof, as can be seen by a comparison of  FIGS. 6 and 7 . A screw  68  extends through an opening  70  in a stem portion  72  of the latch plate  62  in a manner similar to the embodiment of  FIGS. 1-4 . Screw  68  secures latch plate  62  to a plug  74  and is shown fully installed and locked in  FIGS. 7 and 8 . 
   It should be noted that the latch plate  62  has an offset  76  that permits the latch to overlie the raised shoulder  58  and cause the downwardly projecting lip  64  to engage the backside of shoulder  58  and thus lock plug  74  to the socket unit  54 . As the plug  74  is inserted, the curved end  65  facilitates swinging the latch plate  62  to the broken line position ( FIG. 7 ) until the plug  74  is fully inserted, whereupon the plate  62  shifts to the full line position shown where lip  64  engages the backside of the shoulder  58 . As latch plate  62  is composed of a resilient plastic, it snaps into place in the full line position shown in  FIG. 7  to prevent withdrawal of the plug  74 . 
   Another embodiment of the present invention is shown in  FIGS. 9-12  and may be utilized to join two end-to-end cords, one or both of which is severed or otherwise defective and, for example, is provided with a replacement cord cap  80  on the end of a cord  82  connected to a cord  84  provided with a male plug  86  having a configuration similar to plugs  14  and  74  of the embodiments illustrated in  FIGS. 1-8 . As is conventional, the replacement cord cap  80  is provided with a clamp  88  which secures the cord cap  80  to the cord  82  and presents, at its outer end, a socket face  90  which, before modification in accordance with the present invention, is of circular configuration. Socket  90  has openings  92  and  94  therein receiving prongs  96  and  98  respectively of plug  86  connected to hot and grounded wires respectively in cable  84  in the conventional manner, and an opening  100  receiving prong  102  connected to the grounding wire. 
   The male plug  86  is provided with a latch plate  104  of the same configuration as latch plate  40  in  FIGS. 1-4 . The latch plate  104  is secured by a screw  106  to the plug  86  and has an opening  108  therein receiving a shoulder  110  on socket  80  having a front surface  112  coplanar with the face  114  of socket  90 . To accommodate the shoulder  110 , the socket  90  is recessed at  116  to properly position the shoulder  110  for engagement with the latch plate  104  as seen in  FIG. 9  where the socket and plug components  80  and  86  are mated and locked. It should be understood that other latch plates of similar configuration may also be utilized, such as the latch plate  62  illustrated in  FIGS. 5-7  without the offset  76 . 
   It should be appreciated that the embodiment of the invention shown in  FIGS. 9-12  provides the ability to lock two cords together when the female mating end has been damaged and fitted with a replacement cord cap. This is accomplished as set forth above by modification of the cap by the addition of the shoulder  110  in recess  116  to accommodate the latch plate  104  on the male end of the connecting cord. 
   It should be understood that while certain forms of this invention have been illustrated and described, it is not limited thereto except insofar as such limitations are included in the following claims.