Abstract:
A male electrical connector comprising a housing having an abutment and a side. Male electrical contacts project from the abutment, the male electrical contacts are arranged for insertion into a standard 120 Volt female electrical connector. A fastener has a member. The member comprises a first end portion pivotally connected to the side of the housing and a second end portion defining an engaging surface. The engaging surface extends toward the male electrical contacts. The member is selectively pivotable between an engagement position wherein the engagement surface is positioned toward the male electrical contacts and a disengagement position wherein the engagement surface is positioned away from the electrical contacts.

Description:
REFERENCE TO CO-PENDING PATENT APPLICATIONS 
       [0001]    The patent application is a continuation of and claims the benefit of U.S. patent application Ser. No. 11/891,675, filed on Aug. 10, 2007, and entitled “TEMPORARY LIGHTING FIXTURE,” and of U.S. provisional application Ser. No. 60/836,801, filed on Aug. 10, 2006, and entitled “ELECTRICAL CORD,” the entire disclosures of which are incorporated herein by reference. 
     
    
     BACKGROUND 
       [0002]    Electrical cords, and in particular extension cords, are used extensively in many applications, in both residential and commercial applications, because they provide a way to deliver electrical power from an electrical outlet to equipment that is far away from the outlet. However, there are significant issues surrounding safety and convenience that are associated with the use of extension cords. 
         [0003]    One safety issue often associated with construction sites is the use of many extension cords because of the large number of tools that need electricity to operate. Typically these devices may not be plugged into the same cord because they would, in combination, require too much current to be safely provided through a single cord. This safety concern is especially true at construction sites where at least some of the equipment draws a large amount of power. 
         [0004]    Furthermore, additional extension cords may be necessary because different pieces of equipment require different amounts of voltage to operate. For example, most electrically operated devices require a 120V source. However, some devices use a large amount of power and thus require 208V or 240V supplies. 
         [0005]    Extensive usage of extension cords increases the probability of an electrical fault, cord degradation, or cord overloading. Cord degradation and failure when using a high-amperage power source and cord can cause fires, electrical shocks, and other hazards. Existing safety fuses and ground fault interrupter (GFI) circuits within electrical cords can sense sudden catastrophic electrical events, such as power failures, power surges, or other electrical or physical events caused on the source side of the electrical cord. These safety devices are integrated into the electrical cord and allow an electrical cord to disconnect upon occurrence of an electrical event. 
         [0006]    Fuses and GFI circuits may not protect against various types of gradual failures, such as due to physical wear or thermal degradation. Sudden short circuits at the load end of the cord remain unprotected by these devices as well. Additionally, fuses and GFI circuits are typically connected in series with the cord so that if the fuse or GFI circuit is tripped, the entire cord is disabled. When a cord has multiple receptacles providing power to different tools and devices, a failure in one of the devices would trip the fuse or GFI and disconnect power to all of the receptacles and all of the devices that are plugged into the cord. Such an event can be startling and potentially hazardous to other users. 
         [0007]    Heating is another safety problem for both commercial and residential extension cords even when the cord is overloaded. Extension cords that have a flaw such as a loose connector, partially broken wire, or kink have a point of increased resistance that causes resistive heating even when the current drawn through the cord is within its rated capacity. Such conditions can cause the extension cord to overheat and potentially ignite starting a fire, especially if the extension cord is adjacent a flammable material such as wood, clothing, or chemicals. 
         [0008]    Yet another problem relates to extension cords that include locking mechanisms holding the male electrical plug portion in a female socket. These extension cords, called “twist lock” cords, prevent disconnection of the cord in case someone trips on the cord or the cord is otherwise unintentionally pulled from its socket connection to a power source, such as an electrical generator or a wall socket. When connecting a twist lock plug, the user inserts the plug into the receptacle and twists it to lock it in place to prevent it from being accidentally pulled from the receptacle. The difficulty is that the cross-section of the housing for a male twist lock plug is typically circular. Such configurations make it difficult to make a visual determination of whether the plug was properly twisted to lock it into the receptacle. 
         [0009]    Additionally, construction workers and even casual residential users occasionally need to set up temporary power distribution for tools and use temporary lights to illuminate a room, work area, or work product. In some applications, the workers simply lay out a bunch of extension cords on the ground, which is dangerous because they are tripping hazards that the workers can fall over. The cords are also easily disconnected from one another and from their tools causing an unexpected loss of power. For lighting, the workers either plug in temporary lamps that rest on the floor, a table top, or create a temporary string of lights by hard wiring sockets to a pair of wires and hanging them from a ceiling or other structure. However, having to build a dedicated, hard wired light string is expensive and cumbersome. 
       SUMMARY 
       [0010]    One aspect of this patent document is directed to an apparatus for distributing electricity. The apparatus comprises at least two electrical conductors. A male plug is electrically connected to the electrical conductors. A female socket block is positioned along the electrical conductors. The female socket block comprises a housing and two or more electrical contacts positioned within the housing and in electrical communication with at least one of the electrical conductors. The housing comprises an outer surface, and the outer surface comprises a side portion and a non-recessed abutment for engagement by a standard 120 Volt male plug. The abutment defines two or more holes, each hole proximal to at least one of the electrical contacts positioned in the housing. The holes are arranged to receive electrical contacts from a standard 120 Volt male plug. An engaging structure is operatively connected to the outer surface and positioned on the side portion of the housing. The engaging structure has an engagement surface arranged to engage a fastener from a male plug. The engagement surface and the abutment face opposite directions. 
         [0011]    Another aspect of this patent document is directed to a male electrical connector comprising a housing having an abutment and a side. Male electrical contacts project from the abutment, the male electrical contacts are arranged for insertion into a standard 120 Volt female electrical connector. A fastener has a member. The member comprises a first end portion pivotally connected to the side of the housing and a second end portion defining an engaging surface. The engaging surface extends toward the male electrical contacts. The member is selectively pivotable between an engagement position wherein the engagement surface is positioned toward the male electrical contacts and a disengagement position wherein the engagement surface is positioned away from the electrical contacts. 
         [0012]    Yet another aspect of this patent document is directed toward a male electrical connector comprising a housing having an abutment and a side. Male electrical contacts project from the abutment. The male electrical contacts are arranged for insertion into a standard 120 Volt female electrical connector. A fastener has a member comprising a first end portion pivotally connected to the side of the housing at a position proximal to the abutment, a second end portion defining an engagement surface extending toward the male electrical contacts, and a flange extending away from the male electrical contacts. The engagement surface and the flange are positioned on opposite sides of the member. The member is selectively pivotable between an engagement position wherein the engagement surface is positioned toward the male electrical contacts and a disengagement position wherein the engagement surface is positioned away from the electrical contacts. The member is biased toward the disengagement position. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0013]      FIG. 1  is a front view of an extension cord showing a male plug, female sockets, and socket blocks of the cord, in which various aspects of the present disclosure can be implemented; 
           [0014]      FIGS. 2A-2F  are schematic views of various extension cords having integrated ground fault circuit protection; 
           [0015]      FIGS. 3A-3B  are schematic views of circuit sections shown in  FIG. 2A ; 
           [0016]      FIG. 4  is a perspective view of an alternative embodiment of the extension cord shown in  FIG. 1  having an optional adapter for the male plug of the extension cord; 
           [0017]      FIGS. 5A and 5B  are front views of alternative socket block configurations having circuit identifying marks for use with the extension cord shown in  FIG. 1 ; 
           [0018]      FIG. 6  is a perspective view of a female socket and socket block with an optional cap and an optional mooring member; 
           [0019]      FIG. 7  is a front view of the extension cord shown in  FIG. 5  being held off the ground by use of mooring members attached to the socket blocks of the cord; 
           [0020]      FIG. 8A  is a perspective view of a prior art twist lock cord; 
           [0021]      FIG. 8B  is a perspective side view of a male connector for a twist lock cord; 
           [0022]      FIG. 8C  is a functional schematic view of showing locked and unlocked positions of the male twist lock connector shown in  FIG. 8B ; 
           [0023]      FIG. 9A-9B  are schematic views of electricity distribution from an electrical generator; 
           [0024]      FIGS. 10A-10D  are schematic views of various extension cords having integrated thermal failure detection; 
           [0025]      FIGS. 11A-11C  are schematic views of various electrical cords having integrated thermal failure detection; 
           [0026]      FIG. 12  is a front view of an extension cord having a thermochromatic material to indicate temperature of the cord; 
           [0027]      FIG. 13A  is a side view of a female socket having an adjustable anchor in a closed position; 
           [0028]      FIG. 13B  is a front view of the female socket shown in  FIG. 13A  with the adjustable anchor in the closed position; 
           [0029]      FIG. 14A  is a side view of the female socket shown in  FIG. 13A  when the adjustable anchor is in an open position; 
           [0030]      FIG. 14B  is a front view of the female socket shown in  FIG. 13A  when the adjustable anchor is in an open position; 
           [0031]      FIG. 15  is a side view of an extension cord having intermittently spaced sockets and adjustable anchors in an open position and mounted on a vertical surface; 
           [0032]      FIG. 16  is a side view of an extension cord having intermittently spaced sockets and adjustable anchors in a closed position suspended; 
           [0033]      FIG. 17  is a side view of an electrical adaptor having an anchor and a fastener; 
           [0034]      FIGS. 18A and 18B  are perspective and side views, respectively, of the fastener shown in  FIG. 17 ; 
           [0035]      FIG. 19  is a side view of the electrical adaptor shown in  FIG. 17  connecting two extension cords; 
           [0036]      FIG. 20  is a side view of an alternative embodiment of the adaptor of shown in  FIG. 17 ; 
           [0037]      FIG. 21  is a side view of another alternative embodiment of the adaptor shown in  FIG. 17 ; and 
           [0038]      FIG. 22  is a view of a temporary lighting fixture having a fastener to secure the fixture to a female socket. 
       
    
    
     DETAILED DESCRIPTION 
       [0039]    Various embodiments will be described in detail with reference to the drawings, wherein like reference numerals represent like parts and assemblies throughout the several views. Reference to various embodiments does not limit the scope of the claims attached hereto. Additionally, any examples set forth in this specification are not intended to be limiting and merely set forth some of the many possible embodiments for the appended claims. 
         [0040]    Referring to the drawings,  FIG. 1  shows an exemplary extension cord  10  in which aspects of the present disclosure can be implemented. The exemplary cord  10  provides electrical connections at a plurality of locations along its length. The extension cord  10  includes a male plug  12  attached to one end within a housing  13 , with socket blocks  22  housing female sockets  20  disposed along the cord. 
         [0041]    The male plug  12  electrically connects to two or more conducting wires and an optional ground wire, as discussed herein. The conducting wires and optional ground wire are typically bound together into a single cord  16  that is covered by an insulated sheathing  18 . The gauge of the conducting wires is chosen based on the length and expected use of the extension cord. Thicker wires are appropriate for longer cords and for cords used in heavy-duty applications that have large power requirements. Finer gauged wires are used for household extension cords. 
         [0042]    Typically, the socket blocks  22 , insulated sheathing  18 , and the housing  13  of the male plug  12  are constructed from plastics or polymers. In one possible embodiment, the male plug  12 , socket blocks  22 , and insulated sheathing  18  are molded together to form one continuous piece. This continuously molded embodiment of the extension cord is desirable because of the elimination of joints between the sheathing and the plug or socket blocks. Such joints often weaken the cord integrity and may provide an avenue for the entry of moisture into the interior of the cord which may short or damage the conducting wires. 
         [0043]    The socket blocks  22  reside at intervals along the length of the extension cord  10 . These intervals are typically regular, but may also be irregular. Each socket block  22  houses two female sockets  20 . In other possible embodiments, however, the socket blocks  22  house one female socket  20  or three or more female sockets  20 . Yet other possible embodiments of the extension cord  10  include a mixture of sockets blocks containing different numbers of female sockets, such as one female socket in some of the socket blocks and two female sockets in other socket blocks. 
         [0044]    Each of the female sockets  20  is an electrical socket that electrically connects to at least two wires in the cord  10 . In a possible embodiment, one or more of the female sockets  20  is a twist lock socket, as described herein. In another possible embodiment, one or more of the female sockets  20  is a three prong socket and includes the optional ground wire. Additional embodiments of the extension cord described herein are discussed in U.S. Pat. No. 5,902,148, the entire disclosure of which is hereby incorporated by reference. 
         [0045]    Safety devices reside at various locations along the extension cord  10 , which is configurable for use with such devices. The safety devices reside at any of a variety of locations along the extension cord, although in some embodiments the devices reside near the male plug  12  or female socket  20  due to the propensity for electrical fault or failure occurrences in those locations. In a possible embodiment, the housing  13  for the male plug  12  encloses a safety device integrated with the extension cord  10 . In another possible embodiment, the socket block  22  or other female connector housing encloses a safety device as well. In various embodiments, the housings  13  and socket block  22  enclose ground fault circuit interrupters. In other embodiments, the housings  13  and socket block  22  include a thermal or temperature indicator circuit formed by the combination of a thermal switch and an indicator, or some other heat sensing configuration. Additionally, the male plug  12  can include a male twist lock configuration, whether that configuration is a standard configuration or a non-round configuration as described in more detail herein. The female sockets  20  can include a female twist lock configuration, whether that configuration is a standard configuration or a configuration adapted to mate with a non-round male configuration as described in more detail herein. 
         [0046]    In an application of the cord  10 , light sockets can be plugged into one or more of the female sockets  20 . The light sockets can include a clamp or other retaining member to secure the light socket to the female socket blocks  22 . In one possible embodiment, the female socket  20  can include a detent that the clamp mates with and snaps into. Alternatively, the clamp or retaining member can be connected to the female socket  20  and receive the light socket. The light socket can include a basket or similar structure to protect a light bulb inserted in the light socket. One or more light sockets can also be packaged with the electrical cord  10  in a kit. 
         [0047]    Examples of electrical connection configurations between the female sockets  20  and the conducting wires  14   a - 14   g  that include ground fault circuit interrupters  30  are provided in  FIGS. 2A-2F . 
         [0048]    One embodiment of the extension cord  10  of the present disclosure has three conducting wires and is illustrated in  FIG. 2A . This extension cord  10  can be used, for example, with a single phase, three wire 120/240V service. Various embodiments of the extension cord  10  can be used with other service ratings as well, whether the service rating defines a voltage different than 120/240V, current capacity, phase, or any other operating characteristic. This type of service is often available in the United States as the primary connection from electrical transmission lines to residential and commercial properties. The extension cord includes three conducting wires  14   a - c  connecting the male plug  12  to the female sockets  20   a - c . The female sockets  20   a - c  reside within socket blocks  22 , which also include ground fault circuit interrupters  30   a - d.    
         [0049]    In this configuration, one of the conducting wires  14   a  is a neutral wire that is typically held at or near ground. The other two conducting or circuit wires  14   b ,  14   c  are held at about 120V above ground. These latter two wires are typically called “hot” or active wires because they provide a non-zero voltage drop across any grounded object. Each circuit wire is used to establish a separate circuit to which female sockets are attached. 
         [0050]    Female sockets  20   a  and  20   b  are electrically connected to different active wires to create a cord  10  with two electrically isolated circuits. One or more female sockets  20   a  of extension cord  10  electrically connect in parallel to the neutral wire  14   a  and one of the 120V active wires  14   b . One or more female sockets  20   b  electrically connect in parallel to the neutral wire  14   a  and the other 120V active wire  14   c . Each of the female sockets  20   a ,  20   b  is capable of providing 120 volts to electrically operated devices plugged into that socket. In the embodiment shown, one female socket  20   a  or  20   b  is included in each socket block  22 . 
         [0051]    One or more female sockets  20   c  are capable of providing 240 volts, in addition to the female sockets  20   a  and  20   b  which provide 120 volts. The 240 volt female socket  20   c  electrically connects in parallel to both of the 120V active wires  14   b  and  14   c  (and not to the neutral wire  14   a ) and provides 240 volts because the 120V circuit wires are 180° out of phase. Many heavy-duty tools and appliances, such as clothes dryers, require 240 volts, while the majority of electrically operated devices in the United States operate with 120 volts. Only one cord  10  is needed to operate pieces of equipment that have different voltage ratings. 
         [0052]    Each female socket  20   a - c  of  FIG. 2A  includes ground fault circuit interrupters  30   a - d  incorporated within each socket block  22 . The ground fault circuit interrupters  30   a - d  detect sudden imbalances in current flow such as can be caused by grounding of the load. This happens, for example, by a user accidentally stepping in water or otherwise causing a grounding path. The ground fault circuit interrupters  30   a - d  couple across the parallel electrical leads branching from the neutral wire  14   a  and conducting wire  14   b . Each ground fault circuit interrupter  30   a - d  includes a transformer  32 , sense circuitry  34 , one or more switches  36 , and one or more solenoids  38 . Operation of the components of the ground fault circuit interrupters  30   a - d  is discussed in greater detail below in  FIGS. 3A-3B . 
         [0053]    The ground fault circuit interrupters  30   a - d  electrically isolate the female sockets  20   a  and  20   b . If ground fault circuit interrupter  30   a  senses a current imbalance to socket  20   a  within the same socket block  22 , it interrupts current flow to that socket. Electrical connection to socket  20   a  associated with ground fault circuit interrupter  30   d  is not interrupted because it is formed from an electrical circuit parallel to the circuit disconnected by ground fault circuit interrupter  30   a . An electrical tool is capable of being used if connected to any female socket  20   a - b  associated with the non-interrupting ground fault circuit interrupters  30   b - d . Various embodiments also could include an arc fault interrupter in place of the ground fault circuit interrupter  30 . 
         [0054]    Extension cords  10  can also be made for use with voltage services other than the typical 120/240 volt service, and can include ground fault circuit interrupters in various locations along the extension cord. One example is a 120/208 volt service which is often configured as a three-phase, four-wire system.  FIGS. 2B-2D  illustrate alternative embodiments of cords for use with this type of service. 
         [0055]      FIG. 2B  shows an exemplary embodiment of a cord  10  for use with a four-wire service. The cord is substantially similar to the one described in conjunction with  FIG. 2A , except that has a neutral wire  14   d  and three 120V conducting wires  14   e ,  14   f  and  14   g . Three different 120V circuits can be made. One or more female sockets  20   f  electrically connect in parallel to neutral wire  14   d  and active wire  14   e , one or more female sockets  20   g  electrically connect in parallel to neutral wire  14   d  and active wire  14   f , and one or more female sockets  20   h  electrically connect in parallel to neutral wire  14   d  and active wire  14   g . The four circuits corresponding to sockets  20   f ,  20   g , and  20   h , respectively, are electrically isolated due to these parallel connections. In one possible embodiment, an additional female socket  20   i  electrically connects in parallel between any two of the active wires  14   e - 14   g , such as wires  14   e  and  14   f  shown. The socket  20   i  provides 208 volts to any electrically operated devices plugged into the socket. Ground fault circuit interrupters  30   e - h  are coupled across each socket  20   f - i , and operate as described in conjunction with FIGS.  2 A and  3 A-B. As described above, each of the ground fault circuit interrupters  30   e - h  only disconnects electricity to the associated socket  20   f  and  20   g  due to the parallel connection to the conducting wires  14   d - g.    
         [0056]    In an alternative embodiment, the cord  10  has a separate neutral wire associated with each conducting wire  14   e - 14   g . For example, a cord  10  having three conductors  14   d - 14   g  would also include three neutral wires. Each female socket  20  would have a contact connected between the conducting wire and the neural associated with that conducting wire. 
         [0057]      FIG. 2C  shows another possible embodiment of a cord  10  for use with a four wire service as described in conjunction with  FIG. 2B . In this embodiment, each socket block  22  incorporates multiple female sockets  20   j - m , which connect in parallel within each socket block  22  and to the conducting wires  14   d - g . Separate ground fault circuit interrupters  30   i - 1  are associated with each female socket  20   j - m , respectively. In this configuration, one female socket  20  can be disabled within a socket block  22  by a ground fault circuit interrupter  30  while the other female socket within the same socket block  22  remains active. All female sockets  20  in the other socket blocks  22  also remain active. 
         [0058]    In an alternate embodiment (not shown), one ground fault circuit interrupter can be included in each socket block, and is associated with two or more female sockets. In such a configuration, both sockets within the socket block disable upon detection of a fault by a ground fault circuit interrupter. 
         [0059]      FIG. 2D  shows a further possible embodiment of a cord  10  for use with a four wire service as described in conjunction with  FIG. 3B . In this embodiment, female sockets  20   n - p  are distributed along the cord  10 , and electrically connected to two of the wires  14   d - g . A ground fault circuit interrupter  30   m  couples across the wires  14   d - g , and resides within the housing  13  of the male plug  12 . In this configuration, the ground fault circuit interrupter  30   m  detects a zero sum current across all of the conducting wires  14   e - g  and the neutral wire  14   d . Upon detection of a current change, the ground fault circuit interrupter  30   m  disconnects the conducting wires  14   e - g , deactivating all of the sockets  20   n - p  along the cord  10 . 
         [0060]    Two further embodiments are depicted in  FIGS. 2E and 2F  which include a grounding wire  24  incorporated into the extension cord  10 . Typically, grounding wire  24  is locally grounded as opposed to being grounded at the power source as is often the case for neutral wire  14   a  of  FIG. 2A  or wire  14   d  of  FIGS. 2B-2D . 
         [0061]    In  FIG. 2E , the extension cord  10  incorporates a number of female sockets  20   q  electrically connected to a neutral wire  14   a , a 120V conducting wire  14   b , and a grounding wire  24 . The extension cord  10  also incorporates a number of female sockets  20   r  electrically connected to the neutral wire  14   a , the other 120V conducting wire  14   c , and the grounding wire  24 . Each female socket  20   q ,  20   r  resides within a separate socket block, although it is understood that two or more female sockets can be incorporated in each socket block consistent with the principles described above in  FIG. 2C . 
         [0062]    The socket blocks  22  each include ground fault circuit interrupters  30   n - p  coupled across the parallel connections to female sockets  20   p - r , which reside within the socket blocks  22 . This configuration corresponds to the configuration of  FIG. 2A , with inclusion of grounding wire  24 . The ground fault circuit interrupters  30   n - p  are not coupled across the parallel connection to the grounding wire  24 . Current within the grounding wire  24  is therefore not detected using the ground fault circuit interrupters  30   n - p.    
         [0063]      FIG. 2F  has a similar three wire configuration to  FIG. 2E , and also includes grounding wire  24 . Ground fault circuit interrupter  30   q  couples across and detects a zero sum across all of the conducting wires  14   b - c  and the neutral wire  14   a . Current within the grounding wire  24  is not detected using the ground fault circuit interrupter  30   q . Upon detection of a fault, the ground fault circuit interrupter  30   q  disconnects the electrical supply to all of the female sockets  20   s - t.    
         [0064]    The extension cords  10  of the present disclosure, especially those with electrically isolated circuits, are especially useful when heavy power drawing devices or many electrically operated devices are attached to the extension cord. The power load from these devices can be balanced between the two or more isolated circuits so that a single extension cord can be used where two or more extension cords would otherwise be required. By balancing the power load between the isolated circuits, devices may be plugged into a single extension cord and draw power which, when plugged into a typical one circuit cord would otherwise result in tripping a fuse attached to the outlet or the cord; damage the cord or the equipment plugged into it; or even causing a fire. Balancing the power load between the multiple circuits of the extension cord permits more equipment to be operated safely with a single extension cord. Ground fault circuit interruption associated with either the male plug or the female sockets of the extension cords  10  provides additional safety to each female socket  20 . By incorporation of ground fault circuit interruption with each female socket, operation of all devices connected to the cord  10  is not interrupted upon detection of a fault at one female socket. 
         [0065]    Alternatively, if the cord  10  has a separate neutral for each conducting wire, an embodiment can include a separate ground fault interrupter circuit for each separate circuit or pair of conductor and neutral wire. For example, if there are two conductors and two matching respective neutral wires, the cord can include two separate ground fault interrupters  30 . Thus if one circuit fails, the other circuit may still be operating and conducting electricity. 
         [0066]    The alternative embodiments shown in  FIGS. 2A-2F  are merely illustrative. It will be recognized that the same principles can be used to construct extension cords and distribute ground fault circuit interrupters across the cords for any voltage service that has two or more conducting wires. In addition, all of the female sockets represented in each of  FIGS. 2A-2F  are not necessary for a cord constructed according to the principles of the present disclosure. For example, an extension cord can be constructed similar to the embodiment depicted in  FIG. 2A  by including only female sockets  20   a  and  20   b . Such a cord would have two electrically isolated circuits, one of which would provide 120V service and the other 240V service. Extension cords can be constructed having any combination of female sockets connected to different conducting wires and any combination of female sockets within a single socket block. One or more of the electrically isolated circuits or female sockets can include ground fault circuit interrupters, in various configurations as shown above, or a combination thereof. 
         [0067]    Ground fault circuit interrupters operate in electrical installations to disconnect a circuit when imbalanced current flow is detected between a conducting wire and a neutral wire. GFI&#39;s open the circuit because an imbalance might represent current through a person who is accidentally touching the energized part of the circuit and is therefore about to receive a potentially lethal shock. GFI&#39;s include a normally closed switch connected to sense circuitry that is designed to open and disconnect electricity quickly enough to prevent such shocks.  FIGS. 3A and 3B  shows exemplary schematic views of portions of the extension cord  10  of  FIG. 2A  including ground fault circuit interrupters  30   a  and  30   c.    
         [0068]      FIG. 3A  shows ground fault circuit interrupter  30   a  residing within the socket block  22  and coupled across conducting wire  14   b  and neutral wire  14   a . The ground fault circuit interrupter includes a transformer  32 , sense circuitry  34  electrically connected to the transformer  32 , and a switch  36  and solenoid  38  connected to the transformer  32  and sense circuitry  34 . 
         [0069]    The transformer  32  detects current within both the conducting wire  14   b  and the neutral wire  14   a . In normal operation, all of the current flowing along the conducting wire  14   b  returns along neutral wire  14   b . This causes a balanced current state within the cord  10 , and does not induce any current in the transformer  32 . In the case of a sudden change in current flow, for example caused by a person touching a live component in the attached appliance, some of the current takes a different return path. This results in an imbalance in the current flowing in the conductors  14   a  and  14   b  or, more generally, a nonzero sum of currents from among multiple conductors. This difference causes a current to flow in the transformer  32 . 
         [0070]    The sense circuitry  34  detects current flowing to it from the transformer  32 . The sense circuitry  34  activates the solenoid  38 , which in turn disconnects the switch  36 , which in turn disconnects the conducting wire  14   b . Disconnecting the switch  36  opens the circuit defined by the leads  14   a - b  by disconnecting the conducting wire  14   b . The electricity supply to the circuit is interrupted, preventing potential electrocution. 
         [0071]    In a possible embodiment, optional resistor  40  and light emitting diode  42  connect between the conducting wire  14   b  and the return wire  14   a . The resistor  40  and light emitting diode  42  form an indicator circuit configured to illuminate the light emitting diode while the circuit connected to the socket block  22  remains active. In an alternate embodiment, the light emitting diode  42  is replaced by an incandescent bulb or other illumination device. In still other embodiments, all or a portion of the socket block  22  is formed from a translucent material, and illuminates while the light emitting diode  42  remains illuminated. 
         [0072]      FIG. 3B  shows a ground fault circuit interrupter  30   b  coupled across conducting wires  30   b - c . The ground fault circuit interrupter  30   b  operates similarly to the ground fault circuit interrupter  30   a  of  FIG. 3A , but is designed with switches  36  and solenoids  28  connected to the sense circuitry  34  to disconnect both of the conducting wires  14   b  and  14   c  upon detection of imbalanced current flow. Such a configuration is useful for multiphase power connections because it prevents accidental power transmission if the load connected to the female socket is accidentally grounded. 
         [0073]    The ground fault circuit interrupters are designed so that the current is interrupted in a very short time after the imbalanced current is detected, such as a fraction of a second. This greatly reduces the chances of an electric shock being received. 
         [0074]    In additional possible embodiments ground fault circuit interrupters  30  can sense current changes among more than two wires, and may require different electrical connections depending upon the configuration used. For example, a multiphase conducting wire cord may require more than one switch  36  connected to the sense circuitry  34 . For clarity, the basic schematics shown in  FIGS. 3A-3B  are used throughout the present disclosure, but are understood to represent additional possible configurations of ground fault circuit interrupter wiring. 
         [0075]    Referring now to  FIG. 4 , a female socket  20  for use with a standard U.S. 120V male plug from an electrically operated device is shown. In this embodiment, the male plug  12  of the extension cord  10  has four prongs  44  and is configured for attachment to a 120/240V service. One common configuration for a male plug  12  to be used with a 120/240V service is a twist lock plug where the plug is inserted into an appropriate female outlet, not shown, and then the male plug is twisted to securely fasten the prongs  44  of the plug within the outlet. This type of male plug configuration ensures that the plug  12  does not come out of the outlet by simply pulling on the plug  12 . Although the plug  12  shown includes four prongs  44 , plugs with any number of prongs can be used in this twist lock configuration. 
         [0076]    An optional adapter  26  may be provided for adapting this embodiment of the extension cord for use with a 120V source. This adapter  26  has a female portion configured to receive the male plug  12  of the extension cord  10  and a male portion for plugging into a female outlet of a 120V source. If such an adapter were used, for example, with the extension cord configuration of  FIG. 2A , the adapter would include an electrical connection between the two 120V conducting wires  14   b  and  14   c  so that they would be attached to the same prong of the adapter. When using this adapter the electrically operated devices plugged into the extension cord will all be part of the same circuit despite using coupling configurations illustrated in  FIG. 2A  due to the connection of the two circuit wires in the adapter. Furthermore, instead of being a separate attachment, the adapter may alternatively be integrally coupled to the cord  10 . 
         [0077]    Other adapters may be provided for conversion between extension cords of the present disclosure and other voltage source configurations. In addition, adapters may be provided that will convert the prong configuration of the male plug of the extension cord to an appropriate configuration for use in another country or region. 
         [0078]      FIG. 5A  shows a socket block  22  with rectangular female sockets  20 .  FIG. 5B  shows a socket block  22  with circular female sockets  20 . Other socket and socket block configurations are possible. 
         [0079]    In one possible embodiment, a circuit identifying mark  28  is provided proximate each of the female sockets  20 . The circuit identifying mark  28  may be color-coded (see  FIG. 5A ), numbered, lettered (see  FIG. 5B ), stamped, or otherwise configured to indicate the circuit to which the proximate female socket is attached. The circuit identifying mark  28  provides an extension cord user with information about which circuit the device is being plugged into so that the user may balance the power load of the circuit. 
         [0080]    In another possible embodiment, the circuit identifying mark  28  is a light emitting diode or other illumination device. The light emitting diode is configured to illuminate upon connection of a male plug to the female socket  20 , and is color coded to the circuit corresponding to that socket. 
         [0081]      FIGS. 5A and 5B  both show socket blocks  22  for use with extension cords in which the two female sockets  20  of the socket block  22  are each attached to different circuits. However, other configurations are also possible including having the female sockets  20  of each socket block  22  attached to the same circuit or alternatively, having more than one female socket in each socket block attached to the same circuit. For example, in one embodiment, not shown, two out of four female sockets in a socket block are attached to one circuit with the other two sockets attached to a second circuit. 
         [0082]      FIG. 6  shows another alternative embodiment. In this embodiment one or more of the female sockets  20  have a cap  50 . Typically, there is a cap  50  for each female socket  20 . The cap  50  and female socket  20  are configured so that the cap  50  can be placed on or into female socket  20  when the female socket  20  is not in use. The cap  50  provides a safety mechanism for the extension cord  10  to avoid unwanted contact between the active conducting wires  14   a - 14   g  of the extension cord  10  and individuals, moisture, or other external objects. 
         [0083]    Additionally, a mooring member  52  is attached to either the female sockets  20  or the socket blocks  22  which can be used to hold the extension cord  10  in place. For example, the mooring member  52  may be used to fasten the extension cord  10  in a desired place or position or to hold the extension cord  10  off the ground, as depicted in  FIG. 7 . The mooring member may be a loop or ring of material. Alternatively, the mooring member may be a hook, strap, bracket, slot, or similar device which will permit attachment of the cord to an external object. The mooring member  52  may be used with any extension cord, not only those with multiple circuits. In one embodiment, the mooring member is integrally molded to the socket or socket block to provide a stable and durable structure. 
         [0084]    In an alternative embodiment, the extension cord is made of a male plug, two or more conducting wires electrically connected to the male plug, and one or more female sockets electrically connected to the conducting wires with a mooring member attached to the female sockets or to a socket block which houses the female sockets. In this embodiment, the female sockets may all be electrically connected to the same conducting wires, or alternatively, they may be electrically connected to different conducting wires. 
         [0085]      FIG. 8A  shows an extension cord  210  including a male twist lock plug  212 . The extension cord  210  can be used in construction or other high voltage applications. The cord  210  has a male twist lock plug  212 , which includes a housing  213 . The cord also includes a female twist lock socket  220 , configured to mateably receive a male twist lock plug  212 . In use, a male twist lock plug  212  is inserted into a female twist lock socket  20 , and axially rotated (either clockwise or counterclockwise, depending upon the configuration of the plug and socket) into a locked position. Removal of the male plug  212  from the female socket  220  requires twisting the male plug  212  in the opposite direction. 
         [0086]    The male twist lock plug  212  includes a plurality of prongs  215  formed in a circular configuration to lockably mate with a female socket  220 . The male twist lock plug  212  is twisted to securely fasten the prongs  215  of the plug  212  within the outlet. 
         [0087]    The male twist lock plug housing  213  has an oval cross-sectional shape at its face or at any other point within the housing  213 . The oval shape of the housing  213  indicates the rotational position of the plug, which in turn dictates whether the plug  212  is in a locked or unlocked position when inserted into a female socket  220 . In various embodiments, the plug  212  can be other non-circular shapes. Although the plug  212  can retain a circular configuration of the prongs  215 , the housing  213  can have a triangular, rectangular, or any other cross sectional shape capable of indicating the rotational position of the plug  212 . In further embodiments, the male twist lock plug  213  includes an indicator which corresponds to an indicator on a corresponding female twist lock socket  220 . Alignment of the indicators can indicate a locked or unlocked position of the male twist lock plug  212 . 
         [0088]    The female twist lock socket  220  optionally has an oval cross-sectional shape as well. The oval shape of the female twist lock socket  220  aligns with the oval cross sectional shape of a male twist lock plug housing  213  when in either a locked or unlocked position. 
         [0089]      FIG. 8B  shows a perspective side view of a section of an electrical cord  210  including a male twist lock plug  212  with a housing  213  having an oval cross-sectional shape as described in  FIG. 8A . Each of the plurality of prongs  215  connects to an internal conductor, such as the conducting or neutral wires  14  of  FIGS. 2A-2E . The housing  213  has a variable-sized oval cross section, which indicates the rotational position of the plug, showing whether the plug  212  is in a locked or unlocked position when inserted into a female socket  220 . 
         [0090]      FIG. 8C  shows a schematic functional view of a section of an extension cord including a male plug  212  according to an embodiment of the present disclosure. The non-circular cross-section of the housing  213  enables a user to readily ascertain whether the plug is in a locked position. In the embodiment shown, the oval plug is inserted in an askew position, shown in  FIG. 8C  in dotted lines. The askew position corresponds to an unlocked, or insertion position. When the plug  212  is fully inserted and twisted to the locked position, the oval shaped housing  213  is upright, allowing a user to readily determine the locked status of the plug  212 . Alternately, the housing  213  can be in a locked position at a different ascertainable rotational position. 
         [0091]      FIGS. 9A and 9B  show schematic views of the male twist lock plug  212  used in conjunction with a female socket  220  incorporated into an electrical generator  300 . The electrical generator  300  provides a power source  302  that can be used at a construction site, a home, or other location where a portable or backup power supply is desired. The electrical generator  300  generates an electrical current which passes through an electrical cord  210  associated with the male twist lock plug  212  when the cord is connected to the electrical generator. Socket orientation indicia  221  located on a visible face of the socket  220  and/or socket block  222  indicates the locked state, the unlocked state, or both the locked state and the unlocked state of the combination of the male plug  212  and female socket  220 . The socket orientation indicia  221  can include an outline displaying the cross-sectional shape of the male housing  213  when in the locked and/or unlocked positions. 
         [0092]    Additional configurations of the socket orientation indicia  221  are possible as well. For example, a colored indicator located on the male plug can align with a colored indicator on the female socket when in a locked and/or unlocked position. In another alternative embodiment, the socket orientation indicia  221  is defined by a portion of the face of the socket block  222  (or on the face plate enclosing the female socket) that is raised, elevated, or otherwise set-off relative to adjacent portions of the socket block or surrounding structure. The profile of the raised portion of the face plate would match the profile for the face of the male twist lock plug  212 . 
         [0093]    The female socket  220  can optionally be located within a socket block  222  incorporated into the electrical generator  300 . As shown in  FIG. 9A , the socket block  222  can include a ground fault circuit interrupter  30  associated with the female socket  220 . In such a configuration, the ground fault circuit interrupter  30  provides global ground fault protection to any electrical cord plugged into the female socket  220 . 
         [0094]      FIG. 9B  shows socket block  222  incorporated into the electrical generator  300  and including a female twist lock socket  220  including socket orientation indicia  221 . A socket adapter  250  includes a male plug  212 ′ used to connect to a twist lock female socket, such as the socket  220  integrated with the electrical generator  300 . The socket adapter further includes a female plug  220 ′ that can accept other male twist lock plugs, such as the male plug  212  connected to the electrical cord  210 . 
         [0095]    Connection wires connect the male plug  212 ′ to the female socket  220 ′ within a housing  213 ′ of the socket adapter  250 . The socket adapter  250  can optionally include a ground fault circuit interrupter  30  electrically connected between a male plug  212 ′ and a female socket  220 ′. The ground fault circuit interrupter  30  resides within the housing  213 ′ of the socket adapter  250 . 
         [0096]      FIGS. 10A-10D  show schematic views of an extension cord  410  incorporating a thermal indicator circuit according to various embodiments of the present disclosure.  FIG. 10A  shows the cord  410  including a thermal indicator circuit  430   a  located near a male plug  12 . The cord  410  correlates to the cord  10  of  FIG. 3B , in that a four wire configuration is shown. The thermal indicator circuit  430   a  includes a thermal switch  432  and an indicator  434 . 
         [0097]    The thermal indicator circuit  430   a  connects across a conducting wire  14   e  and a neutral wire  14   d  in the extension cord  410 . Additional thermal indicator circuits can connect between the neutral wire  14   d  and other conducting wires  14   f - g , or between two conducting wires. The inclusion of a thermal indicator circuit  430  does not depend upon the specific configuration of the extension cord  410 ; two, three, or four or more wire cords can include thermal protection. In various embodiments, the thermal indicator circuit  430   a  can be located within a housing  13  of the male plug  12  and/or the thermal indicator circuit can be located along the extension cord  410 . 
         [0098]    The thermal switch  432  activates the thermal indicator circuit  430  when a temperature above a specific temperature is detected. In an exemplary embodiment, the thermal indicator circuit  430  is activated without interrupting electrical flow along the electrically conducting wires. For example, as an extension cord wears, added electrical resistance occurs at the wear areas of the cord  410 . This added electrical resistance causes heat. Because cord degradation typically occurs near plug and socket connections, fires and other thermal hazards generally occur in these places as well. The thermal indicator circuit  430  provides a warning to a user of the cord  410  that potentially unsafe temperatures exist within potentially problematic locations within the cord. While the thermal indicator circuit  430  provides the warning, the electrical flow along the electrically conducting wires continues to run and is not interrupted, although other embodiments can include a switch or other mechanism to open the circuit in the event the thermal indicator is tripped. 
         [0099]    In one embodiment, the thermal switch  432  is a thermistor, such as an NTC switching thermistor. In an exemplary embodiment, a thermistor such as an NTC switching thermistor, detects a specific temperature using the following generalized equation (1): 
         [0000]    
       
         
           
             
               
                 
                   T 
                   = 
                   
                     1 
                     
                       a 
                       + 
                       
                         b 
                          
                         
                             
                         
                          
                         ln 
                          
                         
                             
                         
                          
                         R 
                       
                       + 
                       
                         
                           c 
                            
                           
                             ( 
                             
                               ln 
                                
                               
                                   
                               
                                
                               R 
                             
                             ) 
                           
                         
                         3 
                       
                     
                   
                 
               
               
                 
                   ( 
                   1 
                   ) 
                 
               
             
           
         
       
     
         [0000]    where a, b, and c are device-specific parameters, T is the temperature, and R is the resistance of the thermistor. The threshold value for the resistance is selected to correspond to a temperature value at or below a temperature limit for safe operation of the extension cord  410 . When the temperature reaches the threshold, the resistance reaches a low enough level that the circuit is considered to be a “closed” circuit. Other temperature sensitive switches can be used as well. Although equation (1) is presented in this disclosure, various embodiments may operate according to physical and mathematical principles other than those described by equation (1). 
         [0100]    The thermal switch  432  generally operates to connect a circuit upon detection of a minimum temperature. Thermal switches can include thermistors, which are variable-resistance resistors, whose resistance changes according to its temperature. In one possible type of thermistor, a negative temperature coefficient (NTC) thermistor, a decrease in resistance occurs as temperature increases. The thermistor can be made from a semiconducting material, such as a metal oxide. Raising the temperature of such a thermistor increases the number of charge carriers in the thermistor. The more charge carriers that are available, the more current that can be conducted, and the lower the resistance of the material. In another possible type of thermistor, a positive temperature coefficient (PTC) thermistor, an increase in resistance occurs as temperature increases. Thermal switches generally use a switching thermistor (either NTC or PTC), which means that the resistance of the thermistor either rises or falls suddenly at a certain critical temperature. This critical temperature is the critical temperature at which the thermal switch changes state. Other embodiments can include a thermal switch other than a thermistor. 
         [0101]    The indicator  434  is an electrically activated indicator perceptible to a user of the cord, and indicates when the temperature reaches a specific threshold and the thermal switch  432  reaches its “closed” state. The indicator  434  activates upon activation of the thermal switch  432 . The indicator  434  can include a light, such as a light-emitting diode, incandescent bulb, or other display or illumination device. The indicator  434  can also include a fuse or circuit protection device. The indicator  434  can include an audible alarm. A combination of indicators can be used in combination as well, such as multiple lights, a light and an audible alarm, a light and a fuse, or other configurations. Additionally, a light can be positioned within a housing that is at least partially translucent. 
         [0102]      FIG. 10B  shows the cord  410  including a thermal indicator circuit  430   b  that reaches across the entire length L of the cord  410 . The thermal switch  432  spans the length of the cord  410 , and can include one or more indicators  434 , such as one indicator at each end of the cord  410 . The thermal switch  432  activates the thermal indicator circuit  430   b  by activating the indicators  434  upon detection of the threshold temperature (or higher) at any location along the cord  410 . In a further embodiment, the thermal indicator circuit  430   b  spans less than the entire length L of the cord  410 . 
         [0103]    In the embodiment shown, both indicators  434  are the same type of indicator. However, in alternate embodiments various types of indicators can be used in combination, such as an audible alarm and a light emitting diode, or other combinations. In yet another possible embodiment, the indicators are replaced by or positioned in electrical series with a relay having contacts in line with conducting wire  14   e  and an armature activated by the thermal switch  432 . When the thermal switch  432  is tripped, the armature moves the contacts and creates an open circuit in the conducting wire  14   e.    
         [0104]      FIG. 10C  shows the cord  410  including multiple separate circuits including female sockets  20   x - z , and corresponds to  FIG. 3B , above, in that it shows an embodiment of a cord  410  for use with a four-wire service and including a number of socket blocks  22  dispersed along the cord  410 . Each socket block  22  contains one or more female sockets  20   a - c , which can be configured in a manner as described in conjunction with  FIG. 3 . Thermal indicator circuits  430   c - e  reside near each socket block  22 , with at least a portion of the thermal switch  432  located near the junction of the socket block  22  with a flexible portion of the cord  410  due to the high probability of wear at those locations. The thermal indicator circuits  430   c - e  detect thermal degradation near each socket block  22 , such that a user of the cord  410  can choose to continue use of the cord  410  after one socket block  22  becomes unsafe by switching to a separate electrically isolated socket block. The indicator  434  can reside within or be located separate from the socket block  22 . 
         [0105]    In an alternate configuration, a thermal indicator circuit  430   a  can be located proximate to the male plug  412 , and is used in conjunction with the thermal indicator circuits  410   c - e  located near the female sockets  20   x - z.    
         [0106]      FIG. 10D  shows the cord  410  including two thermal indicator circuits  430   f - g .  FIG. 10D  corresponds to  FIG. 10A , but includes a second thermal indicator circuit  430   g  having different operation from the first thermal indicator circuit  430   f.    
         [0107]    Thermal indicator circuit  430   f  includes a thermal switch  432  and an indicator  434 . Thermal indicator circuit  430   g  includes a thermal switch  432 ′ and an indicator  434 ′. Thermal switches  432  and  432 ′ can differ based on threshold temperature, normal state (open or closed), or other factors. Indicators  434  and  434 ′ can be either the same or different indicators selected from among the possible indicators described above in conjunction with  FIG. 10A . 
         [0108]    In a first possible embodiment, second thermal indicator circuit  430   g  is a warning circuit, and has a thermal switch  432 ′ with a lower threshold temperature than thermal switch  432  of thermal indicator circuit  430   f . A user of such a device is provided two levels of severity warnings for use of the electrical cord  410 . In various other embodiments, the thermal switch  432 ′ has inverse operation to the operation of thermal switch  432 . In one implementation of this embodiment, thermal switch  432  is an NTC thermistor and thermal switch  432 ′ is a PTC thermistor, and both switches  432 ,  432 ′ have the same threshold temperature. The circuit  430   g  remains normally connected, activating indicator  434 ′. When the temperature of the cord exceeds the threshold temperature, thermal switch  432 ′ opens and deactivates indicator  434 ′ in thermal indicator circuit  430   g , and thermal switch  432  closes and activates indicator  434  in thermal indicator circuit  430   f . In a possible embodiment, indicator  434 ′ can be a green light emitting diode and indicator  434  can be a red light emitting diode. Illumination of the green light emitting diode indicates safe operation of the cord  410 , and illumination of the red light emitting diode indicates hazardous operation of the cord  410 . Other configuration of indicators and threshold temperatures are possible as well. 
         [0109]      FIGS. 11A-11C  show schematic views of various embodiments of an electrical cord  440  incorporating a thermal indicator circuit  430  into an electrical cord  440 . The electrical cord  440  connects to an electrical tool  450 , and can be either an extension cord as described in  FIGS. 10A-C , or can be non-detachably incorporated onto the electrical tool  450 . The electrical tool  450  can be any of a number of construction tools, such as a rotary saw, a sander, nail gun, drill, or other machinery. The electrical tool  450  can also be unrelated to construction, and can be any other type of electrical device which typically draws a high current or where cord wear could be a concern. Such devices could include, for example, a hair dryer, a microwave or other appliance, a vacuum, or other devices. 
         [0110]      FIG. 11A  corresponds to  FIG. 10A  incorporated with an electrical tool  450 , and shows the electrical cord  440  including a thermal indicator circuit  430   a  near or integrated with a male plug  12  as previously described.  FIG. 11B  corresponds to  FIG. 10B  incorporated with an electrical tool  450 , and shows the electrical cord  440  including a thermal indicator circuit  430   b  spanning the length L of the electrical cord  440  between the male plug  12  and the electrical tool  450 .  FIG. 11C  corresponds to both  FIGS. 10A and 10C , and shows the electrical cord  440  including a thermal indicator circuit  430   a  proximate to the male plug  12  and a second thermal indicator circuit  430   c  proximate to the electrical tool  450 . 
         [0111]    In each of the embodiments shown, the thermal indicator circuit  430  is connected across the neutral wire  14   d  and conducting wire  14   e . In alternate configurations of the electrical tool, additional thermal indicator circuits  430  connect between the neutral wire  14   d  and a different conducting wire  14   e - f  in the electrical cord  440 . The electrical cord  440  can include more or fewer conducting wires  14 , and can include a ground wire (not shown). 
         [0112]      FIG. 12  shows an exemplary extension cord  460  having a male plug  461 , one or more female sockets  463   a  and  463   b , and an electrical conductor  465 . A thermochromatic material  462  forms a thermal indicator and is mounted on or integrated into the extension cord  460  at one or more locations  462   a - 462   h . The thermochromatic material  462  can be formed with any type of temperature sensitive material that changes color in response to temperature as described herein. Examples of possible thermochromatic materials include thermochromatic liquid crystals, polymers, paints, dyes, and inks. 
         [0113]    The thermochromatic material  462  can have different forms and can be applied to the extension cord  460  in different ways. For example, the thermochromatic material  462  can be in the form of a tape, label, or other substrate having an adhesive backing that is applied to the surface of the extension cord  460 . In another possible embodiment, the thermochromatic material  462  can be a coating or material such as polymer, liquid crystal, paint, dye, or ink applied directly to extension cord  460 . In this embodiment, the thermochromatic material  462  can be applied to the surface of the extension cord  460  by any suitable techniques such as brushing, spraying, or otherwise depositing it onto the surface of the extension cord  460 . Alternatively, the male plug  461 , one or more female sockets  463  or insulator on the conductor  465  is formed, at least in part, with the thermochromatic material  462  molded into the extension cord  460 . In these embodiments, the thermochromatic material  462  is applied to the male plug  461  (e.g., thermochromatic material  462   a ), one or more of the female sockets  463  (e.g., thermochromatic material  462   g  and  462   h ), the conductor  465  (thermochromatic material  462   b - 462   f ), or any combination thereof. 
         [0114]    The thermochromatic material  462  can have different sizes and shapes. Thermochromatic material  462  can be applied to the extension cord  460  during the manufacturing process or provided to users to apply to the extension cords  460  as an after-market product. Additionally, thermochromatic materials  462  having different sizes and shapes can be positioned at different locations along a single extension cord  460 . 
         [0115]    In use, the thermochromatic material  462  changes a color upon detecting a temperature at or above a threshold temperature of the extension cord  460  so that it provides a warning that the extension cord  460  might be over-heated. When the portion of the extension cord  460  proximal to the thermochromatic material  462  has a temperature below the threshold temperature, the color of the thermochromatic material  462  has a first color. When the portion of the extension cord  460  proximal to the thermochromatic material  462  reaches a temperature at or above the threshold temperature, the color of the thermochromatic material  462  changes to a second color which is different from the first color. 
         [0116]    In an exemplary embodiment, once the temperature of the extension cord  460  proximal to the thermochromatic material  462  decreases and becomes lower than the threshold temperature, the thermochromatic material  462  changes its color from the second color back to the first color. In another exemplary embodiment, the color of the thermochromatic material  462  does not return to its original color even after the temperature falls below the threshold value. An advantage of applying a thermochromatic material  462  to an extension cord is that it can indicate when the extension cord  460  has reached such a temperature as to become a fire hazard. 
         [0117]    In an alternative embodiment, the thermochromatic material  462  can be made to change a color when the temperature reaches multiple different temperature thresholds so that multiple warnings can be given to a user. For example, when the temperature of the extension cord  460  reaches or exceeds a first threshold temperature, the thermochromatic material  462  changes its color from a first color (e.g., green) to a second color (e.g., orange). This first color gives a user a first warning. When the temperature of the extension cord  460  continues to rise and reaches a second threshold, the temperature sensitive sheet  462  changes its color from the second color (orange) to a third color (e.g., red) and gives the user a second level warning which is more serious than the first warning regarding over heating of the extension cord  460 . The thermochromatic material  462  can further be configured to change from any number of colors to different colors when the temperature reaches a different threshold temperature and then give more levels of warnings as described above. In another possible embodiment, the color of the thermochromatic material  462  may change continuously in responding to the continuous changes of the temperature. 
         [0118]    In one possible application, the thermochromatic material  462  is applied to locations of the extension cord  460  that are most likely subject to failure or resistive heating. Examples of such locations are where the electrical current flows from one electrical conductor to another or the cord is most commonly subject to twisting and bending. Examples of such locations include the male plug  461 , the female sockets  463 , and the portion of the insulator on the conductor  465  that is adjacent to the male plug  461  and the female sockets  463 . In other possible embodiments, the thermochromatic material  462  extends along substantially the entire length of the extension cord  460 . 
         [0119]    Although the thermochromatic material  462  is illustrated as being applied to an extension cord having intermittently spaced female sockets and anchors, it could be applied to many other types of cords. For example, the thermochromatic material  462  can be applied to extension cords having a single female socket or socket block, power cords for electrical devices, and the like. 
         [0120]    Referring now to  FIGS. 13A ,  13 B,  14 A, and  14 B an alternative embodiment of the extension cord  500 , includes a female socket  520  mounted on an electrical conductor  518  having an adjustable anchor  550  that can pivot between at least two positions to enable the extension cord  500  to be either suspended or mounted on a vertical surface such as a wall, studs, or posts. The anchor  550  includes first and second anchor members  551  and  552 , which are pivotally connected to a housing  514  of the female socket  520  by first and second pivots  573  and  574 , respectively. The first anchor member  551  defines a first void  553  and has a first surface  591 . The second anchor member  552  defines a second void  554  and has a second surface  592 . The first and second voids  553  and  554  are sized to receive a hanger for suspending the extension cord  500  and alternatively a fastener such as a screw, nail, pin, or peg to mount the extension cord  500  on a vertical surface. In the exemplary embodiment, the female socket  520  has a generally tear-drop shape configuration. Although the exemplary embodiment illustrates the adjustable anchor as forming a part of the female socket block, other embodiments will have adjustable anchors positioned along the extension cord at locations other than a female socket. 
         [0121]    When the anchor  550  is in a first or closed position (illustrated in  FIGS. 13A and 13B ), the first and second surfaces  591  and  592  of the first and second anchor members  551  and  552 , respectively, are directly adjacent to one another and the first and second voids  553  and  554  are axially aligned to one another. In a second or open position (illustrated in  FIGS. 14A and 14B ), the first and second surfaces  591  and  592  are coplanar and the voids  553  and  554  are parallel to one another and are orthogonal to the first and second surfaces  591  and  592 . The first and second anchor members  551  and  552  can be pivoted between the first and second positions or any other position such as in a 90° arrangement to adapt to a corner. The adjustable anchor  550  provides flexibility to allow the extension cord to be suspended or mounted on a variety of different surfaces having a variety of different orientations and shapes. 
         [0122]    In an exemplary embodiment, the anchor  550  is spring-loaded. For example, the anchor  550  includes first and second springs  575  and  576  which extend around the pivots  573  and  574 , respectively, and between the first and second members  551  and  552  and the housing  514 , respectively. The first and second springs  575  and  576  bias the first and second members  551  and  552  into the first or closed position. Alternative embodiments do not include springs  575  and  576  and the first and second anchor members  551  and  552  are not biased to any particular position. Any suitable structure that biases the first and second anchor members  551  and  552  can be used such as other spring structures. The anchor  550  can also be formed with a resilient material that naturally urges the anchor members  551  and  552  to a predetermined position. In another alternative embodiment, the first and second anchor members  551  and  552  are biased into the second or open position. 
         [0123]    In another possible embodiment, the first and second anchor members  551  and  552  engage the housing  514  with a snap fit when in the first or closed position as described herein. The snap fit can be formed with any suitable structure such as nubs (not shown) on the first and second anchor members  551  and  552  and mating depressions (not shown) in the housing  514 . The snap fit holds the first and second anchor members  551  and  552  in the closed position so that the first and second voids  553  and  554  remain aligned even when a user is not directly grasping the anchor  550 . In another embodiment, the anchor  550  includes a snap fit structure that holds the first and second anchor members  551  and  552  in the second or open position. An advantage of this embodiment is that it can make the female socket  520  and anchor  550  easier to handle when mounting it on a surface as described below in conjunction with  FIG. 15 , especially if the first and second anchor members  551  and  552  are biased in the closed position. 
         [0124]      FIGS. 15 and 16  illustrate alternative ways to use the extension cord  500  and the flexibility provided by the anchor  550 . The extension cord  500  includes a male plug  512 , a conductor  518 , and a plurality of female sockets  520   a - 520   d . In  FIG. 15 , the first and second anchor members  551   a - 551   d  and  552   a - 552   d  are in the second or open position so that the first and second surfaces  591  and  592  for each anchor member  551  and  552  are coplanar and positioned against a vertical surface  593  such as a wall. The first and second anchor members  551   a - 551   d  and  552   a - 552   d  are held in place by fasteners  571   a  and  571   a ′- 571   d  and  571   d ′, respectively, that extend through the first and second voids  553  and  554  and are attached to the vertical surface  593 . The illustrations show the fasteners  571  as screws, but other fasteners or similar structures can be used such as nails, pins, hooks, pegs, and the like. Additionally, the anchors  550   a - 550   d  can be attached to structures other than walls such as studs, posts, and the like. In  FIG. 16 , the first and second anchor members  551   a - 551   d  and  552   a - 552   d  are in the first or closed positions so the first and second voids  553   a - 553   d  and  554   a - 554   d  are axially aligned. The extension cord  500  is then suspended by hooking the anchors  550   a - 550   d  on a hook  581   a - 581   d , respectively, that passes through the first and second voids  553   a - 553   d  and  554   a - 554   d . The hooks  581   a - 581   d  can be attached to an overhead structure  599  such as a ceiling or rafters. Alternatively the hooks  581   a - 581   d  can extend from a wall, from stakes planted in the ground, or from any other structure that can support the extension cord  500 . Also, any structure other than a hook that can pass through the voids  553   a - 553   d  and  554   a - 554   d  can be used. An advantage of these cords is that they can be mounted on or suspended from many different types and orientations of surfaces, which allows the cords to be positioned in safe and convenient locations. 
         [0125]      FIG. 17  is a view of an electrical adaptor  600  that includes a housing  634  and three electrical connectors  636 ,  637 , and  638  which are positioned in the housing  634 . The three electrical connectors  636 ,  637 , and  638  are in electrical communication with each other. The first electrical connector  636  is substantially axially aligned with the second electrical connector  637 . In addition, the third electrical connector  638  is positioned generally orthogonal to the first electrical connector  636  and the second electrical connector  637 . The first electrical connector  636  is a male electrical plug. The second and third electrical connectors  637  and  638  are female electrical sockets. In alternative embodiments, each of the first, second, third connectors  636 ,  637 , and  638  can be either a male electrical plug or a female electrical socket. 
         [0126]    The electrical adaptor  600  also includes fasteners  608   a  and  608   b  positioned proximate to the first electrical connector  636  (male plug) and pivotally connected to the housing  634  and adapted to secure the housing  634  to an extension cord (shown in  FIG. 19 ). The electrical adaptor  600  also includes engaging structures  639   a - 639   d  proximal to the second and third electrical connectors  637  and  638  (female sockets) configured to engage, receive, catch, or otherwise mate with a fastener (similar to fastener  608 ) from other extension cords or power cords from electrical devices. In the exemplary embodiment, the engaging structures  639   a - 639   d  are depressions defined in the housing  634  and arranged to receive the fastener. In alternative embodiments, the engaging structures  639   a - 639   d  are protruding flanges (not shown) or other suitable structure configured to be caught or otherwise engaged by a fastener (similar to fastener  608 ) from other extension cords, power cords, or electrical devices. Although the illustrated embodiment shows the fasteners  608   a  and  608   b  proximal to the male electrical plug and the engaging structures  639   a - 639   d  proximal to the female sockets, other embodiments could reverse this arrangement so the fasteners  608   a  and  608   b  is positioned proximal to the female sockets and the engaging structures  639   a - 639   d  are positioned proximal to the male plugs. 
         [0127]    In alternative embodiments, the fasteners  608   a  and  608   b  are biased to a closed position so that the second portions  624  (described below) for each fastener  608   a  and  608   b  are urged toward one another and toward the center of the housing  634  at the site of the electrical connector  636 . In various embodiments, the fasteners  608   a  and  608   b  can be spring loaded to create the bias or can be formed with a resilient material that naturally returns to the biased position. Additionally, in other embodiments the fasteners engage the housing  634  with a snap fit such as can be formed with a nub and depression arrangement. The snap fit structure can be positioned to hold the fasteners  608   a  and  608   b  in the open position, the closed position, or both. 
         [0128]    In one possible embodiment, the electrical adaptor  600  also includes an anchor  640  operably connected to the housing  634 . The anchor  640  is formed by a hole  649  which is defined in the housing  634 . The housing  634  includes a projecting member  651  to form the anchor  640  and the projecting member  651  defines the hole  649 . In another possible embodiment, the anchor  640  is substantially similar to the anchor discussed above for example in  FIGS. 13A ,  13 B,  14 A, and  14 B. In an alternative embodiment, the anchor  640  is an adjustable anchor as described in more detail herein. 
         [0129]    Generally, the anchor  640  and the third electrical connector  638  are positioned on substantially opposite sides of the housing  634 . In one possible embodiment, the anchor  640  is positioned about half way between the first electrical connector  636  and the second electrical connector  637 . In alternative embodiments, the anchor  640  can be positioned anywhere along the electrical adaptor  600 . 
         [0130]    Referring now to  FIGS. 18A-18B , the fastener  608  has a pivot  623  that pivotally connects to the housing  634  of the electrical adaptor  630 . The fastener  608  has a generally L-shaped member  633  with a first portion  622  and a second portion  624 . The fastener  608  pivots around the pivot  623  so the second portion  624  selectively engages an engaging structure (similar to engaging structure  639 ) on another electrical adaptor, extension cord, power cord, or electrical device. The fastener  608  also has a knob or other projecting member  625  generally parallel to the second portion  624  and projecting from the first portion  622  in a direction opposite to the second portion  624 . The projecting member  625  provides a structure for a user to engage with their finger and pivot the fastener  608  around the pivot  623 . 
         [0131]    The fasteners  608  can have any type of structure that allows a male plug on an electrical adaptor, extension cord, power cord, or electrical device to be secured to a female socket on another electrical adaptor, extension cord, power cord, or electrical device. In lieu of the L-shaped structure illustrated, for example, the fastener  608  can be formed with clips, threaded structures such as nuts or collars, prongs, elastic bands, hook and loop fasteners such as VELCRO® brand fasteners, and the like. Additionally, the engaging structure  639  can be any structure that engages the mating fastener to secure together male plugs and female sockets. Examples other than the illustrated depression include flanges, thread structures, elastic bands, hook and loop fasteners, and the like. In yet other embodiments, the fastener  608  may be able to secure a male plug to a female socket without an engaging structure  639 . 
         [0132]      FIG. 19  is a view of the electrical adaptor  600  including two extension cords  642  and  646 . Each of the extension cords  642  and  646  has intermittently spaced female sockets (not shown) and anchors (not shown) as described in more detail herein, although extension cords having a single female socket can be used. The first extension cord  642  has a female socket  699  connected to the first electrical connector  636  while the second extension cord  646  has a male plug  698  connected to the second electrical connector  637 . The female socket  699  of the first extension cord  642  has engaging structures  639   e  and  639   f  to mate with the fasteners  608   a  and  608   b , respectively. The second extension cord  646  has fasteners  608   c  and  608   d  that mate with the engaging structures  639   a  and  639   b , respectively when the second extension cord  646  connects to the second electrical connector  637 . In addition, a third extension cord or electrical device (not shown) can be connected to the third electrical connector  638 . 
         [0133]    Additionally, alternative embodiments of the electrical adaptor  600  can include any number of electrical connectors and any combination of male plugs and female sockets. Additionally, the electrical connectors (e.g., male plugs and female sockets) can have any orientation with respect to each other including being parallel, orthogonal, or angled. The housing  634  also can have many different configurations other including a t-shape, linear shape, cross, and a 90° bend or corner shape. 
         [0134]    Referring to  FIG. 20 , for example, an electrical adaptor  610  is similar to the electrical adaptor  600  shown in  FIG. 17  except that the electrical adaptor  610  has a linear housing  611  and only first and second electrical connectors  616  and  617  positioned at opposite ends of the housing  611 . The first and second electrical connectors  616  and  617  are substantially axially aligned with each other. The first electrical connector  616  is a male electrical plug. The second electrical connector  617  is a female electrical socket. Fasteners  608   a  and  608   b  are positioned proximal to the first electrical connector  616  and an engaging structure  639  is positioned proximal to the second electrical connector  617 . In the exemplary embodiment, the engaging structure  639  is a groove defined in and extending around the entire circumference of the housing  611 . The electrical adaptor  610  has an anchor  640 . 
         [0135]      FIG. 21  shows an electrical adaptor  620  similar to the electrical adaptor  600  shown in  FIG. 17  except that the electrical adaptor  620  has a fourth electrical connector  641  that is orthogonal to the first, second, and third electrical connectors  636 ,  637 , and  638 . The fourth electrical connector  641  is positioned between the first electrical connector  636  and the second electrical connector  637 . In alternative embodiments, the electrical connectors  636 ,  637 ,  638 , and  641  can be any combination of male plugs and female sockets. 
         [0136]    The electrical adaptors described herein can be used with many different types of extension cords including extension cords having intermittently spaced female sockets and/or intermittently spaced anchors. When used with extension cords having intermittently spaced anchors, the anchor  640  on the electrical adaptor  600  provides a location to suspend the string of extension cords proximal to the connection between the male plug of one cord and the mating female socket of the other cord so that the string of extension cords is supported at that location. For extension cords that have intermittently spaced anchors, but do not have any anchor proximal to the male plug or last female socket, electrical adaptors having an anchor  640  provide a way to further support the cords so the male connector receives support and does not hang down significantly lower than other portions of the extension cords. Additionally, the electrical adaptor  600  enables users to assemble a network of extension cords to establish a power distribution network that can be suspended over head, extend along vertical surfaces such as walls or studs, or simply suspended off of the ground on stakes plated in the ground to keep the extension cords out of puddles and other damp surfaces. 
         [0137]    The electrical adaptors and extension cords also can be used with the temporary light fixtures described in more detail herein to set up temporary and/or emergency lighting at constructions sights. Alternatively, a networks or string of extension cords can be assembled with lighting fixtures connected to only some of the female sockets to provide both temporary lighting and access to electricity for other electrical devices such as tools. Furthermore, the fasteners described herein provide a mechanism to hold the various components together so they do not become inadvertently disconnected causing a sudden and unexpected loss of power that is potentially both inconvenient and dangerous. 
         [0138]    Referring now to  FIG. 22 , a temporary lighting fixture  700  includes a housing  702 , a light-bulb socket  704 , a male electrical plug  706  and fasteners  708   a  and  708   b . The light-bulb socket  704  is positioned in the housing  702 . The male electrical plug  706  is in electrical communication with the light-bulb socket  704 . The fasteners  708   a  and  708   b  are operatively connected to the housing  702  and the fastener  708  is adapted to secure the housing  702  to a female socket on an extension cord, electrical adaptor, or other electrical device. The fasteners  708   a  and  708   b  have substantially similar structure as the fastener  608  discussed in more detail herein and is configured to mate with an engaging structure similar to the engaging structure  639  also described in more detail herein. 
         [0139]    The temporary lighting fixture  700  also includes a protective cover  710 . The protective cover  710  is operatively connected to the housing  702 . In addition, the protective cover  710  defines a void  712  for receiving a light-bulb (not shown) to be connected to the light-bulb socket  704 . In one possible embodiment, the protective cover  710  has a basket or lattice structure. In other possible embodiments, the protective cover  710  is a translucent plastic or glass enclosure. 
         [0140]    In the exemplary embodiment, the temporary lighting fixture  700  also includes a female electrical socket  714  which is positioned in the housing  702  and in electrical communication with the male electrical plug  706 . The female electrical socket  714  also includes an engaging structure (not shown) to mate with a fastener on an extension cord, power cord, or electrical device. The engaging structure is similar to engaging structure  639  described herein, and the fastener is similar to the fastener  608  described herein. 
         [0141]    The various embodiments described above are provided by way of illustration only and should not be construed to limit the claims attached hereto. Those skilled in the art will readily recognize various modifications and changes that may be made without following the example embodiments and applications illustrated and described herein, and without departing from the true spirit and scope of the following claims.